Review Question - QID 211293

A distal femoral physeal injury typically occurs through the weakest portion of the growth plate which is the hypertrophic zone, where chondrocytes are undergoing hypertrophy or an increase in their cell size.

The physis consists of the reserve, proliferative, and hypertrophic zones. The hypertrophic zone is often subdivided into the zone of maturation, the zone of degeneration, and the zone of provisional calcification, which is the transition point between calcified and non-calcified extracellular matrix proteins. This is typically the location of fractures and physeal injuries as this location is weaker than the surrounding bone and ligaments.

Zionts reviewed pediatric fractures around the knee. With regard to distal femur fractures, oblique radiographs or gentle stress radiographs may help elucidate subtle growth plate fractures that aren't apparent on plain radiographs. Furthermore, MRI may be helpful at identifying fractures in patients who have a clinical picture consistent with a physeal injury but normal radiographs.

Caine et al. reviewed 3 potentially serious injuries in the child and adolescent athlete, with physeal injuries being one of them. They reported that physeal injuries disrupt metaphyseal perfusion which in turn inhibits ossification of the chondrocytes in the zone of provisional calcification within the hypertrophic zone of the growth plate. They concluded that when mismanaged, physeal injuries can result in long-term complications including growth premature arrest.

Edwards et al. discussed physeal fractures around the knee. They state physeal fractures of the distal femur often occur secondary to a valgus force across the knee causing medial physeal separation. They recommend radiographic follow up after treatment as these injuries have a high rate of physeal arrest.

Figure A shows a coronal T2 image of a skeletally immature knee with entrapped periosteum in the medial distal femoral physis. Figure B shows a sagittal T2 image with entrapped periosteum in the posterolateral distal femoral physis. Illustration A shows an illustration of the growth plate and the zone of proliferation where cells are increasing in number as well as the zone of hypertrophy where cells are increasing in size.

Incorrect Answers:
Answer 1: The femoral attachment of the ACL is not shown in the given MRI slices.
Answer 2: The meniscocapsular junction of the medial meniscus is intact on the given imaging.
Answer 3: A cartilage and subchondral bone interface injury are consistent with an osteochondral defect which is not seen on advanced imaging.
Answer 4: The growth plate zone where the cells are increasing in number is the zone of proliferation which is not the area where physeal fractures occur.