Post-Reduction Stability of the Proximal Interphalangeal Joint after Dorsal Fracture Dislocation-A Cadaveric Study.

Background: Proximal interphalangeal joint (PIPJ) dorsal fracture dislocations (DFD) are challenging injuries. Treatment aims to achieve stability of the PIPJ after reduction so that early motion can be initiated. We studied how increasing articular destruction would affect post reduction stability and investigate the amount of traction and PIPJ flexion needed to maintain the reduction.

Methods: Increasing amounts (20%, 40% and 60%) of damage to the volar lip of the middle phalanx in cadaveric specimens were created to represent PIPJ DFD that were stable, of tenuous stability and frankly unstable. Traction forces and PIPJ flexion needed to maintain the reduction were then measured.

Results: The PIPJ DFD with 20% damage were stable and did not subluxe while the one with 40% articular involvement was stable after reduction. For unstable the PIPJ with 60% involvement, the more the PIPJ was flexed, the less traction force was needed to hold the joint in reduction. For PIPJ flexion of 20 degrees, a minimum 4.4N of force is needed to maintain reduction while PIPJ flexion of 10 degrees required a minimum 5.0N of force. No amount of force could maintain PIPJ reduction if traction was performed in full extension.

Conclusions: In our model, PIPJ DFD with less than 30% articular damage are stable while those with 30% to 50% of involvement have tenuous stability. For the unstable PIPJ DFD, traction obviates the need for excessive flexion of the PIPJ to maintain joint reduction. This information should be considered in treatment modalities for PIPJ DFD, as well in the design of external traction devices for the treatment of PIPJ DFD.