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Biomedical subjects

W L Bargar

Publications and source records attributed to W L Bargar.

32 records · Page 2Linked to original sources
PubMed1986

The addition of tobramycin to contrast bone cement. Effect on flexural strength.

Samples of polymethylmethacrylate (PMMA) bone cement were polymerized in vitro with no additives and with the following additives: methylene blue dye, tobramycin, methylene blue plus tobramycin. After storage for 7 days in saline, samples were tested to failure in three-point bending. Addition of the antibiotic significantly weakened the cement (to 87% of control). However, the combination of tobramycin plus methylene blue was no weaker than tobramycin alone, suggesting that addition of both dye and antibiotic to bone cement is probably a reasonable clinical practice.

Bone Cements↗
PubMed1986

The calcar bone graft.

A canine model was developed to investigate the use of an autogeneic iliac bone graft to treat the calcar deficiency commonly found at the time of revision surgery for femoral component loosening. Five large male mixed-breed dogs had bilateral total hip arthroplasty staged at three-month intervals, and were sacrificed at six months. Prior to cementing the femoral component, an experimental calcar defect was made, and a bicortical iliac bone graft was fashioned to fill the defect. Serial roentgenograms showed the grafts had united with no resorption. Technetium-99 bone scans showed more uptake at three months than at six months in the graft region. Disulfine blue injection indicated all grafts were perfused at both three and six months. Thin section histology, fluorochromes, and microradiographs confirmed graft viability in all dogs. Semiquantitative grading of the fluorochromes indicated new bone deposition in 20%-50% of each graft at three months and 50%-80% at six months. Although the calcar bone graft was uniformly successful in this canine study, the clinical application of this technique should be evaluated by long-term results in humans.

Animals↗
PubMed1985

Limb-sparing surgery for extremity sarcomas after preoperative intraarterial doxorubicin and radiation therapy.

Complete local control of 25 extremity bone and soft tissue sarcomas was obtained by combined preoperative intraarterial doxorubicin and radiation therapy, followed by limb-sparing resection with reconstruction and adjuvant chemotherapy. At a 32 month median follow-up, there are no local tumor recurrences. Functional limbs were salvaged in 21 patients (84 percent). Fifteen patients (60 percent) were continuously disease-free and overall survival was 80 percent. After the extensive combined modality therapy, extremity complications, including delays in wound healing, occurred in 10 patients. Nevertheless, most complications were resolved with salvage of functional limbs. These results support an aggressive multimodality limb-sparing approach to high-grade extremity sarcomas.

Adult↗
PubMed1984

Late thoracic outlet syndrome secondary to pseudarthrosis of the clavicle.

Successful resolution of a late thoracic outlet syndrome secondary to pseudarthrosis of the clavicle was accomplished by surgical resection of the pseudoarthrosis and mid 3 cm of the clavicle, following conservative therapy which did not alleviate the symptoms. The patient was a 28-year-old woman. Arteriography demonstrated the lesion. A shoulder dislocation preceded the thoracic outlet syndrome; a congenital pseudarthrosis may have been present.

Adult↗
PubMed1983

Contrast bone cement.

The effects of adding 1.0 cc of aqueous methylene blue dye as a visual contrast agent to a standard 40 g pack of acrylic bone cement are determined. These cements are evaluated: Simplex P (Radiopaque), Zimmer Bone Cement, and Zimmer LVC Bone Cement. Seven tests were performed. Leach out is less than 2.0% and was undetectable after day 8. Biocompatibility using a rabbit model shows contrast and white cement to be equivalent. Tension, compression, and 3- and 4-point bending strengths are not significantly altered except for a slight increase in 4-point bending strength for contrast Zimmer (regular) bone cement. Dough, set, and working times are decreased by 30-150 s. The ASTM F451 intrusion standards are met for all three contrast cements. Viscosity increases more rapidly for contrast cement, but remains sufficiently low (less than 100 N-s/m2) early after mixing to allow good penetration into bone. Ease of removal and visualization of contrast cement are shown by revision of cemented femoral total hip components in synthetic and cadaver femurs and by debriding cement particles from a soft tissue background coated with blood. The use of contrast bone cement appears to be both safe and efficacious for use in initial and revision total joint replacements. Because of the decreased working times, its use is recommended only by experienced surgeons.

Animals↗
PubMed1983

A comparison of the mechanical properties of Simplex, Zimmer, and Zimmer low viscosity bone cements.

Many different methods have been used to compare polymethylmethacrylate bone cements. In this paper the three currently available cements were compared in regard to dough and set times, heat of polymerization, compressive, tensile, 3 and 4 point bending strengths, fracture toughness, flexural modulus, void density distribution, and viscosity. Methods used were ASTM designated for bone cement or plastics in general whenever possible. Significant differences in set and dough times and heat of polymerization were noted. All cements were equal in compressive, tensile, and fracture toughness testing; Zimmer Regular Cement was significantly weaker (p less than 0.001) in flexural testing and had a significantly (p less than 0.001) decreased modulus of elasticity when compared to LVC and Simplex Cements. Void density distributions were not significantly different. Viscosity was shown to vary between these cements as well. This data was analysed both to determine differences between various brands of cement and to assess the relevance to clinical use and failure modes in vivo of these different means of testing.

