Results Of Biomechanical Testing Research Articles

Angular Stability of Intramedullary Elastic Osteosynthesis

The article presents results of biomechanical bench tests of bone fragment fixation using the model of a transverse diaphyseal fracture in a long cortical bone in two mutually perpendicular planes for different modes of installation of flexible titanium rods by the flexible intramedullary nailing (FIN) method. The obtained results revealed a significant impact of the bending curvature of the rods, the plane of their placement, and the diameter and inclination of the perforation hole for rod introduction on the rigidity of fixation.

Should orthopedic surgeons consider the effects of gabapentin administration on bone healing while treating a long bone fracture: experimental study in a rat model.

Objective: The main purpose of the present study was to assess the radiographic, histological, and mechanical effects of gabapentin on fracture healing in a rat model of femur fracture. Materials and methods: A standard transverse fracture of the mid-diaphysis was created. A total of 60 female Wistar-Albino rats with the mean age of 13.5 ± 1.2 weeks were used for this experimental trial. The rats were randomized into four groups with 15 animals included in each group. Group A and B were the control groups whereas C and D were the treatment groups. Drugs were delivered by oral gavage twice a day with the daily dosage calculated according to body surface area conversion to the human equivalent dosing regimen of 1200 mg/day. Radiographic, histological, and biomechanical evaluation was performed. Results: We could not detect any statistically significant difference between the control and gabapentin treatment groups according to the comparative assessment of radiographic scores on the 15th and 30th days. Although no significant differences were found between the groups on the 15th day, histological scores were better in the control group on the 30th day. According to the results of biomechanical testing, the fractured femurs resected from the control group exhibited significantly more strength on the 30th day. Conclusions: According to the data we acquired during the present study, administration of gabapentin negatively affects the fracture healing process especially in the aspects of histological progression as well as the biomechanical strength of the callus in a rat model.

Presentation of a novel model of chitosan- polyethylene oxide-nanohydroxyapatite nanofibers together with bone marrow stromal cells to repair and improve minor bone defects.

Various methods for repairing bone defects are presented. Cell therapy is one of these methods. Bone marrow stromal cells (BMSCs) seem to be suitable for this purpose. On the other hand, lots of biomaterials are used to improve and repair the defect in the body, so in this study we tried to produce a similar structure to the bone by the chitosan and hydroxyapatite. In this study, the solution of chitosan-nanohydroxyapatite-polyethylene oxide (PEO) Nanofibers was produced by electrospinning method, and then the BMSCs were cultured on this solution. A piece of chitosan-nanohydroxyapatite Nanofibers with BMSCs was placed in a hole with the diameter of 1 mm at the distal epiphysis of the rat femur. Then the biomechanical and radiographic studies were performed. Biomechanical testing results showed that bone strength was significantly higher in the Nanofiber/BMSCs group in comparison with control group. Also the bone strength in nanofiber/BMSCs group was significant, but in nanofiber group was nearly significant. Radiographic studies also showed that the average amount of callus formation (radio opacity) in nanofiber and control group was not significantly different. The callus formation in nanofiber/BMSCs group was increased compared to the control group, and it was not significant in the nanofiber group. Since chitosan-nanohydroxyapatite nanofibers with BMSCs increases the rate of bone repair, the obtained cell-nanoscaffold shell can be used in tissue engineering and cell therapy, especially for bone defects.

Influence of refrigerated storage on tensile mechanical properties of porcine liver and spleen

Preservation conditions may affect internal organs thus influencing the results of protracted biomechanical tests. The influence of the freeze–thaw cycle on the mechanical behaviour of porcine abdominal organs was reported in our previous work. Here we further investigate the effects of refrigerated storage on the mechanical properties of porcine spleen and liver. Twenty-seven swine were chosen for tensile testing. To simulate the conservation conditions before biomechanical experimentation, the total sample was divided into three groups of nine individuals each and tested in a fresh state, after a freeze–thaw cycle, and after refrigerated storage (+4 °C). Fitted stress–stretch curves for each tissue type were obtained by employing a modified Fung model for isotropic behaviour. The results suggest statistically significant effects of refrigerated storage on the spleen but negligible influence on the liver. Similarly to the impact of the freeze–thaw cycle, refrigerated storage caused a decrease in the mechanical properties of the spleen. This again supports the hypothesized cause of the altered behaviour of spleen due to the autolysis of elastin by elastolytic enzymes during and after the cooling period. Spleen and liver are good examples of tissue with and without elastin. These findings have wide biomechanical and decomposition implications for the study of soft tissues.

