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Biomedical subjects

P Herberts

Publications and source records attributed to P Herberts.

At least 19 recordsLinked to original sources
PubMed2001

Concave versus posterior-stabilized tibial joint surface in total knee arthroplasty: randomized evaluation of 47 knees.

Forty-seven knees in 43 patients with severe deformities randomly received AMK total knee arthroplasty with concave (C, n = 25) or posterior-stabilized (PS, n = 22) polyethylene insert and with resection of the posterior cruciate ligament. Radiostereometric examinations were done postoperatively and after 3, 12, and 24 months. Two patients (1 C, 1 PS) underwent revision surgery. At the 2-year follow-up, the median absolute rotations of the tibial inserts ranged from 0.13 degrees to 0.26 degrees (C vs PS; P =.1-.7). The maximum total point motion was almost identical in the 2 groups (C, 0.38; PS, 0.39; P =.9). Maximum subsidence, lift-off, and Hospital for Special Surgery scores did not differ (P =.1-.6). Recipients of 20 of 24 knees with concave design and 14 of 19 knees with posterior-stabilized design reported that their knee could be regarded as normal or almost normal. Variations of the configuration of the polyethylene insert did not alter the outcome in the short term.

Aged↗
PubMed2001

Outcome after total hip arthroplasty: Part II. Disease-specific follow-up and the Swedish National Total Hip Arthroplasty Register.

The Swedish National Total Hip Arthroplasty Register records primary hip replacements, revisions and surgical technique/environmental factors. The end-point for failure is revision. A prosthesis still in place, however, does not mean success. Clinical and radiographic outcomes should describe in more detail the efficacy of hip replacement surgery instead of the relatively blunt outcome measure that the register can provide. We performed a clinical outcome analysis on patients with primary total hip replacement thus testing the adequacy of the end-point for failure in the Swedish register. 1,113 randomly selected patients who had had total hip replacement surgery between 1986 and 1995 answered a disease-specific self-administered questionnaire (WOMAC). A cohort of 344 patients was studied, using the Harris Hip Score and a conventional radiographic examination as outcome measures. We found clinical failure rates of 13% and 20% for all implants after 10 years, using 60 points or revision as the definition of failure in the Harris Hip Score and WOMAC, respectively. The result, according to the register during the same period, was a 7% revision rate. The clinical failure rate depended on the type of evaluation tool, definition of failure and demographics, which made it difficult to decide whether there was a need for revision. With the exception of pain measured by the Harris Hip Score, the results showed no significant correlation between clinical failure and radiographic failure. Hence, with the knowledge that there is a difference between the revision rate according to the register and clinical outcome, the strict definition of failure in the register is useful as an end-point for primary hip replacement surgery.

Adult↗
PubMed2001

Charnley cups retained during revision of the femoral component: repeated clinical and radiographic observations of 49 cups for 7-15 years.

This article concerns 49 consecutive polyethylene cups retained in cemented first revisions of the femoral component and evaluated on several occasions 7-15 years after the index operation. At the last follow-up 5 cups were revised, 3 were radiographically loose, 1 was revised because of recurrent dislocation and 1 stable cup was revised because the surgeon wished to use a 28 mm head. Moreover, 1 unrevised cup was radiographically loose. This corresponded to a mechanical failure rate of 0.1 (5/49) and revision rate of 0.1 (4/49). 3 cups which were radiographically loose (100% radiolucency) had not been revised when the stem was exchanged. If these cups were excluded, the revision rate would have dropped to 0.02 (1/46) and the mechanical failure rate to 0.04 (2/46). This indicates the importance of careful preoperative radiographic evaluation on both AP and lateral views. Progression of radiolucent lines always occurred as an increase in extension from the periphery to the central region of the interface. In conclusion, Charnley cups with non-circumferential radiolucent lines and little, if any, wear can be retained without compromising the longevity of the implant. However, it should be stressed that this conclusion is based on a patient population in which four-fifths of the patients at the index operation were 65 years of age or older.

Aged↗
PubMed2001

Correlation of wear debris-induced osteolysis and revision with volumetric wear-rates of polyethylene: a survey of 8 reports in the literature.

