Iran Orthopedic Surgery Board Exam cheat sheet

Osteon: concentric lamellae around a central canal; cortical bone is ~80% of skeletal mass but only ~20% of surface area, trabecular bone the reverse.

Wolff law: bone remodels along lines of applied stress; Hueter-Volkmann law: compression slows and tension accelerates physeal growth.

Cartilage is avascular and aneural; superficial zone has highest collagen and lowest proteoglycan, deep zone the reverse - hence superficial partial-thickness defects do not heal.

Neutrophils dominate the first 24-48 h of fracture hematoma; macrophages peak at 48 h; MSC recruitment and soft callus follow, then mineralization.

Hyaline cartilage tensile stiffness is highest in the superficial zone because collagen fibers are parallel to the surface.

Skeletal muscle fiber types: type I slow oxidative, fatigue-resistant; type IIa fast oxidative-glycolytic; type IIx fast glycolytic, most fatigable.

Bone blood supply: nutrient artery supplies inner two-thirds of cortex, periosteal vessels outer third; periosteal stripping devascularizes cortex.

Nerve injury classification (Seddon): neurapraxia reversible conduction block; axonotmesis axonal loss with intact endoneurium; neurotmesis complete transection.

Damage-control orthopedics: early temporary external fixation of long-bone and pelvic fractures in the physiologically unstable patient, then definitive fixation after resuscitation.

Lethal triad: hypothermia, acidosis, coagulopathy; resuscitation targets permissive hypotension, damage-control surgery, and correction of coagulopathy.

Open fracture: urgent IV antibiotics (first-generation cephalosporin; add aminoglycoside for gross contamination), tetanus prophylaxis, debridement, and stabilization.

Gustilo-Anderson: I clean <1 cm; II 1-10 cm without extensive soft-tissue damage; IIIA adequate soft-tissue coverage; IIIB requires flap; IIIC arterial injury requiring repair.

Compartment syndrome: pain with passive stretch is the most reliable early sign; pulselessness and paralysis are late. Fasciotomy is definitive.

Pelvic ring: mechanical instability and hemodynamic instability dictate external fixation or preperitoneal packing; angioembolization for arterial bleeding.

Neck of femur in the elderly: intracapsular fractures carry high avascular necrosis risk; displaced fractures are treated with arthroplasty, not internal fixation.

Tscherne classification grades closed soft-tissue injury from 0 (none) to III (severe, with skin contusion or muscle crush).

Total hip: cup inclination aim ~40° (range 35-45°), combined anteversion ~25-40°; leg-length and offset restoration reduce dislocation risk.

Aseptic loosening is the most common cause of late THA failure; periprosthetic joint infection is the most common cause of early revision.

Knee: mechanical alignment target is neutral (0° ± 3°); varus/valgus deformity correction must balance medial and lateral soft tissues.

Periprosthetic joint infection diagnosis: two positive cultures or sinus tract communicating with the joint; serum CRP and ESR first-line, alpha-defensin and synovial fluid WBC useful.

Shoulder arthroplasty: anatomic for intact rotator cuff with preserved glenoid bone; reverse for cuff tear arthropathy or severe glenoid deficiency.

Aseptic loosening of a cemented component: radiolucent line >2 mm, progressive over time, with component migration.

Prophylaxis for venous thromboembolism after arthroplasty: mechanical plus pharmacologic; aspirin acceptable in low-risk patients per current guidelines.

Revision THA: Paprosky classification grades acetabular bone loss and guides the use of cages, augments, or trabecular metal components.

Cauda equina syndrome: saddle anesthesia, bowel/bladder dysfunction, bilateral leg weakness - surgical emergency, decompress urgently.

Spinal cord injury: ASIA Impairment Scale grades A (complete) to E (normal); neurogenic shock causes hypotension with bradycardia.

Degenerative spondylolisthesis: Meyerding grading I-IV by slip percentage; flexion-extension radiographs assess instability.

Scoliosis: Cobb angle >10° defines scoliosis; >25-30° in a growing child warrants bracing; >45-50° may need surgery.

