[Radiological characteristics of leg length discrepancy and knee varus/valgus deformity among unilateral developmental hip dislocation patients].

OBJECTIVE

To observe the leg length discrepancy and accompanied knee varus/valgus deformity in matured patients with unilateral dislocation of the hip.

METHODS

From March 2011 to December 2012, 28 patients who had unilateral dislocation of hip (Hartofilakidis classification II 17 cases and III 11 cases) were involved in this study.There were 6 male patients and 22 female patients, the age of the patients were 13.4-66.2 years, with mean age of 29.8 years. The standing anteroposterior full leg length X-ray films were obtained. Leg length discrepancy, the length of the femur, the length of the tibia and identified the varus/valgus knee deformities were measured. Statistical analysis was performed. A student's t test for paired samples was done for comparison of the parameters in the same patient between dislocated and undislocated leg, and the χ(2) test were used to assess valgus and varus knees, leg length discrepancy in high dislocation and low dislocation groups.

RESULTS

Seventeen (60.7%) cases had longer femur length on the dislocated side than that on the undislocated side (t = 1.328, P = 0.197), with the maximum lengthening of 32.7 mm and a mean lengthening of 9.5 mm. Twenty-one (75.0%) cases had longer tibia length on the dislocated side (t = 3.039, P = 0.006), with a maximum lengthening of 10.9 mm and a mean lengthening of 4.5 mm. Twenty (71.4%) cases had longer relative leg length on the dislocated side (t = 2.451, P = 0.022), with a maximum lengthening of 25.0 mm and a mean lengthening of 9.4 mm. On the dislocated side of the leg, the degree of valgus angle was 3° ± 4°,while on the undislocated side, that was -3° ± 4°(t = 5.642, P = 0.000). On the dislocated side, 12 cases (42.9%) were of valgus deformities and 1 case was of varus deformity. On the contralateral side, 15 cases of varus deformities (53.6%) and 1 case of valgus deformity were observed(χ(2) = 18.139,P = 0.000).

CONCLUSIONS

Most dislocated legs are longer in length than the contralateral side, both femur and tibia have also lengthened accordingly. Many knees on the dislocated side present valgus deformity, half of the knees on the contralateral side present varus deformity.