Orthopedic Surgery

01 Musculoskeletal Anatomy

Orthopedic surgery covers the entire musculoskeletal system: bones, joints, ligaments, tendons, muscles, cartilage, and the peripheral nerves that innervate them. The specialty's scope extends from skull base (craniocervical junction) to the tips of the fingers and toes, and includes the spine. Understanding skeletal anatomy, joint mechanics, and neurovascular relationships is the foundation of every orthopedic decision.

Bone Classification

The 206 bones of the adult skeleton are classified by shape, and each type has distinct fracture patterns and healing characteristics.

Bone Microstructure

Cortical (compact) bone constitutes ~80% of skeletal mass. It is organized into osteons (Haversian systems) — concentric lamellae of mineralized collagen around a central Haversian canal containing blood vessels and nerves. Osteons are connected by Volkmann's canals running perpendicular to the long axis. Cortical bone provides mechanical strength, particularly in resisting bending and torsional forces. Cancellous (trabecular/spongy) bone fills the metaphyses and epiphyses. Its trabecular architecture aligns along lines of mechanical stress (Wolff's law) and provides compressive strength with less weight. Cancellous bone has a much higher surface area and turnover rate, making it more metabolically active and more susceptible to osteoporosis.

Joint Classification

Synovial joints share a common architecture: articular (hyaline) cartilage covering the bony surfaces, a fibrous joint capsule lined by synovium, synovial fluid for lubrication and nutrition, and stabilizing ligaments. The labrum (hip, shoulder) is a fibrocartilaginous ring that deepens the socket and enhances stability.

Major Muscle Groups & Innervation

Blood Supply to Bone

Long bones receive blood from three sources: the nutrient artery (enters the diaphysis through the nutrient foramen, supplies the inner 2/3 of the cortex and medullary canal), periosteal arteries (supply the outer 1/3 of the cortex — critically important when the nutrient artery is disrupted by fracture or reaming), and metaphyseal/epiphyseal arteries (enter at the bone ends). Certain bones have tenuous blood supply making them vulnerable to avascular necrosis (AVN) after fracture: femoral head (medial femoral circumflex artery via retinacular vessels), scaphoid (dorsal branch of radial artery enters distally, flows retrograde), talus (artery of the tarsal canal, deltoid branches), and the proximal pole of the lunate.

02 The Orthopedic Physical Exam

The orthopedic exam follows a systematic approach: Look (alignment, deformity, swelling, ecchymosis, skin integrity, muscle wasting), Feel (point tenderness, crepitus, effusion, temperature, pulses), Move (active and passive range of motion, stability testing), and Neurovascular status (motor, sensory, vascular). Every injured extremity requires documentation of neurovascular status before and after any intervention.

Range of Motion — Normal Values

Special Tests by Joint — Shoulder

Special Tests — Knee

Special Tests — Hip

Neurovascular Examination

Every injured extremity must be assessed for neurovascular integrity. Motor testing: grade strength 0–5 (0 = no contraction, 1 = flicker, 2 = movement with gravity eliminated, 3 = against gravity, 4 = against resistance, 5 = normal). Sensory testing: light touch and two-point discrimination in the distribution of each peripheral nerve (median = thenar eminence and index fingertip; ulnar = small finger; radial = first dorsal web space; peroneal = first web space of foot; tibial = sole of foot). Vascular: palpate pulses (radial, ulnar, DP, PT), check capillary refill (<2 seconds is normal), and assess for compartment syndrome signs (pain with passive stretch, tense compartments, pain out of proportion).

03 Fracture Fundamentals

Fracture Description System

Every fracture is described using a standardized system. The complete description includes: which bone, location (proximal, mid-shaft, distal; metaphyseal vs diaphyseal vs epiphyseal), pattern (transverse, oblique, spiral, comminuted, segmental, butterfly fragment), displacement (amount in mm or % and direction), angulation (degrees and direction — described by the apex of the angle: apex volar, apex lateral, etc.), shortening (in mm), rotation, articular involvement (intra-articular vs extra-articular), and open vs closed.

Fracture Healing Biology

Fracture healing proceeds through a predictable sequence. Inflammatory phase (days 0–7): fracture hematoma forms, providing a scaffold rich in platelets, macrophages, and growth factors (PDGF, TGF-beta, BMP). Osteocytes in damaged bone undergo apoptosis. Mesenchymal stem cells are recruited from periosteum, endosteum, and bone marrow. Soft callus phase (weeks 1–3): fibroblasts and chondroblasts produce a cartilaginous callus bridging the fracture gap (endochondral ossification). This is visible radiographically as hazy periosteal new bone. Hard callus phase (weeks 3–12): the soft callus is progressively mineralized and replaced by woven bone through osteoblast activity. Radiographically, the callus becomes denser and more organized. Remodeling phase (months to years): osteoclast-mediated resorption of excess callus and osteoblast-mediated deposition of lamellar bone along stress lines (Wolff's law) restores near-normal bone architecture.

Factors Affecting Healing

Nonunion & Malunion

Delayed union: healing has not occurred within the expected time frame but is still progressing (callus visible, fracture line still present). Nonunion: fracture has failed to heal and no further progress is expected — typically defined as no radiographic progression of healing for 3 consecutive months or failure to heal by 9 months. Two types: hypertrophic nonunion (abundant callus, "elephant foot" or "horse hoof" appearance — biology is intact but stability is insufficient; treatment = improve stability with revision fixation) and atrophic nonunion (no callus, sclerotic bone ends — biology is deficient; treatment = debridement of sclerotic bone, restoration of canal, bone grafting + stable fixation). Malunion: fracture has healed in a non-anatomic position (angulation, rotation, shortening) — may require corrective osteotomy if symptomatic.

Open Fracture Classification — Gustilo-Anderson

Open fractures involve a communication between the fracture site and the external environment. The Gustilo-Anderson classification is the universal system, though it has significant inter-observer variability. Definitive grading occurs in the operating room after wound exploration and debridement.

04 Shoulder Pathology Upper Extremity

Rotator Cuff Disease

The rotator cuff consists of four muscles — supraspinatus (abduction initiation), infraspinatus (external rotation), teres minor (external rotation), and subscapularis (internal rotation) — forming a musculotendinous cuff that dynamically stabilizes the humeral head within the glenoid. The supraspinatus tendon is the most commonly torn, particularly in its "critical zone" (an area of relative hypovascularity ~1 cm proximal to its insertion on the greater tuberosity).

Impingement syndrome is the clinical spectrum from tendinopathy to partial-thickness tears to full-thickness tears. Neer's stages: Stage I = edema/hemorrhage (age <25, reversible), Stage II = fibrosis/tendinitis (age 25–40, chronic), Stage III = tendon degeneration/tear (age >40, usually requires surgery if full-thickness). Subacromial impingement occurs when the rotator cuff tendons are compressed between the humeral head and the coracoacromial arch (acromion, coracoacromial ligament, AC joint). A type III (hooked) acromion on supraspinatus outlet view increases impingement risk (Bigliani classification: Type I = flat, Type II = curved, Type III = hooked).

Treatment: Partial tears and tendinopathy: activity modification, physical therapy (eccentric strengthening, scapular stabilization), NSAIDs, subacromial corticosteroid injection (limit to 3 per year — repeated injections weaken tendon). Full-thickness tears: surgical repair (arthroscopic preferred) indicated for acute traumatic tears in active patients, chronic tears with significant functional limitation despite conservative management, or progressive tear enlargement. Repair techniques include single-row, double-row, and transosseous-equivalent (suture bridge) fixation to the greater tuberosity using suture anchors. Massive irreparable tears may be managed with superior capsular reconstruction (SCR), balloon spacer (InSpace), or reverse total shoulder arthroplasty.

Glenohumeral Instability

The shoulder trades bony constraint for mobility — the glenoid covers only ~25% of the humeral head surface. Stability depends on static restraints (labrum, capsule, glenohumeral ligaments) and dynamic restraints (rotator cuff). Anterior dislocation accounts for ~95% of traumatic dislocations — mechanism is typically forced abduction + external rotation. The humeral head displaces anteroinferiorly. Associated injuries: Bankart lesion (avulsion of the anteroinferior labrum from the glenoid — the "essential lesion" of recurrent anterior instability), Hill-Sachs lesion (compression fracture of the posterosuperior humeral head from impaction against the glenoid rim), and axillary nerve injury (test deltoid function and "regimental badge area" sensation). Recurrence risk is strongly age-dependent: >90% in patients under 20, ~25% in patients over 40.

Posterior dislocation accounts for ~2–5% and is classically associated with seizures, electrocution, and electroconvulsive therapy (bilateral posterior dislocations are virtually pathognomonic for seizure). The AP radiograph may appear deceptively normal ("lightbulb sign" — internally rotated humeral head appears rounded). A reverse Hill-Sachs lesion (McLaughlin lesion — compression fracture of the anteromedial humeral head) may be present. Always obtain axillary lateral or scapular-Y views to rule out posterior dislocation.

Treatment of recurrent anterior instability: Arthroscopic Bankart repair (reattachment of the torn labrum with suture anchors) is the standard for younger patients with soft tissue Bankart lesions. In the presence of significant glenoid bone loss (>20–25% — "inverted pear" glenoid on arthroscopy, or critical bone loss on CT), or a large engaging Hill-Sachs lesion, a bony procedure is required: Latarjet procedure (transfer of the coracoid process with the conjoined tendon to the anterior glenoid — provides bone augmentation + dynamic sling effect) or iliac crest bone graft (Eden-Hybinette procedure).

Acromioclavicular (AC) Joint Injuries

The Rockwood classification grades AC joint separations I through VI based on the degree of displacement of the clavicle relative to the acromion and the integrity of the AC and coracoclavicular (CC) ligaments.

05 Proximal Humerus & Clavicle Fractures Upper Extremity

Proximal Humerus Fractures — Neer Classification

The proximal humerus has four "parts" (Neer's parts): greater tuberosity, lesser tuberosity, articular segment (humeral head), and shaft. A part is considered displaced when there is >1 cm of displacement or >45° of angulation. The Neer classification counts the number of displaced parts.

