Stressed or fractured: MRI differentiating indicators of physeal injury.

Objective: To identify MRI findings that can indicate chronic physeal stress injury and differentiate it from acute Salter-Harris (SH) fracture of the pediatric knee or wrist.

Methods: IRB-approved retrospective study of consecutively selected knee and wrist MRIs from 32 athletes with chronic physeal stress injury and 30 children with acute SH fracture. MRI characteristics (physeal patency, physeal thickening, physeal signal intensity (SI), continuity of the zone of provisional calcification (ZPC), integrity of the periosteum and/or perichondrium, pattern of periphyseal and soft tissue edema signal, and joint effusion) were compared.

Results: Forty-eight chronic physeal stress injuries (mean age 13.1 years [8.2-17.5 years]) and 35 SH fractures (mean age 13.3 years [5.1-16.0 years]) were included. Any physeal thickening was more common with chronic stress injury (98% vs 77%, p = 0.003). Abnormal physeal SI was more common with SH fractures (91% vs 67%, p = 0.008). ZPC discontinuity strongly suggested chronic stress injury (79% vs 49%, p < 0.004). Periosteal and/or perichondrial elevation or rupture and soft tissue edema characterized most of the acute SH fractures (p < 0.001) and were seen only in 1 chronic stress injury (< 2%). While periphyseal edema was not significantly different in the two groups (p = 0.890), a joint effusion was associated with acute SH fracture (p < 0.001).

Conclusion: Chronic physeal stress injury of the pediatric knee and wrist shows higher incidence of ZPC discontinuity and focal physeal thickening compared to SH fracture, reflecting disruption in normal endochondral ossification. However, these findings can overlap in the 2 groups. Periosteal and/or perichondrial injury, soft tissue edema signal, and joint effusion strongly suggest SH fracture and are rarely present with chronic stress injury.