Use of computed tomography for shoulder arthroplasty: A systematic review.

Introduction: The prevalence of total shoulder arthroplasties is on the rise annually. Improvements in implant quality, construct stability, and surgical techniques have notably enhanced post-operative results, prompting an expansion of indications for shoulder arthroplasty. Despite its high success rate, opportunities for enhancement remain, especially in preoperative planning and intraoperative execution. Advanced imaging technologies offer significant potential in optimizing implant placement, thus improving the longevity of the procedure. To our knowledge, a comprehensive review examining the impact of advanced imaging on shoulder arthroplasty has yet to be conducted. This systematic review aims to investigate the benefits of advanced imaging technologies in this context, focusing on their application in preoperative planning, osteoarthritis assessment, intraoperative adjustments, patient-specific instrumentation, and navigational aids. Methods: This review utilized a comprehensive search of PubMed to identify relevant studies published from 2000 to 2024, focusing on the application of various imaging techniques in shoulder arthroplasty. The search was conducted by two authors and centered on plain radiography, CT scans, and MRI. The selection criteria included availability of full-text articles, English language, direct comparison of imaging techniques, and a focus on patient outcomes, including discussions on broader applications such as intraoperative navigation and patient-specific instrumentation development. Results: Enhanced imaging techniques, particularly CT scans and MRIs, have been shown to significantly improve outcomes in shoulder arthroplasty. While plain radiographs remain standard, CT scans provide superior bony detail, crucial for evaluating glenoid wear and determining augmentation needs. Preoperative CT imaging has been demonstrated to enhance implant placement accuracy. Moreover, intraoperative technologies based on CT imaging, such as patient-specific instrumentation and navigation systems, contribute to better surgical results. Conclusion: The benefits of CT imaging in shoulder arthroplasty significantly outweigh the associated costs. Current literature strongly supports the adoption of CT imaging in these procedures, particularly when used alongside modern operative technologies.

Inferior Glenoid HyperOSTosis (GHOST) Lesion Development Following Reverse Total Shoulder Arthroplasty.

BACKGROUND: Patients undergoing reverse shoulder arthroplasty (RTSA) have been noted on postoperative radiographs to have a curved bony overgrowth on the inferior glenoid neck. This study aims to investigate potential risk factors for and postoperative effects of these ossifications, here called glenoid hyperostosis (GHOST) lesions due to their location. METHODS: A retrospective review of patients undergoing reverse total shoulder arthroplasty between 2007 and 2020 at a single institution was performed. Predictors including gender, age, implant sizing, and preoperative diagnosis were examined using logistic regression analysis. Outcomes including readmission rate, revision rate, preoperative and postoperative range of motion, visual analog scale (VAS) pain scores, and American Shoulder and Elbow Surgeons (ASES) functional outcome scores were also analyzed using two-sample t-tests. RESULTS: Preoperative and postoperative radiographs of 170 primary reverse shoulder arthroplasty patients were assessed. 25.9% of RTSAs were identified to have a GHOST lesion. When adjusting for race, age, BMI, preoperative diagnosis, male patients were still associated with 2.28 odds of developing a GHOST lesion compared to female patients (95% CI: 1.08 - 4.86). Other elements such as age, race, BMI, laterality, preoperative diagnosis, implant manufacturer, and implant sizing demonstrated no statistically significant association to GHOST lesion presence. Postoperatively, GHOST lesion development was not associated with range of motion or ASES score. However, presence of GHOST lesions on radiographs was associated with increased pain scores for patients at 2 months (p = 0.034) and 12 months (p = 0.029) postoperatively. DISCUSSION: Inferior glenoid hyperostosis (GHOST) lesions is a common and potentially benign finding following reverse shoulder arthroplasty, with unclear etiology. Risk factors for GHOST lesions included male gender, while patient demographics, implant type or size, shoulder lateralization and distalization were not associated with lesion formation. Clinically, greater short-term VAS scores were seen in patients with GHOST lesions. However, there were no differences observed between the two groups in ASES scores or postoperative range of motion at later time points. Further research is needed to identify risk factors and assess the clinical implications of GHOST lesions.

Intraoperative Navigation in Reverse Shoulder Arthroplasty: Advantages and Future Prospects.

