Bovine Tendon Research Articles

Intraoperative Workflow for All-Inside Anterior Cruciate Ligament Reconstruction: An In Vitro Biomechanical Evaluation of Preconditioning and Knot Tying

To evaluate and compare the effect of preconditioning according to intraoperative workflow on the elongation behavior of single-side and fully knotted all-inside anterior cruciate ligament (ACL) reconstruction configurations in a biomechanical invitro study. Four full construct all-inside ACL reconstruction groups (n= 8 per group) were tested using porcine tibias and bovine tendons. Groups included both an all-inside configuration with one- (group 1) and both-side knotted adjustable loop-length devices (group 2), without and with performing intraoperative preconditioning (group 1-intraoperative preconditioned [IPC], group 2-IPC). Adjustable loop-length devices for control groups were knotted according to test configurations. Intraoperative preconditioning specimens were further precycled for 10 times at 0.5Hz and manually retensioned before knotting. All groups underwent dynamic cycling in position and force control mode each for 1,000 cycles at 0.75Hz according to invitro loading parameters replicating the invivo ACL environment. Finally, a load-to-failure test at 50mm/min was performed. Intraoperative preconditioning increases initial graft tension for single- (242 ± 22N vs 174 ± 13N; P < .0001) and both-side knotted configurations (225 ± 15N vs 159 ± 10N; P < .0001) compared with controls and allows maintained graft tension at higher levels until reaching the end of position-controlled cyclic loading. Furthermore, dynamic elongation is reduced for one- (1.93 ± 0.28 vs 0.76 ± 0.12; P < .0001) and both-side knotted (1.84 ± 0.20 vs 0.96 ± 0.32; P < .0001) configurations by 61% and 47%, respectively. No intergroup (group 1 vs group 2 and group 1-IPC vs group 2-IPC) statistically significant differences could be found between one- and both-side knotted configurations. All-inside ACL reconstruction with preconditioning according to intraoperative workflow leads to a statistically significant improved mechanical behavior and may allow for optimizing initial graft tension and elongation for all-inside ACL reconstruction to reduce knee laxity. A single-side knotted configuration achieves similar stabilization strength to fully knotted constructs. Graft insertion until tunnel docking increases the intratunnel graft portion that may optimize graft incorporation. Eliminating a suture knot stack may improve intraoperative workflow and reduce postoperative knot irritation.

A real time complete Stokes polarimetric imager based on a linear polarizer array camera for tissue polarimetric imaging

Tissue polarimetric imaging measures Mueller matrices of tissues or Stokes vectors of the emergent light from tissues (normally using incidence with a fixed polarization state) over a field of view, and has demonstrated utility in a number of surgical and diagnostic applications. Here we introduce a compact complete Stokes polarimetric imager that can work for multiple wavelength bands with a frame-rate suitable for real-time applications. The imager was validated with standard polarizing components, and then employed as a polarization state analyzer of a Mueller imaging polarimeter and a standalone Stokes imaging polarimeter respectively to image the process of dehydration of bovine tendon tissue. The results obtained in this work suggested that the polarization properties of the samples rich of collagen fibres can change with the degree of dehydration, and therefore, dehydration of the samples prepared for polarimetric imaging (e.g. polarimetric microscopy) should be carefully controlled.

Real time complete Stokes polarimetric imager based on a linear polarizer array camera for tissue polarimetric imaging.

Tissue polarimetric imaging measures Mueller matrices of tissues or Stokes vectors of the emergent light from tissues (normally using incidence with a fixed polarization state) over a field of view, and has demonstrated utility in a number of surgical and diagnostic applications. Here we introduce a compact complete Stokes polarimetric imager that can work for multiple wavelength bands with a frame-rate suitable for real-time applications. The imager was validated with standard polarizing components, and then employed as a polarization state analyzer of a Mueller imaging polarimeter and a standalone Stokes imaging polarimeter respectively to image the process of dehydration of bovine tendon tissue. The results obtained in this work suggested that the polarization properties of the samples rich of collagen fibres can change with the degree of dehydration, and therefore, dehydration of the samples prepared for polarimetric imaging (e.g. polarimetric microscopy) should be carefully controlled.

