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Biomedical subjects

M J Yaremchuk

Publications and source records attributed to M J Yaremchuk.

At least 19 recordsLinked to original sources
PubMed1995

Prolonged survival of vascularized limb tissue allografts by donor irradiation.

The clinical feasibility of transplantation of a vascularized limb tissue allograft depends upon reducing immunosuppression and its associated toxicity for the graft recipient. Donor or allograft irradiation would eradicate allogeneic marrow and provide a possible alternative or beneficial addition to host immunosuppression. The effect of irradiation on survival of limb tissue allograft was investigated in this study. In a rat model, knee allografts consisting of bone, cartilage, and soft tissues were transplanted across a strong histocompatibility barrier by femoral vascular microanastomoses. The grafts were harvested 1 and 2 weeks postoperatively for histologic and immunologic assays. Gamma irradiation of the graft immediately before transplant decreased graft rejection slightly. However, total body irradiation of the donor followed by a "waiting period" of 2 or more days before transplant significantly delayed rejection. After such a 6-day and a 2-day pretreatment protocol, the host cellular immune responses were not observed 1 and 2 weeks after transplantation and eventual progression toward graft rejection coincided with emergence of host antibody production. Rejection of vascularized limb tissue allografts after donor irradiation thus appeared to be mediated primarily through the humoral pathway. We conclude that donor irradiation is a potentially useful adjunct in prolonging survival of vascularized limb tissue allografts.

Animals↗
PubMed1995

Cyanoacrylate fixation of the craniofacial skeleton: an experimental study.

This study examined the feasibility of achieving bone fixation of the upper facial skeleton using n-butyl-2-cyanoacrylate. We compared the fixation obtained with this adhesive to that obtained with plates and screws in an animal model. The stability of fixation of both osteotomies and onlay grafts was studied in six minipigs. Three osteotomies were performed on each side of the skull. Additionally, a parietal split-thickness autograft was fixated to the nasal bone as an onlay. Plates and screws were used on the right and adhesive on the left. The animals were killed at 6 weeks, and both sides were compared biomechanically and histologically. Clinical assessment showed stability of all fragments. No statistical difference was found in the comparison of the maximum torque to failure between analogous plated and glued sides. Radiographic cephalometry revealed no significant displacement of the fragments. Histologic analysis demonstrated bony union. In this study, n-butyl-2-cyanoacrylate was as effective as plates and screws in the fixation of surgically created osteotomies of the upper facial skeleton.

Animals↗
PubMed1995

The antithrombotic effects of ticlopidine and aspirin in a microvascular thrombogenic model.

In the effort to reduce a persistently significant failure rate in free tissue transfers and digital replantations, the efficacy of two oral platelet inhibitors, aspirin and ticlopidine, was examined using the arterial inversion graft, a known microvascular thrombogenic model. Forty male New Zealand White rabbits were used to create eighty 5-mm inversion grafts. Four groups were blindly given perioperative oral drug therapy: ticlopidine, aspirin, both, or neither (control). Vessel patency was evaluated at 1 hour and 1 week after surgery. The patency rate for the control group was 20 percent at 1 hour and 5 percent at 1 week. The drug-treated patency rates at 1 hour and 1 week, respectively, were 45 percent (p = 0.046) and 15 percent for ticlopidine, 35 percent and 10 percent for aspirin, and 45 percent (p = 0.046) and 20 percent for the combination therapy. This study shows that ticlopidine alone or in combination with aspirin significantly increases the 1-hour patency rates in a reliable thrombosis model, but it fails to show a significant increase in the final patency rates by either drug administered alone or in combination. The benefit in clinical microvascular surgery of either aspirin or ticlopidine is not determined by this study.

Administration, Oral↗
PubMed1995

Aneurysmal bone cyst of the orbit associated with fibrous dysplasia.

Aneurysmal bone cyst is a rare but recognized osseous lesion of the orbit. We report the presentation, treatment, and postoperative course of an orbital aneurysmal bone cyst in a patient with McCune-Albright syndrome. To our knowledge, this report represents the first description of aneurysmal bone cyst of the orbit in a patient with fibrous dysplasia. Although visual loss in patients with fibrous dysplasia is most commonly due to narrowing of the optic canal, aneurysmal bone cyst should be considered in a patient with fibrous dysplasia who presents with decreasing vision in the face of a rapidly expanding orbital mass. The treatment in this case was drainage and debridement with prompt resolution. Although not necessary in this case, an alternative treatment includes packing with bone chips. Radiation is usually avoided because of the risk of iatrogenically induced sarcoma.

