Crossing the growth plate: distal femoral physeal response to intramedullary nailing in a porcine model

Intramedullary nailing is widely used for femoral stabilization. Yet, its effect on the distal femoral physis in skeletally immature patients remains incompletely defined. In this study, retrograde femoral nailing was performed in 19 juvenile pigs using either titanium or stainless-steel implants, with the contralateral limb serving as an internal control. Growth and alignment were assessed at short-term and long-term follow-up using two-dimensional computed tomography-based measurements and a three-dimensional analysis of femoral length, distal femoral volume, and angular alignment. At short term, femora showed small reductions in relative longitudinal growth and distal femoral volume compared with contralateral non-operated. At long-term follow-up, the mean paired differences between operated and contralateral femora were − 1.3% for relative femoral length (Hodges–Lehmann) estimate − 1.4%, 95% CI − 2.4 to − 0.2) and − 4.3% for distal femoral volume (HL estimate − 5.3%, 95% CI − 8.8 to 0.02). Overall trends were similar for titanium and stainless-steel implants in both short and long-term; however, stainless-steel nails showed a slightly greater distal femoral volume reduction at long-term follow-up. Angular changes were small and variable in direction, with no systematic alignment pattern observed. Overall, limited central violation up to 6% of the distal femoral physis in this porcine model appeared to be well tolerated under controlled experimental conditions and was associated with only small reductions in femoral length and distal volume, without evidence of meaningful angular malalignment.