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Biomedical subjects

H Malchau

Publications and source records attributed to H Malchau.

At least 19 recordsLinked to original sources
PubMed2001

Impaction technique and graft treatment in revisions of the femoral component: laboratory studies and clinical validation.

The micromotions of femoral stems cemented into impacted bone-graft were studied in 23 femora from adult sows. The model was validated against 2 patient groups. Conventional impaction technique and a new impaction technique using polished and rotating impactors were studied in the preclinical model and in 14 and 10 patients with type II defects. The specimens were loaded in an MTS (Minneapolis Testing System) machine for 72,000 cycles at 250N to 3,250N. The bone-graft was rinsed in tepid water, and most of the bone marrow and fat were removed. Radiostereometric measurements revealed small subsidence of the stems cemented into the specimens and the patients 6 weeks after the operation without any difference (median values, -0.06 to -0.16 mm). Further studies of specimens operated with nontreated bone-graft showed that extraction of fat increased the stability. Our findings suggest that the early postoperative implant stability after impaction grafting of the femur mainly is an effect of surgical technique and graft treatment. The new impaction technique, with which we hoped to obtain a more reproducible procedure and less risk for perioperative fracture, resulted in stability equal to that obtained with the conventional technique.

Animals↗
PubMed2000

Hydroxyapatite and tricalcium phosphate-coated cups with and without screw fixation: a randomized study of 64 hips.

Sixty-two patients (64 hips) were provided with porous press-fit cups (Trilogy), plasma-sprayed with a coating consisting of 70% hydroxyapatite and 30% tricalcium phosphate. The patients were randomized to a cup with cluster holes for adjunctive screw fixation (n = 30) or to a cup without holes (n = 34). Radiostereometry was used to study migration and wear. Up to 2 years median translations and rotations <0.2 mm and <0.2 degrees were recorded in the 2 groups, without any difference. The median annual proximal wear (0.11 and 0.12 mm) was within the expected range despite the use of a ceramic coating, and it did not differ between the 2 designs. Radiolucent lines were frequently seen postoperatively but diminished during the follow-up without any sign of migration into the gaps. At 2 years, the median Harris scores were 99 points (range, 51-100 points) in the group with and 98 points (range, 69-100 points) in the group without screws. The results indicate that early fixation can be achieved for ceramic-coated press-fit cups without using additional screw fixation.

Acetabulum↗
PubMed2000

Cemented first-time revisions of the femoral component: prospective 7 to 13 years' follow-up using second-generation and third-generation technique.

In a prospective, consecutive study of first-time cemented femoral revisions, 109 hips were evaluated for a minimum of 7 years. There were 87 Charnley (18 standard, 69 long), 21 Spectron (3 standard, 18 long), and 1 Brunswick long-stem arthroplasties. There was an increased risk for rerevision in younger patients (P = .0001) and with use of standard stems (P = .002). Factors of importance for development of mechanical failure were younger age (P = .0001), presence of more pronounced bone defects (P < .005), use of standard stems (P < .0005), and presence of radiolucencies on the postoperative radiographs (Gruen zones 4 and 6) (P < .01). Our results confirm that cemented femoral revisions are a durable option in elderly patients, when improved cementing techniques and long-stem prostheses are used.

Adult↗
PubMed2000

Are the findings in the Swedish National Total Hip Arthroplasty Register valid? A comparison between the Swedish National Total Hip Arthroplasty Register, the National Discharge Register, and the National Death Register.

The Swedish National Total Hip Arthroplasty (THA) Register was initiated in 1979, and it is one of the oldest quality registers in the world. The register covers all hospitals in Sweden, and today it contains > 205,000 hip arthroplasties. The failure endpoint definition in the register is revision. There is no information about quality of life and mortality. The aim of this study was to validate the results presented by the Swedish THA register by comparison with the Discharge register (the Swedish National Board of Health and Welfare) and to study mortality after hip arthroplasties. All hip arthroplasties from the Discharge register, performed in 1986 and thereafter, were compared with the Swedish THA register. Epidemiologic parameters, including mortality, were documented from the Swedish Death register. The mortality for primary THAs for men was 1% higher and for women 6% higher when compared with an age-matched and sex-matched cohort. For revision, the numbers were 7% and 9% higher. The risk for death compared with an age-matched and sex-matched population was lower for patients with osteoarthrosis treated with hip arthroplasty. The results with revision as failure endpoint showed that the Swedish THA register is reliable. The register includes >95% of the primary and revision THAs performed in Sweden between 1986 and 1995.

