Analysis of the influence of anaesthesia on the clinical and quantitative assessment of the pivot shift: a multicenter international study

Purpose: The main goal of this work was to evaluate the pivot shift test in awake and anesthetized patients by using two different quantitative methodologies and comparing the results with the standard clinical grading, taking advantage of a multicenter international study. Methods: Patients between 16 and 50 years of age undergoing primary unilateral single-bundle anterior cruciate ligament (ACL) reconstruction were considered eligible. The pivot shift test was performed pre-operatively, with the patient awake and again with the patient under general anaesthesia. The pivot shift test was clinically graded as defined by the International Knee Documentation Committee. The instrumented assessment was performed by using two non-invasive acquisition systems; specifically, a system exploiting an inertial sensor and a video-based application developed on a commercial tablet using skin markers. Lateral compartment translation and the tibial acceleration reached during joint reduction were used as quantitative parameters. Results: A total of 103 patients were enrolled in the study. Statistically significant difference was found between the distributions of clinical grade evaluated in awake patients and those under general anaesthesia (P < 0.01). Comparing awake patients to those under general anaesthesia, lower values were found both for tibial acceleration (3.7 ± 1.5 vs 6.0 ± 4.6 m/s², P < 0.01) and lateral compartment translation of the involved limb (2.2 ± 1.7 vs 3.0 ± 2.2 mm, P < 0.01). Conclusions: This study indicated that significant differences in the grading of the pivot shift test exist between awake and anesthetized patients, regardless of the use of quantitative instruments during the evaluation. Actual clinical assessment reported indeed its weakness, presenting subjective variability and dependence on tester’s experience. However, several factors might influence the validity of awake examination such as experience level of examiner and cultural factors, as seen in this international multicenter study. Level of evidence: Prospective comparative study, Level II.