Prospective, Blinded, Randomized Controlled Trial of Stemless Versus Stemmed Humeral Components in Anatomic Total Shoulder Arthroplasty: Results at Short-Term Follow-up

Recent Advances in the Design and Application of Shoulder Arthroplasty Implant Systems and Their Impact on Clinical Outcomes: A Comprehensive Review

Purpose of Review

This narrative review comprehensively aims to analyze recent advancements in shoulder arthroplasty, focusing on implant systems and their impact on patient outcomes. The purpose is to provide a nuanced understanding of the evolving landscape in shoulder arthroplasty, incorporating scientific, regulatory, and ethical dimensions.

Recent Findings

The review synthesizes recent literature on stemless implants, augmented glenoid components, inlay vs onlay configurations, convertible stems, and associated complications. Notable findings include improved patient-reported outcomes with stemless implants, variations in outcomes between inlay and onlay configurations, and the potential advantages of convertible stems. Additionally, the regulatory landscape, particularly the FDA's 510(k) pathway, is explored alongside ethical considerations, emphasizing the need for standardized international regulations.

Summary

Recent innovations in shoulder arthroplasty showcase promising advancements, with stemless implants demonstrating improved patient outcomes. The review underscores the necessity for ongoing research to address unresolved aspects and highlights the importance of a standardized regulatory framework to ensure patient safety globally. The synthesis of recent findings contributes to a comprehensive understanding of the current state of shoulder arthroplasty, guiding future research and clinical practices.

Evolution of Stemless Reverse Shoulder Arthroplasty: Current Indications, Outcomes, and Future Prospects

Reverse total shoulder arthroplasty (rTSA) is increasingly being used as a reliable option for various shoulder disorders with deteriorated rotator cuff and glenohumeral joints. The stemless humerus component for shoulder arthroplasties is evolving with theoretical advantages, such as preservation of the humeral bone stock and decreased risk of periprosthetic fractures, as well as clinical research demonstrating less intraoperative blood loss, reduced surgical time, a lower rate of intraoperative fractures, and improved center of rotation restoration. In particular, for anatomical total shoulder arthroplasty (aTSA), the utilization of stemless humeral implants is gaining consensus in younger patients. The current systematic review of 14 clinical studies (637 shoulders) demonstrated the clinical outcomes of stemless rTSA. Regarding shoulder function, the mean Constant-Murley Score (CS) improved from 28.3 preoperatively to 62.8 postoperatively. The pooled overall complication and revision rates were 14.3% and 6.3%, respectively. In addition, recent studies have shown satisfactory outcomes with stemless rTSA relative to stemmed rTSA. Therefore, shoulder surgeons may consider adopting stemless rTSA, especially in patients with sufficient bone quality. However, further long-term studies comparing survivorship between stemless and stemmed rTSA are required to determine the gold standard for selecting stemless rTSA.

Techniques to Address Humeral Bone Insufficiency During Total Shoulder Arthroplasty With a Nonspherical Humeral Head and Inlay Glenoid

Total shoulder arthroplasty with a humeral head resurfacing (HHR) component and an inlay glenoid (OVOMotion; Arthrosurface) is a successful treatment option for patients with advanced glenohumeral arthritis, an intact rotator cuff, and adequate proximal humeral bone stock. In patients with poor proximal humeral bone, historically stemmed humeral components have been used instead of HHR. However, strategies can be used to successfully optimize HHR implant fixation in suboptimal bone without converting to stemmed implants or in surgical centers where stemmed prostheses are not available. This Technical Note describes 3 techniques-upsizing the humeral taper post, using humeral autograft, and cementation-to improve humeral implant fixation in patients with suboptimal bone stock when using the Arthrosurface OVOMotion implant.

A comparison of revision rates for stemmed and stemless primary anatomic shoulder arthroplasty with all-polyethylene glenoid components: analysis from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

We compared the rate of all-cause revision of 2 classes of primary anatomic shoulder arthroplasty, stemmed (stTSA) and stemless (slTSA), undertaken with cemented all-polyethylene glenoid components.

METHODS

A large national arthroplasty registry identified 2 cohort groups for comparison, stTSA and l undertaken for all diagnoses between January 1, 2011, and December 31, 2021. A subanalysis from January 1, 2017, allowed capturing of additional patient demographics including American Society of Anesthesiologists score, body mass index, and glenoid morphology. The cumulative percent revision (CPR) was determined using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazard models adjusted for age and gender.

