Imaging-assisted intra-operative approach to torsional alignment in paediatric femoral shaft fractures treated with hip spica.

Background: Paediatric femoral fractures in children under 6 years are commonly managed with hip spica, considered the gold standard. While the remodeling potential for shortening and angular deformities is well established, the management of torsional alignment during spica application remains inadequately explored. This study proposes a novel technique to better address torsional alignment during the treatment of paediatric femoral fractures using hip spica.

Methods: This prospective study included 20 children with closed, unilateral diaphyseal femur fractures treated with hip spica. External-rotation of the distal fragment was determined by matching the lesser trochanteric profile of the proximal femurs under image-guidance. Follow-ups at 2, 6 and 12 weeks involved radiographic assessment of fracture overlap, angulation and the novel 'thigh-cast index' was done. At the final follow-up, clinical assessment of the torsional profile and radiographic evaluation of mLDFA were performed.

Results: The mean age was 4.15 ± 1.97years. The pre-spica median external-rotation intended for the injured limb was 18.3°(IQR12.1°-31.0°), while the final median external-rotation in the cast was 9.8°(IQR10.8°-16.0°). Rotational outcomes revealed increased internal-rotation in 39 % and increased external-rotation in 22 % of children. Median pre-spica shortening and post-spica residual overlap were both 1 cm, with a significant positive-correlation (rho = 0.733, p < 0.01). Following spica removal, median coronal plane angulations were 4.7° varus(IQR3.4°-12.2°) in 16 children and 4.9° valgus(IQR3.4°-6.6°) in 4 children. The mean mLDFA difference was 2.64° ± 5.67°(p = 0.061). The mean thigh-cast index decreased from 0.92 ± 0.03 (day 0) to 0.89 ± 0.04(2weeks) and 0.86 ± 0.05(6weeks).

Conclusions: Intra-operative assessment is crucial in guiding the rotational alignment of the distal fragment during spica application. The thigh-cast index provides valuable insights into inevitable thigh muscle wasting, regardless of foot inclusion or exclusion. Long-term follow-ups are necessary to further evaluate rotational remodeling achieved through this image-guided technique.