Shoulder replacement surgery may be recommended where either fractures in bones in the shoulder cannot be repaired or where degenerative arthritis has developed in the shoulder joint.
The two approaches to shoulder replacement surgery are the so-called 'anatomic' approach (also referred to as 'anatomic total shoulder arthroplasty' or 'aTSA'), where prostheses simply replace the existing ball and socket of the joint, and the 'reverse' approach (also referred to as 'reverse total shoulder arthroplasty' or 'rTSA'), where a prosthetic socket replaces the natural ball component at the top of the humerus and the prosthetic ball component is fixed to the glenoid shoulder socket.
With the anatomic approach, existing tendons and muscles in the rotator cuff perform the same function as before, in contrast to the reverse approach, where the biomechanics of the shoulder joint change as the deltoid (and other muscles) take on the role of moving and powering the arm and shoulder instead of the rotator cuff.
The decision on which approach is most suitable is based on the overall health of the shoulder. Patients who have developed either one large tear or several tears in the rotator cuff and/or have developed a type of arthritis of the shoulder known as 'cuff tear arthropathy' may be more suitable to the reverse approach, as the anatomical approach can leave these patients with elevated postoperative pain and in some cases limited range of movement.
Other indications that the reverse approach may be more suitable include…
- Unsuccessful prior shoulder replacement procedure
- Complex shoulder joint fracture / older patients with shoulder fractures
- Chronic shoulder dislocation
- Severe pain in the shoulder combined with difficulty lifting the arm over the head or away from the side
Data contained in the National Joint Replacement Registry Annual Report 2018(1) shows that the reverse shoulder replacement is becoming the more popular of the two approaches, with 43.3% of all shoulder replacements being reverse in 2008, but by 2017 73.6% of all shoulder replacements were using the reverse approach.
Mean age for patients undergoing the reverse procedure is 72.9 for men and 75.4 for women, with the main primary diagnoses being osteoarthritis (44.9%), rotator cuff arthropathy (34.5%) and fracture (15.3%).
Although a 2015 study(2) seemed to indicate a higher complication rate with reverse procedures than in anatomical procedures, more recent data does not bear this out, with the National Joint Replacement Registry Annual Report 2018 showing a 10 year revision rate for the reverse procedure of 6.8% (osteoarthritis) and 6.4% (rotator cuff arthropathy), as against a 13.1% 11 year revision rate for the anatomical procedure. Precise reasons for revision surgery may well be more connected with other factors, such as type of prosthesis used and whether or not prostheses were cemented in place.
NOTES
(1) https://aoanjrr.sahmri.com/documents/10180/576950/Hip%2C%20Knee%20%26%20Shoulder%20Arthroplasty
(2) https://www.sciencedirect.com/science/article/abs/pii/S1058274614004637
