Biomechanical Values Research Articles

Biomechanical properties of the cornea after laser in-situ keratomileusis in myopic patients

AimThe aim of this study was to assess changes in corneal biomechanical properties in myopic eyes after laser in-situ keratomileusis (LASIK) with ocular response analyzer.Materials and methodsCorneal biomechanics was recorded before and 1 month after LASIK was done in 76 eyes for correction of myopia. Central corneal thickness (CCT) was also measured prior and 1 month postoperatively. Preoperative biomechanical values were compared with postoperative values and both were correlated with age, sex, and CCT and tissue ablation depth.ResultsIn all, 76 eyes of 38 patients were involved in this study. Mean preoperative corneal hysteresis (CH) and corneal resistance factor (CRF) were 9.7 ± 1.7 and 10.1 ± 1.7 mmHg respectively. Mean preoperative Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) were 16.2 ± 3.8 and 17.3 ± 3.9 mmHg, respectively. There was a statistically significant reduction of these parameters postoperatively (CH = 8.0 ± 1.6, CRF = 7.4 ± 1.8, IOPg = 11.7 ± 3.1, and IOPcc = 14.4 ± 2.6) mmHg. A moderate positive significant correlation between CCT and CH, CCT and CRF was found.ConclusionCorneal biomechanics represented in CH and CRF showed statistically significant reduction following LASIK.

Biomechanical behavior of MRI-signal-inducing bone cements after vertebroplasty in osteoporotic vertebral bodies: An experimental cadaver study

BackgroundConventional water-free polymethylmethacrylate cements are not MRI visible due to the lack of free protons. A new MRI-visible bone cement was developed through the addition of a contrast agent and either a saline solution or a hydroxyapatite (Wichlas et al., 2010). The purposes of the study were to examine the influence of the two MRI-signal-inducing cements on the biomechanical behavior of cadaveric osteoporotic vertebral bodies after vertebroplasty and to compare the performance of the cements with conventional polymethylmethacrylate cement. MethodsThree different cements were used: standard polymethylmethacrylate cement and two modified MRI-signal-inducing cements that were mixed with either a 0.9% saline solution or a hydroxyapatite. The modulus of elasticity for the standard polymethylmethacrylate cement was 2040MPa, and the moduli for the MRI-signal-inducing cements that were mixed with a 0.9% saline solution and a hydroxyapatite were 1477 and 1225MPa, respectively. The lumbar vertebral bodies from nine osteoporotic spines (mean age=87years, range=78–99years) of female cadavers were examined. Three groups were formed: polymethylmethacrylate cement with saline solution (n=14), polymethylmethacrylate cement with hydroxyapatite (n=12) and polymethylmethacrylate cement (n=13). The vertebral bodies were biomechanically tested before and after vertebroplasty. Stiffness was chosen as the primary biomechanical parameter. FindingsThe vertebral body stiffness was nearly two-fold greater after vertebroplasty, and this increase was statistically significant for every group. All the groups had similar vertebral body stiffness value before and after the vertebroplasty. The UNIANOVA test for multivariate analysis of variance showed no influence of lumbar level, injected cement volume and initial vertebral body stiffness. InterpretationThe elastic moduli of the cements appear to exert little influence on the biomechanical values when the cement is in the vertebral body. Based on the direct comparison with the classic polymethylmethacrylate cement, we believe that the implementation of such cements for MRI-guided vertebroplasties is feasible.

