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Biomedical subjects

T D Cooke

Publications and source records attributed to T D Cooke.

At least 19 recordsLinked to original sources
PubMed1999

Ochronotic arthropathy: case report and review of the literature.

Alkoptonuria is an inherited metabolic disorder which is associated with various systemic abnormalities and related to the deposition of homogentisic acid pigment in connective tissues. These pigmentary changes are termed "ochronosis". We describe two patients with ochronotic arthropathy who presented with progressive and advanced degenerative changes in the lumbo-sacral spine. The literature, differential diagnosis and management of this rare condition are reviewed in this article. Management is usually conservative, but replacement surgery may be offered for severely affected major joints.

Adult↗
PubMed1998

Kinematics of the knee joint in deep flexion: a radiographic assessment.

The purpose of this study is to describe the kinematics of normal knees in vivo, assessed in deep flexion, using bi-planar radiographs. Antero-posterior and lateral views were obtained from five healthy males during three sequential positions of kneeling. In the first position, the subject knelt with the knees fully flexed (deep flexion between 150 and 165 degrees) and torso upright. In the second position, the subject bowed forward to an intermediate position (about 120 degrees of knee flexion). In the third position, the subject bowed further until his head touched the floor, supporting the upper torso with hands and with the knees flexed at about 90 degrees. The results show that past 135 degrees of knee flexion, the patella cleared the femoral groove and was in contact only with the condyles. For these particular postures, and during deep flexion, motion of the femur on the tibia did not reveal the classical femoral 'roll back'. Rather the lateral femoral condyle rolled further over the postero medial aspect of the lateral tibial plateau while contact of the medial femoral condyle occurred more anteriorly, but still in the posterior part of the medial plateau. This asymmetric rolling motion indicated an element of internal tibial rotation. Furthermore, the tibia was found to articulate with the femur at the most proximal points of the condyles in deep flexion. These data on the kinematics and contact characteristics of the tibio-femoral joint must be considered in any approach to design for a Deep Flexion Knee Implant.

Adult↗
PubMed1997

Knee kinematics in-vivo of kneeling in deep flexion examined by bi-planar radiographs.

Squatting and kneeling are important daily activities for Middle and Far East cultures that require positioning the knee in deep flexion. In these activities, the limb becomes fully flexed with a knee flexion angle reaching between 150 and 160 degrees and the heel reaching the posterior surface of the upper thigh. Existing knee prostheses do not allow a full return to normal activities for this large population since they are limited to achieving knee flexion of about 120 degrees. Also, there is very limited information on knee kinematics and/or forces in the range beyond 120 degrees. The purpose of this study is to describe the kinematics of normal knees in-vivo, assessed in deep flexion, using bi-planar radiographs. A-P and lateral views were obtained from 5 healthy subjects during three sequential positions of kneeling. In the 1st position, the subject knelt with the knees fully flexed (deep flexion between 150 degrees and 160 degrees) and torso upright. In the 2nd position, the subject bowed forward to an intermediate position (about 120 degrees of knee flexion). In the 3rd position, the subject bowed further until his/her head touched the floor, supporting the upper torso with hands and attaining a knee flexion of about 90 degrees. The results show that past 135 degrees of knee flexion, the patella was found to clear the femoral groove and was in contact only with the condyles. The results also show that the classical femoral "roll back" does not appear to occur in deep flexion. It seems that the lateral femoral condyle rolls over the postero medial aspect of the lateral tibial plateau while contact of the medial femoral condyle occurs more anteriorly, but still in the posterior aspect of the medial tibial plateau. This asymmetric rolling motion implies an element of internal tibial rotation. Furthermore, the tibia was found to articulate with the femur at the most proximal points of the condyles in deep flexion. These data on the kinematics and contact characteristics of the tibio-femoral joint must be considered in any approach to design for a Deep Flexion Knee Implant.

Biomechanical Phenomena↗
PubMed1995

A quantitative technique for reporting surface degradation patterns of UHMWPE components of retrieved total knee replacements.

A quantitative method of reporting surface degradation of the ultra-high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow-up visits enhanced the assessment of the retrieved TKR.

Biocompatible Materials↗
PubMed1995

Changes in mean trabecular orientation in the medial condyle of the proximal tibia in osteoarthritis.

