Distraction osteogenesis of the femur using conventional monolateral external fixator

The author has developed a new simple technique of distraction osteogenesis using conventional monolateral external fixator for femoral lengthening. The primary purpose of the present study was to evaluate the results of treatment with this new technique of femoral lengthening and also to evaluate the effect of preoperative and intraoperative variables on the outcome of distraction osteogenesis in general.

Fifty-one femora in 50 patients were lengthened. Limb-length discrepancy was the primary indication in all patients. The mean age of the patients at the time of the surgery was 21.9 years (range 5-48 years). The average follow-up period was 24.6 months after removal of the fixator (range 6-120 months). All lengthenings were performed using conventional AO/ASIF external fixator. Twenty-two femora had associated axial or rotational deformities. Gradual distraction was performed to increase length and to correct angular deformity in coronal plane. Acute closed wedge angular correction in sagittal plane or derotation was performed in 12 femora in this study.

The length of the 51 femora was increased by an average 4.4 cm (range 1-13 cm), or 12% (range 2.5-40.9%). The average healing index was 50.5 days/cm (range 22.5-110.6 days/cm). Average gradual angular correction in coronal plane in 14 femora was 20.4 degrees (range 10-45 degrees ). Average acute correction in sagittal plane in five femora was 17 degrees (range 10-20 degrees ). Average acute derotation in six femora was 24.2 degrees (range 10-60 degrees ). There were a total of 61 complications, including 26 problems, 18 obstacles, and 17 sequelae. The overall rate of complications was 1.2 per femur. Fifteen femora had delayed consolidation (healing index >54 days/cm). Three of 51 lengthening procedures did not lead to consolidation (nonunion). A significant negative parabolic relationship was noted between the healing index and the amount of length gained (R = -0.47 and P = 0.004). There was a significantly positive exponential relationship between age and healing index (R = 0.51 and P < 0.001). Acute deformity correction, level of osteotomy (submetaphysis versus diaphysis) had no significant effect on healing index. The greater amount of length gained was associated with complications.

The newly presented technique of distraction osteogenesis is a useful and cost-effective method for femoral lengthening. Increased lengthenings produced a better healing index but might associate with complications. Younger age was associated with better bone healing but age had no effect on complication rate. Level of osteotomy, acute deformity correction had no effect on healing index and rate of complications.