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William H Harris

Publications and source records attributed to William H Harris.

At least 37 records · Page 2Linked to original sources
PubMed2005

Third-body wear testing of a highly cross-linked acetabular liner: the effect of large femoral head size in the presence of particulate poly(methyl-methacrylate) debris.

The hip simulator wear performance of an electron beam cross-linked and subsequently melted ultrahigh molecular weight polyethylene against femoral heads of 28-, 38-, and 46-mm diameter in the presence of poly(methyl-methacrylate) particulate debris was contrasted with that of conventional polyethylene against a 46-mm diameter head. Over 5 million cycles of testing, the average wear rate of the conventional polyethylene liners was 29.3 +/- 3.0 mg per million cycles. All highly cross-linked components exhibited marked reduction in wear, with the highest wear measuring 0.74 +/- 0.85 mg per million cycles. This study, using a clinically relevant third-body material, showed the electron beam cross-linked material to be far more resistant to this third-body wear than conventional ultrahigh molecular weight polyethylene, even when very large diameter femoral heads were used.

Acetabulum↗
PubMed2005

Isolated acetabular revision through the posterior approach: short-term results after revision of a recalled acetabular component.

Isolated acetabular revision is commonly associated with high rates of postoperative dislocation. We hypothesize that the dislocation rate in a series of isolated acetabular revisions for loosening of recalled acetabular components is low when strict intraoperative stability testing is coupled with re-repair of the piriformis tendon. Twenty-six isolated revisions of aseptic, loose recalled acetabular components were performed through the posterior approach by a single surgeon. All piriformis tendon and posterior capsular repairs from the index operation were considered intact at the time of revision. The piriformis tendon was re-repaired in each revision case. The average revision acetabular component was 3 mm larger than the index component. In this select group of isolated acetabular revisions, strict intraoperative stability testing and re-repair of the piriformis tendon yielded zero dislocations.

Acetabulum↗
PubMed2005

Characterization of irradiated blends of alpha-tocopherol and UHMWPE.

Adhesive/abrasive wear in ultra-high molecular weight polyethylene (UHMWPE) has been minimized by radiation cross-linking. Irradiation is followed by melting to eliminate residual free radicals and avoid long-term oxidative embrittlement. However, post-irradiation melting reduces the crystallinity of the polymer and hence its strength and fatigue resistance. We proposed an alternative to post-irradiation melting to be the incorporation of the antioxidant alpha-tocopherol into UHMWPE prior to consolidation. alpha-Tocopherol is known to react with oxygen and oxidized lipids, stabilizing them against further oxidative degradation reactions. We blended GUR 1050 UHMWPE resin powder with alpha-tocopherol at 0.1 and 0.3 wt% and consolidated these blends. Then we gamma-irradiated these blends to 100-kGy. We characterized the effect of alpha-tocopherol on the cross-linking efficiency, oxidative stability, wear behavior and mechanical properties of the blends. (I) The cross-link density of virgin, 0.1 and 0.3 wt% alpha-tocopherol blended, 100-kGy irradiated UHMWPEs were 175+/-19, 146+/-4 and 93+/-4 mol/m3, respectively. (II) Maximum oxidation indices for 100-kGy irradiated UHMWPE previously blended with 0, 0.1 and 0.3 wt% alpha-tocopherol that were subjected to accelerated aging at 80 degrees C in air for 5 weeks were 3.32, 0.09, and 0.05, respectively. (III) The pin-on-disc wear rates of 100-kGy irradiated UHMWPE previously blended with 0.1 and 0.3 wt% alpha-tocopherol that were subjected to accelerated aging at 80 degrees C in air for 5 weeks were 2.10+/-0.17 and 5.01+/-0.76 mg/million cycles, respectively. (IV) Both accelerated aged, alpha-tocopherol-blended 100-kGy irradiated UHMWPEs showed higher ultimate tensile strength, higher yield strength, and lower elastic modulus when compared to 100-kGy irradiated, virgin UHMWPE. These results showed that alpha-tocopherol-blended 100-kGy irradiated UHMWPEs were not cross-linked to the same extent as the 100-kGy irradiated, virgin UHMWPE.

Aging↗
PubMed2005

A review of current cross-linked polyethylenes used in total joint arthroplasty.

