DOUBLE ELEVATING OSTEOTOMY FOR INFANTILE BLOUNT’S DISEASE: THE IMPORTANCE OF CONCOMITANT LATERAL EPIPHYSEODESIS

Abstract

The results of 34 knees with stage IV to VI Blount’s disease were reviewed. 24 patients were treated over the seven-year period from 1994 to 2000.

The surgical technique addressed the medial joint line depression with an elevating osteotomy maintained with a tricortical wedge from the iliac crest. The tibial varus and intorsion was corrected with an osteotomy proximal to the apophysis. In the more recent patients a proximal lateral tibial and fibular epiphyseodesis was done concomitantly. The average preoperative mechanical varus angle of 30.6°(range 14° to 60°) was corrected to 0–4° mechanical valgus in 29 knees. In five knees an undercorrection of 2–4° mechanical varus occurred. At follow-up a further 8 knees developed residual varus due to a delayed epiphyseodesis. The tibial varus angle (ie. angle subtended by the mechanical axis of the tibia with the lateral tibial joint line) increased at an average of 1°/ month due to the inevitable medial growth plate fusion.

The average pre operative joint depression angle of 49° (range 40° to 60°) was corrected to an average of 26°(mean 20°–30°). There was no significant preoperative frontal plane f emoral deformity to warrant a femoral correction. At long term follow up of 3.5 years (range 2 to 5 years) all knees had a full range of movement without any varus instability. However in eight cases a delay of more than six months occurred before a lateral epiphysiodesis was performed, and in these patient’s mechanical axis varus recurred although the joint line correction was maintained. Neutral or valgus mechanical axis was maintained in all patients who underwent an epiphysiodesis within six months.

We concluded that although the joint elevation correction was maintained in our series, mechanical axis varus recurs if lateral epiphysiodesis is not performed early.