Impact of platelet-rich plasma injection timing on healing of Achilles tendon injury in a rat model.

The aim of this study was to evaluate the impact of the timing of platelet-rich plasma (PRP) application on the healing of Achilles tendon injury in a rat model. Fifty-four female Sprague-Dawley rats were divided into 4 groups: PRP preparation group (n=6); Achilles tendon tear and 150 µL of PRP received on the day following the injury (PRP day 0, group 1, n=16); Achilles tendon tear and 150 µL of PRP received on the third day following injury (day 3 , group 2, n=16); Achilles tendon tear and 150 µL of saline received on the day following injury (PRP day 0, group 3, n=16). Rats were sacrificed at 3 weeks. Consequently, biomechanical and histologic analyses were performed. According to histological evaluation, inflammation, fibroblast density, epitenon thickness, and collagen fiber were significantly higher in group 1 than in group 2 (p<0.05). Biomechanical testing results of group 1 and group 2 were inferior to the control group, while the differences were not significant (p>0.05). Based on histological criteria, results of the present study suggest that immediate injection of PRP for tendon injury improves tendon healing in rats. Although the use of PRP is well recognized in orthopedic surgery, we aimed to highlight the importance of immediate application of PRP for acute tendon injury.

Minimally invasive arthrodesis for chronic sacroiliac joint dysfunction using the SImmetry SI Joint Fusion system.

Chronic sacroiliac (SI) joint-related low back pain (LBP) is a common, yet under-diagnosed and undertreated condition due to difficulties in accurate diagnosis and highly variable treatment practices. In patients with debilitating SI-related LBP for at least 6 months duration who have failed conservative management, arthrodesis is a viable option. The SImmetry® SI Joint Fusion System is a novel therapy for SI joint fusion, not just fixation, which utilizes a minimally invasive surgical approach, instrumented fixation for immediate stability, and joint preparation with bone grafting for a secure construct in the long term. The purpose of this report is to describe the minimally invasive SI Joint Fusion System, including patient selection criteria, implant characteristics, surgical technique, postoperative recovery, and biomechanical testing results. Advantages and limitations of this system will be discussed.

Biomechanical effects of pedicle screw fixation on adjacent segments

Various biomechanical investigations have attempted to clarify the aetiology of adjacent segment disease (ASD). However, no biomechanical study has examined in detail the deformation behaviour of the adjacent segments when both pure torque and an angular displacement load are applied to the vertebrae along multiple segments. The purpose of this study is to investigate the biomechanical effects of pedicle screw fixation on adjacent segments. Ten cadaveric lumbar spines (L2-L5) of boars were used. Control and fusion models were prepared by disc damage and pedicle screw fixation of each specimen, and then, bending and rotation tests were performed using a six-axis material tester. In the biomechanical tests regulated by an angular displacement load, the range of motion (ROM) of the cranial and caudal adjacent segments in antero-posterior flexion and lateral bending was increased by about 20% (p<0.05), and the maximal torque in the fusion model was about threefold (p<0.05) that in the control model. And in axial rotation, the ROM of cranial and caudal adjacent segments was increased by about 100% (p<0.001), and the maximal torque was about sixfold (p<0.01) that in the control model. The ROM of adjacent segments was significantly increased after pedicle screw fixation as assessed by biomechanical tests regulated by an angular displacement load, but not in those regulated by torque. We present the results of biomechanical tests regulated by torque and angular displacement and show that the maximum torque of the fusion model was larger than that of the control model in the biomechanical test regulated by an angular displacement load, suggesting that mechanical stress on the segments adjacent to the fused segment is large. We think that ASD arises after spinal fusion surgery as a mechanism to compensate for the ROM lost due to excessive fusion by pedicle screw fixation, so that a large torque may be applied to adjacent segments within a physiologically possible range, and it might gradually lead to a degenerative intervertebral disc or progression of spondylolisthesis in the adjacent segments.

