Surgical Fixation of Metacarpal Fractures



Surgical Fixation of Metacarpal Fractures


William B. Geissler, MD

Christopher A. Keen, MD

Jarrad A. Barber, MD


Dr. Geissler or an immediate family member has received royalties from Acumed, LLC and Arthrex, Inc., Medartis, Integra; is a member of a speakers’ bureau or has made paid presentations on behalf of Acumed, LLC and Arthrex, Inc., Medartis, Integra; and serves as a paid consultant to or is an employee of Acumed, LLC and Medartis, Integra. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter: Dr. Keen and Dr. Barber.



INTRODUCTION

Metacarpal fractures account for as many as one-third of all hand fractures.1,2 The prevalence of metacarpal fractures increases from the radial to the ulnar side of the hand, with fractures of the fifth metacarpal being the most common.3 Metacarpal neck fractures are the most common; these usually involve the ring and small metacarpals.3 Fifth metacarpal neck fractures are commonly referred to as boxer’s fractures. These fractures are rarely seen in professional boxers, however, occurring most often in amateur boxers who have hit solid objects or in street brawlers.

The metacarpals are long tubular bones with a relatively flat dorsal surface and medial and lateral cortices that converge along the volar aspect, creating a triangular cross section. The metacarpals become quite narrow in the mid diaphyseal region. The metacarpals have an abundant blood supply, being surrounded by the volar and dorsal interosseous muscles. Although the abundant blood supply from the interosseous muscles may be a blessing, when the musculature is severely disrupted, it initially can result in disabling scarring and intrinsic contractures. The deep transverse intermetacarpal ligament lies at the level of the metacarpal neck, which helps limit deformity with low-energy injuries. When intact, the deep transverse intermetacarpal ligament usually limits shortening to approximately 5 mm. The extensor apparatus surrounds the metacarpophalangeal (MCP) joint. The collateral ligaments originate from the tubercle of the metacarpal head and pass obliquely to the volar aspect of the base of the proximal phalanx. Scar from these ligaments may lead to an extensor contracture at the MCP joint.

Metacarpal fractures are generally the result of one of two mechanisms. The most common mechanism is an axial load transmitted from the MCP joint proximally down the shaft of the metacarpal (Figure 1). This results in various common injuries, from fifth metacarpal neck fractures to higher-energy injuries such as metacarpal shaft fractures. A less common mechanism of injury for fractures of the metacarpals is a crush injury. Crush injuries typically involve multiple metacarpal fractures and are also associated with other fractures and significant soft-tissue trauma.

Transverse and short oblique metacarpal fractures tend to angle dorsally because of the deforming forces of the extrinsic flexor tendons and the intrinsic musculature on the distal fragment. Cadaver studies have shown that as much as 7° of extensor lag and 8% loss of grip strength occur for each 2 mm of metacarpal shortening.4,5,6 Intrinsic muscle shortening and muscle tension may lead to progressive grip weakness after approximately 30° of dorsal metacarpal angulation.5 Most metacarpal fractures heal uneventfully and do not require surgery, but spiral fractures, multiple metacarpal fractures, and comminuted fractures are more likely to shorten and rotate, resulting in overlapping of the fingers and tendon imbalance (Figure 2). The border (index and small) metacarpals have a tendency to greater shortening compared with the long and ring metacarpals because the former lack the support of the deep metacarpal ligaments. Border metacarpals have a greater tolerance for lateral angulation than do the long and ring metacarpals because of the greater divergence and because the border fingers have only one adjacent finger. Rotation of the metacarpals is poorly tolerated. Each degree of metacarpal fracture rotation may produce as much as 5° of rotation at the fingertips. Royle7 demonstrated that approximately 10° of metacarpal rotation resulted in 2 cm of fingertip overlap. Clinical deformity from lateral metacarpal angulation is best observed with the fingers straight, whereas rotational deformity is best observed with the fingers in flexion.


PATIENT SELECTION

Most metacarpal fractures are treated nonsurgically. The Jahss maneuver is helpful for reduction of a flexed metacarpal. In this maneuver, a nerve block is performed. The metacarpal shaft is stabilized with the MCP joint flexed to 90°. With the fracture site distracted, upward force is applied to the proximal phalanx metacarpal head to realign the neck and shaft. A splint with three-point molding is applied with dorsal compression at the fracture site and volar support for the metacarpal head and
base. Nondisplaced metacarpal fractures are protected in a splint or cast for 3 to 4 weeks, followed by gradual mobilization. The MCP joints should be immobilized in flexion to stretch the MCP joint ligaments to help prevent contracture and to relax the intrinsic musculature to prevent further deformity at the fracture site.






FIGURE 1 Radiographs show metacarpal fractures. A, Oblique view of the hand demonstrates a metacarpal neck fracture of the small finger (boxer’s fracture). These fractures typically are seen in a patient who has punched a solid object. B, PA view of a different patient demonstrates a fourth metacarpal neck fracture. Concomitant fractures of the ring and small metacarpal neck and/or base are commonly seen as a result of an axial loading mechanism, as seen in A.






FIGURE 2 Photograph of the hand of a patient who sustained a spiral fourth metacarpal shaft fracture. Note the rotational deformity of the ring finger and the digital overlap.




PREOPERATIVE IMAGING

Plain radiographs, including AP and lateral oblique views, usually are adequate to assess a metacarpal fracture. Although it is difficult to evaluate a metacarpal fracture on the lateral view, this view is helpful for evaluating subluxation of the MCP or the carpometacarpal joint. The oblique view is particularly useful for measuring flexion deformity at the fracture site. The AP view is especially
helpful for evaluating coronal plane angular malalignment, which usually is clinically relevant. The Brewerton view can be used to assess metacarpal head fractures (Figure 3). The Brewerton view is obtained by placing the supinated hand on the cassette, with the dorsum of the proximal phalanges flat on the radiograph plate and with the MCP joints flexed to 65° and the radiograph tube positioned 15° ulnar to the midline of the hand.






FIGURE 3 Brewerton view of the metacarpal heads in a normal hand. This view provides excellent visualization of the articular surface.


METACARPAL NECK FRACTURES

The amount of angulation that is acceptable in metacarpal neck fractures involving the ring and small metacarpals is controversial. Ford et al8 reviewed 62 fractures of the small metacarpal neck with palmar angulation and concluded that palmar (volar) angulation up to 70° still resulted in good outcomes. In this study, the fracture was not reduced and the hand was immobilized. Eichenholtz and Rizzo9 considered palmar angulation greater than 40° to require correction. Other authors have recommended surgical intervention when angulation is greater than 30°. If rotation or claw deformity is noted with digital overlap or MCP joint hyperextension and proximal interphalangeal joint flexion, then reduction and stabilization should be considered. Because of the more rigid index and long carpometacarpal joints, angulations less than 10° for the index finger and less than 15° for the long finger can be tolerated without surgical stabilization. Metacarpal neck fractures with angulation greater than that stated above require reduction and stabilization.

Feb 2, 2020 | Posted by in ORTHOPEDIC | Comments Off on Surgical Fixation of Metacarpal Fractures
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