The impact of scapular notching on reverse shoulder glenoid fixation

The effect of humeral tray thickness on glenohumeral loads in a reverse shoulder 'smart' implant

PURPOSE

The aim of this study was to observe the effects of changing humeral tray thickness on the resultant of intraoperative glenohumeral joint loads using a load-sensing system (LSS).

METHODS

An rTSA was performed on fresh frozen full-body cadaver shoulders by using an internal proprietary LSS on the humeral side. The glenohumeral loads (Newtons) and the direction of the resultant force applied on the implant were recorded during four standard positions (External rotation, Extension, Abduction, Flexion) and three "complex" positions of Activity Daily Life ("behind back", "overhead reach" and "across chest"). For each position, the thickness was increased from 0 to 6 mm in a continuous fashion using the adjustment feature of the humeral system. Each manoeuvre was repeated three times.

RESULTS

All shoulder positions showed a high repeatability of the glenohumeral load magnitude measured with an intra-class correlation coefficient of over 0.9. For each position, we observed a strong but no linear correlation between humeral tray thickness and joint loads. It was a cubical correlation (rs = 0,91) with a short ascending phase, then a plateau phase, and finally a phase with an exponential growth of the loads on the humeral implant. In addition, an increase in trail-poly thickness led to a recentering of force application at the interface of the two glenohumeral implants.

CONCLUSION

This study provides further insight into the effects of humeral implant thickness on rTSA glenohumeral joint loads during different positions of the arm. Data obtained using this type of device could guide surgeons in finding the proper implant balance during rTSA.

The Delta III and Delta Xtend reverse shoulder arthroplasty-risk of revision and failure mechanisms: a report on 3650 cases from the Norwegian Arthroplasty Register 1994-2021

BACKGROUND

The Delta reverse shoulder arthroplasty (RSA) is commonly used worldwide and is the most frequently used RSA in Norway. The aim of this registry-based study was to report 10- and 20-year implant survival, risk of revision, and reasons for revision in 2 consecutive time periods for Delta III (1994-2010) and Delta Xtend (2007-2021) prostheses.

METHODS

We included 3650 primary RSAs reported to the Norwegian Arthroplasty Register: 315 Delta III (42% cemented stems) and 3335 Delta Xtend (88% cemented stems). We used Kaplan-Meier analyses to investigate implant survival. The reasons for revision were compared for the 2 designs and fixation technique. Factors that could influence the risk of revision, such as implant design, fixation technique, and patient factors, were investigated using Cox regression analyses with adjustments for age, sex, and diagnosis.

RESULTS

Patients operated with Delta III were more likely to be diagnosed with inflammatory disease or fracture sequela, whereas acute fracture, osteoarthritis, and cuff arthropathy were the most frequent indications for Delta Xtend. Ten-year survival was 93.0% (95% confidence interval [CI]: 87.0-99.0) (cemented stem) and 81.6% (95% CI: 75.3-87.9) (uncemented stem) for Delta III and 94.7% (95% CI: 93.3-96.1) (cemented stem) and 95.7% (95% CI: 88.3-100) (uncemented stem) for Delta Xtend. Twenty-year survival for Delta III (uncemented stem) was 68.2% (95% CI: 58.8-77.6). Compared with DeltaXtend (cemented stem) at 10-year follow-up, we found a higher risk of revision for Delta III (uncemented stem) (hazard ratio [HR]: 2.9, 95% CI: 1.7-5.0), whereas no significant difference was found for Delta III (cemented stem) and Delta Xtend (uncemented stem). The most common reason for revision of Delta III (uncemented stem) was glenoid loosening followed by deep infection and instability. Instability was the most frequent revision cause for Delta Xtend (both cemented and uncemented stem). Men had an overall higher revision risk than women (HR: 2.8 [95% CI: 2.0-3.9]), and patients with fracture sequela had increased risk for revision (HR: 2.8, 95% CI: 1.7-4.7) compared with patients with osteoarthritis.

DISCUSSION

We found that Delta III (uncemented stem) had a higher risk of revision compared with Delta Xtend (cemented stem). The risk of revision for glenoid component loosening was lower for Delta Xtend, but revisions due to instability/dislocation are still a concern. This register study cannot determine whether the differences found were caused by differences in implant design or other factors that changed during the study period. Risk of revision may have been affected by the indication for primary operation.

The effect of subscapularis repair in reverse total shoulder arthroplasty depends on the design of the implant: a comparative study with a minimum 2-year follow-up

INTRODUCTION

The role of the subscapularis (Ssc) tendon does not yet have a well-defined role in RSA. The purpose of the present study was to evaluate if the repair of the Ssc in RSA improves overall clinical and radiographic results and if it has the same results using a medialized design humeral stem compared to a lateralized design.

METHODS

Eighty-four consecutive patients undergoing RSA were retrospectively analyzed. Nine patients were lost at FU. Two implants with similar glenosphere design and different stem design (medialized and lateralized) were used. The Ssc was repaired in case of good quality of the fibers and reducibility without tension intraoperatively. Patients were divided into four groups for data analysis depending on whether they had received a medialized or lateralized design and Ssc repair or not. Patients were reviewed at an average follow-up of 40.8 ± 13.1 months. Clinical outcome measures included Active range of motion (ROM), strength, visual analog scale (VAS), Constant-Murley score (CMS), and the American Shoulder and Elbow Surgeons score (ASES). Radiographic evaluation at final follow-up was performed to assess scapular notching, stress shielding, and radiolucent lines.

RESULTS

No statistically significant clinical differences (p > 0.05) emerged between Lat/Ssc+ and Lat/Ssc-. Conversely, the patients belonging to the Med/Ssc- group reported statistically worse (p < 0.05) results than the Med/Ssc + group in terms of VAS, ASES and CMS. Statistically worse (p < .05) results in the Med/Ssc- group than in the Med/Ssc + were found also in active ROM achieved in FE, ABD, ER1 and ER2, and in the strength obtained in FE, ABD and ER2. Scapular notching was reported in 3 shoulders (15.7%) in Lat/Ssc+ group and in 7 shoulders (50%) in Lat/Ssc- group, while it was reported in 4 shoulders (14.2%) in Med/Ssc + group and in 6 shoulders (42.8%) in Med/Ssc- group. Stress shielding was observed in 6 cases in Lat/Ssc+ group (31.6%), in 8 cases in Lat/Ssc- group (57.1%), in 3 cases (10.7%) in Med/Ssc + group and 4 cases in Med/Ssc- group (28.6%).

CONCLUSIONS

Patients undergoing RSA show clinical improvements at mid-term follow-up with a low rate of complications, regardless of the use of a medialized or a lateralized humeral stem design. Ssc repair is associated with better functional outcomes in the cohort of medialized stem, while it did not yield significant differences in the cohort of lateralized stem.

LEVEL OF EVIDENCE

Level III; Retrospective Cohort Comparison; Treatment Study.

Implant breakage after shoulder arthroplasty: a systematic review of data from worldwide arthroplasty registries and clinical trials

BACKGROUND

Implant breakage after shoulder arthroplasty is a rare complication after aseptic loosening, infection or persistent pain, resulting in malfunction of the components requiring revision surgery. This correlates with a high burden for the patient and increasing costs. Specific data of complication rates and implant breakage are available in detailed arthroplasty registries, but due to the rare occurrence and possibly underestimated value rarely described in published studies. The aim of this systematic review was to point out the frequency of implant breakage after shoulder arthroplasty. We hypothesized that worldwide arthroplasty registry datasets record higher rates of implant breakage than clinical trials.

METHODS

PubMed, MEDLINE, EMBASE, CINHAL, and the Cochrane Central Register of Controlled Trials database were utilized for this systematic review using the items "(implant fracture/complication/breakage) OR (glenoid/baseplate complication/breakage) AND (shoulder arthroplasty)" according to the PRISMA guidelines on July 3rd, 2023. Study selection, quality assessment, and data extraction were conducted according to the Cochrane standards. Case reports and experimental studies were excluded to reduce bias. The breakage rate per 100,000 observed component years was used to compare data from national arthroplasty registries and clinical trials, published in peer-reviewed journals. Relevant types of shoulder prosthetics were analyzed and differences in implant breakage were considered.

RESULTS

Data of 5 registries and 15 studies were included. Rates of implant breakage after shoulder arthroplasty were reported with 0.06-0.86% in registries versus 0.01-6.65% in clinical studies. The breakage rate per 100,000 observed component years was 10 in clinical studies and 9 in registries. There was a revision rate of 0.09% for registry data and 0.1% for clinical studies within a 10-year period. The most frequently affected component in connection with implant fracture was the glenoid insert.

CONCLUSION

Clinical studies revealed a similar incidence of implant failure compared to data of worldwide arthroplasty registries. These complications arise mainly due to breakage of screws and glenospheres and there seems to be a direct correlation to loosening. Periprosthetic joint infection might be associated with loosening of the prosthesis and subsequent material breakage. We believe that this analysis can help physicians to advise patients on potential risks after shoulder arthroplasty.

LEVEL OF EVIDENCE

III.

Early clinical outcomes following navigation-assisted baseplate fixation in reverse total shoulder arthroplasty: a matched cohort study

BACKGROUND

Accurate placement of the glenoid baseplate is an important technical goal of reverse total shoulder arthroplasty (RSA). The use of computer navigated instrumentation has been shown to improve the accuracy and precision of intraoperative execution of preoperative planning. The purpose of this study was to compare early clinical outcomes of patients undergoing navigated RSA vs. a non-navigated matched cohort.

METHODS

A retrospective review of a prospectively collected shoulder arthroplasty database was used to identify 113 patients from a single institution who underwent navigated primary RSA with a minimum 2-year follow-up. A matched cohort of 113 non-navigated RSAs was created based on sex, age, follow-up, and preoperative diagnosis. Preoperative and postoperative range of motion, functional outcome scores, and complications were reported.

RESULTS

A total of 226 shoulders with a mean age of 71 years were evaluated after navigated (113) or non-navigated (113) RSAs. The mean follow-up was 32.8 months (range: 21-54 months). At the final postoperative follow-up, the navigated group had better active forward elevation (135° vs. 129°, P = .023), active external rotation (39° vs. 32°, P = .003), and Constant scores (71.1 vs. 65.5, P = .003). However, when comparing improvements from the preoperative state, there was no statistically significant difference in range of motion or functional outcome scores between the groups. Complications occurred in 1.8% (2) of patients undergoing navigated RSA compared with 5.3% (6) in the non-navigated group (P = .28). Scapular notching (3.1% vs. 8.0%, P = .21) and revision surgery (0.9% vs. 3.5%, P = .37) were more common in non-navigated shoulders.

