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Biomedical subjects

W L Bargar

Publications and source records attributed to W L Bargar.

At least 19 recordsLinked to original sources
PubMed1993

Management of bone loss in revision total hip arthroplasty using custom cementless femoral components.

Forty-seven consecutive revision total hip arthroplasties were performed using porous ingrowth custom-made prostheses designed from plain radiographs and computed tomography scans. At an average follow-up period of 30 months (range, 2-4 years), one revision has been required for loosening. The average Harris pain score was 39 and the average total score was 84 at the last follow-up evaluation. Complications included nine cases (19%) with intraoperatively detected fractures of the proximal femur treated with cerclage wires and seven cases (15%) with subsidence greater than 3 mm. There were no postoperative infections and only two dislocations. At the time of surgery local particulate bone graft was used in all cases. Thirty-four percent required structural graft to restore bone stock; no case required grafting for prosthesis stability. Management of bone loss in total hip arthroplasty using a custom cementless prosthesis appears to provide an attractive alternative to massive bone grafting.

Adult↗
PubMed1993

Classification of femoral abnormalities in total hip arthroplasty.

Bony abnormalities of the femur can significantly complicate total hip arthroplasty both for the primary and revision operations. No standard nomenclature exists for the description of these femoral abnormalities. A classification system is presented to standardize nomenclature, assist in preoperative planning, and to assist in the reporting of these defects.

Bone Malalignment↗
PubMed1992

Development of a surgical robot for cementless total hip arthroplasty.

The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and persistent thigh pain after cementless THA remain significant problems, both of which may be alleviated by more precise preparation of the femoral canal and selection of an appropriately sized prosthesis. The objective of this study was to obtain an exact fit for the prosthesis through the use of an image-directed surgical robot for femoral canal preparation.

Arthroplasty↗
PubMed1989

Shape the implant to the patient. A rationale for the use of custom-fit cementless total hip implants.

Most authors agree that "fit" and "fill" of the endosteal canal is critical to the success of cementless femoral components. Yet, there exists a wide variation to the anatomic size and shape of this canal in the normal population. This paper reviews the rationale and the efficacy of using a computed tomography-generated CAD/CAM custom femoral component in cementless total hip arthroplasty. One hundred fifty-six cases (81 primary and 75 revisions) were reviewed with follow-up time of six weeks to three years (mean, 22 months). A subset of 48 hips (25 primary and 23 revisions) has been followed a minimum of two years. For the primary hips, the custom group was found to have statistically higher Harris pain scores (less pain) at all follow-up intervals as compared to a prior series by the same surgeon using an off-the-shelf (OTS) prosthesis. Revision customized hip implants had lower Harris pain and total scores than primary custom hips, but 80% were in the none or slight pain category. In revision cases, the use of custom components decreased the need for structural bone grafting and achieved stability on host bone in situations in which it was not possible using OTS components. Complications included failure by aseptic loosening of one primary and one revision case. Initial subsidence of more than 3 mm of the collarless custom design occurred in 8%, the majority being in revision cases. All cases but one appear to have stabilized. Subsidence occurred mainly in cases done early in the series.(ABSTRACT TRUNCATED AT 250 WORDS)

Artificial Intelligence↗
PubMed1989

Classification and management of acetabular abnormalities in total hip arthroplasty.

Total hip arthroplasty, for both primary and revision operations, frequently involves bony abnormalities of the acetabulum. No standard nomenclature currently exists for the definition of acetabular deficiencies. A classification system is presented to assist in the preoperative evaluation and to provide a treatment protocol for these defects.

Acetabulum↗
PubMed1989

Intraoperative autologous transfusion in orthopaedic patients.

The cases of 175 consecutive patients who had intraoperative autologous transfusion during revision total hip arthroplasty, an elective operation on the spine, repair of trauma to the spine, or open reduction of a fracture of the acetabulum were reviewed to evaluate the applicability of this technique in orthopaedic operations. A separate group of forty-one consecutive patients who had open reduction of a fracture of the acetabulum or the spine before the introduction of the autotransfuser was reviewed and compared with the group that had autotransfusion. An autologous blood predeposit program was used for twenty-five of fifty-two patients who had a procedure on the hip and for fifty-one of fifty-five patients who had an elective procedure on the spine. The mean rate of red blood-cell salvage using the autotransfuser was 60 per cent over-all. The mean transfusion requirements were significantly less (p less than 0.001) in all groups of patients in whom the autotransfuser was used. Use of the autotransfuser reduced the mean requirement for banked blood in patients who had a fracture of the acetabulum from 3.8 to 2.3 units per patient, and significantly reduced the mean need for banked blood in individuals who had trauma to the spine from 2.7 to 1.8 units per patient (p less than 0.01). The use of prebanked autologous blood further reduced the mean requirement for homologous blood from 2.4 to 0.8 unit per patient in those who had revision total hip arthroplasty (p less than 0.005), and from 3.6 to 0.4 unit per patient in those who had an elective procedure on the spine (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion↗
PubMed1988

Effects of estrogen deficiency on the growth of tissue into porous titanium implants.

The effect of systemic deficiency of estrogen on the growth of tissue into porous titanium-fiber implants was studied in ovariectomized Beagle dogs. Five dogs were ovariectomized and five dogs had a sham operation. After waiting four months to allow the levels of circulating estrogen to decline, a titanium-alloy implant that contained four surface pads of titanium-alloy mesh was implanted in the proximal part of the humerus of each dog bilaterally. Two months later, the implants were harvested and subjected to a mechanical push-out test and quantitative histological study. The push-out strength of the implants from the ovariectomized dogs was 31 per cent less than in the control animals. Ovariectomy caused no difference in the amount of ingrowth of bone but resulted in a significant increase in the amount of fibrous connective tissue within the porous pads. The presence of this fibrous tissue appeared to have an important effect on bone-implant fixation: in the control dogs, strength correlated positively with ingrowth of bone and negatively with ingrowth of fibrous tissue, whereas in the ovariectomized dogs, strength correlated positively with ingrowth of fibrous tissue and not at all with ingrowth of bone.

