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Biomedical subjects

C A Engh

Publications and source records attributed to C A Engh.

At least 109 records · Page 6Linked to original sources
PubMed1990

Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components.

Certain roentgenographic signs have value in predicting the fixation of a cementless femoral component to bone by osseointegration. Other signs have value in predicting the gross stability of a cementless femoral component. The authors have determined the specificity and sensitivity of the signs for osseointegration in cases in which the histologic fixation has been confirmed after implant removal. The authors have also determined the specificity and sensitivity of the signs for gross implant stability in cases in which the stability has been confirmed at reoperation. Statistical methods were used to determine a numeric value for each of these roentgenographic signs, and these values were combined into a score. The score was divided into fixation by osseointegration and mechanical implant stability. The two scores were then combined into an overall score. When signs of osseointegration were present, the implant was always stable, and the overall scores were the highest. When signs of osseointegration were absent, the mechanical stability varied, and the scores were lower. A neutral or slightly negative score correlated with failed osseointegration but secondary successful implant stabilization. A very low negative score correlated with gross implant instability. To confirm the validity of the scoring system, the two-year postoperative score was determined for 1005 cases in which the clinical outcome was known. A strong correlation between the presence of symptoms and a low score confirmed the value of the scoring system for diagnosing implant loosening as the cause of symptoms. As a second test, the two-year and five-year postoperative results were compared in the same patients. A high two-year score correlated with durable implant stability through five years. A low two-year score correlated with a higher incidence of late symptomatic loosening.

Adult↗
PubMed1990

The case for porous-coated hip implants. The femoral side.

A series of 1163 total hip arthroplasties (THAs) using porous-coated femoral components were roentgenographically assessed for implant fixation. For 959 primary THAs followed from two to 12 years, the femoral revision rate was 1% and the ten-year survivorship rate was 96.4%; 150 young patients had a fixation failure incidence of only 1.3% at a mean follow-up period of 6.4 years; in 204 revision THAs, the femoral re-revision rate was 4% at a mean follow-up period of 53.4 months. Failures were largely related to inadequate femoral canal filling. Because of refinements in implant design and surgical techniques, a press fit of the implant is currently achieved in 94% of cases compared to 36% during the first five years. Porous-coated femoral components have yielded results equivalent to those with cement in primary THAs. Excellent results were observed in relatively young patients and patients with revisions.

Adolescent↗
PubMed1989

Evaluation of cementless acetabular component migration. An experimental study.

Roentgenograms of two human cadaveric pelves with three implanted acetabular components were taken in anatomic, tilted, and rotated positions to determine their effect on the measurement of cup migration. The best landmark for measuring migration along a vertical axis was the distance between the center of the cup and the teardrop line. The best measurement for cup migration along an horizontal axis was the distance between the center of the cup and the vertical line through the teardrop. When the teardrop is not visible, one should use the distance between the bottom of the cup and the obturator line, and the distance between the center of the cup and Kohler's line. Guidelines for roentgenographic comparability are as follows: at 10% magnification, the variation in distance between the obturator line and the teardrop line should be less than 5 mm, and the distance between the middle of the sacroiliac line and the vertical line through the pubis should be less than 0.5 cm.

Acetabulum↗
PubMed1989

Cementless total hip arthroplasty using the anatomic medullary locking stem. Results using a survivorship analysis.

Three hundred forty-three primary hip arthroplasties performed prior to June 1984 were followed for two years, and an additional 204 were followed for five years. Anteroposterior and lateral roentgenograms taken at annual intervals were used for comparison. At two years, 78% of the hips showed roentgenographic signs of stem osseointegration. Seventeen percent were clinically stable but demonstrated reactive lines surrounding the porous surface, indicating lack of bone-ingrowth fixation. Four percent showed late implant migration. Using late migration as an end point, a survivorship analysis of the stem stability was performed. The cumulative survival rate for stable fixation was 94% at five years and 88% at eight years. Among the 143 undersized stems, 17 showed late migration and two failed by stem fracture at six and eight years, giving a cumulative survival rate of 77% at eight years. By contrast, there were no roentgenographic failures among 200 canal-filling stems. Three stems were revised: two for stem fracture and one for loosening with infection. Proximal stress shielding occurred only in bone-ingrowth stems and was slightly progressive. Unstable implants produced progressive intramedullary canal widening. The clinical results were superior when the roentgenograms showed signs of bone-ingrowth fixation. Functional recovery in such cases was equivalent to that for cemented arthroplasty.

Adolescent↗
PubMed1989

Cementless total hip replacement using the AML stem. 0-10 years results using a survivorship analysis.

