OR3.1-3 | Musculoskeletal Infection — Graded Quiz

Correct. Failure to improve clinically within 36–48 hours and evidence of subperiosteal abscess (periosteal elevation) are clear indications for surgical drainage. Delaying surgery risks avascular necrosis, pathological fracture, and septicaemia.

Indications for surgical drainage in acute osteomyelitis include failure to respond to antibiotics within 36–48 hours, presence of subperiosteal or intraosseous abscess on imaging, pus on aspiration, and periosteal elevation indicating subperiosteal abscess. Periosteal elevation after 72 hours of antibiotics without clinical improvement mandates surgical drainage.

Periosteal elevation on X-ray indicates a subperiosteal abscess has formed. This, combined with failure to respond to 72 hours of antibiotics, is an absolute indication for surgical drainage — continuing medical management alone is unsafe.

Correct. Synovial WBC >50,000 with 90% neutrophils is presumptive septic arthritis. Gram stain negativity does not exclude infection (sensitivity ~50–70%). Immunosuppression lowers clinical inflammatory markers. Urgent IV antibiotics + surgical drainage prevents joint destruction.

A synovial fluid WBC >50,000 with neutrophil predominance is presumptive septic arthritis regardless of Gram stain negativity (Gram stain is positive in only 50–70% of cases). Immunosuppressed patients (RA on methotrexate) are at high risk. Immediate empirical IV antibiotics plus surgical/arthroscopic drainage is mandatory.

A synovial WBC >50,000 with neutrophil predominance demands treatment for septic arthritis regardless of Gram stain result. Immunosuppression (methotrexate) blunts fever and WBC rise, making the clinical picture deceptively mild but the actual risk higher.

Correct. Marjolin's ulcer refers to malignant (usually squamous cell) carcinoma developing in a chronic sinus, burn scar, or ulcer. In chronic osteomyelitis, the sinus tract can undergo this transformation after decades — a rare but important late complication.

Marjolin's ulcer is malignant transformation (typically squamous cell carcinoma) arising in a chronic sinus or burn scar. In chronic osteomyelitis, long-standing sinus tracts can undergo malignant transformation after decades. It is typically a well-differentiated SCC with aggressive behaviour due to delayed presentation.

Marjolin's ulcer is the eponymous term for SCC arising in a chronic wound or sinus tract. Any non-healing chronic wound (burn scar, ulcer, osteomyelitic sinus) can undergo malignant transformation.

Correct. Pott's disease is the classic diagnosis here — insidious onset, thoracic kyphosis (gibbus), vertebral destruction with disc sparing, large psoas cold abscess tracking to the groin, and constitutional symptoms. TB spondylitis is the most common form of skeletal tuberculosis.

Pott's disease (spinal tuberculosis) classically presents with insidious back pain, vertebral body destruction predominantly in the thoracolumbar region, relative anterior disc preservation in early disease, large paravertebral/psoas cold abscess that can track to the groin (presenting as inguinal swelling), and kyphotic gibbus deformity.

The combination of insidious onset, gibbus kyphosis, large cold psoas abscess tracking to groin, and thoracic vertebral destruction with disc preservation is classic for Pott's disease (spinal TB).

Correct. AVN of the femoral head is the most feared complication of delayed septic hip drainage. Rising intraarticular pressure tamponades the retinacular vessels supplying the femoral head, causing ischaemic necrosis particularly in infants where the epiphyseal blood supply is tenuous.

Avascular necrosis (AVN) of the femoral head is the most serious consequence of delayed drainage in paediatric septic hip arthritis. Increased intraarticular pressure compromises blood supply to the capital femoral epiphysis. In children <18 months, the nutrient artery crosses the physis and is especially vulnerable. Early drainage within 4–6 hours of diagnosis is critical.

Avascular necrosis of the femoral head is the primary concern with delayed drainage of septic arthritis of the hip. The retinacular blood supply is compressed by raised intraarticular pressure, leading to irreversible ischaemia.

Correct. Antibiotic-impregnated calcium sulphate beads (resorbable) or PMMA beads placed in the bone defect deliver local concentrations 200x higher than achievable systemically, fill dead space, and avoid systemic toxicity. Calcium sulphate is preferred as it does not require removal.