RESULTS

Of the 7995 stTSA procedures, the CPR at 9 years was 5.6% (95% confidence interval [CI]: 5.0, 6.4), and for 3156 slTSA procedures, the CPR was 4.4% (95% CI: 3.6, 5.5). There was no significant difference in the rate of revision between the study groups (HR = 0.76 [95% CI: 0.51, 1.14], P = .189, adjusted for age, gender, humeral head size, humeral fixation, bearing surface, glenoid design, and mean surgeon volume [MSV]). There was an increased rate of revision for stTSA and slTSA undertaken with humeral head sizes <44 mm (stTSA <44 mm vs. 44-50 mm, HR = 1.56 [CI: 1.18, 2.08], P = .001; slTSA <44 mm vs. 44-50 mm, HR = 2.08 [CI: 1.32, 3.33], P = .001). MSV as a continuous predictor was not a revision risk to stTSA vs. slTSA, but categorically, a low MSV (<10 stTSA + slTSA cases per annum) was associated with a higher revision rate for stTSA (10-20 cases/yr vs. <10 cases/yr, HR = 0.72 [CI: 0.55, 0.95], P = .019) but was not in slTSA. Revision rates were increased for stTSA with non-crosslinked polyethylene (XLPE) glenoids vs. XPLE after 2 years (HR = 2.20 [CI: 1.57, 3.08], P < .001) but did not significantly differ for slTSA. Metal/XPLE (humeral/glenoid) bearing surface of stTSA rate of revision was not different from each combination of slTSA bearing surface. Instability/dislocation was a revision risk for slTSA vs. stTSA (HR = 1.93 [CI: 1.28, 2.91], P = .001), but from 2017, neither of American Society of Anesthesiologists score, body mass index, and glenoid morphology changed the rate of revision.

CONCLUSIONS

Revision rates of stTSA and slTSA did not significantly differ and were associated with humeral head size but not patient characteristics. Surgeon inexperience of anatomic shoulder arthroplasty and non-XLPE glenoids were risk factors for stTSA revision but not slTSA. The metal/XLPE stTSA rate of revision was not found to differ significantly from slTSA regardless of polyethylene or humeral head bearing type. Revision for instability/dislocation was more common for slTSA.

Poor evidence is used to support commercial payers' coverage policies for shoulder arthroplasty

BACKGROUND

The incidence of shoulder arthroplasty has continued to increase over the past decade. In response, commercial payers have implemented strategies to control the medical requirement of these surgeries in attempt to contain the growing costs. For example, most payers require a prolonged trial of conservative management prior to shoulder arthroplasty for patients who may otherwise be surgical candidates. However, little is known regarding the evidence used to support these indications. The purpose of this study was to analyze the references used by commercial payers to substantiate their coverage policies for shoulder arthroplasty.

METHODS

Ten of the leading commercial payers for total shoulder arthroplasty were identified. Publicly available coverage policies were searched on the internet or requested directly from the payer via email or telephone. Cited references were reviewed independently by two authors for type of document, level of evidence, and mention of the efficacy of conservative management.

RESULTS

A total of 5 coverage policies were obtained with 118 references. The most common reference type was primary journal article (n = 70; 59.3%) followed by review or expert opinion articles (n = 35; 29.7%). Most references were of level IV evidence (n = 60; 52.2%), with only 6 (5.2%) of level I or II evidence. Only 4 (3.5%) references mentioned the efficacy of conservative management in patients who may be candidates for shoulder arthroplasty.

CONCLUSION

The majority of references used to substantiate the coverage policies for shoulder arthroplasty among major commercial payers within the United States are of low scientific evidence and fail to demonstrate the success of required nonoperative intervention strategies. Our study underscores the need for high-quality, comparative trials that evaluate the outcomes of conservative management vs. shoulder arthroplasty in end-stage glenohumeral osteoarthritis patients in order to determine the most cost-effective treatment algorithm.

