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Biomedical subjects

C B Frank

Publications and source records attributed to C B Frank.

At least 55 records · Page 3Linked to original sources
PubMed1998

Scar formation and ligament healing.

Ligaments are highly organized, dense, fibrous connective-tissue structures that provide stability to joints and participate in joint proprioception. Injuries to ligaments induce a healing response that is characterized by the formation of a scar. The scar tissue is weaker, larger and creeps more than normal ligament and is associated with an increased amount of minor collagens (types III, V and VI), decreased collagen cross-links and an increased amount of glycosaminoglycans. Studies have shown that certain surgical variables alter the healing of ligaments. Such factors include the size of gap between the healing ligament, ends, the use of motion in a stable joint and the presence of multiple ligamentous injuries. Research on ligament healing includes studies on low-load and failure-load properties, alterations in the expression of matrix molecules, cytokine modulation of healing and gene therapy as a method to alter matrix protein and cytokine production.

Animals↗
PubMed1997

Ligament creep cannot be predicted from stress relaxation at low stress: a biomechanical study of the rabbit medial collateral ligament.

In normal daily activity, ligaments are probably subjected to repeated loading rather than to repeated deformation. The viscoelastic response to repeated loading is creep; this effect has significance for ligament reconstructions, which potentially "stretch out" over time. However, most experimental studies have examined the viscoelastic response to repeated deformation, stress relaxation. We hypothesized that the creep of a ligament could be predicted from its stress-relaxation behaviour. Left and right medial collateral ligaments of eight skeletally mature rabbits were subjected to either creep or stress-relaxation testing under comparable conditions. The time-dependent increase in strain (creep) and reduction in load (relaxation) from the tests were modelled with use of the quasilinear viscoelastic theory and generalized standard linear solid modelling. Ligaments were found to creep distinctly less than would be predicted from relaxation tests. Although the reason for this behaviour remains unknown, we speculate that it is due to the progressive recruitment of collagen fibres during creep.

Animals↗
PubMed1997

Adaptive filtering, modelling and classification of knee joint vibroarthrographic signals for non-invasive diagnosis of articular cartilage pathology.

Interpretation of vibrations or sound signals emitted from the patellofemoral joint during movement of the knee, also known as vibroarthrography (VAG), could lead to a safe, objective, and non-invasive clinical tool for early detection, localisation, and quantification of articular cartilage disorders. In this study with a reasonably large database of VAG signals of 90 human knee joints (51 normal and 39 abnormal), a new technique for adaptive segmentation based on the recursive least squares lattice (RLSL) algorithm was developed to segment the non-stationary VAG signals into locally-stationary components; the stationary components were then modelled autoregressively, using the Burg-Lattice method. Logistic classification of the primary VAG signals into normal and abnormal signals (with no restriction on the type of cartilage pathology) using only the AR coefficients as discriminant features provided an accuracy of 68.9% with the leave-one-out method. When the abnormal signals were restricted to chondromalacia patella only, the classification accuracy rate increased to 84.5%. The effects of muscle contraction interference (MCI) on VAG signals were analysed using signals from 53 subjects (32 normal and 21 abnormal), and it was found that adaptive filtering of the MCI from the primary VAG signals did not improve the classification accuracy rate. The results indicate that VAG is a potential diagnostic tool for screening for chondromalacia patella.

Adult↗
PubMed1997

Injury size affects long-term strength of the rabbit medial collateral ligament.

Long-term effects (104 weeks) of 2 extremes of gap size on the mechanical behavior of the rabbit medial collateral ligament were examined. In the midsubstance of each right medial collateral ligament, either an 8 mm gap injury was created or a 4 mm Z plasty injury was created and repaired. Each group was subdivided into a healing interval of 40, 78, or 104 weeks. Femur-medial collateral ligament-tibia complexes were tested mechanically or examined with light microscopy. Both injuries healed with histologically similar tissue and showed improved mechanical behavior 78 weeks after injury. No further improvement was measurable 104 weeks after injury. Scar material properties remained markedly inferior to normal regardless of injury. Low load and viscoelastic behavior recovered relatively well regardless of gap size. However, gap injuries showed significantly inferior structural properties at all intervals. These results suggest that a large initial gap between ligament ends in the extraarticular space predisposes scars to long term structural weakness. If this principle is true clinically, then patients with large gaps between torn ligament ends (caused by displacement, folding, or retraction) may function well at lower loads, but they may be chronically at greater risk of reinjury at high loads.

Animals↗
PubMed1997

Parametric representation and screening of knee joint vibroarthrographic signals.

We have been investigating analysis of knee joint vibration or vibroarthrographic (VAG) signals as a potential tool for noninvasive diagnosis and monitoring of cartilage pathology. In this paper, we present a comprehensive comparative study of different parametric representations of VAG signals. Dominant poles and cepstral coefficients were derived from autoregressive models of adaptively segmented VAG signals. Signal features and a few clinical features were used as feature vectors in pattern classification experiments based on logistic regression analysis and the leave-one-out method. The results using 51 normal and 39 abnormal signals indicated the superior performance of cepstral coefficients in VAG signal classification with an accuracy rate of 75.6%. With 51 normal and 20 abnormal signals limited to chondromalacia patella, cepstral coefficients again gave the highest accuracy rate of 85.9%.

