Biomedical subjects

W H Harris

Publications and source records attributed to W H Harris.

At least 181 records · Page 10Linked to original sources

PubMed1992

A quantitative evaluation of periprosthetic bone-remodeling after cementless total hip arthroplasty.

Dual-energy x-ray absorptiometry analysis was used to determine the periprosthetic bone-mineral content of ten femora that had been obtained at the autopsies of five elderly patients who had had an AML (anatomic medullary locking) prosthesis in situ for seventeen to eighty-four months. Clinical radiographs showed resorptive remodeling changes characteristic of femora containing this implant. Before the absorptiometry was performed, an identical prosthesis had been inserted into the contralateral, normal femur of each cadaver. The mean difference in the periprosthetic bone-mineral content between the remodeled femora and the femora in which the prosthesis had been implanted post mortem ranged from 7 to 52 per cent, with the bone-mineral content always less in the remodeled femora. The greatest mean decrease in bone-mineral content (45 per cent) occurred adjacent to the proximal one-third of the remodeled femora. The percentage decrease in periprosthetic bone-mineral content in the remodeled femora had an inverse linear relationship with the corresponding bone-mineral content of the contralateral control femora. Preoperative analysis of bone density may therefore be useful for prediction of the extent of resorptive bone-remodeling after total hip replacement.

Absorptiometry, Photon↗

PubMed1992

Revision of the acetabular component with an uncemented Harris-Galante porous-coated prosthesis.

One hundred and forty revisions for loosening of the acetabular component were performed in 124 patients, with the use of an uncemented Harris-Galante acetabular prosthesis. A component was considered loose if there was a change in its position or vertical or horizontal migration, or both, of four millimeters or more, as demonstrated on serial radiographs. All patients were followed prospectively for a mean of forty-one months (range, twenty-four to seventy-six months). Bone-grafting was performed at the time of the revision in 127 of the hips. Identifiable failure of fixation of the acetabular component occurred in only two hips (1 per cent), which had both severe acetabular bone loss and pelvic discontinuity. In one of these hips, fixation of the component could not be achieved during the revision, and the component subsequently migrated. No other components migrated. Only one patient had a revision of the index acetabular operation. A continuous radiolucency developed at the bone-mesh interface of five acetabular components, and in one other hip a small portion of the mesh separated. This hip was reoperated on for a problem with the femur, and the socket was found to be rigidly fixed. No other evidence of loosening was identified. All of the bone grafts united, but partial resorption of the graft occurred in thirty-nine hips. Although there were substantial osseous defects that necessitated major bone-grafting, revision with the uncemented Harris-Galante porous-coated acetabular component provided superior fixation compared with that reported in other series in which cemented acetabular components were used for revision. Of the 140 hips, eighty-nine (64 per cent) had a postoperative score of good or excellent, according to the Harris hip-rating system. Twenty-eight (70 per cent) of the forty hips that had revision of the acetabular component alone were rated as good or excellent.

Acetabulum↗

PubMed1992

The progression of femoral cortical osteolysis in association with total hip arthroplasty without cement.

Twenty hips in twenty patients had development of femoral endosteal cortical erosion after a cementless total hip replacement with the Harris-Galante porous-coated implant. Serial anteroposterior and lateral radiographs of all of the affected femora were reviewed to determine the interval between the operation and the first recognition of the osteolytic lesion or lesions, as well as to evaluate the radiographic appearance and progression of the lesions. The twenty affected hips were followed for an average of fifty-three months (range, twenty to seventy-seven months) after the operation. Osteolysis was first noted radiographically at twelve to sixty-six months (mean, thirty-nine months) postoperatively; in most patients, it occurred around the distal portion of the prosthetic stem. Twelve (60 per cent) of the femoral components were shown to be loose, as proved either radiographically or operatively. Three of these components had been judged radiographically to be stable when the endosteal erosion had first been identified, but they had subsequently migrated. The remaining eight hips had no evidence of loosening. The osteolysis was more severe in the femora in which the component was loose than in those in which it was stable. Of the fourteen patients who were followed, twelve (86 per cent) had an increase in the size of the osteolytic lesions with time, and only one patient had some radiographic evidence of healing.

Adult↗

PubMed1992

Using biological measurements, can patients with benign breast disease who are at high risk for breast cancer be identified?

