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Knee Surg Relat Res. 2017 Dec 1;29(4):302-306. doi: 10.5792/ksrr.17.046.

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

Author information

1
Department of Orthopaedic Surgery, Kyungpook National University Hospital, Daegu, Korea.
2
Department of Preventive Medicine, Eulji University School of Medicine, Daejeon, Korea.

Abstract

Purpose:

This study evaluated the efficacy of a smartphone application in the measurement of rotation angles in porcine knees.

Materials and Methods:

Two 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.

Results:

In 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.

Conclusions:

Using a smartphone application could be a good method of measuring knee rotation.

KEYWORDS:

Knee; Mobile application; Rotation; Smartphone

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