Total knee arthroplasty with a rotating hinge knee with carbon-fibre-reinforced (CFR)-PEEK as an alternative bushing material with enhanced creep, wear and fatigue behaviour has been clinically established [1–4]. The objective of our study was to compare results from in vitro biotribological characterisation to ex vivo findings on a retrievals.

A modified in vitro wear simulation based on ISO 14243-1 was performed for 5 million cycles on rotating hinge knee (RHK) designs (EnduRo®) out of cobalt-chromium and ZrN-multilayer ceramic coating. The rotational & flexion axles-bushings and the flanges are made of CFR-PEEK with 30% polyacrylonitrile fibre content.

Analysis of 12 retrieved EnduRo® RHK systems in cobalt-chromium and ZrN-multilayer in regard to loosening torques, microscopic surface analysis, distinction between different wear modes and classification with a modified HOOD-score has been performed.

For the RHK design with the polyethylene gliding surface and bushings and flanges made out of CFR-PEEK, a cumulative volumetric wear was measured to be 12.9±3.95 mm³ in articulation to cobalt-chromium and 1.3±0.21 mm³ to ZrN-multilayer coating - a significant 9.9-fold decrease (p=0.0072).

For the CFR-PEEK flexion bushing and flanges the volumetric wear rates were 2.3±0.48 mm³/million cycles (cobalt-chromium) and 0.21±0.02 mm³/million cycles (ZrN-multilayer) (p=0.0016). The 5 million cycles of in vitro wear testing reflect a mean in vivo service life of 2.9 years, which is in accordance to the time in vivo of 12-60 months of the retrieved RHK components [5]. The main wear modes were comparable between retrievals and in vitro specimens, whereby the size of affected area on the retrieved components showed a higher variation.

For the EnduRo® RHK design the findings on retrieved implants demonstrate the high suitability of CFR-PEEK as a biomaterial for highly loaded bearings, such as RHK bushings and flanges in articulation to cobalt-chromium and to a ZrN-multilayer coating.

The use of rotating hinge (RH) prostheses for severe primary as well as revision arthroplasty is widely established. Aim of this study was to investigate long term results of a new RH prosthesis (EnduRo®, B Braun, Germany), which uses carbon-fiber reinforced poly-ether-ether-ketone (CFR PEEK) as a new bearing material, first time used in knee arthroplasty.

Fifty-six consecutive patients, who received the EnduRo® RH prosthesis were included in this prospective study: 21 patients (37.5%) received the prosthesis as a primary total knee arthroplasty (TKA) and 35 patients (62.5%) underwent revision total knee arthroplasties (rTKA). Clinical and radiographic examinations were performed preoperatively as well as postoperatively after 3 and 12 months and annually thereafter. Min. Follow up was 7 and mean follow up 9,3 years. Clinical examination included Knee Society Score (KSS), Western Ontario and McMaster Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), and range of motion (ROM). Competing risk analysis was assessed for survival with respect to indication and failure mode.

KSS, WOMAC, OKS, and ROM significantly improved from the preoperative to the follow up investigations (p < 0.0001). There was no difference in clinical outcome between the primary and the revision group. The overall cumulative incidence for revision for any reason was 23.6% and the cumulative incidence for complications associated with failure of the prothesis was 5.6% at 7 years, respectively. Complications occurred more frequently in the revision group (p = 0.002).

The evaluated RH prosthesis provided reliable and durable results with a minimum follow-up of 7 years. Prosthesis survival was successful considering the complexity of cases. The use of this RH system in primary patients showed high survival rates. Long-term functional and clinical results proved to be satisfying in both revision and primary cases. No adverse events were associated with the new bearing material CFR-PEEK.

Ten to twenty percent of patients are dissatisfied with the clinical result after total knee arthroplasty (TKA). Aim of this study was to investigate the impact of personality traits on patient satisfaction and subjective outcome of TKA.

We investigated 80 patients with 86 computer navigated TKAs (Emotion®, B Braun Aesculap) and asked for patient satisfaction. We divided patients into two groups (satisfied or dissatisfied). 12 personality traits were tested by an independent psychologist, using the Freiburg Personality Inventory (FPI-R). Postoperative examination included Knee Society Score (KSS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and the Visual Analogue Scale (VAS). Radiologic investigation was done in all patients.

