MedicalResearch.com Interview with:
Kurt T. Hegmann, M.D., M.P.H.
Director, Rocky Mtn. Center for Occupational and Environmental Health
Chief, Division of Occupational and Environmental Health
The University of Utah Health Care
MedicalResearch.com: What is the background for this study?
Response: This line of work for us began approximately 20 years ago.
Normal tendons never rupture, as the weak point when loading the muscle-tendon unit is either the muscle-tendon junction (i.e., a true muscle strain) or bone-tendon junction. Researchers in the 1960s reported there is poor blood supply in the area of rotator cuff tendon tears, providing one of the two main etiological theories of rotator cuff tears. The other main theory is “impingement syndrome” or a biomechanical impingement in the shoulder joint. Naturally, both theories could co-exist.
Next, we noted rotator cuff tendinitis and shoulder risks from tobacco in other studies. We also reported prior research of increased risks with obesity. These led us to the theory that these rotator cuff tears are likely vascular in etiology. The next problem was to show this.
MedicalResearch.com: Who did you study?
Response: We studied 1,226 workers in Illinois, Utah and Wisconsin. They worked at 17 different employment sites, with a wide range of mostly manual jobs and some clerical workers too. We intentionally enrolled workers in approximately 1/3 low, medium and high job physical demand categories to try to test whether if, and the degree to which job physical demands cause musculoskeletal disorders. All workers completed computerized questionnaires (e.g., smoking histories, job satisfaction), medical histories (e.g., shoulder pain, hand pain) and underwent physical examination tests regardless of whether they had symptoms or not. We measured blood pressure, height and weight. All underwent electrodiagnostic studies for carpal tunnel syndrome.
MedicalResearch.com: What are the main findings?
Response: The prevalence of shoulder joint pain is quite high, with 31.5% having had shoulder pain in the month prior to the study. Additionally, 12.7% met a case definition of rotator cuff tendinitis at baseline by having had glenohumeral joint pain and a positive supraspinatus (or “empty can”) test.
Multivariate analyses adjusted for sex, body mass index, job satisfaction and family problems. Adjusted analyses showed the higher the Framingham risk score, the higher the risk the person has either rotator cuff tendinitis or shoulder joint pain. The more risk factors one has the greater is the association. When one is in the highest group studied, the risk of rotator cuff tendinitis was nearly 6-fold (5.97), while the risk of glenohumeral, or shoulder joint pain was as high as 4.55-fold. Both risks trended higher across higher risk scores.
MedicalResearch.com: What should readers take away from your report?
Response: The magnitudes of association are so high and with a dose-response relationship also shown, it is quite likely that rotator cuff tendinitis is related to impaired vascular supply. It is presumed that this is a microvascular impairment, although this study did not measure that.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Prospective analyses are required. As well, randomized controlled trials providing more intensive cardiovascular disease risk factor management should analyze whether shoulder pain and rotator cuff tendinitis are reduced. If those two findings are confirmed, then the mechanism and theory of the disease would be quite solid.
MedicalResearch.com: Is there anything else you would like to add?
Response: Whether a finding of rotator cuff tendinitis also signifies a higher risk of heart attacks needs to be investigated. These data naturally suggest that is the case. If that were confirmed, someone with rotator cuff tendinitis would be at higher risk of heart disease and in need of more intensive cardiovascular disease risk factor management.
MedicalResearch.com: Any disclosures?
Response: We occasionally testify as to the cause of someone’s shoulder injury. This has not happened recently, but it will likely occur again as these things are commonly seen in the workers compensation clinical setting in which I practice.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Applegate, Kara Arnold BS; Thiese, Matthew S. PhD, MSPH; Merryweather, Andrew S. PhD; Kapellusch, Jay PhD; Drury, David L. MD, MPH; Wood, Eric MD, MPH; Kendall, Richard DO; Foster, James MD, MPH; Garg, Arun PhD; Hegmann, Kurt T. MD, MPHJournal of Occupational & Environmental Medicine:doi: 10.1097/JOM.0000000000000929
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