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Volar Radiocarpal Arthrotomy: An Anatomical and Biomechanical Feasibility Analysis of a Novel Approach for Use in Distal Radius Fracture Repair
Diana G Douleh, MD1, Todd H Baldini, MS1, Michael Rogers, PhD2, Patrick Carry, MS3, Fraser J Leversedge, MD1 and Alexander Lauder, MD4, (1)University of Colorado School of Medicine, Aurora, CO, (2)University of Colorado Denver, Denver, CO, (3)Children's Hospital Colorado, Aurora, CO, (4)Denver Health Medical Center, Denver, CO

Anatomical and biomechanical feasibility of a novel volar radiocarpal arthrotomy for direct articular visualization, pertinent to distal radius (DR) fracture repair was evaluated.

Materials & Methods:
Ten upper extremity matched-pair specimens were tested. For each pair, one limb underwent trans-flexor carpi radials (FCR) approach with volar arthrotomy with partial sectioning of the long radiolunate and short radiolunate ligaments to visualize the DR articular surface (Group 1; Figure 1) and the other underwent standard trans-FCR approach without arthrotomy (Group 2). Following arthrotomy in Group 1 specimens, quantification of the visualized articular surface area was documented by systematic photography. Following biomechanical testing, wrist disarticulation facilitated complete surface area photographic assessment and calculation as to the percentage area visualized via arthrotomy.

Following capsular repair (Group 1), all specimens (Groups 1 and 2) underwent biomechanical testing, including axial, volar, and dorsal loading, to assess carpal instability using both fluoroscopy and motion capture. Incremental weights (0lb, 5lb, 10lb, 20lb, 40lb) during axial loading were applied through a 2mm Steinmann pin placed into the intramedullary canal of the third metacarpal. Volar and dorsal translation was assessed by applying force perpendicular to the long axis of the radius with incremental loads (0lb, 5lb, 10lb, 20lb). Lunate overhang (Lo) was measured as a surrogate for ulnar translation using the Gilula method. Dorsal and volar translation was assessed by measuring Lo over the dorsal or volar radial cortex. Lo was divided by the full width of the lunate to determine a ratio. Relative translation of the lunate and scaphoid (vs radius) was assessed using a MaxTRAQ motion capture system. Statistical comparisons between groups for each loading increment were performed with paired two-tailed t-tests on matched specimens.

76% (range 69-90%) of the DR surface area was visualized utilizing the volar arthrotomy. Ulnar translation of the lunate remained below previously established significance levels of 2 mm in both groups, pre- and post-dorsal capsulotomy at all loads. No significant differences in ulnar, volar, or dorsal translation were identified with increasing loads between groups (P>0.05; Table 1).

Our cadaveric study supports the use of volar radiocarpal arthrotomy during DR fracture repair to provide enhanced visualization of the scaphoid and lunate facets of the DR articular surface without causing iatrogenic biomechanical radiocarpal instability.

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