INERTIA BASED MOTION ANALYSIS TO SUPPORT THE DIAGNOSIS OF MENISCAL TEARS IN PATIENTS INDICATED FOR KNEE ARTHROSCOPY

Abstract

Modern orthopaedics increasingly demands objective functional outcome assessment beyond classic scores and tests suffering from subjectivity, pain dominance and ceiling effects. Inertia based motion analysis (IMA) is a simple method and validated for gait in knee arthroplasty patients. This study investigates whether IMA assessed stair climbing can distinguish between healthy and pathological subjects and is able to diagnose a meniscal tear (MT).

Following standard physical examination (McMurray, rotation pain), 37 patients (18–72yrs) received arthroscopy suspecting a meniscal tear resulting from trauma, degeneration or both. Arthroscopy identified the presence or absence of MT and the osteoarthritis level (Outerbridge).

Prior to arthroscopy, the ascending and descending five stairs twice at preferred speed and without the use of handrails was measured using a triaxial accelerometer (62×41×18mm; m=53g; f=100Hz) taped to the sacrum. Based on peak detection algorithms, temporal motion parameters were derived such as step time up and down (Tup, Tdown), the difference between step time up and down (Tup-down), step irregularity (step time difference of subsequent steps) and step asymmetry (step time difference between affected and non-affected leg).

Patients were compared to a control group of 100 healthy subjects (17–81yrs) without any known orthopaedic pathology. Using the results of arthroscopy, test sensitivity and specificity for differentiating healthy and pathologic subjects and for diagnosing MT were calculated based on threshold values.

Sensitivity and specificity for detecting pathological motion was 0.68 (CI 0.50–0.81) and 0.92 for the most sensitive parameter (Tdown). Sensitivity and specificity to detect MT was 0.74 and 0.25 percent overall compared to 0.53 and 0.50 for the McMurray. Sensitivity increased to 1.00 when MT was combined with a chondropathy scale III or IV (McMurray 0.33).

IMA assessed stair climbing can distinguish healthy and pathological subjects and detect the presence of MT with better sensitivity than classic scores especially when combined with severe chondropathy. IMA is a simple and fast clinical outcome measure suitable for routine follow-up and may support the diagnosis of meniscal tears prior to arthroscopy.