The subcapital fracture of the 5th metacarpal bone is one of the most common bony injuries in the hand skeleton area [1, 2]. It typically results from an axial force acting on the metacarpal bone or blunt force, such as a punch against a hard object or a fall on the fist [3-6]. The subcapital fracture of the 5th metacarpal bone, known as a "boxer's fracture," occurs less frequently in experienced boxers (protected by punching technique, taping, boxing gloves) and more often due to fights outside the boxing ring [7, 8].
If there is a dorsal impact on the distal metacarpal bones with extended fingers, fractures of the metacarpal head occur more frequently, usually resulting in intra-articular fractures. Triggers include falls and direct trauma (e.g., a hammer blow) to the metacarpal head [3-6].
The following factors should be considered when selecting the treatment regimen – conservative or surgical [3, 4, 9, 10]:
- Flexion position, primarily of the distal fragment
- Axial misalignment
- Rotational misalignment of the affected finger
- Shortening of the fractured metacarpal bone
- Fracture type, e.g., intra-articular involvement
- Patient's preference or functional demands
Special cases include open fractures, which should generally be treated surgically. Another special case is multifragment fractures, which also typically require surgical intervention [3].
If there are no significant dislocations, axial deviations, or rotational misalignments, metacarpal fractures can generally be treated conservatively. After a possible closed reduction, a splint immobilization can be performed for fractures that are not significantly displaced and without risk of dislocation. The intrinsic-plus position with a flexion in the metacarpophalangeal joints of 70° should be observed [11].
In subcapital metacarpal fractures, the existing palmar comminution zone and the palmar pull of the musculature often prevent stable retention, and rotational misalignment frequently occurs. Regarding palmar angulation, surgical stabilization is recommended for the 4th and 5th metacarpal bones starting from a palmar dislocation of 40–50° [2, 12]. For the rare subcapital fractures of the 2nd and 3rd metacarpal bones, surgical therapy is advised starting from an angulation of 15°.
The extent of palmar angulation at which open reduction and osteosynthesis are indicated is now inconsistently evaluated in the literature. A systematic review of 18 studies from 2021 found no correlation between the degree of palmar angulation and the clinical functional outcome [13]. Through closed reduction and splint immobilization, an alignment of 9 – 29° can be achieved and maintained. Studies comparing surgical with conservative therapy showed only an improved aesthetic outcome with surgical therapy, not the reduction result and functionality. Additionally, surgical therapy involves a correspondingly higher risk of intervention, higher treatment costs, and a longer rehabilitation phase or work incapacity. As a statement of this work, palmar angulations of up to 70° can be accepted in up to 90% of cases. However, surgical treatment is indicated for patients with special functional demands, with the therapy method of choice still being antegrade intramedullary nailing.
A prospective randomized study of 72 patients from 2020 compared the results between conservative treatment with closed reduction and splint immobilization and buddy taping without reduction [14]. No benefit was found for the group with reduction and splint treatment compared to the buddy tape group. There were no differences in angulation after 9 weeks, and the functional results were better in the functionally treated buddy tape group with a lower complication rate (MCP and PIP contractures were leading in the splint treatment group). Additionally, the duration of work incapacity in the immobilization group was 28 days longer.