Normal biomechanical values of walking for healthy Saudi children in Riyadh city

The study of Biomechanics of walking provides us with reference data needed to distinguish between normal and abnormal walking. The purpose of this study was to determine the normal values of some walking biomechanical variables of Saudi Arabian children between the ages of 7 and 11 years. The present study was also aimed at exploring the differences between age groups in walking biomechanical variables. The study sample consisted of 50 healthy Saudi children without any structural deformities and with a body mass index (BMI) of less than overweight (BMI <20). Before collecting data, reflective markers were attached to joints of the right side in order to help in digitizing and locating three-dimensional coordinates using Motus 8 program. Then, subjects walked on a raised walkway with an AMTI force plate (500 Hz) in its middle and filmed by two cameras (50 Hz) one to the right side and the other to the backside of the subject. Results indicated that there were no significant differences in kinematic variables between groups except in stride and step lengths. In addition, there were no significant differences in kinetic variables between groups except in push of force (Y1). Results also indicated a strong relationship between walking velocity and most of the kinematic variables and the three peaks of vertical force. In conclusion, the results of this study showed clear differences between Saudi children and children of other countries. It is recommended that the values of this study be used as normal values for evaluation of walking of Saudi children between the ages 7 and 11.

Gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens

This study investigated gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens. Thirty male chickens were caponized at 8 weeks (capons); 15 capons were injected with estrogen (5 mg/bird estradiol 3-benzoate) every 2 weeks from 8 to 28 weeks, and 15 sham-operated male (shams) chickens and 15 females were selected for this trial. The results showed that the shams had lower relative abdominal and chest subcutaneous fat than females (P < 0.05). The estrogen-treated capons had greater relative abdominal and chest subcutaneous fat than shams and capons (P < 0.05), which might result from higher blood very low-density lipoproteins and triacylglycerol concentrations (P < 0.05). Caponization could dramatically increase relative abdominal fat (506%; P < 0.05). The shams had higher tibia weight and biomechanical properties, such as maximum bone strength and bending moment values than the capons (P < 0.05). Tibia biomechanical properties were reduced by estrogen treatment (P < 0.05). The females obtained the lowest biomechanical value in all treatments (P < 0.05). Histological examination revealed cavity formation in the cortical bone of estrogen-treated capons and female chickens, which suggested that estrogen reduced bone biomechanical properties by destroying its structural integrity.

Does physical fitness affect the locomotion kinematics of lower limbs in healthy adults

It is well known that obese and elderly subjects show modifications in joint range of motion (ROM) and spatio-temporal gait parameters. This is presumably due to a reduction in muscle strength and flexibility [1], but there are few quantitative studies that objectively measure the influence of physical performance on gait pattern. In this study, we investigated if different levels of strength and flexibility could affect the kinematics of lower limbs in a group of healthy adults. Sixteen normalweight subjects (age, 27.1±5.0 yr; BMI, 22±2.1 kg/m2; preferred walking speed 5.5±0.5 km/h) performed an isometric maximal voluntary contraction (iMVC) on a horizontal leg press equipped with two force plates. The V-sit and reach test was used to assess flexibility. An optoelectronic system was used to measure kinematics while subjects performed 10 min of treadmill walking at 5.5 km/h. We calculated the main spatio-temporal parameters, the ROM and the angular values of pelvis and lower limbs joints at heel strike and toe off events. To find possible associations between physical fitness and biomechanical values, we used the stepwise backward logistic regression analysis, adjusted for age, height and weight. Significant negative associations were identified between iMVC and knee angle at heel strike (F=7.831, p<0.01). Pelvic rotation ROM (F=7.31, p<0.01), knee ROM (F=5.061, p<0.05) and plantarflexion at heel strike (F=4.154, p<0.05) were positively associated with iMVC, as much as flexibility with hip extension at toe off (F=4.355, p<0.05). We found that, in accord with Ko et al. [2], the maximum knee extensor strength was related to modifications of knee ROM. In conclusion, it seems that even in adulthood, different values of strength and flexibility could affect some components of gait kinematics.

