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. 2023 Aug 7;16(4):390–396. doi: 10.1177/17585732231193285

Survivorship analysis of CAD-CAM total shoulder replacement

Sandeep Krishan Nayar 1,✉, David Butt 1, Aditya Prinja 1, Will Rudge 1, Addie Majed 1, Deborah Higgs 1, Mark Falworth 1
PMCID: PMC11418713  PMID: 39318417

Abstract

Background

Glenoid bone loss represents a challenge in shoulder arthroplasty and often precludes standard implants. The CAD-CAM total shoulder replacement (TSR) is an option in these cases. This study aimed to assess survivorship and long-term patient outcomes of the CAD-CAM TSR.

Methods

Fifty-eight patients that underwent a CAD-CAM TSR by three surgeons at a single tertiary referral centre between 2009 and 2017 were reviewed. The mean follow-up was 70 months (28–130). Data was collected on survivorship, range of movement, Oxford shoulder score (OSS, 0–48), subjective shoulder value (SSV, 0–100%), pain score (0–10), and overall patient satisfaction.

Results

CAD-CAM TSR was undertaken as a primary procedure in 28% (n = 16) for end-stage arthritis with severe glenoid bone loss, and as a revision procedure in 72% (n = 42). Of the total, 17% (n = 10) required component revision at a mean of 24 months (4x prosthesis loosening, 3x infection, 3x periprosthetic fracture). Forward elevation improved from 45° ± 27° to 59° ± 29° (P = 0.0056), abduction from 43° ± 29° to 55° ± 26° (P = 0.034) and external rotation from 8° ± 11° to 16° ± 14° (P = 0.031). OSS improved from 15 ± 8 to 29 ± 9 (P = 0.0009), SSV from 18 ± 16 to 62 ± 23 (P < 0.0001), and pain score from 8 ± 2 to 2 ± 2 (P < 0.0001). 88% of patients would undergo the procedure again.

Conclusion

CAD-CAM TSR is reserved for complex cases involving severe glenoid bone loss, offering significant improvements in pain and function with overall positive patient satisfaction.

Keywords: CAD-CAM shoulder, total shoulder arthroplasty, custom shoulder implant, revision shoulder arthroplasty, glenoid bone loss, glenoid deficiency

Introduction

Shoulder arthroplasty is well established in orthopaedic practice, and its use has increased exponentially over recent years. 1 This is particularly pertinent with the rise in the reverse total shoulder replacement (TSR). 2 Indications for the procedure include rotator cuff tear arthropathy, massive irreparable cuff tears, inflammatory arthritis, primary osteoarthritis with glenoid erosion and revision arthroplasty. 3 Associated with this increased use, there has been a greater awareness of the problems of glenoid bone loss.

In cases of severe glenoid erosion and revision arthroplasty, particularly where there is glenoid bone loss greater than 50% of the glenoid vault, the use of standard implants can be a challenge. Various techniques have been described to address this issue, for example eccentric reaming, bone grafting, and reverse shoulder arthroplasty with glenoid baseplate augmentation. 4 However, in the most challenging cases with advanced glenoid bone loss, the success rates from these solutions are limited and lack reproducibility.5,6 One solution in such situations is the use of a computer-aided design–computer-aided manufacturing (CAD-CAM) TSR (Stanmore Implants, Elstree, UK). This is a custom-made implant with a large porous coated acetabulum-like glenoid shell, analogous to that of total hip replacements, with a cemented captive constrained liner, thereby enhancing stability. Unlike the aforementioned techniques, the CAD-CAM shell is secured directly into the scapula using divergent 3.5 mm cortical screw fixation in the base of the coracoid, spine of the scapula, glenoid and lateral column of the scapula, precluding the need for glenoid bone stock (Figure 1). 7 Where indicated, morselised or structural bone graft can also be placed under the glenoid shell.

Figure 1.

Figure 1.

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AP left shoulder radiograph with a CAD-CAM TSR.

