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Objective: Air pollution is increasing and threatening human health. The objective of this study is to investigate the population distribution characteristics of elderly osteoporosis fractures in Hebei Province and Xinjiang Uygur Autonomous Region and to analyze the effects of air pollutants on the number of elderly osteoporosis fracture inpatients in the two regions., Method: A retrospective collection of elderly osteoporosis fracture cases was conducted in selected hospitals in Hebei Province and Xinjiang Uygur Autonomous Region from January 1, 2018 to December 31, 2022. The chi-square test was used to compare the distributional characteristics of the population in the two regions. Additionally, we used a distributed lag nonlinear model (DLNM) in order to assess the effect of air pollutants on the number of daily hospital admissions of elderly osteoporosis fracture patients in different regions., Result: A total of 19,203 elderly osteoporosis fracture patients were included in the study. The average age of these patients was 76.66 ± 7.55 years, and the majority of them were female (13,514 instances, 70.37%). The disparities in age distribution (χ 2  = 133.9 p < 0.001), fracture site (χ 2  = 62.0 p < 0.001), and hospitalization cost (Z = -15.635 p < 0.001) between the two regions were statistically significant. The lag effect curves of PM2.5, PM10, and NO 2 on the number of elderly osteoporosis fracture hospitalizations in Xinjiang Uygur Autonomous Region exhibited a similar pattern resembling a "W"-shaped curve. All three pollutants reached their highest values after a lag time of 14 days (PM2.5: RR = 1.053, 95% CI: 1.031, 1.074; PM10: RR = 1.031, 95% CI: 1.018, 1.043; NO 2 : RR = 1.125, 95% CI: 1.070, 1.182). In Hebei Province, the largest impacts of PM2.5 and PM10 were observed after a lag of 14 days (PM2.5: RR = 1.022, 95% CI: 1.013, 1.028; PM10: RR = 1.013, 95% CI: 1.008, 1.018). Similarly, the maximum effect of NO 2 was observed after a lag of 11 days (RR = 1.020, 95% CI: 1.010, 1.028)., Conclusion: There were differences in the epidemiological characteristics of hospitalized patients with osteoporosis fractures between the two regions, PM2.5, PM10, and NO 2 increased the number of hospitalizations for osteoporosis fractures. Exposure to air pollutants such as PM2.5 increases the risk of osteoporosis fractures in the elderly population., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Comminuted proximal humerus fractures are often repaired by metal plates, but potentially still experience bone refracture, bone "stress shielding," screw perforation, delayed healing, and so forth. This "proof of principle" investigation is the initial step towards the design of a new plate using alternative materials to address some of these problems. Finite element modeling was used to create design graphs for bone stress, plate stress, screw stress, and interfragmentary motion via three different fixations (no, 1, or 2 "kickstand" [KS] screws across the fracture) using a wide range of plate elastic moduli (E P  = 5-200 GPa). Well-known design optimization criteria were used that could minimize bone, plate, and screw failure (i.e., peak stress < ultimate tensile strength), reduce bone "stress shielding" (i.e., bone stress under the new plate ≥ bone stress for an intact humerus, titanium plate, and/or steel plate "control"), and encourage callus growth leading to early healing (i.e., 0.2 mm ≤ axial interfragmentary motion ≤ 1 mm; shear/axial interfragmentary motion ratio <1.6). The findings suggest that a potentially optimal configuration involves the new plate being manufactured from a material with an E P of 5-41.5 GPa with 1 KS screw; but, using no KS screws would cause immediate bone fracture and 2 KS screws would almost certainly lead to delayed healing. A prototype plate might be fabricated using alternative materials suggested for orthopedics and other industries, like fiber-metal laminates, fiber-reinforced polymers, metal foams, pure polymers, shape memory alloys, or 3D-printed porous metals., (© 2024 John Wiley & Sons Ltd.)

The formation of bacterial biofilms in the human body and on medical devices is a serious human health concern. Infections related to bacterial biofilms are often chronic and difficult to treat. Detailed information on biofilm formation and composition over time is essential for a fundamental understanding of the underlying mechanisms of biofilm formation and its response to anti-biofilm therapy. However, information on the chemical composition, structural components of biofilms, and molecular interactions regarding metabolism- and communication pathways within the biofilm, such as uptake of administered drugs or inter-bacteria communication, remains elusive. Imaging these molecules and their distribution in the biofilm increases insight into biofilm development, growth, and response to environmental factors or drugs. This systematic review provides an overview of molecular imaging techniques used for bacterial biofilm imaging. The techniques included mass spectrometry-based techniques, fluorescence-labelling techniques, spectroscopic techniques, nuclear magnetic resonance spectroscopy (NMR), micro-computed tomography (µCT), and several multimodal approaches. Many molecules were imaged, such as proteins, lipids, metabolites, and quorum-sensing (QS) molecules, which are crucial in intercellular communication pathways. Advantages and disadvantages of each technique, including multimodal approaches, to study molecular processes in bacterial biofilms are discussed, and recommendations on which technique best suits specific research aims are provided.

Micromotion exceeding 150μm at the implant-bone interface may prevent bone formation and limit fixation after cementless knee arthroplasty. Understanding the critical parameters impacting micromotion is required for optimal implant design and clinical performance. However, few studies have focused on UKA. This study assessed the impacts of alignment, surgical, and design factors on implant-bone micromotions for a novel cementless UKA design during a series of simulated daily activities. Three validated finite element knee models for predicting cementless micromotions were loaded with design-specific kinematics/loading to simulate gait, deep knee bending, and stair descent. The implant-bone micromotion and the porous surface area ideal for bone ingrowth were estimated and compared. Overall, the peak tray-bone micromotions were consistently found at the lateral aspect of the tibial baseplate and were consistently higher than the femoral micromotions. The femoral micromotion was insensitive to almost all the factors studied, and the porous area favorable for bone ingrowth was no less than 93%. For a medial uni, implanting the tray 1mm medially or the femoral component 1mm laterally reduced the tibial micromotion by 19.3% and 26.3% respectively. A 5 mm more posterior femoral translation increased the tibial micromotion by 35.8%. The presence of the tray keel prevented the spread of the micromotion and increased the overall porous surface area. In conclusion, centralizing the load transfer to minimize tibial tray applied moment and optimizing the fixation features to minimize micromotion are consistent themes for improving cementless fixation in UKA., (Copyright © 2024 by ASME; reuse license CC-BY 4.0.)

Background: Scoliosis is a deformation of the spine and trunk that, in its more severe forms, creates a life-long burden of disease and requires intensive treatment. For its most prevalent form, adolescent idiopathic scoliosis, no underlying condition can be defined, and the pathomechanism appears to be multifactorial; however, it has been suggested that the biomechanics of the spine play a role. For nonidiopathic scoliosis, underlying conditions can be recognized, but what drives the deformity remains unclear. In this study, we examined the early sagittal shape of the spine before the onset of scoliosis in a population with 22q11.2 deletion syndrome (22q11.2DS). This cohort was chosen since children with this syndrome have an approximately 50% chance of developing scoliosis that shares certain characteristics with idiopathic scoliosis, namely, age of onset, curve morphology, and rate of progression., Methods: This prospective cohort study included patients with 22q11.2DS who were followed with the use of spinal radiographs during adolescent growth. All of the children, who initially had no scoliosis while still skeletally immature (Risser stages 0 and 1), were followed at 2-year intervals until they reached skeletal maturity (Risser stages 3 to 5). We assessed the segment of the spine that has previously been shown to be rotationally unstable, the posteriorly inclined segment, to determine if it was predictive of later scoliosis development. For quantification, the area of the "posteriorly inclined triangle" (PIT), a previously described parameter that integrates both the inclination and length of the at-risk segment, was measured., Results: Of the 50 children who initially had no scoliosis (mean age at inclusion, 10.7 ± 1.7 years; mean follow-up, 4.8 ± 1.6 years), 24 (48%) developed scoliosis. Patients with an above-average PIT area (>60 cm2) at inclusion showed a relative risk of 2.55 for scoliosis development (95% confidence interval [CI]:1.22 to 5.34). PIT inclination was correlated with curve type: a taller and steeper hypotenuse predicted later thoracic scoliosis, while a shorter and less steep inclination predicted the development of (thoraco)lumbar scoliosis., Conclusions: This prospective study identified the pre-scoliotic sagittal shape of the spine as a risk factor for the later development of scoliosis in the population of children with 22q11.2DS., Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: No external funding was received for this work. The Article Processing Charge for open access publication was funded by Utrecht University. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/I235)., (Copyright © 2024 The Authors. Published by The Journal of Bone and Joint Surgery, Incorporated.)

Introduction: Adjunctive suture augmentation of patellar plate fixation has yet to be investigated. Our biomechanical study sought to evaluate whether suture augmentation improves dorsal patellar locking plate fixation. Our hypothesis was that suture augmentation would improve fixation of this construct., Methods: A transverse patella fracture in six matched cadaveric pairs was stabilized using a patellar locking plate with or without suture augmentation. Specimens were tested at 60° knee flexion with load placed through quadriceps. Cyclic loading followed by load to failure was done. Stiffness, deformation at peak, and nonrecoverable deformation were calculated., Results: During cyclic loading, suture augmentation demonstrated a higher average stiffness throughout all loads. At the final cycle, deformation was markedly higher without suture augmentation. Average load to failure was higher with suture augmentation. Maximum load to failure occurred at 2500 N in both groups., Conclusion: Suture augmentation in a transverse patellar fracture model improved dorsal plate fixation, leading to less fracture displacement at the final load. Although suture augmentation demonstrated higher stiffness and lower deformation, these trends were not statistically significant. In both groups, plate fixation sustained very high loads, which reflects the fixation strength of the dorsal locking plate and screw construct in this fracture model., (Copyright © 2024 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons.)