Major improvements have been made in new polyethylenes in regards to wear resistance and oxidation resistance. The background for and explanation of these improvements are presented in this study. The various manufacturing processes are described along with the possible features that the differences in manufacturing processes may have on wear, rate of particle generation, oxidation and mechanical properties. The role of some of the new polyethylenes in permitting the use of larger-diameter heads and the advantages of large-head diameters are discussed. Some of the advantages of metal-on-polyethylene versus hard-on-hard bearings also are described.

Arthroplasty, Replacement↗
PubMed2005

Ex vivo wear of conventional and cross-linked polyethylene acetabular liners.

Explanted highly cross-linked polyethylene acetabular liners show third-body scratching. It was suggested that this surface damage could increase the wear rate of highly cross-linked polyethylene. We investigated the wear behavior of surgically explanted highly cross-linked and conventional acetabular liners using a hip simulator. Highly cross-linked explants showed no weight loss. The scratches and original machine marks of the highly cross-linked liners present at explantation remained during testing; the wear rates of these liners were 1.1 +/- 2.3 mg/million cycles, representing weight gain. In contrast, conventional liners showed wear rates of -12.9 +/- 1.4 mg/million cycles, representing weight loss. Wear was associated with rapid surface polishing and scratch elimination. After testing, the liners were melted to trigger shape memory and recover plastic deformation-induced surface changes. Highly cross-linked liners showed substantial recovery of original machining marks after melting, indicating that the scratches were a result of plastic deformation and not wear. None of the conventional polyethylenes showed any recovery after melting. The wear resistance of the highly cross-linked polyethylene studied was not compromised by surface changes that occurred during the first year of in vivo service.

Acetabulum↗
PubMed2004

Optimal low-density lipoprotein is 50 to 70 mg/dl: lower is better and physiologically normal.

The normal low-density lipoprotein (LDL) cholesterol range is 50 to 70 mg/dl for native hunter-gatherers, healthy human neonates, free-living primates, and other wild mammals (all of whom do not develop atherosclerosis). Randomized trial data suggest atherosclerosis progression and coronary heart disease events are minimized when LDL is lowered to <70 mg/dl. No major safety concerns have surfaced in studies that lowered LDL to this range of 50 to 70 mg/dl. The current guidelines setting the target LDL at 100 to 115 mg/dl may lead to substantial undertreatment in high-risk individuals.

Animals↗
PubMed2004

Surface analysis of early retrieved acetabular polyethylene liners: a comparison of conventional and highly crosslinked polyethylenes.

In vivo wear behavior of 16 highly cross-linked and 19 conventional polyethylene acetabular explants, at an average in vivo duration of 6 months were studied. Highly cross-linked groups showed machining marks from the original manufacturing process in some areas and extensive scratching and some polishing of the articulating surfaces. The conventional group showed greater loss of machining marks, scratching, and polishing. Representative samples were melted to allow recovery of plastic deformation and to show true removal of material caused by wear. Melt-recovery experiments consistently showed the disappearance of surface scratches and the restoration of the original machining marks in the highly cross-linked explants. In the conventional group, few of the scratches were eliminated and only limited restoration of the machining marks was apparent. These observations support the hypothesis that the early in vivo scratching of highly cross-linked polyethylene acetabular liners is primarily caused by plastic deformation.

Cross-Linking Reagents↗
PubMed2004

Knee-simulator testing of conventional and cross-linked polyethylene tibial inserts.

We compared the resistance to delamination and to adhesive/abrasive wear of conventional and highly cross-linked polyethylene tibial inserts of a cruciate-retaining total knee design using a knee simulator. Both groups were tested after aggressive, accelerated aging, and 1 set of conventional inserts was studied without aging. Aging oxidized the conventional, but not the highly cross-linked, inserts. The simulated normal gait testing lasted for 5 and 10 million cycles for the conventional and highly cross-linked inserts, respectively. Aged conventional inserts showed delaminations, whereas none were observed in the unaged conventional and aged cross-linked inserts. Wear rates measured by the gravimetric method were 9 +/- 2 mm3, 10 +/- 4 mm3, and 1 +/- 0 mm3 per million cycles; by the metrologic method, they were 8 +/- 1 mm3, 9 +/- 2 mm3, and 3 +/- 0 mm3 for the unaged conventional, aged conventional, and aged highly crosslinked inserts, respectively. In the test model used, oxidation led to delamination, whereas increased cross-link density resulted in reduced adhesive/abrasive wear of tibial inserts.

