Cortical Bone Layer Research Articles

Mechanical properties of temporary anchorage device

Background/purposeIn order to evaluate properly the effect of different geometric designs of mini-implants on their mechanical behavior, finite element analysis (FEA) has long been a popular tool. The aim of the present study was to set up a standardized mechanical experiment to validate the effectiveness and accuracy of FEA. Materials and methodsThree commercially available mini-implants, Mondeal, Osstem, and Bio-Ray were inserted into artificial bone block with homogeneous density to remove the variability associated with bone. FEA and mechanical tests were performed. ResultsFor the bending test, a 7.57% error was found between the mechanical test and FEA. For relative and maximum displacements, results from FEA were compatible with those from mechanical tests. The results of the relative displacement from FEA (Mondeal > Osstem > Bioray) were consistent with those from mechanical tests that Mondeal provided the greatest mean displacement before failure, followed by Osstem and BioRay. Furthermore, after simulating a 2-mm cortical bone layer in the FEA test, the pullout resistance increased for all three mini-implants, yet the variations in between decreased dramatically. ConclusionBy incorporating FEA with real mechanical trial experiments, results from FEA have been validated and proved to be effective in studying the stress and strain distribution of mini-implants subjected to loading. FEA helps to evaluate how geometrical designs of mini-screws affect their clinical performance and may be useful in future improvement of screw designs. Based on our results, we have found that in clinical situations, the cortical bone layer plays an important role in the stability of the mini-implants.

Cemented reconstruction of acetabular ceiling using the vertebroplasty set in treatment of metastatic lesions.

The number of patients suffering from malignant tumors with bony metastases has been increasing. Surgery makes it possible to preserve physical function and decrease pain. Safe and efficient techniques for filling cancer-related bone defects within the pelvis are still being searched for. A total of 13 patients with cancer metastases to the acetabular ceiling area in the hip were operated on using vertebroplasty sets in the Oncological Orthopedics Department in Brzozów in the years 2010-2013. A percutaneous approach was employed in 4 patients, while in 9 the surgery was combined with acetabulofemoral joint resection and arthroplasty. Patient qualification for the treatment took into account the size and shape of the bone defect as determined per computed tomography. Pain intensity (VAS scale) and gait efficiency were evaluated before and after the treatment. All patients reported a distinct decrease in pain intensity. All of them started to ambulate and loading the joint did not aggravate the symptoms. No thrombo-embolic or infectious complications were observed. The mobility of the operated joints was good. The filling of lytic bone defects in the acetabular ceiling area determines walking efficiency and reduced pain intensity. Surgical procedures take a long time, are complicated and associated with a high risk of complications. Percutaneous administration of bone cement may be an alternative solution in patients with an intact cortical bone layer. The literature data indicate good outcomes of this approach, with a minimal number of complications. Acetabuloplasty with bone cement is a safe and effective treatment method in the case of cancer metastases to the acetabular ceiling area.

Comparison of dental implant stabilities by impact response and resonance frequencies using artificial bone

PurposeWe compared implant stability as determined by the peak frequency from the impact response with the implant stability quotient (ISQ) by resonance frequency analysis (RFA) in various artificial bone conditions. The clinical bone conditions were simulated using an artificial bone material with different cortical thicknesses and trabecular densities. Materials and methodsThe artificial bone material was solid, rigid polyurethane. The polyurethane foam of 0.8g/cm3 density was used for the cortical bone layer, and that of 0.08, 0.16, 0.24, 0.32, and 0.48g/cm3 densities for the trabecular bone layer. The cortical bone material of 4 different thicknesses (1.4, 1.6, 1.8, and 2.0mm) was attached to the trabecular bone with varying density. Two types of dental implants (10 and 13mm lengths of 4.0mm diameter) were placed into the artificial bone blocks. An inductive sensor was used to measure the vibration caused by tapping the adapter–implant assembly. The peak frequency of the power spectrum of the impact response was used as the criterion for implant stability. The ISQ value was also measured for the same conditions. ResultsThe stability, as measured by peak frequency (SPF) and ISQ value, increased as the trabecular density and the cortical density increased in linear regression analysis. The SPF and ISQ values were highly correlated with each other when the trabecular bone density and cortical bone thickness changed (Pearson correlation=0.90, p<0.01). The linear regression of the SPF with the cortical bone thickness showed higher goodness of fit (R2 measure) than the ISQ value with the cortical bone thickness. The SPF could differentiate implantation conditions as many as the ISQ value when the trabecular bone density and the cortical density changed. However, the ISQ value was not consistent with the general stability tendency in some conditions. ConclusionThe SPF showed better consistency and differentiability with implant stability than the ISQ value by resonance frequency analysis in the various implantation conditions.

