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Biomedical subjects

A A McBeath

Publications and source records attributed to A A McBeath.

At least 19 recordsLinked to original sources
PubMed1996

Measurement of bone mineral density by dual-energy x-ray absorptiometry in patients with the Wisconsin hip, an uncemented femoral stem.

Although qualitative evidence of femoral bone remodeling, secondary to total hip arthroplasty (THA), is apparent on radiographs, quantification of change in bone mass from radiographs is limited. Dual-energy x-ray absorptiometry overcomes many of the limitations and yields accurate and precise bone mineral density (BMD) data. In this study, regional changes in femoral BMD were examined in 89 THA patients with a 2-year follow-up period. Thirty-two patients were evaluated initially before surgery and followed through the first 2 postoperative years. A second group was comprised of 57 patients whose surgery had been performed 1 to 6 years prior to entry into the study; they were also followed for 2 years hence. Thus, both immediate and later bone responses were evaluated prospectively. Maximal bone remodeling was seen in the first 6 months after THA and with a near plateau by the end of the first year. A slow yearly decline in BMD appeared to occur as long as 8 years after THA, thus demonstrating the long-term effects of the introduction of a femoral stem. Variance in preoperative BMD was explained by disease only; no other factors (age, weight, sex) showed significant associations, and body weight was the only variable that affected rate of remodeling after THA (not age, weight, sex, prosthesis size, nor disease). All patients were healthy, relatively young individuals who were good candidates for uncemented implantation, and none showed evidence of clinical complications or surgical failure. It is therefore suggested that the patterns and results reported here be viewed as normative data, that is, the typical skeletal adaptation to THA. In future application, observation of disparate BMD results as compared with these "normal" data may be predictive of abnormal response to surgery and potential for later problems.

Absorptiometry, Photon↗
PubMed1996

Imaging barium-free bone cement.

Prior to 1972, polymethylmethacrylate, or PMMA, did not contain barium sulfate and was, therefore, radiolucent. We describe a technique using magnetic resonance imaging that is very useful in imaging barium-free PMMA.

Barium Sulfate↗
PubMed1995

The Wisconsin noncemented femoral stem. A prospective study with 5 to 9 years of follow-up evaluation.

In an attempt to decrease aseptic loosening, total joint components are now being used without cement. Most components are designed to achieve fixation biologically. The radiographic results of 144 primary uncemented total hip arthroplasties and the clinical results of 89 arthroplasties that were performed using a proximally porous-coated titanium alloy femoral stem between November 1983 and June 1989 are reported. On the acetabular side, a threaded component or a hemispherical porous-coated component was used. The patients were followed prospectively for 5 to 9 years postsurgery. During the study period, the threaded acetabular component had a high failure rate. Because it was not possible to determine accurately from which component a particular sign or symptom arose, clinical analysis was restricted to only those hips without a failed or revised cup. Eighty-nine hips in 71 patients with a minimum follow-up period of 5 years were available for clinical review. Radiographic review of the femoral stem was completed on all hips with 5 or more years of radiographic follow-up evaluation regardless of the status of the acetabular component. One hundred twelve hips in 85 patients were analyzed radiographically. At a latest mean follow-up period of 6.7 years, the mean Iowa hip score was 91.4 +/- 8.0 with a 5.4% incidence of thigh pain. Throughout the follow-up period, the patients with thigh pain had a statistically lower mean Iowa pain subscore when compared with those patients without thigh pain (P=.0001). Endosteal erosion was seen in two hips (1.8%) and longitudinal loss of the medial neck greater than 2 mm was noted in two hips. One femoral stem was revised for aseptic loosening. The clinical results of this femoral stem equal or exceed the published accounts of other arthroplasties. The results indicate that the stem is associated with good clinical results, minimal bone loss, and little osteolysis. Continued follow-up evaluation of patients with this femoral stem is necessary to assess the durability of these encouraging results.

Adult↗
PubMed1995

Arthrodesis following failed total knee arthroplasty: comprehensive review and meta-analysis of recent literature.

