Will a malunited proximal phalanx affect the outcomes of vascularized PIP joint transfers?

Abstract

Post-traumatic osteoarthritis of the proximal interphalangeal joint (PIPJ) substantially impairs hand function, and vascularized joint transfer (VJT) can be used to restore range of motion (ROM). However, malunion, particularly dorsal angulation of the proximal phalanx (P1), can occur postoperatively. We aimed to analyze the causes and impact of malunited P1 on surgical outcomes in VJT cases and provide insights regarding configuration and corrective osteotomy. The authors retrospectively reviewed 61 VJT cases from 2008 to 2022, with the primary indication being PIPJ osteoarthritis and limited ROM. Malunion was defined as dorsal angulation >10°. Fixation methods and postoperative perfusion were analyzed. The primary outcome was PIPJ ROM, with particular focus on extension lag. Malunion and non-union were identified in 11 (18.0%) and 8 (13.1%) cases, respectively. The average sagittal angulation increased from 3.21° immediately after surgery to 8.23° at follow-up. Ten cases (16.4%) required corrective osteotomy. The average ROM achieved was 59.41°, with no significant difference between cases with and without malunion. Smokers had significantly poorer outcomes, including lower ROM (49.7° vs. 64.5°, p < 0.001) and greater extension lag (20.2° vs. 16.3°, p = 0.238). Shape discrepancy between the P1 shaft of the finger and toe complicates stable osteosynthesis during VJT, and the inherent nature of the muscles increases susceptibility to dorsal angulation malunion. Fixation method and transferred joint perfusion may be associated with malunion. No cause and effect relationship was found between P1 malunion with surgical outcomes. The decision to perform corrective osteotomy should consider other clinical factors.