The CAD-CAM TSR is designed with the aid of preoperative CT images (Figure 2(a)–(c)).4,5 It is comprised of four components: (1) a titanium glenoid shell, which is 2 mm thick and has multiple longitudinal slots for locking or non-locking screw fixation to the scapula. It also has a hydroxyapatite coating to facilitate improved fixation, with its outside diameter determined by the glenoid vault dimensions, as measured on the preoperative CT scan. (2) A high molecular-weight polyethylene constrained liner, which is cemented into the titanium shell thereby allowing optimal version and inclination to be chosen for each patient. The liners’ outer diameter is sized to allow for a 2 mm cement mantle with the glenoid shell. Its inside diameter is matched to the size of the humeral head, with an additional 2 mm depth to allow for a captive-constrained reduction of the humeral head to enhance stability. (3) A cobalt-chrome humeral head (28 or 32 mm), and (4) a cobalt-chrome tapered humeral stem with a neck-shaft angle of 135° designed for cemented fixation (Figure 3). The 135° neck shaft angle allows for the lateralisation of the centre of rotation, thereby also aiding the function and stability of the implant. An uncemented option, with a hydroxyapatite coating and six longitudinal 1 mm fins added to facilitate early stability is also possible. Stem length can be individualised for the anatomical challenges of each patient.

Figure 2.

Figure 2.

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(1) Axial CT showing glenoid bone loss, (2) 3D reconstruction of scapula, (3) 3D template of CADCAM glenoid shell).

Figure 3.

Figure 3.

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CAD-CAM TSR implant.

This design of a CAD-CAM TSR has been utilised at our institution for nearly 20 years, with early results demonstrating it to be a viable option for securing a glenoid component in shoulders with advanced glenoid deficiency not amenable to standard anatomic or reverse total shoulder implants. Furthermore, these studies have revealed good results in terms of symptom relief and improvement in function.7,8 To date, there is limited data on the long-term survivorship and functional outcomes of these novel implants.

The primary objective of this study was to assess the survivorship of the CAD-CAM TSR. The secondary objectives were to assess the long-term outcomes of the prosthesis with regard to pain, function and patient satisfaction.

Methods

Study population

A retrospective cohort study was carried out. All patients who underwent a constrained, anatomic CAD-CAM TSR utilising a glenoid shell between 2009 and 2017 by one of three shoulder and elbow surgeons (AM, DH, and MF) at a single tertiary referral unit were included. All procedures were performed in a standardised manner, in the reclined beach chair position and via a deltopectoral approach.

Outcome measures

The primary outcome of the study was implant survivorship, defined by the incidence of revision. Secondary outcomes were the reasons for revision, pre- and post-operative active range of movement in forward flexion, abduction and external rotation, and patient-reported outcome measures (PROMS). The PROMS considered were:

Oxford shoulder score

This is a validated patient-reported outcome measure of subjective pain and function. It encompasses 12 questions, each scored from zero (worst) to four (best), giving an overall score between 0 and 48.9,10 Oxford shoulder score (OSS) was collected pre- and post-operatively.

Subjective shoulder value

This is a validated patient-reported outcome measure in which patients give a percentage with regard to how ‘normal’ their shoulder feels, graded from 0 (completely useless) to 100 (normal shoulder). 11 Subjective shoulder value (SSV) was collected pre- and post-operatively.

Subjective pain score

This is a numerical pain score from 0 (no pain) to 10 (the worst imaginable pain), which is widely used in a number of clinical settings. This was collected pre- and post-operatively.

Overall patient satisfaction

Patients were asked to answer ‘yes’ or ‘no’, as to whether they were satisfied overall with their procedure and would go through it again, giving reasons if they were not satisfied.

Statistical analysis

Survivorship analysis was carried out using the Kaplan–Meier method. Statistical analysis of secondary outcome measures was performed using paired t-tests. All continuous parameters are presented as mean and standard deviation. Data were analysed with GraphPad Prism 7 (GraphPad Software, CA). A P-value of <0.05 was considered statistically significant.

