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Biomedical subjects

B M O'Brien

Publications and source records attributed to B M O'Brien.

At least 73 records · Page 4Linked to original sources
PubMed1988

The significance of resection length on the patency rate, and the histopathology, of experimentally avulsed and microsurgically repaired blood vessels.

The significance of resection length on patency rate, and the histopathology, of microsurgically repaired avulsed blood vessels was examined at 3 weeks in two groups of experimentally avulsed rabbit femoral arteries repaired by different surgeons and in a single series of avulsed and repaired veins. All veins were patent 3 weeks after avulsion and microsurgical repair. Histopathology indicated that the vast majority of lesions in veins were removed at resection. Surgeon A achieved 75% patent arteries and Surgeon B achieved 100% arterial patency (resecting 3.7 mm more on average than Surgeon A). Histopathology revealed numerous luminal circumferential lesions remained in the avulsed artery wall following resection. These lesions were sites of smooth muscle cell proliferation and neointima formation. Although similar arterial damage occurs in human avulsion, considerably lower patency rates are achieved for human arterial avulsion repair than were reported in this experimental study. Factors in addition to vessel wall damage must therefore be involved in thrombosis and occlusion of repaired avulsed arteries. Such factors might be lengthy ischaemia time and severe spasm.

Anastomosis, Surgical↗
PubMed1988

Intraoral mucosal reconstruction with microvascular free jejunal autografts: an experimental study.

This experimental study investigated the problem of covering bare bone adequately in the oral cavity to provide a stable, functionally acceptable reconstruction. In eight dogs, intraoral mucosal defects were created whilst preserving the mandibular arch. The defects were reconstructed with a microvascular jejunal patch. Six animals had their reconstructions stressed postoperatively by the administration of irradiation and by feeding solid food. Two control dogs did not receive irradiation. Grafts were assessed clinically and histologically for 6 months. Rapid mucosal healing occurred in seven of eight dogs. The grafts conformed well to the mandibular contour and were tolerant of postoperative radiotherapy and the chewing of solid food. Structural integrity of seven grafts was maintained although subtotal villous atrophy occurred in irradiated grafts and to a lesser extent in control grafts. In one animal whose graft mucosa sloughed, the wound was re-epithelialized from the adjacent buccal mucosa. Microvascular jejunal patches therefore provided a durable, functionally adequate reconstruction of the mouth floor.

Animals↗
PubMed1988

Reconstruction of mandibular defects with metallic prostheses and microvascular jejunal autografts: an experimental study.

A study was undertaken to determine the adequacy of vascularised jejunum to provide stable mucosal cover over a non-biological mandibular substitute. Employing a canine model, composite intra-oral bone-mucosal defects were created and reconstructed with a metal plate covered by a microvascular jejunal patch. These were followed for six months and were assessed clinically, histologically and radiologically. Rapid mucosal healing occurred in all cases. The autografts conformed to the contour of the prosthesis and adequate tongue mobility was preserved. All mandibles remained stable throughout the follow-up period. Histologically, short villi covered the jejunal grafts to three months whilst at six months both normal and abnormal jejunal mucosal morphology was evident.

Animals↗
PubMed1988

Effect of the vasodilator peptides calcitonin gene-related peptide and atriopeptin on rabbit microvascular blood flow. Preliminary communication.

A neuropeptide known as calcitonin gene-related peptide (CGRP) has been shown to have vasodilatory properties in the rabbit epigastric island flap of almost equivalent potency to prostacyclin. The latter is currently regarded as the most potent vasodilator yet to be isolated. CGRP, with its longer-lasting effect in blood and its ability to overcome noradrenaline-induced vasospasm, may be promising for use during or after ischaemic flap transfer or replantation. Another known vasodilatory peptide, atriopeptin, was not as potent in the microvascular bed of the cutaneous flap as in major blood vessels.

Animals↗
PubMed1988

The use of tonometry in the assessment of upper extremity lymphoedema.

The use of a specially designed tissue tonometer in 17 lymphoedema patients, who were treated with multiple lymphaticovenous anastomoses, with a follow-up period of up to 18 months, gives a quantitative measurement of "softness" and correlates well with their subjective feeling. It would appear to complement limb volume and circumferential limb measurements.

Anastomosis, Surgical↗
PubMed1988

Changes in area and thickness of expanded and unexpanded axial pattern skin flaps in pigs.

