AUTOMATICALLY DETERMINED MINIMAL JOINT SPACE WIDTH IS LOWER IN SUBJECTS WITH RADIOGRAPHIC HIP OA BUT NOT SIGNIFICANTLY DIFFERENT IF HIP PAIN IS PRESENT: A MULTI-COHORT ANALYSIS

INTRODUCTION

Current epidemiological research on management and prevention of hip OA faces challenges due to the lack of a uniform OA definition. Automated detection of radiographic features on x-ray images across studies such as the minimal JSW (mJSW) could be a solution. However, having radiographic evidence of hip OA does not always imply having symptoms or disability and vice-versa. In order to create an automated hip OA definition, we need to improve our understanding of the interplay between the mJSW and clinical and radiographic factors in a large and diverse population.

OBJECTIVE

To investigate the differences in automatically determined mJSW values between subjects without hip complaints, with radiographic hip OA, and/or with hip pain.

METHODS

We utilized individual participant data (IPD) from two prospective cohort studies: Cohort Hip and Cohort Knee (CHECK), Johnston County Osteoarthritis Project (JoCoOA), and the Multicenter Osteoarthritis Study (MOST). These studies had weight-bearing (CHECK, MOST) or supine (JoCoOA) standardized anteroposterior (AP) pelvic, long-limb, and/or hip radiographs taken and graded for radiographic hip OA (RHOA) with the KLG. Additionally, the presence of hip pain was determined by converting survey questions into a binary variable. We uniformly measured the mJSW by measuring the minimal distance (in mm) between outlines of the femoral head and weight-bearing part of the acetabulum based on linear B-spline interpolation between automatically placed landmark points (Figure 1). Our study population consisted of 2,400 subjects (4,745 hips), of which 64.5% were female, with a mean age of 61.0 years (SD = 9.0) and a mean body mass index of 28.9 kg/m² (SD = 5.5). We used ANOVA with post-hoc pairwise comparisons to analyze differences in mJSW between four groups: subjects without hip pain and RHOA, with only hip pain, with only RHOA (KLG ≥2), or both RHOA and hip pain. To adjust for correlations between subjects and cohorts, a linear mixed-effects model was fitted with a nested intercept for subject and cohort, and with a correction factor for hip side. We performed separate analyses for male and female subjects.

RESULTS

From the total of 4,745 included hips, 2,080 (43.8%) had RHOA, hip pain or both. In both male and female subjects, the mJSW was found to be significantly lower in people with RHOA (Figure 2). Subjects that experienced hip pain did not have a significantly different mJSW than subjects without hip pain, both with and without RHOA present.

CONCLUSION

The automatically measured mJSW showed significant differences in mean values between people with and without RHOA, irrespective of the presence of pain. No significant differences were found between people with and without hip pain, irrespective of RHOA.