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Biomedical subjects

A McGuinness

Publications and source records attributed to A McGuinness.

15 recordsLinked to original sources
PubMed2006

Pontine haemorrhage mimicked by an olanzapine overdose.

Olanzapine, an atypical antipsychotic of the thienobenzodiazepine class, has been on the market since 1996. Its popularity has increased over recent years because of excellent clinical results as well as a favourable side effect profile. Mirroring this increased olanzapine use has been a rise in the number of non-accidental overdoses. The clinical picture of olanzapine overdose can be surprisingly variable. In the case presented, the patient's low Glasgow Coma Score prevented an accurate history being taken. Examination revealed bilateral upgoing plantars, pinpoint pupils, increased tone, and brisk reflexes; however initial investigations, including an urgent CT head, were normal. The patient required 24 hours of intensive care before he regained consciousness and admitted to the overdose. Although there are several reports of olanzapine mimicking opiate intoxication in overdose, this is one of the first cases where overdose has mimicked an intracerebral event. The authors highlight some of the literature regarding clinical presentation and treatment options, and discuss the relation between olanzapine therapy and diabetes.

Antipsychotic Agents↗
PubMed2005

Dual energy X-ray absorptiometry analysis of peri-prosthetic stress shielding in the Birmingham resurfacing hip replacement.

INTRODUCTION: Numerous reports in the literature refer to the femoral neck fracture rate in hip resurfacing. The aim of this study was to determine the bone mineral density and evidence of stress shielding around the femoral component of the Birmingham resurfacing prosthesis. MATERIAL AND METHODS: Twenty-eight patients with primary unilateral osteoarthritis had a Birmingham resurfacing prosthesis. DEXA analysis of the proximal femur and femoral neck was performed and compared with the opposite unaffected side. RESULTS: Total periprosthetic bone mineral density was 0.49% greater than the control, but this did not achieve statistical significance. Although the BMD of the femoral neck was slightly increased on the prosthetic side (1.002 g/cm2) as opposed to the control side, this difference did not reach statistical significance. CONCLUSION: The Birmingham resurfacing prosthesis does not appear to reduce femoral neck bone mineral density in comparison to the normal femoral neck bone density. We conclude that femoral neck fractures are unlikely to be due to stress shielding related to the prosthesis.

Absorptiometry, Photon↗
PubMed2001

The angiogenic response to skeletal injury is preserved in the elderly.

Angiogenesis is essential for normal bone formation and repair. Avascularity characterizes aberrant fracture union in the elderly, while angiogenic mechanisms during cutaneous wound repair are attenuated in aged humans. We hypothesized that skeletal injury results in local (circulating) and systemic (fracture site) 'angiogenic' responses and that these reparative mechanisms are attenuated with advanced patient age. This prospective study examined peripheral blood and fracture hematoma from 32 patients, 16 under 40 years and 16 over the age of 75, undergoing emergent surgery for isolated fracture. The angiogenic cytokines vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) were assayed. Endothelial cell cultures were supplemented with patient plasma and fracture hematoma and angiogenesis determined in vitro by measuring cell proliferation and blood vessel tube formation. Angiogenesis was determined in vivo using a murine dorsal wound pocket model and quantification of new blood vessel formation after 7 days. We found that all injured patients, irrespective of age, have elevated plasma and fracture hematoma levels of VEGF and PDGF. These elevated cytokine concentrations translate into biologically significant angiogenic effects, in vitro and in vivo. These effects are primarily VEGF mediated and are not dependent on patient age. The biological activity of these growth factors does not diminish with advanced age. Thus skeletal injury does result in local and systemic angiogenic responses whereby angiogenic cytokine availability and activity is preserved in the aged suggesting alternative mechanisms for the development of avascularity in delayed and fracture non-union in the elderly.

Adult↗
PubMed2000

Is human fracture hematoma inherently angiogenic?

This study attempts to explain the cellular events characterizing the changes seen in the medullary callus adjacent to the interfragmentary hematoma during the early stages of fracture healing. It also shows that human fracture hematoma contains the angiogenic cytokine vascular endothelial growth factor and has the inherent capability to induce angiogenesis and thus promote revascularization during bone repair. Patients undergoing emergency surgery for isolated bony injury were studied. Raised circulating levels of vascular endothelial growth factor were seen in all injured patients, whereas the fracture hematoma contained significantly higher levels of vascular endothelial growth factor than did plasma from these injured patients. However, incubation of endothelial cells in fracture hematoma supernatant significantly inhibited the in vitro angiogenic parameters of endothelial cell proliferation and microtubule formation. These phenomena are dependent on a local biochemical milieu that does not support cytokinesis. The hematoma potassium concentration is cytotoxic to endothelial cells and osteoblasts. Subcutaneous transplantation of the fracture hematoma into a murine wound model resulted in new blood vessel formation after hematoma resorption. This angiogenic effect is mediated by the significant concentrations of vascular endothelial growth factor found in the hematoma. This study identifies an angiogenic cytokine involved in human fracture healing and shows that fracture hematoma is inherently angiogenic. The differences between the in vitro and in vivo findings may explain the phenomenon of interfragmentary hematoma organization and resorption that precedes fracture revascularization.

Adult↗
PubMed2000

Thromboprophylaxis using a low molecular weight heparin delays fracture repair.

