Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty

Functional internal rotation is associated with subscapularis tendon healing and increased scapular tilt after Grammont style bony increased offset reverse shoulder arthroplasty with 155° humeral implant

BACKGROUND

While forward flexion consistently improves after reverse shoulder arthroplasty (RSA), restoration of internal rotation behind the back (IR1) is much less predictable. This study aims to evaluate the role of the subscapularis tendon in restoration of IR and identify other factors that may influence IR such as anterior scapular tilt and postoperative passive internal rotation at 90° of abduction (IR2). The hypothesis was that IR1 is positively associated with both subscapularis healing, postoperative passive IR2, and anterior scapular tilt.

METHODS

A retrospective review was performed on a consecutive series of Grammont style bony increased offset RSAs performed by a single surgeon between January 2014 and December 2015. Inclusion criteria were: (1) primary RSA for rotator cuff arthropathy, massive irreparable rotator cuff tear, or primary osteoarthritis with B2 glenoid morphology, (2) minimum of two years clinical follow-up, and (3) complete intraoperative repair of a repairable subscapularis tendon. The primary outcomes were postoperative return of IR1 compared to postoperative IR2, healing rate of subscapularis tendon, and scapular tilt.

RESULTS

The cohort included 77 patients, aged 72.6 ± 7.0 years at index surgery and comprising 32 men (42%) and 45 women (58%). At a mean follow-up of 3.3 ± 1.0 years, ultrasound evaluation revealed a successful repair of the subscapularis in 41 patients (53%). Healed subscapularis repair was significantly associated with greater IR1 (85% vs. 53%, P = .031). A multivariate logistic regression revealed functional postoperative IR1 was independently associated with subscapularis healing (odds ratio [OR], 4.3; 95% confidence interval [CI] [1.1-20.2]; P = .046) as well as greater anterior tilt (OR, 1.2; 95% CI [1.1-1.5]; P = .008) and postoperative IR2 (OR, 1.09; 95% CI [1.05-1.14]; P < .001) but lower postoperative passive abduction (OR, 0.96; 95% CI [0.92-1.00], P = .045). The area under receiver operating characteristic curve obtained with the Youden index was 0.88 with a sensitivity of 81.8% and specificity of 90.6%.

CONCLUSIONS

This study revealed that in a Grammont-type RSA, postoperative IR1 recovery is first associated with subscapularis tendon healing, followed by IR2 and finally the ability to tilt the scapula anteriorly. Better understanding of these factors preoperatively may provide greater insight on expected return of functional internal after RSA.

Navigated augmented reality through a head-mounted display leads to low deviation between planned, intra- and postoperative parameters during glenoid component placement of reverse shoulder arthroplasty: a proof-of-concept case series

BACKGROUND

Navigated augmented reality (AR) through a head-mounted display (HMD) has led to accurate glenoid component placement in reverse shoulder arthroplasty (RSA) in an in-vitro setting. The purpose of this study is to evaluate the deviation between planned, intraoperative, and postoperative inclination, retroversion, entry point, and depth of the glenoid component placement during RSA, assisted by navigated AR through an HMD, in a surgical setting.

METHODS

A prospective, multicenter study was conducted. All consecutive patients undergoing RSA in 2 institutions, between August 2021 and January 2023, were considered potentially eligible for inclusion in the study. Inclusion criteria were as follows: age >18 years, surgery assisted by AR through an HMD, and postoperative computed tomography (CT) scans at 6 weeks. All participants agreed to participate in the study and informed consent was provided in all cases. Preoperative CT scans were undertaken for all cases and used for 3-dimensional (3D) planning. Intraoperatively, glenoid preparation and component placement were assisted by a navigated AR system through an HMD in all patients. Intraoperative parameters were recorded by the system. A postoperative CT scan was undertaken at 6 weeks, and 3D reconstruction was performed to obtain postoperative parameters. The deviation between planned, intraoperative, and postoperative inclination, retroversion, entry point, and depth of the glenoid component placement was calculated. Outliers were defined as >5° for inclination and retroversion and >5 mm for entry point.

RESULTS

Seventeen patients (9 females, 12 right shoulders) with a mean age of 72.8 ± 9.1 years (range, 47.0-82.0) met inclusion criteria. The mean deviation between intra- and postoperative measurements was 1.5° ± 1.0° (range, 0.0°-3.0°) for inclination, 2.8° ± 1.5° (range, 1.0°-4.5°) for retroversion, 1.8 ± 1.0 mm (range, 0.7-3.0 mm) for entry point, and 1.9 ± 1.9 mm (range, 0.0-4.5 mm) for depth. The mean deviation between planned and postoperative values was 2.5° ± 3.2° (range, 0.0°-11.0°) for inclination, 3.4° ± 4.6° (range, 0.0°-18.0°) for retroversion, 2.0 ± 2.5 mm (range, 0.0°-9.7°) for entry point, and 1.3 ± 1.6 mm (range, 1.3-4.5 mm) for depth. There were no outliers between intra- and postoperative values and there were 3 outliers between planned and postoperative values. The mean time (minutes : seconds) for the tracker unit placement and the scapula registration was 03:02 (range, 01:48 to 04:26) and 08:16 (range, 02:09 to 17:58), respectively.

CONCLUSION

The use of a navigated AR system through an HMD in RSA led to low deviations between planned, intraoperative, and postoperative parameters for glenoid component placement.

Medialized vs. Lateralized Reverse Total Shoulder Arthroplasty for Proximal Humerus Fractures: A Systematic Review and Meta-Analysis

BACKGROUND

Reverse shoulder arthroplasty (RSA) is increasingly used in the treatment of proximal humerus fractures (PHFs) with reliable clinical improvement. Lateralized RSA implants have conferred superior outcomes compared with the original Grammont design in patients with nontraumatic indications. However, in the setting of a PHF, lateralized components can place increased tension across the tuberosity fracture site and potentially compromise tuberosity healing and outcomes. This systematic review and meta-analysis sought to determine the effect of implant design on clinical outcomes after RSA for PHFs.

METHODS

A systematic review was performed per Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed/MEDLINE, EMBASE, Web of Science, and Cochrane were queried for clinical studies on RSA performed for PHFs that reported implant manufacturer details. Our primary outcomes included postoperative external rotation (ER), forward elevation (FE), abduction, Constant score, rate of greater tuberosity (GT) healing, and the incidence of complications compared between medialized vs. lateralized global implant design.

RESULTS

Globally lateralized RSA cohorts (478 RSAs total with cumulative lateral offset achieved through humeral or glenoid lateralization or both humeral and glenoid lateralization) were found to have a greater mean postoperative Constant score compared with globally medialized (medialized glenoid and medialized humerus) RSA cohorts with 1,494 total medialized RSAs (66 vs. 59, p = 0.006), but there was no significant difference regarding mean postoperative ER (30° vs. 22°, p = 0.078), FE (117° vs. 119°, p = 0.708), or abduction (103° vs. 107°, p = 0.377). On meta-regression, neither implant design nor tuberosity status significantly influenced postoperative ER, FE, abduction, or Constant score on meta-regression independent of mean follow-up and age at surgery. The rate of GT healing was greater in lateralized compared with medialized RSAs (88% vs. 72%, p < 0.001). On meta-regression, medialized RSA design was associated with a 73% lower odds of GT healing (odds ratio = 0.27, 95% confidence interval = 0.11-0.68, p = 0.007) independent of mean follow-up and age at surgery.

CONCLUSION

Lateralized RSA implants conferred no significant functional benefit over medialized implants when used in patients with PHFs.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Instability after reverse shoulder arthroplasty: a retrospective review of thirty one cases

PURPOSE

A retrospectively analyze of instability after RSA in terms of aetiology, treatment and final functional outcome.

METHODS

A bicentric retrospective study of 31 patients (mean age 67.6 years; 42-83) treated for RSA instability using RSA Arrow System (FH Orthopedics, Mulhouse, France), mean follow-up 41months (range 12-158). Aetiologies for dislocation were evaluated using a previously described classification system for RSA instability. Actions performed during the Revision Surgeries were analyzed and grouped into five categories. Clinical outcome measures included range of motion, SSV, VAS, Constant-Murley scores, satisfaction level and recurrence of instability.

RESULTS

The most frequent aetiology for RSA instability was loss of compression (18), followed by impingement (8) and loss containment (5). Total RSA revision (bipolar procedure) involving both distalization and lateralization occurred in 13 instances. Isolated distalization through the humerus was performed in ten patients and Isolated lateralization through the glenoid in three patients. Three cases of components exchange due to mechanical failure were noted. Bone graft was used in nine instances. Three patients (10%) suffered recurrent instability following Revision Surgery and required an additional stabilizing procedure. At final follow-up all 31 RSA were reported as stable with a mean VAS of 1.1, SSV 54.5%, constant score 48.3, constant ponderate 74.9%.

CONCLUSION

The management of unstable RSA represent a challenge that can be successfully overcome with a revision surgery with compromised functional results. Loss of compression was the most common cause for primary and recurrent RSA instability that were treated principally with bipolar revisions involving component lateralization and distalization.

The effect of tuberosity healing on functional outcomes after reverse shoulder arthroplasty for proximal humerus fractures: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis compared clinical outcome measures in patients undergoing reverse shoulder arthroplasty (RSA) for proximal humerus fracture (PHF) with healed versus non-healed greater tuberosity (GT).

METHODS

We performed a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines querying PubMed/MEDLINE, EMBASE, Web of Science, and Cochrane for studies that stratified results by the GT healing status. Studies that did not attempt to repair the GT were excluded. We extracted and compared clinical outcomes including postoperative forward flexion (FF), external rotation (ER), internal rotation (IR), Constant score, and complications and revision rates.

