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Biomedical subjects

W H Harris

Publications and source records attributed to W H Harris.

At least 127 records · Page 7Linked to original sources
PubMed1994

Tensile bonding strength of the cement-prosthesis interface.

A widely held belief among orthopedic surgeons is that there is no adhesion between polymethylmethacrylate bone cement and metal. However, a bond does form between the cement and the standard grit-blasted implant finish. Moreover, it has been shown that disruption of this bond or "debonding" of this interface is a major factor in the initiation of failure of some cemented total joint arthroplasties. It is the purpose of this study to determine the tensile pull-off strength of the bone cement-implant surface interface. A 1.27 cm (0.5 in) layer of Simplex-P bone cement was cured between two Co-Cr-Mo pins of 2.22 cm (0.875 in) diameter which had the standard implant finish on the surface that was interfaced with the cement. The specimens were tested in an MTS machine in stroke control with a cross head rate of 1 in per minute. The maximum load to failure was recorded. Bonding of the cement to the surface does occur. The tensile pull-off strength of the bone cement-implant surface interface is approximately 5 MPa. Other studies have shown that maintaining this bond between the stem and cement is important in maintaining the stability of cemented total joint arthroplasties.

Adhesiveness↗
PubMed1994

Etiology of osteolysis around porous-coated cementless total hip arthroplasties.

The prosthetic components and tissues retrieved from 12 hips with osteolysis in association with well-fixed cementless porous-coated total hip prostheses (5 Porous Coated Anatomic, 6 Harris-Galante Porous, and 1 Omniflex) were examined using a variety specific techniques including electron microscopy, standard histology, immunohistochemistry, and particle identification. The patients were young and active. Extensive osteolysis developed in all 12 femurs and 3 acetabula between 36 and 84 months after arthroplasty (mean, 63 months). All of the polyethylene liners were noted to be worn substantially (mean volumetric wear, 1140 +/- 810 mm3). The wear was unrelated to the head diameter in this small number of cases. In all 12 cases, the articulating surfaces were wear polished and contained numerous fine multidirectional scratches, suggesting 3-body abrasive wear mechanisms in addition to adhesive wear liberating very small (micron to submicron) wear particles. In 4 cases, surface delamination and flaking of polyethylene were also found, suggesting fatigue wear liberating larger wear particles. Nine of 10 cobalt alloy heads showed numerous fine scratches with sharp edges presumably from 3-body abrasive wear. Corrosion and fretting at the femoral head-neck junction in 5 cases, burnishing of the femoral stem against bone in 4 cases, and metal staining of tissues opposite the porous coatings in 7 cases provided evidence for the liberation of fine metal particles from outside the articulation. Histologic and immunohistochemical studies of tissue in the regions of osteolysis in all cases showed numerous focal aggregates of KP1 antibody positive activated macrophages containing large amounts of submicron intracellular particles of polyethylene (presumably related to the 3-body abrasive wear polishing) and giant cells within a fibrous stroma. In 5 cases, some of the macrophages also contained submicron metal particles but smaller in numbers. T lymphocytes, plasma cells, and mast cells that might indicate hypersensitivity were found in 4 of the 12 cases (33%), and none of the cases had B lymphocytes. These data suggest that abrasive wear at the articulation leads to the liberation of abundant fine particulate wear debris of polyethylene into the tissues around cementless prostheses. Small amounts of particulate metal debris are also liberated from corrosion and fretting of the metal components and can contribute to accelerated 3-body abrasive wear at the articulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

A composite plug for occluding the femoral canal prior to cementing a total hip femoral component.

An improved technique is presented for placement of a combined polyethylene and polymethylmethacrylate (PMMA) plug in the femoral medullary canal prior to cementing the femoral component during total hip arthroplasty. PMMA plugs provide excellent occlusion of the canal, but when used alone they often become excessively long. This can make revision surgery, if it becomes necessary, more difficult. By first inserting a polyethylene plug distally in the femoral canal, followed by a bolus of PMMA, the surgeon can limit the length of the cement portion of the plug in the femoral canal while retaining the advantages of a PMMA plug.

Cementation↗
PubMed1994

Osteolysis around uncemented acetabular components of cobalt-chrome surface replacement hip arthroplasty.

Ten cases of major osteolysis were identified in patients with hemispherical cobalt chrome acetabular components of cementless resurfacing total hip prostheses at follow-up examinations ranging from two to five years. All components were porous coated with cobalt chrome spheres and were stabilized initially with screws. Five patients were women and five were men, with ages ranging from 20 to 59 years. The radiolucent cystic lesions with peripheral rims of reactive bone formation appeared one to five years after the operation. They measured from 1.5 to 6 cm in the largest diameter and were most often found adjacent to the screws used to secure the acetabular components to the skeleton. On the radiographs, none of the components appeared to be loose. Three patients had revision surgery. In two of the three cases, the implants were found to be firmly fixed. There was no clinical or bacteriologic evidence of infection. The polyethylene articulating surface showed signs of wear in all three cases and in one of the three it dislocated from the metal shell. Granulation tissue was found in the regions of osteolysis, and the diseased tissue contained numerous macrophages and giant cells. Lymphocytes and plasma cells were rare. Numerous small particles of phagocytosed polyethylene and metal in the cells were noted in two cases, whereas only polyethylene was found in the third.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1994

Long-term results of cemented femoral revision surgery using second-generation techniques. An average 11.7-year follow-up evaluation.

