Dorsal Plating, Lateral Plating, and Intramedullary Screw Fixation of Extra-Articular Proximal Phalangeal Fractures: A Cadaveric Biomechanical Comparison.

PURPOSE: To provide a biomechanical comparison of dorsal plating, lateral plating and intramedullary screw [IMS] fixation for extra-articular proximal phalangeal fractures.

METHODS: Midshaft osteotomies were performed on 36 cadaveric proximal phalanges. The phalanges were fixed by dorsal plating, lateral plating or IMS fixation, and subjected to a four-point bending force. Force was applied to achieve displacement of 1 mm/s, until construct failure or to a maximum of 10 mm of displacement. Clinical failure was defined as 2 mm of displacement, and force required to result in 1 mm and 2 mm of displacement was recorded, as was mode of failure.

RESULTS: Dorsal plating [127.5 N ± 52.6; 46.51-229.17] and lateral plating [77.1 N ± 25.1; 48.3-113.8] required significantly greater force to achieve 1 mm of displacement when compared to IMS [41.2 N ± 12.4; 20.6-62.3]. Dorsal plating [339.2 N ± 91.8; 158.5-538.6] required significantly greater force than lateral plating [154.5 N ± 33.8; 99.0 -204.4] and intramedullary screw fixation [110.0 ± 38.6; 51.1-189.3] to result in 2 mm of displacement. Lateral and dorsal plating constructs failed through plate bending, screw cut-out or plate failure, whilst IMS failed via implant deformity. All three constructs required greater force to result in even 1 mm of displacement than what is likely subjected through rehabilitation via active motion.

CONCLUSIONS: Lateral plating and IMS fixation offer sufficient stiffness to withstand the likely forces subjected via early active motion without displacement.

CLINICAL RELEVANCE: Dorsal plating required significantly greater force than lateral plating and intramedullary screw fixation to achieve 1 mm of displacement when used in extra-articular proximal phalangeal fractures in an in vitro setting. However, all three modalities confer enough stability to likely withstand the forces associated with active range of motion.