Statistical analysis of axial deformity during distraction osteogenesis ofthe tibia

In this study, we documented the prevalence of coronal asis malalignment in a series of 93 tibias (from 54 patients) lengthened with monolateral fixat ion. The average length obtained by distraction osteogenesis was 8.9 cm (ra nge, 3.5-15.6) or 38% of the original bone length (range, 11-78%). Fifty (5 4%) of 93 tibias had documented valgus angulation of greater than or equal to 10 degrees or had fixator manipulation during the lengthening process fo r undesirable or progressive angulation; no cases of varus angulation were noted. Thirteen (14%) segments had later corrective osteotomy for unsatisfa ctory valgus malalignment. Statistical analysis revealed two factors to hav e a significant effect on the rate of malalignment. Those cases that had ti bial osteotomy below the proximal one third of the original tibial length a nd those cases in which the fixator was placed >5 degrees out of parallel h ad higher rates of angulation or manipulation (p < 0.001 and p = 0.002). Al though the percentage of original bone lengthened was not statistically sig nificant (p = 0.083), it did have an important effect on rates of axial mal alignment. From this study we conclude that relatively high rates of malali gnment in the tibia during distraction osteogenesis with monolateral extern al fixation are predominately the result of more distal osteotomies and non parallel fixator placement. Attention to these details in general, and part icularly where long lengthenings are planned, may significantly reduce this common complication.