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Biomedical subjects

D Blanquaert

Publications and source records attributed to D Blanquaert.

9 recordsLinked to original sources
PubMed2002

Alternative bearing surfaces in total hip arthroplasty: zirconia-alumina pairing. Contribution or caveat?

The aim of the present study was to evaluate the zirconia and alumina articulation in total hip arthroplasty in regard to clinical and radiological outcome. This is the first report concerning the clinical application of a hybrid ceramic articulation. Owing to ethical reasons, a limited number of patients was enrolled in the study. Ten consecutive patients with degenerative arthritis were randomly allocated after informed consent to hybrid total hip arthroplasty treatment using an alumina femoral head and an alumina acetabular liner (5 hips), or using a zirconia femoral head and an alumina acetabular liner (5 hips). The median age of patients at index operation was 57.8 years. Current criteria were used for clinical and radiological assessment. The mean follow-up was 5.1 years (5 to 5.3 years). No hip required revision, and no clinical and radiological differences were observed between the two groups of hips. The median preoperative Harris hip score was rated 55.3 points in the control group of hips with alumina head, and 55.6 in the group of hips with zirconia head. The median Harris hip score increased to 94.9 points at the time of follow-up in the control group, and 96 points in the zirconia group. No radiological signs of cup loosening or focal acetabular osteolysis were detected at follow-up. All stems showed stable fixation without radiolucent lines or focal osteolysis. Zirconia femoral heads and alumina acetabular liners have been successfully used in the present series of 5 total hip arthroplasties with a mean follow-up of 5.1 years. Nevertheless, the use of femoral heads made of zirconia in total hip arthroplasties remains an important clinical concern due to the potential genesis of wear microparticles which can lead to progressive osteolysis. Further in-vitro and in-vivo investigations are required to define the value of this alternative bearing surface.

Aged↗
PubMed1991

[Materials and shapes: the compromise].

The development and fabrication of a prosthesis of the knee which for many years will fulfil the functions of a normal knee result from a very complex compromise between materials and shapes. It is essential to select materials and shapes whose characteristics are complying with the specifications laid down for this particular arthroplasty. Materials ans shapes must in the long term be able to solve all the problems of biomechanics, flow, wear, friction and fixation to the osseous elements, without underestimating the interactions between implant and biological environment which may result in deterioration of the bone-implant interface.

Biocompatible Materials↗
PubMed1990

[The influence of the elasticity module of the femoral shaft and neck of a total hip prosthesis on the distribution of stress in the femur ].

Experiments have shown that stress shielding resulting from implantation of a prosthesis is related to the stiffness of the implant. Stiffness depends on the Young's modulus of the material used and the design of the implant. Most published studies have not attempted to define the relative importance of these two components. We have studied the influence of the elastic modulus only in an experiment using implants of a uniform design. Strain gauges were attached to the calcar in five femurs, three of which also had gauges placed on their medial, lateral and anterior aspects. Surface strain was measured in the intact femur and after implantation of cemented prostheses of the same design but manufactured with or without a collar in stainless steel or titanium alloy. The highest level of calcar strain was recorded with the titanium alloy prosthesis, and the presence of a collar appeared to increase the stress transfer of bone. This effect on stiffness was statistically significant, but was limited to the proximal part of the upper femur. It was not significant in the sub-trochanteric area, due to individual variations in bone geometry and cortical thickness. These results indicate that stress shielding can be directly related to the Young's modulus of the material used, independent of the design of the prosthesis.

Biomechanical Phenomena↗
PubMed1988

The use of dense alumina-alumina ceramic combination in total hip replacement.

The purpose of this article was to review the laboratory and clinical performances since 1970 of a total hip prosthesis using alumina-alumina combination. The chemical and physical properties of dense alumina ceramic were studied in relation to biocompatibility, mechanical strength, and surface properties. Through the examination of 35 retrieved implants, it was found that the long-term success of alumina-alumina total hip replacement depends on both the ceramic microstructure (small grain size with uniform distribution, minimum porosity, absence of inclusions) and implant geometry (sphericity deviation +/- 1 micron, radius tolerance between components 7-10 microns). Alumina component wear and fractures have disappeared with the use of high-performance materials and severe manufacturing quality control. Examination of human biopsies from well-fixed prostheses showed that alumina particles deposits increase with time with only a low-grade macrophagic reaction. When loosening occurred, an inflammatory reaction appeared; this reaction was less striking than with loose metal-polyethylene prostheses, however. The long-term behavior of cementless alumina cup fixation depends upon initial positioning and stability; survivorship analysis of the cemented ceramic cups showed an 88% survival probability after 8 years with a 1.6% average annual probability of revision. The percentage of surviving was 100% after 8 years in patients who were less than 50 years old. Aseptic loosenings occurring at the cup-cement interface were assumed to be related to stress protection secondary to the high rigidity of the ceramic leading to a weakening of the spongious bone supporting the cement mantle. Good bone stock quality as well as high-quality ceramic appear to be the prerequisites for durable fixation of alumina sockets.