With the increasing duration of follow up on total knee arthroplasties, more revision arthroplasties are being performed. When revision is not advisable, a salvage procedure such as arthrodesis or resection arthroplasty is indicated. This article provides a comprehensive review of the literature regarding arthrodesis following failed total knee arthroplasty. In addition, a statistical meta-analysis of five studies using modern arthrodesis techniques is presented. A statistically significant greater fusion rate with intramedullary nail arthrodesis compared to external fixation is documented. Gram negative and mixed infections are found to be significant risk factors for failure of arthrodesis.

Adult↗
PubMed1994

Hip replacement with a threaded acetabular cup. A follow-up study.

A study was begun in 1983 to determine the efficacy of a threaded acetabular cup. Fifty-five patients who had a total of sixty-eight threaded titanium cups had a complete clinical and radiographic evaluation yearly. Fifty-two of the arthroplasties had been primary and sixteen, revisions. The average duration of follow-up was six years (range, five to nine years). Seventeen cups had to be revised at an average of sixty-two months (range, twenty-seven to 108 months) after the index operation. Nine additional cups were loose and revision was pending at the most recent follow-up examination. Failure was defined as revision or pending revision. Thus, twenty-six (38 per cent) of the sixty-eight cups failed. Sixteen (31 per cent) of the fifty-two primary arthroplasties failed and ten of the sixteen revision arthroplasties failed. Radiographic changes that were evident in patients who had a failed cup consisted of superomedial migration of the cup with osteolysis in Zone 3, as classified by DeLee and Charnley. These radiographic changes preceded symptoms in most patients. Because of the high rate of failure of this acetabular component at six years, we believe that its use is not warranted.

Acetabulum↗
PubMed1992

Fixation stability of femoral components in a canine hip replacement model.

A canine hip replacement model was used to compare fixation stability in cemented and cementless femoral components. Parameters of comparison were the load-induced positional changes of each prosthesis relative to its proximal femoral cortex, hereafter called relative displacements. Identical femoral components, with the proximal third of their stem porous-coated, were implanted in the right femurs of 10 large, mixed-breed dogs. Five were tightly fit to allow porous ingrowth, and five were cemented into the medullary canal. Four months after implantation, all femurs were harvested. A prosthesis was implanted in the left (normal) femur of each dog ex vivo with fixation identical to the contralateral limb to simulate acute postoperative fixation. Eddy current transducers measured relative displacements under application of static loads, serially applied in the axial, mediolateral, and craniocaudal directions. Thereafter, the femurs were transversely sectioned and morphologically analyzed to correlate bony apposition at the implant surface with relative displacements. We observed no difference in relative displacements between acute and 4-month-cemented groups (e.g., 0.0059 +/- 0.0021 vs. 0.0060 +/- 0.0048 mm, respectively, for 100-N axial loading measured at midstem). With cementless implantation, relative displacements of the acute group were significantly larger (p = 0.007) than those of the 4-month group (e.g., 0.236 +/- 0.257 vs. 0.097 +/- 0.129 mm, respectively, for 100-N axial loading measured at midstem). Cementless components implanted for 4 months were not significantly different than cemented components, but a trend suggested that they were still not as stable as cemented components, particularly for craniocaudal loads. Relative displacements of the 4-month, porous ingrowth group were approximately proportional to the percentage of bony apposition raised to the -1.44 power (r = 0.94).

Animals↗
PubMed1992

Determination of bone mineral density by dual x-ray absorptiometry in patients with uncemented total hip arthroplasty.

Bone remodeling is an expected sequela with total hip arthroplasty (THA). Although there are several methods of estimating bone response in THA patients from radiographs, there are no accurate and generally accepted methods for quantitative determinations in vivo. In this study, we describe an application of dual x-ray absorptiometry (DXA) for measuring bone mineral content and bone mineral density in the proximal femur following THA. DXA is a noninvasive technique with minimal radiation exposure (< 5 mrem). Various aspects of measurement error (accuracy and reliability) of this application of DXA were determined in a series of studies reported here. Accuracy error (how similar are the measured and actual values) was < 1% determined in bone phantoms of four densities. Precision error (how reproducible are the measurements) was also < 1% at all four densities in the phantoms and was only slightly elevated (0.9-1.5%) in repeated measurements of implanted cadaver femora. Precision error in vivo, determined both from multiple replicates on five patients and from duplicate scans on 30 patients, was further elevated but remained < 5%. Contributions to precision error, rotation of the leg, and interoperator variability were assessed; none was found to elevate precision error appreciably. We suggest that DXA is a feasible method for quantifying bone response following THA, and will allow discrimination of small changes (> 5%) not previously measurable.