RESULTS

Of the included patients, 295 (78.5%) demonstrated GT healing while 81 did not (21.5%). The healed GT cohort exhibited increased postoperative FF (P < .001), ER (P < .001), IR (P = .006), and Constant score (P = .006) compared to the non-healed GT cohort. The overall dislocation rate was 0.8% with no study differentiating GT status of dislocation cases.

CONCLUSION

Healing of the GT after RSA for PHF yields improved postoperative range of motion and strength, whereas patient-reported pain and function were largely not affected by GT healing indicating merit to RSA for PHF regardless of the likelihood of the GT healing.

Virtual assessment of internal rotation in reverse shoulder arthroplasty based on statistical shape models of scapular size

Background

The purpose of this study was to assess impingement-free internal rotation (IR) in a virtual reverse shoulder arthroplasty simulation using a Statistical Shape Model based on scapula size.

Methods

A database of over 10,000 scapulae utilized for preoperative planning for shoulder arthroplasty was analyzed with a Statistical Shape Model to obtain 5 scapula sizes including the mean and 2 standard deviations. For each scapula model, one glenosphere size (33-42 mm) was selected as the best fit based on consensus among 3 shoulder surgeons. Virtual implantation variables included 1) lateral offset (0-12 mm in 2-mm increments), 2) inferior eccentricity (0, 2.5, 5, and 7.5 mm), and 3) posterior eccentricity (0, 2.5, and 5 mm). The neck shaft angle was fixed at 135° with an inlay design humeral prosthesis. IR at the side (IR0) and in abduction (IRABD) were then simulated.

Results

Maximum impingement-free IR0 was reached with increasing inferior offset in combination with increasing lateralization. Lateralization was the most important variable in increasing impingement-free IRABD. Maximum IRABD was reached at 4-6 mm of lateralization with smaller scapula (-2 to 0 standard deviation). Increasing lateralization up to 12 mm continues to increase IRABD for larger-sized scapula (+1 to +2 standard deviation). Optimal inferior offset and lateralization to maximize IR did have a small loss of external rotation in neutral abduction. There was no loss of external rotation in 60° of abduction.

Conclusion

In a virtual model, the glenosphere position required to maximize IR varied by scapula size. For smaller scapulae, maximum IR0 was reached with a combination of 2.5-mm inferior offset and 0- 4 mm of lateralization. For larger scapulae, maximum IR0 was reached with a combination of 2.5 mm of inferior offset and 4 mm of lateralization. The amount of lateralization required to maximize IRABD also varies by scapula size. Maximum IRABD was reached in smaller scapula with 4-6 mm of lateralization and at least 12 mm of lateralization in larger scapula. These findings may be applied in the clinical decision-making process knowing that impingement-free IR and IRABD can be maximized with combinations of inferior offset and lateralization based on scapula size with minimal effect on external rotation and external rotation in 60° of abduction.

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.

Posteroinferior glenosphere positioning is associated with improved range of motion following reverse shoulder arthroplasty with a 135° inlay humeral component and lateralized glenoid

BACKGROUND

Optimal glenosphere positioning in a lateralized reverse shoulder arthroplasty (RSA) to maximize functional outcomes has yet to be clearly defined. Center of rotation (COR) measurements have largely relied on anteroposterior radiographs, which allow assessment of lateralization and inferior position, but ignore scapular Y radiographs, which may provide an assessment of the posterior and inferior position relative to the acromion. The purpose of this study was to evaluate the COR in the sagittal plane and assess the effect of glenosphere positioning with functional outcomes using a 135° inlay stem with a lateralized glenoid.

METHODS

A retrospective review was performed on a prospectively maintained multicenter database on patients who underwent primary RSA from 2015 to 2021 with a 135° inlay stem. The COR was measured on minimum 2-year postoperative sagittal plain radiographs using a best-fit circle fit method. A best-fit circle was made on the glenosphere and the center was marked. From there, 4 measurements were made: (1) center to the inner cortex of the coracoid, (2) center to the inner cortex of the anterior acromion, (3) center to the inner cortex of the middle acromion, and (4) center to the inner cortex of the posterior acromion. Regression analysis was performed to evaluate any association between the position of the COR relative to bony landmarks with functional outcomes.

RESULTS

A total of 136 RSAs met the study criteria. There was no relation with any of the distances with outcome scores (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, visual analog scale). In regard to range of motion (ROM), each distance had an effect on at least 1 parameter. The COR to coracoid distance had the broadest association with ROM, with improvements in forward flexion (FF), external rotation (ER0), and internal rotation with the arm at 90° (IR90) (P < .001, P = .031, and P < .001, respectively). The COR to coracoid distance was also the only distance to affect the final FF and IR90. For every 1-mm increase in this distance, there was a 1.8° increase in FF and 1.5° increase in IR90 (β = 1.78, 95% confidence interval [CI] 0.85-2.72, P < .001, and β = 1.53, 95% CI 0.65-2.41, P < .001; respectively).

CONCLUSION

Evaluation of the COR following RSA in the sagittal plane suggests that a posteroinferior glenosphere position may improve ROM when using a 135° inlay humeral component and a lateralized glenoid.

A gender and size specific evaluation of Grammont-type inlay versus lateralizing onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty

INTRODUCTION

In reverse shoulder arthroplasty (RSA) new designs enable greater amounts of lateralization to prevent instability and scapular notching and increase range of motion, however, excessive lateralization leads to stress upon the acromion that can result in scapular spine fatigue fractures. Aim of this study was to gender- and size-specifically assess the influence of glenosphere size and different humeral designs on lateralization, distalization, and bony impingement-free range of motion (ROM) in patients undergoing RSA.

METHODS

Computed tomography scans from 30 osteoarthritic patients (f:15, m:15) and 20 cuff tear arthropathy patients (f:10, m:10) were used to virtually simulate RSA implantation. The efficacy of an inlay Grammont-type system vs. an onlay lateralizing system combined with different glenosphere sizes (36 mm vs. 42 mm) in achieving ROM, lateralization, and distalization was evaluated. Moreover, gender and patient's constitution were correlated to humeral size by radiologically measuring the best-fit circle of the humeral head.

RESULTS

A different amount of relative lateralization was achieved in both genders using large glenospheres and onlay designs. Latter yielded a higher ROM in all planes for men and women with a 42 mm glenosphere; with the 36 mm glenosphere, an increased ROM was observed only in men. The 155° inlay design led to joint medialization only in men, whereas all designs led to lateralization in women. When adjusting the absolute amount of lateralization to humerus' size (or patient's height), regardless of implant type, women received greater relative lateralization using 36 mm glenosphere (inlay: 1%; onlay 12%) than men with 42 mm glenosphere (inlay: -3%; onlay: 8%).

CONCLUSION

The relative lateralization achieved using onlay design is much higher in women than men. Small glenospheres yield greater relative lateralization in women compared to large glenospheres in men. Humeral lateralization using onlay designs should be used cautiously in women, as they lead to great relative lateralization increasing stress onto the acromion.

LEVEL OF EVIDENCE

Basic Science Study, Computer Modeling.

Insertion sites of latissimus dorsi tendon transfer performed during reverse shoulder arthroplasty: A systematic review and meta-analysis

BACKGROUND

Reverse shoulder arthroplasty (RSA) with concurrent latissimus dorsi transfer (LDT) is a potential treatment option for restoration of external rotation (ER). Biomechanical studies have emphasized the importance of the insertion site location for achieving optimal outcomes. In this systematic review and meta-analysis, we aimed to describe what insertion sites for LDT are utilized during concomitant RSA and their associated clinical outcomes.

METHODS

A systematic review and meta-analysis were performed per PRISMA guidelines. We queried PubMed/MEDLINE, Embase, Web of Science, and Cochrane databases to identify articles reporting on patients who received RSA with LDT to restore ER and specified the site of tendon transfer insertion on the humerus. We first describe reported insertion sites in the literature. Secondarily, we present preoperative and postoperative range of motion and Constant score for different insertion sites as well as reported complications.

RESULTS

Sixteen studies, analyzed as 19 separate cohorts (by insertion site and tendon-transfer), reporting on 264 RSAs with LDT (weighted mean age 66 years, follow-up 39 months, 61% female) were evaluated. Of these, 143 (54%) included a concomitant teres major transfer (LDT/TMT) and 121 (46%) were LDT-only. Fourteen cohorts (14/19, 74%) reported insertion at the posterolateral aspect of the greater tuberosity, four cohorts (4/19, 21%) reported insertion site at the lateral bicipital groove, and one cohort (1/19, 5%) reported separate LDT and TMT with insertion of the TMT to the posterolateral aspect of the greater tuberosity and LDT to the lateral bicipital groove. Meta-analysis revealed no differences in range of motion or Constant score based on humeral insertion site or whether the LDT was transferred alone or with TMT. Leading complications included dislocation, followed by infection and neuropraxia. No discernible correlation was observed between postoperative outcomes and the strategies employed for tendon transfer, prosthesis design, or subscapularis management.

CONCLUSION

The posterolateral aspect of the greater tuberosity was the most-utilized insertion site for LDT performed with RSA. However, in the current clinical literature, LDT with or without concomitant TMT result in similar postoperative ROM and Constant score regardless of insertion site. Analysis of various proposed transfer sites reinforce the ability of LDT with RSA to restore both FE and ER in patients with preoperative active elevation and external rotation loss. Meta-analysis revealed significant improvements in range of motion and Constant score regardless of humeral insertion site or whether the LDT was transferred alone or with TMT, although future studies are needed to determine whether an ideal tendon transfer technique exists.

