Reverse Shoulder Arthroplasty System Research Articles

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

The influence of position of the humeral tray (inlay or onlay) on clinical outcomes in reverse shoulder arthroplasty (RSA) is a topic of debate. The purpose of this study was to compare clinical and radiographic outcomes of patients with cuff tear arthropathy treated with RSA systems with inlay or onlay humeral tray design, similar neck-shaft angles, and lateralized glenospheres. This was a retrospective study of prospectively obtained data from 1 tertiary care center. We identified all patients who underwent primary RSA between 2009 and 2017 (N=511). We included 102 patients with diagnosed cuff tear arthropathy treated with RSA prostheses with a lateralized glenosphere and 135° neck-shaft angle (with either an inlay or onlay humeral tray design) who had a minimum of 2 years of follow-up (mean, 44months; range, 24-125months). Sixty-three patients (62%) had an inlay humeral tray (inlay group) and 39 (38%) had an onlay tray (onlay group). All patients underwent preoperative and postoperative evaluations, including measures of patient-reported outcomes (PROs), shoulder range of motion (ROM) testing, and radiographic imaging. Clinical relevance of changes in PROs and ROM was evaluated using published values for minimal clinically important differences. The 2 groups did not differ by demographic characteristics except for a higher proportion of women in the inlay group (75%) than in the onlay group (56%) (P=.04). Preoperative PROs and ROM were not significantly different between groups. At final follow-up, PROs and ROM were not different between groups in terms of statistical significance or clinical relevance. We found no significant differences in the rate of baseplate loosening (inlay, 3.2% vs. onlay, 5.1%, P=.63), revision surgery (inlay, 0% vs. onlay 5.1%, P=.07), acromial stress fracture (inlay, 3.2% vs. onlay, 5.1%, P=.63), prosthesis dislocation (inlay, 0% vs. onlay, 2.6%, P=.20), or scapular notching (inlay, 21% vs. onlay, 7.7%, P=.08). At 2-year minimum follow-up, the position of the humeral tray in RSA prostheses (either inlay or onlay) for cuff tear arthropathy was not associated with PROs, shoulder ROM, or rates of complications, including baseplate loosening, acromial stress fracture, and scapular notching.

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

Reverse shoulder arthroplasty (RSA) designs include multiple options for glenoid component lateralization, and humeral component lateralization and distalization (inlay/onlay constructs). The influence of combined glenoid lateralization, and humeral distalization on acromial and deltoid stresses is not well understood. The purpose of this study was to evaluate changes in deltoid and acromial stresses with variations in glenoid lateralization, and with inlay versus onlay humeral components in RSA. Finite element analysis was performed using a RSA system with both inlay and onlay configurations. Variations in total glenoid lateralization from 3 to 9 mm were evaluated. Deltoid and acromial stresses were determined following virtual implantation and with 50° of external rotation. Increased glenoid lateralization resulted in greater stress of the deltoid and acromion. There was a modest increase in deltoid stress with glenoid lateralization alone (7% and 7.5% with progressive lateralization from 3 to 6 mm and 6 to 9 mm, respectively), but deltoid stress increased substantially with use of an onlay construct (60% at 9 mm of glenoid lateralization). Acromial stress correspondingly increased 37% with glenoid lateralization, and up to 117% with an onlay humeral construct. Increased lateralization of the glenoid component resulted in increased levels of deltoid and acromial stress. For a given amount of glenoid lateralization, utilization of an inlay stem decreased acromial and deltoid stresses compared to onlay constructs. These data allow surgeons to better understand the interactions of glenoid and humeral lateralization and distalization in the setting of contemporary RSA systems.Level of Evidence: Basic Science Study: Computer Modeling.

Lateralization and distalization shoulder angles do not predict outcomes in reverse shoulder arthroplasty for cuff tear arthropathy

In reverse shoulder arthroplasty (RSA), there is a plethora of measurements regarding implant lateralization and distalization to optimize the center of rotation. Two specific measurements known as the lateralization shoulder angle (LSA) and distalization shoulder angle (DSA) have been the recent focus of studies to assess their association with RSA and postoperative function. The aim of this study was to evaluate the prognostic clinical value of the LSA and DSA in a large cohort of patients with cuff tear arthropathy (CTA) who were treated with different RSA systems. Two local shoulder arthroplasty registries were reviewed for all RSA patients documented with a radiological assessment and complete 2-year follow-up examination. The main inclusion criterion was primary RSA for patients with CTA. Any patients with either a complete teres minor tear, os acromiale or acromial stress fractures reported between the time of surgery and the 24-month follow-up were excluded. Five different RSA implant systems with four different neck-shaft angles were assessed. The Constant Score (CS), Subjective Shoulder Value (SSV) and range of motion (ROM) at two years were correlated with both LSA and DSA assessed on 6-month anteroposterior radiographs. Linear and parabolic univariable regressions were calculated for both shoulder angles, for each prosthesis system and for the entire patient cohort. Between May 2006 and November 2019, there were a total of 630 CTA patients who had undergone primary RSA. Of this large cohort, 270 were treated with the Promos Reverse (neck-shaft angle [NSA], 155°), 44 with the Aequalis Reversed II (NSA, 155°), 62 with the Lima SMR Reverse (150°), 25 with the Aequalis Ascend Flex (145°) and 229 with the Univers Revers (135°) prosthesis systems. The mean (standard deviation [SD]) LSA was 78° (10; range, 6-107) and the mean DSA was 51° (10; range, 7-91). The average CS at 24 months follow-up was 68.1 (SD: 13; 13-96) points. Neither the linear nor parabolic regression calculations for LSA or DSA revealed significant associations with any of the clinical outcomes. Different patients may achieve different clinical outcomes despite having identical LSA and DSA values. There is no association between angular radiographic measurements and 2-year functional outcome.

