Orthopedic Trauma, Pediatric Orthopedics, Peripheral Nerve Lesions & Compartment Syndrome

If a patient in a circumferential plaster or fiberglass cast develops worsening pain and paresthesias, the immediate first step is to split (bivalve) or completely remove the cast and all underlying circumferential Webril padding down to the skin and place the limb at heart level (never elevate above the heart, which lowers arterial perfusion pressure!). Compartment syndrome is primarily a clinical diagnosis; when bedside Stryker needle manometry is performed (e.g., in obtunded/intubated trauma patients), emergency surgical fasciotomy is indicated if absolute compartment pressure is ≥30 mmHg OR if the Delta-Pressure (ΔP = Diastolic Blood Pressure − Intra-Compartmental Pressure) is ≤30 mmHg. Delaying fasciotomy leads to rhabdomyolysis (myoglobinuria, hyperkalemia, acute tubular necrosis) and permanent Volkmann ischemic contracture (claw-like flexion deformity of the wrist and fingers from forearm flexor fibrosis).

Fat Embolism Syndrome presents 24–72 hours after a long-bone (femur/tibia) or pelvic fracture (or intramedullary nailing) with the classic triad of (1) Hypoxemic respiratory distress/ARDS, (2) Neurologic dysfunction (confusion, lethargy, seizures, diffuse cerebral “starfield” petechiae on MRI), and (3) Petechial rash over the upper anterior chest, neck, axillae, and conjunctivae (with thrombocytopenia); prevention relies on early fracture immobilization/fixation, and treatment is supportive respiratory/ICU care (heparin and corticosteroids are ineffective). Open (compound) fractures (any bone fracture communicating with a skin laceration) require immediate intravenous antibiotics (cefazolin for all grades; add gentamicin or ceftriaxone/piperacillin-tazobactam for Grade III heavy contamination, and add penicillin for farmyard/soil Clostridium exposure), tetanus prophylaxis, bedside sterile saline-soaked dressing with splinting, and urgent operative irrigation and debridement within 6 hours. Acute Septic Arthritis presents with an acutely hot, swollen, erythematous joint held in the position of maximal intracapsular volume (hip flexed, abducted, and externally rotated) and severe pain with passive micromotion; in sexually active young adults, Neisseria gonorrhoeae causes migratory polyarthralgias, tenosynovitis, and vesiculopustular skin lesions, whereas Staphylococcus aureus is the #1 cause overall across all other age groups (with Salmonella classic in sickle cell disease osteomyelitis). Synovial fluid arthrocentesis showing WBC >50,000/mm3 (>90% neutrophils) mandates immediate surgical joint drainage (arthrotomy for the hip/shoulder; arthroscopy or serial aspiration for the knee) plus empiric IV vancomycin (plus ceftriaxone if Gram-negative rods or gonococcus suspected).

Erb-Duchenne Palsy (C5–C6 Upper Trunk injury) results from downward traction on the head/neck away from the shoulder during difficult vaginal delivery (shoulder dystocia) or falling onto the shoulder; loss of the suprascapular, musculocutaneous, and axillary nerves paralyzes the abductors (deltoid, supraspinatus), external rotators (infraspinatus, teres minor), elbow flexors (biceps brachii, brachialis), and supinators (biceps, supinator), leaving the limb hanging in the classic “waiter's tip” posture: adducted, internally rotated, elbow extended, forearm pronated, and wrist flexed (with intact grasp reflex). Klumpke Palsy (C8–T1 Lower Trunk injury) results from upward traction on an abducted arm (grabbing a tree branch while falling or hyperabduction delivery); loss of the ulnar and median intrinsic hand fibers paralyzes all lumbricals and interossei, producing a total claw hand (MCP hyperextension with PIP/DIP flexion) and sensory loss along the medial forearm/ulnar digits, frequently accompanied by an ipsilateral Horner syndrome (ptosis, miosis, anhidrosis) due to avulsion of T1 preganglionic sympathetic fibers.