In osteoarthritis of the knee, degenerative changes occur in the articular cartilage and underlying subchondral bone, particularly of the medial tibial condyle. Cancellous bone sclerosis that accompanies osteoarthritis is not only the result of an increase in bone volume fraction but also a change in trabecular structure. In a comparison with age-matched controls (n = 4), osteoarthritis (n = 11) demonstrated a significant (P < or = 0.05) increase in bone volume fraction and trabecular thickness. Overall trabecular orientation in the osteoarthritic group was more vertical or perpendicular to the articular surface than the control group (P < or = 0.05) especially in the trabeculae of the cancellous bone layer closest to the articular surface. These alterations in trabecular bone structure could have significant consequences for the mechanical properties of osteoarthritic bone.

Aged↗
PubMed1995

Trabecular microstructure in the medial condyle of the proximal tibia of patients with knee osteoarthritis.

The microstructural characteristics of osteoarthritic subchondral bone in the medial tibial condyle are clearly different from normal age-matched bone. Subchondral sclerosis in osteoarthritis indicates not only an increase in bone volume fraction but also alteration in other microstructural characteristics. Eleven medial tibial condyles were collected from ten subjects during arthroplastic surgery for knee oseoarthritis. They were compared to four medial tibial condyles from four age-matched controls with no history of any bone or joint disorder. Six sections from anterior to posterior and three levels from proximal to distal were evaluated in each medial condyle. Five histomorphometric parameters were measured: bone volume fraction (BVf), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.S), and trabecular connectivity (Tb.C). In general, the osteoarthritic subchondral bone had a higher bone volume fraction than control bone but the microstructure was characterized by fewer, widely spaced, thicker than normal trabeculae. There were also highly localized regional differences by depth from the articular surface and from anterior to posterior across the medial condyle. These variations in OA subchondral bone microstructure may significantly affect biomechanical competence of bone in a way not predictable by bone volume fraction measurements alone.

Aged↗
PubMed1994

Bone strength and histomorphometry of the distal femur.

The ultimate bone strength of the distal femur was measured radially, by indentation testing, around the transepicondylar line in 3 mm depth steps up to 12 mm below the subchondral bone plate. Specimens from 10 cadavers were used. This orientation of specimens was chosen as a way to provide measurement in a more physiologic orientation for load bearing and to standardize the assessment. Bone hardness declined sharply over the first 6 mm below the surface, tending to plateau at deeper levels. Within the top 6 mm layer the lateral condyle was softer than both the medial condyle and the central patellofemoral area (P < .05), but at deeper levels it maintained greater hardness. Of the histomorphometric parameters, those showing the greatest consistent correlation with hardness were bone volume fraction and trabecular separation. When the tibiofemoral and patellofemoral compartments were compared it was found that for a given value of bone volume fraction, condylar bone is marginally harder than patellofemoral bone. The data are relevant to the design of implants that match their geometric and material properties to the shape and strength of the underlying bone.

Adult↗
PubMed1994

Studies of thrombin-induced proteoglycan release in the degradation of human and bovine cartilage.

Because fibrin is commonly observed within arthritic joints, studies were undertaken to determine whether purified coagulation and fibrinolytic proteases degrade cartilage in vitro and to seek evidence for the activation of coagulation in arthritic joints through measurements of the levels of inhibitor-enzyme complexes and several other proteins associated with coagulation and fibrinolysis. The concentrations of 13 plasma proteins and complexes of thrombin and Factor Xa with antithrombin III were measured in synovial fluids recovered at the time of knee replacement surgery. All zymogens necessary to constitute the coagulation cascade were present. Thrombin and the combination of prothrombin plus prothrombinase induced proteoglycan release from both normal and arthritic cartilages. Factor Xa and plasmin induced release from diseased cartilage only, and urokinase, tissue plasminogen activator, and activated protein C were without effect at the levels used. At saturating levels of thrombin (> or = 2.0 microM) 80% of the proteoglycan content of normal cartilage was released within 24 h. Thrombin, which is cationic, reversibly binds cartilage with Kd = 7.0 +/- 1.0 microM and Bmax = 820 +/- 70 ng/mg of human cartilage. Levels of thrombin-antithrombin III complexes in synovial fluids and arthritis were 4-fold higher in osteo (OA) and 43-fold higher in rheumatoid (RA) than in controls (0.98 nM). Factor Xa-antithrombin III complex levels were threefold lower in OA and fivefold higher in RA than in controls (0.24 nM). These elevated levels of enzyme-inhibitor complexes imply a history of activation of coagulation within the joint, especially in RA. Since thrombin degrades cartilage in vitro and had been generated in vivo, as inferred by the existence of thrombin-antithrombin III complexes, intraarticular activation of coagulation may both contribute to the pathology of arthritis and comprise a target for therapy and diagnosis.