CONCLUSION

At early follow-up, navigated and non-navigated RSAs yielded similar rates of improvement in range of motion and functional outcome scores. Notching and reoperation was more common in non-navigated shoulders, but did not reach statistical significance. Longer follow-up and larger cohort size are needed to determine if intraoperative navigation lengthens the durability of RSA results and reduces the incidence of postoperative complications.

Cause analysis of the liner dissociation of a customized reverse shoulder prosthesis based on finite element analysis

Background: Dissociation of the polyethylene liner after reverse shoulder arthroplasty could cause shoulder dislocation that could not achieve closed reduction. The cause of liner dissociation is currently unclear.

Method: Non-homogeneous model of the bone was constructed and dynamic finite element analysis was utilized to simulate the impingement of the polyethylene liner and scapula during humeral adduction. The stress distribution of the fixation claws, their degree of deformation (DOD), and the stress of the impingement sites in three initial humeral postures (neutral, 30° flexion, and 30° extension) were measured and analyzed. The influence of the liner material stiffness was also investigated.

Result: The impingement stress on the liner and scapula was 100–200 MPa, and different humeral postures caused different locations of impingement points. The fixation claws’ maximum principal stress (MPS) results were below 5 MPa. In the connection area between some fixation claws and the liner, compressive stresses on the inside and tensile stresses on the outside were observed, which showed that the fixation claws were prone to deform toward the center direction. The maximum DOD results of three initial humeral postures (neutral, 30° flexion, and 30° extension) were 3.6%, 2.8%, and 3.5%, respectively. The maximum DOD results of neutral initial humeral posture were 0.51% and 11.4% when the elastic modulus of the liner was increased and decreased by a factor of 10, respectively.

Conclusion: The humeral adduction impingement could lead to the deformation of the claw-shaped liner fixation structure, which might be one of the reasons for the liner dissociation. The increased stiffness of the liner material helped to reduce the deformation of the fixation structure.

Reverse shoulder arthroplasty with and without baseplate wedge augmentation in the setting of glenoid deformity and rotator cuff deficiency-a multicenter investigation

INTRODUCTION

Glenoid baseplate augments have recently been introduced as a way of managing glenoid monoplanar or biplanar abnormalities in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the difference in clinical outcomes, complications, and revision rates between augmented and standard baseplates in RSA for rotator cuff arthropathy patients with glenoid deformity.

METHODS

A multicenter retrospective analysis of 171 patients with glenoid bone loss who underwent RSA with and without augmented baseplates was performed. Preoperative inclusion criteria included minimum follow-up of 2 years and preoperative retroversion of 15°-30° and/or a beta angle 70°-80°. Version and beta angle were measured on computed tomographic scans, when available, and plain radiographs. Shoulder range of motion (ROM) and patient-reported outcomes were obtained from preoperative and multiple postoperative time points.

RESULTS

The study consisted of 84 standard baseplate patients and 87 augmented baseplate patients. The augment cohort had greater mean preoperative glenoid retroversion (17° vs. 9°, P < .001). At >5-year follow-up, the increase in postoperative active abduction (52° vs. 31°, P = .023), forward flexion (58° vs. 35°, P = .020), and internal rotation score (2.8° vs. 1.1°, P = .001) was significantly greater in the augment cohort. Additionally, >5-year follow-up American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score (87.0 ± 16.6 vs. 75.9 ± 22.4, P = .022), Constant score (78.0 ± 9.7 vs. 64.6 ± 15.1, P < .001), and Shoulder Arthroplasty Smart score (81.2 ± 6.5 vs. 71.2 ± 13.6, P = .003) were significantly higher in the augment cohort. Revision rate was low overall, with no difference between the augment and no augment groups (0.7% vs. 3.0%, P = .151).

CONCLUSION

In comparing augments to standard nonaugment baseplates in the setting of RSA with glenoid deformity, our results demonstrate greater postoperative improvements in multiple planes of active ROM in the augment cohort. Additionally, the augment cohort demonstrated greater postoperative level and improvement in scores for multiple clinical outcome metrics up to >5 years of follow-up with no difference in complication or revision rates, supporting the use of augmented glenoid baseplates in RSA with glenoid deformity.

Clinical outcomes related to glenosphere overhang in reverse shoulder arthroplasty using a lateralized humeral design

BACKGROUND

Previous studies have demonstrated that decreased impingement-free range of motion (ROM) can adversely influence clinical outcomes following reverse shoulder arthroplasty (RSA). Inferior placement of the glenosphere is thought to minimize impingement and its associated sequelae. This study evaluated the relationship between inferior overhang of the glenosphere and clinical outcomes in patients undergoing primary RSA using a lateralized humeral implant design.

METHODS

By use of a prospectively collected shoulder arthroplasty database, all primary RSAs performed at our institution between 2007 and 2015 with a single implant design (lateralized humerus and medialized glenoid) and minimum 2-year follow-up were evaluated. Glenosphere overhang in relation to the inferior rim of the glenoid was measured in millimeters on postoperative Grashey radiographs of the shoulder and categorized into tertiles (low, <7.1 mm; medium, 7.1 to 9.9 mm; and high, >9.9 mm). Clinical outcomes of interest comprised the changes between preoperative and postoperative values in the following ROM and outcome score measures: active forward elevation (aFE), active external rotation, American Shoulder and Elbow Surgeons score, Constant-Murley score, Shoulder Pain and Disability Index score, and Simple Shoulder Test score. Random-effects linear models were used to assess univariate and multivariable associations between overhang tertile and change in patient outcomes. Differences in outcomes were further compared using the minimal clinically important difference (MCID).

RESULTS

The study identified 284 shoulders in 265 patients. The median follow-up period was 36 months (range, 24-108 months). The median glenosphere inferior overhang was 8.4 mm, with an interquartile range of 6.3-10.6 mm. Plots demonstrated nonlinear relationships between overhang and outcome scores and between overhang and ROM. Patients with high overhang experienced a significantly greater improvement in aFE compared with patients with low overhang (P = .019), which exceeded the MCID. No other differences in ROM and outcome scores between overhang groups exceeded the MCID. For other outcome scores and ROM measurements, there was no significant relationship with glenosphere overhang. Increased overhang was associated with a significantly lower incidence of scapular notching (P = .005).

CONCLUSION

Patients undergoing RSA using a lateralized humerus design with greater inferior overhang of the glenosphere demonstrated a significantly greater improvement in aFE and lower rate of notching compared with those with low overhang. No ideal glenosphere overhang range was identified to maximize function in this study.

Comparative study of 145° onlay curved stem versus 155° inlay straight stem reverse shoulder arthroplasty: clinical and radiographic results with a minimum 2-year follow-up

BACKGROUND

Lateralized onlay reverse shoulder arthroplasty (RSA) is designed to ensure better clinical functional recovery and lower rate of complications compared with Grammont medialized inlay RSA. The purpose of the present study was to compare the clinical and radiographic outcomes between these 2 different designs.

METHODS

Eighty-five consecutive patients who underwent RSA were retrospectively analyzed. Nine patients were lost to follow-up, 34 received a curved onlay with a 145° neck-shaft angle (Ascend Flex group), and 42 received a long straight inlay stem with a 155° neck-shaft angle (Delta Xtend group). Patients were reviewed at an average follow-up of 46.8 ± 13.2 months (Ascend Flex group) and 36 ± 10.8 months (Delta Xtend group). Clinical outcome measures included active range of motion, strength, visual analog scale, Constant-Murley score, and the American Shoulder and Elbow Surgeons score. Radiographic evaluation at the final follow-up was performed to assess scapular notching, stress shielding, acromial or scapular fractures, heterotopic ossification, and radiolucent lines or implant loosening.

RESULTS

No differences emerged between the 2 groups in terms of visual analog scale, American Shoulder and Elbow Surgeons and Constant-Murley scores, pain, function, strength, mobility, active forward elevation, active internal rotation, active external rotation at 0° and 90° of abduction, abduction, forward elevation, and external rotation strength (P = n.s.). Statistically superior active abduction was observed in the Delta Xtend group (P = .0017). Scapular notching was observed in 12 shoulders (35.2%) in the Ascend Flex group (a grade 1) and in 10 shoulders (23.8%) in the Delta Xtend group (P = n.s.). No differences emerged between the 2 groups in terms of humeral or glenoid radiolucency (P = n.s.). Higher rate of humeral stress shielding rate was observed in the Ascend flex cohort (P = n.s.).

CONCLUSIONS

No statistically significant difference emerged between the 145° onlay curved stem vs. the 155° inlay straight stem according to most of the evaluated parameters. Statistically superior active abduction was observed in the 155° group although it did not affect patients' satisfaction.

[Cuff Arthropathy - Inverse Total Shoulder Arthroplasty (iSTEP) - Biomechanical Principles, Complications and Outcomes]

The inverse total shoulder prosthesis is a standard treatment for cuff arthropathy. The number of implanted inverse total shoulder prostheses in Germany is significantly higher than that of the anatomical total shoulder prosthesis. Kaplan-Meier analyses show a 10-year result of inverse total shoulder prostheses after cuff arthropathy of 90%. The extent of the scapular notching correlates with the functional clinical outcome. The humeral anchoring principles of inverse total shoulder prosthesis differ considerably (from purely epiphyseal to diaphyseal). Inverse total shoulder prostheses show significant differences in humeral and glenoid offset as well as in shaft-neck angles. The large number of systems available differ considerably concerning anatomical and biomechanical parameters - the surgeons must be trained accordingly. Still, most shoulder replacements are implanted by surgeons who rarely perform this procedure.

Implant migration and functional outcome of Reverse Shoulder Lateralized Glenosphere Line Extension System: a study protocol for a randomized controlled trial

BACKGROUND

Inferior scapular notching is a complication unique to reverse shoulder arthroplasty. The most efficient technique to avoid inferior scapular notching has been reported to be lateralization of the glenoid offset. This study aims to compare radiological and functional outcomes of the DELTA Xtend® Reverse Shoulder System Lateralized Glenosphere Line Extension (intervention group) with the Standard DELTA Xtend® Reverse Shoulder System (control group). We hypothesize that the lateralization improves the patient outcome by decreasing the risk of inferior scapular notching without increasing the risk of migration and loosening of glenoid component.