Animals↗
PubMed1987

Histologic changes in the dog acetabulum following total hip replacement with current cementing techniques.

Histologic changes in the acetabuli of adult dogs were studied following total hip replacement with current cementing techniques. Active bone remodeling was evident throughout the acetabulum by 2 weeks after operation and continued throughout the 6 months of the study, leading to considerable hypertrophy of the trabecular bone of the acetabulum. By 6 months after operation, a thick (average, 0.4 mm), fibrous membrane had formed at the bone-cement interface in 83 of 84 sections examined. Direct apposition of bone to cement was seen only within the 2-mm fixation holes. Formation of a fibrous membrane appears to be intrinsic to the cementing of the acetabular component, perhaps because geometry of the acetabulum precludes effective pressurization of the cement.

Acetabulum↗
PubMed1987

Efficacy of bone staples for fixation.

The pull-out strength of two types of bone staples (A, Techmedica; B, Richards) was evaluated in a canine model and compared with a control of 6.5 mm cancellous bone screw (Synthes). Fifteen adult mongrel dogs were divided into three groups of five animals each. The implants were placed in the lateral femoral condyle and proximal humerus on the right side at time zero, and on the left side 3 weeks later. The dogs were killed at 6 weeks. In addition a third site, the tibial tubercle, was used to examine the effectiveness of each device for patellar tendon reattachment. The strength of the reattached patellar tendon was measured and compared with a control intact patellar tendon insertion. The pull-out loads from bone of the two staple types are not statistically different. The displacement to failure, however, was found to be 71% greater (p less than 0.007), and the work to failure 128% greater (p less than 0.010) for staple A as compared with staple B. This may be of clinical relevance in avoiding staple back-out. Both staples were inferior to the screw for pull-out load displacement and work to failure (p less than 0.0001). All reattached tendons were significantly weaker (mean 202 N) than the intact tendon (mean 1,448 N) regardless of implant type. The dissected specimens uniformly showed necrosis of the tendon under the implant. Healing was by massive scar formation surrounding the implant.

Animals↗
PubMed1986

In vivo versus in vitro polymerization of acrylic bone cement: effect on material properties.

Flexural strength and molecular weight of polymethylmethacrylate bone cement were determined for cement polymerized in vivo in a canine total hip replacement and cement from the same batch polymerized in vitro. Both in vivo and in vitro samples showed a slight increase in flexural strength and modulus at 2 weeks, followed by a nearly equivalent decline at 8 weeks. In vitro and in vivo samples exhibit a comparable stress to failure, but the in vivo samples show a significantly increased strain and decreased modulus. Cement from the proximal region of the prosthesis has significantly decreased flexural strength, lower modulus, and lower molecular weight than cement from the distal region and plug, suggesting that failures in the proximal region of a prosthesis may be due to inferior physical and mechanical properties of the bone cement in that region.

Animals↗
PubMed1986

Histologic changes in the dog femur following total hip replacement with current cementing techniques.

Histologic changes in the femurs of adult dogs were studied following total hip replacement using current cementing techniques. In the diaphyseal region, remodeling was initiated in the periosteum and progressed centripetally over 3 months. In the proximal (metaphyseal) region, remodeling was seen throughout the section by the second week. No fibrous membrane was formed at the bone-cement interface in the proximal region, and only isolated, non-progressive patches of fibrous membrane were formed in the distal region of the implant. The authors attribute the absence of membrane formation to careful preparation of the cement bed and use of pressurized cement injection. The exact congruence of vascularization and remodeling indicates a vascular etiology for the reaction of bone to cemented implantation. Vascular compromise at the time of operation leads to bone necrosis in the affected regions, and subsequent revascularization is a necessary precursor to bone remodeling. Thermal effects and monomer toxicity are considered unimportant.

Animals↗
PubMed1986

The addition of tobramycin to contrast bone cement. Effect on flexural strength.

Samples of polymethylmethacrylate (PMMA) bone cement were polymerized in vitro with no additives and with the following additives: methylene blue dye, tobramycin, methylene blue plus tobramycin. After storage for 7 days in saline, samples were tested to failure in three-point bending. Addition of the antibiotic significantly weakened the cement (to 87% of control). However, the combination of tobramycin plus methylene blue was no weaker than tobramycin alone, suggesting that addition of both dye and antibiotic to bone cement is probably a reasonable clinical practice.

Bone Cements↗
PubMed1986

The calcar bone graft.

A canine model was developed to investigate the use of an autogeneic iliac bone graft to treat the calcar deficiency commonly found at the time of revision surgery for femoral component loosening. Five large male mixed-breed dogs had bilateral total hip arthroplasty staged at three-month intervals, and were sacrificed at six months. Prior to cementing the femoral component, an experimental calcar defect was made, and a bicortical iliac bone graft was fashioned to fill the defect. Serial roentgenograms showed the grafts had united with no resorption. Technetium-99 bone scans showed more uptake at three months than at six months in the graft region. Disulfine blue injection indicated all grafts were perfused at both three and six months. Thin section histology, fluorochromes, and microradiographs confirmed graft viability in all dogs. Semiquantitative grading of the fluorochromes indicated new bone deposition in 20%-50% of each graft at three months and 50%-80% at six months. Although the calcar bone graft was uniformly successful in this canine study, the clinical application of this technique should be evaluated by long-term results in humans.

Animals↗