Intraoperative navigation is a novel technology that can provide real-time feedback to the surgeon during implantation and enhance the accuracy and precision of glenoid component positioning. Applications of intraoperative navigation systems have demonstrated increased precision in baseplate version and inclination, as well as improved baseplate screw placement, with fewer screws used and greater purchase length achieved when compared to standard instrumentation. Early clinical studies have shown favorable results, with significantly improved patient-reported and clinical outcomes and decreased complications. The implementation of intraoperative navigation is associated with a short learning curve and a minimal increase in operative time. Nevertheless, further research is necessary to substantiate the clinical benefit of navigation and evaluate its economic cost-effectiveness and impact on implant survival. Augmented reality and robotic-assisted surgery are additional emerging technologies that, while novel, hold the potential to further advance the field of shoulder arthroplasty.

Surgical decisions on implant-related parameters can enhance knowledge transfer for glenoid bone grafting in primary reverse shoulder arthroplasty: a scoping review of heterogeneity sources.

Purpose: The purpose of the present scoping review is to identify sources of heterogeneity in reporting domains that have the potential to improve surgical decision-making in reverse shoulder arthroplasty associated with glenoid bone grafting. Methods: A scoping review was conducted according to the JBI and PRISMA ScR guidelines. Articles covering glenoid bone grafting at the time of reverse shoulder replacement, published between 2012 and 2022 in MEDLINE, Scopus, Epistemonikos, Web of Science, and Cochrane Database of Systematic Reviews, were searched. Reporting of core outcome measures, as well as prosthesis-related variables, rehabilitation protocols, radiographic evaluation methods, and bone graft incorporation assessments, were collected. Results: For the final analysis, a total of 14 articles were considered. There were 649 operated shoulders with a mean patient age of 72 years, ranging from 48 to 85 years. Analysis of preoperative ranges of motion and patient-reported outcome measures revealed increased heterogeneity in patient selection between studies. Reporting of implant-related parameters was the most inconsistent. Rehabilitation protocols were scarcely reported. Assessment of graft incorporation and radiographic evaluation of choice revealed that there is no consistent method or measurement and the clinical relevance of radiolucent lines at the graft-glenoid bone interface is unclear. Conclusion: Addressing implant-related reporting gaps has the highest potential to improve surgical decision-making and provide orthopedic surgeons with a more comprehensive understanding of published results on glenoid bone grafting at the time of primary reverse shoulder arthroplasty.

Revision Shoulder Arthroplasty: Predictors of Subsequent Revision Surgery and Economic Burden amongst Medicare Beneficiaries.

BACKGROUND: Revision shoulder arthroplasty continues to add an increasing burden on patients and the healthcare system. This study aimed to delineate long-term shoulder arthroplasty revision incidence, quantify associated Medicare spending, and identify relevant predictors of both revision and spending. METHODS: The complete 2016-2022(Q3) Medicare fee-for-service inpatient and outpatient claims data was analyzed. Patients receiving a primary total shoulder arthroplasty for osteoarthritis, rotator cuff pathology, or inflammatory arthropathy were included and subsequent ipsilateral revision surgeries were identified. The time to revision was modeled using the Prentice, Williams, and Peterson Gap Time Model. Medicare spending within 90 days post-discharge was modeled using a generalized linear model. The analysis was subdivided by index procedure type: anatomic total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA). RESULTS: A total of 82,949 primary TSAs and 172,524 RSAs were identified. Compared to index TSA cases, index RSA cases had a lower first revision rate in an observation window of nearly 7 years (1.9% vs. 3.5%, p<0.001), but a higher rate of second (11.4% vs. 4.9%, p<0.001) as well as third revision (13.8% vs. 13.8%, p=0.449). TSA spending was significantly lower than RSA spending for the index procedure ($21,531 vs. $23,267, p<0.001), first ($23,096 vs. $26,414, p<0.001), and second ($25,060 vs. $29,983, p<0.001) revision. There was no statistically significant difference in third revision between TSA and RSA groups ($31,313 vs. $30,829, p=0.860). Age, sex, race, and rheumatoid arthritis were among the top predictors of revisions. Top predictors of Medicare spending included having a non-osteoarthritis surgical indication, a hospital stay of three or more days, a discharge to a setting other than home, malnutrition, dementia, stroke, major kidney diseases, and being operated on in a teaching hospital. CONCLUSION: Compared with TSA, RSA was associated with a lower first revision rate, but a higher subsequent revision rate. An index RSA procedure was also associated with higher initial Medicare spending as well as subsequent revision surgery spending compared with an index TSA procedure. Demographics and comorbid medical conditions were among the top predictors of revisions, while procedure-related factors predicted Medicare spending.