Bone Cements↗
PubMed1983

The effect of tibia-foot rotatory position on the anterior drawer test.

The effect of the position of the foot and tibia on the anteroposterior drawer test was quantified using a clinical testing device. Maximum laxity occurred at 15 degrees of external rotation of the foot. Extreme rotation of the foot and tibia resulted in reductions of anteroposterior laxity of 63% for internal rotation and 50% for external rotation. The ratio of foot rotation to tibia rotation was approximately 2:1. Medial meniscectomy alone did not result in increased anteroposterior laxities when compared with normal knees. Medial meniscectomy with an unrepaired anterior cruciate ligament tear resulted in increased anteroposterior laxities at 15 degrees, 30 degrees, and maximum external rotation of the foot.

Adult↗
PubMed1980

Results with the constrained total knee prosthesis in treating severely disabled patients and patients with failed total knee replacements.

Fifty-fix constrained total knee replacements (forty Guepar and sixteen Herbert prostheses) were performed in forty-nine severely disabled arthritic patients and they were followed for two to four years. Seventeen of these knees were operated on to salvage a failed prosthesis. Good relief of pain was achieved in 64 per cent of the knees but there was less improvement in walking and function. The over-all range of motion increased because of a reduction in preoperative flexion contractures. The results in the salvage group were less successful than in those patients who underwent a primary operation. Between six months and one year postoperatively, pain had developed in 17 per cent of the fifty-six knees, 9 per cent had walking difficulties, and 7 per cent lost function. Patellofemoral pain accounted for the unfavorable pain ratings in over half of the knees. Zonal roentgenographic analysis of each knee indicated high incidences of radiolucent lines at the cement-bone interface (75 per cent), cement-metal lucencies (68 per cent), and cement deficiencies (73 per cent). Forty-three per cent of the knees showed excessive posterior placement of the prosthesis of more than five millimeters, resulting in flexion contractures of as much as 5 degrees. Complications requiring reoperation developed in nine knees (16 per cent). There was one case of loosening and three knees had deep infections. Chronic postoperative effusions were present in 48 per cent of the knees. The use of either a cemented metal-on-metal hinged knee replacement or a metal-on-polyethylene hinge type of prosthesis was found to result in a relatively high incidence of failures and complications, and did not solve the problem of treating patients with a failed knee prosthesis.

Adult↗
PubMedDate not supplied

The influence of temperature and specimen size on the flexural properties of PMMA bone cement.

A three-stage investigation was undertaken to examine the influence of specimen size and polymerization environment on the flexural properties of PMMA. In the first stage, specimens were cut from large pieces of commercially cast acrylic (lucite) and self-curing dental acrylic. The material properties of the cast acrylic as calculated from the results of flexural testing were not influenced by specimen size in the range of 1 X 10 X 30 to 3 X 10 X 60 mm, whereas 1-mm thick dental cement specimens had 12% (p less than 0.001) higher stress and 24% (p less than 0.001) higher strain to failure than 3-mm specimens cut from the same sample. In the second stage, self-curing dental cement and Simplex P bone cement were molded in different thicknesses. These experiments demonstrated that molding thin 1.6-mm specimens resulted in increases of 14% (p less than 0.001) in stress and 30% (p less than 0.001) in strain to failure as compared with 3.2-mm specimens, which were greater differences than those due to the specimen thickness effects alone. In the third stage, temperatures of cement were monitored during polymerization, and cements were molded at different temperatures. These results demonstrated that thicker cement samples reached higher temperatures and that cement samples polymerized at lower temperatures (21 versus 37 degrees C) had 12% (p less than 0.001) greater stress and 105% (p less than 0.001) greater strain to failure.

Bone Cements↗
PubMedDate not supplied

The incidence of spondylolysis and spondylolisthesis in nonambulatory patients.

Radiographs were obtained of the lumbosacral spines of 143 patients that had never walked. The frequency of spondylolysis and spondylolisthesis was determined, as well as that of other spinal abnormalities. The average age of the patients was 27 years, with a range of 11 to 93 years. The underlying diagnoses responsible for the nonambulatory status varied, but cerebral palsy predominated. No case of spondylolysis or spondylolisthesis was detected, and when compared to the 5.8% incidence in the general population, this finding is significant at the P less than 0.001 level. The incidences of spinal bifida (8.4%) and of transitional vertebrae (10.9%) are similar to those found in the general population. Scoliosis was found in 49% and vertebral body height was increased in 32.9%. Degenerative changes occurred in only 2.8%. These results support the theory that spondylolysis and isthmic spondylolisthesis represent a fatigue fracture resulting from activities associated with ambulation.

Adolescent↗
PubMedDate not supplied

In vivo stability testing of post-meniscectomy knees.

Post-meniscectomy knees examined with an instrumented clinical testing device reveal that meniscectomy alone does not cause a measurable degree of instability. If meniscectomy causes a minor degree of instability, the degree is within the right-left variation for a normal population. Medical meniscectomy in combination with a torn anterior cruciate results in an increased anterior-posterior instability at 20 degrees knee flexion. The device used in this study was more reliable in diagnosing increased anterior-posterior instability secondary to anterior-cruciate tear than was a clinical examiner.

Adolescent↗