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Biomedical subjects

C A Engh

Publications and source records attributed to C A Engh.

At least 73 records · Page 4Linked to original sources
PubMed1996

The influence of clinical factors on periprosthetic bone remodeling.

The femurs of 11 patients with well-functioning unilateral hip replacements were retrieved at autopsy and analyzed for periprosthetic bone remodeling by dual energy xray absorptiometry. Each case involved a femur with a porouscoated endoprosthesis; the endoprosthesis remained implanted for an average of 5.9 years. In the contralateral femur, a matching prosthesis was implanted in vitro, to serve as a control for comparisons. There was an average 22.6% decrease in bone mineral content in the in vivo implanted femur (range, 5.4%-47.4%). Females experienced an average bone loss of 31.2%, which was significantly higher than the 12.3% average loss in males. Longitudinal analysis revealed an average decrease in bone mineral content of 42.1% proximally, 23% in the midsection, and 5.5% distally. Percent decreases in total bone mineral content were correlated with the following clinical variables: weight, age, implant diameter, duration of implantation, and contralateral femoral bone mineral content. Only the bone mineral content of the contralateral femur had a strong predictive value. Bone loss was greater in femurs with low bone mineral content than in those with high bone mineral content. Weight, age, implant diameter, and duration of implantation were not correlated with bone loss.

Absorptiometry, Photon↗
PubMed1996

Structural bulk allografts in acetabular reconstruction. Analysis of two grafts retrieved at post-mortem.

Two acetabula which contained large bone allografts introduced at revision arthroplasty were obtained at post-mortem. The allografts had been placed in superior defects to support cementless acetabular components, and both hips were functioning well at the time of death. Clinical radiographs demonstrated apparent healing of graft to host bone, no graft collapse and stability of the acetabular components. Microscopic examination of sections through these specimens showed that the bulk allografts were encapsulated in fibrous tissue. Vascularity was increased at the host-graft interface, but there was limited evidence of bone union between the graft and the host. In the few areas where union had occurred, revascularisation extended no more than 2 mm beyond the graft-host interface. Within the body of the graft, the acellular matrix of trabecular bone maintained structural integrity up to 48 months after surgery. In areas where the allograft was adjacent to an implant, there was fibrous tissue orientated parallel to the implant surface. The acetabulum which contained a porous-coated component showed evidence of bone growth into the porous surface where it was in contact with viable host bone. No ingrowth occurred in areas where the porous coating was in contact with the graft. Although the grafts were functioning well, allograft revascularisation and remodelling were minimal, and the radiological appearance of healing did not correlate with histological findings.

Acetabulum↗
PubMed1996

The Otto Aufranc Award. Skeletal response to well fixed femoral components inserted with and without cement.

Previous studies evaluating femoral remodeling after total hip arthroplasty have used clinical radiographs and dual energy xray absorptiometry. Limitation of these techniques make it impossible to quantify the magnitude of bone loss in terms of cortical thinning and cortical bone area and bone mineral density changes. Femoral cortical bone remodeling after cemented and cementless replacement was quantified and possible determinants of bone remodeling in terms of clinical and radiographic variables were evaluated. Forty-eight anatomic specimen femora from 24 patients with unilateral cemented and cementless hip replacements were analyzed. Cortical thickness, cortical bone area, and bone mineral density was assessed in 4 quadrants at 5 discrete levels. The maximum cortical bone loss by level was at the middle section for the cemented femurs and at the midproximal and middle sections for the cementless femurs. However, if one examines individual quadrants, the proximal medial cortex still represents the specific region of maximal bone loss for both types of implant fixation. The posterior cortex had substantially more bone loss, even in the diaphyseal levels, than had been previously appreciated. A strong correlation was noted between the bone mineral density of the control femur and the percentage decrease of bone mineral density in the remodeled femur. Based on this data, it seems that the less dense the bone is before hip replacement surgery, the greater the extent of bone loss after total hip arthroplasty regardless of the fixation type.

Adult↗
PubMed1995

Patterns of osteolysis around total hip components inserted with and without cement.