Clavicle Fractures

The clavicle is the most commonly fractured bone in the body (~2.6% of all fractures). Middle third fractures account for ~80% — the clavicle is thinnest here and lacks muscular/ligamentous protection. The lateral third (~15%) and medial third (~5%) are less common.

Treatment of middle third fractures: Non-displaced or minimally displaced: sling for comfort, early ROM as tolerated, heals in 6–12 weeks. Operative indications include: shortening >2 cm, comminution with displacement, open fracture, skin tenting, associated neurovascular injury, floating shoulder (ipsilateral clavicle + scapular neck fracture). Fixation options: superior plate (Acumed, DePuy precontoured anatomic plates) or anterior-inferior plate (theoretical lower prominence), or intramedullary fixation (Rockwood pin, TEN nail — less soft tissue disruption but less rotational control). A landmark RCT (the Canadian Orthopaedic Trauma Society, 2007) showed operative fixation of displaced midshaft fractures reduces nonunion rate from ~15% to ~3% and improves functional outcomes.

Lateral third fractures: Neer classification: Type I = lateral to CC ligaments (stable, nonoperative); Type II = medial to CC ligaments (unstable, high nonunion rate ~30%, often requires fixation — hook plate, CC screw, suture button like TightRope); Type III = intra-articular (uncommon).

06 Elbow Pathology & Fractures Upper Extremity

Distal Humerus Fractures

Distal humerus fractures in adults are complex intra-articular injuries, often from falls or high-energy trauma. The distal humerus forms two columns (medial and lateral) supporting the trochlea and capitellum. The AO/OTA classification divides them into extra-articular (type A), partial articular (type B — affecting one column), and complete articular (type C — both columns, often with intercondylar split). Treatment of displaced intra-articular fractures is ORIF via a posterior approach (typically olecranon osteotomy or triceps-reflecting [Bryan-Morrey] approach) using dual-column plating (perpendicular or parallel 90-90 plating technique). In elderly patients with severely comminuted fractures and poor bone quality, total elbow arthroplasty (TEA) may be preferred over ORIF (the McKee et al., 2003 trial showed TEA had better outcomes than ORIF in elderly patients with comminuted distal humerus fractures).

Olecranon Fractures

The olecranon is subcutaneous and vulnerable to direct blows and falls on the flexed elbow. The triceps inserts on the olecranon, so any displaced fracture disrupts the extensor mechanism. If the patient cannot actively extend the elbow against gravity, the fracture is functionally displaced and requires surgery. Treatment: Non-displaced, stable fractures with intact extensor mechanism: long arm splint at 90°, early ROM. Displaced: tension band wiring (TBW) — two K-wires + a figure-of-8 wire that converts the triceps' tensile force into compression at the articular surface during elbow flexion. This is the classic technique for simple transverse fractures. Comminuted fractures: plate fixation (precontoured olecranon plates — Synthes, Acumed) is superior to TBW for comminuted and oblique patterns. Excision of the fragment with triceps reattachment is an option for elderly/low-demand patients with comminuted fractures involving <50% of the articular surface.

Radial Head Fractures — Mason Classification

Lateral Epicondylitis (Tennis Elbow)

Lateral epicondylitis is a degenerative tendinopathy (not a true inflammatory process) of the extensor carpi radialis brevis (ECRB) origin at the lateral epicondyle. Peak incidence ages 35–55. Pathology shows angiofibroblastic hyperplasia (Nirschl), not acute inflammation — hence "tendinosis" is more accurate than "tendinitis." Treatment: 90% resolve with nonoperative management: activity modification (avoid repetitive gripping/wrist extension), counterforce bracing (forearm strap), eccentric wrist extensor stretching/strengthening, and topical NSAIDs. PRP injections have shown benefit in some studies (Gosens et al., 2011). Corticosteroid injection provides short-term relief but worsens long-term outcomes compared to wait-and-see. Surgical debridement (open or arthroscopic Nirschl debridement) is reserved for refractory cases after 6–12 months.

Medial Epicondylitis (Golfer's Elbow)

Tendinopathy of the flexor-pronator mass (primarily flexor carpi radialis and pronator teres) at the medial epicondyle. Less common than lateral epicondylitis (~10:1 ratio). Must evaluate for concomitant ulnar neuropathy at the cubital tunnel (present in 20–60% of medial epicondylitis cases) — Tinel's at the cubital tunnel, assess intrinsic hand strength and small/ring finger numbness. Treatment parallels lateral epicondylitis; surgery includes debridement with or without ulnar nerve transposition.

07 Wrist & Hand Upper Extremity

Distal Radius Fractures

The most common fracture in the upper extremity and the most common fracture in the ED. Bimodal distribution: young adults (high-energy) and elderly women with osteoporosis (low-energy FOOSH — fall on outstretched hand). Key named patterns: Colles' fracture (dorsally displaced and angulated — the classic "dinner fork" deformity), Smith's fracture (volarly displaced — "reverse Colles'"), Barton's fracture (intra-articular fracture-subluxation — dorsal or volar), Chauffeur's fracture (radial styloid fracture — intra-articular).

Acceptable reduction parameters (Lafontaine criteria for instability when not met): radial inclination >15° (normal 22°), radial height >7 mm (normal 11 mm), volar tilt 0–15° (normal 11° volar), articular step-off <2 mm, ulnar variance <3 mm. Treatment: Stable, extra-articular, acceptable alignment: closed reduction + sugar-tong splint, then short arm cast at 1–2 weeks for a total 6 weeks. Operative indications: intra-articular fractures with >2 mm step-off, loss of reduction, unstable fracture patterns (dorsal comminution, initial shortening >5 mm, volar tilt >20°), associated ulnar styloid base fracture with DRUJ instability. Fixation: volar locking plate (Synthes VA-LCP, Acumed Acu-Loc) is the most common technique — allows early ROM. Fragment-specific fixation for complex articular patterns. External fixation (spanning or non-spanning) for severely comminuted fractures.

Scaphoid Fractures

The scaphoid is the most commonly fractured carpal bone and the most clinically important because of its tenuous blood supply. The dorsal branch of the radial artery enters the scaphoid distally and supplies the proximal pole via retrograde flow — fractures through the waist or proximal pole disrupt this supply, leading to avascular necrosis (AVN) of the proximal fragment in 20–40% of displaced proximal pole fractures. Diagnosis: Tenderness in the anatomical snuffbox (sensitivity ~90%, specificity ~40%) and tenderness with axial compression of the thumb (scaphoid compression test). Initial radiographs may be negative in up to 20% of cases. If clinical suspicion is high with negative radiographs, immobilize in a thumb spica splint and obtain MRI (gold standard, 99% sensitivity) or repeat radiographs at 10–14 days.

Treatment: Non-displaced waist fractures: thumb spica cast for 8–12 weeks (short arm thumb spica is generally adequate; long arm thumb spica adds no benefit per recent evidence). Non-displaced proximal pole fractures: higher nonunion risk, lower threshold for surgical fixation. Displaced (>1 mm step-off on CT) or proximal pole fractures: percutaneous or open headless compression screw fixation (Acutrak, Herbert screw). Established nonunion: open reduction, bone grafting (vascularized or non-vascularized — the 1,2-intercompartmental supraretinacular artery [1,2 ICSRA] vascularized bone graft for proximal pole AVN), and screw fixation. End-stage: scaphoid excision and four-corner fusion (SLAC/SNAC wrist reconstruction).

Carpal Tunnel Syndrome

The most common peripheral nerve entrapment. The median nerve is compressed within the carpal tunnel — a fibro-osseous tunnel bounded by the carpal bones dorsally and the transverse carpal ligament (flexor retinaculum) volarly. Nine flexor tendons (4 FDS, 4 FDP, FPL) accompany the median nerve through the tunnel. Symptoms: Numbness and paresthesias in the median nerve distribution (thumb, index, middle, radial half of ring finger) — classically worse at night and with sustained wrist flexion (Phalen's test positive in 30–60 seconds). Physical exam: Tinel's sign (percussion over the carpal tunnel produces paresthesias), Phalen's test (wrist flexion for 60 seconds), Durkan's (direct compression). Late findings: thenar atrophy (abductor pollicis brevis), decreased two-point discrimination. Diagnosis: Nerve conduction studies (NCS) / electromyography (EMG) confirm median nerve entrapment — distal motor latency >4.2 ms, distal sensory latency >3.5 ms. Treatment: Mild/intermittent: night splinting in neutral wrist position, activity modification, corticosteroid injection (temporary relief, diagnostic utility). Moderate-severe or refractory: carpal tunnel release (CTR) — division of the transverse carpal ligament. Open (2–3 cm incision in line with the ring finger ray) or endoscopic (Agee single-portal or Chow two-portal technique). Success rates exceed 90%.

Trigger Finger (Stenosing Tenosynovitis)

Thickening of the A1 pulley at the level of the MCP joint causes catching or locking of the flexor tendon during finger motion. The ring finger and thumb are most commonly affected. Quinnell grading: Grade I = pain/tenderness at A1 pulley without triggering, Grade II = triggering but patient can actively extend, Grade III = triggering requiring passive extension, Grade IV = fixed locked position. Treatment: Splinting (MCP in extension), corticosteroid injection into the tendon sheath (60–90% success rate for first injection; diabetic patients have lower success rates). Refractory: A1 pulley release (open or percutaneous) — simple and definitive.

De Quervain's Tenosynovitis

Stenosing tenosynovitis of the first dorsal compartment (abductor pollicis longus [APL] and extensor pollicis brevis [EPB]). Finkelstein's test (ulnar deviation of the wrist with the thumb grasped in the fist — pain over the radial styloid) is the classic provocative maneuver. Treatment: thumb spica splint, corticosteroid injection into the first dorsal compartment (85% resolution rate — ensure injection enters the EPB subsheath, which exists as a separate compartment in 30% of patients), and surgical release for refractory cases.

08 Hip Pathology & Fractures Lower Extremity

Hip Fracture Overview

Hip fractures are one of the most consequential injuries in orthopedics — 1-year mortality ranges from 15–30% in the elderly. The primary distinction is intracapsular (femoral neck) vs extracapsular (intertrochanteric, subtrochanteric). This distinction dictates management because the femoral neck is intracapsular, and displaced fractures disrupt the retinacular blood supply to the femoral head, creating high AVN and nonunion risk.

