THE ROLE OF HEMI-ARTHROPLASTY: WHEN HALF A LOAF WILL DO! (2002)

The indications for use of a glenoid component are: 1.) sufficient degenerative changes on the glenoid to expose the subchondral bone 2.) the glenoid should have sufficient glenoid bone stock to allow for secure and longterm fixation of the component, and 3.) the rotator cuff should be intact or repairable and the humeral head should be centred within the glenoid component. Other factors that secondarily affect the decision to use a glenoid component, include the patient’s age and activity level, which should be such that they are not likely to result in multiple revisions for glenoid wear or loosening. Given these factors most patients with osteoarthritis, the leading indication for prosthetic replacement for arthritis should undergo a total shoulder replacement. Patients with acute proximal humeral fractures, the overall leading indication for prosthetic arthroplasty, should have a hemiarthroplasty. Patients with rotator cuff tear arthropathy or crystalline arthropathy are indicated for hemiarthroplasty due to the massive irreparable cuff tears present in these conditions. Patients with rheumatoid arthritis have variable diseases affecting the rotator cuff and variable degrees of bone loss resulting in the need to individualise the indications for the use of a glenoid to the patient’s pathoanatomy. The reason for use of a glenoid component, when indicated, is the fact that pain relief and function is predictably better when compared to hemiarthroplasty for the same indication and pathoanatomy. Proper insertion of a glenoid component requires wide exposure of the glenoid fossa and bone preparation, which for most general orthopaedic surgeons is difficult and not reproducible. This is, in my opinion, the primary reason that hemiarthroplasty or bipolar arthroplasty is used for treatment of many patients with primary osteoarthritis. Both of these procedures result, on average, in a less favourable outcome than non-constrained total shoulder arthroplasty. Osteoarthritis is characterised by flattening and enlargement of the humeral head and is associated with peripheral osteophyte formation. Loss of articular cartilage results in eburnated bone and on the glenoid side posterior bone loss. Capsular contracture results in loss of passive arcs of motion, particularly anteriorly with loss of external rotation. Posterior subluxation of the humeral head can occur, associated with anterior soft tissue contracture and/or posterior glenoid bone loss. The severity of this pathoanatomy is variable among patients with primary osteoarthritis and each of these factors will have a variable effect on outcome of shoulder arthroplasty as well as the indication for hemiarthroplasty versus total shoulder arthroplasty. In a 2–7 year follow-up multicentre study using the DePuy Global Shoulder in 127 patients, those cases with osteoarthritis without humeral head subluxation, severe glenoid bone loss, or rotator cuff tears had the best results, for pain relief and function, with total shoulder arthroplasty. In patients with severe glenoid bone loss total shoulder has improved function when compared to hemiarthroplasty. This finding supports the data of others that demonstrate less favourable results of hemiarthroplasty for treatment of osteoarthritis in cases with eccentric glenoid wear. Patients with humeral head subluxation have less favourable results regardless of the use of a hemiarthroplasty or total shoulder arthroplasty. The presence of a full thickness reparable rotator cuff tear limited to the supraspinatus tendon does not adversely affect outcome or the ability to use a glenoid component. Patients with less than 10° of external rotation achieve statistically less postoperative forward flexion and external rotation than those patients with greater degrees of preoperative external rotation.