Assessing the Efficacy: Mid-Term Clinical and Radiological Outcomes of the Comprehensive Short Stem System in Reverse Shoulder Arthroplasty.

BACKGROUND: For degenerative shoulder disease, reverse shoulder arthroplasty (RSA) has proven successful; however, problems such as scapular notching and instability still exist. These difficulties are intended to be addressed by recently improved prosthesis designs with reduced neck-shaft angles (NSA). Still, there are issues with complications, particularly with the humerus. In an effort to avoid these problems and maintain bone stock, a recently designed straight-short-stem humeral component was used; however, yet its clinical and radiological outcomes in RSA remain largely unexplored. MATERIAL AND METHODS: Using a 55mm straight short stem (Comprehensive Reverse Shoulder System; Zimmer Biomet), a retrospective analysis of 93 patients undergoing primary RSA was carried out. Clinical assessments, including scores and range of motion, were conducted both before and after surgery. Complications, bone adaptation, and stem alignment were all evaluated radiographically. Significant correlations between postoperative shoulder movements and function were linked with angles of prosthesis lateralization and distalization. RESULTS: Patients demonstrated significant improvements in clinical scores at 35-month follow-up on average: Constant-Murley (76.4 ± 13.4), ASES (84.8 ± 16.5), DASH (17.1 ± 15.8), and UCLA (7.1 ± 1.5). Radiographic assessments showed no stem loosening and stable implant attachment. There was no scapular notching, and there were noticeable improvements in shoulder range of motion and function. DISCUSSION AND CONCLUSION: This study validates the efficacy of a straight short stem for acceptable clinical outcomes and implant stability in RSA. Notably, it demonstrates specific angle ranges crucial for optimal post-surgical shoulder function. The findings suggest this stem design presents potential benefits in RSA, highlighting its safety and effectiveness while providing insights for future clinical strategies. The study contributes valuable data toward understanding and enhancing patient outcomes in shoulder arthroplasty procedures.

Stemless Anatomic and Reverse Shoulder Arthroplasty in Patients under 55 years of age with Primary Glenohumeral Osteoarthritis: An analysis of the Australian Orthopaedic Association National Joint Replacement Registry at five years.

BACKGROUND: Primary glenohumeral osteoarthritis in young patients poses challenging treatment decisions. Arthroplasty options have different failure profiles and implant survivorship patterns. This registry study aims to analyze the cumulative per cent revision rate (CPR) of different types of arthroplasties conducted for primary osteoarthritis in patients under 55 years of age. METHODS: This comparative observational national registry study included all shoulder arthroplasty for osteoarthritis in patients under 55 years of age undertaken between January 1st, 2005, and December 31st, 2022. Partial hemi resurfacing and hemi stemless procedures were excluded. The cumulative percentage of revision (CPR) was determined using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazard models adjusted for gender. Reasons for revision of each type of arthroplasty and cumulative incidence of revision diagnoses were analyzed. RESULTS: 2111 primary shoulder arthroplasties were compared. Glenoid erosion is the predominant cause of revision for humeral resurfacing (29.8%) and hemiarthroplasty (35.5%). Instability is the predominant cause of revision for stemmed anatomic total shoulder arthroplasty (ATSA) and reverse total shoulder arthroplasty (RTSA), while loosening is the predominant cause of revision for stemless ATSA. The 6-year CPR is 12.8% for humeral resurfacing (HRA), 14.1% for hemiarthroplasty (HA), 12.4% for stemmed (ATSA), 7.0% for stemless ATSA, and 6.5% for (RTSA). Stemmed ATSA had a higher revision rate than RTSA (entire period HR=2.04 (95% confidence interval (CI) 1.16, 3.57), p=0.012). In contrast, the revision rate of stemless ATSA was not different from RTSA (HR =1.05 (95% CI 0.51, 2.19), p=0.889). Males outnumber females for all shoulder arthroplasty categories. DISCUSSION: RTSA and stemless ATSA are viable options in young patients with primary osteoarthritis. Their short-to medium-term revision rates are comparable to those of older patients and lower than those associated with HRA, HA, and stemmed ATSA. CONCLUSION: In the predominantly male patient population under the age of 55, reverse shoulder arthroplasty and stemless ATSA have a lower short-term revision risk than stemmed ATSA.

