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R H Walker

Publications and source records attributed to R H Walker.

At least 37 records · Page 2Linked to original sources
PubMed1998

100 cemented versus 100 noncemented stems with comparison of 25 matched pairs.

Two series of 100 consecutive primary total hip arthroplasties, each using a single design of noncemented or cemented femoral component (all 28 mm heads), were compared. One cemented and two noncemented stems underwent revision for aseptic loosening. Of unrevised hips, outcome data statistically favored cemented, rather than noncemented, stems. The data for cemented and noncemented stems, respectively, were: An excellent to good result in 97% versus 88%; thigh pain in 3% versus 40%; subsidence in 0% versus 22%; and endosteal cavitation in 6% versus 12%. For patients with 25 unrevised matched pairs, selected by gender, age, diagnosis, and weight, outcome data also statistically favored cemented over noncemented stems, respectively: an excellent or good result in 25 versus 20 hips; thigh pain in two versus eight hips; and subsidence in none versus six hips. Midterm followup data for these concurrent total hip arthroplasty series of a mid 1980s design revealed prevalence of mechanical failure of 1% for cemented stems and 4% for noncemented stems. Corroborating matched pair comparison neutralized selection bias as a causative factor for these differences. These data indicate contemporary cemented femoral stem fixation is superior to second generation noncemented femoral stem fixation. Controlled comparative studies at midterm to long term followup, such as in this report, are needed to define outcome and indications for current third generation noncemented stem fixation.

Adult↗
PubMed1998

Polyethylene wear after total hip arthroplasty: the effect of a modular femoral head with an extended flange-reinforced neck.

The use of modular components in total hip arthroplasty has been thought to contribute to accelerated polyethylene wear. Specifically, a modular femoral head with a flange extension and a longer neck may cause increased wear. The purpose of the current study was to evaluate the effect of a flange extension on polyethylene wear. Ninety-one patients who had had a total of 100 primary total hip arthroplasties were evaluated after an intermediate duration of follow-up. All of the acetabular components consisted of a hemispherical titanium-alloy fiber-mesh porous-coated shell with a nonelevated modular polyethylene liner; they were inserted without cement and with use of supplemental screws through the dome after so-called line-to-line reaming. All of the femoral components consisted of a modular head with a diameter of twenty-eight millimeters and either a long neck (with a flange extension) or a short or medium neck (without a flange extension). The study group comprised sixty-two patients (sixty-six hips) who had had radiographic evaluation that was adequate to allow the valid measurement of polyethylene wear. Thirty-two hips were in men, and thirty-four were in women. The mean age of the patients was fifty-six years, the mean weight was seventy-three kilograms, and the mean duration of follow-up was 6.1 years (range, four to eight years). The rate of polyethylene wear in the eleven hips in which the femoral component had a flange extension was significantly greater than that in the fifty-five in which the femoral component did not have a flange extension (mean, 0.17 compared with 0.11 millimeter per year; p = 0.009). Multivariate analysis showed that the presence of a flange extension was associated with increased polyethylene wear to a greater degree (F = 2.86) than were all other variables that were measured, including a younger age (F = 1.72), a more vertical angle of the acetabular component (F = 0.49), a heavier weight (F = 0.14), male gender (F = 0.11), and a smaller initial thickness of the polyethylene (F = 0.02). These data support an association between the presence of a modular femoral head with a flange extension and an accelerated rate of polyethylene wear. The presumed mechanism is an increase in peripheral, or so-called rim, impingement of the flange-reinforced neck on the acetabulum due to a decrease in the ratio between the diameters of the femoral head and neck.

Adult↗
PubMed1997

Prospective study of 100 consecutive Harris-Galante porous total hip arthroplasties. 4- to 8-year follow-up study.

This prospective study evaluates 100 consecutive Harris-Galante Porous (Zimmer, Warsaw, IN) noncemented femoral prostheses 4 to 8 years after surgery. Two femoral components were revised for aseptic loosening. The mean Harris hip score was 56 before surgery and 92 at final follow-up evaluation, with moderate thigh pain seen in 6%. Ingrowth was classified as bony (89%), stable fibrous (8%), and unstable (3%). A pedestal formed in 18%, measurable subsidence occurred in 22%, and endosteal erosion occurred in 12%. Patients with pedestal formation had a higher incidence of unstable growth pattern (P < .05). Patients with bony ingrowth had a lower mean subsidence (0.38 mm) than those with fibrous stable ingrowth (3 mm) and unstable ingrowth (7.5 mm) (P < .05). Thigh pain correlated with the type of ingrowth, and endosteal erosion with the linear polyethylene wear. Survival analysis was 97.5% at 8 years.

