Thoracic hyperkyphosis (TH – Cobb angle >40°) is correlated with rotator cuff arthropathy and associated with anterior tilting and protraction of scapula, impacting the glenoid orientation and the surrounding musculature. Reverse total shoulder arthroplasty (RTSA) is a reliable surgical treatment for patients with rotator cuff arthropathy and recent literature suggests that patients with TH may have comparable range of motion after RTSA. However, there exists no study reporting the possible link between patient-reported outcomes, humeral retroversion and TH after RTSA. While the risk of post-operative complications such as instability, hardware loosening, scapular notching, and prosthetic infection are low, we hypothesize that it is critical to optimize the biomechanical parameters through proper implant positioning and understanding patient-specific scapular and thoracic anatomy to improve surgical outcomes in this subset of patients with TH. Patients treated with primary RTSA at an academic hospital in 2018 were reviewed for a two-year follow-up. Exclusion criteria were as follows: no pre-existing chest radiographs for Cobb angle measurement, change in post-operative functional status as a result of trauma or medical comorbidities, and missing component placement and parameter information in the operative note. As most patients did not have a pre-operative chest radiograph, only seven patients with a Cobb angle equal to or greater than 40° were eligible. Chart reviews were completed to determine indications for RTSA, hardware positioning parameters such as inferior tilting, humeral stem retroversion, glenosphere size/location, and baseplate size. Clinical data following surgery included review of radiographs and complications. Follow-up in all patients were to a period of two years. The American Shoulder and Elbow Surgeons (ASES) Shoulder Score was used for patient-reported functional and pain outcomes. The average age of the patients at the time of RTSA was 71 years old, with six female patients and one male patient. The indication for RTSA was primarily rotator cuff arthropathy. Possible correlation between Cobb angle and humeral retroversion was noted, whereby, Cobb angle greater than 40° matched with humeral retroversion greater than 30°, and resulted in significantly higher ASES scores. Two patients with mean Cobb angle of 50° and mean humeral retroversion 37.5° had mean ASES scores of 92.5. Five patients who received mean humeral retroversion of 30° had mean lower ASES scores of 63.7 (p < 0 .05). There was no significant correlation with glenosphere size or position, baseplate size, degree of inferior tilting or lateralization. Patient-reported outcomes have not been reported in RTSA patients with TH. In this case series, we observed that humeral stem retroversion greater than 30° may be correlated with less post-operative pain and greater patient satisfaction in patients with TH. Further clinical studies are needed to understanding the biomechanical relationship between RTSA, humeral retroversion and TH to optimize patient outcomes

Background. Though many advantages of reverse total shoulder arthroplasty (RTSA) have been demonstrated, a variety of complications indicate there is much to learn about how RTSA modifies normal shoulder function. This study assesses how RTSA affects deltoid muscle moment arms post-surgery using a subject-specific computational model driven by in vivo kinematic data. Methods. A subject-specific 12 degree-of-freedom (DOF) musculoskeletal model was used to analyze the shoulders of 26 subjects (14 RTSA, 12 Normal). The model was modified from the work of Holzbaur et al. to directly input 6 DOF humerus and scapula kinematics obtained using fluoroscopy. Results. The moment arm of the anterior, lateral and poster aspects of the deltoid was found to be significantly different when comparing RTSA and normal cohorts. Anterior and lateral deltoid moment arms were found to be larger at initial elevation. There was large inter-subject variability within the RTSA group. Conclusion. Placement of implant components during RTSA can directly affect the geometric relationship between the humerus and scapula and the muscle moment arms in the RTSA shoulder. RTSA shoulders maintain the same anterior and posterior deltoid muscle moment arm patterns as healthy shoulders, but they show much greater inter-subject variation and larger moment arm magnitudes. These observations provide a basis for determining optimal implant configuration and surgical placement to maximize RTSA function in a patient-specific manner

Reverse Total shoulder arthroplasty (RTSA) has become an increasingly used solution to treat osteoarthritis and cuff tear arthropathy. Though successful there are still 10 to 65% complication rates reported for RTSA. Complication rates range over different reverse shoulder designs but a clear understanding of implant design parameters that cause complications is still lacking within the literature. In efforts to reduce complication rates (Implant fixation, range of motion, joint stiffness, and fracture) and improve clinical/functional outcomes having to do with proper muscle performance we have employed a computational approach to assess the sensitivity of muscle performance to changes in RTSA implant geometry and surgical placement. The goal of this study was to assess how changes in RTSA joint configuration affect deltoid performance. An approach was developed from previous work to predict a patient's muscle performance. This approach was automated to assess changes in muscle performance over 1521 joint configurations for an RTSA subject. Patient-specific muscle moment arms, muscle lengths, muscle velocities, and muscle parameters served as inputs into the muscle prediction scheme. We systematically varied joint center locations over 1521 different perturbations from the in vivo measured surgical placement to determine muscle activation and normalized operating region for the anterior, lateral and posterior aspects of the deltoid muscle. The joint center was varied from the RTSA subject's nominal surgical position ±4 mm in the anterior/posterior direction, ±12mm in the medial/lateral direction, and −10 mm to 14 mm in the superior/inferior direction. Overall muscle activity varied over 1521 different implant configurations for the RTSA subject. For initial elevation the RTSA subject showed at least 25% deltoid activation sensitivity in each of the directions of joint configuration change(Figure 1A–C). Posterior deltoid showed a maximal activation variation of 84% in the superior/inferior direction(Figure 1C). Deltoid activation variations lie primarily in the superior/inferior and anterior/posterior directions(Figure 1). An increasing trend was seen for the anterior, lateral and posterior deltoid outside of the discontinuity seen at 28°(Figur 1A–C). Activation variations were compared to subject's experimental data (Figure 1). Reserve actuation for all samples remained below 4Nm. The most optimal deltoid normalized operating length was implemented by changing the joint configuration in the superior/inferior and medial/lateral directions. Current shoulder models utilize cadaver information in their assessment of generic muscle strength. In adding to this literature we performed a sensitivity study to assess the effects of RTSA joint configurations on deltoid muscle performance. With this information improvements can be made to the surgical placement and design of RTSA to improve functional/clinical outcomes while minimizing complications

