Intracapsular pressure and interleukin-1β cytokine in hips with acetabular dysplasia

BACKGROUND AND PURPOSE Several studies have demonstrated an increased intracapsular pressure in several hip disorders such as septic arthritis, synovitis, and trauma. We therefore measured the intracapsular pressure in different positions in early dysplasic hips and its relation to the concentration of interleukin-1beta (IL- 1beta), the volume of joint fluid, and the clinical and radiographic findings before a periacetabular osteotomy. METHODS 12 female patients (12 hips, mean age 35 (18-52)) with hip dysplasia were investigated. The intracapsular pressure was recorded and we investigated possible correlations with the Harris hip score, the Tönnis scale, radiographic findings, the volume of joint fluid, and the concentration of IL-1beta. RESULTS An increased intracapsular pressure was noted, especially in flexion or extension with internal rotation. We found positive correlations between the intracapsular pressure and both the volume of joint fluid and the concentration of IL-1beta. INTERPRETATION Increased intracapsular pressure varied with different positions, indicating the presence of synovitis resulting from early osteoarthritis in dysplastic hips. Positive correlations between the pressure and both the concentration of IL-1beta and the volume of joint fluid suggest that the inflammatory cytokines produced by the synovial membrane as a consequence of mechanical instability of the hip joint may be of importance for the initiation and/or development of osteoarthritis in dysplastic hips.