Biomedical subjects

M H Stone

Publications and source records attributed to M H Stone.

At least 73 records · Page 4Linked to original sources

PubMed1998

Prediction of plastic strains in ultra-high molecular weight polyethylene due to microscopic asperity interactions during sliding wear.

Studies of explanted femoral heads have shown that scratches caused by bone cement, bone or metallic particles are present on the rubbing surface. This damage has been cited as a cause of increased wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups and it is known that the particulate wear debris produced leads to osteolysis. A series of explanted Charnley femoral heads have been surface characterized using a Talysurf 6 profilometer and found to have scratches with lip heights in the size range 0.1-3.25 microns with an average height of 1 micron giving an average aspect ratio (defined as height/half-width) of 0.1. These geometries were incorporated into a finite element model of a stainless steel asperity sliding over UHMWPE under conditions similar to those in an artificial hip system. It was found that as the aspect ratio of the asperity lip increased, the plastic strains both on and below the surface of the UHMWPE increased non-linearly, but that the magnitude of the strain was independent of the asperity height. The asperity aspect ratio was also found to affect the position of the maximum sub-surface strain, as the asperity aspect ratio was increased the maximum strain rose to the surface. The high plastic strains predicted offer an explanation for the highly elevated wear rates in scratched counterface tests and the aspect ratio of scratch lips is therefore a critical determinant of plastic strain.

Computer Simulation↗

PubMed1998

Quantitative comparison of wear debris from UHMWPE that has and has not been sterilised by gamma irradiation.

Ultra-high-molecular-weight polyethylene (UHMWPE) components for total joint replacement generate wear particles which cause adverse biological tissue reactions leading to osteolysis and loosening. Sterilisation of UHMWPE components by gamma irradiation in air causes chain scissions which initiate a long-term oxidative process that degrades the chemical and mechanical properties of the polyethylene. Using a tri-pin-on-disc tribometer we studied the effect of ageing for ten years after gamma irradiation in air on the volumetric wear, particle size distribution and the number of particles produced by UHMWPE when sliding against a stainless-steel counterface. The aged and irradiated material produced six times more volumetric wear and 34 times more wear particles per unit load per unit sliding distance than non-sterilised UHMWPE. Our findings indicate that oxidative degradation of polyethylene after gamma irradiation in air with ageing produces more wear.

Air↗

PubMed1998

Quantification of third-body damage and its effect on UHMWPE wear with different types of femoral head.

We examined stainless-steel, cobalt-chrome, titanium and alumina and zirconia ceramic femoral heads retrieved at revision surgery. All the heads had articulated against ultra-high-molecular-weight-polyethylene (UHMWPE) acetabular cups. We studied the simulation of third-body damage and the wear of UHMWPE against the various materials used for the heads. The surfaces of the retrieved heads were analysed using a two-dimensional contacting profilometer. Third-body damage was characterised by the mean height of the scratches above the mean line (Rpm). The alumina ceramic and zirconia ceramic retrieved heads were found to have significantly less damage. In laboratory studies the ceramics were also more resistant to simulated third-body damage than the metal alloys. We studied the wear of UHMWPE against the damaged counterfaces in simple configuration tests. The damaged ceramics produced less polyethylene wear than the damaged metal counterfaces. The wear factor of UHMWPE against the damaged materials was dependent on the amount of damage to the counterface (Rp). Our study has shown the benefit of using the harder and more damage-resistant ceramic materials for femoral heads.

Aluminum Oxide↗

PubMed1998

Out-patient follow-up after total hip replacement in one health region.

A postal survey was carried out of all orthopaedic surgeons in the West Yorkshire Health region enquiring about out-patient follow-up practices after total hip replacement. Follow-up is advised to detect problems that can more effectively be resolved if detected early. A huge variation in the number, timing and nature of appointments following discharge was demonstrated. The total length of follow-up varied between 3 months and indefinite follow-up. The number of visits in the first post-operative year varied between one and four. The considerable variation in post surgery follow-up of these patients has important cost implications. Some patients will have unnecessary appointments whereas others will be inadequately reviewed. Guidance is required on the appropriate review of these patients which will allow early detection of joint failure in a way that is efficient in terms of the time and cost of out-patient follow-up.

Arthroplasty, Replacement, Hip↗

PubMed1998

Man is the measure ... the measurer.

Measures originated from human anatomy. Metrology has moved from man the measure to man the measurer. This transformation is documented using examples taken from the history of metrology. The outcome measure are units constructed and maintained for their utility, constancy and generality.

Anthropometry↗

PubMed1997

Sequential mechanical and pharmacological thromboprophylaxis in the surgery of hip fractures. A pilot study.

