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Objective. To assess the performance of computed tomography (CT) scanning for ascertaining sacroiliitis in patients with suspected spondylarthritis (SpA). Methods. The Echography in SpondylarthritisFrench cohort consists of 489 patients with suspected SpA. At baseline, all patients underwent clinical examination, HLA-B typing, and pelvic radiography. Pelvic CT scanning was performed if sacroiliitis on radiography was considered uncertain or if patients presented with buttock pain duration of >6 months. A set of 100 paired radiographs and CT scans was read in a blinded manner by 2 radiologists, and the kappa coefficient was used to assess their interreader reliability. One of the radiologists read the 173 available pairs of radiographs and CT scans performed at baseline. Results. After training, interreader reliability was moderate for sacroiliitis grading on radiographs ( ‫؍‬ 0.59), excellent on CT scans ( ‫؍‬ 0.91), and excellent for ascertaining sacroiliitis on both radiographs ( ‫؍‬ 1) and CT scans ( ‫؍‬ 0.96). The first and second readers considered the quality of imaging to be excellent in 66% and 67%, respectively, of the radiographs ( ‫؍‬ 0.88) and in 93% and 92%, respectively, of the CT scans ( ‫؍‬ 0.93). Concordance between radiographs and CT scans was low for sacroiliitis grading ( ‫؍‬ 0.08) or ascertainment ( ‫؍‬ 0.16). Definite sacroiliitis was ascertained on radiographs in 6 patients (3.5%) (confirmed by CT scans in 4 patients) and on CT scans in 32 patients (18.5%). A history of uveitis was associated with definite sacroiliitis on radiographs (P ‫؍‬ 0.04) and CT scans (P < 0.0001).Conclusion. Definite sacroiliitis was underestimated by radiography, as compared to CT scanning. CT scanning should facilitate the diagnosis of ankylosing spondylitis in patients with suspected SpA.ClinicalTrials.gov identifier: NCT00794404.

In this study, we tested the hypotheses that (a) both the domain volume (volume of the cell and the matrix it has formed) and matrix volume of juxtametaphyseal hypertrophic chondrocytes in the growth plate is tightly controlled, and that (b) the domain volume of juxtametaphyseal hypertrophic chondrocytes is a strong determinant of the rate of bone length growth. We analyzed the rate of bone length growth (oxytetracycline labeling techniques) and nine stereologic and kinetic parameters related to the juxtametaphyseal chondrocytic domain in the proximal and distal radial and tibial growth plates of 21- and 35-day-old rats. The domain volume increased with increasing growth rates, independent of the location of the growth plate and the age of the animal. Within age groups, the matrix volume per cell increased with increasing growth rates, but an identical growth plate had the same matrix volume per cell in 21- and 35-day-old rats. The most suitable regression model (R2 = 0.992) to describe the rate of bone length growth included the mean volume of juxtametaphyseal hypertrophic chondrocytes and the mean rate of cell loss/cell proliferation. This relationship was independent of the location of the growth plate and the age of the animal. The data suggest that the domain volume of juxtametaphyseal hypertrophic chondrocytes, as well as the matrix volume produced per cell, may be tightly regulated. In addition, the volume of juxtametaphyseal hypertrophic chondrocytes and the rate of cell loss/rate of cell proliferation may play the most important role in the determination of the rate of bone length growth.

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