Abstract
BackgroundMetacarpal shaft fracture is a common fracture in hand trauma injuries. Surgical intervention is indicated when fractures are unstable or involve considerable displacement. Current fixation options include Kirschner wire, bone plates, and intramedullary headless screws. Common complications include joint stiffness, tendon irritation, implant loosening, and cartilage damage.ObjectiveWe propose a modified fixation approach using headless compression screws to treat transverse or short-oblique metacarpal shaft fracture.Materials and methodsWe used a saw blade to model transverse metacarpal neck fractures in 28 fresh porcine metacarpals, which were then treated with the following four fixation methods: (1) locked plate with five locked bicortical screws (LP group), (2) regular plate with five bicortical screws (RP group), (3) two Kirschner wires (K group), and (4) a headless compression screw (HC group). In the HC group, we proposed a novel fixation model in which the screw trajectory was oblique to the long axis of the metacarpal bone. The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; thus, the screw did not damage the articular cartilage. The specimens were tested using a modified three-point bending test on a material testing system. The maximum fracture forces and stiffness values of the four fixation types were determined by observing the force–displacement curves. Finally, the Kruskal–Wallis test was adopted to process the data, and the exact Wilcoxon rank sum test with Bonferroni adjustment was performed to conduct paired comparisons among the groups.ResultsThe maximum fracture forces (median ± interquartile range [IQR]) of the LP, RP, HC, and K groups were 173.0 ± 81.0, 156.0 ± 117.9, 60.4 ± 21.0, and 51.8 ± 60.7 N, respectively. In addition, the stiffness values (median ± IQR) of the LP, HC, RP, and K groups were 29.6 ± 3.0, 23.1 ± 5.2, 22.6 ± 2.8, and 14.7 ± 5.6 N/mm, respectively.ConclusionHeadless compression screw fixation provides fixation strength similar to locked and regular plates for the fixation of metacarpal shaft fractures. The headless screw was inserted obliquely to the long axis of the metacarpal bone. The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; therefore the articular cartilage iatrogenic injury can be avoidable. This modified fixation method may prevent tendon irritation and joint cartilage violation caused by plating and intramedullary headless screw fixation.
Highlights
Metacarpal shaft fractures account for the second highest number of metacarpal fractures, following only metacarpal neck fractures
The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; the screw did not damage the articular cartilage
The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; the articular cartilage iatrogenic injury can be avoidable
Summary
Metacarpal shaft fractures account for the second highest number of metacarpal fractures, following only metacarpal neck fractures. Metacarpal shaft fractures commonly occur due to axial loading, torsion, or direct blows. Fractures can be classified as oblique, transverse, or comminuted. Axial loading and direct blows often cause transverse or comminuted fractures, whereas torsion commonly results in oblique or spiral fractures. Oblique and spiral fractures, which account for approximately 75% of fracture cases, are the most common [2]. The indications for surgery are unstable fractures or overlapping fractured bone ends that cause excessive shortening of bone length, angulation deformity, or the rotation deformity of fracture sites [3]. In short-oblique or transverse metacarpal shaft fractures, fracture sites are subject to angulation deformity because interosseous muscles exert traction force on the fracture site. Surgical intervention is indicated when fractures are unstable or involve considerable displacement. Common complications include joint stiffness, tendon irritation, implant loosening, and cartilage damage
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