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

Background: Pediatric patients with leg length discrepancies and complex deformities may require multiplanar external fixators for correction. We have encountered 4 cases of half-pin breakage with the Orthex hexapod frame. The purpose of this study is to report factors associated with half-pin breakage and compare various deformity correction characteristics between 2 hexapod frames – Taylor Spatial Frame (TSF) and Orthex. Methods: Pediatric patients with lower extremity deformities treated with an Orthex or TSF at a single tertiary children’s hospital between 2012 and 2022 were included for retrospective review. Variables compared between frame groups include frame configuration, half-pin/wire fixation, length achieved, angular correction, and frame time. Results: There were 23 Orthex frames (23 patients) and 36 TSF (33 patients) included. Four Orthex and zero TSF had proximal half-pin breakage. The Orthex group was younger on average (10 vs. 12 y, P =.04*) at the time of frame placement. The majority (52%) of Orthex frames were used for simultaneous lengthening and angular correction, while the majority (61%) of TSF was used for only angular correction. Orthex had more half-pins used for proximal fixation (median 3 vs. 2, P <0.0001*) and more frames with nonstandard configuration (7 (30%) vs. 1 (3%), P =0.004*). Orthex group had a longer total frame time (median 189 vs. 146 days, P =0.012*) and longer time required for regenerate healing (117 vs. 89 d, P =0.02*). There were no significant differences in length gained, angular correction, or healing index between Orthex and TSF. Nonstandard configuration, increased number of proximal half-pins, younger age at index surgery, and increased lengthening were associated with pin breakage. Conclusions: This is the first study to report half-pin breakage while using multiplanar frames in pediatric lower extremity deformity correction. The Orthex and TSF groups consisted of significantly different patients and frame configurations, making it difficult to identify any specific cause for pin breakage. This study shows that pin breakage is likely caused by multiple factors and is associated with the increased complexity of deformity correction. Level of Evidence: Level III—Retrospective Comparison Study.