Comparison between arthroplasty and non-operative treatment for proximal humeral fractures: a systematic review and meta-analysis.

Background: The clinical efficacy of reverse shoulder arthroplasty (RSA), hemiarthroplasty (HA), and non-surgical management in the treatment of proximal humeral fractures (PHFs) is inconclusive. This systematic review and meta-analysis compared the clinical outcomes of arthroplasty and non-surgical management of PHFs. Methods: The databases of PubMed, Embase, Web of Science, and Cochrane Library were searched on 5 May 2023 for studies comparing arthroplasty and non-surgical treatment of PHFs. Both randomized controlled trials (RCTs) and non-randomized controlled trials (nRCTs), were included. Standard methodological quality assessments were conducted for both types of studies. The primary outcome was the Constant-Murley Score (CMS) after surgical or non-surgical treatment. Secondary study outcomes included the visual analog scale (VAS), range of motion, and complications. All functional scores and complications were subjected to subgroup and sensitivity analyses. Results: A total of four RCTs and six nRCTs were included in this study, which provided 508 patients in total for meta-analysis: 238 treated with arthroplasty and 270 treated non-surgically, of which 83 were treated with HA and 155 with RSA. All relevant information was collected, including functional scores, VAS, range of motion, and complications. The study found no significant difference in functional outcomes (mean difference, 2.82; 95% confidence interval, -0.49 to 6.14; P = 0.10; I 2 = 77%) and complications (mean difference, 1.08; 95% confidence interval, 0.51-2.25; P = 0.85; I 2 = 47%) between arthroplasty and non-surgical treatment. Both RCTs and nRCTs showed the same results. However, VAS scores were significantly lower in surgical treatment compared to non-surgical treatment. Subgroup and sensitivity analyses showed that RSA could achieve better functional scores than non-surgical treatment (mean difference, 6.00; 95% confidence interval, 1.97-10.03; P = 0.004; I 2 = 0%), while the results for HA were not significant (P > 0.05). Conclusion: There were no significant differences in complications between arthroplasty and non-surgical treatment for PHFs. RSA could achieve better functional results than non-surgical treatment, while HA could only achieve better forward flexion.

Stress shielding in stemmed reverse shoulder arthroplasty: an updated review.

BACKGROUND: Reverse shoulder arthroplasty (RSA) is popular for the treatment of degenerative glenohumeral joint disease. Bone remodeling around the humeral stem related to stress shielding (SS) has been described. This review focuses on the specific radiological characteristics, risk factors, and clinical consequences of SS in RSA. METHODS: A meticulous review was conducted of articles published between 2013 and 2023. Data on the definition, risk factors, and clinical impact of stress shielding were recorded. RESULTS: Twenty-eight studies describing 2691 patients who had undergone RSA were included. The mean age of patients ranged from 63 to 80 years with mean follow-up periods of 12 months to 9.6 years. The prevalence of SS reached up to 39% at a 2-year follow-up. Females and elderly are typically at higher risk due to osteopenia. SS was more frequent with the use of long stems(>100 mm) compared to short stems(<100 mm). Stem design, onlay or inlay, and neck-shaft-angle did not influence SS. Frontal misalignment and a high filling ratio are riskfactors for SS. Biological factors also contribute to SS, associated with scapular notching. No correlation was found between SS and clinical outcomes. CONCLUSIONS: SS is common in patients with cementless implants after RSA, especially in female and elderly patients. It can be limited by implanting stems with a low diaphyseal filling-ratio, in correct coronal alignment. Risk factors for polyethylene debris, primarily scapular notching, should be avoided. The authors found no clinical consequences of stress shielding, but longer-term follow-up studies are required to confirm these findings.

Mid- to long-term outcome of reverse total shoulder arthroplasty as revision procedure for failed hemiarthroplasty after proximal humerus fracture.

