Bony Increased-offset Reverse Shoulder Arthroplasty Research Articles

Treating posteriorly eroded glenoids with augmented baseplate or bony increased-offset reverse shoulder arthroplasty: a finite element comparison

BackgroundAugmented reverse shoulder arthroplasty (RSA) implants restore glenohumeral joint alignment in cases of asymmetric glenoid wear. However, no consensus has been reached on whether the use of metallic augmented RSA baseplates and bone graft reconstruction are equivalent in terms of implant fixation and risk of implant loosening. Therefore, the purpose of this study was to compare 2 augmented RSA designs by assessing the amount of interfacial micromotion generated under realistic physiological loading. MethodsFinite element analysis models of 9 scapulae with Walch-type B2 or B3 glenoid morphology were virtually implanted with both a metallic augmented baseplate (AUG-RSA) and using the angled bony increased-offset RSA procedure (BIO-RSA). Simulation of physiological loading was performed on each of the 18 finite element analysis models. The relative tangential and normal micromotion at the implant-to-glenoid interface was compared in each anatomical quadrant. ResultsThe AUG-RSA and angled BIO-RSA showed similar magnitudes of micromotion in most anatomical quadrants of the glenoid. Within the superior quadrant, AUG-RSA displayed a higher magnitude of mean and maximum tangential micromotion (mean: 16.6 ± 2.4 μm, P < .000; maximum: 35.1 ± 5.3 μm, P < .000). The proportion of the posterior quadrant experiencing >50 microns of micromotion was also statistically greater with AUG-RSA (5.8 ± 2.5 %, P = .047). ConclusionBecause of its statistically greater micromotion and portions of contact exceeding the accepted 50-micron threshold, the AUG-RSA may be more likely to have inhibited bone on-growth. However, the clinical importance of these differences remains unclear.

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

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. 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. 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). 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.

Bony increased-offset reverse total shoulder arthroplasty (BIO-RSA) associated with an eccentric glenosphere and an onlay 135° humeral component: clinical and radiological outcomes at a minimum 2-year follow-up.

BackgroundVarious implant designs have been proposed to increase active range of motion (ROM) and avoid notching in patients treated by reverse total shoulder arthroplasty (RSA). The purpose of this study was to investigate the efficacy and safety of an onlay prosthesis design combining a 135° humeral neck-shaft angle with the glenoid component lateralized and inferiorized.MethodsA retrospective descriptive study was conducted of the clinical and radiological outcomes at the final follow-up (≥24 months) of all RSAs performed by the same surgeon between September 2015 and December 2016 in the study center. At the last follow-up, patients were clinically assessed for ROM, Constant score, and subjective shoulder value and radiologically for scapular notching and glenoid radiolucent lines. Patients were followed up radiographically at 1 month and clinically at between 6 and 12 months (midterm) and again at between 24 and 48 months (final follow-up). Scapular notching was graded as per the Sirveaux classification at the last follow-up on anterior-posterior radiographs.ResultsSeventy-nine RSAs were included with a mean follow-up time of 31 months. The mean Constant score at the final follow-up was 42 points higher than before surgery (69 vs. 27, P < .001). There were also significant postoperative improvements in ROM (active anterior elevation, active external rotation, and active internal rotation). The final means for motions were 133° for active anterior elevation, 32° active external rotation, and level 7 for active internal rotation. The overall notching rate was 3% (2/67), and there were no cases of severe notching. Radiolucent lines were observed in 8 of 70 prostheses (11.5%) around the peg, and they were observed in 9 prostheses (13%) around the screws. Among the 79 RSAs included, there were 11 complications (13.9%) (two infections, two fractures, four cases of glenoid component loosening, and three cases of instability), 2 reoperations, and 4 prosthesis revisions.ConclusionThis study shows that an RSA design with a 135° humeral neck-shaft angle and an inferiorized and lateralized glenoid component is associated with significant improvements in active ROM, especially in rotation, and a low notching rate. However, rates of 3.8% for dislocation and 5% for glenoid loosening are certainly a concern at such a short follow-up of two years. Future studies with a larger population are needed to confirm these rates.