The Relationship between Corneal Biomechanics and Corneal Shape in Normal Myopic Eyes

Objectives: To investigate the possible association between corneal biomechanical parameters and morphological properties in a normal myopic population.Methods and patients: The study consisted of 480 normal myopic eyes (240 healthy volunteers), with ages ranging from 18 to 44 years (mean, std 23.84 ± 5.08 years), and mean spherical equivalent (MSE) ranging from -14.00 to -1.13 D (mean, std –5.68 ± 2.17 D). Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using the Ocular Response Analyser (ORA; Reichert Ophthalmic Instruments, Depew, New York, USA) in both eyes. Pentacam (Oculus GmbH, Wetzlar, Germany, and software version 1.17r27) were used to obtain corneal central elevation and corneal asphericity (Q value within 6 mm diameters) of both anterior and posterior surfaces, corneal central thickness (CCT), corneal volume (CV) and corneal spherical aberration values. Corneal volume was calculated within diameters from 1.0 to 6.0 mm with 0.5 mm steps centered on the apex to create the corneal-volume distribution. Pearson correlation coefficient was used for analysis on relationships between CH, CRF and Pentacam parameters (CV, elevation, Q-value, spherical aberrations, et al).Result: The values of CH and CRF presented normal distribution and the mean CH was (10.38 ± 1.36) mmHg, and the mean CRF was (10.70 ± 1.59) mmHg. There is a good correlation between CH, CRF and CCT (CH: r=0.54, P=0.000*, CRF: r=0.61, P=0.000*), and a stable correlation with each CV value (r≈0.5, P=0.000*) within central 6 mm diameter corneal region. On the other hand, CH and CRF were negatively correlated with anterior central elevation (CH: r=-0.136*, P=0.002*; CRF: r=-0.152*, P =0.001*), positively correlated with Q value of anterior surface (CH: r=0.136*, P=0.002; CRF: r=0.132*, P=0.003) and corneal spherical aberration (CH: r=0.184*, P=0.000*; CRF: r=0.191*, P =0.000*).Conclusions: There is a homogeneous relationship displayed between corneal biomechanical parameters (CH and CRF) and corneal morphological features. Our results suggest high biomechanical values might be related to central flattening and oblate corneal shape.

Morphometric analysis and functional correlation of tibial and femoral footprints in anatomical and single bundle reconstructions of the anterior cruciate ligament of the knee

The anterior cruciate ligament (ACL) is composed of an infinite number of fibers whose individual anatomical and biomechanical features have been well defined. Although numerous biomechanical studies have shown that reconstruction that is as anatomical as possible results in better control of rotational laxity, very few studies have investigated the surface area of tibial and femoral insertion sites in these reconstructions. The aim of this study was to compare the surface areas of tibial and femoral insertion sites in single and double bundle reconstructions and correlate these findings with the isometry profile obtained. Our hypothesis was that double bundle (DB) reconstruction results in better filling of the native ACL footprint thus increasing the biomechanical value of available graft tissue. Forty-six patients underwent computer navigated ACL using hamstring tendons: 23 underwent single bundle (SB) and 23 DB reconstruction. The Praxim navigation station equipped with ACL logics software made it possible to digitize insertion site footprints, register perioperative data for graft position as well as anteroposterior and rotational laxities and pivot shift. There was a statistically significant difference between the two groups for tibial and femoral insertion site surface areas: 71 mm(2) ± 17 (SB) versus 99.9 mm(2) ± 30 (DB) for the tibia, 67 ± 11 mm(2) (SB) versus 96.9 mm(2) ± 28 (DB) for the femur. Isometry profiles showed that anisometry was favorable in all cases: 2.5 mm ± 2 for SB; 2.9 mm ± 2 for the anteromedial bundle (AMB) with DB and 9.6 mm ± 3.7 for the posterolateral bundle. When both groups were combined, there was a statistically significant correlation between the size of tibial insertion surface area and anteroposterior and rotational laxity. This study confirms that better filling of native ACL footprint surface areas results in better control of anteroposterior laxity. Level IV.

