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Biomedical subjects

M Jasty

Publications and source records attributed to M Jasty.

At least 91 records · Page 5Linked to original sources
PubMed1990

Histomorphological studies of the long-term skeletal responses to well fixed cemented femoral components.

Thirteen femora that were obtained at autopsy from patients in whom a cemented total hip replacement had been implanted from forty months to 17.5 years earlier were evaluated radiographically and morphologically. All of the patients had been functioning well, and only one of the prostheses showed radiographic evidence of loosening. Serial sections of the proximal portion of the femur that enclosed the femoral component of the prosthesis showed that the host bone was intimately and directly apposed to the cement, and fibrous tissue intervened only rarely. The bone-remodeling processes had created a dense shell of substantial new bone around the cement-mantle that resembled a new cortex, attached to the outer cortex by new trabecular struts. Evidence of ingrowth of bone from this dense shell of bone into the undulating surface of the cement was found in many areas. In the adjacent femoral cortex, there was substantial osteoporosis and cortical thinning. The cement-bone interface was intact and excellent throughout, despite the presence of fractures within the cement-mantle and de-bonding at the cement-prosthesis interface in some specimens. The cemented femoral components were well tolerated by the skeleton over a long period of use, and fibrous tissue had rarely formed at the femoral cement-bone interface of these well fixed and clinically successful prostheses. The cement-mantle was well supported by extensive medullary bone-remodeling and formation of a dense shell of new bone. The internal bone-remodeling helped to maintain the cemented femoral components over time and did not cause loosening of the prosthesis.

Adult↗
PubMed1989

The effect of centrifuging bone cement.

We have tested the porosity and fatigue life of five commonly used bone cements: Simplex P, LVC, Zimmer regular, CMW and Palacos R. Tests were conducted with and without centrifugation and with the monomer at room temperature and, except for LVC, at 0 degrees C. We found that the fatigue life of different specimens varied by a factor of nearly 100. It did not depend on porosity alone, but was more influenced by the basic composition of the cement. Simplex P when mixed with monomer at 0 degrees C and centrifuged for 60 seconds had the highest fatigue life and was still sufficiently liquid to use easily.

Bone Cements↗
PubMed1989

Biomechanical and histologic investigation of cemented total hip arthroplasties. A study of autopsy-retrieved femurs after in vivo cycling.

Eleven whole anatomic specimens of the femur were retrieved at autopsy from patients who previously had cemented total hip arthroplasty. Implant duration ranged from 0.5 to 210 months. Clinically and roentgenographically the implants were stable. A detailed biomechanical analysis evaluated bone strains and implant stability in both the single-limb stance and stair-climbing positions using a 100-pound spinal load. The stability offered by cement in these well-fixed prostheses was remarkable, with the maximum axial micromotion being 40 mu. This is a reflection of intimate osseointegration at the bone-cement interface with only rare intervening fibrous tissue. The strain gauge and photoelastic strain-coating studies revealed that marked stress shielding in the proximal medial femoral cortex persists long after a cemented femoral component is inserted. Even 17 years after surgery, the strain in the calcar region did not normalize.

Adult↗
PubMed1989

Bone ingrowth into porous coated canine total hip replacements. Quantification by backscattered scanning electron microscopy and image analysis.

Bone ingrowth into titanium fiber mesh porous-surfaced canine total hip replacement prostheses was evaluated and quantified using a computer assisted image analysis system attached to a scanning electron microscope equipped with a back scattered electron detector. Excellent contrast between the bone, the porous metal and the soft tissues resulted in the backscatter mode, allowing easy differentiation of these components in real time by the image analysis based on gray scales. By three weeks the mean (+/- standard deviation) amount of bone ingrowth expressed as a percentage of porous layer measured 7.2% (+/- 1.5%) for the acetabular components, and 3.9% (+/- 1.7%) for the femoral components. At six weeks the amount of bone ingrowth increased to 10.5% (+/- 1.3%) for the acetabular components and 8.5% (+/- 1.4%) for the femoral components. Cementless prosthetic fixation using porous surfaced prostheses holds great promise in joint replacement surgery, and the ability to quantitate the amount of bone ingrowth will permit the evaluation of the efficacy of various techniques to improve bone ingrowth.

