Static anteroposterior knee laxity tests are poorly correlated to quantitative pivot shift in the ACL-deficient knee: a prospective multicentre study

ObjectiveTo determine the relationship between preoperative static knee joint laxity and non-invasive quantitative pivot shift (QPS) in patients with anterior cruciate ligament (ACL) rupture.MethodsPatients with an ACL injury participating in a multicentre trial were analysed if they had complete preoperative data on the following laxity tests: the rolimeter, the KT-1000 (134 N and manual maximum force), the Lachman, the anterior drawer and QPS. The QPS was assessed via a non-invasive inertial sensor system and an image analysis system for tibial acceleration and lateral tibial translation, respectively. Awake examination and examination under anaesthesia (EUA) were performed. Correlation between absolute values of static laxity and the QPS for each leg was assessed by Spearman’s rho. The Lachman and the anterior drawer were dichotomised into low- and high-grade, and differences between the groups in terms of continuous values of QPS were assessed.ResultsA total of 58 patients were included (41.4% women, mean age 27.1±9.8 years). Awake static laxity and QPS acceleration were negatively correlated in the ACL-deficient knee, meaning that a greater acceleration correlated to a lesser static tibial translation, and vice versa. The mean QPS acceleration correlated with the static tests as follows: the rolimeter r=−0.30 (P=0.024), the KT-1000 134 N r=−0.25 (P=0.06) and the KT-1000 manual maximum r=−0.37 (P=0.004). A negative correlation between awake QPS acceleration and the static tests was also shown for the non-involved knee. Patients with a high-grade Lachman’s test in the EUA had significantly greater QPS acceleration (P=0.0002) and QPS translation (P<0.001) compared with patients with a low-grade. The corresponding analysis for the anterior drawer showed a significantly greater QPS translation in the high-grade group (P=0.01), while no differences were found in the QPS acceleration.ConclusionStatic anteroposterior and dynamic knee laxities, as presented by QPS, are poorly correlated in the ACL-deficient knee and should therefore be considered as separate entities of the knee examination. These findings strengthen the implementation of non-invasive technology for quantification of the pivot shift when establishing treatment algorithms for ACL reconstruction.Level of evidenceLevel III, prospective cohort.