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Biomedical subjects

G Bentley

Publications and source records attributed to G Bentley.

At least 19 recordsLinked to original sources
PubMed1995

Prediction of clinical outcome of THR from migration measurements on standard radiographs. A study of cemented Charnley and Stanmore femoral stems.

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.

Arthritis, Rheumatoid↗
PubMed1994

[Epitopes of the envelope of the hepatitis B virus: a structural approach].

Hepatitis B is a major public health problem. More than 300 million people are chronically infected by the virus. During infection very large quantities of complete virions and empty envelopes, consisting of spherical or filamentous lipoprotein particles, are present in the blood. DNA genome coding for envelopes is divided into three domains, preS1, preS2 and S. All available data suggest that the preS1 and preS2 products are exposed at the surface of the virions. These proteins are more immunogenic than S in terms of in vivo antibody response and the number of epitopes identified. The three dimensional mapping of antigenic sites of the HBV will provide important strategic information for vaccine development and identification of targets for immunorecognition or immunoregulation of the disease.

Epitopes↗
PubMed1992

Woven carbon surface replacement in the knee: independent clinical review.

An independent assessment was performed of the results of woven carbon implants of mesh or rods into articular cartilage defects performed by two surgeons in the knees of 96 patients. Eight had symptomatic osteochondritis, 31 had chondromalacia patellae and 57 had early osteoarthritis. They were reviewed up to 5 yr after operation. Seventy-six patients (79%) experienced an improvement in analogue pain score and similar improvements occurred in a range of functional activities (P = 0.002). No evidence of inflammatory change or deterioration in joint damage was found. It is concluded that this relatively minor procedure is valuable in younger patients with troublesome symptoms due to early articular cartilage damage and does not prejudice further operative treatment.

Adolescent↗
PubMed1992

A randomized controlled trial of early surgery in Duchenne muscular dystrophy.

We performed a randomized controlled trial of early surgical treatment of contractures in 20 boys with Duchenne muscular dystrophy, age 4-6 yr. Surgery consisted of release of hip flexors, removal of iliotibial bands, and lengthening of tendo Achilles bilaterally. All patients were monitored for at least 12 months post-randomization, and assessed quantitatively for muscle strength and function. Surgery corrected the deformities, but had no beneficial effect on strength or function. Indeed, data in the second year showed more rapid deterioration of function in some of the operated boys. There appeared to be continued evolution of pathology following surgery, as assessed by sequential muscle ultrasound and muscle biopsy. We cannot recommend this type of surgery as a routine treatment.

Biopsy↗
PubMed1991

The behavioral effects of heptyl physostigmine, a new cholinesterase inhibitor, in tests of long-term and working memory in rodents.

We assessed the effects of heptyl physostigmine, a new cholinesterase inhibitor, in a mouse tail-flick (TF) test, a mouse and rat passive avoidance test, a rat conditioned suppression-of-drinking (CSD) test, a rat Random Interval (RI) response rate test and a rat delayed matching-to-position (DMTP) test. In the TF test, a dose of 8.0 mg/kg of heptyl induced a significant antinociceptive effect that was in excess of 75% of the maximum possible effect 300 minutes after administration. In the mouse passive avoidance test, a dose of 3.0 mg/kg of heptyl fully reversed, and a dose of 1.0 mg/kg partially reversed, a scopolamine-induced (0.2 mg/kg) deficit. In the rat passive avoidance test, a dose of 8.0 mg/kg fully reversed a scopolamine-induced (0.2 mg/kg) deficit, while a dose of 4.0 mg/kg of heptyl was without effect. In the same experiment, a dose of 0.6 mg/kg of physostigmine partially reversed the scopolamine-induced deficit. In the CSD test, a dose of 8.0 mg/kg of heptyl fully reversed, and doses of 1.0 and 4.0 mg/kg of heptyl partially reversed, the deficit induced by scopolamine (0.4 mg/kg). In the RI response rate test, doses of 8.0 mg/kg and 0.6 mg/kg of physostigmine fully suppressed lever pressing for food rewards. Doses of 4.0 mg/kg of heptyl and below had no effect on lever-pressing rates. In the working memory test (DMTP), 4.0 mg/kg heptyl partially reversed the scopolamine-induced deficit (0.2 mg/kg) in the number of correct choices made, but did not affect the scopolamine-induced deficit in the number of trials completed.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗
PubMed1991

Joint proprioception in normal, osteoarthritic and replaced knees.

We measured joint position sense in the knee by a new method which tests the proprioceptive contribution of the joint capsule and ligaments. The leg was supported on a splint, and held in several positions of flexion. The subjects' perception of the position was recorded on a visual analogue model and compared with the actual angle of flexion. Eighty-one normal and 45 osteoarthritic knees were examined, as were 10 knees with semi-constrained and 11 with hinged joint replacements. All were assessed with and without an elastic bandage around the knee. There was a steady decline in joint position sense with age in subjects with normal knees. Those with osteoarthritic knees had impaired joint position sense at all ages (p less than 0.001). Knee replacement improved the joint position sense slightly (p less than 0.02); semi-constrained replacement had a greater effect than hinged replacement. The effect of an elastic bandage in subjects with poor position sense was dramatic, improving accuracy by 40% (p less than 0.001). It is proposed that reduced proprioception in elderly and osteoarthritic subjects may be responsible for initiation or advancement of degeneration of the knee.

Adolescent↗
PubMed1991

Repair of cartilage lesions using biological implants. A comparative histological and biomechanical study in goats.

