Capstone design focused on medical/assistive devices provides a golden opportunity to educate young biomedical engineers in business and entrepreneurship. What constitutes a healthy balance of engineering and business subject matter, however, remains unclear. The present paper describes the history of the senior capstone design course sequence in Biomedical Engineering (BME) at the author's institution, for which he was lead instructor. The focus is on the business content, which was first increased to encourage an entrepreneurial mind-set among students, then later decreased, based on student feedback, instructor assessment, and related grant proposal reviews, which all suggested that engineering aspects of the design process were being compromised. Business and engineering topics included in the current course sequence are described to help course designers strike a balance that provides students with the skills to be successful as design engineers with healthy business acumen.

STATEMENT OF PROBLEM:Dental zirconia is often marketed and selected for restorative use based upon the biaxial flexural strength of prefabricated specimens (disks) without considering other mechanical and physical properties. PURPOSE:The purpose of this in vitro study was to test whether 4-point flexural strength, biaxial flexural strength, and/or hardness may correlate with failure loads for crowns made of different zirconia materials. MATERIAL AND METHODS:Three brands of zirconia (BruxZir, Cercon, and Katana) were used to fabricate anatomically contoured crowns, rectangular bars, and circular disks. The sample size was n=15 specimens per zirconia brand and specimen shape. The bars were tested for 4-point flexural strength by using the 4-point bending (4PB) test and Vickers hardness (VH), while the disks were tested for biaxial flexural strength by using a piston-on-3 ball (POB) test. Crowns were attached to resin abutments and compressed with a steel spherical indenter through a polyethylene sheet to assess the failure loads by using the "crunch the crown" (CTC) test. One-way ANOVA (α=.05) was used to test for statistically significant differences between groups, and Weibull analysis was used to assess the variability of the measured flexural strengths, failure load, and hardness. RESULTS:Statistical differences (P<.001) were found in comparing Cercon, BruxZir, and Katana ([4260 N=4186 N]>3195 N, respectively) with the CTC test and (396 MPa>[281 MPa=275 MPa], respectively) the 4PB test. No statistical differences (P=.084) were found among the zirconia brands (Cercon [384 MPa]=Bruxzir [359 MPa]=Katana [416 MPa]) for the POB test. No significant correlations (P>.05) were found between the 4PB, POB, or VH tests and the corresponding CTC test. The Weibull modulus varied for the different specimen geometries. CONCLUSIONS:The piston-on-3 ball, 4-point bending, and Vickers hardness test results were not correlated with the corresponding crunch-the-crown test.

STUDY DESIGN:Biomechanical cadaveric study (level V). OBJECTIVE:To evaluate the effectiveness of polyethylene bands looped around the supra-adjacent spinous process (SP) or spinal lamina (SL) in providing strength to the cephalad unfused segment and reducing junctional stress. BACKGROUND:Proximal junctional kyphosis (PJK) is a pathologic kyphotic deformity adjacent to posterior spinal instrumentation after fusion constructs. Recent studies demonstrate a mismatch in stiffness between the instrumented construct and nonfused adjacent levels to be a causative factor in the development of PJK and proximal junction failure. To our knowledge, no biomechanical studies have addressed the effect of different methods of polyethylene band placement at the proximal junction. MATERIALS AND METHODS:Twelve fresh frozen cadavers were divided into 3 groups of 4: pedicle screw-based instrumentation from T10 to L5 ("control"), T10-L5 instrumentation with a polyethylene band to the T9 "SP," T10-L5 instrumentation with 2 polyethylene bands to the T9 "SL." Specimens were tested with an eccentric (10 mm anterior) load at 5 mm/min for 15 mm or until failure occurred. Failure was defined by the inflection point on the load versus deformation curves. Linear regression was utilized to evaluate the effect of augmentation on the load-to-failure. Significance was set at 0.05. RESULTS:Fractures occurred in all specimens tested. The mean peak load to failure was 2148 N (974-3322) for the SP group, and 1248 N (742-1754) for the control group ( P > 0.05) and 1390 N (1080-2004) for the SL group. No difference existed between the control group and the SP group in terms of fracture level ( P > 0.05). Net kyphotic angulation shows no differences among these 3 groups ( P > 0.05). CONCLUSION:Although statistical significance was not achieved, ligament augmentation to the SP increased mean peak load-to-failure in a cadaveric PJK model.