Prosthetic joint infection (PJI) is a major complication following total arthroplasty. Rising antimicrobial resistance (AMR) to antibiotics will further increase therapeutic insufficiency. New antibacterial technologies are being developed to prevent PJI. In vivo models are still needed to bridge the translational gap to clinical implementation. Though rabbit models have been used most frequently, there is no consensus about methodology and measured outcomes. The PubMed, Scopus, and EMBASE databases were searched for literature on PJI in rabbit models. Data extraction included bias control, experimental design, and outcome measures of the NZW rabbit models in the articles. A total of 60 articles were included in this systematic literature review. The articles were divided into six groups based on the PJI intervention: no intervention used (21%), revision surgery (14%), prevention with only antibiotics (21%), prevention with surface modifications (7%), prevention with coatings (23%), and others (14%). Despite the current availability of guidelines and recommendations regarding experimental design, bias control, and outcome measures, many articles neglect to report on these matters. Ultimately, this analysis aims to assist researchers in determining suitable clinically relevant methodologies and outcome measures for in vivo PJI models using NZW rabbits to test new antimicrobial technologies.

Background: Lack of insight into factors that determine purity and quality of human iPSC (hiPSC)-derived neo-cartilage precludes applications of this powerful technology toward regenerative solutions in the clinical setting. Here, we set out to generate methylome-wide landscapes of hiPSC-derived neo-cartilages from different tissues-of-origin and integrated transcriptome-wide data to identify dissimilarities in set points of methylation with associated transcription and the respective pathways in which these genes act., Methods: We applied in vitro chondrogenesis using hiPSCs generated from two different tissue sources: skin fibroblasts and articular cartilage. Upon differentiation toward chondrocytes, these are referred to as hFiCs and hCiC, respectively. Genome-wide DNA methylation and RNA sequencing datasets were generated of the hiPSC-derived neo-cartilages, and the epigenetically regulated transcriptome was compared to that of neo-cartilage deposited by human primary articular cartilage (hPAC)., Results: Methylome-wide landscapes of neo-cartilages of hiPSCs reprogrammed from two different somatic tissues were 85% similar to that of hPACs. By integration of transcriptome-wide data, differences in transcriptionally active CpGs between hCiC relative to hPAC were prioritized. Among the CpG-gene pairs lower expressed in hCiCs relative to hPACs, we identified genes such as MGP, GDF5, and CHAD enriched in closely related pathways and involved in cartilage development that likely mark phenotypic differences in chondrocyte states. Vice versa, among the CpG-gene pairs higher expressed, we identified genes such as KIF1A or NKX2-2 enriched in neurogenic pathways and likely reflecting off target differentiation., Conclusions: We did not find significant variation between the neo-cartilages derived from hiPSCs of different tissue sources, suggesting that application of a robust differentiation protocol such as we applied here is more important as compared to the epigenetic memory of the cells of origin. Results of our study could be further exploited to improve quality, purity, and maturity of hiPSC-derived neo-cartilage matrix, ultimately to realize introduction of sustainable, hiPSC-derived neo-cartilage implantation into clinical practice., (© 2024. The Author(s).)

Ferroptosis plays a crucial role in the progression of diabetic wounds, suggesting potential therapeutic strategies to target ferroptosis. Transient receptor potential ankyrin 1 (TRPA1) is a non-selective calcium channel that acts as a receptor for a variety of physical or chemical stimuli. Cinnamaldehyde (CA) is a specific TRPA1 agonist. In in vitro experiments, we observed that high glucose (HG) treatment induced endothelial cell ferroptosis, impairing cell function. CA successfully inhibited endothelial cell ferroptosis, improving migration, proliferation, and tube formation. Further mechanistic studies showed that CA-activated TRPA1-induced Ca 2+ influx promoted the phosphorylation of calmodulin-dependent protein kinase II (CaMKII) and nuclear factor-E 2-related factor 2 (Nrf2) translocation, which contributed to the elevation of glutathione peroxidase 4 (GPX4), leading to the inhibition of endothelial cell ferroptosis. In addition, CA was incorporated into an MMP-9-responsive injectable duplex hybrid hydrogel (CA@HA-Gel), allowing its efficient sustained release into diabetic wounds in an inflammation-responsive manner. The results showed that CA@HA-Gel inhibited wound endothelial cell ferroptosis and significantly promoted diabetic wound healing. In summary, the results presented in this study emphasize the potential therapeutic application of CA@HA-Gel in the treatment of diseases associated with ferroptosis., Competing Interests: Hankun Hu is currently employed by Hubei Micro-explore Innovative Pharmaceutical Research Co., Ltd and Suzhou Organ-on-a-Chip System Science and Technology Co., Ltd. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Introduction: Tendon injures rank as the second most common hand injuries, and unsatisfactory repair can significantly impact a patient's everyday life. Over the years, various suture techniques have been studied in the pursuit of finding the optimal repair method. The ideal tendon repair should achieve maximum strength, while being easy to perform and minimizing tissue trauma. This study aims to compare the mechanical properties of the cross-locked U-Tang 4-strand suture to its unmodified version, the U-Tang 4-strand suture, to assess which technique offers greater repair strength., Methods: Sixteen Achilles tendons from New Zealand White rabbits were randomly assigned to one of two suture technique groups; an original U-Tang 4-strand suture or a cross-locked U-Tang 4-strand suture, both performed using a 4-0 Supramid thread. The specimens were tested in uniaxial tension after a preconditioning phase. Cross-sectional area, load until failure, gap formation, stiffness, elastic modulus, and failure stress were determined., Results: The standard U-Tang 4-strand suture withstood a maximum force of 25.48 ± 6.06 N, while the cross-locked version endured 33.90 ± 6.09 N. This indicates that the modified version demonstrated significantly greater strength (p = 0.021). The elastic modulus of the cross-locked U-Tang 4-strand suture (0.02 ± 0.003 MPa) was significantly higher than that of the original version (0.01 ± 0.006 MPa) (p = 0.028). No significant differences were observed regarding the cross-sectional area, load at 2 mm gap formation, stiffness and failure stress., Conclusion: Employing the cross-locked U-Tang 4-strand suture results in a significantly greater maximum force and elastic modulus compared to the original U-Tang 4-strand suture, utilizing the same thread and number of strands and knots. Therefore, the cross-locking version provides an alternative for achieving more stable initial repair strength., Competing Interests: The cadaver specimen were tendons from two previous studies, each of which had already undergone ethical review. They were collected from dead New Zealand White rabbits at the end-point. The veterinary application numbers were: ZH 115/2015 and ZH 090/2021. This corresponding project was licensed by the Animal Ethics Committee at local authorities in Switzerland (Canton Zurich ZH). Therefore, no additional veterinary application was required. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Johanna Buschmann reports financial support was provided by 10.13039/501100009396University Hospital Zurich. Johanna Buschmann reports a relationship with University Hospital Zurich that includes: employment. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Background: Restoring medial knee pivot kinematics post-total knee arthroplasty is widely recognized to enhance patient satisfaction. Our study investigates the kinematics of patients who received posterior stabilized implants via robotic-arm assisted surgery, specifically analyzing effects of implant alignment and soft tissue balance on pivot location., Methods: Twelve high-functioning patients with unilateral posterior stabilizing knee implants underwent CT-guided robotic-arm assisted surgery. We then evaluated their knee kinematics using stereo radiography during gait, stair descent, lunge, seated knee extension and leg press. Femoral low-point condylar kinematics were used to calculate the transverse center of rotation, or pivot, using principal component analysis. Linear mixed effects regression was used to identify surgical parameters that influence pivot location across a flexion range., Findings: Across all five activities a central pivot pattern emerged as the primary pivot location (40 %) followed by medial (25 %), no pivot (22 %) and lateral (14 %). Tibial medial resection depth and Tibial implant flexion-extension placement were significantly associated with shifting the pivot location laterally prior to cam-post engagement. Femoral implant external-internal implant placement, and medial compartment laxity in extension were significantly associated with shifting the pivot location laterally during the cam-post engagement, while femoral distal-lateral resection depth was associated with a medial shift., Interpretation: Central and medial pivot locations are predominant in patients with posterior stabilized total knee arthroplasty, facilitated by robotic-arm assisted surgery. Despite significant associations between surgical parameters such as tibial medial resection depth and lateral compartment laxity with medial pivot, these variables explained a small portion of the variability in pivot location. This suggests that while surgical precision influences pivot kinematics, individual patient factors may play a more critical role, suggesting a need for further research into patient-specific biomechanics to optimize post-surgical outcomes., Competing Interests: Declaration of competing interest Sean Edward Higinbotham reports financial support was provided by Stryker Orthopaedics. Azhar Ali reports a relationship with Stryker Orthopaedics that includes: employment. Xiangyi (Cheryl) Liu reports a relationship with Stryker Orthopaedics that includes: employment. Clint B. Blackwood reports a relationship with Stryker Orthopaedics that includes: consulting or advisory. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Purpose: The purpose of this study is to report the parameter characteristics of the femoral anteversion angle (FAA) and tibial tubercle-trochlear groove (TT-TG) distance in patients with patellar instability compared to healthy individuals and to evaluate their reliability in predicting patellar dislocation, providing potential indications for osteotomy., Methods: A retrospective collection of consecutive patients with patellar instability constituted the study group, while individuals without patellofemoral disorder served as the control group. Measurement of the FAA and TT-TG distance were conducted by lower extremity computed tomography scans and knees with true patellar dislocation were recorded. The diagnostic capability of the FAA and TT-TG distance was assessed using receiver operating characteristic curves and area under the curve (AUC), determining the pathological values by sensitivity and specificity., Results: The FAA (21.6 ± 9.0°) and TT-TG distance (20.1 ± 4.8 mm) in the study group were significantly greater than the control group (10.6 ± 7.9° and 15.6 ± 4.6 mm, respectively) (p < 0.001). The AUCs for patellar dislocation were 0.869 for FAA and 0.712 for TT-TG distance, with pathological cut-off values of 18.2° and 18.2 mm, respectively. The odds ratios for FAA and TT-TG distance were 1.185 and 1.125, respectively (p < 0.05)., Conclusions: Patients with patellar instability exhibited significantly greater FAA and TT-TG distance compared to healthy individuals. The FAA demonstrated superior predictive capability for patellar dislocation compared to the TT-TG distance. The FAA (>18.2°) measured by surgical transepicondylar axis and TT-TG distance (>18.2 mm) were the potential pathological thresholds. Additionally, an increase of 1° in FAA and 1 mm in TT-TG distance was associated with a 18.5% and 12.5% increased risk of patellar dislocation, respectively. Surgeons should be aware of the risk of patellar dislocation associated with rotational malalignment., Level of Evidence: Level III., (© 2024 European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Background: There is a lack of procedures that adequately address the subchondral bone structure and function for reconstructing osteochondral defects in the femoral condyles., Purpose: To biomechanically evaluate the tibiofemoral joint contact characteristics before and after reconstruction of femoral condylar osteochondral defects using a novel hybrid reconstructive procedure, which was hypothesized to restore the contact characteristics to the intact condition., Study Design: Controlled laboratory study., Methods: Tibiofemoral contact areas, contact forces, and mean contact pressures were measured in 8 cadaveric knees (mean age 52 ± 11 years; 6 women, 2 men) using a custom testing system and pressure mapping sensors. Five conditions were tested for each condyle: intact, 8-mm defect, 8-mm repair, 10-mm defect, and 10-mm repair. Medial femoral condylar defects were evaluated at 30° of knee flexion and lateral condylar defects were evaluated at 60° of knee flexion, with compressive loads of 50, 100, and 150 N. The defects were reconstructed with a titanium fenestrated threaded implant countersunk in the subchondral bone and an acellular dermal matrix allograft. Repeated-measures analysis of variance with Bonferroni correction for multiple comparisons was used to compare the results between the 5 testing conditions at each load., Results: Medial condylar defects significantly increased mean contact pressure on the lateral side ( P < .042), which was restored to the intact levels with repair. The lateral condylar defect decreased the mean contact pressure laterally while increasing the mean pressure medially. The lateral and medial mean contact pressures were restored to intact levels with the 8-mm lateral condylar defect repair. The medial mean contact pressure was restored to intact levels with the 10-mm lateral condylar defect repair. The lateral mean contact pressure decreased compared with the intact state with the lateral condylar 10-mm defect repair., Conclusion: Tibiofemoral joint contact pressure was restored to the intact condition after reconstruction of osteochondral defects with dermal allograft matrix and subchondral implants for the repair of both 8- and 10-mm lateral condylar defects as well as 8-mm medial condylar defects but not completely for 10-mm medial condylar defects., Clinical Relevance: The novel hybrid procedure for osteochondral defect repair restored tibiofemoral joint contact characteristics to normal in a cadaveric model., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was partially supported by Subchondral Solutions, which also provided the implants and graft material used. D.T.D. has received hospitality payments from Globus Medical, has patents related to the study content, and has stock/stock options in Subchondral Solutions. M.H.M. has stock/stock options in Subchondral Solutions. T.Q.L. has stock/stock options in Subchondral Solutions. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2024.)

