Enthesopathy and Calcifications around the Hip: Should these be Considered Normal Variations?

Abstract

Purpose: Calcific tendinopathy, heterotopic ossification, enthesopathy, and bone erosions are common findings around the hip. These findings, which are typically seen at tendon attachments, may not always be associated with symptomatic disease. Therefore, in this study, we aimed to investigate the prevalence of these findings at eight separate tendon sites around the hip in an asymptomatic population. Material and methods: Our study included 50 patients who underwent a pelvic CT examination for a non-musculoskeletal indication. The patients completed a questionnaire to exclude any hip or pelvic pain, any prior trauma within the hip or pelvis, or any known rheumatological conditions. Two upper-level residents (PGY-4), who received specific training to identify enthesophytes, linear and round calcifications, bone erosions, geodes, and heterotopic bone, independently interpreted the transverse images in a bone kernel. The residents evaluated 8 separate tendon sites around the hip, including: the origins of the conjoint tendon (biceps femoris and semitendinosus) and semimembranosus at the ischial tuberosity; peritrochanteric insertions of gluteus minimus, gluteus medius, and gluteus maximus; the origins of tensor fascia latae and the direct head of rectus femoris; and the insertion of the iliopsoas tendon at the lesser trochanter. At each site, round calcifications, linear calcifications, bone erosions, and enthesophytes were identified, measured, and placed into an appropriate group based on size (< 1mm, 1-5mm, 5-10mm, > 10mm). Descriptive analysis and intraclass correlation coefficients were calculated. Results: The study included 50 patients, 22 men and 28 women, ranging in age from 24 to 94 years (mean age, 61 years). Enthesophytes, which were the most common finding at all the tendon sites, were typically small (< 5 mm); however, larger (> 10 mm) enthesophytes were found at all eight sites. Although less common, linear and round calcifications and erosions were seen at nearly all sites. Geodes, osteophytes, and heterotopic ossification were not identified at any of the investigated sites. The interobserver correlation was good with a calculated intraclass correlation coefficient of 0,697 (95%CI: 0,618-0,759). Conclusion: Enthesophytes are often observed at tendon insertion or origin sites around the hip and are typically asymptomatic, even when larger than 10 mm in size. While calcifications and osseous erosions are less common than enthesophytes, they are also present at nearly all the tendon sites around the hip in asymptomatic populations. Much like enthesophytes, their presence alone should not be attributed to clinical symptoms.