343 primary arthroplasties using the AML stem were performed between 1978 and June, 1984 with a mean follow-up of 4.8 years. All had a two-year reading of stem fixation as: 1) bone ingrown or optimum (81%), 2) fibrous encapsulated or suboptimum stable (16%), or 3) unstable (3%). Using a roentgenographic end-point, we performed a 0-8 year survivor analysis of stem fixation. The cumulative survivorship rate (CSR) was 85% at eight years. Among 142 undersized stems, thirteen failed by migration after one year and two by stem fracture, giving a CSR of 71% at eight years. By contrast, no failure was recorded in 201 canal filling stems. Proximal stress shielding occurred only in bone ingrown stems and was slightly progressive. Widening of the intramedullary canal occurred with unstable stems. The clinical results were superior in patients with bone ingrown stems and functional recovery in those cases was equivalent to that of cemented arthroplasty.

Adolescent↗
PubMed1989

Femoral fracture during non-cemented total hip arthroplasty.

A study of the data on 1,318 consecutive non-cemented total hip-replacement arthroplasties revealed thirty-nine intraoperative fractures of the femur (3 per cent), only half of which were diagnosed intraoperatively. The fractures occurred in the proximal region of the femur or at the tip of the stem of the prosthesis. Most were incomplete and minimally displaced, and they did not jeopardize the stability of the femoral component. All complete proximal fractures were stabilized with a four-fifths-coated or fully coated prosthesis to provide distal fixation, and, when diagnosed intraoperatively, were fixed with cerclage wiring. When an incomplete fracture near the tip of the stem was discovered postoperatively and the posterior part of the femoral cortex was intact, a spica cast was applied, and the patient was instructed in protected weight-bearing. For a complete fracture at the tip of the stem, we recommend open reduction and internal fixation. No statistical difference was found with respect to residual pain, the score for walking, or the stability of the implant when we compared the results for the patients who had a fracture with those for the patients who did not. Modifications in surgical technique resulted in a decrease in the incidence of fractures (p less than 0.05).

Cementation↗
PubMed1988

Radiography and histology of a threaded acetabular implant. One case studied at two years.

Threaded acetabular components are widely used in cementless total hip replacement, despite a poor understanding of the nature of the bone-implant interface. We have examined one case in which the threaded titanium ring appeared to be well incorporated with no discernible radiolucency. Microradiography and histology surprisingly showed that the threads were entirely encapsulated in fibrous tissue. This raises doubt about the relevance of plain radiography to the analysis of the acetabular interface.

Acetabulum↗
PubMed1988

The influence of stem size and extent of porous coating on femoral bone resorption after primary cementless hip arthroplasty.

The influence of stem size and extent of porous coating on femoral bone resorption was examined in 411 cases of primary cementless hip arthroplasty. Moore design, cobalt alloy femoral implants with powder-made sintered porous coating on either one-third, two-thirds, or the full implant length were compared radiographically two years after surgery. A semiquantitative method was adopted for assessing resorption that involved dividing the anteroposterior (AP) and lateral roentgenograms into a total of 16 discrete sites. The 16 sites were qualitatively examined for evidence of resorption by either thinning or darkening of bone relative to the time immediately following surgery. Based on the number of sites that demonstrated resorption, the bone loss was classified as either minor and not likely to cause problems (0 to 4 sites) or pronounced and of potentially harmful clinical consequence (5 or more sites). Pronounced resorption occurred in 18% of the 411 cases. The use of larger stems resulted in increased occurrence of marked bone resorption: stems greater than or equal to 13.5 mm in diameter showed five times the incidence of pronounced resorption compared with stems less than or equal to 12.0 mm in diameter. Stems with two-thirds and full porous coating resulted in a twofold to fourfold increase in the incidence of pronounced bone resorption. The theoretic degree of stress shielding of the femoral shaft in bending was calculated for cases with complete canal filling and a radiographic appearance of bone ingrowth. There was a strong correlation between this theoretic factor and the observed bone resorption.

Aged↗
PubMed1988

Results of cementless revision for failed cemented total hip arthroplasty.

The goals of revision total hip arthroplasty (THA) are to reestablish and maintain stable implant fixation. Based upon promising early results in primary THA, porous-surfaced implants designed for bone ingrowth fixation are being increasingly used in hopes of more successfully achieving these goals than has been the case using cement. One hundred and sixty such revisions were followed for a mean of 4.4 years, with specific reference to implant fixation. Roentgenographic evaluation of implant fixation suggested four categories of femoral and acetabular components: (1) bone ingrown, (2) stable fibrous encapsulation, (3) questionable, with signs of impending instability, or (4) definitely unstable implant migration, indicative of the need for rerevision. Not surprisingly, success in achieving and maintaining stable implant fixation following revision THA is dependent upon component design, surgical technique, and preexistent bone stock damage. This classification according to bone stock damage should be borne in mind when critically evaluating the results from various revision series.

