Empirical relationship between lengthening an anterior cruciate ligament graft and increases in knee anterior laxity: a human cadaveric study

Lengthening of an anterior cruciate ligament (ACL) graft construct can occur as a result of lengthening at the sites of tibial and/or femoral fixation and manifests as an increase in anterior laxity. Although lengthening at the site of fixation has been measured for a variety of fixation devices, it is difficult to place these results in a clinical context because the mathematical relationship between lengthening of an ACL graft construct and anterior laxity is unknown. The purpose of our study was to determine empirically this relationship. Ten cadaveric knees were reconstructed with a double-looped tendon graft. With the knee in 25 degrees of flexion, the position of the proximal end of the graft inside the femoral tunnel was adjusted by moving the femoral fixation device until the anterior laxity at an applied anterior force of 134 N matched that of the intact knee. In random order, the graft construct was lengthened 1, 2, 3, 4, and 5 mm by moving the femoral fixation device distally along the femoral tunnel and anterior laxity was measured. The increase in the length of the graft construct was related to the increase in anterior laxity by a simple linear regression model. Lengthening the graft construct from 1 to 5 mm caused an equal increase in anterior laxity (slope=1.0 mmmm, r(2)=0.800, p<0.0001). Because an anterior laxity increase of 3 mm or greater in a reconstructed knee is considered unstable clinically and because many fixation devices in widespread use clinically allow 3 mm or greater of lengthening in in vitro tests, our empirical relationship indicates that lengthening at the site of fixation probably is an important cause of knee instability following ACL reconstructive surgery. Our empirical relation also indicates that an important criterion in the design of future fixation devices is that lengthening at the sites of fixation in in vitro tests should be limited to less than 3 mm.     

An implantable transducer for measuring tension in an anterior cruciate ligament graft.

The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N.     

A new adhesive technique for internal fixation in midfacial surgery

Background  

The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market.     

A new antigen retrieval technique for human brain tissue

Immunohistochemical staining of tissues is a powerful tool used to delineate the presence or absence of an antigen. During the last 30 years, antigen visualization in human brain tissue has been significantly limited by the masking effect of fixatives. In the present study, we have used a new method for antigen retrieval in formalin-fixed human brain tissue and examined the effectiveness of this protocol to reveal masked antigens in tissues with both short and long formalin fixation times. This new method, which is based on the use of citraconic acid, has not been previously utilized in brain tissue although it has been employed in various other tissues such as tonsil, ovary, skin, lymph node, stomach, breast, colon, lung and thymus. Thus, we reported here a novel method to carry out immunohistochemical studies in free-floating human brain sections. Since fixation of brain tissue specimens in formaldehyde is a commonly method used in brain banks, this new antigen retrieval method could facilitate immunohistochemical studies of brains with prolonged formalin fixation times.     

A new transplant bone for maxillary alveolar cleft

An innovative technique with distraction osteogenesis has been developed in our research group to explore autogenous bone transplantation into craniofacial bone defects. This technique was designed to investigate bone-marrow transplantion using a chondroid or fibula bone graft into simulated alveolar bone defects in mice in terms of the osteogenic process and activity. As an experimental model of maxillary alveolar bone cleft available for testing bone-inductive materials, a critical-size defect was formed in the pre-maxillary bone of male mice using a surgical trephine bur with a low-speed dental engine. Distraction osteogenesis was performed using an external fixation device. The osteotomy site was occupied by an external callus consisting of hyaline cartilage with a large quantity of chondroid bone. Moreover, bone remodelling with new bone formation was demonstrated 30 days after the transplantation. Bone adhesion was better in chondroid bone grafting than in fibula bone grafting. The present findings are the first to demonstrate the potential of chondroid bone transplantation as a new therapeutic system of bone grafting, suitable for bone substitutes in craniofacial bone defects.     

Controlled plastic deformation for the fastening mechanism of an internal fixation device. The new Mennen 3 PeriPro plate

The Mennen femur plate is a fixation device used for the treatment of femoral periprosthetic fractures. It features a novel fastening method where curved prongs are plastically deformed securing the implant to the bone. Although this "clamp-on" method has been successfully used to treat fractures of long bones, there are no literature data assessing the nature of the required plastic deformation. In the present study, the parameters influencing the performance of the prongs were identified and further explored using numerical modeling. The new Mennen 3 PeriPro plate is briefly discussed focusing on the new sculpted formation of the prongs. Their design was optimized to effectively control the magnitude and position of the required plastic deformation achieving enhanced anchorage on the fractured bone with minimum effort. The work presented contains all the necessary steps in analysing a clinical problem using finite elements and illustrates how effective use of simulation techniques can accurately predict and effectively control the required plastic deformation of a structure.     

