Anterior femoroacetabular impingement after femoral neck fractures.

OBJECTIVES

To verify whether anterior femoroacetabular impingement can be a reason for hip pain and loss of motion in patients with a healed femoral neck fracture.

DESIGN

Retrospective clinical, radiologic, and surgical evaluation.

SETTING

Third referral hospital.

PATIENTS: Nine patients who previously sustained a femoral neck fracture were treated between 1995 and 1999 for hip pain and loss of motion. All these mostly young patients (mean age 33.3 years) complained of groin pain. During the physical examination, acute pain could be elicited by passively forcing the femoral neck against the acetabular rim in flexion, adduction, and internal rotation, motions that were all limited.

METHODS

Conventional radiographs and, if possible, arthrographic magnetic resonance imaging scans were followed by a surgical subluxation or dislocation of the femoral head to analyze the sequelae of anterior femoroacetabular impingement. Treatment was based on improvement of the anterior offset (the difference between the anterior contour of the head and the femoral neck) or intertrochanteric osteotomy to ameliorate clearance of the joint.

RESULTS

Intraoperatively in eight patients (one not operated), impingement was found to result from insufficient reduction of the fracture, already visible on the conventional radiographs. Retrotorsion (mean 20 degrees) of the head caused anterior impingement in all patients, additional varus position (mean caput collum diaphysis angle 115 degrees) of the head caused anterolateral impingement in two patients. In all patients, anterior labral and adjacent acetabular cartilage lesions were found during surgical subluxation or dislocation of the femoral head, comparable to those seen on the magnetic resonance imaging scan. They proved to result from repetitive abutment and compression between the head-neck junction and the acetabulum.

CONCLUSION

Femoroacetabular impingement can be a cause for hip pain and loss of motion in patients who previously sustained a femoral neck fracture. The condition causes degenerative anterior labral and adjacent acetabular cartilage lesions. Early treatment is essential to prevent further degeneration and osteoarthrosis of the joint. Prevention is predicated by initial precise anatomic reduction of such fractures in all planes.