CeraNews Issue 11/2016

Infection related revision risk reduced with ceramic bearing components

An analysis of the New Zealand registry by Pitto et al. suggests a correlation between the infection-induced risk for revision surgery and the bearing surface type. This retrospective study comprised 84,894 hip arthroplasties covering a period of 15 years. The lowest hazard ratio (HR) was seen with ceramic-on-ceramic bearings (HR 1), followed by ceramic-on-polyethylene articulations with an HR of 1.3. The hazard ratio of 2.12 for metal-on-polyethylene bearings, on the other hand, was more than twice as high. Metal-on-metal bearings have an HR of 1.75.*

Pitto RP, Sedel L. Periprosthetic Joint Infection in Hip Arthroplasty: Is There
an Association Between Infection and Bearing Surface Type? Clin Orthop
Relat Res, DOI 10.1007/s11999-016-4916-y

* The investigators did not stratify the analysis according to polyethylene quality

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Ceramic fracture very rare

As demonstrated by current registry and o cial data, the fracture of a mixed-ceramic ball head like BIOLOX®delta is an extremely rare event in total hip arthroplasty. For BIOLOX®delta femoral heads the Australian Joint Replacement Registry 2014 lists a fracture rate of 1 : 100,000. The evidence from this registry confirms the CeramTec database which also shows a fracture rate of just 0.001% for the 4.08 million implants worldwide.

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Metal wear damages bone

A study by the University Hospital Charité and the DRK Klinikum Westend (Berlin, Germany) has demonstrated that the chromium and cobalt release in metal-on-metal bearings contributes to the loss of bone lining the implant. Once the dissolved constituents reach the bone marrow, they will damage the mesenchymal stem cells there. In patients exposed to metal wear they had lost all potential of osteogenesis.

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Ceramic against fretting corrosion

One of the hottest topics of the EFORT Congress in Geneva was fretting corrosion of the taper fixation in cobalt-chromium femoral heads on titanium stems. The symptoms noted by the patients resemble those seen in metal-on-metal bearings. While at present the scope of the problem has been somewhat exaggerated, a detailed discussion is rather important because of the severe consequences for the patients, emphasized Prof. Michael M. Morlock, PhD in his comprehensive presentation and described the multifactorial genesis of fretting corrosion.

In particular, the head size and fitting of the taper fixation play an important role, as Prof. Morlock said. He described the failure mechanisms and pointed out the danger of increased metal ion release with its potential of initiating biological reactions. In certain material pairings this corrosion may result in fracture of the stem’s neck. He pointed out that with the use of ceramic femoral ball heads, the risk of fretting corrosion is almost nonexistent. This conclusion is in line with the evidence presented by other speakers and published in the current literature.

Morlock MM, Bünte D, Gührs J, Krull A, Haschke H. The end of the taper disaster. EFORT 2016

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Ceramic-on-ceramic: 99.7% survival rate

A retrospective South Korean study by Kim et al. investigated 1,131 hip arthroplasties with ceramic-on-ceramic bearings (BIOLOX®forte, 28 mm) over a period of 15–20 years (mean 18.8 years). No osteolysis, aseptic loosening or ceramic fracture was seen. The twenty-year Kaplan-Meier survival rate was 100% for the femoral stem and 99.7% for the cup.

Kim YH, Park JW, Kim JS. Longterm results of third-generation ceramic-on-ceramic bearing cementless total hip arthroplasty in young patients. J Arthroplasty [2016], doi: 10.1016/j. arth.2016.03.058. accepted manuscript.

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