Lateralization in reverse shoulder arthroplasty: A review

Reverse Shoulder Arthroplasty for Proximal Humerus Fractures: A Review of Current Evidence

PURPOSE OF REVIEW

The aim of this review is to summarize information published in the recent peer-reviewed literature on reverse shoulder arthroplasty (RSA) for proximal humerus fractures.

RECENT FINDINGS

Although there is still some debate regarding which may be the best treatment for proximal humerus fractures in certain age ranges, RSA seems to offer more predictable results than other surgical treatments for elderly patients. Successful tuberosity healing seems to correlate with better outcomes. Recent trends indicate interest in cementless fixation, fracture-specific stems and a 135-degree polyethylene opening angle. RSA provides a successful surgical solution for selected proximal humerus fractures. Indications, design features, and surgical execution have continued to evolve over the last few years.

Robert H. Cofield, MD, Award for Best Oral Presentation 2023: Up to 8 mm of glenoid-sided lateralization does not increase the risk of acromial or scapular spine stress fracture following reverse shoulder arthroplasty with a 135° inlay humeral component

BACKGROUND

Glenoid-sided lateralization in reverse shoulder arthroplasty (RSA) decreases bony impingement and improves rotational range of motion, but has been theorized to increase the risk of acromial or scapular spine fractures (ASFs). The purpose of this study was to assess if glenoid-sided lateralization even up to 8 mm increases the risk for stress fracture following RSA with a 135° inlay humeral component.

METHODS

A retrospective review was performed from a multicenter prospectively collected database on patients who underwent primary RSA from 2015 to 2021. All RSAs were performed with a 135° inlay humeral component. Varying amounts of glenoid lateralization were used from 0 to 8 mm. Preoperative radiographs were reviewed for the presence of acromial thinning, acromiohumeral distance (AHD), and inclination. Postoperative implant position (distalization, lateralization, and inclination) as well as the presence of ASF was evaluated on minimum 1-year postoperative radiographs. Regression analyses were performed on component and clinical variables to assess for factors predictive of ASF.

RESULTS

Acromial or scapular spine fractures were identified in 26 of 470 shoulders (5.5%). Glenoid-sided lateralization was not associated with ASF risk (P = .890). Furthermore, the incidence of fracture did not vary based on glenoid-sided lateralization (0-2 mm, 7.4%; 4 mm, 5.6%; 6 mm, 4.4%; 8 mm, 6.0%; P > .05 for all comparisons). RSA on the dominant extremity was predictive of fracture (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.20-5.75; P = .037), but there was no relationship between patient age, sex, preoperative acromial thinning, or diagnosis and risk of fracture. Although there was no difference in mean postoperative AHD between groups (P = .443), the pre- to postoperative delta AHD was higher in the stress fracture group (2.0 ± 0.7 cm vs. 1.7 ± 0.7 cm; P = .015). For every centimeter increase in delta AHD, there was a 121% increased risk for fracture (OR 2.21, 95% CI 1.33-3.68; P = .012). Additionally, for every 1-mm increase in inferior glenosphere overhang, there was a 19% increase in fracture risk (P = .025).

CONCLUSION

Up to 8 mm of glenoid-sided metallic lateralization does not appear to increase the risk of ASF when combined with a 135° inlay humeral implant. Humeral distalization increases the risk of ASF, particularly when there is a larger change between pre- and postoperative AHD or higher inferior glenosphere overhang. In cases of pronounced preoperative superior humeral migration, it may be a consideration to avoid excessive postoperative distalization, but minimizing bony impingement via glenoid-sided lateralization appears to be safe.

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.

A narrative review of treatment strategies for major glenoid defects during primary reverse shoulder arthroplasty, with a focus on the use of structural bone graft

Structural glenoid defects are common during primary reverse shoulder arthroplasty (RSA) and are often associated with poor outcomes. The lack of pre-operative imaging protocols for determining the depth and degree of glenoid wear hinders our ability to accurately plan and correct these defects. Although bone grafting has been reported to be effective in reducing glenoid wear during RSA, there is limited information on when to utilise it and how to prepare the graft. We conducted this review to assess the evidence for the management of glenoid defects, with an emphasis on bone grafts to treat structural glenoid bone loss in primary RSA patients.

Factors associated with humeral stem revision in anatomic to reverse total shoulder arthroplasty revision

BACKGROUND

Recent advances in implant technology have allowed for modular or platform humeral stem insertion during initial anatomic total shoulder arthroplasty (TSA). These systems allow for humeral stem retention during conversion to reverse TSA (RTSA). However, some patients still require humeral stem revision when undergoing revision to RTSA. The purpose of this study was to evaluate the association between patient-specific factors and radiographic parameters with humeral stem revision vs. retention during conversion from TSA to RTSA.

