Interspecies differences in bone composition, density, and quality: potential implications for in vivo bone research

Biomechanical evaluation of the porcine carpus as a potential preclinical animal model for the human carpus

Advancing successful treatments for carpal instabilities of the wrist are hindered due, in part, to limited preclinical animal models. The purpose of this study was to evaluate the forelimb of the Yucatan minipig (YP) as a potential preclinical animal model for the human wrist by quantifying carpal biomechanics in vitro in the intact and after two ligament transection conditions. Porcine wrist biomechanics (n = 12, 5M, 7F) were determined in 28 range of motion (ROM) directions, in pronation-supination, and in volar-dorsal translation using a six-axis robotic musculoskeletal simulator. Testing was implemented in three conditions - intact, and after sequential transection of the radial intermediate ligament (RIL) and the dorsal intercarpal ligament (DIC). Mixed models were employed to examine differences in direction and conditions among male and female specimens. The intact ROM envelope was elliptical in shape and oriented toward ulnar flexion with the largest ROM about 15° from the flexion-extension axis. Transection of RIL and DIC did not alter the ROM envelope orientation, however, subtle increases in ROM were observed in extension and radial deviation following transection of both RIL and DIC. Pronation in neutral was greater than supination in all three test conditions. Volar translation increased subtly in the RIL and DIC condition. This novel study investigated the multidirectional biomechanics of the YP forelimb. ROM in the general directions of extension, radial and ulnar deviation were less than in humans, while flexion was substantially larger. These specific ligament transections had minor effects on the biomechanics of the YP forelimb.

Biocompatibility and osteogenic capacity of additively manufactured biodegradable porous WE43 scaffolds: An in vivo study in a canine model

Magnesium is the most promising absorbable metallic implant material for bone regeneration and alloy WE43 is already FDA approved for cardiovascular applications. This study investigates the cyto- and biocompatibility of novel additively manufactured (AM) porous WE43 scaffolds as well as their osteogenic potential and degradation characteristics in an orthotopic canine bone defect model. The cytocompatibility was demonstrated using modified ISO 10993-conform extract-based indirect and direct assays, respectively. Additionally, degradation rates of WE43 scaffolds were quantified in vitro prior to absorption tests in vivo. Complete blood cell counts, blood biomarker analyses, blood trace element analyses as well as multi-organ histopathology demonstrated excellent biocompatibility of porous y WE43 scaffolds for bone defect repair. Micro-CT analyses further showed a relatively higher absorption rate during the initial four weeks upon implantation (i.e., 36 % ± 19 %) than between four and 12 weeks (41 % ± 14 %), respectively. Of note, the porous WE43 implants were surrounded by newly formed bony tissue as early as four weeks after implantation when unmineralized trabecular ingrowth was detected. After 12 weeks, a substantial amount of mineralized bone was detected inside and around the gradually disappearing implants. This first study on AM porous WE43 implants in canine bone defects demonstrates the potential of this alloy for in vivo applications in humans. Our data further underscore the need to control initial bulk absorption kinetics through surface modifications.

Post-blast histological changes to three animal bones exposed to close-range chemical detonation

A range of investigative practices to aid explosive-related death investigations currently exist, although the use of histopathological bone samples to diagnose blast exposure and the distance of individuals from the blast source has not been previously reported. Forensic histopathology has been used effectively on soft tissue samples to define blast-related injuries effectively, analysing human organs such as the lungs, brain, liver, and skeletal muscles, providing important and useful forensic pathology interpretations. However, no studies currently exist examining the post-blast histological changes in human or animal bones subjected to blasts for forensic pathology practice, despite the opportunity that hard tissue bone samples present, given their significantly lower rate of decomposition over soft tissue. This study presents the first evidence-based findings on the post-blast histological changes in three animal bones when exposed to close-range chemical detonation (C4). The study's qualitative findings highlight critical changes in the tissue architecture of three different animal bone sources due to blast effects with range from the blast source. This emphasises the potential use of histopathological bone sample analysis in future blast-related death investigations, while providing ideas to further explore this work using larger-scale experiments and post-blast case studies in aid of applying this work to human samples and forensic pathology practice.

Biomechanical Principles of Intramedullary Nails in Veterinary and Human Medicine

Intramedullary nails are specialized metal rods inserted into the medullary cavity of a fractured bone and secured to reduce load on the fracture site, provide stability, and permit healing. The purpose of this review is to highlight the biomechanics of orthopaedic intramedullary nailing, as well as discuss the biomechanical considerations that have shaped implant design and fixation technique in veterinary and human medicine. Relevant studies were included from the PubMed database and Google Scholar for discussion on the basic science and nail design of intramedullary nails. Implant design and implementation continues to progress, with new innovative designs currently under investigation. A lack of consensus remains on the superior implant material. Recent studies, particularly in human populations, have supported the use of reaming based on reoperation rates, nonunion rates, and dynamization. Design modifications, such as the expandable intramedullary nails and angle-stable interlocking designs, have been investigated as methods of improving cortical contact and resisting torsional stress. Intramedullary nailing is a valuable stabilization technique for long bone fractures across a variety of species. The technology continues to undergo design improvements in both veterinary and human medicine.

Factual observations of dynamic bone crushing

Dynamic bone-crushing, exemplified by the pig bone rib, is characterized thermo-mechanically in relation to the bone's microstructural characteristics. The cortical bone's dominant role consists of shielding the trabecular component by resisting deformation, sustaining high load levels, and ultimately cracking. Here we present a qualitative factual study to show that this behavior is the absolute opposite of its quasi-static counterpart in which the trabecular bone was found to play the dominant role. Using infrared thermography, we observed for the first time a significant localized temperature rise of up to 11 degrees Celsius in both cortical and trabecular damaging regions. Such observations call for additional clinically oriented research. Such a high contrast between static and dynamic failure mechanisms was not reported previously, and it paves the way for forensic-oriented studies in which the nature of the sustained load must be determined.

Influence of varus-producing distal femur osteotomy correction and hinge width in relation to hinge fractures: Biomechanical study on porcine femora

BACKGROUND

Hinge fractures in varus-producing distal femoral osteotomies (DFOs) lead to decreased axial and torsional stability. The purpose of this study was to assess (1) which hinge width has a high risk of hinge fracture in DFO for lateral opening wedge (LOW) and medial closing wedge (MCW) osteotomies, (2) which osteotomies allow for greater correction before risking a fracture, (3) whether patient-specific instrumentation (PSI) allows accurate hinge width planning.

METHODS

Thirty porcine femoral bones were divided into two groups: LOW, MCW with hinge widths of 5 mm, 7.5 mm, and 10 mm as subgroups. Osteotomies were performed in a PSI-navigated fashion. A force parallel to the longitudinal bone axis was applied in a uniaxial testing machine until a fracture occurred.

RESULTS

The maximum correction was 6.7 ± 1.1° for LOW and 13.4 ± 1.9° for MCW (β0 < 0.001, β1 = 0.002, β2 = 0.02, β3 = 0.005). The relative error of the planned hinge width compared with the actual hinge width was -3.7 ± 12.3% for LOW (P = 0.25) and 12.3 ± 13.1% for MCW (P = 0.003).

CONCLUSIONS

Increasing the hinge width allows for greater correction in MCW osteotomies. For LOW osteotomies, a smaller hinge width seems to be advantageous because it allows a greater correction without the risk of hinge fracture. With PSI-guided LOW osteotomies, the planned hinge width could be achieved intraoperatively with greater accuracy than with MCW osteotomies. However, the MCW osteotomy appears to be the preferred option when larger corrections are desired because a larger correction angle can be achieved without the risk of intraoperative hinge fracture.

FixThePig: a custom 3D-printed femoral intramedullary nailing for preclinical research applications

Background

Critical-size bone defects (CSBDs) pose significant challenges in clinical orthopaedics and traumatology. Developing reliable preclinical models that accurately simulate human conditions is crucial for translational research. This study addresses the need for a reliable preclinical model by evaluating the design and efficacy of a custom-made 3D-printed intramedullary nail (IMN) specifically for CSBDs in minipigs. The study aims to answer the following questions: Can a custom-made 3D-printed IMN be designed for femoral osteosynthesis in minipigs? Does the use of the custom-made IMN result in consistent and reproducible surgical procedure, particularly in the creation and fixation of CSBDs? Can the custom-made IMN effectively treat and promote bone consolidation of CSBDs?

Hypothesis

The custom-made 3D-printed IMN can be designed to effectively create, fix and treat CSBDs in minipigs, resulting in consistent surgical outcomes.

Materials and Methods

The IMN was designed based on CT scans of minipig femurs, considering factors such as femoral curvature, length, and medullary canal diameters. It was 3D-printed in titanium and evaluated through both in vitro and in vivo testing. Female Aachen minipigs underwent bilateral femoral surgeries to create and fix CSBDs using the custom-made IMN. Post-operative follow-up included X-rays and CT scans every 2 weeks, with manual examination of explanted femurs to assess consolidation and mechanical stability after 3 months.

