The epidemiology of spondylodiscitis in ankylosing spondylitis--a controlled study

Spondylodiscitis is well recognized in ankylosing spondylitis (AS), but little is known about its epidemiology. We therefore reviewed 147 consecutive patients with AS using lumbar and thoracic spine radiographs. For each patient with spondylodiscitis, two age- and sex-matched controls were selected. Twelve individuals (8%) had spondylodiscitis, affecting a total of 32 disc spaces: 10 thoracic, 22 lumbar. The mean age at onset was 21 +/- 4.1 yr, significantly younger than that of the controls (28.5 +/- 10.1 yr, P = 0.004). Half of the 12 patients had multiple lesions (between two and six levels). The most common site was the lower thoracic spine with additional lumbar spine involvement. Only two of the 12 patients (17%) had symptoms localized to the lesions. Neither trauma nor infection were considered to be causes of the spondylodiscitis.

(1) spondylodiscitis occurs in approximately 8% of patients with AS; (2) these patients have early onset of disease; (3) multiple-level lesions in the spine are not uncommon among those with spondylodiscitis; (4) lesions are usually asymptomatic.