Background

Currently, the gold standard for the microbiological diagnosis remains the culturing of preoperative aspirated joint fluid and intraoperative periprosthetic tissue samples, which give false negative results in about 7 % of cases. Lytic bacteriophages are viruses that specifically infect and lyse bacteria within their replication cycle.

Objective: To find clinically the most suitable tissue-engineered replacement for nucleus pulposus which should be able to prevent, or at least delay, the process of intervertebral disc degeneration, as well as narrowing of the intervertebral disc space after surgery of disc herniation.

Methods: We chose to transplant chondrocytes derived from elastic cartilage in site of previously evacuated nucleus pulposus from the lumbar intervertebral discs of New Zeeland White Rabbits. Elastic cartilage cells of the rabbit ear have been used as an easily accessible and quality source of chondrocytes. A small piece of ear cartilage has been sampled and disintegrated. Free chondrocytes have been isolated and labeled with a fluorescent marker before transplantation procedure in order to trace them after implantation. Both cultured chondrocytes and chondrocytes harvested after isolation have been used as a transplant. Prior to implantation these cells have been divided into two groups – the first group as a cell suspension and the second group as a cellular construct on plasma-thrombin gel as a carrier. Animals were sacrificed in groups: after two weeks, one month and three months, with their lumbar intervertebral discs removed. In control group only nucleus was removed and then replaced either with suspension or carrier without cells. Survival of transplanted cells in the intervertebral disc space and their extracellular matrix synthesis has both been evaluated by fluorescent microscopy, histological and gene expression analysis. Radiological analysis has been used to test the efficiency in preventing the narrowing of intervertebral space after evacuation of nucleus pulposus.

Results: By using labeled transplanted cells we were able to trace their viability with fluorescent microscope up to one month. Thereby we have proven the transplanted cells are able to survive in the environment of the rabbit’s intervertebral disc. In addition, they are able to produce basic structural molecules of extra cellular matrix, histological similar to native nucleus pulposus, in contrast with control group where only remnants of carrier and scar tissue were found. However, the gene expression studies have shown that the cells of the new-formed tissue express less tissue-specific extra cellular matrix genes, e.g. aggrecan, collagen II, then cells in the native tissue. Radiological analysis has not shown any significant differences between the two groups in prevention of intervertebral space narrowing following the discectomy.

Conclusion: Cell therapy has much to offer in the development of tissue-engineered replacements used in clinical orthopedics. results and techniques of this research may turn out to be useful in clinical practice, but further examinations are needed especially on the field of annular closure, before any clinical investigation.

We compared the quality of debridement of chondral lesions performed by four arthroscopic (SH, shaver; CU, curette; SHCU, shaver and curette; BP, bipolar electrodes) and one open technique (OPEN, scalpel and curette) which are used prior to autologous chondrocyte implantation (ACI). The ex vivo simulation of all five techniques was carried out on six juvenile equine stifle joints. The OPEN, SH and SHCU techniques were tested on knees harvested from six adult human cadavers.

The most vertical walls with the least adjacent damage to cartilage were obtained with the OPEN technique. The CU and SHCU methods gave inferior, but still acceptable results whereas the SH technique alone resulted in a crater-like defect and the BP method undermined the cartilage wall. The subchondral bone was severely violated in all the equine samples which might have been peculiar to this model. The predominant depth of the debridement in the adult human samples was at the level of the calcified cartilage. Some minor penetrations of the subchondral end-plate were induced regardless of the instrumentation used.

Our study suggests that not all routine arthroscopic instruments are suitable for the preparation of a defect for ACI. We have shown that the preferred debridement technique is either open or arthroscopically-assisted manual curettage. The use of juvenile equine stifles was not appropriate for the study of the cartilage-subchondral bone interface.

We analysed revised Mathys isoelastic polyacetal femoral stems with stainless-steel heads and polyethylene acetabular cups from eight patients in order to differentiate various types of particle of wear debris. Loosening of isoelastic femoral stems is associated with the formation of polyacetal wear particles as well as those of polyethylene and metal. All three types of particle were isolated simultaneously by tissue digestion followed by sucrose gradient centrifugation. Polyacetal particles were either elongated, ranging from 10 to 150 μm in size, or shred-like and up to 100 μm in size. Polyethylene particles were elongated or granules, and were typically submicron or micronsized.

Polyacetal and polyethylene polymer particles were differentiated by the presence of BaSO₄, which is added as a radiopaque agent to polyacetal but not to polyethylene. This was easily detectable by back-scattered SEM analysis and verified by energy dispersive x-ray analysis.

Two types of foreign-body giant cell (FBGC) were recognised in the histological specimens. Extremely large FBGCs with irregular polygonal particles showing an uneven, spotty birefringence in polarised light were ascribed to polyacetal debris. Smaller FBGCs with slender elongated particles shining uniformly brightly in polarisation were related to polyethylene. Mononucleated histiocytes containing both types of particle were also present.

Our findings offer a better understanding of the processes involved in the loosening of polyacetal stems and indicate why the idea of ‘isoelasticity’ proved to be unsuccessful in clinical practice.

We describe three prostheses with cemented titanium-alloy stems and Al₂O₃ ceramic femoral heads which had to be revised after a mean period of implantation of 78 months. In each case, the neck of the prosthesis had been so severely worn that the profile was elliptical rather than circular. There was severe metallosis of the periprosthetic tissues. Metal particles isolated from the tissues were approximately one nanometre in size and the ratios of titanium, aluminium and vanadium in the particles were the same as in the original alloy. Histologically, the high concentration of metal particles masked the presence of high-density polyethylene (HDP) debris, but again particles about one nanometre in size were isolated from the tissues. The severe necrobiosis and necrosis noted were consistent with other reports of the presence of extensive wear particles in periprosthetic tissues. Wear is presumed to have occurred as a result of mismatch between the shape or size of the taper cone and the femoral head, or to changes in the geometry of loading due to migration of the cup. To facilitate early intervention, patients with this design of prosthesis should be monitored radiologically.