The rotational alignment of the lower limbs in recurrent dislocation of the patella.

The rotational alignment tヲfthe lovver limbs of 24 patients who developed r巴currentdislocation of the patella were measured by means of computed axial tomography. The femoral anteversion and the external rotation of the knee joint of these patients respectively showed 31.9土15.2° and 9.2土6.8° on the average. These figures were significantly larger than those of the control. The average external tibial torsion was 23.l土8.8°,showing no significant difference from that of the control. The external rotation of the knee joint of the patients with generalized joint laxity were significantly greater than that of the patients without g巴neralizedjoint laxity. Such rotational malalignment as observed in these patients can be regarded as a cause of recurr巴ntdislocation of the patella. Introduction Among what hav巴beenreported as possible causes of recurrent dislocation of the patella are trochlea dysplasia, patella dysplasia, vastus medialis obliques dysplasia, increased Q-angle, high riding patella, joint laxity and rotational malalignment such as femoral anteversion or external tibial torsiona,4,s,s,9>. However, the objective analysis of rotational alignment has not been reported in recurrent dilocation of the patella. We report here the measurements of the rotational alignment of the lower limbs of the patients with recurrent dislocation of the patella by computed axial tomography (CAT). Patients and Methods Twenty-five patients, 20 women and 4 men with recurrent dislocation of the patella, participated in the study. Their median age was 21 years, range 13 to 34 y巴ars. The median ag巴at the fin;t dislocation was 14.3 years, range 7 to 20 years. The joint involved consisted of 15 right patellae and 13 left. The rotational alignment of the 48 lower limbs of the 24 patients was ex『 amined by CAT scan of the proximal femur, knee joint and ankle joint. When the CAT scan