From a group of 43 hips in 41 patients, previously reported at an average of six years of follow-up evaluation, in whom second-generation cementing techniques were used during femoral revision hip surgery, 38 hips in 36 patients were rereviewed at an average follow-up period of 11.7 years (range, 118-172 months). The average age of the patients at the time of revision surgery was 52.8 years. Only four femoral components (10.5%) required rerevision for aseptic loosening. Of those not rerevised, the average Harris hip score at the time of follow-up evaluation was 81. Four additional hips (10.5%) had radiographic evidence of definite femoral component loosening. The survival of 90% of the implants of cemented femoral revision surgery and the 79% incidence of well-fixed femoral components for more than 11.7 years is attributed to the improved cementing techniques and modern stem design.

Adult↗
PubMed1994

Surface damage to cobalt-chrome femoral head prostheses.

Fifty-four cobalt-chrome alloy femoral heads were retrieved at revision surgery or at post-mortem; 23 came from uncemented, eight from hybrid and 23 from cemented hip arthroplasties. The uncemented and hybrid implants had porous coating, metal backing and modular femoral heads; with one exception none of the cemented implants had any of these. Twenty-five of the 31 heads from uncemented and hybrid arthroplasties, and 11 of the 23 heads from cemented arthroplasties showed surface damage involving more than 25% of the surface. Scanning electron microscopy revealed multidirectional fine scratches 1 micron to 10 microns in depth and width which appeared to have been made by fine, hard particles. There was a higher rate of such damage in the uncemented and hybrid arthroplasties than in the cemented implants, suggesting that the abrasive particles were mainly released from the metal, rather than from the cement or polyethylene components of the implants.

Adult↗
PubMed1993

Histologic identification of polyethylene wear debris using Oil Red O stain.

Ultra high molecular weight polyethylene (UHMWPE) wear particles are frequently implicated in causing failure of total joint arthroplasties by eliciting a foreign body reaction. The majority of these particles are subcellular and many are submicron in size. Identification of these small particles of UHMWPE by conventional histologic techniques is difficult. We have therefore investigated the utility of Oil Red O (ORO) stain to identify UHMWPE on histologic sections. A wide variety of specimens was studied including an experimental rabbit model with subcutaneous implantation of polyethylene particles as well as specimens from clinical cases with joint arthroplasties. The sensitivity and specificity of ORO stain was compared to conventional polarized light microscopy for the identification of particulate UHMWPE debris. The ORO stain was found to be as sensitive in identifying particulate UHMWPE debris as polarized light microscopy. However, ORO stain was less specific: two specimens did not contain any UHMWPE also stained with ORO. Careful examination of standard hematoxylin and eosin stained sections with polarized light was therefore more specific for the identification of particulate UHMWPE. As a single test, the ORO stain does not appear to offer any clear advantage specifically for the identification of UHMWPE.

Animals↗
PubMed1993

Extensive porosity at the cement-femoral prosthesis interface: a preliminary study.

This study is the first description of the extensive porosity which is preferentially located at the cement-prosthesis interface of cemented femoral components of total hip replacements. The observation is important because the interfacial porosity may decrease the strength of the cement-femoral prosthesis interface and jeopardize the mechanical integrity of the cement mantle. We examined the cement-metal interfaces from a multiplicity of in vivo and in vitro specimens using both optical and scanning electron microscopy. These samples included several stem designs, implants made from either Co-Cr or Ti alloy, implants made with a variety of surface finishes and both centrifuged and uncentrifuged cement. All in vivo and in vitro samples had marked porosity in the cement focally concentrated at the cement-metal interface. The amount of porosity at the interface greatly exceeded the amount of general porosity found throughout the bulk cement. Centrifuging did not affect the interfacial porosity, and neither did alloy nor surface finish. The presence of these pores may be explained by the rheological characteristics of the cement.

Alloys↗
PubMed1993

Comparison of bone ingrowth into cobalt chrome sphere and titanium fiber mesh porous coated cementless canine acetabular components.

