Search PubMed⌕ Search

Biomedical subjects

A H Burstein

Publications and source records attributed to A H Burstein.

At least 19 recordsLinked to original sources
PubMed1996

Qualitative and quantitative analysis of orthotopic bone regeneration by marrow.

A rat model of a femoral segmental defect was used to specifically test the hypothesis that autogenous marrow has the osteogenic capability to heal a bone defect. The variables analyzed included the ratio of the marrow volume to the defect, implantation of live or dead marrow, and remodeling of established nonunions by implantation of live marrow. The uniqueness of this model allows biomechanical evaluation of the new bone formed by the implant. When live marrow was implanted, woven bone formed at 3 weeks, progressing to early lamellar bone at 6 weeks, with subsequent remodeling for as long as 12 weeks in a volumetric fashion (p < 0.05). Bone marrow, when placed in a fresh femoral defect and given in sufficient amounts, produced a rate of union comparable with that of autologous bone grafts. Mature lamellar bone formed by marrow was evaluated biomechanically; the results were statistically comparable with those of cancellous bone grafts at 12 weeks. Significant bone formation occurred when marrow was percutaneously injected in femoral nonunions, although union and remodeling did not take place in this rat model. Implantation of dead marrow resulted in rare cellular infiltration and minimal bone formation in a manner comparable with that of autogenous cancellous bone grafts. These results indicate that bone marrow can lead to structurally functional bone regeneration in an orthotopic location.

Analysis of Variance↗
PubMed1995

Coulomb frictional interfaces in modeling cemented total hip replacements: a more realistic model.

Loosening of cemented femoral hip stems could be initiated by failure of the cement mantle due to high cement stresses. The goals of this study were to determine if realistic stem-cement interface characteristics could result in high cement stresses when compared to a bonded stem-cement interface and to determine if stem design parameters could be chosen to reduce peak cement stresses. Three-dimensional finite-element models of cemented femoral hip components were studied with bonded or realistic Coulomb friction stem-cement interfaces. The results showed that the use of a non-bonded, non-linear Coulomb friction interface resulted in substantially different stress fields in the cement when compared to a bonded stem-cement interface. Tensile stresses in the proximal cement mantel for the Coulomb friction interface case (10.8 MPa) were greater than the fatigue strength of the cement. In contrast, the tensile stresses in the cement mantle were not greater than the fatigue strength for the bonded case (7.5 MPa). Failure of the cement mantle in the proximal femur could therefore be initiated by a lack of a bond at the stem-cement interface. The effect of different cross-sectional stem geometries (medial radii of 3.0, 4.9 and 5.5 mm and antero-posterior widths of 9.8 and 13.7 mm) and different elastic moduli (cobalt chromium alloy and titanium alloy) for the stem material were also evaluated for models with a Coulomb friction interface. Changes in the stem cross-section and elastic modulus had only limited effects on the stress distributions in the cement. Of the parameters evaluated in this study, the characteristics of the stem-cement interface had the largest effect on cement mantle stresses.

Alloys↗
PubMed1995

A custom distal femoral prosthesis for reconstruction of large defects following wide excision for sarcoma: results and prognostic factors.

Between 1979 and 1986, 37 patients with sarcoma of the distal femur underwent limb salvage using a custom prosthetic knee replacement. Thirteen (35%) had early complications. Fourteen (38%) had late complications, which consisted of 6 aseptic femoral loosenings, 1 aseptic tibial loosening, 2 tibial fractures, 2 contractures, 1 femoral fracture, 1 prosthetic fracture, and 1 septic loosening. By 1988, nine patients died. Thirteen prostheses failed in 12 patients, resulting in 9 revisions, 2 above-knee amputations, and 2 Van Nes rotationplasties. The 2- and 5-year prosthetic survival rates were 82% and 57%, respectively. Twenty-two of the 26 survivors (85%) had successful limb salvage. Preventable factors were implicated in the loosening of six femoral components and in one femoral fracture. The mean Hospital for Special Surgery Knee Score was 69 (range: 62 to 86).

Adolescent↗
PubMed1995

Stresses in polyethylene components of contemporary total knee replacements.

