A Comparative Study of Estimation of lower Limb alignment by Physical Examination versus Lower Leg Radiography Measurements

AIMS AND OBJECTIVES: Alignment of the lower limb is a key parameter in the diagnostics and treatment concepts of osteoarthritis, in the treatment of cartilage defects and in ligamentous instabilities. The purpose of this study was to evaluate the relevance of the physical examination in direct comparison to radiographic examination in determination of the mechanical axis of the lower extremities. MATERIALS AND METHODS: A total of 92 Patient with different pathologies of the knee joint have been included. (Male: n=60, Female: n=32; overall BMI 26,7 kg/m2). The physical Examination of the mechanical axis was determined by two independent examiners (orthopaedic surgeons) by clinical estimation using a goniometer. The radiographic measurement of the mechanical axis was performed on full weight-bearing whole Radiographs accordning to the recommendations given by Pauwels and Moreland. All variables failed test for normal distribution, so that Spearman’s ratio and for inter observer reliability Kendall’s tau was performed. For all statistical tests, SPSS was used for statistics. P-values < 0.05 were considered statistical significant. RESULTS: The physical examination has a relevant variance to radiographic determination of the lower limb axis. In comparison to the control (radiographic evaluation), a misinterpretation of 3 degrees or more has been found in 30 % of the physical measurements in the overall study group, while in the subgroup of obese patients (BMI > 30kg/m2) the number of miscalculations increased to 44 %(p<0,05). In addition, a moderate correlation was found between the two independent investigators (r=0,61; p<0,001). Resulting in a low inter observer reliability. Higher degree of malalignment was found to correlate with inferior correlation factors between clinical and radiographic evaluation, while best correlation factors were found in the subgroup of patients without significant malalignment (Percentage of Misinterpretation 5 %). This percentage was significantly higher in valgus (40%) and varus (36%) deformities. CONCLUSION: In conclusion the physical examination has a large insecurity compared with the lower leg radiography. Reliability depends on BMI and failure probability increases in the subgroup of obese patients. With regard to the results of the present study and against the background of the great importance of lower limb alignment in the context of surgical treatments for cartilage defects, osteoarthritis and chronic ligamentous insufficiency, the indication for radiographic evaluation of alignment of the lower limb using full weight bearing AP radiographs should be made generously.