PurposeTo perform qualitative analysis using scanning electron microscopy (SEM) of fracture surfaces for ceramic and polymeric dental materials broken via standardized flexural and crunch-the-crown (CTC) tests. Materials and MethodsZirconia, glass-ceramic, and polymeric (Trilor; TRI, Juvora; JUV, Pekkton; PEK) materials were loaded using crowns for CTC tests, discs (zirconia and glass-ceramics) for piston-on-3 ball tests, bars (polymer) for 3-point bend tests, and bars (zirconia, glass-ceramics) for 4-point bend tests. SEM was used to characterize the fracture surfaces and identify fracture surface features (e.g., origin, mist, hackle, and the direction of crack propagation [DCP]). Electron dispersive spectroscopy was used to identify the local chemistry. ResultsFracture surface features were found to be less visually apparent for glass-ceramics than zirconia. For zirconia bars, fractures originated roughly midway between the corner and center for processing defects related to sintering. Fractures originated at the bottom corners of glass-ceramic bars (void or surface flaw) and PEK bars (surface flaw). TRI bar failures exposed glassy fibers. Fracture features were generally less discernable for discs compared to bars for zirconia and glass-ceramics. Ceramic crowns fractured into 2 to 3 pieces, with fractures originating at the occlusal surface and clear evidence for the DCP. Failures of TRI and JUV specimens (bars and crowns) were less catastrophic than for the ceramics, with exposed fibers (TRI) and surface cracks (JUV). PEK crown and bar fractures presented dimple (ductile) features formed due to microvoid coalescence followed by brittle crack propagation. ConclusionsThe critical flaws responsible for failure initiation were a function of material composition and test configuration. Fractographic analysis can reveal problems associated with the manufacturing of materials, their handling, grinding and finishing/polishing procedures, the structural design and choice of material, and the quality of the final laboratory-delivered restoration.

Background The modern surgeon faces an ever-changing landscape of procedural innovation. The demands of present-day healthcare highlight the importance of successfully developing new medical devices and technologies. This effort requires multidisciplinary collaborations of professionals ranging from manufacturers and engineers to researchers and healthcare providers. Surgeons regularly interact with complex equipment and user interfaces without substantial formal education on their design and development. The objective of this study was to ascertain the impact of a 10-week BME course into a medical school curriculum on surgery-bound students’ knowledge of product design and gauge their ability to develop an actual product to meet a real need in a surgical field. Methods A Medical Device Design and Commercialization co-enrolled elective course was offered to medical students at a single institution. Five students with an expressed surgical and procedural interest were enrolled. At the beginning of the course, they were tasked with developing a product to meet a clinical need they observed. At the conclusion of the course, students filled out a questionnaire about their level of comfort and knowledge of the material using a 5-point Likert scale. This survey was administered to a control group of medical students who did not take the course. Results The BME student cohort was able to successfully identify a post-operative need, develop a prototype of a novel device, and present their product to attending surgeons. A total of 35 survey entries were received: five from the experimental group and 30 from the comparison group. The experimental group scored higher than the comparison group for all survey questions and reached the level of statistical significance in 13 of the 15 questions (p < 0.05). Survey respondents reported similar degrees of knowledge and comfort in recognizing unmet needs in a hospital setting and formulating a comprehensive statement describing them. Conclusion The principles of biomedical engineering are integral to advancing the field of surgery. Presently, a small cohort of medical students/residents successfully acquired and applied basic BME concepts in a relatively short period of time relative to other training paradigms. Our findings also suggest medical students recognize unmet needs in the hospital setting, and those who completed a BME course felt more able to take steps to meet those needs. Early integration of biomedical engineering principles in medical training may help produce more innovative and well-rounded surgeons.

