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Biomedical subjects

C A Engh

Publications and source records attributed to C A Engh.

At least 37 records · Page 2Linked to original sources
PubMed2000

Extended slide trochanteric osteotomy for revision total hip arthroplasty.

BACKGROUND: The purpose of this study was to assess the rate of union, time to union, and complications associated with the extended slide trochanteric osteotomy. We also evaluated how outcomes were influenced by the preoperative cortical-bone thickness, the preoperative cancellous-bone quality of the greater trochanter, the number of cables used to reattach the trochanteric osteotomy fragment, and the use of cortical strut augmentation. METHODS: We reviewed the results for forty-six hips in forty-five patients who underwent a revision total hip arthroplasty with an extended slide trochanteric osteotomy between December 1991 and December 1996. Twenty-three patients were men, and twenty-two were women; the mean age at the time of the operation was 66.3 years. Two hips had an isolated acetabular revision, fifteen had an isolated femoral revision, and twenty-nine had acetabular and femoral revisions. One patient (one hip) was lost to follow-up. RESULTS: At a mean of forty-four months after the operation, the rate of union of the distal osteotomy site was 98 percent (forty-four of forty-five hips), with no change in the femoral component position. The time to union was not significantly correlated with the number of cables, the preoperative cortical-bone thickness, or the preoperative cancellous-bone quality of the greater trochanter. Interestingly, the time to bridging-callus union was significantly longer in the hips with a strut allograft than in the hips without a strut allograft (p = 0.04, t test for independent samples). Two fractures of the osteotomy fragment occurred, but neither necessitated another revision. CONCLUSIONS: The extended slide trochanteric osteotomy allows extensive acetabular and femoral exposure, facilitates removal of distal cement or a well fixed porous-coated stem, and allows reliable reattachment and healing of the trochanteric fragment.

Adult↗
PubMed2000

Osteonecrosis of the femoral head treated with cementless total hip arthroplasty.

BACKGROUND: The treatment of young patients who have osteonecrosis of the femoral head associated with collapse or substantial secondary degeneration remains a therapeutic challenge, with total hip arthroplasty being a treatment of choice. However, concerns about the durability of the results of hip arthroplasty in this population necessitate long-term evaluation of this treatment option. To determine its advantages and limitations, we evaluated the results of cementless total hip arthroplasty in a consecutive series of young patients with advanced osteonecrosis. METHODS: We reviewed the results of fifty-five consecutive primary total hip arthroplasties, after an average of 117 months of follow-up, in forty-five patients with a preoperative diagnosis of advanced osteonecrosis of the femoral head (Ficat and Arlet stage III or IV). The average age was thirty-one years (range, twenty-one to forty years) at the time of the operation. We collected data prospectively with the use of patient questionnaires and radiographs. RESULTS: Five patients died and one patient was lost to follow-up before the time of the minimum five-year follow-up; this left forty-eight hips in thirty-nine patients for inclusion in the study. Ten (21 percent) of the forty-eight hips required revision. No revisions were due to aseptic failure of the femoral component. Of the remaining twenty-nine patients (thirty-eight hips), twenty-seven (93 percent) reported few or no functional limitations and twenty-three (79 percent) could walk an unlimited distance at the time of the latest follow-up. Pain was absent or mild in twenty-five patients (86 percent). Twenty-three patients (79 percent) were employed full-time. Radiographically, thirty-seven femoral components (97 percent) were bone-ingrown and the remaining component was judged to be fibrous stable. All thirty-eight acetabular components were bone-ingrown. CONCLUSIONS: Cementless total hip arthroplasty remains a reasonable treatment option for advanced osteonecrosis of the femoral head. Wear of the bearing surface continues to limit the long-term success rate, but we are encouraged by the predictable long-term stability of the bone-implant interface achieved with cementless fixation. These results compare favorably with those of published reports of total hip arthroplasty with cement in younger patients with osteonecrosis.

Adult↗
PubMed2000

The accuracy and reproducibility of radiographic assessment of stress-shielding. A postmortem analysis.

