Purpose or Case Report: Physeal injuries can result in premature physeal fusion. MR imaging is useful for mapping these bony physeal bridges. Resection of the bony bridge does not reliably restore normal physeal function. We have observed subtle loss of the normal low signal intensity line of the zone of provisional calcification (ZPC) extending beyond areas of physeal bar formation in some patients with prior growth plate fractures. This loss is a marker of disrupted endochondral ossification and likely reflects a more extensive region of physeal damage that might be used to better predict treatment outcomes. Given the subjectivity of visual ZPC assessment, we sought to develop a quantitative 3D map of the periphyseal area of the distal radius using a high resolution 3D fast/turbo spin echo sequence.
Methods & Materials: Evaluation of two patients’ wrist MRI was performed retrospectively with IRB approval. One patient had a prior Salter–Harris type II fracture of the distal radius with a bony bar while the second had a normal wrist MRI performed for non-traumatic reasons.

We developed a program to quantify the MRI signal intensity of the periphyseal region in cross section using a semi-automated approach to provide a more accurate assessment of loss of the ZPC. The normally continuous higher signal band of healthy distal radial physeal cartilage adjacent to the normal low signal intensity ZPC was assessed and compared to the normal distal ulnar periphyseal region. Signal metrics and periphyseal 3D signal maps were obtained. These were evaluated and compared.
Results: Four signal metrics were calculated producing associated signal maps that were color coded: Difference in signal minimums, peak minus minimum ratio, slope of minimums and voxel distance from ZPC to peak. Comparisons were made between the distal radius and ulna and between the 2 subjects with fracture and normal wrist. Signal maps demonstrated visually detectable differences that correlate with loss of the ZPC surrounding the physeal bridge versus normal radius and ulna.
Conclusions: Quantifiable changes in the ZPC can be demonstrated with this model. The model will be applied to MRI’s in patients with prior growth plate fractures and compared with clinical outcomes to determine its utility in providing a more complete assessment of physeal function.