Contributions of the Abductor Muscles to Rotational and Distractive Stability of the Hip in a Biomechanical Cadaveric Model.

Background: The gluteus minimus (GMin) and gluteus medius (GMed) are important dynamic stabilizers of the hip, but quantitative data on their biomechanical roles in stabilizing the hip are currently lacking. Purpose: To (1) establish a reproducible biomechanical cadaveric model of the hip abductor complex and (2) characterize the effects of loading the GMin and GMed on extraneous femoral rotation and distraction. Study Design: Controlled laboratory study. Methods: A total of 10 hemipelvises were tested in 4 muscle loading states: (1) unloaded, (2) the GMin loaded, (3) the GMed loaded, and (4) both the GMin and GMed loaded. Muscle loads were applied via cables, pulleys, and weights attached to the tendons to replicate the anatomic lines of action. Specimens were tested under internal rotation; external rotation; and axial traction forces at 0°, 15°, 30°, 60°, and 90° of hip flexion. Results: When loaded together, the GMin and GMed reduced internal rotation motion at all hip flexion angles (P < .05) except 60° and reduced external rotation motion at all hip flexion angles (P < .05) except 0°. Likewise, when both the GMin and GMed were loaded, femoral distraction was decreased at all angles of hip flexion (P < .05). Conclusion: The results of this study demonstrated that the GMin and GMed provide stability against rotational torques and distractive forces and that the amount of contribution depends on the degree of hip flexion. Clinical Relevance: Improved understanding of the roles of the GMin and GMed in preventing rotational and distractive instability of the hip will better guide treatment of hip pathologies and optimize nonoperative and operative therapies.

Public Perspectives on Decisions About Emergency Care Seeking for Care Unrelated to COVID-19 During the COVID-19 Pandemic.

Importance: Delaying critical care for treatable conditions owing to fear of contracting COVID-19 in the emergency department (ED) is associated with avoidable morbidity and mortality. Objective: To assess and quantify how people decided whether to present to the ED during the COVID-19 pandemic for care unrelated to COVID-19 using conjoint analysis, a form of trade-off analysis that examines how individuals make complex decisions. Design, Setting, and Participants: This cross-sectional survey study was conducted using a nationwide sample from June 1, 2020, during the initial peak of the COVID-19 pandemic. Included participants were adults aged 18 years or older in the US who self-reported that they had not tested positive for COVID-19. Data were analyzed from July 2020 through May 2021. Exposures: Participants completed a self-administered online survey. Main Outcomes and Measures: Using a choice-based conjoint analysis survey, the relative importance was assessed for the following attributes for individuals in deciding whether to seek ED care for symptoms consistent with myocardial infarction or appendicitis: reduction in chance of dying because of ED treatment, crowdedness of ED with other patients, and chance of contracting COVID-19 in the ED. We also performed latent class analyses using conjoint data to identify distinct segments of the respondent population with similar choice patterns. Logistic regression was then used to explore whether patient sociodemographics and political affiliations were factors associated with decision-making. Results: Among 1981 individuals invited to participate, 933 respondents (47.1%) completed the survey; participants' mean (SD) age was 40.1 (13.0) years, and 491 (52.6%) were women. In latent class analyses, 158 individuals (16.9%) with symptoms of myocardial infarction and 238 individuals (25.5%) with symptoms of appendicitis prioritized avoidance of COVID-19 exposure in the ED (ie, chance of contracting COVID-19 in the ED or crowdedness of ED with other patients) over seeking appropriate care for symptoms. Having a usual source of care was a factor associated with lower odds of prioritizing avoidance of COVID-19 exposure (myocardial infarction scenario: adjusted odds ratio, 0.49 [95% CI, 0.32-0.76]; P = .001; appendicitis scenario: adjusted odds ratio, 0.57 [95% CI, 0.40-0.82]; P = .003), but most sociodemographic factors and political affiliations were not factors associated with decision-making. Conclusions and Relevance: This study found that up to one-quarter of individuals were willing to forgo potentially life-saving ED care to avoid exposure to COVID-19. These findings suggest that health care systems and public health organizations should develop effective communications for patients and the community at large that reassure and encourage timely health care for critical needs during the ongoing COVID-19 pandemic and other scenarios.