In order to address the question of whether biological measurements might identify women with benign breast disease (BBD) at particular risk for breast cancer, analyses were performed on cyst fluids aspirated from patients presenting with palpable breast cysts. Electrolyte profiles showed that cyst fluids may be divided into major subpopulations which differ in terms of histological appearance of cyst lining epithelium, pattern of cyst presentation, and levels of other fluid constituents such as androgen conjugates and epidermal growth factor. Analysis of cyst fluids from 18 patients who subsequently developed breast cancer 1 to 8 years later showed that 12 individuals had group A cysts, three had group B cysts, and three presented with a mixture of the two types. Therefore, although this represents an increased proportion of group A cysts as compared with the total population of cyst fluids studied over the same time period, individuals subsequently developing breast cancer were not confined to one subgroup of cysts. Androgen conjugate and growth factor content also did not predict for subsequent cancer. At the present time, it is therefore concluded that biochemical measurements in cyst fluids cannot accurately identify women likely to develop breast cancer. However, the routine aspiration of cysts does provide the opportunity to monitor the local microenvironment of the breast.

Androgens↗

PubMed1992

Prophylaxis for heterotopic bone formation after total hip arthroplasty using low-dose radiation in high-risk patients.

Fifteen consecutive total hip arthroplasties (THAs) in 14 patients considered at risk for developing significant heterotopic ossification (HO) were treated postoperatively with 7.5 Gy of external beam radiation in three fractions. Eight hips in eight of the patients (Group I) had developed previous Brooker Class III or IV HO after THA and were radiated after having excision of HO in conjunction with a revision THA. Three additional hips in three patients (Group II) were radiated after primary THA, because they developed significant HO on the contralateral hip after a previous THA. The remaining four hips in three patients (Group III) were radiated after primary THA because they had bilateral hypertrophic arthritis. Precision shielding was employed to minimize the volume of tissue in the radiation field and to protect the bone-implant interface around porous-coated components and the trochanteric osteotomy sites. Of the eight hips in which Class III or IV bone was excised during revision THA (Group I), no new bone formed in five hips and in the other three hips, only Class I bone formed. No heterotopic bone formed in the remaining seven hips of Groups II and III. All six trochanteric osteotomies healed. There were no wound healing problems. There were no significant radiolucencies around any of the components and there was no radiographic evidence of implant instability. This regimen using 7.5 Gy over three fractions minimizes the radiobiologic impact, whereas the use of precision shielding minimizes the total volume of tissue treated. This regimen is an effective means of preventing significant HO after THA in high-risk patients while minimizing radiation exposure.

Adult↗

PubMed1992

Porous-coated uncemented components in experimental total hip arthroplasty in dogs. Effect of plasma-sprayed calcium phosphate coatings on bone ingrowth.

The effect of a thin plasma-sprayed, calcium phosphate ceramic coating on bone ingrowth into titanium fiber mesh porous-surfaced prostheses was examined in a controlled canine cementless total hip arthroplasty model. Bone ingrowth was quantified using backscattered scanning electron microscopy of undemineralized sections. When good contact between the bone and porous coating was present, the calcium phosphate-coated prostheses contained significantly higher amounts of bone ingrowth at three weeks postimplantation than the uncoated control prostheses. At six weeks, however, there was no significant difference in the amount of bone ingrowth between the coated prostheses and uncoated prostheses. The ingrown bone seemed to be more intimately associated with the calcium phosphate-coated porous surfaces than the uncoated porous surfaces. When gaps at the bone-porous coating interface occurred, the calcium phosphate coating did not enhance bone ingrowth across those gaps. Plasma-sprayed calcium phosphate coatings may be useful in enhancing the early ingrowth of bone into porous-surfaced joint replacement prostheses, but they may lack long-term effectiveness. The coatings were not effective in enhancing bone ingrowth across gaps between the porous surface and the bone bed prepared at surgery.

Acetabulum↗

PubMed1992

Periprosthetic bone loss in total hip arthroplasty. Polyethylene wear debris and the concept of the effective joint space.