Algorithms↗
PubMed1997

Whole joint embedding in polymethylmethacrylate: a method for preparing intact musculoskeletal organ systems for histomorphology and 3-D reconstruction.

Large and medium size undecalcified joints were embedded in methylmethacrylate resin. Sections of 600 microns prepared from polymethylmethacrylate blocks show minimal distortion and are suitable for surface staining and three-dimensional reconstruction. The 5 microns sections prepared from these slabs retain good cytological detail. This method permits the examination of musculoskeletal organ systems at both macroscopic and microscopic levels.

Animals↗
PubMed1996

Screening of vibroarthrographic signals via adaptive segmentation and linear prediation modeling.

This paper proposes a noninvasive method to diagnose chondromalacia patella at its early stages by recording knee vibration signals (also known as vibroarthrographic or VAG signals) over the mid-patella during normal movement. An adaptive segmentation method was developed to segment the nonstationary VAG signals. The least squares modeling method was used to reduce the number of data samples to a few model parameters. Model parameters along with a few clinical parameters and a signal variability parameter were then used as discriminant features for screening VAG signals by applying logistic and discriminant algorithms. The system was trained using ten normal and eight abnormal signals. It correctly screened a separate test set of ten normal and eight abnormal signals except for one normal signal. The proposed method should find use as an alternative technique for diagnosis of knee joint pathology or as a test before arthroscopy or major knee surgery.

Algorithms↗
PubMed1996

Normal and healing ligament vascularity: a quantitative histological assessment in the adult rabbit medial collateral ligament.

Normal and healing adult rabbit medial collateral ligaments (MCL) have been assessed for microvascular anatomy using a quantitative image analysis methodology. MCL preparation by ink-gelatin perfusion enabled acceptable visualisation of microvascular channels within the tissue. Fifteen adult rabbits were studied; 3 normal rabbits formed an external time-zero control group; 12 animals received a standardised gap injury to the right MCL. The ligament injury was permitted to heal for 3, 6, 17 or 40 wk (3 animals in each healing group). Results confirmed that the normal MCL is hypovascular (about 1.46% vascularity by area) and that microvascular channels are highly organised and oriented longitudinally deep within the tissue. Healing MCL scar becomes twice as vascular as normal ligament early on, but returns to near normal values by 40 wk. Microvascular channels appear less organised in scar than in contralateral controls, but remodel with time. The directional scatter and spatial extent of ligament microvascular channels is quantifiable in normal and healing tissues.

Animals↗
PubMed1996

Relationships of the vibromyogram to the surface electromyogram of the human rectus femoris muscle during voluntary isometric contraction.

The relationship between vibromyographic (VMG) and electromyographic (EMG) signals during isometric contraction of the human rectus femoris muscles was studied. The method of least squares was used to obtain the best-fitting linear regression model to the root mean squared (RMS) values of the VMG and the EMG. It is shown that for the rectus femoris of four subjects, a linear VMG versus EMG relationship exists during 20-80% of the maximum voluntary contraction (MVC) at 30 degrees, 60 degrees, and 90 degrees of knee joint flexion angles. The relation between the VMG and the EMG may be explained by the order recruitment of motor units and by the "onion-skin" phenomenon of the firing rates of recruited motor units in the regulation of muscle force production as reported in electro-neurophysiologic studies.

Adult↗
PubMed1995

Intraoperative graft tensioning alters viscoelastic but not failure behaviours of rabbit medial collateral ligament autografts.

The effects of three different degrees of intraoperative graft tensioning on measures of ex vivo laxity, viscoelastic behaviour, and structural and material failure of isolated healing medial collateral ligament autografts were investigated in a rabbit model. The grafts were orthotopically replaced at one of three different loads (too tight, anatomic, or too loose) and were mechanically evaluated after 0, 12, 24, and 48 weeks of healing. Laxity of the ligament was influenced by intraoperative graft tensioning at time zero. However, after 12 weeks of healing, values for laxity were indistinguishable among the experimental groups. Cyclic load relaxation, a measure of viscoelastic behaviour, was significantly influenced by intraoperative graft tensioning, and this effect persisted even after 48 weeks of healing. Grafts placed under excessive tension relaxed one-third less than grafts placed under abnormally low in situ tension. The relevance of these differences remains to be determined. Intraoperative tensioning had no significant influence on characteristics of structural or material failure of the graft during the first year of healing. These results suggest that, in this model, control of graft tension at the time of placement and fixation does not improve the failure characteristics of the medial collateral ligament. The structural strength of the grafts collectively improved to nearly normal values after 48 weeks; however, material recovery was less complete. Failure loads averaged 89% of control values, whereas failure stress averaged only 52% after 48 weeks of healing.

Analysis of Variance↗
PubMed1995

Stress governs tissue phenotype at the femoral insertion of the rabbit MCL.

