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Biomedical subjects

J E Lemons

Publications and source records attributed to J E Lemons.

At least 37 records · Page 2Linked to original sources
PubMed1994

Clinical and laboratory investigations of fretting and corrosion of a three-component modular femoral stem design.

A retrieval analysis of three modular femoral stems in vivo up to 25 months were examined using laboratory-based comparisons of similar devices as controls. The internal taper connection of each retrieved femoral component, and the laboratory controls were evaluated using SEM, EDAX, and epoxy vacuum infiltration. No corrosion of the substrate was detected for any of the retrievals. Fretting was mild on one retrieval and the in vitro-fatigued component, whereas minor fretting was observed for the other retrievals. Particulate debris was not evident as revealed by the epoxy infiltrate of the modular junction.

Adult↗
PubMed1993

Arthroscopy training using a "black box" technique.

In orthopaedic surgery residency, arthroscopic training is an essential component and one of the educational program requirements. A system using standard arthroscopy instrumentation and a "black box" has been developed for the purpose of teaching basic arthroscopic surgical skills in a laboratory setting. The black box component can be used as a dry or wet model, permitting a variety of arthroscopic techniques to be mastered under controlled circumstances. This unit has provided excellent feedback from residents and staff, and is cost effective. The basic principles of the orthopedic black box can be adapted for the development of basic skills in other specialties.

Arthroscopy↗
PubMed1993

Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee.

We performed an anatomical dissection of the medial soft-tissue retinacular fibers that restrain lateral patellar displacement and found that the medial patellofemoral ligament inserts not only on the patella but also on the undersurface of the distal aspect of the quadriceps mechanism. The deep capsular layer contained substantial retinacular fibers that were associated with the medial patellomeniscal ligament. Functional studies of the relative contributions of the medial soft-tissue restraints in the prevention of lateral patellar displacement were also performed. Twenty-five fresh-frozen specimens of the knee, obtained after amputations (nineteen specimens) or from cadavera (six specimens) were tested biomechanically on a universal testing instrument. We ranked the soft-tissue restraints, in order of their relative contributions to the restraining force, on the basis of the percentage of force provided by the retinacular and ligamentous tissue that resisted the lateral displacement of the patella. The medial patellofemoral ligament, although varying in size and importance, was found to be the major medial soft-tissue restraint that prevented lateral displacement of the distal knee-extensor mechanism, contributing an average of 53 per cent of the total force. The patellomeniscal ligament and associated retinacular fibers in the deep capsular layer of the knee, which were previously thought to be functionally unimportant in the stabilization of the patella, contributed an average of 22 per cent of the total force. The previously described retinacular fibers (the patellotibial band) were functionally unimportant in the prevention of lateral displacement.

Adult↗
PubMed1992

In vitro strength analysis of sagittal split osteotomy fixation: noncompression monocortical plates versus bicortical position screws.

An in vitro study using bovine ribs was performed to compare the strength of monocortical plates with bicortical position screws. An osteotomy was created to simulate a sagittal split and a 5-mm bone gap was produced. Four study groups were created: screw nongap, screw with gap, plate nongap, and plate with gap. Parameters of strength were analyzed by elastic deformation, stiffness ratio, permanent deformation, and breaking load. The results showed that monocortical plate fixation in bovine ribs provides less rigidity and is more susceptible to deformation than is bicortical position screw fixation.

Alloys↗
PubMed1992

Intraoral corrosion resulting from coupling dental implants and restorative metallic systems.

Materials used for the construction of dental restorations and implants include a wide range of metals and alloys, ceramics and carbons, and polymers. When metals and alloys are placed in direct contact in the oral cavity, a galvanic cell can be formed that may compromise the longevity of one or more of the materials in the couple. In vitro electrochemical corrosion analyses have proven to be a valuable tool for providing guidance on the selection of metallic materials. These analyses can provide basic data on electrochemical potentials, current rates, and the evaluation of galvanic corrosion conditions. This article seeks to provide the clinician with information that can be valuable in the selection of metallic materials that may be placed in direct contact with one another in the oral cavity.

Copper↗
PubMed1992

Biodegradation of restorative metallic systems.

Metallic materials utilized for the construction of intra-oral and implant dental restorations include a wide range of relatively pure metals and multicomponent alloys. Basic corrosion and biodegradation properties of these alloys have been studied by both in vitro and in vivo techniques. These property characteristics have been shown to be dependent on composition and metallurgical state, combinations within a construct, surface conditions, mechanical aspects of function, and the local and systemic host environment. The susceptibility of these metallic materials to various forms of biodegradation will be presented, with emphasis on corrosion.

Biodegradation, Environmental↗
PubMed1992

Retrieval analyses of a blade implant after 231 months of clinical function.

