Biomedical subjects

R D Bloebaum

Publications and source records attributed to R D Bloebaum.

At least 55 records · Page 3Linked to original sources

PubMed1993

Comparison of human and canine external femoral morphologies in the context of total hip replacement.

The canine is frequently used as a model for human hip arthroplasty research. In order to better understand the appropriateness of the canine as a model for human total hip replacement studies, the external morphology of canine and human femurs were examined and compared. Several differences were found between canine and human femora, including angular measurements, anterior bow, and femoral head position relative to the femoral diaphysis. In addition, the human femur was noted to undergo age-related changes in several of the measured parameters. The canine femur did not exhibit any age-related changes in the measured parameters. This study suggests that there are limitations to the use of the canine model in human hip arthroplasty research, and that discretion must be exercised when attempting to extrapolate results from a canine study to the human clinical condition.

Adolescent↗

PubMed1993

Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue.

Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate. The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues. The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P < or = .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock. The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate.

Alloys↗

PubMed1993

Roentgenographic procedure for selecting proximal femur allograft for use in revision arthroplasty.

A roentgenographic scoring system was developed to help orthopaedic surgeons and bone banks estimate the quality of bone stock in proximal femoral allografts intended to use in revision arthroplasty. This system scores a standardized anteroposterior roentgenograph of the proximal femur using four indices representing morphological features of cancellous and cortical bone known to be clinically associated with bone strength. The indices were combined to give a weighted score, which was thought to reflect the ability of a bone to carry in vivo loads. Thirty bones were evaluated for bone mineral density using dual-photon absorptiometry. They were then sent to another institution and evaluated using the newly devised roentgenographic scoring system. The results showed that the bone score roentgenographic method is a reasonable technique for selecting allograft femurs for transplantation. This roentgenographic technique and scoring system has now been packaged into kits and is available to orthopaedic surgeons and bone banks for evaluating bone stock quality in proximal femoral allografts intended for transplantation.

Absorptiometry, Photon↗

PubMed1993

Comparative study of human cancellous bone remodeling to titanium and hydroxyapatite-coated implants.

The human cancellous bone response was compared in weight-bearing porous hydroxyapatite (HA) and titanium-coated implants placed in the distal medial femoral condyles of consenting staged bilateral knee patients. The Institutional Review Board approved study quantified the amount of bone ingrowth, the mineral apposition rate, and the bone mineral content. Results showed that the osteoconductive HA coating increased the amount of bone ingrowth by 8% (P = .018). The HA coating did not effect the mineral apposition rate of the bone but had an 8% lower bone mineral content at the implant interface (P = .042). The influence of HA coatings on human cancellous bone appears highly focal along the coating surface. Gaps of 50-500 microns filled with fibrous connective tissue were observed along the porous-coated surfaces of both implant types suggesting that HA coatings still require precision placement adjacent to human cancellous bone.

Aged↗

PubMed1993

Osteolysis from a press-fit hydroxyapatite-coated implant. A case study.

The clinical and histological results of hydroxyapatite (HA) coating separation from a press-fit total hip arthroplasty 3.3 years after surgery are documented. Semiquantitative histological analysis showed grade 3+ mononuclear histiocytes and giant cells present in the retrieved capsule and periprosthetic tissues. Grade 3+ (titanium alloy, HA, and polyethylene) particles could be seen throughout the tissues. Backscattered electron and correlated elemental analysis confirmed that the HA coating had migrated to the articulating surface of the polyethylene insert causing third-body wear. The authors suggest that the orthopedic surgeon be cautioned in the routine use of HA-coated implants if osteolysis associated with HA separation and migration is to be avoided.

Acetabulum↗

PubMed1993

Postmortem comparative analysis of titanium and hydroxyapatite porous-coated femoral implants retrieved from the same patient. A case study.

