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Biomedical subjects

T J Slooff

Publications and source records attributed to T J Slooff.

At least 73 records · Page 4Linked to original sources
PubMed1985

Interface stresses in the resurfaced hip. Finite element analysis of load transmission in the femoral head.

The load transmission and interface stresses in the Wagner resurfaced femoral head were evaluated for the purpose of studying possible failure mechanisms. We found that unnatural stress patterns occur in the head and at the implant-bone interfaces, in addition to regions of stress protection in the bone, possibly enhancing interface failure and bone remodelling. However, these stresses are not higher than those reported for other kinds of prostheses, e.g. acetabular cup, tibial plateau. From these findings, together with clinical observations, it is hypothesized that the femoral surface cup is more sensitive to local loosening than other prostheses. This hypothesis would indicate that prosthetic designs should be analysed relative to their potential to provoke failure propagation, rather than only initiation of mechanical failure and loosening.

Bone Cements↗
PubMed1985

Reconstruction of the proximal humerus with tibial autografts after resection of osteochondroma in adolescents.

In a series of five adolescents with osteochondroma of the proximal humerus, resection of the tumor was followed by reconstruction with an autogeneic tibial bone graft. The indications for resection were pain, progressive swelling, and functional impairment. Bone grafting was a precautionary measure against stress fractures caused by the resection of cortical bone surrounding the tumor tissues. On the basis of follow-up examinations with an average of 61 months, the procedure is evaluated as safe and effective.

Adolescent↗
PubMed1984

Bone grafting in total hip replacement for acetabular protrusion.

Total hip replacement combined with acetabuloplasty was performed in 43 hips in 40 patients with protrusion secondary to arthrosis, rheumatoid arthritis or trauma. Depending on the acetabular defect, the acetabuloplasty encompassed reinforcement of the medial wall with bone grafts, vitallium meshes, protrusion rings and cups. The clinical and radiographic results were uniformly good on average 2 years postoperatively. All grafts appeared to be united and incorporated, without evidence of resorption. The only patient suffering from pain had radiographic signs of progressive varus migration of the femoral component.

Acetabulum↗
PubMed1984

Treatment of failed open reduction for congenital dislocation of the hip. A 10-year follow-up of 14 patients.

Fourteen patients with 15 congenital dislocated hips with unsuccessful open reduction were referred for a secondary open reduction. All primary open reductions were incomplete due to an inadequate exposure and insufficient release of muscles and ligaments. The secondary open reduction was technically difficult. The patients were followed for 6-17 years. Six patients had no functional symptoms. Only three hips showed no radiographic deformity. In ten hips, femoral head necrosis was noted and two patients were left with shortening of 4 and 7 cm.

Child, Preschool↗
PubMed1980

Influence of a diphosphonate on the cellular aspect of young bone tissue.

Stimulated by the rather sparse information in the literature on cellular changes induced by EHDP, we carried out electron microscopic investigations on young bone tissue and on de novo bone formation. Cellular changes could be observed during continuous administration of EHDP. The osteoblasts demonstrated temporary storing of crystalloid structures in the mitochondria, and atypical osteocytes showed persistent changes indicative of hyperactivity. The osteoclasts exhibited varying ultrastructural features with respect to the number and appearance of nuclei, Golgi, RER, and lysosomes. These changes under the influence of EHDP could be an indication of altered activity of the osteoclast. The possible interference of EHDP with bone cell metabolism is discussed.

Animals↗
PubMed1979

Arthroscopy in the evaluation of operative treatment of osteochondrosis dissecans.

In an early stage of postoperative evaluation of intra-articular surgery, as in osteochondrosis dissecans, arthroscopic examination is indispensable. In order to compare the results of different cases, a classification is necessary. The arthroscopic grading system presented is valuable for assessing degeneration of the three knee compartments. Early arthroscopic evaluation for follow-up can be used to classify postoperative complications that are not visable radiologically and are not severe enough to justify re-exploration. After follow-up examination with arthroscopy, advice to the patient may halt the progression of deterioration. Further study of the different treatments can help in formulating a plan of management of osteochondrosis dissecans.

Adolescent↗
PubMed1978

The effect of ethane-1-hydroxy-1, 1-diphosphonic acid (EHDP) on matrix induced ectopic bone formation.

