Assessing the effect of physeal biopsy on angular deformity in a rabbit model

Obtaining a biopsy of the physis in a pediatric/juvenile could provide the ability to diagnose and manage children with physeal abnormalities. However, it has not yet been determined whether a physeal biopsy procedure affects angular deformity. We employed a rabbit model to collect biopsies of the distal femoral and proximal tibial physes on anesthetized, 8-week old New Zealand rabbits. The contralateral limb served as a control. At 8 (n = 5) and 16 (n = 5) weeks postbiopsy, animals were euthanized. Micro-computed tomography (CT) was employed to estimate percentage of the physis biopsied and assess structural abnormalities resulting from biopsy. Bone samples were embedded in polymethylmethacrylate and analyzed. The percentage of physis sampled was ≤1.5% of the total femoral physis while all but one of the tibiae had ≤2.3% removed. There were no iatrogenic clinical or radiographic deformities (frontal or sagittal). Micro-CT and histological analysis suggested that physeal defects had signs of healing that did not lead to subsequent angular deviation. A defect caused by physeal biopsy may not lead to angular deformity. Long-term data could help determine the safety and efficacy of collecting biopsies for histological analyses. Advanced imaging may demonstrate a detailed picture of anatomic or structural alteration of a given physis, but provides no functional information. The diagnostic and therapeutic information that could be gleaned from one or more serial biopsy samples could be invaluable in decision making and clinical management (e.g. skeletal dysplasias and metabolic conditions), so long as subsequent deformity is not a future possibility.