KNEE Clinical grading of the pivot shift test correlates best with tibial acceleration Mattias Ahlde ´n • Paulo Araujo • Yuichi Hoshino • Kristian Samuelsson • Kellie K. Middleton • Kouki Nagamune • Jo ´n Karlsson • Volker Musahl Received: 28 November 2011 / Accepted: 22 December 2011 / Published online: 4 January 2012 Ó Springer-Verlag 2012 Abstract Purpose Recently, different measurement systems have been developed to quantitatively measure the pivot shift in vivo. These systems lack validation and a large inter- examiner variability for the manually performed pivot shift test exists. The purpose of this study was to perform objective measurements of the pivot shift using three dif- ferent measurement devices and to examine the correlation of the measurements with clinical grading of the pivot shift. Methods A cadaver knee on a whole lower body speci- men was prepared to display a high-grade pivot shift. The pivot shift tests were performed three times by 12 blinded expert surgeons using their preferred technique. Simulta- neous data samplings were recorded using three different measurement devices: (1) electromagnetic tracking system using bone-attached and skin-fixed sensors, respectively, (2) triaxial accelerometer system, and (3) simple image analysis. The surgeons graded the knee clinically using pivot shift grades I–III. Correlations were calculated using the Spearman’s rank correlation coefficient. Results The expert surgeons average clinical grading was 2.3 (SD ± 0.5). Clinical grading displayed best correlation with the acceleration of reduction as measured by elec- tromagnetic tracking system with bone-attached sensors (r = 0.67, P \ 0.05). Similar correlation coefficient was found for the acceleration of reduction (r = 0.58, P = 0.05) and the ‘‘jerk’’ component of acceleration (r = 0.61, P \ 0.05) measured by means of the triaxial accelerometer system. Conclusion The pivot shift can be quantified by several in vivo measurement devices. Best correlation with clinical grading was found with tibial acceleration parameters. Future studies will have to analyze how quantitative parameters can be utilized to standardize clinical grading of the pivot shift. Level of evidence Diagnostic study, Level II. Keywords Knee Á Anterior cruciate ligament Á Pivot shift Á Laxity Á Kinematics Introduction Control of rotatory laxity is necessary to improve anatomic anterior cruciate ligament (ACL) reconstruction [15, 25, 27]. In contrast to anterior–posterior (AP) laxity testing, the pivot shift has been correlated with functional outcome after ACL injury and ACL reconstruction [13, 14, 16]. The pivot shift test also represents the patients’ most typical symptom of ACL insufficiency, that is, ‘‘giving-way.’’ The pivot shift has been reported to most specifically display the abnormal knee kinematics in ACL-deficient or ACL- reconstructed knees compared with static testing of rota- tional laxity or AP laxity [2, 10, 18–22, 26]. However, the pivot shift test has repeatedly been shown to be subjective in terms of interpretation and conduction [1, 11, 17, 23]. M. Ahlde ´n (&) Á K. Samuelsson Á J. Karlsson Department of Orthopaedics, Sahlgrenska University Hospital/ Mo ¨lndal, 431 80 Mo ¨lndal, Sweden e-mail: mattias.e.ahlden@vgregion.se M. Ahlde ´n Á P. Araujo Á Y. Hoshino Á K. K. Middleton Á V. Musahl Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Pittsburgh, PA 15213, USA K. Nagamune Department of Human and Artificial Intelligent Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan 123 Knee Surg Sports Traumatol Arthrosc (2012) 20:708–712 DOI 10.1007/s00167-011-1863-8