Tracing the humerus from proximal to distal: (1) Surgical neck of the humerus fracture or anterior shoulder dislocation injures the Axillary nerve (C5–C6) and posterior circumflex humeral artery → flattened deltoid contour, inability to abduct the arm from 15 to 90 degrees, and sensory loss over the lateral deltoid (“regimental badge patch”). (2) Midshaft humerus fracture (or Saturday night palsy compression against a chair) injures the Radial nerve (C5–T1) and profunda brachii (deep brachial) artery in the spiral groove → wrist drop (loss of wrist and MCP finger extension), loss of brachioradialis reflex, and sensory loss over the posterior arm/forearm and dorsal 1st web space (triceps extension is often spared if the fracture is distal to the spiral groove because triceps branches arise proximally!). (3) Supracondylar humerus fracture (the most common pediatric elbow fracture after a fall on an outstretched hand [FOOSH], showing a posterior fat-pad [“sail”] sign and displaced anterior humeral line) jeopardizes the Brachial artery (risk of Volkmann ischemic contracture) and the Anterior Interosseous Nerve (AIN, pure motor branch of the Median nerve) (or radial/ulnar nerves) → AIN injury causes inability to flex the thumb IP joint (flexor pollicis longus) and index DIP joint (flexor digitorum profundus), producing a flat “pinch sign” instead of an “OK sign” with zero sensory loss. (4) Medial epicondyle fracture injures the Ulnar nerve (C8–T1) → sensory loss in the 5th and medial 4th digits and ulnar claw hand (hyperextension of 4th/5th MCP joints and flexion of PIP/DIP joints during finger extension; note the Ulnar Paradox: a distal ulnar nerve lesion at the wrist [Guyon canal] produces worse clawing than a proximal lesion at the elbow because a proximal lesion also paralyzes the medial half of flexor digitorum profundus, reducing unopposed DIP flexion!). In the wrist, a FOOSH injury causes a Colles fracture (dorsal angulation/“dinner-fork deformity” of the distal radius with risk of acute carpal tunnel median nerve compression) or a Scaphoid fracture (tenderness in the anatomical snuffbox; retrograde blood supply from the dorsal branch of the radial artery enters the distal pole, placing the proximal pole of the scaphoid at high risk for avascular necrosis—if initial X-rays are negative, immobilize in a thumb spica splint and repeat X-rays in 10–14 days or obtain an immediate MRI).

(1) Superior Gluteal Nerve (L4–S1) innervates the gluteus medius, gluteus minimus, and tensor fasciae latae (hip abductors); iatrogenic injury during posterior hip surgery or misplaced superomedial gluteal intramuscular injection causes a positive Trendelenburg sign—when the patient stands on the affected (lesioned) leg, the contralateral (unaffected) pelvis drops because the ipsilateral gluteus medius cannot stabilize the pelvis, and the patient compensates by leaning their trunk toward the injured side during stance phase (Trendelenburg lurch). (2) Inferior Gluteal Nerve (L5–S2) innervates the gluteus maximus (chief hip extensor) → difficulty rising from a seated position or climbing stairs. (3) Obturator Nerve (L2–L4) (injured during pelvic lymphadenectomy, obturator hernia, or anterior hip dislocation) → loss of thigh adduction and sensory loss over the medial thigh. (4) Femoral Nerve (L2–L4) (compressed by a retroperitoneal iliopsoas hematoma in anticoagulated patients or pelvic fracture) → loss of knee extension (quadriceps), absent patellar reflex, weakened hip flexion, and sensory loss over the anterior thigh and medial leg (saphenous nerve). (5) Common Peroneal (Fibular) Nerve (L4–S2) winds superficially around the neck of the fibula (injured by lateral blow to the knee, fibular neck fracture, or tight leg cast) → loss of ankle dorsiflexion (tibialis anterior) and foot eversion (peroneus longus/brevis), resulting in foot drop with a high-stepping steppage gait and sensory loss over the anterolateral leg and dorsum of the foot (PED: Peroneal = Eversion & Dorsiflexion). (6) Tibial Nerve (L4–S3) (injured in popliteal laceration/Baker cyst or compressed beneath the flexor retinaculum in tarsal tunnel syndrome) → inability to plantarflex the ankle (cannot stand on tiptoes), invert the foot, or flex the toes, absent Achilles reflex, and sensory loss on the sole of the foot (TIP: Tibial = Inversion & Plantarflexion).

