Review Question - QID 9100

The patient sustained a Salter-Harris III ankle fracture. His follow-up radiograph shows evidence of a physeal injury with physeal bar formation, which is caused by injury to the zone of calcification within the hypertrophic zone.

The hypertrophic zone can be subdivided into the zone of maturation, the zone of degeneration, and zone of calcification. Most physeal fracture separations occur at the hypertrophic zone, particularly at the zone of provisional calcification. The zone of provisional calcification is a transition point between calcified and noncalcified extracellular matrix proteins and is weaker than the surrounding bone and ligaments. In Salter-Harris III and IV fractures, the resting and proliferative zones are sometimes involved. Physeal injuries can lead to complications from growth arrest, leading to angular deformities or limb length discrepancies.

Salter et al. published a review of injuries involving the epiphyseal plate. They reported that physeal fractures almost invariably occur on the diaphyseal side of the epiphyseal plate through the zone of hypertrophy and that the fracture line occasionally deviates into the shaft, leaving a triangular fragment of the metaphysis attached to the epiphysis.

Figure A is an AP radiograph of the ankle demonstrating a Salter-Harris type III fracture. Figure B is an AP radiograph of the ankle demonstrating physeal bar formation. Illustration A shows the histology of the physis, which consists of the reserve zone, proliferative zone, hypertrophic zone, and primary spongiosa.

Incorrect Answers:
Answers 1, 2, 4, and 5: Fractures through the physis typically occur in the zone of calcification within the hypertrophic zone.