Femoral neck fracture in acetabular protrusions secondary to rheumatoid arthritis: a case report and literature review

Abstract

The present study shows the case of a patient with acetabular protrusions secondary to rheumatoid arthritis pro-gressing to femoral neck fracture. The patient, a 64 years female, had a history of rheumatoid arthritis for 38 years. The left hip pain and abnormal sound occurred when hip flexion for picking up. She was diagnosed with rheumatoid arthritis secondary to acetabular pelvic retraction and left femoral neck fracture by medical history, physical examination and imaging. Total hip arthroplasty was performed after preoperative examination. Hip dislocation, femoral head removal, acetabular reconstruction, cup fixation, and bone mass assessment are technical challenges during surgery. Based on literature review, this case is belonging to secondary acetabular pelvic retraction, which may be related to acetabular softening caused by rheumatoid arthritis. When the stress from the femoral head exceeds the endurance of the softened acetabulum, the acetabulum protrudes into the pelvis and gradually wraps around the femoral head. Based on the pathological characteristics, it is speculated that the cause of femoral neck fracture is the direct hit of the femoral neck-acetabular rim during hip flexion. In this case, spiral cup prosthesis was used to achieve both the initial stability of the prosthesis and saving bone mass around the acetabulum. The patient was followed up for 3 months with satisfactory position of prosthesis and joint function.