Biomedical subjects

Ole Rahbek

Publications and source records attributed to Ole Rahbek.

4 recordsLinked to original sources

PubMed2005

The influence of surface porosity on gap-healing around intra-articular implants in the presence of migrating particles.

The aim of the present study was to compare the effect of two different porous coatings on bone ongrowth and on the peri-implant migration of polyethylene (PE) particles. Porous-coated cylindrical implants with an either plasma-sprayed closed-pore coating (Pl) or titanium fiber metal open-pore coating (Fi) were inserted intra-articular in exact fit or with a 0.75 mm peri-implant gap. A weight-loaded implant device in the distal femur was used. We used a randomized paired design in eight dogs. PE particles were injected repeatedly intra-articular in the knee until the dogs were killed after 8 weeks. Fi implants had significantly more bone ongrowth 8 (0-21)% compared with Pl implants 0 (0-0)% in gap situations and reduced the number of peri-implant PE particles significantly. Among exact-fitted implants we found that peri-implant tissue around Pl implants consisted of significantly more fibrous tissue than around Fi implants. A sealing effect against the migration of PE particles was found for both Fi and Pl implants in exact fit.

Alloys↗

PubMed2005

Bone compaction enhances fixation of weightbearing titanium implants.

Implant stability is crucial for implant survival. A new surgical technique, compaction, has increased in vitro implant stability and in vivo fixation of nonweightbearing implants. However, the in vivo effects of compaction on weightbearing implants are unknown. As implants inserted clinically are weightbearing, the effects of compaction on weightbearing implants were examined. The hypothesis was that compaction would increase implant fixation compared with conventional drilling. Porous-coated titanium implants were inserted bilaterally into the weightbearing portion of the femoral condyles of dogs. In each dog, one knee had the implant cavity prepared with drilling, and the other knee was prepared with compaction. Eight dogs were euthanized after 2 weeks, and eight dogs were euthanized after 4 weeks. Femoral condyles from an additional eight dogs represented Time 0. Compacted specimens had higher bone-implant contact and periimplant bone density at 0 and 2 weeks, but not at 4 weeks. A biphasic response of compaction was found with a pushout test, as compaction increased ultimate shear strength and energy absorption at 0 and 4 weeks, but not at 2 weeks. This biphasic response indicates that compaction enhances implant fixation by mechanical and biological mechanisms. Therefore, compaction might have potential value in total joint replacement in the future.

Animals↗

PubMed2003

Compacted cancellous bone has a spring-back effect.

A new surgical technique, compaction, has been shown to improve implant fixation. It has been speculated that the enhanced implant fixation with compaction could be due to a spring-back effect of compacted bone. However, such an effect has yet to be shown. Therefore we investigated in a canine model whether implant cavities prepared with compaction had spring back. Before killing the animals, we used one of two surgical techniques to make implant cavities of identical dimensions in both lateral femoral condyles of 7 dogs. One side had the implant cavity prepared with compaction, the other side with drilling. The cavities were left empty in vivo for 10 minutes before the dogs were killed. Postoperative micro-CT scanning showed that the diameters of the compacted cavities were significantly smaller than those of the drilled cavities, although they had had identical dimensions initially. Thus we found a spring-back effect of compacted bone, which may be important for increasing implant fixation by reducing initial gaps between the implant and bone.

Animals↗

PubMed2002

Osteogenic protein 1 device increases bone formation and bone graft resorption around cementless implants.

In each femoral condyle of 8 Labrador dogs, a non weight-bearing hydroxyapatite-coated implant was inserted surrounded by a 3 mm gap. Each gap was filled with bone allograft or ProOsteon with or without OP-1 delivered in a bovine collagen type I carrier (OP-1 device). 300 microg OP-1 was used in the 0.75 cc gap surrounding the implant. After 3 weeks, the OP-1 device enhanced implant fixation by 800% (p <0.05) in the ProOsteon group, but OP-1 bad no significant effect on implant fixation in the allograft group. By adding the OP-1 device, the volume fraction of woven bone close to the implant increased from 12% to 20% (p < 0.05) in the bone allograft group and from 6% to 25% (p < 0.05) in the ProOsteon group. The volume fraction of bone allograft decreased from 29% to 9% (p < 0.05) in the OP-1 treated group versus 33% to 30% in the allograft group not treated with OP-1. No resorption of ProOsteen was found. In conclusion, OP-1 accelerates resorption of bone allograft and enhances new bone formation around cementless implants grafted with bone allograft or semisynthetic hydroxyapatite bone substitute. Our findings do not support the use of ProOsteon alone around cementless implants.

Analysis of Variance↗