Cardiac tissue surrogates show promise for restoring mechanical and electrical function in infarcted left ventricular (LV) myocardium. For these cardiac surrogates to be usefulin vivo, they are required to support synchronous and forceful contraction over the infarcted region. These design requirements necessitate a thickness sufficient to produce a useful contractile force, an area large enough to cover an infarcted region, and prevascularization to overcome diffusion limitations. Attempts to meet these requirements have been hampered by diffusion limits of oxygen and nutrients (100-200 µm) leading to necrotic regions. This study demonstrates a novel layer-by-layer (LbL) fabrication method used to produce tissue surrogates that meet these requirements and mimic normal myocardium in form and function. Thick (1.5-2 mm) LbL cardiac tissues created from human induced pluripotent stem cell-derived cardiomyocytes and endothelial cells were assessed,in vitro, over a 4-week period for viability (<5.6 ± 1.4% nectrotic cells), cell morphology, viscoelastic properties and functionality. Viscoelastic properties of the cardiac surrogates were determined via stress relaxation response modeling and compared to native murine LV tissue. Viscoelastic characterization showed that the generalized Maxwell model of order 4 described the samples well (0.7 <R2< 0.98). Functional performance assessment showed enhanced t-tubule network development, gap junction communication as well as conduction velocity (16.9 ± 2.3 cm s-1). These results demonstrate that LbL fabrication can be utilized successfully in creating complex, functional cardiac surrogates for potential therapeutic applications.

The rapidly changing healthcare landscape requires continuous innovation by clinicians, yet generating ideas to improve patient care is often problematic. This paper describes the development of a digital tool used in an interprofessional program designed to enhance collaborations between clinicians, undergraduate, and graduate STEM students, particularly biomedical engineering (BME). The program founders began by connecting clinicians and students through a course portal in a learning management system (LMS). They eventually secured internal funding to create an open access tool for posting and viewing problems, allowing interprofessional teams to rally around healthcare challenges and create prototypes for solving them. Results after three years of the program's inception have been encouraging, as teams have created devices and processes that have led to intellectual property disclosures, provisional patents, grant funding, and other productive interprofessional relationships. The open access tool has given clinicians and STEM students an outlet for convenient team formation around unsolved clinical problems and allowed a fluid exchange of ideas between participants across a variety of clinical disciplines.

Abstract Background There is substantial interest in electrospun scaffolds as substrates for tissue regeneration and repair due to their fibrous, extracellular matrix-like composition with interconnected porosity, cost-effective production, and scalability. However, a common limitation of these scaffolds is their inherently low mechanical strength and stiffness, restricting their use in some clinical applications. In this study we developed a novel technique for 3D printing a mesh reinforcement on electrospun scaffolds to improve their mechanical properties. Methods A poly (lactic acid) (PLA) mesh was 3D-printed directly onto electrospun scaffolds composed of a 40:60 ratio of poly(ε-caprolactone) (PCL) to gelatin, respectively. PLA grids were printed onto the electrospun scaffolds with either a 6 mm or 8 mm distance between the struts. Scanning electron microscopy was utilized to determine if the 3D printing process affected the archtitecture of the electrospun scaffold. Tensile testing was used to ascertain mechanical properties (strength, modulus, failure stress, ductility) of both unmodified and reinforced electrospun scaffolds. An in vivo bone graft model was used to assess biocompatibility. Specifically, reinforced scaffolds were used as a membrane cover for bone graft particles implanted into rat calvarial defects, and implant sites were examined histologically. Results We determined that the tensile strength and elastic modulus were markedly increased, and ductility reduced, by the addition of the PLA meshes to the electrospun scaffolds. Furthermore, the scaffolds maintained their matrix-like structure after being reinforced with the 3D printed PLA. There was no indication at the graft/tissue interface that the reinforced electrospun scaffolds elicited an immune or foreign body response upon implantation into rat cranial defects. Conclusion 3D-printed mesh reinforcements offer a new tool for enhancing the mechanical strength of electrospun scaffolds while preserving the advantageous extracellular matrix-like architecture. The modification of electrospun scaffolds with 3D-printed reinforcements is expected to expand the range of clinical applications for which electrospun materials may be suitable.