Bone ingrowth into uncemented hemispherical canine acetabular components porous-coated with cobalt chrome spheres was compared to those porous-coated with titanium fiber mesh. While good bone ingrowth was noted in both types of porous coatings at 6 weeks after surgery with no difference in the histologic quality of the ingrown bone, quantitation of bone ingrowth showed that significantly more bone grew into titanium fiber mesh porous-coated components. The mean amount of bone ingrowth measured 10.5% of the area of the porous coating with fiber mesh coatings and only 5.5% of the area of the porous coating with spherical coatings (significant difference at P < .0005). The mean area density of the ingrown bone inside the pores measured 21.5% of the pore area with fiber mesh coatings, also significantly greater than 13.4% of the pore area with sphere coatings (P < .025). The ingrown bone penetrated a mean 66% of the depth of the porous layer with fiber mesh coatings compared to 32% of the depth of the porous layer with spherical coating (significant difference at P < .0005). The mean extent of the periphery of the porous layer with bone ingrowth was 88% for the mesh coatings and 55% for the spherical coatings (also a significant difference at P < .01).

Acetabulum↗
PubMed1993

Challenge to the concept that UHMWPE acetabular components oxidize in vivo.

Severe wear of the ultra-high molecular weight polyethylene (UHMWPE) components of total joint replacements limits their long-term success. In previous studies, the infrared spectra obtained on retrieved UHMWPE components were interpreted as evidence that the UHMWPE oxidizes in vivo. In direct contrast, infrared spectroscopy of the retrieved UHMWPE acetabular components examined in this study demonstrated adsorbed esterified fatty acids, readily extractable by hexane, and no substantial evidence of in vivo oxidation. This emphasizes that special care must be taken when using infrared spectroscopy to assess retrieved components.

Adult↗
PubMed1993

Strength of cement-metal interfaces in fatigue: comparison of smooth, porous and precoated specimens.

Radiographic follow-up studies of cemented total hip arthroplasty have shown that failure of the cement-metal interface of the femoral component is as high as 25% at 10 years. Recent analyses of clinically successful cemented femoral components obtained in toto with the surrounding cement and femurs after many years of in-vivo service have suggested that the mechanism of the initiation of failure of fixation of cemented femoral components is debonding at the cement-metal interface. Since this critical interface is subjected primarily to cyclic loading, the evaluation of different surface preparations should be studied in fatigue, not static testing. In the current study, several contemporary methods for increasing the strength of the cement-metal interface were evaluated by testing the interfacial fatigue pushout strength under varying conditions of cyclic loading. The effect of a smooth 'implant finish' surface, a surface coated with polymethylmethacrylate (PMMA precoated surface), a combination of a textured surface with PMMA precoat, and a porous titanium mesh coated surface were examined. Precoating the metal with a thin film of PMMA significantly increased the number of compressive fatigue loading cycles required for failure of the cement-metal interface under cyclic loading compared to a smooth, uncoated surface. Adding indentations to the surface and then precoating with PMMA further significantly increased the fatigue life of the cement-metal interface. The strongest interface in fatigue was the titanium fibermesh-cement interface.

Bone Cements↗
PubMed1993

In vitro and in vivo studies of pressurization of femoral cement in total hip arthroplasty.

Improvements in cementing techniques in the absence of pressurization of the cement have led to major increases in the long-term success rate of fixation of the femoral components of cemented total hip arthroplasty (THA). The strength of the cement-bone interface is strongly related to cement intrusion into the bone. The depth of cement intrusion, in turn, is correlated with the cement-intrusion pressure. Thus, adding cement pressurization to those current techniques that have already been validated may further increase the long-term durability of fixation of the femoral component of cemented THA. To assess cement pressurization in the proximal femur for THA, the authors compared in vitro the efficacy of three existing pressurization systems (the Johnson and Johnson system [New Brunswick, NJ], the Miller system [Zimmer, Warsaw, IN], and the Zimmer system [Zimmer]) in cadaver femurs using pressure transducers and evaluated their ease and optimization for clinical use. The authors then selected one (the Zimmer system) for use in studies in vivo to quantify the actual pressures achieved in the medullary canal in vivo under surgical conditions using pressure transducers placed throughout the femoral cortex. Each of the three commercially available femoral cement pressurization systems has its own advantages and disadvantages. All three systems were shown to produce average peak cement-intrusion pressures in vitro of over 21 N/cm2 (30 psi) throughout the cement mantle including, importantly, in the proximal portion of the femur.(ABSTRACT TRUNCATED AT 250 WORDS)

Cementation↗
PubMed1993

Placental transfer of local anaesthetics in the premature sheep fetus.

This study was designed to test whether there is any difference in the placental transfer of bupivacaine or lidocaine in the early compared to the late preterm maternal/fetal sheep preparation; and whether the premature lamb fetus reacts to a steady state local anaesthetic infusion differently from the same lamb near term. Eleven ewes were studied in two groups receiving bupivacaine (group A) or lidocaine (group B). Hysterotomy and insertion of fetal and maternal lines were performed at 110 days gestation, and studies were repeated weekly using the same local anaesthetic until delivery. We found no difference in maternal or fetal cardiovascular responses to bupivacaine or lidocaine in the early (mean 119 days) compared to the late (mean 132 days) preparations. The levels of bupivacaine and lidocaine in the fetal blood were similar in early and late fetuses, as were the fetal/maternal ratios of both drugs.

Journal Article↗