Modification of elastic stable intramedullary nailing with a 3rd nail in a femoral spiral fracture model – results of biomechanical testing and a prospective clinical study

BackgroundElastic stable intramedullary nailing (ESIN) is the standard treatment for displaced diaphyseal femoral fractures in children. However, high complication rates (10-50%) are reported in complex fractures. This biomechanical study compares the stiffness with a 3rd nail implanted to that in the classical 2C-shaped configuration and presents the application into clinical practice.MethodsFor each of the 3 configurations of ESIN-osteosynthesis with titanium nails eight composite femoral grafts (Sawbones®) with an identical spiral fracture were used: 2C configuration (2C-shaped nails, 2 × 3.5 mm), 3CM configuration (3rd nail from medial) and 3CL configuration (3rd nail from lateral). Each group underwent biomechanical testing in 4-point bending, internal/external rotation and axial compression.Results2C and 3CM configurations showed no significant differences in this spiroid type fracture model. 3CL had a significantly higher stiffness during anterior-posterior bending, internal rotation and 9° compression than 2C, and was stiffer in the lateral-medial direction than 3CM. The 3CL was less stable during p-a bending and external rotation than both the others. As biomechanical testing showed a higher stability for the 3CL configuration in two (a-p corresponding to recurvation and 9° compression to shortening) of three directions associated with the most important clinical problems, we added a 3rd nail in ESIN-osteosynthesis for femoral fractures. 11 boys and 6 girls (2.5-15 years) were treated with modified ESIN of whom 12 were ‘3CL’; due to the individual character of the fractures 4 patients were treated with ‘3CM’ (third nail from medial) and as an exception 1 adolescent with 4 nails and one boy with plate osteosynthesis. No additional stabilizations or re-operations were necessary. All patients achieved full points in the Harris-Score at follow-up; no limb length discrepancy occurred.ConclusionThe 3CL configuration provided a significantly higher stiffness than 2C and 3CM configurations in this biomechanical model. These results were successfully transmitted into clinical practice. All children, treated by 3CL or 3CM according to the individual character of each fracture, needed no additional stabilization and had no Re-Do operations. As a consequence, at our hospital all children with femoral diaphyseal fractures with open physis are treated with this modified ESIN-technique.

Biomechanical effects of menopause in ovariectomized rats’ femurs

Objective: To demonstrate the biomechanical changes in rat bones occurred by surgical menopause and to search for correlation between biomechanical test results and bone mineral density (BMD) measurements.Methods: Thirty female Wistar-albino rats aged ∼6 months and weighed ∼250–300 g were randomized into ovariectomy, sham and control groups. After 6 months, rats were sacrificed and right femurs were extracted. BMD measurements and three point bending biomechanical tests were made in femurs.Results: The difference among the mean BMD measurements of three groups were found to be statistically significant (Pr > F value <0.0001). Mean elastic module, maximum elongation and femoral diameters were also found to be statistically significantly different (Pr > F value <0.05). Ovariectomised and sham-operated groups were significantly different in terms of elastic modulus. Ultimate force did not differ among the groups significantly. The difference between ultimate strain and maximum elongation of the ovariectomy and sham operated group was statistically significant.Conclusions: Bone quality was deteriorated and fragility was increased in rats 6 months after surgical menopause. Sole BMD measurement might not be reliable in evaluation of osteoporosis and fracture risk. Biomechanical quality of bone is more important than its mineral content in determining fragility.

The biomechanical and histological effects of platelet-rich plasma on fracture healing.

