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.

In this study we randomised 140 patients who were due to undergo primary total knee arthroplasty (TKA) to have the procedure performed using either patient-specific cutting guides (PSCG) or conventional instrumentation (CI).

The primary outcome measure was the mechanical axis, as measured at three months on a standing long-leg radiograph by the hip–knee–ankle (HKA) angle. This was undertaken by an independent observer who was blinded to the instrumentation. Secondary outcome measures were component positioning, operating time, Knee Society and Oxford knee scores, blood loss and length of hospital stay.

A total of 126 patients (67 in the CI group and 59 in the PSCG group) had complete clinical and radiological data. There were 88 females and 52 males with a mean age of 69.3 years (47 to 84) and a mean BMI of 28.6 kg/m² (20.2 to 40.8). The mean HKA angle was 178.9° (172.5 to 183.4) in the CI group and 178.2° (172.4 to 183.4) in the PSCG group (p = 0.34). Outliers were identified in 22 of 67 knees (32.8%) in the CI group and 19 of 59 knees (32.2%) in the PSCG group (p = 0.99). There was no significant difference in the clinical results (p = 0.95 and 0.59, respectively). Operating time, blood loss and length of hospital stay were not significantly reduced (p = 0.09, 0.58 and 0.50, respectively) when using PSCG.

The use of PSCG in primary TKA did not reduce the proportion of outliers as measured by post-operative coronal alignment.

Cite this article: Bone Joint J 2015;97-B:56–63.

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.

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.

Purpose: The purpose of this study was to evaluate ten year outcome of the 28-mm head self-locking cemented Müller THA.

Material and methods: From May 1988 to May 1990, 187 second generation cemented prostheses were implanted via the transgluteal approach for osteoarthritis. The femoral implant was a straight Prostasul 10 implant with a 28-mm modular head and a gamma ray sterilised poly-ethylene cup. At ten years, for the 187 implants: 64 patients had died, 24 patients were contacted by telephone (all with implants in place) nine were lost to follow-up, and 90 implants in 82 patients were reviewed. The reviewed series included 42 women and 49 mean, mean age 65 years. Clinical outcome was noted with the Postel Merle d’Aubigné score (PMA). Radiographical assessment noted lucent lines, granulomas, migrations, wear, and ossification.

Results: Among the 187 implants, two patients required revision: one for infection and the other for posttraumatic dislocation. Among the 82 patients reviewed at ten years, the PMA score was 16.85 (92% good and very good results). Radiographically, the acetabulum showed nine lucent lines measuring greater than 1 mm and progressing between five and ten years, one migration, and two cases of migration as well as three cases of wear greater than 2 mm. Evaluation of the femur showed osteolysis in zone 3 and 4 in one hip and rarified bone in zone 7 in four. Linear penetration of the head in the cup was 0.08 mm/yr. Brooker stage 3 ossifications were found in 27% of the men and 14% of the women.

Discussion: The clinical results were comparable to other series of cemented prostheses. At ten years, potential loosenings were more frequent at the acetabular level with progressive lines always present at five years; and polyethylene wear that was not always associated with osteolysis or granuloma, while osteolysis and granulomas were always associated with wear greater than 2 mm. Furthermore, there was no anatomoclinical relationship and radiographic anomalies did not always have an effect on function. Prevention of ossifications appears to be important, particularly in men.

Purpose: Bone allografting appears to be optimised by in situ stromal cells which have potential to evolve into a bone line. The purpose of this study was to test the bio-compatibility of stromal cells and an allogenic human bone support treated with stromal cells as well as their evolutive potential.

Material and methods: The bone support was a human femoral head allograft harvested during total hip arthroplasty. After validation of the safety of the femoral heads by the bone bank, they were treated using the Osteopure(r) method. Human stromal cells were harvested during cardiac surgery from the sternotomy. The in vitro study was conducted in a sterile atmosphere in an incubator. Different adhesion molecules were used: collagen, gelatin, fibronectin, human serum AB, in addition to an adhesion molecule-free medium. Microscopic qualitative evaluation determined the adhesion of stromal cells and the absence of difference between the morphology of cultured stromal cells and stromal cells found in the bone marrow. Cell counts were made on days 24; 32; 48, and 64. The functional properties of the new cultured stromal cells was evaluated by seeding CD34+ cells on day0 and counting the number of CFC produced on day45 (LTCIC1). This LTCIC1 line was cultured in the different media and re-evaluated at day45 (LTCIC2).

Results: The first microscopic observations showed that the stromal cells oriented naturally in the bone architecture with no particular rejection and that they maintained their adhesion properties with each other and with the bone support. Cell counts showed increased proliferation for the stromal cells cultured on the bone support compared with cultures without bone support. Stromal cultures were favoured by the presence of bone and culture media containing collagen, gelatin, and fibronectin. But the LTCIC2 cultures demonstrated better performance with bone and gelatin.

Discussion: Proliferation of stromal cells cultured in contact with an allograft demonstrated the biocompatibility of stromal cells/treated allografts. After twelve weeks incubation, the first cell counts tended to show that stromal cells cultured in vitro on human bone substitute preserve their functional potential and allow the proliferation of certain cells participating in osteogenesis. Further research to identify the capacity of these cells to induce an osteoblastic line must be conducted to allow in situ graft osteogenesis.