(1/4301) Analysis of 118 second-generation metal-on-metal retrieved hip implants.
Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants. Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 microm for the whole articulation per year in the first year, decreasing to about 5 microm per year after the third. Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis. (+info)
(2/4301) Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A ten-year follow-up report.
We report the results of our continued review of 14 hip arthroplasties using alumina ceramic femoral heads with cross-linked polyethylene cups. There have been no complications and a very low rate of penetration. This was 0.02 mm per year after an initial 'bedding-in' period of two years. There has been no change in the mean rate between our earlier study at six years and the current results at 10 to 11 years. The use of these bearing surfaces appears to reduce the potential amount of polyethylene debris and may provide the next logical stage in the development of the Charnley low-friction arthroplasty. (+info)
(3/4301) Cement migration after THR. A comparison of charnley elite and exeter femoral stems using RSA.
Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail. Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates. Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interfaces. (+info)
(4/4301) Subsidence of a non-polished stem in revisions of the hip using impaction allograft. Evaluation with radiostereometry and dual-energy X-ray absorptiometry.
We revised 24 consecutive hips with loosening of the femoral stem using impaction allograft and a cemented stem with an unpolished proximal surface. Repeated radiostereometric examinations for up to two years showed a slow rate of subsidence with a mean of 0.32 mm (-2.0 to +0.31). Fifteen cases followed for a further year showed the same mean subsidence after three years, indicating stabilisation. A tendency to retroversion of the stems was noted between the operation and the last follow-up. Retroversion was also recorded when displacement of the stem was studied in ten of the patients after two years. Repeated determination of bone mineral density showed an initial loss after six months, followed by recovery to the postoperative level at two years. Defects in the cement mantle and malalignment of the stem were often noted on postoperative radiographs, but did not correlate with the degrees of migration or displacement. After one year, increasing frequency of trabecular remodelling or resorption of the graft was observed in the greater trochanter and distal to the tip of the stem. Cortical repair was noted distally and medially (Gruen regions 3, 5 and 6). Migration of the stems was the lowest reported to date, which we attribute to the improved grafting technique and to the hardness of the graft. (+info)
(5/4301) Determination of Hounsfield value for CT-based design of custom femoral stems.
Ct and advanced computer-aided design techniques offer the means for designing customised femoral stems. Our aim was to determine the Hounsfield (HU) value of the bone at the corticocancellous interface, as part of the criteria for the design algorithm. We obtained transverse CT images from eight human cadaver femora. The proximal femoral canal was rasped until contact with dense cortical bone was achieved. The femora were cut into several sections corresponding to the slice positions of the CT images. After obtaining a computerised image of the anatomical sections using a scanner, the inner cortical contour was outlined and transferred to the corresponding CT image. The pixels beneath this contour represent the CT density of the bone remaining after surgical rasping. Contours were generated automatically at nine HU levels from 300 to 1100 and the mean distance between the transferred contour and each of the HU-generated contours was computed. The contour generated along the 600-HU pixels was closest to the inner cortical contour of the rasped femur and therefore 600 HU seem to be the CT density of the corticocancellous interface in the proximal part of cadaver femora. Generally, femoral bone with a CT density beyond 600 HU is not removable by conventional reamers. Thus, we recommend the 600 HU threshold as one of several criteria for the design of custom femoral implants from CT data. (+info)
(6/4301) Endovascular stent graft repair of aortopulmonary fistula.
Two patients who had aortopulmonary fistula of postoperative origin with hemoptysis underwent successful repair by means of an endovascular stent graft procedure. One patient had undergone repeated thoracotomies two times, and the other one time to repair anastomotic aneurysms of the descending aorta after surgery for Takayasu's arteritis. A self-expanding stainless steel stent covered with a Dacron graft was inserted into the lesion through the external iliac or femoral artery. The patients recovered well, with no signs of infection or recurrent hemoptysis 8 months after the procedure. Endovascular stent grafting may be a therapeutic option for treating patients with aortopulmonary fistula. (+info)
(7/4301) Total knee replacement: should it be cemented or hybrid?
