Clinical outcomes in pediatric tibial lengthening and deformity correction: A comparison of the Taylor Spatial Frame with the Orthex Hexapod System

Abstract

Purpose Comparison of two hexapod frame systems in paediatric tibial deformity correction; the Taylor Spatial Frame (TSF) and Orthex Hexapod System. Methods Paediatric patients with congenital and acquired tibial deformities treated with either TSF (between 2014 and 2016) or Orthex (between 2017 and 2019) frames were included in a retrospective comparative study. Outcome measures were healing index, pin infection rate, regenerate quality and density, software residual rate, deformity correction accuracy, strut exchanges and quality of life (QoL). Results The TSF group had 17 patients (18 frames) and the Orthex group had 21 patients (25 frames). The most common indications for tibial deformity correction were fibular hemimelia (14) and septic or traumatic growth arrest (8). The median time in frame was 230 days (TSF) versus 203 days (Orthex) (p= 0.06). The mean lengthening achieved was 54 mm (TSF) and 51 mm (Orthex) (p = 0.41). The healing index was 41 days/cm (TSF) versus 43 days/cm (Orthex) (p = 0.70). Pin site infections occurred more in the TSF cohort (40%) than in the Orthex cohort (18%) (p < 0.001). The regenerate in the Orthex group showed higher density at three months (p = 0.029) and was more homogenous (p = 0.023) at six months after frame application. Strut exchanges were less frequent with the Orthex system (p < 0.0001). QoL measures were similar in both cohorts (p = 0.92). Conclusions This is the first study to compare two hexapod designs in paediatric orthopaedics. The Orthex system showed superiority in regenerate quality and a significant reduction in pin site infection rates. Both systems delivered predictable and accurate limb deformity correction. Level of evidence III

Half-pin Breakage in Multiplanar External Fixators Used for Pediatric Deformity Correction

“…This is in contrast to Messner et al finding their Orthex group had increased regenerate density at 3 months compared with their TSF group. 9 However, like Messner, we found that, at least when comparing the subset of lengthening patients, both groups had similar healing indices despite frame time and density differences. Without clear indices for multiplanar angular deformities, these results can be more difficult to compare.…”

“…4,7,12 Although there are no biomechanical studies, these configurations have been successfully used in clinical applications. 9,13,14 The Orthex group had a significantly higher proportion of nonstandard configurations, and nonstandard configuration was associated with pin breakage. Since only 1 TSF frame had nonstandard configuration, it is impossible to know from our cohort whether half-pins would be able to withstand similar conditions using this frame type.…”

“…We considered stacked frames and struts placed across a joint, instead of an osteotomy, to be nonstandard because these configurations are performed less often and introduce different biomechanics than what has been traditionally studied in the literature 4,7,12 . Although there are no biomechanical studies, these configurations have been successfully used in clinical applications 9,13,14 . The Orthex group had a significantly higher proportion of nonstandard configurations, and nonstandard configuration was associated with pin breakage.…”

“…Thus far, only 2 studies have compared TSF and Orthex frames. 8,9 At our pediatric hospital, anecdotal benefits and complications have been noted during the clinical use of these 2 frames. Specifically, we observed half-pin breakage.…”

“…Although the new hexapod frame is similar in concept to the TSF, it is not an identical system. Thus far, only 2 studies have compared TSF and Orthex frames 8,9 …”