Injection Technique for Bowler’s Thumb

Indications and Clinical Considerations

Bowler’s thumb is an entrapment neuropathy of the digital nerve on the ulnar side at the base of the thumb that may manifest in either an acute or a chronic form. In bowler’s thumb, compression by the edge of the thumb hole of the bowling ball is the inciting cause ( Fig. 89.1 ). The common clinical feature of bowler’s thumb is a painful digital nerve at the point at which the bowling ball compresses it. The nerve may be thickened, and inflammation of the nerve and overlying soft tissues may be seen ( Fig. 89.2 ). In addition to pain, the patient with bowler’s thumb may also report paresthesias and numbness just below the point of nerve compromise. Other causes of compression of the digital nerve on the ulnar side at the base of the thumb have been identified, such as overuse of scissors by dressmakers, compression of the nerve by overuse of jeweler’s pliers, and cherry pitting. Rarely, primary tumors of the digital nerves may mimic the pain of digital neuroma ( Fig. 89.3 ).

The pain of bowler’s thumb may develop after an acute bowling injury or direct trauma to the soft tissues overlying the digital nerve if the thumb gets stuck in the bowling ball, damaging the nerve. The pain is constant and is made worse with compression of the digital nerve. Patients often also note the inability to hold or close a pair of scissors with the affected thumb. Sleep disturbance is common.

On physical examination, there is tenderness to palpation of the digital nerve on the ulnar side at the base of the thumb. Range of motion of the thumb is normal. Palpation of the affected nerve can cause paresthesias, and continued pressure on the nerve may induce numbness distal to the point of compression.

Electromyography helps distinguish other causes of hand numbness from bowler’s thumb. Plain radiographs are indicated for all patients with bowler’s thumb to rule out occult bony disease, such as bone spurs or cysts, which may be compressing the digital nerve. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, uric acid, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging of the hand can be done to rule out soft-tissue tumors such as ganglia that may be compressing the digital nerve ( Fig. 89.4 ). The injection technique described later serves as both a diagnostic and a therapeutic maneuver.