3D Bio-Cad modeling of human mandible and fabrication by rapid-prototyping technology

The purpose of this study is to prepare a model of the human mandible in accordance with anatomical structure and fabricated by rapid-prototyping (RP) technology. In this study, a computed tomographic (CT) scan of a dentate mandible was obtained with a 0.3 mm voxel resolution with capability to export to DICOM format. The data were cleaned; edited and separated ‘mask’ generated for cortical bone, cancellous bone, and teeth using Mimics 10.01 and Geomagic 11.0 software. The data were imported to Solidworks from Geomagic and converted to the solid model and fabricated by 3D rapid-prototyping technique. The mandible structure was divided into layers and then an average Young’s modulus value was calculated for each layer of cortical bone and cancellous bone using the basis of CT density as in previously published protocols. In this study, the procedure of obtaining bio-CAD model of mandible methodology has nine phases: computed tomography (CT), 2D segmentation, calculating 3D object from scanned data, reverse engineering interface, point cloud data processing, surface reconstruction, solid model reconstruction, obtaining bio-CAD model, and fabricating the model using RP technology. The average Young’s Modulus value of cortical bone and cancellous bone was calculated 30100.88 MPa, and 685.42 MPa, respectively. As a result, according to expert review, examination of the anatomical structure, and literature survey, we concluded that the development of 3D human mandible model can be used to conduct research on human mandible.

Potential risk of asymptomatic osteomyelitis around mandibular third molar tooth for aged people: a computed tomography and histopathologic study.

The purpose of this study was to explore the relationship between bone mineral density and histopathological features of mandibular alveolar bone evaluated quantitatively by Hounsfield units [HU] and by histopathology in human subjects. Fifty-six mandibular molars were extracted in 50 patients. Computed tomography was obtained preoperatively, and a cortical bone biopsy was obtained on the extracted sites for histopathological evaluation. The mean cortical and cancellous bone radiodensity was 1846±118 HU and 926±436 HU, respectively. There was no correlation between age and cortical bone HU (r = −0.004, P = 0.976); however, the correlation between age and cancellous bone HU was significant (r = 0.574, P<0.0000). Significant differences in the cancellous bone between young (0–30 years), middle (31–60 years) and old patient groups (61< years) were evident (P<0.05), whereas the cortical bone presented no significant differences. The histopathological evaluation showed that the young patient group had relatively few osteomyelitis, whereas the old patient group showed 100% focal sclerotic osteomyelitis regardless of the fact that the patients had no clinical symptoms. The mean osteocyte number/unit bone area was 170.7±82.2. Negative correlation between age and osteocyte number was significant (r = −0.51, P<0.0001). Mean lacunae numbers/unit cortical bone area were 413.1±130 with non-significant negative correlation (r = −0.257, P = 0.056). The mean empty lacunae numbers/cortical bone were 242.5±145, with no correlation (r = 0.081, P = 0.559). The young patients had high osteocyte number, whereas the old patients showed reduction of the osteocytes in the cortical bone (P<0.05). Bone quality might correlate better to viable cell numbers, which influenced the osseous healing. It is suggested that the outermost layer of cortical bone may have lost its cellular activities over the years due to chronic infection, which may have provoked sclerotic changes in the cancellous bone around tooth.

