Jessica Sumping, Philippa Weston, Hayley Crosby-Durrani, Rob Pettitt
Background
Retained endochondral cartilage core (RCC) is a developmental condition commonly reported in skeletally immature large-breed dogs but had not previously been described in cats. RCC can result in angular limb deformities (ALDs) when occurring in paired bones like the radius and ulna, due to asynchronous growth. This report details the first known case of histologically confirmed RCC causing thoracic limb ALDs in a cat.
Methods
A 6-month-old female neutered Bengal-cross cat presented with worsening bilateral thoracic limb deformities. Radiographs and CT revealed symmetrical, flame-shaped radiolucent and hypoattenuating defects within the distal ulnar metaphyses, consistent with RCC. Surgical correction of the right limb was prioritized, including radial and ulnar ostectomies with internal fixation. A bone biopsy from the ulnar metaphysis was submitted for histopathology.
Results
Imaging revealed severe antebrachial procurvatum, medial bowing of the radius, carpal valgus, and elbow incongruency. Histopathology confirmed the presence of mature cartilage lacking primary or secondary spongiosa, with areas of necrosis—findings consistent with RCC. Postoperative radiographs showed improved limb alignment, and the cat exhibited resolution of lameness in the right limb at 10-week follow-up.
Limitations
As a single case report, these findings may not be broadly generalizable. Additionally, while histological and imaging findings strongly supported RCC, the pathophysiological mechanisms remain speculative. No data were presented on long-term outcomes or correction of the contralateral limb at the time of writing.
Conclusions
This report provides the first clinical, radiographic, CT, and histologic documentation of RCC-associated ALDs in a cat. RCC should be considered as a differential diagnosis in juvenile cats presenting with limb deformities. Surgical correction can be effective, and CT is useful for preoperative planning. Further study is needed to understand the prevalence and management of RCC in feline patients.
Sagittal computed tomography image in a bone window (window level 350, window width 2700) of the right antebrachium showing the well-defined hypoattenuating retained cartilage core in the distal ulnar metaphysis (solid black arrow). Note the severe procurvatum of the radius and ulna. Similar changes were present affecting the left thoracic limb.
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