Chapter 9 of 158% of exam

Musculoskeletal System

The musculoskeletal block includes trauma, degenerative and rheumatologic disease, pediatric orthopedics, infection, spinal disorders and bone tumors. Many items test the one finding that changes management from routine to urgent.

Urgent joint and limb problems

A hot, swollen joint must be aspirated, and pain out of proportion to an injury must prompt concern for compartment syndrome. Crystal analysis separates gout from pseudogout. Delays in these conditions cost joints and limbs.

Septic arthritis

Aspirate the joint; synovial white count is usually above 50,000/µL with neutrophil predominance.

Merck Manual Professional Edition, Acute Infectious Arthritis

Compartment syndrome

Pain out of proportion and pain with passive stretch; treatment is fasciotomy.

Merck Manual Professional Edition, Compartment Syndrome

Gout

Needle-shaped, negatively birefringent urate crystals; flares treated with NSAIDs, colchicine or glucocorticoids.

Merck Manual Professional Edition, Gout

Pediatric orthopedics

Children often refer hip pain to the thigh or knee, so the hip must be examined. Screening maneuvers detect hip instability in infants. Many adolescent overuse conditions are self-limited.

SCFE

Obese early adolescent with hip, thigh or knee pain; no weight-bearing and screw fixation.

Merck Manual Professional Edition, Slipped Capital Femoral Epiphysis

DDH screening

Barlow pushes an unstable hip out; Ortolani relocates a dislocated hip.

Merck Manual Professional Edition, Developmental Dysplasia of the Hip

Osgood-Schlatter disease

Tender tibial tubercle in active adolescents; analgesics and rest.

Merck Manual Professional Edition, Osgood-Schlatter Disease

Rheumatology and bone density

Joint distribution and associated features sort the arthritides. Inflammatory pain improves with activity, while mechanical pain worsens with use. Bone density is classified by T-score on DXA.

Osteoarthritis vs RA

Heberden (DIP) and Bouchard (PIP) nodes in OA; symmetric wrist and MCP inflammation in RA.

Merck Manual Professional Edition, Osteoarthritis; Rheumatoid Arthritis

Ankylosing spondylitis

Inflammatory back pain improving with activity, sacroiliitis, and HLA-B27.

Merck Manual Professional Edition, Ankylosing Spondylitis

Polymyalgia rheumatica

Proximal stiffness over age 50 with high ESR and rapid response to low-dose prednisone.

Merck Manual Professional Edition, Polymyalgia Rheumatica

Osteoporosis

T-score of -2.5 or lower; osteopenia is between -1.0 and -2.5.

Merck Manual Professional Edition, Osteoporosis

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