Adult↗
PubMed1996

Mathematical calculations in transfusion medicine.

This article provides simple mathematical formulas for approximating values such as blood volume, red cell mass, and plasma volume. Additionally, other useful formulas and examples are given to estimate increments in hemoglobin, platelets, and factor VIII levels following the transfusion of blood components.

Blood Coagulation Factors↗
PubMed1995

Perioperative bladder management after primary total hip arthroplasty.

A retrospective review of 95 consecutive primary total hip arthroplasty patients was performed to assess the clinical outcome of two postoperative bladder management protocols. The first 49 patients (group 1) were treated with a pro re nata straight catheterization protocol. The next 46 patients (group 2) were treated with an indwelling catheterization protocol. There were no differences between the groups with respect to sex or age. The patients in group 2 had significantly lower incidences of urinary retention (P < .0005) and bladder distention (P < .0005) than those in group 1. Preoperative systemic diseases and urologic symptoms did not correlate with the occurrence of postoperative urinary retention or bladder distention. There were no infections in group 1. In group 2, one patient (2%) had bacteriuria and one patient (2%) had a urinary tract infection (P > .1). This trend of increased contamination in the catheterization group may be related to a mean catheterization duration of 72 hours.

Aged↗
PubMed1995

Total hip arthroplasty cemented femoral component distal stem centralizer. Effect on stem centralization and cement mantle.

The effectiveness, benefits, and potential risks of employing a total hip arthroplasty cemented femoral component distal centralizer were evaluated. First postoperative (6-week) radiographs of 100 primary hybrid total hip arthroplasties in consecutive groups of 50 patients without and 50 patients with a femoral stem distal centralizer were retrospectively reviewed. Femoral stems with a distal centralizer were more centralized within the femoral canal (center of stem tip to center of intramedullary canal: mean, 1.1 mm with a centralizer, 3.2 mm without; P<.0001) and more neutrally aligned (mean, 0.7 degrees valgus with a centralizer, 1.3 degrees valgus without; P < .01). Femoral stems with a distal centralizer were less likely to have a cement mantle with suboptimal thickness, that is, less than 2 mm at the medial distal femoral stem (3 of 50 stems with a centralizer, 22 of 50 stems without; chi-square, P<.0001). There were no complications, adverse effects on the cement mantle, radiographic evidence of loosening, or implant failures associated with the use of a distal centralizer, with a minimum follow-up period of 2 years.

Aged↗
PubMed1994

Suboptimal (thin) distal cement mantle thickness as a contributory factor in total hip arthroplasty femoral component failure. A retrospective radiographic analysis favoring distal stem centralization.

One hundred cemented total hip arthroplasties (THAs) were evaluated regarding the potential benefit of THA femoral component distal stem centralization, specifically regarding cement mantle thickness. Factors potentially predictive of femoral component mechanical loosening, both relating (22 factors) and not relating (41 factors) to cement, were analyzed on initial postoperative radiographs. Nine THAs with femoral component mechanical failure (group 1) were compared to (1) 88 non-failed THAs (group 2) and (2) 9 matched-paired, nonfailed THAs (group 3). Significant differences were evident regarding minimum and maximum cement mantle thickness in Gruen zone 5 and combined zones 5/6 (groups 1 vs 2 and groups 1 vs 3), with failed femoral components having thinner cement mantles. Discriminate analysis determined minimum cement mantle thickness in zone 5 to be the factor most predictive of femoral component failure. These data indicate that a suboptimal (thin) cement mantle at the medial diaphysis (Gruen zones 5 and 6) contributed to femoral component mechanical loosening in this THA series. This relationship may not pertain to femoral stems of different materials or cross-sectional characteristics. Many THA systems currently provide for a method of centralization of the femoral component distal stem as a mechanism to ensure an adequate circumferential distal cement mantle. Continued investigation into techniques directed toward centralization of the distal femoral stem is warranted by the findings of this study.

Alloys↗
PubMed1994

The femoral component in total hip arthroplasty. Six to eight-year follow-up of one hundred consecutive patients after use of a third-generation cementing technique.