84% of our patients were satisfied, while 16% were not satisfied with clinical outcome. The FPI-R showed statistically significant influence of four personality traits on patient satisfaction: life satisfaction (ρ = 0.006), performance orientation (ρ =0.015), somatic distress (ρ = 0.001), and emotional stability (ρ = 0.002). All clinical scores (VAS, WOMAC, and KSS) showed significant better results in the satisfied patient group. Radiological examination showed optimal alignment of all TKAs. There were no complications requiring revision surgery in both groups.

The results of our study show that personality traits may influence patient satisfaction and clinical outcome after TKA. Thus, patients personality traits may be a useful predictive factor for postoperative satisfaction after TKA.

Aim

Although established serum inflammatory biomarkers, such as serum C-reactive protein (CRP) and serum white blood cell count (WBC), showed low accuracies in the literature, they are still commonly used in diagnosing periprosthetic joint infections (PJI). For a sufficient preoperative diagnosis novel more accurate serum parameters are needed. The aim of our study was to evaluate the performances of the established and novel routinely available serum parameters in diagnosing periprosthetic joint infections when using the proposed European Bone and Joint Infection Society (pEBJIS) criteria.

Introduction

Cementless total knee arthroplasty (TKA) implants use an interference fit to achieve fixation, which depends on the difference between the inner dimensions of the implant and outer dimensions of the bone. However, the most optimal interference fit is still unclear. A higher interference fit could lead to a superior fixation, but it could also cause bone abrasion and permanent deformation during implantation. Therefore, this study aims to investigate the effect of increasing the interference fit from 350 µm to 700 µm on the primary stability of cementless tibial implants by measuring micromotions and gaps at the bone-implant interface when subjected to two loading conditions.

Introduction

The complex process of inflammation and osteolysis due to wear particles still is not understood in detail. So far, Ultra-high-molecular-weight-polyethylene (UHMWPE) is the bearing material of choice in knee arthroplasty and revision knee arthroplasty, but there is a growing demand for alternative bearing materials with improved wear properties. Lately, increasing interest developed in the use of natural and carbon-fiber-reinforced-poly-ether-ether-ketones (CFR-PEEK).

While there is a lack of data concerning the effects of CFR-PEEK particles on human tissue, the effects of such wear debris in vitro and in animal studies is controversially discussed.

The aim of this study was to analyze human tissue containing CFR-PEEK as well as UHMWPE wear debris.

The authors hypothesized no difference between the used biomaterials because of similar size parameters of the wear particles in a prior knee simulator study of this implant.

Material and Methods

In a prospective randomized study of two groups of 65 patients each, we compared the acetabular component position when usingthe imageless navigation system compared to the freehand conventional technique for cementless total hip arthroplasty. The position of the component was determined postoperatively on computed tomographic scans of the pelvis.

Introduction

In a recent study we evaluated the clinical and radiographic long-term results as well as the serum metal concentrations of 105 cementless primary total hip prosthesis, performed between November 1992 and May 1994 with a 28-mm high-carbide-concentration metal-on-metal articulating surfaces. Forty-one patients who had had a total of forty-four arthroplasties were available for follow-up evaluation at a minimum of seventeen years postoperatively.

The median serum cobalt concentration of the patients with their hip replacement as the only source of cobalt was 0.7 µg/L (range 0.4–5.1µg/L), showing no significant difference to the previous study after a minimum of 10 years follow-up. We were investigating the systemic dissemination, which in turn, did not show more severe effects, such as carcinogenicity or renal failure. There are many complex issues associated with the analysis of metal ions, including collecting technique, analysis and reporting of the results. At the AAOS in March 2013, the Hip Society mentioned, that systemic ion levels are just one factor in the evaluation and should not be relied upon solely to determine the need for revision surgery. Furthermore, the correlation between cobalt or chromium serum, urin or synovial fluid levels and adverse local tissue reactions is incompletely understood.