METHODS

Retrospective chart review was conducted for patients who underwent a revision TSA to RTSA between January 2010 and May 2022 at a single institution. Patients were included if their prosthesis included a convertible humeral stem. Patient demographic information, surgical details, and postoperative outcomes and complications were collected. Radiographic parameters were measured by 2 graders on radiographs taken prior to the revision procedure. The need for humeral stem revision and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) scores (preoperative and 2 years) were also noted. Statistical analysis was performed using chi-square test for categorical variables and t test for continuous variables.

RESULTS

One hundred seven patients were included, with 52 undergoing humeral stem revision. Patients were revised an average of 51.0 ± 54 months after primary TSA. Younger patient age (63.6 vs. 68.5 years, P = .017) and use of a lateralized glenosphere (1.6 mm vs. 0.4 mm, P < .001) were significantly associated with need for humeral stem revision. Glenoid to humeral head cut distance (28.3 mm vs. 26.3 mm, P = .076) approached significant association with the need for humeral stem revision. All other measurements were not associated with the need for humeral stem revision. Improvement of ASES scores at 2 years' follow-up was higher in the nonrevised group (increase of 33.4 points) than the revision group (23.3), but this did not reach significance (P = .149). Estimated blood loss and surgical time were significantly higher in the stem revision group than the non-revised group (P = .048 and P < .001, respectively).

CONCLUSION

Younger patients and those receiving a lateralized glenosphere were more likely to undergo humeral stem revision during conversion from TSA to RTSA. Glenoid to the humeral head cut distance should be studied further as a potential indication for humeral stem revision, as it correlates with the space available for a revision implant. This information can guide surgeons with preoperative planning for a revision arthroplasty.

Narrative review of influence of prosthesis lateralization on clinical outcomes in reverse shoulder arthroplasty: glenoid vs. humerus vs. combined

Background and Objective

Reverse shoulder arthroplasty has become a common orthopaedic procedure, with a growing number of cases annually for multiple indications, such as rotator cuff arthropathy, osteoarthritis, or fractures of the proximal humerus, to reduce pain and restore shoulder mobility. Prosthesis design and various recent improvements aim to enhance range of motion (ROM) and stability and to limit component loosening and other potential complications. Many of these well-known issues could theoretically be improved by glenoid, humeral, or combined component lateralization. The objective of this article is to provide an up-to-date literature overview, present available options, and discuss the rationale behind lateralization of certain components, as well as their combined impact on outcomes of reverse shoulder arthroplasty.

Methods

PubMed and Scopus databases from 2003 to 2023 were searched and screened for studies, including systematic reviews, on the influence of glenoid, humeral, and combined component lateralization that served for narrative review of rationale behind such design.

Key Content and Findings

Currently, a number of computer simulations, anatomic studies, and limited clinical references aim to support the rationale behind glenoid augmentation, variable humeral neck-shaft angle (NSA), or humeral tray design.

Conclusions

The utility of lateralization has not yet been clinically established. Randomized, long-term clinical outcome studies are still needed to reach a verdict going beyond surgeon preference and case-specific indications.

Does glenohumeral offset affect clinical outcomes in a lateralized reverse total shoulder arthroplasty?

BACKGROUND

Reverse total shoulder arthroplasty (rTSA) exhibits high rates of success and low complication rates. rTSA has undergone numerous design adaptations over recent years, and lateralization of implant components provides theoretical and biomechanical benefits in stability and range of motion (ROM) as well as decreased rates of notching. However, the magnitude of implant lateralization and its effect on these outcomes is less well understood. The purpose of this study was to evaluate how increasing glenohumeral offset affects outcomes after rTSA, specifically in a lateralized humerus + medialized glenoid implant model.

METHODS

Primary rTSA using a lateralized humeral + medialized glenoid implant model performed at a single academic institution between 2012 and 2018 were retrospectively reviewed. Patient-reported outcome (PRO) parameters and clinical outcomes including ROM were evaluated both pre- and postoperatively. Pre- and postoperative radiographs were analyzed for measurement of glenohumeral offset, defined as the acromial-tuberosity offset (ATO) distance on the anteroposterior radiograph.