METHODS

In this randomized controlled trial, all Danish citizens with rotator cuff arthropathy or degeneration of the glenohumeral joint with severe posterior wear and allocated for a reverse total shoulder arthroplasty at the department of orthopaedic surgery at Herlev and Gentofte Hospital, Copenhagen University Hospital, will be considered for participation. The exclusion criteria are as follows: below 50 years of age, cognitive or linguistic impairment, insufficient glenoid bone stock, previous fracture in the upper extremity and autoimmune-mediated inflammatory arthritis. There will be included a total of 122 patients of which 56 will participate in the radiostereometric analysis. This number of patients allows 20% to drop out. The co-primary outcomes are the pattern and magnitude of the migration of the glenoid component assessed by radiostereometric analysis and the Western Ontario Osteoarthritis of the Shoulder index. The secondary outcomes are inferior scapular notching, patient-reported and functional outcomes (Oxford shoulder score, Constant-Murley score and pain), side effects and complications, changes in bone mineral density and economy. The included patients will be examined before the surgery, within 1 week and 3, 6, 12 and 24 months after.

DISCUSSION

No previous studies have compared the conventional reverse shoulder arthroplasty with the lateralized reverse shoulder arthroplasty in a randomized controlled trial regarding migration and functional outcome. Furthermore, radiostereometric analysis has not been used to evaluate the migration of reverse shoulder arthroplasty in a randomized controlled trial. This study intends to determine which treatment has the most optimal outcome for the benefit of future patients with an indication for reverse shoulder arthroplasty.

TRIAL REGISTRATION

The study has been notified to Pactius and has approval number P-2021-231. Furthermore, the study will be registered on Clinicaltrials.gov before starting the inclusion.

Central fixation element type and length affect glenoid baseplate micromotion in reverse shoulder arthroplasty

BACKGROUND

Reverse shoulder arthroplasty (RSA) is commonly used to treat patients with rotator cuff tear arthropathy. Loosening of the glenoid component remains one of the principal modes of failure and represents a significant complication that requires revision surgery. This study assessed the effects of various factors on glenoid baseplate micromotion for primary fixation of RSA.

MATERIALS AND METHODS

A half-fractional factorial design of experiment was used to assess 4 factors: central element type (central peg or screw), central cortical engagement according to length (13.5 or 23.5 mm), anterior-posterior peripheral screw type (nonlocking or locking), and cancellous bone surrogate density (160 or 400 kg/m³, 10 or 25 PCF). Glenoid baseplates were implanted into high- or low-density Sawbones rigid polyurethane foam blocks and cyclically loaded at 60° for 1000 cycles (500-N compressive force range) using a custom-designed loading apparatus. Micromotion at the 4 peripheral screw positions was recorded using linear variable differential transformers.

RESULTS

Central peg fixation generated 358% greater micromotion at all peripheral screw positions compared with central screw fixation (P < .001). Baseplates with short central elements that lacked cortical bone engagement generated 328% greater micromotion than those with long central elements (P = .001). No significant effects were observed when varying anterior-posterior peripheral screw type or bone surrogate density. There were significant interactions between central element type and length (P < .001).

DISCUSSION

A central screw and a long central element that engaged cortical bone reduced RSA baseplate micromotion. These findings serve to inform surgical decision making regarding baseplate fixation elements to minimize the risk of glenoid loosening and, thus, the need for revision surgery.

Bony increased-offset reverse shoulder arthroplasty vs. metal augments in reverse shoulder arthroplasty: a prospective, randomized clinical trial with 2-year follow-up

BACKGROUND

Reverse shoulder arthroplasty (RSA) is rapidly being adopted as the standard procedure for a growing number of shoulder pathologies. Lateralization of the glenoid component is known to reduce the incidence of scapular notching and possibly improve postoperative range of motion. A number of methods are used for glenoid component lateralization, including bony increased-offset reverse shoulder arthroplasty (BIO-RSA) and porous metal-augmented baseplates. Presently, there exists little comparative literature on bone vs. metal lateralization. Therefore, the purpose of this study was to compare BIO-RSA to metal-augmented glenoid baseplates by assessing clinical outcomes and baseplate migration using model-based radiostereometric analysis.

METHODS

A power analysis indicated 40 patients would be required for this radiostereometric study. Therefore, 41 shoulders were prospectively randomized to receive either glenoid bone grafting (BIO-RSA) or a porous metal-augmented wedge-shaped titanium baseplate for primary reverse shoulder arthroplasty. At the time of primary surgery, all patients also underwent implantation of 8 tantalum marker beads in the glenoid and coracoid. Following surgery, participants were imaged using a calibrated, stereo radiographic technique. Radiographs were acquired at 6 weeks (baseline), 3 months, 6 months, 1 year, and 2 years postoperatively. Migration of the prosthesis was compared between bone and metal lateralization groups at each time point using a mixed effects model with Bonferroni test for multiple comparisons. Outcome measures were acquired preoperatively and 2 years postoperatively.

RESULTS

No significant differences were observed along any translation or rotation axis at any time point for either glenoid fixation group (P ≥ .175). Mean total glenoid component translation (± standard deviation) 2 years postoperatively was 0.4 ± 0.2 mm and 0.5 ± 0.3 mm for BIO-RSA and metal-augmented baseplates, respectively (P = .784). No significant differences were observed between groups in active range of motion; pain; American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score; Simple Shoulder Test score; Disabilities of the Arm, Shoulder, and Hand score; Constant Shoulder score; or Subjective Shoulder Value (P ≥ .117), with the exception of increased active external rotation in the BIO-RSA cohort (P = .036).

CONCLUSION

This randomized clinical trial assessed reverse shoulder arthroplasty glenoid component migration using model-based radiostereometric analysis. At 2-year follow-up, our results indicate both BIO-RSA and porous metal wedge augmented baseplates provide stable initial fixation, which is maintained at 2 years' follow-up, with no substantial differences in clinical outcomes.

Reverse Shoulder Arthroplasty Biomechanics

The reverse total shoulder arthroplasty (rTSA) prosthesis has been demonstrated to be a viable treatment option for a variety of end-stage degenerative conditions of the shoulder. The clinical success of this prosthesis is at least partially due to its unique biomechanical advantages. As taught by Paul Grammont, the medialized center of rotation fixed-fulcrum prosthesis increases the deltoid abductor moment arm lengths and improves deltoid efficiency relative to the native shoulder. All modern reverse shoulder prostheses utilize this medialized center of rotation (CoR) design concept; however, some differences in outcomes and complications have been observed between rTSA prostheses. Such differences in outcomes can at least partially be explained by the impact of glenoid and humeral prosthesis design parameters, surgical technique, implant positioning, patient-specific bone morphology, and usage in humeral and glenoid bone loss situations on reverse shoulder biomechanics. Ultimately, a better understanding of the reverse shoulder biomechanical principles will guide future innovations and further improve clinical outcomes.

Does Lateralizing the Glenosphere Center of Rotation by 4 mm Decrease Scapular Notching in Reverse Shoulder Arthroplasty with a 135° Humeral Component?

Background

Scapular notching continues to be associated with reverse shoulder arthroplasty (RSA) and is thought to lead to fewer outcomes. Decreasing the humeral neck-shaft angle (NSA) has been associated with decreased incidence of scapular notching. Lateralizing the glenosphere center of rotation (COR) has also been proposed to decrease notching; however, its effect in lower NSA RSA is less understood. The purpose of this study was to compare the impact of the medial (0 mm) and lateral (4 mm) COR on the incidence of scapular notching and clinical outcomes after RSA with a 135° NSA humeral component.

Methods

We performed a multicenter retrospective comparative cohort of 82 patients with cuff tear arthropathy (41 in each cohort) who underwent RSA with a 135° NSA humeral component and a glenosphere COR of either 0 mm (medialized COR [MCOR]) or 4 mm (lateralized COR [LCOR]) of lateralization. RSA was performed using the same 135° humeral system and baseplate design. All patients had 2-year radiographic and clinical follow-up. Postoperative radiographs were evaluated for scapular notching. Clinical outcomes included American Shoulder and Elbow Surgeons scores, visual analog pain scale, Simple Assessment Numeric Evaluation, and active range of motion.

Results

The overall incidence of scapular notching was 22.0%. There was no significant difference in scapular notching between cohorts: 24.4% in the MCOR and 19.5% in the LCOR (P = .625). Both cohorts had significant improvements in American Shoulder and Elbow Surgeons scores, visual analog pain scale, Simple Assessment Numeric Evaluation, and active range of motion postoperatively (P < .005). Improvements did not significantly differ between cohorts. The presence of scapular notching did not have a significant negative effect on any clinical outcome measure. Complications occurred in 5 patients (2 MCORs and 3 LCORs), none of which occurred in patients with scapular notching.

Discussion and conclusion

Lateralizing the glenosphere COR by 4 mm does not significantly affect the incidence of scapular notching in RSA when using a 135° NSA humeral component at short-term follow-up. Furthermore, such offset does not significantly improve functional outcome scoring systems or range of motion when compared with the MCOR (0 mm). Scapular notching did not have a negative impact on any clinical outcome measure or complication rate in this series.

Long-term Reverse Total Shoulder Arthroplasty Outcomes: The Effect of the Inferior Shifting of Glenoid Component Fixation

Backgroud

The 155° Grammont reverse shoulder replacement has a long track record of success, but also a high radiographic notching rate. The increased distance between the scapular pillar and the humeral component theoretically decreases postoperative notching. The glenoid component can be shifted inferiorly relative to the glenoid; however, there also is some concern that shifting the glenoid component too far inferiorly (inferior glenoid component overhang > 3.5 mm) may compromise long-term stability of the glenoid component. This study was conducted to determine if clinical outcomes, scapular notching, and complications vary with more inferior placement of the glenoid component.

Methods

A retrospective analysis of prospectively collected data was performed in order to compare radiographic outcomes (notching rate and signs of glenoid loosening or component disassembly) and clinical outcomes (range of motion, Constant score, subjective shoulder value, and complication rate) of all patients who underwent reverse shoulder replacement with the glenosphere positioned either flush with the inferior rim of the glenoid (flush group) or with at least 3.5 mm of inferior overhang (overhang group) at a minimum follow-up of 60 months. Ninety-seven patients ultimately met the inclusion criteria, with 41 patients with flush glenoid component and 56 patients with at least 3.5 mm of inferior overhang.