A comparative biomechanical analysis of term fetal membranes in human and domestic species

The purpose of this study was to biomechanically characterize and compare human, porcine, equine, and ovine fetal membranes. Noncontact metrology was used for topographic analyses. Uniaxial tensile testing was performed to resolve specific biomechanical values. Puncture force and radial stresses were determined with biaxial puncture testing. Microstructure and surface tortuosity were analyzed histologically. Equine and human membranes sustained larger magnitude loading, but ovine and porcine membranes exhibited stronger material properties. Biaxial puncture validated uniaxial results; human and equine groups accommodated the largest loads but lowest stresses. Equine membranes were mostly vascularized; tortuosity was highest in porcine membranes. Species' gestation length was correlated positively with membrane thickness. The anatomy of placentation and length of species gestation show distinct relationships to membrane biomechanics. Unlike other species, human fetal membranes do not compensate for structural weakness with a thicker membrane. This finding may explain the high incidence of preterm premature rupture of membranes in humans.

Biomechanical Study of SonicWeld Rx Pin in Cortical Bone Graft Layering Technique

The purpose of this in vitro study was to determine the biomechanical values of the SonicWeld Rx pin system in comparison with titanium screws for use in onlay cortical bone grafting. In this study, 2.1-mm SonicWeld Rx pins and 1.5-mm titanium screws, measuring 7 mm in length, were used. Sawbone blocks were positioned to simulate an onlay bone graft, and the pins and screws were used to replicate bicortical fixation. Four groups were designated for vertical load application, and failure of the fixation was determined when stability was compromised. Study groups consisted of fixation material types and number of fixation appliances. A Bose Electroforce 3300 system was used to deliver the force and to obtain data. Comparison of SonicWeld Rx 1-pin fixation with titanium 1-screw fixation showed similar peak resistance loads. Average peak loading resistance for SonicWeld Rx 1-pin fixation was 65.54 N and that for titanium 1-screw fixation was 59.37 N, with no significant difference (P = .9698). Average peak strength of SonicWeld Rx 2-pin and titanium 2-screw fixations was 110.24 and 97.3 N, respectively, with no significant difference (P = .1041). Based on the measured biomechanical values, SonicWeld Rx fixation can withstand similar peak load forces compared with that of titanium screw fixation. The SonicWeld Rx fixation can be an alternative method of fixation for onlay bone grafting in dentoalveolar ridge augmentation.

Load-Bearing at the Meniscofemoral Joint: An in vitro Study in the Canine Knee

ABSTRACT Background The role of the menisci on tibial load transmission and stress distribution has been extensively studied, but few studies have focused on the meniscofemoral joint during physiologic weightbearing. The objective of this study was to determine the contact areas and local contact stresses at the meniscofemoral interface during physiologic range of motion and axial-loading in the canine knee and to determine the influence of a partial or total meniscectomy. Methods Both fresh-frozen knees of 3 hound-type canines were tested in a universal testing machine configured for an axial-load of 90-120 N. Measurement of the contact area and the local contact stress were done at three different knee angles (30; 50; 70) and with both menisci intact, after partial meniscectomy, and after total meniscectomy. Pressure distribution was estimated by using pressure sensitive film inserted above the menisci. Results After partial meniscectomy, contact areas at 50° of knee flexion decreased approximately 25% on both femoral condyles, and local contact stress increased 30% on the medial femoral condyle but remained unchanged on the lateral. After total meniscectomy, contact areas at 50° of knee flexion decreased approximately 75% on both femoral condyles, and local contact stress increased approximately 60% on the medial compartment and 100% on the lateral compartment. Conclusions These data suggest that a conservative partial meniscectomy leaves the meniscus with an inferior weight distribution function; decreasing, but not canceling the protection on the femoral hyaline cartilage. A dramatic decrease of contact area followed by an increase of local contact stress was noted after a total meniscectomy. The clinical value of this study is to emphasize the biomechanical value of surgical procedures addressing the repair of damaged menisci.