Thirty-four hips in which there had been prosthetic replacement were selected for study because of the presence of linear (diffuse) or lytic (localized) areas of periprosthetic bone loss. In all hips, there was careful documentation of the anatomical location of the material that had been obtained for histological analysis, and the specific purpose of the removal of the tissue was for examination to determine the cause of the resorption of bone. Specimens from twenty-three hips were retrieved during an operation and from eleven hips, at autopsy. The area of bone loss was linear only in sixteen hips, lytic only in thirteen, and both linear and lytic in five. In all thirty-four hips, intracellular particulate debris was found in the macrophages that were present in the area of bone resorption. All thirty-four had intracellular particles of polyethylene, many of which were less than one micrometer in size. Thirty-one hips had extracellular particles of polyethylene as well. Twenty-two of the thirty-four hips had intracellular metallic debris; in ten, metallic debris was found extracellularly as well. Ten of the sixteen cemented specimens had intracellular and extracellular polymethylmethacrylate debris. In the mechanically stable prostheses--cemented and uncemented--polyethylene wear debris was identified in areas of bone resorption far from the articular surfaces. The number of macrophages in a microscopic field was directly related to the amount of particulate polyethylene debris that was visible by light microscopy. Although the gross radiographic appearances of linear bone loss and lytic bone loss were different, the histological appearance of the regions in which there was active bone resorption was similar. Regardless of the radiographic appearance and anatomical origin of the specimen, bone resorption was found to occur in association with macrophages that were laden with polyethylene debris. In general, the number of macrophages present had a direct relationship to the degree of bone resorption that was seen. We believe that these findings indicate that joint fluid penetrates far more extensively than previously thought, even in a well fixed component, along the interface between the prosthesis and bone and in the periprosthetic tissues; it is often more extensive than is shown by arthrography. We therefore suggest the concept of the effective joint space to include all periprosthetic regions that are accessible to joint fluid and thus accessible to particulate debris.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1992

Will stress shielding limit the longevity of cemented femoral components of total hip replacement?

One must acknowledge the speculative nature of evaluating whether stress shielding will limit the longevity of cemented femoral components. One can, however, evaluate the data available from patients studied up to 20 years. Stress shielding does lead to disuse osteoporosis, particularly in the proximal medial cortex, and also more slowly and to a lesser extent elsewhere. Concern also exists that progressive endosteal enlargement will lead to failure of many or all cemented femoral stems. No evidence exists that disuse osteoporosis has limited the longevity of cemented femoral stems up to 20 years. Moreover, new data show that what has been described as the normal process of endosteal enlargement after inserting a cemented femoral component is a misinterpretation. What actually happens is that (1) neocortex develops around the cement mantle, (2) the original cortex thins, (3) the trabeculae in the zone of decreased density that develops between them maintain the structural integrity between those two bony masses, and (4) the implant remains rigidly fixed.

Bone Remodeling↗

PubMed1992

The first 32 years of total hip arthroplasty. One surgeon's perspective.

During the first 32 years of total hip arthroplasty, high risk of sepsis, improved prevention of infection, problems of loosening, new disease of bone lysis secondary to particulate debris, and the complexities of cementless fixation have taught orthopedic surgeons many lessons. These lessons include the following: (1) In cemented THA, bone cement can be made five-times stronger just by porosity reduction; the critical interface in a cemented femoral stem is the cement-metal interface, not the cement-bone interface; and no one has solved the long-term fixation problem in cemented sockets. (2) In cementless implants, the disuse osteoporosis that occurs around cementless femoral components can be severe; the use of cementless implants does not eliminate bone lysis; only small amounts of bone ingrowth occur in many cementless implants, particularly in revision cases; and little or no bone ingrowth occurs from grafts. Today, however, some of these lessons are ignored by surgeons. If progress is to be made in arthroplasty, these lessons from the past should be learned and warning signs of the present should be heeded.

Hip Prosthesis↗

PubMed1992

The mechanism of loosening of cemented acetabular components in total hip arthroplasty. Analysis of specimens retrieved at autopsy.

Late aseptic loosening of cemented acetabular components is governed by the progressive, three-dimensional resorption of the bone immediately adjacent to the cement mantle. This process begins circumferentially at the intraarticular margin and progresses toward the dome of the implant. Evidence of bone resorption at the cement-bone interface was present even in the most well-fixed implants before the appearance of lucent lines on standard roentgenographic views. The mechanical stability of the implant was determined by the three-dimensional extent of bone resorption and membrane formation at the cement-bone interface. The leading edge of the membrane is a transition zone from regions of membrane interposition between the cement and the bone to regions of intimate cement-bone contact. Histologic analysis revealed that progressive bone resorption is fueled by small particles of high density polyethylene (HDP) migrating along the cement-bone interface and bone resorption occurs as a result of the macrophage inflammatory response to the particulate HDP. Evidence in support of a mechanical basis for failure of fixation was lacking. The mechanism of late aseptic loosening of a cemented acetabular component is therefore biologic in nature, not mechanical. This is exactly opposite to the mechanism of loosening on the femoral side of a cemented total hip replacement, which is mechanical in nature.