Determining patient treatment preferences for management of acute pain episodes in irritable bowel syndrome.

BACKGROUND: Many patients with irritable bowel syndrome (IBS) experience acute and unexpected pain episodes over and above chronic background symptoms, and there are emerging medications designed to treat such pain. We aimed to use conjoint analysis-a technique that elucidates how people make complex decisions-to examine patient preferences for emerging medicines for breakthrough IBS pain. METHODS: We conducted a cross-sectional conjoint analysis survey among patients with Rome IV IBS and recurrent episodes of acute pain to assess the relative importance of medication attributes in their decision-making. We also assessed what respondents would require of subcutaneous (SQ) therapies to consider their use. KEY RESULTS: Among 629 patients with Rome IV IBS, 606 (96.3%) reported ≥1 acute pain episodes in the past month. For the 461 participants with multiple attacks who completed the conjoint analysis, they prioritized medication efficacy (importance score 34.9%), avoidance of nausea (24.3%), and avoidance of constipation (12.2%) as most important in their decision-making. These were followed by route of administration (10.3%), avoidance of headache (9.3%), and avoidance of drowsiness (8.9%). Moreover, 431 (93.5%) participants would consider SQ therapies for their acute pain; they had varying expectations on the minimum pain decrease and onset and duration of pain relief needed for considering their use. CONCLUSIONS AND INFERENCES: The vast majority of patients with IBS experience breakthrough pain, and when selecting among therapies, they prioritize efficacy and most are willing to use a rapid-acting SQ treatment. These results support development of novel, effective medications-oral or SQ-for management of acute pain attacks.

Neural crest-derived mesenchymal progenitor cells enhance cranial allograft integration.

Replacement of lost cranial bone (partly mesodermal and partly neural crest-derived) is challenging and includes the use of nonviable allografts. To revitalize allografts, bone marrow-derived mesenchymal stromal cells (mesoderm-derived BM-MSCs) have been used with limited success. We hypothesize that coating of allografts with induced neural crest cell-mesenchymal progenitor cells (iNCC-MPCs) improves implant-to-bone integration in mouse cranial defects. Human induced pluripotent stem cells were reprogramed from dermal fibroblasts, differentiated to iNCCs and then to iNCC-MPCs. BM-MSCs were used as reference. Cells were labeled with luciferase (Luc2) and characterized for MSC consensus markers expression, differentiation, and risk of cellular transformation. A calvarial defect was created in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice and allografts were implanted, with or without cell coating. Bioluminescence imaging (BLI), microcomputed tomography (µCT), histology, immunofluorescence, and biomechanical tests were performed. Characterization of iNCC-MPC-Luc2 vs BM-MSC-Luc2 showed no difference in MSC markers expression and differentiation in vitro. In vivo, BLI indicated survival of both cell types for at least 8 weeks. At week 8, µCT analysis showed enhanced structural parameters in the iNCC-MPC-Luc2 group and increased bone volume in the BM-MSC-Luc2 group compared to controls. Histology demonstrated improved integration of iNCC-MPC-Luc2 allografts compared to BM-MSC-Luc2 group and controls. Human osteocalcin and collagen type 1 were detected at the allograft-host interphase in cell-seeded groups. The iNCC-MPC-Luc2 group also demonstrated improved biomechanical properties compared to BM-MSC-Luc2 implants and cell-free controls. Our results show an improved integration of iNCC-MPC-Luc2-coated allografts compared to BM-MSC-Luc2 and controls, suggesting the use of iNCC-MPCs as potential cell source for cranial bone repair.

