Biomedical subjects

J M Spivak

Publications and source records attributed to J M Spivak.

9 recordsLinked to original sources

PubMed1992

Evaluation of a low-temperature calcium phosphate particulate implant material: physical-chemical properties and in vivo bone response.

A study was conducted to evaluate the osteoconductive ability of a particulate, low-temperature hydroxylapatite (HA(LT)) material (OsteoGen; Impladent, Holliswood, NY). An implantable chamber model was used to determine the ability of this material to encourage bone ingrowth into channels lined with either rough-surfaced titanium or rough-surfaced plasma-sprayed hydroxylapatite. The HA(LT) material increased bone ingrowth into the titanium-lined channels comparable with that in plasma-sprayed hydroxylapatite-coated channels. It was incorporated into ingrowing bone without intervening soft tissue, with the bone bonding directly to the material surface in much the same fashion as it bonds at the plasma-sprayed hydroxylapatite surface. Mechanical testing of the ingrown bone showed no weakness because particles were incorporated. At 12 weeks, the particles began to show signs of dissolution. It was concluded that the HA(LT) material is a biocompatible, osteoconductive material that conducts bone ingrowth in much the same way as high-temperature particulate hydroxylapatite ceramics. This material has the additional desirable property of being slowly resorbable, a beneficial characteristic for many bone-filling applications.

Animals↗

PubMed1992

The effect of low-level Nd:YAG laser energy on adult articular cartilage in vitro.

Reports of laser energy applied to soft tissues in vitro and in vivo suggest both stimulation and inhibition of specific metabolic processes, depending on the type of laser, the energy density (ED) used, the mode of delivery, and type of tissue studied. An earlier in vitro study of Nd:YAG laser irradiation of articular cartilage indicated stimulation of both matrix and DNA synthesis for 6 days following laser exposure. In vivo reports on the ability of Nd:YAG laser energy to stimulate the healing of partial-thickness cartilage defects are conflicting. In the present study, a noncontact continuous-wave Nd:YAG laser beam of varying EDs was applied to full-thickness adult articular cartilage explants maintained in organ culture; the metabolic processes of chondrocyte DNA synthesis and matrix synthesis were followed over 2 weeks. For both canine and bovine cartilage, low-levels of laser energy (ED 51-127 J/cm2) stimulated matrix synthesis at 6-7 days following laser exposure, with a concomitant decrease in baseline DNA synthesis. By 12-14 days, however, these dose-dependent effects were no longer seen, with no significant differences from control noted for any of the laser energies studied. Histologic analysis of the cartilage explants following laser exposure showed no significant differences in cell number or morphology between sample and control groups; however, a decrease in matrix proteoglycan staining was seen in the highest laser energy group at all time points. These findings indicate that exposure to low-level noncontact Nd:YAG laser energy promotes a significant stimulation of cartilage matrix synthesis. However, a single exposure may not be sufficient to promote a sustained upregulation of cartilage metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Molecular structure at the bone-implant interface: a vibrational spectroscopic characterization.

Test implant plates surgically retrieved from distal femurs of dogs were studied by Raman spectroscopy in order to characterize the bone-implant interface. The implant surface consisted of phosphate mineral, plasma sprayed on a titanium substrate. On the basis of its spectroscopic signature, the phosphate mineral of bone and the implant surface formed a mixed phase in the interface.

Animals↗

PubMed1991

Fatigue failure of the sliding screw in hip fracture fixation: a report of three cases.

Hardware failure of the sliding screw system used in hip fracture fixation is rare. The fatigue failure of the sliding screw is always related clinically to nonunion or refracture along the path of the screw. In both situations, cyclic loading of the implant exceeds its endurance limit, and failure can ensue. Three cases of failure of the sliding screw are presented: a nonunion of a basicervical fracture, a nonunion secondary to stress fracture at the plate-barrel junction, and a refracture through the femoral neck after healing of an intertrochanteric fracture. A biomechanical analysis of the stresses on the sliding screw focuses on design features such as the internal threaded region used for the compression screw or the barrel length that creates increased stresses in the screw, thus lowering the number of cycles to failure. Based on this analysis, recommendations are made concerning implant design and surgical technique.

Adult↗

PubMed1991

Lower limb-length discrepancy. An epidemiologic study.

Two retrospective epidemiologic studies have examined the incidence and prevalence of significant lower limb-length discrepancy and the number of surgical corrections by lengthening in 1987 in France. The incidence of apparatus prescriptions for asymmetry correction filled was 2.16 per 100,000 population. The prevalence of people using a corrective apparatus was one per 1000 population. The male-to-female ratio was 1.95:1. Because of biases in the study population, the actual incidence and prevalence of significant limb-length discrepancies is likely to be considerably higher. A questionnaire administered to surgeons of the French Orthopedic Society revealed that the majority of surgical lengthenings were performed by large orthopedic teams. In the 418 procedures reported, the tibia was lengthened more often than the femur (ratio 1.1:1). Gradual distraction techniques were used in 89.4% of cases, with the Ilizarov apparatus used in 57.4%, the Wagner apparatus in 20.6%, and the Orthofix fixator in 11.2%. Immediate distraction techniques were used in 7.9% of cases, 85% of which were done on the femur. Average total lengthening was 51 mm for tibia and femur. Average lengthening was greater for methods of gradual distraction (53.5 mm) than for immediate distraction (31.4 mm).

