Introduction. Minimally invasive implanted unicompartmental knee arthroplasty (UKA) leads to excellent functional results. Due to the reduced intraoperative visibility it is difficult to remove extruded bone cement particles, as well as bone particles generated through the sawing. These loose third body particles are frequently found in minimally invasive implanted UKA. The aim of this study was to analyse the influence of bone and cement particles on the wear rate of unicompartmental knee prostheses in vitro. Material & Methods. Fixed- bearing unicompartmental knee prostheses (n = 3; Univation F®, Aesculap, Tuttlingen) were tested with a customized four-station servo-hydraulic knee wear simulator (EndoLab GmbH, Thansau, Germany) reproducing exactly the walking cycle as specified in ISO 14243-1:2002. After 5.0 million cycles crushed cortical bone chips were added to the test fluid for 1.5 million cycles to simulate bone particles, followed by 1.5 million cycles blended with PMMA- particles (concentration of the third-body particles: 5g/l; particle diameter: 0.5- 0.7 mm). Every 500 000 cycles the volumetric wear rate was measured (ISO 14243-2) and the knee kinematics were recorded. For the interpretation of the test results we considered four different phases: breaking in- (during the first 2.0 million cycles), the steady state- (from 2.0 million to 5 million cycles), bone particle- and cement particle phase. Finally, a statistical analysis was carried out to verify the normal distribution (Kolmogorov-Smirnov test), followed by direct comparisons to differentiate the volumetric wear amount between the gliding surfaces (paired Student's t-test, p<0.05). Results. The wear rate was 12.5±0.99 mm. 3. /mio. cycles in the breaking-in phase and decreased during the steady state phase to 4.4±0.91 mm. 3. /mio cycles (not significant, p = 0,3). The bone particles did not have any influence on the wear rate (3.0±1.27 mm. 3. /mio cycles; p = 0,83) compared to the steady state phase. The cement particles, however, lead to a significantly higher wear rate compared to the steady state phase (25.0±16.93 mm. 3. /mio cycles; p<0.05). Discussion. To our knowledge this is the first study demonstrating that free cement debris which can be found after minimally invasive implanted UKA increases significantly the wear- rate. Bone particles generated for instance through sawing during implantation, however, had no influence on the prostheses wear rate. Our Data suggests, that it is extremely important to remove all the extruded cement debris accurately during implantation in order to avoid a higher wear rate which could result in an early loosening of the prostheses

This clinical study analyzes the long-term outcomes and potential complications of the Grammont's reverse prosthesis in case of trauma in elderly population. Between January 1993 and May 2010, thirty-seven consecutive patients with 26 three- and four-part fractures and 11 fracture-dislocations, mean age 75 (58 to 92) were evaluated with a mean follow-up of 7.3 years. Eight complications occurred: 2 complex sympathetic dystrophies, 3 dislocations, 2 deep infections and one aseptic loosening of the base-plate leading to 3 re-operations and 2 prosthesis revisions. The mean Constant's score dropped from 55 at two year follow-up to 52 (20 to 84) at last revision because of an augmentation of the pain and a diminution of the strength which represented 67% of the mean score for the injured side. Mean modified Constant's score was 68. Only 58% were satisfied or very satisfied because of poor internal and external rotations avoiding nourishment with utensils, dressing and personal hygiene when the dominant side was involved. Two complete glenoid borders, fourteen stable inferior spurs, twenty-one inferior scapular notches including ten of them with medial proximal humeral bone loss or radio lucent lines between the bone and the cement were observed. Notches were more important in size when the follow-up was longer. 62% of the patients had worrying images. The crossing of the clinical and radiological data showed a degradation of the mean Constant's score (41) for pain and strength in cases of notches with troubling proximal humeral images. In spite of only one case of aseptic loosening at 12 year follow-up, results are disappointing and complications and revisions rates important. The functional result is never equal to the pre-broken state. New developments in design, bearing surfaces and surgical technique and a more long term results will refine the role of the reverse concept for fracture

Due to increased life expectancy of human population, the amount of total knee replacements (TKR) is expected to increase. TKR reached a high grade of quality and safety, but most often it fail because of aseptic implant loosening caused by polyethylene (PE) wear debris. Wear is generated at the articulating surfaces, e.g. caused by three body particles, like bone fragments or bone cement particles. The aim of this experimental study was to compare the wear of tibial PE inserts combined with metallic and ceramic femoral components at three body wear situation induced by polymethylmethacrylate (PMMA) and zirconia (ZrO2) particles from the bone cement. Wear testing was performed for 5 Mio load cycles, using tibial standard PE inserts combined with the same CR femoral component, in two different materials, Cobalt Chromium (CoCrMo) and Biolox delta ® ceramic (Multigen Plus Knee System, Lima Corporate, Italy). A knee wear simulator, according to ISO 14243 (EndoLab GmbH, Rosenheim, Germany), was used to carry out the tests. The tests were performed in temperature-controlled test chambers at 37 °C, containing calf serum with a protein content of 30 g/l. Polymethylmethacrylate (PMMA) and zirconia (ZrO2) bone cement particles (Palacos R ®) were manufactured to a size of 30 μm. The three body particles were added at all stations onto the articulating surface of the tibial PE insert (7mg per condyle) at every 500,000 cycles. Wear was determined gravimetrically and the surfaces of tibial inserts were analysed by scanning electron microscope (SEM) after finishing the 5 million cycles. Furthermore, roughness of the PE insert surfaces and the articulating surfaces of the different femoral components were detected and the PE wear particles were analysed by SEM. The average gravimetrical wear rates of the tibial PE inserts in combination with CoCr and Biolox delta ® ceramic femoral components amounted to 6.4 ± 0.9 mg and 2.6 ± 0.4 mg per million cycles, respectively. Beside bone cement particles on the articulating surface of the PE inserts, polished surfaces and scratches were detected by SEM. In comparison to the untreated surfaces of the PE inserts at both material pairings the surface roughness at the articulating areas showed deep scratches and polished regions. Analyses of the metallic femoral components showed scratches at the articulating surfaces, none on ceramics. The present study pointed out the effect of femoral component material in an abrasive three body wear situation on the wear properties of TKR. The wear simulator tests showed that wear of PE inserts under three body wear conditions, in combination with ceramic femoral components, was significantly lower than with metallic femoral components. With regard to anti-allergic properties, ceramic femoral components are promising products for TKR