Animals↗
PubMed1988

Limitations of the continuum assumption in cancellous bone.

Most existing stress analyses of the skeleton which consider cancellous bone assume that it can be modelled as a continuum. In this paper we develop a criterion for the validity of this assumption. The limitations of the continuum assumption appear in two areas: near biologic interfaces, and in areas of large stress gradients. These limitations are explored using a probabilistic line scanning model for density measurement, resulting in an estimate of density accuracy as a function of line length which is experimentally verified. Within three to five trabeculae of an interface, a continuum model is suspect. When results as predicted using continuum analyses vary by more than 20-30% over a distance spanning three to five trabeculae, the results are suspect.

Biomechanical Phenomena↗
PubMed1988

Results of total hip reconstruction using acetabular mesh in patients with central acetabular deficiency.

Fifty-three patients (54 hips) treated with cemented total hip reconstruction with the aid of an acetabular mesh made of Vitallium (Howmedica Inc., Rutherford, New Jersey), a cobalt-chrome molybdenum alloy, to reinforce the medial cement for deficient bone stock in the central acetabular region, were evaluated at an average follow-up period of 6.8 years (range, five to ten years). Thirty of these patients (30 hips) were treated with revision operations for either failed cup arthroplasty (ten hips), failed endoprosthesis (six hips), or failed total hip arthroplasty (14 hips) and presented difficult problems for acetabular reconstructions. Although none of the hips required reoperations for acetabular loosening, three patients showed roentgenographic evidence of acetabular component migration, and three others showed signs of impending failure of fixation of the acetabular component. The overall mean Harris hip rating improved from a mean of 43 points preoperatively to 87 points at follow-up evaluations. The extent of bone loss in the central acetabular region had the greatest influence on the results of acetabular fixation at the follow-up evaluation. None of the hips with intact medial acetabular cortex had roentgenographic evidence of failure of fixation, while 14% of the hips with medial cortical defects measuring less than 1 cm, and 75% of the hips with larger defects developed acetabular component loosening. The results of total hip reconstruction using acetabular mesh were unsatisfactory in patients with moderate or severe central acetabular bone loss and defects through the medial wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1988

The effect of centrifugation on the fatigue life of bone cement in the presence of surface irregularities.

Reduction of the porosity of bone cement by centrifugation significantly improves the fatigue life of the cement when smooth, waisted specimens are tested. However, bone cement in vivo has surface irregularities at the interdigitation of the cement with the trabecular bone. The effect of centrifugation on the fatigue life of Simplex P in specimens containing surface irregularities was investigated by examining both composite specimens of trabecular bone and bone cement and specimens containing a sharp, circumferential notch. For the specimens with the sharp notch, the bone cement that had been centrifuged lasted significantly longer in fatigue (47,039 +/- 40,277 cycles) than the uncentrifuged specimens (3103 +/- 1950 cycles). Eleven of 15 uncentrifuged specimens broke at the location of a void, rather than the notch. In contrast, when the porosity was reduced by centrifugation, 13 of the 15 specimens broke at the notch. For the specimens that were a composite of bone cement and trabecular bone, the centrifuged specimens had a significant increase in fatigue life compared to the uncentrifuged specimens when tested at both 7 MPA (641,056 +/- 444,131 cycles vs. 237,969 +/- 124,153 cycles) and 15 MPA (8800 +/- 4673 cycles vs. 1534 +/- 719 cycles). Reduction of porosity in bone cement by centrifugation significantly extends its fatigue life even in the presence of trabecular bone or sharp surface notches as used in total joint replacements. These data support the concept that reduction of porosity of bone cement by centrifugation may extend the duration of fixation of the components in cemented total joint arthroplasties.

Animals↗
PubMed1987

Total hip reconstruction using frozen femoral head allografts in patients with acetabular bone loss.

