Inlay versus onlay humeral design for reverse shoulder arthroplasty: a systematic review and meta-analysis

Lateralisation in reverse shoulder arthroplasty - A narrative review

Reverse shoulder arthroplasty (RSA) has witnessed a significant advancement with the introduction of lateralisation techniques, aiming to enhance shoulder function and implant durability. Traditional medialised designs, following Grammont's principles, have encountered challenges such as scapular notching, reduced rotational strength, and instability. In contrast, lateralisation methods, which reposition the joint center of rotation laterally on the glenoid, humerus, or both, seek to improve deltoid leverage, optimize the rotator cuff muscles' length-tension relationship, and enhance joint stability. Strategies for achieving lateralisation include bone grafts, lateralised glenosphere designs, and metallic augmented base plates. Clinical and biomechanical studies have shown that lateralised RSA designs decrease scapular notching, enhance range of motion, and promote stability. However, these advantages come with drawbacks like heightened shear forces, potential acromial stress fractures, and the risk of joint overstuffing. The future of RSA involves striking a balance between these aspects through tailored implant configurations and the utilization of cutting-edge technologies such as artificial intelligence, 3D modeling, and augmented reality to optimize surgical results. Further research is imperative to validate the long-term efficacy of lateralised RSA and refine these novel approaches to shoulder arthroplasty.

The relationship between design-based lateralization, humeral bearing design, polyethylene angle, and patient-related factors on surgical complications after reverse shoulder arthroplasty: a machine learning analysis

BACKGROUND

Technological advancements in implant design and surgical technique have focused on diminishing complications and optimizing performance of reverse shoulder arthroplasty (rTSA). Despite this, there remains a paucity of literature correlating prosthetic features and clinical outcomes. This investigation utilized a machine learning approach to evaluate the effect of select implant design features and patient-related factors on surgical complications after rTSA.

METHODS

Over a 16-year period (2004-2020), all primary rTSA performed at a single institution for elective and traumatic indications with a minimum follow-up of 2 years were identified. Parameters related to implant design evaluated in this study included inlay vs. onlay humeral bearing design, glenoid lateralization (medialized or lateralized), humeral lateralization (medialized, minimally lateralized, or lateralized), global lateralization (medialized, minimally lateralized, lateralized, highly lateralized, or very highly lateralized), stem to metallic bearing neck shaft angle, and polyethylene neck shaft angle. Machine learning models predicting surgical complications were constructed for each patient and Shapley additive explanation values were calculated to quantify feature importance.

RESULTS

A total of 3837 rTSA were identified, of which 472 (12.3%) experienced a surgical complication. Those experiencing a surgical complication were more likely to be current smokers (Odds ratio [OR] = 1.71; P = .003), have prior surgery (OR = 1.60; P < .001), have an underlying diagnosis of sequalae of instability (OR = 4.59; P < .001) or nonunion (OR = 3.09; P < .001), and required longer OR times (98 vs. 86 minutes; P < .001). Notable implant design features at an increased odds for complications included an inlay humeral component (OR = 1.67; P < .001), medialized glenoid (OR = 1.43; P = .001), medialized humerus (OR = 1.48; P = .004), a minimally lateralized global construct (OR = 1.51; P < .001), and glenohumeral constructs consisting of a medialized glenoid and minimally lateralized humerus (OR = 1.59; P < .001), and a lateralized glenoid and medialized humerus (OR = 2.68; P < .001). Based on patient- and implant-specific features, the machine learning model predicted complications after rTSA with an area under the receiver operating characteristic curve of 0.61.

CONCLUSIONS

This study demonstrated that patient-specific risk factors had a more substantial effect than implant design configurations on the predictive ability of a machine learning model on surgical complications after rTSA. However, certain implant features appeared to be associated with a higher odd of surgical complications.

Whether the Indications for Reverse Shoulder Arthroplasty Should Continue to Be Expanded? A Systematic Review and Meta-Analysis

BACKGROUND

It is still unclear whether reverse total shoulder arthroplasty (RTSA) has advantages over traditional hemiarthroplasty (HA) and anatomic total shoulder arthroplasty (ATSA) in the treatment of complex shoulder joint diseases. Therefore, this study aims to evaluate the clinical effectiveness of RTSA in the treatment of complex shoulder joint diseases and further determine whether it is necessary to expand the indications of RTSA.

METHOD

We conducted a systematic search of studies published between January 1, 2012 and May 31, 2023 in PubMed, Embase, and Cochrane databases. The experimental group included patients who underwent primary reverse total shoulder arthroplasty (RTSA), while the control group consisted of patients who underwent primary hemiarthroplasty (HA) or anatomic total shoulder arthroplasty (ATSA). The minimum follow-up period was 1 year, and a random-effects model was utilized for data synthesis.

RESULTS

A total of 45 studies were included in the meta-analysis. Compare to HA, RTSA showed significant advantages in postoperative ASES scores (p = 0.004), forward flexion (p < 0.0001), and abduction (p < 0.0001). Compare to ATSA, RTSA showed significantly lower postoperative Constant scores (p = 0.004), ASES scores (p = 0.001), SST scores (p < 0.0001), forward flexion (p < 0.0001), abduction (p = 0.011), internal rotation (p < 0.0001), and external rotation (p < 0.0001). Further meta regression analysis was conducted, considering factors such as region, age, gender ratio, and follow-up time, excluding the influence of relevant factors. Overall, RTSA did not demonstrate advantages in postoperative functional scores and range of motion. In terms of complication and revision rates, RTSA had lower rates compared to HA and ATSA, except for the complication rate, where there was no significant difference between RTSA and ATSA (p = 0.521), but statistically significant differences were observed in other measures.

