Bio-Medical Materials and Engineering - Volume 10, issue 2

Authors: Virolainen, Petri | Inoue, Nozomu | Young, David R. | Frassica, Frank J. | Chao, Edmund Y.S.

Article Type: Research Article

Abstract: Mechanical evaluation of fixator augmented bone healing is complicated. When the primary interest is focused on mechanical properties of the healing site, implants may need to be removed before the testing. Cement or bone ingrowth related fixation requires special techniques for successful implant removal. Five canine femurs and five specially designed intramedullary cement fixated segmental replacement prosthesis were used to show that intramedullary cement mantle could be removed safely and the procedure was repeatable without altering the mechanical properties of healing site.

Citation: Bio-Medical Materials and Engineering, vol. 10, no. 2, pp. 51-56, 2000

Authors: Jayabalan, Muthu | Thomas, Vinoy | Sreelatha, P.K.

Article Type: Research Article

Citation: Bio-Medical Materials and Engineering, vol. 10, no. 2, pp. 57-71, 2000

Authors: Hedia, H.S. | Abdel‐Shafi, A.A.A. | Fouda, N.

Article Type: Correction

Abstract: Stresses are generated in implant materials and bone, and at their interfaces. These stresses may affect the structural properties of the implant/bone system, or bring it to failure at some time in the postoperative period. Due to these stresses, acetabular cup loosening becomes an important problem for long term survival of total hip arthroplasty. It was found that metal backing would tend to reduce stresses in the underlying acrylic cement and bone. Yet, recent studies of load transfer around acetabular cups have shown that metal backing generates higher stress peaks in cement at the cup edges, while generates lower stress …peaks in bone at the central part of acetabulum (dome), thus the bone at the dome becomes more stress shielded. In this study a numerical shape optimization procedure in combination with an axisymmetric finite element model was used in order to optimize the shape of a stainless steel metal backing shell. The design was to minimize fatigue notch factor in cement along cement/bone and cement/metal backing interfaces in order to prevent failure of cement mantel and loosening of acetabular components, at the same time increasing fatigue notch factor in bone at the center of acetabulum to prevent stress shielding. The results of this study indicate that cemented acetabular cup designs can be improved by using metal backing shells of non‐uniform thickness, thick at the dome and thin at edges. Fatigue notch factor in cement was reduced by 2.3% at cement/metal backing interface and increased by 1.3% in the central bone of acetabulum. Von Mises stresses in the cement edge were reduced by 17.8% and 19.3% along cement/bone and cement/metal backing interfaces, respectively. Thus the optimal design will reduce the possibility of fatigue fracture of cement and decrease the stress shielding effect and the likely incidence of bone resorption, whereby extend the expected life of the prostheses. Show more

Keywords: Optimization, fatigue notch factor, von Mises stress, stress shielding, metal backing shell

Citation: Bio-Medical Materials and Engineering, vol. 10, no. 2, pp. 73-82, 2000

Authors: Korossis, Sotiris A. | Fisher, John | Ingham, Eileen

Article Type: Research Article

Abstract: The second most common major heart operation in the western world is valve replacement. Any one of the four heart valves may become either so stenotic or regurgitant that it needs to be replaced in order to restore normal heart function. Although replacement surgery of dysfunctional heart valves has a very high success rate, it can provide the surgeon with a difficult decision regarding the choice of a suitable prosthesis for the individual patient. Over the years many different types of artificial heart valves have been devised. Surgeons typically deal with a heart valve replacement by installing a mechanical prosthesis …or by using a bioprosthetic valve, hand‐crafted from animal tissue. Least commonly, valves can be taken from human organ donors. Mechanical valve substitutes have a long fatigue life but the central flow occluders often induce blood cell trauma. Tissue substitutes have an unimpeded central orifice when open, cause minimal cell damage but have a relatively short fatigue life, especially in children where calcification may be a major problem. More recently alternative materials, such as polyurethane, have been used in artificial heart valve design while the new concept of tissue‐engineering has enhanced the prospects towards an ideal cardiac valve replacement. Today’s artificial valves are designed with a better understanding of the cardiovascular system with the aid of computers. Advances in computer software have allowed simulations of fluid flows through valve substitutes, both in cardiac flow simulators and the heart itself. Show more

Citation: Bio-Medical Materials and Engineering, vol. 10, no. 2, pp. 83-124, 2000

Article Type: Correction

Citation: Bio-Medical Materials and Engineering, vol. 10, no. 2, pp. 125-125, 2000