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Biomedical subjects

G P Ashcroft

Publications and source records attributed to G P Ashcroft.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of sensorineural symptoms between UK orthopaedic surgeons and gynaecologists.

BACKGROUND: We have previously described significant differences in self-reported neurological symptoms of orthopaedic surgeons when compared to a group of gynaecologists. We suggested that this may be secondary to occupational sources of hand-transmitted vibration. The original study was intentionally brief and failed to address potential confounders. AIMS: To compare the prevalence of sensorineural symptoms between UK orthopaedic surgeons and gynaecologists and adjust for potential confounding factors. METHODS: Postal questionnaires were sent to 2040 members of the British Orthopaedic Association and 1797 members of the Royal College of Gynaecologists requesting information about demographics and self-reported neurological symptoms. Demographics of the orthopaedic surgeons and gynaecologists were compared using chi-squared tests and independent t-tests. Multiple logistic regressions were carried out to compare the prevalence of symptoms while adjusting for potential confounding factors. RESULTS: Differences in the demographic profile of the orthopaedic surgeons and gynaecologists were identified: orthopaedic surgeons were predominantly male, were more junior in grade, were younger, used double gloving more often, had larger glove size, were more likely to be ambidextrous, to use vibrating tools outside of work and to consume greater amounts of alcohol. Orthopaedic surgeons reported a higher prevalence of tingling and numbness of fingers while at work and at other times. These differences were significant even after adjusting for potential confounding factors. CONCLUSION: Observed differences could be related to exposure to hand-transmitted vibration at work. Further assessment of risk to orthopaedic surgeons from hand-held power tools used in the course of their work is recommended.

Adult↗
PubMed2006

Femoral head viability after Birmingham resurfacing hip arthroplasty: assessment with use of [18F] fluoride positron emission tomography.

BACKGROUND: Total hip resurfacing has become increasingly popular over the last decade. There remains concern about the effect of the surgical approach on femoral head viability and the role of resurfacing in the management of established osteonecrosis. In view of these concerns, we examined femoral head viability following resurfacing through a modified anterolateral approach. METHODS: The viability of the femoral heads of ten patients who had undergone successful unilateral Birmingham hip resurfacing was assessed with use of positron emission tomography in conjunction with the injection of fluorine at a mean of twenty months after surgery. For each patient, in both the hip that had undergone resurfacing and the contralateral nonresurfaced hip, activity was measured in four regions of interest: the lateral aspect of the femoral head, the medial aspect of the femoral head, the lateral aspect of the femoral neck, and the proximal aspect of the femur. The uptake of fluorine in each area was converted to standard uptake volumes. RESULTS: No areas of osteonecrosis were seen in the femoral head of any patient. There were no significant differences in the standard uptake volumes as measured in the four regions of the nonresurfaced hips, whereas the median values were higher in all four regions of the resurfaced hips. The difference between the values in the resurfaced hips compared with those in the nonresurfaced hips was only significant (p < 0.05) in the lateral aspect of the femoral head. CONCLUSIONS: This study establishes positron emission tomography in conjunction with injection of fluorine as a possible modality for the assessment of femoral head viability after hip resurfacing. Viability following successful Birmingham hip resurfacing performed through a modified anterolateral approach has also been demonstrated. The increase in bone activity that was seen in the resurfaced hips in our study group may be related to bone remodeling or reperfusion of small areas of osteonecrosis. This technique offers the potential to study femoral head perfusion and viability following all types of resurfacing. LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Adult↗
PubMed2005

Peri-acetabular radiolucent lines: inter- and intra-observer agreement on post-operative radiographs.

Peri-acetabular radiolucent lines (RLLs) seen on "early" post-operative radiographs have been identified as a potential predictor of long-term implant performance. This study examines the inter- and intra-observer variation encountered when assessing such radiographs. Four consultant orthopaedic surgeons assessed the presence, extent and width of RLLs in 220 radiographs performed on 50 patients taken one to two weeks, six weeks, six months and one year following surgery. Inter-observer agreement was fair at 7-14 days but improved to moderate to good in films at six and 12 months. Intra-observer agreement was moderate to good at 7-10 days but again improved to good at 6 and 12 months. When only the presence or absence of RLLs was considered, both inter-observer and intra-observer agreement improved for both the six-month and one-year radiographs. This experiment shows that caution must be used for the interpretation of RLLs on hip radiographs taken during the very early post-operative period. We recommend that films taken at least six weeks to six months following surgery should be used for assessment to reduce observer variation. For optimum results, a single experienced observer should do the assessment with a simple classification.

Aged↗
PubMed2005

Wire tension in the Ilizarov system: accuracy of the wire-tensioning device.

The Ilizarov fixator consists of tensioned wires that attach bone segments to a modular frame. The aim of this study was to establish the accuracy and precision of the wire-tensioning device supplied with the Ilizarov external fixation system. The device was used to tension a wire in direct opposition to a calibrated load cell. Five subjects tested three devices, at each of their four tension settings, in two separate sessions. Subjects could not see the true tension during the test. There were significant differences between the results for different subjects (p < 0.01) and instruments (p < 0.01) but not for different tension settings or between the two sessions. Overall mean measured tensions were 4.9 per cent (standard deviation, 4.4 per cent) below intended values. Tensions obtained at the maximum edge (completely occluded) on the scale markings were significantly (p < 0.001) closer to the nominal values (mean discrepancy, 3.6 per cent) than those at the minimum edge (mean discrepancy, 17.6 per cent). Several factors influence wire tension. Tensioning devices are not identical and the results obtained with them depend on the user. If the scale markings are completely occluded, the discrepancy between intended and actual tensions of around 5 per cent is likely to be adequate for clinical practice since surgeons do not select the most suitable tension following quantitative data assessment, but rather it is a judgement based on surgical experience and consideration for the patient weight and expected level of activity.

