Parvizi on PJI prevention and treatment
Registry data seem to indicate that the numbers of PJI-related revisions after THA and TKA are increasing. This was confirmed in a recent interview by Javad Parvizi from the Rothman Institute in Philadelphia. He recommends using the criteria of the Musculoskeletal Infection Society (MSIS) for diagnosis, especially to distinguish PJI from aseptic loosening.
For the prevention of surgical site infection (SSI) leading to PJI, Parvizi referred to the recently updated guidelines of the WHO and the Centers of Disease Control (CDC). In the interview, he describes the prevention methods used at the Rothman Institute and points out that the use of ceramic components is associated with a reduced risk of PJI. Concerning the treatment of PJI, he states that there are no clear indications for the choice between retention, one-stage or two-stage exchange arthroplasty. Two-stage revision has to deal with the problem that available spacers do not meet current needs. These and other issues related to orthopaedic infections will be discussed in a second consensus meeting planned for July 25–27, 2018.
“Poisoning” myocardial effects of CoCr ball heads
Using CoCr femoral ball heads will lead to cobalt and chromium deposits in the myocardium, “slowly poisoning your patients”. Robert Trousdale from the Mayo Clinic in Rochester, reached this conclusion in a presentation at a recent VUMEDI Webinar. His study group analyzed cardiac tissue of 94 arthroplasty patients, gathered by the Mayo Autopsy Tissue Registry, from the years 1990–2011. Cobalt levels were significantly higher in patients with artificial joints compared to the control group without implants, rising with time after implantation. The incidence of cardiomegaly and interstitial fibrosis was approximately twice as high with an implant. Trousdale also concluded that THA with ceramic femoral heads might provide the most cost-effective option if used in all patients. He based this statement on studies matching the cost differential between metal and ceramic heads with the costs of diagnosis of metal-related effects in the case of revision arthroplasty.
Ceramic fracture requires synovectomy
For the rare event of a ceramic fracture, Rambani et al. from the United Lincolnshire Hospital (UK) have searched the literature for the best revision practice. In their review, they stress the importance of a complete synovectomy and thorough debridement of the affected tissues. Damaged and malpositioned components also have to be removed. Whenever possible, CoC or CoPE bearings should be used for the revision to avoid third-particle wear.
Once the fracture of the ceramic component has been diagnosed, the revision should be scheduled urgently. According to the authors, the key decision is whether to retain or replace well-fixed implant components. If the damage is minimal, the femoral stem may be retained and revised using a fourth generation ceramic head with a titanium sleeve.
Taper mismatch boosts fracture risk
“Mixing and matching components can put patients at greater risk for ceramic head fracture and must be avoided at all costs.” This conclusion was drawn by Gührs et al. from the Technical University in Hamburg (Germany), who analyzed the fracture resistance of ceramic heads combining head and taper components from different implant providers. The mismatch, while providing a seemingly stable taper connection, markedly reduced the mean fracture strength. The authors hypothesized that the fracture resistance was reduced due to the angular mismatch between the stem tapers and the femoral heads, which was approximately 17 times larger than the commonly tolerated taper angle difference for products from one manufacturer. In addition, the contact area was much smaller and concentrated the load on the proximal end of the taper.
Use of ceramic heads in academic centers in the USA
In US academic centers, almost three quarters of THA patients receive ceramic heads.*
*Sumon Nandi, Matthew S. Austin. Choosing a Femoral Head: A Survey Study of Academic Adult Reconstructive Surgeon J Arthroplasty; Article in press
Academia favors ceramic heads
Reconstructive surgeons involved in academic teaching in the USA use ceramic heads for 72.9% of THA cases. Nandi (University of Toledo, USA) and Austin (Rothman Institute, Philadelphia, USA) conducted a survey in 42 academic centers. Almost half of the surgeons use ceramic heads for all patients. Responding surgeons were far more concerned about taper corrosion with CoCr heads than about ceramic head fracture. The most common reason for not using ceramic heads in all patients was costs. For revision of THA due to corrosion, 96% would use a ceramic head.
Erratum: Handling, not trauma
In the chart “Reasons for post-operative fracture of BIOLOX®delta inserts” published in the issue 2/17 of Monthly CeraNews the two blue colors were mixed up, creating the wrong impression that most ceramic liner fractures were due to trauma. In fact, trauma accounts for only 4% of the recorded fractures and the vast majority of 82% is related to handling or presumed handling failure.