Unhappy triad
Injury due to lateral (valgus) force to the knee, or posterior force. Causes damage to:
- Medial meniscus
- Medial collateral ligament
- ACL
Function and innervation of each component of the rotator cuff
“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
Types of collagen involved in Osteogenesis Imperfecta and Ehlers-Danlos/specific defects in collagen synthesis pathway
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
Blastic, lytic and mixed bone metastases
Blastic: prostate, SCLC, Hodgkin lymphoma
Lytic: multiple myeloma, NSCLC, NHL, RCC, melanoma
Mixed: GI, breast
Carpal tunnel syndrome
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)
Guyon canal syndrome
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
Innervation of thenar vs. hypothenar eminances
Thenar: median (palmar cutaneous branch for sensory)
Hypothenar: ulnar
Osteomyelitis common locations in adults vs. kids
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)
Artery compromised with avascular necrosis of the femoral head
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
Most common extraarticular manifestations of RA
- 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
Onion skinning vs. sunburst sign
- onion skinning: ewing sarcoma (“ew, onions are gross”)
- sunburst sign: osteosarcoma. also codman triangle from elevation of periosteum
Scurvy, osteogenesis imperfecta and ehlers danlos: where in the collagen synthesis pathway they are involved
- 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
