Medial percutaneous hemi-epiphysiodesis improves the valgus tilt of the femoral head in developmental dysplasia of the hip (DDH) type-II avascular necrosis: Good outcome in 11 hips

Background and purpose

Avascular necrosis (AVN) is a major cause of disability after treatment of developmental dysplasia of the hip (DDH), leading to femoral head deformity, acetabular dysplasia, and osteoarthritis in adult life. Type-II AVN is characterized by retarded growth in the lateral aspect of the physis or by premature lateral fusion, which produces a valgus deformity of the head on the neck of the femur. We investigated the effect of medial percutaneous hemi-epiphysiodesis as a novel technique in the treatment of late-diagnosed type-II AVN.

Patients and methods

9 patients (11 hips) with a diagnosis of type-II AVN who underwent medial percutaneous hemi-epiphysiodesis after the surgical treatment for DDH were included in the study. 10 patients (12 hips) with the same diagnosis but who did not undergo hemi-epiphysodesis were chosen as a control group. Preoperative and postoperative articulotrochanteric distances, head-shaft angles, CE (center-edge) angles, and physeal inclination angles were measured. The treatment group underwent medial hemi-epiphysodesis at a mean age of 8 years. The mean ages of the treatment group and the control group at final follow-up were 14 and 12 years respectively. The mean duration of follow-up was 5.7 years in the treatment group and 8.3 years in the control group.

Results

Preoperative articulotrochanteric distance, head-shaft angle, and functional outcome at the final follow-up assessment were similar in the 2 groups. However, preoperative and postoperative CE angles and physeal inclination angles differed significantly in the treatment group (p < 0.05). The final epiphyseal valgus angles were better in the treatment group than in the control group (p = 0.05). The treatment group improved after the operation.

Interpretation

Medial percutaneous epiphysiodesis performed through a mini-incision under fluoroscopic control is a worthwhile modality in terms of changing the valgus tilt of the femoral head.Avascular necrosis (AVN) of the proximal femoral epiphysis is an iatrogenic complication of treatment for developmental dysplasia of the hip (DDH) (Danielsson 2000, Dhar 2003, Domalzki and Synder 2004, Roposch et al.2013). A late abnormality that may be the manifestation of the lateral portion of the capital femoral growth plate in type-II AVN alters the morphology of hip joint (Kalamchi and MacEwen 1980). When a progressive valgus deformity occurs in a patient with type-II AVN, problems associated with hip dysplasia may follow (Siffert 1981, Campbell and Tarlos 1990, Kim et al. 2000, Wu et al. 2010, Herring 2014). Due to inadequate coverage, reduced contact area between acetabulum and femoral head leads to early secondary osteoarthritis (Aronson 1986, Inoue et al. 2000, Herring 2014).The treatment decision for type-II AVN is challenging. Procedures such as varus femoral osteotomy and redirectional acetabular osteotomy have been used with a view to preventing future degenerative disease. However, these procedures are technically difficult and may result in serious complications (Siebenrock et al. 2013). On the other hand, as the main pathology is the growth disturbance at the lateral aspect of the femoral head, some form of arrest of the medial portion of the growth plate may be more logical in the treatment of type-II AVN (Herring 2014). We analyzed the radiographic and clinical outcomes of 11 hips in 9 patients with late-diagnosed type-II AVN who underwent percutaneous hemi-epiphysiodesis of the femoral head.