Aged↗
PubMed2000

Outcome after total hip arthroplasty: Part I. General health evaluation in relation to definition of failure in the Swedish National Total Hip Arthoplasty register.

The Swedish National Total Hip Arthroplasty register, which was started in 1979, is one of the oldest national quality registers in the world and consists of over 160,000 primary operations and 12,500 revisions. The register identifies risk factors for poor outcomes related to the patient, implant and surgical techniques. The end-point for failure, i.e., revision, does not provide information about the patient's general health after the primary procedure. The aim of this study was twofold. First, to validate the end-point for failure in the Swedish National Total Hip Arthroplasty register and secondly, to study general health after total hip arthroplasty. We validated the outcome of 1,056 primary THRs randomly selected from the Discharge register in Sweden by comparing the data to the Swedish THA register. These patients had answered the SF-36 and Nottingham Health Profile questionnaires. By comparing the clinical outcome, measured as general health, with the results obtained from the register, we evaluated the importance of the end-point for failure. We found that the end-point was useful, but further evaluations are desirable. Patients operated on with hip replacement do very well up to 10 years postoperatively and those who are not revised have good general health. The findings in this study can be used as a reference for others as it shows results from a national register, with a random selection of the study cohort.

Activities of Daily Living↗
PubMed2000

Long-term registration has improved the quality of hip replacement: a review of the Swedish THR Register comparing 160,000 cases.

The Swedish Hip Register has defined the epidemiology of total hip replacement in Sweden. Most hip implants are fully cemented. Serious complications and rates of revision have declined significantly despite an increasing number of patients at risk. During the past 5 years, only 8-9% of hip replacements are revisions. Aseptic loosening with or without osteolysis is the major problem and constitutes 71% of the revisions, but the incidence had decreased three times during the past 15 years to less than 3% at 10 years. The effectiveness of the surgical technique is the most important factor for reducing the risk of revision because of aseptic loosening, but choice of implant is also important. In practice, total hip replacement in Sweden has improved, as judged by information from this Register about individualized patient risks, implant safety, and the greater efficacy of surgical and cementing techniques.

Age Distribution↗
PubMed2000

Validity and reliability of Swedish WOMAC osteoarthritis index: a self-administered disease-specific questionnaire (WOMAC) versus generic instruments (SF-36 and NHP).

We assessed whether a disease-specific, self-administered questionnaire could replace a generic instrument as an outcome tool after total hip replacement, and tested the validity and reliability of the Swedish WOMAC osteoarthritis index. 58 patients operated on with total hip arthroplasty 2-10 years ago were randomized to the study. All patients were asked to answer one disease-specific questionnaire (WOMAC osteoarthritis index) and two generic instruments (NUP and SF-36) in the same week. The procedure was repeated after 4 weeks. We tested content validity, construct validity, criterion validity, test-retest reliability and internal consistency reliability according to total score, domains and items. We found that both the generic instruments (NHP and SF-36) and the disease-specific test (WOMAC) had a high validity, i.e., measuring what they were supposed to measure (high validity). The questionnaires were also reproducible over time (high reliability). We suggest the Swedish WOMAC to be used after total hip arthroplasty in future studies.

Aged↗
PubMed2000

Survival of hip replacements. A comparison of a randomized trial and a registry.

At the authors' hospital, 410 primary total hip replacements were performed on 372 patients between September 1, 1985, and May 31, 1989. All hips were assigned randomly to receive a Charnley prosthesis with an ogee flanged cup or a Spectron prosthesis with a metal backed cup. Eleven-year survivor analysis, using revision as the end point definition of failure, revealed a survival rate of 93.2% +/- 5.8% for the Charnley replacement and 95.9% +/- 3.0% for the Spectron. If each component of the systems was analyzed (concerning aseptic loosening), the ogee cup and the Spectron stem had 100% survival. The survivorship for all 410 hips was 94.5% +/- 3.4%. If the end point definition of failure was expanded to include patient dissatisfaction, the survival rate decreased to 86.3% +/- 4.9%. These survival rates were compared with the rates obtained by the Swedish National Hip Registry. The national cohort included all patients in Sweden who were treated surgically with a Charnley (14,053 patients) or Spectron (metal backed cup) prosthesis (726 patients) between September 1, 1985, and May 31, 1989. Eleven-year survivor analysis revealed a national survival rate of 92.1% +/- 0.7% for the Charnley replacement and 88.6% +/- 6.1% for the Spectron. The analyses from the Swedish Registry are based on more than 160,000 primary operations and 11,500 revisions. Despite the enormous amount of data, there are drawbacks, and registries never can replace the prospective, randomized trial. One reason is the Swedish National Registry is unable to discriminate between the individual cup and stem components when analyzing the cause of revision, and no clinical or radiographic information is collected. A potential drawback for the randomized trial is performance bias because surgeons from specialized centers might perform better than the general orthopaedic surgeon.