Adult↗
PubMed1995

Injectable cartilage.

Slowly polymerizing calcium alginate gels were investigated as a means of delivering large numbers of isolated chondrocytes by means of injection to determine if these gels would promote engraftment and could provide three-dimensional templates for new cartilage growth. Chondrocytes isolated from the articular surface of calf forelimbs were added to a 1% sodium alginate dissolved in a 0.1 M potassium phosphate buffer solution (pH 7.4) to generate a final cellular density of 10 x 10(6)/ml (representing approximately 10 percent of the cellular density of human juvenile articular cartilage). The calcium alginate-chondrocyte mixture was injected through a 22-gauge needle in 100-microliters aliquots under the panniculus carnosus on the dorsum of nude mice and incubated for 6 (n = 4), 8 (n = 11), and 12 (n = 12) weeks in vivo. Time-zero specimens (n = 10) consisting of 100-microliters aliquots of the calcium alginate-chondrocyte mixture were used to calculate initial weight. At harvest, all calcium alginate-chondrocyte specimens exhibited a pearly opalescence and were firm to palpation as early as 6 weeks after injection. By 12 weeks of in vivo incubation, the specimens weighed 0.15 +/- 0.04 gm, significantly more than the initial weight of 0.11 +/- 0.01 gm (p < 0.05). Specimens stained with hematoxylin and eosin demonstrated lacunae within a basophilic ground-glass substance. Control specimens of calcium alginate without chondrocytes (n = 4) had a doughy consistency 12 weeks after injection and had no histologic evidence of cartilage formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alginates↗
PubMed1995

Experimental orthotopic transplantation of vascularized skeletal allografts: functional assessment and long-term survival.

Vascularized skeletal tissue allografts would greatly expand the domain of reconstructive surgery. Few studies to date have examined the functional aspects of these allografts or their long-term fate. An orthotopic transplant model of rat distal femur and surrounding muscular cuff was developed to assess graft function in fracture healing and weight bearing. Isografts (RT1l to RT1l, n = 40), weak-barrier allografts (RT1l to RT1lv, n = 40), and strong-barrier allografts (RT1l to RT1n, n = 40) were transplanted. As the histocompatibility barrier increased between the donor and recipient animals, the graft viability and performance deteriorated according to radiographic, histologic, and immunologic analyses. Administration of cyclosporine led to survival of strong-barrier allografts similar to that of isografts. A long-term study of these allografts (RT1l to RT1n) was then performed on various immunosuppressive regimens. After an initial 10-week course of cyclosporine to achieve bony union and remodeling, subsequent cessation (n = 20) or intermittent "pulsing" (n = 20) of the immunosuppressant was insufficient in maintaining graft survival. However, graft viability and function were preserved through 1 year on continuous daily cyclosporine (n = 32). There was no evidence of host renal or hepatic toxicity by serum chemistry or histologic sections. Thus long-term survival of functional skeletal allografts was achieved in this orthotopic model without significant host toxicity from immunosuppression.

Animals↗
PubMed1994

A microsurgical suction mat.

We describe a suction mat used to maintain a bloodless field during microsurgery. The mat is inexpensive, can be quickly fashioned from readily available operating room items, and functions with exceptional reliability.

Humans↗
PubMed1994

Comparison of artifact from craniomaxillofacial internal fixation devices: magnetic resonance imaging.

This study compares artifact from craniomaxillofacial internal fixation devices in magnetic resonance images and examines heating and magnetic deflection effects on these devices. Stainless steel wires, microfixation plates of vitallium and titanium, and minifixation and mandibular reconstruction plates of stainless steel, vitallium, and titanium were evaluated. The plates were mounted on a dry skull and submerged in dilute copper sulfate solution. All images were obtained in duplicate by two independent, nonblinded teams of observers with a 1.5-T Signa magnetic resonance system. Each team ranked artifact size for each material by computerized measurement. The rank order of artifact size for each material within each fixation system group and between fixation groups was identical between the two teams. Bath and plate temperatures were recorded before and after imaging. Artifact production was related to hardware size and composition. Titanium hardware caused the least amount of "black-hole" artifact. Vitallium and stainless steel fixation devices of similar size produced significantly more artifact. No significant heating or magnetic deflection effects were seen with any of the fixation devices.