Major acetabular bone loss associated with failed total hip replacements can be managed successfully using frozen femoral heads as structural allografts during revision surgery. In 29 cases followed for an average period of 3.9 years, all of the grafts showed radiographic evidence of union. Five hips showed clinical or radiographic evidence for acetabular loosening. Three of these hips required reoperations for symptomatic loosening. In two of these, sufficient bone stock was present to permit another revision without further bone grafting. Twenty-five of the remaining 26 hips were functioning satisfactorily with a mean Harris score of 84 points. In view of the major bone loss following multiple previous operative procedures in these young patients, the results of revisions using structural femoral head allografts were clearly superior to those with resection arthroplasty, the most likely alternate solution. Graft resorption, lack of posterior coverage, and incomplete cement mantle contributed to the failures.

Acetabulum↗
PubMed1987

A study of intrusion characteristics of low viscosity cement Simplex-P and Palacos cements in a bovine cancellous bone model.

Aseptic loosening is the most common long-term complication of cemented total hip arthroplasties (THA). The functional longevity of these implants depends on the bone-cement interface. The influence of cement injection pressure, type of cement, ambient temperature, chilling of the monomer, and centrifugation of cement-on-cement intrusion depth was investigated in specimens of bovine cancellous bone. In order to validate the bovine model for comparative purposes relative to use in man, a linear relationship between human and bovine cancellous bone was first demonstrated for various porosities and cement intrusion depth. Three cements (Low Viscosity Cement [LVC], Simplex-P, and Palacos) were intruded at three different pressures (20, 40, and 60 PSI) at the same ambient temperature and relative humidity into commercially prepared plugs of bovine cancellous bone. Cement intrusion depth was proportional to injection pressure for all three cements, but was significantly different for each cement at a given pressure. At 20, 40, and 60 PSI, Palacos had a cement intrusion depth of 1.4, 2.4, and 2.8 mm respectively, while the figures for Simplex-P were 2.2, 4.2, and 5.0 mm, and for LVC were 8.0, 12.0, and 14.6 mm. Ambient temperature had an inverse relationship with cement intrusion depth for all three cements given the same experimental conditions. Chilling the monomer increased the intrusion of Simplex-P to 5.8, 8.2, and 12.7 mm at 20, 40, and 60 PSI injection pressure respectively. Simplex-P intrusion depth was not modified by cement centrifugation at any of the three injection pressures tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Formation of a synovial-like membrane at the bone-cement interface. Its role in bone resorption and implant loosening after total hip replacement.

Histologic evaluation of tissue surrounding the loosened components after joint replacement reveals the presence of a synovial-like lining adjacent to the polymethyl methacrylate cement. The tissue is heavily infiltrated with particulate cement as well as polyethylene associated with a foreign body-type giant cell reaction. That this tissue response may be responsible for the bone lysis associated with loosening is suggested by the demonstration of high prostaglandin E2 levels and enhanced bone resorbing activity in the tissue culture medium of fragments from this membrane.

Arachidonic Acid↗
PubMed1986

Comparison of multinucleated cells elicited in rats by particulate bone, polyethylene, or polymethylmethacrylate.

Osteoclasts, the multinucleated resorbing cells of bone, are identified by their characteristic morphology, unique cell membrane specializations, and more recently by the presence of cell surface antigens recognized by monoclonal antibodies. They are derived from mononuclear precursor cells of hematogenous origin. The precise relationship between osteoclasts and other types of tissue giant cells is unknown. This study was designed to examine factors involved in the recruitment and differentiation of multinucleated cells and to investigate the relationship between so-called foreign body giant cells and bone-resorbing osteoclasts. Particles of various materials were implanted into subcutaneous pockets in rats. Histological, histochemical, and electron microscopic evaluations were made of specimens harvested 12 days after implantation. Large, foamy multinucleated cells were evident around particles of devitalized bone, polyethylene, and polymethylmethacrylate. Bone particles showed scalloped surfaces and were partially resorbed. Those cells adjacent to the bone particles stained positive for tartrate-resistant acid phosphatase, in contrast to the multinucleated cells adjacent to the other materials. All the cell types had extensive rough endoplasmic reticulum, abundant mitochondria, cytoplasmic vacuoles and dense bodies, giant centrospheres, and areas of fusion of plasma membranes. Cells in lacunae on the surface of the bone particles showed a clear zone of attachment to the bone substrate and ruffled borders, a feature characteristic of in osso osteoclasts. Although the giant cells occasionally displayed an extensive clear zone of attachment to the polyethylene and polymethylmethacrylate particles, no ruffled borders were detected. The results of these studies show that the multinucleated cells elicited in response to different materials, although sharing many common features, do demonstrate certain features that are substrate specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1982