Results

Average follow-up was 97.8 months. The overhang group had a lower rate of radiographic notching (37% vs. 82.5%, p < 0.05), better clinical outcomes (improvement in Constant score: +40 vs. +32, p = 0.036), and higher subjective shoulder value (79 vs. 69, p = 0.026) than the flush group. No difference in complications between groups was found.

Conclusions

In this study, at least 3.5 mm of inferior glenosphere overhang relative to the inferior rim of the glenoid was associated with the lower notching rate without negative effect on the clinical outcomes in 155° Grammont-style reverse shoulder replacement. Therefore, no increase in complications should be expected when using this surgical technique.

Stable glenoid component of reverse total shoulder arthroplasty at 2 years as measured with model-based radiostereometric analysis (RSA)

Background and purpose - Reverse total shoulder arthroplasty (TSA) is used for treating cuff arthropathy, displaced proximal humeral fractures (PHF), and in revision shoulder surgery, despite sparse evidence on long-term results. We assessed stability of the glenoid component in reverse TSA, using model-based RSA.Patients and methods - 20 patients (mean age 76 years, 17 female), operated on with reverse TSA at Oslo University Hospital, in 2015-2017 were included. Indications for surgeries were PHFs, malunion, cuff arthropathy, and chronic shoulder dislocation. RSA markers were placed in the scapular neck, the coracoid, and the acromion. RSA radiographs were conducted postoperatively, at 3 months, 1 year, and 2 years. RSA analysis was performed using RSAcore with Reversed Engineering (RE) modality, with clinical precision < 0.25 mm for all translations (x, y, z) and < 0.7° for rotations (x, z). Scapular "notching" was assessed in conventional radiographs.Results - 1 patient was excluded due to revision surgery. More than half of the patients displayed measurable migration at 2 years: 6 patients with linear translations below 1 mm and 8 patients who showed rotational migration. Except for one outlier, the measured rotations were below 2°. The migration pattern suggested implant stability at 2 years. 10 patients showed radiolographic signs of "notching", and the mean Oxford Shoulder Score (OSS) at 2 years was 29 points (15-36 points).Interpretation - Stability analysis of the glenoid component of reversed total shoulder arthroplasty using reversed engineering (RE) model-based RSA indicated component stability at 2 years.

Problems, complications, and reinterventions in 4893 onlay humeral lateralized reverse shoulder arthroplasties, a systematic review: part II-problems and reinterventions

BACKGROUND

Several modifications to the original Grammont reverse shoulder arthroplasty (RSA) design have been proposed to prevent distinctive issues, such as both glenoid and humeral lateralization. The aim of this systematic review was to determine rates of problems, complications, reoperations, and revisions after onlay lateralized humeral stem RSA, hypothesizing that these are design related.

METHODS

This systematic review was performed in accordance with the PRISMA statement guidelines. A literature search was conducted (1 January 2000 to 14 April 2020) using PubMed, Cochrane Reviews, Scopus, and Google Scholar, employing several combinations of keywords: "reverse shoulder arthroplasty," "reverse shoulder prosthesis," "inverse shoulder arthroplasty," "inverse shoulder prosthesis," "problems," "complications," "results," "outcomes," "reoperation," and "revision."

RESULTS

Thirty-one studies with 4893 RSA met inclusion criteria. The 892 postoperative problems and 296 postoperative complications represented overall problem and complication rates of 22.7% and 7.5%, respectively. Forty-one reoperations and 63 revisions resulted, with overall reoperation and revision rates of 1.7% and 2.6%, respectively.

CONCLUSIONS

Problem, complication, and reintervention rates proved acceptable when implanting a high humeral lateralization stem RSA. The most frequent problem was scapular notching (12.6%), and the most common postoperative complication was scapular stress fracture (1.8%). An overall humeral complication rate of 1.9% was identified, whereas no humeral fractures or stem loosening were reported with short stems. Infections (1.3%) were the most common reason for component revision, followed by instability (0.8%).

LEVEL OF EVIDENCE

Systematic review IV.

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.

Reverse total shoulder arthroplasty (RTSA) versus open reduction and internal fixation (ORIF) for displaced three-part or four-part proximal humeral fractures: a systematic review and meta-analysis

Despite rapid medical technology development, various challenges exist in three- and four-part proximal humeral fracture (PHF) management. This condition has led to a notably increased use of the reverse total shoulder arthroplasty (RTSA); however, open reduction and internal fixation (ORIF) is still the most widely performed procedure. Thus, these two modalities are crucial and require further discussion. We aim to compare the outcomes of three- or four-part PHF surgeries using ORIF and RTSA based on direct/head-to-head comparative studies.We conducted a systematic review and meta-analysis based on the Cochrane handbook and PRISMA guidelines. We searched MEDLINE (PubMed), Embase (Ovid), and CENTRAL (Cochrane Library) from inception to October 2020. Our protocol was registered at PROSPERO (registration number CRD42020214681). We assessed the individual study risk of bias using ROB 2 and ROBINS-I tools, then appraised our evidence using the GRADE approach.Six head-to-head comparative studies were included, comprising one RCT and five retrospective case-control studies. We found that RTSA significantly improved forward flexion but was comparable to ORIF in abduction (p = 0.03 and p = 0.47, respectively) and more inferior in external rotation (p < 0.0001). Moreover, RTSA improved the overall Constant-Murley score, but the difference was not significant (p = 0.22). Interestingly, RTSA increased complications (by 42%) but reduced the revision surgery rates (by 63%) compared to ORIF (p = 0.04 and p = 0.02, respectively).RTSA is recommended to treat patients aged 65 years or older with a three- or four-part PHF. Compared to ORIF, RTSA resulted in better forward flexion and Constant-Murley score, equal abduction, less external rotation, increased complications but fewer revision surgeries. Cite this article: EFORT Open Rev 2021;6:941-955. DOI: 10.1302/2058-5241.6.210049.

The effect of glenosphere lateralization and inferiorization on deltoid force in reverse total shoulder arthroplasty

BACKGROUND

A medialized center of rotation (COR) in reverse total shoulder arthroplasty (RTSA) comes with limitations such as scapular notching and reduced range of motion. To mitigate these effects, lateralization and inferiorization of the COR are performed, but may adversely affect deltoid muscle force. The study purposes were to measure the effect of RTSA with varying glenosphere configurations on (1) the COR and (2) deltoid force compared with intact shoulders and shoulders with massive posterosuperior rotator cuff tears (PS-RCT). We hypothesized that the highest deltoid forces would occur in shoulders with PS-RCT, and that RTSA would lead to a decrease in required forces that is further minimized with lateralization and inferiorization of the COR but still higher compared with native shoulders with an intact rotator cuff.

METHODS

In this study, 8 cadaveric shoulders were dissected leaving only the rotator cuff muscles and capsule intact. A custom apparatus incorporating motion capture and a dynamic tensile testing machine to measure the changes in COR and deltoid forces while simultaneously recording glenohumeral abduction was designed. Five consecutive testing states were tested: (1) intact shoulder, (2) PS-RCT, (3) RTSA with standard glenosphere, (4) RTSA with 4 mm lateralized glenosphere, and (5) RTSA with 2.5 mm inferiorized glenosphere. Statistical Parametric Mapping was used to analyze the deltoid force as a function of the abduction angle. One-way repeated-measures within-specimens analysis of variance was conducted, followed by post hoc t-tests for pairwise comparisons between the states.

RESULTS

All RTSA configurations shifted the COR medially and inferiorly with respect to native (standard: 4.2 ± 2.1 mm, 19.7 ± 3.6 mm; 4 mm lateralized: 3.9 ± 1.2 mm, 16.0 ± 1.8; 2.5 mm inferiorized: 6.9 ± 0.9 mm, 18.9 ± 1.7 mm). Analysis of variance showed a significant effect of specimen state on deltoid force across all abduction angles. Of the 10 paired t-test comparisons made between states, only 3 showed significant differences: (1) intact shoulders necessitated significantly lower deltoid force than specimens with PS-RCT below 42° abduction, (2) RTSAs with standard glenospheres required significantly lower deltoid force than RTSA with 4 mm lateralized glenospheres above 34° abduction, and (3) RTSAs with 2.5 mm inferiorized glenospheres had significantly lower deltoid force than RTSA with 4 mm of glenosphere lateralization at higher abduction angles.

CONCLUSIONS

RTSA with a 2.5 mm inferiorized glenosphere and no additional lateralization resulted in less deltoid force to abduct the arm compared with 4 mm lateralized glenospheres. Therefore, when aiming to mitigate downsides of a medialized COR, an inferiorized glenosphere may be preferable in terms of its effect on deltoid force.

Problems, complications, and reinterventions in 4893 onlay humeral lateralized reverse shoulder arthroplasties: a systematic review (part I-complications)

Background

Several modifications to the original Grammont reverse shoulder arthroplasty (RSA) design have been proposed to prevent distinctive issues, such as both glenoid and humeral lateralization. The aim of this systematic review was to determine rates of problems, complications, reoperations, and revisions after onlay lateralized humeral stem RSA, hypothesizing that these are design related.

Methods

This systematic review was performed in accordance with the PRISMA statement guidelines. A literature search was conducted (01.01.2000–14.04.2020) using PubMed, Cochrane Reviews, Scopus, and Google Scholar employing several combinations of keywords: “reverse shoulder arthroplasty,” “reverse shoulder prosthesis,” “inverse shoulder arthroplasty,” “inverse shoulder prosthesis,” “problems,” “complications,” “results,” “outcomes,” “reoperation,” “revision.”

Results

Thirty-one studies with 4893 RSA met inclusion criteria. The 892 postoperative problems and 296 postoperative complications represented overall problem and complication rates of 22.7% and 7.5%, respectively. Forty-one reoperations and 63 revisions resulted, with an overall reoperation rate of 1.7% and overall revision rate of 2.6%.

Conclusions

Problem, complication, and reintervention rates proved acceptable when implanting a high humeral lateralization stem in RSA. The most frequent problem was scapular notching (12.6%), and the most common postoperative complication was scapular stress fracture (1.8%). An overall humeral complication rate of 1.9% was identified, whereas short stems reported no humeral fractures or stem loosening. Infections (1.3%) proved to be the most common reason for component revision, and instability had a complication rate of 0.8%.

