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Biomechanical Analysis of Dual-Plate Allograft Reconstruction for Expansile Bone Lesions of the Metacarpal
Mathangi Sridharan, MD
1, Alyssa Tomkinson, BS
2, Mikayla Mefford, BS
1, Kasra Rahmati, BS
1, Nicholas Bernthal, MD
1, Tyler R. Clites, PhD
3; Lauren E Wessel, MD
4(1)University of California, Los Angeles, Santa Monica, CA, (2)University of California, Los Angeles, Los Angeles, CA, (3)UCLA, Los Angeles, CA, (4)David Geffen School of Medicine at UCLA, Los Angeles, CA
Introduction: Expansile lesions of the metacarpal require unique consideration in oncologic reconstruction given differential needs in weightbearing, motion, and dexterity in the upper extremity. While allograft reconstruction can reliably restore native anatomy, it often requires a period of immobilization to allow for healing at the allograft-host junction prior to commencement of weightbearing. This biomechanical study investigates whether reconstruction of expansile lesions of the metacarpal with fibular allograft and dual-plate construct is strong enough for immediate weight-bearing post-operatively.
Materials and Methods: Twelve cadaveric middle finger metacarpals (6 matched pairs) from adult donors were utilized. One side of each pair was randomly assigned to undergo allograft reconstruction with dual-plating (experimental construct). The matched contralateral side was assigned to the control construct, a transverse fracture with standard, 8-hole dorsal plating, given that this construct allows for immediate weight-bearing in prior cadaveric studies. In the experimental construct, an expansile bone lesion was simulated in the native metacarpal by resecting 1.5cm from the proximal carpometacarpal joint to 1.5cm from the distal articular surface. Fibular allograft equal in length to the resected segment was used to reconstruct the lesion, with orthogonal dual plating. Both constructs used locking screws. Biomechanical testing was performed by a 6-degrees-of-freedom robotic KUKA manipulator. The distal portion of each specimen was clamped in place and a cantilever bending force was applied by the KUKA to test load to failure. Failure was defined as periprosthetic fracture, fracture displacement, or screw pullout. Paired
t-tests were used to compare load to failure between matched pairs (R studio). Significance was set at P<0.05.
Results: The load to failure of dual-plate allograft constructs did not significantly differ from the control construct, 478.5+/-231.3N (95% CI 235.7-721.3N) vs 356.7 +/- 72.9N (95% CI 280.2-433.2N), P=0.2. Dual-plate allograft constructs failed at the proximal allograft-native bone interface followed by screw pullout. Single-plate transverse fracture constructs failed via fracture displacement, then screw pullout from the distal segment.
Conclusion: Dual-plate allograft constructs fail at similar loads and mechanisms to single-plated transverse metacarpal fractures. This suggests that dual-plate allograft reconstruction for expansile bone lesions of the metacarpal may allow patients to begin immediate weight-bearing and motion post-operatively, this decreasing the risk of stiffness and contracture after oncologic reconstruction.
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