The accuracy of clinical examination of rotational and sagittal laxity of the knee

Bezuidenhout, Carel Willem

The accuracy of clinical examination of rotational and sagittal laxity of the knee

Master Thesis

2020

Publisher

University of Cape Town

Department

Division of Orthopaedic Surgery

Faculty

Faculty of Health Sciences

Abstract

Purpose: This study evaluates the accuracy and reliability of clinical examination for knee laxity in degrees and millimetres when compared to movement measured by computer-assisted navigation. Methods: A cadaver lower limb was connected to a computer assisted knee surgery system (CAS) and calibrated through a mini medial parapatellar arthrotomy. Examiners estimated millimetres of sagittal and degrees of rotational laxity of the knee at 30º and 90º of knee flexion. This examination was done in the ligamentous intact knee and again after sequential release of the anterior cruciate ligament (ACL) and anterolateral ligament (ALL). The clinical assessments were compared with measurements produced by CAS. Intraclass correlation coefficient (ICC), correlation coefficient (CC) and Bland Altman plots were used to compare and summarize the data. Results: At least 21 participants assessed the knee after each sequence of ligament sectioning. The reliability of clinical examination when correlated with the CAS measurements was poor for all examination groups. The ICC was poor for sagittal laxity at 30º (R=0.02; p=0.04), rotational laxity at 30º and 90º (R=0.17; p=0.04) (R=0.3; p=0.04) respectively and sagittal laxity at 90º(R=0.47; p=0.04). The correlation coefficients were very weak for sagittal laxity at 30º (R=0.09; p=0.46), weak for rotational laxity at 30º (R=0.24; p=0.06) and 90º (R=0.3; p=0.01) and moderately weak for sagittal laxity at 90º(R=0.4; p=0.001). Clinical examination was only accurate in the detection of sagittal laxity greater than 11.6mm at 30°, and greater than 9.4mm at 90°. Clinical examination for rotational laxity was only accurate for rotational instability greater than 27.7° at 30°flexion, and 28.9° rotation at 90°. Conclusions: There was poor reliability and weak correlation between clinician estimated sagittal and rotational laxity and measurements produced by CAS. This study showed that participants could not accurately estimate laxity in degrees and millimetres and supports the need for accurate objective knee laxity measurements.

Keywords

Orthopaedic Surgery

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