This survey focused on clinical reports of polyethylene wear and osteolysis in total hip replacements. With regard to documentation of clinical wear-rates, 57 publications were reduced to an analysis of 8 reports of THR series, including the incidence of osteolysis. A direct correlation was found among volumetric wear-rates, incidence of osteolysis and revision rates in THR concepts of the 1983-1987 era. As volumetric wear rate increased, the incidence of osteolysis and revision rates increased. With regard to our grading system for volumetric wear, with follow-up in the 4-15 year range, osteolysis was rare in group A (wear = 0-80 mm3/year), ranging from 6% to 31% in group B (wear 40-80 mm3/year) and from 21% to 100% in group C (wear > 140 mm3/year). With regard to cup design, the optimal low-wear group had mainly cemented polyethylene cups with 22 and 28 mm head sizes. The mid-wear group B had metal-backed cemented and uncemented cups, with 28 mm head size, and the high-risk group C had only uncemented, metal-backed cups, with the highest wear in the 32 mm head size. Less than 10 years of follow-up did not distinguish adequately between different designs of THR, except in a few cases which had early failures due to material or design deficiencies. Overall, the cemented all-polyethylene cup combined with the smaller ball head proved to be better.

Bone Cements↗
PubMed2001

Outcome of total hip replacement: a comparison of different measurement methods.

During the past 40 years, improvements have been made in the technique, implant, and surgical environment for total hip replacement, which today is one of the most cost-effective operations done. The aim of this study was to compare different outcome measurement methods and to develop recommendations for optimal followup of total hip replacement. The study involved the outcome of 2604 randomly selected patients in Sweden treated surgically with a modern technique. General questionnaires (the Medical Outcomes Study 36-Item Short-Form Health Survey and the Nottingham Health Profile) were compared with disease-specific questionnaires (the Western Ontario and McMaster University Osteoarthritis Index and the Harris hip score). The study showed a good correlation between the studied questionnaires, and all questionnaires used could be suitable for followup study after hip replacement surgery. In clinical practice and for research, a general and disease-specific self-administered score should be used. Some patients (older and low cerebral capacity) have difficulties answering questions on these questionnaires. A new short self-administered general and disease-specific questionnaire was designed: the Total Hip Replacement score. The Total Hip Replacement score provides information about the result of the hip arthroplasty, and the results can be compared with results of other surgical interventions.

Adult↗
PubMed2001

A low stiffness composite biologically fixed prosthesis.

The current authors addressed the question whether stress-induced adaptive bone remodeling of the proximal femur is a necessary consequence after total hip reconstruction with extensively biologically-fixed femoral components. A novel total hip femoral component was designed to simultaneously achieve stable skeletal fixation, structural durability, and reduced femoral stress shielding. This implant allowed for proximal and distal canal filling, yet was significantly less rigid than all-metallic femoral stems crafted of either cobalt chromium or titanium alloy. A cohort of 366 patients (386 hips) treated at 21 institutions worldwide now have been followed up a mean of 2.4 years postoperatively (range, 3 months-6 years). Two hundred sixty-eight patients have 2 years minimum followup. To date, no femoral implants have failed to achieve bone ingrowth and none have required revision. The implants appear radiographically well-fixed with no progressive radiolucencies or osteolysis. Radiostereometric analysis studies on one subset of patients showed stable initial fixation and minimal stem micromotion. Dual energy xray absorptiometry analysis on another subset of patients revealed excellent periprosthetic bone mineral density retention. Compared with more rigid metal implants, this design shows reduced proximal femoral bone loss secondary to stress-mediated bone resorption.

Absorptiometry, Photon↗
PubMed2000

In vivo kinematics of total knee arthroplasty: flat compared with concave tibial joint surface.

This study evaluated the influence of the geometric configuration of the tibial joint area on the kinematics of the knee. Twenty-two patients with noninflammatory arthritis and minor preoperative deformity were studied. They each received an AMK total knee replacement with retention of the posterior cruciate ligament. Eleven patients without any knee abnormalities were used as controls. The patients were stratified to either the flat (terminology of the manufacturer: standard) or concave (terminology of the manufacturer: constrained) polyethylene insert (n = 11 in each group). Knee kinematics were assessed 1 year after the operation by having the patient ascend a platform corresponding to an extension of the knee from 50 to 70 degrees of flexion. During this motion, two film-exchangers simultaneously exposed six to 13 pairs of serial stereoradiographs. The concave geometric configuration of the tibial insert resulted paradoxically in increased anterior-posterior translations compared with the flat insert but no significant change of rotations and translations in the other directions. Compared with normal knees, the most obvious abnormality was increased anterior-posterior translations (p < 0.004). At 50 degrees of flexion, the implants with the flat tibial polyethylene insert had displaced 2 times and the concave ones had displaced 2.5 times more posteriorly than the normal knees (p < or = 0.001). Less internal tibial rotation was also recorded in the flexed positions for both types of inserts compared with the normal knees (p < 0.02). Four knees in four patients, who reported symptoms of instability and abnormal knee function, showed significantly increased proximal displacement of the center of the tibial plateau in the flexed position. The findings suggest that current prosthetic designs and surgical technique do not restore normal knee kinematics and indicate that design improvements should rely on in vivo kinematic studies.