Time Course of Corneal Biomechanical Parameters After Phacoemulsification With Intraocular Lens Implantation

To assess the time course of corneal biomechanical parameters after phacoemulsification with intraocular lens implantation. We examined 54 eyes of 33 consecutive patients undergoing cataract surgery. We quantitatively assessed the values of corneal biomechanics characterized by corneal hysteresis (CH) and corneal resistance factor (CRF) using an Ocular Response Analyzer before and 1 day, 1 week, 1 month, and 3 months after surgery. We also investigated the relationship between these biomechanical parameters and central corneal thickness 3 months after surgery. The CH was 9.7 ± 1.1 (mean ± SD) mm Hg preoperatively, and 9.0 ± 1.4, 9.7 ± 1.1, 9.7 ± 1.1, and 9.7 ± 1.3 mm Hg 1 day, 1 week, 1 month, and 3 months postoperatively, respectively. The CRF was 9.5 ± 1.1 mm Hg preoperatively, and 8.8 ± 1.2, 9.2 ± 1.3, 9.1 ± 0.9, and 9.2 ± 1.2 mm Hg 1 day, 1 week, 1 month, and 3 months postoperatively, respectively. Multiple comparisons demonstrated significant differences between measurements made before and 1 day after surgery (P = 0.01 for CH and CRF, Dunnett test). Both CH and CRF were significantly correlated with central corneal thickness (Pearson correlation coefficient r = 0.29; P = 0.03 for CH and r = 0.42; P = 0.002 for CRF). Both CH and CRF decreased briefly at 1 day after cataract surgery but soon recovered to the preoperative levels, suggesting that cataract surgery does not induce a significant change in corneal biomechanics, except for 1 day postoperatively. The corneal thickness may play some role in corneal biomechanics even in postcataract eyes.

Descriptive study of topographic patterns in clinically diagnosed keratoconus

Abstract Purpose This study was undertaken with the objective of responding to some questions: how are our patients´s keratoconus? and could we establish unified topographic patterns to describe them? Methods Descriptive analysis of different parameters evaluated by Orbscan corneal topography system (BFS, RCA/RCP, anterior and posterior elevation, Simk, mean pwr, thinnest) and biomechanical indices measured with Ocular Response Analyzer (CRF and CH) as well as topographic patterns that can be found in the clinical keratoconus diagnosed between 2006 and 2009 in ophthalmology service at Hospital Clinico "Lozano Blesa" in Zaragoza. Results We have studied 40 eyes of 24 patients diagnosed with keratoconus.Subclinical keratoconus and those who had received treatment,either rigid contact lenses or implanted intracorneal ring segments were previously excluded. The average age of patients was 33.7+/‐11.1 years. Quantitative topographic descriptors were: BFS = 55.99+/‐3.35 D; RCA/RCP = 1.25+/‐0.04, anterior surface elevation = 48.08+/‐26.66 µ; back surface elevation = 107.18+/‐43.11 µ; simk = ‐5.4+/‐2.6 D, mean pwr = 48.5+/‐3.7 D; thinnest = 423+/‐67 µ; biomechanical values: CRF = 6.9+/‐1.7 and CH = 7.8+/‐1.4. Four topographic patterns are also described depending on the situation of the apex of the cone: 30% central, 35% lower, 30% inferior temporal, 5% inferior nasal. Conclusion There is great morphological variation in keratoconus, it is therefore important to unify criteria for classification. The apex location criteria allows us to make a simple classification of keratoconus and is useful for planning intracorneal ring segments implantation.

