Biomechanical evaluation of 5 fixation devices for proximal interphalangeal joint arthrodesis.

PURPOSE: To determine in a cadaver model which, among 5 fixation methods for proximal interphalangeal (PIP) joint arthrodesis, has the greatest stiffness.

METHODS: Thirty-five cadaver digits were randomly assigned to 1 of 5 fixation groups: oblique K-wire with coronal intraosseous wiring, tension-band wire (TBW), dorsal plate, intramedullary linked screw (IMS), and 90/90 wiring (90/90W). Testing was done by applying bending moments to the PIP joint in the sagittal and frontal planes. The force/displacement curves were used to estimate the stiffness of each construct. Ultimate strength was determined by loading to failure in extension.

RESULTS: The IMS had significantly higher stiffness than all wiring constructs in all planes of motion and significantly greater stiffness in extension than the dorsal plate. The IMS stiffness exceeded 10 N/mm across all bending directions and showed an ultimate strength of 21 N. The plate demonstrated higher stiffness in radial bending than the oblique K-wire with coronal intraosseous wiring and TBW. There were no differences in stiffness between the IMS and plate in all modes of testing except extension. Load-to-failure testing of the devices showed the IMS device to be significantly stronger than the TBW, 90/90W, and plating constructs.

CONCLUSIONS: The IMS resisted larger bending moments than all wiring constructs and showed the greatest ultimate strength when compared with 3 of the tested arthrodesis techniques. The plate was significantly better than 2 of the wiring constructs, but only in radial bending. No differences were found between the, TBW, and 90/90W when compared with each other.

CLINICAL RELEVANCE: The stiffness necessary for a successful PIP joint fusion has not been quantified, but according to this study, the IMS was the most favorable biomechanical construct for initial stability.