Prof. Dr. Harald Böhm (Aschau im Chiemgau; Göttingen), Sophie Reinhold (Wien / AT), PD Dr. Chakravarthy Dussa (Aschau im Chiemgau; Erlangen)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
Background
Leg length discrepancy (LLD) is common in youth. Long leg X-rays is the gold standard technique of measuring LLD. It is highly accurate and reliable compared to clinical method [1], but expose the subject to radiation. Instrumented gait analysis (IGA) can not only be used to measure of the joint kinematics during gait but also may also be used to assess LLD during standing.
Aim
The purpose of this study was to compare different methods of determining the LLD in paediatric population. We hypothesize that IGA using joint centres is more accurate and precise than the tape measurement.
Methods
Thirty-one patients with mean age 12(SD=2) years were included. Their LLD varied between 0-36 mm. Three methods for determining LLD (Abb. 1) were compared to the gold standard of radiography using Bland-Altman analysis: 1. Tape measurement 2. IGA, summarizing the distance from the spina iliaca to the medial malleolus marker via the medial knee condyle 3. IGA, summarizing distances between ankle, knee, and hip joints centres, where the latter was calculated using 3 different regression equations.
Results
The IGA joints method performed better than the tape measurement or IGA markers method. The equations of Davis [2] calculating the hip joint centre had the highest accuracy with mean difference to radiography of 0.7 mm (SD=6.3). The simple Harrington method [3] resulted in a slightly reduced accuracy but higher precision of 0.9 mm (SD=6.2). The Harrington method with leg length as input was less accurate 1.0 mm (SD=6.7), but was still considerably better than the tape measurement 1.8 mm (SD=7.0) or IGA markers method 1.1 mm (SD=11.5).
Conclusion
Determining LLD with IGA using the distances between ankle, knee and hip joints centres is a feasible method that can be applied in clinical practice to calculate LLD.
Sabharwal & Kumar. Clin Orthop Relat Res. 2008; 466(12): 2910-22. Harrington et al. J Biomech. 2007; 40(3): 595-602. Davis et al. Hum. Mov. Sci. 1991; 10: 575–87.