Wear particles are thought to be a major factor causing osteolysis that leads to aseptic loosening. The aim of this study was to investigate the role of primary regulators of osteoclast development, RANKL (also known as osteoclast differentiation factor), its receptor RANK and natural inhibitor osteoprotegerin (OPG) in aseptic loosening. Cells were isolated from periprosthetic tissues taken at revision from more than 30 patients and the expression of these mediators in vivo was assessed using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). These cells were also cultured on dentine to determine their ability to become mature osteoclasts. In situ hybridisation using DIG labelled riboprobes specific for RANK mRNA was used to identify cells likely to become osteoclasts. We were able to compare revison tissues containing several different types of prosthetic wear particles. RANKL, RANK and OPG mRNA were found in samples of periprosthetic revision tissues. Cells derived from this tissue developed into mature osteoclasts capable of resorbing dentine. Cells that rapidly formed osteoblasts expressed a fifteen fold higher ratio of RANKL:OPG mRNA. In situ hybridisation showed RANK expression by macrophages and giant cells, many of which contained wear particles. Significantly, cells from tissues containing silastic wear particles expressed higher levels of RANKL relative to OPG and more produced large numbers of osteoclasts in vitro. This study shows that different bio materials in a particulate form may differ in their ability to form osteoclasts and that the relative levels of RANKL and OPG are likely to be important in determining if osteolysis will occur. In the future molecules that inhibit RANKL binding, such as OPG, may be considered for therapy of periprosthetic osteolysis.
There is a lack of properly undertaken comparative studies of total hip replacement (THR). A randomised trial was established to examine the hypothesis that there are no important differences in clinical outcome at 2 years and at long-term follow-up between cemented and uncemented primary THR in middle aged patients.Eighty-three patients with 90 osteoarthritic hips were randomised to a cemented Exeter THR involving a matte or polished tapered stem (n=47, median age 68yrs) or an uncemented PCA proximally porous-coated cobalt-chrome stem and porous coated press fit cup (n=43, median age 66yrs). Patients underwent immediate full weight bearing post-operatively. The follow-up period is 8 to 16 years. The median Harris hip scores for the cemented and uncemented groups respectively were 92 and 95 at 2 years and 89 and 96 at long-term follow-up. Four cemented hips have been revised for aseptic loosening. There have been no failures of the polished stems. An analysis of a larger series of matt versus polished cemented stems also found that the results of the polished stems were superior. Four uncemented hips have been revised, two more recently for acetabular wear and osteolysis. There was a high rate of radiographic demarcation of the cemented cups. There were no important differences in the clinical scores between cemented and uncemented THR. Some matte surfaced femoral stems failed and this trend was confirmed by analysis of a larger series. Osteolysis around the uncemented acetabular components is a concern. Importantly immediate weight bearing was associated with good results of uncemented stems.
Seven psoas bursae filled with purulent fluid and inspissated debris were revealed at revision operations for failed resurfacing hip arthroplasties, an incidence of 5.8% in such revisions. Histological and microbiological investigations demonstrated that the psoas bursa collections resulted from the tissue response to polyethylene wear debris. None was due to infection.
This paper reports a prospective study of the value of ultrasonography in detecting lesions of the lumbar spine in patients with compressive sciatica. The measurements of the diameter of the spinal canal obtained by using ultrasound were compared with the findings at operation in 17 patients in whom a total of 50 sites were examined. The ultrasound beam failed to penetrate the spinal canal at 15 sites and at only 10 of the remaining 35 sites did the ultrasound correctly detect narrowing. It is concluded that ultrasonography is unreliable in identifying the site of compression of the spinal cord and nerve roots. The technical limitations and the probable causes of failure of the technique are discussed.