One hundred consecutive patients had a primary unilateral total hip arthroplasty with use of a single design of the femoral component (Harris Precoat), inserted with a so-called third-generation cementing technique, between July 1985 and June 1987. There were seventy-four women and twenty-six men. The mean age at the time of the operation was seventy-one years (range, forty-one to ninety-two years) and the mean weight was seventy kilograms (range, forty-eight to 105 kilograms). Eleven of the 100 patients died during the follow-up period, all with the implant in place. Of the eighty-nine surviving patients, one had a revision arthroplasty for aseptic loosening. The mean duration of clinical follow-up for the remaining eighty-eight patients was seven years (range, six to eight years). The mean Harris hip score at the latest follow-up evaluation was 91 points (range, 68 to 97 points). Of the eighty-eight patients, eighty-five (97 percent) had a good or excellent result. Radiographic follow-up was performed for eighty-one patients; none had evidence of loosening of the stem, and five (6 percent) had endosteal cavitation but were asymptomatic. The rate of failure (loosening or revision) of the femoral component in the entire series was 1 per cent (one hip). The low rate of failure and the maintenance of good and excellent clinical and radiographic results during this period of follow-up are consistent with reports from other institutions. This strengthens the argument to retain or widen the existing indications for the insertion of a femoral stem with cement in primary total hip arthroplasty.

Adult↗
PubMed1994

Postoperative surveillance for deep venous thrombosis with duplex ultrasonography after total knee arthroplasty.

Duplex ultrasonography of the lower extremity was used for routine non-invasive screening for asymptomatic proximal and distal deep venous thrombosis, for monitoring of potential propagation of deep venous thrombosis from distal to proximal, and for confirmation of the resolution of proximal deep venous thrombosis after treatment. In the first part of the study, to substantiate the accuracy of duplex ultrasonography, 130 lower limbs (seventy-nine patients) were studied with that modality as well as with venography after a total hip or total knee arthroplasty. Compared with venography, duplex ultrasonography demonstrated 100 per cent sensitivity, specificity, and accuracy for the detection of proximal deep venous thrombosis and 88 per cent sensitivity, 98 per cent specificity, and 98 per cent accuracy for the detection of distal deep venous thrombosis. In the second part of the study, 100 patients who had had a total knee arthroplasty and had been managed with pneumatic stockings and aspirin for prophylaxis against deep venous thrombosis had screening of both lower extremities with duplex ultrasonography on the fourth postoperative day. Duplex ultrasonography demonstrated proximal deep venous thrombosis in seven patients and distal deep venous thrombosis in twenty-two patients; all twenty-nine patients were asymptomatic. The patients who had distal deep venous thrombosis had surveillance with serial duplex ultrasonography on the seventh and fourteenth postoperative days; five of these patients were found to have had propagation of the thrombosis to the proximal deep veins.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

The clinical course of distal deep venous thrombosis after total hip and total knee arthroplasty, as determined with duplex ultrasonography.

Duplex ultrasonography was used to screen 273 consecutive patients, on the fourth day after a total hip or total knee arthroplasty, for the presence of a distal deep venous thrombosis. Patients who had a history of thromboembolic disease or who had an active neoplasm were excluded from the study. Of the 273 patients, twenty-four (9 per cent) were found to have a proximal deep venous thrombosis (a thrombosis involving the femoral or popliteal veins) and forty-one (15 per cent), a distal deep venous thrombosis (a thrombosis involving the veins of the calf). All of the thromboses were asymptomatic. The forty-one patients in whom a distal deep venous thrombosis had been detected with duplex screening subsequently had serial duplex examinations, on the seventh and fourteenth postoperative days. If a proximal deep venous thrombosis was detected, anticoagulation was begun immediately. If no proximal thrombosis was observed, the distal thrombosis was considered stable, the serial duplex examinations were terminated, and clinical observation was continued. Of the forty-one patients who had serial examinations, seven (17 per cent) had a proximal deep venous thrombosis in the ipsilateral limb by the fourteenth postoperative day; all seven were asymptomatic, and all were managed with anticoagulation. Thirty-four patients (83 per cent) were determined to have a stable distal deep venous thrombosis on the fourteenth postoperative day, and no additional duplex examinations were performed. Thirty-three (97 per cent) of these thirty-four patients remained asymptomatic for deep venous thrombosis thereafter; the remaining patient (3 per cent) had a proximal deep venous thrombosis in the ipsilateral limb eleven months postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Secondary prevention of venous thromboembolism in joint replacement using duplex ultrasonography.

