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Instrumented measurement of the posterolateral corner
R M Bleday1, G C Fanelli, B F Giannotti
1Department of Orthopaedics, Geisinger Medical Center, Danville, Pennsylvania 17822, USA.
Summary
The Lars Rotational Laxiometer provides objective measurements for diagnosing knee posterolateral rotatory instability. This study establishes baseline external rotation values in healthy knees using the device.
Area of Science:
- Orthopedics
- Biomechanics
- Medical Device Technology
Background:
- Posterolateral rotatory instability (PLRI) of the knee is a significant clinical challenge.
- Accurate diagnosis of PLRI often relies on subjective clinical examination.
- Objective measurement tools are needed to quantify knee laxity.
Purpose of the Study:
- To introduce the Lars Rotational Laxiometer, a novel device for measuring tibial external rotation.
- To establish normative side-to-side external rotation values in healthy knees.
- To assess the reliability of the Lars Rotational Laxiometer in a clinical setting.
Main Methods:
- The Lars Rotational Laxiometer was used to measure tibial external rotation in 180 healthy knees.
- Measurements were taken at 30 and 90 degrees of knee flexion by three independent examiners.
- Subjects were screened to ensure no history of knee injury, pain, or instability.
Main Results:
- Mean side-to-side difference in external rotation at 90 degrees flexion was 4.4 degrees (range, 3.7–5.1 degrees).
- Mean side-to-side difference in external rotation at 30 degrees flexion was 5.5 degrees (range, 4.7–6.3 degrees).
- No significant differences in measurements were observed based on gender or age.
Conclusions:
- The Lars Rotational Laxiometer provides objective, quantifiable data for tibial external rotation.
- Baseline side-to-side laxity values for the posterolateral complex in normal knees have been established.
- This device holds potential for improving the diagnosis of knee instability.