Glenosphere Design Research Articles

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.

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. 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 ± 13.1months. 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. 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%). 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 III; Retrospective Cohort Comparison; Treatment Study.

Effect of RSA glenoid baseplate central fixation on micromotion and bone stress

BackgroundIn reverse shoulder arthroplasties (RSA), osseous in-growth is promoted if glenoid micromotion does not exceed 150 μm. The purpose of this study was to determine whether the configuration of central fixation for RSA glenoid baseplates reduces implant micromotion or changes scapula bone stresses.MethodsUsing finite element analysis, glenoid baseplate fixation was tested in a cohort of 3 male and 2 female patients who were to undergo RSA. Computer models were created for 3 different RSA glenoid baseplate and 84 glenosphere designs, a central threaded peg (1 variant, D-TP), a central unthreaded peg (2 variants, I- 85 P(15) and I-P(25)), and a central peg with a screw (2 variants, A-PS and I-PS). A compressive and shear force of 756 N was distributed across the glenosphere with the scapula anchored.ResultsDisplacement was within 20-130 μm at the glenosphere baseplate-bone interface for all baseplates. The glenospheres with unthreaded pegs had intermediate displacement values (I-P(15): median, 89 μm; range, 32-112 μm; and I-P(25): median, 93 μm; range, 31-109 μm). The von Mises stresses were 1.8-7.0 MPa within cortical bone and 0.6-1.6 MPa within trabecular bone. Cortical bone stresses were similar with unthreaded pegs (I-P(15): median, 4.2 MPa; range, 1.8-6.0 MPa; and I-P(25): median, 4.2 MPa; range, 1.8-6.1 MPa), whereas mean trabecular stresses were similar for all configurations.ConclusionsAll configurations yielded adequate stability, with micromotions being below 150 μm. The unthreaded pegged designs provided a valid alternative to the stable threaded pegged convex baseplates in terms of micromotions and bone stresses.

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

To determine how different combinations of humeral stem and glenosphere designs for reverse shoulder arthroplasty (RSA) influence range of motion (ROM) and muscle elongation. A computed tomography scan of a non-pathologic shoulder was used to simulate all shoulder motions, and thereby compare the ROM and rotator cuff muscle lengths of the native shoulder versus 30 combinations of humeral components (1 inlay straight stem with 155° inclination and five onlay curved stems with 135°, 145° or 155° inclinations, using concentric, medialized or lateralized trays) and glenospheres (standard, large, lateralized, inferior eccentric and bony increased-offset (BIO-RSA)). Only five of the 30 combinations restored ≥ 50% of the native ROM in all directions: the 145° onlay stem (concentric tray) combined with lateralized or inferior eccentric glenospheres and the 145° stem (lateralized tray) combined with either a large, lateralized or inferior eccentric glenosphere. Lengthening of the supraspinatus and infraspinatus, observed for all configurations, was greatest using onlay stems (7-30%) and BIO-RSA glenospheres (13-31%). Subscapularis lengthening was observed for onlay stems combined with BIO-RSA glenospheres (5-9%), while excessive subscapularis shortening was observed for the inlay stem combined with all glenospheres except the BIO-RSA design (> 15%). The authors suggest implanting 145° onlay stems, with concentric or lateralized trays, together with lateralized or inferior eccentric glenospheres.

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

BackgroundLittle 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.MethodsThree 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.ResultsMean 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).ConclusionDifferent 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 evidenceBasic Science Study, Biomechanical Study.

How common are acromial and scapular spine fractures after reverse shoulder arthroplasty?: A systematic review.

Acromial fractures following reverse shoulder arthroplasty (RSA) have a wide range of incidences in reported case series. This study evaluates their incidence following RSA by systematically reviewing the current literature. A systematic review using the search terms "reverse shoulder", "reverse total shoulder", or "inverted shoulder" was performed using PubMed, Web of Science, and Cochrane databases between 1 January 2010 and 31 March 2018. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used. Studies were included if they reported on RSA outcomes and the incidence rate of acromial and/or scapular spine fractures. The rate of these fractures was evaluated for primary RSA, revision RSA, RSA indications, and RSA implant design. The review included 90 articles out of 686 identified after exclusions. The incidence rate of acromial and/or scapular spine fractures was 2.8% (253/9048 RSAs). The fracture rate was similar for primary and revision RSA (2.8% vs 2.1%; p = 0.4). Acromial fractures were most common after RSA for inflammatory arthritis (10.9%) and massive rotator cuff tears (3.8%). The incidence was lowest in RSA for post-traumatic arthritis (2.1%) and acute proximal humerus fractures (0%). Lateralized glenosphere design had a significantly higher rate of acromial fractures compared with medial glenosphere designs. Based on current English literature, acromial and/or scapular spine fractures occur at a rate of 2.8% after RSA. The incidence is slightly more common after primary compared with revision arthroplasty. Also, higher rates of acromial fractures are reported in RSA performed for inflammatory arthritis and in the lateralized glenoid design. Cite this article: Bone Joint J 2019;101-B:627-634.

