A 3-Dimensional Printed Dynamic External Fixator for the Treatment of Proximal Interphalangeal Fracture-Dislocations: A Biomechanical Study

Purpose: This study evaluated the efficacy of a 3-dimensional printed dynamic external fixator for treating proximal interphalangeal (PIP) fracture-dislocations. The null hypothesis was that there would be no difference in maintaining PIP joint reduction between a 3-dimensional printed dynamic external fixator (3DPDEF) and the pins and rubbers traction system (PRTS).

Methods: Ten cadaveric fingers underwent an oblique osteotomy at the base of the middle phalanx, recreating an unstable dorsal PIP fracture-dislocation. The percentages of compromised articular surface and middle phalanx dorsal displacement were measured. Both fixators were randomly placed on each digit and underwent 1,400 flexion-extension cycles. Efficacy, determined by joint reduction and maintenance of dorsal translation correction, was assessed using fluoroscopy before and after the cycles.

Results: The mean compromised articular surface was 50.8%. After osteotomy, PIP joint subluxation occurred at 37.8° flexion. Dorsal translation after osteotomies was 2.8 mm. After applying the 3DPDEF and the PRTS, it was 0 mm and 0.1 mm, respectively. During the cycles, all the joints remained stable and reduced. Dorsal displacement after cycles was -0.1 mm for the 3DPDEF and 0 mm for the PRTS. The mean translation difference between both fixators was 0.1 and 0 mm before and after the cycles. The translation differences before and after the cycles were 0.1 mm for both dynamic fixators.

Conclusions: The 3DPDEF is a suitable option for PIP fracture-dislocations, providing stability comparable to that of the PRTS while offering benefits, such as easy placement, controlled distraction, and clear visualization of the articular surface.

Clinical relevance: This external fixator, characterized by its efficacy, low cost, and simplicity of application, broadens the options available to address PIP fracture-dislocations.