Biomedical subjects

L Ryd

Publications and source records attributed to L Ryd.

At least 19 recordsLinked to original sources

PubMed1992

The influence of metal backing in unicompartmental tibial component fixation. An in vivo roentgen stereophotogrammetric analysis of micromotion.

The fixation of the tibial component in 36 patients with conventionally cemented unicompartmental knee arthroplasties for femorotibial gonarthrosis was studied using roentgen stereophotogrammetric analysis (RSA). Twenty-four tibial components were all-polyethylene while 12 were metal-backed. The follow-up was for 6 years. Significant migration was detected for all cases but two and ranged from 0.3 mm to 5.4 mm. The greater part of the migration occurred during the first 1-2 years, after which two-thirds of the prostheses remained stable. Seven all-polyethylene components were subjected to a stress examination after 1-2 years and displacement, induced by external forces, was found in all seven. A strong correlation was found between the extension of the radiolucent line and the migration. Otherwise, neither demographic, clinical, nor radiographic data correlated with the RSA results. In this study metal backing did not have any influence on prosthetic fixation as measured by RSA.

Aged↗

PubMed1992

Temperature influence in different orthopaedic saw blades.

Laboratory tests were carried out on ox bone to evaluate the thermal effect of eight different saw blades while cutting cortical bone. These saw blades represented the usual clinical blades as well as saw blades specially manufactured in an attempt to decrease the temperature. Temperatures between 34 degrees C and 450 degrees C were registered in the saw blades. Only three measurements (of 219 tests) were below 44 degrees-47 degrees C, which is a critical limit for heat-induced bone necrosis. This test indicates that alternating saw blade design is not a way to control the temperature elevation during cutting of bone in orthopaedic procedures.

Bone and Bones↗

PubMed1992

Instability after anterior cruciate ligament rupture. Measurements of sagittal laxity compared in 11 cases.

Manual tests and 2 external devices were used together with roentgen stereophotogrammetry (RSA) and an active weight-bearing radiographic method to measure the sagittal laxity in 11 knees with anterior-cruciate-ligament rupture. In 5 knees no ligament surgery had been performed (unstable knees) and in 6 knees a reconstruction had been performed one year before the examination (stable knees). There were positive correlations between all methods, including the manual tests when all knees, both stable and unstable, were analyzed together. However, the mean values of the total displacement differed between the methods, especially when comparing the weight-bearing radiographs with the three other methods. Some knees with substantial displacement during passive loading did not show any displacement when weight bearing; the measurements thus depended on both the ligamentous laxity and the patient's neuromuscular control of the joint. When the stable knees were analyzed separately, higher mean values were recorded with the external devices than with RSA using 180 N load. This could be explained by an error from soft tissue deformation which added to the skeletal displacement when the external devices were used.

Adolescent↗

PubMed1992

The natural history of recurrent dislocation of the patella. Long-term results of conservative and operative treatment.

From 1970 to 1978, 29 patients had a unilateral operation for bilateral recurrent dislocation of the patella. We examined 21 of them at a mean of 14 years postoperatively. Eighteen of these patients had evidence of generalised joint laxity. Six of the operated knees and four of the unoperated knees still had recurrent dislocations. The operated knees were clinically worse, with a significantly higher incidence of osteoarthritis. We concluded that the operations used to treat recurrent dislocation of the patella may have had short-term benefits, but did not cure the patients in the long term.

Adolescent↗

PubMed1992

Proximally cemented versus uncemented Freeman-Samuelson knee arthroplasty. A prospective randomised study.

We studied the effect of a layer of cement placed under the tibial component of Freeman-Samuelson total knee prostheses with a metal back and an 80 mm intramedullary stem, using roentgen stereophotogrammetry to measure the migration of the tibial component during one year in 13 uncemented and 16 cemented knees. The addition of cement produced a significant reduction in migration at one year, from a mean of 1.5 mm to one of 0.5 mm (p less than 0.01), including a significant reduction in pure subsidence. One year postoperatively the clinical results were similar between the groups, but, at three years, one uncemented knee had required revision.

Adult↗

PubMed1992

Hyperthermia during occipito-cervical fusion with acrylic cement. Epidural thermometry in 23 cases.