CONCLUSION

RTSA demonstrates better clinical efficacy compared to HA but is inferior to ATSA. It can be considered for expanding treatment options for elderly patients with 3 or 4-part proximal humeral fractures, but it is not suitable for treating end-stage shoulder arthritis and humeral head necrosis. Overall, the decision to use RTSA should be carefully evaluated based on the extent of the patient's rotator cuff injury.

Evolution of Reverse Shoulder Arthroplasty Design Rationales and Where We Are Now

Reverse shoulder arthroplasty (RSA) will soon reach its 20-year anniversary in the United States and has now become the most performed shoulder arthroplasty in the United States. The evolution from Grammont style implants to lateralized designs continues to generate debate as comparable outcomes have been reported with both types of systems. While early literature focused on fixation and expanded indications, recent studies have evaluated component design and position and their effect on functional outcomes and complications. The purpose of this article was to provide a synopsis of design rationales of current RSA prostheses and review outcomes related to RSA design and position.

Comparing Repaired Subscapularis Tendon Integrity Using Ultrasound in Onlay Versus Inlay Reverse Shoulder Arthroplasty

Background: The importance of the subscapularis tendon in reverse shoulder arthroplasty (RSA) has been increasingly emphasized lately. Recent studies have indicated that a repaired subscapularis tendon has better functional outcomes. This study is aimed at comparing the healing rate of repaired subscapularis tendons between onlay and inlay Bony Increased Offset-Reversed Shoulder Arthroplasty (BIO-RSA). Methods: This retrospective comparative review covers all patients who underwent BIO-RSA at a single center, comprising 189 cases performed by on a single surgeon from January 2012 till December 2021. We included all patients who underwent subscapularis tenotomy repair and who had a tendon ultrasound (US) examination at six months postoperatively (as requested in this single surgeon's usual protocol). These patients were divided into two comparable groups, an onlay group and an inlay group. Healing status was determined using the Sugaya classification, with healed subscapularis tendons defined as having Sugaya type I-III integrity and the unhealed tendons as having Sugaya type IV and V integrity. Results: In total, 2 patients were excluded because ultrasound was not performed (they missed their appointment); 187 patients were evaluated; 98 patients underwent an onlay BIO-RSA; and 89 patients underwent an inlay BIO-RSA. The healing rate of the repaired subscapularis tendon was 73% in the onlay group and 56% in the inlay one (p = 0.020). Conclusions: The onlay systems may enhance subscapularis tendon healing compared to the inlay one, possibly due to the preserved intramedullary vascularity and the near-normal tendon excursion that can be achieved by the onlay system. Choosing an onlay design can minimize bone cuts during RSA, while achieving good subscapularis tendon healing.

Impact of insurance payer type (medicare vs. private) on the patient reported outcomes after shoulder arthroplasty

Background

This study's purpose is to determine if there is a difference in patient-reported outcome measures (PROMs) following shoulder arthroplasty (SA) based upon payer insurance type, with a secondary outcome of determining if any appreciable difference surpasses the minimal clinically important difference (MCID).

Methods

Subjects undergoing anatomic and reverse total shoulder arthroplasty were prospectively enrolled between March 2019 and March 2021. Subjects completed patient reported outcomes measurement information system upper extremity (P-UE), the American Shoulder and Elbow Surgeons score (ASES), and the simple shoulder test (SST) preoperatively and at 2 weeks, 6 weeks, 3 months, 6 months, and 12 months, postoperatively. Descriptive statistics of baseline patient characteristics and preoperative PROMs (ASES, SST, and P-UE) were compared between insurance types.

Results

143 patients were identified who met the inclusion criteria for this study. There were 98 patients within the Medicare cohort and 45 patients with private insurance. Patients in the Medicare cohort were older (mean age 70.5 vs. 61.3 years), with high proportion of smokers, diabetics, and reverse total shoulder arthroplasty compared to the private payor cohort. There were no significant differences between the two cohorts with respect to outcomes scores except for significantly better SST in the private insurance cohort (69.3 vs. 79.4, P = .02). No significant differences were noted for the achievement of MCID between cohorts [P-UE (P = 1.0), ASES (P = .25), and SST (0.52)] and pre-to-postoperative improvements for P-UE (P = .62), ASES (P = .4), or SST (0.66).

Conclusion

Our study demonstrates that, at a tertiary-level academic institution in a metropolitan city, payor type does not have significant impact on achieving MCID or pre-to-postoperative improvements in PROMs after SA.

A reduced scapulo-humeral angle contributes to the development of scapular notching in reverse total shoulder arthroplasty

PURPOSE

Scapular Notching (SN) is one of the most common postoperative complications for a patient after Reverse Total Shoulder Arthroplasty (RTSA). Despite employing various strategies to mitigate SN risk, the overall incidence remains far from zero. This article introduces a new risk factor, the scapulo-humeral angle (SHA), as a key element influencing the risk for SN.

METHODS

A retrospective analysis was conducted on all patients who underwent RTSA for rotator cuff arthropathy at the study centre. The preoperative SHA was measured, and the presence of SN was investigated and graded using the Nerot classification at the latest follow-up.

