ELBOW MR throwing athlete emphasis on the UCL Throwing athlete • baseball pitchers • elbow complaints: > 90% medial • valgus stress: medial distraction • ulnar collateral ligament • flexor-pronator mass Ulnar collateral ligament • anterior bundle – 1° valgus stabilizer • posterior bundle – floor of cubital tunnel • transverse ligament Gray, Henry. Anatomy of the Human Body. 1918 Flexor-pronator mass • pronator teres • flexor carpi radialis • palmaris longus • flexor carpi ulnaris • flexor digitorum superficialis UCL & FPM • functional relationship – during pitch, UCL load >> failure strength – FPM muscles protect UCL · dynamic stabilization of medial elbow · FCU primary, FDS secondary · pronator teres least contributory • anatomical relationship: FDS Park MC, Ahmad CS. JBJS(Am) 2004;86:2268-2274 Pronator teres • major head originates from: – humerus, just prox to med epicondyle – common flexor tendon, intermusc fascia • minor head originates from: – medial aspect of coronoid process FDS: 3 heads • radius (obl line) • coronoid process – prox to pronator teres • med epicondyle – UCL, intermusc fascia Gray, Henry. Anatomy of the Human Body. 1918 FDS: 2 heads • radial head (oblique line) • humeroulnar head – superficial (muscular) fibers · medial epicondyle (common flexor tendon) – deep (tendinous) fibers · surface of UCL anterior bundle · coronoid process, medial aspect Munshi, Resnick et al. Radiology 2004; 231:797-803 • AP, extended • F= flex dig superficialis • mF= superficial muscle • tF= deep FDS tendon • aU= anterior bundle • pU= posterior bundle • me= med epicondyle • c= coronoid process Munshi, Resnick et al. Radiology 2004; 231:797-803 • medial, flexed • F= flex dig superficialis • mF= superficial muscle • tF= deep FDS tendon • aU= anterior bundle • pU= posterior bundle • me= med epicondyle • c= coronoid process Munshi, Resnick et al. Radiology 2004; 231:797-803 Anterior bundle: dissection • single layer of parallel bundles – pseudolaminar appearance – overlying FDS tendinous fibers • arises: medial epicondyle – inferior surface (base), anterior margin – interdigitating fat near attachment site • inserts: medial ulna (sublime tubercle) – up to 3-4mm distal to articular margin Munshi, Resnick et al. Radiology 2004; 231:797-803 Anterior bundle & FDS • dissection – FDS intimate w/ UCL: deep tendinous fibers can merge w/ anterior bundle • MR imaging – deep tendinous fibers of FDS difficult or impossible to visually separate from UCL and coronoid attachment sites – prox UCL tear may reflect FDS incompetence, suggest poor prognosis, performance Elbow: overuse injury • repetitive, cumulative stress • soft tissue, osseous changes – calcification, bony proliferation • degenerative arthropathy – osteophyte, intra-artic loose bodies medial distraction lateral impaction The American Journal of Sports Medicine 33:231-239 (2005) Elbow: overuse injury • UCL: chronic v. acute Δ – thickening (6.3 v. 5mm, 30° flexion) – stretching, partial tearing – degeneration, heterotopic ossification • valgus laxity, microinstability – degenerative joint disease Medial ossific fragment • post-traumatic phenomenon • old fracture fragment • heterotopic ossification – old acute ST trauma – chronic, recurrent injury Medial elbow pain • ulnar collateral ligament – UCL tear (distal, proximal, mid-substance) • flexor-pronator mass – tendon tear, MT strain – flexor digitorum superficialis – pronator teres.