Comparative Analysis of Sagittal-Plane Radiographic Landmarks Used to Identify the Femoral Attachments of Lateral Knee Structures.

PURPOSE: To compare previously described radiographic parameters for the localization of the lateral knee (LK) structures, including the popliteal tendon (Pop), anterolateral ligament (ALL), and lateral collateral ligament (LCL), to determine which method best estimates the femoral attachment of each LK structure. METHODS: Twenty-nine human cadaveric knee specimens were carefully dissected to identify the LCL, ALL, and Pop. The femoral attachment for each structure was labeled with a radiopaque bead. LK radiographic images were obtained using fluoroscopy. Two radiographic approaches were used to identify each LK structure (Pop-A, Pop-B, LCL-A, LCL-B, ALL-A, and ALL-B) via previously published methods based on radiographic landmarks including the posterior femoral cortex and the Blumensaat line. The identification of radiographic landmarks was performed at 2 different time points by 2 different surgeons to determine the Pearson correlation between values, as well as interobserver and intraobserver reliability and reproducibility. The paired t test was conducted to compare the distance between the actual attachment site (as determined by the bead location) and the 2 radiographically identified estimations of attachment locations. RESULTS: For the LCL, the mean difference between the actual location and the estimated location via application of the LCL-B method (5.0 ± 2.4 mm) was significantly less than that estimated using the LCL-A method (8.2 ± 3.3 mm, P < .0001). Likewise, the Pop-B (5.7 ± 2.0 mm) and ALL-B (9.3 ± 4.5 mm) methods were shown to have smaller differences between the actual and estimated femoral attachment sites of the Pop insertion and ALL insertion, respectively (P < .0001). Methods for estimating the ALL femoral origin were the worst among the LK structures analyzed, with 90% of estimated values greater than 5 mm from the anatomic origin. Interobserver and intraobserver intraclass correlation coefficients were 0.785 or higher. CONCLUSIONS: Previously described radiographic methods for localization of the femoral attachment sites of the LK structures resulted in estimated locations that were significantly different from the locations of the radiographic beads placed at the anatomic femoral attachment sites of these structures. Therefore, radiographic methods used to localize the femoral attachments of the LK structures may not be reliable. CLINICAL RELEVANCE: This study shows the variability of the anatomy of the LK structures and the lack of reproducible radiographic criteria to identify these structures. As a result, there will be decreased reliance on radiographic landmarks to identify the placement of femoral grafts and fixation when reconstructing these structures.

Electrospun, synthetic bone void filler promotes human MSC function and BMP-2 mediated spinal fusion.

INTRODUCTION: Synthetic bone grafts are often used to achieve a well-consolidated fusion mass in spinal fusion procedures. These bone grafts function as scaffolds, and ideally support cell function and facilitate protein binding. OBJECTIVE: The aim was to characterize an electrospun, synthetic bone void filler (Reb) for its bone morphogenetic protein (BMP)-2 release properties and support of human mesenchymal stem cell (hMSC) function in vitro, and its efficacy in promoting BMP-2-/bone marrow aspirate-(BMA)-mediated posterolateral spinal fusion (PLF) in vivo. METHODS: BMP-2 release kinetics from Reb versus standard absorbable collagen sponge (ACS) was determined. hMSC adhesion and proliferation on Reb was tested using cell counting, fluorescence microscopy and MTS. Cell osteogenic differentiation was quantified via cellular alkaline phosphatase (ALP) activity. For in vivo analysis, 18 Lewis rats were treated during PLF surgery with the following groups: (I) Reb + BMA, (II) Reb + BMA + BMP-2 and (III) BMA. A safe, minimally effective dose of BMP-2 was used. Fusion consolidation was followed for 3 months using radiography and micro-CT. After sacrifice, fusion rate and biomechanical stiffness was determined using manual palpation, biomechanical tests and histology. RESULTS: In vitro, BMP-2 release kinetics were similar between Reb versus ACS. MSC proliferation and differentiation were increased in the presence of Reb. At 3 months post-surgery, fusion rates were 29% (group I), 100% (group II), and 0% (group III). Biomechanical stiffness was higher in group II versus I. Micro-CT showed an increased bone volume and connectivity density in group II. Trabecular thickness was increased in group I versus II. H&E staining showed newly formed bone in group II only. CONCLUSIONS: Reb possesses a high protein binding affinity and promotes hMSC function. Combination with BMA and minimal dose BMP-2 allowed for 100% bone fusion in vivo. This data suggests that a minimally effective dose of BMP-2 can be used when combined with Reb.

