Measurement of Knee Rotation Angles Using a Smartphone Application: An Experimental Study of Porcine Knees

Abstract

PurposeThis study evaluated the efficacy of a smartphone application in the measurement of rotation angles in porcine knees.Materials and MethodsTwo K-wires were fixated to the femoral condyle and anterior tibial crest of 10 porcine legs. The angle created between the K-wires with an external rotation force applied was measured on a photograph and defined as the true angle. The same force was applied to the legs placed on a splint with a smartphone attached to the plantar side. The angle presented on a smartphone application was determined as the measured angle. The differences between the true and measured angles in 30° and 90° knee flexion and differences in measured angles depending on the status of the popliteus tendon were compared.ResultsIn the intact knees, the mean true angles in 30° and 90° flexion were 20.5°±1.4° and 19.1°±1.3°, respectively, and the mean measured angles in 30° and 90° flexion were 21.1°±0.9° and 18.6°±1.6°, respectively. When the popliteus tendon was cut, the mean true angles in 30° and 90° flexion were 31.4°±1.1° and 38.5°±2.5°, respectively, and the mean measured angles in 30° and 90° flexion were 31.8°±1.2° and 39.2°±2.8°, respectively. The differences between the true and measured angles were not significant. The measured angle increased by more than 10° after cutting of the popliteus tendon in both 30° and 90° flexion.ConclusionsUsing a smartphone application could be a good method of measuring knee rotation.

Comparison of the Effectiveness of Two Management Strategies in the Pandemic COVID-19 Period in Patient Visits (Face-to-Face Visits vs. a Smartphone) in follow-up the Range of Motion of the Knee in Patients with Anterior Cruciate Ligament Reconstruction

“…In the study of Kim et al .,[ 31 ] using a smartphone application could be a useful method for measuring knee rotation angle, which could be applicable with ease in patients with rotatory instability. In the study of Jenny,[ 32 ] therefore, there is a weak correlation between face-to-face and smartphone methods for examining knee extensions. This may be due to the poor quality of imaging by patients and the patient's lack of cooperation using smartphones.…”

Stress radiography at 30° of knee flexion is a reliable evaluation tool for high-grade rotatory laxity in complete ACL-injured knees

“…However, quantitative analysis of the pivot shift examination is not yet possible owing to the complexity of knee kinematics and the difficulty in creating objective measurement instruments; however despite these limitations, many studies have still been performed [14,23,25,29,37]. Various metrics and devices to describe pivot shift have been reported, including anteroposterior translations [5,17,27,38], medial-lateral translations [27], reduction velocities [17,27], axial rotations [7,34], navigation systems [1,6,9,10,18], electromagnetic systems [7,19,32,58], acceleration devices [38,42], smart phones [24], and image systems [18,39,46]. However, no quantitative threshold to confirm the diagnosis of a positive pivot shift in a standard clinical setting has been established.…”