Effect of Tibial Plateau Angle on Cranial Cruciate Ligament Strain: An Ex Vivo Study in the Dog

Objective: To evaluate the relationship between tibial plateau angle (TPA) and strain in the intact cranial cruciate ligament (CCL) during axial loading. Study Design: Ex vivo mechanical testing study. Sample Population: Cadaveric canine stifles (n=6). Methods: A bicentric and uni-radial Slocum saw blade was used to perform the osteotomy on each stifle and a custom designed plate was secured to the leg. Each stifle was loaded and CCL strain and axial displacement were recorded. TPA was adjusted to -20°, -10°, 0°, +10°, +20° of normal. Change in the strain was assessed during the axial loading period. Results: For all specimens, linear displacement of the femur and CCL strain increased with increasing axial load. Mean change in strain was 4.41, 5.26, 6.02, 6.3, and 7.39 at -20°, -10°, 0°, 10°, and 20°, respectively. The R-squared for the linear regression equation was 0.91, suggesting a strong relationship between change in TPA and CCL strain. Conclusions: The mechanical testing model used found CCL strain increased with increasing axial load regardless of the TPA. Decreasing TPA decreased strain in the intact CCL.