Spinal infection: discitis/osteomyelitis often from hematogenous spread; MRI with contrast is the imaging of choice; biopsy before antibiotics if feasible.

Tumor: three-column involvement (Denis) and mechanical instability (SINS score) guide the need for stabilization.

Thoracolumbar fracture: TLICS score (morphology, posterior ligamentous complex, neurologic status) - >4 points suggests operative treatment.

Lumbar disc herniation: L4-5 affects L5 root (foot dorsiflexion), L5-S1 affects S1 (ankle reflex, plantar flexion).

ACL reconstruction: graft options include bone-patellar tendon-bone, hamstring, and quadriceps; tunnel placement is critical to kinematics.

Meniscus: preserve as much as possible - partial meniscectomy for tears not amenable to repair; repair for peripheral vascular zone tears.

Rotator cuff: supraspinatus tears most common; massive tears with fatty infiltration and retraction may need reverse arthroplasty.

Shoulder instability: Bankart lesion (anteroinferior labrum) and Hill-Sachs (posterolateral humeral head impaction) in anterior dislocation.

Anterior cruciate ligament injury: positive Lachman and pivot-shift tests; MRI confirms; return to sport typically 9-12 months.

Cartilage: microfracture best for small (<2 cm²) contained defects; autologous chondrocyte implantation for larger lesions.

Biceps pathology: SLAP tears involve superior labrum; long head tenotomy or tenodesis for refractory symptoms.

Arthroscopic portals: anterolateral and anteromedial for knee; posterior, anterior, and lateral for shoulder.

Developmental dysplasia of the hip: Ortolani (reduction) and Barlow (dislocation) maneuvers in the neonate; Pavlik harness for infants <6 months.

Legg-Calvé-Perthes: avascular necrosis of the femoral head in children 4-8 years; containment treatment; lateral pillar classification predicts outcome.

Slipped capital femoral epiphysis: obese adolescent with groin or knee pain; frog-leg lateral radiograph; in situ pinning.

Clubfoot (talipes equinovarus): Ponseti method - serial casting, Achilles tenotomy, then bracing.

Limb-length discrepancy: scanogram; growth remaining estimated by Greulich and Pyle bone age or multiplier method.

Osteogenesis imperfecta: collagen type I defect; bisphosphonates reduce fracture rate and improve bone density.

Physeal fractures: Salter-Harris I-V; type III and IV cross the physis and risk growth arrest.

Blount disease: tibia vara; infantile form often responds to bracing; adolescent form may need osteotomy.

Nerve repair: primary repair within 24 h for clean lacerations; epineurial or group fascicular repair; tension-free coaptation.

Flexor tendon zones: zone II (no man's land) has the worst prognosis; early controlled mobilization after repair.

Scaphoid fracture: tenderness in anatomic snuffbox; risk of nonunion and avascular necrosis (proximal pole); CT or MRI for occult fracture.

Dupuytren contracture: palmar fascia; treatment options include needle aponeurotomy, collagenase injection, and fasciectomy.

Carpal tunnel syndrome: median nerve compression; night symptoms, thenar atrophy; electrodiagnostic studies and surgical release.

Microsurgery: free flap survival depends on arterial inflow and venous outflow; monitor with Doppler, color, and capillary refill.

Kienböck disease: avascular necrosis of the lunate; treatment depends on Lichtman stage.

Trigger finger: A1 pulley release; steroid injection first-line for mild cases.

Ankle fracture: Weber classification by the level of the fibular fracture relative to the syndesmosis (A below, B at, C above).

Achilles tendon rupture: positive Thompson test; nonoperative functional bracing vs. surgical repair; rerupture risk.

Hallux valgus: first metatarsal angle and intermetatarsal angle guide bunionectomy type.

Plantar fasciitis: morning pain at the medial calcaneal tuberosity; conservative treatment first; consider plantar fascia release for refractory cases.

Lisfranc injury: midfoot instability; weight-bearing radiographs or CT; anatomic reduction is essential.

