Pelvic enthesopathy on CT is significantly more prevalent in patients with diffuse idiopathic skeletal hyperostosis (DISH) compared with matched control patients.

The purpose of this study is to evaluate the prevalence of pelvic enthesopathy on computed tomography (CT) in patients with DISH compared to matched control group. Pelvic CT examinations of patients with DISH (Resnick criteria) were retrospectively evaluated for the presence of enthesophytes at four entheseal sites bilaterally: ischial tuberosity, pubis, greater trochanter, and anterior superior iliac spine (ASIS). This was compared with age- and gender-matched control group of consecutive patients with <2 flowing osteophytes on CT along the entire spine. Multivariate analysis of variance (ANOVA) was applied to examine the degree of difference between pelvic enthesopathy in DISH patients and controls and to estimate the potential predictive ability of the different findings. Logistic regression analysis was used to estimate the odds ratio of the studied findings. Pelvic CTs of 210 patients (149:61, M:F; average age, 72.3 years) were evaluated: DISH group, 104 patients (74:30, M:F); matched control group, 106 patients (75:31, M:F). Mean total and local enthesopathy scores were significantly higher in the DISH group compared with the control group (total 5.03:1.9; ASIS 1.58:0.55; pubis 0.94:0.36; ischial tuberosity 1.47:0.76; greater trochanter 1.04:0.24; p < 0.001). ASIS and greater trochanter enthesophytes were the most robust contributors that significantly distinguished between patients with DISH and those without DISH. Prominent enthesophytes were more common among DISH patients (DISH:controls, 52:13, p = 0.02). Prominent pelvic enthesophytes detected on CT have a strong discriminating power between DISH and non-DISH patients. Results imply that pelvic enthesopathy may be included in the radiographic criteria for DISH.