Biomechanical evaluation of volar locking plates for distal radius fractures.

PURPOSE

Fixed-angle devices have been a major advancement in orthopedic fracture care and have become an attractive option for fixation of distal radius fractures. Several volar locking plates exist, but there is insufficient literature comparing the strengths of these plates. This study compares the biomechanical strength of two popular volar locking plate systems (Synthes LCP and Hand Innovations DVR-A) along with a nonlocking volar T-plate (Synthes).

METHODS

Twenty-three formalin-fixed cadaveric forearms were divided into three groups with similar ages and bone densities. An unstable extra-articular fracture was created using a standardized osteotomy. Each group was fixed with one of the three plates. Each specimen was loaded in axial compression for 2000 cycles at a force of 400 N. Each specimen that completed cyclic testing was loaded to failure. Stiffness, yield point, and ultimate strength were recorded for each construct.

RESULTS

Each fixed-angle construct completed all 2000 cycles. The nonlocking plates failed at an average of 560 cycles. The mean stiffness of the DVR-A, LCP, and the volar T-plates were 277.00, 343.17, and 175.67 N/mm, respectively. There was a statistically significant difference between both fixed-angle plates and the nonlocking plate (p < 0.05). The difference between each fixed-angle construct did not reach significance. Yield point and ultimate strength could only be determined for the two fixed-angle devices. There was no statistically significant difference between the constructs for both yield point (DVR-A = 855.56 N, LCP = 894.15 N) and ultimate strength (DVR-A = 1,021.97 N, LCP = 1,114.87 N).

CONCLUSIONS

Given our data, fixed-angle constructs withstand cyclical loading representing normal physiologic forces encountered during post-operative rehabilitation. There was no significant biomechanical difference between the two fixed-angle constructs. Our results support that volar fixed-angle locking plates are an effective treatment for unstable extra-articular distal radius fractures, allowing early postoperative rehabilitation to safely be initiated.