Hook Of The Hamate

Carpal Tunnel Master And Beyond

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Anatomy

The hamulus, or hook of the hamate, protrudes into the palm surrounded by critical soft-tissue structures. The hook serves as the origin of the flexor and opponens digiti minimi muscles and forms the ulnar border of the carpal tunnel and radial border of Guyon's canal.1 The deep motor branch of the ulnar nerve courses around the base of the hook with the superficial sensory branch remaining in close contact with the tip. The hook also functions as a pulley for the superficial and deep flexor tendons to the small and ring fingers, especially during ulnar deviation involved with power grip. Therefore, fracture and/or fracture nonunion of the hook of the hamate jeopardize injury to any or all of the previously mentioned structures.

The vascular anatomy of the hamate hook has been extensively evaluated.17 Vessels penetrate the radial base as well as the ulnar tip with relatively poor vascular anastomoses between the two.7,17 This resultant vascular watershed predisposes even nondisplaced hook fractures to nonunion.1,17,18

Clinical Features and Evaluation

Hook of the hamate fractures account for only 2% to 4% of all carpal fractures.1 Athletes participating in stick-handling sports account for the vast majority of these injuries and are most at risk of long-term complications secondary to missed or delayed diagnosis.1,2,19,20 The mechanism of injury is either (1) direct

Figure 39-4 Postoperative radiographs: Percutaneous scaphoid stabilization. A, Scaphoid view. B, Oblique view.

impact via the handle of a club, racquet, or bat or (2) shearing forces arising from the hypothenar muscles as well as the flexor tendons to the ring and small fingers. The nondominant hand is most commonly involved in golf and baseball, whereas the dominant hand is more common in tennis and racquetball.1

Early diagnosis is critical to successful management of hook of the hamate fractures. The majority of these injuries will proceed to nonunion if left untreated.20 Fracture nonunion predisposes the athlete to (1) chronic ulnar-side wrist pain, (2) ulnar nerve paresthesias/motor weakness, and/or (3) flexor tenosynovitis with potential flexor tendon rupture. Diagnosis begins with a detailed history focusing on the mechanism and timing of injury. Ulnar wrist pain occurring during stick-handling sports is almost pathognomonic for hook fracture. Athletes with symptoms directed at the carpal tunnel, Guyon's canal, or ulnar-side digital flexors require critical evaluation for established nonunion of the hamate's hook. Tenderness to palpation over the hook, painful grip, pain with resisted small/ring finger flexion, and a high index of suspicion further aid in the diagnosis.

Radiographic evaluation confirms suspected diagnoses. Routine anteroposterior, lateral, and oblique wrist radiographs often do not reveal the fracture.1,17,21 Subtle radiographic signs on anteroposterior projections include (1) absence of the hook, (2) lack of cortical density, and (3) sclerosis.1 Special projections can be useful in establishing the diagnosis. The carpal tunnel view may allow imaging of the hamate hook but requires wrist dorsiflexion often unattainable in patients with wrist injuries (Fig. 39-5).17 Computed tomography is the gold standard for confirming the presence of hook of the hamate fracture and should be obtained in any athlete with ulnar-side wrist pain and negative plain radiographs (see Fig. 39-5).1,2,17 A high index of suspicion for fracture and appropriate radiographic evaluation allow prompt diagnosis, early management, and avoidance of long-term complications.

Treatment Options

Appropriate management of hook of the hamate fractures aims to eliminate the risk of long-term complications and return the athlete to his or her preinjury level of play. Treatment options include cast immobilization, fragment excision, and open reduction and internal fixation.1,17 The choice of management is guided by time from injury to presentation, displacement, and accompanying nerve/tendon pathology.1,17 Athletes must be appropriately counseled regarding the potential complications arising from untreated fractures and fracture nonunions.

Displaced fractures compromise the intricate anatomy and encroach on the vital soft-tissue structures adjacent to the hamate's hook. Neurovascular and tendinous structures are at risk and must be preserved.1,19,20,22 Therefore, all displaced fractures require immediate fragment excision.

B, Computed tomography image: hook fracture (arrow).

Nondisplaced fractures are treated based on the timing from injury to presentation. Acute fractures are defined as those diagnosed and treated within 7 days of injury. Whalen et al23 managed six acute fractures in short-arm casts incorporating the fourth and fifth metacarpophalangeal joints. Successful union was achieved in all acute injuries, with healing times averaging 8 to 12 weeks. Other studies document high rates of nonunion following cast immobilization that is initiated greater than 7 days from injury.10,17,24 Thus, cast immobilization is a viable treatment option only for fractures diagnosed and immobilized within 7 days of injury.1,23 Athletes must be informed of the 3 to 4 months out of competition required for successful conservative management. Fractures presenting more than 7 days from injury require operative intervention.

Operative management consists of fragment excision versus open reduction and internal fixation. Indications for surgery include (1) displaced fractures, (2) fractures accompanied by ulnar nerve paresthesias or tendinous pathology, (3) fractures diagnosed later than 7 days from injury, and (4) athletes unwilling to undergo prolonged immobilization of acute injuries.1,17,24 Open reduction and internal fixation have been described. The small size of the fragment and precarious vascular supply adds complexity and uncertainty to this procedure.1,10 Thus, excising the fractured hook remains the gold standard among operative procedures.1,24,25 A volar approach is used, with care to identify and protect the surrounding neurovascular and tendinous structures. The fragment is subperiosteally excised, and the bone edges smoothed to prevent ulnar nerve irritation or tendon fraying. The wrist is immobilized postoperatively to protect the operative wound.

Postoperative Rehabilitation

Following fragment excision, the wrist is immobilized for 10 to 14 days to protect wound healing. Athletes undergoing prolonged immobilization require hand therapy following cast removal to regain full, painless wrist range of motion.

Criteria for Return to Play

Stable fracture healing and painless full wrist range of motion are required following cast immobilization or open reduction and internal fixation prior to return to play. Athletes undergoing fragment excision may return to competition as tolerated following successful wound healing. The majority of athletes prefer to wear well-padded gloves for several months after treatment to protect the hypothenar eminence from irritation inflicted by their racquet, club, or bat.1,21

Results and Outcomes

The vast majority of athletes return to their previous level of sports participation following hook of the hamate excision.10,19,24 The time to return to full athletics averages 8 weeks with nearly normal grip strength regained within 3 months of fragment exci-sion.2,20 Associated nerve or tendon injury prolongs the time course for return to athletics and complicates the surgical repair and postoperative rehabilitation.22

Complications

The surrounding soft-tissue structures can be irritated and damaged by the fractured hamate hook or callous from a hyper-trophic nonunion. Ulnar nerve compression is common and presents as paresthesias extending into the ring and small fingers.21 The flexor tendons to the small and ring fingers can be abraded by the fractured hook, developing painful

Figure 39-5 Hook of the hamate. A, Carpal tunnel view: hook (arrow).

Figure 39-5 Hook of the hamate. A, Carpal tunnel view: hook (arrow).

tenosynovitis.19,22 Untreated, these tendons are at risk of rupture.19,22 All complications must be promptly identified and treated appropriately along with fragment excision. Early diagnosis is critical in avoiding the late sequelae of hook fracture and nonunion.

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Responses

  • RIIKKA
    What must be immbolized if you break hammate hook?
    27 days ago

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