Aim

S. aureus and coagulase-negative staphylococci are the most frequent bacteria responsible for PJI. In patients with acute PJI (i.e. <1 month following the implantation), DAIR with exchange of removal components followed by a combination of antibiotics that includes rifampin (particularly rifampin+fluoroquinolone) are recommended. Unfortunately, some patients could not receive rifampin due to drug-drug interaction or stopped it due to an adverse event. Finally, it was unclear if the dose and the duration of rifampin influenced the prognosis.

Biphasic calcium phosphates (BCP) are the most frequently used materials because of their mineral analogy with bio-mineral part of bones. Their chemical synthesis can be modulated by doping, in order to respond to the biological needs. We present here the biological responses induced by copper ions in solution, to characterize its cytotoxicity and antibacterial activity. We also investigate the antibacterial property of Cu-doped BCP (Ca10 Cu0.1 (PO4)6 (OH)1.8 O0.2) on a strain of clinical interest: S. aureus, compared to undoped BCP. The sol-gel route has been used to prepare the BCP ceramics. Human BMC (Bone Marrow Cells) were obtained from metaphysal cancellous bone collected during hip arthroplasty and used for cytotoxicity evaluations. A strain of Staphylococcus aureus isolated from an osteoarticular infection after total knee arthroplasty was used to evaluate antibacterial activities. Results indicate that 3 ppm of copper ions leads to the death of all cultured bacteria in 24 hours and 25 ppm caused the death of all cells in 15 days. Regarding BCP, the undoped bioceramics increased the bacterial growth compared to a control without bioceramic. After 16 hours of contact, the copper ions released by the Cu-doped BCP induced a significant decrease of the bacterial concentration, indeed no viable bacteria were found. These materials seem to be a promising alternative for the preparation of multifunctional bone substitutes.

Background

Medical applications of nanotechnology are promising because it allows the surface of biomaterial to be tailored to optimise the interfacial interaction between the biomaterial and its biological environment. Such interfaces are of interest in the domain of orthopaedic surgery as they could have anti-bacterial functions or could be used as drug delivery systems. The development of orthopaedics is moving towards better integration of biology in implants and surgical techniques, but the mechanical properties of implanted materials are still important for orthopaedic applications. During clinical implantation, implants are subjected to large mechanical stresses. In order to obtain the best performance during clinical use, mechanical properties of implants need to be investigated and understood.

Background

External fixation is a method of osteosynthesis currently required in traumatology and orthopaedic surgery. Pin tract infection is a common problem in clinical practice. Infection occurs after a bacterial colonisation of the pin due to its contact with skin and local environment. To prevent such local contamination, one way to handle this issue is to create a specific coating using method which could be applied in the medical field. In this work we develop a surface coating for external fixator pins based on photocatalytic TiOα properties, producing a bactericidal effect with sufficient mechanical strength to be compatible with surgical use.

Purpose of the study: The purpose of this retrospective study was to present the outcomes observed with the Cedior total knee arthroplasty (TKA), and in particular an embedded patellar implant fixed without cement and cemented titanium backed base plate with a press fit stem.

Material and methods: From January 1993 to December 1996, 155 TKA were implanted in 143 patients for degenerative disease of the knee joint. At last follow-up, 55 patients had died, 28 were lost to follow-up 14 were contacted by phone, and 46 were reviewed clinically. Mean age was 62 years (62–80), BMI: 29.9 (22.6–38.2). Mean follow-up was 12 years (10–13). Posterior stabilised implants were used for 33% of the knees and the posterior cruciate was preserved in 67%. For all knees, the thickness of the polyethylene was > 6mm. Outcome was assessed clinically with the IKS, WOMAC, and Charnley scores and radiographically on the basis f lucent lines, osteolysis, and residual misalignment as measured on the standard films and goniometry. Survival was determined with the Greenwood method.

