Evaluation of rotational instability in the anterior cruciate ligament deficient knee using triaxial accelerometer: a biomechanical model in porcine knees

Purpose To measure the acceleration in multiple directions of the rotational instability in ACL deficient models using porcine knees. Methods Ten porcine knees were tested with ACL intact and tear models. The pivot shift test was performed manually, and the acceleration of the pivot shift phenomenon was recorded by the use of a triaxial accelerometer. Tests were repeated in four different ACL states: (1) intact; (2) partial AM deficient; (3) complete AM deficient, and (4) complete ACL (AM and PL) deficient. The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between different ACL conditions. Results Significantly increased accelerations were observed in the complete deficient ACL model, while the partial ACL tear models demonstrated a slight increase without statistical significance. The accelerometer detected stepwise increases in the acceleration with the extent of ACL tear. Additionally, the PL bundle exhibited the largest contribution for rotational instability (80.4%) when compared with the AM (19.5%) bundles. Conclusion Triaxial accelerometer could serve as a quantitative evaluation of rotational instability. The present study demonstrated that PL bundle has the most important contribution for rotational instability (80.4%) when compared to IM bundle (0.01%) and AM bundle (19.5%) in porcine knee model.