Equipment Failure Analysis↗
PubMed2004

Effect of lipid absorption on wear and compressive properties of unirradiated and highly crosslinked UHMWPE: an in vitro experimental model.

Ultra-high molecular weight polyethylene (UHMWPE or polyethylene) components used in total joint arthroplasty absorb lipids in vivo. However, the effect, if any, of this lipid uptake on both the wear and the mechanical properties of polyethylene is not known. We contrasted the effects of lipid diffusion into the polyethylene on the wear and mechanical properties of unirradiated UHMWPE versus that into highly crosslinked UHMWPE preparation (a 95-kGy irradiated and melted UHMWPE). We doped test samples of both types of polyethylenes with either squalene alone or a 15% (w/v) solution of cholestene/squalene (CH/SQ) solution. The diffusion profiles were quantified using infrared microscopy as a function of depth away from free surfaces; we used the 1620 and 1680 cm(-1) absorbances characteristic of CH and SQ, respectively. There were no statistically significant changes in the bi-directional pin-on-disk wear rates of neither type of polyethylene after lipid absorption. On the other hand, compressive modulus and compressive strength of both polyethylenes decreased after doping with either lipid.

Absorption↗
PubMed2004

Comparison of two digital radiostereometric analysis methods in the determination of femoral head penetration in a total hip replacement phantom.

Radiostereometric analysis (RSA) has been used extensively to evaluate the magnitude and direction of penetration of the femoral head into the acetabular component of a total hip replacement as a result of polyethylene wear and creep. The accuracy and precision of an RSA study depends on several factors, including the radiographic technique, the analytical software, and the positioning of the tantalum markers. This study had three sequential purposes. First, an in vitro phantom model was used to quantify the accuracy and precision of digital images versus conventional radiography in RSA measurements of penetration of the femoral head into the acetabular shell in a total hip replacement. The Umeå RSA software package was used for analysis of both the conventional films, which were digitized at a resolution of 300 DPI, and digital radiographs, which were converted from a DICOM format at a resolution of 218 DPI. Digital radiography was found to be superior. Next, two methods of RSA analysis currently in use for determining femoral head penetration into polyethylene of total joint replacements were compared. Using the phantom model, we compared the Umeå RSA system (Biomedical Innovations AB) to the RSA-CMS (RSA Clinical Measurement Solution) and in both cases used the digital radiographs. The Umeå RSA system was found to be superior. Finally, two methods of marking the position of the acetabular component with tantalum beads were compared: one in which beads were inserted into previously described towers protruding from the back of the acetabular shell and another in which beads were placed into the peripheral flange of the polyethylene liner using the Umeå RSA analysis system of the digital radiographs. The results using the two marker configurations were similar.

Arthroplasty, Replacement, Hip↗
PubMed2004

The high hip center.

Revision of a failed acetabular component presents many challenges to the arthroplasty surgeon. The goal in most cases should be to reconstruct the acetabulum by positioning the hip center as close as possible to the anatomic hip center. However, severe acetabular bone stock deficiency and distorted acetabular anatomy often preclude placement of the acetabular component at the true anatomic hip center. In these cases, many options exist for reconstruction of the acetabulum, including placement of the cup superiorly at a high hip center. Although biomechanical studies have shown that superolateral placement of the hip center may lead to increased moments and forces across the hip (leading to potentially higher rates of loosening), superior only displacement of the hip center does not seem to adversely affect the forces about the hip. Proximal placement of the hip center facilitates contact between intact, viable host bone and the acetabular implant, thereby reducing the need for structural bone grafts, and increasing the chances for stable bony ingrowth. With proper patient selection and meticulous surgical technique, the high hip center can be a useful technique for reconstruction of the deficient acetabulum in the patient with a loose acetabular component after total hip arthroplasty.

Acetabulum↗
PubMed2004

Knee simulator wear of polyethylene tibias articulating against explanted rough femoral components.