Reverse total shoulder arthroplasty (RTSA) is an increasingly common treatment for osteoarthritic shoulders with irreparable rotator cuff tears. Although very successful in alleviating pain and restoring some function, there is little objective information relating geometric changes imposed by the reverse shoulder and arm function, particularly the moment generating capacity of the shoulder muscles. Recent modeling studies of reverse shoulders have shown significant variation in deltoid muscle moment arms over a typical range of humeral offset locations in shoulders with RTSA. The goal of this study was to investigate the sensitivity of muscle moment arms as a function of varying the joint center and humeral offset in three representative RTSA subjects that spanned the anatomical range from our previous study cohort. We hypothesized there may exist a more beneficial joint implant placement, measured by muscle moment arms, compared to the actual surgical implant configuration. A 12 degree of freedom, subject-specific model was used to represent the shoulders of three patients with RTSA for whom fluoroscopic measurements of scapular and humeral kinematics during abduction had been obtained. The computer model used subject-specific in vivo abduction kinematics and systematically varied humeral offset locations over 1521 different perturbations from the surgical placement to determine moment arms for the anterior, lateral and posterior aspects of the deltoid muscle. The humeral offset was varied from its surgical position ±4 mm in the anterior/posterior direction, ±12mm in the medial/lateral direction, and −10 mm to 14 mm in the superior/inferior direction. The anterior deltoid moment arm varied up to 20 mm with humeral offset and center of rotation variations, primarily in the medial/lateral and superior/inferior directions. Similarly, the lateral deltoid moment arm demonstrated variations up to 20 mm, primarily with humeral offset changes in the medial/lateral and anterior/posterior directions. The posterior deltoid moment arm varied up to 15mm, primarily in early abduction, and was most sensitive to changes of the humeral offset in the superior/inferior direction. The goal of this study was to assess the sensitivity of the deltoid muscle moment arms as a function of joint configuration for existing RTSA subjects. High variations were found for all three deltoid components. Variation over the entire abduction arc was greatest in the anterior and lateral deltoid, while the posterior deltoid moment arm was mostly sensitive to humeral offset changes early in the abduction arc. Moment arm changes of 15–20 mm represent a significant amount of the total deltoid moment arm. This means there is an opportunity to dramatically change the deltoid moment arms through surgical placement of the joint center of rotation and humeral stem. Computational models of the shoulder may help surgeons optimize subject-specific placement of RTSA implants to provide the best possible muscle function, and assist implant designers to configure devices for the best overall performance

Reverse total shoulder arthroplasty (RTSA) is increasingly used in the United States since approval by the FDA in 2003. RTSA relieves pain and restores mobility in arthritic rotator cuff deficient shoulders. Though many advantages of RTSA have been demonstrated, there still are a variety of complications (implant loosening, shoulder impingement, infection, frozen shoulder) making apparent much still is to be learned how RTSA modifies normal shoulder function. The goal of this study was to assess how RTSA affects deltoid muscle moment generating capacity post-surgery using a subject-specific computational model driven by in vivo kinematic data. A subject-specific 12 degree-of-freedom (DOF) musculoskeletal model was used to analyze the shoulders of 27 subjects (14-RTSA, 12-Normal). The model was modified from the work of Holzbaur et al. to directly input 6 DOF humerus and scapula kinematics obtained using fluoroscopy. Model geometry was scaled according to each subject's skeletal dimensions. In vivo abduction kinematics for each subject were input to their subject-specific model and muscle moment arms for the anterior, lateral and posterior aspects of the deltoid were measured over the arc of motion. Similar patterns of muscle moment arm changes were observed for normal and RTSA shoulders. The moment arm of the anterior deltoid was positive with the arm at the side and decreased monotonically, crossing zero (the point at which the muscle fibers pass across the joint center) between 50°–60° glenohumeral abduction (Figure 1a). The average moment arm of the lateral deltoid was constant and positive in normal shoulders, but showed a decreasing trend with abduction in RTSA shoulders (Figure 1b). The posterior deltoid moment arm was negative with the arm at the side, and increased monotonically to a positive value with increasing glenohumeral abduction (Figure 1c). Subject-specific moment arm values for RTSA shoulders were highly variable compared to normal shoulders. 2-way repeated measures ANOVA showed significant differences between RTSA and normal shoulders for all three aspects of the deltoid moment arm, where the moment arms in RTSA shoulders were smaller in magnitude. Shoulder functional capacity is a product of the moment generating ability of the shoulder muscles which, in turn, are a function of the muscle moment arms and muscle forces. Placement of implant components during RTSA can directly affect the geometric relationship between the humerus and scapula and, therefore, the muscle moment arms in the RTSA shoulder. Our results show RTSA shoulders maintain the same muscle moment arm patterns as healthy shoulders, but they show much greater inter-subject variation and smaller moment arm magnitudes. These observations show directly how RTSA configuration and implant placement affect deltoid moment arms, and provide an objective basis for determining optimal implant configuration and surgical placement to maximize RTSA function in a patient-specific manner

