Carpal Boss in a Baseball Player: Presentation to Treatment

Introduction: Carpal boss is a condition typically presenting in the 3rd to 4th decade of life. It is not commonly found in adolescents. This is a case of a right-handed adolescent pitcher/shortstop presenting for right hand pain. We discuss our diagnostic evaluation of this patient, the proposed mechanism behind the development of a carpal boss, as well as treatment options.

Case Description: A 13-year-old right-handed male presented for evaluation of right-hand pain. This started about a year prior, however it did not impact him significantly until 1.5 months ago when he began increasing his activity. Pain occurs only with batting and activities requiring supination and pronation of the wrist.
More recently, he has become aware of bump on the back of his hand and has noted numbness and tingling radiating from the dorsal aspect of his hand into the first three digits. He denies any discoloration to his fingertips and his sensation is intact.
On exam there was point tenderness on the dorsal aspect of the right hand at the base of the 2nd/3rd metacarpals where there was a <0.5cm firm round mass.
A radiograph of the hand and wrist were obtained that demonstrated no abnormalities which prompted MRI evaluation. MRI demonstrated a carpal boss at base of the 3rd metacarpal, and edema concerning for stress reaction at the base of the 2nd metacarpal.

Discussion: A carpal boss is often misdiagnosed as a ganglion cyst, however the latter would typically present more proximally, be softer in consistency, and transilluminate. Though there are differences in consistency and location, ganglion cysts can develop from a carpal boss. Imaging would be required to differentiate a carpal boss from a ganglion cyst or any other conditions.
Radiographs should be the initial imaging modality however a “carpal boss view” would be required to identify this lesion. This is completed by taking a lateral image of the wrist in flexion, supination of 30-40 degrees, and ulnar deviation of 20-30 degrees.
The etiology remains unknown, but because it more commonly presents in the dominant hand mechanical stress seems to be the leading theory. Additionally, strong repetitive movements involving wrist extension have been shown to be associated with the development of carpal bossing.
First line treatment for this condition would be use of a splint for 4-6 weeks, range of motion exercises, and the use of NSAIDs as needed. For persistent pain corticosteroid injections and extracorporal shockwave therapy can be utilized but with mixed effects. Surgical resection would be an option for those with persistent symptoms, though it may not lead to complete resolution of symptoms.

Conclusion: This patient symptoms improved with the conservative management of a splint along with physical therapy. He was followed for 4 months without recurrence of his symptoms.