Costovertebral joint involvement on CT in SAPHO syndrome: distribution and clinical associations

To characterize the distribution and structural patterns of costovertebral joint (CVJ) lesions on CT in SAPHO syndrome and to evaluate their clinical and laboratory associations.

This retrospective cross-sectional study included 61 patients with SAPHO syndrome who underwent CT (2018-2024); T1-T12 levels were analyzed. Twenty-three matched controls were included for nonspecific findings. Two blinded radiologists classified SAPHO-specific and nonspecific CVJ lesions. Thoracic involvement and costovertebral joint lesion burden were assessed using a unit-based framework. Associations were tested with Spearman correlation and negative binomial regression; disease duration across ordered lesion subtypes was assessed.

SAPHO-specific CVJ lesions were present in 23/61 patients (37.7%), including seven with isolated CVJ involvement. Among affected patients, 268 of 966 CVJ units (27.7%) were abnormal, with vertebral-aspect predominance in unilateral lesions (69 vs 5, p < .001) and a mid-thoracic peak (54.5%, p < .001). Inferior half-unit involvement was more frequent than superior half-unit involvement (59.4% vs 40.6%, p = .005). Compared with controls, SAPHO patients had more nonspecific marginal osteophytes (p < .001). Lesion burden correlated with BASFI and BASDAI (p < .050). In multivariable regression, male sex and BASFI were independently associated with higher lesion burden; results were similar when BASDAI was substituted for BASFI (p < .050). Disease duration did not differ across ordered structural subgroups (p > .050).

CT demonstrates frequent, predominantly vertebral-sided mid-thoracic CVJ involvement in SAPHO syndrome, often affecting inferior half-units and occasionally occurring in isolation. Lesion burden is independently associated with male sex and functional impairment.