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

BACKGROUND: Lateralization and distalization in reverse shoulder arthroplasty (RSA) can be measured on anteroposterior (AP) radiographs using 2 previously described angles: lateralization shoulder angle (LSA) and distalization shoulder angle (DSA). However, these 2 angles measure global lateralization and distalization but do not allow to differentiate how much lateralization or distalization are attributable to the glenoid and the humerus. We hypothesized that new angles could allow us to separately measure glenoid vs. humeral lateralization and distalization. A more precise understanding of independent glenoid and humeral contributions to lateralization and distalization may be beneficial in subsequent clinical research. METHOD: Retrospective analysis of postoperative AP radiographs of 100 patients who underwent primary RSA for cuff-tear arthropathy, massive cuff tear, or glenohumeral osteoarthritis were analyzed. The new angles that we proposed use well-known bony landmarks (the acromion, glenoid, and humerus) and the most lateral point of the glenosphere, which we termed the "glenoid pivot point" (GPP). For lateralization, we used the GPP to split LSA into 2 new angles: glenoid lateralization angle (GLA) and humeral lateralization angle (HLA). For distalization, we introduced the modified distalization shoulder angle (mDSA) that can also be split into 2 new angles: glenoid distalization angle (GDA) and humeral distalization angle (HDA). Three orthopedic surgeons measured the new angles, using the online tool Tyche. Mean values with overall and individual standard deviations as well as intraclass correlation coefficients (ICCs) were calculated. RESULTS: Because the angles form a triangle, the following equations can be made: LSA = GLA + HLA, and mDSA = GDA + HDA. All angles showed excellent inter- and intraobserver reliability (ICC = 0.92-0.97) with low means of individual standard deviations that indicate a precision of 2° for each angle. CONCLUSION: Use of the most lateral part of the glenosphere (termed glenoid pivot point) allows us to separately measure glenoid vs. humeral lateralization and distalization. The 4 new angles (HLA, GLA, GDA, HDA) described in the present study can be used on true AP radiographs, routinely obtained after shoulder replacement, and the measured angles may be used with all types of reverse prostheses available.

Glenoid lateralization and subscapularis repair are independent predictive factors of improved internal rotation after reverse shoulder arthroplasty.

PURPOSE: Reverse shoulder arthroplasty (RSA) has shown improvement in clinical outcomes for various conditions, although some authors expressed concern about the restoration of active internal rotation (AIR). The current study assesses preoperative and intraoperative predictive factors of AIR in patients having a Grammont-style RSA with a minimum five year follow-up. METHODS: We conducted a retrospective multicentric study, including patients operated on with a 155° Grammont-style RSA for cuff-related pathology or primary osteoarthritis with posterior subluxation or an associated cuff tear. Patients were clinically evaluated at a minimum of five year follow-up. Patients with previous surgery or those who had a tendon transfer with the RSA were excluded. Demographic parameters, BMI, preoperative notes, and operative reports were obtained from medical records. AIR was graded according to the constant score system from 0 to 10. RESULTS: A total of 280 shoulders in 269 patients (mean age at surgery, 74.9 ± 5.9 years) met the inclusion criteria and were analyzed. The average follow-up was 8.1 years (range, 5-16 years). Overall, AIR increased from 4.2 (SD 2.5, range 0 to 10) preoperatively to 5.9 (SD 2.6, range 0 to 10) at final follow-up. At the last follow-up, AIR increased in 56% of cases, was unchanged in 26% and decreased in 18%. In 188 shoulders (67%), internal rotation was functional and allowed patients to reach the level of L3 or higher. Multivariable linear regression found the following preoperative clinical factors predictive of worse AIR after RSA: male gender (ß = -1.25 [-2.10; -0.40]; p = 0.0042) and higher values of BMI (ß = -0.085 [-0.17; -0.0065]; p = 0.048). Two surgical factors were associated with better AIR after RSA: glenoid lateralization with BIO-RSA technique (ß = 0.80 [0.043; 1.56]; p = 0.039) and subscapularis repair (ß = 1.16 [0.29; 2.02]; p = 0.0092). CONCLUSIONS: With a mean of eight year follow-up (5 to 16 years), internal rotation was functional (≥ L3 level) in 67% of operated shoulders after Grammont-style RSA; however, two patients out of ten had decreased AIR after surgery. Male patients and those with higher BMIs had worse AIR, with glenoid lateralization (using the BIO-RSA technique) and subscapularis repair, as they are predictive of increased AIR after RSA. LEVEL OF EVIDENCE: Case series, Level IV.