Restoration of External Rotation Following a Lateral Approach for Glenoid Bony Increased-Offset Reverse Shoulder Arthroplasty

Background:Reverse shoulder arthroplasty (RSA) is a recognized therapeutic modality for a massive rotator cuff tear. Some authors recommend lateralization of the center of rotation by bony increased offset (BIO) of the glenoid for improvement of external rotation, while others refute its effects. RSA through the conventional deltopectoral approach sacrifices the subscapularis tendon during the approach. We hypothesized that a lateral approach (LA) for RSA, with less soft-tissue resection, would restore external rotation by allowing retensioning of the remaining rotator cuff with use of a BIO graft.Methods:We retrospectively investigated 36 nonlateralized inlay RSAs performed through a lateral approach (LA non-BIO group) and 40 inlay RSAs performed through a lateral approach with BIO (LA BIO group) for a massive rotator cuff tear. There were 5 patients with a combined loss of active elevation and external rotation (CLEER) in the LA non-BIO group and 6 in the LA BIO group. The Constant score, the UCLA (University of California Los Angeles) score, and range of motion, in particular, external rotation with the arm at 0° (ER0) and at 90° of abduction (ER90), were compared.Results:The mean ER90 in the LA BIO group improved significantly, from 45.8° ± 21.6° to 65.9° ± 15.8° (p = 0.012). Postoperative ER90 in the LA BIO group was significantly higher than in the LA non-BIO group (mean, 65.9° ± 15.8° compared with 53.0° ± 12.3°; p = 0.026). The mean ER0 for the patients with CLEER status significantly improved in the LA BIO group, from −15.8° ± 9.8° to 11.0° ± 15.6° (p = 0.0072). The mean postoperative anterior elevation, UCLA score, and Constant score in the LA BIO group and the LA non-BIO group improved significantly, but there was no difference between the 2 groups (anterior elevation: 131.5° ± 17.6° compared with 121.5° ± 14.1°, p = 0.07; UCLA: 25.5 ± 6.4 compared with 23.4 ± 5.4, p = 0.2; Constant: 74.3 ± 12.0 compared with 73.6 ± 10.1, p = 0.43).Conclusions:LA BIO-RSA was associated with a significant improvement in range of motion, particularly external rotation. Improvements in anterior elevation, the Constant score, and the UCLA score were not significantly different from those noted for LA non-BIO-RSA.Level of Evidence:Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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

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 radiologicoutcomes after bony increased-offset-reverse shoulder arthroplasty (BIO-RSA) using a Grammont-style (medialized) humeral implant. 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. At a mean follow-up of 75 months (range, 60-126 months), the survivorship of the BIO-RSAusing revision as an endpoint was 96%. No cases of dislocationor 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). 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.

Bony increased-offset reverse shoulder arthroplasty: A meta-analysis of the available evidence.

Reverse shoulder arthroplasty (RSA) has revolutionized the management of many shoulder pathologies. Lateralization has become favourable to combat complications (e.g. notching, compromised external rotation), using a metallic, or autogenous bone-graft baseplates - bony increased-offset reverse shoulder arthroplasty (BIO-RSA). We systematically reviewed the literature to determine: Does BIO-RSA improve range of motion and outcome scores?Are notching rates decreased?Does the graft heal? All available prospective studies, trials and case series reporting on BIO-RSA were included. Outcomes were grouped into outcome scores, range of motion and radiographic outcomes. Data were pooled and statistical analysis performed. Eight studies reported on 385 RSA - 235 BIO-RSA and 150 standard-RSA (STD-RSA). Follow-up was 20-36 months; average age 74 years. Outcome scores: Constant-Murley and SSV scores showed statistically significant post-operative benefit of BIO-RSA (mean-difference 4.0 (95% confidence interval (CI): 0.79,7.1) and 6.8 (95% CI: 3.8, 9.9)). No Minimal Clinically Importance Difference was surpassed. Range of motion: No difference was found in any direction. Notching: Notching was less likely with BIO-RSA (odds ratio 0.19 (95% CI: 0.10, 0.38)). Healing and loosening: 92% grafts fully healed/incorporated. Loosening rate was 2.4%. Literature on BIO-RSA is limited with only one randomised controlled trial (RCT). Weak evidence exists for improved outcome scores. Range of motion is equivocal. Notching rates are significantly lower in BIO-RSA. The graft usually heals.

