Bone Changes in Spine Disease Worse With Inflammation
Written by Editor   
Tuesday, May 13, 2014 12:21 PM

Whether inflammation and disease activity correlate with the radiographic damage caused by new spinal bone formation in AS has been a matter of debate, with two main hypotheses emerging. Some have argued that the bone effects are independent of inflammation and others claim that inflammation underlies osteoblast stimulation.

"The first hypothesis states that inflammation, including the upregulation of TNF, triggers local damage and subsequently repair leading to new bone formation and ankylosis. The second hypothesis states that a common trigger is responsible for both inflammation and new bone formation, but that both phenomena further develop in a largely molecularly independent way,"

High disease activity in ankylosing spondylitis (AS) was associated with radiographic disease progression in the spine, a longitudinal study showed.  "We have demonstrated here for the first time that the effect of disease activity on radiographic damage is actually rather impressive."

The reason why progression was more pronounced in the earlier phase of disease may have been that younger patients have greater physical activity that could alter mechanical factors affecting the spine.  "One may reason that younger people with shorter disease duration will usually perform more intensive occupational physical activities with stronger forces acting on the spine."

Patients with very high disease activity -- AS disease activity index (ASDAS) scores of 3.5 at baseline -- had progression of 3.1 units on spine x-ray scores over 2 years, in contrast, those with inactive disease -- ASDAS scores below 1.3 at baseline -- had an average progression of only 0.71 units over that period of time.

The researchers noted that, while disease activity was associated with radiographic progression in this analysis, "we acknowledge that disease activity (inflammation) by far does not fully explain radiographic damage in AS: even without measurable disease activity there is still considerable radiographic progression."  "It seems as if increased bone formation in AS is partly constitutive and partly inflammation-dependent."

Nonetheless, they concluded that inflammation does contribute to bone changes in AS.  "We now have clear evidence that inflammation and new bone formation are related in AS."