Surgical hip dislocation for treatment of cam femoroacetabular impingement

Abstract

Background: Cam femoroacetabular impingement is caused by a misshapen femoral head with a reduced head neck offset, commonly in the anterolateral quadrant. Friction in flexion, adduction and internal rotation causes limitation of the hip movements and pain progressively leading to labral and chondral damage and osteoarthritis. Surgical hip dislocation described by Ganz permits full exposure of the hip without damaging its blood supply. An osteochondroplasty removes the bump at the femoral head neck junction to recreate the offset for impingement free movement.

Materials and methods: Sixteen patients underwent surgery with surgical hip dislocation for the treatment of cam femoroacetabular impingement by open osteochondroplasty over last 6 years. Eight patients suffered from sequelae of avascular necrosis (AVN). Three had a painful dysplastic hip. Two had sequelae of Perthes disease. Three had combined cam and pincer impingement caused by retroversion of acetabulum. All patients were operated by the trochanteric flip osteotomy with attachments of gluteus medius and vastus lateralis, dissection was between the piriformis and gluteus minimus preserving the external rotators. Z-shaped capsular incision and dislocation of the hip was done in external rotation. Three cases also had subtrochanteric osteotomy. Two cases of AVN also had an intraarticular femoral head reshaping osteotomy.

Results: Goals of treatment were achieved in all patients. No AVN was detected after a 6 month followup. There were no trochanteric nonunions. Hip range of motion improved in all and Harris hip score improved significantly in 15 of 16 cases. Mean alpha angle reduced from 86.13° (range 66°-108°) to 46.35° (range 39°-58°).

Conclusion: Cam femoroacetabular Impingement causing pain and limitation of hip movements was treated by open osteochondroplasty after surgical hip dislocation. This reduced pain, improved hip motion and gave good to excellent results in the short term.

Keywords: Cam lesion; Impingement syndrome; femoroacetabular impingement; hip dislocation; pincer impingement; surgical hip dislocation; surgical technique.

Figure 1

X-ray (L) hip joint anteroposterior view in a 14 year old following Perthes disease 4 years ago showing (a) femoral head is extruded anterolaterally with an irregular shape. There is significant pain on sitting in a low chair and on flexion-adduction-internal rotation. (b) After safe surgical dislocation, the femoral head-neck offset is restored after osteochondroplasty. There is no more impingement and hip movements have become free. Harris hip score has improved from 42 to almost 100

Figure 2

X-ray (L) hip joint anteroposterior view in a dysplatic hip in a (a) 16-year-old showing an extrusion of the femoral head is seen antero-laterally giving rise to pain and restricted abduction-internal rotation. (b) After trochanteric osteotomy, osteochondroplasty is performed to restore almost spherical shape and the femoral head-neck offset. Trochanter fixed with 3 screws. Minimum relative neck lengthening has been performed. Harris hip score has improved from 49 to 89

Figure 3

X-ray left hip joint anteroposterior view showing (a) severe avascular necrosis with a saddle shaped head with a large extruded chunk anterolaterally after 2 years fracture neck femur. Range of motion only 60° of flexion. Severe pain. Harris hip score is 39. (b) Lateral X-ray showing loss of sphericity and extrusion of head anteriorly. Saddle shaped depression is also seen in the centre. (c) After the safe surgical exposure, the head is dislocated with the hip in external rotation. The central depression area with severe damage is seen. The medial portion of the head and the lateral extruded portion have reasonably good cartilage cover. (d) The central depressed portion is resected as a trapezoidal wedge. Part on left is extruded portion. The inner cut edges reveal bleeding signifying intact vascularity and efficacy of the safe surgical approach in preserving blood circulation. (e) The two portions of the head are coapted, fixed with screws. Reasonable sphericity is achieved. (f) A reasonably spherical profile of the head is created. Trochanter healed without problems. Hip range of motion has increased to 90° flexion and 25° adduction and abduction each. Rotations were restored minimally after 12 months. At 2 years after surgery, Harris hip score is more than 95. No pain at all and limp is minimal. (g) Postoperative lateral X-ray shows loss of the anterior bump and a reasonably spherical shape which permits flexion to almost 110° and no impingement in adduction-internal rotation.