Mapping Subchondral Bone Density of Selected Donor and Recipient Sites for Autologous Osteochondral Transplantation in the Canine Stifle Joint Using Computed Tomographic Osteoabsorptiometry

To characterize donor and recipient sites for autologous osteochondral transplantation (AOT) in the canine stifle joint with respect to maximal subchondral bone density (mSBD). Descriptive laboratory study. Femora (n=15) of dogs (>20 kg). mSBD at selected donor sites within and outside the femoropatellar joint and at potential recipient sites for both femoral condyles was assessed using nonvolumetric computed tomographic osteoabsorptiometry and normalized to values obtained at the central weight-bearing aspect of the lateral femoral condyle. Only transplants harvested at the axial aspects of the lateral and medial trochlear ridge had a normalized mSBD comparable with the lateral and medial femoral condyle. Grafts from outside the femoropatellar joint, at the most proximal aspect of the medial femoral condyle and at the most distal aspect of the trochlea (the notch area) had mSBD values 13.8-24.4% less than at the femoral condyles. Choosing between donor sites within or outside the femoropatellar joint may significantly affect subchondral bone quality of harvested transplants. Donor sites abaxial to the femoropatellar joint and at the most proximal aspect of the medial femoral condyle may provide transplants of suboptimal bone morphology, challenging their use as primary donor sites for AOT in dogs. However, this statement is based on nonvolumetric assessment of bone density, necessitating verification using volumetric density analysis to finally infer the biomechanical value of different grafts.

Evaluation of bone quality and quantity in osteoporotic mice – The effects of genistein and equol

The technology of gene manipulation is often used in mice. A crucial point for osteoporosis research is the evaluation of biomechanical and morphologic parameters. These parameters, however, are difficult to measure in mice. Nevertheless, this study demonstrates the capability of using techniques for the evaluation of bone quality and quantity after various treatments in osteopenic mice. After ovariectomy, 60 C57BL/6J mice were divided into 4 groups and were fed a soy-free diet (C) supplemented with estradiol, genistein or equol for 3 months. To analyze the osteoprotective effects of the tested supplements, we evaluated the bone biomechanical properties, histomorphometric changes and bone mineral density of the proximal tibiae metaphysis. The biomechanical parameters of genistein (GEN) were shown to be similar to those levels observed with estradiol (E). The biomechanical parameters of both GEN and E were significantly superior to those observed with C. Supplementation with equol (EQO) demonstrated higher mean biomechanical values than those observed with C. The histomorphometric evaluation demonstrated an increased number of nodes in mice treated with GEN and E as compared to the mice treated with EQO and C. Treatment with E and EQO led to improved cortical bone, which was only partly seen with the mice treated with GEN. The analysis of the bone mineral density (BMD) demonstrated that treatment with GEN and E resulted in a significant improvement as compared to the mice treated with C, while the cancellous density was significantly increased in all of the supplementation groups. This study conclusively demonstrated that bone quality and quantity parameters can be measured in mice. Furthermore, biomechanical and morphologic evaluations were shown to be reliable for use in mice. Further studies may combine these techniques with gene manipulation technology to better understand osteoporosis. Treatment with GEN resulted in improved biomechanical results and enhancement of morphologic parameters.

Effects of letrozole on bone biomarkers and femur fracture in female rats

We aimed to investigate the effects of the aromatase inhibitor letrozole on femur fracture and serum levels of alkaline phosphatase (ALP), calcium and phosphate in female rats. Intact 32 Sprague-Dawley female rats were divided into four groups (n=8): control, letrozole 0.2 , letrozole 1 (treatment of 0.2 and 1 mg/kg for six weeks) and recovery (letrozole-treated 1 mg/kg for six weeks then allowed to recover for two weeks). Besides, 24 ovariectomized rats were divided into three groups (n=8): ovariectomized+control, ovariectomized+letrozole and ovariectomized+letrozole+ estradiol (10 microg/rat). After experimental period, rats' femur bones were removed for biomechanical studies following decapitation. Serum ALP, calcium and phosphate were measured. Biomechanical values, ALP and phosphate significantly increased by letrozole in a dose-dependent manner (p<0.05) while calcium levels and net bone area decreased (p<0.05). Ultimate strength was positively correlated with ALP and phosphate and negatively correlated with calcium. The results indicate that letrozole may increase risk of bone fracture and affect bone biomarkers such as ALP, calcium and phosphate in both intact and ovariectomized rats.