In 22 patients, 23 posterior occipito-cervical fusions using acrylic cement were studied; 18 had seropositive rheumatoid arthritis and 4 traumatic atlanto-axial instability. The mean age was 60 (39-75) years. During the curing of the cement, epidural temperature measurements were performed over the cerebellum and between the foramen magnum and C1. Temperatures up to 69 degrees C were recorded. Cooling with profuse surface irrigation using normal saline solution or precooled 8 degrees C fluid did not influence the maximal temperatures recorded under the cement. Even though no gross neurological damage was noted, the epidural temperatures in occipito-cervical fusion with acrylic cement can be of sufficient degree to be hazardous; surface irrigation does not seem to be an effective way to reduce this risk.

Adult↗

PubMed1992

Proteoglycan fragments in joint fluid. Influence of arthrosis and inflammation.

We determined the concentration of proteoglycan fragments in knee joint fluid collected from knee-ligament injured patients more than 6 months after the trauma and from patients with acute pyrophosphate arthritis and arthrosis or with arthrosis only. Injured patients with normal or only mildly altered cartilage at arthroscopy and with normal radiographs, had twice the average concentration of healthy volunteers. Other injured patients with advanced, radiographic signs of arthrosis, had synovial fluid proteoglycan fragment concentrations within the range of healthy volunteers. Patients with pyrophosphate arthritis had the highest concentrations, substantially increased compared with both arthrosis patients, with or without knee injury and healthy volunteers. Likewise, there was an inverse relation between the degree of arthrosis and the concentration of proteoglycan fragments in the joint fluid in patients with pyrophosphate arthritis and arthrosis or with arthrosis only. We conclude that synovial fluid levels of proteoglycan fragments are influenced by the mass of cartilage matrix remaining in the joint, the inflammatory activity in the joint, and the metabolic activity of the cartilage cells.

Adult↗

PubMed1992

Isolated fracture of the lateral malleolus requires no treatment. 49 prospective cases of supination-eversion type II ankle fractures.

54 patients with isolated SE II fractures through the lateral malleolus, with 2 mm maximum dislocation, were treated with an elastic bandage and immediate weight bearing. 2 patients suffered dislocation but both should not, on reassessment, have been included in the study. 49 of the remaining patients were assessed after an average of 1.5 years. All but 4 patients had very minor, if any, symptoms. The average sick leave was 6.3 weeks and the patients were back to normal activity in about 4 months. This virtual nontreatment was safe and beneficial to both the patients and the health service.

Adolescent↗

PubMed1992

Polyethylene wear in unicondylar knee prostheses. 106 retrieved Marmor, PCA, and St Georg tibial components compared.

106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects.

Corrosion↗

PubMed1992

Intermittent micromotion inhibits bone ingrowth. Titanium implants in rabbits.

We studied the effects of micromotion on bone ingrowth into a 1-mm canal through a titanium chamber implanted in the proximal tibia of rabbits. The implant surface became "osseointegrated," but an interior core was movable, allowing the central portion of the canal to be moved in relation to the ends. Thus, the ingrowing bone in the canal had to pass an area of ad latus motion. When implanted in rabbit tibiae, the canal became filled with ingrown cancellous bone. Bone ingrowth was inhibited by 20 cycles of 0.5-mm movement applied during a 30-second period once daily. With this regimen, the canal was usually filled with vascularized fibrous tissue and significantly less bone. The micromotion chamber may enable detailed studies of the effects of different motion variables on ingrowth of bone.

Alloys↗

PubMed1992

Laxity and graft fixation after reconstruction of the anterior cruciate ligament. A roentgen stereophotogrammetric analysis of 11 patients.

The sagittal laxity of the knee was measured in 11 consecutive patients with chronic anterior cruciate ligament deficiency before and 1 year after ligament reconstruction with a free bone-tendon-bone graft from the patellar tendon (modified Clancy technique). Tantalum markers were implanted in the femur, in the tibia, and in the graft for roentgen stereophotogrammetric analysis (RSA) of the sagittal laxity and the migration of the bony ends of the graft. The precision in measurements of total anterior-posterior displacement (+/- 2 SD of the differences between repeated measurements) was 2.2 mm. A decrease in total anterior-posterior displacement from 12 mm before reconstruction of 5 mm 1 year postoperatively using a stress load of 150 N was found. The bony ends of the free graft migrated maximally 0.7 mm, implying adequate fixation.

Adolescent↗

PubMed1992

Roentgen stereophotogrammetric analysis of prosthetic fixation in the hip and knee joint.

