Bone Abstracts

Background: Proteus syndrome (PS) is a rare mosaic disorder comprising asymmetric bony and soft tissue overgrowth leading to significant morbidity. Placement of guided growth hardware with subsequent epiphyseal arrest improves leg length and angular deformities in pediatric patients without PS.

Presenting problem: The purpose of this study was to review the surgical approach and present outcomes, complications, and recommendations in eight patients with PS and leg length discrepancy (LLD). Although children with PS typically appear normal at birth, disproportionate growth of bone and soft tissue is usually identified by 6–18 months of age. PS is caused by a somatic activating mutation in the oncogene AKT1. The overgrowth in patients with PS is asymmetric, distorting, and relentless with a rate and severity that vary greatly among patients.

Clinical management: We conducted a retrospective chart review of eight patients with PS whose primary reason for surgery was LLD. Patients were eligible if they met clinical diagnostic criteria for PS and if the NIH team performed at least one of their surgical interventions between 2005 and 2015. Surgical techniques included guided growth, with tension band plates, applied one or more times, and epiphyseal arrest. Eight patients, followed for an average of 4.6 years (range 1.0–7.1 years) after the index procedure, were included in this analysis. Average age at first LLD surgery was 9.4 years (range 6.1–13.6 years); the average LLD was 3.6 cm (range 0.4–8.9 cm) at presentation, and 5.0 cm (range 1.8–10.0 cm) at the time of the first LLD surgery. Participants underwent 23 total surgeries (range 1–5 per patient) and seven patients have completed surgical intervention. For six patients, the average LLD correction at last follow-up was 3.2 cm (range 0.8–6.6 cm). We encountered three complications: one patient developed a fracture of the fibula and ankle varus following development of a distal lateral tibia exostosis, and two patients developed mild knee valgus, which responded to standard guided growth techniques.

Discussion: This case series suggests that guided growth and epiphyseal arrest in children with PS can reduce leg length discrepancy with few complications. Careful monitoring, rapid mobilization, DVT prophylaxis, and sequential compression devices were also integral elements of our surgical protocol.

Level of Evidence: Level IV: This research was conducted under the National Human Genome Research Institute IRB-approved protocol 94-HG-0132: The Phenotype and Etiology of Proteus Syndrome, and was supported by research funding from the Intramural Research Program of the National Human Genome Research Institute (1 ZIA HG200388).

Disclosure: The authors declared no competing interests.