Acetabulum↗
PubMed1987

A technique of extensile exposure for total hip arthroplasty.

A technique of trochanteric osteotomy that allows extensile exposure of the hip and wide exposure of the proximal femoral diaphysis for total joint replacement is described. Pathologic conditions of the shaft encountered during arthroplasty can therefore be addressed. The approach is based on the preservation of an intact musculoosseous-muscular sleeve comprised of the gluteus medius, greater trochanter, and vastus lateralis and allows physiologic reconstruction of the hip's soft tissue envelope. This versatile approach is particularly useful in revision surgery and in difficult primary interventions where leg length is adjusted. The surgical technique, indications, and advantages are described. Early clinical results of 90 cases are presented.

Femur↗
PubMed1987

Proximal femoral osteotomy as an adjunct in cementless revision total hip arthroplasty.

Cementless total hip replacement techniques are increasingly used in revision arthroplasty. A major challenge is to achieve implant stability in a femur distorted by a failed arthroplasty. Five patients with aseptic loosening of cemented primary or revision total hip replacements complicated by significant proximal femoral disease, four with marked angular deformity of the femur and one with a subtrochanteric nonunion, were treated successfully with cementless revision arthroplasty combined with proximal femoral osteotomy. At follow-up examination, all femoral and trochanteric osteotomies had healed and D'Aubigne and Postel scores for pain, function, and range of motion had improved. All porous prostheses demonstrated radiographic features consistent with bone ingrowth fixation. No progressive stress shielding has been observed. Concomitant femoral osteotomy to correct anatomic deformity, in association with cementless total hip arthroplasty, results in union of the osteotomy and restoration of hip function.

Adult↗
PubMed1987

Porous-coated hip replacement. The factors governing bone ingrowth, stress shielding, and clinical results.

Total hip replacement using porous-coated cobalt-chrome femoral implants designed for biological fixation has been evaluated in 307 patients after two years and in 89 patients after five years. Histological study of 11 retrieved specimens showed bone ingrowth in nine and fibrous tissue fixation in two. Fixation by bone ingrowth occurred in 93% of the cases in which a press fit of the stem at the isthmus was achieved, but in only 69% of those without a press fit. The clinical results at two years were excellent. The incidence of pain and limp was much lower when there was either a press fit of the stem or radiographic evidence of bone ingrowth. Factors such as age, sex, and the disease process did not influence the clinical results. Most cases showed only slight resorptive remodelling of the upper femur, but in a few cases with a larger, more rigid stem, more extensive bone loss occurred. The results after five years showed no deterioration with time. Fixation by the ingrowth of bone or of fibrous tissue both appeared to be stable, but bone ingrowth gave better clinical results.

Aged↗
PubMed1987

Histologic analysis of a retrieved microporous-coated femoral prosthesis. A seven-year case report.

A microporous-coated femoral prosthesis with an average pore size of 80 to 100 microns was retrieved after seven years in a revision operation on a failed cemented acetabular component. The proximal anterior and lateral aspects of the implant were encrusted with bone. The bone was attached to the porous coating in regions of ingrowth. The implant was stable within the femur although most of the porous coating was not bone ingrown. There was progressive bone resorption in the proximal femur, suggestive of a reactive biologic mechanism. There was also a sizable posterior pocket of granulation tissue containing chronic inflammatory round cells associated with numerous birefringent polymeric particles. Polyethylene wear debris and acrylic cement were engulfed by multinucleated giant cells enveloping the loose cup.

Acetabulum↗
PubMed1986

Principles, techniques, results, and complications with a porous-coated sintered metal system.

Experience with biologic fixation hip arthroplasty using the powder-made sintered porous system has been very encouraging over the past 8 years. With simple implant design, accurate instrumentation, and careful attention to surgical technique, the results of surgery can be made equal to those obtained with conventional cemented arthroplasty (using the current improved implant designs and cementing techniques). Most of the problems associated with this new technology have been recognized and solved. The most serious problem is probably that of stress shielding and disuse osteoporosis, and this may well be overcome through judicious design modification. It is the next decade that will determine whether the incidence of late aseptic loosening is reduced through design for a "living" interface between implant and bone.

Acetabulum↗
PubMed1985

Biologic fixation arthroplasty in the treatment of osteonecrosis.

To provide a possible solution to the problem of aseptic loosening of prosthetic hip replacement components, the authors treated selected patients who had stage IV, V, or VI osteonecrosis with uncemented, porous-coated components on the femoral side. These stems are designed for bone ingrowth, with the goal of attaining a more viable and permanent interlocking bone between the implant and host bone. This article presents the necessary surgical principles and techniques for biologic fixation arthroplasty and reports the early results that have been obtained.

Acetabulum↗