Bone fracture plates are usually made from titanium alloy or stainless steel, which are much stiffer than bone. However, overly stiff plates can restrict axial interfragmentary motion at the fracture leading to delayed callus formation and healing, as well as causing bone "stress shielding" under the plate leading to bone atrophy, bone resorption, and plate loosening. Consequently, there have been many prior efforts to develop nonmetallic bone fracture plates with customized material properties using synthetic fibers (e.g., aramid, carbon, glass) in polymer resin. Even so, plant fibers (e.g., flax, roselle, sisal) offer additional advantages over synthetic fibers, such as availability, biodegradability, less toxicity during processing, lower financial cost, and recyclability. As such, there is an emerging interest in using plant fibers alone, or combined with synthetic fibers, to reinforce polymers for various applications. Thus, this is the first review article on the material properties and engineering performance of innovative bone fracture plates made from composite materials reinforced by plant fibers alone or supplemented using synthetic fibers. This article presents material-level fiber properties (e.g., elastic modulus, ultimate strength), material-level plate properties (e.g., fatigue strength, impact toughness), and bone-plate engineering performance (e.g., overall stiffness, plate stress), as well as discussing general findings, study quality, and future work. This article may help engineers and surgeons to design, fabricate, analyze, and utilize novel bone fracture plates.

Purpose: Dural tear (DT) is a well-known complication of spinal surgery. We aimed to systematically review the literature from the past decade and determine the incidence and risk factors for DT in the adult spinal deformity (ASD) population to improve both the surgical strategy and counseling of patients undergoing ASD correction., Methods: A systematic review from 2013 to 2023 utilizing PRISMA guidelines was performed. The MEDLINE database was used to collect primary English language articles. The inclusion criterion for patients was degenerative ASD. Pediatric studies, animal studies, review articles, case reports, studies investigating minimally invasive surgery (MIS), studies lacking data on DT incidence, and articles pertaining to infectious, metastatic or neoplastic, traumatic, or posttraumatic etiologies of ASD were excluded., Results: Our results demonstrate that the incidence of DT in ASD surgery ranges from 2.0% to 35.7%, which is a much broader range than the reported incidence for non deformity surgery. Moreover, the average rate of DT during ASD surgery stratified by surgical technique was greater for osteotomy overall (19.5% +/- 7.9%), especially for 3-column osteotomy (3CO), and lower for interbody fusion (14.3% +/- 9.9%). Risk factors for DT in the ASD surgery cohort included older age, revision surgery, chronic severe compression, higher-grade osteotomy, complexity of surgery, rheumatoid arthritis (RA), and higher Anesthesiology Society of America (ASA) grade., Conclusion: To our knowledge, this is the first systematic review discussing the incidence of and risk factors for DT in the ASD population. We found that the risk factors for DT in ASD patients were older age, revision surgery, chronic severe compression, a greater degree of osteotomy, complexity of surgery, RA, and a higher ASA grade. These findings will help guide spine surgeons in patient counseling as well as surgical planning., (© 2024. The Author(s), under exclusive licence to Scoliosis Research Society.)

Currently available focal knee resurfacing implants (FKRIs) are fully or partially composed of metals, which show a large disparity in elastic modulus relative to bone and cartilage tissue. Although titanium is known for its excellent osseointegration, the application in FKRIs can lead to potential stress-shielding and metal implants can cause degeneration of the opposing articulating cartilage due to the high resulting contact stresses. Furthermore, metal implants do not allow for follow-up using magnetic resonance imaging (MRI).To overcome the drawbacks of using metal based FKRIs, a biomimetic and MRI compatible bi-layered non-resorbable thermoplastic polycarbonate-urethane (PCU)-based FKRI was developed. The objective of this preclinical study was to evaluate the mechanical properties, biocompatibility and osteoconduction of a novel Bionate® 75D - zirconium oxide (B75D-ZrO 2 ) composite material in vitro and the osseointegration of a B75D-ZrO 2 composite stem PCU implant in a caprine animal model. The tensile strength and elastic modulus of the B75D-ZrO 2 composite were characterized through in vitro mechanical tests under ambient and physiological conditions. In vitro biocompatibility and osteoconductivity were evaluated by exposing human mesenchymal stem cells to the B75D-ZrO 2 composite and culturing the cells under osteogenic conditions. Cell activity and mineralization were assessed and compared to Bionate® 75D (B75D) and titanium disks. The in vivo osseointegration of implants containing a B75D-ZrO 2 stem was compared to implants with a B75D stem and titanium stem in a caprine large animal model. After a follow-up of 6 months, bone histomorphometry was performed to assess the bone-to-implant contact area (BIC). Mechanical testing showed that the B75D-ZrO 2 composite material possesses an elastic modulus in the range of the elastic modulus reported for trabecular bone. The B75D-ZrO 2 composite material facilitated cell mediated mineralization to a comparable extent as titanium. A significantly higher bone-to-implant contact (BIC) score was observed in the B75D-ZrO 2 implants compared to the B75D implants. The BIC of B75D-ZrO 2 implants was not significantly different compared to titanium implants. A biocompatible B75D-ZrO 2 composite approximating the elastic modulus of trabecular bone was developed by compounding B75D with zirconium oxide. In vivo evaluation showed an significant increase of osseointegration for B75D-ZrO 2 composite stem implants compared to B75D polymer stem PCU implants. The osseointegration of B75D-ZrO 2 composite stem PCU implants was not significantly different in comparison to analogous titanium stem metal implants., (© 2024 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Objective: To determine the reliability and agreement of manual and automated morphological measurements, and agreement in morphological diagnoses., Methods: Thirty pelvic radiographs were randomly selected from the World COACH consortium. Manual and automated measurements of acetabular depth-width ratio (ADR), modified acetabular index (mAI), alpha angle (AA), Wiberg center edge angle (WCEA), lateral center edge angle (LCEA), extrusion index (EI), neck-shaft angle (NSA), and triangular index ratio (TIR) were performed. Bland-Altman plots and intraclass correlation coefficients (ICCs) were used to test reliability. Agreement in diagnosing acetabular dysplasia, pincer and cam morphology by manual and automated measurements was assessed using percentage agreement. Visualizations of all measurements were scored by a radiologist., Results: The Bland-Altman plots showed no to small mean differences between automated and manual measurements for all measurements except for ADR. Intraobserver ICCs of manual measurements ranged from 0.26 (95%-CI 0-0.57) for TIR to 0.95 (95%-CI 0.87-0.98) for LCEA. Interobserver ICCs of manual measurements ranged from 0.43 (95%-CI 0.10-0.68) for AA to 0.95 (95%-CI 0.86-0.98) for LCEA. Intermethod ICCs ranged from 0.46 (95%-CI 0.12-0.70) for AA to 0.89 (95%-CI 0.78-0.94) for LCEA. Radiographic diagnostic agreement ranged from 47% to 100% for the manual observers and 63%-96% for the automated method as assessed by the radiologist., Conclusion: The automated algorithm performed equally well compared to manual measurement by trained observers, attesting to its reliability and efficiency in rapidly computing morphological measurements. This validated method can aid clinical practice and accelerate hip osteoarthritis research., Competing Interests: GJ reports personal fees from Novartis outside the submitted work. SBZ reports consulting fees from Pfizer Infirst Healthcare and personal fees for being a Deputy Editor for Osteoarthritis and Cartilage outside the submitted work. CL and TC report a patent for an image processing apparatus and method for fitting a deformable shape model to an image using random forest regression voting. CL reports licensing royalties for this patent from Optasia Medical outside the submitted work. AN is an associate editor for Osteoarthritis and Cartilage and is on the OARSI Board of Directors outside the submitted work. AM is on the Editorial Board for the British Journal of Sports Medicine and the Journal of Science and Medicine in Sport outside the submitted work. HW reports being a minority shareholder of Uplanner BV and Replasia BV outside the submitted work., (© 2024 The Author(s).)