We reviewed the radiographs of 137 patients (137 hips) who had been managed with a total hip arthroplasty, with insertion of an extensively porous-coated femoral component without cement, because of osteoarthrosis or avascular necrosis. A porous-coated acetabular component had been inserted with cement in sixty-three of these patients (Group A) and without cement in seventy-four patients (Group B). The radiographs were examined for osteolysis, either directly adjacent to the joint or at locations remote from the joint. The mean duration of follow-up was 105 months (range, fifty-four to 142 months). The rate of osteolysis of the acetabulum in the unrevised hips in which the acetabular component had been inserted with cement was 37 per cent (nineteen of fifty-one). The osteolysis was most frequently of the linear type, a pattern that was associated with a high prevalence of loosening in the hips that had a cemented cup (30 per cent [nineteen of sixty-three]). The rate of acetabular osteolysis (18 per cent [thirteen of seventy-one]) in the patients who had a cup that had not been inserted with cement and that had not been revised was not as high as that associated with the surviving cups that had been inserted with cement (p < 0.05). The osteolysis associated with the cups that had not been inserted with cement was localized and expansile, and it was not associated with loosening of the component. However, it produced more loss of bone than did the linear pattern of osteolysis around the cemented cups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1995

Evaluation of bone ingrowth in proximally and extensively porous-coated anatomic medullary locking prostheses retrieved at autopsy.

Three proximally (40 per cent) and five extensively (80 per cent) porous-coated anatomic medullary locking femoral components were retrieved from seven cadavera at autopsy. Each component (with the surrounding, intact femur), was sectioned transversely at one-centimeter intervals. Backscattered scanning electron microscopy was used to evaluate circumferentially the interface between the bone and the porous surface of each section. Bone ingrowth was considered to be present within a field when bone was in contact with the outermost layer of the sintered beads, it was detected within the porous space, and it had penetrated the porous space to a depth of at least one bead diameter. All eight components had some bone growth into the porous space. A mean of 35 per cent of the surface of the implants had bone ingrowth. In the areas where bone was present, 67 per cent of the available porous space on the extensively coated stems and 74 per cent on the proximally coated stems contained bone. With both types of implants, the greatest amount of compact bone ingrowth was found at the level where the porous coating ended. Transverse sections obtained at this level frequently demonstrated that bone ingrowth had occurred circumferentially and that the ingrowth was continuous with and an integral part of the femoral cortex. These direct connections to the cortex could be predicted from the appearance of the radiographs. In the most proximal transverse sections of both types of implants, bone was most frequently connected to the medial side and corners of the implant.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Morselized allograft in acetabular reconstruction. A postmortem retrieval analysis.

Contained acetabular defects often are repaired at revision surgery using morselized bone allograft. The extent to which this graft becomes incorporated is unknown, and the value of radiographs for predicting allograft incorporation is unclear. To better understand the effectiveness of morselized allograft in revision hip arthroplasty, the authors studied postmortem specimens from 3 patients treated with this type of graft. Histologic analysis of acetabular components in situ for 18 months showed allograft fragments invested with loose myxofibrous tissue. Vascularized tissue had penetrated the allograft fragments to a depth of 4 mm. In peripheral areas, the vascularized ingrowth was accompanied by partial osteoclastic resorption of graft trabeculae and application of living bone to allograft fragments. After 53 months in situ, graft fragments had remodeled and showed progressive vascular ingrowth. By 83 months, the graft almost completely had incorporated. Morselized allograft bone is useful for restoring bone deficiency within contained acetabular defects. The graft does incorporate, but the extent of graft incorporation cannot be predicted accurately by postoperative radiographs.

Acetabulum↗
PubMed1995

Cementless femoral components should be made from cobalt chrome.

Before 1982, the authors performed 177 primary total hip arthroplasties using a single-sized, extensively porous-coated cobalt-chrome femoral prosthesis. The current status of 122 of these arthroplasties is known. Two femoral prostheses have been revised for late symptomatic loosening, 2 for stem fracture, and 1 for infection. From 1982 to 1984, 227 primary arthroplasties were performed using the same stem in multiple sizes. Of these cases, 171 are available for followup. One stem (0.6%) has been revised for symptomatic loosening. Large osteolytic femoral lesions (average size, 8.1 cm2) developed in 3 patients, associated with an unusually large amount of polyethylene wear of their acetabular components. These patients have been treated by exchange of the polyethylene liner within the porous-coated acetabular component and allografting of the osteolytic lesions. The femoral components were not exchanged because osteolysis had not eroded the integrity of the supporting bone-implant interface to a point where loosening occurred. Before 1987, 193 patients with loose femoral components were treated with revision total hip arthroplasty, also using an extensively porous-coated cobalt-chrome femoral stem of similar design. Ten (5.7%) patients have required rerevision of the femoral prosthesis. Six of these 10 rerevisions were performed because of symptomatic loosening. Ninety-three percent of the patients in the primary series had relief of their preoperative pain and have improved functional ability; 94.2% are satisfied with their results. In the revision series, 89.1% of the patients are free of pain and function better than preoperatively, and 89.6% are fully satisfied with their results.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium Alloys↗
PubMed1994

Osteonecrosis of the femoral head treated with total hip arthroplasty without cement.

