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Variable Tension Across the Radiocarpal Joint Can Be Generated Using a Dorsal Spanning Plate
Gregory K Faucher, MD; Neal B Zimmerman, MD; Brent Parks, MSc
Curtis National Hand Center, Baltimore, MD
Introduction: The original technique for dorsal wrist spanning plates used to treat distal radius fractures described using the third metacarpal as the distal fixation point. Many surgeons alternatively choose to fix to the second metacarpal distally. The decision is based largely on “the fracture characteristics and the surgeon’s preference.” Little evidence exists to guide the surgeon’s choice regarding the location of the distal fixation. We hypothesize that fixation of the plate to either the second or third metacarpal will provide a selective distraction force through either the radial or ulnar column of the radius, respectively.
Methods: This is a cadaveric, biomechanical study. 8 specimens consisted of the forearm to the fingertips stripped of soft tissue with care to preserve wrist ligaments, wrist capsule and ulnar sleeve. Each specimen served as its own control. Distraction forces were applied to the second metacarpal and then the third metacarpal, or vice versa. Each radius was osteotomized transversely one centimeter proximal to Lister’s tubercle. The second and third metacarpals were cut and two-hole plates were placed distally to apply the distraction forces. The empty hole was utilized for attachment to a custom fabricated load frame. Load cells were then mounted proximally, one each on the radial and ulnar aspects of the distal radius fragment to measure the differential load applied to the radial and ulnar columns of the distal radius. Load was then applied sequentially through each metacarpal beginning at 4.5 N and ending at 89 N. Load measurements were recorded through both load cells at each force interval.
Results: Loading through the second ray resulted in significantly more distraction force transmitted through the radial column of the distal radius fragment at all the force intervals applied. Likewise, loading through the third ray resulted in significantly higher force transmission through the ulnar column of the distal radius. In both cohorts, force transmission increased linearly in response to higher loads.
Conclusion: Distraction plating to either the second or third metacarpal results in differential tensioning of the ulnar and radial columns of the distal radius. This may assist in fracture reduction and maintenance, thereby guiding the surgeon’s operative strategy.
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