RESULTS

A total of 130 rTSAs were included in the analysis, with a mean follow-up of 35 mo. The mean postoperative absolute ATO was 16 mm, and the mean delta ATO (difference from pre- to postoperatively) was 4.6 mm further lateralized. Among all study patients, improvements in all ROM parameters and all PROs were observed from pre- to postoperative assessments. When assessing for the effects of lateralization on these outcomes, multivariate analysis failed to reveal a significant effect from the absolute postoperative ATO or the delta ATO on any outcome parameter.

CONCLUSIONS

rTSA using a lateralized humeral + medialized glenoid implant model exhibits excellent clinical outcomes in ROM and PROs. However, the magnitude of lateralization as measured radiographically by the ATO did not significantly affect these outcomes; patients exhibited universally good outcomes irrespective of the degree of offset restoration.

Patient Reported Outcomes and Range of Motion After Reverse Total Shoulder Arthroplasty With and Without Subscapularis Repair

Background

In performing reverse total shoulder arthroplasty (rTSA), the role of repairing the subscapularis has been debated. Our objective was to determine the effect of subscapularis repair following rTSA on postoperative shoulder ranges of motion and patient reported outcome scores (PROs).

Methods

A prospective registry was reviewed to establish a cohort of primary rTSA patients with a 135-degree humeral implant, with a minimum of 2 years of follow-up. Variables collected included demographics, subscapularis repair information, diagnosis, glenosphere size, and glenoid lateralization information. Outcomes collected were range of motion measurements, subscapularis strength, and multiple generic and shoulder PROs. Multivariable linear regression models were created to predict these 2-year outcomes.

Results

The 143-patient cohort had a mean age of 69 years with 68% of patients undergoing subscapularis repair. After adjustment in the multivariable models, whether the subscapularis was repaired did not significantly predict a 2-year forward elevation, external rotation, internal rotation, subscapularis strength, Western Ontario Osteoarthritis of the Shoulder score, VR-12 scores, Constant Score, or American Shoulder and Elbow Surgeons Shoulder Scores. Increased glenoid lateralization significantly predicted greater internal rotation, higher VR-12 physical score, and higher Constant Score. There were no dislocations in either group.

Conclusions

After adjusting for patient and implant factors, subscapularis repair was not associated with a 2-year postoperative range of motion, strength, or any PROs suggesting that repairing the subscapularis may not affect functional outcome. Increased glenoid lateralization through the baseplate and glenosphere independently predicted better internal rotation, VR-12 physical score, and Constant Scores indicating a benefit to lateralization during rTSA.

Restoration of active internal rotation following reverse shoulder arthroplasty: anterior latissimus dorsi and teres major combined transfer

BACKGROUND

Reverse shoulder arthroplasty (RSA) for irreparable massive rotator cuff tear (mRCT) and cuff tear arthropathy (CTA) demonstrates satisfactory clinical outcomes. However, many studies have reported no significant improvements in internal and external rotation. To our knowledge, there have been no studies on new attempts to restore active internal rotation following RSA. The purpose of this study was to compare RSA alone and RSA with anterior latissimus dorsi and teres major (aLDTM) tendon transfer in patients with CTA and mRCT with combined loss of active elevation and internal rotation (CLEIR).

METHODS

This retrospective cohort study included patients who underwent RSA with a lateralized design and had CLEIR between October 2014 and January 2019. Two groups were classified: patients who underwent RSA alone (group R, n = 36) and patients who underwent RSA with aLDTM tendon transfer (group T, n = 24). Clinical outcomes, including the visual analog scale score, Constant score, American Shoulder and Elbow Surgeons score, active range of motion, score for activities of daily living requiring active internal rotation (ADLIR), and ability to perform toileting activity, were compared. Moreover, radiologic outcomes and complications were compared.

RESULTS

The mean follow-up period was 36.8 ± 11.6 months (range, 24-67 months). Both group R and group T showed significant improvements in clinical scores and active range of motion preoperatively and postoperatively. In group T, the Constant score (65.2 ± 7.5 vs. 58.1 ± 12.3, P = .008), ADLIR score (26.1 ± 3.1 vs. 20.3 ± 5.0, P < .001), internal rotation level with the arm behind the back (P < .001), and subscapularis-specific physical examination findings (P < .001) were significantly better than in group R. However, no significant difference in the American Shoulder and Elbow Surgeons score, forward flexion, and external rotation at 0° and 90° of abduction were found at final follow-up. Transient axillary nerve palsy was found in 2 patients in group T. However, there were no significant differences in complication rates between 2 groups.

CONCLUSION

Lateralized RSA with aLDTM tendon transfer for patients with CTA and mRCT with CLEIR restored shoulder function and improved clinical outcomes, especially the ability to perform ADLIR and toileting activity.

