Article
Gait analysis study on patients with varus malalignment
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Published: | October 21, 2010 |
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Objective: The correction of leg malalignment usually depends on radiographic measurements observed statically without representing aspects of the loading situation at the knee during dynamic situations. The external knee adduction moment is an often-used predictor of knee joint loading [1] and the most common outcome measure reported from gait analysis in patients with knee osteoarthritis (OA). Moreover, it is a strong contributing factor to articular cartilage degeneration in the medial compartment of the knee joint [2]. However, the dynamic loading situation at the knee in patients with pathological varus alignment but no indication of knee OA has not been previously reported. Therefore, the purpose of this prospective study was to determine knee and hip joint moments and angles in the sagittal, frontal and transverse plane in patients with varus malalignment and healthy control subjects.
Method: Fourteen patients with varus malalignment (8 female and 6 male) with a mean age of 15.1 (±2.2) years and 15 healthy control subjects (9 female and 6 male) with the same mean age of 15.1 (±4.3) years gave informed consent to participate in this prospective study. Kinematic data were collected using an 8-camera Vicon system (Oxford Metrics, UK). Two force plates (AMTI) were used to calculate joint moments. A modified Helen Hayes marker set [3] was applied to determine joint centers. Differences between the samples were tested for significance using student’s t-test with a significance level set at α=0.05. Moreover, an external joint moment convention was used.
Results and Conclusions: Patients with varus malalignment exhibited significantly reduced maximum knee and hip extension moments and angles compared with the control group. As expected, the maximum knee adduction moment in the frontal plane was significantly higher in the patient group. However, the maximum hip adduction moment did not show significant differences between the two groups. Regarding the transverse plane, the maximum knee internal rotation moment and the maximum hip external rotation moment were significantly higher in patients with varus malalignment.
The significantly higher than normal peak knee adduction moment in patients with varus malalignment suggests that these subjects are walking with increased knee joint loads on the medial compartment. Furthermore, abnormally increased knee internal rotation and hip external rotation moments were present in subjects with varus malalignment. These findings imply that varus malalignment is not an isolated problem in the frontal plane.
The three-dimensional gait analysis is a diagnostic tool aimed at receiving a better understanding of the relationship between loading and the onset or progression of articular cartilage degeneration and should therefore be used for clinical decision making in patients with varus malalignment.
References
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- Sharma L, Hurwitz DE, Thonar EJ, Sum JA, Lenz ME, Dunlop DD, Schnitzer TJ, Kirwan-Mellis G, Andriacchi TP. Knee adduction moment, serum hyaluronan level, and disease severity in medial tibiofemoral osteoarthritis. Arthritis Rheum. 1998;41(7):1233-40.
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- van den Noort JC, Scholtes VA, Harlaar J. Evaluation of clinical spasticity assessment in cerebral palsy using inertial sensors. Gait Posture. 2009;30(2):138-43. Epub 2009 Jun 13.