An Ex Vivo Mechanical Evaluation of Single Versus Double Semitubular Plate Fixation of a Transverse Distal-Third Scapular Osteotomy in the Dog

Objective - To compare single versus double semitubular plate fixation for scapular body fractures. Study Design - Ex vivo mechanical study. Sample Population - Eighteen paired cadaveric canine scapulae. Methods - Transverse scapular body osteotomies were created in the distal third of 18 pairs of scapulae. One scapula of each pair was repaired with a single plate, whereas the contralateral scapula was repaired with 2 plates. Initial strength and stiffness of the constructs were measured in 10 pairs of scapulae. Eight pairs of scapulae underwent cyclic loading and then were subjected to failure testing. Results - Double-plate fixation was significantly stronger (3,899 ± 632 N) but not stiffer (614 ± 130 N/mm) than the single-plate fixation (3, 238 ± 935 N and 537 ± 202 N/mm, respectively). Cyclic loading variables were not significantly different between the 2 methods of fixation. After cyclic loading, double-plate fixation was significantly stronger (2,916 ± 618 N) than single-plate fixation (2,347 ± 495 N). There was no significant difference (P = .11) in stiffness between double- versus single-plate fixations: 734 ± 247 N/mm and 595 ± 139 N/mm, respectively. Conclusions - Double-plate fixation was generally stronger and suffer than single-plate fixation. Because all constructs failed at loads that greatly exceeded those estimated to occur clinically, any difference between the 2 methods of fixation probably is not clinically relevant. Clinical Relevance - Single-plate fixation may be of sufficient strength for fixation of scapular body fractures.