Mid-term comparative study between the glenoid and humerus lateralization designs for reverse total shoulder arthroplasty: which lateralization design is better?

INTRODUCTION: The complications of the conventional medialized design for reverse total shoulder arthroplasty (RSA) are increased scapular notching, and decreased external rotation and deltoid wrapping. Currently, lateralization design RSA, which avoid scapular notching and improve impingement-free range of motion, is commonly used. Especially, humeral lateralization design was most commonly used and glenoid lateralization design was preferred for glenoid abnormities. We compared mid-term clinical and radiologic outcomes of glenoid and humeral lateralization RSA in an Asian population in this study. MATERIALS AND METHODS: We enrolled 124 shoulders of 122 consecutive patients (mean age 73.8 ± 6.8 years) who received glenoid or humeral lateralization RSA from May, 2012 to March, 2019. We divided these patients into two groups according to RSA using either glenoid or humeral lateralization design. These different designs were introduced consecutively in Korea. The clinical and radiological results of 60 glenoid lateralization RSA (Group I, 60 patients) and 64 humeral lateralization RSA (Group II, 62 patients) were retrospectively evaluated and also were compared between the two groups. All patients were followed for mean 3 years. RESULTS: The clinical and radiologic outcomes of the two groups did not differ significantly, including scapular notching (p = 0.134). However, humeral lateralization RSA showed a larger glenoid-tuberosity (GT) distance (p = 0.000) and less distalization shoulder angle (DSA) (p = 0.035). The complication rate did not differ significantly either. But, revision surgery was performed for 2 humeral loosening in the Group II. CONCLUSION: The clinical and radiologic outcomes of the two groups did not differ significantly, including scapular notching at mid-term follow-up. However, humeral lateralization design showed larger GT distance and less DSA. Humeral lateralization design RSA could preserve the normal shoulder contour due to a larger GT distance (more lateralization) and provide less deltoid tension due to less DSA (less distalization of COR).

Clinical and radiological outcomes in lateralized versus nonlateralized and distalized glenospheres in reverse total shoulder arthroplasty: a randomized control trial.

BACKGROUND: Lateralization in reverse total shoulder arthroplasty (RTSA) has been used to theoretically offer the potential benefits of reduced scapular notching rates and improved stability and range of motion (ROM), particularly external rotation. The aim of this study was to compare ROM and clinical and radiographic outcomes between patients who underwent RTSA with a lateralized vs. a nonlateralized and distalized glenosphere. METHODS: A single-surgeon randomized control trial was conducted comparing 27 patients with a lateralized glenosphere and 26 patients with a nonlateralized and distalized glenosphere. A total of 66 patients were enrolled, 2 patients died before 2-year follow-up, 4 patients withdrew from the study, and 7 patients were lost to follow-up. All patients in the lateralized group received 6 mm of lateralization through the glenosphere. Participants represented a population presenting to an orthopedics sports medicine clinic with any indication for RTSA including revision arthroplasty. Patients completed preoperative and routine postoperative functional outcome measures 3, 6, 12, and a minimum of 24 months postoperatively, including American Shoulder and Elbow Surgeons, Patient-Reported Outcomes Measurement Information System Physical Function Upper Extremity, and Activities of Daily Living Requiring Active External and Internal Rotation assessments. Patients were also evaluated with ROM and radiographic measurements. The primary outcome of interest in this study was ROM, particularly external rotation. RESULTS: At 2-year follow-up, both groups had significant improvement in their American Shoulder and Elbow Surgeons, Patient-Reported Outcomes Measurement Information System Physical Function Upper Extremity, and Activities of Daily Living Requiring Active External and Internal Rotation scores with no significant difference observed between the groups. There were no statistically significant differences in incidence of scapular notching or acromial stress fractures. ROM in both groups improved significantly at their 2-year assessment with the only exception to this being external rotation at 90° of abduction in the nonlateralized and distalized group (39° ± 31° vs. 48° ± 24°, P = .379). CONCLUSIONS: Regardless of glenosphere lateralization status, patients in both groups had significant improvement in functional outcome scores and ROM, and there were no significant differences observed between the groups at 2-year follow-up. Longer follow-up is needed to determine the effect of implant design on late complications, long-term outcomes, and implant retention.

Glenoid lateralization influences active internal rotation after reverse shoulder arthroplasty.

