Introduction: The Darrach procedure (complete resection of distal ulna) is commonly used for definitive treatment of end- stage distal radioulnar joint (DRUJ) arthritis. This resection alone often results in treatment failure due to ulnar stump instability in a dorsal-palmar direction and ulnar convergence. Modified Darrach procedures with tenodesis have improved outcomes, but none have completely resolved these issues. Thus, we propose a novel technique of fixation via an internal brace.
Purpose: To evaluate stability and degree of dorsal-palmar displacement with an internal brace fixation (IBF) versus a modified extensor carpi ulnaris tenodesis (ECUT) following a Darrach procedure.
Methods: We tested six fresh-frozen cadaveric upper extremities. Specimens underwent identical Darrach procedures and were subsequently divided into two groups: modified ECUT (Group One) (n=3) and IBF (Group Two) (n=3). Rotational force was applied at the metacarpals, measuring the force required to achieve 45 degrees of pronation and 45 degrees of supination. Ulnar displacement was measured using fluoroscopy at each end point as well as in neutral position.
Results: Group Two had significantly greater mean displacement during pronation 0 .9cm dorsally and 0cm in Group One (p=0 .0419). Group Two also had significantly more mean displacement during supination as well with 0.9cm dorsal displacement versus 0.73cm volar displacement in Group One (p=0 .0381). Group One required more force to achieve pronation 3.5kg vs 1.5kg in Group Two (p=0 .0226). Force differences during supination were not significant.
Conclusions: In this series, IBF did not seem to increase ulnar stump stability and was outperformed by ECUT in terms of dorsal-palmar displacement during rotation. Our results showed IBF had greater displacement with less force during pronation when compared to ECUT. Future studies are necessary to establish the viability of this novel technique.
