Subscapularis Strength After Total Shoulder Arthroplasty

Study Design: This is a randomized, double-blinded, standard of care-controlled clinical
trial. All adult patients undergoing anatomic total shoulder arthroplasty for glenohumeral
osteoarthritis will be included and randomized after surgery into either the control group
which is prescribed a standard rehabilitation protocol or the intervention group which also
is prescribed the same standard rehabilitation protocol with the the addition of isolated
subscapularis rehabilitation.

Purpose: To determine the subscapularis strength and function after anatomic total shoulder
arthroplasty (aTSA) in patients who receive isolated subscapularis rehabilitation in addition
to the standard rehabilitation protocol as compared to those who only receive the standard
rehabilitation protocol at 12-month follow up. Specifically the investigators will measure
subscapularis strength utilizing a dynamometer and subscapularis function utilizing isolated
subscapularis physical examination testing: belly-press, bear-hug, and lift-off tests.

Hypothesis: The investigators believe that subscapularis strength can be improved using
isolated subscapularis rehabilitation in addition to standard rehabilitation, leading to
improved outcomes in patients receiving aTSA. This should also improve the post-operative
physical examination predicting a functional subscapularis tendon.

Rationale and expectations: Anatomic total shoulder arthroplasty is often performed in
patients with severe glenohumeral osteoarthritis that have an intact subscapularis. Often
times it is seen that these patients return with positive isolated subscapularis tests,
despite the subscapularis being intact after surgery. If these patients require revision
surgery, an ultrasound is the only test that can be performed to evaluate the status of the
subscapularis tendon. This study is difficult and not 100% accurate. It needs to be
determined if the patient will need a reverse total shoulder arthroplasty due to the positive
subscapularis test findings. Previous studies by Baumgartner et al. showed that patients that
received a total shoulder arthroplasty with tenotomy improved liftoff, and bear-hug strength
testing, but operative shoulder strength remained inferior to strength of the nonoperative
shoulder. Patients with improvements in strength were more likely to have greater
improvements in outcome scores and range of motion. It was noted that improvements in the
shoulder activity level after anatomic total shoulder arthroplasty may be dependent on
improvements in strength. The investigators believe that subscapularis strength can be
improved using isolated subscapularis rehabilitation in addition to standard rehabilitation,
leading to improved outcomes in patients receiving aTSA. This should also improve the post
operative physical examination predicting a functional subscapularis tendon.

Research Plan: Patients to be included in the study will be those with glenohumeral
osteoarthritis with an intact rotator cuff that are undergoing anatomic total shoulder
arthroplasty. Exclusion criteris includes patients undergoing revision shouder arthroplasty,
a previous subscpaularis rotator cuff repair or deficient rotator cuff, patients with
inflammatory arthropathies, such as rheumatoid arthritis, and patients with a history of
infection in the shoulder joint. Reverse total shoulder arthroplasty will be excluded.
Non-English speaking patients will be excluded from the study in order to simplify
communication with study participants. The control population will consist of patients
undergoing the standard rehabilitation protocol for aTSA. Patients will be undergoing
rehabilitation regardless of study participation.

Protocol and Technique:

Recruitment: Patients meeting inclusion criteria undergoing aTSA will be recruited and
consented for participation in the study at their pre-operative clinic visit. Their
pre-operative strength and function testing will occur at this time.

Randomization: Placement into the study group or control group will be randomized and
prospectively followed. The randomization process will remain blinded to surgeon, patient,
and all co-investigators except for the primary physical therapist lead in the project (lead
PT). At the first post-operative visit within the first month post-operatively, the patient
will receive a physical therapy prescription per standard protocol. At the time of physical
therapy initiation, the lead PT in the project will contact the patient's physical therapist
and provide them with instructions regarding the research study, including which group the
patient has been randomized into (standard vs additional subscapularis rehab) and strict
instructions to perform the physical therapy without informing the patient of their
randomized assignment. Upon making contact with the physical therapist, the lead PT provides
them with a manual with the exact rehabilitation protocol assigned to the patient, ensuring
that regardless of which physical therapy the patient elects to undergo treatment by, they
receive the same standard physical therapy, plus the same standard subscapularis
rehabilitation exercises (if randomized into the study group).

Follow up testing: The post-operative strength and function of patients in both treatment
groups, isolated subscapularis rehabilitation with standard rehabilitation and standard
rehabilitation alone, will be measured at subsequent 3 months, 6 months and 12 month
postoperative visits. Measurements taken are outlined above and include shoulder range of
motion (forward flexion, abduction, abduction-erternal rotation, abduction-internal rotation,
external rotation), ability to perform a belly press, lift off, and bear hug test. Strength
for internal rotation and subscapularis strength will be performed, using the dynamometer.

Data: Patients will be asked to fill out questionnaires for this study at each time point
(preoperative, postoperative at months 3, 6, and 12). These include PROMIS Bank v2.0 - Upper
Extremity, PROMIS Bank v1.1 - Pain Interference, and ASES. Strength scores will be assessed
using a Lafayette Manual Muscle Testing System Model 01165 (dynamometer) to measure peak
force in lbs. The means of each group along with standard deviation will be calculated for
each parameter measured. P-value of 0.05 will be utilized for statistically significant
results.

Primary Endpoint: Strength (measured by dynamometer testing) of the subscapularis.

Secondary Endpoint: Function and outcomes as measured by range of motion and questionnaire
scores of pain and satisfaction.

Inclusion Criteria:

- All adult patients over the age of 18

- Must have a diagnosis of glenohumeral osteoarthritis

- Must be scheduled for primary anatomic total shoulder arthroplasty.

Exclusion Criteria:

- History of prior rotator cuff surgery

- Rotator cuff deficiency

- Planned reverse total shoulder arthroplasty

- inflammatory arthropathy

- prior shoulder replacement surgery

- neurologic deficits of the affected extremity

- diagnosis of frozen shoulder

- previous infection in the shoulder.