A blade implant that was retrieved in 1990 after 231 months of clinical function (since 1971) was analyzed with respect to clinical, histological, and biomechanical characteristics. The implant clinical records demonstrated no abnormalities or pathological lesions over the tenure of treatment. The bone to implant interface showed a mixture of interfacial tissue components and conditions with adequate direct bone contact (46.4 to 82.3 percent) for classification as osseointegrated. The abutment fracture leading to removal was characterized as a cyclic fatigue mechanism and the distribution of tissue components along the interface could not be correlated with specific biomechanical loading directions. This report considers the clinical and biomechanical records as they relate to the detailed histological investigation.

Blade Implantation↗
PubMed1991

The influence of radiation therapy on subperiosteal hydroxyapatite implants in rabbits.

Granular hydroxyapatite (HA) was implanted into subperiosteal pockets along both the right and left proximal tibias of 12 adult New Zealand white rabbits. The left extremities of 10 rabbits served as controls, whereas the right sides were irradiated with 2,250 rad in three doses over 5 days. The animals were killed at 1-week intervals starting at 2 weeks postirradiation. One half of each site was evaluated using standard histologic techniques while the other half was examined as a nondecalcified section. The quantity and the quality of new bone formation was determined using a rating scale and histomorphometric digitization. The results of this 4-month study showed that the amount of new bone formation around the HA granules was significantly greater in the irradiated sites. The irradiation produced no deleterious effects on the implant or the surrounding tissue areas.

Animals↗
PubMed1991

In vitro vs in vivo corrosion analyses of two alloys.

The in vitro and in vivo corrosion characteristics of two alloys, cast Co-Cr-Mo (ASTM F75) and wrought Ni-Cr-Mo, were evaluated using electro-chemical corrosion analysis. Two in vitro electrolytic solutions were utilized, an isotonic saline solution consisting of 0.9 w/o NaCl in distilled water and an isotonic saline solution with 10 v/o sterile calf serum. The in vivo environment was created by implanting cylindrically shaped specimens of each alloy into the back muscles of New Zealand white rabbits. Cyclic anodic and cathodic polarization curves were generated for the three test conditions and subsequently were compared. Anodic curves conducted using the isotonic saline and isotonic saline plus serum electrolyte solutions were very similar to the anodic curves generated for the implanted alloy specimens for both alloys. The corrosion rates predicted from the in vitro and in vivo cathodic polarization curves were not statistically different for the three test conditions. Overall, the corrosion data generated using the in vitro environmental conditions adequately predicted the in vivo corrosion behavior of the cast Co-Cr-Mo and wrought Ni-Cr-Mo alloys.

Animals↗
PubMed1991

Evaluation of cryopreserved bone and synthetic biomaterials in promoting spinal fusion.

The purpose of the study was to evaluate the use of cryopreserved allograft bone and tricalcium phosphate in promoting spinal fusion. Nine 20-30 lb swine underwent posterior spinal fusion at T5-T6, T13-T14, and L2-L3. Autogenous bone, cryopreserved allograft bone, or equal parts of allograft bone and tricalcium phosphate were added to the decorticated posterior elements. A total of 27 sites were prepared for fusion. The spines were retrieved at 6 months and evaluated for integrity and stability of the fusion sites by clinical examination, three-point bending tests, multiplanar radiographs, and undecalcified tetracycline-labeled and decalcified histologic sections. The nine sites that received autogenous bone were solidly fused. There were one clinical and two radiographic nonunions in the nine sites that received cryopreserved allograft bone. Sites that received a mixture of allograft bone and tricalcium phosphate demonstrated slight motion at two locations and radiographic evidence of fusion at all levels. The extent and degree of fusion was not site-specific. Three-point bending analysis did not demonstrate a significant trend as to site or materials specificity. No adverse histologic response was noted. Histologic sections and tetracycline labels confirmed abundant new bone formation at all sites at 6 months. Although autogenous bone remains the gold standard for use in spinal arthrodesis, this study demonstrates the value of cryopreserved allograft bone alone and in combination with tricalcium phosphate in promoting spinal fusion.

Animals↗
PubMed1990

Multiaxis cyclic biomechanical testing of Harrington, Luque, and Drummond implants.

The performance characteristics of Harrington-Moe distraction rods, paired wired Luque rods and Drummond's system were evaluated and compared when subjected to nondestructive cyclic, multidirectional biomechanical testing. Twelve fresh, frozen swine spines with intact facet joints and anterior and posterior ligamentous complexes were instrumented and tested in a specially designed pneumatic testing machine. The instrumented spines were subjected to 207 kN/m2 compression and 49 N-m torsion. Each spine was cycled 28,000 times at 1 cycle per second. Linear and angular displacements were determined by digitizing photographs and video tapes made during testing. A computer program developed and refined for the project was used to complete the data analysis. Approximately 540 items of angular and linear displacement data were collected for each spine. Inspection of the spines after cyclic, multidirectional testing revealed no change in their osteoligamentous integrity compared with pre-testing. Pre- and post-testing radiographs showed no evidence of osseous failure, hook dislodgement or wire breakage. Erosion of laminal bone at the Harrington hook attachment sites was observed. Displacement of the Harrington hooks was seen during off-axis compression-torsion testing. Fretting and deposit of metal wear debris occurred between the sublaminal wires and "L" rods. There was no evidence of loosening of either the Drummond or Luque implants or fatigue failure of any component. Analysis of the linear and angular displacement data showed that the Luque and Drummond instrumented spines displaced less in axial compression, off-axis compression and off-axis compression-torsion than the single Harrington-Moe distraction rod.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Dental implant biomaterials.