RESULTS

42 patients were included. 12 presented SN (incidence 28.5%). A statistically significant Pearson coefficient correlation between pre-operative SHA and the incidence of SN was observed (r= -0.6954; 95% C.I. -0,8250 to -0,4963; p < 0.0001). A statistically significant Pearson coefficient correlation was also found between the degree of SN and the pre-operative SHA (r= -0,7045; 95% C.I. -0,8306 to -0,5096; P value (two-tailed) < 0,0001, alpha 0.05).

CONCLUSIONS

The primary finding is a statistically significant correlation between a reduced preoperative SHA and an increased incidence of postoperative SN. The secondary finding is that a smaller preoperative SHA is associated with a more severe degree of SN A SHA cut-off of 50° distinguished patients at high risk of SN from those at low risk. All patients with an SHA below 50° developed SN (10/10), whereas only 6.25% of patients with an SHA exceeding 50° experienced SN (2/32).

Reverse shoulder arthroplasty for patients with cuff tear arthropathy: do clinical outcomes differ by inlay vs. onlay design?

BACKGROUND

The influence of position of the humeral tray (inlay or onlay) on clinical outcomes in reverse shoulder arthroplasty (RSA) is a topic of debate. The purpose of this study was to compare clinical and radiographic outcomes of patients with cuff tear arthropathy treated with RSA systems with inlay or onlay humeral tray design, similar neck-shaft angles, and lateralized glenospheres.

METHODS

This was a retrospective study of prospectively obtained data from 1 tertiary care center. We identified all patients who underwent primary RSA between 2009 and 2017 (N = 511). We included 102 patients with diagnosed cuff tear arthropathy treated with RSA prostheses with a lateralized glenosphere and 135° neck-shaft angle (with either an inlay or onlay humeral tray design) who had a minimum of 2 years of follow-up (mean, 44 months; range, 24-125 months). Sixty-three patients (62%) had an inlay humeral tray (inlay group) and 39 (38%) had an onlay tray (onlay group). All patients underwent preoperative and postoperative evaluations, including measures of patient-reported outcomes (PROs), shoulder range of motion (ROM) testing, and radiographic imaging. Clinical relevance of changes in PROs and ROM was evaluated using published values for minimal clinically important differences.

RESULTS

The 2 groups did not differ by demographic characteristics except for a higher proportion of women in the inlay group (75%) than in the onlay group (56%) (P = .04). Preoperative PROs and ROM were not significantly different between groups. At final follow-up, PROs and ROM were not different between groups in terms of statistical significance or clinical relevance. We found no significant differences in the rate of baseplate loosening (inlay, 3.2% vs. onlay, 5.1%, P = .63), revision surgery (inlay, 0% vs. onlay 5.1%, P = .07), acromial stress fracture (inlay, 3.2% vs. onlay, 5.1%, P = .63), prosthesis dislocation (inlay, 0% vs. onlay, 2.6%, P = .20), or scapular notching (inlay, 21% vs. onlay, 7.7%, P = .08).

CONCLUSION

At 2-year minimum follow-up, the position of the humeral tray in RSA prostheses (either inlay or onlay) for cuff tear arthropathy was not associated with PROs, shoulder ROM, or rates of complications, including baseplate loosening, acromial stress fracture, and scapular notching.

Humeral Stem Design in Reverse Total Shoulder Arthroplasty

PURPOSE OF THE REVIEW

There have been tremendous modifications to the humeral component since Paul Grammont first introduced the reverse total shoulder arthroplasty in 1985. The purpose of this article is to review historical design features and their drawbacks and to summarize the clinical outcomes of modern designs.

RECENT FINDINGS

Decreasing the neck-shaft angle and increasing humeral lateralization have helped address problems of scapular notching and limited internal and external rotation that were common with traditional designs. Advancements in proximal porous coatings have also facilitated the development of short-stem and stemless implants, which decreases the need for cement fixation and allows preservation of bone stock. Moreover, a reduction in stem length with smaller metaphyseal and diaphyseal filling ratios may limit stress shielding. Current humeral implants have an aseptic loosening rate less than 1%. Despite promising results, many of these new humeral design features do not have long-term data and continued surveillance of their performance is necessary. The humeral stem design significantly influences clinical and radiographic outcomes. Surgeons should be mindful of these design variables to increase impingement-free range of motion, minimize scapular notching, reduce stress shielding, and improve implant survivorship.

Acromial and scapular fractures after reverse shoulder arthroplasty: comparison of 3018 reverse total shoulders by inlay and onlay humeral component design

BACKGROUND

Periscapular fractures, specifically acromial and scapular spine fractures, have been identified as one of the leading complications of reverse total shoulder arthroplasty (rTSA). However, very little is known of the etiology of these postoperative fractures, or how variations in humeral designs correlates with the risk of postoperative fracture development. Therefore, the purpose of this study was to analyze the prevalence, timing, and relationship of humeral component design to acromial or scapular spine fractures.