Clinical results of bony increased-offset reverse shoulder arthroplasty (BIO-RSA) associated with an onlay 145° curved stem in patients with cuff tear arthropathy: a comparative study

The main limits of the Grammont design reverse shoulder arthroplasty (RSA) are loss of external rotation and scapular notching. They can be addressed with glenoid or humeral lateralization. The aim of the study was to compare outcomes of lateralized bony increased-offset RSA (BIO-RSA) vs. standard RSA in patients with an onlay 145° curved stem. A comparative cohort study of 29 standard RSAs and 30 BIO-RSAs was performed. At 2 years postoperatively, Constant score, American Shoulder and Elbow Surgeons score, visual analog scale score, range of motion, and radiographs were evaluated. After comparison between the groups, patients were analyzed considering patients younger and older than 65 years. All parameters significantly improved after surgery in both groups. Postoperatively, the 2 groups did not show any clinical and radiographic differences (P > .05). In patients <66 years, BIO-RSA showed a significantly higher value of external rotation (49° ± 12° vs. 30° ± 19° [P = .025], elbow at side; 81° ± 17° vs. 56° ± 22° [P = .016], elbow at 90° of abduction)and a positive trend for all other parameters (P > .05). In patients >65 years, standard technique showed a positive trend for all the parameters (P > .05). No other significant differences were found. At 2 years of follow-up, the use of standard RSA or BIO-RSA in an implant with an onlay 145° curved stem provided similar outcomes. The humeral lateralization alone is sufficient to decrease notching and to improve external rotation. BIO-RSA increases external rotation in patients between 50 and 65 years old. Glenoid bone graft in RSA has a high incorporation rate (completed in 90%).

Standard versus bony increased-offset reverse shoulder arthroplasty: a retrospective comparative cohort study

To date, only a few comparative studies with small sample sizes have compared a traditional reverse shoulder arthroplasty (tRSA) to a bony increased-offset RSA (BIO-RSA). We hypothesized that the BIO-RSA would lead to lower notching rates and improved range of motion (ROM) compared with a tRSA. A retrospective review was performed of 69 tRSAs and 61 BIO-RSAs performed by a single surgeon. At 2 years postoperative, ROM and Constant scores were compared. Radiographs were examined for scapular notching, scapular spurring or ossification, and graft healing. At the 2-year follow-up, the BIO-RSA group demonstrated improved anterior forward flexion compared with the tRSA group (145° ± 20° vs. 138° ± 20°, respectively; P = .017). There was no difference in external or internal rotation between the 2 groups. The BIO-RSA group had a higher Constant score than the tRSA group (69 ± 9 vs. 61 ± 13; P < .001). The radiographs showed no difference between the 2 groups, including scapular notching (P = .150). At the 2-year follow-up, BIO-RSA does not lead to a clinically significantly improvement in ROM, Constant scores, or change in scapular notching compared with a tRSA.

Angled BIO-RSA (bony-increased offset–reverse shoulder arthroplasty): a solution for the management of glenoid bone loss and erosion

