Femoral malalignment deformity acute correction and gradual limb-lengthening by bifocal osteosynthesis with a monorail external fixator

Background. Patients with limb-length discrepancies often present with concomitant distal femoral varus or valgus deformities. With the development of distraction osteogenesis, both deformity correction and limb-lengthening can be performed simultaneously. This novel procedure is being increasingly preferred not only by experts due to the technical advance it implies, but also by patients. The aim of this study was to identify the clinical efficacy of distal femoral malalignment deformity correction and gradual limb-lengthening by bifocal osteotomies. Methods. We analyzed 32 femurs from 30 patients (mean age — 23.8 years) who had undergone bifocal osteotomies followed by the use of the monorail external fixator to correct the distal femoral malalignment deformity acutely and limb-length discrepancy gradually from June 2012 to May 2020. Pre-operative clinical and radiographic data were also obtained. During the follow-up period, deformity correction and bone healing were assessed, complications were identified, and functional outcomes were evaluated. Results. The mean follow-up period was 57.2 months for all the patients. The mean mechanical axis deviation improved from 66.4 mm pre-operatively to 7.5 mm. In patients with varus deformity, the mean mechanical lateral distal femoral angle (mLDFA) decreased from 121.2° pre-operatively to 90.2° after surgery; whereas in patients with valgus deformity, the mean mLDFA improved from 59.2 to 87.1°. The magnitude of lengthening achieved averaged 6.3 cm, and the mean bone healing index was 34.8 days/cm. The final scores defined by the Association for the Study and Application of the Methods of Ilizarov (ASAMI)-Paley were excellent in 93.3% of patients. Conclusions. Acute correction of femoral deformities and gradual lengthening with a monorail external fixator following bifocal osteotomies can be used to treat femoral shortening and distal malalignment deformity. Functional and cosmetic improvements are expected after surgery and post-operative rehabilitation.