Pseudoacetabulum formation on the femur following untreated femoral neck fracture in a juvenile cat: Surgical management and outcome

Abstract

Femoral neck fractures are relatively common in cats and typically result from high-energy trauma, such as falls from significant heights. If left untreated or inadequately managed, these fractures can lead to chronic complications including pseudarthrosis, joint instability, and impaired function. This report describes a rare case of pseudoacetabulum formation secondary to an untreated femoral neck fracture in a juvenile cat. A four-month-old kitten presented following a fall from height and was diagnosed with a femoral neck fracture. Based on the owner’s decision, conservative management was pursued, and surgery was declined. In the months that followed, the patient developed progressive lameness and hip pain. By seven months of age, advanced imaging revealed separation of the femoral head from the anatomical acetabulum and the formation of a pseudoarticulation between the femoral head and proximal femur metaphysis, consistent with a pseudoacetabulum—a phenomenon more commonly described in human medicine following chronic hip dysplasia. In this case, the pseudoacetabulum was attributed to traumatic injury managed conservatively without adequate follow-up. Surgical excision of the femoral head and neck subsequently resulted in satisfactory functional recovery. This case highlights the importance of timely surgical intervention in femoral neck fractures in young cats and emphasizes pseudoacetabulum formation as a rare but clinically significant sequela of delayed or insufficient treatment.