Femoral Neck Fractures — Garden Classification

Intertrochanteric Fractures

Extracapsular fractures between the greater and lesser trochanters. The blood supply to the femoral head is not at risk, so AVN is not a concern. These are treated surgically in virtually all cases (nonoperative management only for non-ambulatory patients with unacceptable surgical risk). Classification — AO/OTA 31-A: A1 = simple (2-part, stable after reduction), A2 = multifragmentary (comminuted, including loss of posteromedial buttress — unstable), A3 = reverse obliquity or transverse (subtrochanteric extension — very unstable).

Fixation: Stable patterns (A1): sliding hip screw (SHS) — lag screw into the femoral head with a side plate. Allows controlled collapse along the screw axis. Tip-apex distance (TAD) <25 mm predicts against cut-out (the most common mode of failure — Baumgaertner et al., 1995). Unstable patterns (A2, A3): cephalomedullary nail (Gamma nail, Synthes TFN/TFNA, Smith+Nephew InterTAN, Stryker Gamma3) — intramedullary device with a lag screw or helical blade into the femoral head. The intramedullary position provides a shorter moment arm and better load sharing than an SHS in unstable fractures. Reverse obliquity (A3) patterns must not be treated with SHS (the fracture will displace along the screw axis).

Avascular Necrosis (AVN) of the Femoral Head

AVN (osteonecrosis) results from disruption of the blood supply to the femoral head, leading to bone cell death and eventual subchondral collapse and secondary osteoarthritis. Etiologies: femoral neck fracture (post-traumatic, most common), corticosteroids (dose-dependent — risk increases significantly above 20 mg/day prednisone for >3 months), alcohol abuse, sickle cell disease, SLE, HIV/antiretroviral therapy, diving (caisson disease), Gaucher's disease, radiation, idiopathic. Ficat & Arlet classification: Stage 0 = preclinical (only biopsy); Stage I = pre-radiographic (normal X-ray, positive MRI/bone scan); Stage II = abnormal X-ray (sclerosis, cysts) but no collapse; Stage III = subchondral collapse (crescent sign on X-ray); Stage IV = secondary OA with acetabular involvement.

Treatment: Pre-collapse (Ficat I–II): core decompression (drilling a channel into the necrotic area to relieve intraosseous pressure and stimulate revascularization — can add bone graft/BMP/stem cells). Non-vascularized or vascularized fibular bone grafting (free vascularized fibula graft — Urbaniak technique). Bisphosphonates may delay collapse. Post-collapse (Ficat III–IV): total hip arthroplasty is the definitive treatment. Young patients with limited head involvement and preserved joint congruency may be candidates for rotational osteotomy (Sugioka).

Hip Dislocation

Posterior dislocation (~90%) — classically from a dashboard injury (knee strikes dashboard, axial force drives the femur posteriorly out of the acetabulum). The leg is held in a characteristic position: flexed, adducted, and internally rotated. Associated injuries: sciatic nerve palsy (10–20% — usually the peroneal division, leading to foot drop), posterior wall acetabular fracture (up to 70%), femoral head fracture (Pipkin classification). Anterior dislocation (~10%) — forced abduction and external rotation. The leg is held in extension, abduction, and external rotation. Associated with femoral head impaction fractures. Both types require emergent closed reduction within 6 hours to minimize AVN risk (each hour of delay increases AVN rate). Post-reduction CT scan is mandatory to assess for acetabular fractures, loose bodies, and concentric reduction.

09 Knee Pathology & Fractures Lower Extremity

ACL Tear

The anterior cruciate ligament (ACL) is the primary restraint to anterior tibial translation and a secondary stabilizer to rotation. It originates from the posteromedial aspect of the lateral femoral condyle and inserts on the anterior tibial spine. Mechanism of injury: non-contact pivoting/deceleration (70%), valgus + rotation, or hyperextension. Physical exam: positive Lachman (most sensitive), positive anterior drawer, pivot shift. MRI confirms the diagnosis and evaluates for associated injuries: meniscal tears (up to 50%), MCL injury ("unhappy triad" = ACL + MCL + medial meniscus), bone bruises of the lateral femoral condyle and posterior lateral tibial plateau (pathognomonic pattern).

Treatment: Non-operative: acceptable for low-demand, older patients without functional instability; involves PT focusing on hamstring strengthening and proprioception. ACL reconstruction is indicated for young/active patients, those with functional instability (giving way episodes), and associated repairable meniscal tears. Graft options: bone-patellar tendon-bone (BTB) autograft (gold standard for return to cutting/pivoting sports — rigid bone-to-bone healing, higher anterior knee pain), hamstring tendon autograft (gracilis + semitendinosus, quadrupled — less donor site morbidity, soft tissue-to-bone healing slower), quadriceps tendon autograft (gaining popularity — thick, strong graft with less anterior knee pain than BTB), and allograft (no donor site morbidity, but higher re-tear rate in young athletes <25 years — Kaeding et al., 2011). Tunnel placement is the most critical factor for success — the femoral tunnel should be in the center of the anatomic ACL footprint.

PCL, MCL, LCL & Multi-Ligament Knee Injuries

PCL tear: Most common mechanism is a dashboard injury (posterior force on the proximal tibia with the knee flexed) or hyperflexion. Isolated PCL tears are often managed non-operatively with quadriceps-intensive rehabilitation. Surgical reconstruction is considered for grade III injuries with combined instability, persistent functional limitation, or multi-ligament injury. MCL tear: Valgus stress mechanism. Graded I–III by medial joint opening (I = 0–5 mm, II = 5–10 mm, III = >10 mm). Isolated MCL tears heal well with protected weight-bearing and hinged knee brace; surgery is rarely needed for isolated injuries. LCL / posterolateral corner (PLC) injury: Varus or hyperextension force. PLC structures include the LCL, popliteus tendon, and popliteofibular ligament. PLC injuries almost always require surgical repair or reconstruction, especially when combined with cruciate tears. Must check peroneal nerve function.

Knee dislocation (multi-ligament injury involving ≥2 cruciate and/or collateral ligaments) is an emergency requiring immediate assessment for popliteal artery injury — occurs in 5–40% of knee dislocations. Mandatory vascular exam: ABI, followed by CTA if ABI <0.9 or any clinical concern. Spontaneous reduction may have occurred before presentation — a multi-ligament injury without a documented dislocation should still prompt vascular assessment.

Meniscal Tears

The menisci (medial and lateral) are C-shaped fibrocartilaginous structures that deepen the tibial plateau, distribute load (transmit 50–70% of the load in extension, up to 85% in flexion), absorb shock, and aid in joint lubrication and proprioception. The vascular zones are critical for treatment decisions: red-red zone (peripheral 1/3 — vascularized, good healing potential, suitable for repair), red-white zone (middle 1/3 — intermediate vascularity, repair may succeed), white-white zone (inner 1/3 — avascular, no healing capacity, typically partial meniscectomy). Tear patterns: vertical longitudinal (bucket-handle tears cause locked knee), radial, horizontal cleavage, flap/oblique, complex/degenerative.

Treatment: Arthroscopic partial meniscectomy for irreparable tears in the white-white zone — remove only the unstable fragment, preserve as much meniscus as possible (total meniscectomy accelerates OA). Meniscal repair for tears in the red-red or red-white zone, especially in young patients and when performed concurrently with ACL reconstruction (the ACL drilling creates a healing response that improves meniscal repair success). Repair techniques: inside-out (gold standard), outside-in, all-inside (meniscal repair devices — FasT-Fix, RapidLoc). Meniscal transplantation (allograft) is considered for young patients with a complete or near-complete meniscectomy who develop pain from the meniscus-deficient compartment, before advanced chondral damage occurs.

Tibial Plateau Fractures — Schatzker Classification

Knee Osteoarthritis

OA is the most common joint disease, affecting >30 million Americans. The knee is the most commonly affected large joint. Pathology: progressive loss of articular cartilage, subchondral bone sclerosis, osteophyte formation, synovial inflammation. Weight-bearing radiographs show: joint space narrowing, subchondral sclerosis, osteophytes, subchondral cysts. Kellgren-Lawrence grading: 0 = normal, 1 = doubtful (minute osteophytes), 2 = mild (definite osteophytes, possible joint space narrowing), 3 = moderate (moderate joint space narrowing, some sclerosis), 4 = severe (bone-on-bone, large osteophytes, sclerosis, deformity). Medial compartment OA is most common, leading to varus (bow-legged) deformity.

Non-operative management: Weight loss (each 1 lb of weight loss = 4 lbs less force across the knee), physical therapy (quadriceps strengthening), activity modification, acetaminophen, topical NSAIDs, oral NSAIDs (ibuprofen, naproxen, meloxicam — shortest duration at lowest effective dose), intra-articular corticosteroid injection (3–4 months relief), hyaluronic acid injection (viscosupplementation — Synvisc, Euflexxa; modest benefit, insurance coverage varies), unloader brace for unicompartmental disease. Surgical: Arthroscopy for OA has no benefit over sham surgery (Kirkley et al., 2008). High tibial osteotomy (HTO) for young patients (<60) with isolated medial compartment OA and varus alignment. Total knee arthroplasty is the definitive treatment for end-stage disease.

10 Ankle & Foot Lower Extremity

Ankle Fractures — Weber Classification

The Weber classification is based on the level of the fibular fracture relative to the syndesmosis (the ligamentous complex connecting the distal tibia and fibula — anterior inferior tibiofibular ligament [AITFL], posterior inferior tibiofibular ligament [PITFL], transverse ligament, and interosseous membrane).

Lauge-Hansen Classification

The Lauge-Hansen system describes the mechanism of ankle fractures based on foot position (first word: supination or pronation) and direction of force (second word: adduction, external rotation, or abduction). It predicts the pattern of ligamentous and bony injury in a sequential manner.

