Prevalence of radiographic hip osteoarthritis is increased in high bone mass

Abstract

Objective: Epidemiological studies have shown an association between increased bone mineral density (BMD) and osteoarthritis (OA), but whether this represents cause or effect remains unclear. In this study, we used a novel approach to investigate this question, determining whether individuals with High Bone Mass (HBM) have a higher prevalence of radiographic hip OA compared with controls.

Design: HBM cases came from the UK-based HBM study: HBM was defined by BMD Z-score. Unaffected relatives of index cases were recruited as family controls. Age-stratified random sampling was used to select further population controls from the Chingford and Hertfordshire cohort studies. Pelvic radiographs were pooled and assessed by a single observer blinded to case-control status. Analyses used logistic regression, adjusted for age, gender and body mass index (BMI).

Results: 530 HBM hips in 272 cases (mean age 62.9 years, 74% female) and 1702 control hips in 863 controls (mean age 64.8 years, 84% female) were analysed. The prevalence of radiographic OA, defined as Croft score ≥3, was higher in cases compared with controls (20.0% vs 13.6%), with adjusted odds ratio (OR) [95% CI] 1.52 [1.09, 2.11], P = 0.013. Osteophytes (OR 2.12 [1.61, 2.79], P < 0.001) and subchondral sclerosis (OR 2.78 [1.49, 5.18], P = 0.001) were more prevalent in cases. However, no difference in the prevalence of joint space narrowing (JSN) was seen (OR 0.97 [0.72, 1.33], P = 0.869).

Conclusions: An increased prevalence of radiographic hip OA and osteophytosis was observed in HBM cases compared with controls, in keeping with a positive association between HBM and OA and suggesting that OA in HBM has a hypertrophic phenotype.

Keywords: DXA; Epidemiology; Osteoarthritis; Osteoporosis; Radiology.

Fig. 1

(A) Selection of HBM case and family control X-rays (process of recruitment to study previously reported¹⁶). (B) Selection of Chingford study female control X-rays. (C) Selection of HCS EPOSA male and female control X-rays. ¹Reason recorded for missing X-ray in HBM cases: unable to travel (n = 7), no X-rays at study centre (n = 23), unable to attend/wait/comply (n = 4), patient declined (n = 8), not done (reason unknown) (n = 9), reside abroad (n = 2), bilateral hip replacements (n = 6). ²Reason recorded for missing X-ray in family controls: did not continue in study (n = 1), unable to travel (n = 1), no X-rays at study centre (n = 9), unable to attend/wait/comply (n = 2), patient declined (n = 4), not done (reason unknown) (n = 3), bilateral hip replacements (n = 1). ³Sampling frame constructed from dates of year 2, 8 and 20 follow-up visits supplied by study team. Reason recorded for missing X-ray in Chingford controls: not found at time of request (n = 6), not digitised (n = 18), unknown reason (n = 15). ⁵Sampling frame constructed from study X-ray appointment dates supplied by study team. ⁶Reason recorded for missing X-ray in HCS controls: bilateral hip replacements (n = 3), unknown (n = 7). ⁷One individual contributed only one hip. ⁸Excluded as missing lateral femoral osteophyte variable. ⁹Excluded as previous fracture with fixation device in situ precluding reliable assessment.

Fig. 2

Figure shows OR for hip OA (defined as Croft score ≥3) in HBM cases vs controls, according to age group, adjusted for gender and BMI. <50 y n (no. of hips) = 324, 81.5% female; 50–60 y n = 420, 89% female; 60–70 y n = 669, 87.4% female; >70 y n = 819, 74% female. GEE used to account for within participant clustering (left/right).