Metal ion levels post primary unilateral total knee arthroplasty

BackgroundMetal ion release from metal implants through the processes of mechanical wear and corrosion has been one of the main concerns post total joint arthroplasty. However, there have been very few studies to show metal ion exposure post total knee implants.AimsThe aim of this study was to investigate whether blood metal ion levels are raised in patients with well-functioning unilateral primary total knee arthroplasty in the short and the long term after surgery.Methods Whole blood Chromium and serum Cobalt levels were measured in 22 patients following primary total knee arthroplasty at a minimum of 12 months after surgery and then repeated at a mean of four years. Eleven patients had the cemented triathlon knee system and 11 patients had an uncemented ACS knee system with multilayer coatings.Results Cobalt levels in our study are low one year after TKR and stayed within normal limits with no significant rise at four years (p=0.300). Chromium levels raised significantly by four years (p=0.007), but remained within normal range with no evidence of toxic systemic effects. Our data showed no statistically significant difference for cobalt and chromium levels between ACS and Triathlon groups (p=0.62; p=0.54 respectively).ConclusionAt an average of 50-months post well-functioning total knee arthroplasty, whole blood Chromium levels and serum Cobalt levels are within the normal range. The use of cement is unlikely to influence metal ion release and titanium nitride coating did not influence metal ion release from TKR implants

Can larger-bodied cemented femoral components reduce periprosthetic fractures? A biomechanical study

Introduction: The risk for late periprosthetic femoral fractures is higher in patients treated for a neck of femur fracture compared to osteoarthritis. It has been hypothesised that osteopenia and consequent decreased stiffness of the proximal femur are responsible for this. We investigated whether a femoral component with a bigger body would increase the torque to failure in a biaxially loaded composite Sawbone model. Material and methods: A biomechanical bone analogue was used. Two different body sizes (Exeter 44-1 vs 44-4) of a polished tapered cemented femoral stem were implanted by an experienced surgeon in 7 bone analogues each and internally rotated at 40°/s until failure. Torque to fracture and fracture energy were measured using a biaxial materials testing device (Instron 8874, MI, USA). The data were non-parametric and therefore tested with the Mann-Whitney U-test. Results: The median torque to fracture was 156.7 Nm (IQR 19.7) for the 44-1 stem and 237.1 Nm (IQR 52.9) for the 44-4 stem (p=0.001). The median fracture energy was 8.5J (IQR 7.3) for the 44-1 stem and 19.5J (IQR 8.8) for the 44-4 stem (p=0.014). Conclusions: The use of a large body polished tapered cemented stems for neck of femur fractures increases the torque to failure in a biomechanical model and therefore is likely to reduce late periprosthetic fracture risk in this vulnerable cohort

Effects of anticoagulants on outcome of femoral neck fracture surgery

PURPOSE To review records of 330 patients who underwent surgery for femoral neck fractures with or without preoperative anticoagulation therapy. METHODS Medical records of 235 women and 95 men aged 48 to 103 years (mean, 81.6; standard deviation [SD], 13.1) who underwent surgery for femoral neck fractures with or without preoperative anticoagulation therapy were reviewed. 30 patients were on warfarin, 105 on aspirin, 28 on clopidogrel, and 167 were controls. The latter 3 groups were combined as the non-warfarin group and compared with the warfarin group. Hospital mortality, time from admission to surgery, length of hospital stay, return to theatre, and postoperative complications (wound infection, deep vein thrombosis, and pulmonary embolism) were assessed. RESULTS The warfarin and control groups were significantly younger than the clopidogrel and aspirin groups (80.8 vs. 80.0 vs. 84.2 vs. 83.7 years, respectively, p<0.05). 81% of the patients underwent surgery within 48 hours of admission. The overall mean time from admission to surgery was 1.8 days; it was longer in the warfarin than the aspirin, clopidogrel, and control groups (3.3 vs. 1.8 vs. 1.6 vs. 1.6 days, respectively, p<0.001). The mean length of hospital stay was 17.5 (SD, 9.6; range, 3-54) days. The overall hospital mortality was 3.9%; it was 6.7% in the warfarin group, 3.8% in the aspirin group, 3.6% in the clopidogrel group, and 3.6% in the control group (p=0.80). Four patients returned to theatre for surgery: one in the warfarin group for washout of a haematoma, 2 in the aspirin group for repositioning of a mal-fixation and for debridement of wound infection, and one in the control group for debridement of wound infection. The warfarin group did not differ significantly from non-warfarin group in terms of postoperative complication rate (6.7% vs. 2.7%, p=0.228) and the rate of return to theatre (3.3% vs. 1%, p=0.318). CONCLUSION It is safe to continue aspirin and clopidogrel prior to surgical treatment for femoral neck fracture. The risk of delaying surgery outweighs the peri-operative bleeding risk

