Rapidly progressive osteoarthritis of hip: establishing and validating diagnostic criteria in the Southeast Asian population

BACKGROUND: The study aimed to establish quantitative diagnostic criteria for rapidly progressive osteoarthritis (RPOA) of the hip and to compare the criteria with those for other pathological hip entities in the Asian population. METHODS: From July 2011 to September 2019, 126 patients who had undergone hip replacement were retrospectively recruited from a fast-track joint replacement list. Patient demographics and radiological parameters were evaluated. Diagnosis of hip RPOA was established based on Lequesne et al’s criteria. The patients with RPOA, hip dysplasia, avascular necrosis, and primary osteoarthritis were allocated to the corresponding groups separately and compared. The diagnostic criteria of RPOA were established and validated in the sample population. RESULTS: Diagnosis of hip RPOA was confirmed in 18 patients. Their mean age at surgery (72 years) was significantly higher in this group than in the dysplasia and avascular necrosis groups. The mean pelvic tilt parameter (0.485) of RPOA group was significantly lower than those of other groups. The mean initial Tonnis angle (8.35°) of RPOA group was significantly higher than those of avascular necrosis and osteoarthritis groups. The differences were statistically significant between RPOA and non-RPOA groups in limb shortening rate, superior joint space narrowing, acetabular destruction, and head destruction (P < 0.05). Tonnis angle and lateral subluxation also increased significantly during the disease progression. CONCLUSION: Posterior pelvic tilt and increased Tonnis angle may contribute to the pathogenesis of RPOA, leading to progressive acquired acetabular obliquity and lateral subluxation. We propose the modern comprehensive diagnostic criteria be based on the existing literature and the current findings. Further external validation is recommended.