BACKGROUND: Although periprosthetic bone loss remains a major concern in total hip arthroplasty, radiographic assessment of such loss is both difficult and subjective. In the present study, we assessed the ability of orthopaedic surgeons to reproducibly recognize changes in periprosthetic bone density on radiographs. We hypothesized that assessment of periprosthetic bone loss on plain radiographs is not reliable enough to justify its use in outcomes research. METHODS: Twenty-nine unilateral total hip replacements and the surrounding bone were retrieved at autopsy, and radiographs were made; radiographs of the contralateral, normal femur were also made after implantation of an identical prosthesis and used as a control. Three orthopaedic surgeons independently examined the specimen radiographs and classified bone loss in each of sixteen femoral zones. Bone loss was recorded as present if the bone of the femur that had had in vivo implantation showed evidence of cortical thinning, increased porosity, or decreased density (either cortical or trabecular) when compared with the control femur. The kappa coefficient was used to quantify interobserver and intraobserver reproducibility in determining bone loss for the 464 zones examined and in determining the Engh and Bobyn stress-shielding classification of each femur. In fourteen femoral pairs, bone loss was also quantified with dual-energy x-ray absorptiometry, and the resulting value was then compared with the bone-loss classification that had been determined radiographically. RESULTS: First, the surgeons agreed on the presence or absence of bone loss in 73 percent (337) of the 464 zones. The interobserver kappa value of 0.58 denoted only good reproducibility. The intraobserver reproducibility was better; the surgeon's initial evaluation of bone loss agreed with his second evaluation for 90 percent of the zones (kappa = 0.74). Second, the three surgeons agreed on the degree of stress-shielding, according to the Engh and Bobyn classification, in 66 percent (nineteen) of the twenty-nine femora. The kappa value for this comparison was only 0.27, indicating marginal reproducibility. Third, although there was some agreement among reviewers when there was 20 to 60 percent reduction in bone-mineral content as determined with dual-energy x-ray absorptiometry, excellent agreement among the examiners (kappa = 0.85) was not achieved until bone loss averaged 70 percent. CONCLUSIONS: On the basis of these results, we suggest caution in interpreting results from studies of femoral bone loss that have used plain radiographic analysis if the authors have not provided interobserver reliability data. We question the utility of evaluating periprosthetic bone loss on radiographs, since the loss is not reproducibly recognized until 70 percent of the bone is gone.

Absorptiometry, Photon↗
PubMed2000

The effect of weight-bearing on the radiographic measurement of the position of the femoral head after total hip arthroplasty.

BACKGROUND: In most radiographic studies of polyethylene wear, investigators have used routine annual radiographs made with the patient in the supine position in order to measure penetration by the femoral head into the polyethylene liner. However, researchers have begun to question the effect of weight-bearing on the position of the head within the acetabular cup and, consequently, the effect of weight-bearing on measurements of penetration by the head. The purpose of the current study was to determine the effect of weight-bearing on the two-dimensional radiographic position of the femoral head within the acetabular cup. METHODS: Thirty-seven patients (forty-seven hips) who had had a total hip arthroplasty had radiographs made at one of two separate institutions. A set of anteroposterior radiographs was made for each patient: one radiograph was made with the patient supine and one was made with the patient upright bearing full weight on the replaced hip. At one of the institutions, a third anteroposterior radiograph was made with the patient in the same upright position but not bearing weight on the replaced hip. All measurements of the two-dimensional position of the head were performed by a single observer with use of a previously published computerized measurement system. RESULTS: Data from both institutions revealed that measurements of the position of the head on radiographs made with the patient supine were strongly and significantly correlated with measurements of the position of the head on radiographs made with the patient bearing weight (r2>0.93, p<0.001 for both regressions). Examination of the differences between the measurements revealed no bias for one set of measurements to consistently underestimate or overestimate the values derived with use of the other method. Moreover, we found a nearly perfect relationship between the measurements of the position of the head on radiographs made with the patient standing and bearing weight and those on radiographs made with the patient standing but not bearing weight (r2 = 0.97, p<0.001, slope = 0.99, intercept = 0.02 millimeter). CONCLUSIONS: On the basis of these findings, there is no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner.

Arthroplasty, Replacement, Hip↗
PubMed1999

Correlation between pre-operative periprosthetic bone density and post-operative bone loss in THA can be explained by strain-adaptive remodelling.