Biomechanical properties of different techniques used in vitro for suturing mid-substance Achilles tendon ruptures

BackgroundThe Dresden technique preserves the paratenon during Achilles tendon repair and may improve the plantarflexor mechanism when combined with mobilization during early rehabilitation. However, the surgical repair design for Achilles tendon ruptures can affect rates of re-rupture or lengthening. Therefore, the aim of this study was to determine the biomechanical properties of the Krackow, Double-Kessler, Double-Dresden, and Triple-Dresden techniques used for repairing mid-substance Achilles tendon ruptures during cyclical and maximum traction. MethodsSixty mid-substance bovine tendons repaired after transverse rupturing were divided randomly into four groups by repair technique: Krackow, Double-Kessler, Double-Dresden, and Triple-Dresden. Cyclical tractions of 4.7, 5.8, 7.9, and 11.7mm (equivalent to 5°, 8°, 10°, and 15° of dorsal flexion, respectively) were applied to determine gapping, tensile strength, nominal suture stress, repair deformation, and specimens with clinical failure (gap>5mm). Maximal traction was applied to measure maximum strength and failure type (i.e. suture, knot, or tendon). FindingsThe Triple-Dresden technique resulted in decreased gapping, nominal suture stress, repair deformation, and quantity of specimens with clinical failure as compared to the other techniques. Furthermore, Triple-Dresden tendons showed greater comparative tensile and maximum strength. During maximal traction testing, this technique presented tendon failure, whereas the Krackow, Double-Kessler, and Double-Dresden techniques had suture failures. InterpretationTriple-Dresden repair results in better cyclical and maximum traction strengths, suggesting that this technique might be more appropriate when performing early mobilization after mid-substance Achilles tendon rupture repair.

Graft Fixation Sequence in One-Stage Anterior Cruciate Ligament and Posterior Cruciate Ligament Reconstruction

According to the results of this study, the best fixation sequence for combined ACL/PCL reconstruction is when the ACL graft fixed first at close to full extension followed by the PCL graft fixation. There is no consensus regarding the best protocol for the sequence of graft tensioning and fixation in one-stage reconstruction of combined anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). This study sought to determine the effect of ACL/PCL graft tensioning and fixation protocol on knee biomechanics. It is hypothesized that the sequence to best restore intact knee kinematics and the intact tibial position will be the ACL graft fixed first at close to full extension and the PCL graft fixed second with the knee flexed. Twelve fresh-frozen mature porcine hind limbs (n=12) were used. The knees were tested using a robotic testing system with a universal force-moment sensor. One-stage, combined anatomic single bundle (SB) ACL and PCL reconstructions were performed with and 8 mm grafts from bovine extensor tendon. The knee states tested were: (1) intact ACL and intact PCL, (2) deficient ACL and deficient PCL, and (3) one-stage ACL and PCL reconstruction. Five fixation sequences were performed in each knee in a randomized order: (1) PCL fixed 1st at 30° and ACL fixed 2nd at 30° (Recon 1), (2) PCL fixed 1st at 90° and ACL fixed 2nd at 30° (Recon 2), (3) ACL fixed 1st at 30° and PCL fixed 2nd at 30° (Recon 3), (4) ACL fixed 1st at 30° and PCL fixed 2nd at 90° (Recon 4) and (5) ACL and PCL fixed simultaneously at 30° (Recon 5). Both grafts were tensioned to 40 N. Two external loading conditions were tested: an 89 N anterior tibial and a posterior tibial load at 30° (full extension in the porcine knee). A 3-dimensional digitizer was used to measure the anterior-posterior (A-P) shift of the tibia in each of the reconstructed knee positions from the intact knee position in the unloaded knee. Data was analyzed using one-way repeated measures ANOVA, and statistical significance was set at p<0.05. None of the reconstructions restored the range of A-P translation to that of the intact knee at 30° of flexion, where the A-P translation is the sum of the anterior tibial translation (ATT) and posterior tibial translation (PTT). The mean A-P translation was: 7.9 ±1.3 mm at intact ACL and PCL, 16.4 ± 3.7 mm at deficient ACL and PCL, 12.3 ± 2.2 mm at Recon 1, 12.1 ± 3.2 mm at Recon 2, 12.8 ± 3.3 mm at Recon 3, 13.5 ± 2.6 mm at Recon 4, and 13.1 ± 2.6 mm at Recon 5. The mean anterior shift was: 2.69 ± 1.41 mm in Recon 1, 2.73 ± 2.88 mm in Recon 2, 0.05 ± 0.60 mm in Recon 3, 0.44 ± 1.27 mm in Recon 4, and 1.02 ± 1.39 mm in Recon 5. From the results of this study, if the PCL graft is fixed first the tibia will shift anteriorly regardless of flexion angle of the knee. However, while the knee is at full extension (30° in the porcine knee), fixation of the ACL graft first only causes a smaller shift of the tibia. Thus, the ACL graft should be fixed first while the knee is at full extension, and then the PCL graft can be fixed at either a low or high flexion angle. While fixation of the ACL graft first at 30° of flexion does not cause a large shift of the tibia, the A-P translation is not restored by any of the five fixation sequences.

