The first joint replacement of any kind was a shoulder replacement. This was performed by a French surgeon in 1893 for the treatment of tuberculosis. Like most things in medicine, much progress has been made.
Early implants were constructed using ivory, plastic then metal. Initially, only the humeral side was replaced then experiments with glenoid components began. These early designs were plagued by loosening and instability.
These innovations evolved into anatomic replacements with a monoblock humeral prosthesis and a polyethylene glenoid component.
Modularity was gradually introduced to adapt the replacement to the patient’s anatomy and there arose the concept of a resurfacing where a metal shell resurfaced the patient’s humeral head with the option of a glenoid component being implanted as well. Furthering this concept, mid-head replacements consist of resecting the humeral head allowing better access for glenoid replacement.
The gap left by cuff deficient shoulders or fractures, where the rotator cuff deficiency leads to ‘rocking’ of the humeral implant on the glenoid causing loosening or instability of the implant, led to the development of the reverse shoulder replacement.
Paul Grammont is seen by many as a central figure in the development of this prosthesis where his design principles of medialisation of the centre of rotation and lengthening of the deltoid provided for stability and optimisation of deltoid function.
The Australian story
Our Australian Joint Registry informs us that since 2008 there has been a 227.8% increase in the number of shoulder arthroplasties performed. Of these, 71% are of the reverse variety. This is due to the expanding indications for the procedure – cuff arthropathy, pseudo-paralysis from cuff deficiency, proximal humeral fractures and arthritis in the cuff-at-risk patient (e.g. elderly, those with partial thickness cuff tears).
The use of primary stemless implants in anatomic total shoulder arthroplasty has increased 825% since 2012, with revision rates of 4.6% at 10 years.
Surgeons are obtaining CT scans in 70% of patients, pre-operatively. These scans assess glenoid morphology, in particular. Posterior glenoid erosion is a common pattern of wear in the arthritic shoulder and CT allows assessment of bone loss and glenoid version. There are now implants which use metal augmentation to accommodate bone loss, and custom implants can be manufactured in the case of severe bone loss.
Advancements & challenges
CT scanning allows accurate 3-dimensional visualisation and pre-operative planning. Modelling of the range of motion, risk of impingement and lengthening of the arm can be done which will hopefully reduce the risk of instability, notching of the humeral prosthesis on the glenoid neck and allow better soft tissue tensioning, reducing the risk of scapula fracture.
Integration of wearable technology with smart devices can assist in reminding patients to perform exercises, track range of motion and complement physiotherapy. Alerts can be set if patients fall behind in meeting milestones.
Enabling technology such as custom guides, navigation and augmented reality are here. These help placement of the implants and correction of version.
Virtual reality visualisation and manipulation of a 3-dimensional plan is coming, which will allow doctors and patients to see a vivid surgical plan. This will also no doubt fascinate and entertain patients as they watch their surgeons pinch and point in thin air as they manipulate things in their virtual world!
As the number of replacements increase, so will the challenge of revision procedures. Encouragingly, the proportion of revision cases reduced to 7.9% in 2022 compared to the peak of 10.9% in 2012. Peri-prosthetic fractures and infections are also challenges, all in more medically complex and older patients. Surgeons are increasingly sharing care with their microbiology and geriatrician colleagues to optimise patient management in these cases.
Practice points
Consider an x-ray for patients presenting with the painful shoulder. Many have only ultrasound then a subacromial injection. Injecting an arthritic shoulder has a small risk of infection greatly increasing the stakes should the joint come to replacement.
In the unhappy anatomic shoulder replacement, consider cuff failure. Look for signs of a high-riding humeral head for example.
In the reverse arthroplasty, assess for loosening, looking for radiolucent lines. An x-ray will also show a dislocation which can be a surprisingly painless condition but leads to loss of function. Scapula spine fractures can lead to a sudden loss of function in the reverse shoulder replacement and may need a CT to make the diagnosis.
Key messages
- The first ever joint replacement was the shoulder
- Since 2008 there has been a significant increase in shoulder arthroplasties
- Virtual reality allows 3D planning of surgery.
Author competing interests – nil