Biomedical subjects

C Anderson Engh

Publications and source records attributed to C Anderson Engh.

22 records · Page 2Linked to original sources

PubMed2003

Effect of terminal sterilization with gas plasma or gamma radiation on wear of polyethylene liners.

BACKGROUND: Although terminal sterilization with gamma radiation in air promotes cross-linking, which improves wear resistance, it also results in free radicals, which can oxidize and degrade the mechanical properties of polyethylene liners used for total hip arthroplasty. For this reason, non-cross-linked polyethylene components have also been sterilized with chemical surface treatments, such as gas plasma. In this study, we tested the hypothesis that conventional polyethylene liners cross-linked by sterilization with gamma radiation in air had better in vivo wear performance than non-cross-linked liners sterilized with gas plasma. METHODS: We retrospectively reviewed the wear rates in a series of hips treated with a Duraloc 100 cup, a 28-mm femoral head, and an Enduron liner that had been sterilized with either gamma radiation (sixty-one hips followed for a mean of 5.2 years) or gas plasma (sixty-three hips followed for a mean of 3.9 years). The irradiated liners had been stored with access to ambient oxygen for an average of 1.0 year (range, 0.05 to 5.72 years) prior to implantation. Multiple linear regression was used to assess the effect of the sterilization method on the wear rate while accounting for the possible influence of other factors, including liner geometry, femoral head material, patient gender, cup abduction angle, and age at surgery. RESULTS: The polyethylene liners that had been sterilized with gamma radiation in air had a significantly lower wear rate than did the gas-plasma-sterilized liners (0.097 compared with 0.19 mm/yr, p < 0.001). The sterilization method (p < 0.001) and age at surgery (p = 0.001) were the only factors that we analyzed that correlated with the wear rate. CONCLUSIONS: The in vivo wear of conventional polyethylene liners that had been sterilized with gamma radiation in air was, on the average, 50% less than that of non-cross-linked liners sterilized with gas plasma. LEVEL OF EVIDENCE: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Gamma Rays↗

PubMed2003

Radiographic definition of pelvic osteolysis following total hip arthroplasty.

BACKGROUND: Radiographs are the standard clinical tool used to monitor patients with pelvic osteolysis after total hip arthroplasty; however, previous reports have questioned the value and accuracy of this method. With use of a cadaveric model, we investigated the accuracy of radiographs in determining the location and size of periacetabular osteolysis. METHODS: We implanted total hip arthroplasty components in eight cadaveric hips and made four radiographs of each hip from different views. We then removed the components and created two pelvic defects in each hip. We measured the volume of each defect, reimplanted the components, and made another set of radiographs. The defects were then enlarged two more times, with the volume measured and another set of radiographs made each time. In total, 128 radiographs were made of forty-eight lesions. An orthopaedist who was blinded to the location of the lesions assessed the radiographs with regard to the presence and size of osteolytic lesions. RESULTS: The overall sensitivity for the detection of osteolysis on a single radiograph was 41.5%, and the overall specificity was 93.0%. Sensitivity was dependent on the location and size of the lesions but not on the radiographic view. Sensitivity ranged from 72% for lesions in the ilium to </=15% for lesions in the ischium and acetabular rim. The detection rate for lesions with a volume of >10 cm (3) was significantly higher than that for smaller lesions (p < 0.001). When all four radiographic views of one lesion were analyzed together, sensitivity increased to 73.6%. Despite the low sensitivity, specificity remained high, indicating that once osteolysis is evident radiographically, the likelihood that a lesion truly exists is high. Additionally, we found that the extent of osteolysis was substantially underestimated on radiographs. CONCLUSIONS: The use of radiographs to assess and monitor osteolysis has both limitations and merits. Using multiple views, an experienced orthopaedist identified only 73.6% of pelvic lesions. However, once a pelvic osteolytic lesion is evident radiographically, the likelihood that it truly exists is high.

Aged↗

PubMed2002

Interobserver and intraobserver variability in radiographic assessment of osteolysis.

This study quantified the variability associated with diagnosing periprosthetic osteolysis from the radiographs of total hip arthroplasty patients. Four joint arthroplasty surgeons independently assessed radiographs of 60 patients for evidence of osteolysis in different zones. The surgeons agreed on the presence of lesions in at most 57% of the zones. kappa coefficients, used to quantify the extent of agreement among the surgeons, denoted poor interobserver reproducibility (kappa =.28 to.44). Intraobserver reliability-determined by comparing 2 reviews of the same radiographs done by 1 surgeon 2 weeks apart-was moderate to excellent (kappa =.48 to.84). We also compared the results from the most recent radiograph with those from a time series. Agreement improved when a series was reviewed. Reliable comparisons cannot be made with osteolysis rates reported by different observers. In the research setting, osteolysis rates are more reliable if they are determined by a single reviewer whose intraobserver variability has been reported. In assessing a patient for osteolysis, it is more accurate to analyze a series of radiographs than the most recent radiograph.

Arthroplasty, Replacement, Hip↗

PubMed2002

Extensively porous-coated femoral revision for severe femoral bone loss: minimum 10-year follow-up.

Of 275 femoral revisions done at our institution from 1982 to 1986, we identified 34 patients (35 hips) who represented the senior author's (C.A.E., Sr.) most difficult revision cases as a result of extensive femoral bone loss at least 10 cm below the lesser trochanter. The patients were revised with fully porous-coated femoral components >or=190 mm. We evaluated 25 of the patients (26 hips) who had a minimum 10-year follow-up (mean, 13.3 years). Survivorship was 89% at 10 years with femoral revision as the endpoint (Kaplan-Meier). The femoral aseptic loosening rate was 15% (4 of 26). Three stems were loose but did not warrant reoperation. One stem was revised for aseptic loosening, 1 was revised for septic loosening, and 1 was revised for a fractured femoral component. Bypassing weak or absent femoral bone with an extensively porous-coated stem is an effective reconstructive technique for patients with extensive femoral bone loss.

Adult↗