Highly cross-linked and melted polyethylene tibial inserts have recently been introduced for clinical use to reduce fatigue damage and adhesive wear in tibial inserts. Other authors have studied the effect of counterface roughness on the wear behavior of polyethylene tibial inserts in knee simulators using femoral components that were roughened artificially. They reported a higher wear rate with highly cross-linked polyethylene than with unirradiated polyethylene tibial inserts. Artificial roughening of femoral components may not be clinically relevant. To evaluate this concern, we studied the wear behavior of highly cross-linked and conventional polyethylene tibial inserts articulating in vitro against surgically retrieved femoral components that had become roughened in vivo. The wear rate of the highly cross-linked polyethylene (5.9 and 6.8 mg/1 million cycles with 100 and 50% serum) was 80% lower than the wear rate of the conventional polyethylene (33.5 and 32.2 mg/1 million cycles with 100 and 50% serum) tibial inserts after 2 million cycles of simulated gait. This study suggests that during in vivo use, scratches that are generated on the femoral components are likely to produce a higher wear rate with both cross-linked and conventional polyethylene than a smooth femoral component, but that this wear rate is likely to be higher with conventional polyethylene than with highly cross-linked polyethylene tibial inserts.

Femur↗
PubMed2004

Conquest of a worldwide human disease: particle-induced periprosthetic osteolysis.

It is rare in the long history of human disease to encounter a completely unique disease. In the 21st century, when it does occur, the disease commonly is man-made, as is true for periprosthetic osteolysis. However, it also is rare to unravel the mysteries of a biologic process as complex as periprosthetic osteolysis in slightly longer than one generation and even less common to create the means for the worldwide prevention of an entire disease. Such is the story of periprosthetic osteolysis. The adventure from the iatrogenic creation of the disease to the identification of its pathology, to the understanding of its molecular biology and, subsequently, to its prevention, during a period of four decades, is a fascinating story of medical detective work.

Arthroplasty, Replacement↗
PubMed2004

Highly cross-linked, electron-beam-irradiated, melted polyethylene: some pros.

Extensive new evidence generated within the past the year provides strong support for the use of electron-beam highly cross-linked, subsequently melted ultra-high molecular weight polyethylene in total hip replacement arthroplasty. In terms of wear reduction, three studies involving three different demographic groups and two different measurement techniques have found that the femoral head penetration with this type of polyethylene after bedding in has finished taking place is less than 10 micra per year. This wear rate is similar to the wear rate of metal-on-metal and ceramic-on-ceramic articulations. Retrieval specimens up to 3 years after insertion confirmed the minimal wear by exhibiting persisting machine marks throughout the inside diameter of the liner. Extensive studies show no evidence of oxidation, confirming the absence of residual free radicals. No evidence of fatigue failure exists except three known cases out of 150,000, in which malposition of the acetabular component produced abnormally high contact stresses on unsupported polyethylene. The in vivo wear, oxidation resistance, and mechanical properties of this alternative bearing material are excellent, with in vivo durations now exceeding five years. The other major advantages over hard-on-hard bearings including familiarity, adaptability, forgiveness, and cost seem to be compelling.

Adult↗
PubMed2004

Cementless acetabular revision with the Harris-Galante porous prosthesis. Results after a minimum of ten years of follow-up.

BACKGROUND: Revisions of the acetabular component of a total hip arthroplasty have a higher rate of complications, particularly loosening and dislocation, than do primary procedures. The purpose of this study, in which the results of a consecutive series of revisions performed with the Harris-Galante Porous acetabular component by a single surgeon were evaluated at an average of twelve years, was to quantify the complications and outcomes of acetabular revision. METHODS: Clinical and radiographic results were evaluated to assess loosening, lysis, radiolucencies, and trochanteric union in 188 hips (170 patients) treated between 1984 and 1990. One hundred and twenty-two hips in 110 patients were followed for at least ten years, which was required for inclusion in the study. Thirty-one patients (thirty-six hips) died less than ten years postoperatively, and twenty-nine patients (thirty hips) were lost to or refused to return for follow-up. RESULTS: The average Harris hip score was 78 points at an average of 12.5 years after revision, which was a 29-point improvement compared with the preoperative score. The rate of repeat revision because of aseptic loosening of the acetabular shell was 4% (five of 122). The rate of repeat revision of the shell for any reason was 15% (eighteen of 122). Eight unrevised sockets were loose radiographically, for a total rate of aseptic loosening of 11% (thirteen of 122). CONCLUSIONS: This study demonstrated that most acetabular revisions with this cementless hemispherical socket were successful. Few structural grafts and no cages were used. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Acetabulum↗
PubMed2004

Isolated acetabular revision with use of the Harris-Galante Cementless Component. Study with intermediate-term follow-up.

