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Richard L Wixson

Publications and source records attributed to Richard L Wixson.

9 recordsLinked to original sources
PubMed2006

Total hip arthroplasty with the porous-coated anatomic hip prosthesis: results at 11 to 18 years.

The authors had previously reported good results with apparent fixation of a series of porous-coated anatomic hips at 2 to 4 years. In a larger series of 133 hips with porous-coated anatomic uncemented components, 91 hips in 82 patients were available for a follow-up of 11 years or greater. Although 3.1% of acetabular cups had migrated or had been revised at 2 to 4 years; at 11 to 18 years, there was 37% lysis, 21.7% migration, and 32.3% revision. For the femur at 2 to 4 years, there was 3.1% migration and 1.5% revision. At 11 to 18 years, there was 27.2% lysis (proximal only), 6.6% migration, and 3.2% revision. Survival analysis for migration or revision for the femoral was 94%, and for the acetabular component, 63%, deteriorating markedly after 10 years.

Adolescent↗
PubMed2006

Computed tomographic follow-up evaluation of operative intervention for periacetabular lysis.

Computed tomography (CT) accurately evaluates periacetabular lytic lesions. The purpose of this study is to determine the fate of osteolytic lesions after treatment with liner exchange and bone grafting. Fifteen patients who had undergone liner exchange with grafting for progressive lytic lesions, as demonstrated by preoperative CT scans, were identified. Postoperative CT scans were performed at a minimum of 2 years post revision. The largest cross sectional lytic area was compared with the postoperative scan to determine the fate of the lesion. The mean size of the measured lytic lesions preoperatively was 6.38 cm(2). Postoperatively, lesions decreased to 2.94 cm(2) (P = .000). Modular liner exchange with grafting is effective in treating osteolytic lesions in the pelvis, as demonstrated by CT.

Acetabulum↗
PubMed2005

Total hip arthroplasty through a minimal posterior approach using imageless computer-assisted hip navigation.

With decreased exposure in a minimal posterior hip incision, navigation with computer assistance provides an alternative method to accurately place the components. This study compares the results of a series of 82 navigated total hips to a retrospective cohort of 50 hips done with conventional instruments. The surgical incision split the gluteus maximus but did not extend distally into the fascia. The goal of cup placement was 40 degrees to 45 degrees of abduction (ABD) and 17 degrees to 23 degrees of flexion (FLX). Postoperative radiographs were digitized and analyzed. In the study group, 82 hips were done with computer assistance and compared with 50 done with conventional methods (manual) through the same incision. Radiographic analysis showed that there were significantly fewer cases inside the desired range of ABD and FLX in the manual group (6%) compared with the navigation group (30%), P = .001, with significant differences in the variances of ABD and FLX (P = .011 and .028). Improved accuracy of cup placement was found with increased experience in the use of navigation by the surgeon over the time of the series. The use of a computer-assisted surgery navigation system with a minimal posterior incision for a total hip arthroplasty results in significantly more reproducible acetabular component placement.

Adult↗
PubMed2005

Computer assisted navigation in total knee arthroplasty: improved coronal alignment.

The use of a computer navigation system is intended to optimize implant positioning. This study compares prospectively followed total knee arthroplasty (TKA) done with imageless computer-assisted navigation with a cohort of TKA done with manual instruments. Primary TKAs were performed on 147 knees, with 78 in the manual group and 69 in the navigated group. Coronal alignment was determined by postoperative full-length standing radiographs. The 2 groups had similar mean values for radiographic mechanical axis at 0.4 degrees . There was a larger variation in alignment in the manual group, with 58% of the manual group within 2 degrees of neutral compared with 78% of the navigated group (P = .008). The navigation system reproducibly resulted in a more reliable reproduction of the mechanical axis.

Aged↗
PubMed2002

Effect of initiation chemistry on the fracture toughness, fatigue strength, and residual monomer content of a novel high-viscosity, two-solution acrylic bone cement.

Porous-free, two-solution bone cements have been developed in our laboratory as an alternative to commercial powder/liquid formulations. Each pair of solutions consist of poly(methyl methacrylate) (PMMA) powder dissolved in methyl methacrylate (MMA) monomer, with benzoyl peroxide (BPO) added to one solution as the initiator and N,N-dimethyl-p-toluidine (DMPT) added to the other as the activator. When mixed, the solutions polymerize via a free radical reaction, which is governed by the concentrations of initiator and activator and their molar stoichiometry. Previous work by the authors has demonstrated that these two-solution cement compositions are comparable to Simplex P bone cement in polymerization exotherm, setting time, and flexural mechanical properties. This study was designed to evaluate the effect of BPO and DMPT concentrations, along with their molar ratio, on the fracture toughness, fatigue strength, and residual monomer content of the experimental compositions. The results showed that fracture toughness and fatigue strength for the solution cements were comparable to Simplex P and were not significantly affected by the BPO concentration or the BPO:DMPT molar ratio; however, the highest DMPT concentration yielded significantly lower values for both variables. Residual monomer content was significantly affected by both the individual concentrations of BPO and DMPT and their molar ratios. The two-solution cements had significantly higher residual monomer contents versus Simplex P; however, this can be attributed to their higher initial monomer concentration rather than a lower degree of conversion.

