Excision of the Hook of the Hamate

Anand Shah

Reid Abrams

Hamate fractures are rare, but account for approximately 2% of all carpal fractures, with hook fractures being the most common type of hamate fracture (1). The incidence of these fractures seems to be increasing because of the popularity of sports, such as golf, tennis, baseball, and hockey (2,3). With the advent of improved diagnostic tools, and increased clinical awareness, hamate hook fractures are also being more readily detected (4).

Hamate hook fractures can be caused by blunt trauma during a fall or with the direct impact of the butt of a club on the hook. Repeated microtrauma to the hook, during sports such as golf, is thought to be responsible for stress fractures. These fractures typically occur in the nondominant hand when both hands are used in the swinging motion (5). During indirect trauma, forces are transmitted to the hook through its ligamentous and muscular attachments (transverse carpal ligament, pisohamate ligament, and hypothenar musculature), causing avulsion fractures of the hook. Sports that require power grip may also fracture the hook of the hamate, because of the shearing forces that are applied to the hook by the extrinsic finger flexors (6).

Indications and Contraindications

Controversy exists over the appropriate treatment of hamate hook fractures. Short-arm cast immobilization, including the fourth and fifth metacarpophalangeal joints, for 6 to 8 weeks has been advocated for acute nondisplaced fractures diagnosed within the first 7 days (7). Nonunion rates as high as 80% to 90% have, however, been reported with conservative management (8). Difficulty in making the diagnosis and the consequent delayed presentation are significant factors in the guarded prognosis of conservative treatment.

Hamate hook fractures are susceptible to nonunion, especially when displaced, because of the fracture site motion influenced by the multiple muscular and ligament attachments, delayed diagnosis, and poor blood supply. Hook excision has been recommended when fractures are displaced 1 to 2 mm or more or evidence of nonunion exists (1,6).

Excision of the hook may only partly alleviate a patient’s symptoms. Persistent pain can be caused by alterations in the attachments of the pisohamate ligament, transverse carpal ligament, and the flexor and opponens digiti minimi muscles. In addition, the hook has been shown to act as a pulley for the ulnar extrinsic finger flexors, especially in ulnar deviation and with power grip. A biomechanical cadaveric study on flexor tendon function after hamate hook excision revealed decreased flexor tendon force, increased excursion of the flexor digitorum profundus tendons, and ulnar shift of the small finger flexor tendon after hook excision (9). Therefore, removal of the hook could lead to grip weakness and continued pain. Residual pain after excision has also been associated with new bone formation after subperiosteal hook excision (10). Nevertheless, we still prefer subperiosteal dissection when performing excision owing to the close proximity of the deep motor branch of the ulnar nerve.

Additional treatment options for displaced hook fractures or nonunions include open reduction and internal fixation (ORIF), with or without bone grafting, in an attempt to restore the normal anatomy of the hamate hook and its soft tissue attachments, as well as its biomechanical function (11).
Most studies comparing excision versus ORIF have few patients, with variability in the patients’ ages and expectations, and are therefore difficult to interpret (6,12).

We prefer excision of the hook of the hamate for most displaced hook fractures or nonunions. The patient’s age, lifestyle, and occupation, as well as the size, location, and vascularity of the fragment must, however, be considered before deciding on the optimal treatment.

Preoperative Planning

Evaluation of the patient is difficult owing to the often vague complaints and nonspecific physical findings. A history of a recent inciting event is helpful, but infrequently uncovered. Patients often complain of diminished grip strength, vague palmar pain, and occasionally present with ulnar nerve paresthesisas or carpal tunnel syndrome (13,14). Clinical findings may include tenderness along the hypothenar eminence exacerbated by grasping, pain with resisted ring and small finger flexion, and with dorsoulnar wrist deviation (12). Occasionally, patients present with signs of flexor tenosynovitis or attritional rupture secondary to long-standing nonunion (15).

Radiographic evaluation is essential, but up to 39% of hamate hook fractures are missed on standard radiographs (4

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