Platelet-rich plasma (PRP) includes growth factors and proteins that accelerate and stimulate bone regeneration and tissue recovery. The aim of this study was to evaluate the effects of PRP on fracture healing in terms of biomechanics and histology. Seventy female rats were included in this experimental study. They were divided into three groups: Group I (no PRP, n = 30), Group II (PRP added, n = 30) and Group III (control, n = 10). The left femurs of the rats in Groups I and II were osteotomized and fixed by K-wires. Although no additional intervention was performed on Group I rats, PRP was applied to the fracture sites of Group II rats. The remaining ten rats were used as the control group of the biomechanical test (Group III). In the fourth week, nine femurs from Group I and ten femurs from Group II, and in the ninth week, nine femurs from each group were removed, and bone recovery was assessed histologically according to Modified Lane-Sandhu histological scoring criteria. Three-point bending test was applied to femurs for biomechanical evaluation in the ninth week. Histological healing was found to be significantly higher in Group II than in Group I (p < 0.05). Furthermore, biomechanical test results showed that healing quantity and bone strength were significantly better in Group II than in Group I (p < 0.05). PRP is a widely studied material in the physiology of fracture healing. The results of this study demonstrated the ameliorative biomechanical effects of PRP on fracture healing, in addition to accelerating the histological union of fractures. In the light of these results, PRP could be a viable alternative to accelerate the healing of fractures, late unions or non-unions. Prospective comparative study, Level II.

Sheep colon acellular matrix: Immunohistologic, biomechanical, scanning electron microscopic evaluation and collagen quantification

Colon decellularization provides three-dimensional biologic scaffold without any cell elements with preservation of extracellular matrix in order to enable autologous cell seeding for tissue augmentation without any immunological response. This study was performed to investigate the safety and feasibility of sheep colon decellularization as a first step of colon tissue engineering. The process of sheep colon decellularization was done in four stages which included scaffold preparation, histologic examination and microscopic investigations to reveal the remaining cellular deposits, biomechanical evaluation and collagen quantification studies by measurement of hydroxyproline content of normal and decellularized sheep colon. Decellularized colon scaffold revealed complete cell removal under a light microscope while 4',6-diamidino-2-phenylindole, di-hydrochloride (DAPI) staining confirmed no deoxyribonucleic acid (DNA) residues. Decellularized colon displayed preserved ultrastructure, comparable biophysical properties (resistance to unidirectional stretch forces) and higher hydroxyproline content. The results of biomechanical tests proved that the decellularized matrix did not bear any unexpected damages or structural changes which would make it unable to tolerate in vivo forces and stretches. The microscopic images captured after staining the tissue with Picro-sirius red also showed that the collagen in extracellular matrix is well preserved; this was confirmed by scanning electron microscopy. This implies that the scaffold prepared by this method is suitable for tissue augmentation or transplantation.

The Effect of Heparan Sulfate Application on Bone Formation during Distraction Osteogenesis

Bone morphogenetic proteins (BMPs) are recognized for their ability to induce bone formation in vivo and in vitro. Their osteogenic and osteoinductive properties are tightly regulated by the secretion of specific BMP antagonists, which have been shown to physically bind and sometimes be blocked by the extracellular proteoglycan heparan sulphate side chains (from hereon referred to as HS). The purpose of this study was to investigate if local application of 5 µg of HS proteoglycan to a bone regenerate site in a mouse model of distraction osteogenesis (DO) can accelerate bone healing and affect the expression of key members of the BMP signaling pathway. DO was performed on the right tibia of 115 adult male wild-type mice. At mid-distraction (day 11), half the group was injected locally with 5 µg of HS, while the other half was injected with saline. The mice were sacrificed at 2 time-points: mid-consolidation (34 days) and full consolidation (51 days). The distracted tibial zone was then collected for analysis by μCT, radiology, biomechanical testing, immunohistochemistry, and histology. While μCT data showed no statistically significant difference in bone formation, the results of biomechanical testing in stiffness and ultimate force were significantly lower in the HS-injected bones at 51 days, compared to controls. Immunohistochemistry results also suggested a decrease in expression of several key members of the BMP signaling pathway at 34 days. Furthermore, wound dehiscence and infection rates were significantly elevated in the HS group compared to the controls, which resulted in a higher rate of euthanasia in the treatment group. Our findings demonstrate that exogenous application of 5 µg of HS in the distracted gap of a murine model had a negative impact on bone and wound healing.

