Failure Mode and Bending Moment of Canine Pancarpal Arthrodesis Constructs Stabilized with Two Different Implant Systems

Objective— To compare failure mode and bending moment of a canine pancarpal arthrodesis construct using either a 2.7 mm/3.5 mm hybrid dynamic compression plate (HDCP) or a 3.5 mm dynamic compression plate (DCP). Study Design— Paired in vitro biomechanical testing of canine pancarpal arthrodesis constructs stabilized with either a 2.7/3.5 HDCP or 3.5 DCP. Sample Population— Paired cadaveric canine antebrachii (n=5). Methods— Pancarpal arthrodesis constructs were loaded to failure (point of maximum load) in 4‐point bending using a materials‐testing machine. Using this point of failure, bending moments were calculated from system variables for each construct and the 2 plating systems compared using a paired t‐test. To examine the relationship between metacarpal diameter and screw diameter failure loads, linear regression was used and Pearson' correlation coefficient was calculated. Significance was set at P <.05. Results— HDCP failed at higher loads than DCP for 9 of 10 constructs. The absolute difference in failure rates between the 2 plates was 0.552±0.182 N m, P =.0144 (95% confidence interval: −0.58 to 1.68). This is an 8.1% mean difference in bending strength. There was a significant linear correlation r=0.74 ( P ‐slope=.014) and 0.8 ( P ‐slope=.006) between metacarpal diameter and failure loads for the HDCP and 3.5 DCP, respectively. Conclusion— There was a small but significant difference between bending moment at failure between 2.7/3.5 HDCP and 3.5 DCP constructs; however, the difference may not be clinically evident in all patients. Clinical Relevance— The 2.7/3.5 HDCP has physical and mechanical properties making it a more desirable plate for pancarpal arthrodesis.