Reverse total shoulder arthroplasty (RTSA) is an increasingly common treatment for osteoarthritic shoulders with irreparable rotator cuff tears. Although very successful in alleviating pain and restoring some function there is little objective information relating geometric changes imposed by the reverse shoulder and the moment generating capacity of the shoulder muscles. Recent modeling studies of reverse shoulders have shown significant variation in deltoid muscle moment arms over varied joint centers for shoulders with RTSA. The goal of this study was to investigate the sensitivity of muscle moment arms as a function of varying the joint center in one representative RTSA subject. We hypothesized there may exist a more beneficial joint implant placement, measured by muscle moment arms, compared to the actual surgical implant placement. A 12 degree of freedom, subject-specific model was used to represent the shoulder of a patient with RTSA for whom fluoroscopic measurements of scapular and humeral kinematics during abduction had been obtained. The computer model used these abduction kinematics and systematically varied joint center locations over 1521 different perturbations from the surgical placement to determine moment arms for the anterior, lateral and posterior aspects of the deltoid muscle. The joint center was varied from its surgical position ±4 mm in the anterior/posterior direction, 0–24 mm in the medial/lateral direction, and −10 mm to 14 mm in the superior/inferior direction. The anterior deltoid moment arm varied up to 16mm with center of rotations variations, primarily in the medial/lateral and superior/inferior directions (Figure 2, Table 1(Figure 1)). Similarly, the lateral deltoid moment arm demonstrated variations up to 13 mm, primarily with joint center changes in the anterior/posterior and superior/inferior directions. The posterior deltoid moment arm varied up to 10mm, primarily in early abduction, and was most sensitive to changes of the joint center in demonstrated a sensitivity of 6 mm corresponding to variations in the superior/inferior directions (Figure 2). The goal of this study was to assess the sensitivity of the deltoid muscle moment arms as a function of joint configuration for an existing RTSA subject. High variations were found for all three deltoid components. Variation over the entire abduction arc was greatest in the anterior and lateral deltoid, while the posterior deltoid moment arm was mostly sensitive to joint center changes early in the abduction arc. Moment arm changes of 10–16mm represent a significant amount of the total deltoid moment arm. This means there is an opportunity to dramatically change the deltoid moments arms through surgical placement of the joint center of rotation. Computational models of the shoulder may help surgeons optimize subject-specific placement of RTSA implants to provide the best possible muscle function, and assist implant designers to configure devices for the best overall performance

Introduction. Reverse Total Shoulder Arthroplasty (rTSA) is currently advised against in patient populations with movement disorders, due to potential premature failure of the implants from the use of walking assistive devices. The objective of this study is to measure the amount of displacement induced by the simulated loading of axillary crutches on a rTSA assembly in a laboratory mimicking immediate postoperative conditions. Methods. 8 reverse shoulder baseplate/glenosphere assemblies (Equinoxe, Exactech, Inc) were fixated to 15 lb/ft3 density rigid polyurethane bone substitute blocks. Displacement of the assemblies in the A/P and S/I axes was measured using digital displacement indicators by applying a physiologically relevant 357N shear load parallel to the face of the glenosphere, and a nominal 50N compressive axial load perpendicular to the glenosphere. Westerhoff et al. reported in vivo shoulder loads while ambulating with axillary crutches had a maximum resultant force of 170% times the patient's bodyweight with the arm at 45.25° of abduction1. This was recreated by applying a 1435.4N compressive load (Average bodyweight of 86.1kg*170%) to a humeral liner and reverse shoulder assembly in an Instron testing apparatus at 45.25° of abduction as shown in Figure 1. The glenosphere was rotated about the humeral component through the arc of the axillary crutch swing, from −5° of extension to 30° of flexion as shown in Figure 2 for 183,876 cycles2. The number of cycles was based on number of steps taken in a day from pedometer data reported by Tudor Locke et al. for patients with movement disorders, extrapolated out to a 6 week postoperative recovery period3. A Student's one-tailed, paired t-test was used to identify whether or not significant displacement occurred, where p<0.05 denoted a significant difference. Results. Displacement in the A/P and S/I axes before and after cyclic loading are presented in Table 1. The S/I direction showed no significant difference in displacement (p≤.0801), whereas the A/P direction showed significant increase in displacement (p≤.0340). The average increase in displacement in the A/P and S/I directions was 43.5 and 35.8 microns, respectively. Discussion and Conclusions. This study was designed to represent a worst case scenario, as a patient is unlikely to bear full bodyweight on crutches immediately postoperatively, and is also unlikely to take as many steps as a healthy individual until full recovery occurs. For these reasons, early results indicate statistically significant displacement could occur if a patient bears full bodyweight on axillary crutches immediately postoperatively. This risk could be lowered after the postoperative recovery period in combination with non-full weight bearing devices such as a cane or a walker. To view tables/figures, please contact authors directly