Glenoid deficiency and erosion (excessive retroversion/inclination) must be corrected in reverse shoulder arthroplasty (RSA) to avoid prosthetic notching or instability and to maximize function, range of motion, and prosthesis longevity. This study reports the results of RSA with an angled, autologous glenoid graft harvested from the humerus (angled BIO-RSA). A trapezoidal bone graft, harvested from the humeral head and fixed with a long-post baseplate and screws, was used to compensate for residual glenoid bone loss/erosion. For simple to moderate (<25°) glenoid defects, standardized instrumentation combined with some eccentric reaming (<15°) was used to reconstruct the glenoid and obtain neutral implant alignment. For severe (>25°) and complex (multiplanar) glenoid bone defects, patient-specific grafts and guides were used after 3-dimensional planning. Patients were reviewed with minimum 2 years of follow-up. Mean follow-up was 36 months (range, 24-81 months). Preoperative and postoperative measurements of inclination and version were performed in the plane of the scapula on computed tomography images. The study included 54 patients (41 women, 13 men; mean 73 years old). Fifteen patients had combined vertical and horizontal glenoid bone deficiency. Among E2/E3 glenoids, inclination improved from 37° (range, 14° to 84°) to 10.2° (range -28° to 36°, P < .001). Among B2/C glenoids, retroversion improved from -21° (range, -49° to 0°) to -10.6° (-32° to 4°, P = .06). Complete radiographic incorporation of the graft occurred in 94% (51 of 54). Complications included infection in 1 and clinical aseptic baseplate loosening in 2. Mild notching occurred in 25% (13 of 51) of patients. Constant-Murley and Subjective Shoulder Value assessments increased from 31 to 68 and from 30% to 83%, respectively (P < .001). Angled BIO-RSA predictably corrects glenoid deficiency, including severe (>25°) multiplanar deformity. Graft incorporation is predictable. Advantages of using an autograftharvested in situ include bone stock augmentation, lateralization, low donor-site morbidity, low relative cost, and flexibility needed to simultaneously correct posterior and superior glenoid defects.

Utilité du scanner pour la détection de la résorption des greffes osseuses glénoïdiennes dans les prothèses inversées d’épaule

IntroductionGlenoid bone grafting is often used in cases of reverse shoulder arthroplasty (RSA) with glenoid deficiency. Additionally, bony increased-offset RSA (BIO-RSA) uses a cylindrical bonegraft harvested from the humeral head and is positioned beneath the glenoid baseplate to increase lateralization. Post-operative computed tomography (CT) has been used to detect glenoid bonegraft resorption, which is typically identified by a gap between the bonegraft and baseplate; however, CT images are often degraded by implant metal artifact. The purpose of this CT imaging study was to determine if a simulated bonegraft resorption gap is detectable following RSA with glenoid bone grafting. HypothesisCT is unable to detect bone graft resorption following reverse shoulder arthroplasty conducted with bone grafting beneath the glenoid baseplate. Materials and methodsRSA with glenoid bone grafting was performed on four cadaver shoulders. Glenoid bonegraft resorption gaps were simulated by fixing the implant at six different gap widths (0, 1, 2, 4, 6 and 8mm). Clinical CT scans were acquired for each gap resulting in six scans per specimen. Two experienced observers (blinded) analyzed DICOM images in the axial and coronal directions, and measured gap widths using Mimics® software. Approximately 200images per specimen were viewed by each observer, for a total of 1600 images. ResultsThe sensitivity of CT imaging to positively identify bonegraft resorption was 38%, with an accuracy of 46%. Inter-observer agreement was 92%. Observers tended to visualize no-gap for most conditions. Resorption gap width measurements were consistently underestimated. DiscussionMetal artifact prevented identification of simulated bonegraft resorption gaps and observers most often determined that there was bonegraft-to-implant “healing” on CT, when in fact a gap was clinically present. This study illustrates the need for more effective imaging techniques to determine if bonegraft resorption has occurred following RSA. Level of evidenceLevel IV. Basic science; cadaveric study.