Results

Demographic information

Overall, 58 patients were identified and included in the study. The mean age at the time of operation was 70.8 years (range 48 to 86). Forty-four patients (75.9%) were female. CAD-CAM TSR was carried out as a primary procedure in 16 cases (28%) due to end-stage glenohumeral arthritis with severe glenoid bone loss and as a revision procedure in the remaining 42 cases (72%). From these 42 cases, 14 were revised from a previous hemiarthroplasty and the remainder from a reverse shoulder replacement. Eight cases (three hemiarthroplasties and five reverse shoulder prostheses) had a history of infection necessitating revision to the CAD-CAM TSR. Figure 4 illustrates the number of cases performed each year.

Figure 4.

Figure 4.

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Number of cases performed each year.

Implant survivorship

Follow-up ranged from 28 to 130 months, with a mean of 70 months. Reoperation was required in 11 patients (19%) with component revision in 10 (17%) at a mean time of 24 months; four (6.9%) for prosthesis loosening, three (5.2%) for infection and three (5.2%) for periprosthetic fracture. The prosthesis loosening cases required revision at 8, 10, 17 and 28 months. Revision for the infected cases occurred at 6, 24 and 27 months. Implant revision for periprosthetic fractures took place at 4, 48 and 71 months. The remaining case involved the excision of a painful screw, which was carried out at 25 months post-operatively. This case was not considered a revision as the main components were retained. The Kaplan–Meier curve for implant survivorship is illustrated in Figure 5.

Figure 5.

Figure 5.

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Kaplan–Meier survivorship curve. Solid line = actual survivorship; dotted lines = 95% confidence intervals.

Secondary outcomes

Active forward elevation improved from 45° ± 27° to 59° ± 29° (14° mean difference) (P = 0.0056), abduction improved from 43° ± 29° to 55° ± 26° (12° mean difference) (P = 0.034) and external rotation improved from 8° ± 11° to 16° ± 14° (8° mean difference) (P = 0.031). The OSS improved from 15 ± 8 points to 29 ± 9 points (14-point mean difference) (P = 0.0009), the SSV improved from 18 ± 16 points to 62 ± 23 points (44% mean difference) (P < 0.0001), and pain score improved from 8 ± 2 to 2 ± 2 (6-point mean difference) (P < 0.0001) (Table 1). Eighty-eight percent of patients stated they would undergo the procedure again.

Table 1.

Comparison of pre- and post-operative clinical outcomes.

Pre-operative Post-operative (latest follow-up) P-value
Active ROM
Forward elevation, ° 45 ± 27 59 ± 29 0.0056
Abduction, ° 43 ± 29 55 ± 26 0.034
External rotation, ° 8 ± 11 16 ± 14 0.031
PROMS
OSS (0- to 48-point scale) 15 ± 8 29 ± 9 0.0009
SSV, % 18 ± 16 62 ± 23 <0.0001
Pain score (0 to 10 scale) 8 ± 2 2 ± 2 <0.0001
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Values are presented as mean ± standard deviation. OSS, Oxford shoulder score; SSV, subjective shoulder value; PROMS, patient-reported outcome measures.

Discussion

Over recent years, the volume of shoulder arthroplasty procedures has continued to rise. 2 This has inevitably been coupled with an increase in the number of implant failures necessitating surgical revision. 12 Such cases are complex in nature due to the excessive loss of glenoid bone stock, and securing the glenoid component remains a challenge. One solution has been the use of the CAD-CAM TSR. The primary goal of this study was to assess the survivorship of this implant as well as the long-term outcomes including pain, function and patient satisfaction.

All 58 cases were performed between 2009 and 2017 with an implant survival rate of 83% at a mean follow-up of 6 years (range 28 months to 10 years). To date, there have been no implant revisions beyond six years. Whilst this survivorship is lower when compared to other shoulder prostheses used in primary arthroplasty,13–20 there is limited data on implant survival in the context of complex shoulder arthroplasty with severe glenoid bone loss, particularly in cases of revision surgery. Jeske et al. reported outcomes from the Epoca-Reconstruction-(Reco)®-Glenoid (Synthes, Solothurn, Switzerland), which is a semi-constrained anatomic design utilising an oversized glenoid shell secured to the scapula. Their study identified a revision rate of 21.7% from 23 patients with a mean follow-up of 37.5 months. 21 Boileau et al. reported 19 cases of revision arthroplasty with the Grammont-style Delta reverse shoulder prosthesis (DePuy International Ltd, Leeds, UK). At a mean follow-up of 40 months, eight patients (42.1%) required reoperation, with component revision in five (26.3%). 22 Results from this study corroborate with findings from a previously investigated single surgeon cohort of 37 patients that received a CAD-CAM TSR between 2006 and 2013, with component revision required in 16.2% at a mean follow-up of 5 years. 8