Two hundred and thirty-eight patients with femoral neck fractures were entered into a randomised pilot study comparing the use of sequential treatment by 'Flowtron DVT' garments in the perioperative period followed by Enoxaparin (Clexane-Rhône-Poulenc Rorer), and Enoxaparin alone. One hundred and ninety-three patients were excluded indicating the difficulty of achieving pure comparisons in this population. The remaining 44 were randomised: 21 received Enoxaparin from the time of admission, and 23 had sequential treatment. There was no statistically significant difference in the incidence of thromboembolism. Patient preference did not indicate a favoured treatment subjectively. The operation field was drier in the sequential group, although this did not reach significance. Sequential treatment was not shown to be better or worse than treatment with Enoxaparin, but the trends favoured sequential treatment rather than drug treatment alone. The technique allows the operation to be carried out without the problems produced by low dose heparins and mobilisation is not hindered by compression garments.

Adult↗

PubMed1997

Specificity of resistance training responses in neck muscle size and strength.

This study examined hypertrophy after head extension resistance training to assess which muscles of the complicated cervical neuromuscular system were used in this activity. We also determined if conventional resistance exercises, which are likely to evoke isometric action of the neck, induce generalized hypertrophy of the cervical muscle. Twenty-two active college students were studied. [mean (SE) age, weight and height: 21 (1) years, 71 (4) kg and 173 (3) cm, respectively]. Subjects were assigned to one of three groups: RESX (head extension exercise and other resistance exercises), RES (resistance exercises without specific neck exercise), or CON (no training). Groups RESX (n = 8) and RES (n = 6) trained 3 days/week for 12 weeks with large-muscle mass exercises (squat, deadlift, push press, bent row and mid-thigh pull). Group RESX also performed three sets of ten repetitions of a head extension exercise 3 days/week with a load equal to the 3 x 10 repetition maximum (RM). Group CON (n = 8) was a control group. The cross-sectional area (CSA) of nine individual muscles or muscle groups was determined by magnetic resonance imaging (MRI) of the cervical region. The CSA data were averaged over four contiguous transaxial slices in which all muscles of interest were visible. The 3 x 10 RM for the head extension exercise increased for RESX after training [from 17.9 (1.0) to 23.9 (1.4) kg, P < 0.05] but not for RES [from 17.6 (1.4) to 17.7 (1.9) kg] or CON [from 10.1 (2.2) to 10.3 (2.1) kg]. RESX showed an increase in total neck muscle CSA after training [from 19.5 (3.0) to 22.0 (3.6) cm2, P < 0.05], but RES and CON did not [from 19.6 (2.9) to 19.7 (2.9) cm2 and 17.0 (2.5) to 17.0 (2.4) cm2, respectively]. This hypertrophy for RESX was due mainly to increases in CSA of 23.9 (3.2), 24.0 (5.8), and 24.9 (5.3)% for the splenius capitis, and semispinalis capitis and cervicis muscles, respectively. The lack of generalized neck muscle hypertrophy in RES was not due to insufficient training. For example, the CSA of their quadriceps femoris muscle group, as assessed by MRI, increased by 7 (1)% after this short-term training (P < 0.05). The results suggest that: (1) the splenius capitis, and semispinalis capitis and cervicis muscles are mainly responsible for head extension; (2) short-term resistance training does not provide a sufficient stimulus to evoke neck muscle hypertrophy unless specific neck exercises are performed; and (3) the postural role of head extensors provides modest loading in bipeds.

Adult↗

PubMed1997

New uses for gentamicin-impregnated polymethyl methacrylate spacers in two-stage revision hip arthroplasty.

The use of antibiotic-impregnated cement as a bone spacer in two-stage revision hip surgery has been well described. Two additional placements for spacers are described: within the trochanteric osteotomy and overlying the greater trochanter. These spacers have been found to dramatically facilitate exposure at the second-stage procedure and are now being incorporated into all two-stage revision hip arthroplasties at The General Infirmary at Leeds.

Anti-Bacterial Agents↗

PubMed1997

A new method of treatment for periprosthetic supracondylar fractures of the femur for prostheses with a stemmed femoral component.

Knee arthroplasty periprosthetic supracondylar fracture of the femur is a well-recognized problem that is likely to be seen more frequently with the increasing number of knee arthroplasties being performed. Treatment of this fracture is difficult. A new method of internal fixation for supracondylar fractures around a stemmed femoral component using a custom-made extension to the femoral stem is described. This technique allowed early mobilization of the patient, with restoration of a good range of movement of the knee and fracture union within 1 year.

Aged↗

PubMed1997

The effects of gamma-oryzanol supplementation during resistance exercise training.