Aluminum↗
PubMed1988

Role of stem design and material on stress distributions in cemented total hip replacement.

The risk of fatigue fractures of the femoral stem in a cemented total hip arthroplasty can be minimized by either increasing the stem cross-section and/or using a very high strength alloy. The object of this study was to compare important mechanical characteristics of five selected stem designs, differing in configuration and material (stainless steel, cast chrome cobalt alloy, nickel based alloy and titanium alloy). The stain pattern on the stem was analysed in a 3-point-bending jig and also after cementing it into cadaver femurs. Regardless of stem type or test method, the typical tensile stress distribution on the lateral stem was a bell shaped curve. For the cobalt-chrome and stainless steel stems, the larger the stem the lower were the stem stresses and the stress gradient, and the higher was the factor of safety. However, the factor of safety was increased even further by the use of super alloys such as MP35N and Ti6Al4V. In addition, Ti6Al4V alloy allowed the use of larger and stronger stems without the extra penalty of rigidity, which was enforced by either the steel or cobalt based alloy.

Biomechanical Phenomena↗
PubMed1985

Carbon-PGLA prostheses for ligament reconstruction. Experimental basis and short-term results in man.

The efficiency of a pure carbon prosthesis to reconstruct intra-articular ligamentous loss of substance was evaluated on 14 sheep with an 18-month follow-up study of recent and old ACL experimental injuries. Functional results showed a correlation between a tightened implant, the stability of the knee, and the absence of severe arthritis. The rupture strength of the newly formed ligament amounts to about 300 Newtons (N). That of the normal ACL amounts to 250-550 N. The structure gives a viscoelastic behavior to the prosthesis. This tissue was made of collagen fibers surrounding the carbon fibers and running generally in the direction of the ligament. In the osseous tunnels, the newly formed lamellar bone invaded and surrounded the implant. Carbon fiber fragmentation occurred, and fibers were found in the synovia and in the homolateral, inguinal, and paraaortic lymph nodes. No degeneration, necrosis of tissue, or cellular toxicity was found. On these bases, the carbon prosthesis was modified by adding a resorbable copolymer of polyglycollic (PGA) and polylactic acid (PLA) around the fibers and a resorbable sheath of the same polymer. This carbon-PGA/PLA prosthesis was used in 23 patients with a three- to 12-month follow-up period. Patients were evaluated by clinical tests and by functional control of the ligament. The indications for prosthetic replacement were: recent mop-end tears of the ACL, cruciate ligament reconstruction in chronic knee instability, and wide rotator cuff loss of substance. Five complications occurred because of hematomas and/or sepsis and prosthesis breakage. Eighteen of 23 patients had good clinical results with good function in five. The conclusions are that PGA/PLA produces a clean and flexible ligament, thus eliminating carbon fiber articular deposits and allowing a normal function. Inflammatory postoperative reactions seem to be more frequent than with other procedures and call for operative and clinical care in order to eliminate hematoma and sepsis. The efficiency of a rehabitable carbon-PGA/PLA prosthesis in intra-articular ligamentous defects in man will be confirmed only by controlled long-term clinical observations.

Adult↗
PubMed1983

[Replacement of the anterior cruciate ligament by carbon fibers. An experimental study].

The authors have excised the anterior cruciate ligament in 14 sheep and replaced it by carbon fibres. The animals were sacrificed after 12 to 18 months. Eight had a satisfactory new ligament without any evidence of arthrosis and with stability of the knee. In 2 cases, there was moderate instability and arthrosis associated with a lax ligament and in 3 cases the new ligament had ruptured with severe instability and arthrosis. Microscopic examination shows a satisfactory acceptance of the carbon filament both inside the bone as well as in the joint. There was no difference between cases repaired immediately or 6 months after excision of the ligament. A study of aortic lymph nodes showed the presence of carbon particles. The rupturing strength of the new ligaments and of normal ligaments were similar. The visco-elasticity of the new ligaments was also studied and was found to be satisfactory. It was considered that the use of carbon fibre may be valuable but more studies should be done to improve the elasticity and to decrease the migration of carbon material.

Animals↗
PubMed1981

[A study of the mechanical properties of alumina-on-alumina total hip prosthesis (author's transl)].

The authors describe the results obtained between 1970 and 1980 (more than 1205 cases) with an original prosthesis made of alumina (aluminium oxide) for the frictional torque. In the first stage some failures were encountered due to disruptures between the ball and the stem. A new type of union was designed in which the ball is peroperatively placed on a titanium alloy stem by conical fixation. This ceramic material exhibits a very low friction, negligible wear and excellent biocompatibility. These prosthesis can be inserted with or without cement.

Aged↗