Level of evidence

Systematic review IV

The glenoid-intramedullary humeral angle: a measurement of compensatory scapular abduction in advanced rotator cuff arthropathy and its potential effects on implant choice

Background

This study establishes measurements to evaluate pathologic compensation in rotator cuff tear arthropathy and resultant considerations for reverse shoulder arthroplasty.

Methods

Radiographs of patients with intact rotator cuffs were measured establishing interobserver and intraobserver reliability. Reverse shoulder arthroplasty cases performed by a single surgeon were then retrospectively reviewed. One year of follow-up radiographs were required for inclusion. Preoperative radiographs were analyzed for relative humeral head elevation ratio and humeral abduction relative to the glenoid face, termed the glenoid-intramedullary humeral angle. Statistical analyses assessed associations for radiographic measurements with presence and severity of scapular notching based on the Nerot-Sirveaux classification system.

Results

A total of 221 patients met inclusion criteria. At the 1-year follow-up, 61 (27.6%) shoulders had radiographic notching. There was a moderately strong (r = -0.56) negative correlation between glenoid-intramedullary humeral angle and humeral head elevation ratio. Patients with humeral head elevation ratio ≥ 20% were significantly (P = .024) and 9.2 times more likely to have notching of any grade. Patients with glenoid-intramedullary humeral angle ≤ 5 degrees were significant (P < .0001) and 6.7 times more likely to have notching of any grade and significantly (P = .00018) and 145 times more likely to have high-grade (3 and 4) notching.

Conclusions

Preoperative humeral head elevation and compensatory scapular rotation with relative adduction of the humerus have significant associations with high-grade notching. These radiographic findings have potential to help surgeons in preoperative decision-making regarding implant choice and patient education.

Long-term impact of scapular notching after reverse shoulder arthroplasty

BACKGROUND

Because it medializes the centre of rotation, one of the drawbacks of reverse shoulder arthroplasty (RSA) is the risk of impingement between the humerus and lateral border of the scapula resulting in scapular notching. The long-term impact of this notching is not well known, either on function or the risk of glenoid loosening. The aim of this longitudinal study was to analyze the drawbacks of this notching.

METHODS

Between 1993 and 2006, 81 patients (91 shoulders) underwent RSA for primary glenohumeral osteoarthritis or massive cuff tear with or without osteoarthritis. This cohort was followed longitudinally with post-operative assessments done at one to two  years (T1), three to eight  years (T2), and nine+ years (T3). Before T3, 25 patients had died, nine were lost to follow-up, five  had the implants changed, and seven  had incomplete records. Thus, 45 shoulders were available for follow-up beyond nine years (mean follow-up of 12 years) and were used to determine the long-term impact of notching. Survival curves were generated using the occurrence of Sirveaux grade 3 or 4 notching and the presence of aseptic glenoid loosening as endpoints.

RESULTS

The survivorship before grade 3 or 4 notching developed was 83% at five years, 60% at 10 years, and 43% at 15 years. In the end, aseptic glenoid loosening occurred in four shoulders, all of which had developed grade 4 notching. No glenoid loosening occurred in the population with grade 0, 1, 2, or 3 notching (p = 0.02). The Constant score significantly decreased between T2 and T3, although it was not different between shoulders with and without advanced notching.

CONCLUSIONS

Beyond the second year post-RSA, the number of shoulders with grade 3 or 4 notching increases steadily up to the longest follow-up. Grade 4 notching always preceded the occurrence of late glenoid loosening. The functional outcomes become significantly worse after the 9th year post-RSA, although they were not correlated to the presence of high-grade scapular notching.

An update on reverse total shoulder arthroplasty: current indications, new designs, same old problems

Reverse total shoulder arthroplasty (RTSA) was originally developed because of unsatisfactory results with anatomic shoulder arthroplasty options for the majority of degenerative shoulder conditions and fractures.

After initial concerns about RTSA longevity, indications were extended to primary osteoarthritis with glenoid deficiency, massive cuff tears in younger patients, fracture, tumour and failed anatomic total shoulder replacement.

Traditional RTSA by Grammont has undergone a number of iterations such as glenoid lateralization, reduced neck-shaft angle, modular, stemless components and onlay systems.

The incidence of complications such as dislocation, notching and acromial fractures has also evolved.

Computer navigation, 3D planning and patient-specific implantation have been in use for several years and mixed-reality guided implantation is currently being trialled.

Controversies in RTSA include lateralization, stemless humeral components, subscapularis repair and treatment of acromial fractures.

Cite this article: EFORT Open Rev 2021;6:189-201. DOI: 10.1302/2058-5241.6.200085

Reverse Total Shoulder Arthroplasty with a Superior Augmented Glenoid Component for Favard Type-E1, E2, and E3 Glenoids

BACKGROUND

Uncorrected superior glenoid wear in patients managed with reverse total shoulder arthroplasty (rTSA) can result in increased complications, including baseplate failure. The present study quantifies the clinical and radiographic outcomes of patients with Favard type-E1, E2, and E3 glenoid deformity who were managed with rTSA with use of a superior or superior/posterior augmented glenoid baseplate.

METHODS

We retrospectively reviewed the records for 68 patients with shoulder arthritis and Favard type-E1, E2, or E3 glenoid deformity who were managed with primary rTSA and a 10° superior augmented or 10° superior/8° posterior augmented baseplate. The mean duration of follow-up was 40 months (range, 24 to 85 months). Outcomes were assessed preoperatively and at the latest follow-up with shoulder range of motion and use of outcome scores including the Simple Shoulder Test (SST), University of California Los Angeles (UCLA) score, American Shoulder and Elbow Surgeons (ASES) score, Constant score, and Shoulder Pain and Disability Index (SPADI) score. Radiographs were evaluated preoperatively and at the time of the latest follow-up. Differences in preoperative and postoperative range of motion and outcome metrics were assessed with use of a 2-tailed Student t test.

RESULTS

The majority of patients experienced clinically meaningful improvements in terms of pain and function following rTSA with a superior or superior/posterior augment, with 94% of patients rating themselves as "much better" (73.5%) or "better" (20.5%) at the time of the latest follow-up. At least 88% of the patients exceeded the minimum clinically important difference (MCID) threshold, and 75% of patients exceeded the substantial clinical benefit (SCB) threshold, for each of the clinical outcome metrics and range of motion. Five complications were reported (prevalence, 7.4%), including acromial stress fracture (2 patients), posttraumatic scapular neck fracture (1 patient), chronic shoulder pain (1 patient), and aseptic glenoid loosening (1 patient).

CONCLUSIONS

The present short-term clinical and radiographic study demonstrated that shoulder arthropathy with superior glenoid wear patterns (Favard types E1, E2, and E3) can be successfully treated with rTSA with a superior or superior/posterior augmented baseplate. Longer-term clinical and radiographic follow-up is necessary to confirm that these promising short-term results are durable.

LEVEL OF EVIDENCE

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

Computer navigation leads to more accurate glenoid targeting during total shoulder arthroplasty compared with 3-dimensional preoperative planning alone

BACKGROUND

Commercially available preoperative planning software is now widely available for shoulder arthroplasty. However, without the use of patient-specific guides or intraoperative visual guidance, surgeons have little in vivo feedback to ensure proper execution of the preoperative plan. The purpose of this study was to assess surgeons' ability to implement a preoperative plan in vivo during shoulder arthroplasty.

METHODS

Fifty primary shoulder arthroplasties from a single institution were retrospectively reviewed. All surgical procedures were planned using a commercially available software package with both multiplanar 2-dimensional computed tomography and a 3-dimensional implant overlay. Following registration of intraoperative visual navigation trackers, the surgeons (1 attending and 1 fellow) were blinded to the computer navigation screen and attempted to implement the plan by simulating placement of a central-axis guide pin. Malposition was assessed (>4 mm of displacement or >10° error in version or inclination). Data were then blinded, measured, and evaluated.

RESULTS

Mean displacement from the planned starting point was 3.2 ± 2.0 mm. The mean error in version was 6.4° ± 5.6°, and the mean error in inclination was 6.6° ± 4.9°. Malposition was observed in 48% of cases after preoperative planning. Malposition errors were more commonly made by fellow trainees vs. attending surgeons (58% vs. 38%, P = .047).

CONCLUSIONS

Despite preoperative planning, surgeons of various training levels were unable to reproducibly replicate the planned component position consistently. Following completion of fellowship training, significantly less malposition resulted. Even in expert hands, the orientation of the glenoid component would have been malpositioned in 38% of cases. This study further supports the benefit of guided surgery for accurate placement of glenoid components, regardless of fellowship training.

Effect of Reverse Shoulder Arthroplasty Lateralization Design on Scapular Notching: A Single-Surgeon Experience

Scapular notching remains a concern with both medialized and lateralized reverse shoulder arthroplasty (RSA) designs. Few studies have directly compared the rate of notching among various designs. The purpose of this study was to compare a single surgeon's rate of scapular notching in relation to RSA design. A total of 156 primary RSAs were performed for cuff tear arthropathy or osteo-arthritis with rotator cuff insufficiency by a single surgeon. Follow-up was controlled to between 3 and 5 years. Shoulders were grouped according to implant design: medialized center of rotation (CoR; n=17), lateralized CoR (n=14), and lateralized humerus (n=125). Objective clinical outcomes, patient-reported outcomes, and radiographic outcomes were compared. Scapular notching occurred more frequently with medialized CoR (82%) and lateralized CoR (57%) designs compared with a lateralized humerus design (22%; P<.001). Mean notching grade was also lower in the lateralized humerus design (0.2) compared with the medialized CoR (2.1; P<.001) and lateralized CoR (1.1; P=.01) designs. Postoperative pain, range of motion, and patient-reported outcomes were not significantly different among groups. A low rate of reoperation was seen in all groups. The lateralized humeral RSA design showed less frequent and less severe scapular notching compared with medialized CoR and lateralized CoR designs. There were no observed differences in range of motion or patient-reported outcomes between different implant designs. [Orthopedics. 2020;43(6):e585-e591.].

Bony increased-offset-reverse shoulder arthroplasty: 5 to 10 years' follow-up

BACKGROUND

Glenoid lateralization has been shown to be the most imortant factor in maximizing passive range of motion and shoulder stability while preventing scapular impingement and notching. We aimed to evaluate mid- to long-term functional and radiologic outcomes after bony increased-offset-reverse shoulder arthroplasty (BIO-RSA) using a Grammont-style (medialized) humeral implant.

