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Biomedical subjects

M A Freeman

Publications and source records attributed to M A Freeman.

At least 73 records · Page 4Linked to original sources
PubMed1993

A new radiographic method for detection of tibial component migration in total knee arthroplasty.

In a prospective study the accuracy of a new radiographic method, Matched Indicators for Radiographic Assessment (MIRA), used to assess tibial component migration in total knee arthroplasty was evaluated. Radiopaque markers were placed in the tibial component and the tibial metaphysis in a standardized way so that four vertical distances could be measured on standard radiographs. Subsidence during the first postoperative year was measured both with this new method and with roentgen stereophotogrammetric analysis in 27 Freeman-Samuelson total knee arthroplasties. The error of measurement of MIRA was determined using the known error of roentgen stereophotogrammetric analysis. The new method was found to be promising with an accuracy of 1 mm, and the correlation between MIRA and roentgen stereophotogrammetric analysis was high when subsidence exceeded this value. Therefore, subsidence of clinical importance should be detected with MIRA. The method is simple and well suited for routine follow-up examination of large patient materials.

Aged↗
PubMed1993

Pre-clinical testing of hip prosthetic designs: a comparison of finite element calculations and laboratory tests.

To investigate the accuracy of finite element (FE) models for pre-clinical testing of unbounded hip prostheses, relative to aspects of load transfer and micromobility, two previously published laboratory experiments were simulated, using three-dimensional FE models. It was found for the load-transfer analyses that the experiment and the FE study revealed results that were very similar. The trends in the mobility experiments were also reproduced in the FE simulations, although quantitative differences were found. It is concluded that FE analysis can effectively be used for design evaluation of hip prostheses before prototypes are made.

Acrylic Resins↗
PubMed1993

Tibial high-density polyethylene wear in conforming tibiofemoral prostheses.

We have studied 27 tibial prostheses retrieved from knee replacements after 1 to 9 years. In 22 the femoral components were of cobalt-chrome, in five polyacetal. The design of the components gave a nominal contact area of 320 mm2 on each condyle. The tibial component was of high-density polyethylene (HDP) at least 6 mm thick, and not heat-treated. In the metal/HDP prostheses the average wear rate was 0.025 mm/year. The relative wear on the medial and lateral sides was related to the leg axis. None of the retrieved prostheses showed any severe disruption of their surface. The polyacetal/HDP prostheses showed similar wear with a statistically insignificant trend towards slower penetration. We conclude that the rate of wear of HDP in a conforming tibiofemoral bearing with a fixed tibial component at least 6 mm thick and not heat-treated is slow enough to be safe in clinical practice.

Acetals↗
PubMed1993

The evaluation of prosthetic components in total joint replacement.

Evaluation of prosthetic components for total joint replacement has been attempted using a number of methods, most of which have defects. Clinical studies using scores have severe limitations; survivorship studies represent a fairly crude way of assessing new prosthetic components, and they require long periods of observation. Radiological evaluation is often subjective, as are most studies on component migration. There are fortunately alternative methods, such as roentgen stereophotogrammetric analysis, which give objective results within short delays; new methods are being developed which can provide similar information at a more reasonable expense. Illustrative studies are reported, and it is concluded that new components should be evaluated by measuring their early migration rate, which is shown to have a predictive value.

Acetabulum↗
PubMed1992

T cell responses to synthetic TSH receptor peptides in Graves' disease.

Twenty-eight peptides, representing the entire extracellular domain of the TSH receptor, were synthesised to investigate which parts of this autoantigen may be targets for the T cell response in Graves' disease (GD). T cells from 11 of 21 controls and 26 of 36 newly diagnosed GD patients proliferated in response to one or more peptides with a stimulation index (SI) of greater than 2.0 (chi 2 = 2.31, P greater than 0.1). The response of patients and controls to any of the individual peptides was also not statistically different. However, individual patients gave high SIs with certain peptides to which controls either gave an absent or very weak response. HLA-DR3 was not associated with any particular response to TSHR peptides. Three out of seven GD patients whose T cells were evaluated before and after treatment showed a response of this kind only early in the course of their disease. Intrathyroidal T cells from four GD patients did not give a consistent proliferative response to pools of five peptides, and depleting peripheral blood T cells of their CD8+ population did not affect the proliferative response. These results indicate that the T cell response to the TSH receptor in GD does not seem to be directed against any one particular epitope on the peptides we have tested which cover the extracellular domain.

Amino Acid Sequence↗
PubMed1992

One-stage reimplantation for infected total knee arthroplasty.

One-stage reimplantation for the salvage of infected total knee arthroplasty in 18 patients was reviewed at an average follow-up of five years. There had been one recurrence and one new infection, both in rheumatoid patients with another focus of infection. In four other patients the clinical result was impaired by pain after walking (2) and limited flexion (2). Our results suggest that one-stage reimplantation is a reasonably reliable procedure for the management of a loose infected prosthesis.

Adult↗
PubMed1992

Proximally cemented versus uncemented Freeman-Samuelson knee arthroplasty. A prospective randomised study.

