Posterior Interosseous Nerve Syndrome (PINS)
PINS is the name given to compression of the posterior interosseous nerve (PIN) – a branch of the radial nerve – as it travels through the lateral (outside) aspect of the elbow. It differs from Radial Tunnel Syndrome in that the compression is severe enough to cause motor loss to the muscles in the forearm and fingers that are innervated by the PIN. The most common causes of PIN syndrome include benign tumours (most commonly lipomas and ganglia), peri-elbow synovitis associated with rheumatoid arthritis, septic arthritis of the elbow, synovial chrondromatosis or vasculitis. PIN Syndrome typically presents as pain in the forearm and wrist with weakened wrist, finger and thumb extension movements. In severe cases it can present as dropped fingers and thumb and may be accompanied with atrophy (muscle wasting) of the forearm muscles if left unresolved.
PIN Syndrome may be confused with Radial Tunnel Syndrome or Lateral Epicondylitis.