Lateralized glenosphere reverse shoulder arthroplasty: inlay and onlay designs have similar clinical outcomes in patients with glenohumeral osteoarthritis.

Whether or how the position of the humeral tray (inlay or onlay) in reverse shoulder arthroplasty (RSA) affects outcomes is unclear. Our goal was to compare the clinical and radiographic results of RSA systems with inlay vs. onlay designs but with similar neck shaft angles (NSAs) and lateralized glenospheres. We screened the institutional database at our tertiary academic center for patients who underwent primary RSA (with a lateralized glenosphere and a 135° NSA) from 2009 through 2017. The indication for surgery was glenohumeral osteoarthritis with glenoid bone loss (Walch classification A2, B2, B3, or C) and an intact rotator cuff. All patients were followed for a minimum of 2 years (mean, 47 months; range, 24-123 months). The humeral tray design was inlay for 79 patients and onlay for 71. All patients underwent preoperative and postoperative evaluations, including physical examination, radiography, and patient-reported outcome measures (visual analog scale for pain, American Shoulder and Elbow Surgeons score, Simple Shoulder Test, and Western Ontario Osteoarthritis of the Shoulder index). Compared with preoperative values, both groups achieved minimal clinically important differences in range of motion and patient-reported outcomes at the final follow-up. We found no significant differences between groups in any of these measures at the final follow-up. Rates of revision (inlay, 3.8% vs. onlay, 1.4%), scapular notching (inlay, 5.1% vs. onlay, 7.0%), acromial stress fracture (inlay, 0% vs. onlay, 2.8%), and tuberosity resorption (inlay, 25% vs. onlay, 27%) were not significantly different between groups (all, P > .05). For patients with glenohumeral osteoarthritis with glenoid bone loss and an intact rotator cuff who underwent RSA using a lateralized glenosphere prosthesis with a 135° NSA, there were no significant differences between the inlay and onlay groups for range of motion, patient-reported outcomes, or complication rates. These findings are limited to this off-label indication for RSA.

The influence of reverse arthroplasty humeral component design features on scapular spine strain

Reverse shoulder arthroplasty (RSA) humeral implant parameters have been previously studied with respect to range of motion, deltoid function, and stability. However, limited literature exists on the influence of humeral design features on scapular spine strain. The purpose of this cadaveric biomechanical simulator study was to evaluate the role of humeral component lateralization and neck-shaft angle (NSA) on scapular spine strain. Eight fresh-frozen cadaveric shoulders were tested using an invitro shoulder simulator. A custom-designed modular RSA system was implanted that allowed for the in situ adjustment of humeral lateralization and NSA. Scapular spine strain was measured by strain gauges placed along the acromion and scapular spine in clinically relevant positions representative of the Levy fracture zones. All testing was conducted in both abduction and forward elevation. In Levy zones 2 and 3, increasing humeral lateralization caused significant incremental decreases in scapular spine strain at 0° and 90° abduction (P < .042). Strain decreases as high as 34% were noted with increases in humeral lateralization from -5 to 15 mm (P = .042). Changing NSA had no statistically significant effect on scapular spine strain (P > .14). Some humeral implant design features in RSA have effects on scapular spine strain. Humeral component lateralization had significant effects, whereas adjusting NSA resulted in no substantial differences in scapular spine strain. Understanding humeral component variables is important to allow for design optimization of future RSA implants.