Medium-Term Clinical Outcomes of the Global Icon Stemless Shoulder System: Results of a 2-Year Follow-Up

The primary aim of this study was to assess the medium-term outcomes of the Global Icon stemless shoulder replacement in patients who have undergone primary total shoulder arthroplasty (TSA) for glenohumeral joint osteoarthritis. A retrospective review of patients who had undergone a TSA using the Global Icon stemless shoulder system was performed. The Western Ontario Osteoarthritis Shoulder (WOOS) Index and Oxford Shoulder Score (OSS) were evaluated pre-operatively and at 12 to 24 months post-operatively. Radiological outcomes, operation time, and post-operative complications were reported. Primary analysis for the WOOS Index and OSS focused on detecting within-group treatment effects at 24 months using a repeated measures ANOVA. Thirty patients were included in the study. Post-surgery, there was a significant improvement at 24 months on the OSS (ES = 0.932, CI: 41.7 to 47.7, p < 0.001) and the WOOS Index (ES = 0.906, CI: 71.9 to 99.8, p < 0.001). Radiographs revealed that no component loosened, migrated, or subsided. The median operative time was 75.5 (IQR: 12.25, range: 18 to 105) min. No implant-related complications were reported. The Global Icon stemless replacements have excellent clinical outcomes in this cohort at 12- and 24-month follow-up with no implant-related complications.

Outcomes Between Stemmed and Stemless Total Shoulder Arthroplasty: A Systematic Review and Meta-analysis of Randomized Controlled Trials

INTRODUCTION

Both stemmed and stemless designs for total shoulder arthroplasty (TSA) have demonstrated efficacious outcomes for the surgical treatment of primary glenohumeral joint osteoarthritis. The purpose of this systematic review and meta-analysis was to compare the clinical outcomes of stemmed versus stemless TSA in randomized controlled trials. We hypothesized that there would be no differences in Constant Score (CS), range of motion, or adverse events, such as periprosthetic fracture and/or revision surgery.

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, a systematic review of the literature was done using MEDLINE, SPORTDiscus, Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Registry of Controlled Trials, Embase, and Web of Science databases. Outcomes of interest included CS, range of motion, and adverse events (periprosthetic fracture and revision). Summary effect estimates of the mean difference between stemmed and stemless TSA for each outcome were estimated in random effects models.

RESULTS

The search yielded 301 articles with 4 appropriate for qualitative analysis, including the results of 229 stemmed and 358 stemless TSAs. No significant difference was observed in postoperative CS (P = 0.36), forward flexion (P = 0.93), abduction (P = 0.30), or external rotation (P = 0.34) between stemmed and stemless TSA. No significant difference was observed in change in CS (P = 0.27), forward flexion (P = 0.25), or external rotation (P = 0.74). A change in abduction was significantly different between stemmed and stemless TSA (standardized mean difference = -0.64; 95% confidence interval, -1.20 to -0.08) in favor of stemmed TSA (P = 0.02), attributed to preoperative differences. No significant difference was observed in periprosthetic fractures (P = 0.07) or revision (P = 0.90).

CONCLUSION

TSA with stemless versus stemmed humeral components was not associated with notable differences in functional and clinical outcomes. No difference was observed between stemmed and stemless designs in postoperative forward flexion, abduction, or external rotation. Similarly, there was no difference in change in forward flexion or external rotation. A markedly greater improvement in abduction was observed with stemmed TSA, likely due to the lower preoperative motion in the stemmed cohort in one of the studies. No differences were observed between stemmed and stemless designs in the rate of humeral fracture or risk of revision.

LEVEL OF EVIDENCE

Level II; systematic review and meta-analysis of prospective randomized controlled trials.

Stemless anatomic total shoulder arthroplasty: surgical technique and review of the literature

Stemless anatomic total shoulder arthroplasty (aTSA) is a promising option for the treatment of degenerative disease in patients. This novel technique avoids the stem-related complications associated with the traditional stemmed aTSA. Stemless aTSA offers additional benefits such as decreased operative time, preservation of bone stock, improved radiographic outcomes, and easier revision. Moreover, loading of the metaphyseal region rather than the diaphysial region with traditional stemmed implants can decrease stress shielding. When compared to stemmed-implants, stemless aTSA has demonstrated similar outcomes and complication rates. The purpose of this article is to analyze published outcomes and complications following the utilization of stemless aTSA. Additionally, key aspects of the surgical technique that may promote optimal results in stemless aTSA implantation are presented.

Can the Single Assessment Numeric Evaluation (SANE) be used as a stand-alone outcome instrument in patients undergoing total shoulder arthroplasty?

BACKGROUND AND HYPOTHESIS

There is no consensus as to which patient-determined shoulder outcome scores should be considered when analyzing patient outcomes for either clinical or research purposes. Use of multiple patient-determined outcomes may be redundant and cause increased responder burden. To date, the Single Assessment Numeric Evaluation (SANE) has not been widely accepted as a stand-alone shoulder-specific outcome measure. The hypothesis of this study was that the SANE would correlate with and be equal or superior in responsiveness to other outcome measures that have been used in a stand-alone fashion in patients undergoing total shoulder arthroplasty (American Shoulder and Elbow Surgeons [ASES], Western Ontario Osteoarthritis of the Shoulder [WOOS], and Simple Shoulder Test [SST] scores). In addition, it was hypothesized that the SANE would be more relevant to each patient than the ASES assessment, further supporting the use of the SANE as a stand-alone shoulder-specific outcome measure.

