Evaluation of Shoulder Strength and Deltoid Stiffness After Reverse Shoulder Arthroplasty (RSA)

The goal of this observational study is to test the strength of the shoulder joint and elasticity of the deltoid muscle of the patients who had a reverse shoulder arthroplasty. The main questions are: • Whether there is a difference between the operated and healthy shoulders in terms of strength and deltoid elasticity of the patients. • Is there any correlation between the functional status, elasticity and strength of the operated shoulder? Participants will be asked to attend the isokinetic shoulder strength tests and shear wawe ultrasound elastography measurements. They will be also asked to fill the quick DASH and Constant score forms.

The ultrasound elastography is a measurement method that has become increasingly common recently and can measure some mechanical properties of tissue. Measurements can be made using two different techniques: strain and shear wave elastography (SWEUS). SWEUS provides objective and reproducible data collection about the elasticity of the tissue and is less affected by the user than the strain technique. The mechanical properties of the deltoid muscle are among the main factors affecting surgical results in patients undergoing reverse shoulder replacement surgery. Glenohumeral joint function is affected by the post-operative tension of the deltoid. Excessive tension in the deltoid muscle may cause restriction of movement and pain, as well as conditions such as instability and insufficient force production. Lack of elasticity of deltoid muscle may also lead to functional deficit of shoulder. Previous studies have found a linear correlation between muscle activity and muscle elasticity values measured by MR elastography (MRE). However, MRE is an expensive method that requires large equipment and space, and it is a more difficult method for patients, which may include various difficulties in patient positioning. Ultrasound elastography is a method that is highly investigated for clinical use because it is cheaper and easier to apply than MRE. Isokinetic dynamometer is one of the most objective methods used to measure muscle activity and strength.Thus, it is imperative to reveal the mechanical properties of deltoid muscle, which carries the most of the mechanical load in the shoulder region after the operation, as well as the relationship between them.

The medical history of patients who had undergone reverse prosthesis surgery in the Department of Orthopedics and Traumatology, and their postoperative files will be screened. Patients who meet the inclusion and exclusion criteria will be invited to the study.

Their demographic information will be recorded. The visual pain scale (VAS) and will be questioned to evaluate the pain status. Functional status of the patients, and the patients will be asked to complete the Constant score and the quick arm, shoulder and hand problems questionnaire (Q-DASH) under supervision. They will be asked to answer. Shear wave elastographic measurement and isokinetic tests of both shoulders will be carried out in the sports medicine department. Measurement outcomes of both shoulders will be compared.

Eligibility Criteria:
Inclusion Criteria:

* Having undergone reverse shoulder arthroplasty surgery due to arthropathy because of unilateral rotator cuff tear
* Followed for at least 12 months after surgery.
* The other unoperated shoulder is healthy.

Exclusion Criteria:

* Patients with revision reverse shoulder arthroplasty
* Having inflammatory diseases
* Not having adequate range of motion to be able to perform isokinetic test