Results

The custom-made IMN effectively fitted the minipig femoral anatomy and facilitated reproducible surgical outcomes. Symmetric double osteotomies were successfully performed, and allografts showed minimal morphological discrepancies. However, proximal fixation faced challenges, leading to non-union in several cases, while most distal osteotomy sites achieved stable consolidation.

Discussion

The custom-made 3D-printed IMN demonstrated potential in modelling and treating CSBDs in minipigs. While the design effectively supported distal bone healing, issues with proximal fixation highlight the need for further refinements. Potential improvements include better screw placement, additional mechanical support, and adaptations such as a reduction clamp or a cephalic screw to enhance stability and distribute forces more effectively.

A critical assessment of the diatom test of rib bone marrow as a supporting procedure in the case of drowning

Diatoms (Bacillariophyta), being single-celled photosynthetic organisms, are widely distributed in aquatic ecosystems around the globe. Their exoskeletons are resistant to most environmental factors as well as chemical reagents in laboratory settings. Moreover, the ornamentation featured on exoskeletons can be used to identify individual diatomaceous species. As a result, the detection of diatoms in the internal organs, and especially rib marrow, of corpses found in water can serve as an important tool for diagnosing drowning as the cause of death as long as passive postmortem penetration of diatoms into those organs is excluded. In the environmental experiments described in this paper, diatoms were detected in rib marrow only when contamination resulted from a mechanical breach of bone integrity and structure, irrespective of the residence time of bone material in the aquatic environment. Our research suggests that the presence of diatom in the rib marrow may be the gold standard in the diagnosis of drowning in the future. Our animal model research dispels one of the doubts, such as the possibility of passive penetration of diatoms into the bone marrow, which is still under discussion in the forensic medicine community.

Biomechanical comparison of ultra-high molecular weight polyethylene sutures of different thicknesses of the tensile strength for pullout repair of medial meniscal posterior root tear

Purpose

Medial meniscus posterior root tears (MMPRT) are a risk factor for knee osteoarthritis. The predominant treatment for MMPRT is transtibial pullout repair, and loop suture remains the gold standard procedure. This study aimed to investigate the structural properties of the meniscus-suture-tibia (MST) complex after loop stitch using ultra-high molecular weight polyethylene (UHMWPE) suture tape of different thicknesses.

Methods

This study used 20 fresh porcine MMPRT model knees. All specimens were randomised into two treatment groups: (1) pullout repair using 1.3 mm suture tape (thin group, n = 10; 1.3 mm PERMATAPE, Mitek Sports Medicine) fixation and (2) pullout repair using 2.5 mm suture tape (thick group, n = 10; 2.5 mm PERMATAPE, Mitek Sports Medicine) fixation. The single-loop stitch MS technique was utilised. The MST complex specimens were placed on a tensile tester. The structural properties of the MST complex (yield load, maximum load, liner stiffness, and elongation at failure) were identified.

Results

No significant differences were found between the thin and thick groups in terms of maximum load (108.8 ± 49.6 vs. 90.1 ± 33.6 N; p = 0.34), yield load (43.8 ± 15.2 vs. 39.4 ± 15.5 N; p = 0.53), liner stiffness (12.6 ± 8.4 vs. 11.2 ± 5.5 N/mm; p = 0.45), and elongation at failure (27.1 ± 19.4 vs. 19.9 ± 10.0 mm; p = 0.32).

Conclusion

The structural properties of the thickness of the different UHMWPE were comparable in MMPRT repair. Additionally, 1.3 mm PERMATAPE may demonstrate similar repair potential as 2.5 mm PERMATAPE.

Level of Evidence

Level Ⅳ.

Male porcine stifle joint: Insights into osteology and meniscus anatomy for orthopaedic research

INTRODUCTION

Utilizing large animal model like male pig for biomechanical studies offers a cost-effective approach to understanding human joint and tissue mechanics. Our study explores the osteology and meniscus anatomy of the male porcine stifle joint and compares it to human knee joint parameters, aiming to provide a valuable reference for orthopaedic research and surgical training.

METHODS

We examined 60 male porcine stifle joints and analyzed their menisci and bones. Dissections were meticulously performed, with measurements taken using digital Vernier calipers and ImageJ software. These dimensions included bone morphology and meniscal width, height, and volume, followed by statistical analysis using unpaired Student's t-tests.

RESULTS

The various measurements of bones and menisci indicated a high degree of anatomical similarity to human knees. The anterior width of the medial meniscus was 12.545 ± 1.763 mm, while the lateral meniscus was 14.99 ± 1.720 mm. The middle width of the medial meniscus was 12.065 ± 1.691 mm, compared to the lateral meniscus at 14.375 ± 1.732 mm. The posterior width was 15.25 ± 1.741 mm for the medial meniscus and 16.39 ± 1.662 mm for the lateral meniscus. The femoral intercondylar notch dimensions widened and became shallower with age, resembling the maturation patterns seen in human knee development. The average volume of the medial meniscus was 4.30 ± 0.13 ml, while the lateral meniscus was 5.9 ± 0.29 ml. The aspect ratio of the femoral condyles was 1.04 ± 0.04 (0.95-1.11), while the aspect ratio of the tibial condyles was 0.65 ± 0.02 (0.61-0.70), measured via digital Vernier calipers. These findings were statistically significant, showcasing the male porcine model's relevance in replicating human knee mechanics (p < 0.05).

CONCLUSION

Male porcine stifle joints present a valid and accessible model for knee anatomy research. Our study underscores the value of the male porcine model in understanding human knee joint biomechanics and supports its continued use in orthopaedic research and training. These findings have significant implications for advancing orthopaedic research methodologies and enhancing surgical training practices by providing a reliable and anatomically comparable model.

Assessment of injuries patterns produced by a 9mm P.A.K "rubber ball" blank firing weapon: porcine model

The use of less lethal weapons aims to mitigate civilian casualties caused by firearm use. However, due to numerous cases in which these weapons caused serious injuries, even lethal injuries, both legislation and the forensic field are interested in characterizing and regulating them better. In the forensic field, there is a lack of strong research about injury patterns of these weapons which makes it difficult to identify the type of weapon employed. In this study, the main objective was to characterize the injury pattern produced by the impact of the 9 mm P.A.K. projectile. A porcine model was used. Four different distances were studied: firm contact, 10 cm, 60 cm and 110 cm, using 3 of the more representative anatomical sites: the head, the hind leg and the ribs. The average measurement of the entrance orifice varied according to the anatomical site, being 6.67 mm wide and 6.25 mm long in the thorax, 7.3 mm wide and 8.8 mm long in the hind legs, and 7.62 mm wide and 7.54 mm long in the head. The variation in width and length measurements was not found to be directly related to the shot distance. The gunshot residues had similar characteristics to those of conventional lead projectiles, however there was more unburned powder deposit near the wounds, with a less dense soot and more dense powder tattoo. Depth varied widely regardless of tissue and firing distance, although loss of penetrating power and injury is observed as one moves away from the target.

Technical note: Temperature estimation accuracy based on colourimetry of embalmed human and fresh non-human burned bone

Estimation of the exposure temperature of skeletal remains can be done by means of colourimetry and a previously published decision model for the colourimetric data, resulting in clusters that represent a range of exposure temperature. The method was based on thermally altered freshly burned human skeletal remains. However, in practice the origin or pre-burning condition of (possibly fragmentary) burned remains can be unknown. Further, in order to use the colourimetric analysis, and accompanying decision model, it is important to have a reference or test set. Fresh human material is not available for this purpose in all countries. Hence, the classification accuracy of the decision model was tested for, in some countries more readily available substitutes for fresh bone; embalmed human bone and non-human bone. The model yielded high accuracies for these sample materials, making it possible to create a reference or test set from fresh non-human and embalmed human bone as substitute for human, and also to use the decision model for these deviating samples in practice.

The relationship between intraosseous catheter tip placement, flow rates, and infusion pressures in a high bone density cadaveric swine (Sus scrofa) model

Background

Intraosseous (IO) infusion is a life-preserving technique when intravenous access is unobtainable. Successful IO infusion requires sufficiently high flow rates to preserve life but at low enough pressures to avoid complications. However, IO catheter tips are often misplaced, and the relative flow rates and pressures between IO catheter tips placed in medullary, trabecular, and cortical bone are not well described, which has important implications for clinical practice.

Objectives

We developed the Zone Theory of IO Catheter Tip Placement based on bone density and proximity to the venous central sinus and then tested the influence of catheter tip placement locations on flow rates and pressures in a cadaveric swine model.

Methods

Three cross-trained participants infused 500 mL of crystalloid fluid into cadaveric swine humerus and sternum (N = 210 trials total) using a push‒pull method with a 60 cm3 syringe. Computed tomography scans were scored by radiologists and categorized as zone 1 (medullary space), zone 2 (trabecular bone), or zone 3 (cortical bone) catheter tip placements. Differences between zones in flow rates, mean pressures, and peak pressures were assessed using analysis of variance and analysis of covariance to account for participant and site differences at the p < 0.05 threshold.

