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: FDSPark 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 coronoidattachment 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

The American Journal of Sports Medicine 33:231-239 (2005)

medial distraction

lateral impaction

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