Achilles Tendon Rupture

Typically occurs in 30–50-year-old men during sports ("weekend warrior" demographic). The tendon ruptures 2–6 cm above its calcaneal insertion — the watershed zone of poorest vascularity. Patients report a "pop" or sensation of being kicked. Physical exam: Palpable gap in the tendon, positive Thompson test (squeezing the calf does not produce plantar flexion of the foot), loss of resting tension (foot hangs in dorsiflexion when prone). Treatment: Operative repair (Krackow suture technique, with or without augmentation) vs functional non-operative treatment (equinus casting followed by progressive dorsiflexion, early weight-bearing with a boot and heel wedges). Landmark studies (STAR trial — Costa et al., BMJ 2020) suggest similar outcomes with accelerated functional rehabilitation vs surgery, though re-rupture rates are slightly higher non-operatively (4–6% vs 1–2%). Operative repair is generally preferred for young, active patients and competitive athletes.

Lisfranc Injury

Injuries to the tarsometatarsal (TMT) joint complex, named for the Lisfranc ligament — a strong ligament connecting the medial cuneiform to the base of the 2nd metatarsal. This is the "keystone" of the midfoot. Mechanism: axial load on a plantarflexed foot (classically a horse stirrup injury, now more often motor vehicle or athletic). Frequently missed — subtle injuries present with midfoot swelling, plantar ecchymosis (pathognomonic), and inability to bear weight. Diagnosis: Weight-bearing AP foot X-ray: look for diastasis between the 1st and 2nd metatarsal bases (>2 mm) and loss of alignment between the medial border of the 2nd metatarsal and the medial border of the middle cuneiform. CT scan for subtle or equivocal cases. Treatment: Purely ligamentous injuries: primary arthrodesis (fusion) of the TMT joints (better outcomes than ORIF for ligamentous injuries — Ly & Coetzee, 2006). Fracture-dislocations: anatomic ORIF with screws and/or plates.

Calcaneal Fractures

The most commonly fractured tarsal bone, usually from a fall from height (axial loading). 10% bilateral, 10% associated with lumbar spine compression fracture (always check the spine). The Bohler's angle (normally 20–40°) measures the relationship between the posterior facet and the tuberosity — a decreased or negative Bohler's angle indicates subtalar joint depression and predicts worse outcomes. The Sanders classification (based on coronal CT through the widest part of the posterior facet) guides treatment: Type I = non-displaced → nonoperative; Type II = 2 fragments → ORIF; Type III = 3 fragments → ORIF; Type IV = >3 fragments (comminuted) → primary subtalar arthrodesis. The extensile lateral approach (L-shaped incision) provides excellent visualization but has wound complication rates of 10–25%; sinus tarsi approach (minimally invasive) has lower wound complications and is increasingly favored for Type II fractures.

11 Cervical Spine Spine

Cervical Spine Fractures

Atlas (C1) fractures — Jefferson fracture: Axial load (diving, fall onto head) fractures the C1 ring at 2–4 points. Lateral mass overhang >6.9 mm (combined bilateral) on open-mouth odontoid view indicates transverse ligament rupture (unstable — Rule of Spence). Stable Jefferson: rigid cervical collar. Unstable: halo vest or surgical fusion (C1–C2).

Axis (C2) fractures: Three main types: Odontoid (dens) fractures — Anderson & D'Alonzo classification: Type I = tip avulsion (rare, generally stable, may be unstable if associated with occipitocervical dissociation); Type II = base of the dens (most common and most problematic — high nonunion rate of 20–40% in elderly with displacement >5 mm, age >50; treatment: rigid collar for non-displaced, halo or anterior odontoid screw for displaced, posterior C1–C2 fusion [Harms technique: C1 lateral mass screws + C2 pedicle or pars screws] for elderly/nonunion); Type III = extends into the C2 body (good cancellous healing potential, usually treated in cervical collar). Hangman's fracture (bilateral C2 pars interarticularis fracture) — Levine classification: Type I = <3 mm displacement, no angulation → rigid collar; Type II = >3 mm or >11° angulation → halo vs surgical fusion; Type IIA = minimal displacement but severe angulation (flexion-distraction) → do NOT apply traction → halo or surgery; Type III = bilateral facet dislocation → surgery.

Subaxial cervical fractures (C3–C7): Classified by the Subaxial Cervical Spine Injury Classification (SLIC) system, which scores morphology (compression = 1, burst = 2, distraction = 3, translation/rotation = 4), disco-ligamentous complex integrity (intact = 0, indeterminate = 1, disrupted = 2), and neurological status (intact = 0, root injury = 1, complete cord = 2, incomplete cord = 3, ongoing compression with neuro deficit = +1). Score ≤3: nonoperative; Score = 4: surgeon discretion; Score ≥5: surgical stabilization.

Facet injuries: Unilateral facet dislocation = ~25% anterior subluxation on lateral X-ray + radiculopathy; bilateral facet dislocation = ~50% anterior subluxation + high risk of spinal cord injury. Treatment: closed reduction with traction (after MRI to rule out disc herniation in alert patients), then anterior or posterior stabilization.

Cervical Myelopathy

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction in adults >55. Caused by spinal cord compression from disc osteophyte complexes, ligamentum flavum hypertrophy, and OPLL (ossification of the posterior longitudinal ligament). Symptoms: progressive gait difficulty (broad-based, spastic), hand clumsiness (loss of fine motor function — difficulty with buttons, dropping objects), upper extremity numbness/weakness, urinary urgency/retention (late). Signs: hyperreflexia, clonus, Hoffmann's sign (flicking the middle fingertip produces thumb/index flexion), Babinski sign, inverted radial reflex (brachioradialis tap produces finger flexion instead of elbow flexion), Lhermitte's sign (neck flexion causes electric shock sensation down the spine). Treatment: Surgery for moderate-severe myelopathy — CSM is progressive and rarely improves spontaneously. Anterior cervical discectomy and fusion (ACDF) for 1–2 level anterior compression. Anterior cervical corpectomy and fusion (ACCF) for retrovertebral compression. Laminoplasty (expansive open-door technique) or laminectomy with posterior fusion for multi-level compression (≥3 levels) with maintained cervical lordosis.

Cervical Radiculopathy

Nerve root compression from disc herniation (younger patients) or foraminal stenosis from osteophytes (older patients). The most commonly affected levels are C5–C6 (C6 root) and C6–C7 (C7 root). Key dermatome/myotome relationships:

Treatment: 80–90% resolve with conservative management: activity modification, NSAIDs, oral corticosteroid taper (methylprednisolone dose pack), cervical epidural steroid injection (fluoroscopic-guided transforaminal or interlaminar). PT with cervical traction. Surgery (ACDF, posterior cervical foraminotomy) for failure of 6–12 weeks conservative treatment, progressive neurological deficit, or intractable pain.

12 Thoracolumbar Spine Spine

Thoracolumbar Fractures

The thoracolumbar junction (T11–L2) is the most common site of spinal fractures — it is the transition zone between the rigid thoracic spine (stabilized by the rib cage) and the mobile lumbar spine. The Denis three-column model divides the spine into: anterior column (anterior 2/3 of vertebral body and disc, anterior longitudinal ligament), middle column (posterior 1/3 of vertebral body and disc, posterior longitudinal ligament), and posterior column (pedicles, facets, laminae, spinous process, posterior ligamentous complex [PLC — supraspinous ligament, interspinous ligament, ligamentum flavum, facet joint capsules]). Instability requires involvement of ≥2 columns.

Thoracolumbar Injury Classification and Severity Score (TLICS)

Score ≤3: nonoperative (TLSO brace). Score = 4: surgeon discretion. Score ≥5: operative stabilization. Neurological deficit from canal compromise generally warrants surgical decompression.

Fracture Types

Compression fracture: Flexion mechanism, anterior column failure only. Loss of anterior vertebral body height with intact posterior wall and middle column. Kyphotic angulation >30° or >50% height loss suggests PLC injury — obtain MRI. Treatment: TLSO brace for 8–12 weeks if stable; vertebral augmentation (kyphoplasty or vertebroplasty) for intractable pain in osteoporotic fractures. Burst fracture: Axial compression mechanism, anterior and middle column failure. Retropulsed bone fragments may compromise the spinal canal. Treatment depends on neurological status, PLC integrity, and degree of canal compromise — may be braced if neurologically intact with intact PLC, or may require surgical stabilization. Flexion-distraction (Chance fracture): Distraction mechanism with failure of the posterior and middle columns in tension — "seatbelt fracture." May be purely bony (extends through the vertebral body — better prognosis, can heal in extension brace) or ligamentous/combined (PLC disrupted — requires surgical stabilization). Associated with abdominal injuries (small bowel, mesentery, pancreas) in up to 50% — CT abdomen/pelvis required. Fracture-dislocation: All three columns fail, with translation or rotation — most unstable pattern. High rate of neurological injury. Requires surgical stabilization (posterior pedicle screw fixation ± anterior column support).

Lumbar Spinal Stenosis

Central canal narrowing causing neurogenic claudication — bilateral leg pain, heaviness, and weakness with walking or standing that is relieved by sitting or leaning forward (flexion opens the central canal). Distinguished from vascular claudication by the "shopping cart sign" (patients lean forward over shopping carts for relief). Diagnosis: MRI shows central canal stenosis, often at multiple levels (L3–L4, L4–L5 most common). The SPORT trial (Weinstein et al., NEJM 2008) demonstrated that surgical decompression provided significantly better outcomes than conservative treatment for moderate-severe stenosis at 4-year follow-up, though crossover rates were high. Treatment: Conservative: PT, epidural steroid injections, activity modification. Surgical: laminectomy (decompression of the central canal) — the standard procedure. If associated instability or spondylolisthesis: laminectomy with posterolateral fusion ± pedicle screw instrumentation. Interspinous process spacers (Superion, X-STOP) are a minimally invasive option for mild-moderate stenosis.

13 Degenerative Disc Disease & Spondylolisthesis Spine

Degenerative Disc Disease (DDD)

The intervertebral disc consists of the nucleus pulposus (gelatinous center, high water content, provides compressive resistance) and the annulus fibrosus (concentric collagen lamellae providing tensile strength). Disc degeneration begins in the 2nd decade — progressive desiccation, loss of disc height, annular fissuring, and altered biomechanics. The disc is largely avascular (nutrition by diffusion from the vertebral endplates), so healing capacity is minimal. Disc herniation refers to displacement of disc material beyond the normal disc space margin: protrusion (base wider than dome), extrusion (dome wider than base), sequestration (free fragment, separated from parent disc).

