Introduction A compressive neuropathy of the PIN which affects the nerve supply of the forearm extensor compartment Epidemiology incidence reported as 3 per 100,000 people yearly demographics more common in manual laborers, males and bodybuilders Pathophysiology mechanism of injury microtrauma from repetitive pronosupination movements trauma fracture/dislocation (e.g., monteggia fx, radial head fx, etc) space filling lesions e.g. ganglion, lipomas, etc inflammation e.g. rheumatoid synovitis of radiocapitellar joint iatrogenic (surgery) pathoanatomy: five potential sites of compression include fibrous tissue anterior to the radiocapitellar joint between the brachialis and brachioradialis “leash of Henry” are recurrent radial vessels that fan out across the PIN at the level of the radial neck extensor carpi radialis brevis edge medio-proximal edge of the extensor carpi radialis brevis "arcade of Fröhse" which is the proximal edge of the superficial portion of the supinator supinator muscle edge distal edge of the supinator muscle Anatomy PIN origin PIN is a branch of the radial nerve that provides motor innervation to the extensor compartment course passes between the two heads of origin of the supinator muscle direct contact with the radial neck osteology passes over abductor pollicis longus muscle origin to reach interosseous membrane transverses along the posterior interosseous membrane innervation motor common extensors ECRB (often from radial nerve proper, but can be from PIN) Extensor digitorum communis (EDC) Extensor digiti minimi (EDM) Extensor carpi ulnaris (ECU) deep extensors Supinator Abductor pollicis longus (APL) Extensor pollicus brevis (EPB) Extensor pollicus longus (EPL) Extensor indicis proprius (EIP) sensory sensory fibers to dorsal wrist capsule provided by terminal branch which is located on the floor of the 4th extensor compartment no cutaneous innervation Presentation Symptoms insidious onset, often goes undiagnosed defining symptoms pain in the forearm and wrist location depends on site of PIN compression e.g., pain just distal to the lateral epicondyle of the elbow may be caused by compression at the arcade of Frohse weakness with finger, wrist and thumb movements Physical exam inspection chronic compression may cause forearm extensor compartment muscle atrophy motion weakness finger metacarpal extension weakness wrist extension weakness inability to extend wrist in neutral or ulnar deviation the wrist will extend with radial deviation due to intact ECRL (radial n.) and absent ECU (PIN). provocative tests resisted supination will increase pain symptoms normal tenodesis test tenodesis test is used to differentiate from extensor tendon rupture from RA Evaluation Radiographs indications not commonly needed for the diagnosis of PIN compression syndrome MRI indications not commonly needed for the diagnosis of PIN compression syndrome may be help to site and delineate the soft tissue mass responsible for compression helpful for surgical planning of mass resection Studies EMG indications may help identify the level of nerve compression may be used to rule out differential diagnoses of neuropathy Differential Cervical spine nerve compression Brachial plexus compression Peripheral neuropathy Treatment Nonoperative rest, activity modification, stretching, splinting, NSAIDS indications recommended as first-line treatment for all cases lidocaine/corticosteroid injection indications a compressive mass, such as lipoma or ganglion, has been ruled out isolated tenderness distal to lateral epicondyle trial of rest, activity modification, anti-inflammatories were not effective technique single injection 3-4 cm distal to lateral epicondyle at site of compression surgical decompression indications symptoms persist for greater than three months of nonoperative treatment compressive mass detected on imaging outcomes results are variable spontaneous recovery of motor function was seen in 75 - 97% of non-traumatic case series may continue to improve for up to 18 months Technique Surgical decompression approach anterolateral approach to elbow is most common approach may also consider posterior approach decompression decompression should begin with release of fibrous bands connecting brachialis and brachioradialis leash of Henry fibrous edge of ECRB radial tunnel, including arcade of Frosche and distal supinator Complications Neglected PIN compression syndrome muscle fibrosis of PIN innervated muscles resulting in tendon transfer procedures to re-establish function Chronic pain
QUESTIONS 1 of 2 1 2 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ12.274) Compressive injury to the posterior interosseous nerve will lead to EMG fibrillations in which of the following muscles? Review Topic QID: 4634 1 Extensor Carpi Radialis Longus/Extensor Carpi Radialis Brevis/Brachoradialis 7% (295/4063) 2 Extensor Carpi Radialis Longus/Supinator/Abductor Pollicis Longus 7% (265/4063) 3 Extensor Pollicis Longus/Supinator/Abductor Pollicis Longus 67% (2732/4063) 4 Brachoradialis/Supinator/Extensor Pollicis Longus 5% (203/4063) 5 Extensor Pollicis Longus/Supinator/Abductor Pollicis Brevis 13% (533/4063) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 3