LEVEL OF EVIDENCE

IV.

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.

Optimizing Muscle-Tendon Lengths in Reverse Total Shoulder Arthroplasty: Evaluation of Surgical and Implant-Design-Related Parameters

BACKGROUND

Optimizing the function of muscles that cross the glenohumeral articulation in reverse total shoulder arthroplasty (RTSA) is controversial. The current study used a geometric model of the shoulder to systematically examine surgical placement and implant-design parameters to determine which RTSA configuration most closely reproduces native muscle-tendon lengths of the deltoid and rotator cuff.

METHODS

A geometric model of the glenohumeral joint was developed and adjusted to represent small, medium, and large shoulders. Muscle-tendon lengths were assessed for the anterior deltoid, middle deltoid, posterior deltoid, and supraspinatus from 0 to 90° of scaption; for the subscapularis from 0° to 60° of internal rotation (IR) and 0° to 60° of scaption; for the infraspinatus from 0° to 60° of external rotation (ER) and 0° to 60° of scaption; and for the teres minor from 0° to 60° of ER at 90° of scaption. RTSA designs were virtually implanted using the following parameters: (1) surgical placement with a centered or inferior glenosphere position and a humeral offset of 0, 5, or 10 mm relative to the anatomic neck plane, (2) implant design involving a glenosphere size of 30, 36, or 42 mm, glenosphere lateralization of 0, 5, or 10 mm, and humeral neck-shaft angle of 135°, 145°, or 155°. Thus, 486 RTSA-shoulder size combinations were analyzed. Linear regression assessed the strength of association between parameters and the change in each muscle-tendon length from the native length.

RESULTS

The configuration that most closely restored anatomic muscle-tendon lengths in a small shoulder was a 30-mm glenosphere with a centered position, 5 mm of glenoid lateralization, 0 mm of humeral offset, and a 135° neck-shaft angle. For a medium shoulder, the corresponding combination was 36 mm, centered, 5 mm, 0 mm, and 135°. For a large shoulder, it was 30 mm, centered, 10 mm, 0 mm, and 135°. The most important implant-design parameter associated with restoration of native muscle-tendon lengths was the neck-shaft angle, with a 135° neck-shaft angle being favored (β = 0.568 to 0.657, p < 0.001). The most important surgical parameter associated with restoration of native muscle-tendon lengths was humeral offset, with a humeral socket placed at the anatomic neck plane being favored (β = 0.441 to 0.535, p < 0.001).

CONCLUSIONS

A combination of a smaller, lateralized glenosphere, a humeral socket placed at the anatomic neck plane, and an anatomic 135° neck-shaft angle best restored native deltoid and rotator cuff muscle-tendon lengths in RTSA.

CLINICAL RELEVANCE

This study of surgical and implant factors in RTSA highlighted optimal configurations for restoration of native muscle-tendon lengths of the deltoid and rotator cuff, which has direct implications for surgical technique and implant selection. Additionally, it demonstrated the most influential surgical and implant factors with respect to muscle-tendon lengths, which can be used to aid intraoperative decision-making.

Is preoperative 3D planning reliable for predicting postoperative clinical differences in range of motion between two stem designs in reverse shoulder arthroplasty

BACKGROUND

We aim to predict a clinical difference in the postoperative range of motion (RoM) between 2 reverse shoulder arthroplasty (RSA) stem designs (Inlay-155° and Onlay-145°) using preoperative planning software. We hypothesized that preoperative 3D planning could anticipate the differences in postoperative clinical RoM between 2 humeral stem designs and by keeping the same glenoid implant.

METHODS

Thirty-seven patients (14 men and 23 women, 76 ± 7 years) underwent a BIO-RSA (bony increased offset-RSA) with the use of preoperative planning and an intraoperative 3-dimensional-printed patient-specific guide for glenoid component implantation between January 2014 and September 2019 with a minimum follow-up of 2 years. Two types of humeral implants were used: Inlay with a 155° inclination (Inlay-155°) and Onlay with a 145°inclination (Onlay-145°). Glenoid implants remained unchanged. The postoperative RSA angle (inclination of the area in which the glenoid component of the RSA is implanted) and the lateralization shoulder angle were measured to confirm the good positioning of the glenoid implant and the global lateralization on postoperative X-rays. A correlation between simulated and clinical RoM was studied. Simulated and last follow-up active forward flexion (AFE), abduction, and external rotation (ER) were compared between the 2 types of implants.

RESULTS

No significant difference in RSA and lateralization shoulder angle was found between planned and postoperative radiological implants' position. Clinical RoM at the last follow-up was always significantly different from simulated preoperative RoM. A low-to-moderate but significant correlation existed for AFE, abduction, and ER (r = 0.45, r = 0.47, and r = 0.57, respectively; P < .01). AFE and abduction were systematically underestimated (126° ± 16° and 95° ± 13° simulated vs. 150° ± 24° and 114° ± 13° postoperatively; P < .001), whereas ER was systematically overestimated (50° ± 19° simulated vs. 36° ± 19° postoperatively; P < .001). Simulated abduction and ER highlighted a significant difference between Inlay-155° and Onlay-145° (12° ± 2°, P = .01, and 23° ± 3°, P < .001), and this was also retrieved clinically at the last follow-up (23° ± 2°, P = .02, and 22° ± 2°, P < .001).

CONCLUSIONS

This study is the first to evaluate the clinical relevance of predicted RoM for RSA preoperative planning. Motion that involves the scapulothoracic joint (AFE and abduction) is underestimated, while ER is overestimated. However, preoperative planning provides clinically relevant RoM prediction with a significant correlation between both and brings reliable data when comparing 2 different types of humeral implants (Inlay-155° and Onlay-145°) for abduction and ER. Thus, RoM simulation is a valuable tool to optimize implant selection and choose RSA implants to reach the optimal RoM.

Restoration of internal rotation after reverse shoulder arthroplasty may vary depending on etiology in patients younger than 60 ​years of age: a multicenter retrospective study

BACKGROUND

Reverse shoulder arthroplasty (RSA) offers promising functional outcomes for young patients, yet challenges persist in restoring internal rotation (IR). This study aimed to assess the restoration of IR after RSA in patients younger than 60 years of age and analyze the factors affecting IR recovery.

METHODS

A retrospective multicenter study was conducted, examining the functional outcome of patients who underwent RSA, with a minimum follow-up period of 2 years. Two subgroups of patients who underwent primary RSA were analyzed separately with respect to active internal rotation with the elbow at the side (AIR1): "difficult AIR1" and "easy AIR1."

RESULTS

The study included 136 patients (overall series) with a mean age of 51.6 years. The overall series showed statistically significant improvement in active range of motion (RoM), pain, and Constant scores, especially with active IR (p ​< ​0.01). According to etiology, statistically significant improvement (p ​< ​0.05) in active IR was observed for fracture sequelae, primary osteoarthritis, and rheumatoid arthritis, whereas no statistically significant improvement in IR was observed for tumor, revision, and cuff-tear arthropathy (p ​> ​0.05). In subgroup analysis, patients with easy AIR1 displayed a statistically significant lower body mass index and better Constant score mobility, as well as improved motion in forward elevation and active IR (p ​< ​0.05). No statistically significant associations were found between improved IR and prosthetic design or subscapularis repair. Scapular notch, lysis of the graft, and teres minor atrophy were significantly associated with better active IR (p ​< ​0.05).

CONCLUSION

RSA improves active RoM, pain, and functional outcomes in patients aged under 60. However, the degree of improvement in IR may vary depending on several factors and the underlying etiologies. These insights are crucial for patient selection and counseling, guiding RSA optimization efforts.

LEVEL OF EVIDENCE

IV.

Metallic Lateralized-Offset Glenoid Reverse Shoulder Arthroplasty

Background

Metallic lateralized-offset glenoid reverse shoulder arthroplasty (RSA) for cuff tear arthropathy combines the use of a metallic augmented baseplate with a metaphyseally oriented short stem design that can be applied at a 135° or 145° neck-shaft angle, leading to additional lateralization on the humeral side. Lateralization of the center of rotation decreases the risk of inferior scapular notching and improves external rotation, deltoid wrapping, residual rotator cuff tensioning, and prosthetic stability1-4. Metallic increased-offset RSA (MIO-RSA) achieves lateralization and corrects inclination and retroversion while avoiding graft resorption and other complications of bony increased-offset RSA (BIO-RSA)5-8. Reducing the neck-shaft angle from the classical Grammont design, in combination with glenoid lateralization, improves range of motion9,10 by reducing inferior impingement during adduction at the expense of earlier superior impingement during abduction2,11. Lädermann et al.12 investigated how different combinations of humeral stem and glenosphere designs influence range of motion and muscle elongation. They assessed 30 combinations of humeral components, as compared with the native shoulder, and found that the combination that allows for restoration of >50% of the native range of motion in all directions was a 145° onlay stem with a concentric or lateralized tray in conjunction with a lateralized or inferior eccentric glenosphere. In addition, the use of a flush-lay or a slight-onlay stem design (like the one utilized in the presently described technique) may decrease the risk of secondary scapular spine fracture13,14. The goal of this prosthetic design is to achieve an excellent combination of motion and stability while reducing complications.

