Early proximal tibial valgus osteotomy as a very important prognostic factor in Thai children with infantile tibia vara.

OBJECTIVES: To find the effectiveness of the early surgery (2-3 years of age)as a very important prognostic factor affecting the outcomes in Thai children with infantile tibia vara and all the prognostic factors including the usefulness of arthrographic study in correcting the deformity.

MATERIAL AND METHOD: From 1994 to 2004, sixteen children aged average 3.61 years old (2.08-7.0) were treated in Siriraj Hospital and diagnosed as infantile tibia vara by Langenskiold radiographic staging were included in the present study and retrospectively reviewed with an average of 6.4 years follow up (range 6 month - 11.1 years). All cases were initially treated by surgery because of low compliance for brace or brace failure. They consisted of 3 boys and 13 girls. There were 24 legs including the bilateral involvement in 8 cases (2 boy and 6 girls). After arihrography, the midshaft fibular osteotomy was performed then the proximal tibial dome-shaped valgus osteotomy was done and fixed with 2 pins. The desired position was 12 degree knee valgus . The patients were divided in two groups, 1)group A,the successful group with the knee becoming normal without any deformity after single osteotomy, 2)group B,the recurrent group with recurrence of the varus deformity required further corrective osteotomies to make normal axis of the knee. All variables were analyzed and compared between group A and group B. The general characteristics and radiographic findings were recorded in 1)age, 2)sex, 3)side, 4)weight in kilogram and in percentage of normal or overweight(obesity) compared with the standard Thai weight chart, 5)tibiofemoral angle (TFA) pre and postoperative treatment, 6) metaphyseal diaphyseal angle (MDA), 7)the medial physeal slope angle (MPS, 8)The preoperative arthrographic articulo-diaphyseal angle (ADA), 9.arthrographic articulo-medial physeal angle (AMPA).

RESULTS: There were 14 legs in group A and the remaining 10 legs were in group B (average 2.4 operations). All cases healed in good alignment of the legs without major complication. All patients who were operated on early before 3 years old were 100% cured by single osteotomy in group A(11 legs). Arthrography was useful in evaluating the knee joint and drawing the angle. Considering the prognostic factors affecting the outcomes after surgery, there were 6 prognostic factors . First, the age less than 3 years old (P<0.001). Second, the normal weight (P<0.047). Third, the Langenskiold stage 1-2 (P=0.002). Fourth, the MPS angle equal or less than 59 degree (P < 0.001). Fifth, the ADA preperative angle equal or less than 18 degrees (P<0.001). Sixth and the last factor, the TFA angle postoperative treatment, equal or more than 10 degrees valgus (mean 13 degrees valgus) (P=0.009).In multivariate analysis with stepwise logistic regression of these 6 prosnostic factors, the MPS angle had the most important significance. The proximal tibial valgus osteotomy was a very important factor(P < 0.001).

CONCLUSION: The 6 prognostic factors and usefulness of arthrography were identified. The authors suggest that surgery should be performed early in Thai children who have met these criterias 1)age of the patients more than 2 years old, 2)Langenskiold roentgenographic characteristics of infantile tibia vara stage 2 or more at the time of diagnosis, 3)Low compliance for brace treatment.or brace failure but not more than 3 years old. The surgery should not be delayed more than 3 years of age by waiting for effectiveness of brace treatment in Thai children with infantile tibia vara. The early proximal valgus dome- shaped osteotomy was a very important controllable prognostic factor by surgeon decision.