The normal thicknesses of entheseal insertions in the lower limbs of Japanese individuals

Abstract

Purpose: Ultrasound examination of enthesitis is used to diagnose spondyloarthritis (SpA) early and to evaluate SpA activity. We used the Glasgow ultrasound enthesitis scoring system (GUESS) to screen and evaluate SpA. GUESS defines the cut-off values for the thicknesses of entheseal insertions. However, the thicknesses of entheseal insertions among Japanese individuals is not known. We aimed to clarify the normal thicknesses of entheseal insertions in the lower limbs of Japanese individuals. Subjects and Methods: We evaluated subclinical sites in 77 individuals (770 sites) to screen for SpA and excluded persons with radiographic evidence of enthesophytes, inflammatory bowel disease, psoriasis, and collagen diseases such as SpA and rheumatoid arthritis. Results and Discussion: We evaluated 41 insertions of the quadriceps muscle, 58 insertions of the proximal patellar tendon, 53 insertions of the distal patellar tendon, 24 insertions of the Achilles tendon, and 39 plantar fascia. The mean thickness of quadriceps muscle insertions was 5.11 mm (95% confidence interval [CI], 4.88-5.34, p<0.01). The mean thickness of proximal patellar tendon insertions was 3.25 mm (95% CI, 3.08-3.43, p<0.01). The mean thickness of distal patellar tendon insertions was 3.84 mm (95% CI, 3.64-4.05, p<0.01). The mean thickness of Achilles tendon insertions was 4.16 mm (95% CI, 3.90-4.43, p<0.01). The mean thickness of the plantar fascia was 2.69 mm (95% CI, 2.46-2.92, p<0.01). Conclusion: Our results provide a useful guide for the average thicknesses of entheseal insertions among Japanese individuals. The normal thicknesses should be validated in a larger Japanese cohort to consider factors such as activities of daily living, body shape, participation in sports, sex, radiographic evidence of enthesophytes, and disease.