Intraoperative picture of hip joint lesion in ankylosing spondylitis: data from a retrospective analysis

In population of Russian patients with ankylosing spondylitis (AS), the frequency of clinical manifestations (pain and limitation of functions) of coxitis reaches 56%. Total hip arthroplasty (THA) can be considered as the only alternative that can relieve the suffering of the patient. Radiography and magnetic resonance imaging are widely used methods for assessing structural damage to the hip joint in AS. However, at the moment these methods can’t allow us to fully describe the lifetime changes of these joints. The aim of the study: to analyze the external changes of the femoral heads (HF) and acetabulums during the THA in patients with AS. Materials and methods. The retrospective study included 170 patients with a reliable diagnosis of AS, who met the modified New York criteria of 1984, who were treated in the traumatological and orthopedic department of the V.A. Nasonova Research Institute of Rheumatology in the period from 1998 to 2020, all patients underwent THA as planned. Most of them were male (80.6%). The average age of patients was 38.1±11.3 years and the average duration of the disease since the onset of the first symptoms was 17.0±8.5 years. The duration of pain in hip joints before performing THA is 7.4±4.8 years. The assessment of macroscopic changes in the FH and acetabulum was performed intraoperatively. Results and discussion. Acetabulum protrusion was detected in 108 (63.5%) patients, bone cysts – in 65 (38.2%). Filling of acetabulum with granulation tissue was recorded in 155 (91.2%) patients, presence of osteophytes on its edges – in 153 (90%). Cartilage in the acetabulum was completely absent in 122 (71.8%) patients. FH deformation was detected in 98.2% of cases, erosion in 46.4%. Cartilage on FH was completely absent in 130 (76.5%) patients. In 119 (70%) patients, macroscopic signs of osteonecrosis of FH were found. 79 (46.4%) patients had ankylosis of the hip joint, including fibrous ankylosis – in 77.2% of patients and bone ankylosis – in 22.8%. Conclusion. In patients with AS, the necessity for THA occurs on average after 7.4±4.8 years from the moment of the appearance of first clinical signs of coxitis. In 70% of cases, the macroscopic picture of hip joint lesion was characterized by the development of Avascular necrosis of the femur head (AVNFH), in most patients there was no cartilage in the most loaded segments of acetabulum and FH, in almost half of cases – ankylosis of hip joint and mainly fibrous (77.2%).