Hook of Hamate Fracture

History of present illness:

This patient is a 22-year-old gentleman, who works as a barista in a coffee shop. Over the course of  two-and-a-half weeks, he developed increasing numbness and tingling in his left small finger. It wakes him up at night. He has not noticed weakness. He has done some stretching exercises and taken naproxen. This has not improved his symptoms significantly. He does not recall any particular injury or incident in the past.  He reports similar symptoms on the right side, but to a lesser degree.

Physical examination:

Physical exam of the upper extremities demonstrates strong thenar and intrinsic muscles. He has a negative Froment’s sign, negative Wartenberg’s sign. Carpal tunnel compression test produces paresthesias. There is some vague tenderness over the hook of the hamate. Cubital tunnel compression does not produce paresthesias, but compression at Guyon’s canal at the wrist produces tingling in the small finger.

Two point discrimination on the right side is 4 mm and small finger is 6 mm. On the left side, two point discrimination is 4 mm in all fingertips. There is normal finger range of motion bilaterally. All fingers are well-perfused. Allan’s test shows an open palmar arch.

Radiographs of the wrists including a carpal tunnel view suggested a nonunited fracture of the hook of the hamate bilaterally. Further evaluation with MRI scan confirmed the diagnosis.

Hook of hamate fracture nonunion on carpal tunnel view

Electrodiagnostic tests revealed a mild degree of carpal tunnel syndrome.

Treatment:

The patient underwent operative excision of the ununited fragments of the hook of the hamate, combined with endoscopic carpal tunnel release.  No other pathology within Guyon’s canal was noted.

The patient was symptom free after recovery and a course of about 6 weeks of occupational hand therapy.

Review:

Hook of the Hamate fractures are rare, but often missed resulting into nonunion.  The mechanism of injury is often athletes that use rackets or bats or clubs.  In the acute phase simple cast or splint immobilization of the wrist will result into union.

Patient present with pain in the hypothenar eminence, tenderness to palpation, weak grip, and paresthesias of the ring and small fingers. Pain with resisted finger flexion is greater with the wrist in ulnar than in radial deviation. Because the hook of the hamate constitutes the ulnar wall of the carpal tunnel acting as a tendon pully, the flexor tendons of the ring or small finger can attenuate and even rupture, causing loss of active finger flexion.

Radiographically, the fracture can be demonstrated by a carpal tunnel view, or a view in slight supination with the wrist radially deviated and dorsiflexed.   

Treatment of acute fractures is usually cast immobilization.  If the fracture results into nonunion and is symptomatic, then excision rather than fixation of the fracture fragment is recommended.  Complications such as flexor tendon subluxation, weakness, and rupture have been reported but are rare.

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