Can Dual Mobility Cups Reduce Revision and Dislocation Risks? An Analysis of 107,528 Primary Total Hip Arthroplasties in the United States.

BACKGROUND: Dual mobility acetabular cups (DMC) were designed to increase the effective femoral head size and improve stability with the goal of reducing revision risk at the potential cost of polyethylene thickness. We sought to evaluate revision risk following primary elective total hip arthroplasty with DMC compared to highly cross-linked polyethylene (XLPE). METHODS: A cohort study was conducted using data from a Kaiser Permanente's total joint arthroplasty registry. Patients ≥18 years who underwent primary elective total hip arthroplasty using DMC, unipolar Metal-on-XLPE (MoXLPE), or unipolar Ceramic-on-XLPE (CoXLPE) were identified (2010 to 2021). The final sample comprised 2,219 DMC, 48,251 MoXLPE, and 57,058 CoXLPE. Multiple Cox proportional hazard regressions were used to evaluate aseptic revision and any dislocation regardless of revision within 6 years follow-up. RESULTS: In adjusted analyses, no differences in aseptic revision risk were observed for MoXLPE (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 0.72 to 1.51) or CoXLPE (HR = 0.98, 95% CI = 0.69 to 1.40) compared to DMC. No differences in dislocation risk were observed for MoXLPE (HR = 1.42, 95% CI = 0.93 to 2.15) or CoXLPE (HR = 1.25, 95% CI = 0.84 to 1.87) compared to DMC. CONCLUSIONS: In a US-based cohort, 6-year aseptic revision risk of DMC was similar to metal or ceramic femoral head unipolar constructs. Furthermore, no difference in dislocation risk was observed. Continued longer-term follow-up may reveal if there is a reduced risk of dislocation that comes at the cost of increased late revision. LEVEL OF EVIDENCE: Level III.

Does Aseptic Revision Risk Differ for Primary Total Knee Arthroplasty Patients Who Have and Do not Have a Prior Primary or Revision Arthroplasty?

BACKGROUND: We sought to evaluate the risk of aseptic revision in total knee arthroplasty (TKA) patients who have and do not have a history of primary or revision arthroplasty of a different major joint. METHODS: We conducted a matched cohort study using data from Kaiser Permanente's arthroplasty registries. Patients who underwent primary unilateral TKA (index knee) were identified (2009-2018). Two matches based on exposure history were performed: (1) 33,714 TKAs with a history of primary arthroplasty of a different joint (contralateral knee, either hip, and/or either shoulder) were matched to 67,121 TKAs without an arthroplasty history and (2) 597 TKAs with a history of aseptic revision in a different joint were matched to 1,190 TKAs with a history of a prior arthroplasty in a different joint, but without any revision. After the matches were performed, Cox regressions were used to evaluate aseptic revision risk of the index knee using the no history groups as the reference in regression models. RESULTS: No difference in aseptic revision risk for the index knee was observed when comparing patients who had a prior primary arthroplasty in a different joint to those who did not have an arthroplasty history (hazard ratio = 0.95, 95% CI = 0.86-1.06). Those patients who did not have any prior aseptic revision history in a different joint had higher risk of aseptic revision in the index knee (hazard ratio = 2.06, 95% CI = 1.17-3.63). CONCLUSION: Patients who had a prior revision history had over a 2-fold higher risk of aseptic revision in the index knee, warranting close surveillance of these patients. LEVEL OF EVIDENCE: Level III.

Single Wedge Femoral Stem Designs are Associated With a Higher Risk for Revision After Cementless Primary Total Hip Arthroplasty.

BACKGROUND: Cementless total hip arthroplasty (THA) femoral stems are the most commonly selected prostheses in the United States. Optimal stem geometry remains controversial with excellent survivorship reported for many designs. We compared cause-specific stem revision of single-wedge versus double-wedge designs from a multicenter US cohort. METHODS: Data from an integrated healthcare network's total joint replacement registry were used to conduct a cohort study. Primary elective cementless THAs were identified (2001 to 2018). Implant exposure groups were classified by design geometry using the system proposed by Khanuja et al. Type 1 single-wedge (n = 11,082) and type 2 double-wedge (n = 32,380) designs were compared, and other design types were excluded; the final study cohort comprised 43,462 THAs. Cause-specific multivariable Cox regressions were used to evaluate risk for revision due to infection or aseptic reasons, including loosening, instability, periprosthetic fracture, or other reasons. RESULTS: After adjustment for covariates, a higher aseptic revision risk was observed for type 1 when compared to type 2 designs (hazard ratio = 1.91, 95% confidence interval = 1.33-2.75). When looking at specific revision reasons, revision for aseptic loosening (hazard ratio = 3.46, 95% confidence interval = 2.24-5.34) was higher for type 1 versus type 2 designs. No differences were found for septic revision, instability, periprosthetic fracture, or revisions for other reasons. CONCLUSIONS: Type 1 single-wedge designs were found to have a higher risk of revision due to aseptic loosening relative to type 2 double-wedge designs. Femoral stem geometry should be considered when selecting a cementless femoral implant. LEVEL OF EVIDENCE: Level III.

