The influence of distal screw length on the primary stability of volar plate osteosynthesis-a biomechanical study

Background: Extensor tendon irritation is one of the most common complications following volar locking plate osteosynthesis (VLPO) for distal radius fractures. It is most likely caused by distal screws protruding the dorsal cortex. Shorter distal screws could avoid this, yet the influence of distal screw length on the primary stability in VLPO is unknown. The aim of this study was to compare 75 to 100 % distal screw lengths in VLPO. Methods: A biomechanical study was conducted on 11 paired fresh-frozen radii. HRpQCT scans were performed to assess bone mineral density (BMD) and bone mineral content (BMC). The specimens were randomized pair-wise into two groups: 100 % (group A) and 75 % (group B) unicortical distal screw lengths. A validated fracture model for extra-articular distal radius fractures (AO-23 A3) was used. Polyaxial volar locking plates were mounted, and distal screws was inserted using a drill guide block. For group A, the distal screw tips were intended to be flush or just short of the dorsal cortex. In group B, a target screw length of 75 % was calculated. The specimens were tested to failure using a displacement-controlled axial compression test. Primary biomechanical stability was assessed by stiffness, elastic limit, and maximum force as well as with residual tilt, which quantified plastic deformation. Results: Nine specimens were tested successfully. BMD and BMC did not differ between the two groups. The mean distal screw length of group A was 21.7 +/- 2.6 mm (range: 16 to 26 mm),for group B 16.9 +/- 1.9 mm (range: 12 to 20 mm). Distal screws in group B were on average 5.6 +/- 0.9 mm (range: 3 to 7 mm) shorter than measured. No significant differences were found for stiffness (706 +/- 103 N/mm vs. 660 +/- 124 N/mm),elastic limit (177 +/- 25 N vs. 167 +/- 36 N),maximum force (493 +/- 139 N vs. 471 +/- 149 N),or residual tilt (7.3 degrees +/- 0.7 degrees vs. 7.1 degrees +/- 1.3 degrees). Conclusion: The 75 % distal screw length in VLPO provides similar primary stability to 100 % unicortical screw length. This study, for the first time, provides the biomechanical basis to choose distal screws significantly shorter then measured

The influence of distal screw length on the primary stability of volar plate osteosynthesis-a biomechanical study

Background: Extensor tendon irritation is one of the most common complications following volar locking plate osteosynthesis (VLPO) for distal radius fractures. It is most likely caused by distal screws protruding the dorsal cortex. Shorter distal screws could avoid this, yet the influence of distal screw length on the primary stability in VLPO is unknown. The aim of this study was to compare 75 to 100 % distal screw lengths in VLPO. Methods: A biomechanical study was conducted on 11 paired fresh-frozen radii. HRpQCT scans were performed to assess bone mineral density (BMD) and bone mineral content (BMC). The specimens were randomized pair-wise into two groups: 100 % (group A) and 75 % (group B) unicortical distal screw lengths. A validated fracture model for extra-articular distal radius fractures (AO-23 A3) was used. Polyaxial volar locking plates were mounted, and distal screws was inserted using a drill guide block. For group A, the distal screw tips were intended to be flush or just short of the dorsal cortex. In group B, a target screw length of 75 % was calculated. The specimens were tested to failure using a displacement-controlled axial compression test. Primary biomechanical stability was assessed by stiffness, elastic limit, and maximum force as well as with residual tilt, which quantified plastic deformation. Results: Nine specimens were tested successfully. BMD and BMC did not differ between the two groups. The mean distal screw length of group A was 21.7 +/- 2.6 mm (range: 16 to 26 mm),for group B 16.9 +/- 1.9 mm (range: 12 to 20 mm). Distal screws in group B were on average 5.6 +/- 0.9 mm (range: 3 to 7 mm) shorter than measured. No significant differences were found for stiffness (706 +/- 103 N/mm vs. 660 +/- 124 N/mm),elastic limit (177 +/- 25 N vs. 167 +/- 36 N),maximum force (493 +/- 139 N vs. 471 +/- 149 N),or residual tilt (7.3 degrees +/- 0.7 degrees vs. 7.1 degrees +/- 1.3 degrees). Conclusion: The 75 % distal screw length in VLPO provides similar primary stability to 100 % unicortical screw length. This study, for the first time, provides the biomechanical basis to choose distal screws significantly shorter then measured