METHODS

A retrospective review of a database of patients undergoing total shoulder arthroplasty was performed, in which the SANE score was recorded simultaneously with the ASES, WOOS, and/or SST score. Correlations were determined using the Pearson coefficient. Subgroup analysis was performed to determine whether correlations differed in (1) preoperative outcome and (2) postoperative outcome determinations. Responsiveness was determined by calculating the standardized response mean and the effect size of all scores. The relevance of the SANE and ASES assessments was examined using the scores of 150 consecutive patients to determine the number of questions on each assessment that were not answered.

RESULTS

Correlation was excellent for the SANE score and the ASES score (n = 1447, r = 0.82, P < .0001), WOOS score (n = 1514, r = 0.83, P < .0001), and SST score (n = 1095, r = 0.81, P < .0001). The correlation of preoperative scores was moderate and that of postoperative scores was strong-moderate when the SANE score was compared with all 3 other scores. All scores were highly responsive, with standardized response mean values of 2.2 for the SANE score, 2.3 for the ASES score, 1.4 for the WOOS score, and 1.6 for the SST score. The effect size of the SANE score was 2.9; ASES score, 2.9; WOOS score, 2.9; and SST score, 2.3. One hundred percent of the SANE questions were answered completely compared with 61% of the ASES questions (P < .0001).

CONCLUSION

In patients undergoing total shoulder arthroplasty, the SANE score highly correlated with the WOOS, ASES, and SST scores, which have been used as stand-alone shoulder-specific outcome measures. The SANE score may provide the same information as the WOOS, ASES, and SST score regarding outcomes with a significant reduction in responder burden. It is logical that the SANE can be used as a stand-alone instrument for patients undergoing total shoulder arthroplasty.

A Comparison of Operative Time and Intraoperative Blood Volume Loss Between Stemless and Short‐stem Anatomic Total Shoulder Arthroplasty: A Single Institution's Experience

There has been increasing interest in the use of stemless humeral implants for total shoulder arthroplasty when compared with both short-stem (SS) and standard-length implants. Although evidence for decreased surgical time and blood loss exists for stemless versus standard-length stems, far less literature exists comparing these clinical parameters for stemless versus SS implants.

Substantial Inconsistency and Variability Exists Among Minimum Clinically Important Differences for Shoulder Arthroplasty Outcomes: A Systematic Review

BACKGROUND

As the value of patient-reported outcomes becomes increasingly recognized, minimum clinically important difference (MCID) thresholds have seen greater use in shoulder arthroplasty. However, MCIDs are unique to certain populations, and variation in the modes of calculation in this field may be of concern. With the growing utilization of MCIDs within the field and value-based care models, a detailed appraisal of the appropriateness of MCID use in the literature is necessary and has not been systematically reviewed.

QUESTIONS/PURPOSES

We performed a systematic review of MCID quantification in existing studies on shoulder arthroplasty to answer the following questions: (1) What is the range of values reported for the MCID in commonly used shoulder arthroplasty patient-reported outcome measures (PROMs)? (2) What percentage of studies use previously existing MCIDs versus calculating a new MCID? (3) What techniques for calculating the MCID were used in studies where a new MCID was calculated?

METHODS

The Embase, PubMed, and Ovid/MEDLINE databases were queried from December 2008 through December 2020 for total shoulder arthroplasty and reverse total shoulder arthroplasty articles reporting an MCID value for various PROMs. Two reviewers (DAK, MAM) independently screened articles for eligibility, specifically identifying articles that reported MCID values for PROMs after shoulder arthroplasty, and extracted data for analysis. Each study was classified into two categories: those referencing a previously defined MCID and those using a newly calculated MCID. Methods for determining the MCID for each study and the variability of reported MCIDs for each PROM were recorded. The number of patients, age, gender, BMI, length of follow-up, surgical indications, and surgical type were extracted for each article. Forty-three articles (16,408 patients) with a mean (range) follow-up of 20 months (0.75 to 68) met the inclusion criteria. The median (range) BMI of patients was 29.3 kg/m2 (28.0 to 32.2 kg/m2), and the median (range) age was 68 years (53 to 84). There were 17 unique PROMs with MCID values. Of the 112 MCIDs reported, the most common PROMs with MCIDs were the American Shoulder and Elbow Surgeons (ASES) (23% [26 of 112]), the Simple Shoulder Test (SST) (17% [19 of 112]), and the Constant (15% [17 of 112]).