Reverse total shoulder arthroplasty with latissimus dorsi and teres major transfer: biomechanical and electromyographical outcomes

PURPOSE

There is controversy regarding the optimal treatment for patients with rotator cuff arthropathy with external rotation deficit (CLEER group). This study analyzes the biomechanical and electromyographical outcomes of reverse total shoulder arthroplasty (RTSA) with latissimus dorsi and teres major transfer. The primary objective of this study is to compare the biomechanical and electromyographical outcomes between the treated and contralateral shoulder. Secondary objective is to define clinical and functional outcomes, and to report the radiological findings. Our hypothesis is that with this technique patients regain at least 50% of the strength in external rotation of the contralateral shoulder, and that the transferred muscles remain EMG active over time.

MATERIALS AND METHODS

All patients who underwent RTSA with latissimus dorsi and teres major transfer in our hospital between 2007 and 2015 were included. From 16 eligible patients, 10 were finally reviewed. Biomechanical assessment of rotation strength was performed postoperatively in both shoulders, and fine needle EMG of latissimus dorsi and teres major muscles was recorded at the same time in both shoulders. Constant test and clinical evaluation (Lag sign and Hornblower test) were obtained preoperative and at final follow up. Radiological (X-ray, US) assessment was also obtained for both shoulders at final follow up.

RESULTS

External rotation strength of the operated shoulder was higher than 50% the strength of the contralateral shoulder, and the differences were statistically significant (p < 0.05). No statistically differences were found regarding to internal rotation. The electromyographic assessment found no significant differences (p > 0.05) between the treated and contralateral shoulders. The mean Constant-Murley score significantly increased (30.9 points) after surgery (p < 0.01). Lag sign and Hornblower test were negative in all patients.

CONCLUSIONS

Performing RTSA with latissimus dorsi and teres major transfer is an effective procedure improve function and to restore ER strength in patients in CLEER group. The EMG records shows that transposed latissimus dorsi and teres major adapt to their new function and remain functional over time, even in elderly patients.

Reverse shoulder arthroplasty used for revision of reverse shoulder arthroplasty: a systematic review

Background

As reverse shoulder arthroplasty (RSA) cases increase, so too will the need to revise subsequent failures. Many of the complications associated with revising anatomic total shoulder and hemiarthroplasty have been adequately addressed by RSA including glenoid bone deficiency, instability, and functional outcomes. However, the risk for complication when revising a failed reverse prosthesis may be more pronounced with increased bone and soft tissue deficiency. The ability for the reversed prosthesis to accommodate these insufficiencies following a prior reversed prosthesis is unclear.

Methods

PubMed, Embase, and Google Scholar were queried for articles which fit the inclusion criteria of a reversed prosthesis used to revise a failed primary reverse prosthesis with a minimum follow-up of 12 months and clinical outcome reporting.

Results

After exclusions, 9 studies reporting on 242 reverse shoulders with a mean follow-up of 40.29 months were analyzed. The differences between preoperative and postoperative weighted means were not significant for Constant (P = .26), American Shoulder and Elbow Surgeons Shoulder score (P = .61), SSV (P = .57), and visual analog scale for pain (P = .48). Functional improvements in elevation (74°-102°) and external rotation (18°-21°) were consistent with those reported for primary reverse procedures, although differences in preoperative and postoperative measures were not statistically significant. Patient satisfaction was 89% with a major complication rate of 25%.

Discussion

The reverse shoulder prosthesis has proven satisfactory in revising hemiarthroplasty and anatomic total shoulder arthroplasty. The current results indicate RSA is also a satisfactory treatment option when revising a prior reverse prosthesis. Inherent to revision shoulder surgery is the obstacle of humeral and glenoid bone loss, an attenuated soft-tissue envelope, and instability. The reverse prosthesis may adequately address these commonly confronted difficulties with its inherent design characteristics. RSA provides a secure glenoid fixation for bone grafting, the ability to increase construct stability with component sizing, and a reliance on the deltoid for function. As our learning about revision of RSA improves, so will our ability to preemptively address potential issues which may lead to decreased complications in these cases. Despite the 25% rate of major complication, patients reported satisfaction of 89% which demonstrates the improvements in function and pain relief that are provided by the reverse prosthesis.

Similar optimal distalization and lateralization angles can be achieved with different reverse shoulder arthroplasty implant designs

Background

Optimal postoperative distalization (DSA) and lateralization (LSA) shoulder angles have been described as radiological measurements correlated with function after reverse shoulder arthroplasty (RSA). The proposed optimal values are DSA between 40° and 65° and LSA between 75° and 95°; however, whether these values can be reached with different implant designs is unclear.