Introduction. The purpose of this study was to compare implant survivorship and functional outcomes in patients undergoing reverse total shoulder arthroplasty (RTSA) for acute proximal humeral fracture (PHF) with those undergoing elective RTSA in a population-based cohort study. Methods. Prospectively collected data from the New Zealand Joint Registry from 1999 to 2021 and identified 7,277 patients who underwent RTSA. Patients were categorized by pre-operative indication, including acute PHF (10.1%), rotator cuff arthropathy (RCA) (41.9%), osteoarthritis (OA) (32.2%), rheumatoid arthritis (RA) (5.2%) and old traumatic sequelae (4.9%). The PHF group was compared with elective indications based on patient, implant, and operative characteristics, as well as post-operative outcomes (Oxford Shoulder Score [OSS], and revision rate) at 6 months, 5 and 10 years after surgery. Survival and functional outcome analyses were adjusted by age, sex, ASA class and surgeon experience. Results. Implant survivorship at 10 years for RTSA for PHF was 97.3%, compared to 96.1%, 93.7%, 92.8% and 91.3% for OA, RCA, RA and traumatic sequelae, respectively. When compared with RTSA for PHF, the adjusted risk of revision was higher for traumatic sequelae (hazard ratio = 2.29; 95% CI:1.12–4.68, p=0.02) but not for other elective indications. At 6 months post-surgery, OSS were significantly lower for the PHF group compared to RCA, OA and RA groups (31.1±0.5 vs. 35.6±0.22, 37.7±0.25, 36.5±0.6, respectively, p<0.01), but not traumatic sequelae (31.7±0.7, p=0.43). At 5 years, OSS were only significantly lower for PHF compared to OA (37.4±0.9 vs 41.0±0.5, p<0.01), and at 10 years, there were no differences between groups. Discussion and Conclusion. RTSA for PHF demonstrated reliable long-term survivorship and functional outcomes compared to other elective indications. Despite lower functional outcomes in the early post-operative period for the acute PHF group, implant survivorship rates were similar to patients undergoing elective RTSA

Glenoid bone grafting in reverse total shoulder arthroplasty (RTSA) has emerged as an effective method of restoring bone stock in the presence of complex glenoid bone loss, yet there is limited published evidence on efficacy. The aim of this study was to conduct an analysis of clinical and radiographic outcomes associated with glenoid bone grafting in primary RTSA. Patients who underwent a primary RTSA with glenoid bone grafting were retrospectively identified from the databases of two senior shoulder surgeons. Inclusion criteria included minimum of 12 months clinical and/or radiographical follow up. Patients underwent preoperative clinical and radiographic assessment. Graft characteristics (source, type, preparation), range of movement (ROM), patient-reported outcome measures (Oxford Shoulder Scores [OSS]), and complications were recorded. Radiographic imaging was used to analyse implant stability, graft incorporation, and notching by two independent reviewers. Between 2013 and 2021, a total of 53 primary RTSA procedures (48 patients) with glenoid bone grafting were identified. Humeral head autograft was used in 51 (96%) of cases. Femoral head allograft was utilised in two cases. Depending on the morphology of glenoid bone loss, a combination of structural (corticocancellous) and non-structural (cancellous) grafts were used to restore glenoid bone stock and the joint line. All grafts were incorporated at review. The mean post-operative OSS was significantly higher than the pre-operative OSS (40 vs. 22, p < 0.001). ROM was significantly improved post-operatively. One patient is being investigated for residual activity-related shoulder pain. This patient also experienced scapular notching resulting in the fracturing of the inferior screw. One patient experienced recurrent dislocations but was not revised. Overall, at short term follow up, glenoid bone grafting was effective in addressing glenoid bone loss with excellent functional and clinical outcomes when used for complex bone loss in primary RTSA. The graft incorporation rate was high, with an associated low complication rate

Proximal humerus fractures (PHF) are common, accounting for approximately 5% of all fractures. Approximately 30% require surgical intervention which can range from open reduction with internal fixation (ORIF) to shoulder arthroplasty (including hemiarthroplasty, total shoulder arthroplasty, (TSA) or reverse total shoulder arthroplasty (RTSA)). The aim of this study was to assess trends in operative interventions for PHF in an Australian population. Data was retrospectively collected for patients diagnosed with a PHF and requiring surgical intervention between January 2001 and December 2020. Data for patients undergoing ORIF were extracted from the Medicare database, while data for patients receiving arthroplasty for PHF were obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Across the study period, ORIF was the most common surgical procedure for management of PHFs. However, since 2019, RTSA has surpassed ORIF as the most common surgical procedure to treat PHFs, accounting for 51% of operations. While the number of RTSA procedures for PHF has increased, ORIF and shoulder hemiarthroplasty has significantly reduced since 2007 (p < 0.001). TSA has remained uncommon across the follow-up period, accounting for less than 1% of all operations. Patients younger than 65 years were more likely to receive ORIF, while those aged 65 years or greater were more likely to receive hemiarthroplasty or RTSA. While the number of ORIF procedures has increased during the period of interest, it has diminished as a proportion of overall procedure volume. RTSA is becoming increasingly popular, with decreasing utilization of hemiarthroplasty, and TSA for fracture remaining uncommon. These trends provide information that can be used to guide resource allocation and health provision in the future. A comparison to similar data from other nations would be useful

