MSK

Question 1

Unhappy triad

Answer 1

Injury due to lateral (valgus) force to the knee, or posterior force. Causes damage to:

• Medial meniscus
• Medial collateral ligament
• ACL

Question 2

Function and innervation of each component of the rotator cuff

Answer 2

“SITS”
Supraspinatus (suprascapular n.) - abduct arm to 15 degrees

Infraspinatus (suprascapular n.) - externally rotate

Teres minor (axillary n/) - adduct and externally rotate

Subscapularis (subscapular nerves) - adduct and internally rotate

Question 3

Types of collagen involved in Osteogenesis Imperfecta and Ehlers-Danlos/specific defects in collagen synthesis pathway

Answer 3

OI: type I (bONE) - multiple fractures, blue sclerae, dental imperfections, hearing loss. Problem with forming triple helix (procollagen)

ED: type 5 most common (found at DEJ); type 3 for vascular type (found in BV’s). Hyperextensibility, hypermobile joints, easy bruising. Problems with forming cross-links to create collagen fiber

Question 4

Blastic, lytic and mixed bone metastases

Answer 4

Blastic: prostate, SCLC, Hodgkin lymphoma
Lytic: multiple myeloma, NSCLC, NHL, RCC, melanoma
Mixed: GI, breast

Question 5

Carpal tunnel syndrome

Answer 5

Median nerve entrapment in carpal tunnel. Nerve is sandwiched btwn flexor digitorum superficialis and profundus tendons. The canal runs below the transverse carpal ligament (flexor retinaculum) and above the carpal bones. Causes tingling, numbness in first 3.5 digits. Thenar eminance atrophies but sensation spared (bc innervated by palmar cutaneous branch of median n. which is outside the tunnel). Can also be caused acutely by dislocation of lunate (FOOSH)

Question 6

Guyon canal syndrome

Answer 6

Compression of ulnar n. at wrist, in guyon’s canal (runs btwn hook of hamate and pisiform). Seen in cyclists d/t pressure from handlebars

Question 7

Innervation of thenar vs. hypothenar eminances

Answer 7

Thenar: median (palmar cutaneous branch for sensory)

Hypothenar: ulnar

Question 8

Osteomyelitis common locations in adults vs. kids

Answer 8

Most commonly bacterial; arises via hematogenous spread.

• Kids: transient bacteremia, seeds metaphysis
• Adults: open-wound bacteremia seeds epiphysis. Vertebral body = most common location for osteomyelitis in adults (also the location of osteomyelitis d/t TB: Pott’s dz)

Question 9

Artery compromised with avascular necrosis of the femoral head

Answer 9

Medial circumflex artery of the femoral head. Anastomoses with lateral circumflex and superior/inferior gluteal arteries, but main contributor of femoral head blood supply is MEDIAL circumflex

Question 10

Most common extraarticular manifestations of RA

Answer 10

• rheumatoid nodules in SQ tissue and lung (+ pneumoconiosis = Caplan syndrome)
• interstitial lung disease**
• pleuritis**
• pericarditis**
• anemia of chronic disease
• neutropenia and splenomegaly (Felty)
• AA amyloidosis
• Sjogren syndrome
• scleritis
• carpal tunnel

Question 11

Onion skinning vs. sunburst sign

Answer 11

• onion skinning: ewing sarcoma (“ew, onions are gross”)

- sunburst sign: osteosarcoma. also codman triangle from elevation of periosteum

Question 12

Scurvy, osteogenesis imperfecta and ehlers danlos: where in the collagen synthesis pathway they are involved

Answer 12

• Scurvy: vit C deficient –> can’t hydroxylate pro and lys residues (requires vit C) on preprocollagen. eventually preprocollagen forms a triple helix (procollagen)
• OI: can’t properly make triple helix (procollagen); reduced prodxn of otherwise nromal type I collagen
• ED: and end of pathway; can’t cross-link tropocollagen (modified procollagen that has left the cell) to form final collagen fiber. Stabilized by lysyl oxidase