Spinal position sense in ankylosing spondylitis.

STUDY

DESIGN

A cross-sectional comparison of spinal position sense in 50 patients with mild ankylosing spondylitis and 50 healthy controls.

OBJECTIVES

To determine if spinal position sense is impaired in patients with mild ankylosing spondylitis.

SUMMARY OF BACKGROUND DATA: Pathologic processes in ankylosing spondylitis target sites in the spine where joint capsules, ligaments, and tendons attach into bone. Because these sites contain receptors conveying position sense, proprioception may become impaired, and this may contribute to the spinal deformity that often develops in the more advanced stages of the disease. If deficits in proprioception are apparent then specialized exercise regimes aimed at improving proprioception in ankylosing spondylitis patients could prove beneficial.

METHODS

Position sense was assessed in patients and controls by determining the absolute error in reproducing upright and flexed postures in the coronal and sagittal planes using an electromagnetic tracking device, the 3-Space Fastrak (Polhemus, Colchester, VT). Measurements were taken from sensors placed on the skin overlying T1, T7, L1, and S2. In patients, the association between position sense and validated radiographic, disease activity, and functional scores was explored.

RESULTS

No deficits in spinal position sense were found in patients with mild ankylosing spondylitis. In these subjects, repositioning errors were < or = 3.88 degrees in flexed postures and < or = 2.76 in upright postures. Corresponding results for controls were < or = 4.86 degrees and < or = 3.42 degrees, respectively. Weak correlations were found between position sense and other ankylosing spondylitis outcome measures, which included indexes of function, disease activity, and posture and mobility, but in all cases, the overall trend was for position sense acuity to improve slightly with more advanced disease.

CONCLUSION

Spinal position sense is unaffected in patients with mild ankylosing spondylitis and is therefore unlikely to be a useful outcome measure in this condition.