Acromial Stress Research Articles

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

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). 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 . 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. 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 ± 2mm, 10 ± 2mm, 2 ± 2mm, 30 ± 4mm, 16 ± 16%, respectively. On 2D CT, the corresponding mean values were 4.7 ± 2.5mm, 10.8 ± 2.65mm, 2.45 ± 2.35mm, 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. 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.

Reliable technique for acromion density assessment on CT.

Acromial stress fracture (ASF) is an uncommon but acknowledged complication of reverse total shoulder arthroplasty (RTSA). There is no standardised method to directly measure the bone mineral density of the acromion to allow a detailed analysis of the potential mechanism of ASF. The aim is to establish a reliable and reproducible technique for measurement of acromial density on computer tomography (CT). A retrospective review on CT scans obtained for three groups of patients: those planned for RTSA (n = 26); age and gender-matched non-operative (n = 26); and young non-operative patients (n = 28) were performed. Standardised axial images of 1 mm thickness at 1 mm increments were created following horizontal straightening on the coronal and sagittal views. To assess inter-rater reliability, two senior CT radiographers performed density measurements using standard region of interest (ROI) tool on the CTs with the ROI placed on the mid (ROI 1) and posterior (ROI 2) acromion. ROIs were selected as the most common locations for acromion fracture post RTSA. Measurements were repeated at least 6 weeks apart. Intra-class coefficients (ICC) were used to determine intra- and inter-rater reliability. ICCs demonstrated good to high intra-rater and inter-rater reliability for both ROI 1 and ROI 2 across all three groups. The lower margin of 95% confidence intervals was more than 0 for all intra-class coefficients. This study demonstrates a reliable method of measuring acromion density on CT. This method can be used to assess bone mineral density in the clinical setting and in future studies investigating ASF following RTSA.

High delta angle after reverse total shoulder arthroplasty increases stresses of the acromion: biomechanical study of different implant positions

BackgroundAcromial fractures after Reverse Total Shoulder Arthroplasty (RTSA) are a common complication. Nevertheless, only a few studies have identified risk factors for acromial fractures after RTSA. High delta angle (combination of inferiorization and medialization of the center of rotation) after RTSA was identified as a risk factor in recent studies. The aim of this study was the biomechanical exploration of different delta angles and implant configurations with regard to the acromial stress. MethodsIn a rigid body model of the upper extremity muscle, forces of the deltoid muscle were calculated before and after implanting RTSA in different arm and implant positions. The deltoid muscle was divided into an anterior, middle, and posterior part. Implant positions of the glenoid components were changed in the medialization, lateralization and inferiorization of the center of rotation (COR) as well as lateralization of the humeral component. Further, in a finite element model of the upper extremity, the stresses of the acromion in the same implant design configurations were measured. ResultsDifferences in acromial stress between different delta angle model configurations were observed. Lateralization (5 mm, 10 mm) of the glenosphere reduced maximal acromial stress by 21% (1.5 MPa) and 31% (1.3 MPa), respectively. Inferiorization (5 mm, 10 mm) of the glenosphere increased maximal acromial stress by 5% (2.0 MPa) and 15% (2.2MPa), respectively. Changes in positioning the humeral component was found to have the highest impact in this model configuration. A 10 mm lateralized humeral component reduced acromial stress by 37% (1.2 MPa) while in the 6 mm medialized configuration, an increase in acromial stress by 83% (3.48 MPa) was observed. There was a high correlation between delta angle and acromial stress (R-squared = 0.967). ConclusionImplant design configuration has an impact on the acromial stress. High delta angles correlate with an increase in acromial stress. Both lateralization of the COR and the humerus decreased the acromial stress in our study. The lateralization of the humerus has the highest impact in influencing acromial stress. Due to contrary results in the current literature, further studies with focus on the acromial stress influenced by different anatomical variants of the shoulder and the acromion are needed before a clinical recommendation can be made.

Implant-Positioning and Patient Factors Associated with Acromial and Scapular Spine Fractures After Reverse Shoulder Arthroplasty