Glenosphere design affects range of movement and risk of friction-type scapular impingement in reverse shoulder arthroplasty.

Scapular notching is a frequently observed radiographic phenomenon in reverse shoulder arthroplasty (RSA), signifying impingement of components. The purposes of this study were to evaluate the effect of glenoid component size and glenosphere type on impingement-free range of movement (ROM) for extension and internal and external rotation in a virtual RSA model, and to determine the optimal configuration to reduce the incidence of friction-type scapular notching. Preoperative CT scans obtained in 21 patients (three male, 18 female) with primary osteoarthritis were analyzed using modelling software. Two concurrent factors were tested for impingement-free ROM and translation of the centre of rotation: glenosphere diameter (36 mm vs 39 mm) and type (centred, 2 mm inferior eccentric offset, 10° inferior tilt). Glenosphere size was most predictive of increased extension and external rotation, whereas lateralization of the centre of rotation was the most predictive factor for internal rotation. A larger diameter of glenosphere combined with a 10° tilted configuration demonstrated superior values for extension and external rotation, whereas the eccentric component improved internal rotation by a mean 8.9° (standard deviation 2.7°) compared with a standard concentric glenosphere. Glenosphere configuration can be modified to increase range of movement in RSA. Friction-type scapular notching was most effectively reduced by use of a large-diameter glenosphere with 10° inferior tilt. Cite this article: Bone Joint J 2018;100-B:1182-6.

Influence of Glenosphere Design on Outcomes and Complications of Reverse Arthroplasty: A Systematic Review.

BackgroundDifferent implant designs are utilized in reverse shoulder arthroplasty. The purpose of this systematic review was to evaluate the results of reverse shoulder arthroplasty using a traditional (Grammont) prosthesis and a lateralized prosthesis for the treatment of cuff tear arthropathy and massive irreparable rotator cuff tears.MethodsA systematic review of the literature was performed via a search of two electronic databases. Two reviewers evaluated the quality of methodology and retrieved data from each included study. In cases where the outcomes data were similar between studies, the data were pooled using frequency-weighted mean values to generate summary outcomes.ResultsThirteen studies met the inclusion and exclusion criteria. Demographics were similar between treatment groups. The frequency-weighted mean active external rotation was 24° in the traditional group and 46° in the lateralized group (p = 0.0001). Scapular notching was noted in 44.9% of patients in the traditional group compared to 5.4% of patients in the lateralized group (p = 0.0001). The rate of clinically significant glenoid loosening was 1.8% in the traditional group and 8.8% in the lateralized group (p = 0.003).ConclusionsBoth the traditional Grammont and the lateralized offset reverse arthroplasty designs can improve pain and function in patients with diagnoses of cuff tear arthropathy and irreparable rotator cuff tear. While a lateralized design can result in increased active external rotation and decreased rates of scapular notching, there may be a higher rate of glenoid baseplate loosening.

Biomechanical evaluation of inferior scapula notching of reverse shoulder arthroplasty depending on implant configuration and scapula neck anatomy

Purpose:The presence of inferior scapula notching is significantly affected by the anatomy the scapula and can be influenced by the glenosphere design and position and the onlay type.Materials and Methods:A biomechanical study was undertaken with 13 human shoulder specimens in a robot-assisted shoulder simulator. Inferior scapula contact during adduction of the humerus was detected using a contact pressure film. Computed tomography scans with three-dimensional reconstructions of each specimen were performed.Results:The greatest improvement of the scapula notching angle (SNA) was achieved by simultaneous implantation of a shallow humeral onlay and an eccentric glenosphere design: 16.3-19.0° (P < 0.005). The SNA was significantly decreased by 5.8° when shifting from a 38 mm centric glenosphere to a 42 mm centric glenosphere (P < 0.005) and by 8.9° comparing the 38 mm centric glenosphere with 38 mm eccentric glenosphere (P < 0.005). The solitary implantation of a shallow onlay significantly decreased the SNA depending on the glenosphere size between 7.4° and 8.0° (P = 0.001). A more inferior position of the metaglene as well as a long scapula neck (P = 0.029) and a large lateral scapula pillar angle (P = 0.033) were correlated with a lower SNA.Conclusion:This study demonstrates the importance of inferior glenosphere placement and the benefit of eccentric glenosphere and shallow humeral cup design to reduce the adduction deficit of the reverse shoulder. The presence of a short neck of the scapula can have a negative prognostic effect on inferior impingement during adduction of the arm.Level of Evidence:Basic Science Study

Influence of glenosphere design and material on clinical outcomes of reverse total shoulder arthroplasty.