Three new Drosophila markers of intracellular membranes

The need for cellular markers that permit a quick and accurate evaluation of a protein's subcellular localization has increased with the surge of new data generated by the Drosophila genome project. In this report, we present three ubiquitously expressed Drosophila transgenes that expressed a green fluorescent protein variant (enhanced yellow fluorescent protein) that has been targeted to different intracellular membrane targets: the Golgi apparatus, mitochondria, and endoplasmic reticulum. These markers serve as an internal standard for characterizing a protein's subcellular localization or as a means of tracking the dynamics of intracellular organelles during normal or abnormal cellular or developmental processes. We have also examined fixation artifacts using these constructs to illustrate the effects that fixation and permeabilization have on intracellular membrane organization.     

Stereotactic-computerized tomography interface device

A mechanical stereotactic-computerized tomography interface device (SCID) is attached to the head at three bony fixation points and, after rigid fixation to the scanning gantry, is zeroed to make scan and stereotactic space identical. The system is simple, reproducible, accurate and reliable and has been used for tumour and excisional biopsy, radiation planning and instillation of radioisotopes.     

生物固氮在我国农业生产中的研究现状及发展对策

简述了生物固氦在我国农业生产中3个热点的研究现状:提高现有固氦生物的固氦能力、化学模拟固氦酶、固氦微生物的生物工程,同时提出了生物固氦在令后生态农业中的发展对策。     

Woroschiloff's locating device for interventions on the spinal cord and its influence on spinal stereotaxis

111 years ago the first locating device for the spinal cord was constructed, which became the basis for the contemporary spinal cord stereotaxy. Woroschiloff invented this device to operate stereotactically in different spinal cord segments. Nowadays only the fixation of the spinal cord stereotactic device to the wound retractor has changed from his concept, and control of the surgical instrument has been improved in three perpendicular planes corresponding to the special stereotactic maps of the human spinal cord.     

Lamellar split osteotomy: a new craniofacial technique

Craniofacial osteotomies have by convention been bilamellar translocations of the entire substance of the dysmorphic bone. This approach limits the surgeon by reducing the stable bone mass available for fixation, creating dependence on concave surfaces. Most important, it changes the bony topography that determines the preoperative plan. This paper presents a new craniofacial concept and technique used in 26 patients with various dysmorphic syndromes who were reconstructed by performing a lamellar split osteotomy. This technique maintains the internal lamella in its native position, thereby allowing it to act as a reference for the bony topography and providing a stable facial framework for rigid fixation. This interlamellar osteotomy has led to improved aesthetic results in the orthomorphic reconstructions of congenital and other deformities. It can be used in any aesthetic patient in whom contour changes or augmentation of form is desired. It is recommended as a preferred method for achieving quantitative contour improvement in patients over 3 years of age.     

Static and fatigue strength of a fixation device transducer for measuring anterior cruciate ligament graft tension

To determine which exercises do not overload the graft-fixation complex during intensive rehabilitation from reconstructive surgery of the anterior cruciate ligament (ACL), it would be useful to measure ACL graft loads during rehabilitative activities in vivo in humans. A previous paper by Ventura et al. (1998) reported on the design of an implantable transducer integrated into a femoral fixation device and demonstrated that the transducer could be calibrated to measure graft loads to better than 10 percent full-scale error in cadaveric knees. By measuring both the static and fatigue strengths of the transducer, the purpose of the present study was to determine whether the transducer could be safely implanted in humans without risk of structural failure. Eight devices were loaded to failure statically. Additionally, seven devices were tested using the up-and-down method to estimate the median fatigue strength at a life of 225,000 cycles. The average ultimate strength was 1856 +/- 74 N and the median fatigue strength was 441 N at a life of 225,000 cycles. The maximum graft load during normal daily activities is estimated to be 500 N and the 225,000 cycle life corresponds to that of the average healthy individual during a 12-week period. Considering that patients who have had an ACL reconstruction are less ambulatory than normal immediately following surgery and that biologic incorporation of the graft should be well developed by 12 weeks thus decreasing the load transmitted to the fixation device, the FDT can be safely implanted in humans without undue risk of structural failure.     