Functionally Distinct Tendons From Elastin Haploinsufficient Mice Exhibit Mild Stiffening and Tendon-Specific Structural Alteration.

Elastic fibers are present in low quantities in tendon, where they are located both within fascicles near tenocytes and more broadly in the interfascicular matrix (IFM). While elastic fibers have long been known to be significant in the mechanics of elastin-rich tissue (i.e., vasculature, skin, lungs), recent studies have suggested a mechanical role for elastic fibers in tendons that is dependent on specific tendon function. However, the exact contribution of elastin to properties of different types of tendons (e.g., positional, energy-storing) remains unknown. Therefore, this study purposed to evaluate the role of elastin in the mechanical properties and collagen alignment of functionally distinct supraspinatus tendons (SSTs) and Achilles tendons (ATs) from elastin haploinsufficient (HET) and wild type (WT) mice. Despite the significant decrease in elastin in HET tendons, a slight increase in linear stiffness of both tendons was the only significant mechanical effect of elastin haploinsufficiency. Additionally, there were significant changes in collagen nanostructure and subtle alteration to collagen alignment in the AT but not the SST. Hence, elastin may play only a minor role in tendon mechanical properties. Alternatively, larger changes to tendon mechanics may have been mitigated by developmental compensation of HET tendons and/or the role of elastic fibers may be less prominent in smaller mouse tendons compared to the larger bovine and human tendons evaluated in previous studies. Further research will be necessary to fully elucidate the influence of various elastic fiber components on structure-function relationships in functionally distinct tendons.

Changes in frictional coefficient with increased tendon surface tear—An experimental animal model

AimSurface tribological properties of a tendon in terms of coefficient of friction and lubrication mechanism are expected to change with the progression of surface tears which can affect the optimal function of the tendon. This study investigated whether coefficient of friction proportionally increases with the progression of a surface tear in a bovine tendon model. MethodsThe study was performed using a pin-on-glass tribometer and bovine tendon samples (n=16) divided into 4 groups. One group of tendons had no surface tears and thus served as a control, whilst the other 3 groups comprised tendons with increasing severity of artificially-induced surface tears. The coefficient of friction and the lubrication mechanism of the four groups of samples were investigated, calculated and compared. ResultsStatistical analysis showed significant change in coefficient of friction between the control group and the group with minimal tear (p<0.05) while no difference noted between the groups of moderate to severe tear suggesting that the coefficient of friction increases initially with appearance of surface tears, though further progression to a significant tear do not cause a further increase in the frictional coefficient. There was no change in the lubrication mechanism between the groups. ConclusionThis finding appears to contradict the speculation that the frictional coefficient continues to increase with an increase in surface tear severity. The finding has not been reported before and requires validation in future with testing in human tissue.

