Onlay Versus Inlay Humeral Component in Reverse Total Shoulder Arthroplasty

Onlay Versus Inlay Humeral Component in Reverse Total Shoulder Arthroplasty: A Prospective, Randomized Trial

The goal of this study is to compare the effect of different ways to place the component that goes at the top of the humerus (upper arm) in reverse total shoulder replacement. Some surgeons place the humeral tray component sitting on the bone while others place it in the bone. Changing the way that the humeral component is placed may change how much the arm can raise up or turn out/in after surgery for some patients. This study compares patients with inlay humeral component (tray sits in the upper arm bone) versus onlay humeral component (tray sits on top of the upper arm bone) to see if there are differences in range of motion or function after surgery.

This study aims to determine if active external rotation two years postoperatively varies based on whether an inlay or onlay humeral component is used in reverse shoulder arthroplasty (RTSA). The study also aims to determine whether active forward elevation, abduction, scapular notching, and functional outcomes two years postoperatively vary based on whether an inlay or onlay humeral component is used in reverse shoulder arthroplasty. Patients undergoing primary RTSA by Dr. J. Michael Wiater, Dr. Brett Wiater, or Dr. Alexander Martusiewicz at Beaumont Health will be screened for eligibility. Following informed consent, participants will be randomised (1:1) to one of the following groups: 1) RTSA with inlay humeral component (Tornier Perform Stem Reverse+) or 2) RTSA with onlay humeral component (Tornier Ascend Flex stem). At baseline, participants will complete study questionnaires, receive a range-of-motion (ROM) exam, and standard of care x-rays and computed tomography (CT) scans. These evaluations will be repeated at 3 months, 12 months and 24 months.

Inclusion Criteria:

• Patients undergoing primary reverse total shoulder arthroplasty with the following components:

  1. Onlay group: Ascend Flex stem, Perform Reversed standard +3 lateralized 25mm baseplate with standard 36 mm glenosphere or +6 lateralized 25mm baseplate with 39mm glenosphere
  2. Inlay group: Perform Stem Reverse, Perform Reversed +3 lateralized 25mm baseplate with standard 36mm glenosphere or +6 lateralized 25mm baseplate with 39mm glenosphere

• Diagnosis of cuff tear arthropathy, massive cuff tear, or primary osteoarthritis with cuff tear

• Negative external rotation lag sign, ability to externally rotate beyond neutral

• Age 18 years or older

Exclusion Criteria:

• Revision arthroplasty
• Prior open shoulder surgery
• Concomitant tendon transfer (Latissimus Dorsi, Pectoralis Tendon, Lower Trapezius)
• Diagnosis of rheumatoid arthritis, infection, acute trauma or instability
• Patients not willing to undergo a standardized physical therapy protocol or home therapy program after surgical intervention
• Patient anatomy does not accommodate the study implants per surgeon discretion
• Pregnant, patient-reported
• Minors (under 18 years of age)
• Cognitively impaired based on a diagnosis of dementia, psychiatric disorder, or any cognitive deficit that will not allow for proper informed consent or answering of study questionnaires