Results

Zone 1 and zone 2 placements were essentially identical in flow rates, mean pressures, and peak pressures (each p > 0.05). Zone 1 and zone 2 placements were significantly higher in flow rates and lower in pressures than zone 3 placements (each p < 0.05 or less).

Conclusion

Within the limitations of an unpressurized cadaveric swine model, the present findings suggest that IO catheter tip placements need not be perfect to acquire high flow rates at low pressures, only accurate enough to avoid the dense cortical bone of zone 3. Future research using in vivo animal and human models is needed to better define the clinical impact of IO catheter placement on infusion flow rates and pressures.

Significance and considerations of establishing standardized critical values for critical size defects in animal models of bone tissue regeneration

Establishing animal models with critical size defects (CSDs) is critical for conducting experimental investigations engineering of bone tissue regeneration. Currently, a standardised protocol for establishing an animal CSDs model has not been developed. Furthermore, a consensus has not been reached regarding the critical values of CSDs. Successful establishment of animal models for CSDs is a complex process that requires researchers to meticulously consider a variety of factors such as age, species, bone defect size and anatomic location. The specific numerical values for CSDs in small animal models vary, and a clear definition of the critical value for large animal CSDs models in the literature is still lacking. This review consolidates the advancements in critical bone defects animal models by outlining the research landscape across variables, including animal species, age groups, bone defect sites, and sizes, to offer valuable guidance and a theoretical framework for the establishment of pertinent experimental animal models.

A proposed method for differentiating knives from cut marks on bone: A forensic anthropological approach

Knife cut marks have been extensively studied in forensic literature, and the results have been beneficial in identifying both the cut mark and implement type on bone. For this study, an assessment in differentiating knife cut marks has been attempted by using sword cut mark characteristics. In addition, a flowchart was created to assist in interpreting such marks. Knives of different serrations (non-serrated, macro- and micro-serrated) were used to inflict cut marks on pig ribs with a forward and backward stab thrust. The analysis revealed that some traits adapted from previous studies applied to knife cut marks and that non-serrated and serrated marks could be distinguished accurately using the flowchart. The distinction between different types of serrated blades was not as successful. However, results show that further research and development of the flowchart can be invaluable in similar analyses.

Influence of physicochemical characteristics of calcium phosphate-based biomaterials in cranio-maxillofacial bone regeneration. A systematic literature review and meta-analysis of preclinical models

Objectives

Calcium phosphate-based biomaterials (CaP) are the most widely used biomaterials to enhance bone regeneration in the treatment of alveolar bone deficiencies, cranio-maxillofacial and periodontal infrabony defects, with positive preclinical and clinical results reported. This systematic review aimed to assess the influence of the physicochemical properties of CaP biomaterials on the performance of bone regeneration in preclinical animal models.

Methods

The PubMed, EMBASE and Web of Science databases were searched to retrieve the preclinical studies investigating physicochemical characteristics of CaP biomaterials. The studies were screened for inclusion based on intervention (physicochemical characterization and in vivo evaluation) and reported measurable outcomes.

Results

A total of 1532 articles were retrieved and 58 studies were ultimately included in the systematic review. A wide range of physicochemical characteristics of CaP biomaterials was found to be assessed in the included studies. Despite a high degree of heterogeneity, the meta-analysis was performed on 39 studies and evidenced significant effects of biomaterial characteristics on their bone regeneration outcomes. The study specifically showed that macropore size, Ca/P ratio, and compressive strength exerted significant influence on the formation of newly regenerated bone. Moreover, factors such as particle size, Ca/P ratio, and surface area were found to impact bone-to-material contact during the regeneration process. In terms of biodegradability, the amount of residual graft was determined by macropore size, particle size, and compressive strength.

Conclusion

The systematic review showed that the physicochemical characteristics of CaP biomaterials are highly determining for scaffold's performance, emphasizing its usefulness in designing the next generation of bone scaffolds to target higher rates of regeneration.

The Species Effect: Differential Sphingosine-1-Phosphate Responses in the Bone in Human Versus Mouse

The deterioration of osteoblast-led bone formation and the upregulation of osteoclast-regulated bone resorption are the primary causes of bone diseases, including osteoporosis. Numerous circulating factors play a role in bone homeostasis by regulating osteoblast and osteoclast activity, including the sphingolipid-sphingosine-1-phosphate (S1P). However, to date no comprehensive studies have investigated the impact of S1P activity on human and murine osteoblasts and osteoclasts. We observed species-specific responses to S1P in both osteoblasts and osteoclasts, where S1P stimulated human osteoblast mineralisation and reduced human pre-osteoclast differentiation and mineral resorption, thereby favouring bone formation. The opposite was true for murine osteoblasts and osteoclasts, resulting in more mineral resorption and less mineral deposition. Species-specific differences in osteoblast responses to S1P were potentially explained by differential expression of S1P receptor 1. By contrast, human and murine osteoclasts expressed comparable levels of S1P receptors but showed differential expression patterns of the two sphingosine kinase enzymes responsible for S1P production. Ultimately, we reveal that murine models may not accurately represent how human bone cells will respond to S1P, and thus are not a suitable model for exploring S1P physiology or potential therapeutic agents.

Quantitative color analysis of burned bone to predict DNA quantity, quality, and genotyping success

Badly burned skeletal remains are commonly submitted to forensic laboratories for victim identification via DNA analysis methods. Burned skeletal remains present many challenges for DNA analysis as they can contain low amounts of DNA which can also be damaged and degraded, resulting in partial or no STR profiles. Therefore, a simple, but effective screening method that identifies which samples may provide the most successful STR or mtDNA typing results for identification would enable forensic laboratories to save time, money, and resources. One metric that can be used and a screening method is the color of burned bone, as bone color changes with exposure to fire as temperature and length of exposure increase. This research developed a quantitative screening method based on the surface color of burned bone. The different visual bone colors (light brown, dark brown, black, gray, and white) were quantified using the Commission on Illumination L*a*b color space. These values were then compared to DNA yield, STR, and mtDNA profile completeness to identify whether the L*a*b values can predict genotyping success. A Bayesian network was constructed to determine the probability of STR typing success, given a set of L*a*b values. Results demonstrated that samples with an a* value greater than or equal to one and b* value greater than eight (light brown and dark brown burned samples) were the most predictive of STR typing success and mtDNA typing success. A decision tree for processing burned bones was constructed based on the color value thresholds.

Femoral Fixation Strength as a Function of Bone Plug Length in Anterior Cruciate Ligament Reconstruction Utilizing Interference Screws

PURPOSE

 To determine femoral construct fixation strength as bone plug length decreases in anterior cruciate ligament reconstruction (ACLR).

METHODS

 Sixty fresh-frozen bone-patellar tendon-bone allografts were utilized and divided into 20-, 15-, and 10-mm length bone plug groups, subdivided further so that half utilized the patella side (P) for testing and half used the tibial side (T). Ten mm diameter recipient tunnels were created within the anatomic anterior cruciate ligament footprint of 60 cadaveric femurs. All bone plugs were 10 mm in diameter; grafts were fixed using a 7 × 23 mm metal interference screw. An Instron was used to determine the load to failure of each group. A one-way multivariate analysis of variance (MANOVA) was conducted to test the hypothesis that there would be one or more mean differences in fixation stability between 20- or 15-mm plug lengths (P or T) versus 10 mm T plug lengths when cross-compared, with no association between other P or T subgroups.

RESULTS

 The mean load to failure of the 20 mm plugs (20 P + T) was 457 ± 66N, 15 mm plugs (15 P + T) was 437 ± 74N, and 10 mm plugs (10 P + T) was 407 ± 107N. There was no significant difference between P + T groups: 20-versus 15-mm (p = 1.000), 15-versus 10-mm (p = 0.798), and 20-versus 10-mm (p = 0.200); P + T MANOVA (p = 0.291). Within groups, there was no significant difference between patella and tibial bone plug subgroups with a pullout force range between 469 ± 56N and 374 ± 116N and p-value ranging from p = 1.000 for longer bone plugs to p = 0.194 for shorter bone plugs; P versus T MANOVA (p = 0.113).

CONCLUSION

 In this human time zero cadaver model, there was no significant difference in construct failure between 20-,15-, and 10-mm bone plugs when fixed with an interference screw within the femoral tunnel, although fixation strength did trend down when from 20- to 15- to 10-mm bone plugs.

CLINICAL RELEVANCE

 There is a balance between optimal bone plug length on the femoral side for achieving adequate fixation as well as minimizing donor site morbidity and facilitating graft passage in ACLR. This study reveals utilizing shorter plugs with interference screw fixation is potentially acceptable on the femoral side if shorter plugs are harvested.