Adult↗
PubMed1999

[Many years of registration have improved the quality of hip arthroplasty].

The Swedish Hip Replacement Registry has defined the epidemiology of total hip replacement in this country. Most hip replacements are fully cemented. Serious complication and revision rates associated with total hip replacement have declined significantly despite increase in the number of patients at risk. During the past five-year period, only 8(9 per cent of hip replacement procedures have been revisions. Although aseptic loosening with or without osteolysis is the major problem, accounting for 73 per cent of revisions, its incidence has decreased four-fold over the past 15 years to less than three per cent at 10-year follow-up. Quality of the surgical technique is the crucial determinant of the risk of revision due to aseptic loosening, but the choice of implant is also important. Total hip replacement practice in Sweden has improved due to the information available from the registry concerning individual risk factors, implant safety, and the efficacy of improving surgical and cementing techniques.

Arthroplasty, Replacement, Hip↗
PubMed1999

Determination of inter-spinous process distance in the lumbar spine. Evaluation of reference population to facilitate detection of severe trauma.

Fracture of a spinal segment with minimal or no compression of the vertebral body can be highly unstable. Screening for such an injury in the lumbar spine is often obstructed in a multi-injured patient, because of difficulty in obtaining adequate sagittal radiographs. The position of the spinous processes in relation to each other is the key for proper evaluation of the status of the posterior stabilising structures. The amount of separation or axial rotation of the posterior part of the vertebra that can occur before failure of the posterior structures has not been unambiguously defined. Despite this, it can be assumed that severe separation of the spinous processes indicates a more or less pronounced loss of mechanical support. An analysis of how the posterior spinous processes relate to each other on an anteroposterior (AP) radiograph could obviate this problem. A new, simple and reproducible radiographic tool is presented for screening of an eventual rupture of posterior structures of the lumbar spine. This method is based on measurements of the variation in interspinal process distance between adjacent levels in lumbar spine in a normal population. Two hundred normal AP radiographs of non-injured thoracolumbar spine were studied. The interspinal process distance was measured as the distance between the cranial ends of the adjacent projections of spinous processes on AP radiographs. The mean values and 99% confidence limits for changes in the interspinal process distances between adjacent spinal levels were determined and analysed in relation to age, gender and spinal segment level. An upper limit of a normal difference in distance between the spinous processes at two adjacent levels was determined to be 7-10 mm, depending on age and location in the lumbar spine. A difference in interspinal process distance exceeding 7 mm between two adjacent lumbar levels should alert a surgeon to severe and unstable injury.

Adult↗
PubMed1999

Porous cups with and without hydroxylapatite-tricalcium phosphate coating: 23 matched pairs evaluated with radiostereometry.

Migration, wear, and presence of radiolucencies were studied in 23 matched pairs of patients operated with porous-coated acetabular cups with additional screw fixation. All implants had the same type of titanium fiber mesh. In each pair, one of the cups was plasma-sprayed with a coating consisting of 70% hydroxylapatite (HA) and 30% tricalcium phosphate (TCP). Radiostereometric analysis up to 2 years after the operation revealed smaller rotations around the horizontal axis in cups with HA/TCP coating. The migration of the cup center was not significantly influenced. Evaluation of femoral head penetration in 12 of the matched pairs did not reveal any significant difference. Immediately after operation, implants with HA/TCP coating had more central radiolucencies, which, despite minimal migration, disappeared during the follow-up. The clinical results did not differ between the 2 groups. The findings of less tilting and diminishing radiolucencies in the cups with HA/TCP coating suggest a more complete ingrowth of bone and a better sealing of the interface.

Bone Screws↗
PubMed1999

The Charnley versus the Spectron hip prosthesis: clinical evaluation of a randomized, prospective study of 2 different hip implants.

