Clustered Occurrence of Osteitis Condensans Ilii in Patients with Symptomatic Hip Dysplasia

Background: Osteitis condensans ilii (OCI) is a relatively rare benign disease of the lower anterior sacroiliac joint (SIJ) region that can cause symptoms such as low back pain (LBP), lateral hip pain and nonspecific hip or thigh pain. Its exact pathoetiology remains to be clarified. The aim of this study is to determine the prevalence of OCI in patients with symptomatic developmental dysplasia of the hip (DDH) undergoing periacetabular osteotomy (PAO) to identify potential clustering of OCI in a with altered biomechanics of hip and SIJs. Methods: A retrospective investigation of all patients who underwent periacetabular osteotomy in a tertiary reference hospital from January 2015 to December 2020. Clinical and demographic data were retrieved from the hospital's internal medical records. Radiographs and magnetic resonance images (MRIs) were reviewed for the presence of OCI. A t-test for independent variables was conducted to identify differences between patients with and without OCI. A binary logistic regression model was established to determine the influence of age, sex and body mass index (BMI) on the presence of OCI. Results: The final analysis included 306 patients (81% female). In 21.2% of the patients (f: 22.6%; m: 15.5%), OCI was present. BMI was significantly higher in patients with OCI (23.7 kg/m(2) vs. 25.0 kg/m(2); p = 0.044). Binary logistic regression revealed that a higher BMI increased the likelihood of sclerosis in typical osteitis condensans locations, OR = 1.104 (95%-CI [1.024, 1.191]), as did female sex, OR = 2.832 (95%-CI [1.091, 7.352]. Conclusions: Our study revealed a considerably higher prevalence of OCI in patients with DDH than in the general population. Furthermore, BMI was shown to have an influence on the occurrence of OCI. These results support the theory that OCI is attributable to altered mechanical loading of the SIJs. Clinicians should be aware that OCI is common in patients with DDH and a potential cause of LBP, lateral hip pain and nonspecific hip or thigh pain.