Acetabulum↗

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

Effect of hand mixing tobramycin on the fatigue strength of Simplex P.

In a recent study, we showed that the presence of gentamicin in Palacos R or erythromycin plus colistin in Simplex P bone cement did not significantly decrease the fatigue strength of the cement. [J.P. Davies, D.O. O'Connor, D.W. Burke, and W.H. Harris, "Influence of antibiotic impregnation on the fatigue life of Simplex P and Palacos R acrylic bone cements, with and without centrifugation," J. Biomed. Mater. Res., 23, 379-397 (1989)] However, the commercially prepared Palacos R with Gentamicin and AKZ (Simplex P with colistin and erythromycin) which were tested are not approved by the FDA for use in the United States. Because of this, many surgeons in the United States hand mix tobramycin with the cement in the operating room if a case calls for the use of antibiotic-impregnated cement. In this study, we determined the effect of adding 1.2 g of tobramycin to one pack (40 g) of Simplex P powder on the fatigue strength of the cement. The effect of centrifugation on the fatigue strength of Simplex P with the tobramycin added was also assessed. Simplex P was prepared according to the manufacturer's instructions with and without the addition of 1.2 g tobramycin per 40-g pack and with and without centrifugation. Fifteen specimens of each of the four cement preparations were tested in fully reversed tension-compression fatigue at +/- 15 MPa, 2 Hz. The fatigue strength of the uncentrifuged and centrifuged Simplex P was not significantly reduced by the tobramycin. Centrifugation significantly increased the fatigue life of Simplex P both with and without the addition of tobramycin. The fatigue life of the Simplex P with tobramycin was increased by a factor of 8 by centrifugation.

Bone Cements↗

PubMed1991

Alterations in femoral and acetabular bone strains immediately following cementless total hip arthroplasty: an in vitro canine study.

Alterations in strain patterns in both the femur and acetabulum of the dog, due to cementless total hip arthroplasty (THA), were evaluated by monitoring cortical bone strains before and immediately following implantation of components, using an accurate in vitro jig, simulating the loading of the canine hip in vivo. Femoral arthroplasty with straight stem, canal-filling, femoral components, made of titanium-based alloy, led to a statistically significant reduction of proximal femoral bone strains, with proximal medical compressive strains reduced, on average, to only 22% of intact strain magnitude (p less than 0.01), even though the prostheses contained collars and were not fixed with cement. Strain alterations on the acetabulum, following cementless THA, were more complex and variable. Laterally, a significant decrease (p less than 0.01) in periacetabular strains to between 20 and 60% of the intact state was observed, while medial wall strains varied inconsistently after arthroplasty. These strain alterations reflect major changes in mechanical loading of both the femur and acetabulum immediately following cementless THA, using components similar to those used clinically in humans. Major reductions in strains on the proximal femur occurred with cementless femoral components, while the change in strains on the acetabulum were variable, and could be a result of variations in fit and placement of components inherent even in well-controlled implantation techniques. The physiologic in vitro loading of the canine femur with the pelvis, used to obtain these data, can be applied to future investigations exploring stress transfer around uncemented components and the relationship of stress transfer to morphological changes of bone, in the canine model.

Acetabulum↗

PubMed1991

Cost-effectiveness of prophylaxis in total hip replacement.

A theoretical analysis was performed regarding the cost-effectiveness in terms of lives saved (reduction of fatal pulmonary embolism [PE]) and in terms of money (dollars spent for prevention and treatment) of seven strategies in the management of venous thromboembolic disease in patients over 39 years of age undergoing elective total hip replacement (THR). Strikingly, this theoretical analysis suggests that low-dose warfarin combined with clinical surveillance of deep vein thrombosis would reduce the incidence of fatal PE from 20 per 1,000 patients to 4 per 1,000 patients and simultaneously reduce the charges for venous thromboembolic disease from $550,000 to about $400,000 per 1,000 patients. Based on this analysis, we strongly recommend this measure on a routine basis. Adding venography or duplex sonography routinely to this prophylactic regimen would, in this theoretical analysis, reduce the incidence of fatal PE from 4 per 1,000 patients to 0.15 per 1,000, but adds charges of $200,000 per extra life saved in the case of routine venography and $50,000 in the case of routine sonography. Low-dose warfarin prophylaxis combined with routine sonography does not generate more charges than no prophylaxis with no screening while drastically reducing the incidence of fatal PE from 20 to 0.3 per 1,000 patients. Where duplex sonography is not easily available, a 12-week postoperative course of low-dose warfarin for every patient with no routine screening will be efficacious in reducing fatal PE and as cost-effective.

