Purpose: Patients with advanced Blount disease present severe metaphyseal varus associated with an oblique medial tibial plateau. Prior to 1987, we used tibial wedge osteotomy to correct the varus deformation and in certain situations also raised the medial plateau with the wedge. From 1987, we performed both procedures during the same operation. The purpose of this work was to describe our technique and evaluate the results of the dual technique.

Material and methods: Between 1987 and 2000, we performed 31 dual procedures. Fifteen patients who had advanced-stage Blount disease were seen late (eight before complete fusion of the growth cartilage and seven as adults). Thirteen children presented recurrent varus deformation after osteotomy during childhood. One patient presented tibia vara during adolescence and three others had poly-epiphyseal dysplasia. Mean age at osteotomy was 17 years (range 10–40). For all patients, the operative technique consisted in lateral closed wedge osteotomy associated with a second access for an oblique osteotomy directed towards the tibial spikes to insert the lateral wedge medially and raise the medial plateau. A mid-third fibular osteotomy was also performed together with stapling for tibial epiphysiodesis superior and lateral when the growth cartilage was still active. We recorded pre- and postoperatively: mechanical femoro-tibial angle, the tibial and femoral mechanical angles to determine intra-osseous deformation, the slope of the medial plateau, and the length of the lower limbs at the end of growth.

Results: Mean follow-up was eight years. Fusion was achieved in all patients. The mechanical femoro-tibial angle was 148.5 (mean) preoperatively giving 31.5° (20–42) varus and 178° postoperatively. The mean femoral mechanical angle was 94°, giving 4° valgus (range 88–102°) preoperatively, with no change postoperatively. The mean mechanical tibial angle was 71° preoperatively (intra-osseous varus of 19°) and 89° postoperatively. The medial tibial plateau slope was 45° preoperatively and 22° postoperatively. Leg length discrepancy was 2.2 cm at last follow-up (range 0.5–5 cm).

Discussion: Different techniques have been described for correcting two deformation components during the same operation. Here, we used the metaphyso-epiphyseal oblique osteotomy technique. This technique assumes that the medial part of the cartilage has already fused and requires fusion of the lateral part when it is active. Currently, we use chondrodiastasis with a special external fixator when the cartilage is still active. This corrects the alignment and raises the plateau, treating the length discrepancy by lengthening. The dual osteotomy technique is reserved for patients with total physis fusion. A long-term analysis after dual osteotomy in comparison with chondrodiastasis will be needed to determine the relative merits of the two techniques and the frequency of secondary osteoarthritis. This work is being conducted at the orthopaedic surgery department of the Fort-de-France University Hospital in Martinique.