Cardiac tamponade is a life-threatening compression of the heart due to accumulation of fluid surrounding the heart. It occurs in two out of 10 000 people annually and is universally fatal if the fluid is not timely drained.1 The more rapidly accumulation occurs, the quicker the patient develops symptoms, including dyspnoea, fatigue and chest pain.2 Vital sign changes include tachycardia, tachypnoea and hypotension with a narrow pulse pressure. Pericardiocentesis is the required treatment to drain this fluid improving cardiac output.3 Simulation is an adjunct education tool to practise rare but crucial procedures.1 Current manikins do not have the capabilities to practise pericardiocentesis. Only torso task trainers are available.4 5 Our objective was to develop a pericardiocentesis trainer model that could both reliably recreate the procedure and be placed in a manikin, with no fluid leakage. ### Model assembly and design The Department of Biomedical Engineering collaborated with the Department of Pediatrics to build an inexpensive pericardiocentesis model with the following constraints: 1. Fit existing child simulators without significant chest wall distortion. 2. Have components to protect simulator both structurally and electronically from fluid spills using self-sealing technology. 3. Provide realistic fluid removal. 4. Have easily refillable fluid compartment that does not require direct access to task trainer. 5. Costs less than $500 budget. The final design encompasses a two-piece tray system, a top and bottom tray, attached by a peg …

Beginning in the 1970s, device retrieval analysis was conducted at our institution, the University of Alabama at Birmingham, to better understand surgical implant device biocompatibilities through studies of element (biomaterial) and force (biomechanical) transfers at host-device interfaces. Multidisciplinary investigations were initiated from analyses of clinical outcomes and examination of explants. Analyses included physical, mechanical, chemical, electrical, and combinations thereof for orthopedic and dental implants fabricated from synthetic origin biomaterials, with more than 8,000 specimens received. Hypotheses were tested concerning cause-effect relationships using a tiered classification approach, which resulted in peer-reviewed presentations and publications (STP1560, Metal-on Metal Total Hip Replacement, and STP1591, Modularity and Tapers in Total Joint Replacement Devices). In the 1990s, the focus evolved to include the analysis of function of implants obtained through postmortem retrieval, with more than 1,000 "en bloc" specimens collected. Opportunities included longer-term evaluations of human outcomes for devices that were in place and functional at the time of donation. Direct comparisons of devices and tissues with laboratory and in vivo studies tested theories about cause-effect relationships. Selected studies are presented as examples that include the application of calcium phosphate coatings, particulates and porous blocks for bone grafting with dental implants, and surface stability of a contemporary total knee replacement intended to reduce the generation of wear debris. We conclude with recommendations for expanded analysis of postmortem specimens by qualified investigators as input to new consensus standards.

There exists a need for educational processes in which students gain experience with design and commercialization of medical devices. This manuscript describes the implementation of, and assessment results from, the first year offering of a project course sequence in Master of Engineering (MEng) in Design and Commercialization at our institution. The three-semester course sequence focused on developing and applying hands-on skills that contribute to product development to address medical device needs found within our university hospital and local community. The first semester integrated computer-aided drawing (CAD) as preparation for manufacturing of device-related components (hand machining, computer numeric control (CNC), three-dimensional (3D) printing, and plastics molding), followed by an introduction to microcontrollers (MCUs) and printed circuit boards (PCBs) for associated electronics and control systems. In the second semester, the students applied these skills on a unified project, working together to construct and test multiple weighing scales for wheelchair users. In the final semester, the students applied industrial design concepts to four distinct device designs, including user and context reassessment, human factors (functional and aesthetic) design refinement, and advanced visualization for commercialization. The assessment results are described, along with lessons learned and plans for enhancement of the course sequence.

It is well documented that electrospun tissue engineering scaffolds can be fabricated with variable degrees of fiber alignment to produce scaffolds with anisotropic mechanical properties. Several attempts have been made to quantify the degree of fiber alignment within an electrospun scaffold using image-based methods. However, these methods are limited by the inability to produce a quantitative measure of alignment that can be used to make comparisons across publications. Therefore, we have developed a new approach to quantifying the alignment present within a scaffold from scanning electron microscopic (SEM) images. The alignment is determined by using the Sobel approximation of the image gradient to determine the distribution of gradient angles with an image. This data was fit to a Von Mises distribution to find the dispersion parameter κ, which was used as a quantitative measure of fiber alignment. We fabricated four groups of electrospun polycaprolactone (PCL) + Gelatin scaffolds with alignments ranging from κ = 1.9 (aligned) to κ = 0.25 (random) and tested our alignment quantification method on these scaffolds. It was found that our alignment quantification method could distinguish between scaffolds of different alignments more accurately than two other published methods. Additionally, the alignment parameter κ was found to be a good predictor the mechanical anisotropy of our electrospun scaffolds. The ability to quantify fiber alignment within and make direct comparisons of scaffold fiber alignment across publications can reduce ambiguity between published results where cells are cultured on "highly aligned" fibrous scaffolds. This could have important implications for characterizing mechanics and cellular behavior on aligned tissue engineering scaffolds. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1680-1686, 2016.

