Short summary

What are the relation between metabolic syndrome and shoulder pain, and how does metabolic syndrome impact treatment of shoulder pain? These questions, as well as evaluation of other prognostic factors, will be investigated in this trial. At the shoulder Unit, Orthopeadic Department at Vejle Hospital, we will perform a longitudinal cohort study, including 2500 patients with shoulder pain, following the recomendations from "The PROGnosis RESearch Strategy. (PROGRESS) partnership. 

Rationale

A common shoulder related complaint is Rotator Cuff Related Shoulder Pain (RCRSP), which is considered an umbrella term covering tendinopathy in the rotator cuff and biceps tendon. Conservative treatment strategy for RCRSP mostly consists in exercises, concomitant corticosteroid injections, medication (such as nonsteroidal anti-inflammatory) and manual tissue techniques. Several studies have shown that conservative treatments lead to moderate to large effects sizes. However, approximately 30-40% of patients with RCPS fails conservative treatment, and are referred for SubAcromial Decompression (SAD) surgery. SAD surgery consists of removal of the subacromial bursae, release of the coracoacromiale ligament and removal of the inferior parts of the acromion, aiming at increasing the subacromial space.

Although acceptable effect sizes support their use based on evaluation of improvements in pain and function, several studies have indicated that exercises and surgery are no better than placebo (i.e. wait and see strategy, ineffective ultrasound, bursectomi only, arhtroscopic evaluation with no removal of bone or bursae), that there is no difference in effect between exercise and surgery, or that the type of exercises are irrelevant. The use of corticosteroid injections are also questioned, as evidence suggests that it leads to only moderate short term effects and furthermore, corticosteroid injections might cause toxicity in the tendons. Therefore, evidence for treatments effects for RCRSP are conflicting both for exercises, corticosteroid and surgery.

Increased focus has risen upon factors associated with tendinopathy and the relation to treatment. Studies has shown significant associations between noncommunicable diseases such as high BMI/waist circumference, increased blood level lipids, cholesterol, glucose and risk of tendinopathy which also is predictors for metabolic syndrome, and diagnosed as any 3 out of central adipositas, Hypertension, elevated serum triglycerids, low serum high-density lipoprotein (HDL) and insulin resistance. Metabolic Syndrome may therefore be a relevant factor in treating tendinopathy and predicting treatment response. In the general population it is estimated that 20% has metabolic syndrome, whereas in populations with tendinopathy associations have shown OR of 1.15-5.6 for having metabolic syndrome or one or more of the key elements of metabolic syndrome when compared to populations not having tendinopathy. 

Especially central adiposity is considered a strong predictor for metabolic syndrome. Obesity in general is recognized as a chronic low-grade, systemic inflammatory state, and is linked, among other, to cardiovascular disease, type 2 diabetes and musculoskeletal disorders. Of clinical relevance, central obesity measured by Waist-To-Height ratio (WTHr) is an easy measurement to obtain in all clinical settings, and also a modifiable factor through diet and physical activity, causing lower risk of metabolic syndrome, chronic systemic inflammation and less musculoskeletal pain conditions if decreased. 

However, causality has not been established - is patients obese because they have shoulder pain and therefore less active, or does obesity cause a chronic systemic inflammatory state predisposing for shoulder disorder? If RCRSP patients are more obese/have higher incidence of metabolic syndrome then shoulder patients in general, and further if patients with metabolic syndrome whom are diagnosed with RCRSP has a poorer prognosis then other shoulder diagnosis, when the metabolic syndrome/central obesity is not taken into account in the treatment, the causality tips towards the later. 

At the time being, existing prognostic studies in relation to shoulder patients has been criticized for having methodological flaws and presents high risk of bias, why their results cannot be applied in clinical practice, and large high quality prognostic trials, evaluating a wide range of prognostic factors are warranted. Overall, large high quality longitudinal studies, is considered highly important for optimizing treatment strategy and securing patient centered care. 

Therefore, the objective of VHS Cohort Project I is to evaluate general prognostic and individual risk factors, with a specific focus on evaluation of the association between metabolic syndrome influence and tendinopathy, while simultaneous adjusting for other potential prognostic candidate variables (PROGRESS Theme I-II). In VHS Cohort Project II, the objective is to develop a prognostic model for the treatment effect of RCRSP (PROGRESS Theme III).

Description of the cohort

Adult patients referred to shoulder sector at Lillebaelt Hospital (Vejle) due to suspicion of shoulder disorder and diagnosed with shoulder disorder at medical examination. 

Data and biological material

From three different data sources (Patient reported, Clinical assessment and Registry data) prognostic candidate variables will be gathered. 

Collaborating researchers and departments

Shoulder Unit, Orthopeadic Department, Vejle Hospital

• DM Jette Vobbe

Department of Clinical medicine, Aarhus University

• Associated professor, David Christiansen

Musculoskeletal Statistics Unit, The Parker Institute, Bispebjerg and Frederiksberg Hospital & Research Unit of Rheumatology, 

Department of Clinical Research, University of Southern Denmark, Odense University Hospital, 

• Professor Robin Christensen

Department of rehabilitation, Faculty of Medicine, Université Laval, Canada

• Professor Jean-Sébastien Roy