Altered bone development and turnover in transgenic mice over‐expressing Lipocalin‐2 in bone

Lipocalin-2 (LCN2) is a protein largely expressed in many tissues, associated with different biological phenomena such as cellular differentiation, inflammation and cancer acting as a survival/apoptotic signal. We found that LCN2 was expressed during osteoblast differentiation and we generated transgenic (Tg) mice over-expressing LCN2 in bone. Tg mice were smaller and presented bone microarchitectural changes in both endochondral and intramembranous bones. In particular, Tg bones displayed a thinner layer of cortical bone and a decreased trabecular number. Osteoblast bone matrix deposition was reduced and osteoblast differentiation was slowed-down. Differences were also observed in the growth plate of young transgenic mice where chondrocyte displayed a more immature phenotype and a lower proliferation rate. In bone marrow cell cultures from transgenic mice, the number of osteoclast progenitors was increased whereas in vivo it was increased the number of mature osteoclasts expressing tartrate-resistant acid phosphatase (TRAP). Finally, while osteoprotegerin (OPG) levels remained unchanged, the expression of the conventional receptor activator of nuclear factor-κB ligand (RANKL) and of the IL-6 was enhanced in Tg mice. In conclusion, we found that LCN2 plays a role in bone development and turnover having both a negative effect on bone formation, by affecting growth plate development and interfering with osteoblast differentiation, and a positive effect on bone resorption by enhancing osteoclast compartment.

Anatomic Study for the Horizontal Cut of the Sagittal Split Ramus Osteotomy

The purpose of this study was to determine the posterior extension of trabecular bone and the height at which both the lateral and medial cortical bone layers of the mandibular ramus merge, using a reference point on the anterior margin of the mandibular ramus. A total of 80 adult human mandibles were studied. Starting at reference point X, we marked a line running from the anterior margin to the posterior margin of the mandibular ramus on the medial aspect of the study samples. On 2 vertical sections of the right ramus, the level at which both the medial and lateral cortical bone layers merged was determined-H1 and H2, respectively. On the horizontal cross section of the left mandible at point X, the posterior extension of trabecular bone was determined. The median values of H1 and H2 were 10.45 mm and 4.52 mm, respectively. The median value of H2 was inversely proportional to the width of the ramus. The mean extension of trabecular bone posterior to point Z (where the upper margin of the lingula merges into the continuous medial aspect of the ramus) was 17.17 mm, bearing no correlation with the ramus width. Point X is a safe and easy-to-find anatomic reference to establish the level of a sagittal split ramus osteotomy (SSRO) horizontal cut. The wider the mandibular ramus, the closer to the mandibular foramen the SSRO horizontal cut should be performed. An SSRO horizontal cut should not be performed farther than 4 mm above line X. A safe posterior limit for the SSRO horizontal cut could not be determined.

Three Dimensional Finite Element Analysis of Stress Distribution Around Implant with Straight and Angled Abutments in Different Bone Qualities

The aim of the study was to compare the stress distribution around implant in different bone qualities of D1, D2, D3, and D4 with straight and angled abutments using three dimensional finite element analysis. A three dimensional finite element model of the premaxilla region, and two solid 4.3×10mm implant, one with a straight abutment and the other with an angled abutment was done. Four distinctly different bone qualities of D1, D2, D3, and D4 were made. A static load of 178N was applied at the centre of incisal edge along the long axis of each abutment. The maximum equivalent von Misses stress values around the implants were recorded. The distribution of stresses changed considerably with abutment angulation. As angulation increased from 0° to 15° the concentration of Von Misses stresses shifted to the cortical layer of bone on the facial side of the fixture. Although Von Misses stress increased in straight abutment as the bone quality changed from D1 to D4, it was more noticeable under the loading side of the angulated abutments. The high stresses induced through angled abutments at the cervical zone of the implant due to forces and moments could be a dominant factor that may aggravate the peri-implant bone loss or changes the existing peri-implantitis direction.