There is a global shift in the teaching methodology of science and engineering toward multidisciplinary, team-based processes. To meet the demands of an evolving technical industry and lead the way in engineering education, innovative curricula are essential. This paper describes the development of multidisciplinary, team-based learning environments in undergraduate and graduate engineering curricula focused on medical device design. In these programs, students actively collaborate with clinicians, professional engineers, business professionals, and their peers to develop innovative solutions to real-world problems. In the undergraduate senior capstone courses, teams of biomedical engineering (BME) and business students have produced and delivered numerous functional prototypes to satisfied clients. Pursuit of commercialization of devices has led to intellectual property (IP) disclosures and patents. Assessments have indicated high levels of success in attainment of student learning outcomes and student satisfaction with their undergraduate design experience. To advance these projects toward commercialization and further promote innovative team-based learning, a Master of Engineering (MEng) in Design and Commercialization was recently launched. The MEng facilitates teams of graduate students in engineering, life sciences, and business who engage in innovation-commercialization (IC) projects and coursework that take innovative ideas through research and development (R&D) to create marketable devices. The activities are structured with students working together as a “virtual company,” with targeted outcomes of commercialization (license agreements and new start-ups), competitive job placement, and/or career advancement.

Accessible high-capacity weighing scales are scarce in healthcare facilities, in part due to high device cost and weight. This shortage impairs weight monitoring and health maintenance for people with disabilities and/or morbid obesity. We conducted this study to design and validate a lighter, lower cost, high-capacity accessible weighing device. A prototype featuring 360kg (800 lbs) of weight capacity, a wheelchair-accessible ramp, and wireless data transmission was fabricated. Forty-five participants (20 standing, 20 manual wheelchair users, and five power wheelchair users) were weighed using the prototype and a calibrated scale. Participants were surveyed to assess perception of each weighing device and the weighing procedure. Weight measurements between devices demonstrated a strong linear correlation (R-2=0.997) with absolute differences of 1.4 +/- 2.0% (mean +/- SD). Participant preference ratings showed no difference between devices. The prototype weighed 11kg (38%) less than the next lightest high-capacity commercial device found by author survey. The prototype's estimated commercial price range, $500-$600, is approximately half the price of the least expensive commercial device found by author survey. Such low cost weighing devices may improve access to weighing instrumentation, which may in turn help eliminate current health disparities. Future work is needed to determine the feasibility of market transition.

Category: Hindfoot Introduction/Purpose: Hindfoot arthrodesis is often the treatment of choice for hindfoot pain due to arthritis or advanced deformity. Good results are dependent on secure fixation while avoiding hardware related side effects. A small radiolucent locking dorsal circular plate placed into the talonavicular and calcaneocuboid joints may provide a low-profile solution for secure fixation of these joints. The goal of this study is to compare the fixation strength of a locking dorsal circular plate to that of the current gold standard technique of screw fixation. Methods: Eight matched fresh-frozen cadaveric foot-ankle pairs were obtained for comparison of the two fixation methods. One side of each matched pair was plated with a locking dorsal circular plate and the contralateral foot was fixed with partially threaded 4.5 mm cannulated screws. All subtalar joints were fixed with two 7.3 mm cannulated screws. Translational forces through a mechanical testing system (MTS) were applied to the constructs cyclically for 40 cycles followed by loading to failure. Displacement was recorded using two high-speed infrared cameras, following sets of orthogonal marker systems attached to each bone. Results: Cyclical loading trials found there to be no significant difference in resistance to motion between the two methods. However, specimens instrumented with plates had an approximately 400% higher load to failure (513.3 N vs 127.7 N) than specimens instrumented with screws. Conclusion: Locking dorsal circular plates are a viable option that provide equivalent and possibly better fixation strength than screw fixation for the talonavicular and calcaneocuboid components of a triple arthrodesis of the hindfoot. These plates are radiolucent allowing easy assessment of the fusion site. In addition, these plates have the theoretical benefit of being low profile to decrease tendon irritation and wound healing problems.