XRF identification of sharp-force trauma in fresh and dry human bone under varied experimental heat conditions

Heat-induced fractures can be hard to distinguish from sharp force traumas. This challenge can negatively impact medico-legal analysis. The present study aimed to experimentally assess if X-ray fluorescence (XRF) can be used to detect chemical traces transferred from the blade of a sharp instrument onto both fresh and dry human bones. This was performed by inducing sharp force traumas with five different instruments on 20 fresh and 20 dry human clavicles. All bone samples were probed before and after experimental burning (at 500 °C, 700 °C, 900 °C and 1100 °C). Our results show that XRF is potentially useful for detecting iron traces in fresh human bone, both unburned and burned. However, we were not able to clearly detect iron traces from the blades in bones that have been previously inhumed, since exogenous iron acquired during diagenesis masks the iron traces originating from the blade.

Effect of Press-Fit Size on Insertion Mechanics and Cartilage Viability in Human and Ovine Osteochondral Grafts

OBJECTIVE

The osteochondral allograft procedure uses grafts constructed larger than the recipient site to stabilize the graft, in what is known as the press-fit technique. This research aims to characterize the relationships between press-fit size, insertion forces, and cell viability in ovine and human osteochondral tissue.

DESIGN

Human (4 donors) and ovine (5 animals) articular joints were used to harvest osteochondral grafts (4.55 mm diameter, N = 33 Human, N = 35 Ovine) and create recipient sites with grafts constructed to achieve varying degrees of press fit (0.025-0.240 mm). Donor grafts were inserted into recipient sites while insertion forces were measured followed by quantification of chondrocyte viability and histological staining to evaluate the extracellular matrix.

RESULTS

Both human and ovine tissues exhibited similar mechanical and cellular responses to changes in press-fit. Insertion forces (Human: 3-169 MPa, Ovine: 36-314 MPa) and cell viability (Human: 16%-89% live, Ovine: 2%-76% live) were correlated to press-fit size for both human (force: r = 0.539, viability: r = -0.729) and ovine (force: r = 0.655, viability: r = -0.714) tissues. In both species, a press-fit above 0.14 mm resulted in reduced cell viability below a level acceptable for transplantation, increased insertion forces, and reduced linear correlation to press-fit size compared to samples with a press-fit below 0.14 mm.

CONCLUSIONS

Increasing press-fit size required increased insertion forces and resulted in reduced cell viability. Ovine and human osteochondral tissues responded similarly to impact insertion and varying press-fit size, providing evidence for the use of the ovine model in allograft-related research.

Biomechanical Stability of Third-Generation Adjustable Suture Loop Devices Versus Continuous Loop Button Device for Cortical Fixation of ACL Tendon Grafts

Background

Concerns regarding the primary stability of early adjustable loop button (ALB) devices for cortical fixation of tendon grafts in anterior cruciate ligament reconstruction (ACLR) have led to the development of new implant designs.

Purpose

To evaluate biomechanical stability of recent ALB implants in comparison with a continuous loop button (CLB) device.

Study Design

Controlled laboratory study.

Methods

ACLR was performed in a porcine model (n = 40) using 2-strand porcine flexor tendons with a diameter of 8 mm. Three ALB devices (Infinity Button [ALB1 group]; Tightrope II RT [ALB2 group]; A-TACK [ALB3 group]) and 1 CLB device (FlippTack with polyethylene suture) were used for cortical tendon graft fixation. Cyclic loading (1000 cycles up to 250 N) with complete unloading were applied to the free end of the tendon graft using a uniaxial testing machine, followed by load to failure. Elongation, stiffness, yield load, and ultimate failure load were recorded and compared between the groups using a Kruskal-Wallis test with post hoc Dunn correction.

Results

Elongation after 1000 cycles at 250 N was similar between groups (ALB1, 4.5 ± 0.7 mm; ALB2, 4.8 ± 0.8 mm; ALB3, 4.5 ± 0.6 mm; CLB, 4.5 ± 0.8 mm), as was load to failure (ALB1, 838 ± 109 N; ALB2, 930 ± 89 N; ALB3, 809 ± 103 N; CLB, 842 ± 80 N). Stiffness was significantly higher in the ALB1 group compared with the CLB group (262.3 ± 21.6 vs 229.3 ± 15.1 N/mm; P < .05). No significant difference was found between the 4 groups regarding yield load. Constructs failed either by rupture of the loop, breakage of the button, or rupture of the tendon.

Conclusion

The tested third-generation ALB devices for cortical fixation in ACLR withstood cyclic loading with complete unloading without significant differences to a CLB device.

Clinical Relevance

The third-generation ALB devices tested in the present study provided biomechanical stability comparable with that of a CLB device. Furthermore, ultimate failure loads of all tested implants exceeded the loads expected to occur in the postoperative period after ACLR.

Biomechanical Performance of Transtibial Pull-Out Posterior Horn Medial Meniscus Root Repair Is Improved With Knotless Adjustable Suture Anchor-Based Fixation

Background

While posterior medial meniscus root (PMMR) techniques have evolved, there remains a need to both optimize repair strength and improve resistance to cyclic loading.

Hypothesis

Adjustable tensioning would lead to higher initial repair strength and reduce displacement with cyclic loading compared with previously described transtibial pull-out repair (TPOR) fixation techniques.

Study Design

Controlled laboratory study.

Methods

A total of 56 porcine medial menisci were used. Eight intact specimens served as a control for the native meniscus. For the others, PMMR tears were created and repaired with 6 different TPOR techniques (8 in each group). Fixed PMMR repairs were executed using 4 different suture techniques (two No. 2 cinch sutures, two cinch tapes, two No. 2 simple sutures, and two No. 2 sutures in a Mason-Allen configuration) all tied over a cortical button. Adjustable PMMR repairs using Mason-Allen sutures were fixed with an adjustable soft tissue anchor fixation tensioned at either 80 N or 120 N. The initial force, stiffness, and relief displacement of the repairs were measured after fixation. Repair constructs were then cyclically loaded, with cyclic displacement and stiffness measured after 1000 cycles. Finally, the specimens were pulled to failure.

Results

The PMMR repaired with the 2 cinch sutures fixed technique afforded the lowest (P < .001) initial repair load, stiffness, and relief displacement. The adjustable PMMR repairs achieved a higher initial repair load (P < .001) and relief displacement (P < .001) than all fixed repairs. The 2 cinch sutures fixed technique showed an overall higher cyclic displacement (P < .028) and was completely loose compared with the native meniscus functional zone. Repairs with adjustable intratunnel fixation showed displacement with cyclic loading similar to the native meniscus. With cyclic loading, the Mason-Allen adjustable repair with 120 N of tension showed less displacement (P < .016) than all fixed repairs and a stiffness comparable to the fixed Mason-Allen repair. The fixed Mason-Allen technique demonstrated a higher ultimate load (P < .007) than the adjustable Mason-Allen techniques. All repairs were less stiff, with lower ultimate failure loads, than the native meniscus root attachment (P < .0001).

Conclusion

Adjustable TPOR led to considerably higher initial repair load and relief displacement than other conventional fixed repairs and restricted cyclic displacement to match the native meniscus function. However, the ultimate failure load of the adjustable devices was lower than that of a Mason-Allen construct tied over a cortical button. All repair techniques had a significantly lower load to failure than the native meniscus root.

Clinical Relevance

Knotless adjustable PMMR repair based on soft anchor fixation results in higher tissue compression and less displacement, but the overall clinical significance on healing rates remains unclear.

Animal Models for Investigating Osseointegration: An Overview of Implant Research over the Last Three Decades

Dental implants and bone augmentation are among dentistry's most prevalent surgical treatments; hence, many dental implant surfaces and bone grafts have been researched to improve bone response. Such new materials were radiologically, histologically, and histomorphometrically evaluated on animals before being used on humans. As a result, several studies used animals to evaluate novel implant technologies, biocompatibility, surgical techniques, and osseointegration strategies, as preclinical research on animal models is essential to evaluate bioactive principles (on cells, compounds, and implants) that can act through multiple mechanisms and to predict animal behavior, which is difficult to predict from in vitro studies alone. In this study, we critically reviewed all research on different animal models investigating the osseointegration degree of new implant surfaces, reporting different species used in the osseointegration research over the last 30 years. Moreover, this is the first study to summarize reviews on the main animal models used in the translational research of osseointegration, including the advantages and limitations of each model and determining the ideal location for investigating osseointegration in small and large animal models. Overall, each model has advantages and disadvantages; hence, animal selection should be based on the cost of acquisition, animal care, acceptability to society, availability, tolerance to captivity, and housing convenience. Among small animal models, rabbits are an ideal model for biological observations around implants, and it is worth noting that osseointegration was discovered in the rabbit model and successfully applied to humans.

The potential of sheep in preclinical models for bone infection research - A systematic review

Background

Reliable animal models are critical for preclinical research and should closely mimic the disease. With respect to route of infection, pathogenic agent, disease progression, clinical signs, and histopathological changes. Sheep have similar bone micro- and macrostructure as well as comparable biomechanical characteristics to humans. Their use in bone research is established, however their use in bone infection research is limited. This systematic review will summarise the key features of the available bone infection models using sheep, providing a reference for further development, validation, and application.

