Evaluation of the external fixator TrueLok Hexapod System for tibial deformity correction in children.

ABSTRACT

BACKGROUND: Tibial deformities are common in paediatric orthopaedic practice. Correcting multiplanar tibial deformities associated with lower limb length discrepancy can be challenging. Hexapod external fixation with gradual correction has been proven effective in this situation. OBJECTIVE: To assess clinical and radiological outcomes of gradual tibial deformity correction using the external fixator TL-HEX™ (Orthofix) in children. HYPOTHESIS: TL-HEX™ is effective in correcting tibial deformities in children. PATIENTS AND METHODS: This multicentre retrospective study collected data from the medical files of 26 patients with 31 tibial deformities treated by gradual correction using TL-HEX™. The tibial deformities were due to congenital defects in 11 (35%) cases, Blount's disease in 9 (29%) cases, pseudo-achondroplasia in 4 (13%) cases, and other causes in 7 (23%) cases. Mean age at surgery was 11.9 years. In each patient, antero-posterior long leg radiographs obtained pre-operatively and at last follow-up were used to measure parameters including the mechanical axis deviation (MAD), medial proximal tibia angle (MPTA), and leg length discrepancy (LLD). RESULTS: The mean healing index was 39.3 days/cm (range, 32-58 days/cm). The overall complication rate was 61%, with 11 unplanned visits. Superficial pin tract infection was the most common complication. Significant decreases between the pre-operative and post-operative assessments occurred in mean MAD (from 32.1mm to 10.2mm, P<0.001) and mean LLD (from 36.8mm to 9.1mm, P<0.001). Patients who underwent proximal tibial osteotomy had a significant improvement in MPTA, from 80.6° to 88.5° (P=0.006). DISCUSSION: This is the first clinical study specifically designed to assess outcomes of TL-HEX™ limb lengthening and deformity correction. MAD, MPTA, and LLD were significantly improved at last follow-up. MAD was greater than 10mm at last follow-up in only 11patients. The complication rate was similar to those reported with other external fixators. TL-HEX™ is effective in the management of tibial deformities in children. LEVEL OF EVIDENCE IV (retrospective study).