BACKGROUND: Isolated revision of an acetabular total hip component is associated with special problems related to the retention of the femoral component. We reviewed the intermediate-term results of a series of such operations with use of the Harris-Galante Porous acetabular component. METHODS: We retrospectively studied the results of ninety-five isolated acetabular revisions, specifically focusing on sixty-three that had been followed for a minimum of sixty months (average, 130 months). Evaluation measures included the Harris hip score, radiographic analysis, complications, and prosthetic survival. Follow-up information was obtained with self-administered questionnaires, telephone contact, and/or clinical examination. The effects of a femoral component with a modular neck-head junction and of trochanteric osteotomy on the dislocation rate were evaluated. RESULTS: Nine shells were rerevised: four because of recurrent dislocation, four because of aseptic loosening, and one because of dissociation of the liner. The survival rate with rerevision of the shell as the end point was 90.5% at 120 months. Pelvic osteolysis occurred in 4% of the cases. The dislocation rate for the sixty-three hips was 8%. When femoral component modularity was accounted for, the analysis of the dislocations revealed a significantly higher dislocation rate for the hips without a trochanteric osteotomy (p = 0.04). Eight arthroplasties were complicated by nerve palsies, seven of which resolved fully or nearly so. CONCLUSIONS: Isolated acetabular revision with use of the Harris-Galante Porous acetabular component was associated with a low rate of loosening, lysis, and rerevision of the shell at the time of intermediate-term follow-up. However, there was a high rate of complications, including trochanteric nonunion, dislocation, and nerve palsy. The performance of a trochanteric osteotomy was associated with a decreased rate of dislocation.

Adult↗
PubMed2003

Association of hospital and surgeon volume of total hip replacement with functional status and satisfaction three years following surgery.

OBJECTIVE: To evaluate whether hospital volume and surgeon volume of total hip replacements (THRs) are associated with patient-reported functional status and satisfaction with surgery 3 years postoperatively. METHODS: We performed a population-based cohort study of a stratified random sample of Medicare beneficiaries who underwent elective primary or revision THR in Ohio, Pennsylvania, or Colorado in 1995. The primary outcomes were the self-reported Harris hip score and a validated scale measuring satisfaction with the results of surgery. Both outcomes were assessed 3 years postoperatively. Hospital volume was defined as the aggregate number of elective primary and revision THRs performed on Medicare beneficiaries in the hospital in 1995. High-volume hospitals were defined as those in which >100 such procedures are performed annually, and low-volume centers were defined as those in which </=12 procedures (primary THR cohort) or </=30 procedures (revision cohort) are performed annually. RESULTS: In unadjusted analyses, patients who underwent surgery in low-volume centers had worse functional status 3 years following primary and revision THR compared with patients whose surgery was performed in higher-volume centers. Patients whose revision THR was performed by a low-volume surgeon also had worse function. After adjustment for sociodemographic and clinical variables, however, the association between higher hospital volume and better functional status following primary THR was weak and statistically nonsignificant, and no statistically significant or clinically important associations between hospital or surgeon volume and functional status following revision THR was observed. Patients who underwent elective primary THR in low-volume centers were more likely to be dissatisfied with the results of surgery compared with patients whose surgeries were performed in high-volume centers. Similarly, patients whose surgeons performed </=12 procedures per year were more likely to be dissatisfied with the results of revision THR than were patients whose surgeons performed >12 procedures per year. CONCLUSION: Hospital volume and surgeon volume have little effect on 3-year functional outcome following THR, after adjusting for patient sociodemographic and select clinical characteristics. However, satisfaction with primary THR is greater among patients who underwent surgery in high-volume centers, and satisfaction with revisions is greater among patients whose operations were performed by higher-volume surgeons. Referring clinicians should incorporate these findings into their discussion of referral choices with patients considering THR. Conclusions regarding the effect of volume on longevity of the implants must await longer-term followup studies. Finally, further research is warranted to better understand the association between hospital and surgeon procedure volume and patient satisfaction with surgery.

Aged↗