Histologic and Biomechanical Studies of Tendon-To-Bone Healing After Autologous and Allogeneic Bone Transplants

Compare histologic and biomechanical differences of tendon-to-bone healing between autologous and allogeneic bone transplants. Adult, healthy, New Zealand white rabbits were used to establish the extra-articular tendon-to-bone healing model with the left hind limb transplanted with allogeneic bone and the right hind limb transplanted with autologous bone. After 3, 6, and 12 weeks after the transplant, the rabbits were killed to collect tendon-to-bone specimens, and then the healing processes in tendon-to-bone interfaces were examined. All rabbits grew well after incision without infection and can freely move. Histologic observations 3 and 6 weeks after surgery and biomechanical test results 6 weeks after surgery were statistically different between the autologous and the allogeneic transplants (P < .05). After 12 weeks, histologic observations and biomechanical test results showed no difference between the 2 transplants (P > .05). Allogeneic bone transplant has a relatively slower tendon-to-bone healing than does autologous bone transplant, but finally allogeneic and autologous bone transplants have the same extent of tendon-to-bone healing.

Iterative design and testing of a modular anterior plate for lumbar spine fixation applications

In this study, a modular anterior lumbar plate is designed and tested in an iterative fashion. The study starts with a basic design that is built by combining same-sized modules; an approach that allow inventory costs to be decreased. The basic design is iteratively improved guided by the results of biomechanical tests performed on each new design. At the end of three iterations of improvements, the design is complete and the plate is of sufficient quality for it to be used in anterior surgical operations. Using these plates creates the advantage of being able to increase the size and slot count during surgical operations, even when some of the modules are already fixed to vertebrae. The designed modular plate is shown to be as safe for use as a rigid plate in terms of its static and fatigue biomechanical performances.

The Effect of Platelet Rich Plasma from Bone Marrow Aspirate with Added Bone Morphogenetic Protein-2 on the Achilles Tendon-Bone Junction in Rabbits

BackgroundTo determine if exogenously injected bone marrow derived platelet-rich plasma (PRP) plus bone morphogenetic protein (BMP)-2 could accelerate the healing of bone-tendon junction injuries and increase the junction holding strength during the early regeneration period.MethodsA direct injury model of the bone-tendon junction was made using an Achilles tendon-calcaneus bone junction in a rabbit. In the PRP/BMP-2/fibrin group, 0.05 mL of bone marrow derived PRP and 100 ng/mL of BMP-2 both incorporated into 0.1 mL of fibrin glue were injected into Achilles tendon-calcaneus bone junctions. The effect of the intervention was tested by comparing the results of an intervention group to a control group. The results of biomechanical testing, and histological and gross analyses were compared between the 2 groups at the following time points after surgery: 2 weeks, 4 weeks, and 8 weeks.ResultsHistologic examinations showed that woven bone developed in tendon-bone junctions at 2 weeks after surgery in the PRP/BMP-2/fibrin group. Mechanical test results showed no significant difference between the PRP/BMP-2/fibrin and control groups at 2 and 4 weeks after surgery, but the mean maximal load in the PRP/BMP-2/fibrin group was significantly higher than in the control group (p < 0.05) at 8 weeks after surgery.ConclusionsBone marrow derived PRP and BMP-2 in fibrin glue accelerated healing in a rabbit model of tendon-bone junction injury.

Histologic Stages of Healing Correlate with Restoration of Tensile Strength in a Model of Experimental Tendon Repair

Much current research is focused on biologic enhancement of the tendon repair process. To evaluate the different methods, which include a variety of gene therapy and tissue engineering techniques, histological and biomechanical testing is often employed. Both modalities offer information on the progress and quality of repair; however, they have been historically considered as two separate entities. Histological evaluation is a less costly undertaking; however, there is no validated scoring scale to compare the results of different studies or even the results within a given study. Biomechanical testing can provide validated outcome measures; however, it is associated with increased cost and is more labor intensive. We hypothesized that a properly developed, objective histological scoring system would provide a validated outcome measure to compare histological results and correlate with biomechanics. In an Achilles tendon model, we have developed a histological scoring scale to assess tendon repair. The system grades collagen orientation, angiogenesis, and cartilage induction. In this study, histology scores were plotted against biomechanical testing results of healing tendons which indicated that a strong linear correlation exists between the histological properties of repaired tendons and their biomechanical characteristics. Concordantly, this study provides a pragmatic and financially feasible means of evaluating repair while accounting for both the histology and biomechanical properties observed in surgically repaired, healing tendon.