Lumbar disc herniation: Most commonly posterolateral (the posterior longitudinal ligament is weakest laterally). L4–L5 and L5–S1 account for 95% of lumbar herniations. A posterolateral herniation at L4–L5 compresses the traversing L5 nerve root (not the exiting L4 root). A far lateral (foraminal) herniation at L4–L5 compresses the exiting L4 root. Key lumbar root findings:

Treatment: 90% of lumbar disc herniations resolve with conservative management: NSAIDs, activity modification (avoid prolonged sitting), PT (McKenzie extension exercises, core stabilization), and epidural steroid injections. Surgical indication: microdiscectomy (standard of care) for progressive neurological deficit, cauda equina syndrome (surgical emergency — saddle anesthesia, urinary retention, bilateral leg weakness; requires emergent decompression within 24–48 hours), or failure of 6–12 weeks of conservative treatment with persistent radiculopathy. The SPORT trial showed microdiscectomy provided faster recovery, though long-term (8-year) outcomes were similar between operative and nonoperative groups.

Spondylolisthesis

Anterior displacement of one vertebra relative to the one below. Wiltse classification by etiology: Type I = dysplastic (congenital facet abnormality), Type II = isthmic (pars interarticularis defect — spondylolysis; most common at L5–S1 in young athletes, especially gymnasts and football linemen), Type III = degenerative (facet arthropathy and disc degeneration; most common at L4–L5 in elderly women), Type IV = traumatic, Type V = pathologic (tumor, infection), Type VI = iatrogenic (post-surgical). Meyerding grading by percentage of slip: Grade I = 0–25%, Grade II = 25–50%, Grade III = 50–75%, Grade IV = 75–100%, Grade V = spondyloptosis (>100%).

Treatment of isthmic spondylolisthesis: Low-grade (I–II), asymptomatic or mild symptoms: activity modification, PT (core and hamstring flexibility), bracing for symptomatic pars defect in adolescents (TLSO brace for 3–6 months may allow pars healing). Surgery for refractory symptoms, neurological deficit, or high-grade slip: posterolateral or interbody fusion (PLIF, TLIF) with pedicle screw instrumentation. Reduction of slip is controversial for high-grade — incomplete reduction is often accepted to avoid neurological injury (L5 root stretch). Treatment of degenerative spondylolisthesis: The SPORT trial showed surgery (decompressive laminectomy + fusion) was superior to conservative treatment for symptomatic degenerative spondylolisthesis with stenosis at 4 years.

14 Pelvic & Acetabular Fractures Trauma

Pelvic Ring Fractures — Young-Burgess Classification

The pelvis is a ring structure: disruption at one point implies disruption (bony or ligamentous) at a second point. The posterior ring (sacroiliac joints, sacrum, posterior ligamentous complex) contributes ~60% of pelvic stability. Pelvic fractures are classified by the mechanism of injury.

Acetabular Fractures — Letournel Classification

The Letournel system describes acetabular fractures based on which columns and walls are involved. The acetabulum is formed by two columns: the anterior column (iliopectineal line on X-ray — pubis to anterior AIIS) and the posterior column (ilioischial line — ischium to greater sciatic notch). The anterior wall and posterior wall are the articular portions of their respective columns.

Treatment principles: Anatomic reduction of the articular surface is essential for long-term outcomes. Operative indications: >2 mm articular step-off, hip instability, incarcerated fragments, posterior wall fractures involving >40% of the wall (hip unstable), associated fracture patterns. Surgical approaches: Kocher-Langenbeck (posterior — for posterior wall/column, transverse, T-type), Ilioinguinal (anterior — for anterior column/wall, both column, anterior column + posterior hemitransverse), modified Stoppa (intrapelvic — alternative anterior approach with better visualization of the quadrilateral plate). Timing: ideally within 5–10 days (after resuscitation, before callus formation complicates reduction). In elderly patients with severe comminution and osteoporosis, acute THA with acetabular reconstruction may be preferable to ORIF.

15 Femoral & Tibial Shaft Fractures Trauma

Femoral Shaft Fractures

High-energy injuries in young adults (MVC, fall from height); low-energy in elderly with osteoporosis. The femur is the longest and strongest bone in the body. Fractures cause significant hemorrhage (each femur fracture can lose 1–1.5 L of blood into the thigh). Winquist-Hansen classification by comminution: Type 0 = no comminution, Type I = small butterfly fragment (<25% cortex), Type II = butterfly 25–50% cortex, Type III = >50% cortex comminution (no cortical contact after nailing), Type IV = segmental bone loss (circumferential comminution).

Treatment: Antegrade intramedullary nailing (IMN) is the gold standard for virtually all femoral shaft fractures. Entry point: piriformis fossa (standard) or greater trochanter tip (trochanteric entry nail — Synthes Expert, Smith+Nephew T2). Reaming the canal before nail insertion improves cortical blood flow long-term and allows a larger nail diameter. Static locking (interlocking screws at both ends) controls length and rotation. Dynamization (removal of one set of interlocking screws at 3–4 months) may be performed for delayed union to allow axial compression. Retrograde nailing (entry through the intercondylar notch via the knee) is an alternative for ipsilateral femoral neck/shaft combination, distal fractures, bilateral fractures (allows nailing in supine position), obesity, or pregnant patients. Plate fixation (submuscular/bridge plating) is reserved for narrow canal, adolescents with open physis, severe deformity, or periprosthetic fractures around implants. External fixation: damage control for polytrauma (see below).

Tibial Shaft Fractures

The tibia is the most commonly fractured long bone. The anteromedial surface is subcutaneous (no muscle coverage), which explains the high rate of open fractures (20–30% of tibial shaft fractures are open). Treatment: Non-displaced, stable, closed fractures: long leg cast (bent at knee to prevent rotation) for 4–6 weeks, then patellar tendon-bearing (PTB) short leg cast/functional brace for another 6–12 weeks. Operative indications: displaced, unstable, open fracture, associated compartment syndrome, floating knee (ipsilateral femur + tibia fractures), polytrauma. Intramedullary nailing is the gold standard for displaced fractures — entry at the proximal tibia through a suprapatellar or infrapatellar approach. Reamed nailing provides better union rates than unreamed nailing for closed fractures. For open fractures, either reamed or unreamed nailing is acceptable (the SPRINT trial — Study to Prospectively Evaluate Reamed Intramedullary Nails in Tibial Fractures, 2008 — showed reamed nailing reduced the need for secondary procedures). External fixation for severe open fractures (temporary or definitive in Gustilo IIIB/C). Plate fixation (MIPO — minimally invasive plate osteosynthesis) for proximal or distal metaphyseal fractures where nailing is difficult.

16 Open Fractures Trauma

Open fractures involve a breach in the skin and soft tissues communicating with the fracture site. The management principles are detailed in Section 03 (Gustilo-Anderson classification and acute management protocol). This section covers additional operative principles and special considerations.

Surgical Debridement Principles

The cornerstone of open fracture management is thorough, systematic debridement. Skin: Extend the wound to visualize the entire zone of injury; excise non-viable skin edges (minimal). Subcutaneous tissue and fascia: Excise all non-viable tissue. Muscle: Apply the "4 C's" test — Color (viable muscle is beefy red, not pale or dark), Consistency (not mushy), Contractility (twitches when stimulated with forceps or cautery), and Capacity to bleed (viable muscle bleeds when cut). Bone: Remove small, completely devitalized cortical fragments that are not attached to soft tissue. Preserve larger fragments and those with periosteal attachment. Neurovascular structures: Preserve and tag injured nerves and vessels. Repeat debridement at 48–72 hours is standard for type III injuries to reassess tissue viability.

Soft Tissue Coverage

The goal is definitive soft tissue coverage within 72 hours to 7 days of injury. Options by defect location (tibial shaft — the most common site requiring flap coverage): Proximal third: gastrocnemius rotational flap (medial head most commonly used). Middle third: soleus rotational flap. Distal third: free tissue transfer (free latissimus dorsi, free rectus abdominis, free anterolateral thigh [ALT] flap) — requires microsurgical anastomosis. Negative pressure wound therapy (VAC — vacuum-assisted closure) is a temporizing measure between debridements but should not delay definitive coverage.

Antibiotic Prophylaxis Duration

Current evidence supports 24 hours of prophylactic antibiotics after definitive wound management for open fractures (Lack et al., 2015). Extended courses do not reduce infection rates and increase antibiotic resistance. For contaminated wounds, additional targeted antibiotics may be appropriate based on the contamination source.

17 Pathologic Fractures & Polytrauma Trauma

Pathologic Fractures

A pathologic fracture occurs through bone weakened by an underlying process — most commonly metastatic disease (breast, prostate, lung, kidney, thyroid — "BLT with a Kosher Pickle"), multiple myeloma, osteoporosis, Paget's disease, or primary bone tumors. Impending fracture: The Mirels' scoring system predicts pathologic fracture risk (site, pain, type of lesion, size — score ≥9 out of 12 warrants prophylactic fixation). Workup: Obtain staging studies before fixation (unless the patient is in immediate need of stabilization): chest CT, bone scan or PET-CT, labs (CBC, CMP, alkaline phosphatase, PSA in males, SPEP/UPEP for myeloma), and biopsy if the primary is unknown (biopsy track must be in line with the planned surgical approach). Treatment: Stabilize the fracture to restore function and reduce pain. Options: intramedullary nail (protects the entire bone from additional metastatic fractures), plate fixation (with PMMA cement augmentation for lytic defects), or endoprosthetic reconstruction (proximal femoral replacement for extensive proximal femur disease). Post-operative radiation therapy to treated sites prevents disease progression and improves fixation longevity.