OBJECTIVE: To compare the complication rates associated with total knee arthroplasty against the types of fixation (hybrid or cemented), using a single total knee design (the anatomic modular knee [AMK] prosthesis). DESIGN: A prospective, nonrandomized, controlled trial. SETTING: University Hospital in London, Ont., a tertiary care teaching centre. PATIENTS: Two groups made up of 484 knees in 395 patients (89 bilateral). INTERVENTIONS: In 260 knees a hybrid configuration (cemented tibia and noncemented femur) was used (group 1). In 224 knees the femoral and tibial components were cemented (group 2). All patellae were cemented in both groups. MAIN OUTCOME MEASURES: Clinical results were assessed by The Knee Society Clinical Rating Scores at 3 months, 6 months and yearly intervals. Radiographic results were determined by 3-foot standing radiographs and at each follow-up visit standing knee radiographs, lateral and skyline views. Radiographs were analysed for alignment, presence or absence of radiolucent lines or changes in the position of the implant. All reoperations and nonoperative complications were recorded. RESULTS: At an average follow-up of 4.8 years, 8 knees (1.6%) required reoperation. An analysis of the complications leading to reoperation demonstrated no difference between the 2 groups. CONCLUSIONS: There was no difference in outcome whether the femoral component was cemented or not. Medium-term results of the AMK are excellent with a very low reoperation rate. (+info)
(8/4301) Bileaflet mechanical prostheses for aortic valve replacement in patients younger than 65 years and 65 years of age or older: major thromboembolic and hemorrhagic complications.
OBJECTIVE: To determine major thromboembolic and hemorrhagic complications and predictive risk factors associated with aortic valve replacement (AVR), using bileaflet mechanical prostheses (CarboMedics and St. Jude Medical). DESIGN: A case series. SETTING: Cardiac surgical services at the teaching institutions of the University of British Columbia. PATIENTS AND METHODS: Patients 2 age groups who had undergone AVR between 1989 and 1994 were studied. Group 1 comprised 384 patients younger than 65 years. Group 2 comprised 215 patients 65 years of age and older. RESULTS: The linearized rates of major thromboembolism (TE) occurring after AVR were 1.54%/patient-year for group 1 and 3.32%/patient-year for group 2; the rates for major TE occurring more than 30 days after AVR were 1.13%/patient-year for group 1 and 1.55%/patient-year for group 2. The crude rates for major TE occurring within 30 days of AVR were 1.04% for group 1 and 3.72% for group 2. The death rate from major TE in group 1 was 0.31%/patient-year and in group 2 was 0.88%/patient-year. Of the major TE events occurring within 30 days, 100% of patients in both age groups were inadequately anticoagulated at the time of the event, and for events occurring more than 30 days after AVR, 45% in group 1 and 57% in group 2 were inadequately anticoagulated (INR less than 2.0). The overall linearized rates of major hemorrhage were 1.54%/patient-year for group 1 and 2.21%/patient-year for group 2. There were no cases of prosthesis thrombosis in either group. The mean (and standard error) overall freedom from major TE for group 1 patients at 5 years was 95.6% (1.4%) and with exclusion of early events was 96.7% (1.3%); for group 2 patients the rates were 90.0% (3.2%) and 93.7% (3.0%), respectively. The mean (and SE) overall freedom from major and fatal TE and hemorrhage for group 1 patients was 90.1% (2.3%) and with exclusion of early events was 91.2% (2.3%); for group 2 patients the rates were 87.9% (3.1%) and 92.5% (2.9%), respectively. The 5-year rate for freedom from valve-related death for group 1 patients was 96.3% (2.1%) and for group 2 patients was 97.2% (1.2%). CONCLUSION: The thromboembolic and hemorrhagic complications after AVR with bileaflet mechanical prostheses occur more frequently and result in more deaths in patients 65 years of age and older than in patients years younger than 65 years. (+info)