METHODS

A retrospective study was conducted of primary rTSA performed for elective and traumatic indications from 2 tertiary institutions. Exclusions consisted of primary oncologic reconstructions, diagnosis of osteogenesis imperfecta, and less than 1 year of clinical follow-up. A total of 3018 primary rTSAs were included with a cohort of 1739 (57.6%) females, a mean age of 71 years (range, 20-94 years), a mean body mass index of 30.6 ± 6.6, and a mean follow-up of 6.4 ± 3.8 years. The implants used varied based on surgeon preference and included 9 different types. The humeral component of the rTSA was categorized as an inlay design (n = 762; 25.2%), defined as a humeral component where the tray is seated within the metaphysis, or an onlay design (n = 2256; 74.8%) defined as a humeral component where the humeral tray sits on the metaphysis at the level of the humeral neck cut.

RESULTS

A fracture of the acromion or scapular spine was radiographically identified in 64 of 3018 (2.1%) rTSAs at an average of 8.5 ± 12.6 months after surgery. The majority of fractures included the acromion (n = 57; 89.1%) and scapular spine (n = 7; 10.9). Nonoperative management (n = 60; 93.8%) was the predominant treatment strategy for fractures, whereas 4 (6.2%) rTSAs underwent open reduction and internal fixation. When compared by humeral component design (inlay vs. onlay), there were no differences in the rates of acromial or scapular spine fractures (2.6% vs. 2.0%; P = .264). Similarly, there were no treatment differences between nonoperative (90% vs. 95.5%) and operative management (10% vs. 4.5%) of the fractures based on the type of humeral component design (P = .403).

CONCLUSIONS

Acromial and scapular spine fractures complicated the postoperative course of 2.1% of primary rTSAs when performed across 2 high-volume shoulder arthroplasty centers with multiple surgeons including a wide range of implant types. Most of the fractures involve the acromion, with less frequent involvement of the spine of the scapula. When comparing by inlay vs. onlay humeral component design, the rates of postoperative acromial or scapular spine fractures were statistically similar.

Increased Deltoid and Acromial Stress with Glenoid Lateralization and Onlay Humeral Stem Constructs in Reverse Shoulder Arthroplasty

Background

Reverse shoulder arthroplasty (RSA) designs include multiple options for glenoid component lateralization, and humeral component lateralization and distalization (inlay/onlay constructs). The influence of combined glenoid lateralization, and humeral distalization on acromial and deltoid stresses is not well understood. The purpose of this study was to evaluate changes in deltoid and acromial stresses with variations in glenoid lateralization, and with inlay versus onlay humeral components in RSA.

Methods

Finite element analysis was performed using a RSA system with both inlay and onlay configurations. Variations in total glenoid lateralization from 3 to 9 mm were evaluated. Deltoid and acromial stresses were determined following virtual implantation and with 50° of external rotation.

Results

Increased glenoid lateralization resulted in greater stress of the deltoid and acromion. There was a modest increase in deltoid stress with glenoid lateralization alone (7% and 7.5% with progressive lateralization from 3 to 6 mm and 6 to 9 mm, respectively), but deltoid stress increased substantially with use of an onlay construct (60% at 9 mm of glenoid lateralization). Acromial stress correspondingly increased 37% with glenoid lateralization, and up to 117% with an onlay humeral construct.

Discussion

Increased lateralization of the glenoid component resulted in increased levels of deltoid and acromial stress. For a given amount of glenoid lateralization, utilization of an inlay stem decreased acromial and deltoid stresses compared to onlay constructs. These data allow surgeons to better understand the interactions of glenoid and humeral lateralization and distalization in the setting of contemporary RSA systems.Level of Evidence: Basic Science Study: Computer Modeling.

Reverse shoulder arthroplasty design-inlay vs. onlay: does it really make a difference?

BACKGROUND

The design of reverse shoulder arthroplasty (RSA) implants has evolved significantly over the past 50 years. Today there are many options available that differ in design of the glenoid and humeral components, fixation methods, sizes, and modularity. With respect to the humeral component, the literature has generally focused on the differences between inlay and onlay designs and the potential impact on outcomes. However, inlay and onlay design represents only one factor of many.

METHODS

It is our hypothesis that separating onlay and inlay designs into 2 distinct entities is an oversimplification as there can be a wide overlap of the 2 designs, depending on surgical technique and the implant selected. As such, the differences between inlay and onlay designs should be measured in absolute terms-meaning combined distalization and lateralization.

RESULTS

By reviewing the many factors that can contribute to the glenosphere-humerus relationship, the role of inlay and onlay humeral designs as an important distinguishing feature is shown to be limited. Preliminary studies suggest that the amount of distalization and lateralization of the construct may be the most accurate method of describing the differences in the constructs.

CONCLUSIONS

Inlay and onlay humeral component design represents only one factor of many that may impact outcomes. A more accurate method of defining specific design and technique factors in RSA is the degree of lateralization and distalization.

Cost-effectiveness of shoulder arthroplasty for osteoarthritis and rotator cuff tear arthropathy. An economic analysis using real-world data

INTRODUCTION

This study aimed to assess cost-effectiveness of shoulder arthroplasty for osteoarthritis (OA) and rotator cuff tear arthropathy (CTA) from the perspective of a publicly funded health care system using patient data, health utilities and costs from a real-world situation.

HYPOTHESIS

Our hypothesis was that arthroplasty for OA is more cost-effective than for CTA.