Time Course of Corneal Biomechanical Parameters after Laser in situ Keratomileusis

Purpose: To assess the time course of corneal biomechanics after laser in situ keratomileusis (LASIK). Methods: We examined 36 eyes of 20 consecutive patients undergoing LASIK for low to moderate myopia. We quantitatively assessed the values of corneal biomechanics characterized by corneal hysteresis (CH) and corneal resistance factor (CRF) using an Ocular Response Analyzer™ (Reichert Ophthalmic Instruments) before and 1 week, 1, 3, and 6 months after surgery. We carried out this measurement 3 times, and the average value was used for statistical analysis. Results: The CH was 10.6 ± 1.7 (mean ± SD) mm Hg preoperatively, and 8.6 ± 1.2, 9.0 ± 1.7, 9.0 ± 1.4, and 8.9 ± 1.5 mm Hg 1 week, 1, 3, and 6 months postoperatively, respectively. The CRF was 10.0 ± 1.7 mm Hg preoperatively, and 7.3 ± 1.5, 7.6 ± 2.0, 7.8 ± 1.6, and 7.7 ± 1.6 mm Hg 1 week, 1, 3, and 6 months postoperatively, respectively. The variances of the data were statistically significant (p < 0.001 for both CH and CRF). Multiple comparisons demonstrated significant differences between measurements made before surgery and at all postoperative times (at 1 week and 1, 3, and 6 months; p < 0.001 for CH and CRF, Fisher’s least significant difference test). Conclusions: Over the study period, the largest changes in corneal biomechanical parameters occurred within 1 week after surgery, and these then became nearly stable. No progressive deterioration of the corneal biomechanics was observed at any time during the 6-month follow-up period.

Vitex agnus castus as prophylaxis for osteopenia after orchidectomy in rats compared with estradiol and testosterone supplementation

Osteoporosis research undertaken in males is rare and there are only a few therapeutic options. Phytoestrogens might be a safe alternative for prophylaxis. Sixty 3-month-old male rats were orchidectomized and divided into five groups. The groups either received soy-free food (C), estradiol (E), testosterone (T) or Vitex agnus castus in different concentrations (AC high/AC low) for 12 weeks. The tibia metaphysis was tested biomechanically and histomorphometrically. The AC high group reached 87% of the biomechanical values of the estradiol group and was significantly superior to the control group. Testosterone supplementation resulted in poor biomechanical properties. The cortical bone parameters of the AC group were similar to the control group, while supplementation with estradiol and testosterone demonstrated a reduction of cortical bone. The AC high group reached 88.4% of trabecular bone area, 80.7% of trabecular number and 66.9% of the number of trabecular nodes compared with estradiol supplementation. Vitex agnus castus demonstrated osteoprotective effects in males. It preserves the cortical as well as the trabecular bone and might be a safe alternative for HRT. Testosterone supplementation has positive effects on trabecular bone, which are concurrently counteracted by the loss of cortical bone.

Biochemical and biomechanical properties of tendons in two commercial types of chickens

The quality of the attachment of meat to bone is often reported to be insufficient by more and more poultry’s consumers. This is particularly true for thigh meat in broilers. The aim of this study was to compare muscle to bone attachment (namely, tendons) from a biomechanical and a biochemical point of view in 50 standard (S) and 50 Label Rouge (LR) chickens. Carcasses weighted around 1.7 kg in the two groups. Two tendons were harvested and proceeded for passive stretch tests, prior to cooking or not, to determine main mechanical characteristics (maximum load, stiffness and longitudinal strain). Biochemical parameters such as dry matter percentage, total collagen content, collagen solubility and sulphated glycosaminoglycans (sGAGs) content were also determined. Results showed that biomechanical values differ largely between the two studied tendons. For a given tendon, the values were also different between the two groups of chickens mainly after cooking. The results clearly showed that, mainly after cooking, the mechanical resistance of tendon to stretch was better in LR than in S chickens. LR chickens were reported to have tendons with higher collagen and sGAGs contents associated with a lower collagen solubility. These differences may explain biomechanical differences observed for the two types of tendons and could be due to increased age and/or higher physical activity of LR chickens.