Method

This systematic review was designed according to the PRISMA guidelines and registered with PROSPERO. Quality was assessed using SYRICLE's risk of bias tool adapted for animal studies. PubMed, MEDLINE, Web of Science and EMBASE were searched until March 2022.1921 articles were screened by two independent reviewers, and 25 were included for analysis.

Results

Models have been developed in nine different breeds. Staphylococcus aureus was used in the majority of models, typically inoculating 108 colony forming units in tibial or femoral cortical defects. Infection was established with either planktonic or biofilm adherent bacteria, with or without foreign material implanted. Most studies used both radiological and microbiological analyses to confirm osteomyelitis.

Conclusions

There is convincing evidence supporting the use of sheep in bone infection models of clinical disease. The majority of sheep studied demonstrated convincing osteomyelitis and tolerated the infection with minimal complications. Furthermore, the advantages of comparable biology and biomechanics may increase the success for translating in vivo results to successful therapies.

The Translational potential of this article

In the realm of preclinical research, the translation to viable clinical therapies is often perilous, and the quest for reliable and representative animal models remains paramount. This systematic review accentuates the largely untapped potential of sheep as large animal models, especially in bone infection research. The anatomical and biomechanical parallels between sheep and human bone structures position sheep as an invaluable asset for studying osteomyelitis and periprosthetic joint infection. This comprehensive exploration of the literature demonstrates the robustness and translational promise of these models. Furthermore, this article underscores the potential applicability for sheep in developing effective therapeutic strategies for human bone infections.

Comparison of Time-Zero Primary Stability Between a Biodegradable Magnesium Bone Staple and Metal Bone Staples for Knee Ligament Fixation: A Biomechanical Study in a Porcine Model

Background

Bone staples have been shown previously to be a viable modality for cortical tendon graft fixation in ligament knee surgery. However, soft tissue reactions have been reported, making implant removal necessary. Magnesium alloys are a promising material for biodegradable orthopaedic implants, with mechanical properties closely resembling those of human bone.

Purpose

To compare the primary stability of a biodegradable bone staple prototype made from magnesium to bone staples made from metal in the cortical fixation of tendon grafts during knee surgery.

Study Design

Controlled laboratory study.

Methods

Primary stability of peripheral tendon graft fixation was assessed in a porcine model of medial collateral ligament reconstruction. Two commercially available metal bone staples (Richards fixation staple with spikes [Me1] and spiked ligament staple [Me2]) were compared with a magnesium bone staple prototype for soft tissue fixation. Primary stability was assessed using a uniaxial materials testing machine. Cyclic loading at 50 and 100 N was applied for 500 cycles each, followed by load-to-failure testing.

Results

After 500 cycles at 50 N, elongation was 1.5 ± 0.5 mm in the Me1 group, 1.9 ± 0.5 mm in the Me2 group, and 1.8 ± 0.4 mm in the magnesium group. After 1000 cycles of loading (500 cycles at 50 N and 500 at 100 N), elongation was 3.6 ± 0.9 mm in the Me1 group, 3.5 ± 0.6 mm in the Me2 group, and 4.1 ± 1.0 mm in the magnesium group. No significant differences regarding elongation were found between the groups. Load to failure was 352 ± 115 N in the Me1 group, 373 ± 77 N in the Me2 group, and 449 ± 92 N in the magnesium group, with no significant difference between the groups.

Conclusion

In this study, the magnesium bone staples provided appropriate time-zero biomechanical primary stability in comparison with metal bone staples and may therefore be a feasible alternative for cortical fixation of tendon grafts in knee surgery.

Clinical Relevance

The biodegradability of magnesium bone staples would eliminate the need for later implant removal.

Usefulness of fat-containing agents: an initial study on estimating fat content for magnetic resonance imaging

This initial study aimed at testing whether fat-containing agents can be used for the fat mass estimation methods using magnetic resonance imaging (MRI). As an example for clinical application, fat-containing agents (based on soybean oil, 10% and 20%), 100% soybean oil, and saline as reference substances were placed outside the proximal femurs obtained from 14 participants and analyzed by 0.3 T MRI. Fat content was the estimated fat fraction (FF) based on signal intensity (SIeFF, %). The SIeFF values of the femoral bone marrow, including the femoral head, neck, shaft, and trochanter area, were measured. MRI data were compared in terms of bone mineral content (BMC) and bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) in the proximal femur. Twelve pig femurs were also used to confirm the correlation between FF by the DIXON method and SIeFF. According to Pearson's correlation coefficient, the SIeFF and total BMC and BMD data revealed strong and moderate negative correlations in the femoral head (r <  - 0.74) and other sites (r =  - 0.66 to - 0.45). FF and SIeFF showed a strong correlation (r = 0.96). This study was an initial investigation of a method for estimating fat mass with fat-containing agents and showed the potential for use in MRI. SIeFF and FF showed a strong correlation, and SIeFF and BMD and BMC showed correlation; however, further studies are needed to use SIeFF as a substitute for DXA.

Biological performance of a novel bovine hydroxyapatite in a guided bone regeneration model: A preclinical study in a mandibular defect in dogs

OBJECTIVES

This preclinical model study aims to evaluate the performance and safety of a novel hydroxyapatite biomaterial (Wishbone Hydroxyapatite, WHA) on guided bone regeneration compared to a commercially available deproteinized bovine bone mineral (Bio-Oss, BO).

MATERIAL AND METHODS

Twenty-four beagle dogs were allocated to three timepoint cohorts (4, 12, and 26 weeks) of eight animals each. In all animals, four critical-sized, independent wall mandibular defects were created (32 defects/cohort). Each animal received all four treatments, allocated randomly to separated defects: WHA + collagen membrane (M), BO + M, no treatment (Sham, Sh), and Sh + M. At each timepoint, the specimens were harvested for histologic and histomorphometric analyses to determine the newly formed bone and osteoconductivity.

RESULTS

At 4 weeks, bone regeneration was significantly higher for WHA + M (46.8%) when compared to BO + M (21.4%), Sh (15.1%), and Sh + M (23.1%) (p < 0.05); at 12 and 26 weeks, regeneration was similar for WHA and BO. Bone-to-material contact increased over time similarly for WHA + M and BO + M. From a safety point of view, inflammation attributed to WHA + M or BO + M was minimal; necrosis or fatty infiltrate was absent.

CONCLUSIONS

WHA + M resulted in higher bone regeneration rate than BO + M at 4 weeks. Both BO + M and WHA + M were more efficient than both Sh groups at all timepoints. Safety and biocompatibility of WHA was favorable and comparable to that of BO.

Saw marks in bone: A preliminary empirical study to inform decision making and best practice

Forensic toolmark examiners compare marks between those observed on an item/surface and those made by a reference implement, such as a particular tool or weapon, to provide an opinion of the likelihood of common origin. It is widely accepted that such comparison opinions need to be underpinned by empirical research, and this study aimed to add to the knowledge base relied upon when developing and comparing saw marks in bone, a substrate encountered in body dismemberment cases. Porcine bones were used as a human proxy; they were either fresh with residual soft tissue and bodily fluids present ('wet') to replicate dismembered bones shortly post-mortem, or processed to remove soft tissue and moisture content ('dry') to represent cases of dismemberment after an extended period of decomposition and exposure. The bones were cut using one implement of each of five classes: hand saw, mitre saw, reciprocating saw, oscillating saw, and serrated knife. They were cut, either completely through (except for serrated knife), giving two surfaces per cut to examine, or to a depth up to 3 mm (false starts). Five replicates per combination of bone condition, saw, and cut type gave 130 bone samples. These were then cleaned and cast using Isomark Silicone Polymer Compound or Mikrosil, giving 260 cast samples. All bone and cast samples were photographed, examined for various class characteristic markers, and specific markers measured. No significant differences between Isomark and Mikrosil casts were observed when compared side-by-side, demonstrating suitability of both materials for casting of saw marks on bone. Although saw marks presented more class characteristic markers on dry than wet bones, calculations of tooth distances and measurements of kerf width (KW) from marks did not significantly differ between bone conditions, with exception of the reciprocating saw that produced false start marks with significantly larger minimum KW on wet than dry samples. Further analysis supported that tooth distances on marks made by hand and oscillating saws are sufficiently accurate for the determination of saw teeth per inch (TPI). However, one tooth distance on marks made by reciprocating saws did not accurately represent TPI. Finally, examination of presence or absence of class characteristic markers on each saw mark demonstrated consistent variation between saw classes. These results enabled the development of exclusion-based decision trees, and a reference database (available on request), for use by toolmark examiners in their evaluation of saw types based on class characteristic markers observed in cut bone.

X-ray generation by fs-laser processing of biological material

The use of ultrashort pulse lasers in medical treatments is increasing and is already an essential tool, particularly in the treatment of eyes, bones and skin. One of the main advantages of laser treatment is that it is fast and minimally invasive. Due to the interaction of ultrashort laser pulses with matter, X-rays can be generated during the laser ablation process. This is important not only for the safety of the patient, but also for the practitioner to ensure that the legally permissible dose is not exceeded. Although our results do not raise safety concerns for existing clinical applications, they might impact future developments at higher peak powers. In order to provide guidance to laser users in the medical field, this paper examines the X-ray emission spectra and dose of several biological materials and describes their dependence on the laser pulse energy.

