Corrado Piconi

Alumina Matrix Composites in Arthroplasty

It is well known that the introduction of zirconia into the alumina matrix has a positive effect on bending strength of the material, and especially on toughness which is the main limit of alumina ceramics. While the many attempts made in the past to develop alumina matrix composites suitable for biomedical applications containing zirconia as a toughening phase (Zirconia Toughened Alumina – ZTA) did not leave the developmental stage, recently ball heads and inlays for THR bearings made out a three phase alumina matrix composite were introduced into the market. In the alumina matrix of this material both zirconia and exagonal aluminate platelets are distributed, and then it belongs to the class of Zirconia and Platelets Toughened Alumina – ZPTA. Besides ball heads and inlays, also several other innovative orthopedic devices made out this new ceramic biomaterial are in different development stage. This paper reviews the present status of alumina matrix composites in orthopedic application, with special attention to ZPTA.

Safety Issues in the Use of THR Ceramic Heads and Cups

The safety of ceramic bearings are depending not only on the design and characteristics of the ceramic components, but also on the characteristics of the metallic tapers used for their connection to the stem and to the metal back in THRs. The modularity of today’s THRs offer the advantage of selecting the implant size that better suits the patient’s anatomy, but in this selections of the coupling several pitfalls have to be avoided. This paper is aimed to reviews the characteristics of the ceramic-metal interfaces and their influence on the behavior of the components of ceramic bearings.

Clinical outcomes of ceramicized ball heads in total hip replacement bearings: a literature review

Background Metallic ball heads for total hip replacement (THR) bearings with ceramicized surfaces were introduced in orthopedics during the second half of the 1980s, with the aim of decreasing the wear of polyethylene cups. Methods An analysis was made of the literature regarding outcomes for metallic ball heads with ceramicized surfaces now in clinical use (TiN, TiNbN, ZrN, monoclinic ZrO2), as well as carbon coatings (pyrolytic carbon, diamond-like carbon) and silicon nitride as coatings in ball heads for THR bearings. Results Notwithstanding the diffusion of ceramicized ball heads in THRs, there are few reports about their clinical outcomes in hip arthroplasty. In addition, several clinical studies and some registry data are putting under scrutiny the clinical advantages of ceramicized ball heads over cobalt chrome (CoCr) alloy and ceramic ball heads. Conclusions The wear of THR bearings with ceramicized ball heads looks like it depends more on the behavior of the polyethylene cups than on the treatment of the ball head surface. The risk of coating damage and of its consequences has to be taken into account in selecting this type of bearing.

Tissue Reactions to Ceramic Wear Debris: Clinical Cases vs. Animal Model

Wear is the main limiting factor to artroprostheses’ lifetime: at local level the cascade of events induced by reactions to wear debris is still the most frequent cause of implant failure and revision, while the ions released by wear debris originate systemic reactions, depending on their transport by the blood flow to peripheral organs, thanks to the vascularization of the reactive membrane surrounding the implant. (Schmalzried and Callaghan 1999, Urban et al. 2000, Archimbeck et al. 2000, Fisher et al 2001, Sedel 2001, Dumbleton et al. 2002).

Early failure of a locked titanium plate in a proximal humeral fracture: Case report and metallurgic analysis

Angular stability locking plates are commonly used in proximal humeral fractures, especially in old patients with osteoporotic bones. These implants show good results in short and midterm follow-up, but complications are not uncommon. Here we present a case report to describe a case of early failure of a proximal angular stability plate implanted in a 72 years old female with a highly unstable two part proximal humeral fracture. An optical and metallurgic analysis was also conducted to study the modalities of failure. We concluded that anatomic reduction and restoration of the medial cortical support are crucial in order to minimize the mechanical load on the bone–metal interface and to prevent mechanical failure, in particular when the fracture rim drop in the weak point of the plate that was found in the proximal two symmetric holes (Holes E).

Ceramic Roles in Aseptic Loosening: In Vivo Macro- and Microscopic Histological Evaluation

Prosthetic loosening in absence of infection (aseptic loosening) is the most common reason for revision of Total Hip Replacements (THR) Alumina and/or zirconia-based ceramic materials generally displayed high wear resistance and are considered suitable for load bearing application. To characterize the possible chronic cellular reactions to ceramic debris is then relevant in view of their long-term implantation. Low density ceramic pellets obtained by alumina and zirconia (Y-TZP) medical-grade precursors, were sintered at intermediate density and implanted in the patellar tendon of 24 NZW adult rabbits (group A). In this way the progressive release into the joint space of grains detached from surface of the pellets by the motion of the joint. Other 24 NZW rabbits (group B) received 5mg of powders injected in the articular capsule. Animals were killed at different intervals (1,3,6,12 months). Retrieved knee joints underwent X-Ray, histological and ultrastructural analysis. Peripheral organs (liver, kidney, lung, spleen, brain) were collected at same time. For, histologic analysis of tissue specimens collected in revision surgeries were fixed in 10% formalin, then decalcified ethylendiamintetracetic acid (EDTA), dehydrated and embedded in paraffin, sectioned and stained with hematoxylin-eosin. Histologic reaction was similar for the two ceramics and independent of the physical form (powders or pellets). Ceramic particulate was observed in the periprosthetic tissue membrane, the smaller inside mononuclear histiocyte-like cells in granuloma-like tissue, while the largest were in a synovial-like membrane inside a stroma poor in vessel containing mononuclear cells and rarely giant cells. No toxic nor carcinogenic effects were observed in peripheral organs retrieved at different time intervals. Although the ankyloses of the joints is a limiting factor for the duration of the test, this method may be a useful tool to evaluate the reactions to wear debris, and may result suitable also to evaluate the chronic response to metals or polymers of clinical interest.

Ultrastructural analysis of retrieved ceramic ball heads

Surface modification of alumina heads retrieved for aseptic loosening (6 cases) has been analysed using scanning electron microscopy, coupled with energy dispersive X-ray microanalysis. Ultrastruct...

Histologic and ultrastructural analysis in a case of massive failure of Zirconia ball head

The in vivo histological and ultrastructural analysis of periprosthetic tissue collected at time of revision surgery for failure of a 28 mm yttria-tetragonal zirconium oxide polycrystal (YTZP) ball head, 2 years after implantation is reported. Histologic analysis showed Zirconia particles, rounded to polygonal ranging from 2m to more than 10m intra or extra cellular in a stroma without vessels with few giant cells. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) showed the different shape from rounded to polygonal of Zirconia. SEM analysis of the internal part of Zirconia ball head showed the presence of different fracture lines especially in the internal surface (Hip International 2002; 4: 388-93).