Temporal Trends in Deep Surgical Site Infections After Six Orthopaedic Procedures Over a 12-year Period Within a US-based Healthcare System.

INTRODUCTION: Centers of excellence and bundled payment models have driven perioperative optimization and surgical site infection (SSI) prevention with decolonization protocols and antibiotic prophylaxis strategies. We sought to evaluate time trends in the incidence of deep SSI and its causative organisms after six orthopaedic procedures in a US-based integrated healthcare system. METHODS: We conducted a population-level time-trend study using data from Kaiser Permanente's orthopaedic registries. All patients who underwent primary anterior cruciate ligament reconstruction (ACLR), total knee arthroplasty (TKA), elective total hip arthroplasty (THA), hip fracture repair, shoulder arthroplasty, and spine surgery were identified (2009 to 2020). The annual incidence of 90-day deep SSI was identified according to the National Healthcare Safety Network/Centers for Disease Control and Prevention guidelines with manual chart validation for identified infections. Poisson regression was used to evaluate annual trends in SSI incidence with surgical year as the exposure of interest. Annual trends in overall incidence and organism-specific incidence were considered. RESULTS: The final study sample was composed of 465,797 primary orthopaedic procedures. Over the 12-year study period, a decreasing trend in deep SSI was observed for ACLR and hip fracture repair. Although there was variation in incidence rates for specific operative years for TKA, elective THA, shoulder arthroplasty, and spine surgery, no consistent decreasing trends over time were found. Decreasing rates of Staphylococcus aureus infections over time after hip fracture repair, shoulder arthroplasty, and spine surgery and decreasing trends in antibiotic resistance after elective THA and spine surgery were also observed. Increasing trends of polymicrobial infections were observed after TKA and Cutibacterium acnes after elective THA. CONCLUSIONS: The overall incidence of deep SSI after six orthopaedic procedures was rare. Decreasing SSI rates were observed for ACLR and hip fracture repair within our US-based healthcare system. Polymicrobial infections after TKA and Cutibacterium acnes after elective THA warrant closer surveillance. LEVEL OF EVIDENCE: IV.

Safety and Efficacy of Lenabasum, a Cannabinoid Receptor Type 2 Agonist, in Patients with Dermatomyositis with Refractory Skin Disease: A Randomized Clinical Trial.

BACKGROUND: Treatment options are limited for skin disease in dermatomyositis. Lenabasum is a cannabinoid receptor type 2 agonist that triggers the resolution of inflammation. OBJECTIVE: The objective of this study was to evaluate the safety and efficacy of lenabasum in patients with refractory cutaneous dermatomyositis. DESIGN: This study was a single-center, double-blind, randomized, placebo-controlled phase 2 study conducted from July 2015 to August 2017. POPULATION: The population included subjects aged ≥18 years with at least moderately active dermatomyositis skin activity by Cutaneous Dermatomyositis Disease Area and Severity Index activity ≥ 14 and failure or intolerance to hydroxychloroquine. INTERVENTION: Participants received 20 mg lenabasum daily for 28 days and then 20 mg twice per day for 56 days or placebo. MAIN OUTCOMES AND MEASURES: The primary outcome was a change in Cutaneous Dermatomyositis Disease Area and Severity Index activity. Safety and other secondary efficacy assessments were performed till day 113. RESULTS: A total of 22 subjects were randomized to lenabasum (n = 11) or placebo (n = 11). No serious or severe adverse events were related to lenabasum, and no participants discontinued the study. The adjusted least-squares mean for Cutaneous Dermatomyositis Disease Area and Severity Index activity decreased more for lenabasum, and the difference was significant on day 113 (least-squares mean [standard error] difference = ‒6.5 [3.1], P = 0.038). Numerically greater improvements were seen in multiple secondary efficacy outcomes and biomarkers with lenabasum. CONCLUSION: Lenabasum treatment was well tolerated and was associated with greater improvement in Cutaneous Dermatomyositis Disease Area and Severity Index activity and multiple efficacy outcomes. TRIAL REGISTRATION: This study was registered at ClinicalTrials.gov, NCT02466243.