Reverse Total shoulder arthroplasty (RTSA) was initially introduced to treat rotator cuff arthropathy. With proven successful long-term outcomes, it has gained a noteworthy surge in popularity with its indications consequently being extended to treating various traumatic glenohumeral diseases. Several countries holding national registries remain a guide to the use the prosthesis, however a notable lack of epidemiological data still exists. More so in South Africa where the spectrum of joint disease related to communicable diseases such as HIV and tuberculosis may influence indications and patient demographics. By analysing the epidemiology of patients who underwent RTSA at our institution, we aimed to outline the local disease spectrum, the patients afflicted and indications for surgery. A retrospective review of all patients operated within the sports unit between 1 January 2019 and 31 December 2022 was conducted. An analysis of the epidemiological data pertaining to patient demographics, diagnosis, indications for surgery and complications were recorded. Included in the review were 58 patients who underwent primary RTSA over the 4-year period. There were 41 females and 17 male patients, age <55 years (n= 14) >55 years (n=44). The indications included 23 rotator cuff arthropathy (40%), 12 primary glenohumeral osteoarthritis (OA) (20%), 10 avascular necrosis (AVN) humeral head (17%), 7 inflammatory OA (12%), 4 chronic shoulder dislocation (7%) and 2 sequalae of proximal humerus fractures (4%). The study revealed RTSA being performed in patients older than 55 years of age, the main pathologies included rotator cuff arthropathy and primary OA, however AVN and shoulder dislocations secondary to trauma contributed significantly to the total tally of surgeries undertaken. This highlights the disease burden of developing countries contributing to patients presenting for RTSA

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder. Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed. For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency. Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision

Traditionally, open reduction and internal fixation (ORIF) and hemiarthroplasty (HA) have been the surgical treatments of choice for displaced proximal humerus fractures (PHF) despite high rates of fixation failure and tuberosity nonunion, especially in the elderly population with poor bone quality. Recently, there has been a significant increase in the use of reverse total shoulder arthroplasty (RTSA) as a treatment option in both acute fractures, as well as a salvage procedure for fracture sequelae (i.e., malunion, nonunion, fixation failure, tuberosity non-union). Despite the growing enthusiasm it remains unknown whether functional outcomes after RTSA as a salvage procedure are similar to those following acute RTSA. As a result, the purpose of this systematic review was to compare functional outcomes after RTSA as a primary versus salvage procedure for displaced PHF in the elderly. A literature search of the electronic databases EMBASE, MEDLINE, and PubMed was conducted to identify all studies comparing RTSA as a primary treatment for displaced PHF and as a salvage procedure for failed initial management. Only studies with a minimum follow-up of two years were included. Data pertaining to range of motion, patient reported outcome measures and complications were extracted from eligible studies and entered into a meta-analysis software package (RevMan version 5.1, The Cochrane Collaboration) for pooled analysis. The Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of eligible studies. The search identified four studies consisting of 200 patients with a mean age of 73.3 years and a mean follow-up of 3.2 years. There were a total of 76 patients (75% female) who underwent acute RTSA following displaced PHF, while 124 patients (77% female) required salvage RTSA for failure of initial treatment. Primary RTSA was found to have significantly higher American Shoulder and Elbow (ASES) (P = 0.04), Constant (P = 0.01) and University of California at Los Angeles (UCLA) (P = 0.0004) scores compared to salvage RTSA. Forward flexion (P = 0.001) and external rotation (P< 0.0001) were significantly greater amongst those undergoing RTSA acutely versus as a salvage procedure. The odds of having a complication (e.g., infection, dislocation, fracture) were 76% lower amongst those who had primary RTSA compared to salvage RTSA (P = 0.02). The overall quality of eligible studies was moderate to high. Based on the current available evidence, elderly patients with displaced PHF have significantly greater range of motion, higher patient reported outcomes and lower risk of complications with primary RTSA compared to those undergoing RTSA as a salvage procedure. Additional prospective studies are warranted to confirm these findings