Low molecular weight heparins are significantly superior to unfractionated heparin or warfarin in the prevention of thromboembolic episodes associated with orthopaedic surgery. Therapeutic doses of heparin and warfarin have been shown to delay bone repair in a rabbit model. The current study investigated the effect of prophylactic administration of a low molecular weight heparin, enoxaparin, on the healing of a closed rabbit rib fracture. Fracture healing was assessed using histomorphometric, histologic, and immunohistochemical methods at 3, 7, and 14 days, and biomechanical testing with torsional loading was assessed after 21 days. Bone repair was significantly attenuated at all times in animals receiving subcutaneous enoxaparin compared with that of the control animals. Numerous putative mechanisms for this phenomenon are discussed, and additional studies are proposed to elucidate the effects of this pharmacologically diverse group of compounds on all aspects of bone physiology and repair.

Animals↗
PubMed1996

A reappraisal of axial and nonaxial lower leg fascial flaps: an anatomic study in human cadavers.

The aim of this study was to determine the sources of blood supply to the deep fascia of the lower leg and therefore to identify potential new sites where axial and nonaxial flaps might be raised. The deep fascia was harvested from 18 embalmed cadaver lower legs. The blood supply to the deep fascia was examined with the aid of a dissecting microscope. Four clinically important sources of supply to the deep fascia were identified. These were (1) axial and nonaxial fasciocutaneous perforators, (2) nonaxial musculocutaneous perforators, (3) axial cutaneous branches of the sural arteries, and (4) an axial fascial branch from the saphenous artery (present in 75 percent of the dissections). This study has highlighted the potential for utilizing not only the fasciocutaneous system and sural system of vessels but also the fascial branch of the saphenous artery in the design of lower leg axial fascial flaps. Nonaxial fascial island flaps may be raised utilizing not only the fasciocutaneous system of vessels but also the musculocutaneous system of vessels.

Arteries↗
PubMed1995

The anatomic basis for arteriovenous shunting in human lower leg fascial flaps.

Clinical experience has suggested that arteriovenous shunting may occur in fascial flaps. The anatomic basis for this has not been fully established. The aim of this study was to determine the size, location, and nature of arteriovenous shunts in human lower leg deep fascia. Deep fascia was harvested from the limbs of nine embalmed cadavers. Small pieces of fascial tissue were studied with the aid of three staining techniques (methylene blue, oil red-O triethyl phosphate, and Gomori's rapid one-stage trichrome technique), which were used to enable the microvascular anatomy to be visualized more clearly. Arteriovenous anastomoses proximal to the capillary bed and with an external diameter greater than 50 microns were identified in the suprafascial, subfascial, and intrafascial plexuses but were not found to be a common feature of the microvascular anatomy. Thoroughfare channels within the capillary bed and with an external diameter ranging from 12 to 25 microns were frequently identified in all three levels of the fascial plexus. The results of this study establish an anatomic basis for arteriovenous shunting in fascial flaps.

Arteriovenous Anastomosis↗
PubMed1993

Early experience with leg lengthening by callotasis and chondrodiastasis.

Over a four year period, 20 segments in 16 patients were treated by lengthening by callotasis or chondrodiastasis. The indications for treatment were leg length discrepancy in 13 patients and short stature in three. Patients with leg length discrepancy were all treated by femoral lengthening; the mean length gained was 4.4 cm (range 2.5 to 6.Ocm). For patients with short stature, the mean femoral length gain was 10.0 cm (9.0 to 10.5 cm), and the mean tibial length gain was 8.0 cm (6.5 to 9.0 cm). The commonest problem was pin tract infection, but this always settled with antibiotic therapy. Most other complications were also successfully dealt with, and did not compromise the outcome of treatment. At the time of review, 13 of the 16 patients said they were very happy with the result; two patients were reserving judgement until completion of treatment, and, only one thought the treatment had been of no benefit. Our initial experience, with callotasis in particular, has been that it is a highly satisfactory method of limb lengthening, has an acceptable complication rate, and involves minimal hospitalization as compared with older techniques.

Adolescent↗
PubMedDate not supplied

Decline in the incidence of late diagnosed congenital dislocation of the hip.

INTRODUCTION: We reviewed the incidence of early and late diagnosed CDH over a 13 yr period in a single maternity with a well established follow-up program and a stable population base. In March 1991, all newborn infants were nursed in the lateral or supine position, having previously been nursed prone. In addition, a dedicated hip screener was appointed in October 1992. We wished to determine whether these changes could have led to a reduction in late diagnosed CDH. METHODS: Babies with suspected CDH were seen by a single consultant orthopaedic surgeon within 1 week of birth. Splints were not applied until diagnosis was confirmed by the orthopaedic surgeon. The study period was from January 1983 to December 1995, inclusive. RESULTS: 37,383 babies were born during the study period, an average of 2,876 births per annum. The average rate of babies referred to the orthopaedic surgeon was 12.8 per 1,000 (range 5.5-28.2 per 1,000). The average incidence of babies splinted early was 7.19 per 1,000 (range 4.0-14.1 per 1,000) with no discernible increase or decrease over the yrs. In contrast, there was a clear reduction in the incidence of late diagnosed CDH; 42/24,713 births (January 1983-February 1992) compared to only 2/12,673 births (March 1992-December 1995; p < 0.0001. Twelve of the 44 infants (27 per cent) diagnosed with late diagnosed CDH were discovered by the policy of routine hip radiographs at 6 months of age of all babies born by breech presentation (2/12) or those with a positive family history of CDH in a first degree relative (10/12). Six others had a diagnosis of CDH confirmed by X-rays done at 6 months of age because of doubts about their examination in the newborn period. CONCLUSIONS: Nursing infants in the supine or lateral position and the introduction of a single hip screener were associated with a reduction in the incidence of late diagnosed CDH. Routine hip radiographs of high risk infants at 6 months of age proved to be a valuable safety net in detecting a significant proportion of previously undetected infants with CDH.

Breast Feeding↗