Collagenase treatment enhances proteomic coverage of low-abundance proteins in decellularized matrix bioscaffolds.

There is great interest in the application of advanced proteomic techniques to characterize decellularized tissues in order to develop a deeper understanding of the effects of the complex extracellular matrix (ECM) composition on the cellular response to these pro-regenerative bioscaffolds. However, the identification of proteins in ECM-derived bioscaffolds is hindered by the high abundance of collagen in the samples, which can interfere with the detection of lower-abundance constituents that may be important regulators of cell function. To address this limitation, we developed a novel multi-enzyme digestion approach using treatment with a highly-purified collagenase derived from Clostridium Histolyticum to selectively deplete collagen from ECM-derived protein extracts, reducing its relative abundance from up to 90% to below 10%. Moreover, we applied this new method to characterize the proteome of human decellularized adipose tissue (DAT), human decellularized cancellous bone (DCB), and commercially-available bovine tendon collagen (BTC). We successfully demonstrated with all three sources that collagenase treatment increased the depth of detection and enabled the identification of a variety of signaling proteins that were masked by collagen in standard digestion protocols with trypsin/LysC, increasing the number of proteins identified in the DAT by ∼2.2 fold, the DCB by ∼1.3 fold, and the BTC by ∼1.6 fold. In addition, quantitative proteomics using label-free quantification demonstrated that the DAT and DCB extracts were compositionally distinct, and identified a number of adipogenic and osteogenic proteins that were consistently more highly expressed in the DAT and DCB respectively. Overall, we have developed a new processing method that may be applied in advanced mass spectrometry studies to improve the high-throughput proteomic characterization of bioscaffolds derived from mammalian tissues. Further, our study provides new insight into the complex ECM composition of two human decellularized tissues of interest as cell-instructive platforms for regenerative medicine.

"Tissue Papers" from Organ-Specific Decellularized Extracellular Matrices.

Using an innovative, tissue-independent approach to decellularized tissue processing and biomaterial fabrication, the development of a series of "tissue papers" derived from native porcine tissues/organs (heart, kidney, liver, muscle), native bovine tissue/organ (ovary and uterus), and purified bovine Achilles tendon collagen as a control from decellularized extracellular matrix particle ink suspensions cast into molds is described. Each tissue paper type has distinct microstructural characteristics as well as physical and mechanical properties, is capable of absorbing up to 300% of its own weight in liquid, and remains mechanically robust (E = 1-18 MPa) when hydrated; permitting it to be cut, rolled, folded, and sutured, as needed. In vitro characterization with human mesenchymal stem cells reveals that all tissue paper types support cell adhesion, viability, and proliferation over four weeks. Ovarian tissue papers support mouse ovarian follicle adhesion, viability, and health in vitro, as well as support, and maintain the viability and hormonal function of nonhuman primate and human follicle-containing, live ovarian cortical tissues ex vivo for eight weeks postmortem. "Tissue papers" can be further augmented with additional synthetic and natural biomaterials, as well as integrated with recently developed, advanced 3D-printable biomaterials, providing a versatile platform for future multi-biomaterial construct manufacturing.

In vitro studies to evaluate the effect of varying culture conditions and IPL fluencies on tenocyte activities.

Tendons are dense, fibrous connective tissues which carry out the essential physiological role of transmitting mechanical forces from skeletal muscle to bone. From a clinical perspective, tendinopathy is very common, both within the sporting arena and amongst the sedentary population. Studies have shown that light therapy may stimulate tendon healing, and more recently, intense pulsed light (IPL) has attracted attention as a potential treatment modality for tendinopathy; however, its mechanism of action and effect on the tendon cells (tenocytes) is poorly understood. The present study therefore investigates the influence of IPL on an in vitro bovine tendon model. Tenocytes were irradiated with IPL at different devise settings and under variable culture conditions (e.g. utilising cell culture media with or without the pH indicator dye phenol red), and changes in tenocyte viability and migration were subsequently investigated using Alamar blue and scratch assays, respectively. Our data demonstrated that IPL fluencies of up to 15.9J/cm2 proved harmless to the tenocyte cultures (this was the case using culture media with or without phenol red) and resulted in a significant increase in cell viability under certain culture conditions. Furthermore, IPL treatment of tenocytes did not affect the rate of cell migration. This study demonstrates that irradiation with IPL is not detrimental to the tenocytes and may increase their viability under certain conditions, thus validating our in vitro model. Further studies are required to elucidate the effects of IPL application in the clinical situation.