Synthetic materials for surgical implant devices have evolved from the early metallic systems to a variety of material combinations and composites. Current biomaterial and biomechanical properties provide relatively optimal stable bone and soft tissue interfaces and simplified restorative treatments. Further improvements in existing systems require a continuation of the multidisciplinary approach to laboratory, experimental animal, and human clinical research.

Biocompatible Materials↗
PubMed1990

Histologic response after implantation of porous hydroxylapatite ceramic in humans.

After periods of observation from 3 to 36 months, biopsies were obtained from 22 patients in whom porous block and particulate hydroxylapatite ceramic (Interpore 200) had been used for augmentation procedures and in two patients in whom nonporous particulate hydroxylapatite (Calcitite) had been used. Histologic examination of serial sections of decalcified specimens revealed vital bone formation in relation to the blocks, whereas the particulate was encapsulated in fibrous tissue. The differences in biological behavior are discussed.

Adult↗
PubMed1990

Clinical longevities of ramus frame implants.

A variety of ramus frame dental implant designs is indicated for endosseous restoration to retain lower dentures, and the different designs utilize various alloys. The objective of this study was to present an analysis of the clinical applications for ramus frame dental implants with emphasis on the statistics of clinical longevities. The investigation involved an extensive statistical evaluation and, when possible, metallographic, scanning electron microscopic, histological, mechanical, and stereomicroscopic surface evaluations. The statistical analysis presents averages and percentages of devices in place vs. devices removed. Analyses of survival probability were also determined by means of the Kaplan-Meier statistical methods. A comparison of these results with the general criteria listed in the Harvard Conference shows that more than 75% of the implant devices were in place after five years.

Dental Alloys↗
PubMed1990

Bioceramics. Is there a difference?

Bioceramics of aluminum oxide and calcium phosphate have a wide range of applications in orthopedic surgery. Each type of bioceramic is substantially different from the other, and variations exist within each type depending on the source and intended application. The physical, mechanical, chemical, and biologic properties are specific to each bioceramic. Significantly different tissue responses have been demonstrated among the various aluminum oxide, hydroxylapatite, and tricalcium phosphate bioceramics. Since the prospects for expanded clinical applications are excellent, the clinical community should become better acquainted with these types of biomaterials.

Biocompatible Materials↗
PubMed1990

Metal-induced sarcoma. A case report and literature review.

The overall biocompatibility characteristics of metallic implants are important considerations in orthopedic surgery. A review of the literature shows very few reports of neoplasms in association with metallic implants. This case report demonstrates osteogenic sarcoma at the site of a Smith-Petersen nail that had been implanted for nine years in a 65-year-old woman for fixation of a femoral neck fracture. Gross examination revealed debris at the tumor site, with a concentration of 14 ppm of nickel within the tumor tissue. Experimental investigations support the possibility of neoplastic induction by heavy metals, particularly cobalt, cadmium, and nickel. Circumstantial evidence shows osteogenic sarcoma that developed at the site of this device, possibly in response to metal or factors at the site of metal.

Aged↗
PubMed1989

Corrosion of copper, nickel, and gold dental casting alloys: an in vitro and in vivo study.

The corrosion behavior of commercially available copper, nickel, and gold alloys for dental castings was investigated. The alloys investigated included: three copper alloys (76-87Cu, 6-11A1, 0-12Zn, 1-5Ni, 0-4Fe, 0.5-1.2Mn), two nickel alloys (68-78Ni, 12-16Cr, 4-14Mo, 0-1.7Be), and one gold alloy (77Au, 14Ag, 8Cu, 1Pd). Anodic and cathodic polarization curves, long-term immersion tests in saline and artificial saliva solutions, and dog crown studies were conducted to evaluate both the in vitro and in vivo corrosion characteristics of the alloys. All evaluations conducted demonstrated that the copper alloys were highly susceptible to corrosion attack. High corrosion currents were observed in the in vitro tests, and SEM of the alloys specimens showed significantly altered surfaces. The anodic polarization curves predicted that the beryllium-containing nickel alloy should be susceptible to localized corrosion and SEM revealed an etched surface with corrosion of certain microstructural features. No significant corrosion was predicted or observed for the non-beryllium nickel alloy and the gold alloy. The in vitro corrosion evaluations predicted the in vivo corrosion behavior for the alloys. Since the three copper alloys and the beryllium-containing nickel alloy demonstrated significant corrosion under the tested conditions, the use of these alloys for restorative procedures is questionable due to the release of significant levels of selected ions to the oral cavity.

Animals↗