Description

This procedure is performed via a deltopectoral approach with the patient in the beach-chair position under general anesthesia combined with a regional interscalene nerve block. Subscapularis tenotomy and capsular release are performed, the humeral head is dislocated, and any osteophytes are removed. An intramedullary cutting guide is placed for correct humeral resection. The osteotomy of the humeral head is performed in the anatomical neck with an inclination of 135° and a retroversion of 20° to 40°, depending on the anatomical retroversion. The glenoid is prepared as usual. The lateralized, augmented baseplate is assembled with the central screw and the baseplate-wedge-screw complex is placed by inserting the screw into the central screw hole. Four peripheral screws are utilized for definitive fixation. An eccentric glenosphere with inferior overhang is implanted. The humerus is dislocated, and the metaphysis is prepared. Long compactors are utilized for proper stem alignment, and an asymmetric trial insert is positioned before the humerus is reduced. Stability and range of motion are assessed. The definitive short stem is inserted and the asymmetric polyethylene is impacted, resulting in a neck-shaft angle of 145°. Following reduction, subscapularis repair and wound closure are performed.

Alternatives

BIO-RSA is the main alternative to MIO-RSA. Boileau et al.15 demonstrated satisfactory early and long-term outcomes of BIO-RSA for shoulder osteoarthritis. A larger lateral offset may also be achieved with a thicker glenosphere2,16. Mark A. Frankle developed an implant that addressed the drawbacks of the Grammont design: a lateralized glenosphere combined with a 135° humeral neck-shaft angle. The 135° neck-shaft angle provides lateral humeral offset, preserving the normal length-tension relationship of the residual rotator cuff musculature, which optimizes its strength and function. The lateralized glenosphere displaces the humeral shaft laterally, minimizing the potential for impingement during adduction2,9,17,18. The advantage of BIO-RSA and MIO-RSA over lateralized glenospheres is that the former options provide correction of angular deformities without excessive reaming, which can lead to impingement19.

Rationale

BIO-RSA has been proven to achieve excellent functional outcomes15,20,21; however, the bone graft can undergo resorption, which may result in early baseplate loosening. Bipolar metallic lateralized RSA is an effective strategy for achieving lateralization and correction of multiplanar defects while avoiding the potential complications of BIO-RSA6,7,22-24. MIO-RSA also overcomes another limitation of BIO-RSA, namely that BIO-RSA is not applicable when the humeral head is not available for use (e.g., humeral head osteonecrosis, revision surgery, fracture sequelae).

Expected Outcomes

A recent study evaluated the clinical and radiographic outcomes of metallic humeral and glenoid lateralized implants. A total of 42 patients underwent primary RSA. Patients were documented prospectively and underwent follow-up visits at 1 and 2 years postoperatively. That study demonstrated that bipolar metallic lateralized RSA achieves excellent clinical results in terms of shoulder function, pain relief, muscle strength, and patient-reported subjective assessment, without instability or radiographic signs of scapular notching23. Kirsch et al.25 reported the results of primary RSA with an augmented baseplate in 44 patients with a minimum of 1 year of clinical and radiographic follow-up. The use of an augmented baseplate resulted in excellent short-term clinical outcomes and substantial deformity correction in patients with advanced glenoid deformity. No short-term complications and no failure or loosening of the augmented baseplate were observed. Merolla et al.7 compared the results of 44 patients who underwent BIO-RSA and 39 patients who underwent MIO-RSA, with a minimum follow-up of 2 years. Both techniques provided good clinical outcomes; however, BIO-RSA yielded union between the cancellous bone graft and the surface of the native glenoid in <70% of patients. On the other hand, complete baseplate seating was observed in 90% of MIO-RSA patients.

Important Tips

When performing subscapularis tenotomy, leave an adequate stump to allow end-to-end repair.Tenotomize the superior part of the subscapularis tendon in an L-shape, sparing the portion below the circumflex vessels.As glenoid exposure is critical, perform a 270° capsulotomy.Continuously check the orientation of the baseplate relative to the prepared hole and reamed surface to ensure accurate implantation of the full wedge baseplate to achieve a proper fit.Aim for 70% to 80% seating of the baseplate onto the prepared glenoid surface. Avoid overtightening or excessive advancement of the baseplate into the subchondral bone. Gaps between the baseplate and glenoid surface should also be avoided.In order to avoid varus or valgus malpositioning of the final implant, obtain proper diaphyseal alignment by following "the three big Ls": large, lateral, and long. Use a large metaphyseal component to fill the metaphysis. Place the guide pin for the reaming of the metaphysis slightly laterally into the resected surface of the humerus. Use long compactors for diaphyseal alignment to avoid varus or valgus malpositioning of the final implant.Use an intramedullary cutting guide for correct humeral resection.Utilize the correct liner in order to obtain proper tensioning and avoid instability.

Acronyms and Abbreviations

K wire = Kirschner wireROM = range of motion.

Preoperative diagnosis and rotator cuff status impact functional internal rotation following reverse shoulder arthroplasty

PURPOSE

This study aimed to evaluate whether functional internal rotation (fIR) following reverse shoulder arthroplasty (RSA) differs based on diagnosis of either: primary osteoarthritis (OA) with intact rotator cuff, massive irreparable rotator cuff tear (MICT) or cuff tear arthropathy (CTA).

METHODS

A retrospective review was carried out on RSAs performed by a single surgeon with the same implant over a 5-year period. Minimum 2-year follow-up was available in 235 patients; 139 (59.1%) were female, and the mean patient age was 72 ± 8 years. Additional clinical evaluation included the Subjective Shoulder Value and Constant score. Postoperative internal rotation was categorized as type I: hand to the buttock or hip; type II: hand to the lower lumbar region; or type III: smooth motion to at least the upper lumbar region. Type I was considered "nonfunctional" internal rotation, and type II and III were fIR.

RESULTS

Preoperatively, internal rotation was classified as type I in 60 patients (25.5%), type II in 114 (48.5%), and type III in 62 (26%). Postoperatively, internal rotation was classified as type I in 70 patients (30%), type II in 86 (36%), and type III in 79 (34%). Compared with preoperative status, fIR improved significantly in OA patients (P < .001), with 49 (52.6%) classified as type II or III postoperatively. In CTA patients, there was no significant change (P = .352). In patients with MICTs, there was a significant loss in fIR postoperatively (P = .003), with 25 patients (30.8%) deteriorating to type I after having either type II or III preoperatively, and only 5 patients (6.1%) improving to either type II or III.

CONCLUSIONS

Patients who undergo RSA for primary OA have a better chance of postoperative fIR improvement. A decrease in fIR is common after RSA for MICTs.

Can we separately measure glenoid vs. humeral lateralization and distalization in reverse shoulder arthroplasty?

BACKGROUND

Lateralization and distalization in reverse shoulder arthroplasty (RSA) can be measured on anteroposterior (AP) radiographs using 2 previously described angles: lateralization shoulder angle (LSA) and distalization shoulder angle (DSA). However, these 2 angles measure global lateralization and distalization but do not allow to differentiate how much lateralization or distalization are attributable to the glenoid and the humerus. We hypothesized that new angles could allow us to separately measure glenoid vs. humeral lateralization and distalization. A more precise understanding of independent glenoid and humeral contributions to lateralization and distalization may be beneficial in subsequent clinical research.

METHOD

Retrospective analysis of postoperative AP radiographs of 100 patients who underwent primary RSA for cuff-tear arthropathy, massive cuff tear, or glenohumeral osteoarthritis were analyzed. The new angles that we proposed use well-known bony landmarks (the acromion, glenoid, and humerus) and the most lateral point of the glenosphere, which we termed the "glenoid pivot point" (GPP). For lateralization, we used the GPP to split LSA into 2 new angles: glenoid lateralization angle (GLA) and humeral lateralization angle (HLA). For distalization, we introduced the modified distalization shoulder angle (mDSA) that can also be split into 2 new angles: glenoid distalization angle (GDA) and humeral distalization angle (HDA). Three orthopedic surgeons measured the new angles, using the online tool Tyche. Mean values with overall and individual standard deviations as well as intraclass correlation coefficients (ICCs) were calculated.

RESULTS

Because the angles form a triangle, the following equations can be made: LSA = GLA + HLA, and mDSA = GDA + HDA. All angles showed excellent inter- and intraobserver reliability (ICC = 0.92-0.97) with low means of individual standard deviations that indicate a precision of 2° for each angle.

CONCLUSION

Use of the most lateral part of the glenosphere (termed glenoid pivot point) allows us to separately measure glenoid vs. humeral lateralization and distalization. The 4 new angles (HLA, GLA, GDA, HDA) described in the present study can be used on true AP radiographs, routinely obtained after shoulder replacement, and the measured angles may be used with all types of reverse prostheses available.

[Reverse Shoulder Arthroplasty - Current Concepts]

Due to first promising long term outcome data, reverse shoulder arthroplasty experienced an immense increase of usage during the past decade. Moreover, the initial Grammont concept has constantly been refined and adapted to current scientific findings. Therefore, clinical and radiological problems like scapular notching and postoperative instability were constantly addressed but do still remain an area of concern.This article summarises current concepts in reverse shoulder arthroplasty and gives an overview of actual indications like cuff tear arthropathy, severe osteoarthritis, proximal humerus fractures, tumours, fracture sequelae as well as revision surgery and their corresponding clinical and radiological results.

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.

Can Distalisation and Lateralisation Shoulder Angles in Reverse Arthroplasty Interfere with the Functional Results in Patients with Rotator Cuff Arthropathy?