Composition of chitosan-hydroxyapatite-collagen composite scaffold evaluation after simulated body fluid immersion as reconstruction material

Hydroxyapatite (HA) formation is one of the most important aspects of bone regeneration. Because domestically made chitosan-hydroxyapatite-collagen composite scaffolding from crab shell and bovine bone and tendon has potential as a maxillofacial reconstruction material, the material’s HA-forming ability requires evaluation. The aim of this research is to investigate chitosan-hydroxyapatite-collagen composite scaffold’s potential as a maxillofacial reconstruction material by observing the scaffold’s compositional changes. Scaffold specimens were immersed in 37°C simulated body fluid (SBF) for periods of 2, 4, 6, and 8 days. Scaffold composition was then evaluated by using energy dispersive spectroscopy (EDS). The calcium (Ca) and phosphorus (P) percentages of the scaffold were found to increase following SBF immersion. The high Ca/P ratio (3.82) on the scaffold indicated HA formation. Ion exchange played a significant role in the increased percentages of Ca and P, which led to new HA layer formation. The scaffold’s HA acted as a nucleation site of Ca and P from the SBF, with collagen and chitosan as the scaffold’s matrix. Chitosan-hydroxyapatite-collagen composite scaffold shows potential as a maxillofacial reconstruction material, since its composition favors HA formation.

Tendon end separation with loading in an Achilles tendon repair model: comparison of non-absorbable vs. absorbable sutures

BackgroundRupture of the Achilles tendon often leads to long-term morbidity, particularly calf weakness associated with tendon elongation. Operative repair of Achilles tendon ruptures leads to reduced tendon elongation. Tendon lengthening is a key problem in the restoration of function following Achilles tendon rupture. A study was performed to determine differences in initial separation, strength and failure characteristics of differing sutures and numbers of core strands in a percutaneous Achilles tendon repair model in response to initial loading.MethodsNineteen bovine Achilles tendons were repaired using a percutaneous/minimally invasive technique with a combination of a modified Bunnell suture proximally and a Kessler suture distally, using non-absorbable 4-strand 6-strand repairs and absorbable 8-strand sutures. Specimens were then cyclically loaded using phases of 10 cycles of 100 N, 100 cycles of 100 N, 100 cycles of 190 N consistent with early range of motion training and weight-bearing, before being loaded to failure.ResultsPre-conditioning of 10 cycles of 100 N resulted in separations of 4 mm for 6-strand, 5.9 mm for 4-strand, but 11.5 mm in 8-strand repairs, this comprised 48.5, 68.6 and 72.7% of the separation that occurred after 100 cycles of 100 N. The tendon separation after the third phase of 100 cycles of 190 N was 17.4 mm for 4-strand repairs, 16.6 mm for 6-strand repairs and 26.6 mm for 8-strand repairs. There were significant differences between the groups (p < 0.0001). Four and six strand non-absorbable repairs had significantly less separation than 8-strand absorbable repairs (p = 0.017 and p = 0.04 respectively).The mean (SEM) ultimate tensile strengths were 4-strand 464.8 N (27.4), 6-strand 543.5 N (49.6) and 8-strand 422.1 N (80.5). Regression analysis reveals no significant difference between the overall strength of the 3 repair models (p = 0.32) (4 vs. 6: p = 0.30, 4 vs. 8: p = 0.87; 6 vs. 8: p = 0.39). The most common mode of failure was pull out of the Kessler suture from the distal stump in 41.7% of specimens.ConclusionThe use of a non-absorbable suture resulted in less end-to-end separation when compared to absorbable sutures when an Achilles tendon repair model was subject to cyclical loading. Ultimate failure occurred more commonly at the distal Kessler suture end although this occurred with separations in excess of clinical failure. The effect of early movement and loading on the Achilles tendon is not fully understood and requires more research.