RESULTS

The ranges of MCID values for each PROM varied widely (ASES: 6.3 to 29.5; SST: 1.4 to 4.0; Constant: -0.3 to 12.8). Fifty-six percent (24 of 43) of studies used previously established MCIDs, with 46% (11 of 24) citing one study. Forty-four percent (19 of 43) of studies established new MCIDs, and the most common technique was anchor-based (37% [7 of 19]), followed by distribution (21% [4 of 19]).

CONCLUSION

There is substantial inconsistency and variability in the quantification and reporting of MCID values in shoulder arthroplasty studies. Many shoulder arthroplasty studies apply previously published MCID values with variable ranges of follow-up rather than calculating population-specific thresholds. The use of previously calculated MCIDs may be acceptable in specific situations; however, investigators should select an anchor-based MCID calculated from a patient population as similar as possible to their own. This practice is preferable to the use of distribution-approach MCID methods. Alternatively, authors may consider using substantial clinical benefit or patient-acceptable symptom state to assess outcomes after shoulder arthroplasty.

CLINICAL RELEVANCE

Although MCIDs may provide a useful effect-size based alternative to the traditional p value, care must be taken to use an MCID that is appropriate for the particular patient population being studied.

Surgical time and outcomes of stemmed versus stemless total shoulder arthroplasty

BACKGROUND

Stemless total shoulder arthroplasty (TSA) was approved for use in the United States in 2015, and there remains a paucity of data on its performance in this market. Decreased operative time without compromise of clinical outcomes is a theoretical advantage of stemless TSA, but no studies have evaluated this in a comparative study to date. Herein, the operative times and clinical outcomes of stemless vs. conventional stemmed TSA are investigated.

METHODS

This is a retrospective cohort study, evaluating all consecutive TSAs performed by a single surgeon between 2015 and 2018. Data were collected from 59 patients who underwent TSA with conventional, stemmed humeral implants and 115 patients in whom a stemless humeral implant was used. Operative times and demographic data were collected retrospectively from the anesthesia record, and prospectively collected patient-reported outcome measures were collected from the Surgical Outcomes System database. For patient-reported outcome measure, visual analog scale, American Shoulder and Elbow Surgeons, and Single Assessment Numerical Evaluation scores were recorded serially until a minimum 2-year follow-up.

RESULTS

The average operative time was 24 minutes less in the stemless cohort compared with the stemmed cohort (104 minutes vs. 128 minutes, P < .001). Cost analysis showed a decreased personnel cost of 15.9% that correlates to a 3.1% overall reduction in operating room-associated cost. Patient-reported outcome scores significantly improved postoperatively in both cohorts across all time points. There was no difference found in visual analog scale, American Shoulder and Elbow Surgeons, and Single Assessment Numerical Evaluation scores between the cohorts at the 2-year follow-up.

CONCLUSIONS

Stemless TSA significantly reduces operative time with equivalent functional outcomes at a minimum 2-year follow-up.

Stemless reverse total shoulder arthroplasty: a systematic review

BACKGROUND

The use of reverse total shoulder arthroplasty and stemless anatomic total shoulder replacement has been increasing in the United States every year. Stemless humeral components in reverse total shoulder arthroplasty are only approved for clinical trials in the United States with an investigational device exception with limited data.

METHODS

A systematic review on stemless reverse total shoulder arthroplasty was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A search was conducted on November 25, 2020, using the MEDLINE/PubMed, Cochrane, and Embase databases. All articles were reviewed by 2 independent evaluators, with any conflicts or issues resolved by consensus or a final decision by the senior author. The primary outcomes extracted were complications, radiographic results, and outcome scores.

RESULTS

We evaluated 10 studies that used either the Total Evolutive Shoulder System (TESS) or Verso implant. There were 430 total patients and 437 total procedures; 266 patients in the TESS group underwent a total of 272 procedures, and 164 patients in the Verso group underwent a total of 165 procedures. The mean age at the time of surgery was 73.8 years (range, 38-93 years). The mean follow-up period ranged from 6.4 to 101.6 months per study. There was an overall trend of improved clinical outcome scores, a 0.2% humeral component loosening rate, and an 11.2% complication rate.