Secreted protein acidic and rich in cysteine (SPARC) is the most abundant glycoprotein in bone and is thought to play a critical role in bone remodeling and homeostasis. However, the effect of SPARC in relation to gender and exercise on bone quality is not well understood. The purpose of this study was to quantify differences in the structural and biomechanical properties between calvarial and femoral bone from male and female wild-type (WT) and SPARC null (SPARC (-/-) ) mice as well as the ability of exercise to rescue bone health. Male and female WT and transgenic SPARC (-/-) mice were given either a fixed or rotating running wheel for exercise. Bone structural, biomechanical, and morphological parameters were quantified using micro computed tomography, push out testing for the calvaria, three-point flexural testing for the femurs, histological and immunofluorescent staining. Similar reductions in structural and biomechanical strength were observed in both male and female SPARC (-/-) calvaria, most of which were not significantly affected by exercise. In femurs, SPARC (-/-) had a significant effect on structural parameters in both sexes, but was more pronounced in females with some properties being rescued with running. Interestingly, the effect of SPARC (-/-) on bone mineral density was only detected in female SPARC (-/-) mice, not males, and was subsequently rescued with exercise. This study emphasizes the differences between sexes in WT and SPARC (-/-) mice in regard to structural parameters and biomechanical properties. Research into gender differences can help inform and personalize treatment options to more accurately meet patient needs., (© 2024 Orthopaedic Research Society.)

Objective:  The aim of the study was to compare the stiffness and cyclic fatigue of locking compression plate constructs from three manufacturers, DePuy Synthes (DPS), Knight Benedikt (KB), and Provet Veterinary Instrumentation (Vi), under cyclic torsion., Methods:  The constructs of DPS, KB, and Vi were assembled by fixing a 10-hole 3.5-mm stainless steel locking compression plate 1 mm away from a validated bone model with a fracture gap of 47 mm. The corresponding drill guides and locking screws were used. Three groups of six constructs were tested in cyclic torsion until failure., Results:  There was no significant difference in initial stiffness between DPS constructs (28.83 ± 0.84 N·m/rad) and KB constructs (28.38 ± 0.81 N·m/rad), and between KB constructs and Vi constructs (27.48 ± 0.37 N·m/rad), but the DPS constructs were significantly stiffer than the Vi constructs. The DPS constructs sustained the significantly highest number of cycles (24,833 ± 2,317 cycles) compared with KB constructs (16,167 ± 1,472 cycles) and Vi constructs (19,833 ± 4,792 cycles), but the difference between KB and Vi constructs was not significant. All constructs failed by screw damage at the shaft between the plate and the bone model., Conclusion:  DPS constructs showed superior initial torsional stiffness and cyclic fatigue life than Vi constructs, whereas KB and Vi constructs shared comparable results. Further investigation is required to assess the clinical significance of these biomechanical differences., Competing Interests: D.R.J. is an occasional presenter and consultant on the products of Knight Benedikt. None of the other authors have any conflicts of interest to declare., (Thieme. All rights reserved.)

As North America is largely industrialized with a variety of available private transportation options, trauma is a common occurrence, resulting in significant burdens of disability and costs to the health care system. To meet increasing trauma care needs, there is a robust organization of trauma and rehabilitation systems, particularly within the United States and Canada. The American and Canadian health care systems share multiple similarities, including well-equipped Level I trauma centers, specialized inpatient rehabilitation units for polytrauma patients, and thorough evaluations for recovery and post-discharge placement. However, they also have several key differences. In Canada, the criteria for admission to inpatient rehabilitation vary by location, and inpatient rehabilitation is universally accessible, whereas outpatient rehabilitation services are generally not covered by insurance. In the United States, these admission criteria for post-acute inpatient rehabilitation are standardized, and both inpatient and outpatient services are covered by private and government-funded insurance with varying durations. Overall, both health care systems face challenges in post-acute rehabilitation, including benefit limitations and limited provider access in rural areas, and must continue to evolve to meet the rehabilitation needs of injured patients as they reintegrate into their communities., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2024 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the Orthopaedic Trauma Association.)

Background: The utilization of short humeral stems in reverse total shoulder arthroplasty has gained attention in recent times. However, concerns regarding the risk of misalignment during implant insertion are associated with their use., Methods: Eight fresh-frozen cadaveric shoulders were prepared for dissection and biomechanical testing. A bespoke humeral implant was fabricated to facilitate assessment of neutral, varus, and valgus alignments using a single stem, and 10° was established as the maximum permissible angle for misalignments. Shift in humerus position and changes in deltoid length attributable to misalignments relative to the neutral position were evaluated using a Microscribe 3DLx system. The impingement-free range of motion, encompassing abduction, adduction, internal rotation, and external rotation (ER), was gauged using a digital goniometer. The capacity for abduction was evaluated at maximal abduction angles under successive loading on the middle deltoid. A specialized traction system coupled with a force transducer was employed to measure anterior dislocation forces., Results: Relative to the neutral alignment, valgus alignment resulted in a more distal (10.5 ± 2.4 mm) and medial (8.3 ± 2.2 mm) translation of the humeral component, whereas the varus alignment resulted in the humerus shifting more superiorly (11.2 ± 1.3 mm) and laterally (9.9 ± 0.9 mm) at 0° abduction. The valgus alignment exhibited the highest abduction angle than neutral alignment (86.2°, P < .001). Conversely, the varus alignment demonstrated significantly higher adduction (18.4 ± 7.4°, P < .001), internal rotation (68.9 ± 15.0°, P = .014), and ER (45.2 ± 10.5°, P = .002) at 0° abduction compared to the neutral alignments. Anterior dislocation forces were considerably lower (23.8 N) in the varus group compared to the neutral group at 0°ER (P = .047). Additionally, abduction capability was markedly higher in varus alignment at low deltoid loads than the neutral alignment (5N, P = .009; 7.5 N, P = .007)., Conclusions: The varus position enhances rotational range of motion (ROM) but increases instability, while the valgus position does not significantly impact ROM or instability compared to the neutral position., (Copyright © 2024. Published by Elsevier Inc.)

We conducted an explorative prospective cohort study with 6 months follow-up to 1) identify different pain and disability trajectories following an episode of acute neck pain, and 2) assess whether neuroimmune/endocrine, psychological, behavioral, nociceptive processing, clinical outcome, demographic and management-related factors differ between these trajectories. Fifty people with acute neck pain (ie, within 2 weeks of onset) were included. At baseline, and at 2, 4, 6, 12, and 26 weeks follow-up, various neuroimmune/endocrine (eg, inflammatory cytokines and endocrine factors), psychological (eg, stress symptoms), behavioral (eg, sleep disturbances), nociceptive processing (eg, condition pain modulation), clinical outcome (eg, trauma), demographic factors (eg, age), and management-related factors (eg, treatment received) were assessed. Latent class models were performed to identify outcome trajectories for neck pain and disability. Linear mixed models or the Pearson chi-square test were used to evaluate differences in these factors between the trajectories at baseline and at each follow-up assessment and over the entire 6 months period. For pain, 3 trajectories were identified. The majority of patients were assigned to the "Moderate pain - Favourable recovery" trajectory (n = 25; 50%) with smaller proportions assigned to the "Severe pain - Favourable recovery" (n = 16; 32%) and the "Severe pain - Unfavourable recovery" (n = 9; 18%) trajectories. For disability, 2 trajectories were identified: "Mild disability - Favourable recovery" (n = 43; 82%) and "Severe disability - Unfavourable recovery" (n = 7; 18%). Ongoing systemic inflammation (increased high-sensitive C-reactive protein), sleep disturbances, and elevated psychological factors (such as depression, stress and anxiety symptoms) were mainly present in the unfavorable outcome trajectories compared to the favorable outcome trajectories. PERSPECTIVE: Using exploratory analyses, different recovery trajectories for acute neck pain were identified based on disability and pain intensity. These trajectories were influenced by systemic inflammation, sleep disturbances, and psychological factors., (Copyright © 2024 United States Association for the Study of Pain, Inc. Published by Elsevier Inc. All rights reserved.)

Background: Increased load bearing across the patellofemoral and tibiofemoral articulations has been associated with total knee arthroplasty (TKA) complications. Therefore, the purpose of this study was to quantify the biomechanical characteristics of the patellofemoral and tibiofemoral joints and simulate varying weight-bearing demands after posterior cruciate ligament-retaining (CR) and posterior-stabilized (PS) TKAs., Methods: Eight fresh-frozen cadaveric knees (average age, 68.4 years; range, 40-86 years) were tested using a custom knee system with muscle-loading capabilities. The TKA knees were tested with a CR and then a PS TKA implant and were loaded at 6 different flexion angles from 15° to 90° with progressively increasing loads. The independent variables were the implant types (CR and PS TKA), progressively increased loading, and knee flexion angle (KFA). The dependent variables were the patellofemoral and tibiofemoral kinematics and contact characteristics., Results: The results showed that at higher KFAs, the position of the femur translated significantly more posterior in CR implants than in PS implants (36.6 ± 5.2 mm and 32.5 ± 5.7 mm, respectively). The patellofemoral contact force and contact area were significantly greater in PS than in CR implants at higher KFAs and loads (102.4 ± 12.5 N and 88.1 ± 10.9 N, respectively). Lastly, the tibiofemoral contact force was significantly greater in the CR than the PS implant at flexion angles of 45°, 60°, 75°, and 90° KFA, the average at these flexion angles for all loads tested being 246.1 ± 42.1 N and 192.8 ± 54.8 N for CR and PS implants, respectively., Conclusions: In this biomechanical study, CR TKAs showed less patellofemoral contact force, but more tibiofemoral contact force than PS TKAs. For higher loads across the joint and at increased flexion angles, there was significantly more posterior femur translation in the CR design with a preserved posterior cruciate ligament and therefore significantly less patellofemoral contact area and force than in the PS design. The different effects of loading on implants are an important consideration for physicians as patients with higher load demands should consider the significantly greater patellofemoral contact force and area of the PS over the CR design., Competing Interests: CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported., (Copyright © 2024 by The Korean Orthopaedic Association.)