Benefits were also demonstrated with the CAD-CAM TSR in terms of PROMS and active range of motion. OSS improved by 14 (P = 0.0009), exceeding a minimal clinically important difference (MCID) of 4.3 as reported in the literature in the context of shoulder arthroplasty, hence including a significant improvement in subjective function. 23 This was coupled with a six-point reduction in pain score (P < 0.0001), exceeding an MCID of 1.4 for shoulder arthroplasty, 24 and an improvement in how ‘normal’ the shoulder feels by 44% (P < 0.0001).

Regarding range of motion, forward elevation improved by 14° (P = 0.0056) abduction by 12° (P = 0.034) and external rotation by 8° (P = 0.031). Whilst these increases can be considered modest, they are clinically significant. MCID following shoulder arthroplasty has been reported as 12° for active forward elevation, 7° for active abduction and 3° for active external rotation. 25 These improvements are comparable to other anatomic prostheses used in revision arthroplasty, however, are less when compared to reverse shoulder prostheses in this setting.21,26 This is likely multifactorial and reflected by the complexity of cases with a very low baseline range of motion in the majority of patients, as well as the constrained design of the CAD-CAM TSR with a maximal angular rotation of 60° around the centre of the prosthesis. 8

As technology evolves, there are an increasing number of options for revision shoulder arthroplasty. The use of patient-matched instrumentation or navigation allows for customisation in order to overcome difficult anatomy and ensure optimal position and orientation of the glenoid component.27,28 However, the standard implants used still rely on fixation into the glenoid bone and do not overcome the issue of extensive glenoid bone loss. Bone graft reconstruction techniques can be used when bone loss is sufficiently severe to prevent standard implants from being inserted but, in some cases, bone loss is so severe that a stable construct is not achievable. Augmented implants can be used to compensate for glenoid bone loss by wedge augmentation of the glenoid component. There is laboratory and finite element analysis evidence to support the use of these implants but there is still a lack of long-term clinical evidence.29,30 In addition, this technique is only useful for lesser degrees of bone loss. Custom-made glenoid implants that are specific to patients’ anatomy are being used but the technology is at an early stage, and whilst it may be an option for massive bone deficits in the future, there is little evidence in the literature to support its use at the present time. Furthermore, with the data collected from this cohort of patients, regular size options of the glenoid shells and stems are being noted, which could result in the development of an off-the-shelf implant system, thereby minimising costs of bespoke implants, which in turn will offer health economic advantages. The CAD-CAM TSR pre-dates the widespread use of custom reverse TSRs, which at present lack long-term data. It therefore remains a viable alternative for the most challenging cases with advanced glenoid bone loss.

This study has limitations, including the retrospective design, and whilst it captured the CAD-CAM TSRs performed over a 9-year period, given the rarity of indications for the use of such a prosthesis, there remains a relatively small cohort of patients. Additionally, there is a variable follow-up period with a minimum 28 month follow-up. However, this follow-up period encompasses the time in which most revisions are observed. Furthermore, to date, there is no established best practice for situations in which the CAD-CAM TSR is indicated and thus no accurate control group for comparison. Notably, both primary and revision cases have been combined in this series, with the main indication being extensive glenoid bone loss regardless of whether used in the primary or revision setting. These patients were treated prior to the widespread use of patient-specific instrumentation and the availability of custom glenoid implants, which are becoming more common. The introduction of these technologies has resulted in a decrease in the frequency of use of CAD-CAM implants in this cohort however, even with this technology, some of these cases will have only been successfully treated with this type of shell and captive liner.