Animals↗
PubMed1994

Patterns of knee arthrosis and patellar subluxation.

This study was based on the unexpected observation of lateral patellofemoral subluxation in the varus osteoarthritic knee. Standardized radiographs of 109 knees (65 patients with osteoarthritis) were selected randomly from the authors' database and retrospectively reviewed. Hip-knee-ankle alignment data were correlated with patellofemoral subluxation and tilt, as well as with radiographic patellofemoral grades for arthrosis. The amount and site of patellofemoral arthrosis were correlated with patellar position and limb alignment. Patellae that were located centrally in the trochlear groove had the lowest radiographic score for arthrosis. Subluxation of the patella, either medially or laterally, was correlated with increased radiographic scores. Limb alignment was not correlated with the radiographic score. A significant percentage of varus knees (28%) had unexpected lateral subluxation of the patella. This observation has not been reported previously. It may have an impact on surgical decision-making for total knee arthroplasty and osteotomy.

Biomechanical Phenomena↗
PubMed1994

Radiographic assessment of bony contributions to knee deformity.

Our recommendations for standing radiography of the lower limb are that assessments be standardized with respect to limb rotation and fixed relative positions of the hip, knee, and ankle. Specifically, a neutral knee rotation position should be set up, defined as alignment of the flexion plane straight ahead. For a complete appraisal, there should be both AP and lateral views in which the positioning of the patient is the same in all respects. The QPR frame greatly assists in achieving these objectives. Furthermore, the presence of a calibration system adds to the reliability and reproducibility of data by compensating for errors of position or alignment arising from the placement of the source and the film. Standardization of positioning also improves the detectability of axial-rotational deformities on comparison of AP and lateral views, providing more reliable indications of the need for CT than possible with nonstandardized short views. When a skyline patellar radiograph is added to the QPR routine, the end result is an excellent appraisal of lower limb alignment, providing a solid basis for diagnosis and planning of appropriate surgical remedies.

Adolescent↗
PubMed1993

Toxicity of complement for chondrocytes. A possible source of cartilage degradation in inflammatory arthritis.

Cartilage from patients with rheumatoid arthritis and from animals with antigen-induced arthritis is frequently contaminated with complement-containing immune complexes. A possible role for complement activation in cartilage degradation was modeled in vitro by exposing cultured bovine chondrocytes to homologous serum, and determining cytotoxicity by monitoring the release of intracellular 51Cr. Complement activation was found to be cytotoxic, having maximal effect at 20-30% serum by 18 h. Serum toxicity was ablated by heat (50 degrees C, 20 min) or methylamine treatment but not by EGTA, suggesting that in these experiments activation occurred by the alternate route. The implications of the results are discussed in relation to ultrastructural evidence for the involvement of complement in the pathogenesis of cartilage degradation in inflammatory arthritis.

Animals↗
PubMed1993

Stereoradiogrammetric technique for estimating alignment of the joints in the hand and wrist.

A method and apparatus for quantitative measurement of the alignment and motion of the joints of the hand in three dimensions has been developed using stereoradiogrammetric principles. Alignment in planes of flexion-extension and radial-ulnar deviation can be determined to within 2.5 degrees; rotation about the long axis of the metacarpals or phalanges is more difficult to determine, and can be measured to within 7 degrees. Stereo views subtending angles in the range of 40 degrees were found to optimize the total system accuracy.

Calibration↗
PubMed1993

Mechanisms of cartilage degradation in inflammatory arthritis: interaction between chondrocytes and immunoglobulin G.

A possible role for immune complexes in the degradation of cartilage (rheumatoid arthritis and antigen induced arthritis) has been modelled in vitro by studying interactions between cultured bovine chondrocytes and monomeric (M) or heat aggregated (HA) IgG. Concentrations of IgG used were within the range of values reported in the synovial fluids of rheumatoid joints. ELISA and rosetting assays revealed Fc receptor mediated binding of MIgG and HAIgG to chondrocytes that had been cultured, but not to freshly isolated cells. Both forms of IgG stimulated the production of metalloprotease, but only HAIgG boosted generation of superoxide anion and reduced proteoglycan synthesis. HAIgG also stimulated cells to produce immunoreactive interleukin 1 although no biological activity was apparent. It is concluded that the equivalent behavior of chondrocytes in vivo, triggered by immune complexes, could contribute or lead directly to matrix degradation.

Animals↗