Biomechanical and Radiographic Comparison of Demineralized Bone Matrix, and a Coralline Hydroxyapatite in a Rabbit Spinal Fusion Model

The use of bone grafts is an essential component in spinal fusion. Autologous bone has been shown to result in long-term stable arthrodesis between spinal motion segments. However, autograft can be associated with significant morbidity and a limited supply. Alternatives, such as allogeneic demineralized bone matrix (DBM), are a potential source and supplement to autograft bone. The current study compares the ability of a DBM product (BioSet RT) and a coralline hydroxyapatite (Pro Osteon 500R), for inducing spinal fusion in a rabbit model. BioSet RT, alone or in combination with autograft, and Pro Osteon 500R were implanted in the posterior lateral inter-transverse process region of the rabbit spine. The spines were evaluated at 18 weeks for fusion of the L4-L5 transverse processes using a total of 33 skeletally mature male rabbits; 4 naïve animals were also included in the study. Samples were evaluated radiographically, histologically, by palpation, and through mechanical strength testing. Radiographical, histological, and palpation measurements demonstrated the ability of BioSet RT to induce new bone formation and bridging fusion comparable to autograft. This material performed well alone or in combination with autograft material. Despite significantly higher biomechanical testing results, minimal bone formation and fusion was recorded for the Pro Osteon 500R-treated group. This in vivo study demonstrates the ability of BioSet RT to induce new bone formation, and there was a clear relationship between bridging bone and mechanical strength.

Hip Protectors for Preventing Hip Fractures Among Elderly Adults

Prevention of fractures in the elderly consists of prevention and treatment of osteoporosis, prevention of falling and prevention of fractures using injury-site protection. Since the majority of hip fractures in elderly people are caused by a sideways fall with direct impact on the greater trochanter of the proximal femur, one option to prevent the fracture is a biomechanically effective external hip protector. The biomechanical test results of an energy-shunting and energy-absorbing hip protector have demonstrated that this type of hip protector can provide an effective impact force attenuation in typical falling conditions of older adults by reducing the initial force down to the seventh part. Recent meta-analyses and systematic reviews combining findings of all different types of hip protectors suggest that in care homes and institutions with high rates of hip fracture, the use of hip protectors might help to reduce the risk of fracture to 20–60%, but there is no evidence of a public health level benefit from hip protectors for lower-risk (usually home-dwelling) elderly people.

The evaluation of mechanical properties of animal tendons after corticosteroid therapy.

The purpose of the study was to examine the effect of systemic glucocorticosteroids administration on mechanical properties of animal tendons. Twenty female Wistar rats were divided into two groups and those that formed experimental group were subjected activity of hydrocortisone given to the peritoneum. Mechanical tests were performed. Hydrocortisone administration caused reduction of force value and the increase of strain, also the value of elasticity module was significantly smaller comparing to the control group. The results of biomechanical tests suggested that glucocorticoids produce less stiffness tendon, which fails in maximum point of load. This study revealed that systemic hydrocortisone administration changes significantly mechanical properties of tendons, which may cause frequent failure of the tendon.

Biomechanical evaluation of a pre-contoured clavicle plate

Recent attention has been focused on the operative treatment of mid-shaft fractures of the clavicle. This study compares the in-vitro biomechanical properties of a pre-formed titanium clavicle plate (Acumed) to a Synthes 3.5 mm limited-contact dynamic-compression (LCDC) plate using a cadaveric osteotomy model. An osteotomy was performed on 7 pairs of human clavicles and were randomly plated with either a Synthes 3.5 mm LCDC stainless steel plate or an Acumed titanium pre-contoured clavicle plate. After plating, specimens were tested on an EnduraTEC material testing apparatus for axial compression and tension strength, as well as torsional strength in compression and tension. Biomechanical test results for plated specimens are reported for the LCDC plate and the Acumed plate, and the 2 plates are compared. This exploratory study supports investigations with larger sample sizes to determine if the Acumed pre-contoured plate differs from the LCDC plate in biomechanical properties and the clinical implications of such differences.