A biomechanical and histological evaluation of a bioresorbable lumbar interbody fusion cage

Novel spinal interbody fusion cages made of bioactive and bioresorbable composites by a unique forging process were developed. Previous in vitro study demonstrated that these cages marked excellent biomechanical values. The purpose of the present in vivo study was to evaluate the viability and advantage of this forged composite of uncalcined hydroxyapatite/poly L-Lactide (F-u-HA/PLLA) cage radiographically, biomechanically, and histologically, when compared to conventional autologous iliac bone (AIB) and carbon fiber cage (CFC). Twenty-five mature sheep underwent posterior lumbar interbody fusion at L2-3 level with pedicle screws system made of titanium. Three types of interbody fusion implants were grafted: AIB (n=7), CFCs (n=9), F-u-HA/PLLA cages (n=9). Two types of cages were packed with autologous fragmented cancellous bone harvested locally. All animals were euthanized at 120 days after surgery. The fusion scoring using the coronal view CT scans was designed to three-dimensionally evaluate fusion quality within and around cages. The mean CT scores of three groups were 33.3 points, 35.0 points, and 33.6 points in AIB, CFC, and F-u-HA/PLLA cage groups, respectively (full-score: 56 points). Statistical differences were not detected among the three groups. The mean range of motion values among fused groups had no significant difference under all pure loadings. The range of motion showed strong and significant correlation with the CT fusion scores. Histologic results demonstrated that F-u-HA/PLLA cages contacted with the surrounding bone directly, and CFC was encircled with thick fibrous tissue layers without any sign of inflammation around cages. The fusion quality of fused spinal segment using F-u-HA/PLLA cages was equal to that of AIB or CFCs both radiographically and biomechanically. In the histological observation, biocompatibility of F-u-HA/PLLA cage was obviously superior to CFC. It has been confirmed that the novel bioactive and bioresorbable cages had valuable advantages over existing CFC for use in spinal reconstructive surgery.

Load bearing at the menisco-femoral joint: an in vitro study in the canine knee (SS-22)

Background: The role of the menisci on tibial load transmission and stress distribution has been extensively studied, but few studies have focused on the meniscofemoral joint during physiologic weightbearing. The objective of this study was to determine the contact areas and local contact stresses at the meniscofemoral interface during physiologic range of motion and axial-loading in the canine knee and to determine the influence of a partial or total meniscectomy. Methods: Both fresh-frozen knees of 3 hound-type canines were tested in a universal testing machine configured for an axial-load of 90120 N. Measurement of the contact area and the local contact stress were done at three different knee angles (30; 50; 70) and with both menisci intact, after partial meniscectomy, and after total meniscectomy. Pressure distribution was estimated by using pressure sensitive film inserted above the menisci. Results: After partial meniscectomy, contact areas at 50° of knee flexion decreased approximately 25% on both femoral condyles, and local contact stress increased 30% on the medial femoral condyle but remained unchanged on the lateral. After total meniscectomy, contact areas at 50° of knee flexion decreased approximately 75% on both femoral condyles, and local contact stress increased approximately 60% on the medial compartment and 100% on the lateral compartment. Conclusions: These data suggest that a conservative partial meniscectomy leaves the meniscus with an inferior weight distribution function; decreasing, but not canceling the protection on the femoral hyaline cartilage. A dramatic decrease of contact area followed by an increase of local contact stress was noted after a total meniscectomy. The clinical value of this study is to emphasize the biomechanical value of surgical procedures addressing the repair of damaged menisci.