Prospective, randomized studies must be performed when new surgical techniques or implants are evaluated. In this study, a new implant system was compared with the Charnley prosthesis, which over the years has been the most used hip implant in Sweden. Between 1985 and 1989, 410 hips were randomized to treatment with a Charnley or a Spectron total hip arthroplasty: 206 Charnley and 204 Spectron prostheses were implanted. The patients were operated on by a standardized procedure using a contemporary cementing technique. The patients were followed prospectively by an independent observer after 1, 3, 5 to 6, and 10 years. Harris Hip Score and patient satisfaction were recorded in the outcome evaluation. A total of 144 patients with 164 hips were deceased, and 15 patients (8 Charnley and 7 Spectron) have required a revision. Nine hips were revised because of aseptic loosening (5 Charnley stems and 4 Spectron metal-backed cups). The Charnley stem as well as the metal-backed Spectron cup had a higher risk for revision because of aseptic loosening. The Charnley ogee cup and the Spectron stem have performed remarkably well with no revision of these components. Seven Charnley prostheses dislocated, but no dislocation was recorded in the Spectron group. Survivorship calculations with a mean follow-up of 10 years revealed an overall 11-year survivorship of 94.5% +/- 3.4% (Charnley, 93.2% +/- 5.8%; Spectron, 95.9% +/- 3.0%). The clinical outcome did not differ between the 2 systems. The overall results in this old population, using a contemporary surgical technique, illustrate that cemented hip arthroplasty is an excellent treatment alternative for elderly patients.

Aged↗
PubMed1999

The Charnley versus the Spectron hip prosthesis: radiographic evaluation of a randomized, prospective study of 2 different hip implants.

A total of 410 hips were randomized to treatment with either a Charnley (206 hips) or a Spectron (204 hips) total hip arthroplasty. The patients were operated on by a standardized procedure using a contemporary cementing technique and were followed after 1, 3, 5 to 6, and 10 years. The postoperative radiographs showed a significantly increased rate of malalignment and consequently low grade of cement mantle quality of the Charnley stem compared to the Spectron. No differences concerning cement mantle quality or positioning were found between the Charnley ogee cup and the metal-backed Spectron. Evaluation of the follow-up radiographs revealed 10 loose Charnley stems and 1 loose Spectron stem and 4 loose Charnley ogee cups and 23 loose Spectron metal-backed cups. The differences of revision rate for the femoral and acetabular components of the 2 prostheses were significant (P = .03, Charnley femoral component more frequent; P = .03, Spectron acetabular component more frequent). The radiographic evaluation strengthened this disparity. Poor wear characteristics of the metal-backed Spectron cup are perhaps the main reason for the highly significant difference in mechanical failure rate between the 2 cups. We therefore propose that metal-backing of cemented cups should be avoided, at least when combined with larger femoral heads. The difficulty in positioning the Charnley stem with an adequate cement mantle, especially in the absence of trochanteric osteotomy, might explain the inferior Charnley stem longevity in this study.

Aged↗
PubMed1999

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.

Absorptiometry, Photon↗
PubMed1999

Poor outcome of the PCA and Harris-Galante hip prostheses. Randomized study of 171 arthroplasties with 9-year follow-up.

155 patients (171 hips) with a mean age of 50 years (24-64) were randomized to uncemented PCA (84 hips) or Harris-Galante type I (87 hips) total hip arthroplasty. Clinical and radiographic evaluations were done regularly. The improvements in the Harris hip and pain scores did not differ. Osteolysis developed in 5 PCA and 17 Harris-Galante hips. 13 hips in the PCA and 16 in the Harris-Galante (HG) group were revised because of mechanical failures and 1 hip (HG) because of infection after a mean follow-up of 9 years. Decreased 10-year survival rate, based on revision as end-point, was noted for the PCA (85%), compared with the Harris-Galante cup (99%). The corresponding survival rate of the PCA stem (96%) was higher than that observed for the Harris-Galante design (86%). When radiographic failures were included, the survival rates of the 4 different components dropped to between 73% and 94%. These findings indicate that further revisions will be necessary and continuous radiographic follow-up is indicated to enable revision before severe bone destruction has occurred. Although the PCA and the Harris-Galante designs differed as regards the survival of the individual components, the overall clinical and radiographic survival rates of these cementless total hip arthroplasties were poor.

Adult↗
PubMed1999

The economics of preventing revisions in total hip replacement.

We showed that the selection of a cost-effective type of cement and method of prophylaxis against deep infections for patients undergoing total hip replacement depended on the number of arthroplasties performed each year at individual hospitals. When 100 arthroplasties were performed each year, the use of Palacos cement and systemic antibiotics reduced the total costs to the department, i.e., the cost of cement, infection prophylaxis and revisions. The use of gentamicin-impregnated cement in combination with systemic antibiotics will further reduce the risk of revision and is another cost-effective strategy. The most effective infection prophylaxis would be achieved with a combination of gentamicin-impregnated cement, systemic antibiotics and surgical enclosure. However, the additional cost of the surgical enclosure would not be offset by cost savings due to reduced risk of revisions.

Anti-Bacterial Agents↗