PURPOSE The pivot shift (PS) test is commonly used to diagnose and evaluate the dynamic instability of the knee joint in cases of anterior cruciate ligament (ACL) tear. There is a need of a reliable and inexpensive tool which is easily available to measure PS objectively in a clinical setting. The purpose of this study was to evaluate the use of a smartphone, which is readily available, to assess the PS phenomenon. METHODS Seventeen patients with unilateral ACL-injured knees, undergoing ACL reconstruction, were enrolled in the study. PS was initially graded according to the International Knee Documentation Committee classification by two observers. The PS test was then performed by them in normal and injured knees under anaesthesia using a smartphone attached to Gerdy's tubercle. Acceleration changes during the PS test were recorded using the smartphone accelerometer application. Intra-observer and inter-observer reliability of the test among the two observers were evaluated. Acceleration changes were compared between the injured and normal knees, and also between the clinical grades of PS. Diagnostic utility of the smartphone accelerometer was examined by a receiver operating characteristic curve analysis. RESULTS Intra-observer and inter-observer reliability were high for the smartphone accelerometer. The acceleration change was higher in the ACL-injured knees than in normal knees. The mean acceleration change was 2.54 m/s2 (SD = 0.97) in ACL-injured knees and 0.73 m/s2 (SD = 0.19) in normal knees (p < 0.001). The mean acceleration change of Grade 1 knees was 1.89 m/s2 (SD = 0.57), and that of knees of Grade 2 and above were 2.99 m/s2 (SD = 0.95) (p < 0.05). Sensitivity was 94% and specificity was 100% for the acceleration change required to detect ACL injury, i.e., 1.24 m/s2. CONCLUSIONS The results show that a smartphone can be used to evaluate the PS quantitatively and reliably, in the diagnosis of ACL injury. LEVEL OF EVIDENCE II.

中文翻译：

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使用智能手机加速度计对枢轴位移测试进行定量评估。

目的枢轴移位（PS）测试通常用于诊断和评估前交叉韧带（ACL）撕裂时膝关节的动态不稳定性。需要一种可靠且廉价的工具，该工具可容易地用于在临床环境中客观地测量PS。这项研究的目的是评估易于使用的智能手机对PS现象的评估。方法纳入17例单侧ACL受伤的膝关节患者，进行ACL重建。最初由两名观察员根据国际膝关节文献委员会的分类对PS进行分级。然后，使用附在Gerdy结节上的智能手机，在麻醉下在正常膝盖和受伤膝盖中对他们进行PS测试。使用智能手机加速度计应用程序记录了PS测试期间的加速度变化。评估了两个观察员之间的观察者内部和观察者之间的可靠性。比较受伤和正常膝盖之间的加速度变化，以及PS的临床等级之间的加速度变化。通过接收器工作特性曲线分析检查了智能手机加速度计的诊断工具。结果智能手机加速度计的观察者内和观察者间可靠性很高。ACL受伤的膝盖的加速度变化高于正常膝盖。ACL受伤的膝盖的平均加速度变化为2.54 m / s2（SD = 0.97），而正常膝盖的平均加速度变化为0.73 m / s2（SD = 0.19）（p <0.001）。1级膝盖的平均加速度变化为1.89 m / s2（SD = 0.57），而2级及以上的膝盖则为2.99 m / s2（SD = 0.95）（p <0.05）。检测ACL损伤所需的加速度变化的灵敏度为94％，特异性为100％，即1.24 m / s2。结论结果表明，智能手机可用于定量和可靠地评估ACL损伤的PS。证据级别II。