Periprosthetic adaptive bone remodelling after total hip arthroplasty can be simulated in computer models, combining bone remodelling theory with finite element analysis. Patient specific three-dimensional finite element models of retrieved bone specimens from an earlier bone densitometry (DEXA) study were constructed and bone remodelling simulations performed. Results of the simulations were analysed both qualitatively and quantitatively. Patterns of predicted bone loss corresponded very well with the DEXA measurements on the retrievals. The amount of predicted bone loss, measured quantitatively by simulating DEXA on finite element models, was found to be inversely correlated with the initial bone mineral content. It was concluded that the same clinically observed correlation can therefore be explained by mechanically induced remodelling. This finding extends the applicability of numerical pre-clinical testing to the analysis of interaction between implant design and initial state of the bone.

Absorptiometry, Photon↗
PubMed1999

Factors affecting femoral bone remodeling after cementless total hip arthroplasty.

We performed a postmortem comparison of femurs from two patients who had bilateral cementless total hip arthroplasties with femoral prostheses of different stiffness implanted in their right and left hips. Radiographs of transverse sections of the four femurs demonstrated that all the prostheses were bone ingrown with the most ingrowth occurring distally where the porous coating contacted diaphyseal bone. In both patients, dual-energy x-ray absorptiometry analysis revealed that the femur implanted with the stiffer prosthesis had a 65% to 79% greater loss of proximal periprosthetic bone than the femur implanted with the more flexible prosthesis. One patient, however, had a dramatically greater total loss of bone from side to side than the other patient. In this patient, we believe that it was host factors more than the differences in stem stiffness that affected the bone-remodeling pattern. Although the two femurs with the stiffer prostheses had the greatest bone loss, the two femurs with the more flexible prostheses demonstrated radiographic signs of cantilever bending of the prosthetic stem and failure of proximal osseointegration. We are not aware of any other bilateral human postmortem analysis that so clearly illustrates the effect of stem stiffness on bone remodeling.

Absorptiometry, Photon↗
PubMed1999

Two-dimensional versus three-dimensional radiographic measurements of polyethylene wear.

Because polyethylene wear adversely affects the outcome of total hip arthroplasty, reliable techniques for in vivo radiographic evaluation of femoral head penetration into the polyethylene liner are needed. With the recent development of software to measure three-dimensional femoral head penetration, the adequacy of two-dimensional head penetration measurements to estimate a three-dimensional process has been questioned. Thus, the purpose of the current study was to compare directly two-dimensional and three-dimensional radiographic measurements of femoral head penetration. Using two computer assisted radiographic techniques, the authors of this study measured the two-dimensional and the three-dimensional penetration of the femoral head into the polyethylene liner in 202 hips implanted with porous coated acetabular components. A comparison of two-dimensional and three-dimensional measurements showed that, on average, the mean amount of three-dimensional head penetration was larger than the mean amount of two-dimensional head penetration. However, linear regression analysis showed that the two measurements were highly correlated (r2 = 0.87, slope = 0.99, intercept = 0.08 mm). For most patients (95%), two-dimensional and three-dimensional measurements of femoral head penetration were nearly equal. However, there was a small subset of patients (5%) for whom three-dimensional radiographic penetration measurements were three times greater than corresponding two-dimensional radiographic penetration measurements. No common risk factor among this small subset of patients was identified. The current study provides practical information for the orthopaedic surgeon trying to assess polyethylene wear in hip replacement cases. It shows that for most patients head penetration can be measured sufficiently from anteroposterior radiographs alone. However, in a small percentage of patients (5% in the current study) the femoral head also moves perpendicular to the plane of the anteroposterior radiograph. For these cases, accurate analysis of head penetration requires three-dimensional analysis using anteroposterior and lateral radiographs.

Acetabulum↗
PubMed1999

The role of acetabular component screw holes and/or screws in the development of pelvic osteolysis.