MATERIAL AND METHODS

We gathered a cohort of patients with 153 anatomic total shoulder arthroplasty (TSA) for OA and 107 reverse shoulder arthroplasty (RSA) for CTA between years 2016-2020 at a university hospital. Short-term (mean 2.8years) shoulder function, health utilities and costs were obtained from prospectively collected data, and a Markov cohort simulation was carried out to assess lifetime cost-utility. The primary outcome measures were change in 15D score to calculate gain in quality-adjusted life years (QALYs) and change in Western Ontario osteoarthritis score of the shoulder (WOOS).

RESULTS

Both TSA and RSA restored shoulder function well, WOOS improvement was 59.7 (95% CI: 56.2-63.2) and 55.8 (95% CI: 50.4-61.2), respectively. The cost/QALY gained was 20,846.82 € for TSA and 38,711.90 € for RSA. The cost-utility was not remarkable sensitive to costs, discounting of future costs or estimated revision rates. However, the cost-effectiveness was very sensitive to change in 15D health utility scores and thus QALY gain, especially for RSA patients.

DISCUSSION

Shoulder arthroplasty restores shoulder function well in both OA and CTA. In health economic terms, RSA is less cost-effective than TSA in an everyday setting, mainly due to inferior improvement of health-related quality-of-life and reduced life expectancy of CTA patients.

LEVEL OF EVIDENCE

III; case series.

Influence of design features and brand of reverse shoulder arthroplasties on survivorship and reasons for revision surgery: results of 5,494 arthroplasties with up to 15 years' follow-up reported to the Norwegian Arthroplasty Register 2007-2022

BACKGROUND AND PURPOSE

We aimed to report the survival of different reverse shoulder arthroplasty (RSA) designs and brands, and factors associated with revision. The secondary aim was to evaluate the reasons for revision.

METHODS

We included 4,696 inlay and 798 onlay RSAs reported to the Norwegian Arthroplasty Register (NAR) 2007-2022. Kaplan-Meier estimates of survivorship and Cox models adjusted for age, sex, diagnosis, implant design, humeral fixation, and previous surgery were investigated to assess revision risks. The reasons for revision were compared using competing risk analysis.

RESULTS

Overall, the 10-year survival rate was 94% (confidence interval [CI] 93-95). At 5 years all brands exceeded 90%. Compared with Delta Xtend (n = 3,865), Aequalis Ascend Flex (HR 2.8, CI 1.7-4.6), Aequalis Reversed II (HR 2.2, CI 1.2-4.2), SMR (HR 2.5, CI 1.3-4.7), and Promos (HR 2.2, CI 1.0-4.9) had increased risk of revision. Onlay and inlay RSAs had similar risk of revision (HR 1.2, CI 0.8-1.8). Instability and deep infection were the most frequent revision causes. Male sex (HR 2.3, CI 1.7-3.1), fracture sequelae (HR 3.1, CI 2.1-5.0), and fractures operated on with uncemented humeral stems had increased risk of revision (HR 3.5, CI 1.6-7.3).

CONCLUSION

We found similar risk of revision with inlay and onlay designs. Some prosthesis brands had a higher rate of revision than the most common implant, but numbers were low.

Varus-valgus alignment of humeral short stem in reverse total shoulder arthroplasty: does it really matter?

BACKGROUND

The utilization of short humeral stems in reverse total shoulder arthroplasty has gained attention in recent times. However, concerns regarding the risk of misalignment during implant insertion are associated with their use.

METHODS

Eight fresh-frozen cadaveric shoulders were prepared for dissection and biomechanical testing. A bespoke humeral implant was fabricated to facilitate assessment of neutral, varus, and valgus alignments using a single stem, and 10° was established as the maximum permissible angle for misalignments. Shift in humerus position and changes in deltoid length attributable to misalignments relative to the neutral position were evaluated using a Microscribe 3DLx system. The impingement-free range of motion, encompassing abduction, adduction, internal rotation, and external rotation (ER), was gauged using a digital goniometer. The capacity for abduction was evaluated at maximal abduction angles under successive loading on the middle deltoid. A specialized traction system coupled with a force transducer was employed to measure anterior dislocation forces.

RESULTS

Relative to the neutral alignment, valgus alignment resulted in a more distal (10.5 ± 2.4 mm) and medial (8.3 ± 2.2 mm) translation of the humeral component, whereas the varus alignment resulted in the humerus shifting more superiorly (11.2 ± 1.3 mm) and laterally (9.9 ± 0.9 mm) at 0° abduction. The valgus alignment exhibited the highest abduction angle than neutral alignment (86.2°, P < .001). Conversely, the varus alignment demonstrated significantly higher adduction (18.4 ± 7.4°, P < .001), internal rotation (68.9 ± 15.0°, P = .014), and ER (45.2 ± 10.5°, P = .002) at 0° abduction compared to the neutral alignments. Anterior dislocation forces were considerably lower (23.8 N) in the varus group compared to the neutral group at 0°ER (P = .047). Additionally, abduction capability was markedly higher in varus alignment at low deltoid loads than the neutral alignment (5N, P = .009; 7.5 N, P = .007).

CONCLUSIONS

The varus position enhances rotational range of motion (ROM) but increases instability, while the valgus position does not significantly impact ROM or instability compared to the neutral position.

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.

Glenoid notching after reverse shoulder arthroplasty: The influence of different neck-shaft angles

Background

The implications of notching in reverse shoulder arthroplasty (RSA), and its relation with the rate of complications are still unclear. Our main aim was to retrospectively study the notching incidence in the three most used implants in our practice, considering their different neck-shaft angle (NSA) and determine its relation with implant failure, or other complications.