Association Between the Femoral Stem Design Type and the Risk of Aseptic Revision After Hemiarthroplasty.

INTRODUCTION: Although noncemented hemiarthroplasty has been associated with a higher risk of revision surgery as compared with cemented fixation, it remains uncertain whether this increased risk applies to all noncemented stem design types or only a subset. The purpose of this study was to assess the risk of aseptic revision associated with three common types of noncemented stem designs as compared with cemented fixation in the hemiarthroplasty treatment of femoral neck fractures in the elderly patients. METHODS: This was a retrospective cohort study of patients aged 60 years and older who sustained a hip fracture and underwent hemiarthroplasty between 2009 and 2018 at one of 35 hospitals owned by a large US health maintenance organization. Hemiarthroplasty fixation was categorized as cemented or noncemented, with the noncemented stems further classified as single wedge without collar, fit and fill without collar, or fit and fill with collar. The primary outcome was aseptic revision, and the median follow-up time was 4.8 years. RESULTS: Of 12,071 patients who underwent hemiarthroplasty during the study period (average age 82.0 ± 8.4 years, 67.9% women), 807 (6.7%) received a single-wedge stem without collar, 2,124 (17.6%) received a fit-and-fill stem without collar, 2,453 (20.3%) received a fit-and-fill stem with collar, and 6,687 (55.4%) received a cemented stem. Compared with cemented fixation, all the noncemented stem design types were associated with a markedly higher risk of aseptic revision in the multivariable analysis, including single wedge without collar (hazard ratio [HR] 2.00, 95% confidence interval [CI], 1.38 to 2.89, P < 0.001), fit and fill without collar (HR 1.52, 95% CI, 1.14 to 2.04, P = 0.005), and fit and fill with collar (HR 2.11, 95% CI, 1.63 to 2.72, P < 0.001). CONCLUSION: In the hemiarthroplasty treatment of elderly patients with hip fracture, all routinely used noncemented stem design types were associated with a higher risk of aseptic revision as compared with cemented fixation.

Cannabinoid type 2 receptor (CB2R) distribution in dermatomyositis skin and peripheral blood mononuclear cells (PBMCs) and in vivo effects of LenabasumTM.

BACKGROUND: Lenabasum is a cannabinoid type 2 receptor (CB2R) reverse agonist that demonstrates anti-inflammatory effects in vivo and in vitro in dermatomyositis (DM) and is currently being investigated for therapeutic potential. The purpose of our study is to investigate CB2R distribution as well as the effects of lenabasum in DM. METHODS: Immunohistochemistry staining (IHC) was utilized to examine immune cell and cytokine production changes in lesional DM skin biopsies from lenabasum and placebo-treated patients. CB2R expression in various immune cell populations within DM skin was investigated with image mass cytometry (IMC), whereas flow cytometry elucidated CB2R expression in DM peripheral blood mononuclear cells (PBMCs) as well as cytokine production by CB2R-expressing cell populations. RESULTS: After 12 weeks of lenabasum treatment, IHC staining showed that CD4+ T cells, CB2R, IL-31, IFN-γ, and IFN-ß cytokines were downregulated. IFN-γ and IFN-ß mRNA decreased in lesional DM skin but not in PBMCs. IMC findings revealed that CB2R was upregulated in DM lesional skin compared to HC skin and DM PBMCs (p<0.05). In DM skin, CB2R was upregulated on dendritic cells, B cells, T cells, and macrophages while dendritic cells had the greatest expression in both DM skin and PBMCs (p<0.05). These CB2R+ cells in the skin produce IL-31, IL-4, IFN-γ, and IFN-ß. CONCLUSION: Our findings of differential CB2R expression based on location and cell type suggest modes by which lenabasum may exert anti-inflammatory effects in DM and highlights dendritic cells as potential therapeutic targets.

Revision Risk in a Cohort of US Patients Younger Than 55 Undergoing Primary Elective Total Hip Arthroplasty.

