Isolated Fourth Carpometacarpal Joint Injury in High-Level Baseball Players: A Case Series.

Abstract

We present a case series of high-level baseball players having sustained a rare, isolated injury to the fourth carpometacarpal joint of the nondominant or bottom hand during a jammed swing. Ten patients were evaluated for ulnar-sided wrist pain and were subsequently diagnosed with fourth carpometacarpal joint synovitis based on physical examination and magnetic resonance imaging revealing increased signal intensity within the joint. Conservative treatment modalities including rest, nonsteroidal anti-inflammatory medications, splinting, and corticosteroid injections resulted in return to play within 4 weeks for all patients. We propose a mechanism of injury involving the bottom hand in relative pronation receiving a dorsally directed force from bat during a jammed swing resulting in isolated injury to the fourth carpometacarpal joint. This report serves to highlight this rare injury in high-level baseball players and recommend a treatment algorithm for early return to play.