Background: Anatomic patellar components for total knee arthroplasty (TKA) have demonstrated favorable in vivo kinematics. A novel failure mechanism in TKA patients with an anatomic patellar component was observed prompting an investigation to identify patient- and implant-related factors associated with suboptimal performance., Methods: A retrospective evaluation was performed comparing 100 TKA patients with an anatomic patellar component to 100 gender-, age-, and body mass index-matched patients with a medialized dome component. All surgeries were performed with the same posterior-stabilized TKA system with minimum of 1-year follow-up. Several radiographic parameters were assessed. A separate computational evaluation was performed using finite-element analysis, comparing bone strain energy density through the patella bone remnant., Results: Patients with an anatomic patellar component had significantly higher rates of anterior knee pain (18 versus 2%, P < .001), chronic effusions (18 versus 2%, P < .001), and superior patellar pole fragmentation (36 versus 13%, P < .001) compared to those with a dome component. Radiographically, the anatomic group demonstrated more lateral patellar subluxation (2.3 versus 1.1 mm, P < .001) and lateral tilt (5.4 versus 4.0 mm, P = .013). Furthermore, there were more revisions in the anatomic group (7 versus 3, P = .331). On computational evaluation, all simulations demonstrated increased bone strain energy density at the superior patellar pole with the anatomic patella. Resection thickness <13 mm resulted in over 2-fold higher strain energy density, and negative resection angle of 7° resulted in 6-fold higher superior pole strain energy., Conclusions: Patients with an anatomic patellar component showed higher rates of anterior knee pain, chronic effusion, and superior pole fragmentation compared to patients with a dome patella, with higher superior patellar pole strain energy confirmed on computational evaluation. Avoiding higher resection angles and excessive patellar resection may improve the performance and survivorship of the anatomic patella., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Reconstruction nails are commonly used to treat proximal femur fractures, with cephalic screw placement for femoral neck "prophylaxis" becoming standard practice. These implants are traditionally introduced through piriformis fossa (PF) or greater trochanter (GT) entry portals. A third "central collinear" (CC) portal has been proposed that allows entry along the femoral anatomic axis and central placement of cephalic screws. The present study aimed to quantify and compare the CC portal femoral neck strength with the two traditional (PF and GT) entry portals., Materials and Methods: Eighteen cadaveric femur specimens (nine matched pairs) were divided into three groups using a balanced incomplete block design to control for variations in age and sex: (1) GT, (2) CC, and (3) PF entry points. Specimens and implants were cut to a standard length and instrumented with straight or valgus bend nails of appropriate laterality and two cephalic screws. Specimens were mounted on a custom jig replicating load distribution along the mechanical axis. A 100 N compressive preload was applied to the femoral head, followed by loading to failure at a rate of 10 mm/s until fracture, indicated by 30 % drop in axial force., Results: THE THREE ENTRY POINTS DID NOT DIFFER IN LOAD-TO-FAILURE: GT (6378.7 ± 1494.9 N), P (6912.4 ± 4924.1 N) and CC (7044.2 ± 2911.4 N) (P = 0.948) or maximum displacement, stiffness, and toughness. Most PF specimens failed at the basicervical neck, whereas most GT specimens failed at the subcapital neck; these differences were not significant. CC specimens failed evenly split between subcapital and basicervical., Conclusion: There were no significant difference in femoral neck load-to-failure after placement of a reconstruction nail through a CC entry portal when compared to both GT and PF entry. Clinically, this suggests the CC entry portal is a viable option when clinical considerations warrant its use., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Sapan Shah reports financial support and equipment, drugs, or supplies were provided by AOTNA. Melodie Metzger reports a relationship with Arthrex Inc that includes: funding grants. Geoffrey Marecek reports a relationship with Bone Support AB that includes: consulting or advisory. Geoffrey Marecek reports a relationship with DePuy Orthopaedics Inc that includes: consulting or advisory. Geoffrey Marecek reports a relationship with Globus Medical Inc that includes: consulting or advisory, equity or stocks, and funding grants. Geoffrey Marecek reports a relationship with NuVasive Inc that includes: consulting or advisory. Geoffrey Marecek reports a relationship with Orthofix Medical Inc that includes: consulting or advisory. Geoffrey Marecek reports a relationship with restore 3D that includes: consulting or advisory and equity or stocks. Geoffrey Marecek reports a relationship with Siemens Medical Solutions USA Inc that includes: consulting or advisory. Geoffrey Marecek reports a relationship with Zimmer Inc that includes: consulting or advisory. Melodie Metzger reports a relationship with Robson Forensic Inc that includes: paid expert testimony. Geoffrey Marecek - AAOS Comprehensive Review editorial board, AOTNA committee member If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Statistical shape models (SSMs) are useful tools in evaluating variation in bony anatomy to assess pathology, plan surgical interventions, and inform the design of orthopaedic implants and instrumentation. Recently, by considering multiple bones spanning a joint or the whole lower extremity, SSMs can support studies investigating articular conformity and joint mechanics. The objective of this study was to assess tradeoffs in accuracy between SSMs of the femur or tibia individually versus a combined joint-level model. Three statistical shape models were developed (femur-only, tibia-only, and joint-level) for a training set of 179 total knee arthroplasty (TKA) patients with osteoarthritis representing both genders and several ethnicities. Bone geometries were segmented from preoperative CT scans, meshed with triangular elements, and registered to a template for each SSM. Principal component analysis was performed to determine modes of variation. The statistical shape models were compared using measures of compactness, accuracy, generalization, and specificity. The generalization evaluation, assessing the ability to describe an unseen instance in a leave-one-out analysis, showed that errors were consistently smaller for the individual femur and tibia SSMs than for the joint-level model. However, when additional modes were included in the joint-level model, the errors were comparable to the individual bone results, with minimal additional computational expense. When developing more complex SSMs at the joint, lower limb, or whole-body level, the use of an error threshold to inform the number of included modes, instead of 95 % of the variation explained, can help to ensure accurate representations of anatomy., Competing Interests: Competing interests William Fugit and Riza Bayoglu have no conflicts of interest. Luke Aram was an employee of DePuy Synthes. Peter Laz received institutional research support from DePuy Synthes., (Copyright © 2024. Published by Elsevier Ltd.)

Background: Acromial 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 [COR]) 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., Methods: In 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 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., Results: Differences in acromial stress between different delta angle model configurations were observed. Lateralization (5 and 10 mm) of the glenosphere reduced the maximal acromial stress by 21% (1.5 MPa) and 31% (1.3 MPa), respectively. Inferiorization (5 and 10 mm) of the glenosphere increased the maximal acromial stress by 5% (2.0 MPa) and 15% (2.2 MPa), 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), whereas in the 6-mm-medialized configuration, an increase in acromial stress by 83% (3.48 MPa) was observed. There was a high correlation between the delta angle and acromial stress (R 2  = 0.967)., Conclusion: Implant 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. Because of contrary results in the current literature, further studies with focus on the acromial stress influenced by different anatomic variants of the shoulder and the acromion are needed before a clinical recommendation can be made., (Copyright © 2024. Published by Elsevier Inc.)

Background: The aim of this systematic review was to investigate the available literature on the biomechanical characteristics of the acromioclavicular (AC) joint to identify trends in translational parameters and contributions of the various ligamentous structures supporting the joint., Methods: A comprehensive literature search was conducted in the Web of Science, Scopus, and PubMed databases until October 2023 to identify articles reporting on the biomechanical characteristics of the AC joint. Non cadaveric or projects involving reconstruction were excluded. Consistent parameters evaluated were anterior, posterior, superior, and inferior translation. The data were extracted from the included articles and summarized., Results: 11 biomechanical papers were reviewed from six different countries - United States (n = 6), France (n = 1), Austria (n = 1), Thailand (n = 1), United Kingdom (n = 1), and Japan (n = 1). The total number of specimens included across the reviewed papers was 141. All 11 papers reported the data on an intact model (coracoclavicular and AC ligaments intact). Seven papers assessed the translational results of the AC sectioned condition, finding a greater increase in anterior-posterior (AP) laxity relative to SI. 3 papers evaluated coracoclavicular ligament sectioning, finding increased superior-inferior laxity relative to AP. Only one study involved ligament sectioning isolating the anterior-inferior bundle of the AC joint., Conclusion: This review highlights the key AP and superior-inferior constraints of both the intact and ligament sectioned AC joint. The inconsistency of AC joint testing parameters and the lack of thorough translation studies indicate a necessity for increased attention in the overall assessment of shoulder stability to close the gap in the foundational biomechanical research., (© 2024 The Author(s).)