Anecdotal reporting of osteolysis around cementless modular acetabular components with holes through the metal shell and/or iliac fixation screws has raised concern that such designs may generate excessive particulate debris and/or permit direct access of particulate debris to iliac bone. To address this issue, incidence data are reported on 513 total hip replacements from six different single-surgeon series of total hip arthroplasties performed with six different porous ingrowth acetabular components. With follow-up ranging from 40 to 108 months, a total of 45 pelvic osteolytic lesions were observed (8.8 per cent). Pelvic osteolysis was seen nearly as frequently in the ischium and pubis (21 lesions) as it was in the ilium (24 lesions). It was not possible to explain ischial and pubic osteolysis by holes and/or screws through the acetabular component shell. There was no direct correlation between the presence of screw holes or screws and the incidence of pelvic osteolysis. The incidence of pelvic osteolysis around modular components with holes through the shell was 4.5 per cent (14 of 313 hips). The incidence of pelvic osteolysis with solid-shell components was 15.5 per cent (31 of 200). The incidence of pelvic osteolysis around acetabular reconstructions with screws was 2.3 per cent (3 of 133). The incidence of pelvic osteolysis in reconstructions without screws was 11.1 per cent (32 of 380). The incidence of pelvic osteolysis in one-piece acetabular components (polyethylene pre-fixed in the metal shell) was 12.7 per cent (21 of 165) and the incidence of pelvic osteolysis with the modular components was 6.9 per cent (24 of 348). In each comparison, the incidence of pelvic osteolysis was actually lower in the group assumed to be at increased risk. Based on this review there does not appear to be a direct relationship between holes and/or screws through an acetabular component and the development of pelvic osteolysis. The incidence of pelvic osteolysis was associated with larger head diameters and longer follow-up. While screw holes may provide an access channel in specific cases, the present data indicate that the simple elimination of holes through the acetabular shell will not eliminate pelvic osteolysis. Regardless of other acetabular component design features, joint fluid and polyethylene wear particles from the femoral-acetabular articulation can gain access to bone behind an acetabular component via the peripheral implant-bone interface through regions without sufficient contact or tissue ingrowth. The development of pelvic osteolysis is multifactorial and includes the total volumetric wear of polyethylene as well as specific features of the acetabular component design and reconstruction technique.

Adult↗
PubMed1999

Analysis of temporal wear patterns of porous-coated acetabular components: distinguishing between true wear and so-called bedding-in.

BACKGROUND: Standard radiographic assessment of penetration by the femoral head into a polyethylene liner does not enable clinicians to distinguish between the two processes that cause movement of the head: true wear (the removal of polyethylene particles) and so-called bedding-in (other factors, such as creep and settling-in of the liner). By analyzing radiographs made over time, researchers can distinguish true wear from the bedding-in process. The purpose of the current study was to compare the wear performance of the initial modular acetabular cup design (so-called first-generation components) of three different manufacturers with that of a so-called second-generation component made by one of the manufacturers. METHODS: A two-dimensional computerized radiographic method was used to analyze 1300 radiographs of 315 hips that were followed for 3.0 to 10.5 years. Temporal penetration by the head in the three groups of first-generation cups was compared with penetration in the group of second-generation cups. Multiple linear regression analysis was used to model penetration-versus-time data as a line for each group. The slope of each regression line indicated the true rate of wear, and the intercept of the regression line indicated the amount of bedding-in. RESULTS: Modifications in the design of the second-generation components, including thicker polyethylene and an improved locking mechanism, led to a decrease in the mean penetration by the head; however, the second-generation component did not have a lower true rate of wear than two of the first-generation components. Rather, the decreased penetration by the head into the second-generation component resulted from decreased bedding-in of the liner. CONCLUSIONS: These findings and this technique of analysis are clinically relevant to surgeons who evaluate polyethylene wear radiographically. First, penetration by the head in the early postoperative years might not be due entirely to abrasive wear of the polyethylene liner but, rather, to a change in the position of the head resulting from the bedding-in process. The inclusion of bedding-in in calculations of wear artificially inflates the rate of wear and may result in a misrepresentation of the potential risk of wear-related complications. This is especially true with regard to comparisons of different designs of modular cups, in which conformity and tolerances between the polyethylene liner and the metal shell can vary greatly. Second, analysis of penetration by the head at multiple time-intervals can be used to distinguish true polyethylene wear from the bedding-in process. Such an analysis allows more accurate determination of the true rates of wear of different designs of modular cups and, therefore, of potential wear-related complications.

Acetabulum↗
PubMed1999

Analysis of prosthetic femoral heads retrieved at autopsy.