Polytrauma Priorities — Damage Control Orthopedics (DCO)

In the multiply injured patient, the "lethal triad" — hypothermia, acidosis, and coagulopathy — drives mortality. Damage control orthopedics prioritizes physiological resuscitation over definitive fracture fixation in the unstable polytrauma patient. Principles: (1) Hemorrhage control and resuscitation take priority. (2) Temporary stabilization of long bone fractures with external fixation ("ex-fix and resuscitate") rather than prolonged definitive surgery. (3) Pelvic binder or external fixation for unstable pelvic fractures. (4) Fasciotomy if compartment syndrome is suspected. (5) Definitive fixation (conversion to intramedullary nail or ORIF) performed during the "window of opportunity" — typically days 5–10, after resuscitation and before the immunologic "second hit."

The decision between Early Total Care (ETC) — definitive fixation within 24 hours — and DCO depends on patient physiology. ETC is preferred for hemodynamically stable patients and is standard for isolated femoral shaft fractures (early nailing within 24 hours reduces ARDS, fat embolism, and ICU length of stay). DCO is indicated for: ISS >40, hypothermia (<35°C), coagulopathy (PT >1.5x normal), acidosis (pH <7.24, base deficit >-8), massive transfusion (>10 units PRBC), bilateral femur fractures in the hemodynamically borderline patient, and associated severe thoracic injury (bilateral pulmonary contusions, flail chest).

18 Total Hip Arthroplasty (THA) Joint Replacement

Indications

End-stage osteoarthritis (most common), inflammatory arthritis (RA), AVN, post-traumatic arthritis, displaced femoral neck fracture in the elderly, failed prior fixation, dysplasia, and tumor reconstruction. Non-operative management should be exhausted before considering THA (activity modification, weight management, PT, NSAIDs, injections).

Surgical Approaches

Implant Components

A THA has four components: (1) Acetabular cup — most commonly an uncemented titanium hemispherical shell with porous surface (press-fit, ± supplemental screws) + a polyethylene, ceramic, or metal liner. (2) Femoral stem — uncemented (press-fit with porous coating for bone ongrowth/ingrowth) or cemented (PMMA cement fixation — preferred in elderly with Dorr type C femurs and narrow, osteoporotic canals). Common stems: Corail (DePuy), Taperloc (Biomet), Accolade II (Stryker), Exeter (cemented). (3) Femoral head — metal (CoCr) or ceramic (alumina, BIOLOX delta). Sizes 28 mm, 32 mm, 36 mm, 40 mm — larger heads reduce dislocation risk but increase volumetric wear and risk of trunionosis. (4) Bearing surface (liner) — determines wear characteristics.

Bearing Surfaces

THA Complications

Dislocation: 2–5% overall; highest with posterior approach (mitigated by posterior capsular repair and larger heads). Most dislocations are posterior — hip is flexed, adducted, and internally rotated. Prevention: precautions (avoid hip flexion >90°, adduction past midline, internal rotation), larger femoral heads (36 mm+), dual-mobility cups (articulation within an articulation — increasingly used for high-risk patients). Periprosthetic joint infection (PJI): See Section 20. Leg length discrepancy (LLD): Ideally <1 cm; intraoperative assessment with templating, shuck test, and landmarks. Periprosthetic fracture: See Section 20. DVT/PE: Chemoprophylaxis is mandatory — aspirin 81 mg BID (low-risk) or enoxaparin 40 mg daily or rivaroxaban 10 mg daily (higher-risk) for 2–6 weeks post-op. Heterotopic ossification (HO): Ectopic bone formation in soft tissues; prophylaxis with indomethacin 75 mg daily for 6 weeks or single-dose radiation (700 cGy) within 72 hours post-op.

19 Total Knee Arthroplasty (TKA) Joint Replacement

Indications & Planning

End-stage knee OA (most common), inflammatory arthritis, post-traumatic arthritis, and severe valgus/varus deformity with pain. Pre-operative planning includes weight-bearing full-length standing radiographs (hip-to-ankle mechanical axis film) to assess alignment, templating, and evaluation of bone stock and deformity.

Alignment Philosophy

The historic goal has been mechanical alignment — restoring the mechanical axis (a straight line from the center of the femoral head to the center of the ankle) to neutral (0 ± 3°). Femoral component: cut at 5–7° of valgus relative to the femoral shaft axis to produce a cut perpendicular to the mechanical axis. Tibial component: cut perpendicular to the tibial mechanical axis, with 3–7° of posterior slope. Kinematic alignment is an alternative philosophy that aims to restore the patient's constitutional (pre-disease) joint line obliquity rather than forcing neutral mechanical alignment. Proponents argue it produces more natural kinematics and better patient satisfaction; critics cite concerns about long-term survivorship of residual malalignment. Robotic-assisted TKA (Mako/Stryker, ROSA/Zimmer-Biomet, CORI/Smith+Nephew) improves precision of bone cuts and component positioning, though long-term outcome advantages over conventional TKA have not been conclusively demonstrated.

Implant Types

The most common bearing in modern TKA is cobalt-chromium femoral component on highly cross-linked polyethylene (XLPE) tibial insert. Tibial component: titanium or CoCr baseplate with modular PE insert. Patellar component: all-polyethylene dome resurfacing (most common); debate persists on whether to routinely resurface the patella, but most high-volume centers resurface. Fixation: cemented TKA is the gold standard (hybrid or fully cemented); cementless TKA (porous-coated titanium for biologic fixation) is gaining acceptance but lacks long-term data comparable to cemented.

TKA Complications

Stiffness: Flexion <90° at 6–12 weeks warrants manipulation under anesthesia (MUA). Instability: Flexion vs extension gap mismatch, ligament incompetence — may require revision to higher-constraint implant. Periprosthetic fracture: Supracondylar femur fractures are most common — treatment depends on implant stability and fracture location (retrograde nail, plate, or revision). Extensor mechanism disruption: Patellar tendon rupture, quadriceps tendon rupture, patellar fracture — devastating complications, often require allograft reconstruction. Aseptic loosening: Most common cause of late TKA failure — polyethylene wear debris triggers osteolysis. Component malalignment: Varus tibial component or internally rotated femoral component leads to poor outcomes and early failure.

20 Revision Arthroplasty, Periprosthetic Fractures & PJI Joint Replacement

Periprosthetic Joint Infection (PJI)

PJI is the most devastating complication of joint replacement, occurring in 1–2% of primary THA/TKA. The Musculoskeletal Infection Society (MSIS) 2018 criteria define PJI with major and minor criteria. Major criteria (either one is diagnostic): Two positive cultures of the same organism from periprosthetic tissue, or a sinus tract communicating with the joint. Minor criteria (combined score ≥6 is diagnostic): elevated serum CRP (>10 mg/L, 2 points), elevated D-dimer (>860 ng/mL, 2 points), elevated synovial WBC (>3,000 for knee, >3,000 for hip, 3 points), elevated synovial PMN% (>80%, 2 points), positive alpha-defensin (3 points), elevated synovial CRP (>6.9 mg/L, 1 point), positive purulence (3 points), one positive culture (2 points).

Treatment: Acute PJI (<4 weeks from surgery or <3 weeks of symptoms with a well-fixed implant): DAIR (debridement, antibiotics, irrigation, and retention of implant) — exchange the modular components (polyethylene liner, femoral head), aggressive debridement, followed by 6 weeks of IV antibiotics + prolonged oral suppression. Success rate ~50–70%. Chronic PJI: Two-stage exchange arthroplasty is the gold standard — Stage 1: remove all implants and cement, thorough debridement, place an antibiotic-impregnated cement spacer (static or articulating), 6–8 weeks of IV antibiotics. Stage 2: reimplantation of new prosthesis after infection markers normalize (ESR, CRP trending down, joint aspiration negative). Success rate: 85–95%. One-stage exchange (removal and reimplantation in a single procedure) is gaining acceptance for select patients with a known organism, adequate soft tissue, and good bone stock — common in Europe, growing in North America.

Periprosthetic Fractures — Vancouver Classification (Hip)

Aseptic Loosening

The most common cause of late arthroplasty failure. Mechanism: particulate wear debris (polyethylene, metal, ceramic) is phagocytosed by macrophages, triggering a cytokine cascade (TNF-alpha, IL-1, IL-6, RANKL) that activates osteoclasts → periprosthetic osteolysis → progressive loosening. Radiographic signs: progressive radiolucent lines at the bone-implant interface (≥2 mm or progressive), component migration, subsidence, or cement fracture. Treatment: revision arthroplasty — address bone loss with grafting, augments, or revision implants with increased constraint.

21 Bone Tumors Oncology

Approach to Bone Lesions

The initial evaluation of a bone lesion uses radiographic features to narrow the differential. Key descriptors: location in bone (epiphyseal, metaphyseal, diaphyseal), pattern of bone destruction (geographic [well-defined, slow-growing], moth-eaten [intermediate aggression], permeative [aggressive, malignant]), margin (sclerotic rim = slow-growing vs ill-defined = aggressive), periosteal reaction (solid/uninterrupted = benign; interrupted/sunburst/onion-skin/Codman triangle = aggressive/malignant), matrix (osteoid = cloud-like density; chondroid = rings-and-arcs calcification), and soft tissue mass.

Common Benign Bone Tumors

Primary Malignant Bone Tumors

22 Metabolic Bone Disease Special

Osteoporosis

Systemic skeletal disease characterized by low bone mass and microarchitectural deterioration, leading to increased fracture risk. Affects ~10 million Americans; causes ~2 million fractures annually (hip, vertebral compression, distal radius). Diagnosis: DEXA scan (dual-energy X-ray absorptiometry) — T-score compares BMD to a young adult reference: T-score ≥ -1.0 = normal, -1.0 to -2.5 = osteopenia, ≤ -2.5 = osteoporosis, ≤ -2.5 with fragility fracture = severe osteoporosis. Screening recommended for all women ≥65 and men ≥70, or younger patients with risk factors.

