Photodynamic therapy (PDT) requires a photosensitiser, a light source of an appropriate wavelength, and the presence of molecular oxygen. Once stimulated to its excited phase by the light, the photosensitiser reacts with oxygen to form free radicals of ‘singlet oxygen’ which is cytotoxic to microorganisms. We aim to demonstrate the effectiveness of PDT as an A PDT treatment protocol was devised using lawns of bacteria on agar plates. PDT was targeted towards the bacteria and the remaining microorganisms were quantified using a serial dilution technique. In order to assess the ability of photodynamic therapy to target biofilms on metallic implants, biofilms were cultured on polished titanium and hydroxyapatite-coated titanium discs and subjected to PDT.Aim
Method
Long-term survival of massive prostheses used to treat bone cancers is associated with extra-cortical bone growth and osteointegration into a grooved hydroxyapatite coated collar positioned adjacent to the transection site on the implant shaft [1]. The survivorship at 10 years reduces from 98% to 75% where osteointegration of the shaft does not occur. Although current finite element (FE) methods successfully model bone adaption, optimisation of adventitious new bone growth and osteointegration is difficult to predict. There is thus a need to improve existing FE models by including biological processes of osteoconduction and osteoinduction. The principal bone adaptation criteria is based on the standard strain-energy remodeling algorithm, where the rate of remodeling is controlled by the difference in the stimulus against the reference value [3]. The additional concept of bone connectivity was introduced, to limit bone growth to neighbouring elements (cells) adjoining existing bone elements. The algorithm was developed on a cylindrical model before it was used on an ovine model. The geometry and material properties from two ovine tibiae were obtained from computed tomography (CT) scans and used to develop FE models of the tibiae implanted with a grooved collar. The bones were assigned inhomogeneous material properties based on the CT grey values and typical ovine walking load conditions were applied. The FE results show a region of bone tissue growth below the implanted collar and a small amount of osteointegration with the implant, which is in good agreement to clinical results. Some histological results suggest that further bone growth is possible and potential improvements to the model will be discussed. In summary, by including an algorithm that describes osteoconduction, adventitious bone growth can be predicted.
To assess the extent of osteointegration in two designs of shoulder
resurfacing implants. Bony integration to the Copeland cylindrical
central stem design and the Epoca RH conical-crown design were compared. Implants retrieved from six patients in each group were pair-matched.
Mean time to revision surgery of Copeland implants was 37 months
(standard deviation (Aims
Patients and Methods
We reviewed the outcome of 69 uncemented, custom-made,
distal femoral endoprosthetic replacements performed in 69 patients
between 1994 and 2006. There were 31 women and 38 men with a mean
age at implantation of 16.5 years (5 to 37). All procedures were
performed for primary malignant bone tumours of the distal femur.
At a mean follow-up of 124.2 months (4 to 212), 53 patients were
alive, with one patient lost to follow-up. All nine implants (13.0%)
were revised due to aseptic loosening at a mean of 52 months (8
to 91); three implants (4.3%) were revised due to fracture of the
shaft of the prosthesis and three patients (4.3%) had a peri-prosthetic
fracture. Bone remodelling associated with periosteal cortical thinning
adjacent to the uncemented intramedullary stem was seen in 24 patients
but this did not predispose to failure. All aseptically loose implants
in this series were diagnosed to be loose within the first five
years. The results from this study suggest that custom-made uncemented
distal femur replacements have a higher rate of aseptic loosening
compared to published results for this design when used with cemented
fixation. Loosening of uncemented replacements occurs early indicating
that initial fixation of the implant is crucial. Cite this article:
We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem. We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified. There was significantly more ingrowth (p = 0.012) and attachment of bone (p >
0.05) to the porous HA surface (mean bone ingrowth 29.093 ± 2.019%; mean bone attachment 37.287 ± 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 ± 2.068%; mean bone attachment 18.9411 ± 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time. This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.