Plating of Metacarpal Fractures with Locked or Nonlocked Screws, a Biomechanical Study: How Many Cortices are Really Necessary?

Abstract

Background Dorsal plate and screw fixation is a popular choice for metacarpal stabilization. The balance between construct stability and soft tissue dissection remains a surgical dilemma. Historically, six cortices of bone fixation on either side of a fracture were deemed necessary. This study aims to elucidate whether four cortices of locked fixation on either side of the fracture is equivalent to the current gold standard of six cortices of nonlocked fixation on either side of the fracture. If so, less dissection to insert shorter plates with fewer screws could be used to stably fix these fractures. Methods With biomechanical testing-grade composite Sawbones, a comminuted metacarpal fracture model was used to test two fixation constructs consisting of a standard dorsal plate and either six bicortical nonlocking screws (three screws per segment) or four bicortical locking screws (two screws per segment). Thirty specimens were tested to failure in cantilever bending and torsion. Results There was statistical equivalence between the locking and nonlocking constructs in cantilever bending stiffness, torsional stiffness, maximum bending load, and maximum torque. Conclusion The tested metacarpal fracture model had equivalent biomechanical properties when fixed with a standard dorsal plate and either six bicortical nonlocking screws or four bicortical locking screws. By utilizing fewer cortices of fixation, there will be less dissection and less soft tissue stripping during fixation of metacarpal fractures. This will also be of benefit in very proximal or distal fractures as multiple cortices of fixation are often difficult to obtain during stabilization of these challenging fractures.

New fixation approach for transverse metacarpal neck fracture: a biomechanical study

“…The crosshead speed was 10 mm/min. The experimental setup was similar to that used in other studies [ 12 , 15 ]. Force–displacement data were recorded, and the bending stiffness of each specimen was determined.…”

“…Plates, available in regular and locking forms, are internal fixation devices commonly used for metacarpal neck fractures. They provide high mechanical strength, but many complications have been reported, including metacarpal head avascular necrosis, nonunion, severe tendon irritation, and high rate of stiffness due to excessive soft tissue damage [ 1 , 7 , 12 – 14 ]. For the minimization of soft tissue damage and reduction of implant profiles in ORIF, we propose a novel fixation method that integrates K-wires with a cerclage wire.…”

Metacarpal fractures in the athlete

“…A smaller study of open or closed fractures of the metacarpals and phalanges showed equally good results using less prominent plates of 0.6 mm compared to 1.3 mm thickness, without any cases of tendon rupture, nonunion, or hardware removal among the 21 metacarpal fractures [15]. Also, biomechanical studies of newer constructs, including locking plates, shorter length plates, double-row plates (sometimes called "cage," "ladder," or "three-dimensional"), and smaller dual orthogonal plates demonstrate equivalent or superior fixation to standard constructs, thus potentially minimizing soft tissue dissection and/or hardware prominence [16][17][18][19].…”

Practical Management of Metacarpal Fractures

“…A recent anatomical study suggests that when a locking plate is used, two bicortical screws on each side of the fracture is as biomechanically stable as a conventional plate with three bicortical screws on each side of the fracture. 21 (If unicortical locking screws are placed, three should be placed on each side of the fracture.) Furthermore, locking plates are advantageous in fractures that are located very distally or proximally within the metacarpal, where conventional bone screws may have poor purchase.…”