Background: This study aimed to identify implant positioning parameters and patient factors contributing to acromial stress fractures (ASFs) and scapular spine stress fractures (SSFs) following reverse shoulder arthroplasty (RSA). Methods: In a multicenter retrospective study, the cases of patients who underwent RSA from June 2013 to May 2019 and had a minimum 3-month follow-up were reviewed. The study involved 24 surgeons, from 15 U.S. institutions, who were members of the American Shoulder and Elbow Surgeons (ASES). Study parameters were defined through the Delphi method, requiring 75% agreement among surgeons for consensus. Multivariable logistic regression identified factors linked to ASFs and SSFs. Radiographic data, including the lateralization shoulder angle (LSA), distalization shoulder angle (DSA), and lateral humeral offset (LHO), were collected in a 2:1 control-to-fracture ratio and analyzed to evaluate their association with ASFs/SSFs. Results: Among 6,320 patients, the overall stress fracture rate was 3.8% (180 ASFs [2.8%] and 59 SSFs [0.9%]). ASF risk factors included inflammatory arthritis (odds ratio [OR] = 2.29, p < 0.001), a massive rotator cuff tear (OR = 2.05, p = 0.010), osteoporosis (OR = 2.00, p < 0.001), prior shoulder surgery (OR = 1.82, p < 0.001), cuff tear arthropathy (OR = 1.76, p = 0.002), female sex (OR = 1.74, p = 0.003), older age (OR = 1.02, p = 0.018), and greater total glenoid lateral offset (OR = 1.06, p = 0.025). Revision surgery (versus primary surgery) was associated with a reduced ASF risk (OR = 0.38, p = 0.019). SSF risk factors included female sex (OR = 2.45, p = 0.009), rotator cuff disease (OR = 2.36, p = 0.003), osteoporosis (OR = 2.18, p = 0.009), and inflammatory arthritis (OR = 2.04, p = 0.024). Radiographic analysis of propensity score-matched patients showed that a greater increase in the LSA (ΔLSA) from preoperatively to postoperatively (OR = 1.42, p = 0.005) and a greater postoperative LSA (OR = 1.76, p = 0.009) increased stress fracture risk, while increased LHO (OR = 0.74, p = 0.031) reduced it. Distalization (ΔDSA and postoperative DSA) showed no significant association with stress fracture prevalence. Conclusions: Patient factors associated with poor bone density and rotator cuff deficiency appear to be the strongest predictors of ASFs and SSFs after RSA. Final implant positioning, to a lesser degree, may also affect ASF and SSF prevalence in at-risk patients, as increased humeral lateralization was found to be associated with lower fracture rates whereas excessive glenoid-sided and global lateralization were associated with higher fracture rates. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Does prior rotator cuff surgery influence the outcomes and complications after reverse total shoulder arthroplasty in patients with cuff tear arthropathy or massive rotator cuff tear? A propensity score-matched study

BackgroundThe aim of this study was to compare outcomes and complications in patients with and without a history of prior rotator cuff surgery who underwent reverse total shoulder arthroplasty (RTSA). MethodsTwo-hundred and nine consecutive patients who had undergone RTSA for rotator cuff insufficiency with a minimum 12-months follow-up period were reviewed. A total of 35 patients with a history of prior rotator cuff surgery were made the study group (PS group). Using propensity score matching for age and sex, these patients were matched 1:3 with a control group of 105 patients with no history of prior surgery (NPS group). The mean follow-up period was 41.4 months. ResultsBoth groups showed a significant improvement of clinical scores and range of motion after RTSA. The PS group showed a significantly higher final visual analog scale (VAS) pain score compared with the NPS group (P = 0.020). The PS group showed a significantly higher incidence of acromial stress fracture compared with the NPS group (17.1% vs 4.8%, P = 0.018), but no significant difference in the overall complication rate was observed (25.7% vs 13.3%, P > 0.05). The PS group showed a significantly higher reoperation rate compared with the NPS group (14.3% vs 1.9%, P = 0.004). ConclusionsOur study demonstrated that a history of prior rotator cuff surgery was associated with a high incidence of acromial stress fracture and reoperation after RTSA as well as a high final VAS pain score, although satisfactory clinical outcomes after RTSA were achieved in both groups.

Glenoid structural bone grafting in reverse total shoulder arthroplasty: clinical and radiographic outcomes

IntroductionCurrent options for reconstruction of large glenoid defects in reverse total shoulder arthroplasty (RTSA) include structural bone grafting, utilization of augmented components, or 3D printed custom implants. Given the paucity in the literature on structural bone grafts in RTSA, this study reflects our experience on clinical and radiographic outcomes of structural bone grafts utilized for glenoid defects in RTSA. MethodsWe identified 33 consecutive patients who underwent RTSA utilizing structural bone grafts for glenoid bone loss between 2008 and 2019. Twenty-six patients with mean clinical follow-up of 4.4 ± 3.9 years and mean radiographic follow-up of 2.7 ± 3.2 years were included. Patient demographic data, peri-operative functional outcomes, radiographic outcomes, complications, and re-operation rates were determined. ResultsBetween 2008 and 2019, 26 RTSAs were performed utilizing structural autograft or allograft for glenoid defects. There were 20 females (77%) and 6 males (23%), with mean presenting age of 68 years (range 41-86), mean BMI of 29 (range 21-44) and mean Charlson Comorbidity Index of 3 (range 0-8). There were 19 cases of central glenoid defects, and 7 were combined central and peripheral defects. Structural grafts included humeral head autograft (7), proximal humerus autograft (7), iliac crest autograft (7), distal clavicle autograft (2), and femoral head allograft (3). All eighteen revision RTSA cases had simultaneous humeral-sided revision. There was significant postoperative improvement in ASES scores (27.0 ± 12.6 preop vs. 59.8 ± 24.1 postop; p<0.001) and VAS scores (8.1 ± 3.6 preop vs. 3.0 ± 3.2 postop; p<0.001). Range of motion improved significantly for active forward elevation (63 ± 36º preop vs. 104 ± 36º postop; p<0.001) and external rotation (21 ± 20º preop vs. 32 ± 23º postop, p=0.036). Eighty-eight percent (23/26) of cases had successful reconstruction of the glenoid, defined as no visible radiolucent lines nor glenoid component migration at final follow-up. Re-operation rate was 19% (5/26) Postoperative complications included 2 cases of acromial stress fractures that were treated non-operatively, for a total complication rate (including re-operation) of 27% (7/26 cases). ConclusionsThe use of structural bone autografts and allografts in RTSA was associated with improved outcome scores and range of motion. A reoperation rate of 19% and total complication rate of 27% were reported for these challenging cases. However, 86% of these complications were not related to structural glenoid reconstruction failure. Structural grafts are a reasonable option for glenoid reconstruction in RTSA cases with glenoid bone loss.