Interference screws manufactured from magnesium display similar primary stability for soft tissue anterior cruciate ligament graft fixation compared to a biocomposite material - a biomechanical study

PURPOSE

Biodegradable interference screws (IFS) can be manufactured from different biomaterials. Magnesium was previously shown to possess osteoinductive properties, making it a promising material to promote graft-bone healing in anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare IFS made from magnesium to a contemporary biocomposite IFS.

METHODS

In a porcine model of ACL reconstruction, deep porcine flexor tendons were trimmed to a diameter of 8 mm, sutured in Krackow technique, and fixed with either 8 × 30 mm biocomposite IFS (Bc-IFS) or 8 × 30 mm magnesium IFS (Mg-IFS) in an 8 mm diameter bone tunnel in porcine tibiae. Cyclic loading for 1000 cycles from 0 to 250 N was applied, followed by load to failure testing. Elongation, load to failure and stiffness of the tested constructs was determined.

RESULTS

After 1000 cycles at 250 N, elongation was 4.8 mm ± 1.5 in the Bc-IFS group, and 4.9 mm ± 1.5 in the Mg-IFS group. Load to failure was 649.5 N ± 174.3 in the Bc-IFS group, and 683.8 N ± 116.5 in the Mg-IFS group. Stiffness was 125.3 N/mm ± 21.9 in the Bc-IFS group, and 122.5 N/mm ± 20.3 in the Mg-IFS group. No significant differences regarding elongation, load to failure and stiffness between Bc-IFS and Mg-IFS were observed.

CONCLUSION

Magnesium IFS show comparable biomechanical primary stability in comparison to biocomposite IFS and may therefore be an alternative to contemporary biodegradable IFS.

Dental implants in large animal models with experimental systemic diseases: A systematic review

This systematic review aims to identify and discuss the most used methodologies in pre-clinical studies for the evaluation of the implementation of dental implants in systemically compromised pigs and sheep. This study provides support and guidance for future research, as well as for the prevention of unnecessary animal wastage and sacrifice. Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) was used as a guideline; electronic searches were performed in PubMed, Scopus, Scielo, Web of Science, Embase, Science Direct, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Directory of Open Access Journals, Database of Abstracts of Reviews of Effects, and gray literature until January 2022 (PROSPERO/CRD42021270119). Sixty-eight articles were chosen from the 2439 results. Most studies were conducted in pigs, mainly the Göttinger and Domesticus breeds. Healthy animals with implants installed in the jaws were predominant among the pig studies. Of the studies evaluating the effect of systemic diseases on osseointegration, 42% were performed in osteoporotic sheep, 32% in diabetic sheep, and 26% in diabetic pigs. Osteoporosis was primarily induced by bilateral ovariectomy and mainly assessed by X-ray densitometry. Diabetes was induced predominantly by intravenous streptozotocin and was confirmed by blood glucose analysis. Histological and histomorphometric analyses were the most frequently employed in the evaluation of osseointegration. The animal models presented unique methodologies for each species in the studies that evaluated dental implants in the context of systemic diseases. Understanding the most commonly used techniques will help methodological choices and the performance of future studies in implantology.

Efficacy of imaging techniques for the diagnosis of apical periodontitis: A systematic review

BACKGROUND

Apical periodontitis (AP) is a chronic inflammatory response of microbial aetiology. Pathological changes associated with AP may not be visible on radiographic images and may linger without causing any symptoms. Clinicians rely mostly on clinical examination and imaging techniques to establish a diagnosis.

OBJECTIVES

The aim of this review was to answer the following question using the PICO format: In the adult human permanent dentition (P), what is the efficacy of diagnostic imaging of the periapical tissues (I) using histopathology as a reference standard (C) in the diagnosis of apical periodontitis, in terms of diagnostic accuracy (O).

METHODS

MEDLINE, EMBASE, Scopus and Cochrane Library were searched for English articles published through October 2021. At least two independent reviewers evaluated the study design, imaging modality used, histopathological assessment, outcome measures, results and conclusions for each article. The risk of bias was assessed using the Quality Assessment Tool for Diagnostic Accuracy Studies-2.

RESULTS

The initial search strategy identified 544 articles. Seven articles were included for analysis in the final review, all of which involved tissue samples obtained from cadavers. No clinical studies were identified that met the eligibility criteria. A consistently low sensitivity score and negative predictive value were reported for periapical radiography, especially in comparison to CBCT, which scored highly. Both modalities achieved high scores for specificity and positive predictive value. Diagnostic accuracy of CBCT was lower for root-filled teeth in comparison to non-root-filled teeth.

DISCUSSION

Assessment of the periapical tissues using periapical radiographs was shown to have a low to moderate agreement with the histopathological assessment. CBCT was reported to be more accurate than PR and demonstrated a good agreement with histopathology, especially for non-root-filled teeth.

CONCLUSIONS

This review identified a need for greater standardization in methodology and reporting, and as the findings are based on cadaver studies, their clinical relevance must be interpreted with caution.

REGISTRATION

PROSPERO (CRD42021272147).

Biomechanical Comparison of 3 Adjustable-Loop Suspensory Devices for All-Inside ACL Reconstruction: A Time-Zero Full-Construct Model

Background

Little is known about the stability of adjustable-loop devices (ALDs) for anterior cruciate ligament (ACL) reconstruction (ACLR).

Purpose

To evaluate the stabilization behavior of 3 different types of ALDs for all-inside ACLR in a full-construct surgical technique-based manner.

Study Design

Controlled laboratory study.

Methods

The femoral and tibial devices of Ultrabutton (Smith & Nephew), Infinity (Conmed), and TightRope II (Arthrex) were applied to quadrupled bovine tendon grafts (n = 8 each) with tibial-sided traction applied (350 N) for graft tensioning in a simulated fully extended knee. Knotless femoral graft fixation was based on either a suture-locking device (SLD; Ultrabutton), button-locking device (BLD; Infinity), or dual-locking device (DLD; TightRope II). All constructs were progressively loaded (50 N/500 cycles) from 50 to 300 N for 3000 cycles (0.75 Hz), including complete unloading situations and pull to failure (50 mm/min). Construct elongation, stiffness, and ultimate load were analyzed.

Results

BLD showed significantly greater initial elongation (-2.69 ± 0.15 mm) than DLD (-3.19 ± 0.21 mm; P < .001) but behaved similarly to SLD (-2.93 ± 0.23 mm). While DLD and SLD had the smallest initial elongation at the same significance level, they behaved opposite to each other with gradually increasing peak loading. At the end of testing, DLD had the lowest (-0.64 ± 0.32 mm) and SLD the highest (3.41 ± 1.01 mm) total elongation (P < .003 for both). SLD displayed significantly higher dynamic elongation (6.34 ± 0.23 mm) than BLD (3.21 ± 0.61 mm) and DLD (2.56 ± 0.31 mm) (P < .001 for both). The failure load of BLD (865.0 ± 183.8 N) was significantly lower (P < .026) compared with SLD and DLD (>1000 N). The predominant failure mode was suture rupture and tibial bone breakage with button subsidence (SLD, n = 4). No significant difference in stiffness between constructs was found.

Conclusion

While DLD successfully restricted critical construct elongation, BLD partially and SLD completely exceeded the clinical failure threshold (>3 mm) of plastic elongation with loop lengthening during increasing cyclic peak loading with complete unloading. Higher failure loads of SLD and DLD implants (>1000 N) were achieved at similar construct stiffness to BLD.

Clinical Relevance

A detailed biomechanical understanding of the stabilization potential is pertinent to the continued evolution of ALDs to improve clinical outcomes.