To determine the effectiveness of gamma-oryzanol supplementation, weight-trained males were randomly divided into supplemented (G-O) and control placebo (Con) groups. The G-O group ingested 500 mg.day-1 of gamma-oryzanol according to manufacturer's instructions. Test batteries were administered before (T1), after 4 weeks (T2), and after 9 weeks (T3) of a periodized resistance exercise program. Both groups demonstrated significant increases in 1 repetition maximum muscular strength (bench press and squat) and vertical jump power, with no differences between the groups. No differences between groups were observed for measures of circulating concentrations of hormones (testosterone, cortisol, estradiol, growth hormone, insulin, beta-endorphin), minerals (calcium, magnesium), binding protein (albumin), or blood lipids (total cholesterol, triglycerides, HDL-cholesterol). Resting cardiovascular variables decreased similarly for both groups. These data suggest that 9 weeks of 500 mg.day-1 of gamma-oryzanol supplementation does not influence performance or related physiological parameters in moderately weight-trained males.

Adult↗

PubMed1997

Resistance training and human cervical muscle recruitment plasticity.

This study examined cervical neuromuscular adaptations to resistance training. The ResX group performed conventional resistance training plus head-extension exercise. Another group performed only conventional resistance training, and the control group performed no resistance exercise. Muscle use during head extension was determined by quantifying shifts in T2 in serial-transaxial magnetic resonance images of the neck. ResX was the only group that showed a training effect. Training decreased (P < 0.05) the cross-sectional area (CSA) of cervical muscle used to perform submaximal head extension by 31%. This reflected a decrease (P < 0.05) in relative use of the splenius capitis, semispinalis capitis, and semispinalis cervicis and multifidus muscles by about one-third; their percentage of CSA showing contrast shift was reduced from 60 to 40% on average. This same exercise evoked no contrast shift in the levator scapulae, longissimus capitis and cervicis, and scalenus medius and anterior muscles posttraining, yet 20% or more of their CSA was engaged pretraining. The relative CSA of cervical musculature that was used to perform maximal head extension was increased (P < 0.05) 16% by training. The findings suggest functional redundancy of neck musculature that can be modified by training; submaximal tasks can be performed despite cessation of recruitment of individual muscles, yet recruitment can be increased for maximal efforts. These results also suggest that neuromuscular adaptations to training require a specific cervical exercise.

Adaptation, Physiological↗

PubMed1997

Relationship between body image and percent body fat among male and female college students enrolled in an introductory 14-week weight-training course.

Students (39 men and 27 women) from a southern university, who were enrolled in a 14-wk. introductory weight-training course, were administered a 20-item body-image questionnaire and subsequently underwent skinfold measurements to assess percent body fat. Mean scores were correlated with percent body fat. For men, women, and both sexes combined correlations were significant and inverse (rs = -.68, -.41, -.66, respectively). Body image as measured was inversely related to percent body fat among these college students. Researchers should examine how dietary and exercise-induced changes in adiposity (pre-post design) influence scores on body image.

Adipose Tissue↗

PubMed1996

A comparison of intermittent calf compression and enoxaparin for thromboprophylaxis in total hip replacement. A pilot study.

A prospective randomised trial was carried comparing the use of Enoxaparin with intermittent pneumatic calf compression garments for thromboprophylaxis in total hip replacement. Fifty consecutive patients were studied and randomised to evaluate these two methods. There were 2 deep vein thromboses, one in each group, and no cases of pulmonary embolism. The operative field was judged to be drier in the compression group, but the mean fall in the postoperative haemoglobin level was the same in each. In the peroperative period, 6 patients in the Enoxaparin group needed 2 units of blood and one 3 units. In the compression group, 3 patients needed transfusions of 2 units. Intermittent calf compression has fewer problems than the use of Enoxaparin and has no contraindications.

Adult↗

PubMed1996

Nutritional status and lipid profiles of trained steroid-using bodybuilders.

Fourteen trained male anabolic steroid-using bodybuilders (SBBs) (19-41 years) were recruited for the study. Three-day diet records were obtained from SBBs and analyzed. A resting venous blood sample was drawn, and serum/plasma was subsequently analyzed for various nutritionally related factors. Results showed that mean dietary energy (4,469 +/- 1,406 kcal), protein 252 +/- 109 g), and vitamin and mineral intakes of SBBs greatly exceeded U.S. Recommended Dietary Allowances. Dietary cholesterol intake was 2.8 times the recommended levels. Mean serum/plasma nutrient concentrations of SBBs were within normal range. However, individual SBBs had a number of serum/plasma values outside of the normal or recommended range, the most notable of which was hypercalcemia, which was present in 42% of SBBs. Serum/plasma lipids were such as to increase the risk of cardiovascular disease in these subjects.