We studied the effect of a layer of cement placed under the tibial component of Freeman-Samuelson total knee prostheses with a metal back and an 80 mm intramedullary stem, using roentgen stereophotogrammetry to measure the migration of the tibial component during one year in 13 uncemented and 16 cemented knees. The addition of cement produced a significant reduction in migration at one year, from a mean of 1.5 mm to one of 0.5 mm (p less than 0.01), including a significant reduction in pure subsidence. One year postoperatively the clinical results were similar between the groups, but, at three years, one uncemented knee had required revision.

Adult↗
PubMed1992

Early migration of prostheses related to long-term survivorship. Comparison of tibial components in knee replacement.

We determined the cumulative survival rates, in arthroplasty of the knee, of three designs of tibial component, using a change of position on standard radiographs or revision for aseptic loosening as criteria of failure. The average migration of each of the three designs in the first postoperative year is known from roentgen stereophotogrammetric analysis reported by other authors. The ranking order of the components as judged by cumulative survival is the same as that determined by early migration. This finding supports the view that the measurement of early migration can predict late aseptic loosening and therefore that such measurements are clinically of value.

Bone Cements↗
PubMed1992

Hydroxyapatite coating of hip prostheses. Effect on migration into the femur.

We studied two groups of femoral hip prostheses: 43 TiAlV ridged press-fit stems, and 26 with similar stems coated with hydroxyapatite on the proximal half. At one year, radiological measurement showed a mean downward migration of 0.99 mm for the TialV prostheses and 0.12 mm for the HA-coated prostheses (p = 0.0002). Hydroxyapatite coating appeared to provide effective bio-active supplementary fixation.

Adult↗
PubMed1992

Accuracy of the Nunn method in measuring acetabular cup migration.

The accuracy of the Nunn method in measuring acetabular component migration was compared with 3 other radiological methods and with roentgen stereophotogrammetry in 34 pelvic radiographs. The Nunn method seems to have the same or better accuracy than the other non-computerized methods, but less accuracy than the computerized EBRA method.

Acetabulum↗
PubMed1992

The scientific basis of cement versus cementless fixation.

The arguments for and against three implant materials (polymethylmethacrylate, cobalt-chrome alloy, and titanium aluminium vanadium alloy) when used as interfaces between a loaded implant and bone are reviewed from mechanical and biologic standpoints. It is concluded that there is neither an overwhelming advantage nor a disadvantage for any one of them.

Alloys↗
PubMed1991

The effect of hydroxyapatite coating on ingrowth of bone into cavities in an implant.

A canine implant study was performed to assess whether hydroxyapatite (HA) could induce bone to close gaps at the bone-prosthesis junction. Titanium alloy (TiAlV) plates with varying grooves cut into them (1, 2, and 3 mm deep) and identical on both sides were sprayed on one side with HA and left as bare metal on the other. These were then implanted into the distal femora of dogs that were killed 4 and 8 weeks afterwards. Specimens were analyzed using optical microscopy and microradiography. Results show that the presence of HA induces bone to grow almost completely down the deepest groove by 8 weeks. In the 1- and 2-mm grooves at 4 weeks the depth of penetration of bone into the grooves was greater on the HA coated side (but the actual volume of bone in the grooves was greater on the TiAlV side because the bone present was more dense). We conclude that the presence of HA induces bone to close relatively large gaps. Although bone does not grow all the way into uncoated defects there can be more bone here in the short term. This feature of HA may be of great value in hip implant fixation.

Animals↗
PubMed1991

Exposure of the hip using a modified anterolateral approach.

This report outlines an exposure to the hip using one curved skin incision, permitting retention of the femoral neck, and allowing access to both the anterior and posterior aspects of the hip, the whole of the proximal femur, and the circumference of the acetabulum. This approach is useful in revision surgery. The anterior abductors are mobilized using partial sharp release. A review of postoperative abductor function is presented, demonstrating satisfactory function after partial sharp release.

Gait↗
PubMed1991

Sensitivity to titanium. A cause of implant failure?

Tissues from five patients who underwent revision operations for failed total hip replacements were found to contain large quantities of particulate titanium. In four cases this metal must have come from titanium alloy screws used to fix the acetabular component; in the fifth case it may also have originated from a titanium alloy femoral head. Monoclonal antibody labelling showed abundant macrophages and T-lymphocytes, in the absence of B-lymphocytes, suggesting sensitisation to titanium. Skin patch testing with dilute solutions of titanium salts gave negative results in all five patients. However, two of them had a positive skin test to a titanium-containing ointment.

Antibodies, Monoclonal↗
PubMed1990

The effect of retention of the femoral neck and of cement upon the stability of a proximal femoral prosthesis.

Radiological measurements of downward femoral component migration are reported for 203 hips in the first 2 years following total hip arthroplasty. The femora differed with respect to the retention of the femoral neck--in 167 it was retained and in 36 it was damaged--and to the use of cement--142 hips were press-fits and 61 were cemented. Multivariate analysis demonstrated that both retention of the neck and the use of cement retarded migration (ie, increased stability) of the femoral component (P = .0003 and .0037, respectively).

Cementation↗