Prophylaxis of venous thromboembolism can be categorized as primary prevention and secondary prevention. Primary prevention is the deterrence of a disease process before it begins. Secondary prevention is the detection and treatment of an asymptomatic disease process before it becomes symptomatic. This discussion deals with duplex ultrasonography as a method of secondary prevention of venous thromboembolism after total joint replacement. Routine screening by venography and by duplex ultrasonography has been advocated by several authors in cases of total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, compared with venography, duplex ultrasonography has the advantages of being portable, painless, noninvasive, without side effects, less expensive and, depending on the institution, reliable as a screening and surveillance tool for managing deep vein thrombosis (DVT). Part one of a three-part study was designed to substantiate reliability of duplex ultrasonography in detecting DVT after total joint replacement in the lower extremity at our institution (Scripps Clinic and Research Foundation in La Jolla, Calif). Parts two and three were designed to evaluate the utility of duplex ultrasonography for routine screening and surveillance of DVT after THA and TKA.

Hip Prosthesis↗
PubMed1994

Routine postoperative duplex ultrasonography screening and monitoring for the detection of deep vein thrombosis. A survey of 110 total hip arthroplasties.

The use of duplex ultrasonography for routine noninvasive screening, monitoring, and management of deep venous thrombosis after total hip arthroplasty was evaluated. The reliability of duplex ultrasonography for detection of deep vein thrombosis was confirmed in an initial cohort of 51 total hip arthroplasty patients (102 lower extremities), demonstrating 91% sensitivity, 98% specificity, and 97% accuracy when compared with venography. A second cohort of 110 total hip arthroplasty patients using pneumatic compression stockings and aspirin as deep vein thrombosis prophylaxis underwent screening duplex ultrasonography of both lower extremities on postoperative Day 4. Duplex ultrasonography screening showed 10 (9.1%) patients with proximal deep vein thrombosis and 10 (9.1%) with distal deep vein thrombosis, all of whom were asymptomatic. The 10 patients with proximal deep vein thrombosis on duplex ultrasonography were prescribed therapeutic anticoagulation. Duplex ultrasonography subsequently confirmed resolution of proximal deep vein thrombosis in these patients before discontinuation of anticoagulation; none developed symptomatic pulmonary embolism through 12-month clinical followup. The 10 patients with distal deep vein thrombosis diagnosed by duplex ultrasonography were not treated with anticoagulation, but were monitored by serial duplex ultrasonography through postoperative Day 14 for propagation of distal to proximal deep vein thrombosis; none manifested symptomatic deep vein thrombosis or pulmonary embolism through 12-month clinical followup. The 90 patients with negative duplex ultrasonography results were followed clinically; 3 developed late symptomatic proximal deep vein thrombosis (1 of these later manifested pulmonary embolism). Therefore, duplex ultrasonography was used after total hip arthroplasty for the following: (1) to screen routinely in the hospital for asymptomatic proximal and distal deep vein thrombosis; (2) to monitor for potential propagation of distal to proximal deep vein thrombosis; (3) to minimize exposure to therapeutic anticoagulation by confirming the absence of proximal deep vein thrombosis in 97 of 110 patients; and (4) to demonstrate the effectiveness of mechanical and systemic deep vein thrombosis management by confirming the absence or resolution of deep vein thrombosis in all 110 patients.

Anticoagulants↗
PubMed1993

Dendritic domains of medium spiny neurons in the primate striatum: relationships to striosomal borders.

Medium spiny neurons are the projection neurons of the striatum. They receive the majority of striatal afferents, and they make up the vast majority of all neurons in the striatum. These densely spiny cells thus constitute a major substrate for input-output processing in the striatum. In the experiments described here we analyzed the dendritic fields of spiny neurons in the squirrel monkey striatum and plotted their orientations with respect to the borders between striosomes and matrix. Medium-sized spiny neurons in the caudate nucleus were filled intracellularly in a fixed-slice preparation with the fluorescent dye Lucifer Yellow. Dendritic arbors were reconstructed following immunostaining of the injected neurons with antiserum to Lucifer Yellow and counterstaining for striosome/matrix compartments. A majority of the medium spiny neurons studied had dendritic arborizations that remained within their compartment of origin. Thus the striosome/matrix subdivision not only partitions neurotransmitter molecules and extrinsic striatal connections into two domains in the primate caudate nucleus, but also constrains the dendritic arbors of many projection neurons there. Other medium spiny neurons, however, in both striosomes and matrix, had dendrites that crossed from one compartment into the other. About a quarter of the spiny neurons reconstructed had at least one such crossing dendrite. These results suggest that compartmentalization of afferent and efferent processing by projection neurons in the primate striatum is not absolute. For a subpopulation of spiny neurons in striosomes and matrix, inputs to one compartment could have a direct influence on output cells of the other.