METHODS

The study included 143 consecutive shoulders (140 patients; mean age, 72 years) treated with a BIO-RSA for rotator cuff deficiency. A cylinder of autologous cancellous bone graft, harvested from the humeral head, was placed between the reamed glenoid surface and baseplate; fixation was achieved using a long central peg (25 mm) and 4 screws. A large baseplate (29 mm) with a small baseplate sphere (36 mm) was used in 77% of cases, and a Grammont-style (medialized) humeral implant with 155° of inclination was used in all cases. All patients underwent clinical and radiographic assessment at a minimum of 5 years after surgery; in addition, 86 cases (60%) underwent computed tomography scan assessment.

RESULTS

At a mean follow-up of 75 months (range, 60-126 months), the survivorship of the BIO-RSA using revision as an endpoint was 96%. No cases of dislocation or humeral loosening were observed. Overall, 118 patients (83%) were either very satisfied (61%) or satisfied (22%). The adjusted Constant score improved from 40% ± 18% to 93% ± 23%, and the Subjective Shoulder Value improved from 31% ± 15% to 77% ± 18% (P < .001). The humeral bone graft incorporated completely in 96% of cases (137 of 143). Severe inferior scapular notching (grade 3 or 4) occurred in 18% (24 of 136). The risk of postoperative notching correlated to a lower body mass index (P < .05), superior glenosphere inclination (P = .02), and high or flush glenosphere positioning (P = .035).

CONCLUSIONS

BIO-RSA is a safe and effective technique to lateralize the glenoid, providing consistent bone graft healing, excellent functional outcomes, a low revision rate, and a high rate of patient satisfaction. Thin patients (with a low body mass index) and glenosphere malposition (with persistent superior inclination and/or insufficient lowering of the baseplate and sphere) are associated with higher risk of scapular notching.Our data confirm the importance of implanting the baseplate with a neutral inclination (reverse shoulder arthroplasty angle < 5°) and with sufficient glenosphere inferior overhang (>5 mm) in preventing scapular notching. The use of a less medialized humeral implant (135° or 145° inclined) and smaller (25-mm) baseplate (when using a small, 36-mm sphere) should allow reduction in the incidence of scapular notching.

Impact of scapular notching on glenoid fixation in reverse total shoulder arthroplasty: an in vitro and finite element study

BACKGROUND

The high incidence of scapular notching in reverse total shoulder arthroplasty (RTSA) has spurred several methods to minimize bone loss. However, up to 93% of RTSAs accompanying scapular notching have been reported to maintain good implant stability for over 10 years. This study was conducted to investigate the relationship between scapular notching and glenoid fixation in RTSA.

METHODS

Cadaveric testing was performed to measure the notch-induced variations in strain on the scapular surface and micromotion at the bone-prosthesis interface during arm abductions of 30°, 60°, and 90°. Finite element analysis was used to further study the bone and screw stresses as well as the bone-prosthesis micromotion in cases with a grade 4 notch during complicated arm motions.

RESULTS

The notch resulted in an apparent increase in inferior screw stress in the root of the screw cap and at the notch-screw conjunction. However, the maximum stress (172 MPa) along the screw after notching is still much less than the fatigue strength of the titanium screw (600 MPa) under cyclic loading. The bone-prosthesis micromotion results did not present significant notch-induced variations.

CONCLUSIONS

Scapular notching will lead to few impacts on the stability of an RTSA on the glenoid side. This finding may explain the long-term longevity of RTSA in cases of severe scapular notching. The relationship between scapular notching and weak regions along the inferior screw may explain why fractures of the inferior screw are sometimes reported in patients with RTSA clinically.

Clinical implications of scapular notching at 2 and 5-year follow-up after reverse total shoulder arthroplasty

Objective

Scapular notching is a unique radiographic sequela of reverse total shoulder arthroplasty (rTSA) with unclear long-term clinical consequences.

Methods

Our retrospective review of a single surgeon, single implant, primary rTSA database investigates the incidence of scapular notching at 2 and 5-year follow-up. Various patient outcome scores were also obtained.

Results

Of 158 primary rTSAs performed, 82 (52%) patients completed 2-year and subsequent 5-year follow-up. The incidence of scapular notching at 2 and 5-years was 11.9% and 19.5%, respectively.

Conclusion

Scapular notching negatively affects validated post-operative outcome scores, active range of motion and total complications, and furthermore increases with time.

The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part I

Background

Globally, reverse shoulder arthroplasty (RSA) has moved away from the Grammont design to modern prosthesis designs. The purpose of this 2-part study was to systematically review each of the most common complications of RSA, limiting each search to publications in 2010 or later. In this part (part I), we examined (1) scapular notching (SN), (2) periprosthetic infection (PJI), (3) mechanical failure (glenoid or humeral component), and (4) neurologic injury (NI).

Methods

Four separate PubMed database searches were performed following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Overall, 113 studies on SN, 62 on PJI, 34 on mechanical failure, and 48 on NI were included in our reviews. Univariate analysis was performed with the χ² or Fisher exact test.

Results

The Grammont design had a higher SN rate vs. all other designs combined (42.5% vs. 12.3%, P < .001). The onlay humeral design had a lower rate than the lateralized glenoid design (10.5% vs. 14.8%, P < .001). The PJI rate was 2.4% for primary RSA and 2.6% for revision RSA. The incidence of glenoid and humeral component loosening was 2.3% and 1.4%, respectively. The Grammont design had an increased NI rate vs. all other designs combined (0.9% vs. 0.1%, P = .04).

Conclusions

Focused systematic reviews of the recent literature with a large volume of RSAs demonstrate that with the use of non-Grammont modern prosthesis designs, complications including SN, PJI, glenoid component loosening, and NI are significantly reduced compared with previous studies. As the indications for RSA continue to expand, it is imperative to accurately track the rates and types of complications to justify its cost and increased indications.

Lateralization in reverse shoulder arthroplasty: A review

Reverse shoulder arthroplasty, as originally designed by Grammont, has revolutionized the treatment of rotator cuff arthropathy as well as fractures about the proximal humerus. The original design consisted of glenoid and humeral components with a medialized center or rotation compared to the native shoulder. Long term outcome studies on this design demonstrated high rates of scapular notching as well as significant loss of external rotation. To combat these flaws, prosthesis design has evolved to include the concept of lateralization whereby the center of rotation is moved laterally compared to the Grammont prosthesis via either the glenoid or humeral components. Lateralization via the glenoid component has sought to reduce scapular notching, however, concerns over early loosening have been raised secondary to increasing stress at the glenosphere/glenoid interface. Lateralization via the humeral component has been theorized to improve the mechanics of the remaining rotator cuff and deltoid musculature while avoiding the problems inherent with glenoid lateralization. While limited clinical evidence is available currently to support one design over the other, multiple biomechanical studies have shown improvements in rates of scapular notching and post-operative external rotation for lateralized humeral and glenoid components. Future research should aim to delineate advantages of one design over the other or optimal combinations of the two designs.

Can small glenospheres with eccentricity reduce scapular notching as effectively as large glenospheres without eccentricity? A prospective randomized study

BACKGROUND

The objective of this study was to analyze whether small glenospheres with eccentricity were comparable to large glenospheres in scapular notch development.

METHODS

This prospective randomized study included 82 patients who had undergone a reverse shoulder arthroplasty with a 2-year follow-up period. After randomization, 43 patients were allocated to receive a 42-mm glenosphere and 39 patients were allocated to receive a 38-mm glenosphere with 2 mm of eccentricity. Scapular notch development was defined after examination of an anteroposterior radiograph at the end of follow-up. Functional outcomes were recorded using the Constant score before surgery and at the end of follow-up.

RESULTS

Scapular notch development was present in 16.6% of patients who received a 42-mm glenosphere and 34.2% of patients who received a 38-mm eccentric glenosphere. No significant difference was found between the groups with the number of cases available (P = .07). Functional outcomes significantly increased from preoperatively to postoperatively in both groups, with no significant difference found between them (P = .77). The mean glenosphere overhang measure was 6.3 mm in patients with a 42-mm glenosphere and 6.0 mm in those with a 38-mm eccentric glenosphere (P = .68). No significant differences were noted between patients with a scapular notch and patients without a scapular notch in terms of functional outcomes.

DISCUSSION

Small glenospheres with eccentricity fared slightly worse than large glenospheres regarding scapular notch development, even though no significant differences were noted. Functional outcomes were comparable between the 2 designs.

Influence of Glenosphere and baseplate parameters on Glenoid bone strains in reverse shoulder Arthroplasty

Background

Little is known about the strains at the glenoid near the bone-implant interface in reverse shoulder arthroplasty. The purpose of the current study was to evaluate the strains on the glenoid bone under a compressive load after implantation of three different sizes of metal-backed baseplates in either inferior or superior position in combination with three different sizes of glenospheres and three different glenosphere designs.

Methods

Three sizes of baseplates (small, medium, large) were implanted in thirty-six paired human cadaveric scapulae either inferior, flush with the glenoid neck, or with a 5 mm superior offset. Glenospheres were available in three sizes (36 mm, 39 mm, 42 mm) and designs (standard, 4 mm lateralized, 2.5 mm inferiorized). Specimens were mounted in a servo-hydraulic testing apparatus at a 60° angle between the glenoid and actuator holding the humeral component. Four strain-gauge rosettes were placed around the glenoid rim to measure strains transferred to the scapular bone under a compressive load (750 N) relative to the various baseplate-glenosphere combinations. Following repeated compression, a load-to-failure test was performed.

Results

Mean overall registered strains were 161με (range: − 1165 to 2347) at the inferior sensor, −2με (range: − 213 to 90) at the superior sensor, −95με (range: − 381 to 254) at the anterior sensor, and 13με (range: − 298 to 128) at the posterior sensor. Measured bone strains did not show any significant differences across tested baseplate and glenosphere design, size, or positioning combinations (p > 0.05 for all sensors). Furthermore, linear regression analysis did not identify any of the evaluated parameters as an independent influential factor for strains (p > 0.05 for all sensors). Mean load-at-failure was significantly higher in the group of inferior (3347.0 N ± 704.4 N) compared to superior (2763.8 N ± 927.8 N) positioned baseplates (p = 0.046).

