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Biomedical subjects

A A Hofmann

Publications and source records attributed to A A Hofmann.

At least 37 records · Page 2Linked to original sources
PubMed1997

Postmortem analysis of consecutively retrieved asymmetric porous-coated tibial components.

The objective of this investigation was to conduct a postmortem analysis of 8 porous-coated asymmetric tibial components to measure the extent of radiolucencies and bone ingrowth. With the use of radiographic, electron microscope, and histologic analysis techniques, a quantitative postmortem study of 8 consecutively retrieved porous-coated tibial components was conducted. Time in situ averaged 47+/-36 months. The components were secured with 4 pegs and 2 screws. Autograft bone chips were applied to the resected tibia during implantation. Contact radiographs of an average of 8 3-mm sections from each implant revealed that 73%+/-17% of the porous coating had no apparent radiolucencies present between the host bone and porous coating for the series. Backscattered electron imaging showed that the bone ingrowth averaged 6%+/-2%. Histologic analysis was unable to demonstrate any adverse cellular response. The analysis suggested that this asymmetric implant design is stable and biocompatible and has potential for long-term clinical durability.

Aged↗
PubMed1997

Analysis of particles in acetabular components from patients with osteolysis.

Acetabular polyethylene components were quantitatively analyzed for the presence of third body particles from 38 consecutively retrieved components. Backscattered electron imaging and correlated energy dispersive x-ray analysis were used for the assessments. Retrievals were divided into 4 groups based on methods of fixation and metal alloy types: 8 hydroxyapatite coated, 6 cobalt chrome porous coated, 17 titanium porous coated, and 7 cemented implants were evaluated. The backscattered electron imaging data showed that the components from the hydroxyapatite coated implants had larger particles than did the components from the cemented group. The hydroxyapatite group had 51 +/- 52 particles per mm2. The cobalt chrome alloy group had 10 +/- 9 particles per mm2, and the titanium alloy group had 9 +/- 16 particles per mm2. The cemented group had 5 +/- 4 particles per mm2. The difference between the cement group and the hydroxyapatite group was statistically significant. The elemental analysis showed that 70% of the particles in the hydroxyapatite group had calcium and phosphorus elements. Third body particles likely contribute to particulate generation. The results suggest that the hydroxyapatite coated components have the potential for producing greater amounts of particulate debris. Continued analysis of retrieved components for the presence of the third body particles is required.

Acetabulum↗
PubMed1997

Progression of human bone ingrowth into porous-coated implants. Rate of bone ingrowth in humans.

We report the measured progression of human cancellous bone ingrowth into load-bearing porous-coated titanium implants over 5 time periods (0, 3, 6, 9, and 12 months). There was a statistically significant progression of bone ingrowth into the implants over a 9-month period, but the 9- and 12-month data were not different. Investigators are advised to analyze time "0" implants in order to distinguish mechanical impaction of bone from the biological process of bone ingrowth.

Aged↗
PubMed1995

Treatment of infected total knee arthroplasty using an articulating spacer.

Twenty-six patients with late infected total knee arthroplasties were treated by debridement and removal of components and all cement, preserving collateral ligaments. At time of debridement, an articulating spacer was fashioned to allow partial weightbearing and knee range of motion (ROM) during rehabilitation. This spacer was implanted using antibiotic-impregnated bone cement. For this purpose, 4.8 g of powdered tobramycin was mixed with each 40-g batch of Simplex cement. Cement was applied early to the components, but applied late to the femur, tibia, and patella to allow molding to the defects and bone without adherence to bone. Patients received tailored intravenous antibiotic therapy for 6 weeks in addition to this antibiotic-impregnated cement for treatment of a variety of gram positive and gram negative organisms. All patients had cemented revision total knee arthroplasty using antibiotic-impregnated cement with standard cementing techniques used. All patients but 1 had reimplantation; this patient died of unrelated causes before revision. Range of motion before revision was 10 degrees to 95 degrees. Followup averaged 30 months (range, 13-70 months). The average Modified Hospital for Special Surgery Knee Score after revision was 87 points (range, 53-100 points), with 92% good to excellent results. Range of motion after reimplantation was 5 degrees to 106 degrees. There have been no recurrences of infection. Use of an articulating spacer to treat infected total knee arthroplasty improves ultimate ROM and soft tissue health and significantly decreases the risk of reinfection.

Adult↗
PubMed1994

Mineral apposition rates of human cancellous bone at the interface of porous coated implants.

Human cancellous bone ingrowth studies were conducted on 19 consenting bilateral total knee arthroplasty (TKA) patients. Titanium porous coated cylinders were implanted into the medial femoral condyle of the contralateral knee during the first of two TKAs. Retrieval was performed at the time of the second TKA (6-131 weeks later), and fluorochrome analysis was conducted. Mean mineral apposition rates (MAR) at the interface measured 1.0 micron/day, whereas 4 mm away, the peripheral bone had a mean MAR of 0.8 micron/day. This represented a 25% acceleration in the interface bone remodeling rate when compared with the periphery (P < .05). This study showed the bone advanced appositionally at the interface at a rate of approximately 1 micron/day. Analysis showed that when bone was over 50 microns from the porous coating, bone ingrowth did not occur. These results emphasize the need for surgical precision and careful postoperative management to achieve bone ingrowth.

Aged↗
PubMed1994

Analysis of the bone surface area in resected tibia. Implications in tibial component subsidence and fixation.

Anterior subsidence of the tibial component is still a clinical complication requiring revision in total knee replacement. Using the scanning electron microscope, a quantitative 3-dimensional stereoscopic and digitizing study was conducted on the cortical and cancellous bone surface area from 10 resected human cadaveric tibia. The data demonstrated that the cortical bone surface area covered an average of 6% of the total tibial surface area, cancellous bone 18%, and bone marrow space 76%. By conducting anatomic regional analysis, the data showed significantly higher (p < or = 0.05) bone quantities in the posteromedial and medial regions as compared with the anterior and anterolateral regions. These data help to explain why tibial component subsidence occurs anteriorly in total knee replacement. The data also suggest that if long-term component subsidence and loosening is to be limited, either biologic cement or bone cement would be required to increase the surface attachment between the tibial component and resected cancellous bone.

Adult↗
PubMed1994

Complications with hydroxyapatite particulate separation in total hip arthroplasty.

This study reports on the results of the implant and tissue analysis of clinically retrieved hydroxyapatite (HA)-coated implants. Five of the patients with fixed HA-coated stems had been clinically diagnosed with osteolysis. The semiquantitative histologic grading in these patients showed HA, polyethylene, and metal particles were all present (Grade 3+) in the osteolytic regions of the periprosthetic tissue. Additionally, inflammatory cells (Grade 3+) were present in these regions. Back-scattered electron (BSE) and correlated elemental analysis showed HA particulate was present in the polyethylene inserts. The HA could be distinguished from bone chips in the polyethylene based on morphology and anatomic number gray level differences. This study was limited in that no clinical results of particular HA-coated implant series were reported. Careful follow-up care in patients with coated devices is recommended.

Adult↗
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↗
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↗