Elastic Stable Intramedullary Nailing for High-Risk Proximal Femoral Unicameral Bone Cysts in Children: A Retrospective Case Series

Abstract

Background Proximal femoral unicameral bone cysts (UBCs) are challenging in children because the lesions occur in a weight-bearing region near the proximal femoral physis. This study describes outcomes after elastic stable intramedullary nailing-(ESIN)–based treatment and the indication-based use of selective transphyseal nail advancement. Methods We retrospectively reviewed consecutive skeletally immature patients with pathologically confirmed proximal femoral UBCs treated at 2 centers with curettage, high-speed burring, allogeneic bone grafting, and 2 titanium elastic nails. Minimum follow-up was 12 months. Outcomes included Ratliff and modified Neer status, recurrent or persistent cystic change, unplanned reoperation, complications, and growth-related radiographic findings. Results Thirty-eight patients were included: 31 underwent physeal-sparing ESIN, and 7 underwent selective transphyseal ESIN because physeal-sparing fixation provided insufficient proximal purchase. Median follow-up was 30.0 months. At the final follow-up, all patients had good Ratliff outcomes; modified Neer grade I was achieved in 26 patients (68.4%) and grade II in 12 (31.6%). Recurrent or persistent cystic change occurred in 9 patients, and 10 underwent unplanned reoperation. Among the 7 transphyseal cases, no clinically apparent progressive proximal femoral angular deformity or definite growth disturbance attributable to nail placement was identified during available follow-up. Conclusions ESIN-based management yielded satisfactory final outcomes. A physeal-sparing trajectory should remain preferred. Selective transphyseal advancement may provide proximal purchase in carefully selected juxtaphyseal lesions, but the small subgroup and absence of follow-up to skeletal maturity preclude conclusions regarding long-term physeal safety. Key Concepts (1) Elastic stable intramedullary nailing–based treatment produced good final clinical and radiographic outcomes in this high-risk pediatric proximal femoral unicameral bone cyst series.(2) A physeal-sparing nail trajectory should remain preferred when stable proximal purchase can be achieved.(3) Selective transphyseal advancement may be considered when a juxtaphyseal lesion prevents secure physeal-sparing fixation.(4) No definite growth disturbance attributable to nail passage was identified in 7 transphyseal cases during available follow-up.(5) The small subgroup and lack of follow-up to skeletal maturity preclude conclusions about long-term physeal safety. Level of Evidence IV, Case Series