Contemporary knee designs differ considerably in the conformity that exists between the articulating surfaces of the femoral and tibial components. The thickness of the polyethylene components also varies from design to design. Conformity and thickness affect the stresses associated with surface damage and the subsequent generation of harmful polyethylene debris. In this study, the stresses and strains caused by contact were calculated for 8 contemporary knee prostheses. Finite element analysis using large-strain theory was used to determine the stresses and strains for the minimum available polyethylene thickness and for the knee in flexion. The greatest differences among designs was for the von Mises strain, which reached its maximum beneath the surface. The differences in stresses were less notable because of the nonlinear material behavior of the polyethylene. This study also confirmed the advantages of designs that have more conforming articulating surfaces and thicker polyethylene components.

Humans↗
PubMed1994

The interaction of the macrophage and the osteoblast in the pathophysiology of aseptic loosening of joint replacements.

Macrophage phagocytosis of cement particles with production of inflammatory mediators is a component of the underlying mechanism of aseptic loosening of joint prostheses. Prostaglandin E2 (PGE2), a bone resorbing mediator, has been implicated in the loosening process. Investigations have shown that macrophage phagocytosis of cement particles leads to production of bone-resorbing mediators other than PGE2. In this study, conditioned medium from macrophages exposed to crushed simplex cement particles stimulated osteoblasts to release radiolabeled arachidonic acid and metabolites. Incubation of osteoblasts in conditioned medium from macrophages exposed to cement particles small enough to be phagocytized increased PGE2 release 80-fold over unexposed osteoblasts (P < 0.001). Incubation of osteoblasts in conditioned medium from macrophages exposed to particles too large to be phagocytized, or to bone cement filtrate, did not stimulate PGE2 release. We propose that the role of the macrophage in aseptic loosening is primarily to recognize the mechanical failure of the cement mantle by phagocytosis of cement particles and subsequent production of small amounts of specific mediators. These mediators stimulate surrounding osteoblasts to secrete PGE2, which then amplifies the inflammatory response and ultimately results in bone resorption and aseptic loosening.

Arachidonic Acid↗
PubMed1994

Ticarcillin-clavulanic acid pharmacokinetics in preterm neonates with presumed sepsis.

The objective of the reported study was to characterize the pharmacokinetics of ticarcillin and clavulanic acid in premature low-birth-weight (less than 2,200 g) neonates with presumed sepsis. Eleven infants received 12 courses of ticarcillin-clavulanic acid at 75 mg/kg of body weight intravenously every 12 h. Blood samples were collected at 0.5, 1.5, 4, and 8 h following the infusion of the initial dose. The concentrations of ticarcillin and clavulanic acid were determined by a microbiologic assay. Median (interpatient coefficients of variation) values for the volume of the central compartment, total steady-state volume, distributional clearance, total clearance, and terminal elimination half-life for ticarcillin were 0.030 liter/kg (21%), 0.26 liter/kg (48%), 0.41 liter/h/kg (47%), 0.047 liter/h/kg (47%), and 4.2 h (45%), respectively. For clavulanic acid the parameters were 0.28 liter/kg (32%), 0.36 liter/kg (34%), 11 liters/h/kg (36%), 0.12 liters/h/kg (72%), and 1.95 h (40%), respectively. Our results suggest that the current dosing recommendations of 75 mg/kg every 12 h risk subtherapeutic clavulanic acid concentrations and that 50 mg/kg every 6 h is a more rational dosing strategy.

Anti-Bacterial Agents↗
PubMed1993

Studies of the mechanism by which the mechanical failure of polymethylmethacrylate leads to bone resorption.

The purpose of this study was to examine the relationship between the mechanical failure of polymethylmethacrylate and bone resorption at the bone-cement interface of a prosthesis. Evaluation of tissue that had been retrieved from the cement-bone interface of eighteen femoral components of total hip prostheses that were loose without associated infection revealed that a critical factor associated with bone resorption was the presence of particles that were small enough (one to twelve micrometers) to be phagocytized by macrophages. To study this phenomenon in vitro, macrophages in tissue culture were exposed to three preparations of polymethylmethacrylate cement. A novel method of cement preparation was used with control for solid and soluble contaminants, which provided a sensitive and specific technique for the determination of which mediators were released from the macrophages. Electron microscopy demonstrated phagocytosis of particles of less than twelve micrometers in size, regardless of the type of cement preparation. Exposure to all three cement preparations resulted in toxicity, as reflected by inhibition of 3H-thymidine incorporation. Exposure also led to increased release of tumor necrosis factor, but none of the three preparations resulted in release of prostaglandin E2. Division of the cement preparations into two groups on the basis of the size of the particles demonstrated that exposure to particles that were small enough to be phagocytized led to inhibition of 3H-thymidine incorporation and release of tumor necrosis factor, while exposure to particles that were too large to be phagocytized did not. Neither exposure to small particles nor exposure to large particles of cement led to release of prostaglandin E2. Our results show that when the mechanical failure of cement produces particles that are small enough to be phagocytized, phagocytosis of the particles results in the increased production of tumor necrosis factor by the macrophages, which may in turn lead to bone resorption and prosthetic loosening. These small particles also decrease 3H-thymidine uptake by the macrophages.