Artifacts↗
PubMed1994

The roles of revascularization and resorption on endurance of craniofacial onlay bone grafts in the rabbit.

A total of 32 New Zealand white rabbits underwent subperiosteal implantation of fresh autogenous unicortical calvarial and iliac crest grafts on their snouts with microscrew rigid fixation. After 3 and 10 days, vascularity was assessed by latex casting, and osteoclastic activity was determined by histochemical staining for tartrate-resistant acid phosphatase. After 70 days, volumetric analysis and tartrate-resistant acid phosphatase staining were performed on six animals. The calvarial grafts demonstrated greater volume maintenance than the iliac bone (72 percent versus 32 percent, p < 0.025). There were significantly greater osteoclastic activity and revascularization in the cancellous portion of calvarial and iliac crest bone grafts by the 10th day of onlay grafting. Minimal activities were present at the cortical bone. Because calvarial grafts contain more cortical bone, its superior volume maintenance can be understood by the architectural influence on revascularization and resorption.

Animals↗
PubMed1994

Experimental studies addressing rigid fixation in craniofacial surgery.

This article has reviewed several experimental studies that address certain aspects of the use of rigid fixation in clinical craniofacial surgery. The effect of rigid fixation on growth was studied in an infant Rhesus monkey model. It showed that osteotomy and fixation resulted in subtle changes in skull shape and that the severity of the deformity was related to the complexity of the fixation employed. Deformities were seen with wire fixation alone, however. A study using a rabbit model showed that the revascularization and resorption of onlay bone grafts immobilized with a microscrew occurred primarily in the cancellous portion of the graft. This led Chen et al to speculate that the volume of cranial bone grafts persists better than with iliac crest grafts, because they contain relatively less cancellous bone and more cortical bone, which is slower to revascularize and resorb. Fiala et al studied the artifacts seen in CT and MR scans associated with plate and screw fixation devices. They showed that, compared with stainless steel and vitallium, titanium resulted in less "starburst" and "black hole" artifact in CT and MR images, respectively. Amarante et al compared butyl-2-cyanoacrylate adhesive fixation with fixation by plates and screws of osteotomized bone segments in a minipig model. They found it to be as effective as plates and screws for bone fixation in this model. In the future, this material, together with resorbable plates and screws, may provide a means of fixation of the craniofacial skeleton and can be anticipated to receive further experimental and clinical study.

Animals↗
PubMed1994

The effects of rigid fixation on craniofacial growth of rhesus monkeys.

A male infant rhesus monkey model was used to examine the growth effect on the craniofacial skeleton caused by osteotomy and three types of fixation: interfragmentary wiring, microplate and screw fixation, and "extensive" microplate and screw fixation. The animals (n = 12) were allowed to mature until cranial growth was at least 95 percent complete. Direct craniometric measurements were obtained and analyzed for differences in the three treated groups. A group of unoperated male animal skulls also was analyzed as controls (n = 5). A subtle visible and measurable restriction of growth in the operated area occurred in all treatment groups. Significant differences (p < 0.05) were found in only 4 of the 39 craniometric chords measured. Interfragmentary wiring showed fewer growth-restrictive effects than standard use of microfixation plates. Extensive use of rigid fixation devices caused the greatest degree of growth disturbance. Osteotomy and fixation in the infant rhesus monkey affect craniofacial growth, with the degree of growth restriction increasing with the amount of fixation hardware.

Animals↗
PubMed1993

An objective assessment of treatment for orbital hypertelorism.

A retrospective statistical analysis of orbital hypertelorism correction was performed by comparing the preoperative and postoperative intercanthal distances of these patients with published age-matched normal values. Forty-five patients who had undergone surgery over a 15-year period with an average follow-up of 5 years (6 months to 14 years) were evaluated. Comparison of age-normalized preoperative and postoperative intercanthal distances revealed a significant difference for orbital hypertelorism patients as a group (p < 0.0001), patients with clefts (p < 0.0001), patients with nasoencephalocele (p < 0.01), and patients with frontonasal dysplasia (p < 0.05), but not for those patients with craniofacial dysostosis (p < 0.20). Multiple analyses of variance revealed a significant interaction existing between the extent of preoperative deformity and the cause of hypertelorism for both the postoperative deformity and the total amount of correction achieved, but not for the type of surgery or for the age at which the surgery was performed.