Osteocalcin, also known as bone γ-carboxyglutamate protein (Bglap), is expressed by osteoblasts and is commonly used as a clinical marker of bone turnover. A mouse model of osteocalcin deficiency has implicated osteocalcin as a mediator of changes to the skeleton, endocrine system, reproductive organs and central nervous system. However, differences between mouse and human osteocalcin at both the genome and protein levels have challenged the validity of extrapolating findings from the osteocalcin-deficient mouse model to human disease. The rat osteocalcin (Bglap) gene locus shares greater synteny with that of humans. To further examine the role of osteocalcin in disease, we created a rat model with complete loss of osteocalcin using the CRISPR/Cas9 system. Rat osteocalcin was modified by injection of CRISPR/Cas9 mRNA into the pronuclei of fertilized single cell Sprague-Dawley embryos, and animals were bred to homozygosity and compound heterozygosity for the mutant alleles. Dual-energy X-ray absorptiometry (DXA), glucose tolerance testing (GTT), insulin tolerance testing (ITT), microcomputed tomography (µCT), and a three-point break biomechanical assay were performed on the excised femurs at 5 months of age. Complete loss of osteocalcin resulted in bones with significantly increased trabecular thickness, density and volume. Cortical bone volume and density were not increased in null animals. The bones had improved functional quality as evidenced by an increase in failure load during the biomechanical stress assay. Differences in glucose homeostasis were observed between groups, but there were no differences in body weight or composition. This rat model of complete loss of osteocalcin provides a platform for further understanding the role of osteocalcin in disease, and it is a novel model of increased bone formation with potential utility in osteoporosis and osteoarthritis research.

One approach to encourage and facilitate exercise is through interaction with virtual environments. The present study assessed the utility of Microsoft Kinect as an interface for choosing between multiple routes within a virtual environment through body gestures and voice commands. The approach was successfully tested on 12 individuals post-stroke and 15 individuals with cerebral palsy (CP). Participants rated their perception of difficulty in completing each gesture using a 5-point Likert scale questionnaire. The "most viable" gestures were defined as those with average success rates of 90% or higher and perception of difficulty ranging between easy and very easy. For those with CP, hand raises, hand extensions, and head nod gestures were found most viable. For those post-stroke, the most viable gestures were torso twists, head nods, as well as hand raises and hand extensions using the less impaired hand. Voice commands containing two syllables were viable (>85% successful) for those post-stroke; however, participants with CP were unable to complete any voice commands with a high success rate. This study demonstrated that Kinect may be useful for persons with mobility impairments to interface with virtual exercise environments, but the effectiveness of the various gestures depends upon the disability of the user.

BACKGROUND:Good outcomes have been described for pediatric lateral condyle fractures treated by open reduction and fixation using either screws or Kirschner wires (K-wires). No studies have compared the biomechanical properties of the 2 fixation methods. We hypothesized that screw fixation would be more biomechanically stable than K-wire fixation.METHODS:Synthetic humerus models were used for biomechanical testing, following a previously published protocol. A miter saw was used to make an oblique cut to simulate a Milch type II fracture. Fractures were anatomically reduced and fixed with either 2 divergent 0.062-inch K-wires placed bicortically or a 4.0-mm lag screw placed obliquely (perpendicular to the fracture line). Specimens were then embedded in polymethyl methacrylate bone cement for testing. Mechanical testing using displacement control was performed applying compression or distraction from 0 to 1.5 mm at a rate of 0.5 mm/s for 10 cycles. The maximum force was calculated based on the maximum force averaged over the 10 cycles. Stiffness was calculated based on the slope of the force-displacement curve of the 10th cycle. A 2-sample t test was used to determine significant differences between the stiffness and maximum force comparing the K-wire and screw groups. A P-value of <0.05 was considered statistically significant.RESULTS:Stiffness and maximum force in tension testing were significantly greater with screw fixation compared with K-wire fixation. Testing in compression revealed statistically significant increased maximum force and a trend towards increased stiffness.CONCLUSION:Screw fixation in a synthetic bone model of pediatric lateral condyle fractures (Milch type II) provides increased biomechanical stability of the construct as compared with K-wires.CLINICAL RELEVANCE:If similar effects were seen in vivo, increased biomechanical stability with screw fixation could decrease the occurrence of complications such as loss of reduction and nonunion.