Supplementary information for the article: Djinović, Z., Pavelka, R., Tomić, M., Sprinzl, G., Müller, J. G., & Traxler, H. (2021). Experimental study of an implantable fiber-optic microphone on human cadavers. Hearing Research, 410, 108351. https://doi.org/10.1016/j.heares.2021.108351

In the supplement, a few audio records in a time duration of about 1-3 min, which are acquired during experiments performed on skull head #7587, are given. The signals have been on-line processed by TIFOS system and recorded by an HP notebook audiocard without any frequency equalizing. The sound pressure level was measured by Bruel & Kjaer 2250 sound meter (dBA, slow). The sound of piano and violin in Schubert’s Rondo in Fig. S1a are of high fidelity. High frequency tones in the aria from “La-Traviata” performed by famous Russian-Austrian operatic soprano Anna Netrebko (Fig. S1d) are also very clear and dynamic. The famous speech of Martin Luther King (Fig. S1b) is completely intelligible, as well as the resignation speech of former British prime minister Theresa May (Fig. S1c). The individual characteristics of the well-known voices are easily recognizable.Related to the peer-reviewed manuscript: [https://hdl.handle.net/21.15107/rcub_dais_12143]Supplementary information for the article: [http://dx.doi.org/10.1016/j.heares.2021.108351]Related to the published version: [https://hdl.handle.net/21.15107/rcub_dais_12259

Using self-drilling screws in volar plate osteosynthesis for distal radius fractures: a feasibility study

Background: Symptomatic extensor tendon irritation is a frequent complication in volar plate osteosynthesis of distal radius fractures. It is typically caused by dorsal screw protrusion and overdrilling of the dorsal cortex. The use of self-drilling locking screws (SDLS) could overcome both causes. The practical applicability of SDLS depends on two prerequisites: (1) the feasibility of preoperative distal screw length determination, and (2) sufficient primary biomechanical stability of SDLS compared to standard locking screws (SLS). Methods: We first assessed the feasibility of preoperative screw length determination (1): Distal radius width, depth and distal screw lengths were measured in 38 human radii. Correlations between distal radius width and depth were assessed, a cluster analysis (Ward's method and squared Euclidean distance) for distal radius width conducted, and intra-cluster screw lengths analyzed (ANOVA). The biomechanical performance of SDLS (2) was assessed by comparison to SLS in a distal radius fracture model (AO-23 A3). 75 % distal screw length was chosen for both groups to simulate a worst-case scenario. Uniaxial compression tests were conducted to measure stiffness, elastic limit, maximum force and residual tilt. Statistics comprised of independent sample t-tests and a Bonferroni correction (p 36.9 mm. ANOVA and Tukey post-hoc analysis revealed significantly different volar-dorsal depths (p < 0.05) for nearly all screws. (2) To assess biomechanical stability nine specimens were tested each;no significant differences were found between the SDLS and SLS groups. Conclusions: This feasibility study demonstrates that (1) distal radius width can be used as a predictor for distal screw length and (2) that SDLS provides mechanical stability equivalent to SLS. These results highlight the feasibility of applying SDLS screws in volar plate osteosynthesis at least in extraarticular fractures