The pig buttock flap model was used firstly, to compare changes in expanded axial skin flap area with control flaps prior to flap elevation and 3 or 4 months post-flap inset and, secondly, to compare the thickness of expanded and control flaps at elevation and for 3 to 6 months post-flap inset. Following 5 weeks' expansion and prior to elevation, the expanded tissue had gained a significant 63.3% mean increase in area compared with the control tissue (p less than 0.01). Immediately post elevation and inset, the expanded flaps were still significantly larger than the control flaps by a mean 29.8% (p less than 0.01) but had lost 56% of the original area gained. Little change in area occurred in the 3 months post-flap inset as the expanded flaps were still a mean 23.4% larger than the control (p less than 0.01). Dermal and cellular non-keratinised epidermal layers thickened markedly in expanded skin compared to control skin. Following elevation and inset of the flaps, both dermis and epidermis thickened in expanded and control flaps.

Animals↗
PubMed1988

Comparative viability of expanded and unexpanded axial pattern skin flaps in pigs.

A comparison of viable areas of axial pattern flaps post inset was made between expanded and non-expanded pig buttock island flaps. The deep circumflex iliac artery and vein supply approximately the proximal 14 x 10 cm area of this flap. Larger flaps were raised on expanded and control sides of eight pigs to determine if expansion increased the area of survival. In six of eight pigs whose initial tissue expansion did not create more than approximately a 50% increase in skin area, the expanded flaps had a statistically significant increase in viable skin area (proportionally) 10 days post inset than their control flaps (p less than 0.05). Two other pigs did not conform to this pattern. Their initial tissue expansion was greater than 50%, and the resulting area of flap viability was proportionally less in expanded flaps than the control flaps.

Animals↗
PubMed1988

The use of long synthetic microvascular grafts to vascularise free flaps in rabbits.

A 5 cm length of 2 mm internal diameter (i.d.) synthetic, expanded polytetrafluoroethylene (PTFE, or Gore-Tex) vascular graft was used to connect 25 rabbit inferior epigastric flaps to the contralateral femoral vessels. In 15 animals an expanded PTFE graft connected the opposite femoral artery to the flap while the ipsilateral venous drainage remained intact. In the remaining 10 animals an expanded PTFE graft was used to replace the venous drainage of the flap and connected to the opposite femoral vein while the ipsilateral femoral artery supplied the flap. Flap survival and graft patency were evaluated over 3 weeks. Ten of 15 flaps with intra-arterial grafts survived at 3 weeks (67%). Only 27% (4/15) of their supplying grafts remained patent for 3 weeks, although 67% (10/15) were patent at 10 days. All 10 flaps, where expanded PTFE grafts replaced venous outflow, failed within 36 hours. At exploration these grafts were thrombosed or collapsed. In conclusion, currently available 2 mm (i.d.) expanded PTFE vascular graft cannot maintain patency in a low blood flow circulation supplying an isolated free flap.

Animals↗
PubMed1988

Long microvenous allografts in rabbit femoral arteries and veins.

In this study the patency of long microvenous allografts in rabbits with and without immunosuppressive drug therapy was investigated. Eighty-two microvenous autografts (controls) and allografts were transplanted into rabbit femoral vessels. Veno-venous autograft controls were 100% patent at 3 weeks. Rejection of non-immunosuppressed veno-venous allografts consistently produced occlusion between 15-20 days. Thrombus filled the lumen, and a leucocyte invasion destroyed the graft wall. In contrast vein allografts into arteries were 100% patent at 3 weeks; this was reduced to 50% at 4 weeks. Low (5 mg/kg/day) and high (20 mg/kg/day) doses of hydrocortisone over 21 days improved the 3 week patency in veno-venous allografts to 28.5% and 57.0% respectively. Cyclosporin A (15 mg/kg/day) over 8 or 22 days significantly increased the patency rate of veno-venous allografts to 100%. Only cyclosporin A treated rabbits maintained allografts of normal vein morphology to 3 weeks.

Animals↗
PubMed1988

Long-term follow-up of free vascularized joint transfers to the hand in children.

Toe-to-hand vascularized joint transfers in four children were reviewed 6 to 8 years after operation (average, 6.6 years). Two children had vascularized metatarsophalangeal (MTP) joints. Both children have near normal active range of motion. The transferred epiphyses have provided a major contribution to digital growth. The other two children had second toe proximal interphalangeal (PIP) joints transferred to damaged hand joints. Active PIP joint extension has been disappointing, and the overall growth contribution of the transferred epiphysis has been small. We conclude that MTP to metacarpophalangeal vascularized joint transfer can provide painless, functional, stable motion, with near normal growth potential, and the usefulness of toe PIP to hand PIP joint transfer is limited by the inability to achieve good active extension and limited growth potential.

Child↗
PubMed1988

Anastomosis of vessels of unequal diameter using an interpositional vein graft.