The results of bilateral postmortem analysis of titanium and plasma-sprayed hydroxyapatite (HA) porous-coated femoral components of the same Anatomic Porous Replacement design retrieved from a 35-year-old female donor are reported. Analysis was conducted using backscattered electron imaging, histology, and radiographic techniques. The appositional bone index, percent bone ingrowth, and mineral content were measured for both implants. The results showed a 177% higher appositional bone index (P = .014) for the HA porous-coated Anatomic Porous Replacement component compared to the titanium Anatomic Porous Replacement component. Backscattered electron analysis showed 50% more bone in the HA porous-coated implant (P = .028). The mineral content analysis demonstrated that the bone ingrown into the HA porous-coated device was 23% less mineralized (P = .016). The data from this case study suggested that plasma-sprayed HA porous-coated implants may assist in increasing the amount of bone ingrowth and skeletal attachment in total hip arthroplasties.

Adult↗

PubMed1993

The interosseous membrane of the forearm: structure and its role in Galeazzi fractures.

A cadaveric study was performed to anatomically describe and mechanically document the interosseous membrane of the forearm using gross, histologic, scanning electron microscopic, and mechanical testing. The membrane was found to be a complex structure composed of nerves and vessels but mainly of collagen fibers that thicken to form bands coursing from radius to ulna. Strain-gauge studies demonstrated that the load transfer occurs from the radius to the ulna via the membrane and changes with supination or pronation. With specimens under a specific test load, sectioning of the membrane allowed the fractured radius to shorten by 6.25 mm and sectioning of the triangular fibrocartilage complex resulted in shortening of 7.7 mm. Total shortening after osteotomy and sectioning of the complex structure and membrane ranged from 15 to 40 mm. In Galeazzi fractures, the interosseous membrane acts as a constraint to radial shortening. Anatomic reduction with internal fixation is indicated for this fracture-dislocation.

Aged↗

PubMed1992

Histologic analysis of a retrieved expanded polytetrafluoroethylene posterior cruciate ligament.

An expanded polytetrafluoroethylene (PTFE) prosthesis used to reconstruct the posterior cruciate ligament in a 37-year-old Caucasian male was retrieved and histologically examined in this study. Backscattered electron (BSE) microscopy, utilized to observe the mineralized tissue ingrowth into the retrieved specimen, revealed an absence of bony ingrowth within the graft. Light microscopy demonstrated an exuberant foreign body giant cell response surrounding and invading the substance of the graft, and also revealed evidence of graft degradation. These observations indicate that PTFE may not be as favorable a material for reconstruction of ligamentous tissues as previously reported.

Adult↗

PubMed1992

Hyaluronan solution as a cartilage antidesiccant.

During arthrotomy, desiccation of the articular cartilage of synovial joints by the ambient environment of the operating room causes chondrocyte death and may promote degenerative changes within the joint. This study documents the efficacy of a biomaterial, hyaluronan (HY) solution, to maintain chondrocyte viability during desiccation. Rabbit patellar articular cartilage was air-dried for 2 h with and without application of the HY solution. As assessed by 35SO4 uptake and autoradiography, the HY solution helped maintain chondrocyte viability, when compared to air dried specimens (p less than or equal to 0.02). HY solution applied to the articular surfaces of joints undergoing arthrotomy may offset the detrimental effects of desiccation, such as chondrocyte death and degenerative joint changes.

Animals↗

PubMed1992

Microscopic analysis of autograft bone applied at the interface of porous-coated devices in human cancellous bone.

This study describes the response of human cancellous bone when autologous bone chips are added at operation to the interface between host bone and porous-coated implants. During the first operation of a staged bilateral total knee arthroplasty, seven patients consented to have paired porous-coated devices implanted into their opposite medial femoral condyle. One device of each pair had autologous bone chips applied to the porous-coating, and the other was not grafted and was a control. The devices were removed en bloc at the second total knee arthroplasty 6 to 49 weeks later. Backscattered electron imaging showed significantly more bone (p < or = 0.05) in the porous-coating of the implant treated with autologous bone chips which significantly increased (p < or = 0.05) the amount of bone available at the interface. The grafted devices had a mineral apposition rate of 1.04 +/- 0.20 microns/day for the interface and 0.81 +/- 0.09 microns/day for the peripheral bone. This compared with corresponding figures of 1.03 +/- 0.38 microns/day and 0.79 +/- 0.19 microns/day at the ungrafted devices. The mineral apposition rate at the interface of the porous-coated implants was significantly increased (p < or = 0.05) relative to the host bone in the periphery. Our results support the view that autologous bone chips are effective in attaching cementless porous-coated total knee replacements to the human skeleton by bone ingrowth.