Humeral Component Version Has No Effect on Outcomes Following Reverse Total Shoulder Arthroplasty: A Prospective, Double-Blinded, Randomized Controlled Trial.

Controversy exists regarding the ideal humeral component version to optimize humeral rotation and patient outcomes in reverse total shoulder arthroplasty (rTSA). Patients undergoing primary rTSA for rotator cuff tear arthropathy, a massive rotator cuff tear, or primary osteoarthritis with a rotator cuff tear were randomized to placement of the humeral component in neutral version or 30° of retroversion. Shoulder active range of motion and strength and visual analog scale (VAS) pain, American Shoulder and Elbow Surgeons (ASES), and Patient-Reported Outcomes Measurement Information System Global 10 (PROMIS-10) scores were collected up to 2 years postoperatively. The goal of the study was to determine whether humeral external rotation and internal rotation are affected by humeral component version following rTSA at 2 years postoperatively. Sixty-six patients were included in the analysis. The median follow-up was 26 months for the neutral and 27 months for the 30° retroversion group. No differences between the groups were observed with respect to the primary diagnosis, sex, age, body mass index, or American Society of Anesthesiologists (ASA) class. The 2 groups did not differ significantly in terms of improvement at 2 years in active shoulder abduction (p = 0.969), forward elevation (p = 1.000), internal rotation measured as the highest spinal level reached (p = 1.000), internal rotation with the arm abducted 90° (p = 0.451), external rotation (p = 0.362), or muscle strength in forward elevation (p = 1.000), abduction (p = 1.000), external rotation (p = 0.617), or internal rotation (p = 1.000). The 2 groups did not differ significantly in terms of improvement in postoperative ASES (p = 1.000), PROMIS-10 physical (p = 1.000), or VAS pain scores (p = 0.718) at the time of final follow-up. In the neutral version group, 1 patient underwent revision for instability and 1 for stiffness. One acromial stress fracture occurred in the 30° humeral retroversion group. Scapular notching was observed in 7 (21.2%) of the patients in neutral version group and 5 (15.2%) of the patients in the 30° retroversion group (p = 0.750). Securing the humeral component at neutral version or 30° of retroversion in rTSA resulted in similar active shoulder external rotation, internal rotation, forward elevation, abduction, and strength measurements, complication rates, and VAS pain, PROMIS-10 physical, and ASES scores at 2 years postoperatively. Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Reverse shoulder arthroplasty for patients with cuff tear arthropathy: do clinical outcomes differ by inlay vs. onlay design?

The influence of position of the humeral tray (inlay or onlay) on clinical outcomes in reverse shoulder arthroplasty (RSA) is a topic of debate. The purpose of this study was to compare clinical and radiographic outcomes of patients with cuff tear arthropathy treated with RSA systems with inlay or onlay humeral tray design, similar neck-shaft angles, and lateralized glenospheres. This was a retrospective study of prospectively obtained data from 1 tertiary care center. We identified all patients who underwent primary RSA between 2009 and 2017 (N=511). We included 102 patients with diagnosed cuff tear arthropathy treated with RSA prostheses with a lateralized glenosphere and 135° neck-shaft angle (with either an inlay or onlay humeral tray design) who had a minimum of 2 years of follow-up (mean, 44months; range, 24-125months). Sixty-three patients (62%) had an inlay humeral tray (inlay group) and 39 (38%) had an onlay tray (onlay group). All patients underwent preoperative and postoperative evaluations, including measures of patient-reported outcomes (PROs), shoulder range of motion (ROM) testing, and radiographic imaging. Clinical relevance of changes in PROs and ROM was evaluated using published values for minimal clinically important differences. The 2 groups did not differ by demographic characteristics except for a higher proportion of women in the inlay group (75%) than in the onlay group (56%) (P=.04). Preoperative PROs and ROM were not significantly different between groups. At final follow-up, PROs and ROM were not different between groups in terms of statistical significance or clinical relevance. We found no significant differences in the rate of baseplate loosening (inlay, 3.2% vs. onlay, 5.1%, P=.63), revision surgery (inlay, 0% vs. onlay 5.1%, P=.07), acromial stress fracture (inlay, 3.2% vs. onlay, 5.1%, P=.63), prosthesis dislocation (inlay, 0% vs. onlay, 2.6%, P=.20), or scapular notching (inlay, 21% vs. onlay, 7.7%, P=.08). At 2-year minimum follow-up, the position of the humeral tray in RSA prostheses (either inlay or onlay) for cuff tear arthropathy was not associated with PROs, shoulder ROM, or rates of complications, including baseplate loosening, acromial stress fracture, and scapular notching.