In this study, 100 rabbits were used to assess the efficacy of five different methods of microvascular anastomosis where a vessel diameter discrepancy of 5:1 existed. The inferior vena cava of the rabbit was used as a graft in the femoral artery. In 50 percent of the rabbits the graft was reversed to assess the effects on flow. When explored between 7 and 10 days after anastomosis, an overall patency rate of 96 percent was recorded. Three grafts were not patent in the reversed group and one was not patent in the nonreversed group. There was no significant statistical difference in patency rates between any of the groups, as calculated by the Fisher's exact probability test. The tapered end-to-end and side-to-end anastomoses were found to be the most rapid and simplest methods to perform.

Anastomosis, Surgical↗
PubMed1988

Folded free vascularized fibula transfer.

A technique of improved free vascularized fibula grafting for bone defects up to 15 cm in length is presented with three illustrative cases. By dividing a harvested free fibula graft at its midpoint without dividing its vascular pedicle, two vascularized bone lengths are produced that require only one set of anastomoses. This folded fibula provides twice the cross-sectional area of a single fibula transfer and allows biomechanically improved graft placement. This technique has been successfully used in long bone defects of the upper and lower limbs.

Adolescent↗
PubMed1988

The long-term fate of microvenous autografts.

Changes in length, external diameter, wall thickness, and morphology were examined in 60 intraarterial vein grafts and 30 intravenous vein grafts inserted in rabbit femoral vessels. Half of each graft type was explored at 6 or 12 months, giving four experimental groups. The overall patency for intraarterial grafts at exploration was 98 percent and for intravenous grafts 100 percent. In comparison with the initial graft length resected, all four groups were significantly shorter at the completion of anastomosis, and three of the four groups also were significantly shorter at exploration. The overall loss in length of grafts varied between 26 and 30 percent of original length. External diameter was significantly increased (from between 133 and 201 percent) in all four groups at exploration compared to the normal femoral vein. Intravenous grafts maintained normal vein morphology to 12 months. Intraarterial grafts were modified by the ingrowth of smooth-muscle cells from the recipient artery, thereby creating a neointima that significantly thickened their walls at both 6 and 12 months.

Animals↗
PubMed1988

Changes in the blood biochemistry following experimental flap ischaemia.

The purpose of this study was to elucidate tissue changes occurring within an ischaemic flap by monitoring the blood biochemistry, and to evaluate these changes in relation to ultimate flap viability. A rabbit epigastric free flap was made ischaemic for 4 days at 6 degrees C, then revascularized by anastomosis of its femoral artery and vein. An identical free flap immediately revascularized in another group of rabbits served as a control. The viability of the free flap, as well as various biochemical parameters studied by drawing blood from a catheter in the ear vein, were observed daily. Immediately after the revascularization of ischaemic flaps, there was a 16-fold increase in the plasma levels of creatine kinase (CK) and a smaller but significant 1.5-fold to 2.0-fold increase in lactate dehydrogenase (LDH) and aspartate aminotransferase (AST). In flaps which ultimately failed by 7 days post-ischaemia, the plasma levels of CK, LDH and AST peaked at day 2 post-ischaemia at 68, 13 and 8 times normal respectively, whereas in flaps which survived, the levels of these enzymes recovered to normal by day 3 post-ischaemia. These enzymic changes are probably due to a combination of ischaemic changes in the flap vasculature, ischaemic changes in the flap muscle, and inflammatory changes in the surrounding abdominal tissue. The plasma levels of CK at any time post-ischaemia, and particularly in the first 24 h, were significantly higher in ischaemic flaps which failed compared with those which survived. This parameter is therefore proposed as a possible means of predicting potential flap failure after ischaemic insult, in time to make appropriate surgical intervention.

Animals↗
PubMed1988

Experimental microvascular growth plate transfers. Part I--Investigation of vascularity.

A model was developed in the dog to allow both the metaphysis and epiphysis of the distal ulnar growth plate to be microsurgically revascularised from the pedicle of the anterior interosseous vessels. With both circulations revascularised, grafts retained their structural integrity and growth continued at rates only slightly less than normal (mean 85%). If either or both circulations were not revascularised, growth rates were lower and were associated with skeletal collapse in the ischaemic bone segment.

Animals↗
PubMed1988

Experimental microvascular growth plate transfers. Part 2--Investigation of feasibility.

We investigated the feasibility in the dog of using transfers of the distal ulna into the radius either as growth plate replacements or as accessory growth plates in the diaphysis. Preliminary work determined the most satisfactory method of skeletal fixation. The experimental study showed that transfers used as growth plate replacements grew at almost normal rates, uniting with the recipient bone in a mean of 7.1 weeks. Transfers into the diaphysis initially nearly doubled the growth rate of the radius, although in the long-term results were unsatisfactory, because of fracture of the graft after a mean period of 8.2 weeks.

Animals↗