The pericellular matrix (PCM) surrounding chondrocytes is essential for articular cartilage tissue engineering. As the current isolation methods to obtain chondrocytes with their PCM (chondrons) result in a heterogeneous mixture of chondrocytes and chondrons, regenerating the PCM using a tissue engineering approach could prove beneficial. In this study, we aimed to discern the behavior of articular chondrocytes (ACs) in regenerating the PCM in such an approach and whether this would also be true for articular cartilage-derived progenitor cells (ACPCs), as an alternative cell source. Bovine ACs and ACPCs were encapsulated in agarose microgels using droplet-based microfluidics. ACs were stimulated with TGF-β1 and dexamethasone and ACPCs were sequentially stimulated with BMP-9 followed by TGF-β1 and dexamethasone. After 0, 3, 5, and 10 days of culture, PCM components, type-VI collagen and perlecan, and ECM component, type-II collagen, were assessed using flow cytometry and fluorescence microscopy. Both ACs and ACPCs synthesized the PCM before the ECM. It was seen for the first time that synthesis of type-VI collagen always preceded perlecan. While the PCM synthesized by ACs resembled native chondrons after only 5 days of culture, ACPCs often made less well-structured PCMs. Both cell types showed variations between individual cells and donors. On one hand, this was more prominent in ACPCs, but also a subset of ACPCs showed superior PCM and ECM regeneration, suggesting that isolating these cells may potentially improve cartilage repair strategies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Patellar tendon (PT) complaints are frequent in competitive alpine skiers and such complaints are characterized by a long-lasting affection. Since PTs are subject to maturation up to 1-2 years after growth spurt, this early career stage may be decisive for the further course of complaints. The aim of this study was to investigate the evolution of PT complaints and shear wave velocity patterns among competitive alpine skiers during a 4-year post-growth spurt follow-up. The PT complaints and SWV patterns of forty-seven skiers were analysed at baseline (i.e., immediately after their peak height growth at 13-15 years of age) and were re-analysed at 4-year follow-up. The PTs were scanned via three-dimensional SWE. Symptomatic skiers were identified based on pain sensation under loading and pressure-induced pain around the PT. The prevalence of PT complaints decreased from 29.8% at baseline to 12.8% at follow-up (Pearson's χ 2 = 9.429; p = 0.002). SWV decreased from the baseline assessment to the follow-up in the proximal and distal regions ( p < 0.05). SWV coefficient of variation (CV) in the distal and mid-portion regions was greater at baseline than at follow-up ( p < 0.05). At the follow-up assessment, compared to "healthy" skiers, "healed" skiers who recovered from PT complaints had lower SWVs in the proximal region ( p = 0.020) and greater SWV CVs in the proximal region ( p = 0.028). Moreover, symptomatic skiers had significantly greater SWV CVs in the mid-portion region than did "healthy" subjects with no history of PT complaints ( p = 0.020). The average SWV was negatively correlated with the SWV (proximal: r = -0.74, p < 0.001; mid-portion: r = -0.37 p = 0.011; and distal: r = -0.58, p < 0.001). The occurrence of PT complaints decreased over a 4-year post-growth spurt follow-up. "Healed" skiers who were symptomatic at baseline had an even greater average decrease in the proximal and mid-portion SWV than "healthy" skiers with no history of PT complaints. This may lead to the hypothesis that PT complaints in adolescent skiers are not self-eliminating towards the end of adolescence, as at least structural irregularities appear to persist for several years after the onset of initial symptoms. Furthermore, "healed" and symptomatic tendons exhibited increased SWV variability, supporting the hypothesis that SWV CV may provide additional valuable information on the mechanical properties of PTs affected by overuse-related complaints., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Hanimann, Fitze, Götschi, Fröhlich, Frey, de Bruin, Sutter and Spörri.)

Background: The Latarjet procedure is increasingly being utilized for the treatment of glenoid bone loss and has a relatively high neurological complication rate. Understanding the position-dependent anatomy of the axillary nerve (AN) is crucial to preventing injuries., Purpose: To quantify the effects of changes in the shoulder position and degree of glenoid bone loss during the Latarjet procedure on the position of the AN., Study Design: Controlled laboratory study., Methods: A total of 10 cadaveric shoulders were dissected, leaving the tendons of the rotator cuff and deltoid for muscle loading. The 3-dimensional position of the AN was quantified relative to the inferior glenoid under 3 conditions: (1) intact shoulder, (2) Latarjet procedure with 15% bone loss, and (3) Latarjet procedure with 30% bone loss. Measurements were obtained at 0°, 30°, and 60° of glenohumeral abduction (equivalent to 0°, 45°, and 90° of shoulder abduction) and at 0°, 45°, and 90° of humeral external rotation (ER)., Results: Abduction of the shoulder to 60° resulted in a posterior (9.5 ± 1.1 mm; P < .001), superior (3.0 ± 1.2 mm; P = .013), and lateral (19.1 ± 2.3 mm; P < .001) shift of the AN, and ER to 90° resulted in anterior translation (10.0 ± 1.2 mm; P < .001). Overall, ER increased the minimum AN-glenoid distance at 30° of abduction (14.9 ± 1.3 mm [0° of ER] vs 17.3 ± 1.5 mm [90° of ER]; P = .045). The Latarjet procedure with both 15 and 30% glenoid bone loss resulted in a superior and medial shift of the AN relative to the intact state. A decreased minimum AN-glenoid distance was seen after the Latarjet procedure with 30% bone loss at 60° abduction and 90° ER (17.7 ± 1.6 mm [intact] vs 13.9 ± 1.6 mm [30% bone loss]; P = .007), but no significant differences were seen after the Latarjet procedure with 15% bone loss., Conclusion: Abduction of the shoulder induced a superior, lateral, and posterior shift of the AN, and ER caused anterior translation. Interestingly, the Latarjet procedure, when performed on shoulders with extensive glenoid bone loss, significantly reduced the minimum AN-glenoid distance during shoulder abduction and ER. These novel findings imply that patients with substantial glenoid bone loss may be at a higher risk of AN injuries during critical portions of the procedure. Consequently, it is imperative that surgeons account for alterations in nerve anatomy during revision procedures., Clinical Relevance: This study attempts to improve understanding of the position-dependent effect of shoulder position and glenoid bone loss after the Latarjet procedure on AN anatomy. Improved knowledge of AN anatomy is crucial to preventing potentially devastating AN injuries during the Latarjet procedure., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: A.C. has received support for education and grants from Arthrex and Smith & Nephew; support for education from Micromed, Medwest Associates, and Saxum Surgical; and hospitality payments from Stryker. M.B.B. has received consulting fees from Stryker, Smith & Nephew, and Vericel and support for education from Micromed, Saxum Surgical, and Arthrex. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Background: This study experimentally validated a computationally optimized screw number and screw distribution far cortical locking distal femur fracture plate and compared the results to traditional implants., Methods: 24 artificial femurs were osteotomized with a 10 mm fracture gap 60 mm proximal to the intercondylar notch. Three fixation constructs were used. (i) Standard locking plates secured with three far cortical locking screws inserted according to a previously optimized distribution in the femur shaft (n = 8). (ii) Standard locking plates secured with four standard locking screws inserted in alternating plate holes in the femur shaft (n = 8). (iii) Retrograde intramedullary nail secured proximally with one anterior-posterior screw and distally with two oblique screws (n = 8). Axial hip forces (700 and 2800 N) were applied while measuring axial interfragmentary motion, shear interfragmentary motion, and overall stiffness., Findings: Experimental far cortical locking plate results compared well to published computational findings. Far cortical locking femurs contained the highest axial motion within the potential ideal range of 0.2-1 mm and a sheer-to-axial motion ratio < 1.6 at toe-touch weight-bearing (700 N). At full weight-bearing (2800 N), Standard locking-plated femurs had the only axial motion within 0.2-1 mm but had an excess shear-to-axial motion ratio. Nail-implanted femurs underperformed at both forces., Interpretation: For toe-touch weight-bearing, the far cortical locking construct provided optimal biomechanics to allow moderate motion, which has been suggested to encourage early callus formation. Conversely, at full weight-bearing, the standard locking construct offered the biomechanical advantage on fracture motion., Competing Interests: Declaration of competing interest Emil H. Schemitsch previously received personal fees and research support from Zimmer Biomet. Radovan Zdero previously received “in kind” research support from Zimmer Biomet. No conflicts exist for the other authors., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

A major problem after tendon injury is adhesion formation to the surrounding tissue leading to a limited range of motion. A viable strategy to reduce adhesion extent is the use of physical barriers that limit the contact between the tendon and the adjacent tissue. The purpose of this study was to fabricate an electrospun bilayered tube of hyaluronic acid/polyethylene oxide (HA/PEO) and biodegradable DegraPol® (DP) to improve the anti-adhesive effect of the implant in a rabbit Achilles tendon full laceration model compared to a pure DP tube. Additionally, the attachment of rabbit tenocytes on pure DP and HA/PEO containing scaffolds was tested and Scanning Electron Microscopy, Fourier-transform Infrared Spectroscopy, Differential Scanning Calorimetry, Water Contact Angle measurements, and testing of mechanical properties were used to characterize the scaffolds. In vivo assessment after three weeks showed that the implant containing a second HA/PEO layer significantly reduced adhesion extent reaching levels comparable to native tendons, compared with a pure DP implant that reduced adhesion formation only by 20 %. Tenocytes were able to attach to and migrate into every scaffold, but cell number was reduced over two weeks. Implants containing HA/PEO showed better mechanical properties than pure DP tubes and with the ability to entirely reduce adhesion extent makes this implant a promising candidate for clinical application in tendon repair., Competing Interests: Declaration of competing interest The authors declare that they do not have any competing interests., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The goal of this article was to review studies on distal humerus fracture plates (DHFPs) to understand the biomechanical influence of systematically changing the plate or screw variables. The problem is that DHFPs are commonly used surgically, although complications can still occur, and it is unclear if implant configurations are always optimized using biomechanical criteria. A systematic search of the PubMed database was conducted to identify English-language biomechanical optimization studies of DHFPs that parametrically altered plate and/or screw variables to analyze their influence on engineering performance. Intraarticular and extraarticular fracture (EAF) data were separated and organized under commonly used biomechanical outcome metrics. The results identified 52 eligible DHFP studies, which evaluated various plate and screw variables. The most common plate variables evaluated were geometry, hole type, number, and position. Fewer studies assessed screw variables, with number and angle being the most common. However, no studies examined nonmetallic materials for plates or screws, which may be of interest in future research. Also, articles used various combinations of biomechanical outcome metrics, such as interfragmentary fracture motion, bone, plate, or screw stress, number of loading cycles to failure, and overall stiffness (Os) or failure strength (Fs). However, no study evaluated the bone stress under the plate to examine bone "stress shielding," which may impact bone health clinically. Surgeons treating intraarticular and extraarticular distal humerus fractures should seriously consider two precontoured, long, thick, locked, and parallel plates that are secured by long, thick, and plate-to-plate screws that are located at staggered levels along the proximal parts of the plates, as well as an extra transfracture plate screw. Also, research engineers could improve new studies by perusing recommendations in future work (e.g., studying alternative nonmetallic materials or "stress shielding"), clinical ramifications (e.g., benefits of locked plates), and study quality (e.g., experimental validation of computational studies)., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Radovan Zdero et al.)