Adult↗

PubMed1991

A three-dimensional non-linear finite element study of the effect of cement-prosthesis debonding in cemented femoral total hip components.

A three-dimensional non-linear finite element analysis of a cemented femoral component in which the component was partially debonded from the cement mantle was used to assess the effects of debonding on stresses in the cement. Three cases of partial cement-metal debonding were modelled with debonding of the proximal portion of the implant down to a horizontal plane which was 35, 62.5, or 82.5 mm below the prosthesis collar. Each situation was studied under loads simulating both gait and stairclimbing. Also, complete debonding between the implant and the surrounding cement mantle was modeled for loads simulating gait. Under stair climbing loads with partial cement-mental debonding, hoop stresses of 13-18 MPa were observed in the cement at the cement-metal interface at the proximal postero-medial corner of the implant. Similarly, in stair climbing, the maximum principal stresses in the cement were also adjacent to the proximal postero-medial region of the implant. These stresses were compressive and increased from 15 MPa with fully bonded interfaces to 48 MPa with debonding down to 82.5 mm below the prosthesis collar. Under gait loads, complete debonding caused high compressive stresses up to 34.9 MPa in the cement distal to the prosthesis tip. Thus, cement failure subsequent to prosthesis debonding is likely in the proximal region in a partially debonded implant due to stair climbing loads and is likely below the prosthesis tip in a fully debonded implant due to gait loading.

Body Weight↗

PubMed1991

A finite element study of the effect of diametral interface gaps on the contact areas and pressures in uncemented cylindrical femoral total hip components.

Uncemented femoral total hip components rely entirely on contact with the prepared femur for their initial fixation. The contact areas and stresses between a straight tubular bone and a metal cylindrical prosthesis 12.5 cm long and 13 mm in diameter were calculated in a finite element model which includes uniform diametral gaps varying from 20 to 500 microns, using transverse loads from 100 to 2000 N. Frictionless three-dimensional contact elements were used between the bone and the prosthesis. Contact stresses were high and irregular in all cases, and the contact areas were small. Two regions of contact were apparent for lower loads and larger gaps. A third region of contact occurred near the distal tip of the implant at higher loads. This region of contact markedly increased the contact stresses at the distal tip of the prosthesis. A 20 microns overlap between bone and implant was modelled to assess a slight interference fit. The contact stress distribution in this case was markedly different from the stress distribution with a 20 microns diametral gap. The data collectively indicates that gaps of less than 20 microns between bone and implant can substantially change contact stress distributions.

Bone Cements↗

PubMed1991

Technique to detect migration of femoral components of total hip arthroplasties on conventional radiographs.

Critical to the evaluation of patients with painful total hip arthroplasties and to the assessment of the efficacy of fixation of new prosthetic designs and/or new insertion techniques is the ability to detect migration of the femoral components. The authors present a simple and effective technique using plain radiography that can detect migration of 1 mm with a high degree of accuracy.

Equipment Failure↗

PubMed1991

Range of motion in contemporary total hip arthroplasty. The impact of modular head-neck components.

The prosthetic range of motion (PROM) of two modular total hip arthroplasty (THA) systems and one older nonmodular comparison system was evaluated. The head-neck geometry of the modular systems resulted in a smaller PROM than the nonmodular system. Longer head-neck components commonly had flanges, which caused the greatest reduction in PROM. This effect became more pronounced as head size decreased. Modular head-neck components offer recognized benefits but can be associated with notably smaller ROM and increased risk of prosthetic impingement. The surgeon should be aware that in modern systems PROM decreases when neck width is increased. Moreover, in cases of prosthetic instability the potential role of the flange of a modular head should be evaluated. Methods are suggested for maximizing PROM clinically through preoperative planning, optimal femoral neck resection, and implant utilization.

Hip Prosthesis↗