The aim of this multicentre retrospective study was to compare reverse total shoulder arthroplasty clinical outcomes with glenospheres of different diameters, designs and materials. Between 2003 and 2008, 133 patients were divided into three groups: 60 (45%) with 36-mm standard CoCrMo (group A), 21 (16%) with 36-mm eccentric cobalt-chromium-molybdenum (CoCrMo) (group B) and 52 (39%) with 44-mm cross-linked ultra-high molecular weight polyethylene (X-UHMWPE) (group C) glenospheres. Mean (SD) follow-up was 38.7 (17.4) months. Clinical evaluation included Constant score and range of motion. Radiographic analysis included radiolucent lines, instability, loosening and assessment of scapular notching. Mean Constant score significantly increased for all groups (Wilcoxon test, p < 0.001). Group C allowed a higher and stable increase in range of motion. After 12 months and 24 months, groups C and B showed less pain than group A (Mann-Whitney U-test, p < 0.05). Group C had significantly lower scapular notching than group B (Mann-Whitney U-test, p = 0.001) and A (Mann-Whitney U-test, p = 0.009) at 12 months, 24 months and 36 months. Groups A and C presented 5 (8.3%) and 4 (7.6%) early complications, respectively. The present study reported good results for all groups, although groups C and A presented better clinical outcomes, significantly lower notching and instability. A 44-mm X-UHMWPE glenosphere allowed a faster and more stable functional recovery, despite poorest pre-operative conditions. Additional long-term studies are needed to evaluate survivorship.

Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty

Scapular notching is a common observation during radiological follow-up of reverse shoulder arthroplasty. The purpose of this study was to evaluate the effect of glenosphere design and humeral component retroversion on movement amplitude in the scapular plane and inferior scapular impingement. The Aequalis Reversed Shoulder Prosthesis (Tornier) was implanted into 40 cadaver shoulders. On the glenoid side, 8 different combinations were tested: 36-mm glenosphere: centered (standard), eccentric, with an inferior tilt, or with the center of rotation (COR) lateralized by 5 or 7 mm; and 42-mm centered glenosphere: used alone or with the COR lateralized by 7 or 10 mm. The humeral component was positioned in 0°, 10°, 20°, 30°, and 40° of retroversion. Maximum adduction and abduction were measured when inferior impingement and superior impingement, respectively, were detected. The average increase in abduction amplitude was 10° and inferior impingement occurred 18° later with a 42-mm glenosphere, especially when it was lateralized by 10 mm, relative to a 36-mm centered glenosphere (P < .05). These 2 combinations provided a 28° increase in the movement amplitude in the scapular plane. Positioning of the humeral component in 10° or 20° of retroversion or in anatomical retroversion was most effective at avoiding inferior impingement but had less effect on abduction range of motion (except with the 42-mm glenosphere). Our study confirmed published results with various glenosphere designs but was unique in describing the effect of humeral retroversion on scapular impingement. Inferior scapular notching can be most effectively prevented by using large-diameter glenospheres with lateralized COR and by making sure to replicate the patient's native humeral retroversion.

Wear simulation of reverse total shoulder arthroplasty systems: effect of glenosphere design

Although early results with reverse total shoulder arthroplasty (rTSA) have been promising, concern exists about the high reported rates of scapular notching and the potential for catastrophic failure of glenoid component fixation. Generation of polyethylene wear debris may also contribute to notching and osteolysis of the scapula. A testing model for polyethylene wear is currently unavailable for reverse shoulder prostheses. The goal of this study was to develop a testing protocol using a commercially available hip simulator. Component design may also influence the generation of polyethylene debris. It is hypothesized that increased polyethylene wear occurs in glenospheres with holes in the articulating surface. Custom fixtures were fabricated to simulate both glenohumeral abduction and flexion on a 12-station hip wear simulator. Loading profiles for both abduction and flexion were alternated every 250,000 cycles for a total of 5 million cycles. Gravimetric analysis of humeral cups throughout the test was used to characterize wear. Lubricant fluid was collected throughout the test and digested for polyethylene particle analysis. Comparisons of volumetric wear rates and total volume loss between glenospheres with and without holes and between flexion and abduction loading profiles showed similar results. Particle analysis displayed fibrillar particles with an equivalent circle diameter of 0.3 ± .1 μm and an aspect ratio of 2.5±1.4. This study represents the first wear simulation and particle characterization of reverse shoulder systems. No significant difference in wear was reported between glenospheres with and without holes.