Objective:  To evaluate the influence of radiographic values on clinical and functional results in patients treated with reverse arthroplasty for rotator cuff arthropathy (RCA) using a lateralized design. Methods:  A retrospective analysis was performed. Patient demographics were recorded, as well as preoperative and postoperative range of motion. Function was calculated using the Constant-Murley score both before and after the procedure. Pre and postoperative anteroposterior and axial radiographs of the affected shoulder were analysed. In the preoperative images, the following was calculated: acromiohumeral distance (AHD) and lateral humeral offset (LHO). Postoperative measurements included: AHD, LHO, distalization shoulder angle (DSA) and lateralisation shoulder angle (LSA). Linear regression and quadratic regression analysis was performed to determine their degree of association with final functional outcomes. By applying a quadratic regression analysis and ROC curves, the cut-off values were determined with respect to the above-mentioned angles and the positive predictive value was calculated. Results:  The greater anterior elevation (AE) ranges were found with DSA between 40-45° and LSA among 80°- 90°, while better ABD was observed with LSA of 90-100°. Preoperative AHD was correlated to RE (r s :0.47; p:0.049). Postoperative AHD was found to be in a directly proportional relationship with AE (r s :0.49; p:0.03). Postoperative ABD showed an inverse linear regression with preoperative AHD (r s : -0.44, p:0.047). LSA and DSA were inversely related. Conclusion:  We found that a DSA between 40-45° and a LSA of 80-100° could lead to better range of motion regarding AE and ABD in patients with rotator cuff arthropathy treated with RSA.

Impact of constrained humeral liner on impingement-free range of motion and impingement type in reverse shoulder arthroplasty using a computer simulation

BACKGROUND

Dislocation is a major complication of reverse total shoulder arthroplasty (RSA). The humeral liner may be changed to a constrained type when stability does not improve by increasing glenosphere size or lateralization with implants, and patients, particularly women with obesity, have risks of periprosthetic instability that may be secondary to hinge adduction on the thorax, but there are few reports on its impact on the range of motion (ROM). This study aimed to determine the influence of humeral liner constraint on impingement-free ROM and impingement type using an RSA computer simulation model.

METHODS

A virtual simulation model was created using 3D measurement software for conducting a simulation study. This study included 25 patients with rotator cuff tears and rotator cuff tear arthropathy. Impingement-free ROM and impingement patterns were measured during flexion, extension, abduction, adduction, external rotation, and internal rotation. Twenty-five cases with a total of 4 patterns of 2 multiplied by 2, making a total of 100 simulations: glenosphere (38 mm normal type vs. lateralized type) and humeral liner constraint (normal type vs. constrained type). There were 4 combinations: normal glenosphere and normal humeral liner, normal glenosphere and constrained humeral liner, lateralized glenosphere and normal humeral liner, and lateralized glenosphere and constrained humeral liner.

RESULTS

Significant differences were found in all impingement-free ROM in 1-way analysis of variance (abduction: P = .01, adduction: P < .01, flexion: P = .01, extension: P = .02, external rotation: P < .01, and internal rotation: P < .01). Tukey's post hoc tests showed that the impingement-free ROM was reduced during abduction, external rotation, and internal rotation with the combination of the normal glenosphere and constrained humeral liner compared with the other combinations, and improved by glenoid lateralization compared with the combination of the lateralized glenosphere and constrained humeral liner. In the impingement pattern, the Pearson χ2 test showed significantly greater proportion of impingement of the humeral liner into the superior part of the glenoid neck in abduction occurring in the combination of the normal glenosphere and constrained humeral liner group compared with the other groups (P < .01). Bonferroni post hoc tests revealed that the combination of the normal glenosphere and constrained humeral liner was significantly different from that of the lateralized glenosphere and constrained humeral liner (P < .01). Using constrained liners resulted in early impingement on the superior part of the glenoid neck in the normal glenosphere, whereas glenoid lateralization increased impingement-free ROM.

CONCLUSION

This RSA computer simulation model demonstrated that constrained humeral liners led to decreased impingement-free ROM. However, using the lateralized glenosphere improved abduction ROM.

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.

Glenoid component placement in reverse shoulder arthroplasty assisted with augmented reality through a head-mounted display leads to low deviation between planned and postoperative parameters

BACKGROUND

Navigated augmented reality (AR) through a head-mounted display (HMD) may lead to accurate glenoid component placement in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the deviation between planned, intra- and postoperative inclination, retroversion, entry point, depth, and rotation of the glenoid component placement assisted by a navigated AR through HMD during RSA.

METHODS

Both shoulders of 6 fresh frozen human cadavers, free from fractures or other bony pathologies, were used. Preoperative computed tomography (CT) scans were used for the 3-dimensional (3D) planning. The glenoid component placement was assisted using a navigated AR system through an HMD in all specimens. Intraoperative inclination, retroversion, depth, and rotation were measured by the system. A postoperative CT scan was performed. The pre- and postoperative 3D CT scan reconstructions were superimposed to calculate the deviation between planned and postoperative inclination, retroversion, entry point, depth, and rotation of the glenoid component placement. Additionally, a comparison between intra- and postoperative values was calculated. Outliers were defined as >10° inclination, >10° retroversion, >3 mm entry point.

RESULTS

The registration algorithm of the scapulae prior to the procedure was correctly completed for all cases. The deviations between planned and postoperative values were 1.0° ± 0.7° for inclination, 1.8° ± 1.3° for retroversion, 1.1 ± 0.4 mm for entry point, 0.7 ± 0.6 mm for depth, and 1.7° ± 1.6° for rotation. The deviation between intra- and postoperative values were 0.9° ± 0.8° for inclination, 1.2° ± 1.1° for retroversion, 0.6 ± 0.5 mm for depth, and 0.3° ± 0.2° for rotation. There were no outliers between planned and postoperative parameters.

CONCLUSION

In this study, the use of a navigated AR system through an HMD for RSA led to low deviation between planned and postoperative values and between intra- and postoperative parameters.

Angled BIO-RSA leads to better inclination and clinical outcomes compared to Standard BIO-RSA and eccentric reaming: A comparative study

Background

Two surgical techniques were compared : Standard BIO-RSA, performed with a glenoid eccentric reaming along with a cylindric bone graft augmentation vs. the Angled BIO-RSA, performed with a glenoid concentric reaming and a defect correction with an angled bone graft.

Methods

Patients undergoing RSA from January 2016 to April 2019, with one of the two techniques being performed, were retrospectively reviewed. Glenoids were classified according to Favard. Clinical (Constant-Murley, VAS and ROM) and radiographic (superior tilt correction) data were collected pre-operatively and at 12 months post-operatively.

Results

141 shoulders were included. Angled BIO-RSA group showed statistically significant better outcomes in terms of forward flexion (149.9° Vs 139.3°) and abduction (136.4° Vs 126.7°). The use of an Angled BIO-RSA showed a statistically significant better superior tilt correction (1.252° Vs 4.09°). Angled BIO-RSA, leads to a better inclination correction and a mean postoperative tilt value inferior to 5° in E1 and E3 differently from standard BIO-RSA.

Discussion

Both techniques were able to correct glenoid superior inclination with excellent postoperative short-term results. However, angled BIO-RSA technique appears to be more effective in ensuring a correct inclination of the prosthetic glenoid component with better clinical outcomes.

Comparative Analysis of Eccentric Glenosphere in Reverse Total Shoulder Arthroplasty: A Computer Simulation Study

Objective

The aim was to evaluate the effects of different glenosphere eccentricities on impingement, range of motion (ROM), and muscle length during standard activities in reverse total shoulder arthroplasty (RSA).

Methods

In this study, we utilized computational modeling techniques to create native shoulder and shoulder models undergoing RSA and simulate shoulder movements in all abduction-adduction, flexion-extension, and rotation. We tested a total of 36 different glenosphere configurations, which included three different inferior tilts (0°, +10°, +20°) and two different lateral offsets (0 mm and +4 mm), as well as six different glenosphere eccentricities (concentricity, inferior, posterior, anterior, anteroinferior, and posteroinferior). We evaluated the maximum impingement-free ROM, impingement sites, and muscle lengths.

Results

All glenosphere configurations exceeded 50% of native shoulder ROM in three planes and total global ROM. In abduction-adduction, there was no significant difference among the different glenosphere eccentricities (p > 0.05). In flexion-extension, the posteroinferior eccentricity had the maximum ROM among the different eccentricities, but no significant difference among the different glenosphere eccentricities (p > 0.05). In rotation, there was a significant difference overall, and anteroinferior eccentricity had a significant advantage over concentricity (p < 0.05). In total global ROM, anteroinferior eccentricity had a significant advantage over concentricity when lateral offset was 0 mm (p < 0.05). In all models of glenosphere eccentricities, only the elongation of the infraspinatus muscle was statistically significant (p < 0.05).

Conclusion

Glenosphere eccentricity significantly influenced rotation, total global ROM, and the length of the subscapularis muscle. Among them, anteroinferior offset achieved the maximum ROM in abduction-adduction, rotation, and total global activities. Both anteroinferior and inferior glenoid eccentricity showed significant advantages over the concentricity in rotation and total global ROM.

Level of Evidence

Basic Science Study; Computer Modeling.

The Real Post-Operative Range of Motion Differs from the Virtual Pre-Operative Planned Range of Motion in Reverse Shoulder Arthroplasty

INTRODUCTION

The purpose of this study was to analyze the real range of motion (RoM) measured in patients operated on for reverse shoulder arthroplasty (RSA) and compare it to the virtual RoM provided by the preoperative planning software.

HYPOTHESIS

There was a difference between virtual and real RoM, which can be explained by different factors, specifically the scapula-thoracic (ST) joint.

METHODS

Twenty patients with RSA were assessed at a minimum follow-up of 18 months. Passive RoM in forward elevation abduction, without and with manually locking the ST joint, and in external rotation with arm at side were recorded. The humerus, scapula, and implants were manually segmented on post-operative CTs. Post-operative bony structures were registered to preoperative bony elements. From this registration, a post-operative plan corresponding to the real post-operative implant positioning was generated and the corresponding virtual RoM analysis was recorded. On the post-operative anteroposterior X-rays and 2D-CT coronal planning view, the glenoid horizontal line angle (GH), the metaphyseal horizontal line angle (MH), and the gleno-metaphyseal angle (GMA) were measured to assess the extrinsic glenoid inclination, as well as the relative position of the humeral and glenoid components.