BACKGROUND: Improvement in internal rotation (IR) is not reliably achieved after reverse total shoulder arthroplasty (RSA). The purpose of this study was to evaluate the relationship between postoperative IR and glenoid-sided lateralization following RSA in an implant using metallic lateralization. METHODS: A multicenter retrospective study of RSAs with minimum 1-year clinical follow-up was performed. Patients were stratified based on the amount of glenoid-sided implant lateralization into 4 groups: 0-2 mm (n = 57), 4 mm (n =238), 6 mm (n = 95), and 8 mm (n = 65). The primary study outcome was active IR at a minimum of 1 year postoperatively, measured both by spinal level and in degrees with the shoulder abducted to 90°. Secondary outcomes were active forward flexion and external rotation, belly press strength, and subjective patient-reported outcome (PRO) measures. Comparisons were made with 1-way analyses of variance. Linear regression analyses evaluating for the association of glenoid lateralization with active IR were also performed to control for additional confounders, including demographics and other implant variables such as glenosphere diameter, humeral lateralization, humeral version, and whether the subscapularis was repaired. RESULTS: A total of 455 patients were included in the study. The mean age was 69 years, and 48% of patients were male. IR differences varied by the method of measurement (spinal level vs. IR in degrees with arm abducted). Overall, patients with 8 mm of glenoid lateralization had significantly improved IR compared with all other lateralization groups. Patients with 6 mm of glenoid lateralization had significantly improved IR compared with the 0-2- and 4-mm groups. There were no significant differences in the secondary outcomes or PROs between lateralization groups. In the regression analysis, glenoid lateralization was the only implant-related variable that was significantly associated with improved IR for both measurement methods. Glenosphere diameter and humeral version were both significantly associated with IR measured in degrees with the arm abducted but not spinal level. CONCLUSIONS: For the studied implant system, glenoid lateralization of 6-8 mm was associated with improved active IR at 1 year compared to patients with less glenoid lateralization with no significant differences in active forward flexion, external rotation, or PROs. In a multivariable analysis, increased humeral retroversion was associated with increased IR at 90° and increasing glenosphere diameter was associated with decreased IR at 90°, whereas BMI, subscapularis repair, and humeral lateralization did not significantly affect active IR.

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.

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.

Comparative clinical and radiologic evaluation between patients undergoing standard reversed shoulder arthroplasty or bony increased offset.

BACKGROUND: Modifications of the medialized design of Grammont-type reverse shoulder arthroplasty (RSA) using a bony increased offset (BIO-RSA) has shown better clinical results and fewer complications. The aim of this study is to compare the clinical results, complications, and radiological outcomes between patients undergoing standard RSA and BIO-RSA. METHODS: A retrospective review was performed of 42 RSA procedures (22 standard RSA and 20 BIO-RSA). With a minimum of 1 year of follow-up, range of motion (ROM), Constant shoulder score (CSS), visual analog scale (VAS), and subjective shoulder score (SSS) were compared. Radiographs and computed tomography (CT) scan were examined for scapular notching, glenoid and humeral fixation, and graft healing. RESULTS: At a mean follow-up of 27.6 months (range, 12-48 months), a significant difference was found for active-internal rotation (P=0.038) and for passive-external rotation (P=0.013), with better results in BIO-RSA. No other differences were found in ROM, CSS (P=0.884), VAS score, and SSS. Graft healing and viability were verified in all patients with CT scan (n=34). The notching rate was 28% in the standard RSA group and 33% in the BIO-RSA group, but the standard RSA had more severe notching (grade 2) than BIO-RSA (P=0.039). No other significative differences were found in glenoid and humeral fixation. CONCLUSIONS: Bone-graft lateralization is associated with better internal and external rotation and with less severe scapular notching compared to the standard RSA. Integration of the bone graft occurs effectively, with no relevant changes observed on radiographic evaluation.

Can surgeons optimize range of motion and reduce scapulohumeral impingements in reverse shoulder arthroplasty? A computational study.