Why Animal Experiments Are Still Indispensable in Bone Research: A Statement by the European Calcified Tissue Society

Major achievements in bone research have always relied on animal models and in vitro systems derived from patient and animal material. However, the use of animals in research has drawn intense ethical debate and the complete abolition of animal experimentation is demanded by fractions of the population. This phenomenon is enhanced by the reproducibility crisis in science and the advance of in vitro and in silico techniques. 3D culture, organ-on-a-chip, and computer models have improved enormously over the last few years. Nevertheless, the overall complexity of bone tissue cross-talk and the systemic and local regulation of bone physiology can often only be addressed in entire vertebrates. Powerful genetic methods such as conditional mutagenesis, lineage tracing, and modeling of the diseases enhanced the understanding of the entire skeletal system. In this review endorsed by the European Calcified Tissue Society (ECTS), a working group of investigators from Europe and the US provides an overview of the strengths and limitations of experimental animal models, including rodents, fish, and large animals, as well the potential and shortcomings of in vitro and in silico technologies in skeletal research. We propose that the proper combination of the right animal model for a specific hypothesis and state-of-the-art in vitro and/or in silico technology is essential to solving remaining important questions in bone research. This is crucial for executing most efficiently the 3R principles to reduce, refine, and replace animal experimentation, for enhancing our knowledge of skeletal biology, and for the treatment of bone diseases that affect a large part of society. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Colonization of diatoms in and on porcine bone substrate and considerations of diatom ecology for forensic science

The presence of diatom algae in bone marrow has been used as forensic evidence of drowning for several decades; however, these studies are based on known or suspected recent drowning events. This study addresses the potential for diatoms to enter the bone marrow of skeletal remains, that is, de-fleshed long bones post-mortem. In laboratory and field experiments, bones were either inflicted with two access points by a cut and acid pitting or left intact. The bones were submerged in water for at least 1 week and up to 3 months. Samples of the bone surface and marrow were inspected for diatoms. The analysis considered the time required for diatoms to enter marrow and whether genus characteristics like size or mobility affect entry. The presence of an access point influenced diatom entry in that bones without an introduced access point had zero to one diatom present in the marrow, whereas a bone with an access point had >150 diatoms present in the marrow. The results of both laboratory and field phases suggest that diatoms will reliably colonize bone in as quickly as 1 week, establishing and maintaining communities for at least 3 months. However, the bone surface assemblages differ from the source community. Bone marrow displayed even more restrictive access to diatom colonization, resulting in communities dominated by small raphid diatoms. Based on these findings, we suggest some caveats on the use of diatoms as trace evidence in forensic science with recommendations for future avenues of research.

The influence of sex and age on bone turnover markers in the adult to geriatric Kangal shepherd dogs

OBJECTIVES

The objective of this research was to learn more about bone metabolism in intact female and male Kangal shepherd dogs during the aging process following skeletal maturity. It also evaluated the potential application of biochemical bone indicators in veterinary clinical practice.

METHODS

Bone markers were determined as bone alkaline phosphatase (BALP), osteocalcin (OC), C-terminal telopeptide of type I collagen (CTX), and cross-linked C-telopeptide of type I collagen (ICTP) in this study. Kangal shepherd dogs of different age (adult, senior, and geriatric) and sex (male and female) groups were split into six groups of equal numbers (n = 8/group).

RESULTS

In this study, the effect of age was observed on serum BALP, OC, CTX, and ICTP concentrations. Specifically, BALP was highest in geriatric female Kangal shepherd dogs, while serum OC, CTX, and ICTP concentrations were highest in geriatric male Kangal shepherd dogs. However, no effects of sex and age-sex interactions were identified. Moreover, the effects of age, sex, and age-sex interactions had no significant effect on serum creatinine, CK, LDH, Mg, and P concentrations or ALT activities. However, only sex was found to affect serum AST activities and gradually decreased with age in females. The effect of age and age-sex interactions on serum Ca concentrations was significant (the lowest serum Ca concentrations were in geriatric females), but the effect of sex was not.

CONCLUSIONS

These results show the effect of age and sex on bone turnover in Kangal shepherd dogs and provide information about bone biomarkers.

Human cells with osteogenic potential in bone tissue research

Bone regeneration after injury or after surgical bone removal due to disease is a serious medical challenge. A variety of materials are being tested to replace a missing bone or tooth. Regeneration requires cells capable of proliferation and differentiation in bone tissue. Although there are many possible human cell types available for use as a model for each phase of this process, no cell type is ideal for each phase. Osteosarcoma cells are preferred for initial adhesion assays due to their easy cultivation and fast proliferation, but they are not suitable for subsequent differentiation testing due to their cancer origin and genetic differences from normal bone tissue. Mesenchymal stem cells are more suitable for biocompatibility testing, because they mimic natural conditions in healthy bone, but they proliferate more slowly, soon undergo senescence, and some subpopulations may exhibit weak osteodifferentiation. Primary human osteoblasts provide relevant results in evaluating the effect of biomaterials on cellular activity; however, their resources are limited for the same reasons, like for mesenchymal stem cells. This review article provides an overview of cell models for biocompatibility testing of materials used in bone tissue research.

Quantifying microcracks on fractured bone surfaces – Potential use in forensic anthropology

Bone fracture surface morphology (FSM) can provide valuable information on the cause of failure in forensic and archaeological applications and it depends primarily on three factors, the loading conditions (like strain rate), the ambient conditions (wet or dry bone material) and the quality of bone material itself. The quality of bone material evidently changes in taphonomy as a result of the decomposition process and that in turn is expected to affect FSM. Porcine bones were fractured by a standardised impact during the course of soft tissue decomposition, at 28-day intervals, over 140 days (equivalent to 638 cooling degree days). Measurements of the associated microcracks on the fractured cortical bone surfaces indicated a progressive increase in mean length during decomposition from around 180 μm-375 μm. The morphology of these microcracks also altered, from multiple intersecting microcracks emanating from a central point at 0-28 cumulative cooling degree days, to longer linear cracks appearing to track lamellae as soft tissue decomposition progressed. The implications of these findings are that taphonomic changes of bone may offer the real possibility of distinguishing perimortem and taphonomic damage and also provide a new surrogate parameter for estimation of post-mortem interval (PMI) in forensics.

The effect of surgical revascularization on the mechanical properties of cryopreserved bone allograft in a porcine tibia model

Cryopreserved bone allografts(CBA) are susceptible to infection, nonunion, and late stress fracture. Although surgical revascularization by intramedullary implantation of an arteriovenous bundle (AV bundle) generates a neoangiogenic blood supply, there is potential for vascular ingrowth-mediated bone resorption to weaken the graft. For this reason, we have evaluated changes in CBA mechanical properties of structural tibial allografts with and without surgically induced angiogenesis. Cryopreserved tibia bone allografts were transplanted to reconstruct a 3.5 cm segmental tibial defect in 16 Yucatan mini pigs. Surgical revascularization was performed in half by implantation of a cranial tibial AV bundle, (revascularization group). A control group of identical size had a ligated AV bundle implanted, (ligated group). At 20 weeks micro-computed tomography (CT) measured bone mineral density (BMD) as well as bone union. Reference point indentation (RPI) compared cortex material properties, and axial compression determined the allotransplant compressive modulus. Seven of eight tibiae in the angiogenesis group were healed at both junction points at 20 weeks. Only four of eight tibiae healed in the ligated control group. There was no significant difference between the revascularization and ligated control groups in BMD and axial compression test. Similarly, RPI parameters were statistically equal. In paired comparisons with contralateral tibias, however, some RPI values were significantly worse in the ligated control group tibiae. This study demonstrates no adverse effect of surgical angiogenesis on cryopreserved structural bone allograft biomechanical properties in a large animal orthotopic segmental tibial defect model. These data suggest the potential value of surgical angiogenesis in clinical limb-sparing reconstructive surgery.

Regenerative Potential of Hydroxyapatite-Based Ceramic Biomaterial on Mandibular Cortical Bone: An In Vivo Study

Reconstruction of bone defects and maintaining the continuity of the mandible is still a challenge in the maxillofacial surgery. Nowadays, the biomedical research within bone defect treatment is focussed on the therapy of using innovative biomaterials with specific characteristics consisting of the body’s own substances. Hydroxyapatite ceramic scaffolds have fully acceptable phase compositions, microstructures and compressive strengths for their use in regenerative medicine. The innovative hydroxyapatite ceramics used by us were prepared using the tape-casting method, which allows variation in the shape of samples after packing hydroxyapatite paste to 3D-printed plastic form. The purpose of our qualitative study was to evaluate the regenerative potential of the innovative ceramic biomaterial prepared using this method in the therapy of the cortical bone of the lower jaw in four mature pigs. The mandible bone defects were evaluated after different periods of time (after 3, 4, 5 and 6 months) and compared with the control sample (healthy cortical bone from the opposite side of the mandible). The results of the morphological, clinical and radiological investigation and hardness examination confirmed the positive regenerative potential of ceramic implants after treatment of the mandible bone defects in the porcine mandible model.

Evaluation of Feline Permanent Canine Tooth Mineral Density Using Micro-Computed Tomography

The tooth is made up of three mineralized tissues, enamel, dentin, and cementum, which surround a non-mineralized tissue called the dental pulp. Micro-computed tomography (mCT) is an imaging technology based on X-rays that allows non-invasive visualization of objects at a microscopic scale, according to their radiopacity and in three dimensions (3D). Likewise, it allows the subsequent execution of morphological and quantitative analysis of the objects, such as, for example, the determination of the relative mineral density (MD). The present work aimed to describe the MD of feline teeth using mCT. The studied sample consisted of four European Shorthair cats, from which nine canine teeth were extracted per medical indication. These teeth were evaluated through dental radiography before and after their extraction. Using mCT and the CTAn software, the values of the relative mineral density of the root of each tooth and of specific segments corresponding to the coronal, middle, and apical thirds of the root were determined. Mean MD of root tissues was 1.374 ± 0040 g·cm−3, and of hard root, tissues was 1.402 ± 0.035 g·cm−3. Through mCT, it was possible to determine the mean MD values of feline canine teeth. The study of MD could become an ancillary method for the diagnosis and characterization of dental pathology.