Conclusion

Different baseplate positions, baseplate sizes, glenosphere sizes, and glenosphere design or various combinations of these parameters did not significantly influence the measured bone strains at the glenoid near the bone-implant interface in a contemporary reverse shoulder arthroplasty system.

Level of evidence

Basic Science Study, Biomechanical Study.

Impact of scapular notching on reverse total shoulder arthroplasty midterm outcomes: 5-year minimum follow-up

BACKGROUND

The impact of scapula notching on reverse total shoulder arthroplasty (rTSA) clinical outcomes is controversial. The purpose of this study was to conduct a sufficiently statistically powered analysis to quantify the impact of scapular notching on midterm rTSA outcomes.

METHODS

There were 324 rTSA patients with 5 years of minimum follow-up evaluated. Patients were stratified according to the presence of a scapular notch at latest follow-up; radiographs were also assessed at each time point for patients with notching to determine the time for notch grade development. A 2-tailed, unpaired t-test compared preoperative, postoperative, and preoperative to postoperative outcomes between cohorts.

RESULTS

There were 324 patients having an average follow-up of 75.1 months assessed; 47 (14.5%) patients had scapular notching. For scapular notching patients, the average notching grade was 1.7 ± 0.8 (24 grade 1, 15 grade 2, and 8 grade 3). The average time to notch development was 51.4 ± 24.1 months; grade 1, grade 2, and grade 3 notches developed at 49.0 ± 22.1 months, 57.5 ± 22.6 months, and 71.6 ± 15.8 months, respectively. No preoperative differences were observed between cohorts. At latest follow-up, scapular notching patients had significantly worse outcome scores and significantly less active abduction, forward flexion, and strength. Finally, scapular notching patients had significantly more complications, revisions, and humeral radiolucent lines.

CONCLUSIONS

Scapular notching patients had significantly worse clinical outcomes and less range of motion than patients without scapular notching; these differences exceeded the minimal clinically important difference threshold for several outcome metrics. Based on these results, we recommend minimizing scapular notching through patient and implant selection and technique modification.

Reverse Total Shoulder Arthroplasty: Biomechanics and Indications

PURPOSE OF REVIEW

Over the past decade, our understanding of the biomechanics of the reverse total shoulder arthroplasty (RTSA) has advanced, resulting in design adjustments, improved outcomes, and expanding indications. The purpose of this review is to summarize recent literature regarding the biomechanics of RTSA and the evolving indications for its use.

RECENT FINDINGS

While Grammont's principles of RTSA biomechanics remain pillars of contemporary designs, a number of modifications have been proposed and trialed in later generations to address complications such as impingement and glenoid failure. Clinical and biomechanical literature suggest that less medialized, more inferior glenospheres result in less impingement and notching. On the humerus, a more vertical neck cut is associated with less impingement. Indications for RTSA continue to expand beyond the classic indication of cuff tear arthropathy (CTA). Patients without a functional cuff but no arthritis now have a reliable option in the RTSA. RTSA has also replaced hemiarthroplasty as the implant of choice for displaced three- and four-part proximal humerus fractures in the elderly. Finally, updated design options and modular components now allow for treatment of glenoid bone loss, failed arthroplasty, and proximal humerus tumors with RTSA implants. Reverse total shoulder arthroplasty design has been modernized on both the glenoid and humerus to address biomechanical challenges of early implants. As outcomes improve with these modifications, RTSA indications are growing to address complex bony pathologies such as tumor and bone loss. Longitudinal follow-up of patients with updated designs and novel indications is essential to judicious application of RTSA technology.

Impact of screw length and screw quantity on reverse total shoulder arthroplasty glenoid fixation for 2 different sizes of glenoid baseplates

Background

Little guidance exists regarding the minimum screw length and screw quantity necessary to achieve fixation in reverse total shoulder arthroplasty (rTSA); to that end, this study quantified the displacement of 2 different sizes of glenoid baseplates using multiple different screw lengths and quantities of screws in a low-density polyurethane bone-substitute model.

Methods

Testing of rTSA glenoid loosening was conducted according to ASTM F 2028-17. To independently evaluate the impact of screw quantity and screw length on rTSA glenoid fixation for 2 different sizes of glenoid baseplates, baseplates were constructed using 2 screws, 4 screws, or 6 screws (with the latter being used for the larger baseplate only) with 3 different poly-axial locking compression screw lengths.

Results

Both sizes of glenoid baseplates remained well fixed after cyclic loading regardless of screw length or screw quantity. Baseplates with 2 screws had significantly greater displacement than baseplates with 4 or 6 screws. No differences were observed between baseplates with 4 screws and those with 6 screws (used for the larger baseplate). Both sizes of baseplates with 18-mm screws had significantly greater displacement than baseplates with 30- or 46-mm screws. For larger baseplates, those with 30-mm screws had significantly greater displacement than those with 46-mm screws in the superior-inferior direction.

Discussion

For the 2 different sizes of baseplates tested in this study, rTSA glenoid fixation was impacted by both screw quantity and screw length. Irrespective of screw quantity, longer screws showed significantly better fixation. Irrespective of screw length, the use of more screws showed significantly better fixation, up to a point, as the use of more than 4 screws showed no incremental benefit. Finally, longer screws can be used as a substitute for additional fixation if it is not feasible to use more screws.

Lateralization in reverse shoulder arthroplasty: a descriptive analysis of different implants in current practice

INTRODUCTION

Since its first description, the concept of reverse shoulder arthroplasty (RSA) has evolved. The term lateralization remains unclear and is used to describe implants that lateralize on the glenoid side, the humeral side, or both. The objective of this study was to provide a clear definition of lateralization and to measure the lateralization achieved by the most commonly used implants.

MATERIALS AND METHODS

Twenty-eight different configurations with 22 different implants were analyzed. Glenoid, humeral, and global lateralization was measured on digitized templates. Implant lateralization was normalized to the lateral offset of the Delta III. Each implant was defined as a combination of one of two glenoid categories (medialized glenoid (MG), lateralized glenoid (LG), and one of four humeral categories (medialized humerus (MH), minimally lateralized humerus (LH), lateralized humerus (LH+). In addition, implants were separated in categories of 5-mm increments for global offset (medialized RSA (M-RSA), minimally lateralized RSA (ML-RSA), lateralized RSA (L-RSA), highly lateralized RSA (HL-RSA), and very highly lateralized RSA (VHL-RSA).

RESULTS

The global lateral offset of the Delta III was 13.1 mm; global lateral offset of all designs in this study varied between 13.1 and 35.8 mm. Regarding their global lateral offset, five implants are M-RSA (lateral offset < 18.1 mm), five ML-RSA (18.1-23.1 mm), seven L-RSA (23.1-28.1 mm), six HL-RSA (28.1-33.1 mm), and one VHL-RSA (33.1-38.1 mm).

CONCLUSION

There is high variability in the amount of lateralization provided by the majority of RSAs currently available. This descriptive analysis can help surgeons understand the features of implants in the market based on their lateralization in order to adapt the surgical technique depending on the expected lateral offset of the design being implanted.

Factors contributing to glenoid baseplate micromotion in reverse shoulder arthroplasty: a biomechanical study

BACKGROUND

Reverse shoulder arthroplasty (RSA) is typically performed in patients with cuff tear arthropathy. A common type of RSA baseplate has a central peg and 4 peripheral screws inserting into the glenoid surface. Baseplate failure is a significant postoperative complication that reduces prosthetic longevity and usually requires revision surgery. This study evaluated the contribution of mechanical factors on initial baseplate fixation.

MATERIALS AND METHODS

This study simulated glenoid baseplate loading in a RSA. A half-fractional factorial design was used to test 5 factors: bone density (160 or 400 kg/m³), screw length (18 or 36 mm), number of screws (2 or 4), screw angle (neutral or diverging), and central peg length (13.5 or 23.5 mm). Trials were cyclically loaded at a 60° angle with 500 N for 1000 cycles. Micromotion at 4 peripheral screw positions was analyzed using a multifactorial analysis of variance (P < .05).

RESULTS

We found an increase in micromotion with 3 scenarios: (1) lower bone density at all screw positions; (2) shorter central peg length at the inferior, superior and anterior screws; and (3) shorter screw length at the inferior and anterior screws. There were interactions between bone density and screw length at the inferior and anterior screws and between bone density and central peg length at the inferior, superior, and anterior screws.

DISCUSSION

Greater bone density, a longer central peg, and longer screws provide improved initial glenoid fixation in an RSA, whereas the number of screws, and the angle of screw insertion do not. These findings may help minimize baseplate failure and revision operations.

Long - Term survivorship and clinical and radiological follow - up of the primary uncemented Delta III reverse shoulder prosthesis

Background

Purpose of this study was to evaluate the long - term survivorship and clinical and radiological results of a primary reverse total shoulder arthroplasty (RTSA) performed with uncemented stems.

Methods

From 2001 until 2006 61 primary uncemented RTSAs were implanted, which were included in a Kaplan-Meier survival analysis. Range of motion, functional scores and radiological follow - up was obtained. 27 patients were available for follow - up. Mean follow-up was 9.2 years (SD 2.4).

Results

Mean cumulative survival was 82.4% (95% CI: 50.7-94.6%) of the total construct and 98.3% (CI: 88.8-98.8%) of the uncemented humeral stem after 12.5 years. Five revisions occurred (8.2%). Mean anteflexion improved from 69.3 to 111.9° (p < 0.0001), lateral elevation from 65.9 to 101.3° (p < 0.0001), Constant-Murley score from 39.1 to 66.9 (p < 0.0001), Simple Shoulder Test from 1.5 to 7.1 (p < 0.0001), and VAS-pain from 65.5 to 6.6 at final follow-up (p = 0.0003). Scapular notching was present in 94.1% of the patients.

Conclusions

The present study shows that the long-term clinical results of the primary Delta III RTSA seem very encouraging and survivorship of, in particular, its uncemented humeral stem is good.