Introduction. Clinical decision support tools are software that match the input characteristics of an individual patient to an established knowledge base to create patient-specific assessments that support and better inform individualized healthcare decisions. Clinical decision support tools can facilitate better evidence-based care and offer the potential for improved treatment quality and selection, shared decision making, while also standardizing patient expectations. Methods. Predict+ is a novel, clinical decision support tool that leverages clinical data from the Exactech Equinoxe shoulder clinical outcomes database, which is composed of >11,000 shoulder arthroplasty patients using one specific implant type from more than 30 different clinical sites using standardized forms. Predict+ utilizes multiple coordinated and locked supervised machine learning algorithms to make patient-specific predictions of 7 outcome measures at multiple postoperative timepoints (from 3 months to 7 years after surgery) using as few as 19 preoperative inputs. Predict+ algorithms predictive accuracy for the 7 clinical outcome measures for each of aTSA and rTSA were quantified using the mean absolute error and the area under the receiver operating curve (AUROC). Results. Predict+ was released in November 2020 and is currently in limited launch in the US and select international markets. Predict+ utilizes an interactive graphical user interface to facilitate efficient entry of the preoperative inputs to generate personalized predictions of 7 clinical outcome measures achieved with aTSA and rTSA. Predict+ outputs a simple, patient-friendly graphical overview of preoperative status and a personalized 2-year outcome summary of aTSA and rTSA predictions for all 7 outcome measures to aid in the preoperative patient consultation process. Additionally, Predict+ outputs a detailed line-graph view of a patient's preoperative status and their personalized aTSA, rTSA, and aTSA vs. rTSA predicted outcomes for the 7 outcome measures at 6 postoperative timepoints. For each line-graph, the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) patient-satisfaction improvement thresholds are displayed to aid the surgeon in assessing improvement potential for aTSA and rTSA and also relative to an average age and gender matched patient. The initial clinical experience of Predict+ has been positive. Input of the preoperative patient data is efficient and generally completed in <5 minutes. However, continued workflow improvements are necessary to limit the occurrence of responder fatigue. The graphical user interface is intuitive and facilitated a rapid assessment of expected patient outcomes. We have not found the use of this tool to be disruptive of our clinic's workflow. Ultimately, this tool has positively shifted the preoperative consultation towards discussion of clinical outcomes data, and that has been helpful to guide a patient's understanding of what can be realistically achieved with shoulder arthroplasty. Discussion and Conclusions. Predict+ aims to improve a surgeon's ability to preoperatively counsel patients electing to undergo shoulder arthroplasty. We are hopeful this innovative tool will help align surgeon and patient expectations and ultimately improve patient satisfaction with this elective procedure. Future research is required, but our initial experience demonstrates the positive potential of this predictive tool

INTRODUCTION. Determining proper joint tension in reverse total shoulder arthroplasty (rTSA) can be a challenging task for shoulder surgeons. Often, this is a subjective metric learned by feel during fellowship training with no real quantitative measures of what proper tension encompasses. Tension too high can potentially lead to scapular stress fractures and limitation of range of motion (ROM), whereas tension too low may lead to instability. New technologies that detect joint load intraoperatively create the opportunity to observe rTSA joint reaction forces in a clinical setting for the first time. The purpose of this study was to observe the differences in rTSA loads in cases that utilized two different humeral liner sizes. METHODS. Ten different surgeons performed a total of 37 rTSA cases with the same implant system. During the procedure, each surgeon reconstructed the rTSA implants to his or her own preferred tension. A wireless load sensing humeral liner trial (VERASENSE for Equinoxe, OrthoSensor, Dania Beach, FL) was used in lieu of a traditional plastic humeral liner trial to provide real-time load data to the operating surgeon during the procedure. Two humeral liner trial sizes were offered in 38mm and 42mm curvatures and were selected each case based on surgeon preference. To ensure consistent measurements between surgeons, a standardized ROM assessment consisting of four dynamic maneuvers (maximum internal to external rotation at 0°, 45°, and 90° of abduction, and a maximum flexion/extension maneuver) and three static maneuvers (arm overhead, across the body, and behind the back) was completed in each case. Deidentified load data in lbf was collected and sorted based on which size liner was selected. Differences in means for minimum and maximum load values for the four dynamic maneuvers and differences in means for the three static maneuvers were calculated using 2-tailed unpaired t-tests. RESULTS. No significant differences were observed for the flexion/extension maneuver between the 38mm and 42mm liner sizes, but a significant difference was observed for every internal/external rotation assessment at 0°, 45°, and 90° of abduction. No significant differences were observed for the across the body and overhead maneuvers, but a significant difference was observed for the behind the back maneuver (p = 0.015). Standard deviations were pronounced across all maneuvers. CONCLUSION. This study observed significant differences in intraoperative load values in rTSA when comparing different humeral liner sizes. Limitations of this study include the small sample sizes and large standard deviations observed, as well as comparing across multiple patients and multiple surgeons. Area for future work includes comparing load values with postoperative functional results and complication risks for short, midterm, and long-term outcomes in efforts to find the optimal load range for a given patient