Absorptiometry, Photon↗
PubMed1991

Canine intersegmental hip joint forces and moments before and after cemented total hip replacement.

Intersegmental forces and moments (i.e. resultant free body forces and moments computed at the joint centers) were studied in canine hindlimbs before and after cemented total hip replacement (THR). Five large, adult, mixed-breed dogs were selected. Their gait was recorded (while leash-walked) before surgery using high-speed cinematography and a force plate. Cemented total hip replacement was unilaterally performed on each dog. Gait was again recorded at one and four months after surgery. Segmental properties (mass, center of mass, and mass moment of inertia) of the hindlimbs were experimentally determined, and an inverse dynamics approach was used to compute intersegmental forces and moments in the sagittal plane. Significant reductions in intersegmental joint forces and moments were observed in the operated hindlimb one month after surgery, although kinematic gait parameters were unaltered. Decreases of 77.0% for vertical forces, 61.9% for craniocaudal forces, and 66.2% for extension moments were determined. Four months after surgery, the joint forces and moments had returned to their preoperative values. This experiment demonstrates that the dynamics of normal walking can be restored in a canine model by four months after THR. It also shows that kinetic (rather than kinematic) parameters are more descriptive of antalgic gait in the canine.

Animals↗
PubMed1990

Femoral strain adaptation after total hip replacement: a comparison of cemented and porous ingrowth components in canines.

The purpose of this study was to investigate if experimental strain analysis is predictive of femoral adaptation after total hip replacement (THR). Ten large adult dogs underwent unilateral THR with identical implants. Five implants were press fit for porous ingrowth fixation, and five were cemented. Four months after surgery femora were harvested. Strain gauge rosettes were applied to the femora at eight proximal locations. Femora were compressively loaded on the head of the femur or femoral component. Strain data represented three conditions: preoperative, acutely postoperative, and four-month postoperative. The unoperated femur of each dog was used to simulate preoperative and acutely postoperative behavior of the contralateral implanted femur. Strains from each condition were compared. Transverse femoral sections were obtained through the levels of the strain gauges. Fine detailed radiographs were used to quantify morphological changes. Results showed cemented and uncemented implantations produce similar trends but different amounts of bone adaptation. Adaptations were generally consistent in direction with strain perturbations caused by implantation, but the extent of adaptation did not strongly correlate with the magnitude of perturbations. Also, there was no consistent trend towards normalization of altered strains. Results suggest that strain perturbations after THR may be mechanical triggers for morphological changes, but caution is required when predicting the extent of these changes or the autoregulatory role of strain.

Adaptation, Physiological↗
PubMed1990

K-edge digital subtraction arthrography of the painful hip prosthesis: a feasibility study.

K-edge energy subtraction radiography is a method for detecting the presence of iodinated contrast material by subtracting two digital radiographs produced by X-ray beams with energies above and below the iodine K edge. We performed a feasibility study on the application of K-edge energy digital subtraction arthrography (KEDSA) to painful hip prostheses. During arthrography, loosening of the prosthesis is implied if contrast material is seen dissecting around the prosthesis, an often difficult detection task because of adjacent prosthesis metal or cement. In conventional arthrography a preliminary mask image is thus used from which films obtained after injection of iodinated contrast material are subtracted. Movement by the patient during this process may preclude subsequent subtraction. With KEDSA, since multiple image pairs may be obtained after the injection of contrast material, the problem of patient motion is virtually eliminated. A conventional X-ray tube operating between 55 and 65 kVp was alternately filtered by iodine and cerium filters to produce the KEDSA images. The apparatus was capable of producing a subtracted image within 3 sec. The technique was applied to phantoms and to six patients immediately after hip arthrography that had been positive for prosthesis loosening. Although of lower spatial resolution, the KEDSA images were, in all cases, positive for loosening in a pattern consistent with the conventional arthrographic images. KEDSA was shown to be successful in detecting extraarticular contrast material. During a single study, subtraction in various imaging planes as well as postexercise subtraction imaging can be accomplished-techniques not heretofore possible in routine subtraction arthrography.