Scapular Notching in Reverse Total Shoulder Arthroplasty

Scapular notching is a common radiographic finding occurring after reverse total shoulder arthroplasty, and it refers to an erosive lesion of the inferior scapular neck because of the impingement of the humeral implant during adduction. The clinical importance of notching is unclear, and the optimal treatment of severe notching is unknown. The incidence and severity of scapular notching is related to prosthetic design and surgical technique. Implant design factors include size, shape, and position of the glenosphere, inclination of the humeral neck-shaft angle, implant offset, and native scapular anatomy. Scapular notching may lead to deterioration of functional outcomes and glenoid implant loosening and failure. Lateral offset, inferior glenosphere overhang, and careful consideration of the presurgical glenoid morphology may help prevent scapular notching. Currently, there is limited evidence to direct the management of scapular notching, and further research is needed to elucidate optimal prevention and treatment strategies.

Clinical outcomes and complications of cementless reverse total shoulder arthroplasty during the early learning curve period

Background

Reverse total shoulder arthroplasty (RTSA) is a treatment option for patients with severe osteoarthritis, rotator cuff arthropathy, or massive rotator cuff tear with pseudoparalysis. We are to deduce not only the early functional outcomes and complications of cementless RTSA during the learning curve period but also complication-based, and operation time-based learning curve of RTSA.

Methods

Between March 2010 and February 2014, we retrospectively evaluated 38 shoulders (6 male, 32 female). The average age of the patients was 73.0 years (range, 63 to 83 years), and the average follow-up was at 24 months (range, 12–53 months). The visual analog scale (VAS), University of California Los Angeles (UCLA) score and constant score were used to evaluate the clinical outcomes. We evaluated patients radiographically at 2 weeks, 3 months, 6 months, 1 year, and then annually thereafter for any evidence of complications.

Results

The VAS score improved from 4.0 to 2.8 (p = 0.013). The UCLA score improved from 16.0 to 27.9 (p = 0.002), and the constant score improved from 41.4 to 78.9 (p < 0.001), which were statistically significant. While active forward flexion, abduction, and internal rotation improved (p value = 0.001, < 0.01, 0.15), external rotation did not show significant improvement (p = 0.764). Postoperative complications included acromion fracture (one case), glenoid fracture (one case), peripristhetic humeral fracture (one case), axillary nerve injury (one case), infection (one case), and arterial injury (one case). Our study presented an intraoperative complication-based learning curve of 20 shoulders, and operation time-based learning curve of 15 shoulders.

Conclusions

The clinical outcomes of RTSA were satisfactory with overall complication rates of 15.7%. An orthopedic surgeon within the learning curve period for the operation of RTSA should be cautious when selecting the patients and performing RTSA.

Trial registration

Retrospectively registered.

Proximal Humerus Fractures: Evaluation and Management in the Elderly Patient

Introduction:

Proximal humerus fractures are common in the elderly. The evaluation and management of these injuries is often controversial. The purpose of this study is to review recent evidence and provide updated recommendations for treating proximal humerus fractures in the elderly.

Methods:

A literature review of peer-reviewed publications related to the evaluation and management of proximal humerus fractures in the elderly was performed. There was a focus on randomized controlled trials and systematic reviews published within the last 5 years.

Results:

The incidence of proximal humerus fractures is increasing. It is a common osteoporotic fracture. Bone density is a predictor of reduction quality and can be readily assessed with anteroposterior views of the shoulder. Social independence is a predictor of outcome, whereas age is not. Many fractures are minimally displaced and respond acceptably to nonoperative management. Displaced and severe fractures are most frequently treated operatively with intramedullary nails, locking plates, percutaneous techniques, or arthroplasty.

Discussion:

Evidence from randomized controlled trials and systematic reviews is insufficient to recommend a treatment; however, most techniques have acceptable or good outcomes. Evaluation should include an assessment of the patient’s bone quality, social independence, and surgical risk factors. With internal fixation, special attention should be paid to medial comminution, varus angulation, and restoration of the calcar. With arthroplasty, attention should be paid to anatomic restoration of the tuberosities and proper placement of the prosthesis.

Conclusion:

A majority of minimally displaced fractures can be treated conservatively with early physical therapy. Treatment for displaced fractures should consider the patient’s level of independence, bone quality, and surgical risk factors. Fixation with percutaneous techniques, intramedullary nails, locking plates, and arthroplasty are all acceptable treatment options. There is no clear evidence-based treatment of choice, and the surgeon should consider their comfort level with various procedures during the decision-making process.

Glenosphere size in reverse shoulder arthroplasty: is larger better for external rotation and abduction strength?

BACKGROUND

The role of glenosphere size in reverse shoulder arthroplasty (RSA) may be important in prosthetic stability, joint kinematics, rotator cuff tension and excursion, scapular impingement, humeral lateralization, deltoid wrap, and the occurrence of "notching." This study compared short- and midterm clinical and radiographic outcomes for 2 different glenosphere sizes of a single RSA type with respect to implant positioning, glenoid size, and morphology.

METHODS

This retrospective analysis included 68 RSA procedures that were prospectively documented in a local register during a 5-year postoperative period. Two glenosphere diameter sizes of 36 mm (n = 33) and 44 mm (n = 35) were used. Standard radiographs were made preoperatively (ie, baseline) and at 6, 12, 24, and 60 months after surgery. Range of motion, strength, the Constant-Murley score, and the Shoulder Pain and Disability Index were also assessed at all follow-up visits. The effect of glenosphere size on measured outcomes was adjusted for baseline values, patient gender, and humeral head diameter.

RESULTS

No significant differences were found in the functional scores between treatment groups at all follow-up assessments. At the 12-month follow-up, patients with a 44-mm glenosphere had greater external rotation in adduction (mean difference, 12°; P = .001) and abduction strength (mean difference, 1.4 kg; P = .026) compared with those with the smaller implant. These differences remained at 60 months. Scapular notching was observed in 38% of all patients, without any relevant difference between the groups.

CONCLUSION

An increase in glenosphere diameter leads to a clinically moderate but significant increase in external rotation in adduction and abduction strength at midterm follow-up.

Reverse total shoulder glenoid baseplate stability with superior glenoid bone loss

BACKGROUND

Superior wear of the glenoid bone is common in patients with rotator cuff arthropathy. This can become a treatment challenge for patients who require shoulder arthroplasty. In reverse shoulder arthroplasty (RSA), glenoid bone loss may affect the stability of baseplate fixation. The primary purpose of this biomechanical laboratory study was to assess the initial fixation stability of RSA glenosphere baseplates in the presence of variable amounts of superior glenoid bone loss.

MATERIALS AND METHODS

High-density solid rigid polyurethane foam (30 pounds/cubic foot) was machined to model the glenoid with variable superior defects that provided different levels of support (100%, 90%, 75%, and 50%) for the glenosphere baseplate. The samples were cyclically loaded (0-750 N at 1 Hz for 5000 cycles) at a 60° glenohumeral angle. The micromotion and migration of the baseplate were calculated from displacement data captured during the loading tests with an array of 3 linear variable differential transformers mounted around the baseplate.

RESULTS

Micromotion was significantly greater in samples with 50% defects compared with those with smaller defects. Migration was significantly greater after testing for all defect sizes.

CONCLUSIONS

Initial fixation of RSA glenosphere baseplates was significantly reduced in models with 50% bone loss on the superior edge compared with models with less bone loss in this high-density bone foam model.

3D image-based morphometric analysis of the scapular neck length in subjects undergoing reverse shoulder arthroplasty

Scapular notching after RSA may, in part, be related to a patient's scapular morphology. The purpose of this study was to develop a novel 3 D measurement technique to describe infraglenoid tubercle morphometry. We hypothesize that the parameters describing infraglenoid tubercle would be normally distributed and would correlate with individual's demographics and glenoid morphometry. A group of 110 subjects treated with RSA were evaluated. Scapular geometry was obtained from pre-operative CT scans. The scapular neck length was defined in anterior and posterior view as the orthogonal distance between the glenoid surface and (a) the point of most significant change of curvature on lateral pillar; (b) the most lateral portion of the infraglenoid tubercle. Scapular neck angle, maximum anatomical adduction angle, glenoid width, height and version were also measured. Scapular neck length measured in the anterior and posterior view were normally distributed with mean values of 17.6 ± 2.8 mm and 7.9 ± 2.5 mm, respectively. Scapular neck angle was on average 112.4 ± 10.6° and maximal adduction angle was 17.6 ± 2.8°. No significant associations between infraglenoid tubercle morphometric parameters, demographic, glenoid size or version were identified. Improved understanding of the patient-specific risk factors for scapular notching will help surgeons with pre-surgical planning and implant selection. Parametrization of the infraglenoid tubercle presented in this study showed normal distribution in the population unrelated to gender, side or demographics. The size of the infraglenoid tubercle is a unique trait, pre-operative evaluation of the scapular neck should be always warranted to decrease the incidence of post-operative notching. Clin. Anat. 31:43-55, 2018. © 2017 Wiley Periodicals, Inc.

Impact of scapular notching on clinical outcomes after reverse total shoulder arthroplasty: an analysis of 476 shoulders

BACKGROUND

Scapular notching is a complication unique to reverse total shoulder arthroplasty (rTSA), although its clinical implications are unclear and remains controversial.

METHODS

We retrospectively reviewed rTSA patients of a single implant design in 476 shoulders with a minimum 2-year clinical and radiographic follow-up. Clinical measures included active range of motion and American Shoulder and Elbow Surgeons scores, in addition to one or more of the Constant score, Shoulder Pain and Disability Index, Simple Shoulder Test (SST), and University of California, Los Angeles Shoulder Rating Scale. Complications and rates of humeral radiolucencies were also recorded.

RESULTS

Scapular notching was observed in 10.1% (48 of 476) of rTSAs and was associated with a longer clinical follow-up, lower body weight, lower body mass index, and when the operative side was the nondominant extremity. Patients with scapular notching had significantly lower postoperative scores on the Shoulder Pain and Disability Index, Constant, Simple Shoulder Test, and University of California, Los Angeles, Shoulder Rating Scale compared with patients without scapular notching. Patients with scapular notching also had significantly lower active abduction, significantly less strength, and trended toward significantly less active forward flexion (P = .0527). Finally, patients with scapular notching had a significantly higher complication rate and trended toward a significantly higher rate of humeral radiolucent lines (P = .0896) than patients without scapular notching.

CONCLUSIONS

This large-scale outcome study demonstrates that patients with scapular notching have significantly poorer clinical outcomes, significantly less strength and active range of motion, and a significantly higher complication rate than patients without scapular notching. Longer-term follow-up is necessary to confirm that these statistical observations in the short-term will result in greater clinically meaningful differences over time.