Can larger cemented femoral components reduce periprosthetic fractures?

Introduction The risk for late periprosthetic fractures is higher in patients treated for a neck of femur fracture compared to those treated for osteoarthritis. It has been hypothesised that osteopenia and consequent decreased stiffness of the proximal femur are responsible for this. We investigated if a femoral component with a bigger body would increase the torque to failure in a biaxially loaded composite sawbone model. Method A biomechanical composite sawbone model was used. Two different body sizes (Exeter 44-1 vs 44-4) of a polished tapered cemented stem were implanted by an experienced surgeon, in 7 sawbones each and loaded at 40 deg/s internal rotation until failure. Torque to fracture and fracture energy were measured using a biaxial materials testing device (Instron 8874). Data are non-parametric and tested with Mann-Whitney U-test. Results The mean torque load to fracture was 154.1 NM (SD 4.4) for the 44-1 stem and 229 NM (SD10.9) for the 44-4 stem (p = 0.01). The mean fracture energy was 9.6 J (SD1.2) for the 44-1 stem and 17.2 J (SD2.0) for the 44-4 stem (p = 0.14). Conclusion the use of a large body polished tapered cemented stem for neck of femur fractures increases the torque to failure in a biomechanical model and therefore is likely to reduce late periprosthetic fracture risk in this vulnerable cohort

Hospital mortality after arthroplasty using a cemented stem for displaced femoral neck fractures

Purpose To review hospital mortality after hemiarthroplasty or total hip arthroplasty (THA) using a cemented stem for displaced femoral neck fractures. Methods Medical records of 284 hips in 70 men and 209 women aged 45 to 106 (mean, 81.3) years who underwent hemiarthroplasty (n=232) or THA (n=52) with a cemented stem using third-generation cementing techniques (including use of a plug, lavage, and cement pressurisation) for displaced femoral neck fractures were retrospectively reviewed. According to the American Society of Anesthesiologists (ASA) grading, 6 patients were classified preoperatively as grade 1, 77 as grade 2, 148 as grade 3, 47 as grade 4, and one as grade 5. Patients were operated on within 48 hours. Patients were rehabilitated in the hospital until discharge. The primary outcome measure was hospital mortality, including the cause of death. Results The mean length of hospital stay was 9.2 (standard deviation, 4.1) days. The hospital mortality was 5.7% (n=16). Of the 16 patients who died, 3 were classified preoperatively as ASA grade 2, 6 as grade 3, and 7 as grade 4. One patient died during the operation. One patient died in the recovery room within 6 hours. Both died from a cardiac arrest and were classified as ASA grade 4. Six patients died within the first 5 days. The causes of death were aspiration pneumonia (n=5), cardiac arrest (n=3), bowel perforation (n=2), multiple organ failure (n=3), type 2 respiratory failure (n=1), heart failure (n=1), and subarachnoid bleeding after a hospital fall (n=1). Conclusion Hemiarthroplasty or THA using a cemented stem resulted in low hospital mortality in our hospital dedicated to the treatment of geriatric hip fractures. Hospital mortality was higher in patients with ASA grade 3 or higher