PT Classroom - Reverse Total Shoulder Arthroplasty (TSA) ׀ by David Clark, MD

With a standard total shoulder arthroplasty (TSA) it relies on an intact rotator cuff to control the humeral component much like the native shoulder. Because of superior humeral head migration, eccentric loading on the glenoid component resulted in a “rocking-horse” motion and loosening of the glenoid component. As a result of this loosening, this procedure would be abandoned for a more yielding procedure, the reverse total shoulder arthroplasty.

The reverse total shoulder arthroplasty was first developed in Europe by Paul Grammont and was approved in the US by the FDA in March of 2004. With this procedure, the socket and metal ball are switched in the joint. This involves a metal ball being attached to the glenoid component and a plastic socket being attached to the humeral component. As a result of this design there is a small lateral offset secondary to the absence of the component neck which places the center of rotation more medially and reduces the torque at the glenoid-bone interface. The lever arm distance (L) is increased and deltoid force (F) is increased by lowering and medializing the center of rotation which is now also fixed. Torque (F x L) in abducting the arm is also increased. (see image below)

When examining the biomechanics involved with a reverse TSA more closely, it is revealed that this procedure alters the biomechanics of the shoulder by changing the position of the humeral and glenoid components. The center of rotation of the joint moves medially and inferiorly. Deltoid resting muscle tone is increased to allow it to become the primary mover for shoulder elevation in the presence of rotator cuff dysfunction. This also allows the deltoid to provide stability in a rotator cuff deficient shoulder.

Indications for a reverse total shoulder arthoplasty includes:
• Failed hemiarthroplasty with irreparable rotator cuff tears
• Pseudoparalysis (i.e., inability to lift the arm above the horizontal) because of massive, irreparable rotator cuff tears
• Some reconstructions after tumor resection
• Some fractures of the shoulder (Neer three-part or four-part fracture)
• Severe proximal humerus fractures with tuberosity malposition or non-union

Contraindications for a reverse total shoulder arthroplasty includes:
• Primary osteoarthritis or osteonecrosis where the articular surface – tuberosity relationships are normal and the rotator cuff is intact
• Marked deltoid deficiency, as the shoulder will not function well and will be prone to dislocate
• History of previous infection – recurrent infection high
• Use sparingly in patients less than 65 years old, as long-term survivorship and complication rates are unknown

Complication rates have been found to be higher intraoperatively and postoperatively for reverse TSA (mean 24%) vs. conventional TSA (mean 15%). Besides cuff arthropathy, reverse TSA are still regarded a salvage procedure for failed hemiarthroplasties. If these salvage procedures are excluded, the complication rate is less. Recent postoperative or acute complications includes: hematoma, dislocation, prosthesis loosening, infection, periprosthetic fracture, and metaglene migration. Late postoperative period or chronic complications includes: scapular erosion, osteophyte formation, heterotopic ossification and acromion or scapular stress fractures.

A potential complication for a reverse TSA is anterior-superior dislocation as a result of unopposed pull or inadequate tension of the deltoid muscle. It has also been found that 20% of reverse TSA had dislocations in one series. Shoulder dislocation precautions includes: no shoulder motion behind back (NO combined shoulder adduction, internal rotation, and extension), and no glenohumeral (GH) extension beyond neutral. (Precautions should be implemented for 12 weeks postoperatively unless surgeon specifically advises patient or therapist differently)

The postoperative rehab protocol may vary from surgeon to surgeon. Factors affecting rehabilitation can include: the patient’s premorbid level of function, the type of prosthetic utilized, bone stock, patient compliance post operatively and the ability of patient to activate deltoid postoperatively. Communication with the surgeon to discuss post operative rehabilitation is imperative when working with patients who have undergone this procedure. Internet searches of rehab protocols have revealed a wide array of slightly different takes from various surgeons for a post operative protocol. The protocols appeared to differ mostly on return to activity and progression from PROM to AAROM to AROM. More research is needed to identify the most efficacious post operative rehabilitation protocol following Reverse TSA.

Below is a general protocol for reverse TSA which we recommend to physical therapists who work with our patients:

Initial Stage
• From POD 1 to 6 weeks post operatively
• Maximum protection of joint
• Attain full PROM (educate family as to definition of PROM)
• Reinforce use of sling for 2-6 weeks post operatively
• AROM of elbow/wrist/hand
• Cryotherapy

Initial Stage Precautions
• In supine, arm should be supported by pillow to avoid shoulder extension
• NO SHOULDER AROM
• No lifting or weight bearing
• Keep incision clean & dry
• No pools or jacuzzi for 4-6 weeks

Stage II (6-16 weeks)
• Increase PROM to tolerance
• Gently introduce AROM
• Continue modalities for inflammation reduction PRN
• Improve Scapular stability
• Avoid hyperextension

• Begin PROM internal rotation in plane of scapula
• 8-10 weeks initiate AAROM forward flexion, elevation, ER and IR in plane of scapula in supine then progress to sitting/standing
• 8-10 weeks initiate Sub-maximal isometrics for IR & ER
• 8-10 weeks initiate Deltoid and Scapular isotonic exercises
• 10-14 weeks initiate AROM forward flexion and elevation in plane of scapula with low resistance
• 10-14 weeks initiate AROM glenohumeral ER/IR (isotonics)
• By end of stage II, patient should possess ability to recruit Deltoid as primary mover of shoulder

Stage III (16 weeks to one year)
• Continue to progress flexion and elevation with resistance per patient tolerance
• Comprehensive HEP
• Gradual return to premorbid functional and recreational activities within limits of precautions established by surgeon and therapist
• D/C from PT when patient attains functional AROM (about 100 degrees elevation) with good shoulder arthrokinematics
• Progress isotonics as tolerated
• Continue to reinforce gradual return to activities such as tucking in a shirt at 14 - 16 weeks to prevent dislocation
• Continue to improve upper quarter muscle strength gradually over time to ensure successful post surgical outcome

For more information about reverse total shoulder arthroplasty please contact Dr. Clark of South Shore Orthopedic Surgery Group at info@ss-ortho.com.