Conclusions

CAD-CAM TSR should be reserved for complex cases, involving severe glenoid bone loss, that are not amenable to standard implants or where the use of patient-matched instrumentation or navigation will not achieve adequate results. In such instances, CAD-CAM implants offer significant improvements in pain and function with overall positive patient satisfaction.

Footnotes

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding: The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD: Sandeep Krishan Nayar https://orcid.org/0000-0003-2202-580X

References

  • 1.Kim SH, Wise BL, Zhang Y, et al. Increasing incidence of shoulder arthroplasty in the United States. J Bone Joint Surg Am 2011; 93: 2249–2254. [DOI] [PubMed] [Google Scholar]
  • 2.Familiari F, Rojas J, Doral MN, et al. Reverse total shoulder arthroplasty. EFORT Open Rev 2018; 3: 58–69. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Smithers CJ, Young AA, Walch G. Reverse shoulder arthroplasty. Curr Rev Musculoskelet Med 2011; 4: 183–190. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Bodendorfer BM, Loughran GJ, Looney AM, et al. Short-term outcomes of reverse shoulder arthroplasty using a custom baseplate for severe glenoid deficiency. J Shoulder Elbow Surg 2021; 30: 1060–1067. [DOI] [PubMed] [Google Scholar]
  • 5.Hsu JE, Ricchetti ET, Huffman GR, et al. Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty. J Shoulder Elbow Surg 2013; 22: 1298–1308. [DOI] [PubMed] [Google Scholar]
  • 6.Iannotti JP, Frangiamore SJ. Fate of large structural allograft for treatment of severe uncontained glenoid bone deficiency. J Shoulder Elbow Surg 2012; 21: 765–771. [DOI] [PubMed] [Google Scholar]
  • 7.Uri O, Beckles V, Falworth M, et al. Revision arthroplasty with a hip-inspired computer-assisted design/computer-assisted manufacturing implant for glenoid-deficient shoulders. J Shoulder Elbow Surg 2014; 23: 205–213. [DOI] [PubMed] [Google Scholar]
  • 8.Chammaa R, Uri O, Lambert S. Primary shoulder arthroplasty using a custom-made hip-inspired implant for the treatment of advanced glenohumeral arthritis in the presence of severe glenoid bone loss. J Shoulder Elbow Surg 2017; 26: 101–107. [DOI] [PubMed] [Google Scholar]
  • 9.Dawson J, Rogers K, Fitzpatrick R, et al. The Oxford shoulder score revisited. Arch Orthop Trauma Surg 2009; 129: 119–123. [DOI] [PubMed] [Google Scholar]
  • 10.Olley LM, Carr AJ. The use of a patient-based questionnaire (the Oxford shoulder score) to assess outcome after rotator cuff repair. Ann R Coll Surg Engl 2008; 90: 326–331. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Noorani AM, Roberts DJ, Malone AA, et al. Validation of the Stanmore percentage of normal shoulder assessment. Int J Shoulder Surg 2012; 6: 9–14. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Lädermann A, Schwitzguebel AJ, Edwards TB, et al. Glenoid loosening and migration in reverse shoulder arthroplasty. Bone Joint J 2019; 101-B: 461–469. [DOI] [PubMed] [Google Scholar]
  • 13.Deshmukh AV, Koris M, Zurakowski D, et al. Total shoulder arthroplasty: long-term survivorship, functional outcome, and quality of life. J Shoulder Elbow Surg 2005; 14: 471–479. [DOI] [PubMed] [Google Scholar]
  • 14.Khan A, Bunker TD, Kitson JB. Clinical and radiological follow-up of the Aequalis third-generation cemented total shoulder replacement: a minimum ten-year study. J Bone Joint Surg Br 2009; 91: 1594–1600. [DOI] [PubMed] [Google Scholar]
  • 15.Young A, Walch G, Boileau P, et al. A multicentre study of the long-term results of using a flat-back polyethylene glenoid component in shoulder replacement for primary osteoarthritis. J Bone Joint Surg Br 2011; 93: 210–216. [DOI] [PubMed] [Google Scholar]
