Assessment of five interleukins in human synovial fluid as possible markers for aseptic loosening of hip arthroplasty.

One of the most important factors that seems to be involved in total hip replacement is periprosthetic osteolysis. As it is well documented that several interleukins (ILs) are triggered in periprosthetic osteolysis, this article investigates the role of five ILs in primary and replacement total hip arthroplasty, understanding if one of them can also predict hip implant loosening, secondary surgery, and prosthesis breakage. The levels of IL-1alpha, 1beta, 6, 8, and 10 in synovial fluid were examined, using a high sensitivity enzyme-linked immunosorbent assay (ELISA) test kit (Pierce Biotechnology, Inc., Rockford, IL, USA) to determine whether these cytokines could be used as markers of enhanced periprosthetic osteolysis, leading to aseptic loosening of total/partial hip arthroplasty or revision surgery. Synovial fluid was harvested from 23 patients undergoing primary total hip arthroplasty and 35 patients undergoing total/partial hip revision due to aseptic loosening. In the revision group, four cases had suffered a prosthesis fracture and five were second revisions. ILs 6 and 8 were significantly higher in the revisions (305 and 817 pg/mL) compared with the primary arthroplasties (151 and 151 pg/mL), including cases with prosthesis fracture and those requiring a second revision. IL-10 levels were lower (not significantly) in second revision samples compared with those of revision samples. IL-1beta levels were significantly higher in prosthesis fracture samples compared with those of all the other revision samples. No statistically significant differences in IL levels were found between osteoarthritis samples and those of other diseases. These results are a step forward to elucidating the complex network of events that are involved in loosening of hip implants.

Relationship between obesity and early failure of total knee prostheses.

BACKGROUND: Obesity is a risk factor for knee arthritis. Total knee arthroplasty is the definitive surgical treatment of this disease. Therefore, a high percentage of subjects treated are overweight. Since 2000 in the Emilia-Romagna Region the Register of Orthopedic Prosthetic Implantology, RIPO, has recorded data of all the primary and revision operations performed on the knee; height and weight of patients at the time of surgery have also been recorded. METHODS: To understand how overweight and obesity affect the outcome of knee arthroplasty, a population of subjects treated with cemented total knee arthroplasty between 2000 and 2005 was studied. 9735 knee prostheses were implanted in 8892 patients; 18.9% of the patients were normal weight, 48.2% were overweight (25 < Body Mass Index <= 30), 31.1% were obese (30 < BMI <= 40), and 1.8% were morbidly obese (BMI > 40). Mean and range of follow-up were respectively 3.1 and 1.5-6 yrs. Implant failure was defined as the exchange of at least one component for whatever reason. RESULTS: In normal weight patients there were 36 failures out of 1840 implants (1.96%), in overweight patients there were 87 out of 4692 (1.85%), in obese 59 out of 3031 (1.94%), and in morbidly obese there were 4 out of 172 (2.3%). The mean time to failure for each class was 1.57, 1.48, 1.60, 1.77 yrs. Cox regression analyses showed that the risk of implant failure was not influenced by BMI, absolute body weight, or sex. Conversely, an increased failure risk was observed in mobile meniscus prostheses in comparison with those with a fixed meniscus (Rate Ratio 1.88); an increased failure risk was also related to age (Rate Ratio 1.05 per year). These results were also confirmed when considering septic loosening as the end-point. There were no differences in the rate of perioperative complications and death in the 4 classes of BMI. CONCLUSION: In conclusion, cemented knee prostheses, implanted in patients with arthritis do not have significantly different rates of survival or perioperative complications in obese subjects compared with normal weight subjects, at least up to 5 years after surgery. The conclusion also applies to subjects affected by morbid obesity, although this findings should be regarded with caution due to the small sample examined.

Structural behaviour and strain distribution of the long bones of the human lower limbs.

Although stiffness and strength of lower limb bones have been investigated in the past, information is not complete. While the femur has been extensively investigated, little information is available about the strain distribution in the tibia, and the fibula has not been tested in vitro. This study aimed at improving the understanding of the biomechanics of lower limb bones by: (i) measuring the stiffness and strain distributions of the different low limb bones; (ii) assessing the effect of viscoelasticity in whole bones within a physiological range of strain-rates; (iii) assessing the difference in the behaviour in relation to opposite directions of bending and torsion. The structural stiffness and strain distribution of paired femurs, tibias and fibulas from two donors were measured. Each region investigated of each bone was instrumented with 8-16 triaxial strain gauges (over 600 grids in total). Each bone was subjected to 6-12 different loading configurations. Tests were replicated at two different loading speeds covering the physiological range of strain-rates. Viscoelasticity did not have any pronounced effect on the structural stiffness and strain distribution, in the physiological range of loading rates explored in this study. The stiffness and strain distribution varied greatly between bone segments, but also between directions of loading. Different stiffness and strain distributions were observed when opposite directions of torque or opposite directions of bending (in the same plane) were applied. To our knowledge, this study represents the most extensive collection of whole-bone biomechanical properties of lower limb bones.