Early to short-term radiographic follow-up of metal-augmented baseplates in reverse shoulder arthroplasty for treatment of glenoid deformity in glenohumeral arthritis and rotator cuff arthropathy

Hypothesis and backgroundAs reverse total shoulder arthroplasty (rTSA) has evolved, the use of augmented glenoid baseplates has increased. While there are benefits of metal augmentation, literature concerning the mid- to long-term follow-up of these implants is emerging. The purpose of this study is to report early to short-term radiographic follow-up of patients with glenoid deformity treated with a metal-augmented glenoid baseplate. Our hypothesis is that we will see a low incidence of osteolysis, loosening, complications, and revision of these implants regardless of diagnosis, augment type, or patient demographics. MethodsWe performed a single-center retrospective review of all patients undergoing primary reverse shoulder arthroplasty with an augmented metallic baseplate for rotator cuff arthropathy and glenohumeral arthritis. Patients undergoing revision procedures or reverse arthroplasty for fractures were excluded. All patients had a minimum of 1-year radiographic follow-up. Preoperative imaging was reviewed to confirm the diagnosis and glenoid deformity classification. Postoperative radiographs were reviewed for evidence of complications, revisions, osteolysis, baseplate loosening, and failure. Clinical data were reviewed for complications. ResultsPrimary rTSA with a metal-augmented baseplate (38 full wedge and 22 half wedge augments) was performed on 60 patients who met inclusion criteria (mean age 74 ± 7). The average radiographic follow-up of all patients was 17 months. In our cohort, there was one patient with aseptic loosening of a full wedge implant that was not revised. There were no other complications, revision surgeries, baseplate failures, or acromial stress fractures. Six patients developed scapular notching, and five patients were found to have asymptomatic glenoid osteolysis. Two patients with full wedge implants developed aseptic humeral loosening. Pearson chi-square post hoc analysis found no correlation between augment type, gender, or glenoid deformity classification and radiographic changes such as glenoid or humeral osteolysis, loosening, or scapular notching. We did find a statistically significant correlation (P = .018) between patients with body mass index > 35 and glenoid osteolysis. Discussion and conclusionPrimary rTSA for patients with rotator cuff arthropathy or glenohumeral arthritis with glenoid deformity corrected with metal-augmented glenoid baseplates results in a low complication rate and an acceptable outcome at a minimum 1-year follow-up. Compared to other similar cohorts, our patients did not experience any acromial stress fractures, and only one patient had loosening of the glenoid component that was not ultimately revised. Further studies with longer follow-up will be needed, but early outcomes are promising and support the increase in the use of these implants.

Clinical and radiological outcomes with an augmented baseplate for superior glenoid wear in reverse shoulder arthroplasty.

This study aimed to assess the impact of using the metal-augmented glenoid baseplate (AGB) on improving clinical and radiological outcomes, as well as reducing complications, in patients with superior glenoid wear undergoing reverse shoulder arthroplasty (RSA). From January 2016 to June 2021, out of 235 patients who underwent primary RSA, 24 received a superior-AGB after off-axis reaming (Group A). Subsequently, we conducted propensity score matching in a 1:3 ratio, considering sex, age, follow-up duration, and glenoid wear (superior-inclination and retroversion), and selected 72 well-balanced matched patients who received a standard glenoid baseplate (STB) after eccentric reaming (Group B). Superior-inclination, retroversion, and lateral humeral offset (LHO) were measured to assess preoperative glenoid wear and postoperative correction, as well as to identify any complications. Clinical outcomes were measured at each outpatient visit before and after surgery. There were no significant differences in demographic data and preoperative characteristics between the two groups. Both groups showed significant improvements in patient-reported outcome measures (visual analogue scale for pain, visual analogue scale for function, American Shoulder and Elbow Surgeons, Constant, and Simple Shoulder Test scores) from preoperative to final assessment (p < 0.001). However, AGB showed no additional benefit. Notably, within range of motion, Group B showed significant postoperative decrease in both external rotation and internal rotation, unlike Group A (p = 0.028 and 0.003, respectively). Both groups demonstrated a significant correction of superior-inclination after surgery, while patients in Group B exhibited a significant decrease in LHO postoperatively (p = 0.001). Regarding complications, Group A experienced more acromial stress fractures (3 cases; 12.5%), whereas Group B had a higher occurrence of scapular notching (24 cases; 33.3%) (p = 0.008). Both eccentric reaming with STB and off-axis reaming with AGB are effective methods for addressing superior glenoid wear in RSA, leading to improved clinical outcomes. However, it is important to be aware of the potential risks associated with eccentric reaming, which include excessive bone loss leading to reduced rotation and scapular notching.