Methods

We retrospectively reviewed medical and imaging records of 259 patients who underwent RSA in our hospital, including surgery reports, prosthesis designs and techniques. We assessed all radiographs taken during the follow up to evaluate notching incidence, progression and signs of failure.

Results

Notching occurred in 35% cases. The average time to notch development was 19 months. Implants with a lower NSA showed significantly lower incidence of notching when compared to other implants (P < 0.001). In a multivariate analysis, the NSA proved to be an independent predictor for the occurrence of notching in this series.

Discussion

According to our results, higher NSA is an independent predictor of the occurrence of notching. There was significant increase in the notching rate with follow up. In the future, larger case series with longer follow-up are necessary to evaluate the relation between notching and radiological and clinical complications.

Inlay vs. onlay humeral components in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BACKGROUND

Both inlay and onlay humeral implants are available for reverse total shoulder arthroplasty (rTSA), but biomechanical data comparing these components remain limited. This study investigated the effects of inlay and onlay rTSA humeral components on shoulder biomechanics using a biorobotic shoulder simulator.

METHODS

Twenty fresh-frozen cadaveric shoulders were tested before and after rTSA with either an inlay or onlay humeral implant. Comparisons were performed between the most commonly implanted configurations for each implant (baseline) and with a modification to provide equivalent neck-shaft angles (NSAs) for the inlay and onlay configurations. Specimens underwent passive range-of-motion (ROM) assessment with the scapula held static, and scapular-plane abduction was performed, driven by previously collected human-subject scapulothoracic and glenohumeral kinematics. Passive ROM glenohumeral joint angles were compared using t tests, whereas muscle force and excursion data during scapular-plane elevation were evaluated with statistical parametric mapping and t tests.

RESULTS

Maximum passive elevation was reduced for the inlay vs. onlay humeral components, although both implants caused reduced passive elevation vs. the native joint. Inlay rTSA also demonstrated reduced passive internal rotation at rest and increased external rotation at 90° of humerothoracic elevation vs. the native joint. All preoperative planning estimates of ROM differed from experiments. Rotator cuff forces were elevated with an onlay vs. inlay humeral implant, but simulated muscle excursions did not differ between systems. Compared with the native joint, rotator cuff forces were increased for both inlay and onlay implants and deltoid forces were reduced for inlay implants. Muscle excursions were dramatically altered by rTSA vs. the native joint. Comparisons of inlay and onlay humeral implants with equivalent NSAs were consistent with the baseline comparisons.

CONCLUSIONS

Rotator cuff forces required to perform scapular-plane abduction increase following rTSA using both inlay and onlay implants. Rotator cuff forces are lower with inlay implants compared with onlay implants, although inlay implants also result in reduced passive-elevation ROM. Deltoid forces are lower with inlay implants in comparison to the native joint but not with onlay implants. The differences between inlay and onlay components are largely unaffected by NSA, indicating that these differences are inherent to the inlay and onlay designs. In those patients with an intact rotator cuff, decreased rotator cuff forces to perform abduction with an inlay humeral implant compared with an onlay implant may promote improved long-term outcomes owing to reduced deltoid muscle fatigue when using an inlay implant.

Reverse shoulder arthroplasty for primary glenohumeral osteoarthritis: significantly different characteristics and outcomes in shoulders with intact vs. torn rotator cuff

PURPOSE

To compare outcomes of reverse shoulder arthroplasty (RSA) for primary osteoarthritis (OA) with and without rotator cuff (RC) tears to those with secondary OA due to RC tears.

METHODS

We reviewed records of all patients who received RSA for primary OA or secondary OA. All patients had preoperative radiographs, computed tomographic arthrography (CTA), and/or magnetic resonance imaging (MRI) scans of their shoulders to assess their etiology, glenoid morphology, and fatty infiltration. Pre- and postoperative (at minimum follow-up of 2 years) Constant scores and range of motion were compared between patients who had RSA for primary OA with and without RC tears to those with secondary OA due to RC tears.

RESULTS

Of the initial cohort of 605 shoulders (583 patients), 153 were lost to follow-up (25.3%), 25 required revision with implant removal (4.1%), and 13 died of causes unrelated to the surgery (2.1%), and left a final cohort of 414 patients. Of the final cohort, 97 had primary OA with intact RC, 62 had primary OA with RC tears, and 255 had secondary OA. Postoperative Constant scores were significantly higher for primary OA with intact RC (73.8 ± 14.3), compared with both primary OA with RC tears (66.1 ± 14.6, P < .001) and secondary OA (64.1 ± 14.8, P < .001). There were no differences in pre- or postoperative scores between primary OA with RC tears and secondary OA.

CONCLUSION

At 2 or more years following RSA, Constant scores were significantly higher for primary OA with intact RC, compared to either primary OA with RC tears or secondary OA, whereas there were no differences in pre- or postoperative scores of shoulders that had primary OA with RC tears vs. secondary OA. The authors recommend distinguishing primary OA with intact RC from primary OA with RC tears, as the two have considerably different characteristics and prognosis following RSA.