Generalized method for computation of true thickness and x-ray intensity information in highly blurred sub-millimeter bone features in clinical CT images

In clinical computed tomography (CT) images, cortical bone features with sub-millimeter (sub-mm) thickness are substantially blurred, such that their thickness is overestimated and their intensity appears underestimated. Therefore, any inquiry of the geometry or the density of such bones based on these images is severely error prone. We present a model-based method for estimating the true thickness and intensity magnitude of cortical and trabecular bone layers at localized regions of complex shell bones down to 0.25 mm. The method also computes the width of the corresponding point spread function. This approach is applicable on any CT image data, and does not rely on any scanner-specific parameter inputs beyond what is inherently available in the images themselves. The method applied on CT intensity profiles of custom phantoms mimicking shell-bones produced average cortical thickness errors of 0.07 ± 0.04 mm versus an average error of 0.47 ± 0.29 mm in the untreated cases (t(55) = 10.92, p ≪ 0.001)). Similarly, the average error of intensity magnitude estimates of the method were 22 ± 2.2 HU versus an error of 445 ± 137 HU in the untreated cases (t(55) = 26.48, p ≪ 0.001)). The method was also used to correct the CT intensity profiles from a cadaveric specimen of the craniofacial skeleton (CFS) in 15 different regions. There was excellent agreement between the corrections and µCT intensity profiles of the same regions used as a ‘gold standard’ measure. These results set the groundwork towards restoring cortical bone geometry and intensity information in entire image data sets. This information is essential for the generation of finite element models of the CFS that can accurately describe the biomechanical behavior of its complex thin bone structures.

Computertomografische Auswertung von humanen Unterkiefern hinsichtlich der Schichtstärke und Knochendichte der Kortikalis

Application of function-restoring individual implants for the bridging of defects in mandibles with continuity separation requires a stable fixation with special use of the cortical bone stumps. Five section planes each of 100 computed tomographies of poly-traumatized patients' jaws were used for measuring the thickness of the cortical layer and the bone density of the mandible. The CT scans of 28 female and 72 male candidates aged between 12 and 86 years with different dentition of the mandible were available. The computed tomographic evaluations of human mandibles regarding the layer thickness of the cortical bone showed that the edge of the mandible in the area of the horizontal branch possesses the biggest layer thickness of the whole of the lower jaws. The highest medians of the cortical bone layer thickness were found in the area of the molars and premolars at the lower edge of the lower jaws in 6-o'clock position, in the area of the molars in the vestibular cranial 10-o'clock position and in the chin region lingual-caudal in the 4-o'clock position. The measurement of the bone density showed the highest values in the 8-o'clock position (vestibular-caudal) in the molar region in both males and females. The average values available of the bone density and the layer thickness of the cortical bone in the various regions of the lower jaw, taking into consideration age, gender and dentition, are an important aid in practice for determining a safe fixation point for implants in the area of the surface layer of the mandible by means of screws or similar fixation elements.

Three dimensional quantification of mandibular bone remodeling using standard tessellation language registration based superimposition

The aim of this study was to evaluate a new method to quantify longitudinal mandibular bone remodeling three-dimensionally by superimposition of cone beam computed tomography images. This method is used to quantify the treatment effects of implant-retained overdentures in 20 patients aged 52-79 at recruitment after 1 and 2 years post treatment. Three dimensional models of pre- and post-treatment were reconstructed for each patient and superimposed using Standard Tessellation Language registration method and segmentation. Color maps of the differences generated by superimposition allow detailed examination and quantification of the progressive dimensional changes of bone in a three-dimensional manner and enable the visualization of the apical displacement and thinning of the cortical layer of bone underneath the denture base. Most of the remodeling changes took place during the first year with a mean decrease in volume of 3.7% (SD = 4.4%; range = +3.7% to -15.9%, median = -3.7%). This remodeling pattern continued during the second year, but at a reduced rate of 2.5% per year (SD = 4.2%; range = +2.1% to -11.3%, median = -3.9%). Standard Tessellation Language registration based superimposition of cone beam computed tomography images may be considered an objective and reproducible method to three-dimensionally quantify mandibular bone remodeling.