We report the experimental use of three different biological implants to restore articular surface defects: glutaraldehyde-fixed bovine meniscal xenograft, glutaraldehyde-fixed bovine costal cartilage xenograft, and viable osteochondral allografts. The grafts were implanted in the knees of 19 goats who were allowed free-field activity and were studied for up to one year. The natural articular surfaces of meniscal fibrocartilage provided excellent articular surfaces at all times. Equally good articular surfaces were restored by host tissue growth covering costal cartilage grafts at six months, but by 12 months this surface had degenerated. The majority of the allografts survived and integrated with the host at six months, but many showed signs of failure at 12 months. Only three out of seven ungrafted defects healed completely at six months and the healed surfaces were degenerating at 12 months.

Animals↗
PubMed1991

Three-dimensional collagen architecture in bovine articular cartilage.

The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair.

Animals↗
PubMed1991

Standards of care: integrating nursing care plans and quality assurance activities.

Traditionally, standards are used to define the level of care that a patient can expect to receive in a given institution or on a given nursing unit. These standards are the foundation of quality assurance programs. Unfortunately, with the increased emphasis on monitoring care, many standards are being written after the quality assurance activities have been developed and are in place. Often, standards are placed neatly in a book that is dusted off and brought out when the Joint Commission for Accreditation of Healthcare Organizations representative (JCAHO) visits. The nursing staff at the unit level has no real knowledge or understanding of the standards. This may result in a nonfunctioning quality assurance program.

Humans↗
PubMed1991

Roentgenographic assessment in hallux valgus.

Which simple roentgenographic angle should be used to assess medial (varus) deviation of the first metatarsal in cases of hallux valgus has been a topic of debate. Measurements were made from roentgenograms of 100 symptomatic feet in women with hallux valgus. These were compared with similar measurements obtained from symptomatic normal feet of women of a similar age distribution. The hallux valgus angle was associated with medial deviation of the first metatarsal measured by all three of the parameters defined and tested, i.e., the intermetatarsal, metatarsus primus varus, and metatarsus omnis varus angles. Of these, the best measure was the intermetatarsal angle, which in the hallux valgus feet differed significantly from controls more than the other measurements. No evidence was found to support any concept of second metatarsal deviation from normal.

Adolescent↗
PubMed1990

Phenotypic modulation in sub-populations of human articular chondrocytes in vitro.

Human articular cartilage has been separated into surface (approx. 15% of tissue depth) and deep zones (remaining tissue) and the constituent chondrocytes released by enzymic digestion. Subsequent culture either as a low density monolayer or as a suspension over agarose revealed distinct morphological and synthetic behaviour in the two populations. Whilst in monolayer these morphological differences disappeared with time in culture, over agarose they remained. Surface zone cells formed two types of cell cluster; one that was highly cellular with little extracellular matrix, and the other less frequent, which formed copious amounts of fibrillar matrix. Both types of cluster were surrounded by a layer of flattened chondrocytes. In contrast, deep cells formed a single cluster type that lacked a surrounding cell layer, but formed large amounts of sparse cartilage-like matrix and comprised morphologically typical chondrocytes. In monolayer, both populations gradually ceased to synthesise cartilage matrix components with the exception of link protein. In suspension, whilst the chondrogenic phenotype per se was preserved, there was, nevertheless, a loss in qualitative synthetic heterogeneity, which exists between surface and deep cells, that was not accompanied by changes in the differential rate of 35S incorporation into proteoglycan. Under these conditions, surface cells that normally do not synthesise keratan sulphate initiated de novo synthesis of this glycosaminoglycan. Consequently, it appears that the observed modulation in synthetic ability of the cell sub-populations is independent of the cluster morphology, which, once established, remains constant throughout the culture period.

Cartilage, Articular↗
PubMed1990

Degenerative arthritis after intra-articular fractures of the knee. Long-term results.

We reviewed 31 of 33 consecutive patients with intra-articular fractures of the knee at 6 to 22 years (average 14). Of these, 77% had excellent or good results; the others had various degrees of degenerative osteoarthritis. There was no significant difference between the results after surgical or conservative treatment. Secondary degeneration was not related to cause or type of fracture, but its incidence increased with the patient's age at the time of injury, though not with the length of follow-up. Early mobilisation appeared to be beneficial in preventing later degenerative changes.

Adult↗
PubMed1990

A role for hyaluronan in joint development.

Hyaluronan, a common connective tissue component, influences cell adhesion, migration and cytodifferentiation in vitro, and because of these properties has been postulated to have a role in morphogenesis. Its role in the development of cartilage-associated structures, such as joints, has yet to be defined. Using a biotinylated hyaluronan-binding region-link protein complex, free hyaluronan binding sites have been localised in the joint region concomitant with the first signs of cavitation (Stage 37), whereafter it is localised in the joint space and is maintained here as this enlarges. The application of our results is discussed in the context of a primary role for hyaluronan in joint cavity formation.

Animals↗
PubMed1989

Anterior knee pain: diagnosis and management.

Anterior knee pain is caused by a number of distinct conditions which can only be diagnosed accurately by arthroscopy. Chondromalacia patellae is an important cause of disability in young people which rarely progresses to osteoarthritis. Treatment is by non-operative quadriceps strengthening exercises or by conservative surgery combined with careful supervised rehabilitation.

Arthroscopy↗
PubMed1988

The effect of suction drains after total hip replacement.

A prospective study of 120 consecutive total hip replacements showed that deep suction drains produced maximal drainage volumes in the first 24 hours. Their continued presence resulted in minimal further drainage, did not reduce the likelihood of haematoma formation and led in some cases to the spread of skin organisms into the wound.

Hematoma↗