Results: Two patients (2 posterior stabilised TKA) with residual varus > 6 (> 15 preoperatively) were revised for loosening. At last follow-up, the postoperative IKS was 164, the WOMAC 28. Two patients were dissatisfied. Radiographically residual alignment was less than 3 in 56%, 3 to 6 in 41% and > 6 in 3%. For the femur, there were two lucent lines in a single zone. For the tibia, six lines in zone 7, none around the stem. For the patella, two implants presented significant asymptomatic osteolysis and there were two spontaneous (5 and 8 years) and asymptomatic fractures. Survival was 98.1±4.6% for revision and 96.2±6.9% for aseptic loosening.

Discussion: Our results are comparable with 10-year outcomes published in the literature where the survival has ranged from 92% to 99%. The titanium back cemented under the bas without cementing the sanded stem provides satisfactory results. The two loosening occurred for a residual varus > 6. The embedded, non-cemented patellar implant gave satisfactory results but the two cases of osteolysis led us to propose cementing.

Purpose of the study: The purpose of this work was to report the outcome at minimum ten years follow-up of cemented Muller total hip arthroplasty (THA) with a metal-on-metal bearing and a CLS cup.

Material and methods: From June 1995 to August 1997, 110 THA were implanted in 102 patients for degenerative hip disease. At last follow-up, 23 patients had died, four were lost to follow-up, and 67 were reviewed. Mean age was 56 years (29–71). BMI: 26.2 (17.9–33.6). Mean follow-up was 12 years (10–13). The same operative technique was used for all implantations: transgluteal approach, Palacos Gentamycine^® cement, straight femoral stem, Muller prosthesis made of Protasul^®10, with a Metasul^® head and a CLS cup with a polyethylene sandwich Metasul^® insert. Outcome was assessed clinically with the Merle score, radiographically searching for signs of loosening using the Harris criteria for the femoral component and the Hodgkinson criteria for the acetabular component. Migration was measured with the Nunn method for the cup and the Sutherland method for the femur. Dobbs actuarial survival was determined.

Results: Nine patients (9THA) underwent revision for acetabular migration (n=4), cup fracture by cam effect (n=1), psoas syndrome (n=2), retarded hypersensitivity (n=1), infection (n=1). At last follow-up, the clinical outcome was good or very good (n=64), fair (n=2), poor (n=1). Radiologically, for the femur: lucent lines (n=0), osteolysis (n=4), migration (n=0); for the cup: lucent line < 1mm stable and non migrating (n=3), global lucent line with migration > 5mm (radiological loosening) (n=1). No correlation between clinical and radiographic outcomes. Survival was 89.4±7.6% for revision outside infection and 92.6±6.9% for aseptic loosening.

Discussion: The failures at ten years were all acetabular, but related to various causes. Defective fixation could be related to the implant design or to the use of a hard-on-hard bearing increasing peripheral stress. Hypersensitivity and a cam effect related directly to using the metal-on-metal bearing. The psoas syndrome was not related to the type of cup.

Conclusion: Use of a metal-on-metal bearing, which theoretically improves wear, leads to other constraints in terms of fixation, technique, and context which must be taken into consideration to improve outcomes.

Introduction: The aim of this prospective, randomized, monocentric study was to compare wear of polyethylene when using a 28 mm diametre ceramic head versus a metallic head.

Material and Method: 226 THR performed between 1988 and 1990 were evaluated in 2005: 111 patients had died, 28 were lost of follow up and in 17 cases radiological assessment was not possible. 74 arthroplasties have been analyzed. In all cases, a straight femoral stem in protasul 10 (Zimmer), and a polyethylene cup sterilized under gamma radiation were used. In 37 cases the bearing surface used a metal head and in 37 cases a ceramic head. Radiolucent lines were analysed on AP x-rays. Aseptic loosening was defined according to Hodgkinson and Harris criteria. The penetration of the femoral head was measured with a special software (M.P.H. Wear) on digitalised x-rays.

Results: The two groups were statistically comparable (p = 0.0857). For metallic heads, linear wear was 0,102 mm/year (62.8 mm3/year volumetric wear). For ceramic heads, linear wear was 0,058 mm/year (volumetric wear 35.7 mm3/year. It represents a significant reduction (p = 0.0004) 44% of penetration. There was a penetration higher than 0.1 mm per year in thirteen cases of metal heads and in only one case of ceramic head. It was noted four aseptic loosening. In these four cases penetration was greater than 0.2 mm per year. In three cases, it was a metal head and in one case, a ceramic head.