In the knee, a non-contact pivoting injury or lateral valgus blow (Unhappy Triad of O'Donoghue) tears the Anterior Cruciate Ligament (ACL) (rapid acute hemarthrosis with a “pop”; Lachman test at 20–30 degrees of flexion is the most sensitive bedside exam, superior to the anterior drawer test at 90 degrees), the Medial Collateral Ligament (MCL) (laxity on valgus stress at 30 degrees), and the Medial Meniscus (which is more frequently torn than the lateral meniscus in the classic triad because the medial meniscus is firmly attached to the deep MCL, though acute ACL tears overall often involve the lateral meniscus; meniscal tears cause joint-line tenderness, locking/catching, and a positive McMurray or Thessaly test). A direct dashboard impact to the proximal tibia in a flexed knee tears the Posterior Cruciate Ligament (PCL) (positive posterior drawer and posterior sag sign). In acute ankle inversion/eversion injuries (where the anterior talofibular ligament [ATFL] is the #1 sprained ligament), the Ottawa Ankle Rules indicate ankle radiographs only if there is bony tenderness along the posterior edge or tip of the distal 6 cm of the lateral or medial malleolus OR inability to bear weight for 4 steps both immediately and in the ED (foot radiographs if tenderness at the base of the 5th metatarsal [Jones vs. pseudo-Jones avulsion fracture] or the navicular bone). An unstable rotational ankle injury that fractures the medial malleolus, lateral malleolus (distal fibula), and posterior malleolus of the distal tibia (Volkmann's triangle) is a Trimalleolar Fracture (Trimal Fracture)—an inherently unstable intra-articular injury requiring prompt closed reduction and splinting (immediately if skin tenting or neurovascular compromise is present) followed by surgical Open Reduction and Internal Fixation (ORIF).

(1) Developmental Dysplasia of the Hip (DDH) (risk factors: Female sex, Firstborn, Frank breech presentation, Family history, Oligohydramnios) is screened at every well-baby visit using the Barlow maneuver (gentle posterior/adduction pressure dislocates an unstable hip) and Ortolani maneuver (abduction and anterior lift reduces a dislocated femoral head back into the acetabulum with a palpable “clunk”), along with asymmetric gluteal/thigh skin folds and the Galeazzi sign (apparent femoral shortening when knees are flexed). Because the femoral head does not ossify until 4–6 months of age, Hip Ultrasound is the diagnostic test of choice under 4 months of age (AP pelvis radiographs are used after 4–6 months), and first-line treatment before 6 months is abduction splinting in a Pavlik harness. (2) Legg-Calvé-Perthes Disease (LCPD) is idiopathic avascular necrosis of the capital femoral epiphysis typically affecting boys aged 4–8 years; children present with an insidious, painless (or mildly painful) limp and restricted hip abduction/internal rotation without fever or leukocytosis (initial X-rays may be normal or show a small, sclerotic, flattened/fragmented femoral head; MRI is most sensitive early; management is containment via observation/physical therapy or femoral/pelvic osteotomy). (3) Slipped Capital Femoral Epiphysis (SCFE) is a Salter-Harris Type I shear displacement through the hypertrophic zone of the proximal femoral physis in obese adolescents aged 10–15 years (or children with hypothyroidism, growth hormone deficiency, or renal osteodystrophy—screen with TSH/free T4 if atypical age <10 yr or non-obese!), where the femoral neck displaces anteriorly/superiorly while the femoral head remains posteriorly in the acetabulum. Patients present with dull hip/groin or referred medial knee pain, an externally rotated gait, and obligatory external rotation of the hip upon passive hip flexion (Drehman sign). Diagnosis is confirmed by frog-leg lateral and AP pelvic radiographs showing the displaced femoral head resembling “ice cream slipping off a cone” (Klein's line drawn along the superior femoral neck fails to intersect the lateral femoral head). Treatment is an orthopedic surgical emergency: immediately place the patient on strict non-weight-bearing (wheelchair/crutches) and perform urgent in-situ single-screw internal fixation (pinning) to prevent catastrophic avascular necrosis and chondrolysis.