Antibiotic-impregnated calcium sulphate beads or PMMA beads (e.g., gentamicin or tobramycin) are used after sequestrectomy to fill the dead space and deliver local antibiotic concentrations 200x higher than systemic levels with minimal systemic toxicity. Calcium sulphate beads are resorbable; PMMA beads require a second surgery for removal.

Antibiotic-impregnated local delivery beads (calcium sulphate or PMMA) are the adjunct of choice after sequestrectomy to fill dead space and provide sustained local antibiotic elution without systemic toxicity.

Correct. WBC >12,000 (yes), ESR >40 (yes), fever >38.5°C (NO — 38.3°C), inability to weight-bear (NO — partial weight-bearing). 2 definite criteria + the clinical picture warrants urgent investigation; however the classic Kocher count is 2 here. Urgent aspiration under anaesthesia is indicated regardless. Note: some studies add CRP >2 as a 5th criterion.

This child meets 3/4 Kocher criteria (WBC >12,000, ESR >40, partial weight-bearing — NOT counted as non-weight-bearing; temperature 38.3 < 38.5 threshold). Three criteria confer ~93% probability of septic arthritis. Urgent aspiration under anaesthesia and likely surgical drainage is indicated.

Carefully apply each Kocher threshold: WBC >12,000 (13,500 — YES), ESR >40 (48 — YES), fever >38.5°C (38.3°C — NO, threshold not met), non-weight-bearing (partial — NO). Classic Kocher = 2 criteria. However CRP 8 mg/dL is markedly elevated; the modified Kocher (adding CRP >2) would score 3, conferring ~93% probability.

Correct. All septic joints require drainage in addition to antibiotics. For the hip, formal arthrotomy (or arthroscopic washout in experienced centres) is required given the deep anatomy. Antibiotics alone without drainage invariably lead to cartilage destruction and joint failure.

Septic arthritis of the hip (or any large joint) requires both systemic antibiotics AND surgical drainage. Antibiotics alone are insufficient because (1) penetration into avascular pus is poor, (2) ongoing cartilage destruction from neutrophil enzymes occurs despite bacteriostatic/cidal effects, and (3) raised intraarticular pressure risks AVN. Arthrotomy or arthroscopic washout is mandatory.

Surgical drainage is the essential companion to antibiotics in septic arthritis. Antibiotics without drainage are insufficient — the avascular pus environment and ongoing enzymatic cartilage destruction demand mechanical clearance.

Correct. Salmonella species are the classic 'second organism' in sickle cell osteomyelitis, uniquely elevated due to functional asplenia. Empirical antibiotics in sickle cell osteomyelitis should cover both S. aureus and Salmonella.

Salmonella species (typically non-typhoidal Salmonella) are classically associated with osteomyelitis in sickle cell disease due to (1) splenic infarction/functional asplenia impairing opsonisation of encapsulated organisms, (2) intestinal ischaemia allowing gut bacterial translocation, and (3) bone marrow infarcts providing a nidus. The diaphysis is preferentially affected, unlike haematogenous osteomyelitis in normal children where the metaphysis is predominantly involved.

Salmonella osteomyelitis is classically associated with sickle cell disease due to functional asplenia from repeated splenic infarction, and the diaphysis is the typical site (unlike metaphyseal in normal host).

Correct. Sequestrum = avascular dead bone, dense on X-ray, harbours bacteria. Involucrum = living reactive new bone formed by the periosteum to wall off the infection. The cloaca is the hole in the involucrum through which sinus tracts form.

The sequestrum is avascular, necrotic dead bone (cannot be resorbed, appears dense on X-ray, harbours bacteria within Haversian canals). The involucrum is the new reactive living bone formed by the elevated periosteum surrounding the sequestrum. The cloaca is the opening in the involucrum through which pus discharges. Sequestrectomy removes the dead bone; saucerisation converts the cavity to an open defect.

Sequestrum (dead) vs involucrum (living reactive) is a core pathological distinction in chronic osteomyelitis. The involucrum is periosteal new bone; the sequestrum is avascular dead medullary/cortical bone.