Effectiveness of CT for the detection of glenoid bone graft resorption following reverse shoulder arthroplasty

IntroductionGlenoid bone grafting is often used in cases of reverse shoulder arthroplasty (RSA) with glenoid deficiency. Additionally, bony increased-offset RSA (BIO-RSA) uses a cylindrical bonegraft harvested from the humeral head and is positioned beneath the glenoid baseplate to increase lateralization. Postoperative computed tomography (CT) has been used to detect glenoid bonegraft resorption, which is typically identified by a gap between the bonegraft and baseplate; however, CT images are often degraded by implant metal artifact. The purpose of this CT imaging study was to determine if a simulated bonegraft resorption gap is detectable following RSA with glenoid bone grafting. HypothesisCT is unable to detect bone graft resorption following reverse shoulder arthroplasty conducted with bone grafting beneath the glenoid baseplate. Materials and methodsRSA with glenoid bone grafting was performed on four cadaver shoulders. Glenoid bonegraft resorption gaps were simulated by fixing the implant at six different gap widths (0, 1, 2, 4, 6 and 8mm). Clinical CT scans were acquired for each gap resulting in 6 scans per specimen. Two experienced observers (blinded) analyzed DICOM images in the axial and coronal directions, and measured gap widths using Mimics® software. Each observer had access to approximately 200 images per condition per specimen. ResultsThe sensitivity of CT imaging to positively identify bonegraft resorption was 38%, with an accuracy of 46%. Inter-observer agreement was 92%. Observers tended to visualize no-gap for most conditions. Resorption gap width measurements were consistently underestimated. DiscussionMetal artifact prevented identification of simulated bonegraft resorption gaps and observers most often determined that there was bonegraft-to-implant “healing” on CT, when in fact a gap was clinically present. This study illustrates the need for more effective imaging techniques to determine if bonegraft resorption has occurred following RSA. Level of evidenceLevel IV. Basic Science; Cadaveric Study.

Bony Increased-Offset Reverse Shoulder Arthroplasty

Bony Increased-Offset Reverse Shoulder Arthroplasty

Bilateral bony increased-offset reverse shoulder arthroplasty in rheumatoid arthritis shoulder with severe glenoid bone defect: a case report

Bilateral bony increased-offset reverse shoulder arthroplasty in rheumatoid arthritis shoulder with severe glenoid bone defect: a case report

Does bony increased-offset reverse shoulder arthroplasty decrease scapular notching?

The purpose of this cohort study was to compare scapular notching rates, range of motion, and functional outcomes between patients who underwent a standard Grammont-style reverse shoulder arthroplasty (RSA) and patients who underwent bony increased-offset reverse shoulder arthroplasty (BIO-RSA) at a minimum of 2 years' follow-up. We hypothesized that the BIO-RSA cohort would have lower notching rates and improved rotational range of motion; however, validated outcome scores between cohorts would be no different. A comparative cohort study was designed after a sample size calculation. A total of 40 patients were studied with 20 in each cohort (RSA vs BIO-RSA). All patients underwent an interview and physical examination. Outcomes included range of motion; shoulder strength; Disabilities of the Arm, Shoulder and Hand (DASH) score; American Shoulder and Elbow Surgeons score; Simple Shoulder Test score; Constant score; and Global Rating of Change scale score. Radiographs were obtained for all patients and examined for scapular notching. When we compared demographic characteristics between the standard RSA and BIO-RSA cohorts, including age, sex, and follow-up duration, there were no significant differences between groups (P > .05). In addition, there were no significant differences between cohorts when we compared forward elevation (P = .418); external rotation (P = .999); internal rotation (P = .071); strength (P > .376); Disabilities of the Arm, Shoulder and Hand score (P = .229); American Shoulder and Elbow Surgeons score (P = .579); Simple Shoulder Test score (P = .522); Constant score (P = .917); or Global Rating of Change scale score (P = .167). The frequency of scapular notching, however, was significantly higher (P = .022) in the RSA cohort than in the BIO-RSA cohort: 75% versus 40%. Although the scapular notching rate was significantly higher in the standard RSA group, no other outcome measures were statistically different, including range of motion, strength, and validated outcome scores.

