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Biomedical subjects

A W McCaskie

Publications and source records attributed to A W McCaskie.

15 recordsLinked to original sources
PubMed1999

The inadequacy of standard radiographs in detecting flaws in the cement mantle.

Radiological assessment of the cement mantle is used routinely to determine the outcome of total hip replacement. We performed a simulated replacement arthroplasty on cadaver femora and took standard postoperative radiographs. The femora were then sectioned into 7 mm slices starting at the calcar, and high-resolution faxitron radiographs were taken of these sections. Analysis of the faxitron images showed that defects in the cement mantle were observed up to 100 times more frequently than on the standard films. We therefore encourage the search for a better technique in assessing the cement mantle.

Arthroplasty, Replacement, Hip↗
PubMed1998

Randomised, prospective study comparing cemented and cementless total knee replacement: results of press-fit condylar total knee replacement at five years.

Early implants for total knee replacement were fixed to bone with cement. No firm scientific reason has been given for the introduction of cementless knee replacement and the long-term survivorship of such implants has not shown any advantage over cemented forms. In a randomised, prospective study we have compared cemented and uncemented total knee replacement and report the results of 139 prostheses at five years. Outcome was assessed both clinically by independent examination using the Nottingham knee score and radiologically using the Knee Society scoring system. Independent statistical analysis of the data showed no significant difference between cemented and cementless fixation for pain, mobility or movement. There was no difference in the radiological alignment at five years, but there was a notable disparity in the radiolucent line score. With cemented fixation there was a significantly greater number of radiolucent lines on anteroposterior radiographs of the tibia and lateral radiographs of the femur. At five years, our clinical results would not support the use of the more expensive cementless fixation whereas the radiological results are of unknown significance. Longer follow-up will determine any changes in the results and conclusions.

Adult↗
PubMed1998

Further uses of polymethylmethacrylate in orthopaedic surgery.

For over 30 years polymethylmethacrylate (PMMA) has been used in orthopaedic surgery to fix prosthetic components. Two additional uses, relying on the moulding properties previously utilized in dentistry, are described here: the use of PMMA as a bone graft template and as a femoral window plug in total hip replacement.

Arthroplasty, Replacement, Hip↗
PubMed1998

Current practice in primary total hip replacement: results from the National Hip Replacement Outcome Project.

As part of the National Study of Primary Hip Replacement Outcome, 402 consultant orthopaedic surgeons from three regions were contacted by postal questionnaire which covered all aspects of total hip replacement (THR). There was a 70% response rate of which 71 did not perform hip surgery, a further 33 refused to take part, leaving 181 valid responses. Preoperative assessment clinics were used by 89% of surgeons, but anaesthetists and rehabilitation services were rarely involved at this stage. Of respondents, 99% used routine thromboprophylaxis, with 79% using a combination of mechanical and chemical methods. Of surgeons, 84% routinely used stockings, whereas 95.5% used chemical prophylaxis, 63% employed low molecular weight heparins. Theatre facilities were shared with other surgical specialties by 6% of surgeons and 18% regularly used body exhaust suits for THR. Antibiotic loaded cement was used by 69% of surgeons, the majority (65%) used a single brand of normal viscosity cement with 9% using reduced viscosity formulations. Modern cementing techniques were commonly used at least in part, 87% used a cement gun and 94% a cement restrictor for femoral cementing. On the acetabulum, 47% pressurised the cement. In all, 36 different femoral stems and 35 acetabular cups were in routine use, but the majority of surgeons (55%) used Charnley type prostheses. Of the surgeons, 57% performed only cemented THR, while 3% exclusively used uncemented THR. Of consultants, 21% followed up their patients to 5 years, the majority discharge patients within the first year. Of concern is a large proportion of surgeons using low molecular weight heparins despite a lack of evidence with regard to reducing fatal pulmonary embolism, and also the small number of surgeons using prostheses of unproven value. Third generation cementing techniques have yet to be fully adopted. The introduction of a national hip register could help to resolve some of these issues.

Arthroplasty, Replacement, Hip↗
PubMed1997

Cement pressurisation during hip replacement.

The newer techniques of cementing aim to improve interlock between cement and bone around a femoral stem by combining high pressure and reduced viscosity. This may produce increased embolisation of fat and marrow leading to hypotension, impaired pulmonary gas exchange and death. For this reason the use of high pressures has been questioned. We compared finger-packing with the use of a cement gun by measuring intramedullary pressures during the cementing of 31 total hip replacements and measuring physiological changes in 19 patients. We also measured pressure in more detail in a laboratory model. In the clinical series the higher pressures were produced by using a gun, but this caused less physiological disturbance than finger-packing. The laboratory studies showed more consistent results with the gun technique, but for both methods of cementing the highest pressures were generated during the insertion of the stem of the prosthesis.