Pharmacologic treatment (indicated for T-score ≤ -2.5, or T-score -1.0 to -2.5 with fragility fracture or FRAX 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20%):

Paget's Disease of Bone

Chronic disorder of bone remodeling with excessive osteoclastic resorption followed by disorganized osteoblastic new bone formation, producing enlarged, structurally weak bone. Affects 1–3% of adults >55; often asymptomatic and discovered incidentally. Common sites: pelvis, femur, tibia, skull, spine. Radiographic features: cortical thickening, coarsened trabecular pattern, "cotton wool" skull, "picture frame" vertebrae, bowing deformities of long bones. Labs: markedly elevated alkaline phosphatase (ALP) with normal calcium and phosphorus. Complications: pathologic fracture (transverse "chalk-stick" pattern), secondary OA (from deformed bone/joints — TKA and THA are technically challenging in Paget's), sarcomatous degeneration (osteosarcoma — rare, ~1%, but prognosis is dismal), hearing loss (skull base involvement), high-output cardiac failure (increased bone vascularity). Treatment: Zoledronic acid 5 mg IV (single infusion normalizes ALP in >90%, effect lasts years) or risedronate 30 mg daily × 2 months.

23 Pediatric Orthopedics Special

Growth Plate (Physis) Injuries — Salter-Harris Classification

The physis (growth plate) is the weakest link in the pediatric musculoskeletal system — it is 2–5x weaker than surrounding ligaments and bone. Physeal injuries account for 15–30% of childhood fractures. The Salter-Harris classification (mnemonic: SALTR) is universal:

Supracondylar Humerus Fracture

The most common elbow fracture in children (ages 5–7). >95% are extension-type (fall on outstretched hand with elbow hyperextended). Gartland classification: Type I = non-displaced (posterior fat pad sign may be the only finding; treat with long arm cast at 90°). Type II = displaced with intact posterior cortex (angulated but hinged; closed reduction + long arm cast or percutaneous pinning). Type III = completely displaced (no cortical contact; closed reduction + percutaneous pin fixation [2 lateral pins or crossed medial/lateral pins — medial pin risks ulnar nerve injury]). Neurovascular complications: anterior interosseous nerve (AIN) injury is most common (loss of FPL and FDP to index finger — unable to make "OK" sign); brachial artery injury (check radial pulse, hand perfusion — "pink and pulseless" hand may be observed vs explored). Volkmann's ischemic contracture — compartment syndrome of the forearm from brachial artery injury or post-reduction swelling — is the most feared complication; leads to irreversible flexor muscle fibrosis and claw-hand deformity.

Developmental Dysplasia of the Hip (DDH)

Spectrum from mild acetabular dysplasia to complete hip dislocation. Risk factors: female sex (4:1), firstborn, breech presentation, family history, oligohydramnios. Screening: Barlow test (adduct and push posteriorly — does the hip dislocate?) and Ortolani test (abduct with anterior lift — does a dislocated hip reduce with a palpable "clunk"?). Asymmetric skin folds, limb length discrepancy, and limited abduction are additional signs. Ultrasound screening at 6 weeks for high-risk infants (or those with abnormal exam). Treatment by age: 0–6 months: Pavlik harness (flexion/abduction positioning — 95% success for reducible hips; contraindicated in irreducible dislocations and children >6 months). 6–18 months: closed reduction under anesthesia + spica cast ± adductor tenotomy; arthrogram to confirm concentric reduction. 18 months–5 years: open reduction (medial or anterior approach) + pelvic osteotomy (Pemberton, Dega, or Salter). >5 years: treatment becomes increasingly complex with poorer outcomes.

Slipped Capital Femoral Epiphysis (SCFE)

The femoral epiphysis slips posteriorly and inferiorly relative to the metaphysis through the physis. Affects obese adolescents (10–16 years) during the growth spurt. Bilateral in 20–40%. Presents with hip or referred knee pain (always examine the hip when a child presents with knee pain), antalgic gait, and obligate external rotation with hip flexion. Radiographs: AP pelvis + frog-lateral — the frog-lateral is more sensitive; look for the Klein's line (a line along the superior femoral neck should intersect the lateral epiphysis — in SCFE it does not) and Southwick angle (measures slip severity: <30° mild, 30–60° moderate, >60° severe). Classification: Stable (able to bear weight, even with crutches) vs Unstable (unable to bear weight). This distinction is the most important prognostic factor — unstable SCFE has a 20–50% AVN rate vs <5% for stable. Treatment: In situ percutaneous screw fixation (single cannulated screw across the physis, centered in the epiphysis) — for all stable SCFE, even severe slips. Do NOT attempt to reduce a stable slip (reduction maneuvers increase AVN risk). Unstable SCFE: urgent surgical stabilization; gentle reduction (capsulotomy to decompress hematoma may be beneficial — Ziebarth et al., 2009) + screw fixation. Prophylactic contralateral pinning is controversial but often performed in high-risk patients (age <12, endocrinopathy, Modified Oxford Score).

Legg-Calve-Perthes Disease

Idiopathic AVN of the femoral head in children, typically ages 4–8. Four phases: (1) necrosis/initial, (2) fragmentation, (3) re-ossification, (4) remodeling. Younger age at onset and greater femoral head involvement correlate with better outcomes (the acetabulum can remodel around a deformed head). The Herring lateral pillar classification predicts prognosis: Group A (lateral pillar maintained at full height — good prognosis), Group B (>50% lateral pillar height maintained — intermediate), Group C (<50% lateral pillar height — poor prognosis in older children). Treatment: containment of the femoral head within the acetabulum — abduction bracing or surgical containment (femoral varus osteotomy or Salter innominate osteotomy) for older children (>8 years) with lateral pillar B or C disease.

24 Compartment Syndrome & CRPS Special

Acute Compartment Syndrome

A limb-threatening emergency where increased pressure within a closed fascial compartment compromises tissue perfusion. Most common in the leg (four compartments: anterior, lateral, superficial posterior, deep posterior) and forearm (three compartments: volar, dorsal, mobile wad). Etiologies: fractures (tibial shaft #1), crush injuries, vascular injury, burns, post-ischemic reperfusion, tight casts/dressings, bleeding in anticoagulated patients.

Diagnosis is clinical: the "5 P's" — Pain (out of proportion to injury, especially with passive stretch of the muscles in the affected compartment — the earliest and most reliable sign), Pressure (tense/firm compartment on palpation), Paresthesias (nerve ischemia), Paralysis (late — indicates irreversible damage), Pulselessness (very late — compartment syndrome occurs at pressures far below arterial occlusion pressure). Intracompartmental pressure measurement: Stryker needle or arterial line manometer. Absolute pressure >30 mmHg or delta pressure (ΔP) <30 mmHg (ΔP = diastolic blood pressure − compartment pressure) warrants fasciotomy. In a hypotensive patient, compartment syndrome occurs at lower absolute pressures — always use delta pressure.

Treatment: Emergent fasciotomy — release ALL compartments at risk. Leg: two-incision technique (anterolateral incision releases anterior and lateral compartments; posteromedial incision releases superficial and deep posterior compartments). Forearm: volar Henry approach (curvilinear incision from proximal to carpal tunnel) releases all three volar compartments; dorsal incision if dorsal compartment involved. Wounds are left open with a vessel-loop shoelace or negative-pressure dressing; delayed primary closure or skin grafting at 48–72 hours when swelling resolves. Delayed fasciotomy (>8 hours) is associated with significantly higher rates of amputation, infection, and permanent nerve damage.

Complex Regional Pain Syndrome (CRPS)

A chronic pain condition characterized by pain disproportionate to the inciting event, accompanied by autonomic, sensory, motor, and trophic changes. CRPS Type I (formerly reflex sympathetic dystrophy [RSD]): occurs without a definable nerve lesion — commonly after fractures, surgery, or immobilization. CRPS Type II (formerly causalgia): occurs after a defined peripheral nerve injury. Diagnosis uses the Budapest criteria: (1) continuing pain disproportionate to the inciting event, (2) at least one symptom in 3 of 4 categories (sensory [hyperesthesia/allodynia], vasomotor [temperature/color asymmetry], sudomotor/edema [swelling, sweating changes], motor/trophic [weakness, tremor, dystonia, nail/hair/skin changes]), (3) at least one sign at evaluation in 2 of 4 categories, (4) no other diagnosis better explains the findings.

Treatment: Multimodal and multidisciplinary. Physical/occupational therapy (graded motor imagery, mirror therapy, progressive loading) is the cornerstone. Medications: gabapentin/pregabalin (neuropathic pain), low-dose naltrexone, NSAIDs, topical lidocaine, short courses of oral corticosteroids in acute inflammatory CRPS. Interventional: sympathetic nerve blocks (stellate ganglion block for upper extremity, lumbar sympathetic block for lower extremity), spinal cord stimulation for refractory cases. Bisphosphonates (particularly IV alendronate or pamidronate) have shown benefit in randomized trials. Vitamin C 500 mg daily after distal radius fracture reduces CRPS incidence (Zollinger et al.).

25 Fracture Fixation Hardware Procedures

Plates & Screws

Cortical screws: Fully threaded, engage both cortices. Thread pitch designed for dense cortical bone. Used for interfragmentary compression (lag technique — gliding hole in near cortex, threads engage only far cortex → compression). Cancellous screws: Partially threaded (threads only at the tip), larger thread pitch for purchase in softer cancellous bone. Used in metaphyseal and epiphyseal regions (e.g., cannulated screws for femoral neck fractures). Locking screws: Thread into the plate as well as the bone, creating a fixed-angle construct. Locking plates function as internal external fixators — they do not require bone-plate friction for stability, making them ideal for osteoporotic bone, periarticular fractures, and bridge plating where anatomic reduction is not possible.

Plate types: Dynamic compression plate (DCP) — uses the oval hole design to generate interfragmentary compression as screws are tightened. Limited-contact DCP (LC-DCP) — reduced plate-bone contact to preserve periosteal blood supply. Locking compression plate (LCP) — combination holes accept both locking and conventional screws. Reconstruction plate — can be contoured in three dimensions (used for pelvis, clavicle). Periarticular anatomic plates — precontoured for specific anatomic locations (proximal humerus [Philos], distal radius [VA-LCP], proximal/distal tibia, distal femur). Bridge plating — plate spans comminuted zone without compressing individual fragments, relying on secondary bone healing (relative stability). One-third tubular plate — low-profile plate for lateral malleolus and other subcutaneous bones.

