Novel imaging modalities in spondyloarthritis

Defining the imaging diagnostic criteria for adult chronic non-bacterial osteitis

Osteitis of the sternocostoclavicular (SCC) region, referred to as sternocostoclavicular hyperostosis (SCCH), is the clinical expression of chronic non-bacterial osteitis (CNO) in adults with this rare chronic auto-inflammatory disorder of the axial skeleton. The diagnosis is based on distinctive computerized tomography (CT) features of sclerosis and hyperostosis of the SCC region, and local increases in osteoid formation visualized by high radiopharmacon uptake on skeletal scintigraphy but clear radiologic diagnostic criteria are lacking. In a cross-sectional study, CT scans and whole-body skeletal scintigraphy images obtained in 169 patients seen at the Center for Bone Quality of the Leiden University Medical Center between 2008 and 2018 with a suspected diagnosis of CNO of the SCC region were re-evaluated by 2 skeletal radiologists and 2 nuclear physicians. The diagnosis was confirmed in 118 (70%) predominantly female patients (n = 103, 89.2%); median age at first symptoms 45 years (range 20-73). The diagnosis was excluded in the remaining 51 "non-CNO" patients. Increased radiopharmacon uptake at the SCC region was observed in 82% CNO patients, with the manubrium sterni having the highest predictive ability to discriminate on both imaging modalities. The prevalence of sclerosis of the clavicles, manubrium and first ribs was significantly higher in CNO patients (P < 0.001). Hyperostosis was not observed in non-CNO patients. 46 CNO versus only 2 non-CNO patients had costoclavicular ligament calcification. Our findings identify CT scan features of sclerosis and hyperostosis of manubrium sterni, medial end of clavicles and first ribs, and calcification of costoclavicular ligaments, associated with increased tracer uptake on skeletal scintigraphy at the SCC region, specifically manubrium sterni, as well-defined imaging diagnostic criteria for adult CNO. Pitfalls encountered in the diagnosis of CNO are highlighted. These defined imaging diagnostic criteria for adult CNO should facilitate the diagnosis of this rare auto-inflammatory bone disease across the spectrum of its early to late stages.

Enthesitis: A hallmark of psoriatic arthritis

OBJECTIVE

To describe the growing importance of enthesitis in patients with psoriatic arthritis (PsA) and discuss the advantages and disadvantages of clinical and imaging methods currently used to assess enthesitis.

METHODS

PubMed literature searches were conducted using the terms psoriatic arthritis, entheses, enthesitis, pathology, imaging, ultrasound, magnetic resonance imaging, clinical, and indices. Articles were deemed relevant if they provided insight into the pathology, monitoring, and/or diagnosis of enthesitis in PsA, or if they discussed clinical or imaging indices used to assess enthesitis.

RESULTS

Enthesitis is an early manifestation of PsA that is associated with increased disease activity and reduced quality of life. A variety of clinical indices exist to assess enthesitis in PsA; however, the Leeds Enthesitis Index and Maastricht Ankylosing Spondylitis Enthesitis Score index have been the most frequently used indices in recent clinical trials. Limitations of these indices include an inability to discern structural involvement, risk of missing subclinical enthesitis, and lack of sensitivity in detecting enthesitis, especially in patients with central sensitization and/or pain amplification. Such limitations have led to the emergent importance of imaging techniques in the assessment of enthesitis. Although there have been recent advances in magnetic resonance imaging, ultrasound (US) appears to be the preferred method for detecting enthesitis because it allows for accurate assessment of the soft-tissue components of entheses and also for new bone formation. Hypoechogenicity, increased thickness of tendon insertion, calcifications, enthesophytes, erosions, and Doppler activity have been identified as important US characteristics of enthesitis.

CONCLUSION

Enthesitis is thought to be integrally involved in the pathogenesis of PsA and is associated with worse prognostic outcomes in patients with PsA. A validated US index with entheses that are less confounded by mechanical factors and obesity would be the most effective measure of enthesitis in PsA. As imaging techniques continue to advance, our understanding of enthesitis and its involvement in PsA will also improve.