Optimal glenosphere size cannot be determined by patient height

Glenosphere size remains 1 surgeon-controlled variable that can affect patient outcomes following reverse shoulder arthroplasty (RSA). There remains no objective criterion to guide surgeons in choosing glenosphere size. This study's purpose was to evaluate range of motion (ROM) as a function of patient height and glenosphere size to determine the optimal glenosphere size based on patient height. We retrospectively reviewed 589 primary RSAs from a multicenter shoulder arthroplasty database of a single RSA system with multiple glenosphere sizes. Shoulders were separated into groups based on glenosphere size (38 or 42 mm). Predictive accuracy was calculated in relation to height and sex for predicting glenosphere size. Improvements in active ROM and patient-reported outcome measures (PROMs) were compared based on glenosphere size as a function of height. Logistic regression analysis demonstrated a strong association of height and sex with surgeon selection of glenosphere size, with shorter heights preferentially treated with 38-mm glenospheres and taller heights with 42-mm glenospheres. There were no statistically significant interaction effects of glenosphere size and height on improvements in ROM or PROMs. These results indicate that for a given glenosphere size, there is not an optimal height range to maximize improvements in postoperative outcome measures. Height and sex are highly correlated with a surgeon's choice of glenosphere size. However, on the basis of improvements in ROM and PROMs, no recommendation can be made for surgeons to select a particular glenosphere size based on a patient's height. Surgeons should consider other variables when selecting a glenosphere size.

Restoration of External Rotation Following Reverse Shoulder Arthroplasty without Latissimus Dorsi Transfer.

Background:Latissimus dorsi transfers have been considered necessary to restore active external rotation following reverse shoulder arthroplasty (RSA). The purpose of this study was to assess the effectiveness of an RSA system that lateralizes the center of rotation in restoring active external rotation without a latissimus dorsi transfer in patients with a preoperative external rotation deficit (external rotation of <0°).Methods:We retrospectively reviewed the records of patients who had undergone RSA with a lateralized center of rotation without a latissimus dorsi transfer. All patients had had a preoperative external rotation deficit (active external rotation of <0°), and all were followed for a minimum of 2 years. Patients were stratified into 2 groups on the basis of the preoperative diagnosis: (1) those with a combined loss of active elevation and external rotation as a result of rotator cuff tear arthropathy (CLEER group) and (2) those with a combined loss of active elevation and external rotation as a result of other posttraumatic etiologies (non-CLEER group). The mean improvement of external rotation was analyzed. Subgroup analysis was performed on the basis of the Goutallier classification, glenosphere lateralization, and total prosthetic lateralization.Results:Thirty-three patients (24 in the CLEER group and 9 in the non-CLEER group) met the inclusion criteria. The average follow-up was 43.4 months (range, 24 to 77 months). External rotation improved significantly in both the CLEER group (from −21° preoperatively to 28° postoperatively; p < 0.001) and the non-CLEER group (from −19° preoperatively to 26° postoperatively; p = 0.001). Goutallier classification, glenosphere lateralization, and total prosthetic lateralization were not correlated with the degree of improvement of external rotation in either group (p > 0.05 for all).Conclusions:RSA with a lateralized center of rotation can effectively restore external rotation without the use of a latissimus dorsi transfer in patients with a preoperative external rotation deficit as a result of rotator cuff arthropathy or other posttraumatic etiologies.Level of Evidence:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Paper #5 - Restoration of External Rotation after Reverse Shoulder Arthroplasty Without Latissimus Dorsi Transfer

Background: For patients with a preoperative external rotation (ER) deficit, latissimus dorsi transfers have been thought necessary to restore active ER following reverse shoulder arthroplasty (RSA). The purpose of this study was to assess the effectiveness of a RSA system that lateralizes the center of rotation (COR) in restoring active ER without the use of latissimus dorsi transfer in a subset of patients with a preoperative ER deficit (ER < 0°).

Inter and intra-system size variability of reverse shoulder arthroplasty polyethylene inserts.

Background:As the incidence of reverse shoulder arthroplasty (RSA) increases, so will the revision burden. At times, the revision surgeon may be faced with a well-fixed component on one side of the joint and revision implants from a different manufacturer. The ability to use glenoid and humeral implants from different manufacturers could simplify the revision procedure. This study hypothesized that across a range of RSA systems, some implants would demonstrate high size compatibility and others would demonstrate low compatibility.Materials and Methods:Six polyethylene inserts each from eight reverse total shoulder arthroplasty systems were examined (48 total inserts). All inserts were scanned using a laboratory micro-computed tomography scanner at 50 μm isotropic voxel spacing, and their surface geometries were reconstructed. The different implant geometries were co-registered, and the three-dimensional (3D) variability between the articular surfaces of the different implant systems was measured. Intrasystem manufacturing variability was also determined by measuring the 3D variability of inserts from the same system.Results:The intersystem polyethylene articular surface deviations between same-size systems were not significantly different (P = 0.61) and were a mean maximum of 60 ± 16 μm (range: 30-80 μm). Intrasystem manufacturing variability was equivalent between all but two models, averaging 49 ± 17 μm (range: 23-99 μm).Discussion:Differences in articular geometry between same-size inserts from different systems were on the same scale as intrasystem manufacturing variability, suggesting that different implant systems of the same nominal diameter could potentially be used interchangeably in revision or extenuating circumstances.Conclusion:The results of this study suggest that surgeons can theoretically interchange same-sized implant components from the different RSA systems tested when conducting revisions.