Purpose: To investigate the effectiveness of bursal acromial resurfacing (acromiograft) on acromiohumeral distance, subacromial contact area, and pressure in a cadaveric model of massive rotator cuff tear., Methods: Eight fresh-frozen cadaveric shoulders were tested using a customized shoulder testing system. Humeral head translation, subacromial contact pressure, and the subacromial contact area were evaluated across 4 conditions: (1) intact shoulder; (2) simulated massive rotator cuff tear, (3) 3-mm acromiograft condition, and (4) 6-mm acromiograft condition. The acromiografts were simulated using Teflon and a reported technique. The values were measured at 0°, 20°, and 40° abduction and 0°, 30°, 60°, and 90° external rotation for each abduction status., Results: Compared with a massive cuff tear, the 6-mm acromiograft significantly reduced the superior translation of the humeral head at all abduction/external rotation angles (P < .05). The 3-mm acromiograft also decreased superior translation of the humeral head compared with massive cuff tear, but not all differences were significant. The 3- and 6-mm acromiografts significantly decreased the subacromial contact pressure and increased the subacromial contact area in almost all positions (P < .05). The 3-mm acromiograft maintained biomechanical properties similar to the intact condition, whereas the 6-mm acromiograft increased the contact area., Conclusions: This biomechanical study demonstrated that both 3- and 6-mm acromiografts using Teflon in a cadaveric model of a massive cuff tear resulted in recentering of the superiorly migrated humeral head, increased the subacromial contact area, and decreased the subacromial contact pressure. The 3-mm graft was sufficient for achieving the intended therapeutic effects., Clinical Relevance: The acromiograft can normalize altered biomechanics and may aid in the treatment of massive cuff tears. Because grafting the acromion's undersurface is new with limited clinical outcomes, further observation is crucial. Using a Teflon instead of an acellular dermal matrix allograft for bursal acromial resurfacing could yield different results, requiring careful interpretation., Competing Interests: Disclosures The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Y-S.K. reports personal fees and nonfinancial support from Corentec, outside the submitted work. Some equipment, drugs, or supplies were provided by Smith and Nephew. T.Q.L reports grants, personal fees, and nonfinancial support from Arthrex; personal fees from CONMED Linvatec; personal fees from Smith & Nephew, all outside the submitted work. All other authors (S-H.C., C-J.P., S-J.K, K-G.L., G.R.B, M-S.C., A.T.H., M.H.M.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Study Design: In-vitro cadaveric biomechanical study., Objectives: Long posterior spinal fusion is a standard treatment for adult spinal deformity. However, these rigid constructs are known to alter motion and stress to the adjacent non-instrumented vertebrae, increasing the risk of proximal junctional kyphosis (PJK). This study aimed to biomechanically compare a standard rigid construct vs constructs "topped off" with a semi-rigid construct. By understanding semi-rigid constructs' effect on motion and overall construct stiffness, surgeons and researchers could better optimize fusion constructs to potentially decrease the risk of PJK and the need for revision surgery., Methods: Nine human cadaveric spines (T1-T12) underwent non-destructive biomechanical range of motion tests in pure bending or torsion and were instrumented with an all-pedicle-screw (APS) construct from T6-T9. The specimens were sequentially instrumented with semi-rigid constructs at T5: (i) APS plus sublaminar bands; (ii) APS plus supralaminar hooks; (iii) APS plus transverse process hooks; and (iv) APS plus short pedicle screws., Results: APS plus transverse process hooks had a range of motion (ie, relative angle) for T4-T5 and T5-T6, as well as an overall mechanical stiffness for T1-T12, that was more favourable, as it reduced motion at adjacent levels without a stark increase in stiffness. Moreover, APS plus transverse process hooks had the most linear change for range of motion across the entire T3-T7 range., Conclusions: Present findings suggest that APS plus transverse process hooks has a favourable biomechanical effect that may reduce PJK for long spinal fusions compared to the other constructs examined., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose: Risk factors for the development of symptomatic cyclops lesion after anterior cruciate ligament reconstruction (ACLR) surgery are not entirely identified yet. This study aimed to investigate whether the choice of hamstring graft (semitendinosus-gracilis; STG vs. semitendinosus; ST) affects the risk of developing a symptomatic cyclops lesion after ACLR., Methods: This retrospective cohort study included 1416 patients receiving either an ST graft (n = 1209) or an STG graft (n = 207) ACLR with a follow-up of at least 2 years. A persisting extension limitation was clinically determined, and cyclops lesions were confirmed by magnetic resonance imaging (MRI) and second-look arthroscopy. Graft-specific incidence of cyclops lesions was examined with χ 2 test and combined with the factors number of graft bundles, graft diameter and sex evaluated with a binominal logistic regression model., Results: In total, 46 patients developed symptomatic cyclops lesions (3.2%), with 36 having ACLR with an ST graft (3.0%) and 10 with an STG graft (4.8%) (n.s). The mean time from ACLR to the second-look arthroscopy for cyclops removal was 1.1 ± 0.6 years. Female patients were 2.5 times more likely to develop a cyclops lesion than male patients. Patients with an STG graft and larger graft diameters did not have a higher risk of developing cyclops lesions. Patients who received an STG graft with both tendons folded four times (double-quadruple) had significantly higher risk of developing a cyclops compared with all other numbers of graft bundles combined (8.3%, respectively 3.0%; p = 0.014)., Conclusion: This study could not prove an increased risk of developing a symptomatic cyclops lesion for patients with an STG graft compared with an ST graft used for ACLR. However, patients with a double-quadruple ACLR had a higher percentage of cyclops lesions compared with all other numbers of graft bundles. Female sex was associated with an increased risk of developing cyclops lesions., Level of Evidence: Level III., (© 2024 European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Hip and knee biomechanics measured during a drop vertical jump (DVJ) can be used to assess patients undergoing rehabilitation after anterior cruciate ligament (ACL) reconstruction. To confidently interpret such data for use as outcome measures, additional information about reliability and validity is required. Therefore, the objective of this study was to estimate the test-retest reliability and longitudinal validity of selected lower limb biomechanics assessed during a DVJ in patients undergoing rehabilitation after ACL reconstruction. Biomechanical analysis of the DVJ in primary unilateral ACL reconstruction patients (22.3 ± 5.5y) were tested twice within 1 week at 6 months post-surgery (n = 46), and again at 12 months post-surgery (n = 36). Peak and initial contact knee angles and moments, hip impulse, vertical ground reaction forces (VGRF), isokinetic knee extension and flexion strength, and global ratings of change (GRC) were assessed. Reliability was evaluated based on the 6-month post-surgery data using intraclass correlation coefficients (ICC 2,1 ), standard errors of measurement and minimum detectable change. Longitudinal validity was evaluated by assessing change from 6 to 12 months, using standardized response means (SRM), and by assessing the correlation (Pearson's r) of change in landing biomechanics with change in strength, and GRC. ICCs ranged from 0.58 to 0.90 for peak knee abduction and flexion moments, 0.44-0.85 for knee flexion and abduction angles, 0.82-0.93 for VGRFs, and 0.42-0.65 for hip impulse. SRMs and correlations of change ranged from 0.00 to 0.50. Reliability and longitudinal validity of DVJ measures varied, ranging from poor-to-excellent; the present results assist in their interpretation when assessed during rehabilitation after ACL reconstruction., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Background: Even with the best conservative care, patients with Charcot neuroarthropathy (CN) of the foot and ankle often ulcerate, increasing their risk of infection, amputation, and death. Surgical fixation has been associated with risk of recurrent ulceration, potentially due to poor bone quality prone to recurrent deformity and ulceration. We propose midfoot beam reconstruction with PMMA augmentation as a novel means of improving fixation., Methods: A protocol was developed to create characteristic CN midfoot fragmentation both visually and fluoroscopically in each of 12 matched-pair cadaveric feet. Afterward, the pairs were divided into 2 groups: (1) midfoot beam fusion surgery alone, and (2) midfoot beam fusion surgery augmented with PMMA. A solid 7.0-mm beam was placed into the medial column and a solid 5.5-mm beam was placed across the lateral column. In the PMMA group, 8 to 10 mL of PMMA was inserted into the medial column. The hindfoot of each specimen was potted and the metatarsal heads were cyclically loaded for 1800 cycles, followed by load to failure while load and displacement were continually recorded., Results: One specimen in the beam alone group failed before reaching the 1800th cycle and was not included in the failure analysis. The midfoot beam only group demonstrated greater mean displacement during cycle testing compared with the PMMA group, P  < .05. The maximum force (N), stiffness (N/mm), and toughness (Nmm) were all significantly greater in the group augmented with PMMA, P  < .05., Conclusion: In a CN cadaveric model, PMMA augmentation significantly decreased gapping during cyclic loading and nearly doubled the load to failure compared with midfoot beams alone., Clinical Relevance: The results of this biomechanical study demonstrate that augmentation of midfoot beams with PMMA increases the strength and stiffness of the fusion construct. This increased mechanical toughness may help reduce the risk of nonunion and infection in patients with neuropathic midfoot collapse., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Kinematic tracking of native anatomy from stereo-radiography provides a quantitative basis for evaluating human movement. Conventional tracking procedures require significant manual effort and call for acquisition and annotation of subject-specific volumetric medical images. The current work introduces a framework for fully automatic tracking of native knee anatomy from dynamic stereo-radiography which forgoes reliance on volumetric scans. The method consists of three computational steps. First, captured radiographs are annotated with segmentation maps and anatomic landmarks using a convolutional neural network. Next, a non-convex polynomial optimization problem formulated from annotated landmarks is solved to acquire preliminary anatomy and pose estimates. Finally, a global optimization routine is performed for concurrent refinement of anatomy and pose. An objective function is maximized which quantifies similarities between masked radiographs and digitally reconstructed radiographs produced from statistical shape and intensity models. The proposed framework was evaluated against manually tracked trials comprising dynamic activities, and additional frames capturing a static knee phantom. Experiments revealed anatomic surface errors routinely below 1.0 mm in both evaluation cohorts. Median absolute errors of individual bone pose estimates were below 1.0 ∘ or mm for 15 out of 18 degrees of freedom in both evaluation cohorts. Results indicate that accurate pose estimation of native anatomy from stereo-radiography may be performed with significantly reduced manual effort, and without reliance on volumetric scans., (© 2024. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Recent advancements in computational modeling offer opportunities to refine total knee arthroplasty (TKA) design and treatment strategies. This study developed patient-specific simulator external boundary conditions (EBCs) using a PID-controlled lower limb finite element (FE) model. Calibration of the external actuation required to achieve measured patient-specific joint loading and motion was completed for nine patients with telemetric implants during gait, stair descent, and deep knee bend. The study also compared two EBC scenarios: activity-specific hip AP motion and pelvic rotation (that was averaged across all patients for an activity) and patient-specific hip AP motion and pelvic rotation. Including patient-specific data significantly improved reproduction of joint-level loading, reducing root mean squared error between the target and achieved loading by 28.7% and highlighting the importance of detailed patient data in replicating joint kinematics and kinetics. The principal component analysis (PCA) of the EBCs for the patient dataset showed that one component represented 77.8% of the overall variation, while the first three components represented 97.8%. Given the significant loading variability within the patient cohort, this group of patient-specific models can be run individually to provide insight into expected TKA mechanics variability, and the PCA can be utilized to further create reasonable EBCs that expand the variability evaluated.

