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Gastrocnemius Muscle-Tendon Unit Tension Affects Cranial Tibial Translation
07 August 2019 (online)
Introduction: Cranial cruciate ligament (CrCL) deficiency is a leading cause of canine lameness. The circumstances that promote CrCL injury remain largely unknown. We hypothesized that gastrocnemius muscle-tendon unit (GMT) tension induced by tarsal flexion plays a role in generating cranial tibial translation (CTT) in the CrCL-deficient stifle.
Materials and Methods: The effects of stifle and hock angles on CrCL length, CTT, and GMT length in intact and CrCL-deficient cadaveric canine pelvic limbs (n = 10) were measured by tracking fiduciary markers in the attachments of the CrCL and GMT during in vitro loading (20% body weight) of limb specimens at 3 stifle and 3 tarsal angles. Repeated measures ANOVA assessed the effects of CrCL condition (intact, cut), limb load (unloaded, loaded), and stifle flexion (80, 100, and 120°), tarsal flexion (90, 110, and 130°) angles on CrCL length, CTT, and GMT length.
Results: Mean CrCL length was longer in loaded CrCL-deficient limbs only in combined tarsal flexion and stifle extension (p = 0.018). Tarsal flexion had a large effect on GMT length, particularly in combination with stifle extension (p < 0.001). CTT was greater with stifle extension (p < 0.001), and with tarsal flexion (p < 0.001).
Discussion/Conclusion: The data support the hypothesis that CrCL-deficient canine stifles exhibit greater CTT due to GMT tension induced by tarsal flexion. Whole limb biomechanics should be considered in approaches to treatment of CrCL disruption.
Acknowledgment: Center for Companion Animal Health, Students Training in Advanced Research, and Veterinary Student Scholars Program, Morris Animal Foundation. There are no conflicts of interest.