Benzoyl Peroxide↗
PubMed2002

Use of helical computed tomography for the assessment of acetabular osteolysis after total hip arthroplasty.

BACKGROUND: Acetabular osteolysis is a major problem affecting long-term survival of total hip prostheses. Since lytic lesions may be asymptomatic until extensive bone loss has occurred, early detection of lytic lesions is important. The purposes of this study were to determine the efficacy and potential role of high-resolution helical (or spiral) computed tomography with metal-artifact minimization in the early detection of osteolysis of the pelvis and to use the method to determine if there was a relationship between the extent of osteolysis and the amount of polyethylene wear. METHODS: Forty patients (fifty hips) who had undergone primary cementless total hip arthroplasty between 1988 and 1994 were evaluated as part of an ongoing prospective study. These patients had a history of high-level activity that was believed to place them at increased risk for accelerated polyethylene wear. The most recent follow-up radiographs were compared with the three-month postoperative radiographs. Helical computed tomography scans with metal-artifact minimization were made, and evidence of osteolytic lesions on these scans was compared with that on the radiographs. Two-dimensional wear analysis was performed with use of digitized radiographs, and the results were compared with loss of bone volume as calculated from the computed tomography scans. RESULTS: Acetabular lysis was identified on the radiographs of sixteen hips and on the computed tomography scans of twenty-six hips. Radiographs underestimated the extent of the lysis in thirteen of the sixteen hips. There was no correlation (r = 0.036) between linear wear and the measured volume of bone loss, with the numbers available. On the basis of the amount of lysis seen on the computed tomography scans, one patient underwent a revision procedure. CONCLUSIONS: Helical computed tomography with metal-artifact minimization is more sensitive for identifying and quantifying osteolysis after total hip arthroplasty than is plain radiography. Since computed tomography scans show both the extent and the location of lytic lesions, they are useful to guide treatment decisions as well as to assist in planning for surgical intervention, when needed, in patients with suspected osteolysis.

Acetabulum↗
PubMed2002

A prospective, randomized study of preoperative autologous donation for hip replacement surgery.

BACKGROUND: Preoperative autologous blood donation is commonly performed to meet potential perioperative transfusion needs and is a common practice prior to total hip arthroplasty. Using standardized transfusion guidelines, we prospectively analyzed the effectiveness of preoperative autologous donation as a method for decreasing allogeneic transfusion among patients undergoing unilateral primary total hip replacement who were eligible to donate autologous blood. METHODS: Patients who were scheduled for primary total hip replacement surgery and who had a preoperative baseline hemoglobin level >or=120 g/L were randomized either to donate two units of blood (autologous donors) or not to donate any blood (nondonors). The donors and nondonors were compared with regard to demographic data, blood-loss volumes, hemoglobin measurements, and transfusion rates. Randomization continued until data were obtained from at least forty patients per treatment group. RESULTS: Of the ninety-six patients who completed the study, forty-two were autologous donors and fifty-four were nondonors. There were no significant differences between the donors and nondonors with regard to age, male:female ratio, estimated blood volume, baseline physical condition, or operative blood loss. The hemoglobin values at the time of enrollment (baseline), at the time of hospital discharge, and six weeks postoperatively were not significantly different between the two groups, although values at the time of admission (129 +/- 13 g/L versus 138 +/- 12 g/L) and in the recovery room (104 +/- 12 g/L versus 115 +/- 13 g/L) were significantly lower in the autologous donor group (p < 0.05). No patient in either group required an allogeneic transfusion. Twenty-nine (69%) of the forty-two donors received an autologous transfusion. Thirty-four (41%) of eighty-two autologous units were wasted. At a charge of $379 per autologous unit, there was an additional cost of $758 for each patient in the donor group. CONCLUSIONS: Preoperative autologous donation provided no benefit for nonanemic patients undergoing primary total hip replacement surgery. Preoperative autologous donation increased the likelihood of autologous transfusion, wastage of predonated units, and costs.

Aged↗