Central hypersensitivity in patients with subacromial impingement syndrome.
OBJECTIVE
To investigate the presence of primary and secondary hyperalgesia among subjects with chronic subacromial impingement syndrome (SIS) compared with pain-free controls.


METHODS
Cross-sectional design.


METHODS
Outpatient rehabilitation clinic, urban, academic medical center.


METHODS
Volunteer sample (N=62) (31 with SIS, 31 controls).


METHODS
Not applicable.


METHODS
Pressure-pain thresholds (PPTs) were measured at the middle deltoid of the affected/dominant arm (primary or secondary hyperalgesia) and the middle deltoid and tibialis anterior of the unaffected/nondominant side (secondary hyperalgesia) in SIS and healthy controls, respectively. Differences in PPTs were analyzed by Wilcoxon rank sum test and with linear regression analysis controlling for sex, a known confounder of PPTs.


RESULTS
After adjusting for sex, subjects with SIS had significantly lower PPTs than did controls at all locations. Controls had a 1.4 kg/cm(2) (95% confidence interval [CI], 1.2-1.5) higher PPT at their affected shoulder than did those with SIS, a 0.7 kg/cm(2) (95% CI, 0.5-0.9) higher PPT at their nonaffected shoulder, and a 1.1 kg/cm(2) (95% CI, 1.1-1.2) higher PPT at their contralateral tibialis anterior. Observers were not blinded to patient groupings but were blinded to the level of applied pressure.


CONCLUSIONS
This study provides further evidence that patients with SIS have significantly lower PPTs than do controls in both local and distal areas from their affected arm consistent with primary and secondary hyperalgesia, respectively. Data suggest the presence of central sensitization among subjects with chronic SIS.
Case Western Reserve University School of Medicine, Cleveland, OH, USA.
Tracy Maria
TM
Paul
Jennifer
J
Soo Hoo
John
J
Chae
Richard D
RD
Wilson
D000328:Adult; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000453:epidemiology*; D008297:Male; D017288:Pain Threshold; D012047:Rehabilitation Centers; D019534:Shoulder Impingement Syndrome / Q000453:epidemiology*