Intramedullary Nails

Nails are load-sharing devices placed within the medullary canal that provide alignment, length, and rotational control for long bone fractures. Advantages: biological fixation (preserves periosteal blood supply — no need to expose the fracture site), load-sharing (rather than load-bearing as with plates), early weight-bearing. Reaming the canal before insertion increases cortical contact and allows a larger-diameter nail, but strips the endosteal blood supply (temporarily — recovers within weeks). Static interlocking (screws through holes in both ends of the nail) controls length and rotation; dynamic interlocking (screws at one end only) allows axial compression. Common nails: tibial nail (suprapatellar or infrapatellar entry), femoral nail (piriformis or trochanteric entry, antegrade; or intercondylar, retrograde), cephalomedullary nail (trochanteric entry with lag screw into femoral head — for intertrochanteric/subtrochanteric fractures — Gamma3, TFN, InterTAN), humeral nail (antegrade through rotator cuff or retrograde through olecranon fossa).

External Fixation

Pins placed into bone proximal and distal to the fracture, connected by external bars or rings. Indications: temporary stabilization in damage control (polytrauma, open fractures), definitive treatment when internal fixation is contraindicated (severe soft tissue compromise, infection), periarticular fractures (spanning ex-fix bridges the joint), distraction osteogenesis (Ilizarov method for bone transport and limb lengthening), correction of complex deformities (Taylor Spatial Frame — hexapod frame that can correct six axes of deformity simultaneously using a computer-generated correction plan). Complications: pin site infection (the most common complication, 2–30%), pin loosening, fracture through pin sites, joint stiffness.

Other Fixation Devices

Kirschner wires (K-wires): Smooth pins of varying diameter used for temporary fixation, small bone fractures (phalanges, metacarpals), and as guide wires. Tension band: Converts tensile forces to compression (olecranon, patella, greater tuberosity). Cerclage wires/cables: Circumferential wires around bone — used to hold fracture fragments together (periprosthetic fractures, trochanteric fractures) or to reduce spiral/oblique fractures before plating. Suture anchors: Devices placed into bone that provide a suture attachment point for soft tissue repair (rotator cuff, labrum, ligaments). Interference screws: Used to fix soft tissue grafts within bone tunnels (ACL reconstruction).

26 Arthroscopy Procedures

General Principles

Arthroscopy is the insertion of a small camera (arthroscope, typically 4.0 mm, 30° angled lens) and instruments through small portals into a joint for diagnostic and therapeutic purposes. Benefits over open surgery: smaller incisions, less soft tissue damage, faster recovery, ability to visualize the entire joint.

Shoulder Arthroscopy

Indications: rotator cuff repair, labral repair (Bankart, SLAP), subacromial decompression (acromioplasty), distal clavicle excision (Mumford procedure for AC joint arthritis), capsular release for adhesive capsulitis, biceps tenotomy/tenodesis, removal of loose bodies. Standard portals: posterior (primary viewing portal, placed 2 cm inferior and 1 cm medial to the posterolateral corner of the acromion), anterior (working portal, in the rotator interval), lateral (subacromial space — for subacromial decompression and rotator cuff repair). The patient is positioned in beach chair or lateral decubitus.

Knee Arthroscopy

The most commonly performed orthopedic arthroscopic procedure. Standard portals: anterolateral and anteromedial (flanking the patellar tendon). Indications: meniscal surgery (partial meniscectomy, meniscal repair), ACL/PCL reconstruction, loose body removal, synovectomy, cartilage procedures (microfracture, OATS, ACI/MACI), lateral release for patellar maltracking. The systematic diagnostic arthroscopy evaluates: suprapatellar pouch, patellofemoral joint, medial gutter, medial compartment (medial meniscus, MFC, medial tibial plateau), intercondylar notch (ACL, PCL), lateral compartment, and lateral gutter.

Hip Arthroscopy

Rapidly growing field. Indications: femoroacetabular impingement (FAI) — cam (femoral-sided bump) and/or pincer (acetabular over-coverage) resection, labral repair/reconstruction, loose body removal, iliopsoas release, ligamentum teres debridement, capsular plication for instability. Performed in the supine or lateral position on a fracture table with traction to distract the joint. Portals: anterolateral, mid-anterior, and distal anterolateral accessory. Traction neuropraxia of the pudendal or lateral femoral cutaneous nerve is a recognized complication — limit traction time and force.

Cartilage Restoration Procedures

Microfracture: Arthroscopic awl creates perforations in the subchondral bone plate to allow marrow elements (MSCs, growth factors) to fill a chondral defect with fibrocartilage. Best for lesions <2 cm². Fibrocartilage is biomechanically inferior to hyaline cartilage but provides functional improvement. OATS (Osteochondral Autograft Transfer System): Cylindrical plug(s) of osteochondral tissue harvested from a non-weight-bearing area (lateral trochlear ridge) and transplanted into the defect. Best for lesions 1–4 cm². Osteochondral allograft (OCA): Fresh cadaveric osteochondral grafts for large defects (>2–4 cm²). ACI/MACI (Autologous Chondrocyte Implantation / Matrix-assisted ACI): Two-stage procedure — first stage harvests cartilage cells, which are expanded in culture; second stage implants them into the defect under a periosteal patch (ACI) or on a collagen scaffold (MACI — now the standard). Best for large lesions (>2 cm²) in young patients.

27 Arthroplasty Implants & Bearing Surfaces Procedures

Implant details for THA and TKA are covered in Sections 18 and 19. This section covers additional arthroplasty concepts.

Cemented vs Uncemented Fixation

Cemented fixation uses polymethylmethacrylate (PMMA) bone cement to fill the gap between the implant and bone, providing immediate mechanical fixation. Modern cementing technique (3rd generation): pulsatile lavage of the canal, retrograde cement insertion with a cement gun, canal plug (restrictor) to pressurize cement, centralization of the stem. Best for: elderly patients, osteoporotic bone (Dorr type C), cemented all-poly tibial components, revision with bone loss. Uncemented fixation relies on press-fit initial stability followed by biological fixation (bone ongrowth/ingrowth into porous surface coatings — hydroxyapatite, titanium plasma spray, trabecular metal [tantalum]). Best for: young, active patients with good bone quality. The trend in primary THA is toward uncemented acetabular cups (near-universal) and uncemented stems (majority in North America); cemented stems remain the standard in the UK/Scandinavia (excellent long-term registry data). In primary TKA, cemented fixation remains the gold standard globally.

Special Implant Concepts

Dual-mobility cups: An articulation within an articulation — the inner bearing (small head within a mobile polyethylene liner) and the outer bearing (the liner within the metal shell). Significantly reduces dislocation risk (<1% in primary THA vs 2–5% with fixed bearings). Increasingly used for fracture THA, revision, and patients at high dislocation risk. Constrained liners: Mechanically prevent dislocation by capturing the head within a locking ring — reserved for recurrent dislocation after failed closed reduction and soft tissue procedures, or abductor deficiency. Megaprostheses (endoprosthetic reconstruction): Large modular implants that replace segments of bone (proximal femur, distal femur, proximal tibia, proximal humerus). Used after tumor resection or massive periprosthetic bone loss. Systems: Stryker GMRS, Biomet OSS, Zimmer Segmental.

28 Spine Surgery Techniques Procedures

Anterior Cervical Discectomy and Fusion (ACDF)

The most commonly performed cervical spine surgery. Approach: Smith-Robinson anterior approach — transverse skin incision on the left side of the neck (protects the recurrent laryngeal nerve, which has a more consistent course on the left), dissect between the carotid sheath laterally and the trachea/esophagus medially. Retract the longus colli muscles laterally to expose the anterior cervical spine. Use fluoroscopy to confirm the level. Perform complete discectomy, decompress the neural foramen, place an interbody spacer (PEEK cage, titanium cage, allograft, or polyetheretherketone) filled with bone graft, and apply an anterior cervical plate with screws. Complications: dysphagia (most common, 2–50% depending on definition; usually transient), recurrent laryngeal nerve injury (hoarseness), esophageal perforation (rare, 0.1–0.3%), vertebral artery injury (rare), graft/hardware failure, adjacent segment disease (the most important long-term concern — accelerated degeneration at levels adjacent to the fusion, occurring in 2.9% per year). Cervical disc replacement (CDR) is an alternative that preserves motion and may reduce adjacent segment disease — FDA-approved devices include Prestige (Medtronic), ProDisc-C (Synthes), Mobi-C (Zimmer-Biomet).

Posterior Cervical Surgery

Laminectomy: Removal of the lamina to decompress the spinal canal — typically combined with posterior instrumented fusion (lateral mass screws at C3–C6, pedicle screws at C2 and C7) if instability is present or created. Laminoplasty: The lamina is hinged open on one side (open-door technique — Hirabayashi) or both sides (French-door technique) and held in the expanded position with spacers or plates. Preserves motion, avoids fusion, maintains posterior tension band. Best for multilevel stenosis with maintained lordosis. Posterior cervical foraminotomy: Keyhole decompression of a single nerve root without fusion — ideal for lateral disc herniations causing radiculopathy, allowing motion preservation.

Lumbar Fusion Techniques

Pedicle Screw Fixation

The foundation of modern spine instrumentation. Screws are placed through the pedicle into the vertebral body, connected by rods to create a rigid construct. Provides three-column fixation (most stable posterior construct). Screw diameter, length, and trajectory are determined by pedicle anatomy (CT-guided planning, navigation, or robotic assistance improves accuracy). Complications: screw misplacement (medial breach → spinal cord/nerve root injury; lateral breach → vascular/visceral injury), screw loosening (especially in osteoporotic bone — augment with PMMA cement, use larger screws, extend the construct, or use cortical bone trajectory screws), rod fracture (at the level of pseudarthrosis), adjacent segment disease, proximal junctional kyphosis (PJK) after long constructs.

29 Imaging & Diagnostics

Imaging Modalities in Orthopedics

Key Radiographic Lines & Angles

30 Classification Systems (All)

This section consolidates all major classification systems in orthopedic surgery for quick reference. Detailed descriptions are found in the relevant clinical sections.

Fracture Classifications

Grading & Staging Systems

31 Medications Master Table

32 Abbreviations Master List

33 Risk Factors & Comorbidities

Fracture Risk Factors

Surgical Complication Risk Factors

34 Key References

The following landmark studies and guidelines are referenced throughout this specialty page and form the evidence base for modern orthopedic practice.