Aim

To determine which RSA implant could achieve higher rates of optimal DSA and LSA, to determine any association between each implant and optimal DSA and LSA, and to assess the correlation of the preoperative critical shoulder angle (CSA) and acromial index (AI) with the DSA and LSA.

Methods

This was a retrospective comparative study of all patients who underwent primary RSA for rotator cuff arthropathy. Three RSA implant designs were included, based on which patients were divided into three groups: group 1 (FH Arrow™; 16 patients) comprised onlay implants with a 135° neck-shaft angle (NSA); group 2 (Biomet Comprehensive™; 20 patients) comprised onlay implants with a 147° NSA; group 3 (Mathys Affinis™; 15 patients) comprised inlay implants with a 155° NSA. The AI and CSA were measured on preoperative radiographs. The DSA and LSA were measured on true AP postoperative radiographs.

Results

The mean DSAs were 44°, 46°, and 46° (P = 0.671) and the mean LSAs were 92°, 91°, and 82° for groups 1, 2, and 3, respectively (P = 0.003). Group 3 had lower LSA than groups 1 (-10°; P = 0.005) and 2 (-9°; P = 0.002). Optimal DSA and LSA were achieved in 71% and 73% of all arthroplasties, respectively. No association between implant designs and achieving an optimal DSA or LSA was observed. None of the implant designs had DSA >65°. The most common cause of failure to reach an optimal LSA in onlay implants was a combination of LSA >95° and DSA <40°. The most common cause of failure in group 3 was DSA <40°. The DSA was negatively correlated with the AI (-0.384; P = 0.006) and CSA (-0.305; P = 0.033). No correlation was observed between the LSA and AI (P = 0.312) or CSA (P = 0.137).

Conclusion

The LSA is lower with the Mathys Affinis™ implant than with the Biomet Comprehensive™ and FH Arrow™ implants; however, most LSAs are in the optimal ranges, and no association is observed between different implant designs and optimal DSA and LSA. Implant design, CSA, and AI should be considered during preoperative planning to achieve optimal DSA and LSA.

Prosthesis Designs and Tuberosity Fixation Techniques in Reverse Total Shoulder Arthroplasty: Influence on Tuberosity Healing in Proximal Humerus Fractures

Reverse total shoulder arthroplasty (RTSA) is increasingly used for the treatment of complex proximal humerus fractures and fracture sequelae. In 2021, half a dozen models of fracture stems are commercially available, reflecting its growing utility for fracture management. Prosthesis designs, bone grafting and tuberosity fixation techniques have evolved to allow better and more reliable fixation of tuberosities and bony ingrowth. Patients with anatomical tuberosity healing not only have an increased range of active anterior elevation and external rotation, but also experience fewer complications and longer prosthesis survival. This review provides an overview of recent evidence on basic and fracture-specific RTSA design features as well as tuberosity fixation techniques that can influence tuberosity healing.

Can Lateralization of Reverse Shoulder Arthroplasty Improve Active External Rotation in Patients with Preoperative Fatty Infiltration of the Infraspinatus and Teres Minor?

(1) Background: Postoperative recovery of external rotation after reverse shoulder arthroplasty (RSA) has been reported despite nonfunctional external rotator muscles. Thus, this study aimed to clinically determine the ideal prosthetic design allowing external rotation recovery in such a cohort. (2) Methods: A monocentric comparative study was retrospectively performed on patients who had primary RSA between June 2013 and February 2018 with a significant preoperative fatty infiltration of the infraspinatus and teres minor. Two groups were formed with patients with a lateral humerus/lateral glenoid 145° onlay RSA-the onlay group (OG), and a medial humerus/lateral glenoid 155° inlay RSA-the inlay group (IG). Patients were matched 1:1 by age, gender, indication, preoperative range of motion (ROM), and Constant score. The ROM and Constant scores were assessed preoperatively and at a minimum follow-up of two years. (3) Results: Forty-seven patients have been included (23 in OG and 24 in IG). Postoperative external rotation increased significantly in the OG only (p = 0.049), and its postoperative value was significantly greater than that of the IG by 11.1° (p = 0.028). (4) Conclusion: The use of a lateralized humeral stem with a low neck-shaft angle resulted in significantly improved external rotation compared to a medialized humeral 155° stem, even in cases of severe fatty infiltration of the infraspinatus and teres minor. Humeral lateralization and a low neck-shaft angle should be favored when planning an RSA in a patient without a functional posterior rotator cuff.