BACKGROUND: Insufficient tuberosity healing is the most common reason for poor outcome after treatment of proximal humerus fractures (PHFs) using hemiarthroplasty (HA). In these cases, revision to reverse total shoulder arthroplasty (RTSA) can improve function and reduce pain in the short term, however, long-term results remain scarce. Aim of this study was to evaluate the clinical and radiological mid- to long-term results in patients with a revision RTSA after failed HA for PHF. METHODS: In this retrospective study all patients that received a revision to RTSA after failed fracture HA between 2006 and 2018 were included. A total of 49 shoulders in 48 patients (38 female, 10 male; mean age 82 ± 9 years) were identified in our database. A total of 20 patients (17 female, 3 male; mean age was 79 ± 9 years) were available for follow-up examination after a mean time period of approximately eight years (3-14 years) after revision surgery. At final follow-up, patients were assessed using a subjective shoulder value (SSV), range of motion (ROM), visual analogue score (VAS), the Constant Score (CS) and the 12-Item Short Form Survey (SF-12). RESULTS: At final follow-up, mean CS was 55 ± 19 (19-91), VAS averaged 3 ± 3 (0-8) and mean SSV was 61 ± 18% (18-90%). Mean SF-12 was 44 (28-57) with a mean physical component summary (PCS) of 38 (21-56) and a mean mental component summary (MCS) of 51 (29-67). On average active forward flexion (FF) was 104° (10-170°), active abduction (ABD) was 101° (50-170°), active external rotation (ER) was 19° (10-30°) and active internal rotation (IR) of the lumbosacral transition was reached. Three patients presented with a periprosthetic humeral fracture after RTSA implantation and underwent a reoperation (15%) during follow-up period. CONCLUSIONS: Revision RTSA results in promising clinical results in patients after initial failed HA after PHF. A complication and reoperation rate of 15% is tolerable in consideration of satisfactory functional and psychological outcome. TRIAL REGISTRATION: Retrospectively registered.

Can ChatGPT Answer Patient Questions Regarding Reverse Shoulder Arthroplasty?

INTRODUCTION: In recent years, Artificial Intelligence (AI) has seen substantial progress in its utilization, with Chat Generated Pre-Trained Transformer (ChatGPT) emerging as a popular language model. The purpose of this study was to test the accuracy and reliability of ChatGPT's responses to frequently asked questions (FAQ) pertaining to reverse shoulder arthroplasty (RSA). METHODS: The ten most common FAQs were queried from institution patient education websites. These ten questions were then input into the chatbot during a single session without additional contextual information. The responses were then critically analyzed by two orthopedic surgeons for clarity, accuracy, and the quality of evidence-based information using The Journal of the American Medical Association (JAMA) Benchmark criteria and the DISCERN score. The readability of the responses was analyzed using the Flesch-Kincaid Grade Level. RESULTS: In response to the ten questions, the average DISCERN score was 44 (range 38-51). Seven responses were classified as fair and three were poor. The JAMA Benchmark criteria score was 0 for all responses. Furthermore, the average Flesch-Kincaid Grade Level was 14.35, which correlates to a college graduate reading level. CONCLUSION: Overall, ChatGPT was able to provide fair responses to common patient questions. However, the responses were all written at a college graduate reading level and lacked reliable citations. The readability greatly limits its utility. Thus, adequate patient education should be done by orthopedic surgeons. This study underscores the need for patient education resources that are reliable, accessible, and comprehensible. LEVEL OF EVIDENCE: IV.

Instability after reverse shoulder arthroplasty: a retrospective review of thirty one cases.

PURPOSE: A retrospectively analyze of instability after RSA in terms of aetiology, treatment and final functional outcome. METHODS: A bicentric retrospective study of 31 patients (mean age 67.6 years; 42-83) treated for RSA instability using RSA Arrow System (FH Orthopedics, Mulhouse, France), mean follow-up 41months (range 12-158). Aetiologies for dislocation were evaluated using a previously described classification system for RSA instability. Actions performed during the Revision Surgeries were analyzed and grouped into five categories. Clinical outcome measures included range of motion, SSV, VAS, Constant-Murley scores, satisfaction level and recurrence of instability. RESULTS: The most frequent aetiology for RSA instability was loss of compression (18), followed by impingement (8) and loss containment (5). Total RSA revision (bipolar procedure) involving both distalization and lateralization occurred in 13 instances. Isolated distalization through the humerus was performed in ten patients and Isolated lateralization through the glenoid in three patients. Three cases of components exchange due to mechanical failure were noted. Bone graft was used in nine instances. Three patients (10%) suffered recurrent instability following Revision Surgery and required an additional stabilizing procedure. At final follow-up all 31 RSA were reported as stable with a mean VAS of 1.1, SSV 54.5%, constant score 48.3, constant ponderate 74.9%. CONCLUSION: The management of unstable RSA represent a challenge that can be successfully overcome with a revision surgery with compromised functional results. Loss of compression was the most common cause for primary and recurrent RSA instability that were treated principally with bipolar revisions involving component lateralization and distalization.