Purpose To compare and analyze biomechanical properties and histological characteristics of flexor tendons either repaired by a 4-strand modified Kessler technique or using barbed suture with a knotless repair technique in an in vivo model.Methods A total of 25 chickens underwent surgical transection of the flexor digitorum profundus tendon followed by either a 4-strand Kessler repair or a knotless repair with barbed suture. Chickens were randomly assigned to 1 of 3 groups with various postoperative times to death. Harvested tendons were subjected to biomechanical testing or histologic analysis.Results Harvested tendons revealed failures in 25% of knotless repairs (8 of 32) and 8% of 4-strand Kessler repairs (2 of 24). Biomechanical testing revealed no significant difference in tensile strength between 4-strand Kessler and barbed repairs; however, this lack of difference may be attributed to lower statistical power. We noted a trend toward a gradual decrease in strength over time for barbed repairs, whereas we noticed the opposite for the 4-strand Kessler repairs. Mode of failure during testing differed between repair types. The barbed repairs tended toward suture breakage as opposed to 4-strand Kessler repairs, which demonstrated suture pullout. Histological analysis identified no difference in the degree of inflammation or fibrosis; however, there was a vigorous foreign body reaction. around the 4-strand Kessler repair and no such response around the barbed repairs.Conclusions In this model, knotless barbed repairs trended toward higher in vivo failure rates and biomechanical inferiority under physiologic conditions, with each repair technique differing in mode of failure and respective histologic reaction. We are unable to recommend the use of knotless barbed repair over the 4-strand modified Kessler technique.Clinical relevance For the repair techniques tested, surgeons should prefer standard Kessler repairs over the described knotless technique with barbed suture. Copyright (C) 2015 by the American Society for Surgery of the Hand. All rights reserved.

Purpose To determine biomechanical differences between a fixed-angle locking volar titanium plate (VariAx; Stryker, Kalamazoo, MI) and a fixed-angle compression locking volar stainless steel plate (CoverLoc Volar Plate; Tornier, Amsterdam, Netherlands) in the fixation of simulated AO C3 distal radius fractures.Methods Eighteen cadaveric upper extremities (9 matched pairs) with an average age of 54 years were tested. A 4-part AO C3 fracture pattern was created in each specimen. The fractures were reduced under direct vision and fixed with either the fixed-angle locking volar titanium plate or the fixed-angle compression locking volar stainless steel plate. Motion tracking analysis was then performed while the specimens underwent cyclic loading. Changes in displacement, rotation, load to failure, and mode of failure were recorded.Results The fragments, when secured with the fixed-angle compression locking stainless steel construct, demonstrated less displacement and rotation than the fragments secured with the fixed-angle locking titanium plate under physiological loading conditions. In the fixed-angle compression locking stainless steel group, aggregate displacement and rotation of fracture fragments were 5 mm and 3 less, respectively, than those for the fixed-angle locking titanium group. The differences between axial loads at mechanical failure and stiffness were not statistically significant. The compression locking stainless steel group showed no trend in mode of failure, and the locking titanium plate group failed most often by articular fixation failure (5 of 9 specimens).Conclusions The fixed-angle compression locking stainless steel volar plate may result in less displacement and rotation of fracture fragments in the fixation of AO C3 distal radius fractures than fixation by the fixed-angle locking volar titanium plate. However, there were no differences between the plates in mechanical load to failure and stiffness.Clinical relevance Fixation of distal radius AO C3 fracture patterns with the fixed-angle compression locking stainless steel plate may provide improved stability of fracture fragments. (J Hand Surg Am. 2015;40( 10):2032-2038. Copyright (C) 2015 by the American Society for Surgery of the Hand. All rights reserved.)