Does the stemless reverse arthroplasty compare to a conventional stemmed implant? Clinical and radiographic evaluation at 2 years’ minimum follow-up

AimReverse shoulder arthroplasty (RSA) is a well recognized treatment for many shoulder conditions, including rotator cuff arthropathy, primary glenohumeral joint arthritis, rheumatoid arthritis and can be utilized in both trauma and revision settings. Over the past 10 years its popularity in New Zealand has been increasing, with a 6-7% annual growth during this period. The proposed advantages of a stemless (sRSA) design are to preserve humeral bone stock, limit periprosthetic fractures and can be indicated in patients with abnormal diaphyseal humeral anatomy. To date there is only one study evaluating the outcomes of Lima stemless SMR implant. We present our data with an aim to report how the stemless reverse arthroplasty compares to a conventional stemmed implant. MethodsA retrospective review was performed of a consecutive series from a single institution between 2015 to 2020. Endpoints were defined as final follow-up at a minimum of 2 years. Patients were excluded from final analysis if they had a revision. Thirty-three patients were identified as having had sRSA. Thirty patients had PROMS and radiographs at minimum 2 years follow-up. Three patients were revised within 2 years. The same sample size (n=33) of stemmed RSA was selected for comparison ResultsA total of 60 patients were included in the final analysis, of which 30 were stemless and 30 stemmed. The demographic characteristics of the two groups were comparable except age at operation which was statistically significant (P=0.001), 77 years (stemmed) vs 65 years (stemless). The mean OSS score in the stemless group was 40.1 versus 40 in the stemmed group. The ASES was 72.9 in the stemless group and 79 in the stemmed group. The patient reported outcome measures, pain scores or satisfaction were not statistically significant between the two groups. In terms of radiographic data, subsidence of two sRSA was observed but the patients had no clinical symptoms. Also in the sRSA group one patient had an acromial stress fracture, and one patient had a superficial wound infection successfully treated with oral antibiotics. In terms of revisions in the sRSA group, one patient was revised due to chronic infection, one revised as a result of a periprosthetic fracture following a fall and one revised for gross instability. ConclusionsEarly results of sRSA are promising and show similar outcomes to a conventional stemmed implant.

Acromial bony adaptations in rotator cuff tear arthropathy facilitates acromial stress fracture following reverse total shoulder arthroplasty

BackgroundAcromial stress fractures (ASFs) after reverse total shoulder arthroplasty (RSA) can have a potentially devastating impact on shoulder function. They are often difficult to effectively treat. Multiple studies have shown a higher incidence of ASF after RSA in patients with cuff tear arthropathy (CTA). This study introduces and explores a new hypothesis. Our hypothesis is that 1) patients with CTA experience a preoperative pathologic superiorly directed force on their acromion, and 2) this leads to acromial bending moments on the acromion that are very different from patients with glenohumeral osteoarthritis (GHOA) and after RSA, and finally 3) these pathologic loads may result in abnormal bony remodeling and adaptations in CTA, which may then predispose patients to ASF after RSA. MethodsA finite element analysis model was developed to compare three loading conditions on the acromion: preoperative CTA, preoperative GHOA, and postoperative-RSA. Regions of the highest tensile and compressive stresses were identified and compared between groups. ResultsThe finite element analysis model presented shows that patients with a preoperative diagnosis of CTA experience a stress distribution reversal after RSA, whereas GHOA patients do not. The results support that in CTA, the humerus produces pathologic strains and torques on the acromion. Over time, the acromion may slowly remodel in response, resulting in bony adaptations. Abrupt reversal of stresses and strains in CTA after RSA may lead to ASFs, as the acromion has adapted to a different stress pattern. ConclusionThis study introduces one potential contributing factor for the higher rates of ASF after RSA in patients with a preoperative diagnosis of CTA; understanding this phenomenon is the first step to preventing it. Once the forces seen in CTA are abruptly reversed after RSA, the biological race is on between the formation of an acromial stress fracture and the body’s ability to again remodel the acromion to accommodate its new loading state. Additional clinical studies are needed to further investigate this new theory.

Increased Deltoid and Acromial Stress with Glenoid Lateralization and Onlay Humeral Stem Constructs in Reverse Shoulder Arthroplasty.

Reverse shoulder arthroplasty (RSA) designs include multiple options for glenoid component lateralization, and humeral component lateralization and distalization (inlay/onlay constructs). The influence of combined glenoid lateralization, and humeral distalization on acromial and deltoid stresses is not well understood. The purpose of this study was to evaluate changes in deltoid and acromial stresses with variations in glenoid lateralization, and with inlay versus onlay humeral components in RSA. Finite element analysis was performed using a RSA system with both inlay and onlay configurations. Variations in total glenoid lateralization from 3 to 9 mm were evaluated. Deltoid and acromial stresses were determined following virtual implantation and with 50° of external rotation. Increased glenoid lateralization resulted in greater stress of the deltoid and acromion. There was a modest increase in deltoid stress with glenoid lateralization alone (7% and 7.5% with progressive lateralization from 3 to 6 mm and 6 to 9 mm, respectively), but deltoid stress increased substantially with use of an onlay construct (60% at 9 mm of glenoid lateralization). Acromial stress correspondingly increased 37% with glenoid lateralization, and up to 117% with an onlay humeral construct. Increased lateralization of the glenoid component resulted in increased levels of deltoid and acromial stress. For a given amount of glenoid lateralization, utilization of an inlay stem decreased acromial and deltoid stresses compared to onlay constructs. These data allow surgeons to better understand the interactions of glenoid and humeral lateralization and distalization in the setting of contemporary RSA systems.Level of Evidence: Basic Science Study: Computer Modeling.