Effect of Cortical Bone Layer on Fast and Slow Waves in Cancellous Bone: Investigations Using Stratified Models

Fast and slow longitudinal waves can propagate through cancellous bone in the direction of the strong trabecular orientation. In in vivo experiments, the cortical bone layer surrounding cancellous bone is considered to affect the fast and slow wave propagations. In this study, the effects of the cortical bone layer were investigated using the stratified models of cancellous bone. In the experimental and simulated results, it was shown that the boundary condition between the cancellous and cortical bone regions affected both the fast and slow waves, particularly the slow wave. The slow wave could be clearly observed for the stratified bone model with a distinct boundary, but the slow wave amplitude decreased as the boundary became less distinct. This was because the generation of the slow wave was interrupted by the gradually varying pore spaces. Moreover, it was shown that the reflected waves within the cortical bone layer could affect the observation of the fast and slow waves. Despite the effects of the cortical bone layer, both the fast and slow waves could be observed for all stratified bone models.

Effect of Cortical Bone Layer on Fast and Slow Waves in Cancellous Bone: Investigations Using Stratified Models

Fast and slow longitudinal waves can propagate through cancellous bone in the direction of the strong trabecular orientation. In in vivo experiments, the cortical bone layer surrounding cancellous bone is considered to affect the fast and slow wave propagations. In this study, the effects of the cortical bone layer were investigated using the stratified models of cancellous bone. In the experimental and simulated results, it was shown that the boundary condition between the cancellous and cortical bone regions affected both the fast and slow waves, particularly the slow wave. The slow wave could be clearly observed for the stratified bone model with a distinct boundary, but the slow wave amplitude decreased as the boundary became less distinct. This was because the generation of the slow wave was interrupted by the gradually varying pore spaces. Moreover, it was shown that the reflected waves within the cortical bone layer could affect the observation of the fast and slow waves. Despite the effects of the cortical bone layer, both the fast and slow waves could be observed for all stratified bone models.

Numerical investigation of ultrasound reflection properties in cancellous bone

Bone is composed of two components of cancellous and cortical bones, and cancellous bone is generally surrounded by cortical bone. Therefore, ultrasound waves propagating in bone can reflect at the boundary between cancellous and cortical bones. In this study, the ultrasound reflection properties in cancellous bone were numerically simulated using a finite-difference time-domain (FDTD) method with microcomputed tomographic (μCT) models of the bone. From the simulated results, it was investigated how the ultrasound waves propagating in cancellous bone could reflect at the boundary. The reflected waveform at normal incidence to the boundary was calculated using the numerical model comprised of two layers of cancellous and cortical bones, and only the reflection properties were derived by subtracting the waveform calculated using the model adopting the absorbing boundary condition instead of the cortical bone layer. In the case of the strong trabecular orientation parallel to the ultrasound propagation, the reflections of both fast and slow longitudinal waves could be observed.

50 Years Ago in CORR: Anterior Excision and Vertebral Body Fusion for Intervertebral Disk Syndromes of the Lower Lumbar Spine: Three- to Five-Year Results in 224 Cases Paul H. Harmon, MD, FACS CORR 1963;26:107-127