The Effect of Smoking on Outcomes of Reverse Total Shoulder Arthroplasty.

BACKGROUND: The effect of smoking status on clinical outcomes in reverse total shoulder arthroplasty (rTSA) has not been thoroughly characterized. We sought to compare pain and functional outcomes, complications, and revision-free survivorship between current smokers, former smokers, and non-smokers undergoing primary rTSA. METHODS: We retrospectively reviewed a prospectively-collected shoulder arthroplasty database from 2004-2020 to identify patients who underwent primary rTSA. Three cohorts were created based on smoking status: current smokers, former smokers, and non-smokers. Outcome scores (SPADI, SST, ASES, UCLA, Constant), range of motion (ROM) (external rotation [ER], forward elevation [FE], abduction, internal rotation [IR]) and shoulder strength (ER, FE) evaluated at 2-4-year follow-up were compared between cohorts. The incidence of complication and revision-free implant survivorship were evaluated. RESULTS: We included 676 primary rTSAs, including 38 current smokers (44±47 pack-years), 84 former smokers who quit on average 20±14 years (range: 0.5-57 years) prior to surgery (38±32 pack-years), and 544 non-smokers. At 2-4-year follow-up, current smokers had less favorable SPADI, SST, ASES scores, UCLA scores, and Constant scores compared to former smokers and non-smokers. On multivariable analysis, current smokers had less favorable SPADI, SST, ASES score, UCLA score, and Constant score compared to non-smokers. There were no significant differences between cohorts in complication rate and revision-free survivorship. CONCLUSION: Our data showed that current smokers may have poorer functional outcomes after rTSA compared to former smokers and non-smokers despite the incidence of complications and revision surgery not differing significantly between cohorts.

Non-vascularized coracoid process autograft for glenoid reconstruction in revision shoulder arthroplasty.

PURPOSE: To report the radiological and clinical outcomes of non-vascularized coracoid process autografts used for glenoid reconstruction during revision shoulder arthroplasty. MATERIAL AND METHOD: This is a retrospective, monocentric study from January 2016 to October 2022 targeting patients treated with a coracoid bone graft for glenoid reconstruction during revision of shoulder arthroplasty. The primary outcome measures were coracoid graft union rate and graft-implant osseointegration. Secondary outcome measures included clinical and CT-scan identified radiological complications and functional outcomes as measured by the Visual Analog Scale (VAS), Range of Motion (ROM), Subjective Shoulder Value (SSV), Constant score (absolute and ponderate), and ASES score. RESULTS: Fifteen patients (9 males, 6 females; mean age 66.9 years, range 38-85) were included. At a mean follow-up of 20.9 months (range 12-56 months), 93.3% achieved complete graft integration. One case of partial lysis without baseplate loosening was noted. Regarding range of motion, the mean forward elevation was 130° (range 90°-170°), external rotation at the side 25° (range 10°-40°), external rotation in 90° of abduction 45° (range 10°-80°), and internal rotation 52° (range 10-80°). The mean VAS for pain was 1.1 (range 0-8), mean SSV 67.3% (range 40-90%), mean ASES score 85.5 (range 65-98.3), mean Absolute Constant score 58.6 (range 21-83), and mean Ponderate Constant score 77.5% (range 28.8-110.7%). No neurological injuries were reported. CONCLUSION: Utilizing a non-vascularized coracoid graft during shoulder arthroplasty revision is a safe, reproducible, and time-efficient technique that demonstrated satisfactory osseointegration, implant stability, good functional results, and a low complication rate.

The acetabularization index: a novel measure of acromial bone loss prior to reverse shoulder arthroplasty.