Bone Cements↗
PubMed1993

Custom-designed femoral prostheses in total hip arthroplasty done with cement for severe dysplasia of the hip.

A custom-designed femoral prosthesis was implanted with cement and a standard acetabular component was used to treat nineteen severely dysplastic hips in fourteen consecutively managed patients. Components that had been custom-designed with the use of plain radiography were used because the anatomical reconstructive goals could not be achieved with commercially available implants. These goals were to match the offset of the femoral head and the length of the lower limb with those on the normal side for patients who had unilateral involvement and to provide an average (thirty to forty-millimeter) offset with equal limb lengths for patients who had bilateral involvement. A retrospective clinical and radiographic analysis was performed. The diagnoses included coxa vara (one hip), congenital dislocation (twelve hips), achondroplasia (three hips), and spondyloepiphyseal dysplasia (three hips). The mean age at the time of the reconstruction was forty-nine years (range, twenty-two to seventy-three years), and the mean duration of follow-up was fifty-seven months (range, twenty-seven to 108 months). In five hips, bone-grafting of the acetabulum was needed to obtain superolateral coverage. The clinical result was excellent in eighteen hips and good in one. No revisions have been performed to date. Two femoral components were possibly loose radiographically. One was associated with a definite loosening of the acetabular cup. In addition, one other cup was possibly loose. There was a 100 per cent rate of survival if only a revision procedure was considered as a failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Dislocation following THA: comparison of two acetabular component designs.

One hundred ninety-seven consecutive primary cemented total hip arthroplasties using 22 mm heads were evaluated for the rate of dislocation. All surgery was performed by one surgeon through a posterior approach. A Charnley type femoral component was used in each case. Patients were divided into three groups based on the acetabular component used. Group I had 60 Charnley HPW cups implanted between January 1985 and December 1986; group II had 70 Tibac cups implanted between January 1987 and August 1987; and group III had 67 Charnley HPW cups implanted between September 1987 and February 1988. The groups were similar with regards to age, sex, original diagnosis, and surgical technique. There was a total of 11 dislocations (5.6%), of which 8 (11.4%) occurred in group II (Tibac cup). Furthermore, 6 patients (3%) developed recurrent hip dislocations, 5 (7.1%) of which were from group II. Group II had a statistically significant increase in the dislocation rate (P < .05). The authors conclude that the dislocation rate with the 22 mm Tibac cup is unacceptably high and that the design of the Charnley cup affords greater stability to the artificial hip joint than the hemispherical design of the Tibac cup.

Adult↗
PubMed1992

Custom total shoulder arthroplasty in inflammatory arthritis. Preliminary results.

Twenty-three patients with inflammatory arthritis and rotator cuff deficiency have undergone 27 custom-fit total shoulder arthroplasties. The design used included a short-stem humeral component and a metal-backed glenoid component with an offset keel. The glenoid component was custom-fit to provide maximum coverage of the glenoid surface. The average age of the patients at the time of surgery was 55 years (range, 20-75 years). All patients had inflammatory arthritis, 16 were on steroids, and all had some degree of rotator cuff involvement ranging from small to complete tears. The average length of follow-up study was 5 years (range, 3-7 years). The average preoperative shoulder score was 36 points (range, 15-50 points) with an average pain score of 7 (of 30) points. Postoperatively, the shoulder score improved to 85 points with a pain score of 28 points. Twenty-one shoulders scored a good to excellent result. Two patients required reoperation, both for recurrent rotator cuff tears, one of which occurred after a fall. Radiographic analysis revealed no incidence of humeral radiolucency and six cases of glenoid radiolucency. Only two of these were progressive and both were associated with irreparable rotator cuff tears. Thus, in the early follow-up, this design of glenoid has decreased the incidence of glenoid radiolucency in this difficult patient population.

