Biomedical subjects

M A Tuke

Publications and source records attributed to M A Tuke.

7 recordsLinked to original sources

PubMed1999

In vivo biocompatibility and mechanical study of novel bone-bioactive materials for prosthetic implantation.

Two epoxy materials with or without adhesively bonded hydroxyapatite (HA) coatings were studied for their biocompatibility and mechanical pushout strength using in vivo implantation in the rabbit lower femur for a duration of 10 days to 6 months. Both were two-part epoxies cured at room temperature for 24 h, with material 1 (Ampreg 26; SP Systems Limited, Cowes, UK) postcured at 110 degrees C (Tg approximately 80 degrees C) and Material 2 (CG5052; Ciba Geigy Limited, Cambridge, UK) at 125 degrees C (Tg approximately 120 degrees C). Implantation in dead rabbit bone was performed to provide mechanical baseline levels. Polymethylmethacrylate (PMMA) and conventionally HA-coated titanium alloy (Ti-6Al-4V) were used as control materials. In the biological study, different fluorescent dyes were used to label newly formed bone. After 6 weeks of implantation, results from mechanical pushout tests showed that the interfacial shear strength (ISS) values were significantly higher than for dead bones with each of the different implants (p < .01-.001). HA-coated material 2 showed a significantly higher ISS value than the uncoated material (p < .05) after 6 weeks' implantation. However, the ISS value for the uncoated material 2 was significantly higher than for PMMA controls (p < .05). No significant differences in the ISS values were shown between HA-coated materials 1 and 2 and Ti-6Al-4V on in vivo implantation for 6 weeks. Failure points of the pushout test from the three HA-coated materials were defined by scanning electron microscopy. Specimens implanted with both HA-coated epoxies were fractured within the HA-coatings or the bone, while with HA-coated Ti-6Al-4V cracked between the coating and metal implant. The percentage of bone in contact with the implant surface was obtained by image analysis which showed that there were no significant differences between different materials after short time implantation (up to 6 week). Long-term implantation of the HA-coated material 2 showed that the percentage of bone contact had increased from 52.8+/-1.1% (6 week) to 80.0+/-0.3% (3 months) (p < .01) and remained at 81.0+/-0.8% (6 months). Measurements of bone mineralization rate (BMR) showed that after 3 weeks of implantation, there were no significant differences between PMMA and uncoated materials 1 and 2. After 6 weeks, the BMRs in animals implanted with either HA-coated material 1 or 2 were significantly higher than with HA-coated Ti-6Al-4V (p < .05-.0001 in both cases), but with HA-coated material 2 was lower than with this material uncoated (p < .05-.001). No significant differences were found between the two HA-coated epoxy materials. In addition, there were always lower BMRs during the third week of implantation than other periods regardless of biomaterial implanted. The study indicated that the adhesively bonded HA-coated novel epoxy materials were superior to conventional plasma-sprayed Ti-6Al-4V implants with respect to both BMR and bone integration with the implant surfaces. Adhesively bonded HA-coated epoxy materials had similar ISS values to HA-coated Ti-6Al-4V, but the former failed within the bone and coating, while the latter showed splitting between coating and metal.

Algorithms↗

PubMed1994

Wear induced by motion between bone and titanium or cobalt-chrome alloys.

We studied the wear generated by motion between polished and shot-blasted titanium-alloy (Ti-6Al-4V) or cobalt-chrome alloy (Co-Cr) surfaces and cortical bone in vitro. Semicircular sections of human proximal femoral cortex were reamed to fit metal cylinders of each alloy. The cylinders were then fitted in the bone, loaded and rotated in physiological saline. Ti-alloy resulted in more wear both of the bone and of the metal than did Co-Cr alloy. Metal wear was reduced and bone wear was increased by shot-blasting, a procedure which introduces surface residual stresses and roughens the metal surface. We conclude that when there is gross motion between a metal implant and bone, Ti-alloy is likely to generate more wear debris than Co-Cr alloy. The least wear both of bone and of metal was produced by polished Co-Cr.

Bone Density↗

PubMed1993

Evaluation of wear in an all-polymer total knee replacement. Part 2: clinical evaluation of wear in a polyethylene on polyacetal total knee.

In an effort to improve the long-term result of total joint replacement arthroplasty, we have investigated the use of a polymer-on-polymer articular replacement arthroplasty. Because of their known biocompatibility and previous use in orthopedic surgery, polyethylene and polyacetal (copolymer, Hoechst) were selected. Polyethylene served in its usual role as the concave member of the articulation; polyacetal formed the convex number. Formal wear testing using a multi-channel hip simulator demonstrated superior wear characteristics of the polymer-on-polymer configuration compared to a conventional chrome-cobalt versus polymer (polyethylene) configuration. A clinical series of relatively high-activity patients having a minimum five-year follow-up (N = 26) showed no specific unfavorable reaction to this material combination in a total knee replacement. Given certain potential advantages of polymeric materials, as well as some theoretical disadvantages of metallic materials, a polymer-on-polymer design for a large joint replacement may have some merit.