Assessment of a novel biomechanical fracture model for distal radius fractures

Background: Distal radius fractures (DRF) are one of the most common fractures and often need surgical treatment, which has been validated through biomechanical tests. Currently a number of different fracture models are used, none of which resemble the in vivo fracture location. The aim of the study was to develop a new standardized fracture model for DRF (AO-23.A3) and compare its biomechanical behavior to the current gold standard. Methods: Variable angle locking volar plates (ADAPTIVE, Medartis) were mounted on 10 pairs of fresh-frozen radii. The osteotomy location was alternated within each pair (New: 10 mm wedge 8 mm / 12 mm proximal to the dorsal / volar apex of the articular surface; Gold standard: 10 mm wedge 20 mm proximal to the articular surface). Each specimen was tested in cyclic axial compression (increasing load by 100 N per cycle) until failure or -3 mm displacement. Parameters assessed were stiffness, displacement and dissipated work calculated for each cycle and ultimate load. Significance was tested using a linear mixed model and Wald test as well as t-tests. Results: 7 female and 3 male pairs of radii aged 74 +/- 9 years were tested. In most cases (7/10), the two groups showed similar mechanical behavior at low loads with increasing differences at increasing loads. Overall the novel fracture model showed a significant different biomechanical behavior than the gold standard model (p < 0,001). The average final loads resisted were significantly lower in the novel model (860 N +/- 232 N vs. 1250 N +/- 341 N; p = 0.001). Conclusion: The novel biomechanical fracture model for DRF more closely mimics the in vivo fracture site and shows a significantly different biomechanical behavior with increasing loads when compared to the current gold standard

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

Background: During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA. Materials and Methods: An MS TKA was performed in seven fresh-frozen human specimens successively with 0 degrees, 3 degrees, and 6 degrees of PTS. After each modification, weight-bearing deep knee flexion (30-130 degrees) was performed, and femorotibial kinematics were analyzed. Results: A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0 degrees PTS anterior tibial translation -9.09 (+/- 9.19) mm, 3 degrees PTS anterior tibial translation -11.03 (+/- 6.72) mm, 6 degrees PTS anterior tibial translation 11.86 (+/- 9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3 degrees PTS, the design-specific medial rotation point was achieved more accurately. Conclusions: According to our findings, we recommend a PTS of 3 degrees when implanting the MS prosthesis used in this study

An International Partnership of 12 Anatomy Departments - Improving Global Health through Internationalization of Medical Education

Background: At a time of global interconnectedness, the internationalization of medical education has become important. Anatomy as an academic discipline, with its close connections to the basic sciences and to medical education, can easily be connected with global health and internationalization of medical education. Here the authors present an international program based on a partnership between twelve anatomy departments in ten countries, on four continents. Details of a proposed plan for the future direction of the program are also discussed. Objective: The aim is to improve global healthcare by preparing future global healthcare leaders via early international networking, international collaboration and exchange, intercultural experience, and connecting two seemingly distant academic disciplines - anatomy and global health - via internationalization of medical education. Methods: Based in the anatomy course, the program involved early international collaboration between preclinical medical and dental students. The program provided a stepwise progression for learning about healthcare and intercultural topics beyond pure anatomy education - starting with virtual small groups of international students, who subsequently presented their work to a larger international audience during group videoconferences. The above progressed to in-person visits for research internships in the basic sciences within industrialized countries. Findings: Students appreciated the international and intercultural interaction, learned about areas outside the scope of anatomy (e.g., differences in healthcare education and delivery systems, Public and Global Health challenges, health ethics, and cultural enrichment), and valued the exchange travel for basic sciences research internships and cultural experience. Conclusions: This unique collaboration of international anatomy departments can represent a new role for the medical anatomy course beyond pure anatomy teaching - involving areas of global health and internationalization of medical education - and could mark a new era of international collaboration among anatomists.Peer reviewe

Alternatives to Student Outbound Mobility-Improving Students' Cultural Competency Skills Online to Improve Global Health Without Travel.

