Background Rheumatoid arthritis (RA) in hip can cause severe joint destruction and may require total hip replacement surgery to retain normal joint function. With continuing synovial inflammation within the hip joint, the joint destruction progresses. It results in joint space narrowing, marginal and central erosions, and acetabular protrusion. In most of studies on joint damage in RA patients, the evaluation of joint destruction focuses only on small joints, because radiographic damage was scored according to the Sharp method as modified by van der Heijde, which includes the hands and feet. However, there is limited data on joint destruction of large load-bearing joints such as the hip.
Objectives To study the destruction patterns of the hip joint in RA patients and to examine the relationships between destruction patterns and variables.
Methods Serial hip radiographs of 50 RA patients (62 hips) undergoing total joint replacement were evaluated. The male/female ratio of the subjects was 38/2. The mean age was 59.8 years, and the mean duration of illness was 18.2 years. The mean duration of the period between hip pain onset and the time of surgery was 2.0 years. Biologics were used in six patients. 70% were concomitantly receiving prednisolone (mean dose: 3.0 mg/day). The relationships between destruction patterns of hip joint and variables was analyzed.
Results Joint space narrowing (JSN) was seen in 28% of patients and acetabular protrusion (AP) in 45%. Additional destruction patterns included axial migration of the femoral head with hip dysplasia, avascular necrosis of the femoral head and rapidly destructive arthropathy (RDS). In patients with long-standing disease, JSN developed to acetabular protrusion in serial hip radiographs. In AP, mean protrusion distance was 5.1mm (1-15mm). Patients with biologics showed secondary osteoarthritis-like findings such as osteophytosis and subchondral sclerosis. AP and RDS were more frequently seen in patients with multiple joint destruction, compared with JSN. In AP, CRP and rheumatoid factor were significantly higher compared with JSN (p>0.05). The duration of illness and the duration of the period between hip pain onset and the time of surgery were long and prednisolone dose were high in AP compared with JSN, although no significant difference was observed.
Conclusions Joint space narrowing of the hip joint developed to acetabular protrusion in RA patients with high activity and long-standing disease.
Disclosure of Interest None declared