Objective: To review the hip subluxations or dislocations occurring during femoral lengthening in patients with congenital longitudinal lower limb deficiencies.

Methods: Sixty-three patients with congenital longitudinal lower limb deficiencies underwent femoral lengthening using either De Bastiani, Villarubias or Ilizarov technique. Acetabular index, medial joint space, CE angle of Wiberg, acetabular angle of Sharp and neck-shaft angle were measured on anteroposterior radiographs of hip before, during and after lengthening. The Acetabulum was considered dysplastic when the Sharp angle was more than 45 degrees. Hip was considered to be subluxed when the medial joint space increased during lengthening.

Results: During femoral lengthening, eleven hips sub-luxed as measured by the increase in medial joint space and one hip dislocated. All these hips had a preoperative acetabular index more than 25 degrees, CE angle less than 20 degrees and Sharp angle more than 45 degrees. The average neck-shaft angle was 75 degrees. Following subluxation, lengthening was stopped and the hips were reduced in hip spica after adductor and sartorius tenotomies. In one patient femoral shortening and acetabulo-plasty had to be done to reduce the subluxation. No case of avascular necrosis was noted.

Conclusion: Hip subluxation during femoral lengthening of congenital longitudinal lower limb deficiencies tends to occur when the acetabular index is more than 25 degrees, Sharp angle is more than 45 degrees, CE angle is less than 20 degrees and when there is associated femoral coxa vara. Careful preoperative assessment is required, and if need be hip reconstruction prior to lengthening. Close monitoring during lengthening is recommended.