Amino acid composition in determination of collagen origin and assessment of physical factors effects

The amino acid composition of collagen is a characteristic feature of this protein. Collagen, irrespective of its origin, contains 19 amino acids, including hydroxyproline which does not occur in other proteins. Its atypical amino acid composition is characterized by high content of proline and glycine, as well as the absence of cysteine.This paper shows the comparison of qualitative composition of amino acids of fish skin (FS) collagen, bovine Achilles tendon (BAT) collagen, and bone collagen. Results demonstrate that FS collagen as well as BAT collagen contains no cysteine and significantly different amount of hydroxyproline. In BAT collagen hydroxyproline content is 30% higher than hydroxyproline content of FS collagen. In bone collagen the amount of hydroxyproline is two times more than in FS collagen.Furthermore, it is shown that sensitivity to radiation of individual amino acids varies and depends on the absorbed dose of ionizing radiation. The changes observed in the amino acid composition become very intense for the doses of 500kGy and 1000kGy.

Comparison of thermal properties of fish collagen and bovine collagen in the temperature range 298–670 K

The increased interest in fish collagen is a consequence of the risk of exposure to Creutzfeld-Jacob disease (CJD) and the bovine spongiform encephalopathy (BSE), whose occurrence is associated with prions carried by bovine collagen.Collagen is the main biopolymer in living organisms and the main component of the skin and bones. Until the discovery of the BSE, bovine collagen had been widely used. The BSE epidemic increased the interest in new sources of collagen such as fish skin collagen (FSC) and its properties.Although the thermal properties of collagen originating from mammals have been well described, less attention has been paid to the thermal properties of FSC. Denaturation temperature is a particularly important parameter, depending on the collagen origin and hydration level. In the reported experiment, the free water and bound water release processes along with thermal denaturation process were studied by means of the differential scanning calorimetry (DSC). Measurements were carried out using a DSC 7 instrument (Elmer-Perkin), in the temperature range 298–670K. The study material was FSC derived by acidic hydration method. The bovine Achilles tendon (BAT) collagen type I was used as the control material. The thermograms recorded revealed both, exothermic and endothermic peaks. For both materials, the peaks in the temperature range of 330–360K were assigned to the release of free water and bound water. The denaturation temperatures of FSC and BAT collagen were determined as 420K and 493K, respectively. Thermal decomposition process was observed at about 500K for FSC and at about 510K for BAT collagen. These results show that FSC is less resistant to high temperature than BAT collagen.

Fabrication and characterization of a decellularized bovine tendon sheet for tendon reconstruction.

Obtaining a performing decellularized tendon scaffold with proper dimensions and adequate availability is highly desirable. However, the combined study of complete decellularization and detailed characterization of native tendon extracellular matrix (ECM) from large animals is still lacking. In the present study, we developed a new decellularization protocol, including physical methods and enzymatic solutions for processing bovine Achilles tendons, and produced a decellularized bovine tendon sheet (DBTS) scaffold for tendon reconstruction. The decellularization effectiveness was demonstrated by DNA quantification and histological qualification. The removal of the alpha-gal epitopes was confirmed by ELISA analysis and immunohistochemical staining. After decellularization, there were no significant alterations of the native tendon extracellular matrix (ECM) properties, including the internal ultrastructure, biochemical compositions such as collagen, glycosaminoglycans (GAGs), basic fibroblast growth factor (bFGF) and transforming growth factor-β1 (TGF-β1), fibronectin and decorin, as well as substantial mechanical strength. Furthermore, the DBTS scaffold showed no cytotoxic and promoted the proliferation of NIH-3T3 fibroblasts in vitro. When implanted into rat subcutaneous tissue, the DBTS scaffold displayed excellent histocompatibility in vivo. Our results, while offering a new decellularization protocol for large tendons, can provide a promising biologic scaffold with a combination of mechanical strength and tendon ECM bioactive factors that may have many potential applications in tendon reconstruction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2299-2311, 2017.