Stomaching: a new concept in bacteriological sample preparation

An entirely new mixing device, particularly suitable for preparing bacterial suspensions from foods, fabrics, swabs, and other fairly soft materials, has been developed. With this technique the sample and diluent are put into an inexpensive, sterile plastic bag which is vigorously pounded on its outer surfaces by paddles when placed inside the machine. The resulting compression and shearing forces effectively remove even deep-seated bacteria. After samples are taken for analysis the bag and its remaining contents are thrown away. Labor involved in cleaning and sterilizing reusable homogenizer cups or probes is eliminated, and the device is immediately ready for reuse. Running costs are thus drastically reduced, compared with conventional homogenizers. Additional advantages of this device, which is simple and inexpensive to manufacture, are low noise level, negligible temperature rise, and the small storage space required for bags.     

Updating the asymmetric osmium-catalyzed dihydroxylation (AD) mnemonic: Q2MM modeling and new kinetic measurements

The mnemonic device for predicting stereoselectivities in the Sharp-less asymmetric dihydroxylation (AD) reaction has been updated based on extensive computational studies. Kinetic measurements from competition reactions validate the new proposal. The interactions responsible for the high stereoselectivity in the title reaction are analyzed in detail and mapped onto the mnemonic device.     

A new membraneless device for preparative disc electrophoresis permitting concentrated elution

A new device for preparative disc electrophoresis is described.Its main characteristics are the funnel shape of the separating chamber, which causes the discs to concentrate as they move downwards and the absence of a semipermeable membrane in the elution chamber which has a volume of only about 0.1 ml.The usefulness of the apparatus has been demonstrated with the fraction of an alkaline protease produced by a Bacillus strain.     

Assessment of a new utero-tubal junction insemination device in dairy cattle

A new artificial insemination device for semen deposition near the utero-tubal junction in cattle (Ghent device) has been developed at the Ghent University (Belgium). In this study, the effect of the new insemination device on sperm quality was evaluated. Moreover, in a field trial 4064 dairy cows were inseminated by 12 inseminators to examine the efficacy of the device under field conditions.The Ghent device is a disposable plastic catheter which can easily follow the curvature of the uterine horns and thus reach the utero-tubal junction (UTJ). After expulsion of the inseminate with 0.7 or 1.7 ml of air, 19.0% of the insemination dose remained in the insemination catheter. Sperm loss can be diminished to 9.0% of the original insemination dose when the insemination catheter is flushed with 0.1 ml of air, followed by 0.6 ml of physiological saline solution. No toxic effect of the insemination catheter on sperm quality or fertilizing capacity was found. In the field trial, sperm were inseminated in dairy cattle which were divided in three groups. The first group was inseminated in the uterine body with the conventional insemination device, the second group in the uterine body with the Ghent device, and the third group in the tip of both uterine horns with the Ghent device. Each insemination was performed with 10 x 10(6) to 15 x 10(6) frozen-thawed spermatozoa. The pregnancy rates (PRs) were significantly affected by the insemination technique (P = 0.02), by the inseminator (P = 0.01), by heifer or cow (P < 0.01), and by the insemination number (P < 0.01). Pregnancy rates obtained with the conventional insemination device (57.6%) were significantly better than those obtained with the Ghent device in the uterine body (52.7%) (P < 0.01), but did not differ significantly from those obtained after deep insemination into both uterine horns (53.8%) (P = 0.27). It can be concluded that the Ghent device is suitable for utero-tubal junction insemination of dairy cattle under field conditions. Whether the Ghent device is also suitable for insemination with lower insemination doses is at present under investigation.     