Bone Wires↗
PubMed2002

Convection warmers--a possible source of contamination in laminar airflow operating theatres?

This work results from concerns that forced-air convection heaters applied to patients in the operating theatre might interfere with ultra-clean ventilation system and thus be a potential source of wound contamination. Air samples were taken in the operative field and the bacterial load calculated by estimating the number of colony forming units per cubic metre of air (cfu/m(3)). Six tests were carried out, two in empty theatres and four during standard orthopaedic operating lists. Differences were seen between empty theatres and those standing empty for short periods during busy operating lists. Increases were seen on entry to theatre of staff and patients with the convection heaters off. A further small rise was seen after the convection heaters were turned on when applied to patients. This study showed that use of warm air convection heaters on patients produced a small increase in the number of colony forming units in ultra-clean air theatres but the levels were unlikely to have clinical significance. By far the greatest effect on numbers was movement and presence of the patient and theatre staff in the theatre.

Air Microbiology↗
PubMed2001

Distraction lengthening of the radius for radial longitudinal instability after distal radio-ulnar subluxation and excision of the radial head: a case report.

The results of late surgery for symptomatic proximal migration of the radius after resection of the radial head for trauma are usually disappointing. Ulnar variance increases when the interosseous membrane is disrupted. Its integrity should be assessed to predict the results of further surgery. We describe a 29-year-old patient in whom distraction lengthening of the radius through an Ilizarov frame allowed him to regain pain-free function of the wrist and elbow after a complex Essex-Lopresti fracture dislocation and late symptoms of ulnar carpal impingement.

Adult↗
PubMed2000

Removal of the subchondral plate in acetabular preparation.

Retention of the subchondral plate during acetabular preparation in total hip replacement is believed to be an important part of modern cementing techniques. We have constructed a two-dimensional finite element analysis to assess the effect of retention and removal of this relatively stiff structure. The finite element analysis demonstrates increased stiffness and stress concentrations at the bone-cement interface that may have an adverse effect. Although further study is required, it may be that subchondral bone retention is not advantageous.

Acetabulum↗
PubMed1999

Abductor weakness and stresses around acetabular components of total hip arthroplasty: a finite element analysis.

Abductor weakness, and the resulting Trendelenburg gait, after total hip arthroplasty is believed to be associated with a poor long-term outcome. We have constructed a two-dimensional finite element analysis using load cases to mimic this abductor weakness. The finite element analysis demonstrates slightly increased stresses, particularly at the bone-cement interface in the DeLee-Charnley zone I, which does not seem sufficient to explain the adverse effect of abductor weakness.

Acetabulum↗
PubMed1995

Measurement of lower limb blood flow in patients with neurogenic claudication using positron emission tomography.

STUDY DESIGN: Ten subjects (seven with neurogenic claudication and three control subjects) underwent examination of lower limb muscle blood flow before and after exercise using positron emission tomography. OBJECTIVES: To investigate the hypothesis that lower limb muscle ischemia was the origin of symptoms in neurogenic claudication. BACKGROUND: Patients with neurogenic claudication secondary to spinal stenosis experience lower limb discomfort after exercise similar to that of ischemic claudication. However, they do not have clinical evidence of peripheral vascular disease. The authors postulated that the lower limb discomfort in patients with neurogenic claudication may arise from muscle ischemia due to inadequate dilatation of arterioles in response to exercise, this itself arising secondary to sympathetic dysfunction due to spinal stenosis. METHOD: Using O15-labeled water and positron emission tomography measured thigh and leg muscle blood flow response to exercise bilaterally in seven patients with unilateral neurogenic claudication and three control subjects were measured. RESULTS: The average values obtained for mid-thigh and mid-calf muscle perfusion at rest were 2.57 ml/min/100 g tissue (2.23-3.90) and 2.39 ml/min/100 g tissue (2.03-3.46), respectively. The average values obtained from mid-thigh and mid-calf perfusion after exercise were 4.41 ml/min/100 g tissue (2.8-6.0) and 4.87 ml/min/100 g (2.2-11.7). We found no difference in muscle perfusion between symptomatic and asymptomatic limbs in this group of patients. CONCLUSION: These studies suggest that muscle ischemia is not the origin of symptoms in most patients with neurogenic claudication.

Adult↗
PubMed1995

A new functional brace for the treatment of Colles' fractures.

A new prefabricated brace for the functional treatment of Colles' fractures has been developed. It is applied at fracture reduction and maintains fracture position by the application of three-point loading. In a prospective randomized clinical trial treating 85 displaced Colles' fractures, with blind independent follow-up, the brace gave better functional results than conventional plaster treatment. The improved function was apparent up to 6 months after injury. Finger function and pinch strength were also better in the brace-treated patients. Anatomical results were similar in the two groups.

Adult↗
PubMed1995

Lap seat-belts: still trouble after all these years.

A series of three cases of severe injury caused by involvement in an accident while wearing lap seat-belts is presented. More than 30 years after the term 'seat-belt syndrome' was coined, attention still requires to be drawn to the likely combination of severe spinal and intra-abdominal injuries in such patients.

Abdominal Injuries↗