This study examined 24 prosthetic femoral heads retrieved at autopsy from patients with clinically and radiographically successful arthroplasties. Four alumina ceramic and 20 cobalt chrome heads in service for an average of 8.5 years were examined with a contact and a laser stylus profilometer. The authors documented general increases in surface roughness of the cobalt chrome and ceramic femoral heads attributable to in vivo articulation and also observed wear polishing around the apical region of the cobalt chrome heads. The roughness of the prosthetic femoral heads was compared with the polyethylene wear in the matching liners. No relationship was found between femoral head roughness values and polyethylene wear or component duration in situ. The only variable related to the pattern of head roughness and polyethylene wear was the presence of embedded particle debris in the polyethylene liner. Roughness parameters for cobalt chrome heads without embedded debris in the polyethylene liner were fairly uniform around the head. Roughness values, which were higher for heads associated with debris, had a decreasing gradient of surface roughness from the equator to the apex. In addition, the polyethylene wear rate for cups with embedded particle debris in the liner was significantly greater than the wear rate for cups without embedded debris. This study also showed a strong correlation between surface roughness values measured with the contact profilometer and values measured with the noncontact laser profilometer. However, laser profilometer values were four to six times higher, indicating that roughness parameters measured by the two different profilometers cannot be compared directly. Findings of this study point consistently to the influence of third body wear particles on prosthetic femoral head roughness and polyethylene wear. These results stress the importance of minimizing all foreign body debris in maintaining a well functioning articular couple.

Adult↗
PubMed1998

Examination of wear in Duraloc acetabular components: two- to five-year evaluation of Hylamer and Enduron liners.

To help increase the longevity of polyethylene components used in total joint arthroplasty, new forms of ultrahigh molecular weight polyethylene (UHMWPE) have been developed. This study reports on the in vivo performance of Hylamer (DePuy DuPont Orthopaedics, Newark, DE), a high crystalline form of UHMWPE, and on the performance of conventional Enduron polyethylene (DePuy, Warsaw, IN). With the use of a specially designed computer system, the time course of two-dimensional femoral head penetration into 80 Hylamer and 140 Enduron acetabular liners in situ from two to five years was compared. At the most recent follow-up (mean, 3.6 years), the rate of femoral head penetration into the Hylamer liners was lower than the rate of head penetration into the Enduron liners (0.15 mm/year versus 0.20 mm/year, P = . 10). Temporal analysis revealed that the Hylamer liners had lower penetration rates than those of the conventional polyethylene liners in the first three postoperative years, but that head-penetration rates between the two groups became similar with increased time in situ. Continued examination of both types of polyethylene components is imperative before conclusions on long-term performance can be drawn.

Acetabulum↗
PubMed1998

Total hip arthroplasty with porous-coated prostheses fixed without cement in patients who are sixty-five years of age or older.

We reviewed the results of 212 total hip arthroplasties performed without cement in 203 unselected, consecutive patients who were sixty-five years of age or older. The outcome was known for 196 hips, thirty-seven of which had been followed until the death of the patient and 159 of which had been followed for a minimum of five years. A reoperation was done in 4 percent (seven) of the 196 hips. These reoperations included one revision because of loosening of the stem and five revisions of the cup. Three of the acetabular revisions were done because of fracture due to polyethylene wear; one, because of recurrent dislocation; and one, because of polyethylene wear and a fracture due to lysis. In the seventh reoperation, a cup and stem were exchanged because of infection. The probability that a hip prosthesis would survive twelve years without a reoperation was 0.92 (95 percent confidence interval, 0.85 to 0.99). We evaluated the clinical results for 152 patients who had not had a reoperation and had been followed for at least five years (mean, 8.5 years; range, five to fourteen years). Of these patients, thirteen (9 percent) had pain that limited activity: five (3 percent) had pain in the thigh (four patients) or groin (one patient), and eight (5 percent) had trochanteric pain and tenderness. One hundred and forty-four (95 percent) of the patients noted an improvement in overall function, and 149 (98 percent) reported satisfaction with the outcome. One hundred and thirty-five hips that were not revised were followed radiographically for at least five years (mean, 8.2 years; range, five to fourteen years). In this group, osteolysis was observed in three hips (2 percent); loosening of the cup, in three (2 percent); and loosening of the stem, in one (1 percent). Stress-shielding was seen on the two-year postoperative radiographs of forty-five (26 percent) of the 174 hips that were followed for at least that duration. The prevalence of osteolysis, loosening of a component, and reoperations was no greater in this subgroup than in the overall group. These results indicate that total hip arthroplasty without cement can be successful in older patients. This study also provides a reference for comparison with the results of total hip arthroplasty performed with cement and those of so-called hybrid total hip arthroplasty (an acetabular component fixed without cement and a femoral component fixed with cement) in patients who are sixty-five years of age or older.

Aged↗