Two-year clinical outcomes and complication rates in anatomic and reverse shoulder arthroplasty implanted with Exactech GPS intraoperative navigation.

We compared the 2-year clinical outcomes of both anatomic and reverse total shoulder arthroplasty (ATSA and RTSA) using intraoperative navigation compared to traditional positioning techniques. We also examined the effect of glenoid implant retroversion on clinical outcomes. In both ATSA and RTSA, computer navigation would be associated with equal or better outcomes with fewer complications. Final glenoid version and degree of correction would not show outcome differences. A total of 216 ATSAs and 533 RTSAs were performed using preoperative planning and intraoperative navigation with a minimum of 2-year follow-up. Matched cohorts (2:1) for age, gender, and follow-up for cases without intraoperative navigation were compared using all standard shoulder arthroplasty clinical outcome metrics. Two subanalyses were performed on navigated cases comparing glenoids positioned greater or less than 10° of retroversion and glenoids corrected more or less than 15°. For ASTA, no statistical differences were found between the navigated and non-navigated cohorts for postoperative complications, glenoid implant loosening, or revision rate. No significant differences were seen in any of the ATSA outcome metrics besides higher internal and external rotation in the navigated cohort. For RTSA, the navigated cohort showed an ARR of 1.7% (95% CI 0%, 3.4%) for postoperative complications and 0.7% (95% CI 0.1%, 1.2%) for dislocations. No difference was found in the revision rate, glenoid implant loosening, acromial stress fracture rates, or scapular notching. Navigated RTSA patients demonstrated significant improvements over non-navigated patients in internal rotation, external rotation, maximum lifting weight, the Simple Shoulder Test (SST), Constant, and Shoulder Arthroplasty Smart (SAS) scores. For the navigated subcohorts, ATSA cases with a higher degree of final retroversion showed significant improvement in pain, Constant, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), SST, University of California-Los Angeles shoulder score (UCLA), and Shoulder Pain and Disability Index (SPADI) scores. No significant differences were found in the RTSA subcohort. Higher degrees of version correction showed improvement in external rotation, SST, and Constant scores for ATSA and forward elevation, internal rotation, pain, SST, Constant, ASES, UCLA, SPADI, and SAS scores for RTSA. The use of intraoperative navigation shoulder arthroplasty is safe, produces at least equally good outcomes at 2 years as standard instrumentation does without any increased risk of complications. The effect of final implant position above or below 10° of glenoid retroversion and correction more or less than 15° does not negatively impact outcomes.

Functional and radiographic outcomes of octogenarians undergoing primary reverse total shoulder arthroplasty: a retrospective study

BackgroundAs the demand for primary reverse total shoulder arthroplasty (RTSA) increases due to an aging population and expanding indications, it is crucial to understand the effects of the age on outcomes, particularly in patients 80 years or older. The purpose of this study was to determine postoperative patient-reported outcomes and evaluate postoperative imaging of octogenarian patients (≥80 year old) who underwent primary RTSA with a minimum 12-month follow-up. MethodsIn this retrospective case series, all consecutive patients aged 80 years or older who underwent primary RTSA at a tertiary health-care system were included from April 2012 to January 2022. Patient demographic and preoperative comorbidity data were collected, and the corresponding standard comorbidity indices were determined for each patient. Primary outcomes included postoperative patient-reported functional outcomes, while the secondary outcomes were adverse radiographic findings, mortality, and 90-day postoperative complications. Statistical analysis included descriptive analyses and a Wilcoxon Signed-Rank test for comparisons. A P < .05 was considered to be statistically significant. ResultsA total of 59 patients were included in the analysis, with a mean age of 84.21 ± 3.24 years and 39 (66.1%) female patients. All patient-reported outcome measures significantly improved postoperatively, including the Single Assessment Numeric Evaluation and American Shoulder and Elbow Surgeons scores, the Visual Analog Scale, and range of motion. The most common adverse radiographic outcome was scapular notching (27.1%), followed by acromial stress fractures (5.1%). Eight (13.6%) complications were observed, requiring four revision surgeries. ConclusionIn conclusion, RTSA leads to significant improvements in patient-reported outcomes with an acceptable rate of adverse radiographic outcomes in patients aged 80 years or older. Despite the potential for increased risk of adverse events in the elderly population, our study did not find an increase in complications within this age group when compared to rates previously reported in literature. Our findings suggest that RTSA is a safe and effective option in octogenarian patients.

Concomitant open distal clavicle excision is associated with greater improvement in range of motion without increased risk of acromial stress fracture after reverse total shoulder arthroplasty: a retrospective cohort study.