Background: Early glenohumeral impingement leads to poor range of motion and notching in reverse shoulder arthroplasty. The aim was to find from planning software which implant configuration provides the best motions in reverse shoulder arthroplasty. Patients and Methods: Reverse shoulder arthroplasty planning (Glenosys) was made in 31 patients (12 men, 19 women, 76 ± 6 yo) and impingements were analyzed. Inlay (155°-inclined) and Onlay (145°-inclined) humeral designs were tested. Four configurations were tested for each shoulder: "INLAY": non-lateralized glenoid-inlay humerus, "BIO-INLAY": lateralized glenoid (BIO-RSA)-inlay humerus, "ONLAY": non-lateralized glenoid-onlay humerus, and "BIO-ONLAY": lateralized (BIO-RSA) glenoid-onlay humerus. Results: BIO-ONLAY and BIO-INLAY groups presented a significantly better result in all tested motion (p < 0.001 for all tests). BIO-ONLAY allowed a significantly better external rotation, extension and adduction than BIO-INLAY with decreased impingements with the pilar. BIO-INLAY presented a significantly better abduction. In abduction, an abutment of the greater tuberosity against the acromion was associated with a lower range of motion (p < 0.0001) and did not depend on the lateralization. Conclusion: Glenoid lateralization delays the glenohumeral impingement in reverse shoulder arthroplasty and gives the best rotations, adduction and extension when associated with neutral inclination and humeral 145° inclination. Greater tuberosity abutment has to be avoided in abduction and the Inlay design provides the best abduction.

Lateralized versus nonlateralized reverse total shoulder arthroplasty.

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

Mid-term outcomes of bony increased offset-reverse total shoulder arthroplasty in the Asian population.

BACKGROUND: To evaluate clinical and radiological outcomes of bony increased offset-reverse total shoulder arthroplasty (BIO-RSA) in the Asian population at mid-term follow-up. METHODS: From June 2012 to August 2017 at a single center, 43 patients underwent BIO-RSA, and 38 patients with minimum 2 years follow-up were enrolled. We evaluated the clinical and radiological outcomes, and complications at the last follow-up. In addition, we divided these patients into notching and no-notching groups and compared the demographics, preoperative, and postoperative characteristics of patients. RESULTS: Visual analogue scale, American Shoulder and Elbow Surgeons, University of California-Los Angeles Shoulder Scale, and Simple Shoulder Test scores improved significantly from preoperative (5.00, 3.93, 1.72, 3.94) to postoperative (1.72, 78.91, 28.34, 7.66) (p<0.05) outcomes. All range of motion except internal rotation improved significantly at the final follow-up (p<0.05), and the bone graft was well-incorporated with the native glenoid in all patients (100%). However, scapular notching was observed in 20 of 38 patients (53%). In the comparison between notching and no-notching groups (18 vs. 20 patients), there were no significant differences in demographics, radiological parameters, and clinical outcomes except acromion-greater tuberosity (AT) distance (p=0.003). Intraoperative complications included three metaphyseal fractures and one inferior screw malposition. Postoperative complications included ectopic ossification, scapular neck stress fracture, humeral stem relaxation, and late infection in one case each. CONCLUSIONS: BIO-RSA showed improved clinical outcomes at mid-term follow-up in Asian population. However, we observed higher scapular notching compared to the previous studies. In addition, adequate glenoid lateralization with appropriate humeral lengthening (AT distance) might reduce scapular notching.

Reverse shoulder arthroplasty glenoid lateralization influences scapular spine strains.

BACKGROUND: Scapular spine insufficiency fractures following reverse shoulder arthroplasty are poorly understood. There exists limited literature regarding the role of reverse shoulder arthroplasty lateralization on scapular spine strains and fractures. The purpose of this cadaveric biomechanical simulator study was to evaluate the role of glenoid lateralization on scapular spine strain. METHODS: Eight cadaveric shoulders were tested using an in-vitro simulator. A custom modular reverse shoulder arthroplasty was implanted that allowed for in-situ glenoid lateralization adjustment. Scapular spine strain was measured by strain gauges placed in clinically relevant Levy zones along the scapular spine. All specimens were tested in loaded forward elevation and abduction. RESULTS: Glenoid lateralization from 0 to 5 mm caused negligible changes in scapular spine strains. Lateralization from 5 to 10 mm, however, caused significant increases in strain at 0° forward elevation in all strain gauges (p < 0.026). Strains measured in Levy zone 2 were significantly higher than all other locations (p < 0.039). Additionally, forward elevation resulted in significantly higher strain values than abduction (p = 0.001). CONCLUSIONS: Glenoid lateralization is an important parameter in reverse shoulder arthroplasty; however, our results demonstrate higher degrees of lateralization may place higher strains on the scapular spine. An understanding of reverse shoulder arthroplasty lateralization and scapular spine strains is important to optimize parameters and to mitigate negative effects. LEVEL OF EVIDENCE: Basic Sciences Study, Cadaveric Model, Biomechanics.