Adolescent↗

PubMed1990

A new canine model to evaluate the biological response of intramedullary bone to implant materials and surfaces.

A new canine model utilizing an implantable chamber with multiple bone ingrowth channels has been used to study the response of intramedullary bone to various implant materials and surfaces. The first group of dogs received implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated (HA-coated) titanium alloy, and polyethylene. A pattern of early initial bone ingrowth by 2 weeks, becoming maximal at 6 to 12 weeks with remodeling to a more mature lamellar bone, and later resorption by 24 weeks was seen for all test groups, with fibrous tissue interfaces covering the smooth test coupons at all time points. Significantly increased bone ingrowth in the sputter-HA coated group was found only at 6 weeks. The second group of dogs received implants with channels lined by surface-roughened coupons of either titanium or plasma-HA-coated titanium, half of which were also packed with a crystalline-HA grouting at the time of surgery. At both 6 and 12 weeks, bone ingrowth was greatly enhanced by the presence of the plasma-HA coating or the crystalline-HA grouting as compared to the uncoated titanium channels. Histologically, bone was seen to bond directly to the plasma-HA coating and the crystalline-HA grouting. A thin fibrous tissue layer was noted between bone and the titanium in most areas, but evidence of direct bone contact to the metal surface was seen. Mechanical testing in tension of intact coupon-bone-coupon units revealed significant strength of the bone-plasma-HA bond, with failure initiating at the metal-HA interface with forces of 15.3 N at 6 weeks, increasing to 44.8 N at 12 weeks. Plasma-HA-lined channels with crystalline-HA packing required similar forces for failure. No significant adhesion strength was noted for the titanium channels at 6 weeks, and only the crystalline-HA-filled channels displayed measurable strength of the bone-titanium interface at 12 weeks, with a force of 9 N needed for failure.

Animals↗

PubMed1990

A new canine model to evaluate the biological effects of implant materials and surface coatings on intramedullary bone ingrowth.

A new animal model for examining the intramedullary bone response to various implant materials and surfaces is presented, utilizing an implantable chamber with multiple bone ingrowth channels placed through a cortical defect in the lateral aspect of the distal femur. Twelve adult mongrel dogs received bilateral implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated titanium alloy, and UHMW polyethylene. A pattern was detected for all test groups of early initial bone ingrowth by two weeks, which became maximal at six to twelve weeks, followed by remodelling to a more mature lamellar bone and later resorption by 24 weeks, with fibrous tissue interfaces covering the smooth test coupons of all groups at all times. Significantly increased bone ingrowth in the sputter-HA coated group was found only at six weeks.

Animals↗

PubMed1989

Hydroxyapatite ceramics and the nature of the bone-ceramic interface.

Hydroxyapatite ceramics have been used as bone implants in a number of experimental systems and clinical applications. We have developed a unique experimental model that allows study of the interface between bone and implant materials. A comparison of titanium and hydroxyapatite materials, using this model, has demonstrated the osteoconductive nature of hydroxyapatite and its ability to bond directly to bone.

Animals↗

PubMed1988

Meniscal repair using an exogenous fibrin clot. An experimental study in dogs.

UNLABELLED: To evaluate the ability of a fibrin clot to stimulate and support a reparative response in the avascular portion of the meniscus, two-millimeter-diameter full-thickness lesions in the avascular portion of the medial meniscus of twelve adult dogs were filled with an exogenous fibrin clot that had been prepared from each animal. The healing response was then examined using histology and autoradiography with 35SO4 at intervals from one week to six months. The defects that had been filled with a fibrin clot healed through a proliferation of fibrous connective tissue that eventually modulated into fibrocartilaginous tissue. The fibrin clot appeared to act as a chemotactic and mitogenic stimulus for reparative cells and to provide a scaffolding for the reparative process. The origin of these reparative cells was not determined in this study, but they were thought to arise from the synovial membrane as well as the adjacent meniscal tissue. Control defects remained empty. While the reparative tissue was grossly and histologically different from the normal adjacent meniscal tissue, it was morphologically similar to the reparative tissue that was previously observed in the vascular area of the meniscus. CLINICAL RELEVANCE: The ability of an exogenous fibrin clot to stimulate and support a reparative response in the avascular portion of the meniscus may represent a potential method of avascular meniscal repair.

Animals↗