Surgeries for reverse total shoulder arthroplasty (RTSA) significantly increased in the last ten years. Initially developed to treat patients with cuff tear arthropathy (CTA) and pseudoparalysis, wider indications for RTSA were described, especially complex proximal humerus fractures. We previously demonstrated in patients with CTA a different sequence of muscular activation than in normal shoulder, with a decrease in deltoid activation, a significant increase of upper trapezius activation and slight utility of the latissimus dorsi. There is no biomechanical study describing the muscular activity in patients with RTSA for fractures. The aim of this work is to describe the in vivo action of RTSA in patients with complex fractures of the proximal humerus. We conducted an observational prospective cohort study comparing 9 patients with RTSA for complex humerus fracture (surgery more than 6 months, healed tuberosities and rehabilitation process achieved) and 10 controls with normal shoulder function. Assessment consisted in a synchronized analysis of range of motion (ROM) and muscular activity on electromyography (EMG) with the use of 7 bipolar cutaneous electrodes, 38 reflective markers and 8 motion-recording cameras. Electromyographic results were standardized and presented in muscular activity (RMS) adjusted with maximal isometric contractions according to the direction tested. Five basic movements were evaluated (flexion, abduction, neutral external rotation, external rotation in 90° of abduction and internal rotation in 90° of abduction). Student t-test were used for comparative descriptive analysis (p < 0,05). The overall range of motion with RTSA is very good, but lower than the control group: flexion 155.6 ± 10 vs 172.2 ± 13.9, p<0.05, external rotation at 90° 55.6 ± 25 vs 85.6 ± 8.8, p<0,05, internal rotation at 90° 37.8 ± 15.6 vs 52.2 ± 12, p<0,05. The three heads of the deltoid are more stressed during flexion and abduction in the RTSA group (p. The increased use of the 3 deltoid chiefs does not support the hypothesis proposed by Grammont when the RTSA is performed for a complex proximal humerus fracture. This can be explained by the reduced dispalcement of the rotation center of the shoulder in these patients compared to those with CTA. These patients also didn't present shoulder stiffness before the fracture. The maximal muscle activity of the trapezius in flexion and of the latissimus dorsi in flexion and abduction had not been described to date. These new findings will help develop better targeted rehabilitation programs. In addition, the significant role of the latissimus dorsi must question the risks of its transfer (L'Episcopo procedure) to compensate for external rotation deficits

Introduction. Machine learning is a relatively novel method to orthopaedics which can be used to evaluate complex associations and patterns in outcomes and healthcare data. The purpose of this study is to utilize 3 different supervised machine learning algorithms to evaluate outcomes from a multi-center international database of a single shoulder prosthesis to evaluate the accuracy of each model to predict post-operative outcomes of both aTSA and rTSA. Methods. Data from a multi-center international database consisting of 6485 patients who received primary total shoulder arthroplasty using a single shoulder prosthesis (Equinoxe, Exactech, Inc) were analyzed from 19,796 patient visits in this study. Specifically, demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures, post-operative PROMs and ROM measures, pre-operative and post-operative radiographic data, and also adverse event and complication data were obtained for 2367 primary aTSA patients from 8042 visits at an average follow-up of 22 months and 4118 primary rTSA from 11,754 visits at an average follow-up of 16 months were analyzed to create a predictive model using 3 different supervised machine learning techniques: 1) linear regression, 2) random forest, and 3) XGBoost. Each of these 3 different machine learning techniques evaluated the pre-operative parameters and created a predictive model which targeted the post-operative composite score, which was a 100 point score consisting of 50% post-operative composite outcome score (calculated from 33.3% ASES + 33.3% UCLA + 33.3% Constant) and 50% post-operative composite ROM score (calculated from S curves weighted by 70% active forward flexion + 15% internal rotation score + 15% active external rotation). 3 additional predictive models were created to control for the time required for patient improvement after surgery, to do this, each primary aTSA and primary rTSA cohort was subdivided to only include patient data follow-up visits >20 months after surgery, this yielded 1317 primary aTSA patients from 2962 visits at an average follow-up of 50 months and 1593 primary rTSA from 3144 visits at an average follow-up of 42 months. Each of these 6 predictive models were trained using a random selection of 80% of each cohort, then each model predicted the outcomes of the remaining 20% of the data based upon the demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures inputs of each 20% cohort. The error of all 6 predictive models was calculated from the root mean square error (RMSE) between the actual and predicted post-op composite score. The accuracy of each model was determined by subtracting the percent difference of each RMSE value from the average composite score associated with each cohort. Results. For all patient visits, the XGBoost decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. However for patients with 20+ month visits only, the random forest decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. The linear regression model was the least accurate predictive model for each of the cohorts analyzed. However, it should be noted that all 3 machine learning models provided accuracy of ∼85% or better and a RMSE <12. (Table 1) Figures 1 and 2 depict the typical spread and RMSE of the actual vs. predicted total composite score associated with the 3 models for aTSA (Figure 1) and rTSA (Figure 2). Discussion. The results of this study demonstrate that multiple different machine learning algorithms can be utilized to create models that predict outcomes with higher accuracy for both aTSA and rTSA, for numerous timepoints after surgery. Future research should test this model on different datasets and using different machine learning methods in order to reduce over- and under-fitting model errors. For any figures or tables, please contact the authors directly

