Evaluation and Management of Carpal Fractures Other Than the Scaphoid

Louis W. Catalano III, MD; Shobhit V. Minhas, MD; David J. Kirby, MD

Disclosures

J Am Acad Orthop Surg. 2020;28(15):e651-e661. 

In This Article

Hamate

Hamate fractures may be more common than previously thought, with a recent study demonstrating that they are one of the most frequent hand injuries in professional-level baseball.[31] The hamate articulates distally with the fourth and fifth metacarpals and proximally with the lunate and triquetrum. The volar hook serves at the origin for the hypothenar muscles and transverse carpal ligament and as the borders of the carpal tunnel and Guyon's canal. The proximal pole is covered by articular cartilage and depends on an intrinsic retrograde blood supply, whereas the body receives volar and dorsal blood supplies. The hook is dependent on volar vasculature, which results in a watershed zone at the base of the hook.[32]

Acute hook fractures may demonstrate swelling in the ulnar palm, ecchymosis over the volar hamate, and point tenderness. Chronic injuries may only have point tenderness over the hook, which can be palpated approximately 2 cm distal and 1 cm midline to the pisiform on the volar aspect of the hand.[7] Owing to the proximity to the neurovascular bundle, the patient may complain of ulnar nerve paresthesia. Becauce the flexor tendons use the hook as a pulley, patients will classically complain of pain with resisted small finger flexion and wrist ulnar deviation. Loss of the knuckle contour for the fourth or fifth metacarpal head is suggestive of a CMC dislocation. On radiographs, body fractures can be better evaluated with a 45° pronated oblique view (Figure 9, A). The carpal tunnel view is useful in evaluating hook fractures. The "ring sign," seen as discontinuity of the cortical ring on a PA view, has a sensitivity and specificity of 57.5% and 93.1%, respectively, and is the most sensitive sign of a hook of hamate fracture on a PA view.[33] Plain radiographs have an overall sensitivity of 70% to 80% for hamate fractures, therefore CT is still often necessary for identification.[33]

Figure 9.

Imaging of a hamate body fracture that was treated with open reduction and internal fixation (B). Preoperative radiograph demonstrates dorsal dislocation of the CMC joint (A). The metacarpals have been pinned to assist with maintaining the reduction.

Hamate fractures are classified based on the fracture location in the body (type 1) or hook (type 2)[34] (Table 1). Transverse fractures are associated with perilunate fracture-dislocations, with the proximal pole shearing off during translation. Coronal fractures of the hamate are associated with CMC fracture-dislocation and are the most commonly injured CMC articulation outside of the first digit[35] (Figure 9). Body fractures that are nondisplaced and extra-articular can be treated with an ulnar gutter cast for 3 weeks, followed by a short arm cast for 3 weeks. Fractures with displacement or intra-articular extension can be managed initially with closed reduction and percutaneous pinning. If the fracture is unable to be reduced, open reduction and internal fixation is appropriate. Achieving optimal articular congruity is paramount for the hamate CMC articulation and to that of the trapezoid CMC. This is in relation to the increased mobility of the fourth and fifth CMC, as opposed to the inherently stable second/third CMC, which makes the joints more mobile and therefore more prone to posttraumatic arthritis. A dorsal approach should be used to address the body fracture, and fixation can be achieved with interfragmentary screws, plating, or K-wires. Any screws driven dorsal to volar for fixation should be done with care because the motor branch of the ulnar nerve is near the volar cortex. If subluxation/dislocation of the metacarpals has occurred, they will need to be reduced with longitudinal traction and reduction maintained with K-wires driven through the fourth and fifth metacarpals into the third metacarpal and/or capitate (Figure 9, B). Acute hook of hamate fractures can be managed initially with an ulnar gutter cast for 3 weeks, followed by a short arm cast for 3 weeks that limits wrist and ulnar digit motion, thereby limiting potential tendon irritation. Alternatively, the hook can be surgically excised if there is notable displacement, given the likelihood of nonunion. Chronic symptomatic hook nonunions should be excised. For hook excision, an approach through Guyon's canal limits the risk for injury to the ulnar nerve branches, ulnar artery, and flexor tendons.[36]

Hamate fractures have approximately a 10% nonunion rate, particularly hook fractures treated nonsurgically.[32] Hamate body fractures, even when properly reduced, can result in posttraumatic arthritis, and the proximal pole, given the retrograde blood flow, is at risk for osteonecrosis.[32] Surgical excision of the hook has a 25% incidence of postoperative transient ulnar nerve dysfunction with the sensory branch being affected in 70% of cases.[37]

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