Acetals↗

PubMed1976

The effects of proteolytic enzymes on the mechanical properties of adult human articular cartilage.

The effects of the lysosomal proteinase cathepsin D on the mechanical properties of adult human articular cartilage were examined in detail in 7 joints within the age range 21 to 72 years. The results of a preliminary study on the effects of the lysosomal proteinase cathepsin B1 and clostridial collagenase on the mechanical properties of cartilage are also presented. Cartilage which had been incubated with either cathepsin D or cathepsin B1 showed increased deformation in uniaxial compression perpendicular to the articular surface. The enzyme-treated cartilage also showed decreased tensile stiffness at low values of stress. This effect was more pronounced in specimens from the deeper zone of cartilage than in specimens from the superficial zone. It was also more pronounced in specimens which were aligned perpendicular to the predominant alignment of the collagen fibres in the superficial zone than in specimens which were parallel to the collagen fibres. At higher stresses the tensile stiffness of the treated cartilage was not significantly different from that of the untreated tissue. The tensile fracture stress of the cartilage was also not significantly reduced by the action of cathepsin D. In contrast to the effects observed with the cathepsins, the preliminary results obtained by incubating cartilage for 24 h with clostridial collagenase showed that both the tensile stiffness and the fracture stress were considerably lower than the corresponding values for the untreated tissue. Biochemical analysis of the incubation media, and the specimens, revealed that a large proportion of the proteoglycans was released from the cartilage by each of the three enzymes. The proportion of the total collagen which was released from the cartilage was different for each enzyme: cathepsin D released between 0 and 1.5 per cent, cathepsin B1 released between 2.3 and 4.3 per cent and collagenase released between 5.3 and 27.8 per cent of the collagen after 24 h.

Adult↗

PubMed1975

Engineering considerations in the design of an ankle joint.

A prothesis has been designed to replace the articulating surfaces of the human ankle joint. The prothesis is in two parts, each forming a segment of a right circular cylinder with a single axis of rotation. The concave tibial component is manufactured from ultra-high molecular weight polyethylene and the talar component is manufactured from medical grade stainless steel. It is likely, however, that the talar component will be commercially manufactured from cobalt chrome alloy (Vitallium or Vinertia). The two components are secured to the cancellous bone by polymethylmethacrylate bone cement and laboratory tests have indicated that the bond should be strong enough to withstand the loads encountered at the ankle joint in vivo. The tests have also shown that the stability and strength of the ankle are not seriously reduced by implantation of the prosthesis. Laboratory wear tests and clinical experience over the last two years encourage optimism over the long term performance of the prothesis.

Adult↗

PubMedDate not supplied

Development and evolution of the ICLH ankle replacement.

In 1972 the original ICLH ankle was first used clinically, and since then the authors have implanted 75 ICLH ankles. The overall percentage of acceptable results in this series is about 70%. The most frequent complication seen was delayed wound healing. Talomalleolar contact with resultant pain was a significant problem early in the series. Partial collapse of the talus has occurred in five ankles. Our experience has shown that it is possible to replace the ankle and initially achieve a functioning, pain-free arthroplasty. There are many factors that may adversely influence the ultimate outcome; and thus, the procedure should be approached with caution.

Ankle Joint↗

PubMedDate not supplied

Implant arthroplasty in the adult hindfoot.

In patients with mild to moderate valgus deformity and localized pain due to lateral impingement, the subtalar implant has been effective in controlling position and relieving localized pain. When used in conjunction with a talonavicular resurfacing prosthesis in the absence of talonavicular subluxation, the implant has been effective in relieving pain and maintaining the foot in a normal or nearly normal position. In feet with valgus deformity and talonavicular subluxation, both the subtalar implant and the talonavicular prosthesis with a built-in stop must be used. Use of these implants requires that the foot be supple and correctable to at least neutral position at surgery. The valgus hindfoot with a subluxated but otherwise normal talonavicular joint presents a greater problem. In this condition correction can be maintained only if the subtalar implant is used in conjunction with the modified talonavicular joint with a built-in stop. External supports in the shoe have not been routinely used in all patients after operation for a variety of reasons (mostly nonmedical). It may be advisable in patients who have had correction of a deformity to continue to use some sort of support in the shoe for most ambulation. Arthroplasty early in the disease course, before severe deformities develop, may prevent progression of the disorder, but more experience is necessary to validate clinical impressions.

Arthroplasty↗