Most contemporary reports of the results of surgical procedures routinely describe complications. (A symposium in this issue—Volume 470 Issue No. 6 of CORR—is devoted to complications of spinal surgery.) Harmon, in 1960 [1] and 1963 [2], described in detail an anterior surgical approach for treating disc protrusion and degenerated discs, “utilizing a surgical approach that is free of the hazard of blood loss and where vision of the pathology is optimal” [1]. Complications were not always emphasized in reports from the literature of that time. In these two articles, Harmon mentions medical complications only several times, despite reporting large numbers of cases (250 in the 1960 article and 650 in the 1963 article): “…there has been only a single case (from a total of 550 cases) with neurologic complications…” and “The mortality has been nil, neurologic complications negligible, and the morbidity from all causes has been less than 1 per cent” [2]. He considered pseudarthrosis a “severe complication.” Harmon emphasized surgical techniques in both articles (the earlier article [1] contains two-parts, with the second devoted to technique). Figures 10 and ​and1111 from his 1963 article illustrate the types of grafts he considered essential to achieve fusion. “Definite trabecular osseous union has been observed in 95 per cent with autogenous grafts. A rate of union 10 per cent lower has been observed with frozen homogenous grafts.” He favored autogenous “sandwich grafts” consisting of alternate layers of tibial cortical and cancellous bone. Fig. 10 Halftone drawings, demonstrating a transvertebral grafting procedure on the anterior aspect of the lumbosacral joint. The lower right-hand figure shows insertion of full -thickness iliac graft, “coin” type. Two such grafts per level are ... Fig. 11 An alternative technique of preparation of graft bed and insertion of 2 rectangular grafts illustrated for the L-4 level: (A) incision in the anterior ligament; (B) preparation of graft bed; (C) completed grafting procedure. (Reprinted with permission ... Harmon used a characteristic categorical rating of the times: “Good and excellent results are both highly acceptable; in the former arc persons exhibiting only occasional and fleeting nonincapacitating reminders of their former disorder, while in the latter, the patients are entirely without symptoms. Fair results describe patients who are occasionally disabled with recurrent low back pains and/or radicular pain, but are improved as compared with their preoperative state. Unimproved (or poor) is self-explanatory.” In various subcategories, he reported 80% to 96% good or excellent results. “Considering all diagnostic subdivisions and all age groups, good and excellent results have been obtained in slightly more than 90 per cent of the cases.” Such categories are rarely used in contemporary reporting because they are subjective, various surgeons would rate patients differently, and because we emphasize validated patient-generated evaluations. Today, most reports give complications more attention, perhaps owing to the emphasis on patient safety. Harmon’s reports were characteristic for the time, but we wonder how rigorously complications, including the less severe complications, were recorded: certainly they were not always reported. Nonetheless, he seemed to improve most of his patients using meticulous techniques.

THE INNOVATED LASER ASSISTED FLAPLESS CORTICOTOMY TO ENHANCE ORTHODONTIC TOOTH MOVEMENT

Introduction: Corticotomy-facilitated orthodontics provides a means for rapidly moving teeth purportedly with little damaging effects to the periodontium and with greatly reduced treatment time. The aim of this study was to enhance the orthodontic tooth movement by reducing the cortical bone layer (resistant to bone re-sorption relative to spongious bone) following Erbium, Chromium doped Yttrium Scandium Gallium Garnet (Er-Cr: YSGG)laser irradiation, without reflection of surgical soft tissue flap. Methods: In the present experimental study, 8 New Zealand Male rabbits were the samples for the research. The right first premolar of each rabbit (experiment group) underwent treatment for mesial movement with 75 gram of orthodontic force by using closed Ni-Ti coil spring (Dentaurum®). Coil spring was fixed in the cervical region of first premolars by means of ligature wire and No-Mix composite (Dentaurum®) and also activated to the cervical site of incisors. The left first premolars of the subjects were considered as the control group. Laser corticotomy was performed in anesthetized rabbits. Samples were sacrificed for determination of tooth movement after initiating premolar protraction on the 21 th day. The amount of orthodontic tooth movement was assessed by using a metal feeler gauge with the precision of 0.01 mm, between mesial surface of the second premolars and distal surfaces of the first premolars. The statistical package of SPSS (Kolmogorov - Smirnov and ANOVA test) was used for analytical evaluation of the measurements. Results: The amount of orthodontic tooth movement in the experimental group (mean=1.653±0.34 mm) was significantly (p<0.001) greater than that of the control group (mean=0.936 ±0.28 mm). The innovated laser assisted corticotomies enhanced the rate of orthodontic tooth movement on the intervention side, significantly (p<0.001). Conclusion: The innovated method of laser assisted flapless corticotomy is a useful procedure for reducing treatment time and damage to periodontium. It also eliminates the necessity of more invasive intervention of flap surgery.