BACKGROUND: As indications for elective total hip arthroplasty (THA) expand to younger patients, we sought to (1) compare revision risk following primary elective THA in patients <55 years at the time of their THA to patients aged ≥65 years and (2) identify specific risk factors for revision in patients <55 years. METHODS: A Kaiser Permanente's total joint replacement registry was used to conduct a cohort study including primary elective THA patients aged ≥18 (2001-2018). In total, 11,671 patients <55 years and 53,106 patients ≥65 years were included. Multiple Cox regression was used to evaluate cause-specific revision risk, including septic revision, aseptic loosening, instability, and periprosthetic fracture. Stepwise Cox regression was used to identify patient and surgical factors associated with cause-specific revision in patients <55 years. RESULTS: Patients <55 years had a higher risk of septic revision (hazard ratio [HR] = 1.30, 95% confidence interval [CI] = 1.02-1.66), aseptic loosening (HR = 2.60, 95% CI = 1.99-3.40), and instability (HR = 1.35, 95% CI = 1.09-1.68), but a lower risk of revision for periprosthetic fracture (HR = 0.36, 95% CI = 0.22-0.59) compared to patients aged ≥65 years. In the <55 age group, risk factors for septic revision included higher body mass index, drug abuse, and liver disease. Hypertension, anterior approach, and ceramic-on-ceramic were associated with aseptic loosening. White race, American Society of Anesthesiologists classification ≥3, smoker, paralysis, posterior approach, ceramic-on-ceramic, and smaller head diameter were associated with instability. CONCLUSION: Identified risk factors varied depending on the cause for revision. Although septic revisions were related to patient characteristics, more modifiable factors, such as implant or surgical approach, were associated with revision due to aseptic loosening and instability. LEVEL OF EVIDENCE: III.

The Role of Intraoperative Urinary Catheters on Postoperative Urinary Retention after Total Joint Arthroplasty: A Multi-Hospital Retrospective Study on 9,580 Patients.

BACKGROUND: Urinary catheters (UC) are used by some surgeons during total joint arthroplasty (TJA). This study investigated the impact of intraoperative urinary catheters on postoperative urinary retention (POUR) following TJA cases. METHODS: We conducted a retrospective comparative study across 11 medical centers on 9,580 TJA patients. Visits to urgent care or the emergency department within 7 and 30 postoperative days were reviewed. Medical records over a 12-month period for all patients older than 18 years old were used to gather demographic and surgical data as well as the incidence of urinary tract infection (UTI). Chi-squared tests (RStudio) were used to determine statistical significance against P-Values (P) < 0.05. RESULTS: 13 (0.14%) patients returned within 7 days for POUR. POUR was more common in males [10 (0.3%) vs. 3 (0.1%) females, (P = 0.01)]. There was no difference in POUR when comparing total hip and knee arthroplasty procedures [0.16% vs. 0.12%, (P = 0.60)]. Of all operations, 25% had intraoperative UC use. There was no difference in POUR between the UC and no UC groups [0.21 vs. 0.11%, (P = 0.26)]. However, there was an increase in UTI in UC vs. no UC use within 7 postoperative days [0.92 vs. 0.43%, (P = 0.005)] and 30 postoperative days [2.60 vs. 1.50 %, (P < 0.001)]. CONCLUSION: In our study, there was no difference in POUR rates between the intraoperative UC vs. no UC groups. Therefore, the use of intraoperative UC may not decrease the rate of POUR following TJA procedures. Additionally, UTI risk was higher in the UC group which may be attributable to other factors, especially when comparing female vs. male patients.

Association Between Same-Day Discharge Total Joint Arthroplasty and Risk of 90-Day Adverse Events in Patients with ASA Classification of ≥3.

