Sumary PIN compression syndrome is a compressive neuropathy of the PIN which affects the nerve supply of the forearm extensor compartment. Diagnosis is made clinically with weakness of thumb and wrist extensors without sensory deficits. Treatment is a course of conservative management with splinting and surgical decompression reserved for persistent cases lasting > 3 months. Epidemiology Incidence ~ 3 per 100,000 annually Demographics more common in manual laborers, males and bodybuilders Etiology Pathophysiology mechanism of injury microtrauma login to view 1 more bullet trauma login to view 1 more bullet space filling lesions login to view 1 more bullet inflammation login to view 1 more bullet iatrogenic (surgery) pathoanatomy: five potential sites of compression include login to view 10 more bullets 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 login to view 11 more bullets sensory login to view 3 more bullets Presentation Symptoms insidious onset, often goes undiagnosed defining symptoms pain in the forearm and wrist login to view 2 more bullets weakness with finger, wrist and thumb movements Physical exam inspection chronic compression may cause forearm extensor compartment muscle atrophy motion weakness login to view 4 more bullets provocative tests resisted supination login to view 1 more bullet normal tenodesis test login to view 1 more bullet 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 Diagnosis Clinical diagnosis is made with careful history and physical examination Treatment Nonoperative rest, activity modification, stretching, splinting, NSAIDS indications login to view 1 more bullet lidocaine/corticosteroid injection indications login to view 3 more bullets technique login to view 1 more bullet surgical decompression indications login to view 2 more bullets outcomes login to view 3 more bullets Technique Surgical decompression approach anterolateral approach to elbow is most common approach may also consider posterior approach decompression decompression should begin with release of login to view 4 more bullets Complications Neglected PIN compression syndrome muscle fibrosis of PIN innervated muscles resulting in tendon transfer procedures to re-establish function Chronic pain