Influence of residual composition on the structure and properties of extracellular matrix derived hydrogels

In this work, hydrolysates of extracellular matrix (hECM) were obtained from rat tail tendon (TR), bovine Achilles tendon (TAB), porcine small intestinal submucosa (SIS) and bovine pericardium (PB), and they were polymerized to generate ECM hydrogels. The composition of hECM was evaluated by quantifying the content of sulphated glycosaminoglycans (sGAG), fibronectin and laminin. The polymerization process, structure, physicochemical properties, in vitro degradation and biocompatibility were studied and related to their composition. The results indicated that the hECM derived from SIS and PB were significantly richer in sGAG, fibronectin and laminin, than those derived from TAB and TR. These differences in hECM composition influenced the polymerization and the structural characteristics of the fibrillar gel network. Consequently, the swelling, mechanics and degradation of the hydrogels showed a direct relationship with the remaining composition. Moreover, the cytocompatibility and the secretion of transforming growth factor beta-1 (TGF-β1) by macrophages were enhanced in hydrogels with the highest residual content of ECM biomolecules. The results of this work evidenced the role of the ECM molecules remaining after both decellularization and hydrolysis steps to produce tissue derived hydrogels with structure and properties tailored to enhance their performance in tissue engineering and regenerative medicine applications.

Biomechanical comparison of four coupled fixation systems for ACL reconstruction with bone socket or full-tunnel on the tibial side

BackgroundTo compare in an animal model the biomechanical properties of four coupled fixation devices currently used in ACL reconstruction. Three out of four devices used a full tibial tunnel with an interference screw, while the other one system used a tibial socket and an adjustable loop suspension device. The null hypothesis is that there are no biomechanical differences between all the techniques tested. MethodsThirty two femur–graft–tibia complexes were mounted on a tensile machine using bovine digital extensor tendons, porcine knees and four different fixation device combinations:–Group A: EndoButton CL and BioRCI–Group B: Rigidfix and Intrafix–Group C: Transfix and Deltascrew–Group D: TightRope-RT with the All-inside GraftLink technique.After a preconditioning with a tensile load of 90N for five minutes, 1000cycles between 0 and 150N were applied to the complex before the final pulled to failure. Stiffness and strength were evaluated at the final pullout, as was the displacement (slippage) at one, 100, 500, and 1000cycles. ResultsThe multiple mean comparison led to a significant difference for the case of stiffness, with worse results in group C compared to group A (p=0.037). Conversely, no differences were found in UFL and slippage between all groups (p>0.05). ConclusionAll the tested systems demonstrated in an animal model sufficient properties for a safe postoperative rehabilitation both for strength and for stiffness and slippage under cyclic loading.

Preparation of Chitosan/Collagen Blend Membranes for Wound Dressing: A Study on FTIR Spectroscopy and Mechanical Properties

The effect of different gamma-ray irradiations on the functional groups and the mechanical properties of chitosan, collagen, and chitosan/collagen blend have been studied. Commercially available chitosan and extract of collagen from bovine tendon by acid dissolution method were employed. Chitosan, collagen and chitosan/collagen blend membranes were prepared using the solvent evaporation method. The dried membranes were subjected to gamma-ray irradiation using 0, 15, and 25 kGy. The membranes then characterized by Infrared spectroscopy and measured in tensile and elongation at break. The irradiated chitosan membranes displayed reduced intensity of -OH, -CH, -NH and -C-O-C groups, whereas, the collagen membranes revealed amide I, II and III groups. The irradiated chitosan/collagen (50/50%) blend membranes demonstrated the decreased intensities in the –OH and amide groups. The application of gamma-ray irradiation had produced chitosan/collagen blend membranes with a tensile strength and elongation at break between the chitosan and collagen membranes. It was further determined that the decrease in the mechanical properties of the membranes was likely to be due to some changes of the functional groups.