Adult↗
PubMed1991

Telemeterized in vivo hip joint force data: a report on two patients after total hip surgery.

Two telemeterized femoral components were implanted in two patients as part of normal total hip replacement procedures. The two components were instrumented to measure the three force components directed along: (a) the neck axis, (b) transverse to the neck axis and in the plane of the prosthesis, and (c) transverse to the neck axis and perpendicular to the plane of the prosthesis. Data were collected at multiple sessions during the early postoperative period for a number of standard activities, including gait, stair climbing, rising from a chair, single leg stance, double leg stance, ipsilateral and contralateral straight leg lifts while supine, ipsilateral flexion and extension while standing, and ipsilateral abduction while standing and lying on the contralateral side. These data are summarized and compared with the published results from analytic studies and with the results from previous studies using instrumented femoral components. Peak loads for gait during the period of study were roughly 2.7 body weights (BW) when the patients walked at their normal pace. Contact forces at the hip during stationary single leg stance approximated the peak loads during gait with values ranging from 2.1 to 2.8 BW. The highest forces recorded reached values approaching 5.5 BW and occurred during periods of instability while the patient engaged in stationary single leg stance. Our in vivo data indicate that forces generated during the above activities increase in magnitude quite rapidly during the early postoperative period and that during this period the patients have the ability to perform the activities of daily living without generating the high amplitude joint contact forces suggested by the results of dynamic studies. Joint contact forces during gait were found to depend on speed, but the high absolute magnitudes predicted by model studies were not supported by the in vivo data.

Aged↗
PubMed1989

Prevention of ligament and meniscus atrophy by active joint motion in a non-weight-bearing model.

This study describes the effect of active joint motion on the maintenance of ligament and meniscus mass in a non-weight-bearing model of disuse. Denervation and fixation models of immobilization have shown that resorption of isotope and atrophy of mass occurred for hard tissue (bone) and soft tissues (ligament, tendon, or meniscus). A unilateral ankle disarticulation model of disuse that maintains active knee motion without weight bearing was studied for 8 weeks in dogs that were chronically prelabeled with three different isotopes. The effects of non-weight-bearing without denervation or fixation were analyzed for the resorption of isotopes, and net atrophy of bone mass (femur or tibia) and soft-tissue mass (collateral or cruciate ligaments, menisci). A large and similar loss of all three isotopes, as well as collagen and calcium mass occurred for whole femur and tibia; this indicated that mass loss was equivalent to bone resorption and suggests little replacement with new bone. No loss of isotope or mass per whole tissue occurred for the collateral and cruciate ligaments or menisci. The strength of the femur-anterior cruciate ligament-tibia complex was analyzed by a tensile failure test when a fast rate of deformation was applied; the results did not differ qualitatively or quantitatively between control and experimental limbs. The absence of weight bearing for 8 weeks resulted in marked bone atrophy without resorption or atrophy of soft tissues, or decrease of the mechanical strength for the femur-ligament-tibia complex.

Animals↗
PubMed1988

Telemetric force measurements across the hip after total arthroplasty.

A telemeterized total hip prosthesis was implanted in one patient and force-data were obtained. Thirty-one days postoperatively, the magnitude of the joint-contact force during double-limb stance was 1.0 times body weight. During ipsilateral single-limb stance the joint-contact force was 2.1 times body weight, and during the stance phase of gait the peak force typically was 2.6 to 2.8 times body weight, with the resultant force located on the anterosuperior portion of the ball. During stair-climbing, the force was 2.6 times body weight. At peak loads, the angle between the resultant force and the axis of the neck was 30 to 35 degrees and that between the resultant force and the plane of the prosthesis was 20 degrees. During stair-climbing or straight-leg raising, the out-of-plane orientation of the resultant force increased substantially. These data provide information concerning the forces that must be sustained by prosthetic hip joints during a number of common activities of daily living within the first month after implantation. The results also provide insight into the progression of early recovery and demonstrate the variety of forces that are generated during this period.

Aged↗