Aged↗

PubMed1992

Bone ingrowth into porous-coated tibial components implanted with autograft bone chips. Analysis of ten consecutively retrieved implants.

Ten asymmetric porous-coated tibial knee components were consecutively retrieved from nine patients with implantation times ranging from 1 week to 48 months. Morselized autograft bone chips were applied to the resected surface of the tibia prior to component implantation. Microradiographic analysis showed bone in contact with 64 +/- 10% of the porous-coated interface. Backscattered electron imaging of the bone-implant interface revealed bone within 8-22% of the porous coating. Although bone in the form of autograft bone chips was observed in the porous coating of the 1 and 3 week specimens, it was not connected to the host bone. By 3 and 6 months, the bone chips were integrated and connected to the host bone providing osseous continuity from the porous coating to the skeleton. This study shows that reproducible bone ingrowth into porous-coated tibial components is achievable using autograft bone chips to promote bone fixation.

Aged↗

PubMed1992

Implications of reference axes used for rotational alignment of the femoral component in primary and revision knee arthroplasty.

A careful review of the literature revealed that no data had been reported on the angular difference or similarity between the posterior condylar axis used by many surgeons for primary total knee arthroplasty and the transepicondylar axis, which has been considered a useful anatomical landmark for femoral component placement in revision total knee arthroplasty. The purpose of this study was to determine whether measurable differences exist between the posterior condylar axis and the transepicondylar axis of the human femur. Nineteen pairs of human donor femora were measured. This study demonstrated that when the posterior condylar axis was taken as 0 degrees of rotation, the transepicondylar axis was found to be approximately 5 degrees externally rotated for both right and left femora, a significant difference (P < .05). However, there was no statistically significant difference in the angle measured between the posterior condylar axis and the transepicondylar axis when comparisons were made between matched right and left femora (P > .05). It is suggested that this information can be applied to improving the techniques currently used in the placement of both primary and revision femoral knee components.

Adolescent↗

PubMed1992

Results of implant retrieval from postmortem specimens in patients with well-functioning, long-term total hip replacement.

The evaluation of postmortem specimens provides a unique opportunity to gain understanding of the interface between host and well-functioning prostheses unavailable from revision specimens that, by nature, are accompanied by the artifacts generated during their removal. The preliminary findings from the relatively limited number of specimens described in this collaborative study demonstrate the value of the effort and are presented to encourage surgeons to participate in this program and to make their patients aware of the value of the information they may provide.

Adult↗

PubMed1991

Retrieval analysis of a hydroxyapatite-coated hip prosthesis.

A 61-year-old woman fitted with a hydroxyapatite (HA)-coated macrotexture all-purpose hip prosthesis died three weeks after implantation. The retrieved femoral and acetabular components were examined using contact roentgenograms, the back-scattered mode of the scanning electron microscope, and light microscopy. Newly formed bone was observed in the marrow spaces and along the morselized autograft bone chips, which had been surgically placed in the medullary canal at the time of implantation. New bone was observed along 10% of the HA surface of the femoral component and 20% of the acetabular component. Some bone was also observed connecting the surrounding bone chips to the HA coating. Light microscopy showed the presence of osteoid on 20% of the femoral component and on 40% of the acetabular component. HA coating on total hip prostheses appears to enhance early skeletal attachment, which may be attributed to the osteoconductive properties of the composite.

Durapatite↗

PubMed1991

Investigation of early surface delamination observed in retrieved heat-pressed tibial inserts.