BACKGROUND: Acromial stress fractures following reverse shoulder arthroplasty (RSA) have gained attention among specialized surgeons over the past decades craving answers regarding predisposing factors and technical aspects as how to avoid the complication. This study introduces the acetabularization index (AI) for the preoperative estimation of acromial bone loss attributed to acetabularization in cases of cuff tear arthropathy (CTA). METHODS: The acromiohumeral interval (AHI), extent of acromial acetabularization (AA), acromial height (AH), and width of acetabularization (r) were measured on preoperative radiographs and two-dimensional computed tomography scans (2D CT) of patients who underwent RSA within the timeline 2019-2023 for CTA. The AI calculated AI % = AA mm ÷ AH mm . The CTA grade was determined according to the Hamada classification. The AI values on radiographs and 2D CT were compared by a Student's t-test. Possible correlation between the AI and AHI was investigated via Pearson's coefficient. The intraclass correlation coefficient (ICC) was employed to test the interobserver reliability among two independent testers. RESULTS: The radiographs and 2D CT scans of thirty-three patients who underwent RSA were analyzed. The mean AHI, AH, AA, r, and AI values on radiographs were 5.5 ± 2 mm, 10 ± 2 mm, 2 ± 2 mm, 30 ± 4 mm, 16 ± 16%, respectively. On 2D CT, the corresponding mean values were 4.7 ± 2.5 mm, 10.8 ± 2.65 mm, 2.45 ± 2.35 mm, and 30 ± 4.5, and 22.3 ± 22%, respectively. There was a statistically significant difference between the AI values on radiographs and 2D CT (P = .000). The Pearson's correlation coefficient demonstrated a negative correlation between AI and AHI (r = - 0.33). Excellent reliability was observed by the ICC values for all parameters in both groups among two testers. CONCLUSION: The AI is a reliably measurable tool on radiographs and 2D CT scans; however, the measurements derived from radiographs vary significantly from CT based measurements due to projection restrictions. Grade IVB of the Hamada/Fukuda classification is associated with the highest AI values. Further research is warranted to assess the clinical utility of this index as a predictive tool for postoperative acromial stress fractures.

Finite element analysis part 1 of 2: Influence of short stem implant polyethylene configuration on glenohumeral joint biomechanics.

Purpose: Stress shielding in short-stem arthroplasty can cause critical metaphyseal bone loss. If the size and shape of the humeral shaft are important factors, it is unknown whether the shape of the polyethylene component in reverse shoulder arthroplasty (RSA) affects bone stress around or within the stem. We explored the impact of polyethylene shape on humeral and scapular stress distribution using a finite element model. Methods: We developed a shoulder-specific finite element model. A defined set of muscle forces was applied to simulate movements. An intact rotator cuff state and a superior deficient rotator cuff state were modelled. We used the FX V135 short stem in three conditions: total shoulder arthroplasty (TSA), and RSA with symmetrical and asymmetrical polyethylene (145°/135°). We measured biomechanical markers related to bone stress for different implant sizes. Joint kinematics and the mechanical behaviour of the implant were compared. Results: Rupture of the supraspinatus muscle produced a functionally limited shoulder. The placement of an anatomic TSA with an intact rotator cuff restored function similar to that of a healthy shoulder. RSA in the rotator cuff-deficient shoulder restored function regardless of stem size and polyethylene shape. While stem size had an impact on the stress distribution in the bone and implant, it did not show significant potential for increasing or decreasing overall stress. For the same stem, stress distribution at the humerus is different between TSA and RSA. Polyethylene shape did not alter the transmission of stress to the bone in RSA. Asymmetric polyethylene produced a greater abduction range of motion. Conclusions: In terms of bone stress distribution, smaller stems seemed more appropriate for TSA, while larger stems may be more appropriate for RSA. Polyethylene shape resulted in different ranges of motion but did not influence bone stress. Level of Evidence: Diagnostic Tests or Criteria; Level IV.

Finite element analysis part 2 of 2: Glenohumeral bone stress distribution depends on implant configuration for anatomic and reverse stemless shoulder implants.

Purpose: Our purpose was to quantify stresses in the bone surrounding stemless implants in various configurations. Methods: A detailed finite element model of the glenohumeral joint was used to simulate abduction kinematics before and after arthroplasty and to measure bone stresses around the implants. Two digital patients were simulated: one healthy and one with supraspinatus muscle impairment (deficiency). Two anatomic total shoulder arthroplasty (TSA) configurations were placed in a 135° cutting plane. Two reverse shoulder arthroplasty (RSA) configurations with cutting angles of 135° and 145° were simulated with asymmetrical and symmetrical polyethylene cups, respectively, to obtain humeral neck-shaft angles of 145°. Results: Compared with preoperative models, TSA preserved and RSA restored abduction kinematics. The bone mechanical stresses were located mainly around the central stud of the TSA and were more peripheral to the RSA humeral components. The RSA configuration with the 145° cutting angle and symmetrical cup generated the lowest maximal bone stress and bone volume involvement. Stresses in the scapular cortical bone were highest in the supraspinatus fossa for TSA and the crest of the acromion for RSA. Conclusion: Early stability and glenohumeral bone stress change with implant configuration and should not be extrapolated from anatomic clinical data to reverse configurations. Level of Evidence: Diagnostic tests or criteria; Level IV.