The Influence of Component Design and Positioning on Soft-Tissue Tensioning and Complications in Reverse Total Shoulder Arthroplasty: A Review

» Reverse total shoulder arthroplasty was designed to function in the rotator cuff deficient shoulder by adjusting the glenohumeral center of rotation (COR) to maximize deltoid function.» Adjustments in the COR ultimately lead to changes in resting tension of the deltoid and remaining rotator cuff, which can affect implant stability and risk of stress fracture.» Soft-tissue balance and complication profiles can be affected by humeral component (version, neck shaft angle, and inlay vs. onlay) and glenoid component (sagittal placement, version, inclination, and lateralization) design and application.» A good understanding of the effects on soft-tissue balance and complication profile is critical for surgeons to best provide optimal patient outcomes.

Analysis of three different reverse shoulder arthroplasty designs for cuff tear arthropathy - the combination of lateralization and distalization provides best mobility

BACKGROUND

The two major reverse shoulder arthroplasty (RSA) designs are the Grammont design and the lateralized design. Even if the lateralized design is biomechanically favored, the classic Grammont prosthesis continues to be used. Functional and subjective patient scores as well as implant survival described in the literature so far are comparable to the lateralized design. A pure comparison of how the RSA design influences outcome in patients has not yet been determined. The aim of this study was a comparison focused on patients with cuff tear arthropathy (CTA).

METHODS

We analyzed registry data from 696 CTA patients prospectively collected between 2012 and 2020 in two specialized orthopedic centers up to 2 years post-RSA with the same follow-up time points (6,12 24 months). Complete teres minor tears were excluded. Three groups were defined: group 1 (inlay, 155° humeral inclination, 36 + 2 mm eccentric glenosphere (n = 50)), group 2 (inlay, 135° humeral inclination, 36 + 4 mm lateralized glenosphere (n = 141)) and group 3 (onlay, 145° humeral inclination, + 3 mm lateralized base plate, 36 + 2 mm eccentric glenosphere (n = 35)) We compared group differences in clinical outcomes (e.g., active and passive range of motion (ROM), abduction strength, Constant-Murley score (CS)), radiographic evaluations of prosthetic position, scapular anatomy and complications using mixed models adjusted for age and sex.

RESULTS

The final analysis included 226 patients. The overall adjusted p-value of the CS for all time-points showed no significant difference (p = 0.466). Flexion of group 3 (mean, 155° (SD 13)) was higher than flexion of group 1 (mean, 142° (SD 18) and 2 (mean, 132° (SD 18) (p < 0.001). Values for abduction of group 3 (mean, 145° (SD 23)) were bigger than those of group 1 (mean, 130° (SD 22)) and group 2 (mean, 118° (SD 25)) (p < 0.001). Mean external rotation for group 3 (mean, 41° (SD 23)) and group 2 (mean, 38° (SD 17)) was larger than external rotation of group 1 (mean, 24° (SD 16)) (p < 0.001); a greater proportion of group 2 (78%) and 3 (69%) patients reached L3 level on internal rotation compared to group 1 (44%) (p = 0.003). Prosthesis position measurements were similar, but group 3 had significantly less scapular notching (14%) versus 24% (group 2) and 50% (group 1) (p = 0.001).

CONCLUSIONS

Outcome scores of different RSA designs for CTA revealed comparable results. However, CTA patients with a lateralized and distalized RSA configuration were associated with achieving better flexion and abduction with less scapular notching. A better rotation was associated with either of the lateralized RSA designs in comparison with the classic Grammont prosthesis.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Comparison of Functional Outcomes and Complications of Inlay and Onlay Reverse Shoulder Arthroplasty in Neer Type 4 Proximal Humerus Fractures and Cuff Tear Arthropathy: A Multicentric Study

Background

This multicenter retrospective study was conducted with the objective of comparing the outcomes and complications between inlay and onlay reverse shoulder arthroplasty (RSA) in patients presenting Neer Type 4 proximal humerus fractures and cuff tear arthropathy. The primary aim of this investigation was to assess and juxtapose the clinical as well as functional outcomes of individuals who underwent onlay reverse shoulder arthroplasty with those who underwent inlay reverse shoulder arthroplasty.

Methods

A retrospective cohort study was conducted, involving patients who had undergone reverse shoulder arthroplasty between the period of 2016 and 2022. The study divided the population into two groups: Group A received inlay humeral components, while Group B received onlay humeral components. Functional outcomes were evaluated using the American Shoulder and Elbow Surgeons (ASES) and Constant scores. Range of motion, infection, periprosthetic fractures, and nerve injuries were also assessed.

Results

The study included 67 patients in Group A and 62 patients in Group B. Group A had significantly better functional outcomes, as indicated by higher ASES and Constant scores (p < 0.05). Group A also had greater shoulder joint motion (p < 0.05). Periprosthetic fractures were significantly more common in Group B (p < 0.05). However, complication rates, including infection and instability, did not significantly differ between the groups (p > 0.05). Nerve injuries occurred in both groups, with slightly higher occurrence in Group B.

Conclusion

Inlay humeral components in reverse shoulder arthroplasty for Neer Type 4 fractures and cuff tear arthropathy resulted in better functional outcomes, increased range of motion, and lower incidence of periprosthetic fractures compared to onlay components. Onlay components showed potential advantages in reducing instability rates. Further studies with larger samples and standardized protocols are needed to confirm these findings.

Medium-term results of inlay vs. onlay humeral components for reverse shoulder arthroplasty: a New Zealand Joint Registry study

BACKGROUND

The purpose of this study was to compare medium-term results of inlay and onlay humeral components in reverse shoulder arthroplasty (RSA). Specifically, we report differences in revision rate and functional outcomes between the 2 designs.