Osteopetrosis. A morphological study of twenty-one cases.

Twenty-one patients, two months to seventy-eight years old, with clinically diagnosed osteopetrosis showed radiographic and histological variations in the formation of radiodense skeletal tissue at all ages. Pathologically the abnormal tissue was composed of both lamellar bone and calcified cartilage. We deduced that the abnormality or abnormalities of osteoclast function that cause the observed changes vary in severity from time to time in individual patients. Periods of remission in the less severely affected patients apparently had permitted the formation of bone-marrow spaces and allowed hematopoietic tissue to form in these patients. The patients who died of the disease did so because of anemia or its resulting complications. Some children with a lethal form of the disease had rickets and epiphyseal fractures in addition to the osteopetrosis. Focal areas of osteomalacia were observed in two specimens from adults. Traumatic and stress fractures were frequent complications at all ages.

Adolescent↗
PubMedDate not supplied

Determination of loading parameters in the canine hip in vivo.

The loading parameters in the canine hip were determined from multiple studies, involving the collection of kinematic and force plate data in vivo joint reaction force from an instrumented hip replacement prosthesis, and in vivo femoral cortical bone strain gauge data in different dogs. In the middle of the stance phase of gait the canine femur was flexed 110 degrees with respect to the pelvis and formed a 20 degree angle relative to the floor. At this point in the gait cycle, a line passing from the superior to the inferior aspect of the pubic symphysis was parallel to the floor. The joint reaction force measurements showed that the net force vector during midstance was directed inferiorly, posteriorly, and laterally, with a peak magnitude of up to 1.65 times the body weight. A torsional moment of 1.6 N m is exerted about the femoral shaft. In vivo strain data showed that during gait peak compressive strains of -300 to -502 microstrain were produced on the medial aspect of the femoral cortex and peak tensile strains of +250 to +458 midstrain were produced on the femoral cortex. At the midstance phase of gait, principal cortical bone strains were rotated up to 29 degrees relative to the long axis of the femur, suggesting torsional loads on the femur. These data in combination provide valuable insights on the loading parameters of the canine hip which can be used in future applications of the canine as a model for evaluating mechanically based phenomena such as bone ingrowth and remodeling or hip prostheses.

Animals↗
PubMedDate not supplied

Biomechanics of cemented and cementless prostheses.

The success of the cemented arthroplasty is due primarily due to excellent initial stability, intimate contact with the prepared bone and the isoelastic properties provided by the cement. In an experimental in vitro study, the initial stability of both the cemented and uncemented femoral components was measured and it was found that they were both very stable in simulated single limb stance (maximum motion of less than fifty microns). However, in simulated stair climbing, the uncemented components were more unstable than the cemented components (maximum micromotion of 76 microns for cemented and 280 microns for uncemented), and this relative instability of the uncemented femoral components could compromise the bone ingrowth. Studies on femurs retrieved at autopsy from patients who underwent cemented total hip arthroplasty two week sup to seventeen years earlier and were functioning well, have shown that the failure of cemented femoral components is initiated primarily by mechanical factors, consisting of debonding at the cement-prosthesis interface and fractures of the cement rather than lack of bone ingrowth or fibrous tissue formation at the interface. Thus the problems with using cemented femoral components involve the poor strength of the cement-prosthesis interface and the cement, while the problems with cementless components involve the difficulties in precisely machining the femoral canal, and providing rigid stability as well as accurate fit.

Adult↗