SummaryRecent results indicate varying degrees of bone ingrowth into porous metal and ceramic bodies. Such homogeneously porous ceramic and metal implants generally possess inadequate mechanical properties, limiting their application to low stress or nonstructural applications. An experiment was performed wherein titanium porous coatings were applied to a wrought titanium bone implant. These surfaces were achieved by plasma spraying of titanium hydride powder, depositing a mixture of wellbonded titanium-titanium oxide with pore diameters varying from .002 to ,005 in.Implant specimens were placed in sheep femora for periods of 14 and 26 weeks.Interface shear strengths were determined by torque tests which indicated approximately a twenty-fold increase over similar tests performed on uncoated control specimens.No adverse affects were noted.

Experience with the HA-type coated hip implants demonstrates substantially higher degree and quality of osteointegration in the porous titanium alloy/HA type implants.

Porous metallic/bioceramic composite coatings, produced by plasma arc deposition incorporating highly crystalline hydroxylapatite (HA) in a porous structure of titanium or cobalt-chromium-molybdenum, have been developed for medical and dental device applications. An otherwise brittle and weak HA coating has been anchored by a porous metallic underlayer which is strongly bonded to the substrate. Implants with such coatings have the advantage of mechanical fixation by bony ingrowth into the porous metallic structure coupled with enhanced biocompatibility achieved through the use of HA. This combination produces a more stable bone/implant interfacial region as compared to that achieved by a HA coating applied directly on the implant surface. Once bony ingrowth has taken place, strong bonding has been achieved even if bone resorption of the HA were to take place. Various thicknesses, densities and pore sizes of such composite coatings have been applied to dental and orthopedic devices and have been implanted in the U.S.A., Japan, and Europe showing excellent post insertion clinical results. Physical, mechanical, and chemical properties of selected coatings have been characterized and are reported herein.

The object of this work was to determine mechanical properties of implants with graded porous coatings without reference to the properties of the ingrown bone. Optimum strength of a bone/implant interface consisting of porous metal and ingrown bone requires a gradation from base metal to the original bone. The composite metal-bone interface can be obtained by applying a metal coating of graded porosity, varying from near zero at the substrate surface to more than 50% at the outermost layer, on the original implant. Graded porous coatings of titanium or Ti-6Al-4V were obtained by plasma spraying of selected particle size fractions in three layers of successively decreasing density, the top coat being made with 300 to 850 μm powder. Tensile and shear strengths of the coatings were determined by cementing coated samples face to face with an adhesive resin to simulate ingrown bone. Data from these tests are given. Shear strength values ranged from 5.6 to 9.9 MPa (815 to 1430 psi) and tensile strength values were 5.1 to 25.5 MPa (745 to 3700 psi). Failure occurred within the porous coating and not at the interface between the substrate and the coating. Corrosion fatigue tests in Hanks' solution at 37°C (98.6°F) and a pH of 7.4, with a cyclic, fully reversed, peak torsional shear strain of ±0.01, gave lifetimes comparable to or better than those reported for mill-annealed Ti-6Al-4V, except for the samples that had been sintered.

Th e role of ni c kel in regard to whj s ke r· matrix bo ndin g in a co mpos ite of ni c ke l-coated sap phire wh is ke rs inserted into a matrix of aluminum-lO percent sili con al loy by mea ns of liquid phase hotpress ing wa s investi gated. Th e s tud y was ca rri e d out with th e aid o f o pti ca l and e lectron mi c rosco py , e lectron probe m ic roa nalys is, and mi c rohardn ess meas ure ments . Res ults s how th at mos t of th e ni c ke l is di s tributed within the matrix alloy.So me of the ni c ke l appar e nt ly int e rac ts with the matr ix and fo rm s NiAb. Th e prese nce of NiAl3 in thi s form incr eases the average hardn ess of the co mposite but. apparently does not co ntribute s ignifi ca ntly to s tre ngth e nin g of the alloy . Occasionally, c lus te r s or c lumps of ni c ke l-ri c h ma t.e ri a l whic h a lso cont.ains a luminum a re found at or very nea r whi s ker-matr ix interfa ces. It is co nc lud e d that if any bondin g of the ni c ke l to the sa pphire occ urred , it was in th ese regio ns. F inall y, a heat treatment to improve nic ke l to sa pphire bonding a nd hence bondin g of t.h e e ntire compos ite is s ugges ted .Key Word s: AI-IO pe rce nt Si alloy , e lectron prob e mi croa naiyze r, fib e r co mpos ite, matrixwh is ke r bondin g, Ni coated sapphire whi s ke rs, optical me tallograp hy, sapp hire whi ske rs.