Ankle arthritis: tibiotalar arthrodesis vs. total ankle arthroplasty; arthroplasty preserves motion but has higher revision rates.

Diabetic foot: Charcot arthropathy - rocker-bottom foot, midfoot collapse; total contact cast and offloading.

Tarsal tunnel syndrome: posterior tibial nerve compression; burning pain in the sole; release of the flexor retinaculum.

Osteosarcoma: most common primary malignant bone tumor in children and adolescents; metaphysis of long bones; sunburst periosteal reaction.

Ewing sarcoma: diaphysis, small round blue cells, t(11;22) translocation; systemic chemotherapy plus local control.

Giant cell tumor: epiphysis of long bones in young adults; soap-bubble appearance; curettage and cementing.

Bone metastases: most common malignant bone tumor overall; breast, prostate, lung, kidney, thyroid; pathologic fracture risk assessed by Mirels score.

Multiple myeloma: lytic lesions, hypercalcemia, renal failure, anemia; bone pain; serum protein electrophoresis.

Osteoporosis: DXA T-score ≤ -2.5 defines osteoporosis; bisphosphonates and denosumab reduce fracture risk.

Paget disease: increased bone turnover; mosaic pattern on histology; bisphosphonate treatment for symptoms.

Osteoid osteoma: night pain relieved by NSAIDs; nidus with surrounding sclerosis; radiofrequency ablation.

Periprosthetic joint infection: most common organisms are Staphylococcus aureus and coagulase-negative staphylococci; two-stage revision for chronic infection.

Surgical site infection prevention: preoperative antibiotics within 60 min of incision, normothermia, glucose control, and hair removal by clipping.

Osteomyelitis: acute hematogenous in children; chronic with sequestrum and involucrum; prolonged antibiotics and debridement.

Necrotizing fasciitis: surgical emergency; broad-spectrum antibiotics and urgent debridement; group A streptococcus or polymicrobial.

Venous thromboembolism: prophylaxis after major orthopedic surgery; low-molecular-weight heparin or aspirin per risk.

Fat embolism syndrome: after long-bone fractures; hypoxemia, petechiae, confusion; supportive care.

Complex regional pain syndrome: disproportionate pain, swelling, and skin changes after trauma or surgery; early mobilization and sympathetic blockade.

Perioperative glycemic control: HbA1c >8% increases infection risk; optimize before elective arthroplasty.

Rehabilitation phases: protection, early mobilization, strengthening, return to function; progress by tissue healing timeline.

Continuous passive motion after knee arthroplasty improves early range of motion but does not change long-term outcomes.

Prosthetics: transfemoral socket design (quadrilateral vs. ischial containment); transtibial uses patellar tendon-bearing socket.

Orthotics: ankle-foot orthosis for foot drop; knee-ankle-foot orthosis for knee instability; spinal orthosis for fracture or deformity.

Functional scores: Harris Hip Score, Knee Society Score, DASH for upper extremity, and SF-36 for quality of life.

Amputee rehabilitation: early prosthetic fitting and gait training improve function; energy cost higher with more proximal amputation.

Cerebral palsy gait: crouch gait, equinus, and scissoring; gait analysis guides tendon lengthening or transfer.

Return-to-work assessment: consider physical demands, pain, and functional capacity; graded return improves outcomes.

Informed consent: disclose diagnosis, proposed treatment, alternatives, and material risks; document the discussion.

Patient safety: WHO surgical safety checklist - sign in, time out, sign out; reduces wrong-site surgery and retained items.

Research design: randomized controlled trial is the strongest design for treatment efficacy; blinding reduces bias.

Levels of evidence: Level I systematic reviews of RCTs; Level V expert opinion.

Sensitivity and specificity: sensitivity detects disease when present; specificity excludes disease when absent; PPV and NPV depend on prevalence.

Conflict of interest: disclose financial relationships; institutional review board approval for human subjects research.

Error disclosure: disclose harmful errors to patients; apologize and explain; supports patient trust and safety culture.

Statistical significance: p < 0.05 conventional; confidence intervals convey precision and clinical relevance.