Bone Cements↗
PubMed1997

Sectioning fresh human bone: the reduction of aerosol and physical hazards.

Musculoskeletal research demands an accurate model on which to work, and fresh frozen human bone is an ideal material. However, there is increasing concern over the biohazard that this represents. A method is reported that reduces the biohazard, and two research situations are described. Both use polymethylmethacrylate (PMMA) bone cement as an interface between the human tissue and the cutting device, which allows solid and suitable geometry for vice fixation. A method of bone cutting that enables remote operation is described; this method may reduce the risk of disease transmission by aerosol, and prove useful to all in this field of research.

Aerosols↗
PubMed1996

Radiological evaluation of the interfaces after cemented total hip replacement. Interobserver and intraobserver agreement.

Three radiological methods are commonly used to assess the outcome of total hip replacement (THR). They aim to record the appearance of lucent areas and migration of the prosthesis in a reproducible manner. Two of them were designed to monitor the implant through time and one to grade the quality of cementing. We have measured the level of inter- and intraobserver agreement in all three systems. We randomised 30 patients to receive either finger packing or retrograde gun cementing during Charnley hip replacements. The postoperative departmental radiographs were evaluated in a blinded study by two orthopaedic trainees, two consultants and two experts in THR. The trainees and consultants repeated the exercise at least two weeks later. We used the unweighted kappa statistic to establish the levels of agreement. In general, intraobserver agreement was moderate but interobserver agreement was poor, with levels similar to or less than those expected by chance. Our results indicate that such systems cannot provide reliable data from centres in different parts of the world, with various levels of surgeon evaluating radiographs at differing time intervals. We discuss the problem and suggest some methods of improvement.

Bone Cements↗
PubMed1995

Chronic ankle instability: the value of talar tilt under general anaesthesia.

Ankle inversion injuries are the most common injury in sport and yet treatment is controversial. One result is chronic ankle instability, an injury for which criteria for surgical intervention are unclear. This prospective study of 14 patients showed that a large proportion of patients had no detectable abnormality on preoperative investigation, but were subsequently shown to have an abnormality under general anaesthesia. This suggests that a good history of chronic instability is more sensitive an indicator than conventional investigations. Stress views under anaesthesia may confirm the problem.

Adolescent↗
PubMed1995

Single-photon-emission computerised tomography compared with planar bone scan to assess femoral head vascularity.

We performed single-photon-emission CT (SPECT) and planar bone scans to assess femoral head vascularity in ten patients with displaced intracapsular hip fracture. The heads were labelled with tetracycline and after excision at hemiarthroplasty were assessed for tetracycline uptake distribution by fluorescence under UV light. The four which had the greatest tetracycline uptake were normal on SPECT and planar imaging. In two cases the planar bone scans were normal although SPECT suggested avascularity thus giving false-negative results. Surgeons should be aware of this; SPECT may prove to be a more accurate method of assessing vascularity of the femoral head in fractures of the femoral neck.

Arthroplasty↗
PubMed1995

Human tissue retrieval at post-mortem for musculoskeletal research.

Laboratory experimentation must attempt to reduce animal involvement, and human cadaveric tissue can be a suitable alternative; however, this tissue is a potential biohazard, with the transmission of human immunodeficiency and hepatitis viruses presenting a very serious problem. In this paper we discuss how human tissue can be obtained at hospital post-mortem, and how it can then be stored and handled in a laboratory environment, focusing particularly on safety issues. We discuss the way in which the Department of Orthopaedic Surgery at Leicester University obtained human tissue for research into hip replacement. It is hoped that the article will serve as a 'blue-print' for other related research projects, where human tissue is required for experimentation.

Autopsy↗
PubMed1991

A case of dextrocardia with normal situs.

We report here a case of dextrocardia with normal situs in an 81-year-old man who died from non-pulmonary causes. Removal of the chest wall revealed a large, but otherwise anatomically normal, left lung occupying the entire left hemithorax and extending across the midline to overlap the left border of the heart which was positioned in the right hemithorax. The gross anatomy of the heart was normal save its position and the presence of only 2 pulmonary veins. Dissection of the heart showed all chambers in their classically described position, and there were no valvular defects. The anatomy of the great vessels was also normal. The right lung was hypoplastic and lay posterior to the heart. This lung lacked any lobular structure, but the presence of carbon particles throughout it suggested that it was capable of normal inflation.

Aged↗