BACKGROUND: Although safety in same-day discharge total joint arthroplasty (TJA) has been reported, findings are limited to healthier patients, specific surgeons, and/or specific institutions. Indications for same-day discharge TJA have expanded to include patients with multiple comorbidities; however, safety in this specific patient population remains unknown. Therefore, we sought to compare the risk of 90-day adverse events in higher-risk patients undergoing same-day discharge versus inpatient TJA. METHODS: The Kaiser Permanente Total Joint Replacement Registry was utilized to conduct a cohort study. All patients with an American Society of Anesthesiologists (ASA) classification of ≥3 who underwent primary elective TJA for osteoarthritis from 2017 through 2018 were identified. The risk of 90-day adverse events (i.e., emergency department visits, unplanned readmissions, complications, and mortality) was evaluated with use of propensity score-weighted Cox proportional hazard regression including noninferiority testing with a margin of 1.10. RESULTS: The cohort included a total of 5,250 patients who underwent total hip arthroplasty and 9,752 patients who underwent total knee arthroplasty, of whom 1,742 (33.2%) and 3,283 (33.7%) had same-day discharge, respectively. Same-day discharge hip arthroplasty was noninferior to an inpatient stay in terms of emergency department visits (hazard ratio [HR], 0.73; 1-sided HR 95% upper bound [UB], 0.84), readmissions (HR, 0.47; 95% UB, 0.61), and complications (HR, 0.63; 95% UB, 0.75); we did not have evidence of noninferiority for mortality (HR, 0.84; 95% UB, 1.97). Same-day discharge knee arthroplasty was noninferior to an inpatient stay in terms of emergency department visits (HR, 0.79; 95% UB, 0.87), readmission (HR, 0.80; 95% UB, 0.95), complications (HR, 0.72; 95% UB, 0.82), and mortality (HR, 0.53; 95% UB, 1.03). CONCLUSIONS: We found that same-day discharge TJA did not increase the risk of emergency department visits, unplanned readmissions, and complications compared with an inpatient stay for higher-risk patients, suggesting that it is possible to expand indications for same-day discharge TJA in the hospital setting while maintaining safety. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Frequency and Timing of Complications and Catastrophic Events After Same-Day Discharge Compared With Inpatient Total Hip Arthroplasty.

BACKGROUND: Same-day discharge total hip arthroplasty (THA) has grown in utilization although concerns exist regarding early complications and catastrophic events. We sought to compare the risk of complications and catastrophic events for same-day and inpatient stay THA. METHODS: A cohort study was conducted using Kaiser Permanente's total joint replacement registry. Primary elective THA were identified (2017-2018). Propensity score-weighted Cox proportional hazards regression was used to evaluate risk for 90-day incident events, including emergency department (ED) visit, unplanned readmission, cardiac complication, deep infection, venous thromboembolism (VTE), and mortality, by in-hospital length of stay: same-day vs 1-2-night inpatient stay. RESULTS: The study sample comprised 13,646 THA, 6033 (44.1%) with a same-day discharge. Median days-to-events for same-day vs inpatient was 11 vs 12 for ED visit, 23 vs 20 for readmission, 38 vs 12 for cardiac complication, 28 vs 24 for deep infection, 14.5 vs 23.5 for VTE, and 7 vs 35.5 for mortality. In propensity score-weighted models, same-day discharge THA had a lower risk for 90-day ED visit (HR = 0.82, 95% CI = 0.72-0.94), readmission (HR = 0.75, 95% CI = 0.61-0.92), and cardiac complication (HR = 0.60, 95% CI = 0.47-0.76), compared with inpatient stay THA; no difference was observed for deep infection (HR = 1.59, 95% CI = 0.81-3.12), VTE (HR = 0.90, 95% CI = 0.52-1.58), or mortality (HR = 0.81, 95% CI = 0.27-2.40). CONCLUSION: We observed a lower or no difference in risk for complications and catastrophic events after same-day THA than an inpatient stay. Catastrophic events were more likely to occur early in the 90-day period, but an inpatient stay did not preclude events.

Factors Influencing Patient Satisfaction With Care and Surgical Outcomes for Total Hip and Knee Replacement.

INTRODUCTION: Although patient satisfaction with total joint arthroplasty has been a well-measured outcome, little is known about how preadmission and post-discharge care experiences affect patients' rating of satisfaction. OBJECTIVE: This work aimed to identify actionable factors associated with better ratings of overall care and surgical results. METHODS: A 36-item survey assessing care in the preoperative, perioperative, and post-discharge phases of care and across all phases was mailed to 7,031 patients who underwent primary unilateral elective total hip arthroplasty and total knee arthroplasty in 2018. Exploratory factor analysis identified 7 actionable domains. Stepwise logistic regression models identified domains associated with ratings of overall care and satisfaction with surgical outcome. RESULTS: Of the 3,026 (43%) patients who returned the survey; 2,814 (93%) rated their overall experience of care as very good or excellent and satisfaction with surgical results as ≥ 7 on a 10-point scale. In exploratory factor analysis, four factors predicted higher ratings of both overall care and surgical outcome: knowing what to do with symptoms and pain during recovery (factor 1), self-reported health (factor 3), knowing what to expect before surgery (factor 4), and shared decision making (factor 6). Coordinated information among providers (factor 2), home health experience (factor 5), and patient-provider relationships (factor 7) also predicted overall care ratings. CONCLUSION: Patient-centered quality improvement in total joint replacement care requires thinking of care across the entire episode, including before and after the hospital stay for surgery, in addition to perioperative care. The actionable factors identified from this study can be incorporated into total joint replacement care to improve patients' satisfaction with overall care and surgical results.

