Comparative Kinematic Evaluation of TPLO and TPLO Combined with Extra-articular Augmentation: A Biomechanical Study

Introduction: Pivot shift, a phenomenon describing rotational and translational stifle instability, has been reported as a cause of ongoing lameness in dogs after TPLO and has encouraged surgeons to combine TPLO with an extra-articular lateral stabilization in selected cases, such as hyperlax stifles. At present, no clinical tests evaluate combined rotational and craniocaudal instability.

Materials and Methods: Traditional tibia compression test (TCT), TCT combined with an external (pTCText) and internal rotational moment (pTCTint) were performed on cadaveric hind limbs. Kinetic and 3D-kinematic data were collected and compared among the conditions (1) normal, (2) cranial cruciate ligament deficient, (3) TPLO and (4) TPLO combined with lateral suture augmentation (TPLO-IB).

Results: TCT did not detect a difference in cranial tibial translation when comparing intact to TPLO (p = 0.17), while pTCText and pTCTint resulted in greater translation after TPLO (p < 0.001). Cranial translation with TCT, pTCText, and pTCTint was not different between intact and TPLO-IB. pTCText led to internal tibial rotation relative to the starting point and was greater in TPLO compared with intact (p = 0.002), but not different between intact and TPLO-IB (p = 1).

Discussion/Conclusion: Our Results provide evidence that, in contrast to traditional TCT, a rotational moment combined with TCT leads to severe cranio-caudal and rotational instability in TPLO-stabilized stifles. TPLO-IB neutralized both cranial tibial thrust and internal rotational instability when performing any of the tests. Further clinical studies should evaluate the application of these new tests in the assessment of rotational stability before and after TPLO.

Acknowledgement: The senior author is a consultant and receives financial compensation from Arthrex.

Publication History

Article published online:
26 October 2022