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Quantifying Proximal Tibial Physeal Injury in Rigid Intramedullary Nailing in Adolescent Patients
Stephanie T Kha1, Michael Johnston2, Justin R Ryan3,4
1Division of Orthopedics, Rady Children's Hospital.
Background:
Rigid intramedullary nailing (RIMN) is increasingly used to treat tibia fractures in skeletally immature patients; however, the volume of injury to the proximal tibial physis and subsequent risk of abnormal growth is unknown. This study aimed to determine volume of proximal tibial physeal injury during RIMN of the tibia in skeletally immature adolescents.
Methods:
The volume of injury to the proximal tibial physis was measured through computer simulation modeling of RIMN using three-dimensional (3D) models. Sixteen normal pediatric knee CT scans (ages 10 to 13 y) with open physes were reconstructed and tibial tubercle ossification stage (TTOS) determined. Opening reamers of 9.75 mm, 11.0 mm, and 12.0 mm diameters were virtually simulated from a standardized suprapatellar starting point and trajectory. Boolean intersection modeling quantified the reamed physeal volume as a percentage of the total physis. A secondary analysis simulated ±10 degrees sagittal trajectory variation for reamer insertion.
Results:
Simulated reaming demonstrated increasing physeal injury with larger reamer diameters. The average percentage of total physeal volume injury simulated by the 9.75 mm, 11.0 mm, and 12.0 mm reamers, respectively, was 3.32%, 4.26%, and 5.15% in the TTOS 0 group; 3.17%, 3.99%, and 4.73% in the TTOS 1 group; and 2.26%, 2.89%, and 3.46% in the TTOS 2 group. Trajectory variation demonstrated that a 10-degree more vertical reamer trajectory change in the sagittal plane increased the volume of physeal injury 1.09 times more than the standard reference trajectory in the TTOS 1 group, while trajectory variations in the TTOS 0 and TTOS 2 groups resulted in minimal volume changes.
Conclusions:
Computer simulation modeling can quantify the volume of injury to the proximal tibial physis during RIMN in skeletally immature patients. The volume of physeal injury appears to remain below the classically described level of concern of 7%. These findings provide a foundation for further investigation into physeal injury thresholds and growth modulation.
Clinical Relevance:
This simulation study informs surgical decision-making and provides insights on growth plate violation when using RIMN to treat skeletally immature tibia fractures.
