Quantitative assessment of the pivot shift test with smartphone accelerometer.

Area of Science:

• Orthopedics
• Biomechanics
• Medical Technology

Background:

• The pivot shift (PS) test is crucial for diagnosing knee joint dynamic instability in anterior cruciate ligament (ACL) tears.
• Objective and reliable clinical assessment tools for the PS phenomenon are currently lacking.
• This study explores the potential of readily available smartphones as a diagnostic aid.

Purpose of the Study:

• To evaluate the feasibility of using smartphone accelerometers to objectively assess the PS phenomenon.
• To determine the reliability and diagnostic utility of smartphone-based PS testing in ACL-injured knees.

Main Methods:

• Seventeen patients with unilateral ACL tears undergoing reconstruction were enrolled.
• The PS test was performed under anesthesia, with a smartphone attached to Gerdy's tubercle to record acceleration changes.
• Intra-observer and inter-observer reliability were assessed, and acceleration data were compared between injured and normal knees and across clinical PS grades.

Main Results:

• High intra-observer and inter-observer reliability were found for the smartphone accelerometer method.
• ACL-injured knees exhibited significantly higher acceleration changes (2.54 m/s²) compared to normal knees (0.73 m/s²).
• The smartphone method achieved 94% sensitivity and 100% specificity for detecting ACL injury with a threshold of 1.24 m/s².

Conclusions:

• Smartphones equipped with accelerometers provide a reliable and quantitative method for evaluating the PS phenomenon.
• This technology offers a promising, inexpensive, and accessible tool for the objective diagnosis of ACL injuries in clinical practice.