RESULTS

There were some significant differences between virtual and post-operative passive abduction and forward elevation, with (55° and 50°, p < 0.0001) or without ST joint participation (15° and 27°, p < 0.002). For external rotation with arm at side, there was no significant difference between planning (24° ± 26°) and post-operative clinical observation (19° ± 12°) (p = 0.38). For the angle measurements, the GMA was significantly higher (42.8° ± 15.2° vs. 29.1°± 18.2°, p < 0.0001), and the GH angle, significantly lower on the virtual planning (85.2° ± 8.8° vs. 99.5° ± 12.5°, p < 0.0001), while the MH was not different (p = 0.33).

CONCLUSIONS

The virtual RoM given by the planning software used in this study differs from the real post-operative passive RoM, except for external rotation. This can be explained by the lack of ST joint and soft tissues simulation. However, in focusing on the virtual GH participation, the simulation looks informative. Some modifications between the glenoid and humerus starting positions before running the motion analysis could be provided for making it more realistic and predictive of the RSA functional results.

LEVEL OF EVIDENCE

III.

Reverse shoulder arthroplasty using an onlay humeral prosthesis, offset humeral tray, and augmented glenoid baseplate: surgical technique and review of the impact of prosthesis design on scapular fractures following reverse shoulder arthroplasty

Reverse total shoulder arthroplasty (RSA) has become the most utilized form of arthroplasty of the shoulder. Acromial stress fractures and scapular spine stress fractures are rare, yet well-recognized complications of RSA with ongoing studies identifying whether patient factors or prosthetic designs serve as risk factors. Specifically, it remains unclear if or how the position of the humeral tray (inlay or onlay) in RSA affects rates of periscapular fractures. The purpose of this article is to describe our technique for RSA using an onlay prosthesis, a variable-offset humeral tray, and an augmented glenoid baseplate, as well as to review the published results of acromial and scapular spine fractures after RSA based on humeral implant design.

Treatment of proximal humerus fractures using reverse shoulder arthroplasty: do the inclination of the humeral component and the lateral offset of the glenosphere influence the clinical outcome and tuberosity healing?

INTRODUCTION

The employment of reverse shoulder arthroplasty for dislocated proximal humerus fractures of elderly patients becomes increasingly relevant. The standard inclination angle of the humeral component was 155°. Lately, there is a trend towards smaller inclination angles of 145° or 135°. Additionally, there has been an increased focus on the lateralization of the glenosphere. This retrospective comparative study evaluates clinical and radiological results of patients treated for proximal humerus fractures by reverse shoulder arthroplasty with different inclination angles of the humeral component, which was either 135° or 155°. Additionally, a different lateral offset of the glenosphere, which was either 0 mm or 4 mm, was used.

METHODS

For this retrospective comparative analysis, 58 out of 66 patients treated by reverse total shoulder arthroplasty for proximal humerus fractures were included. The minimum follow-up was 24 months. Thirty (m = 3, f = 27; mean age 78 years; mean FU 35 months, range 24-58 months) were treated with a standard 155° humeral component and a glenosphere without lateral offset (group A), while 28 patients (m = 2, f = 26; mean age 79 years; mean FU 30 months, range 24-46 months) were treated with a 135° humeral component and a glenosphere with a 4 mm lateral offset (group B). We determined range of motion, Constant score, and the American Shoulder and Elbow Surgeons Shoulder score as clinical outcomes and evaluated tuberosity healing as well as scapula notching.

RESULTS

Neither forward flexion (A = 128°, B = 121°; p = 0.710) nor abduction (A = 111°, B = 106°; p = 0.327) revealed differences between the groups. The mean Constant Score rated 63 in group A, while it was 61 in group B (p = 0.350). There were no differences of the ASES Score between the groups (A = 74, B = 72; p = 0.270). There was an increased risk for scapula notching in group A (47%) in comparison to group B (4%, p = 0.001). Healing of the greater tuberosity was achieved in 57% of group A and in 75% of group B (p = 0.142). The healing rate of the lesser tuberosity measured 33% in group A and 71% in group B (p = 0.004).

CONCLUSIONS

Both inclination angles of the humeral component are feasible options for the treatment of proximal humerus fractures in elderly patients. Neither the inclination angle nor the lateral offset of the glenosphere seem to have a relevant influence on the clinical outcome. The healing rate of the lesser tuberosity was higher in implants with a decreased neck-shaft angle. There is an increased risk for scapula notching, if a higher inclination angle of the humeral component is chosen.

LEVEL OF EVIDENCE

III. Retrospective comparative study.

Factors affecting internal rotation following total shoulder arthroplasty

Background

Reverse shoulder arthroplasty (RSA) was developed in the late twentieth century to provide a stable arthroplasty option for patients with rotator cuff deficiency arthropathy. Since its inception, there have been changes in materials, design, and positioning. One of the persistent clinical issues has been difficulty with internal rotation (IR) and the associated difficulty with behind the back activities. Implant design, positioning, and the available soft tissues may influence IR after RSA. The purpose of this systematic review is to assess factors that impact IR following RSA.

Methods

The literature search, based on PRISMA guidelines, used 4 databases: Pubmed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials. We included clinical trials that compared different implantation and design modifications and assessed IR.

Results

Of the 617 articles identified in the initial search, 46 satisfied the inclusion criteria. The articles explored multiple factors of RSA and their effects on IR, including humeral and glenoid components and muscle function and integrity. Among humeral factors affecting rotation, there was a broad consensus that: IR decreases as retroversion increases, humeral neck-shaft angle less than 155° improves IR, lateralized humeral offset does not improve IR, and shallow cups improve IR. Insert thickness was not associated with a reproducible effect. Of the studies evaluating the effect of glenoid components, there was majority agreement that glenosphere lateralization improved IR, and there were mixed results regarding the effects of glenosphere size and tilt. Others included one study in each: glenoid overhang, retroversion, and baseplate. One study found an association between teres minor insufficiency and improved IR, with mixed results in the presence of fatty infiltration in both teres minor and subscapularis. Most studies noted subscapularis repair had no effect on IR.

Conclusion

Prosthetic variables affecting IR are not widely studied. Based on the existing literature, evidence is conflicting. More research needs to be undertaken to gain a greater understanding regarding which factors can be modified to improve IR in RSA patients.

Considerations for Shoulder Arthroplasty Implant Selection in Primary Glenohumeral Arthritis With Posterior Glenoid Deformity

Glenoid deformity has an important effect on outcomes and complication rates after shoulder arthroplasty for primary glenohumeral arthritis. The B2/B3 glenoid has particularly been associated with a poorer outcome with shoulder arthroplasty compared with other glenoid types. One of the primary challenges is striking a balance between deformity correction and joint line preservation. Recently, there has been a proliferation of both anatomic and reverse implants that may be used to address glenoid deformity. The purpose of this review was to provide an evidence-based approach for addressing glenoid deformity associated with primary glenohumeral arthritis.

Patient-specific instrumentation reduces deviations between planned and postosteotomy humeral retrotorsion and height in shoulder arthroplasty

BACKGROUND

Patient-specific instrumentation (PSI) may potentially improve humeral osteotomy in shoulder arthroplasty. The purpose of this study was to compare the deviation between planned and postosteotomy humeral inclination, retrotorsion, and height in shoulder arthroplasty, using PSI vs. standard cutting guides (SCG).

METHODS

Twenty fresh-frozen cadaveric specimens were allocated to undergo humeral osteotomy using either PSI or SCG, such that the 2 groups have similar age, gender, and side. Preosteotomy computed tomography (CT) scan was performed and used for the 3-dimensional (3D) planning. The osteotomy procedure was performed using a PSI designed for each specimen or an SCG depending on the group. A postosteotomy CT scan was performed. The preosteotomy and postosteotomy 3D CT scan reconstructions were superimposed to calculate the deviation between planned and postosteotomy inclination, retrotorsion, and height. Outliers were defined as cases with 1 or more of the following deviations: >5° inclination, >10° retrotorsion, and >3 mm height. The deviation and outliers in inclination, retrotorsion, and height were compared between the 2 groups.

RESULTS

The deviations between planned and postosteotomy parameters were similar among the PSI and SCG groups for inclination (P = .260), whereas they were significantly greater in the SCG group for retrotorsion (P < .001) and height (P = .003). There were 8 outliers in the SCG group, compared with only 1 outlier in the PSI group (P = .005). Most outliers in the SCG group were due to deviation >10° in retrotorsion.

CONCLUSION

After 3D planning, PSI had less deviation between planned and postosteotomy humeral retrotorsion and height, relative to SCG.

Innovations in Shoulder Arthroplasty

Innovations currently available with anatomic total shoulder arthroplasty include shorter stem designs and augmented/inset/inlay glenoid components. Regarding reverse shoulder arthroplasty (RSA), metal augmentation, including custom augments, on both the glenoid and humeral side have expanded indications in cases of bone loss. In the setting of revision arthroplasty, humeral options include convertible stems and newer tools to improve humeral implant removal. New strategies for treatment and surgical techniques have been developed for recalcitrant shoulder instability, acromial fractures, and infections after RSA. Finally, computer planning, navigation, PSI, and augmented reality are imaging options now available that have redefined preoperative planning and indications as well intraoperative component placement. This review covers many of the innovations in the realm of shoulder arthroplasty.