Aged↗
PubMed2000

Intramuscular pressure of the infra- and supraspinatus muscles in relation to hand load and arm posture.

In work engaging the upper extremities, the musculoskeletal system of the shoulder is sometimes exposed to prolonged excessive load, leading to musculoskeletal disorders of the shoulder. One way of reducing work-related shoulder disorders is to establish guidelines for working postures. The purpose of this study was to identify harmful working positions, by performing a comprehensive survey of the intramuscular pressure (IMP) in the infra- and supraspinatus muscles in relation to different arm positions and external loads. Ten healthy males participated, and the IMP in the infra- and supraspinatus muscles was studied in a total of 112 combinations of arm positions and hand loads at levels that occur frequently in industrial work. High-precision spatial recordings were accomplished with a three-dimensional motion-analysis system, and the IMP was measured using the microcapillary infusion technique. The mean IMP of the infraspinatus muscle as well as that of the supraspinatus muscle increased continuously from a resting pressure at 0 degrees of upper arm elevation to a maximal pressure at 90 degrees of upper arm elevation, for all elevation planes. The mean IMP of the supraspinatus muscle appeared to be more dependent upon the elevation plane and less dependent upon the hand load, compared to the infraspinatus muscle. Even during only moderate arm elevation, the mean IMP of the infra- and supraspinatus muscles, presented here in polar diagrams, had already exceeded the levels of reduced recovery from local muscle fatigue and blood flow impairment. The elevation angle and the hand load primarily influence the development of IMP in the infra- and supraspinatus muscles.

Adult↗
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

Tibial component fixation in porous- and hydroxyapatite-coated total knee arthroplasty: a radiostereo metric evaluation of migration and inducible displacement after 5 years.

A total of 51 knees (45 patients) with osteoarthrosis were stratified in a randomized study to receive a hydroxyapatite-coated Freeman-Samuelson (FS HA) or a porous-coated Miller-Galante II (MG II) uncemented total knee arthroplasty. Repeated clinical, radiographic, and radiostereometric analysis (RSA) evaluations of the tibial components were done for 5 years. The clinical outcome was equal at the 5-year follow-up (mean Hospital for Special Surgery score, 93). Standard radiographs displayed more zones around the tibial stem in the MG II group. RSA revealed that the FS HA components migrated less (smaller maximum total point motion and maximum subsidence) after 5 years and showed less inducible displacements at the 1-year follow-up. The stability of the implants obtained is equal to or better than cemented implants after 5 years. Key words: knee prosthesis, cementless, hydroxyapatite, radiostereometry, inducible displacement.

Aged↗
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

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

Assessment of workload and arm position during different work sequences: a study with portable devices on construction workers.

It is recognised that work related shoulder pain is overrepresented among construction workers compared to other occupations. Studies have shown that working with hands above shoulder level increases the shoulder load. Most studies have been confined to the laboratory. The present project was carried out to map the muscular engagement and postures of construction workers undertaking ceiling fitting, and to compare the results to those of the laboratory studies. Two ambulatory devices were used, one allowing recording of electromyographic (EMG) signals bilaterally from the trapezius muscle, and the other to record the position of both arms and back by means of measuring the angles between the vertical line and the back and both upper arms. These recordings were performed during 1.5-2 h work sequences. The results show that the work was mostly performed in an upright position, that both arms were used to a similar amount and that the workers for a large proportion of their working time had their upper arms at levels that are considered harmful in view of shoulder load. The EMG data showed that nearly 50% of the work was spent with trapezius activity that exceeded that of the reference contraction used (about 15% of maximal voluntary contraction) and that the time spent in muscular relaxation was 10%. It was concluded that the exposure of construction workers undertaking ceiling fitting meets the criteria formulated on the basis of laboratory experiments with respect to a high risk of acquiring chronic shoulder pain, due to rotator cuff tendinitis.

Adult↗