THE ABG-HA ANATOMIC STEM AND FEMORAL DYSPLASIA IN PATIENTS WITH SEQUELAR CONGENITAL HIP DISLOCATION

Abstract

Purpose of the study: The natural history of congenital hip dysplasia with weight-bearing usually progresses towards degenerative joint disease. The anatomic type of the dislocation, whether treated or not, was well classified by Crowe who described four types.

Material and methods: Since 1989, we have used an ABG hydroxyapatite (HA) coated prosthesis for the treatment of congenital hip dysplasia. The hemispheric acetabular implant is coated with hydroxyapatite and the femoral implant, which is inserted in an anatomic position with anteversion, antetorsion and anteflexion, has a HA-coated stem. Forty-three Crowe type 3 or 4 hips (high position) were treated with this technique:

1. implantation of the cup in the paleoacetabulum;

2. screwed autograft harvested from the femoral head to fill the bony defect;

3. implantation of an anatomic stem, without cement but with HA-coated shaft.

Results: Cup implantation in the paleoacetabulum was achieved in all patients except two. A screwed autograft was inserted in 75% and remained stable over time for the larger grafts but tended to resorb for smaller grafts. For femoral anteverions, an ABG implant was used in 34 cases: 21 ABG1 stems, 11 ABF2 stems, and one ABG revision stem. The ABG stem enabled satisfactory anatomic restoration in 20 hips but with postoperative stiffness. For 14 hips, due to the important femoral anteversion related to the dysplasia, a reversed ABG-HA implant was used: eight left implants for right hips and six right implants for left hips. This «reversed» curvature gained 24° in the femoral anteversion plane. The outcome was excellent in these 14 cases, particularly with a clear improvement in postoperative external rotation. At close to 15 years follow-up we have had no case of femoral loosening, nor of femoral shaft osetolysis, with this type of implant.

Discussion: Certain authors propose using a custom-made implant for sequelar congenital hip dysplasia, but we prefer the proposed technique which provides very satisfactory results and limits the need for custom-made material.