Using highly accurate roentgen stereophotogrammetric analysis (RSA), migration and cyclic displacement of prosthetic components can be assessed. In arthroplasty of the knee, all tibial components migrate during the first year but stabilize thereafter in a majority of cases. They also display inducible displacement in response to external forces. The effects of alterations in design or different modes of fixation may be readily detected using this noninvasive method. Three patients, who later developed mechanical loosening, migrated continuously and were identified by RSA already during the first year, indicating a clinical significance of continuous migration in terms of future mechanical loosening. Also in the hip, abnormally migrating femoral and acetabular components may be identified at an early stage. Using conventional clinical assessment, ten years and a large number of patients are often needed, while with RSA, new prosthetic devices may be assessed at a much earlier stage.

Cementation↗

PubMed1991

On the problem of heat generation in bone cutting. Studies on the effects on liquid cooling.

A saw blade was made from two standard oscillating blades which were fixed to each other with channels between, so that cooling fluid could be directed to the saw teeth. The blade was connected to a standard arthroscopy pump which delivered a flow of 80 ml/min through the blade. The performance of this blade was compared with that of a standard saw blade, cutting ox-bone in the laboratory. Irrigation of the standard saw blade with saline delivered by a syringe only slightly diminished the maximum temperature. Pumped irrigation was more effective but required large volumes of fluid. The heat generated by the internally cooled saw blade was negligible and the temperatures achieved (19 degrees C to 34 degrees C) fell well below the critical level for bone death (44 degrees C to 47 degrees C).

Equipment Design↗

PubMed1991

Surface flatness after bone cutting. A cadaver study of tibial condyles.

A methodologic study with which the cut surface could be quantified was performed on cadaveric tibial bone prepared for endoprosthetic components. Using sterilized, dental-imprint material and measuring with a Zeiss UMC 850, the characteristics of the cut surface were defined. A clinically flat surface was found to be uneven, with a maximum roughness between the uppermost and lowermost points of 1.0 and 2.4 mm for the bone surface and between 1.2 and 2.3 mm for the imprint. The flatness, defined as the standard deviation of the measuring points, was between 0.15 and 0.40 mm for the bone and 0.20 and 0.42 mm for the imprint. This lack of flatness creates gaps between the prosthesis and the bone.

Bone and Bones↗

PubMed1991

Cement interface temperature in hip arthroplasty.

The temperature was measured using thermocouples in the bone-cement interface during cement curing in 30 total hip replacement operations. A modern technique was used, including lavage and precooled vacuum-mixed cement. The mean maximum temperature in the acetabulum was 43 (38-52) degrees C and in the femur 40 (29-56) degrees C. The use of a precooled femoral prosthesis did not affect the peak temperature.

Bone Cements↗

PubMed1990

The effect of a stem on the tibial component of knee arthroplasty. A roentgen stereophotogrammetric study of uncemented tibial components in the Freeman-Samuelson knee arthroplasty.

We studied the effect of a metal tray with an intramedullary stem on the micromotion of the tibial component in total knee arthroplasty. Of 32 uncemented Freeman-Samuelson knee arthroplasties performed in London and Gothenburg, nine had a metal backing and stem added to the tibial component. Micromotion of the tibial components, expressed as migration and inducible displacement, was analysed using roentgen stereophotogrammetric analysis up to two years follow-up. The addition of a metal back and a 110 mm stem to the standard polyethylene component significantly reduced both migration over two years and inducible displacement.

Adult↗

PubMed1990

Cold flow reduced by metal backing. An in vivo roentgen stereophotogrammetric analysis of unicompartmental tibial components.

Thirty-six cases of unicompartmental arthroplasty for gonarthrosis were followed for 6 years. The arthroplasties were prepared for roentgen stereophotogrammetric analysis (RSA) by marking the tibial components and the tibial methaphysis with tantalum balls. Nineteen out of 24 cases with a polyethylene tibial component had an increase in intermarker distances signifying progressive enlargement of the prosthesis due to cold flow. The enlargement was up to 2.8 percent of the circumference and was greater for 9 mm than for 12 mm thick components. Twelve cases with a metal-backed tibial component showed no cold flow. No correlation between cold flow and demographic, clinical, or radiographic data was found.

Aged↗

PubMed1990

An internally cooled saw blade for bone cuts. Lower temperatures in 30 knee arthroplasties.

A saline-cooled saw, which has been shown to give good control of the heat generation during bone cutting under laboratory conditions, was tested in in vivo. With a saline flow of 80 mL/min, the maximum cutting temperature in 30 knee prosthetic operations was 32 (25-37) degrees C in the saw blade and respectively 30 (26-35) degrees C and 29 (26-34) degrees C 2 and 3 mm underneath the cut surface. Because the temperature generated by conventional osteotomy equipment may exceed 70 degrees C, the use of our cooled double saw blade during joint replacement prevents heat osteonecrosis.

Arthroplasty↗