Clinical Research Progress of Internal Brace Ligament Augmentation Technique in Knee Ligament Injury Repair and Reconstruction: A Narrative Review

Knee ligament injuries are most common in sports injuries. In general, ligament repair or reconstruction is necessary to restore the stability of the knee joint and prevent secondary injuries. Despite advances in ligament repair and reconstruction techniques, a number of patients still experience re-rupture of the graft and suboptimal recovery of motor function. Since Dr. Mackay's introduction of the internal brace technique, there has been continuous research in recent years using the internal brace ligament augmentation technique for knee ligament repair or reconstruction, particularly in the repair or reconstruction of the anterior cruciate ligament. This technique focuses on increasing the strength of autologous or allograft tendon grafts through the use of braided ultra-high-molecular-weight polyethylene suture tapes to facilitate postoperative rehabilitation and avoid re-rupture or failure. The purpose of this review is to present detailed research progress in the internal brace ligament enhancement technique of knee ligament injury repair as well as the reconstruction from biomechanical and histological research and clinical studies and to comprehensively assess the value of the application of this technique.

Veldt fires in South Africa: Implications on osteometry and the biological profile

Standard operating procedures for forensic anthropological analyses dictate that thermally altered remains should not be measured, hindering the creation of a biological profile. Few studies have addressed estimating biological parameters from burned remains, with the greatest focus of this research area being on cremated remains. However, veldt fires are more common than cremation in the South African forensic context. The aim of this study was to explore the degree of structural changes observed in domestic pig (Sus scrofa) bones associated with thermal destruction and the potential impact on the estimation of a biological profile using standard osteometric methods. A total of 96 pig femora were divided equally into two categories: fresh and dry. Within each category, equal samples were exposed to different durations of burning, namely, 5, 10, and 20 min. Ten standard femoral anthropological measurements were collected before and after burning. Technical error of measurement and Wilcoxon signed-rank tests were used to assess changes in the femoral dimensions before and after burning. Most measurements were significantly different after burning, with the fresh bones decreasing in size by up to 7.8% and the dry bones decreasing in size by up to 4.0%. The magnitude of post-burning measurement changes for both burn conditions was similar to, or smaller than has previously been reported for observer measurement errors of commonly used variables investigated for standard osteometric studies. Veldt fires are less intense than cremation, thus causing less shrinkage.

Advances in Animal Models for Studying Bone Fracture Healing

Fracture is a common traumatic injury that is mostly caused by traffic accidents, falls, and falls from height. Fracture healing is a long-term and complex process, and the mode of repair and rate of healing are influenced by a variety of factors. The prevention, treatment, and rehabilitation of fractures are issues that urgently need to be addressed. The preparation of the right animal model can accurately simulate the occurrence of fractures, identify and observe normal and abnormal healing processes, study disease mechanisms, and optimize and develop specific treatment methods. We summarize the current status of fracture healing research, the characteristics of different animal models and the modeling methods for different fracture types, analyze their advantages and disadvantages, and provide a reference basis for basic experimental fracture modeling.

Accuracy of partially and fully guided surgical techniques for immediate implant placement: An in vitro assessment

STATEMENT OF PROBLEM

Optimal implant positioning is essential to achieving predictable results. Computer-guided surgery has been reported to be an accurate technique for implant placement in healed sites, but the accuracy of guided techniques for immediate implant placement into fresh sockets is still unclear.

PURPOSE

The purpose of this experimental randomized split-mouth study in pig jaws was to determine the accuracy of partially and fully guided surgical techniques for immediate implant placement into fresh sockets and to compare 2 different methods of implant position deviations analysis.

MATERIAL AND METHODS

Twenty implants were installed in 10 pig jaws using 2 different techniques: partially guided (n=10) and fully guided (n=10). Cone beam computed tomography and digital scanning were performed before and after the surgical procedure to plan the virtual implant position and fabricate the surgical guide, as well as to determine implant position deviations. Two methods were used to evaluate implant deviations: tomographic and digital scanning. The Shapiro-Wilk test of normality was used. Deviation comparisons were carried out by using paired t tests (α=.05), and intraclass correlation coefficient (ICC) was computed to assess the agreement between the 2 methods of implant deviation analysis.

RESULTS

In the tomographic analysis, the partially guided technique resulted in significantly higher global apical and lateral coronal deviations (2.25 ±0.59 mm; 0.96 ±0.55 mm) than fully guided (1.52 ±0.89 mm; 0.75 ±0.52 mm) (P<.01 and P<.05, respectively). The analysis performed using digital scanning showed significantly higher angular, global apical, and lateral apical deviations in the partially guided (6 ±3.28 degrees; 2.49 ±1.03 mm; 2.16 ±1.07 mm) technique than in the fully guided (3.32 ±1.84 degrees; 1.5 ±0.58 mm; 0.98 ±0.67 mm) (P<.05). An ICC of 0.522 between the 2 methods of implant deviation analysis was obtained.

CONCLUSIONS

The partially guided technique was less accurate than the fully guided technique for immediate implant placement into fresh sockets. A moderate concordance was observed between cone beam computed tomography and digital scanning analyses, suggesting that more studies are required to validate and to define the most reliable method of measuring implant deviation.

Straight-segment mandibulectomy: a reproducible porcine mandibular critical-size defect model

Porcine mandibular defect models are commonly used for the preclinical evaluation of reconstruction techniques. Existing studies vary in technique, complexity, and postoperative outcomes. The procedures are complex and often described without sufficient detail. We describe in detail a simple and reproducible method for creating a critical-size mandibular defect in a porcine model. Seven hemimandibular critical size defects were created in five male Yorkshire-Landrace pigs, three with unilateral defects and two with bilateral defects. A transverse incision was made over the mandibular body. Periosteum was incised and elevated to expose the mandibular body and a critical-size defect of 30 × 20 mm created using an oscillating saw. The implant was inserted and fixed with a titanium reconstruction plate and bicortical locking screws, and the wound closed in layers with resorbable sutures. Intraoral contamination was avoided. Dentition was retained and the mental nerve and its branches preserved. The marginal mandibular nerve was not encountered during dissection. All pigs retained normal masticatory function, and there were no cases of infection, wound breakdown, haematoma, salivary leak, or implant-related complications. The procedure can be performed bilaterally on both hemimandibles without affecting load-bearing function. All pigs survived until the end point of three months. Postoperative computed tomographic scans and histology showed new bone formation, and a three-point bend test showed the restoration of biomechanical strength. Straight-segment mandibulectomy is a simple and reproducible method for the creation of critical-size mandibular defects in a porcine model, simulating a load-bearing situation.

Biomechanical comparison of proximal, distal, and anatomic tibial tunnel for transtibial posterior cruciate ligament reconstruction

No consensus has been reached on the optimal position of PCL tibial tunnel. The purpose of this study was to compare the biomechanical properties of proximal, distal and anatomic tibial tunnel in transtibial posterior cruciate ligament reconstruction. An in-vitro model of transtibial posterior cruciate ligament reconstruction was simulated using porcine tibias and bovine extensor tendons. Two models of biomechanical testing, load-to-failure loading, and cyclic loading, were performed in this study. The load-to-failure loading found that distal tibial tunnel resulted in greater ultimate load and yield load than the anatomic and proximal tunnel group (p < 0.05), whereas there were no significant differences in mean tensile stiffness among three groups (p > 0.05). The cyclic loading found no differences in the graft displacement at 250, 500, and 1000 cycles among three groups (p > 0.05). It was found that distal tibial tunnel showed superior ultimate load and yield load in load-to-failure loading testing compared with proximal and anatomic tibial tunnels, whereas no significant difference was found in terms of the mean displacement of the survived grafts in cyclic loading testing among three groups.

Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy Sensitivity to the Thermal Decay of Bone Collagen

The analysis of collagen stability is of interest in forensics, archaeology, and molecular paleontology. Collagen decay rates are often measured by thermal kinetic studies that employ liquid chromatography mass spectrometry (LC-MS) to assay collagen quantities. However, these kinetic studies generally focus on measuring the decreasing levels of collagen instead of an exact molecular concentration of each sample. Thus, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy can offer a simpler and less expensive alternative to LC-MS. The application of a new protocol to determine decreasing amounts of bone collagen in artificially decayed porcine and bovine bone was assessed. The protocol uses a forensic application of ATR FT-IR spectroscopy on size-restricted bone powder from three uniformly high temperature conditions. Also, for the first time, collagen-specific second-harmonic generation (SHG) imaging was also applied to artificially aged bone to add an independent, qualitative perspective to parallel FT-IR assessments. SHG images and ATR FT-IR spectra together reveal the same orderly bone collagen decay as found in previous thermal kinetic studies. Resulting Arrhenius plots with r² values > 0.95 suggest that the ATR FT-IR-based protocol has potential as a precise and simple tool for measuring bone collagen decay rates. The results are significant for applications of thermal kinetic studies, and our protocol can serve as an inexpensive, precise, and pragmatic means of evaluating bone collagen stability within an array of conditions.