Ceramics are used in hip prostheses in approximately 40% of the implants (ce/ce and ce/pe). The increase of the diameters (32 and 36 mm) in order to improve the stability and the Range of Motion of the prostheses is now the topic. Research and development has allowed creating new alumina inserts with smaller out diameter (39 mm for the 32 mm bearing and of 44 mm for the 36 mm ones). The new alumina matrix composite has allowed the realization of ceramic revision ball-heads. This system, made of 28 or 32 mm ball-heads with a titanium slivers (12714 internal cone), will allow applications of the ceramic ball-head on an in situ damaged taper. Beyond S, M and L lengths, will be available also an XL version. A femoral knee component, still in phase of study, has shown advanced resistances of 5, 8 and 15 times the body-weight in different load configurations. Have been carry out some tests in order to estimate the adhesion between the ceramic and the cement of different thickness and have been caught up values of 6,17 MPa (2 mm) and 14,90 MPa (0,7mm).

Aim: To provide information on treatment outcomes for patients who received an acetabular component inserted with a polyethylene liner and to compare the results with those of patients who received the same acetabular component inserted with an alumina liner.

Methods Sixty consecutive patients (60 hips) with osteoarthrosis were allocated to two matched-pair groups. The patients were matched for age, gender, body-mass-index, level of activity, and bone stock. The first group of 30 hips (control group) received a total hip arthroplasty with a press-fit acetabular component, a polyethylene liner and an alumina femoral head. The second group of 30 hips (alumina group) was operated on using the same prosthesis, but an alumina liner was inserted instead of polyethylene.

Results: At a mean follow-up of five years (4.5 to 5.5 years) the mean Harris hip score was 94.1 points in the control group, and 92.7 points in the alumina group. No hip required revision, and there was no radiographic evidence of aseptic loosening.

Discussion: Modular acetabular components with alumina liners are currently used in total hip arthroplasty, but concerns have emerged regarding their high stiffness, which could cause impairment of stability, stress-shielding phenomena, and early loosening. In the present study, the acetabular components with an alumina liner functioned well overall and patient satisfaction was high at an average of five years postoperatively. Clinical and radiological results did not contrast with those achieved using the same prosthesis with a polyethylene liner.

Limitations of the range of motion (ROM) of total hip prostheses lead to impingement causing dislocation and material failure. Due to wear, the femoral head penetrates polyethylene (PE)-sockets by about 0,1 mm/year (ceramic on PE) and 0,2–0,6 mm/year (metal on PE). Wear rate increases with steep acetabular cup position. In contrast to polyethylene, wear of alumina-ceramic cups appears to be independent from inclination angle and is only about 0,001 mm/year. Wear and design features may restrict the artificial joint mobility. The purpose of this study is to determine the effects of head penetration on ROM in relation to different cup positions.

Computer simulation was carried out with a three-dimensional CAD-program. 3-D models of modular cup, spherical head, and stem with cylindrical neck and 12/14 taper were generated. The femoral head was shifted 0, 1, 2, and 5 mm towards the pole of the cup. According to mean direction of penetration measured in retrieved PE-sockets, femoral head was also moved 0, 1, 2, and 5 mm in vertical direction. The joint motions were measured at different cup positions.

The study demonstrates that ROM is clearly reduced by increasing head penetration. After 2 mm penetration, e.g. maximum flexion is reduced by approx. 15° at 45° cup inclination. Restriction of flexion is more pronounced in the vertical penetration path. If the socket is placed in more horizontal position, less ROM of flexion, extension and abduction is observed. With steeper cup positions ROM of flexion increases but, as well as risk of dislocation, wear and penetration rate of PE sockets increase.

Modern hip prostheses should provide sufficient joint movements, precise implant positioning and low wear bearing couples avoiding penetration of femoral head. Additionally, design aspects like liner geometry, head-neck ratio have to be considered preventing impingement, dislocation or early failure by aseptic loosening.

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.