When a child aged 3–8 years presents with acute hip pain and a limp 1–2 weeks after a viral upper respiratory infection, Transient (Toxic) Synovitis must be differentiated from surgical emergency Septic Arthritis of the Hip using the four Kocher Criteria: (1) Fever >38.5°C, (2) Non-weight-bearing (refusal to walk), (3) ESR ≥40 mm/hr (or CRP >2.0 mg/dL), and (4) Serum WBC >12,000/mm3. A child with 0–1 Kocher criteria has Transient Synovitis (well-appearing, afebrile, mildly elevated/normal ESR, able to bear weight with a limp; managed with NSAIDs [ibuprofen] and rest), whereas ≥2–3 Kocher criteria mandates ultrasound-guided hip aspiration and open surgical arthrotomy if septic. Pediatric growth-plate fractures are classified by the Salter-Harris system (SALTR): Type I (Same—transverse fracture purely through the radiolucent physis; X-ray may appear normal), Type II (Above—fracture through the physis and up into the metaphysis; most common type, >75%, excellent prognosis), Type III (Lower—intra-articular fracture through the physis and down through the epiphysis; requires ORIF), Type IV (Through—fracture passing through metaphysis, physis, and epiphysis; requires ORIF), and Type V (Rammed—axial crush compression of the germinal physeal plate; worst prognosis due to premature growth arrest and limb-length discrepancy). Two classic outpatient pediatric entities complete the shelf blueprint: Osgood-Schlatter disease (traction apophysitis of the tibial tubercle at the patellar tendon insertion in athletic adolescents aged 10–15 who jump/run, presenting with localized pain/swelling over the tibial tubercle reproduced by resisted knee extension; managed conservatively with rest, ice, NSAIDs, and quadriceps stretching) and Nursemaid's elbow (radial head subluxation) (annular ligament slips over the radial head after longitudinal axial traction on a toddler's extended, pronated arm at age 1–4 years; the child holds the arm slightly flexed and pronated against the side and refuses to use it; no X-ray is needed—reduce immediately at the bedside via hyperpronation [preferred] or supination with full elbow flexion).

Osteochondroma is the most common benign bone tumor overall, presenting in males <25 years old as a painless lateral bony projection (exostosis) capped by hyaline cartilage arising from the metaphysis of the distal femur or proximal tibia; radiographs show direct continuity of the cortex and medullary cavity with the underlying bone (rare <1% transformation to chondrosarcoma if painful enlargement occurs after skeletal maturity or in hereditary multiple exostoses). Osteoid Osteoma occurs in young adults (<25 years) in the cortex of the diaphysis (femoral neck/tibia), presenting with nocturnal bone pain that is dramatically and completely relieved by NSAIDs/aspirin (because the osteoid nidus secretes prostaglandin E2); radiographs show a small radiolucent nidus <2 cm surrounded by dense reactive cortical sclerosis (treated with CT-guided radiofrequency ablation). By contrast, Osteoblastoma is a larger lesion (>2 cm) located in the posterior elements of the vertebrae with dull pain unresponsive to NSAIDs. Giant Cell Tumor of Bone (Osteoclastoma) occurs in young adults aged 20–40 years (after physeal closure) in the epiphysis of the distal femur or proximal tibia (around the knee); radiographs show an eccentric, lytic, multiloculated “soap-bubble” lesion, and histology reveals multinucleated RANK-positive osteoclast-like giant cells dispersed among neoplastic RANKL-expressing mononuclear stromal cells (locally aggressive; treated with curettage or the anti-RANKL monoclonal antibody denosumab).

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents (excluding multiple myeloma in older adults), exhibiting a bimodal age distribution: a primary peak at age 10–20 years (associated with the adolescent growth spurt and germline RB1 [bilateral retinoblastoma] or TP53 [Li-Fraumeni] mutations) and a secondary peak in adults >60 years secondary to Paget disease of bone, bone infarcts, or prior radiation. It arises in the metaphysis of the distal femur or proximal tibia (around the knee), elevates serum alkaline phosphatase and LDH, and shows a mixed osteolytic/osteoblastic mass that lifts the periosteum to form a Codman triangle with a spiculated “sunburst” periosteal reaction; biopsy reveals pleomorphic malignant osteoblasts producing pink lace-like osteoid matrix (treated with neoadjuvant chemotherapy + limb-sparing surgical resection). Ewing Sarcoma occurs in boys aged 5–20 years in the diaphysis (medullary shaft) of the femur, tibia, pelvis, or ribs, driven by a pathognomonic t(11;22) translocation fusing the EWSR1 and FLI1 genes. Patients frequently present with localized pain, swelling, fever, leukocytosis, and elevated ESR/CRP that closely mimic acute osteomyelitis! Radiographs show a permeative (“moth-eaten”) diaphyseal lesion with concentric layered “onion-skin” periosteal reaction, and biopsy shows sheets of uniform small round blue cells of neuroectodermal origin (CD99/MIC2-positive, PAS-positive cytoplasmic glycogen; responsive to multi-agent chemotherapy plus surgical resection/radiation). Chondrosarcoma occurs in older adults (50–70 years) in the axial skeleton (pelvis, proximal femur, ribs) as a glistening, lobulated cartilaginous mass with “popcorn” or ring-and-arc calcifications on X-ray; unlike osteosarcoma and Ewing sarcoma, chondrosarcoma is chemo- and radio-resistant and treated strictly with wide surgical excision.