A new device to measure the structural properties of the femur-anterior cruciate ligament-tibia complex

Previous studies of biomechanical properties of femur-anterior cruciate ligament-tibia complex (FATC) utilized a wide variety of testing methodologies, particularly with respect to ligament orientation relative to loading direction. A new device was designed and built to test the anterior-posterior displacement of the intact porcine knee at 30 and 90 deg of flexion, as well as the tensile properties of the FATC at any loading direction and flexion angle. Tensile tests were performed with the knees at 30 and 90 deg of flexion with the loading direction along either the axis of the tibia (tibial axis) or the axis of the anterior cruciate ligament (ligament axis). The results showed that the stiffness, ultimate load and energy absorbed were all significantly increased when the FATC was tested along the ligament axis. This study demonstrates the importance of alignment in the evaluation of the biomechanical characteristics of the femur-ACL-tibia complex.     

A new head clamp for stereotactic and intracranial procedures. Technical note

The authors have devised a clamp to fix the head to the surgical table during stereotactic procedures for placement of depth electrodes. The main advantages of this device derive from the rigid immobilization of the head. The clamp facilitates fixation of the stereotactic frame to the head, percutaneous twist drill trephination of any site of the skull, X-ray centering with a laser beam, mobilization of contrast material during ventriculography or pneumoencephalography, and placement of epidural screws. This head clamp can also be used during craniotomies for fixation of the head and support for brain retractors.     

A Novel Fixation Method for Variable-Sized Endoscopic Submucosal Dissection Specimens: An In Vitro Animal Experiment

Background

Endoscopic submucosal dissection is considered a curative and minimally invasive treatment for early gastric cancer; however, precise pathologic assessment of resected specimens is required to develop further treatment plans. Human error during specimen handling can affect objective assessment of resected specimens. In this study, we investigated whether a novel tissue fixation device offered more objective and standardized pathologic evaluation than conventional manual tissue fixation.

Methods

We developed a novel tissue fixation device for endoscopic submucosal dissection specimens. Two circular tissue samples 2, 3, and 4 cm in diameter were obtained from the body of 45 porcine stomachs. One specimen sample was placed in a fixation device; the other was manually fixed on corkboard. We used a pressure indicator to ensure constant pressure in the resected specimens in the fixation device. We measured submucosal diameter and thickness after 24 hr.

Results

The diameters for 2, 3, and 4 cm resected tissue samples were 23.85, 32.30, and 45.0 mm and 21.0, 32.0, and 44.50 mm for the fixation device and manual pinning groups, respectively. The submucosal thicknesses in the fixation device group were 397.09, 381.43, and 415.51 μm and 393.76, 529.69, and 603.82 μm by manual pinning for 2, 3, and 4 cm tissue samples, respectively. Analysis of standard deviation revealed that the submucosal thickness in the manual fixation group was much more variable than in the fixation device group (p = 0.012, 0.042, and 0.001 for 2, 3, and 4 cm tissue specimens, respectively; Fligner-Killeen test of homogeneity of variances).

Conclusions

Among variously sized resected tissue specimens, submucosal thicknesses were more variable in the conventional fixation group, while the thicknesses were comparatively consistent in the fixation device group. After endoscopic submucosal dissection, pathologic preparation using this fixation device could offer more objective assessment of specimens.     

Investigating the primary stability of the transversal support tibial plateau concept to retain both cruciate ligaments during total knee arthroplasty

Purpose: The important roles of the anterior cruciate ligament regarding knee stability, physiologic kinematics, and proprioception are unquestioned. Thus, various efforts have been made to retain the ACL during total knee arthroplasty (TKA). Neither of the existing solutions to this problem, i.e. bicruciate retaining prostheses and implantation of two unicondylar prostheses, has been successful because of concept-specific problems as well as general difficulties with implant fixation.?The new transversal support tibial plateau concept is a prosthesis of two individual joint surfaces reinforced beneath the articular line by joint surface supports and buttressed by a single transversal support. This configuration, which enables retention of both cruciate ligaments, should provide good bone fixation and ensure long-term alignment of the individual joint surfaces. Methods: In the current study, four prototypes based on this novel concept were developed and the resulting primary stability was analyzed using adapted load testing. The test set-up, with the model-loading of specially prepared Sawbones? and a sinusoidal oscillating load transmission with 25 000 cycles over 10 increasing load levels, achieved subsidence, which enabled comparison of the four different model variants regarding primary stability in view of bone anchoring.Results: The model variant (TSmobile) that allowed transverse glide of the joint surface supports along the transversal support revealed the largest subsidence.Conclusions: A rigid attachment of the joint surface supports of the transversal support tibial plateau thus appears to offer increased primary stability regarding bone anchoring.