The purpose of this study was to evaluate the effect of concomitant open distal clavicle excision (DCE) on postoperative clinical outcomes and incidence of acromial and scapular stress fractures (ASFs) in patients with symptomatic acromioclavicular joint osteoarthritis (ACJ OA) undergoing reverse total shoulder arthroplasty (RTSA). A single-surgeon retrospective cohort study was conducted including patients who underwent primary elective RTSA with or without DCE from 2015 to 2019 with a minimum 6-month follow-up period. Shoulder active range of motion (AROM) and visual analog scale (VAS) pain were recorded preoperatively and postoperatively. ASFs and other adverse events were identified using postoperative notes and/or radiographs. Characteristics and outcomes were compared between the RTSA and RTSA-DCE groups. Forty-six RTSA patients (mean age, 67.9±8.7 years; 60.9% male; mean follow-up, 24.9±16.6 months) and 70 RTSA-DCE patients (mean age, 70.2±8.9 years; 20.0% male; mean follow-up, 22.7±12.9 months) were included. There were no significant intergroup differences in rates of ASF (RTSA, 0.0% vs. RTSA-DCE, 1.4%; P=1.00), stress reactions (RTSA, 8.7% vs. RTSA-DCE, 11.4%; P=0.76), reoperation, revision, or infection (all P>0.05), or in pre-to-postoperative reduction in VAS pain (P=0.17) at latest follow-up. However, the RTSA-DCE group had greater pre-to-postoperative improvement in flexion AROM (RTSA, 43.7°±38.5° vs. RTSA-DCE, 59.5°±33.4°; P=0.03) and internal rotation (IR) AROM (P=0.02) at latest follow-up. Concomitant DCE in RTSA improves shoulder flexion and IR AROM, alleviates shoulder pain, and does not increase the risk of ASFs. Level of evidence: III.

Incidence, risk factors, and complications of acromial stress fractures after reverse total shoulder arthroplasty

An acromial stress fracture (ASF) is an uncommon complication after reverse total shoulder arthroplasty (RTSA) that can have severe clinical consequences on shoulder function. Although patient-specific factors have been identified to influence the risk of ASFs, it is unclear whether modifying these factors can minimize risk. Moreover, there is limited information on the treatment outcomes of these fractures. Therefore, the purpose of this study was to determine modifiable risk factors of ASFs and the complication and revision rates of conservatively and operatively managed ASFs. The PearlDiver database was queried to identify a cohort of patients who underwent RTSA with minimum 2-year follow-up. Current Procedural Terminology (CPT) and International Classification of Diseases (ICD) codes were used to compare the demographics, comorbidities, and medication use of patients with and without ASFs. Surgical complication and revision rates were compared between operatively and conservatively treated fractures. The overall incidence of ASFs was 1.4%. Patient-specific factors that were independently associated with the occurrence of an ASF included osteoporosis, rheumatologic disease, shoulder corticosteroid injection within 3 months before surgery, and chronic oral corticosteroid use. Among patients with osteoporosis, the initiation of physical therapy within 6 weeks after surgery also increased the risk of ASF. Patients who underwent surgical treatment of ASFs had a revision arthroplasty rate of 7.0% compared to a rate of 3.2% among those with conservatively managed fractures. ASFs are an infrequent complication that can occur after RTSA. Preoperative factors that affect the quality of bone independently increase the fracture risk. Moreover, this risk can be minimized by avoiding shoulder corticosteroid injections 3 months before surgery and delaying physical therapy exercises among patients with osteoporosis. Surgical fixation of these fractures should be reserved to instances when conservative management has failed given high rates of infection, instability, and revision shoulder arthroplasty.

Lateralization and distalization shoulder angles do not predict outcomes in reverse shoulder arthroplasty for cuff tear arthropathy

In reverse shoulder arthroplasty (RSA), there is a plethora of measurements regarding implant lateralization and distalization to optimize the center of rotation. Two specific measurements known as the lateralization shoulder angle (LSA) and distalization shoulder angle (DSA) have been the recent focus of studies to assess their association with RSA and postoperative function. The aim of this study was to evaluate the prognostic clinical value of the LSA and DSA in a large cohort of patients with cuff tear arthropathy (CTA) who were treated with different RSA systems. Two local shoulder arthroplasty registries were reviewed for all RSA patients documented with a radiological assessment and complete 2-year follow-up examination. The main inclusion criterion was primary RSA for patients with CTA. Any patients with either a complete teres minor tear, os acromiale or acromial stress fractures reported between the time of surgery and the 24-month follow-up were excluded. Five different RSA implant systems with four different neck-shaft angles were assessed. The Constant Score (CS), Subjective Shoulder Value (SSV) and range of motion (ROM) at two years were correlated with both LSA and DSA assessed on 6-month anteroposterior radiographs. Linear and parabolic univariable regressions were calculated for both shoulder angles, for each prosthesis system and for the entire patient cohort. Between May 2006 and November 2019, there were a total of 630 CTA patients who had undergone primary RSA. Of this large cohort, 270 were treated with the Promos Reverse (neck-shaft angle [NSA], 155°), 44 with the Aequalis Reversed II (NSA, 155°), 62 with the Lima SMR Reverse (150°), 25 with the Aequalis Ascend Flex (145°) and 229 with the Univers Revers (135°) prosthesis systems. The mean (standard deviation [SD]) LSA was 78° (10; range, 6-107) and the mean DSA was 51° (10; range, 7-91). The average CS at 24 months follow-up was 68.1 (SD: 13; 13-96) points. Neither the linear nor parabolic regression calculations for LSA or DSA revealed significant associations with any of the clinical outcomes. Different patients may achieve different clinical outcomes despite having identical LSA and DSA values. There is no association between angular radiographic measurements and 2-year functional outcome.