Aged↗
PubMed1988

Subtrochanteric osteotomy with intramedullary fixation for arthroplasty of the dysplastic hip. A case report.

Hip dysplasia in its end stage may require arthroplasty, and often extreme femoral anteversion is present. To correct rotational alignment of knee and hip joints yet preserve part of the femoral neck during total hip arthroplasty, a subtrochanteric derotational osteotomy was performed in a 37-year-old woman. Intramedullary fixation of the osteotomy was secured using a custom-fitted femoral component alone.

Adult↗
PubMed1986

Metastatic breast cancer in the femur. A search for the lesion at risk of fracture.

Clinical records and radiographs of 203 female patients with 516 metastatic breast lesions located in the proximal femur were examined retrospectively to determine: the dimensions of those lesions that were at risk of fracture; and the relationship of other variables (bone pain, body habitus, age, and radiation treatment) with the occurrence of a pathologic fracture. Twenty-three patients sustained 26 pathologic fractures. Their average age, height, and weight were not significantly different from the 180 patients without fractures. Similarly, moderate to severe bone pain was experienced by a great majority of the total patient population, yet only 11% sustained fractures. Fifty-six patients received radiation treatment of a femoral metastasis. Ten of these patients subsequently sustained fractures. Radiation treatment relieved bone pain but did not have any consistent curative effect on the lesion itself. Finally, the authors were unable to identify either a specific percent involvement of the bone or a critical diameter for metastases that fractured because: 296 (57%) of the 516 metastases were permeative lesions and unmeasurable; 14 (54%) of the 26 pathologic fractures observed occurred through unmeasurable lesions; and the 12 measurable lesions that fractured had the same range of percent involvement as the 208 measurable lesions that did not fracture. Breast metastases at risk of fracture cannot be identified by measurements obtained from standard radiographs alone.

Adult↗
PubMed1985

Some common causes of hip pain. Physical diagnosis is the key.

A variety of disorders can cause pain about the hip. The significance of these various disorders varies. Obviously, appropriate treatment cannot be initiated until a correct diagnosis is made. The classic methods of physical diagnosis must be used. X-ray studies or bone scans are most often only confirmatory but frequently necessary.

Adolescent↗
PubMed1984

Hip arthrodesis in young patients. A long-term follow-up study.

We evaluated the results in fifty-three patients who had had a successful hip arthrodesis at least twenty years (average, thirty-eight years) prior to the study and who had been less than thirty-five years old at the time of operation. We determined the functional history of each patient and the current status of the opposite hip, the knees, and the back. Radiographs were made and each joint was rated according to standard clinical scales. Seventy-eight per cent of the patients were satisfied with the arthrodesis, and all were able to work. Fifty-seven per cent had some low-back pain and 45 per cent, some knee discomfort. Only seven patients (13 per cent) had had a total hip arthroplasty on the arthrodesed hip.

Activities of Daily Living↗
PubMed1981

Effects of 1,24 dihydroxyvitamin D3 and calcitonin on fracture healing in adult rats.

Calcitonin and 1.25(OH)2D3 have opposite effects on the serum concentrations of Ca and P, as well as on bone resorption, and can be observed in the process of healing of standardized fracture in adult rats. The rats given 1.25(OH)2D3 had a stronger fracture callus and slightly less pronounced postfracture osteopenia. Calcitonin did not significantly influence the fracture healing but had a pronounced effect in preventing the osteopenia. The effects of 1.25(OH)2D3 are believed to be indirect, i.e., through the changes in the serum Ca X P product, whereas the osteopenia preventing action of calcitonin may come from direct effect on bone.

Animals↗