Hydroxyapatite coating enhances fixation of porous coated implants: A comparison in dogs between press fit and noninterference fit

Abstract

Intimate contact at the bone-porous surface interface is not always achievable in noncemented prosthetic implantation. We investigated the effect of hydroxyapatite (HA) coating on skeletal attachment in noninterference fit 4 weeks after implantation in 6 mature dogs. The pushout test of HA-coated implants surrounded by a 1-mm gap showed a twofold increased shear strength and fivefold increased shear stiffness compared with titanium alloy (Ti) coated implants. The fixation of Ti implants was reduced by two thirds when inserted in a gap as compared with press fit, whereas HA-coated implants in gap showed anchorage close to implants in press fit. Only minor differences were found between HA and Ti implants in press fit. Histomorphometric analysis showed a significant increase in bone in direct contact to HA-coated implant as compared with Ti implants inserted both in gap and press fit. The study indicates that tightness of surgical fit is an important factor for sufficient fixation of the implant. However, our results demonstrate that hydroxyapatite coating almost eliminates the negative influence of noninterference fit between bone and unloaded implant.The quantity of bone ingrowth into porous-coated implants depends, among other factors, on the interference fit obtained with the surrounding bone (Albrektsson and Albrektsson 1987, Cameron et al. 1976, Carlsson et al. 1988a, Harris et al. 1983, Sandborn et al. 1988). In the clinical situation, however, direct apposition of implant to bone is not always achievable Engh 1984, Engh et al. 1987 Schimmel and Huiskes 1988). Lack of optimal flatness after bone cutting, implant design deficiencies, and anatomic variations may result in gaps between the implant surface and surrounding bone Albrektsson 1987, Larsen andRyd 1990).Calcium phosphates in the form of granules have been employed to fill in gaps between bone and implant with no demonstrable effect on bone ingrowth at early time periods (Eschenroeder et al. 1987, Russotti et al. 1986. Recently, deposition of dense hydroxyapatite (HA) on titanium alloy (Ti) by plasma spraying technique has been shown to improve the HA-metal substrate interface shear strength , Thomas et al. 1987. HA coating provides earlier bone ingrowth compared with Ti (Geesink et al. 1988, Saballe et al. 1989a, b, c, Thomas et al. 1987.We examined the effect of HA coating on skeletal attachment of unloaded porous titanium implants inserted in noninterference fit compared with press fit insertion. Material and methodsExperimental design. Six skeletally mature labrador dogs of both sexes weighing 28 (22-31) kg comprised the material. Ti-and HA-coated implants were inserted in press fit or in noninterference fit in the distal femoral condyles. The dogs were killed after 4 weeks and the results were evaluated by the mechanical push-out test and histomorphometric analysis.Bone-density measurements. To investigate bone density at implantation site, CT scanning of the distal femora was performed 1 week before surgery as previously described (Saballe ...

Tissue ingrowth into titanium and hydroxyapatite‐coated implants during stable and unstable mechanical conditions

“…Thus, as suggested by Page et al (2Y), relative movements at the fracture site lead both to the inhibition of angiogenesis and to the subsequent differentiation of cartilage. Whether the fibrocartilage found around the unstable HA-coated implants in the present study will be replaced later by bone by endochondral ossification is yet unknown, but stud--_ _ anchorage and bony ingrowth into HA-coated implants compared with porous coated Ti implants (35)(36)(37). This was confirmed by the present study concerning the stable implants that were unloaded to ensure rigid stability.…”

“…Reduced bony ingrowth and weakened mechanical anchorage of the porous coated implant may occur if the bone stock is osteopenic (34), in the absence of initial contact between bone and implant (9, [35][36][37]40), if the pore size of the surface coating is too small (38), or with lack of initial mechanical stability between bone and implant (7,8,14,17,21, 30,40). However, hydroxyapatite (HA) coating has been demonstrated to increase bone ingrowth and anchorage strength of porous coated implants Experimental studies of cementless tibial components implanted into cadaver tibias have shown micromovements ranging between 200 and 500 pm at loads in the low physiologic range (6, 33,39,47).…”

“…The pushout tests were performed with a universal test machine (Instron Ltd.) (34)(35)(36). The specimens were placed on a metal platform with a central circular opening supporting the bone to urithin SO0 pm of the interface.…”

Locally delivered TGF-β1 and IGF-1 enhance the fixation of titanium implants: A study in dogs

“…Some authors have reported that as little as 10-20% of a press-fit inserted prosthesis is in contact with the bone (Noble et al 1988, Schimmel andHuiskes 1988, Geesink 2002). Our previous work with gap implants has consistently shown abundant ongrowth of fibrous tissue, inferior bony ongrowth, and poor mechanical fixation (Soballe et al 1990, Elmengaard et al 2005. In previous studies, the titanium implant surface has been shown to be similar to that of commercially available prostheses with a plasma spray titanium coating (Soballe et al 1992(Soballe et al , 1993.…”

The Effect of Platelet-Rich Plasma on the Bone Healing around Calcium Phosphate?Coated and Non-coated Oral Implants in Trabecular Bone

“…7 The use of calcium phosphate (CaP) coatings has also been shown to benefit the bone response during the initial healing period after implant insertion. 8 Various animal studies have proved that CaP-coated implants show greater bone contact than non-coated implants. 9,10 In addition to surface quality, growth factors can also stimulate bone healing around implants.…”