Lumbar Spinal Stenosis (hypertrophy of the ligamentum flavum, facet joint osteophytes, and disc bulging in adults >60 years) causes Neurogenic Claudication (Pseudoclaudication): bilateral buttock, thigh, and calf pain/weakness that is worse with lumbar EXTENSION (standing upright or walking downhill) and relieved by lumbar FLEXION (sitting down, leaning forward over a shopping cart [“shopping cart sign”], or walking uphill), with preserved pedal pulses (unlike Vascular Claudication, where pain is relieved by standing still regardless of spinal posture and pedal pulses/ABI are diminished). In the shoulder, the Rotator Cuff (SITS muscles) comprises the Supraspinatus (initiates the first 15° of abduction; innervated by the suprascapular nerve; most commonly torn tendon, tested via the Empty Can / Jobe test and Neer/Hawkins subacromial impingement signs), Infraspinatus and Teres Minor (external rotation), and Subscapularis (internal rotation; tested via the Lift-Off and Belly-Press tests). Distinguish Rotator Cuff Tear (where passive range of motion is 100% preserved, but active abduction is weak/painful with a positive Drop-Arm test) from Adhesive Capsulitis (“Frozen Shoulder”, strongly associated with diabetes mellitus and hypothyroidism, where BOTH active and passive range of motion are severely restricted in all planes).

Five classic hand/wrist conditions are tested on clinical clerkships: (1) Carpal Tunnel Syndrome (compression of the median nerve beneath the transverse carpal ligament, associated with pregnancy, hypothyroidism, diabetes, rheumatoid arthritis, acromegaly, and dialysis amyloidosis): presents with nocturnal paresthesias in the palmar thumb, index, middle, and radial ring fingers (sparing the palm, which is supplied by the superficial palmar cutaneous branch passing superficial to the carpal tunnel!), positive Phalen and Tinel signs, and late thenar eminence atrophy; treat initially with neutral wrist splinting at night (+ corticosteroid injection), and perform surgical carpal tunnel release if thenar atrophy/weakness is present or conservative therapy fails (confirmed by nerve conduction study). (2) De Quervain Tenosynovitis: non-inflammatory stenosing thickening of the 1st dorsal extensor compartment (Abductor Pollicis Longus [APL] and Extensor Pollicis Brevis [EPB]) at the radial styloid in new mothers lifting infants (“mommy thumb”); diagnosed by a positive Finkelstein test (ulnar deviation of the wrist with the thumb clasped inside the fist reproduces sharp radial wrist pain) and treated with a thumb spica splint, NSAIDs, or steroid injection. (3) Trigger Finger (Stenosing Flexor Tenosynovitis): catching/locking of the flexor digitorum tendon at the A1 pulley over the palmar MCP head (treated with local corticosteroid injection into the tendon sheath). (4) Dupuytren Contracture: painless nodular fibromatosis of the palmar fascia causing progressive flexion contracture of the 4th (ring) and 5th (small) fingers in men of Northern European descent, alcoholics, and diabetics (treated with collagenase Clostridium histolyticum injection or surgical fasciectomy when MCP contracture ≥30° or any PIP contracture develops). (5) Dorsal Wrist Ganglion Cyst: mucoid degeneration of the scapholunate joint capsule that transilluminates with a penlight (managed with reassurance/observation or aspiration).