CONCLUSIONS

This review shows that the clinical and functional outcomes following stemless or metaphyseal reverse total shoulder arthroplasty are quite promising, especially with the low rate of humeral-sided complications. There continues to be a need for additional long-term studies and randomized clinical trials.

Early fixation of the humeral component in stemless total shoulder arthroplasty : a radiostereometric and clinical study with 24-month follow-up

AIMS

Stemless humeral implants have been developed to overcome stem-related complications in total shoulder arthroplasty (TSA). However, stemless implant designs may hypothetically result in less stable initial fixation, potentially affecting long-term survival. The aim of this study is to investigate early fixation and migration patterns of the stemless humeral component of the Simpliciti Shoulder System and to evaluate clinical outcomes.

METHODS

In this prospective cohort study, radiostereometric analysis (RSA) radiographs were obtained in 24 patients at one day, six weeks, six months, one year, and two years postoperatively. Migration was calculated using model-based RSA. Clinical outcomes were evaluated using the visual analogue scale (VAS), the Oxford Shoulder Score (OSS), the Constant-Murley Score (CMS), and the Disabilities of the Arm, Shoulder and Hand (DASH) score.

RESULTS

At two years, median translation along the x-, y-, and z-axis was -0.12 mm (interquartile range (IQR) -0.18 to 0.02), -0.17 mm (IQR -0.27 to -0.09), and 0.09 mm (IQR 0.02 to 0.31). Median rotation around the x-, y-, and z-axis was 0.12° (IQR -0.50 to 0.57), -0.98° (IQR -1.83 to 1.23), and 0.09° (IQR -0.76 to 0.30). Overall, 20 prostheses stabilized within 12 months postoperatively. Four prostheses showed continuous migration between 12 and 24 months. At two-year follow-up, with the exception of one revised prosthesis, all clinical scores improved significantly (median VAS difference at rest: -3.0 (IQR -1.5 to -6.0); OSS 22.0 (IQR 15.0 to 25.0); CMS 29.5 (IQR 15.0 to 35.75); and DASH -30.0 (IQR -20.6 to -41.67) (all p < 0.001)) with the exception of one revised prosthesis.

CONCLUSION

In conclusion, we found that 20 out of 24 implants stabilized within 12 months postoperatively. The significance of continuous migration in four implants is unclear and future research on the predictive value of early migration for future loosening in TSA is required. Clinical results revealed a clinically relevant improvement. Cite this article: Bone Joint J 2022;104-B(1):76-82.

Sex-related differences in stemless total shoulder arthroplasty

Background

Methods

Results

Conclusion

Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants

Background

The purpose of this study was to compare the accuracy of anatomic reconstruction of three different humeral head designs after anatomic total shoulder arthroplasty.

Methods

Postoperative radiographs of 117 patients who underwent anatomic total shoulder arthroplasty with three different implant designs (stemmed spherical, stemless spherical, and stemless elliptical) were analyzed for landmarks that represented the prearthritic state and final implant position. We assessed the change in center of rotati7on and humeral head height on the anteroposterior view and the percentage of prosthesis overhang on the axillary lateral view. A modified anatomic reconstruction index, a compound score that rated each of the 3 parameters from 0 to 2, was created to determine the overall accuracy of the reconstruction.

Results

Excellent modified anatomic reconstruction index scores (5 or 6 points) were achieved by 68.1% of the cases in the stemless elliptical group compared with 33.3% of the cases in the stemless spherical group and by 28.3% of the cases in the stemmed spherical group (P = .001).The mean difference in restoration of humeral head height (P < .001) and percentage of prosthesis overhang (P < .001) was superior for the stemless elliptical group compared with the two other spherical head groups. There was no difference between groups for the shift in center of rotation (P = .060).

Conclusions

In this radiographic investigation comparing three different humeral head designs with respect to anatomic restoration parameters, the stemless elliptical implant more closely restored the geometry of the prearthritic humeral head as assessed by humeral head height, prosthesis overhang, and a compound reconstruction score.

Prevalence of Shoulder Arthroplasty in the United States and the Increasing Burden of Revision Shoulder Arthroplasty

Existing data on the epidemiology of shoulder arthroplasty are limited to future projections of incidence. However, the prevalence of shoulder arthroplasty (the number of individuals with a shoulder arthroplasty alive at a certain time and its implications for the burden of revision procedures) remains undetermined for the United States. Hence, the purpose of this study was to estimate the prevalence of shoulder arthroplasty in the United States.