Orthopaedic Systems Response to and Return from the COVID-19 Pandemic: Lessons for Future Crisis Management.

The coronavirus disease 2019 (COVID-19) pandemic has become the dominant health-care issue of this generation and has reached every corner of the health-care delivery spectrum. Our 3 orthopaedic departments enacted a response to the COVID-19 pandemic within our organizations. We discuss our health-care systems' response to the outbreak and offer discussion for the recovery of the orthopaedic service line within large health-care systems.

Lower-extremity total joint arthroplasty in shoulder arthroplasty patients: does the order of the lower-extremity total joint arthroplasty matter?

BACKGROUND: As total joint arthroplasty (TJA) utilization increases, arthroplasties of multiple joints in a patient are more common. An understanding of the success of shoulder arthroplasty patients also requiring a lower-extremity (hip or knee) TJA is lacking. We evaluated the following questions: (1) Is there a difference in the revision risk following shoulder arthroplasty in patients who also undergo a lower-extremity TJA compared with those who do not? (2) Does the revision risk differ depending on the sequence of the procedures? METHODS: Patients who underwent elective primary shoulder arthroplasty from 2009 through 2015 were identified using Kaiser Permanente's shoulder arthroplasty registry. Patients with a lower-extremity TJA were identified using the institution's total joint replacement registry. Revision related to the index shoulder was modeled via Cox regression stratified by procedure type and adjusted for confounders. RESULTS: Of the 4751 shoulder arthroplasties identified, 1285 (27.0%) underwent a prior hip and/or knee arthroplasty and 483 (10.2%) underwent a hip and/or knee arthroplasty following the index shoulder arthroplasty. No difference was found in all-cause shoulder revision risk with lower-extremity TJA before (hazard ratio, 1.38; 95% confidence interval, 0.97-1.96) or after (hazard ratio, 1.30; 95% confidence interval, 0.82-2.06) the index shoulder arthroplasty compared with patients who underwent a shoulder arthroplasty only. CONCLUSION: In our study sample, we did not observe shoulder revision surgery risk to be different in patients who also underwent a lower-extremity TJA, regardless of the sequence of the 2 procedures. Future prospective studies should investigate whether the timing of the lower-extremity TJA in relation to the shoulder procedure impacts the latter's success.

Histology and Biaxial Mechanical Behavior of Abdominal Aortic Aneurysm Tissue Samples.

Abdominal aortic aneurysms (AAAs) represent permanent, localized dilations of the abdominal aorta that can be life-threatening if progressing to rupture. Evaluation of risk of rupture depends on understanding the mechanical behavior of patient AAA walls. In this project, a series of patient AAA wall tissue samples have been evaluated through a combined anamnestic, mechanical, and histopathologic approach. Mechanical properties of the samples have been characterized using a novel, strain-controlled, planar biaxial testing protocol emulating the in vivo deformation of the aorta. Histologically, the tissue ultrastructure was highly disrupted. All samples showed pronounced mechanical stiffening with stretch and were notably anisotropic, with greater stiffness in the circumferential than the axial direction. However, there were significant intrapatient variations in wall stiffness and stress. In biaxial tests in which the longitudinal stretch was held constant at 1.1 as the circumferential stretch was extended to 1.1, the maximum average circumferential stress was 330 ± 70 kPa, while the maximum average axial stress was 190 ± 30 kPa. A constitutive model considering the wall as anisotropic with two preferred directions fit the measured data well. No statistically significant differences in tissue mechanical properties were found based on patient gender, age, maximum bulge diameter, height, weight, body mass index, or smoking history. Although a larger patient cohort is merited to confirm these conclusions, the project provides new insight into the relationships between patient natural history, histopathology, and mechanical behavior that may be useful in the development of accurate methods for rupture risk evaluation.