Knot of Henry Variation and the Effect on Plantar Flexion Strength.

BACKGROUND: The flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are commonly used for tendon transfer in reconstructive foot and ankle procedures. Some patients experience great toe weakness and loss of push-off strength. The objective of this biomechanical study was to quantify plantarflexion force after FHL and FDL harvest and correlate it to variations in tendon crossover patterns at the knot of Henry to determine if specific patterns have an increased tendency toward forefoot weakness. METHODS: Simulated loads through the Achilles, FHL, and FDL were applied to cadaveric specimens while plantarflexion force was measured using a pressure mapping system. Force was recorded with the FDL and FHL unloaded to simulate tendon transfer. Afterward, specimens were dissected to classify the tendinous slips between the FHL and FDL based on a previously determined system. Functional and anatomical relationships between the classification type and loading patterns were analyzed. RESULTS: There were no statistical differences between the tendon crossover patterns in forefoot force reduction after FHL or FDL harvest. Average decrease in great toe and total forefoot pressure after FHL harvest was 31% and 22%, respectively. Average decrease in lesser toe and total forefoot push-off force after FDL harvest was 23% and 9%, respectively. CONCLUSION: This study quantified loss of plantarflexion force after simulated FHL and FDL harvest and correlated these losses to variations in anatomic crossover patterns at the knot of Henry. Variations at the knot of Henry do not contribute to differences in forefoot weakness. CLINICAL RELEVANCE: The decrease in forefoot pressure seen here would help explain the clinical scenario where a patient does note a loss of great toe strength after FHL transfer.

Biomechanical Comparison of Achilles Tendon Pullout Strength Following Midline Tendon-Splitting and Endoscopic Approaches for Calcaneoplasty.

BACKGROUND: Calcaneoplasty is a common procedure performed for the management of Haglund's syndrome when nonoperative management fails. Midline tendon-splitting and endoscopy are 2 common approaches to calcaneoplasty. Studies have suggested that an endoscopic approach may allow earlier return to activity and superior outcomes, but there are no biomechanical or clinical studies to validate these claims. The goal of this study was to quantify and compare Achilles tendon pullout strength following midline tendon-splitting and endoscopic calcaneoplasty in cadaveric specimens. METHODS: Twelve match-paired cadaveric specimens were randomly divided into 2 groups: endoscopic and midline tendon-split. Following calcaneoplasty, fluoroscopy was used to match bone resection and the Achilles was loaded to failure in a mechanical testing system. A paired-samples t test was conducted to compare bone resection height, bone resection angle, load to failure, and mode of failure. RESULTS: The endoscopic approach yielded a 204% greater postsurgical pullout strength for the Achilles tendon than the midline tendon-split (1368 ± 370 N vs 450 ± 192 N, respectively) (P < .05). There were no differences in resection angle or resection height. All specimens failed due to bone or tendon avulsion. CONCLUSION: Endoscopic calcaneoplasty had more than 3 times greater pullout strength than the midline tendon-splitting approach. CLINICAL RELEVANCE: This may allow earlier return to functional rehabilitation following endoscopic calcaneoplasty, but further studies are needed to determine if these differences are clinically significant. Further understanding of the time-zero biomechanics following calcaneoplasty may provide guidance regarding postoperative management with respect to surgical approach.