No abstract

The simulator study allowed an exact characterization of the running-in period and showed a delayed onset of running-in wear. In contrast, the clinical data showed a slow increase in measured ion concentrations. These different wear patterns are probably due to the effects of distribution, accumulation, and excretion of particles and ions in vivo.

No abstract

Gel-like carrier materials were introduced into cell therapy of cartilage lesions to improve chondrocyte retention and distribution in the defect. Mesenchymal stem cells (MSC) are now discussed as an alternative cell source for repair. We here asked whether distinct gel-like carriers can support chondrogenesis of MSC in vitro and lead to stable cartilage-like transplants in vivo. Chondrogenesis of MSC embedded in collagen type I gel, fibrin glue, Matrigel and PuraMatrix peptide hydrogel was assessed and gene expression analysis, proteoglycan content, and collagen synthesis were quantified. Differentiated constructs were transplanted subcutaneously into SCID mice. All carriers supported chondrogenesis in vitro, but displayed material-dependent differences on COL2A1 gene expression, total collagen synthesis and proteoglycan deposition. The undesired calcification and microossicle formation in ectopic transplants in vivo was consistently suppressed by Matrigel. In sum, gel-like biomaterials were suitable carriers for MSC and promoted chondrogenesis. Suppression of calcification by particular gel-like materials makes their use even more attractive for MSC-based tissue engineering approaches in cartilage repair.

Retrospective therapeutic study, Level IV.

For these patients, serum cobalt and chromium ion levels were not acutely affected by patient activity. Periodic measurements of serum ion levels could be used to monitor the tribologic (lubrication, friction, and wear) performance of a metal-on-metal bearing without adjusting for patient activity. Additional research is needed into the kinetics of ion production, transport, and excretion.

Regardless of achieving a low recurrence rate and satisfactory functional results, we found a high complication rate after implantation of a megaprosthesis. This was particularly evident for extraarticular resections and cemented fixation, which should be avoided when possible.

Introduction The aim of the study was to compare the mortality risk and complication rate after operative treatment of pertrochanteric fractures with primary arthroplasty, dynamic hip screw (DHS) or proximal femoral nail (PFN). Patients and methods Clinical records including X-rays of all patients with trochanteric femoral fractures, except pathologic fractures and a minimum age of 60 years, which were treated between 1992 and 2005 were entered in this retrospective study. Of these 283 patients, 132 were treated by primary arthroplasty, 109 with a DHS and 42 with a PFN. Survival after 1 year and complications, which had to be treated within this period were our main outcome measurement. InXuencing cofactors such as age, gender and comorbidities were reduced by multivariate logistic regression analysis. Results Mortality was signiWcantly inXuenced by age, gender and amount of comorbidities but not by fracture classiWcation. Primary hip arthroplasty did not bear a higher 1-year mortality risk than osteosynthesis in a multiple regression analysis. The main complication with DHS and PFN were cutting out of the hip screw and non-union with a revision rate of 12.8%. With the introduction of hemiarthroplasty, the postoperative dislocation rate decreased from 12 to 0%. Conclusion For stable fractures a dynamic hip screw (DHS) and for unstable fractures a short proximal femoral nail (PFN) can be recommended. The mortality risk of primary cemented arthroplasty did not diVer signiWcantly from the other treatment groups and because of its low complication rate it is a viable treatment option for trochanteric fractures if osteoporosis prevents from full weight bearing or if osteoarthritis makes further operations likely. Primary total hip replacement should be handled with care due to its signiWcantly higher dislocation rate compared with hemiarthroplasty especially in unstable fractures.