The objective was to examine possible reasons for delamination observed in tibial inserts of the porous-coated anatomic (PCA) knee replacement. To date, 33 PCA inserts have been forwarded to the authors' labs. Of these 33, 52% showed severe delamination within four years of implantation. Visual, structural, and mechanical analyses were conducted and data compared on the heat-pressed PCA type and the common machined inserts. Twenty inserts of the two different types were examined. Visual data using polarized light microscopy showed the presence of a surface layer separated from the middle region of the heat-pressed inserts by a line of demarcation 250-580 microns beneath the articulating surface. This anomaly was not observed in machined inserts. Structural analysis showed the new heat-pressed inserts had increased crystallinity in the surface layer when compared to new machined inserts. The retrieved heat-pressed inserts showed increased crystallinity in the surface and middle regions. There was a slight increase in surface crystallinity in the retrieved machined inserts. Microhardness data showed that there was an increased hardness associated with the crystallinity seen on the heat-pressed inserts. Orthopedic surgeons should be aware of early delamination and surface failure in heat-pressed inserts.

Hardness↗

PubMed1991

Bilateral tibial components of different cementless designs and materials. Microradiographic, backscattered imaging, and histologic analysis.

Postmortem evaluation was conducted on two cementless knee prostheses considered clinically successful. The two retrieved uncemented porous-coated tibial components of different designs, and materials were evaluated by microradiography, backscattered electron (BSE) imaging, and light microscopy. The right prosthesis, in place for 25 months, was a Porous-Coated Anatomic (PCA) implant with double-layered, sintered, cobalt-chromium alloy beads. The left prosthesis was a Natural-Knee (N-K) implant with a porous coating of cancellous-structured pure titanium implanted for 19 months. A quantitative microradiographic index, the appositional bone index (ABI), was developed to indicate the probability of bone ingrowth occurring into the porous coating. The ABI is a ratio of bone in apposition with porous coating divided by the total amount of porous coating available. The PCA had an average ABI of 9%, and the N-K, 67%. BSE images of the PCA demonstrated no bone within the porous coating. BSE images of the N-K implant showed bone ingrowth into 22% of the pore volume when porous coating was in apposition to host bone. Histology of the PCA revealed fibrous connective tissue throughout the porous coating and between the porous coating-bone interface. Histology of the N-K implant revealed bone ingrowth and osteoblastic activity along the bone within the porous coating.

Aged↗

PubMed1990

Reproducible methods for calibrating the backscattered electron signal for quantitative assessment of mineral content in bone.

Backscattered electron (BSE) imaging shows promise for orthopaedic and bone research. BSE images of bone may be captured on-line directly from the scanning electron microscope (SEM), and then analyzed to produce a backscattered electron profile (BSEP), a modified image graylevel histogram which is representative of the mineral content in bone. The goals of this work were 1) develop a reproducible graylevel calibration technique for bone specimens, and 2) determine a conservative time interval during which SEM operating conditions would remain stable. Calibration standards containing pure aluminum and pure magnesium wires were placed in the SEM with human cancellous bone. Baseline imaging conditions were first established by adjusting the SEM until the bone image displayed good resolution and graylevel separation between regions of different mineral content. Microscope brightness and contrast controls were randomly changed to initiate the new operating conditions of another imaging session, and graylevel values from the calibration metals were used to readjust the microscope back to baseline operating conditions. Weighted mean graylevel values of the BSEPs from calibration trials were compared to those of the baseline. Data showed that bone images could be reproduced within 1.2 percent. It was also concluded that our equipment required calibration checks at 20 minute intervals.

Animals↗

PubMed1990

Backscattered electron imaging: the role in calcified tissue and implant analysis.

The working distance and tilt studies helped to clarify the influences of specimen variability when the BSE mode is used in calcified tissue research. This work has shown that the BSEPs of cortical bone may be accurately maintained within 2 percent error over a 10 degree range of tilt, or 300 microns working distance variation. If future bone and implant investigators wish to conduct accurate, quantitative mineral microanalysis in bone, then standard grinding and polishing techniques should be adequate if calibration procedures are developed. The BSEP characteristics of the pure metals make them suitable to be used for calibrating the BSE signal. BSE analysis, with correlated biomechanical studies, will lead us to a better understanding of the relationships between structure, function, and mineral content in bone. On-line BSEP analysis techniques will expand our understanding of the mineralization events in bone which are associated with aging, weightlessness, pharmaceutical therapies, and the presence of biomaterials. The future of the BSE imaging technology and the contributions to be made in understanding the histometry, biomechanics and mineral content of bone as well as bone's response to implant materials has just begun to unfold.

Biocompatible Materials↗