Analysis of Variance↗
PubMed1993

Microfixation of acute orbital fractures.

Microfixation techniques were used as an adjunct to the use of miniplates and screws in the acute treatment of fractures involving the orbit in 42 patients over a 2-year period. Miniplates were used in all fractures at the Le Fort I level and at the zygomatic-frontal suture in high-energy injuries. Microfixation was used to stabilize all other fractures of the zygomatic, nasoethmoid, and frontal areas. Problems with plate visibility and objectionable palpability through thin periorbital skin were eliminated. The use of microplates allowed more precise positioning of small fragments than possible with miniplates or interfragmentary wires. Fracture reduction remained clinically stable in the frontal and nasoethmoid areas. Microplates were inadequate to resist soft tissue deforming forces along the infraorbital rim and the zygomatic arch in high-energy injuries.

Adult↗
PubMed1993

The role of three-dimensional computed tomography in the evaluation of acute craniofacial trauma.

Three-dimensional computed tomographic (3-D CT) reformations together with their corresponding conventional axial two-dimensional (2-D) CT images of 20 patients with facial fractures were compared with 2-D CT alone to define their usefulness in the determination of facial skeletal fracture patterns. Nine surgeons with three different levels of experience and training evaluated the presence and spatial arrangement of fractures in all 2-D CT and 3-D CT scans. Comparisons were made between their evaluations of 2-D CT alone and 2-D CT plus 3-D CT scans. Statistical analysis with Friedman's test were performed. The addition of 3-D CT did not alter the interpretation of 2-D CT in 75% of evaluations. The number and accuracy of the changes made with the aid of 3-D CT reflected the experience of the observers. Overall, there was no improvement in the accuracy of interpretations with the addition of 3-D CT.

Facial Bones↗
PubMed1993

An electronic device for surgical glove testing.

An electronic glove tester complying with safety regulations for electric current flow is described. In our laboratory, it was able to detect 100 percent of glove punctures caused by 4-0 and 6-0 surgical needles. When used regularly in the surgical suite, this device may help to minimize the surgeon's exposure to patients' blood and body fluids.

Electronics, Medical↗
PubMed1993

Comparison of CT imaging artifacts from craniomaxillofacial internal fixation devices.

This study compares the artifacts caused by craniomaxillofacial internal fixation devices in CT images. Mandibular reconstruction and "mini" titanium, Vitallium, and stainless steel systems, "micro" titanium and Vitallium systems, and stainless steel wires were evaluated. The hardware was placed on a nylon grid and submerged in water. CT images were obtained with both bone and soft-tissue window settings. All artifacts were compared and graded after a minimum of five observations each. The severity of "starburst" artifact was found to be related to the physical size of the fixation hardware and its composition. Titanium hardware caused the least amount of artifact. Vitallium and stainless steel fixation devices, with the exception of interfragmentary wiring, produced significantly more artifact. These results agree with theoretical predictions. The data indicate that when postoperative imaging is an important clinical consideration, (1) the least amount of implant material necessary to achieve stable fixation should be used, (2) the proximity of implant material to the area of interest should be considered, and (3) titanium implants produce less artifact than Vitallium or stainless steel implants.

Artifacts↗
PubMed1992

Complex orbital fracture repair using rigid fixation of the internal orbital skeleton.

Large orbital fractures involving more than one orbital wall are frequently associated with enophthalmos and vertical globe dystopia. The authors repaired 22 orbits in 20 patients using the technique of rigid fixation of the internal orbital skeleton. Eleven orbits were reconstructed with titanium or vitallium implants that were custom-shaped to span the bony defect and fixed to the orbital rim. Seven orbits were reconstructed with bone grafts rigidly supported by a miniplate, and, in four cases, direct lag screw support of bone grafts was used. The intraoperative goal was to restore the native orbital anatomy and volume. Autologous calvarial bone grafts were used to supplement the repair to achieve the desired volumetric effect and to cover additional wall defects. A reoperation for additional orbital augmentation was needed in one enophthalmic and one anophthalmic orbit. There were no cases of overcorrection, migration, infection, or extraocular muscle entrapment. In complex orbital fractures, the technique of rigid internal orbital fixation appears to yield a stable and predictable result with the prevention of postoperative globe malposition.

Adult↗