Discussion: Our results are comparable to those found in the literature when the follow up is more than ten years as reported by Schuller, Oonichi and Hernigou. For authors with follow up shortest than ten years, it is reported identical outcomes between ceramic head and metal head (as reported Jenni, Devane and Sychterz).

Conclusion: This is the first randomized prospective study with two identical populations, showing a statistical significant difference of wear of polyethylene between ceramic and metallic prosthesis head.

Purpose of the study: The mechanical and radiological course of bone allografts is often favorable but osteointegration properties could be improved. We associated a safe allograft with mesenchymatous bone marrow stem cells (MSC) with known osteogenic potential. The purpose of this preliminary study was to study the biocompatibility of the treated allograft, assess the osteoblastic differentiation properties of the MSC, and determine the optimal period for colonizing the bone matrix.

Material and methods: The support was a safe bone allograft preserved in a collagenic grid (Osteopure™). MSC harvested by adherence were seeded in a medium favoring osteoblastic differentiation by comparison with standard culture medium. Culture conditions varied to study the influence of the presence or not of support, the culture time, or the presence of human serum in the culture medium. For each culture medium, we noted: the number of cells, osteoblastic differentiation using markers: alkaline phosphate and osteocalcin. A histological study was also performed.

Results: Peak cell amplification was achieved at three weeks culture. Presence of osteoblastic differentiation markers was clearly identified in cultures grown in the presence of support material. Microscopy demonstrated that cells stimulated by the differentiation medium adhered strongly to the bone network. Histology revealed the presence of osteoblastic activity in differentiation medium with cells taking on the classical cytological aspect of osteoblasts. Cell proliferation was at least equivalent in medium with human serum as with fetal calf serum.

Discussion: This study demonstrated that the allogenic matrix does not modify the capacity of human MSC for colonization and differentiation. The cell organization is optimal compared with the absence of supporting material. Use of the patient’s own serum in the culture medium was validated enabling an autologous procedure. Use of a complex cell graft appears to be optimal after three weeks of culture. This first step proves the feasibility of the concept designed to optimize the support with the patient’s own MSC. The next step is to develop an in vivo model.

Purpose of the study: Bearing wear debris from total hip arthroplasty (THA) appears to be the main cause of prosthetic loosening. RSA is the most accurate for measuring THA wear. It is the gold standard but remains difficult to use in routine practice. We therefore developed a computer-assisted method for measuring wear on plain x-rays. The purpose of this work was to determine the accuracy and reproducibility of MPH Wear 4 for measuring bearing wear.

Material and methods: The accuracy of measurements were assessed on several types of new implants or implants worn by movement simulators. X-rays of these implants were taken after implantation using a phantom simulating soft tissue and radiographic deformation. Accuracy was defined as the difference between the measurement produced by the computer-assisted tool and the reference metrology. Reproducibility was studied on ten x-rays of THA in ten patients (five men and five women, mean age 77.9 ± 4.4 years). Intraobserver reproducibility was studied with ten successive measurements on the same image by the same observer. Interobserver reproducibility was studied with a series of ten measurements on ten different images by two observers.

Results: The accuracy of the method was 0.09 mm on average (range 0.06–0.13 mm). The standard deviation giving the intraobserver reproducibility was 0.005 (i.e. 5.96% of the mean value). The standard deviation giving the interobserver reproducibility was 0.02.

Discussion: The methods used for determining the accuracy of a wear measurement system are poorly defined in the literature. It is thus difficult to compare different measurement methods. It can be considered that methods displaying an accuracy less than or equal to the mean annual polyethylene wear can be retained since they can easily identify significant wear (from the third year on). Our method is easily applied in routine practice, retrospectively if needed, offering an adapted accuracy and good reproducibility. However, this method is currently applied to cemented acetabular implants. The software is currently being adapted for study of implant migration and metal-backed implants.