Animals↗
PubMed1993

Dendritic arbors of spiny neurons in the primate striatum are directionally polarized.

Despite the relatively unfeatured cytoarchitecture of the striatum, this large subcortical region has been found to have a modular macroscopic substructure comprising the neurochemically distinct striosomes and matrix, and, within the matrix, patchy input and output arrangements called matrisomes. In the study reported here, we explored the possibility that the cellular architecture of the striatum is also more specialized than previously suspected. We injected medium spiny neurons in lightly fixed slices of the squirrel monkey caudate nucleus, reconstructed their dendritic arbors, and analyzed the orientations of these arbors with respect to the cardinal planes of the striatum. The data were unequivocal in suggesting that many spiny neurons, whether near striosomes or not, have dendritic arbors with preferred orientations along a diagonal axis running from rostral, dorsal, and medial to caudal, ventral, and lateral. This axis corresponds to the orientations of many striosomes and matrisomes in the squirrel monkey's caudate nucleus. We therefore suggest that the primate striatum is characterized not only by a macroscopic organization dividing it into striosomes and matrisomes, but also by a microscopic architecture observed by the dendritic arbors of many of its projection neurons. We obtained comparable supplementary observations for the ferret caudate nucleus, suggesting that such spatial alignment of spiny dendritic arbors may be a general feature of striatal organization. These polarized dendritic arrangements could provide a cellular framework for compartmental input-output processing within the striatum.

Animals↗
PubMed1993

Pelvic reconstruction/total hip arthroplasty for metastatic acetabular insufficiency.

Four cases of pathologic periacetabular insufficiency/fracture in patients with extensive neoplastic metastatic involvement of the hemipelvis were treated by pelvic reconstruction with hemipelvis pin reinforcement with total hip arthroplasty (THA). Reconstruction was reserved for patients with limited other bony or visceral metastases, and had extreme narcotic-dependent pain and debilitation, or failed prior management, but had reasonable life/activity expectancy. Tumor palliation and hemipelvis reconstruction was obtained by ilioinguinal (pelvic) and posterolateral (hip) incisions. Iliac crest exposure allowed iliacus elevation, debulking of any intrapelvic soft-tissue mass, and exposure of the medial acetabulum. Rows of threaded Steinman pins were selectively passed from iliac crest (ilioinguinal incision) to superior and medial acetabular deficiencies (hip incision) in guided antegrade fashion. A reinforced polymethylmethacrylate (PMMA) acetabular reconstruction was then created, with PMMA incorporating medial and superior pins, an anti-protrusio ring, and a standard cemented acetabular component. A long-stem cemented femoral component was placed for proximal femoral metastasis prophylaxis. Postoperative rehabilitation (mean hospitalization, 12.7 days) was as for cemented THA. Mean survival was 15 months with integrity of the hip construct maintained throughout. All four patients progressed to independent ambulation with walking aids and were gratified that they had elected surgical treatment with reconstruction.

Acetabulum↗
PubMed1993

The 1990 Comprehensive Blood Bank Surveys of the College of American Pathologists.

The performance of participants on the 1990 Comprehensive Blood Bank Surveys of the College of American Pathologists was consistent with the high quality of past surveys. The surveys include challenges in ABO and Rh typing, crossmatching, transfusion decisions, unexpected antibody detection and identification, and supplemental questions to assess contemporary practices. As in previous years, a recurrent serologic problem has been the reporting of antibodies not present in serum (anti-E in Set J-B, and anti-K in Set J-D). Such overidentification of antibodies has little implication for transfusion safety and may, in fact, represent an artifact of the survey's samples and reporting practices.

Blood Banks↗
PubMed1993

Noninfectious risks and new trends in transfusion practice.

HIV infection and hepatitis are considered major transfusion risks, but there are other serious adverse effects; circulatory overload, acute hemolytic transfusion reaction, and graft-versus-host disease. Each can be minimized by attention to preventative measures. Current transfusion practice emphasizes the appropriate use of selected components, promotion of autologous transfusions, single donor apheresis platelets, and intraoperative blood salvage. Blood cell growth factors are important in the management of patients with production disorders. Tracking of bones and tissues used as allografts will become an important function for health-care facilities.

Aged↗