INTRODUCTION: Student outbound mobility is a major element in internationalization of medical education and global health education. However, this approach is often criticized, as it is inherently inequitable. Internationalization at home is a newer concept that aims to provide students with international skills and experiences without exchange travel. We report detailed outcomes of an international online program during the COVID-19 pandemic, which aimed to include acquisition of cultural awareness and competency-similar to what the students would have obtained if they had travelled abroad. METHOD: Sixty-eight students from 12 international universities participated in international small peer group collaborative work, and online networking. Perceived improvement of cultural competency using Likert scale and open-ended questions was used as a measure of success. Furthermore, students' definition of cultural competency in the different countries was obtained. RESULTS: Students improved their cultural competency skills. Data analysis supported statistically significant improvement of the above skills after the program, in comparison to the start of the program. DISCUSSION: Internationalization of medical education can be achieved at home-via structured online peer exchanges-and can provide students with intercultural skills and networking opportunities that are typically achieved via international in-person travel. The above represents a socially just and equitable way to reach all students and can result in improvement of their cultural competency, preparing them for their work in global health, and thereby resulting in improvement of global health. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40670-021-01332-9

Simultaneous Modification of Properties Relevant to the Processing and Application of Virgin and Post-Consumer Polypropylene

Post-consumer recyclates often have a property profile that results from mixing a variety of products, which are made from different materials, produced by different processing methods, and coming from applications with different lifetimes. This usually leads to a mixture of all these material properties in the recycling process. In contrast, virgin materials are specifically designed for applications and thus offer all the necessary properties for the intended products. In order to be able to use recycled materials for specific and demanding applications, not only the viscosity, which is important for processing and often varies greatly with recyclates, but also the mechanical properties, particularly the tensile modulus and impact strength, must be adjusted. For this purpose, various virgin materials of polypropylene homopolymers, random copolymers, and block copolymers with different flowabilities were mixed in different proportions and their properties were determined. The flowability of homopolymers and random copolymers in the blend behaved very similarly, while block copolymers exhibited a different behavior in some cases. By incorporating homopolymers into blends, the stiffness of the resulting material blend can be very well adjusted. The addition of random copolymers can increase strain at break, and the addition of block copolymers results in a significant increase in impact strength. In numbers, the maximum adjustment range for tensile modulus, yield stress, strain at break, and impact strength are 880 MPa, 14 MPa, 185%, and 6.9 kJ/m2, respectively. While a good and reliable prediction of property profile is possible for polymer blends with different virgin materials, the resulting material properties for polymer blends of virgin and recycled materials are also influenced by impurities. In this work, however, a good prediction was also achieved for recyclate blends

Assessment of a novel biomechanical fracture model for distal radius fractures

Background: Distal radius fractures (DRF) are one of the most common fractures and often need surgical treatment, which has been validated through biomechanical tests. Currently a number of different fracture models are used, none of which resemble the in vivo fracture location. The aim of the study was to develop a new standardized fracture model for DRF (AO-23.A3) and compare its biomechanical behavior to the current gold standard. Methods: Variable angle locking volar plates (ADAPTIVE, Medartis) were mounted on 10 pairs of fresh-frozen radii. The osteotomy location was alternated within each pair (New: 10 mm wedge 8 mm / 12 mm proximal to the dorsal / volar apex of the articular surface; Gold standard: 10 mm wedge 20 mm proximal to the articular surface). Each specimen was tested in cyclic axial compression (increasing load by 100 N per cycle) until failure or -3 mm displacement. Parameters assessed were stiffness, displacement and dissipated work calculated for each cycle and ultimate load. Significance was tested using a linear mixed model and Wald test as well as t-tests. Results: 7 female and 3 male pairs of radii aged 74 +/- 9 years were tested. In most cases (7/10), the two groups showed similar mechanical behavior at low loads with increasing differences at increasing loads. Overall the novel fracture model showed a significant different biomechanical behavior than the gold standard model (p < 0,001). The average final loads resisted were significantly lower in the novel model (860 N +/- 232 N vs. 1250 N +/- 341 N; p = 0.001). Conclusion: The novel biomechanical fracture model for DRF more closely mimics the in vivo fracture site and shows a significantly different biomechanical behavior with increasing loads when compared to the current gold standard