Calcaneal enthesial reaction and "divots" lack specificity
The study by Feydy and colleagues1 clearly evidences the importance of controls for assessment of the significance of clinical/radiologic observations/signs. Their eloquent study appropriately challenges the preconceived notion that enthesitis or enthesial reaction is an identifier for spondyloarthropathy2-5 and confirms the perceptions derived from studies of human skeletal collections.6,7 Those studies revealed no statistically significant correlation of enthesitis with presence of inflammatory arthritis.7
Enthesial discontinuities ("divots"), originally thought to be erosive in nature, were rare on examination of defleshed skeletons and their presence did not correlate with presence of underlying disease.7 Examination of skeletons also did not reveal any difference in the character of enthesopathy occurring in spondyloarthropathy and that occurring in the general population (healthy individuals) and led us to speculate that MRI might provide insights. We suggested that these lesions might actually be analogous to those found in the distal femur, attributed to tendon avulsion injuries.7
Feydy's study1 is precisely on point. They demonstrated no significant difference in character of lesions, with one exception: bone edema. Perhaps bone edema may well be the response to an acute or subacute avulsion, which resolves with chronicity? Sedimentation rates appear inconsistent in patients with spondyloarthropathy. It will be interesting if Feydy's group can correlate MRI findings of bone edema with laboratory measures of injury, rather than invoke inflammation.
1. Feydy A, Lavie-Brion M-C, Gossec L, et al. Comparative study of MRI and power Doppler ultrasonography of the heel in patients with spondyloarthritis with and without heel pain and in controls. Ann Rheum Dis 10.1136/annrheumdis-2011-200336
2. Mander M, Simpson JM, McLellan A, et al. Studies with an enthesitis index as a method of clinical assessment in ankylosing spondylitis. Ann Rheum Dis 1987;46:197-202.
3. Hueft-Dorenbosch L, Spoorenberg A, van Tubergen A, et al. Assessment of enthesitis in ankylosing spondylitis. Ann Rheum Dis 1003;62:127-32.
4. de Miguel E, Cobo T, Mu?oz-Fern?ndez S, et al. Validity of enthesis ultrasound assessment in spondyloarthropathy. Ann Rheum Dis 2009;68:169-74.
5. D'Agostino MA, Said-Nahal R, HaCQUARD-Bouder C, et al. Assessment of peripheral enthesitis I the spondyloarthropathyies by ultrasonography combined with power Doppler: A cross-sectional study. Arthritis Rheum 2003;48:523-33.
6. Dutour O. Enthesopathies (Lesions of muscular insertions) as indicators of the activities of Neolithic Saharan populations. Amer J Phys Anthropol 1986;71:221-224.
7. Shaibani A, Workman R, Rothschild B. The Significance of enthesophyte/enthesopathy as a skeletal Phenomenon. Clin Exp Rheumatol 1993;11:399-403.
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