Load-induced Changes in Glenohumeral Translation in Patients With Rotator Cuff Tear

The study is to investigate the dose-response relationship between load-induced muscle activation (liMA) and load-induced glenohumeral translation (liTr) in patients with rotator cuff tears and asymptomatic control subjects.

Furthermore the study is to investigate the in vivo dose-response relationship between additional weight and glenohumeral translation, to understand the biological variation in liTr, the influence of disease pathology on the liTr, the potential compensation by muscle activation and muscle size, and the influence of liTr on patient outcomes.

This project is to test the overall hypothesis that rotator cuff tear affects glenohumeral translation and that this functional instability depends on additional load applied, on anatomical and morphological variations, and on type and severity of the injury. The study is to investigate the dose-response relationship between load-induced muscle activation (liMA) and load-induced glenohumeral translation (liTr) in patients with rotator cuff tears and asymptomatic control subjects.

Furthermore the study is to investigate the in vivo dose-response relationship between additional weight and glenohumeral translation, to understand the biological variation in liTr, the influence of disease pathology on the liTr, the potential compensation by muscle activation and muscle size, and the influence of liTr on patient outcomes.

This study entails cross-sectional experimental multimodal (clinical, biomechanical, radiological) data collection with multiple conditions and a control group.

Eligibility Criteria:
We will examine a cohort of 75 subjects:

* Group 1: 25 patients with unilateral symptomatic rotator cuff tear between 45 and 85 years
* Group 2: 25 asymptomatic control subjects (age and sex distribution matching the patient group) Group 3: 25 sex matched young asymptomatic control subjects between 20 and 30 years

Inclusion criteria patients:

* Diagnosed unilateral rotator cuff tear
* Partial or complete supraspinatus muscle tear
* With or without injury to other rotator cuff muscles

Exclusion criteria patients:

* Prior operative treatment of the ipsilateral shoulder or elbow
* Clinical history or symptoms of the contralateral glenohumeral joint
* Range of motion \<30° in abduction and flexion

Inclusion criteria asymptomatic control subjects:

- No previous known elbow and shoulder injury or symptoms

Exclusion criteria asymptomatic control subjects:

* Clinical history of the glenohumeral joint
* Prior conservative or operative treatment of the shoulder or elbow
* Range of motion \<90° in abduction and flexion

General exclusion criteria:

* Inability to provide informed consent
* Body mass index (BMI) \> 35 kg/m2 (Excessive skin movement)
* Neuromuscular disorders affecting upper limb movement
* Additional pathologies that influence the mobility of the shoulder joints
* Contraindications for MRI (e.g. neurostimulator and claustrophobia)
* Prior neuromuscular impairment (e.g. stroke)
* Diagnosed active rheumatic disorder
* Other major medical problems
* Pregnancy
* Patients currently enrolled in another experimental (interventional) protocol