Clinical and Radiological Outcomes in Lateralized versus Non-lateralized and Distalized Glenospheres in Reverse Total Shoulder Arthroplasty: A Randomized Control Trial.

Lateralization in reverse total shoulder arthroplasty (RTSA) has been used to theoretically offer the potential benefits of reduced scapular notching rates and improved stability and range of motion (ROM), particularly external rotation. The aim of this study was to compare ROM, clinical and radiographic outcomes between patients who underwent RTSA with a lateralized versus a non-lateralized and distalized glenosphere. A single surgeon randomized control trial was conducted comparing 27 patients with a lateralized glenosphere and 26 patients with a non-lateralized and distalized glenosphere. 66 patients were enrolled, two patients died prior to two-year follow-up, four patients withdrew from the study and seven patients were lost to follow-up. All patients in the lateralized group received 6 mm of lateralization through the glenosphere. Participants represented a population presenting to an orthopedics sports medicine clinic with any indication for RTSA including revision arthroplasty. Patients completed preoperative and routine postoperative functional outcome measures 3, 6, 12, and a minimum of 24 months postoperatively including American Shoulder and Elbow Surgeons (ASES), Patient-Reported Outcomes Measurement Information System Physical Function Upper Extremity (PROMIS PF UE) and Activities of Daily Living Requiring Active External and Internal Rotation (ADLEIR) assessments. Patients were also evaluated with ROM and radiographic measurements. The primary outcome of interest in this study was ROM, particularly external rotation. At two-year follow-up, both groups had significant improvement in their ASES, PROMIS PF UE and ADLEIR scores with no significant difference observed between groups. There were no statistically significant differences in incidence of scapular notching or acromial stress fractures. ROM in both groups improved significantly at their two-year assessment with the only exception to this being external rotation at 90° of abduction in the non-lateralized and distalized group (39° ± 31° versus 48° ± 24°, p=0.379). Regardless of glenosphere lateralization status, patients in both groups had significant improvement in functional outcome scores and ROM and there were no significant differences observed between groups at two-year follow-up. Longer follow-up is needed to determine the effect of implant design on late complications, long-term outcomes and implant retention.

Revision of total shoulder arthroplasty to hemiarthroplasty: results at mean 5-year follow-up.

Although there is a trend to manage failed anatomic total shoulder arthroplasties (aTSA) with revision to a reverse total shoulder arthroplasty, such revisions can be complicated by difficulties in baseplate fixation, instability, and acromial stress fractures. Some cases of failed aTSA may be safely revised to a hemiarthroplasty (HA). The objectives of this study were to report patient-reported outcomes after conversion from aTSA to HA and assess patient and shoulder characteristics associated with a successful outcome. Patients who underwent revision from aTSA to HA between 2009 and 2018 were contacted. Patient demographics, surgical history, intraoperative findings, and microbiology results were collected. Patient-reported outcomes were collected with minimum 2-year follow-up. Preoperative radiographic characteristics were reviewed for component positioning and component loosening. Patients with a clinically significant improvement exceeding the minimal clinically important difference (MCID) of the Simple Shoulder Test (SST) were compared with those patients who did not improve past the MCID. Twenty-nine patients underwent conversion from aTSA to HA with a mean follow-up of 4.5±1.8 years. Intraoperative glenoid or humeral component loosening was found in all 29 patients. Pain improved in 25 of 30 patients (87%), and mean pain scores improved from 6.2±2.3 to 3.1±2.4 (P<.001). SST scores improved from 4.1±3.1 to 7.3±3.2 (P<.001), and 18 of 29 patients (62%) had improvement above the SST MCID threshold of 2.4. The mean American Shoulder and Elbow Surgeons score at the latest follow-up was 64±19, and the Single Assessment Numeric Evaluation score was 65±23. Twenty-two of 29 (76%) patients were satisfied with the procedure. Four patients (14%) required conversion to total shoulder arthroplasty-2 to anatomic and 2 to reverse. An additional 3 patients (10%) had a revision HA performed. No significant differences in patient or shoulder characteristics were found in those patients who improved greater than the MCID of the SST compared patients who improved less than the MCID of the SST. Fifty-nine percent of patients had ≥2 positive cultures with the same bacteria, and 82% of these were with Cutibacterium. Seven of 8 patients (88%) with a loose humeral component had ≥2 positive cultures with the same bacteria. Component loosening is a common failure mode after aTSA. Revision to HA can improve pain and patient-reported outcomes in most patients.