Eric Benson MD1 George Athwal MD2 and Kenneth Faber MD2 1New Hampshire Orthopaedic Center, Nashua, NH, USA 2Division of Orthopaedic Surgery, Department of Surgery, Western University, London, ON, Canada As the number of primary total shoulder arthroplasties continues to increase worldwide, the decision to use a particular style of glenoid component remains an important one in the effort to improve outcomes and prevent future revision surgery. Two glenoid component designs are most commonly used: keeled and pegged. One of the most important outcome measures for any joint replacement procedure is the rate of revision‐free survivorship. In total shoulder arthroplasty (TSA), a frequent cause for revision in medium‐ and long‐term follow‐up is glenoid component failure.1–4 It is important, then, to identify the best component design as well as clinical markers that can help identify component failure. There is a growing body of peer‐reviewed literature exploring keeled versus pegged glenoid component design and correlation with implant survivorship and clinical outcomes. The current literature is limited by the variety of glenoid components used, analytic approaches, and outcome reporting. However, there are two level I studies as well as some level III and IV studies to help us answer this question. Two level I studies address radiolucency about the glenoid component in an attempt to use radiographic parameters to establish whether pegged or keeled components perform best. Rahme et al. performed radiostereometric analysis on 26 shoulders comparing results of inline pegged and keeled all‐polyethylene components.5 They found that only one glenoid (keeled) had any radiolucency on immediate postoperative radiographs. Nine of 12 keeled and 8 of 14 pegged glenoids showed radiolucency at two‐year follow‐up (p = 0.429), but that none of these showed Grade 4 or 5 lucency using the Gartsman classification. There was a trend toward glenoids with Grade 2 or 3 radiolucency showing more micro‐migration than glenoids with Grade 0 or 1 radiolucency. However, this study was not powered to directly correlate radiolucency to micro‐migration. Edwards et al. report a prospective randomized trial of pegged versus keeled all‐polyethylene components including 46 shoulders at 26 months to determine the effect of glenoid component design on immediate and follow‐up radiographs.6 For both immediate and follow‐up radiographic evaluation, they selected the presence of at least Grade 2 lucency as their outcome. They concluded that there was no statistically significant difference between pegged and keeled glenoids on immediate postoperative radiographs (p = 0.128). They did find statistically significant differences between the two designs at 26 months, with 46% of keeled and 15% of pegged glenoids showing at least Grade 2 radiolucency (p = 0.044). Vavken et al. did a meta‐analysis looking at rates of loosening and radiolucency in keeled versus pegged glenoids.7 They found a small difference between the component styles. The pooled risk ratio for revision was 0.27 (95% confidence interval [CI]: 0.08–0.88) in favor of pegged glenoids. Throckmorton et al., in a retrospective case‐control study, looked at 50 keeled and 50 inline pegged glenoids at approximately four‐year follow‐up.8 There was no difference in glenoids that were at risk for loosening based on radiographic evaluation (p = 0.74). There was also no difference in clinical outcomes as measured by improvements in pain and range of motion from preoperatively (p ≥0.20). Papadonikolakis et al. performed a systematic review of failures of anatomic total shoulder arthroplasties.3 In this study, they noted limitations of the wide variability of reporting measures, but that overall, there was no detectable difference between pegged and keeled glenoids with respect to component failure. They did note that for asymptomatic radiolucent lines, there was a greater rate for keeled versus pegged glenoids (overall odds ratio = 2.37; p = 0.01). In efforts to improve survivorship of glenoid components, some authors recommend the use of newer patient‐specific components or of intraoperative navigation technology. The hope is that, by improving the accuracy of placing the glenoid component, failure rates will improve. Glenoid morphology can be difficult to assess and alignment difficult to recreate and optimize in the placement of glenoid components during TSA. Authors hypothesize that use of the new technology will improve the surgeon’s ability to accurately place the glenoid component intraoperatively. There are few studies looking at patient‐specific systems or intraoperative navigation for glenoid placement, but there is one level I and one level II study that investigates the effectiveness over standard techniques for glenoid placement. Several biomechanical studies also provide information. Hendel et al. performed a randomized prospective clinical trial evaluating standard surgical technique compared to the use of patient‐specific instrumentation for placement of the glenoid in TSA.9 They found that patient‐specific instrumentation led to improved inclination and mediolateral offset (p <0.05), but there was no statistical difference for version. In glenoids with the most retroversion preoperatively (>16°), the patient‐specific instrumentation showed the greatest benefit with only 1.2° deviation from optimal position versus 10° with standard instrumentation. There was also a significant reduction in the incidence of significant malpositioning (>10° of either version and/or inclination from the optimal preoperative plan) from 75 to 27% (p <0.01).
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Glenoid Components in Total Shoulder Arthroplasty
Clinical scenario
Top three questions
Question 1: In patients with primary osteoarthritis, do keeled or pegged glenoid components correlate with lower revision rates?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Level I studies
Level III studies
Level IV studies
Resolution of clinical scenario
Question 2: In patients with primary osteoarthritis, do patient‐specific components or intraoperative navigation, compared to traditional techniques, improve accuracy compared to traditional instrumentation?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Level I studies
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