  • 16.Beck S, Beck V, Wegner A, et al. Long-term survivorship of stemless anatomical shoulder replacement. Int Orthop 2018; 42: 1327–1330. [DOI] [PubMed] [Google Scholar]
  • 17.Guery J, Favard L, Sirveaux F, et al. Reverse total shoulder arthroplasty. Survivorship analysis of eighty replacements followed for five to ten years. J Bone Joint Surg Am 2006; 88: 1742–1747. [DOI] [PubMed] [Google Scholar]
  • 18.Favard L, Young A, Alami G, et al. Survivorship of the reverse shoulder arthroplasties (RSA) with a minimum follow up of 10 years. Bone Joint J 2012; 94-B: 24. [Google Scholar]
  • 19.Mizuno N, Denard PJ, Raiss P, et al. Reverse total shoulder arthroplasty for primary glenohumeral osteoarthritis in patients with a biconcave glenoid. J Bone Joint Surg Am 2013; 95: 1297–1304. [DOI] [PubMed] [Google Scholar]
  • 20.Cuff DJ, Pupello DR, Santoni BG, et al. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency: a concise follow-up, at a minimum of 10 years, of previous reports. J Bone Joint Surg Am 2017; 99: 1895–1899. [DOI] [PubMed] [Google Scholar]
  • 21.Jeske HC, Wambacher M, Dallapozza C, et al. Functional and clinical outcome of total shoulder arthroplasty with oversized glenoid. Arch Orthop Trauma Surg 2012; 132: 927–936. [DOI] [PubMed] [Google Scholar]
  • 22.Boileau P, Watkinson D, Hatzidakis AM, et al. Neer Award 2005: the Grammont reverse shoulder prosthesis: results in cuff tear arthritis, fracture sequelae, and revision arthroplasty. J Shoulder Elbow Surg 2006; 15: 527–540. [DOI] [PubMed] [Google Scholar]
  • 23.Nyring MRK, Olsen BS, Amundsen A, et al. Minimal clinically important differences (MCID) for the Western Ontario osteoarthritis of the shoulder Index (WOOS) and the Oxford shoulder score (OSS). Patient Relat Outcome Meas 2021; 12: 299–306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Tashjian RZ, Hung M, Keener JD, et al. Determining the minimal clinically important difference for the American shoulder and elbow surgeons score, simple shoulder test, and visual analog scale (VAS) measuring pain after shoulder arthroplasty. J Shoulder Elbow Surg 2017; 26: 144–148. [DOI] [PubMed] [Google Scholar]
  • 25.Simovitch R, Flurin P-H, Wright T, et al. Quantifying success after total shoulder arthroplasty: the minimal clinically important difference. J Shoulder Elbow Surg 2018; 27: 298–305. [DOI] [PubMed] [Google Scholar]
  • 26.Kim K, Elbuluk A, Jia N, et al. Revision shoulder arthroplasty: patient-reported outcomes vary according to the etiology of revision. J Orthop 2018; 15: 922–926. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Dallalana RJ, McMahon RA, East B, et al. Accuracy of patient-specific instrumentation in anatomic and reverse total shoulder arthroplasty. Int J Shoulder Surg 2016; 10: 59–66. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.Levy JC, Everding NG, Frankle MA, et al. Accuracy of patient-specific guided glenoid baseplate positioning for reverse shoulder arthroplasty. J Shoulder Elbow Surg 2014; 23: 1563–1567. [DOI] [PubMed] [Google Scholar]
  • 29.Hermida JC, Flores-Hernandez C, Hoenecke HR, et al. Augmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis. J Shoulder Elbow Surg 2014; 23: 347–354. [DOI] [PubMed] [Google Scholar]
  • 30.Allred JJ, Flores-Hernandez C, Hoenecke HR, et al. Posterior augmented glenoid implants require less bone removal and generate lower stresses: a finite element analysis. J Shoulder Elbow Surg 2016; 25: 823–830. [DOI] [PubMed] [Google Scholar]

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