Biomechanical Investigation of Different Preparation Techniques of Tripled Soft Tissue ACL Grafts

Aims and Objectives:The purpose was to investigate biomechanical properties of different preparation techniques of tripled soft tissue ACL grafts to avoid early mechanical graft failure. It was hypothesized that 1) a graft with a quadrupled femoral portion results in higher load to failure and stiffness compared to a uniformly tripled graft, and 2) a Krackow stitch technique is superior to both baseball stitch and whipstitch technique.Materials and Methods:Forty-eight bovine flexor tendons (eight per group) with a final graft length of 8 cm were used for the present study and randomly assigned to the two graft configuration groups: A) quadrupled femoral portion with a tripled tibial portion, and B) uniformly tripled soft tissue graft. Within the two groups, three different stitching techniques were applied: 1) Whipstitch technique, 2) Krackow stitch, and 3) Baseball stitch. After preconditioning, the grafts were cyclically loaded for 1000 cycles between 50 and 200 N (1 Hz) with consecutive load to failure testing using a constant elongation of 30 mm/min. During biomechnical testing, graft elongation was evaluated with an optical tracking system. For statistical analysis a two-way analysis of variance with a post-hoc Holm-Sidak test was performed. To evaluate the failure mode the Fisher’s exact test was used. The significance level was set at p #CHR: lesslike# 0.05.Results:Considering load to failure, quadrupling the femoral portion of the graft significantly increased the load to failure (p = 0.003) while varying the stitching technique had no influence (p = 0.998). Additionally, graft elongation was lower in group A, but difference was not significant (p = 0.058). Lowest graft elongation was observed when a Krackow stitch was applied, followed by the baseball stitch, and the whipstitch technique (p = 0.035). In group A, all the constructs (graft including sutures) failed at the suture, whereas in group B the failure mode was a slippage of the free femoral graft strand in seven of eight grafts (p = 0.005).Conclusion:When using tripled ACL soft tissue grafts in combination with an extracortical fixation device, the femoral portion should be quadrupled whereas the stitching technique does not have a significant influence on the biomechanical properties. To achieve a higher load to failure with less graft elongation at time zero, the free femoral strand of the tendon graft should be wrapped around the femoral graft tendon loop. This could reduce early graft failure due to slippage of the third free femoral graft strand.

Interlocking horizontal mattress suture versus Kakiuchi technique in repair of Achilles tendon rupture: a biomechanical study

BackgroundIn recent years, the type of surgical treatment for Achilles tendon rupture has been the subject of controversial debate. This biomechanical study evaluates for the first time in literature the ultimate failure load (UFL) of interlocking horizontal mattress (IHM) suture as compared with Kakiuchi suture in Achilles tendon rupture. The hypothesis is that IHM suture can be performed also for Achilles tendon rupture and ensures higher resistance compared with the traditional Kakiuchi suture.Materials and methodsTwenty fresh bovine Achilles tendons were obtained. Ten preparations were randomly assigned to each of two different groups: group A (10 specimens) sutured by IHM technique, and group B (10 specimens) sutured by Kakiuchi technique. Each construct was mounted and fixed on a tensile testing machine. Static preconditioning of 50 N was applied for 5 min as initial tensioning to stabilize the mechanical properties of the graft, then a load to failure test was performed at crosshead speed of 500 mm/min.ResultsTen specimens were tested for each group. The mean UFL was 228.6 ± 98.6 N in the IHM suture group and 96.57 ± 80.1 N in the Kakiuchi suture group. Statistical analysis showed a significant difference (p < 0.05) with better UFL in the IHM group. In both groups, the failure mode registered in each specimen was suture breakage (rupture of suture thread).ConclusionsIHM suture achieved better UFL compared with Kakiuchi suture in an animal model of Achilles tendon repair. These results seem to support IHM as a valid option in Achilles tendon rupture.