Glenoid Component Placement Assisted by Augmented Reality Through a Head-Mounted Display During Reverse Shoulder Arthroplasty

Component positioning is a key factor for avoiding complications and improving functional outcomes in reverse shoulder arthroplasty. Preoperative planning can improve component positioning. However, translating the preoperative plan into the surgical procedure can be challenging. This is particularly the case for the glenoid component positioning in severe deformity or limited visualization of the scapula. Different computational-assisted techniques have been developed to aid implementation of the preoperative plan into the surgical procedure. Navigated augmented reality (AR) refers to the real world augmented with virtual real-time information about the position and orientation of instruments and components. This information can be presented through a head-mounted display (HMD), which enables the user to visualize the virtual information directly overlaid onto the real world. Navigated AR systems through HMD have been validated for shoulder arthroplasty using phantoms and cadavers. This article details a step-by-step guide use of a navigated AR system through HMD, in the placement of the glenoid bony-augmented component.

Patient Posture Affects Simulated ROM in Reverse Total Shoulder Arthroplasty: A Modeling Study Using Preoperative Planning Software

BACKGROUND

Component selection and placement in reverse total shoulder arthroplasty (RTSA) is still being debated. Recently, scapulothoracic orientation and posture have emerged as relevant factors when planning an RTSA. However, the degree to which those parameters may influence ROM and whether modifiable elements of implant configuration may be helpful in improving ROM among patients with different postures have not been thoroughly studied, and modeling them may be instructive.

QUESTIONS/PURPOSES

Using a dedicated expansion of a conventional preoperative planning software, we asked: (1) How is patient posture likely to influence simulated ROM after virtual RTSA implantation? (2) Do changes in implant configuration, such as humeral component inclination and retrotorsion, or glenoid component size and centricity improve the simulated ROM after virtual RTSA implantation in patients with different posture types?

METHODS

In a computer laboratory study, available whole-torso CT scans of 30 patients (20 males and 10 females with a mean age of 65 ± 17 years) were analyzed to determine the posture type (Type A, upright posture, retracted scapulae; Type B, intermediate; Type C, kyphotic posture with protracted scapulae) based on the measured scapula internal rotation as previously described. The measurement of scapular internal rotation, which defines these posture types, was found to have a high intraclass correlation coefficient (0.87) in a previous study, suggesting reliability of the employed classification. Three shoulder surgeons each independently virtually implanted a short, curved, metaphyseal impaction stem RTSA in each patient using three-dimensional (3D) preoperative surgical planning software. Modifications based on the original component positioning were automatically generated, including different humeral component retrotorsion (0°, 20°, and 40° of anatomic and scapular internal rotation) and neck-shaft angle (135°, 145°, and 155°) as well as glenoid component configuration (36-mm concentric, 36-mm eccentric, and 42-mm concentric), resulting in 3720 different RTSA configurations. For each configuration, the maximum potential ROM in different planes was determined by the software, and the effect of different posture types was analyzed by comparing subgroups.

RESULTS

Irrespective of the RTSA implant configuration, the posture types had a strong effect on the calculated ROM in all planes of motion, except for flexion. In particular, simulated ROM in patients with Type C compared with Type A posture demonstrated inferior adduction (median 5° [interquartile range -7° to 20°] versus 15° [IQR 7° to 22°]; p < 0.01), abduction (63° [IQR 48° to 78°] versus 72° [IQR 63° to 82°]; p < 0.01), extension (4° [IQR -8° to 12°] versus 19° [IQR 8° to 27°]; p < 0.01), and external rotation (7° [IQR -5° to 22°] versus 28° [IQR 13° to 39°]; p < 0.01). Lower retrotorsion and a higher neck-shaft angle of the humeral component as well as a small concentric glenosphere resulted in worse overall ROM in patients with Type C posture, with severe restriction of motion in adduction, extension, and external rotation to below 0°.

CONCLUSION

Different posture types affect the ROM after simulated RTSA implantation, regardless of implant configuration. An individualized choice of component configuration based on scapulothoracic orientation seems to attenuate the negative effects of posture Type B and C. Future studies on ROM after RTSA should consider patient posture and scapulothoracic orientation.

CLINICAL RELEVANCE

In patients with Type C posture, higher retrotorsion, a lower neck-shaft angle, and a larger or inferior eccentric glenosphere seem to be advantageous.

Influence of scapular neck length on the extent of impingement-free adduction after reverse total shoulder arthroplasty

BACKGROUND

Following reverse total shoulder arthroplasty, a short scapular neck length (SNL) decreases postoperative impingement-free adduction, and impingement between the neck of the scapula and the humeral polyethylene cup may cause scapular notching. However, no reports have evaluated the influence of SNL on impingement-free adduction. The purposes of this study were to evaluate the influence of SNL on impingement-free adduction and to examine the effect of glenoid component lateralization and inferiorization on impingement-free adduction.

METHODS

By use of 3-dimensional templating software, a virtual reverse total shoulder arthroplasty model was created in 15 patients who had no osteoarthritic change or any other bony deformity. We measured SNLs separately before implant placement (preoperative SNL) and after implant placement (postoperative SNL). The implant used was the Comprehensive Reverse Shoulder System (Zimmer Biomet, Warsaw, IN, USA), and baseplate bony lateralization of 0, 5, and 10 mm, with inferior eccentricity of 0.5 or 4.5 mm, was tested for impingement-free adduction. Correlations between the preoperative and postoperative SNLs and impingement-free adduction were analyzed.

RESULTS

The mean preoperative SNL was 8.2 ± 1.9 mm (range, 5.0-11.7 mm), and the mean postoperative SNL was 6.0 ± 2.0 mm (range, 2.1-9.8 mm). There was a moderate correlation between the preoperative SNL and impingement-free adduction (r = 0.628, P = .12) and a strong correlation between the postoperative SNL and impingement-free adduction (r = 0.771, P = .001). Use of the model with 10 mm of bony lateralization and 4.5 mm of inferior eccentricity provided the best results in terms of impingement-free adduction.

CONCLUSION

There were correlations between both the preoperative and postoperative SNLs and impingement-free adduction. Although the lateralized and inferiorized center of rotation may increase the risk of loosening of the glenoid component, this offset significantly increased impingement-free adduction.

Relationship between postoperative integrity of subscapularis tendon and functional outcome in reverse shoulder arthroplasty

HYPOTHESIS AND BACKGROUND

The role of the subscapularis in reverse shoulder arthroplasty (RSA) remains controversial. Studies have shown that subscapularis repair has no significant influence on the functional outcomes of patients. However, few studies have assessed the postoperative integrity of the subscapularis tendon after RSA. The aims of this study were to investigate the postoperative healing of the subscapularis after RSA via ultrasound and to evaluate the relationship between tendon integrity and functional outcomes. We hypothesized that subjects with a healed subscapularis after RSA would have higher Constant scores and better internal rotation (IR) than those without a healed subscapularis.

METHODS

This was a retrospective review of all patients who underwent primary RSA with subscapularis tenotomy repair performed by a single surgeon with a minimum 2-year follow-up period. The inclusion criteria were (1) primary RSA and (2) complete intraoperative repair of the subscapularis tenotomy if the tendon was amenable to repair. The total Constant score and active and passive range of motion were measured preoperatively and at every postoperative visit. IR was further subcategorized into 3 functional types (type I, buttock or sacrum; type II, lumbar region; and type III, T12 or higher). The integrity of the subscapularis on ultrasound at 2 years was reported using the Sugaya classification. The correlation between subscapularis integrity and functional outcomes including functional IR was evaluated.

RESULTS

A total of 86 patients (mean age, 73 ± 7.4 years; age range, 50-89 years) were evaluated. The mean postoperative Constant score for all patients significantly improved from 38 points to 72 points (P < .001) at last follow-up (mean, 3.3 years). There was significant improvement in all Constant score functional subscales and in terms of range of motion. The rate of sonographic healing of the subscapularis was 52.6%. There was no difference in Constant scores between "intact" and "failed" tendon repairs; however, intact tendons demonstrated significantly better IR with no difference in external rotation (P < .01).

CONCLUSION

The healing rate of the subscapularis following RSA was only 52.6%. IR function in patients with an intact subscapularis at 2 years after RSA was significantly better than in patients with failed or absent tendon repairs. Primary repair of reparable subscapularis tendons during RSA should be strongly considered.

Lateralization in Reverse Shoulder Arthroplasty

Indications for Reverse Shoulder Arthroplasty (RSA) have been extended over the last 25 years, and RSA has become the most frequently implanted shoulder arthroplasty worldwide. The initial Grammont design with medialization of the joint center of rotation (JCOR), placement of the JCOR at the bone–implant interface, distalization and semi-constrained configuration has been associated with drawbacks such as reduced rotation and range of motion (ROM), notching, instability and loss of shoulder contour. This review summarizes new strategies to overcome these drawbacks and analyzes the use of glenoid-sided, humeral-sided or global bipolar lateralization, which are applied differently by surgeons and current implant manufacturers. Advantages and drawbacks are discussed. There is evidence that lateralization addresses the initial drawbacks of the Grammont design, improving stability, rates of notching, ROM and shoulder contour, but the ideal extent of lateralization of the glenoid and humerus remains unclear, as well as the maximal acceptable joint reaction force after reduction. Overstuffing and spine of scapula fractures are potential risks. CT-based 3D planning as well as artificial intelligence will help surgeons with planning and execution of appropriate lateralization in RSA. Long-term follow-up of lateralization with new implant designs and implantation strategies is needed.

