Is preoperative elevated glycated hemoglobin (HbA1c) a risk factor for postoperative shoulder stiffness after posterior-superior rotator cuff repair?

Background

Postoperative shoulder stiffness (POSS) affects a large number of patients undergoing rotator cuff repair (RCR). Diabetes may increase the risk of POSS. Preoperative glycated hemoglobin (HbA1c) is a convenient measure of glucose control in this group. The aim of the present study was to determine a relationship between preoperative HbA1c and POSS in patients undergoing postero-superior RCR.

Methods

Two hundred fifty patients with full-thickness postero-superior rotator cuffs who underwent RCR were followed for 6 months. Pre- and post-operative external rotation with arm by the side at 3 and 6 months were measured. Patient demographics, tear characteristics, preoperative HbA1c level, and surgical details were recorded. Patients with subscapularis tears, concomitant instability, partial thickness tears, arthritis, and irreparable rotator cuff tears were excluded. Univariate and multivariate logistic regression were used to determine the association between patient characteristics and POSS at 6 months.

Results

At the end of 6 months, 16% (41/250) of patients had POSS. Multivariate analysis demonstrated an elevated preoperative HbA1c level was a statistically significant predictor of POSS at 6 months (odds ratio 7.04, P < .01) after posterior superior RCR. Lower preoperative external rotation (P = .02) and female sex (P < .01) were also risk factors associated with POSS. Age, hand dominance, worker's compensation claim status, etiology, and size of the tear, surgical technique, and additional treatments were not statistically significant predictors.

Conclusion

Elevated preoperative HbA1c level is associated with POSS after RCR. Measuring HbA1c preoperatively may assist clinicians to identify patients at risk of POSS. HbA1c is a modifiable parameter that could then be optimized preoperatively in order to improve outcomes.

Oral glucose tolerance test does not affect degree of hemoglobin glycation as measured by routine assay

BACKGROUND

Hemoglobin A1c (HbA1c) is an accurate index of fluctuation in glycemia over the 2-3 months prior to quantitative assessment. During this time, hemoglobin (Hb) slowly glycates until it shows the properties of advanced glycation end-products. Glycation kinetics is intensified by prolonged glucose exposure. In subjects undergoing oral glucose tolerance testing (OGTT), immediately after ingestion, glucose is ostensibly transported by the glucose transporter 1 (GLUT1) to erythrocyte corpuscular hemoglobin. The earliest significant measurable level of hemoglobin glycation associated with this transportation is still not clear.

SUBJECTS AND METHODS

We attempted to explore the early impact of short-term glucose load on HbA1c levels, because it is now known that transmembrane GLUT1-mediated glucose transport occurs immediately. A total of 88 participants (46 patients and 42 clinically healthy controls) underwent fasting plasma glucose quantitation during an OGTT. HbA1c, revealed by a monoclonal anti-glycation epitope antibody and adiponectin, was quantitated before (T0) and 2 hours (T120) after 80 g glucose ingestion.

RESULTS

Wilcoxon test revealed that the HbA1c values did not significantly vary (P=0.15) during the OGTT, whereas glucose concentration varied strongly between T0 and T120.

DISCUSSION

It is well known that quantitative estimation of HbA1c is informative for clinical care, independently of glucose level. The molecular mechanisms and dynamics by which glucose enters/exits red blood cells are incompletely known and may differ between individuals. We here show, for the first time, that HbA1c levels do not significantly increase during OGTT, supporting the view that non-enzymatic glycation of hemoglobin occurs slowly and that glycation during the 2 hours of an OGTT is insignificant.