INTRODUCTION. 3D preoperative planning software for anatomic and reverse total shoulder arthroplasty (ATSA and RTSA) provides additional insight for surgeons regarding implant selection and placement. Interestingly, the advent of such software has brought previously unconsidered questions to light on the optimal way to plan a case. In this study, a survey of shoulder specialists from the American Shoulder and Elbow Society (ASES) was conducted to examine thought patterns in current glenoid implant selection and placement. METHODS. 172 ASES members completed an 18-question survey on their thought process for how they select and place a glenoid implant for both ATSA and RTSA procedures. Data was collected using a custom online Survey Monkey survey. Surgeon answers were split into three cohorts based on their responses to usage of 3D preoperative planning software: high users, seldom users, and non-users. Data was analyzed for each cohort to examine differences in thought patterns, implant selection, and implant placement. RESULTS. 76 surgeons were grouped into the high user cohort, 66 into the seldom user cohort, and 30 into the non-user cohort. 61.9% of high users and 74.1% of seldom users performed >75 shoulder arthroplasties per year, whereas only 19.9% of non-users performed >75 arthroplasties per year (Figure 1). When questioned on glenoid implant type selection (augmented vs. non-augmented components), 80.3% of high users reported augment usage for both ATSA and RTSA, with using augments >45% of the time in 18.4% of ATSA cases and in 22.3% of RTSA cases. For seldom users, 80.3% reported augment usage in ATSA cases, and 70.3% in RTSA cases. Seldom users reported augment usage >45% of the time in 4.5% of ATSA cases and in 1.6% of RTSA cases. For non-preoperative planning users, 53.3% reported using augments in ATSA cases, and 48.3% for RTSA cases. Non-users used augmented glenoid components >45% of the time in 6.6% of ATSA cases and in 6.8% of RTSA cases. For resultant implant superior inclination in RTSA, 40.8% of high users aim for 0° of inclination, followed by 31.8% for seldom users and 16.7% of non-users (Figure 2). CONCLUSION. The results of this study show that 3D preoperative planning software has an influence on the decision making process when planning a shoulder arthroplasty. High volume shoulder arthroplasty surgeons report higher preoperative planning software usage than low volume surgeons, suggesting the utility of such software. Augmented glenoid component usage for both ATSA and RTSA is also higher for surgeons that use preoperative planning software, which either suggests the utility of augmented glenoid components, or that the use of such software creates the perceived need for augmented glenoid components. Lastly, surgeons who preoperatively plan tend to orient their glenoid components differently, which could suggest either a better understanding of the anatomy through the use of the software, or an influence on mindset regarding implant orientation resulting from software usage. This highlights an area for future work that could correlate clinical outcome data to implant selection and placement to prove what is the optimal plan for a given patient. For any figures or tables, please contact the authors directly

Glenoid baseplate positioning for reverse total shoulder replacements (rTSR) is key for stability and longevity. 3D planning and image-derived instrumentation (IDI) are techniques for improving implant placement accuracy. This is a single-blinded randomised controlled trial comparing 3D planning with IDI jigs versus 3D planning with conventional instrumentation. Eligible patients were enrolled and had 3D pre-operative planning. They were randomised to either IDI or conventional instrumentation; then underwent their rTSR. 6 weeks post operatively, a CT scan was performed and blinded assessors measured the accuracy of glenoid baseplate position relative to the pre-operative plan. 47 patients were included: 24 with IDI and 23 with conventional instrumentation. The IDI group were more likely to have a guidewire placement within 2mm of the preoperative plan in the superior/inferior plane when compared to the conventional group (p=0.01). The IDI group had a smaller degree of error when the native glenoid retroversion was >10° (p=0.047) when compared to the conventional group. All other parameters (inclination, anterior/posterior plane, glenoids with retroversion <10°) showed no significant difference between the two groups. Both IDI and conventional methods for rTSA placement are very accurate. However, IDI is more accurate for complex glenoid morphology and placement in the superior-inferior plane. Clinically, these two parameters are important and may prevent long term complications of scapular notching or glenoid baseplate loosening. Image-derived instrumentation (IDI) is significantly more accurate in glenoid component placement in the superior/inferior plane compared to conventional instrumentation when using 3D pre-operative planning. Additionally, in complex glenoid morphologies where the native retroversion is >10°, IDI has improved accuracy in glenoid placement compared to conventional instrumentation. IDI is an accurate method for glenoid guidewire and component placement in rTSA

To determine whether pre-operative cessation of anticoagulant or antiplatelet medication is necessary for patients undergoing total shoulder arthroplasty (TSA) or reverse total shoulder arthroplasty (RTSA). A prospectively maintained database was used to identify 213 consecutive patients treated with TSA or RTSA performed by a single surgeon across 3 centres. This cohort included 24 patients on an anticoagulant agent (warfarin, apixaban, rivaroxaban, dabigatran), 52 patients on an antiplatelet agent (aspirin, clopidogrel), and a control group of 137 patients not on anticoagulant or antiplatelet medication. Patients on anticoagulant or antiplatelet medications continued these agents peri-operatively. Outcomes included haemoglobin drop, intra-operative blood loss, operative time, transfusion requirements and post-operative complications. The mean age of the cohort was 74.3 years (range 47 – 93) and 75 (35.2%) of the patients were male. TSA was performed in 63 cases and RTSA in 150 cases. The mean haemoglobin drop in the control group was 17.3 g/L, compared to 19.3 g/L in the anticoagulant group (p = 0.20) and 15.6 g/L in the anti-platelet group (p = 0.14). The mean intra-operative blood loss in the control group was 107.8 mL, compared to 143.0 mL in the anticoagulant group (p = 0.03) and 134.3 mL in the anti-platelet group (0.02). The mean operative time in the control group was 49.3 minutes, compared to 47.1 minutes in the anticoagulant group (p = 0.56) and 50.3 minutes in the anti-platelet group (p = 0.78). Post-operatively no patients developed a wound infection or haematoma requiring intervention. Three patients not on anticoagulant or antiplatelet medication developed pulmonary embolism. Continuing anticoagulant or antiplatelet medication was associated with higher intra-operative blood loss, but produced no statistically significant differences in haemoglobin drop, operative time, transfusion requirements or post-operative complications. We now do not routinely stop any anticoagulant or antiplatelet medication for patients undergoing total shoulder arthroplasty