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The Glenoid: To Replace or Not Replace?

Authors: Ofer Levy

References: Presented at ICSES 2010

Considerable controversy remains in the literature as to whether hemiarthroplasty (HHR) or total shoulder arthroplasty (TSA) is the better treatment option for patients with shoulder arthritis. Several cohort studies have compared the outcomes of stemmed prostheses and had inconsistent conclusions as to which procedure is best. Most are retrospective non-randomised case studies and meta-analysis of multiple case studies, only few are randomised controlled studies. It has been stated often that HHR has the benefits of decreased operative time, decreased blood loss, and less technical difficulty, yet there is concern regarding the progression of glenoid arthritic changes and the need for future revision surgery or conversion to TSA. TSA is associated with increased operative time and blood loss, is more technically challenging, and incurs risks of potential glenoid loosening and polyethylene wear. Is this really true? Is HHR really technically less challenging than TSA? Whether the difference noticed between TSA and HHR in these studies are due to this inherent bias in concept? Radnay et al . (2007) found in their meta analysis that compared with HHR, TSR provided significantly greater pain relief, forward elevation, gain in external rotation, and patient satisfaction. Only 6.5% of all TSAs required revision surgery, compared with 10.2% of patients undergoing HHR. AAOS Clinical Practice Guideline regarding the treatment of glenohumeral osteoarthritis (2010), (based on only 2 level II evidence studies: Gartsman et al , and Lo et al .) concluded that global health assessment scores and pain relief were statistically significantly better after TSA. Function and quality-of-life outcome measures in both studies showed no statistically significant differences between groups. No TSA required revision to hemiarthroplasty in these studies. 14% of patients treated with a hemiarthroplasty required revision to a TSA. May be that ignoring the glenoid at the time of surgery, not performing as thorough release around the glenoid as is done when performing TSA have some contribution to the difference in results and later glenoid erosion? Edwards et al . (2003) reported the results of the multicentre study comparing hemiarthroplasty with total shoulder arthroplasty for the treatment of osteoarthritis using the Aequalis prosthesis (1542 primary shoulder arthroplasties). 56% of TSA had radiolucent lines around the glenoid components. The estimated survival of TSA was much worse than HHR (approximately 97% for HHR and 69% for TSA at 9 years). The poor longevity of TSA was ascribed to the use of the metal-backed glenoid component. However, in a follow up report using data from the same Aequalis multicentre group Pfahler et al. found radiolucent lines around 67.9% of the cemented glenoid implants when metal-backed components were excluded. 50% of these radiolucent lines were progressive. In our series comparing hemiarthroplasty and TSA using surface replacement arthroplasty, of 340 CSRA cases performed between 1987-2003. 218 Humeral Surface Arthroplasty (hemiarthroplasty) (HSA) and 122 TSA. There was very little difference in the functional outcome and pain between the groups early, as well as, later after surgery. An important point is that even when performing hemiarthroplasty we address the glenoid in relation to soft tissue release and soft tissue balance. In our series we use the microfracture technique on the glenoid surface to encourage fibrocartilage cover. Mean post-operative Constant score was 89.2% (59.8 points) for TSA and 87.9% (62.3 points) for HSA with no statistically significant differences (t-test, p=0.61). A highly significant difference between the overall proportions of revised cases observed, with (21/122) 17.2% and (6/218) 2.8% of TSA and HSA cases revised, respectively (p<0.0001). HSA prostheses survive significantly longer than TSA prostheses with 95.8% (92.3% to 99.3%) and 89.7% (84.0% to 95.5%) respectively (95% CI). The difference between the survival curves was highly significant, both in the earlier post-operative period (Wilcoxon's test, p=0.0053) as well as the later on (Log-rank test, p=0.0026). Long-term survival of total joint replacement may be related to polyethylene wear debris from the glenoid implant, leading to polyethylene wear and glenoid loosening. The difference between this series and those with stemmed prostheses regarding the incidence of glenoid wear, may be explained by the fact that with surface replacement the normal anatomy for each patient can be mimicked easier with less place for error than with stemmed prostheses, where stem positioning, height and version should be separately controlled, as well as offset and modular head sizing. Any mistake in any of these variables may lead to glenoid uneven or point pressure that may lead to glenoid erosion, deficient soft tissue balance and less favourable result. We have found that humeral head re centring can occur following hemiarthroplasty
tissue balance. This may explain why humeral surface arthroplasty (HSA) has excellent outcomes even when there is glenoid erosion and biconcavity preoperatively. It is possible that soft tissue imbalance may lead to glenoid erosion. We have found symptomatic glenoid erosion as the cause of pain and failure in only 5 patients (out of over 700 patients).
In the majority of patients with painful and symptomatic hemiarthroplasty it is related to other causes such as: impingement syndrome & rotator cuff problems, tears and insufficiency, long head of biceps problems, AC joint pain and only rarely to glenoid erosion. Unfortunately, we as surgeons have a Knee-Jerk Reaction to blame the glenoid (glenoid erosion) in any painful hemiarthroplasty.
To conclude, the pain and functional results of TSA and HHR are comparable with minimal advantage to the TSA in the short term. Survivorship of the HHR is much better than TSA, mainly due to glenoid components problems. It may be that surface replacement is slightly different from stemmed implants in this respect. Soft tissue releases and balance should be addressed the same meticulous way when performing hemiarthroplasty and TSA. Look for other common reasons for painful hemiarthroplasty first - glenoid erosion as the cause of pain is relatively rare.Some deterioration in pain and function with time is expected due to rotator cuff failure over time (this may affect TSR and hemiarthroplasty alike).



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