The effect of diphosphonates (EHDP) was studied on induced ectopic osteoneogenesis. Decalcified allogeneic bone matrix was implanted into the lumbar muscles in rabbits for an ectopic osteoinductor. The ectopic new bone formation was studied under continuous EHDP administration and after discontinuation of EHDP. Although there was no inhibitory effect of EHDP on the osteoinduction, the calcification of the new bone and the resorption of the implanted matrix was retarded. The induced "osteoid-like" tissue had an atypical structure with a small number of cells and a deficiency in collagen fiber bundles. There were also large fields of new cartilage formation. Thus remodelling and mineralization were inhibited under the influence of continuous administration of EHDP. After discontinuation of EHDP administration a recovery phase was observed which seemed to lead to the formation of a normal ossicle.

Animals↗
PubMed1976

Strontium 87mSr bone scanning for the evaluation of total hip replacement.

In a series of seventeen patients with unilateral osteoarthritis of the hip a scintiscanning follow-up study was made before and after total hip replacement for the assessment of the normal course of the 87mSr-scintiscan. In another series of twenty-eight patients with total hip replacement a photoscan was made as a supplement for the diagnosis of loosening of one or both components of a total hip implant. In most of these cases it proved to be a useful method, especially when clinical and raidological examination was inconclusive. It is concluded that up to six months after operation increased osteoblastic activity exists; the scintiscan became normal after that time. 87mSr scintiscanning offers a safe and simple technique for the assessment of the success and stability of total hip arthroplasty. It is also a useful aid for the early detection of loosening and infection. The procedure can help in the differential diagnosis of complaints after total hip replacement.

Arthroplasty↗
PubMed1975

Dimensional behavior of curing bone cement masses.

The curing of bone cements is accompanied by release of polymerization heat and, hence, by a temperature rise of the curing cement mass. This temperature rise causes expansion of enclosed air bubbles and evaporation of the volatile monomer. An overall expansion of 3 to 5 vol % has been mentioned in the literature. It has often been stated that this expansion favours the fixation of metal endoprostheses in the marrow cavity of bone. To check for the influence of this expansion on linear dimensions of the cured cement mass we filled stainless steel cylinders with a precision bore of 22,000 +/- 0,005 mm and a length of 120 mm with bone cement. After curing of the cement in a environment of 37 degrees C the resulting cement rod was released from the cylinder and the diameter of the rod was measured at 37 degrees C. The influence of the "foaming effect" on the transverse dimensions of the rods was studied by curing the cement at 37 degrees C and 2 atm air pressure in a high-pressure-vessel. This method of curing eliminates porosity in the cement almost completely, so that curing shrinkage is to be expected rather than expansion of the cement mass. The results indicate that a volumetric expansion of the cement during curing of cylindrical rods in laboratory experiments, can be accompanied by a linear diametrical shrinkage of the cement mass. The explanation of this phenomenon is to be sought in the fact that the volumetric expansion takes place at a time when the cement is still plastic; by the formation of gas bubbles, the cement is forced in longitudinal direction into the cylinder and when the temperature of the mass has passed through a maximum, the cooling of the cement mass results in a thermal shrinkage of approximately 0.4% linearly. Extrapolating this laboratory result to clinical situation one might doubt whether the overall expansion of bone cements during curing will result in a permanent positive pressure on the walls of marrow cavity and whether it will contribute to a better fixation of endoprostheses than in the case of a, still hypothetical, nonporous cement.

Bone Cements↗
PubMed1975

Characterization of bone cements.

Properties of acrylic bone cements during and after curing were determined for three brands of bone cement. Curing time and consistency were chosen for the characterization of the handling and working behavior of these materials. The performance of bone cements after curing may be related amongst other things to the following properties: water resorption, solubility/disintegration, flexural modulus of elasticity, yield stress, proportional limit, flexural strength and impact strength. Methods to determine these handling and material properties are described. The influence of radiopacifying and antibiotic additives on these properties is evaluated as well as the influence of porosity on flexural strength and impact strength. The results indicate that considerable differences in the handling properties occur. The material properties of the three brands tested do not show marked differences. Radiopacifying and antibiotic additives appear to have a negative effect on material properties; the effect of porosity as it develops during curing under simulated clinical conditions is more pronounced.

Acrylates↗