With use of porous-coated implants, total hip arthroplasty was performed in a consecutive series of thirty patients (thirty-five hips) who had a preoperative diagnosis of late-stage (Ficat and Arlet stage-III or IV) osteonecrosis of the femoral head. The patients were evaluated clinically and radiographically, and the data were recorded in a prospective manner. The average duration of follow-up was seven and one-half years (range, five to ten years). The average age of the patients at the time of the operation was thirty-two years (range, twenty-one to forty years). Signs of osseointegration of the femoral stem to the host bone were demonstrated in thirty-three hips (94 per cent). In the porous-coated hemispherical acetabular cups of these hips, an optimum bone-implant interface was identified and maintained, suggesting bone ingrowth. The rate of revision was 3 per cent (one hip) for the femoral side and 6 per cent (two hips) for the acetabular side, for an over-all rate of 6 per cent. All patients maintained a high level of activity postoperatively. There was moderate or severe remodeling of proximal femoral resorptive bone and stress-shielding in six hips (17 per cent) and osteolytic reactions in six hips. Complications were frequent (six hips) and included one deep infection; two dislocations; two instances of heterotopic ossification; and one fracture of the calcar femorale, which occurred intraoperatively. The thirty patients had a lower rate of revision and improved clinical outcomes compared with other reported series of young patients managed with total hip arthroplasty with cement who had the same diagnosis and similar postoperative follow-up. However, the latter series involved implants of an earlier design that had been inserted with older techniques of cementing. When arthroplasty is considered for the treatment of late-stage osteonecrosis of the femoral head in young patients, the use of total hip implants without cement that allow for bone ingrowth appears to be a viable alternative to arthroplasty with use of cement. However, longer follow-up is needed to determine the outcome of the osteolytic reactions that we observed. We therefore recommend this procedure with some caution because of the high rate of complications and the potential for failure of the arthroplasty related to the osteolytic reactions.

Activities of Daily Living↗
PubMed1994

Outcome of revision hip arthroplasty done without cement.

Between 1980 and 1986, ninety-three femoral revision arthroplasties without cement were performed on ninety-one patients who had symptomatic loosening of a stemmed femoral component of a total hip prosthesis. Eighty-one of these patients (eighty-three hips) were followed for at least five years (range, five to thirteen years; mean, nine years). Forty-three hips also had a revision of a cemented acetabular component with use of a hemispherical, porous-coated implant inserted without cement. The results are presented in a traditional manner in terms of implant survivorship, radiographic evaluation for stability of the implant, and standardized hip scores. Changes due to the treatment are presented as outcomes in terms of the physician's criteria for the success of the operation, the patient's criteria for the success of the operation, and the patient's economic status. No hips that needed additional operations were excluded, and we reported the outcome regardless of any interim operative procedures (including re-revisions). At the latest follow-up examination, nineteen (23 per cent) of the eighty-three hips had had an additional operation, including seventeen hips (20 per cent) for which re-revision had been necessary. In ten (12 per cent) of the eighty-three hips, the re-revision had involved an index implant. The rate of re-revision of the index femoral component was 10 per cent and the rate of mechanical loosening of that component was 11 per cent. The rate of re-revision of the index acetabular component was 7 per cent and the rate of mechanical loosening of that component was 11 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1994

Late mechanical stability of the proximal coated AML prosthesis.

Micromotion of a bone-ingrown anatomic medullary locking (AML) femoral component was evaluated in a specimen retrieved from a 66-year-old man who died 4 years following total hip replacement. Radiographic signs suggested bone ingrowth into the proximal porous coating, but a radiolucent line surrounded by a sclerotic line was present around the distal stem. Both torsional and axial loading to physiologic levels elicited minimal micromotion at the proximal bone-prosthesis interfaces. However, medial-lateral micromotion at the distal tip was found to be as high as 44 microns with axial load. An AML femoral component of similar design was inserted into the opposite normal femur using the cementless press-fit technique originally used for the implanted specimen. Micromotion proximally was much greater in the freshly implanted systems in response to both torsional and axial loading than in the bone ingrown specimen. However, distal medial-lateral micromotion was much greater for the bone-ingrown stem. These findings show that bone ingrowth provides rigid fixation of the implant to bone; however, flexibility of the femur causes increased micromotion of the femur around the smooth distal stem despite initial tight distal fit.

Aged↗