Background: Immigrants and refugees face unique challenges navigating the health care system to manage severe arthritis, because of unfamiliarity, lack of awareness of surgical options, or access. The purpose of this study was to assess total knee arthroplasty (TKA) uptake, surgical outcomes, and hospital utilization among immigrants and refugees compared with Canadian-born patients., Methods: We included all adults undergoing primary TKA from January 2011 to December 2020 in Ontario. Cohorts were defined as Canadian-born or immigrants and refugees. We assessed change in yearly TKA utilization for trend. We compared differences in 1-year revision, infection rates, 30-day venous thromboembolism (VTE), presentation to emergency department, and hospital readmission between matched Canadian-born and immigrant and refugee groups., Results: We included 158 031 TKA procedures. A total of 11 973 (7.6%) patients were in the immigrant and refugee group, and 146 058 (92.4%) patients were in the Canadian-born group. The proportion of TKAs in Ontario performed among immigrants and refugees nearly doubled over the 10-year study period ( p < 0.001). After matching, immigrants were at relatively lower risk of 1-year revision (0.9% v. 1.6%, p < 0.001), infection ( p < 0.001), death ( p = 0.004), and surgical complications ( p < 0.001). No differences were observed in rates of 30-day VTE or length of hospital stay. Immigrants were more likely to be discharged to rehabilitation ( p < 0.001) and less likely to present to the emergency department ( p < 0.001) than Canadian-born patients., Conclusion: Compared with Canadian-born patients, immigrants and refugees have favourable surgical outcomes and similar rates of resource utilization after TKA. We observed an underutilization of these procedures in Ontario relative to their proportion of the population. This may reflect differences in perceptions of chronic pain or barriers accessing arthroplasty., Competing Interests: Competing interests:: J. Michael Paterson reports research funding from Arthritis Society Canada and the Canadian Institutes of Health Research. No other competing interests were declared., (© 2024 CMA Impact Inc. or its licensors.)

Bone fracture plates are usually made from steel or titanium, which are much stiffer than cortical bone. This may cause bone 'stress shielding' (i.e. bone resorption leading to plate loosening) and delayed fracture healing (i.e. fracture motion is less than needed to stimulate callus formation at the fracture). Thus, the authors previously designed, fabricated, and mechanically tested novel 'hybrid' composites made from inorganic and organic materials as potential bone fracture plates that are more flexible to reduce these negative effects. This is the first study to measure the cytotoxicity of these composites via the survival of rat cells. Cubes of carbon fiber/flax fiber/epoxy and glass fiber/flax fiber/epoxy had better cell survival vs. Kevlar fiber/flax fiber/epoxy (57% and 58% vs. 50%). Layers and powders made of carbon fiber/epoxy and glass fiber/epoxy had higher cell survival than Kevlar fiber/epoxy (96%-100% and 100% vs. 39%-90%). The presence of flax fibers usually decreased cell survival. Thus, carbon and glass fiber composites (with or without flax fibers), but not Kevlar fiber composites (with or without flax fibers), may potentially be used for bone fracture plates., (© 2024 IOP Publishing Ltd.)

The hip capsule is a ligamentous structure that contributes to hip stability. This article developed specimen-specific finite element models that replicated internal-external (I-E) laxity for ten implanted hip capsules. Capsule properties were calibrated to minimize root mean square error (RMSE) between model and experimental torques. RMSE across specimens was 1.02 ± 0.21 Nm for I-E laxity and 0.78 ± 0.33 Nm and 1.10 ± 0.48 Nm during anterior and posterior dislocation, respectively. RMSE for the same models with average capsule properties was 2.39 ± 0.68 Nm. Specimen-specific models demonstrated the importance of capsule tensioning in hip stability and have relevance for surgical planning and evaluation of implant designs.

Background: Superior capsular reconstruction (SCR) and lower trapezius tendon transfer (LTT) have recently been used to manage irreparable posterosuperior rotator cuff tears (PSRCTs). There has been a paucity of comparative biomechanical considerations between the 2 procedures., Purpose: To compare the glenohumeral stability and biomechanical properties between SCR and LTT in PSRCTs involving the entire infraspinatus tendon region., Study Design: Controlled laboratory study., Methods: Eight fresh-frozen cadaveric shoulders were tested at 0°, 20°, and 40° of shoulder abduction. Maximum internal, external, and total humeral range of motion (ROM), superior translation of the humeral head, and subacromial contact characteristics were compared among 4 conditions: (1) intact rotator cuff, (2) PSRCTs involving the entire infraspinatus tendon region, (3) LTT using Achilles allograft (12 N and 24 N of loading), and (4) SCR using fascia lata allograft., Results: Although a decrease in total ROM was noted in LTT with 12 N compared with the tear condition, LTT with both 12 N and 24 N as well as SCR did not restrict total rotational ROM compared with the intact condition. LTT had decreased total ROM compared with tear condition at 20° of abduction ( P = .042), while no significant decrease was confirmed at all abduction angles after SCR. SCR and LTT with 24 N decreased superior translation compared with the PSRCT condition at 0° and 20° of abduction ( P < .037) but not significantly at 40° of abduction, whereas LTT with a 24-N load decreased glenohumeral superior translation at all abduction angles ( P < .039). Both SCR and LTT decreased subacromial contact pressure compared with the tear condition ( P < .014) at all abduction angles. SCR decreased subacromial contact pressure at 0° and 40° of abduction ( P = .019 and P = .048, respectively) compared with LTT with 12 N of loading, while there was no difference between SCR and LTT with 24 N of loading in all abduction angles. SCR increased the contact area compared with the PSRCT condition at all abduction angles ( P < .023), whereas LTT did not increase the contact area., Conclusion: SCR and LTT decreased glenohumeral superior translation and contact pressure compared with PSRCT conditions. The LTT was superior to SCR in terms of superior translation of the humeral head at a higher shoulder abduction angle, whereas the SCR showed more advantageous subacromial contact characteristics compared with LTT., Clinical Relevance: These biomechanical findings provide insights into these 2 fundamentally different procedures for the treatment of young and active patients with PSRCTs involving the entire infraspinatus tendon region., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: Funding was provided by Yeosu Baek Hospital, Yeosu-si, Jeollanam-do, Republic of Korea. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Background: Scrub nurses play a crucial role in facilitating orthopaedic surgeries, and thus intraoperative scrub nurse turnover may disrupt the workflow of the surgical team and prolong duration of surgery (DOS). The purpose of this study was to quantify the impact of intraoperative scrub nurse turnover on operative time of orthopaedic surgeries lasting less than 3h in duration., Methods: Prospectively collected databases from two institutions were retrospectively queried to identify all orthopaedic procedures of maximum mean duration of 180min from March 4th, 2018 to August 31st, 2022. Cases were divided into two groups, those with scrub nurse turnover and those without. Propensity score matching was conducted to match groups by surgeon, hospital, patient age, gender, and ASA classification. Unpaired t-tests were used to compare mean DOS for each surgical procedure. Average treatment effect on treated (ATET) with 95% confidence intervals (CIs) were calculated., Results: Scrub nurse turnover significantly prolonged DOS for both bone forearm facture open reduction and internal fixation (ORIF) (ATET=21.08, p=0.001), ankle ORIF (ATET=21.26, p<0.001), clavicle ORIF (ATET=16.16, p=0.028), femur intramedullary nail (ATET=11.52, p=0.003), rotator cuff repair (ATET=16.88, p<0.001), partial discectomy (ATET=10.52, p=0.001), total knee arthroplasty (TKA) (ATET=5.69, p<0.001), anterior total hip arthroplasty (THA) (ATET=8.80, p<0.001), lateral THA (ATET=7.02, p<0.001), and uncemented hip hemiarthroplasty (ATET=16.79, p=0.049)., Conclusion: Intraoperative scrub nurse turnover significantly prolongs surgical times in orthopaedic surgeries lasting up to 3h in duration. This highlights the importance of developing strategies to prevent intraoperative scrub nurse turnover to improve OR efficiency and decrease healthcare costs., (Copyright © 2024 FECA. Publicado por Elsevier España, S.L.U. All rights reserved.)

Quorum sensing (QS) is a complex communication system in bacteria, directing their response to the environment. QS is also one of the main regulators of bacterial biofilms' formation, maturation and dispersion. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) is a molecular imaging technique that allows the mapping of QS molecules in bacterial biofilms. Here, we highlight the latest advances in MALDI-MSI in recent years and how this technology can improve QS understanding at the molecular level., (© 2024. The Author(s).)