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.
Highlights
There are several types of rotatory instability of the knee joint including posterolateral rotatory instability (PLRI) due to pos terolateral corner (PLC) injury, internal tibial rotatory instability due to anterolateral ligament (ALL) injury, and anteromedial instability
This study evaluated the rotation angles of porcine knees using a smartphone application and compared the differences with measurement using photographs
Injuries to the PLC can cause PLRI of the knee joint, which is often accompanied by anterior cruciate liga ment (ACL) or posterior cruciate ligament (PCL) tears10,11)
Summary
There are several types of rotatory instability of the knee joint including posterolateral rotatory instability (PLRI) due to pos terolateral corner (PLC) injury, internal tibial rotatory instability due to anterolateral ligament (ALL) injury, and anteromedial instability. The obliquity of a reconstructed anterior cruciate liga ment (ACL) could affect rotatory instability and long-term. The dial test was popularized in evaluating PLRI2); several authors used rotational knee laxity measurement devices, such as RO TAM (Genourob, Laval, France), Lars Rotational Laxiometer (Lars Inc., Dijon, France), or a custom-made isotonic rotation machine[3,4,5]). The knee laxity measurement devices are advantageous for accurate mea surement, but it has disadvantages of bulky size and high cost
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