Stress analysis of glenoid component in design of reverse shoulder prosthesis using finite element method

This study aims to clarify the effect of various designs of reverse shoulder prosthesis (RSP) on stress variation of its glenoid component using 2-dimensional (2D) finite element analysis (FEA). This FEA study provides future reference for the optimal design of glenoid component of RSP. In this study, a 2D finite element (FE) model of human shoulder with implementation of RSP was developed by commercial FE software. The proper material properties were adopted in our model. Various design factors were simulated and all the mechanical profile data were investigated by FEA. Both distal placement and increased lateral offset of glenosphere induce higher stress over glenoid-baseplate junction. Increased thickness of graft, inferiorly tilting of the baseplate, and adoption of BIO-RSA (bony increased-offset reverse shoulder arthroplasty) incur higher stresses over glenoid screws. The inferior screw attains more stress than superior screw. Maximum stress occurs at the base of inferior screw. Increased eccentric offset and lateral offset of glenosphere, although being able to reduce notching, may pay the penalty of significant stress concentration over glenoid and its subsequent loosening. Maximum stress occurs at the base of inferior screw elucidate the direct contact failure mode at the middle of inferior screw. This study provides an alternative tool for the optimal design of glenoid component of RSP in the future.

Activities of daily living with reverse prostheses: importance of scapular compensation for functional mobility of the shoulder

The nonanatomical design of reverse shoulder prostheses induce medial displacement of the center of rotation, impingements and may reduce the mobility of the shoulder. The aim of this study is to test the hypothesis that during activities of daily living functional mobility of the shoulder can be restored by scapular compensation. A numerical 3-dimensional model was developed to reproduce the movement of the scapula and humerus, during 4 activities of daily living measured experimentally. This hypothesis was tested in 4 configurations of the aequalis reverse prosthesis (standard 36-mm glenosphere, 42-mm glenosphere, lateralized 36-mm glenosphere, lateralized Bony Increased-Offset ReverseShoulder Arthroplasty [BIO-RSA]), which were implanted in the virtual model. Allimpingement positions were evaluated, as the required scapular compensation to avoid impingements. With the 36-mm glenosphere, impingements occurred only for rest of hand to back-pocket positions. The 42-mm partly improved the mobility. The 2 lateralized glenospheres were free of impingement. When impingements occurred, the scapular compensation was less than 10°. Most reverse prostheses impingements reported in clinical and biomechanical studies can be avoided, either by scapular compensation or by a glenosphere lateralization. After reverse shoulder arthroplasty, a fraction of the mobility of the gleno-humeral is transferred to the scapulo-thoracic joint.

Bony Increased-offset Reversed Shoulder Arthroplasty: Minimizing Scapular Impingement While Maximizing Glenoid Fixation

Scapular notching, prosthetic instability, limited shoulder rotation and loss of shoulder contour are associated with conventional medialized design reverse shoulder arthroplasty. Prosthetic (ie, metallic) lateralization increases torque at the baseplate-glenoid interface potentially leading to failure. We asked whether bony lateralization of reverse shoulder arthroplasty would avoid the problems caused by humeral medialization without increasing torque or shear force applied to the glenoid component. We prospectively followed 42 patients with rotator cuff deficiency treated with bony increased-offset reverse shoulder arthroplasty. A cylinder of autologous cancellous bone graft, harvested from the humeral head, was placed between the reamed glenoid surface and baseplate. Graft and baseplate fixation was achieved using a lengthened central peg (25 mm) and four screws. Patients underwent clinical, radiographic, and CT assessment at a minimum of 2 years after surgery. The humeral graft incorporated completely in 98% of cases (41 of 42) and partially in one. At a mean of 28 months postoperatively, no graft resorption, glenoid loosening, or postoperative instability was observed. Inferior scapular notching occurred in 19% (eight of 42). The absolute Constant-Murley score improved from 31 to 67. Thirty-six patients (86%) were able to internally rotate sufficiently to reach their back over the sacrum. Grafting of the glenoid surface during reverse shoulder arthroplasty effectively creates a long-necked scapula, providing the benefits of lateralization. Bony increased-offset reverse shoulder arthroplasty is associated with low rates of inferior scapular notching, improved shoulder rotation, no prosthetic instability and improved shoulder contour. In contrast to metallic lateralization, bony lateralization has the advantage of maintaining the prosthetic center of rotation at the prosthesis-bone interface, thus minimizing torque on the glenoid component. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.