Journal of Hand Surgery | 2017, Aug. Volume 42, Issue 9, Pages 748.e1–748.e8
Purpose: To compare the biomechanical properties of second versus third metacarpal distal fixation when using a radiocarpal spanning distraction plate in an unstable distal radius fracture model.
Methods: Biomechanical evaluation of the radiocarpal spanning distraction plate comparing second verus third metacarpal distal fixation was performed using a standardized model of an unstable wrist fracture in 10 matched-pair cadaveric specimens. Each fixation construct underwent a controlled cyclic loading protocol in flexion and extension. The resultant displacement and stiffness were calculated at the fracture site. After cyclic loading, each specimen was loaded to failure. The stiffness, maximum displacement, and laod to failure were compared between the 2 groups.
Results: Cyclic loading in flexion demonstrated that distal fixation to the third metacarpal resulted in grater stiffness compared with the second metacarpal. There was no significant difference between the 2 groups with regards to maximum displacement at the fracture site in flexion. Cyclic loading in extension demonstrated no significant difference in stiffness or maximum displacement between the 2 groups. The average load to failure was similar for both groups.
Conclusions: Fixation to the third metacarpal resulted in greater stiffness in flexion. All other biomechanical parameters were similar when comparing distal fixation to the second or third metacarpal in distal radius fractures stabilized with a spanning internal distraction plate.
Clinical relevance: The treating surgeon should choose distal metacarpal fixation primarly based on fracture pattern, alignment, and soft tissue integrity. If a stiffer construct is desired, placement of the radiocarpal spanning at the third metacarpal is preferred.