Bifocal tibial corrective osteotomy with lengthening in achondroplasia: an analysis of results and complications.

The results and complications of bifocal tibial osteotomies with gradual correction and lengthening by Ilizarov ring fixator performed in 47 tibiae in 24 achondroplastic patients were analyzed. Comparison was made between the parameters of angular and torsional deformities of the tibia preoperatively, at fixator removal, and at last follow-up. Of these parameters, statistically significant change was seen postoperatively in the values of medial proximal tibial angle, lateral distal tibial angle, mechanical axis deviation, and tibial torsion, which changed from 78.8 +/- 7.05 degrees, 103.2 +/- 11.8 degrees, 25.1 +/- 14.6 mm (medial), and 22.7 +/- 10 degrees (internal) preoperatively to 87.3 +/- 6.3 degrees, 90.9 +/- 5.4 degrees, 5.3 +/- 10 cm (medial), and 15.8 +/- 4.2 degrees (external), respectively, at the time of fixator removal; and this correction was maintained during the follow-up period. Mean total tibial lengthening was 6.84 +/- 1.3 cm. Average healing index was 26.06 days/cm. Complications observed were 15 pin tract infections, 1 residual varus, 1 overcorrection into valgus, 2 recurrence of varus, 22 equinus contractures, 2 premature consolidations, and 3 fibula malalignments. Recurrence of varus was observed in limbs with a residual abnormal medial mechanical axis deviation due to femoral deformity. A hundred percent incidence of equinus was observed in limbs with tibial lengthening of more than 40%, with distal tibial lengthening of more than 15%. To minimize the risk for occurrence of equinus, we recommend restriction of distal tibial lengthening in achondroplasia to less than 15%, although total tibial lengthening may exceed 40%. Fibula malalignment was not observed after double fibula osteotomy. This procedure is safe and efficacious if performed with strict adherence to prescribed technique.