The cells in the midsubstance portion of skeletal ligaments typically have elongated shapes, but where ligaments insert into bone the cells appear very rounded and the tissue phenotype is that of fibrocartilage. Between the midsubstance and the insertions there is a gradient in cell shape and tissue phenotype that has been hypothesized to reflect a gradient of mechanical stresses. To test this hypothesis, cell shapes (an index of tissue phenotype) were quantified in the central part of the femoral insertion of the rabbit medial collateral ligament by computer-assisted histomorphometry. Morphometric measurements were correlated with the mechanical stresses and strains in the central part of the insertion as predicted by finite element analysis. Throughout the ligament the direction of the predicted principal tensile stresses coincides with the direction of the collagen fibers which curve from the midsubstance to meet the femur at nearly right angles. Principal compressive stresses also occur within the ligament: the highest are localized near the bone; the lowest in the midsubstance. The areas with the roundest cells correspond to the areas with the highest principal compressive stresses in the model; the areas with the flattest cells correspond to the areas with the lowest compressive stresses in the model. A correlation between cell shape and mechanical stresses suggests that physiological loading of the MCL is important for the maintenance of tissue phenotype throughout this insertion. We theorize that the cells in ligament insertions adapt to the prevailing local mechanical environment.

Adaptation, Physiological↗
PubMed1995

Hamstring spasm in anterior cruciate ligament injuries.

The accurate diagnosis of an anterior cruciate ligament (ACL) injury continues to be a challenge to clinicians, and often requires magnetic resonance imaging or arthroscopy for confirmation. We present a literature review of the currently known physical signs of ACL injury, followed by three case reports that describe a sign we believe may be helpful in the diagnosis of acute/semi-acute ACL injury: involuntary hamstring spasm.

Adult↗
PubMed1995

Localization of knee joint cartilage pathology by multichannel vibroarthrography.

This paper proposes non-invasive techniques to localize sound or vibroarthrographic (VAG) signal sources in human knee joints. VAG signals from normal subjects, patients who subsequently underwent arthroscopy, and cadavers with arthroscopically-created lesions, obtained by stimulation with a finger tap over the mid-patella and swinging movement of the leg, were analyzed for time delays using cross-correlation functions for source localization. Correct results were obtained for 13 of the 14 subjects tested by finger stimulation, and for 11 of the 12 subjects whose VAG signals during swinging movement were analyzed. The techniques could be valuable in the diagnosis and treatment of knee pathology before and after joint surgery or drug therapy.

Arthroscopy↗
PubMed1995

A new device and method for controlling the load in rabbit medial collateral ligament reconstructions.

In order to study the effect of intra-operative tensioning on the laxity and strength of healing ligament grafts in an animal model, a method of quantifying graft tension was needed. In this study a sensitive ligament tensioning device was developed to measure accurately the prefixation loads in the rabbit medial collateral ligament (MCL) graft. To verify that reproducible changes in ligament tension could be created with the tensioning device, a group of animals had their MCL grafts replaced at one of three different graft loads (tight, anatomic, or loose). The tensioning device consists of two posts which move relative to one another by means of an axial screw. The movable post, which is inserted into the tibial bone island of the MCL graft has a series of strain gauges which can measure the tension applied to the graft. The stationary post attaches to the tibial shaft, permitting the ligament graft to be tensioned relative to this fixed point. After graft tensioning and fixation, the animals were euthanized immediately postoperatively and their ligament load-deformation behavior was measured using an Instron materials testing machine. Specific measures of low load behavior was taken to quantify ligament laxity. Our results demonstrate that the tensioning device was capable of reproducibly altering prefixation graft load intra-operatively as well as MCL laxity immediately postoperatively. A baseline of laxity values was thus developed to follow changes in this laxity measure for future studies of MCL graft healing in this model.

Animals↗
PubMed1995

Variations in rupture site and surface strains at failure in the maturing rabbit medial collateral ligament.

The relationship between the pattern of surface strain and the site of failure in maturing rabbit ligaments was studied in vitro. Bone-medial collateral ligament (MCL)-bone complexes of 24 female New Zealand White rabbits at 3, 6, 9 and 12 months of age (n = 6 rabbits, 12 MCLs per group) were tested in tension to failure. A video dimension analysis (VDA) system was used to map the surface strain at failure across the width and along the length of the medial side of each MCL during testing. Results showed that the highest strains were consistently located at the femoral insertion decreasing towards the midsubstance, with the highest strain occurring in the anterior portion of the MCL immediately adjacent to the femoral insertion. Strains of the complex at failure increased with rabbit maturation. The strain distribution however, did not change dramatically, even though the locations of MCL failure changed from exclusively tibial avulsion in the three month old rabbits to predominantly midsubstance failures in the 12 month old rabbits. In the six month old rabbits, there was a particular dissociation with all MCLs failing near the tibial insertion while femoral strains were apparently the highest. These results suggest two possibilities beyond that of some unknown artifacts of optical strain measurement. First, since failure sites rarely correlated with areas of maximum surface strain in this study, it seems possible that higher strains could exist deeper in the tissue, particularly at the bone-ligament interface of the tibial insertion in immature animals and somewhere within the midsubstance of the MCL in the adult. Secondly, it is possible that the ligament material may be heterogeneous.

Age Factors↗