METHODS

The 3 most used inlay (in-RSA) and onlay (on-RSA) implants by volume from the New Zealand Joint Registry were included in the study. In-RSA was defined as having a humeral tray that recessed within the metaphyseal bone, whereas on-RSA was defined as having a humeral tray that rested on the epiphyseal osteotomy surface. The primary outcome was revision up to 8 years postsurgery. Secondary outcomes included the Oxford Shoulder Score (OSS), implant survival, and revision cause for in-RSA and on-RSA as well as individual prostheses.

RESULTS

There were 6707 patients (5736 in-RSA; 971 on-RSA) included in the study. For all causes, in-RSA demonstrated a lower revision rate compared to on-RSA (revision rate/100 component years: in-RSA 0.665, 95% confidence interval [CI] 0.569-0.768; on-RSA 1.010, 95% CI 0.673-1.415). However, the mean 6-month OSS was higher for the on-RSA group (mean difference 2.20, 95% CI 1.37-3.03; P < .001). However, this was not clinically significant. At 5 years, there were no statistically or clinically significant differences between the 2 groups with respect to the OSS.

CONCLUSION

The medium-term survival of in-RSA was higher than that of on-RSA. However, functional outcomes at 6 months were better for on-RSA compared to in-RSA. Further follow-up is required to understand the long-term survivorship and functional outcomes between these designs.

Factors that affect external rotation following reverse shoulder arthroplasty: a retrospective multi-centre study on 501 shoulders

INTRODUCTION

The purpose of this multi-centre study was to assess external rotation in a large cohort following reverse shoulder arthroplasty (RSA) at a minimum follow-up of 2 years, and identify factors that influence postoperative and/or net-improvement of external rotation.

METHODS

The authors retrospectively reviewed records of 743 RSAs performed between January 2015 and August 2017 by 16 surgeons that participated in a large national society symposium; 193 (25.7%) were lost to follow-up, 16 (2.1%) died, and 33 (4.4%) were revised with implant exchange, which left 501 available for assessment at 2.0-5.5 years. Pre- and post-operative active forward elevation, active external rotation (ER1), active internal rotation (IR1) and constant score (CS) were collected. Regression analyses were performed to determine associations of patient demographics, surgical and implant parameters, rotator cuff muscles status and radiographic angles with ER1.

RESULTS

Multivariable analyses revealed postoperative ER1 decreased with age (β, - 0.35), increased with lateralisation shoulder angle (LSA) (β, 0.26), and was better in shoulders operated by the antero-superior (AS) approach (β, 11.41), but worse in shoulders with absent/atrophic teres minor muscles (β, - 10.06). Net-improvement of ER1 increased with LSA (β, 0.39), was better with inlay stems (β, 8.33) and BIO RSA (β, 6.22), but worse in shoulders operated for primary OA with rotator cuff (RC) tears (β, - 16.26), for secondary OA due to RC tears (β, - 16.06), or for mRCT (β, - 18.96).

CONCLUSIONS

This large multi-centre study revealed that, at a minimum of 2 years following RSA, ER1 improved by 16.1°. Postoperative ER1 was better in shoulders which had normal or hypertrophic teres minor muscles, were operated by the AS approach, or with greater LSA. Net-improvement of ER1 was better in shoulders with inlay stems, with BIO RSA, or with greater LSA, but worse in shoulders with rotator cuff deficiency.

LEVEL OF EVIDENCE

IV.

Reverse shoulder arthroplasty: State-of-the-art

The reverse shoulder arthroplasty conceived by Paul Grammont in 1985 has gradually gained popularity as a treatment for multiple shoulder diseases. Unlike previous reverse shoulder prosthesis characterized by unsatisfactory results and a high glenoid implant failure rate, the Grammont design has immediately shown good clinical outcomes. This semi constrained prosthesis solved the issues of the very first designs by medializing and distalizing the center of rotation with an increased stability of the replacement of the component. The indication was initially limited to cuff tear arthropathy (CTA). It has then been expanded to irreparable massive cuff tears and displaced humeral head fractures. The most frequent problems of this design are a limited postoperative external rotation and scapular notching. Different modifications to the original Grammont design have been proposed with the aim of decreasing the risk of failure and complications and improving the clinical outcomes. Both the position and version/inclination of the glenosphere and the humeral configuration (e.g. neck shaft angle) influence the RSA outcomes. A lateralized glenoid (whether with bone or metal) and a 135° Inlay system configuration leads to a moment arm which is the closest to the native shoulder. Clinical research will focus on implant designs reducing bone adaptations and revision rate, strategies to prevent more effectively infections. Furthermore, there is still room for improvement in terms of better postoperative internal and external rotations and clinical outcomes after RSA implanted for humeral fracture and revision shoulder arthroplasty.

[Conversion of anatomic to reverse shoulder arthroplasty : Does it make sense?]

We can observe increasing numbers for the implantation of shoulder endoprostheses in developed industrial countries. This is accompanied by a certain number of revision surgeries. The conversion to reverse arthroplasty systems is by far the most common revision procedure. Depending on the primary implant and the individual situation, the surgical effort and consumption of resources can be substantial. Particularly favorable revision scenarios exist in the conversion of stemless primary implants that are part of a platform system and allow a partial exchange and easy conversion from anatomical to reverse implants.