Mechanical complications and fractures after reverse shoulder arthroplasty related to different design types and their rates: part I

The initial reverse shoulder arthroplasty (RSA), designed by Paul Grammont, was intended to treat rotator cuff tear arthropathy in elderly patients. In the early experience, high complication rates (up to 24%) and revision rates (up to 50%) were reported.The most common complications reported were scapular notching, whereas clinically more relevant complications such as instability and acromial fractures were less commonly described.Zumstein et al defined a 'complication' following RSA as any intraoperative or postoperative event that was likely to have a negative influence on the patient's final outcome.High rates of complications related to the Grammont RSA design led to development of non-Grammont designs, with 135 or 145 degrees of humeral inclination, multiple options for glenosphere size and eccentricity, improved baseplate fixation which facilitated glenoid-sided lateralization, and the option of humeral-sided lateralization.Improved implant characteristics combined with surgeon experience led to a dramatic fall in the majority of complications. However, we still lack a suitable solution for several complications, such as acromial stress fracture. Cite this article: EFORT Open Rev 2021;6:1097-1108. DOI: 10.1302/2058-5241.6.210039.

Biomechanics of anatomic and reverse shoulder arthroplasty

The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics.With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening.The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis.The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont's reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the deltoid moment arm.More modern reverse designs have maintained the element of restored stability but sought a more anatomic postoperative position to minimize complications and maximize rotational range of motion. Cite this article: EFORT Open Rev 2021;6:918-931. DOI: 10.1302/2058-5241.6.210014.

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.

Lateralized versus nonlateralized reverse total shoulder arthroplasty

Throughout the history of reverse total shoulder arthroplasty, the extent of lateral offset has changed considerably from "too lateral" to "too medial" and has been lately swinging back towards a point somewhere in between. Nonlateralized designs minimize shear forces on the glenoid and decrease force required by the deltoid. Glenoid lateralization decreases impingement and scapular notching and improves range of motion. Humeral lateralization achieves a more anatomic position of the tuberosities while maintaining a nonlateralized center of rotation. Several factors play a role in choosing the extent of lateral offset and method of lateralization.

Treating cuff tear arthropathy by reverse total shoulder arthroplasty: do the inclination of the humeral component and the lateral offset of the glenosphere influence the clinical and the radiological outcome?

PURPOSE

Reverse total shoulder arthroplasty is widely used for the treatment of cuff tear arthropathy. Standard implants consist of a humeral component with an inclination angle of 155° and a glenosphere without lateral offset. Recently, lower inclination angles of the humeral component as well as lateralized glenospheres are implanted to provide better rotation of the arm and to decrease the rate of scapular notching. This study investigates the clinical and radiological results of a standard reverse total shoulder in comparison with an implant with an inclination angle of 135° in combination with a 4 mm lateralized glenosphere in context of cuff tear arthropathy.

MATERIAL AND METHODS

For this retrospective comparative analysis 42 patients treated by reverse total shoulder arthroplasty for cuff tear arthropathy were included. Twenty-one patients (m = 11, f = 10; mean age 76 years; mean follow-up 42 months) were treated with a standard 155° humeral component and a standard glenosphere with caudal eccentricity (group A), while twenty-one patients (m = 5, f = 16; mean age 72 years; mean follow-up 34 months) were treated with a 135° humeral component and 4 mm lateral offset of the glenosphere (group B). At follow-up patients of both groups were assessed with plain X-rays (a.p. and axial view), Constant Score, adjusted Constant Score, the subjective shoulder value and the range of motion.

RESULTS

The clinical results were similar in both groups concerning the Constant Score (group A = 56.3 vs. group B = 56.1; p = 0.733), the adjusted CS (group A = 70.4% vs. group B = 68.3%; p = 0.589) and the SSV (group A = 72.0% vs. group B = 75.2%; p = 0.947). The range of motion of the operated shoulders did not differ significantly between group A and group B: Abduction = 98° versus 97.9°, p = 0.655; external rotation with the arm at side = 17.9° versus 18.7°, p = 0.703; external rotation with the arm positioned in 90° of abduction = 22.3° versus 24.7°, p = 0.524; forward flexion = 116.1° versus 116.7°, p = 0.760. The rate of scapular notching was higher (p = 0.013) in group A (overall: 66%, grade 1: 29%, grade 2: 29%, grade 3: 10%, grade 4: 0%) in comparison to group B (overall: 33%, grade 1: 33%, grade 2: 0%, grade 3: 0%, grade 4: 0%). Radiolucency around the humeral component was detected in two patients of group B. Stress shielding at the proximal humerus was observed in six patients of Group A (29%; cortical thinning and osteopenia in zone M1 and L1) and two patients of group B (10%; cortical thinning and osteopenia in zone M1 and L1). Calcifications of the triceps origin were observed in both groups (group A = 48% vs. group B = 38%).

CONCLUSION

Theoretically, a lower inclination angle of the humeral component and an increased lateral offset of the glenosphere lead to improved impingement-free range of motion and a decreased rate of scapular notching, when compared to a standard reverse total shoulder implant. This study compared two different designs of numerous options concerning the humeral component and the glenosphere. In comparison to a standard-fashioned implant with a humeral inclination of 155° and a standard glenosphere, implants with a humeral inclination angle of 135° and a 4 mm lateralized glenosphere lead to comparable clinical results and rotatory function, while the rate of scapular notching is decreased by almost 50%. While the different implant designs did not affect the clinical outcome, our results indicate that a combination of a lower inclination angle of the humeral component and lateralized glenosphere should be favored to reduce scapular notching.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Factors Influencing Appropriate Implant Selection and Position in Reverse Total Shoulder Arthroplasty

Reverse shoulder arthroplasty has increased in popularity and has provided improved but somewhat variable results. These variable outcomes may be related to many factors, including implant design, component positioning, specific indication, and patient anatomy. The original Grammont design provided a solution to the high failure rate at the time but was found to have a high rate of scapular notching and poor restoration of rotation. Modern lateralized designs are more consistent in reducing scapular notching while improving range of motion, especially in regards to external rotation. This review article summarizes the effects of modern reverse shoulder prostheses on outcomes.

Reverse total shoulder arthroplasty clinical and patient-reported outcomes and complications stratified by preoperative diagnosis: a systematic review

OBJECTIVE

This systematic review aimed to investigate differences in clinical outcomes, patient-reported outcomes (PROs), and complication types and rates among preoperative diagnoses following reverse total shoulder arthroplasty (RTSA): rotator cuff tear arthropathy, primary osteoarthritis, massive irreparable rotator cuff tear, proximal humeral fracture, rheumatoid arthritis (RA), and revision of anatomic arthroplasty (Rev).

LITERATURE SEARCH

Three electronic databases were searched from inception to January 2020.

STUDY SELECTION CRITERIA

The inclusion criteria were (1) patients with a minimum age of 60 years who underwent RTSA for the stated preoperative diagnoses, (2) a minimum of 2 years' follow-up, and (3) preoperative and postoperative values for clinical outcomes and PROs.

DATA SYNTHESIS

Risk of bias was determined by the Methodological Index for Non-randomized Studies tool and the modified Downs and Black tool. Weighted means for clinical outcomes and PROs were calculated for each preoperative diagnosis.

RESULTS

A total of 53 studies were included, of which 36 (68%) were level IV retrospective case series. According to the Methodological Index for Non-randomized Studies tool, 33 studies (62%) showed a high risk of bias; the 3 randomized controlled trials showed a low risk of bias on the modified Downs and Black tool. RTSA improved clinical outcomes and PROs for all preoperative diagnoses. The Rev group had poorer final outcomes as noted by a lower American Shoulder and Elbow Surgeons score (69) and lower pain score (1.8) compared with the other preoperative diagnoses (78-82 and 0.4-1.4, respectively). The RA group showed the highest complication rate (28%), whereas the osteoarthritis group showed the lowest rate (1.4%).

CONCLUSION

Studies in the RTSA literature predominantly showed a high risk of bias. All preoperative diagnoses showed improvements; Rev patients showed the worse clinical outcomes and PROs, and RA patients showed higher complication rates. The preoperative diagnosis in RTSA patients can impact outcomes and complications.

A systematic review of tuberosity healing and outcomes following reverse shoulder arthroplasty for fracture according to humeral inclination of the prosthesis

BACKGROUND

Proximal humerus fractures are common in the elderly population and are often treated with reverse shoulder arthroplasty (RSA). The purpose of this systematic review was to compare tuberosity healing and functional outcomes in patients undergoing RSA with humeral inclinations of 135°, 145°, and 155°.

METHODS

A systematic review was performed of RSA for proximal humerus fracture using Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guidelines. Radiographic and functional outcome data were extracted to evaluate tuberosity healing according to humeral inclination. Analysis was also performed of healed vs. nonhealed tuberosities.

RESULTS

A total of 873 patients in 21 studies were included in the analysis. The mean age was 77.5 years (range of 58-97) and the mean follow-up was 26.2 months. Tuberosity healing was 83% in the 135° group compared with 69% in the 145° group and 66% in the 155° group (P = .030). Postoperative abduction was highest in the 155° group (P < .001). No significant difference was found in forward flexion, external rotation, or postoperative Constant score between groups. Patients with tuberosity healing demonstrated 18° higher forward flexion (P = .008) and 16° greater external rotation (P < .001) than those with unhealed tuberosities.

CONCLUSION

RSA for fracture with 135° humeral inclination is associated with higher tuberosity healing rates compared with 145° or 155°. Postoperative abduction is highest with a 155° implant, but there is no difference in in postoperative forward flexion, external rotation, or Constant score according to humeral inclination. Patients with healed tuberosities have superior postoperative forward flexion and external rotation than those with unhealed tuberosities.