Adult↗

PubMed1996

Carbohydrate ingestion/supplementation or resistance exercise and training.

The physiological and performance effects of carbohydrate ingestion/supplementation on aerobic endurance exercise have been extensively studied. However, little attention has been given to the effects of carbohydrate ingestion on resistance exercise and training. Recent evidence suggests that resistance exercise can elicit a considerable glycogenolytic effect, which can lead to fatigue and strength loss. The ability of carbohydrate ingestion immediately before and during resistance exercise to enhance performance is unclear at present, however carbohydrate ingestion following resistance exercise has been shown to enhance muscle glycogen resynthesis. This may decrease recovery time following resistance exercise and enable an increase in training volume which may enhance physiological adaptations. Also, carbohydrate ingestion during or immediately after resistance exercise has been shown to increase postexercise insulin and growth hormone levels, which may lead to increased protein synthesis and hypertrophy, although this has not been systematically investigated. Despite the potential benefits of carbohydrate ingestion for performance of resistance exercise and adaptation to resistance training, at present little empirical evidence is available to support this hypothesis.

Carbohydrate Metabolism↗

PubMed1995

The acute immune response to exhaustive resistance exercise.

Ten young male adults (mean age 46.9 +/- 1.2 yrs) with 9.2 +/- 1.4 years of weight training experience and the ability to parallel squat at least 1.5 times their body mass were selected as subjects. The exercise session consisted of sets of 10 repetitions at 65% 1-RM of the parallel leg squat, with a cadence of one rep every 6 sec and 3 min rest between sets, to muscular failure. The average subject lifted a total of 9711 +/- 1576 kg during 98 +/- 14 reps for a total work output of 72.5 +/- 10.5 kJ before muscular failure occurred. Mean oxygen consumption during exercise was 1.58 +/- 0.06 l/min at 42.5 +/- 2.0% peak VO2. A strong leukocytosis, lymphocytosis, and lymphocytopenia, similar to what has been reported following high-intensity cardiorespiratory exercise, were measured following leg squat exercise. Con A-stimulated lymphocyte proliferation (unadjusted) rose 50% above preexercise levels (p = 0.07), but when these data were adjusted on a per T cell (CD3+) basis, no change from rest was observed. Natural killer cell cytotoxic activity (NKCA), when adjusted on a per NK cell (CD56+) basis, was decreased about 40% below preexercise levels for at least 2 h post-exercise. No significant increase in cortisol was seen after exercise, although norepinephrine and epinephrine increased moderately (465% and 133%, respectively), immediately following exercise. The data demonstrate that leg squat exercise to muscular failure results in a very similar immune response to that associated with intense endurance exercise, despite a lower mean oxygen consumption and only a moderate hormonal response.

Adult↗

PubMed1994

Bulk autograft for a deficient acetabulum in Charnley low-friction arthroplasty. A 2-9-year follow-up study.

The authors assessed 40 hips in 36 patients where a bulk femoral head autograft was used to supplement deficient acetabulum while performing Charnley low-friction arthroplasty. The majority of the hips were congenitally dysplastic or dislocated with secondary arthritis. The average age at surgery was 47.5 years and the average follow-up period was 4 years. The graft provided a cover between 10 and 42% (mean, 23%) of the socket hemisphere. Union of the graft was evident on the radiograph in 35 hips. There was no graft resorption in 28 hips. Mild graft resorption was seen in 11 cases, and moderate graft resorption was seen in 1 case. In 24 cases, there was no demarcation at the bone-cement interface of the socket. Asymptomatic demarcation of 1 mm thickness or less was seen in 16 hips, of which only 2 showed demarcation at the cement-graft interface. All 40 cases were clinically asymptomatic and successful thus far, with the mean d'Aubigne and Postel score improving from 3.1, 2.8, and 2.9 before surgery to 5.9, 5.4, and 4.9 after surgery for pain, function, and movement, respectively.

Acetabulum↗

PubMed1994

A sociometric test to identify emergent leader and member roles: phase I.

This is the first phase in the design of a sociometric test for the empirical identification of four leadership roles: Task, Emotional, Scapegoat, and Defiant Leaders and one Nonleader member role. Eighteen different questions have been used in studying 273 cases in 31 closed psychotherapy groups. (1) A factor analysis identified two factors that describe an involvement/commitment dimension (Factor 1) and a positive/negative change dimension (Factor 2). (2) A discriminant function analysis showed that the five roles were differentiated at a statistically significant level. (3) Role assignments, based on weights, produced by this test were compared to clinically identified leaders with an overall hit rate of 97%, indicating a low error factor when the formulas were applied to this data base. Steps for the next phases in the construction of this test are outlined.

Group Processes↗