Factors affecting stresses in cortical bone around miniscrew implants

To evaluate various types of stress in cortical bone around miniscrew implants using finite element analysis. Twenty-six three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using Abaqus (Dassault Systèmes Simulia Corp, Providence, RI), a commercial finite element analysis software package. The model variables included implant design factors and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone were compared between the different models for each factor. The results demonstrated that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (thread shape, thread pitch, and cortical bone thickness). Miniscrew implant diameter, head length, and thread size as well as the elastic modulus of cancellous bone affect the stresses in cortical bone layer surrounding the miniscrew implant and may therefore affect its stability.

Estudo biomecânico da fixação transcortical ou transesponjosa do enxerto de tendão patelar com pinos bioabsorvíveis na reconstrução do LCA em ovinos

OBJETIVO: Determinar a resistência inicial de fixação do sistema RigidFix® e comparar com o método tradicional de fixação que utiliza parafusos de interferência metálicos. Avaliar a resistência da fixação com o sistema RigidFix® ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. MÉTODOS: 40 espécimes de joelhos (soldras) de ovinos, foram submetidos à reconstrução do ligamento cruzado anterior (LCA)utilizando enxerto osso-tendão-osso. Em 20 espécimes utilizou-se o método RigidFix®, este grupo foi subdividido em dois, 10 joelhos foram utilizados para fixação através da esponjosa e 10 para fixação cruzando a tábua óssea cortical. Nos 20 espécimes restantes fixou-se o enxerto com parafusos de interferência metálico de 9mm. RESULTADOS: A comparação do método RigidFix® com o método de fixação com parafuso de interferência metálico não mostrou diferenças estatisticamente significativas ao se considerar carga máxima e rigidez, também não houve diferenças estatisticamente significativas ao se modificar o posicionamento rotacional do bloco ósseo no interior do túnel femoral. Para estas avaliações considerou-se o p < 0,017. CONCLUSÃO: A fixação do enxerto osso-tendão-osso com dois pinos bioabsorvíveis, independente do posicionamento rotacional no túnel femoral, permite uma fixação comparável em termos de resistência inicial ao parafuso de interferência metálico neste modelo experimental.

BIOMECHANICAL STUDY OF TRANSCORTICAL OR TRANSTRABECULAR BONE FIXATION OF PATELLAR TENDON GRAFT WITH BIOABSORBABLE PINS IN ACL RECONSTRUCTION IN SHEEP

Objective: To determine the initial resistance of fixation using the Rigid Fix® system, and compare it with traditional fixation methods using metal interference screws; and to evaluate the resistance of the fixation with the rigid fix system when the rotational position of the bone block is altered in the interior of the femoral tunnel. Methods: forty ovine knee specimens (stifle joints) were submitted to anterior cruciate ligament reconstruction (ACL) using a bone-tendon-bone graft. In twenty specimens, the Rigid Fix method was used; this group was subdivided into two groups: ten knees the pins transfixed only the spongious area of the bone block, and ten for fixation passing through the layer of cortical bone. In the twenty remaining specimens, the graft was fixed with 9mm metal interference screws. Results: comparison of the RIGIDFIX® method with the metal interference screw fixation method did not show any statistically significant differences in terms of maximum load and rigidity; also, there were no statistically significant differences when the rotational position of the bone block was altered inside the femoral tunnel. For these evaluations, a level of significance of p < 0.017 was considered. Conclusion: fixation of the bone-tendon-bone graft with 2 bioabsorbable pines, regardless of the rotational position inside the femoral tunnel, gave a comparable fixation in terms of initial resistance to the metal interference screw, in this experimental model.

Preliminary analysis of the sacroiliac joint in the hyperlordotic spine, a finite element model

Preliminary analysis of the sacroiliac joint in the hyperlordotic spine, a finite element model