Ludloff’s medial approach has never been used for other hip surgeries especially not for THR.

47 patients (26 men/21 women) provided informed consent to participate in the study. The inclusion criterion for the study was the diagnosis of osteoarthritis of the hip joint. The average age at operation was 53.7±10.4years. All patients were provided with a CUT^® prosthesis.

All patients were examined clinically and X-rayed preoperatively as well as postoperatively at three days, two weeks, six weeks and six months. The functional hip scores according to Harris and the Oxford hip score were obtained preoperatively and at the defined intervals postoperatively. The surgical duration and the intraop-erative as well as the postoperative blood loss were measured for each patient. Abductor muscle function and the number of steps a patient was able to walk without walking aids on a treadmill at a velocity of 5km/h (a maximum of 100steps was measured) were assessed.

Multifactorial analyses of variance and Chi-square tests were performed.

Based on the numbers available there were no significant differences between the two groups in the distribution of patient age (p=0.604), gender (p=0.654), weight (p=0.180) and height (p=0.295). No significant differences in the calculated Harris score (p=0.723) were found pre-operatively. The amount of steps the patient was able to walk was not different between the approach groups (p=0.636).

The total amount of blood loss (intra- + post-OP) was even significantly lower in the medial approach group (p=0.009).

Three days post-operatively the leg lengths were assessed. The difference was not statistically significant based on the numbers available (p=0.926). The overall correlation between Harris and Oxford score was significant (r²=0.63, p< 0.001).

Three days post-operatively a slight, but significant better Harris (p< 0.001) and Oxford scores (p=0.001) could be observed in the medial approach group. The number of steps the patient was able to walk without help or crutches was significantly higher in the medial approach group (p=0.001). The Trendelenburg sign (p< 0.001) and the limping criterion (p< 0.001) were significantly less in the medial approach group.

Two weeks post-operatively the Harris (p=0.001) and the Oxford (p=0.046) scores were significantly better for the medial approach group. The number of steps the patient was able to walk without help or crutches was significantly higher in the medial approach group (p< 0,001).

The medial approach is clinically feasible to perform the implantation of a femoral neck prosthesis. The accuracy of the stem implantation reflected in both the leg lengths and the postoperative X-ray alignment was not different between the groups.

After six months there was no significant difference between the conventional anterolateral approach and the medial approach in the presented study.

Introduction: Autologous osteochondral transfer is an option for the treatment of articular defects. However, there are concerns about graft integration and the nature of the tissue forming the cartilage-cartilage interface. Chondrocyte viability at graft and recipient edges is stated to be an important determinant of the success of repair.

As a tool, water jet (WJ) provides a cold cutting process. The cut is performed using water under high pressure (potential energy) by transforming it into water with high velocity (kinetic energy) using a nozzle.

This study evaluates the feasibility of performing selective cutting on the cortical bone and articular cartilage tissue by the use of plain water jetting.

Materials and Methods: Fresh full thickness cartilage explants were obtained from the stifle joints of 5 young calves (6–8 months old). Full thickness cartilage explants were removed from the femoral condyles using a scalpel. A specially designed water jet system was used for the study. The intensifier pump allowed pressure variations between 100–700 bars. The nozzle (Ø=0.2mm) was mounted on a gantry with two degrees of freedom. The cutting experiments were performed in displacement control mode, with cartilage held stationary and the nozzle moving at a traverse speed of 1mm/s. To calculate the energy typically required for consistent material removal, 40 cartilage samples were cut at various pressure levels using the water jet. Depths of the cut were measured by a Vernier caliper.

Multi- and one-way analyses of variance were computed with cutting depth as dependent variable.

In the second part of the study osteochondral cylinders were obtained from the femoral condyles using:

8 mm diameter Arthrex OATS punch,

Plugs were then assessed for cell viability along the cut periphery by performing live-dead cell staining and viewing under the confocal laser scanning microscope.

Results: There was a significant correlation between pressure and kerf depth (p< 0.001). At a relatively high transverse speed of 1mm/s cartilage was cut smoothly and easily. The typical material removal energy for bovine cartilage is 7,38.109 J/m³. Using Equation 1, the resultant kerf depths of multiple jet parameter can be calculated easily.

The margin of superficial zone cell death at the curved edge was significantly greater in the OATS punch group (390±18μm) and in the diamond drill group (440±18μm), when compared to the WJ group (10±4 μm).

Discussion: The dead at the cutting edge was greatly for WJ cut samples, making it a promising technology for cartilage repair. The results of the present study suggest that water jet cutting has the potential to be developed as an alternative means to prepare the cartilage for patients undergoing cartilage transplantation.

Introduction: The today’s applied osteotomy techniques in surgical orthopaedics have to adapt on the requirements on modern operationprocedures. The application of abrasive water jets offers the possibility to realize a self-defined, athermic precise cut in biological hard tissues. The small process forces indicate the application of modern handling systems. Process engineering and visions of a clinical conversion were demonstrated. Methods: With biocompatible crystalline abrasives freely defined separation cuts and open space geometries, which correspond to the contour of a knee endoprosthesis, were realized at human bones for the first time. The used abrasives (sucrose, xylitol) and can be added in mass flows of 10–20% and the physiological osmolarity is not exceeded after material removal and following dissolution. The necessary pressure level was 75MPa, which only corresponds to a fraction of the necessary pressure of pure water jet. The analysis about quality of the cut-surfaces was done laser-optical. Results: The transect performances of the used abrasives are similar. The arithmetic roughness Ra was 5μm with a pressure level of 75MPa. The value was found by surface detection 3mm under the point of entrance of the water jet in the bones. The flow mass of the abrasives showed only a small influence on the roughness. Conclusion: The results concerning angle deviation and surface seems to be were very promising.

Ceramic-on-ceramic was shown to have advantageous tribologic properties (low wear and friction). For medical applications two ceramics, alumina and zircona, are available. This case study shows that the combination of different ceramics for hard-hard pairings can be critical.

A 57 year old patient received a total hip prosthesis (cementless stem with a ceramic head and a monolithic ceramic cup). Thirty-five months postoperatively the patient complained about squeaking noises during walking and stair climbing. Clinical diagnoses showed a good range of motion and no signs of loosening. Conventional rehabilitation did not improve the situation and 43 months after primary surgery the cup and the head had to be revised on the patients request. Intraoperatively no loosening indications were found. The explanted components were analysed using a 3D co-ordinate measuring machine.

The head and the cup were made of different ceramics. The zirconia (ZrO2) head occurred rather white whereas the alumina (Al2O3) cup was yellow-reddish. The inner articulating surface of the cup showed no decoloration or wear. The surface of the head contained mated areas with surface defects in equatorial regions (maximum wear depth 9μm).

The head and the cup were combined from different manufacturers. The distinct surface changes and wear marks of the zirconia head probably caused the squeaking noise after 3 years in situ. Zirconia for medical applications is generally Y-TZP ceramic. Pressure, heating, and water can cause severe surface embrittlement. Pre-damaging due to the manufacturing process or friction in the joint might be the mechanism leading to pre-mature wear and failure. Joint components from different manufacturers should only be implanted with proper official authorisation.