Although femoral head and neck fractures from trauma are common, they can also occur spontaneously in young, obese, neutered male cats. Neutering reportedly causes a delay in growth-plate closure in the femoral capital physis and other locations. Furthermore, reduced testosterone leads to a delay in physeal cartilage maturation and closure. In cases of spontaneous capital physeal fracture (also called slipped capital physis or physeal dysplasia syndrome), both hindlimbs may be affected at the same time or a spontaneous fracture may later develop in the opposite limb. Essentially, the differential list for any young cat presenting with hindlimb lameness/weakness should include fractures of the femoral head and neck, regardless of whether the event was associated with trauma. Radiographs in a “frog-legged” position may improve visualization of capital physeal fractures that are not obvious on an extended view. Treatment may be surgical or conservative, although the latter carries a risk for nonunion. Conservative treatment includes exercise restriction (crate confinement for at least 4 weeks) and analgesia. Surgical stabilization with K-wires can be performed but should be done within 3 to 4 days of the fracture to minimize alterations in vascularization of the epiphysis and remodeling of the metaphysis. Total hip replacement has also been successful but requires greater surgical expertise. Chronic fractures in which bone remodeling can already be visualized radiographically are best managed with a femoral head and neck excision (FHNE). Surgical correction carries a good to excellent prognosis, although arthritis and bony remodeling are possible with any approach.

Commentary: Fractures of the femoral head and neck in cats likely have a similar pathophysiology to Legg-Calvé-Perthes disease in small-breed dogs, although blood supply to the epiphysis through the ligament of the femoral head is much more robust in cats. Pain and lameness in cats are often underdiagnosed, and this review highlights the importance of radiography in pursuing a diagnosis. Sometimes with capital femoral growth-plate fractures in cats and small dogs, a delayed presentation will cause primary repair to lead to hip arthritis. Therefore, FHNE may be an appropriate first approach. Options for oral pain control are buprenorphine, oxycodone, gabapentin, amantadine, dexmedetomidine, or tramadol.—Jonathan Miller, DVM, Diplomate ACVS

Young, male, neutered, obese, lame? Non-traumatic fractures of the femoral head and neck. Lafuente P. J FELINE MED SURG 13:498-507, 2011.