A gender and size specific evaluation of Grammont-type inlay versus lateralizing onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty.

INTRODUCTION: In reverse shoulder arthroplasty (RSA) new designs enable greater amounts of lateralization to prevent instability and scapular notching and increase range of motion, however, excessive lateralization leads to stress upon the acromion that can result in scapular spine fatigue fractures. Aim of this study was to gender- and size-specifically assess the influence of glenosphere size and different humeral designs on lateralization, distalization, and bony impingement-free range of motion (ROM) in patients undergoing RSA. METHODS: Computed tomography scans from 30 osteoarthritic patients (f:15, m:15) and 20 cuff tear arthropathy patients (f:10, m:10) were used to virtually simulate RSA implantation. The efficacy of an inlay Grammont-type system vs. an onlay lateralizing system combined with different glenosphere sizes (36 mm vs. 42 mm) in achieving ROM, lateralization, and distalization was evaluated. Moreover, gender and patient's constitution were correlated to humeral size by radiologically measuring the best-fit circle of the humeral head. RESULTS: A different amount of relative lateralization was achieved in both genders using large glenospheres and onlay designs. Latter yielded a higher ROM in all planes for men and women with a 42 mm glenosphere; with the 36 mm glenosphere, an increased ROM was observed only in men. The 155° inlay design led to joint medialization only in men, whereas all designs led to lateralization in women. When adjusting the absolute amount of lateralization to humerus' size (or patient's height), regardless of implant type, women received greater relative lateralization using 36 mm glenosphere (inlay: 1%; onlay 12%) than men with 42 mm glenosphere (inlay: -3%; onlay: 8%). CONCLUSION: The relative lateralization achieved using onlay design is much higher in women than men. Small glenospheres yield greater relative lateralization in women compared to large glenospheres in men. Humeral lateralization using onlay designs should be used cautiously in women, as they lead to great relative lateralization increasing stress onto the acromion. LEVEL OF EVIDENCE: Basic Science Study, Computer Modeling.

Computer modeling and validation testing for glenoid component rotation and optimal glenoid screw angles for reverse shoulder arthroplasty in an Asian population.

PURPOSE: Good initial fixation of glenoid component for reverse total shoulder arthroplasty (RTSA) relies on component placement and screw purchase in the scapula bone. This is especially difficult in an Asian population with small glenoid geometry. Optimal glenoid component roll angle and screw angulation to achieve the longest screws for best fixation has not been defined in the current literature. METHODS: Computer 3D modelling of 133 scapulas with RTSA performed were analyzed to determine patient specific optimal glenoid roll angle (GRA) for the longest bi-cortical screws attainable. The cranial-caudal angle (CCA), anterior-posterior angle (APA) and lengths for the superior and inferior screws were measured. Validation testing using calculated average (CA) angles and rounded average (RA) angles to the nearest 5 degree were recomputed for each case to determine the bi-cortical screw lengths achievable. The CA and RA screw lengths were compared against patient specific modelling using paired-sample t-tests. RESULTS: Average GRA was - 1.6°, almost perpendicular to the long axis of the glenoid and achieves an average bi-cortical screw length of 51.3 mm and 45.5 mm for the superior and inferior screws respectively. The CCA and APA were 9.1° cranial and 6.5° posterior for the superior screw and screw angulation of 11.2° caudal and 0.7° anterior for the inferior screw. Validation testing shows statistically shorter screw lengths in the CA and RA models compared to patient specific modelling (p < 0.01). CONCLUSION: Validation testing with average angles for GRA, CCA and APA demonstrates strong patient heterogeneity and anatomical variation. Despite this, screw lengths attainable in the RA group were > 38 mm with good safety profile. Surgeons may consider the additional use of navigation-assisted, or 3D printed patient specific instrumentation to optimize baseplate and screw configuration for RTSA.