These authors determined a "cumulative" HbA1c, that uses HbA1c values over time to estimate the total disease burden that the patient experiences over a period. They evaluated whether a correlation existed between cumulative HbA1c levels in diabetic patients and the prevalence of frozen shoulder using a retrospective review of patients from a single institution for which HbA1c values were available. The exclusion criteria were age younger than 18 years, HbA1c levels greater than 15, and patients who had 1 year or less of single or consecutively recorded HbA1c levels. A total of 24,417 patients met the inclusion criteria.
They found that cumulative HbA1c was positively associated with adhesive capsulitis. The effect size of cumulative HbA1c on adhesive capsulitis was significant; for each unit of time that the HbA1c level was greater than 7, there was a 2.77% increase in the risk of adhesive capsulitis.
Comment: The mechanism of joint stiffness in individuals with abnormal sugar metabolism is thought to be non-enzymatic gycosylation, causing abnormal cross links between collagen fibers resulting in increased stiffness.
Surgeons performing surgical releases for stiff diabetic shoulders often note increased thickness and toughness of the capsular tissue. Surgeons attempting to manage diabetic stiff shoulders with manipulation are often frustrated for the same reason.
This paper would have been stronger if the authors had provided the diagnostic criteria used for making the diagnosis of adhesive capsulitis (if indeed these criteria were standardized across the practice) and if they had performed a multivariate analysis that included all the data they collected: patient age, sex, BMI, length of time over which the HbA1c data were collected (range, 12-207 months), thyroid status, and insulin dosage at the time of diagnosis.
In any event, this study reminds us that, in addition to its effect on surgical complications, glycemic control may affect the success of procedures designed to improve shoulder motion, including shoulder arthroplasty.
Information about shoulder exercises can be found at this link.
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