Is ceramic the most economical option?
When the costs of diagnosis and revision related to taper corrosion are taken into account, ceramic femoral heads can be more cost-effective than cobalt-chrome femoral heads. Regarding latest findings on these metal related issues, Wyles et al. calculated the overall financial burden. In their best-case scenario 0.875% of all THA receive an adverse local tissue reaction (ALTR) work-up leading to revision in 0.11% of the patients. In the worst-case scenario, 3.5% of all THA patients receive an ALTR work-up and 1.75% are revised. They concluded that for the US health system “wholesale use (of ceramic femoral heads) in THAs may in fact provide the most economical option on a societal scale.”
Medicare patients and THA bearing outcomes: Study insights
Elderly THA patients from the Medicare data base with CoP bearings show a reduced risk of dislocation, infection and mortality when compared to patients with MoP bearings. Kurtz et al. examined 315,784 US Medicare patients aged 65 years and older. They also found a trend towards reduced risk of revision with CoP in comparison to MoP bearings but the data did not reach statistical significance. When comparing patients with CoC and MoP bearings, there was no significant difference in risk of dislocation, revision, or mortality. However, there was a reduced risk of infection for patients with CoC bearings compared to MoP.
The Charlson comorbidity index was consistently one of the most important predictors for mortality, dislocation and revision as well as infection. Obesity was the most important risk factor for infection and the second most important factor for revision. The authors conclude that ceramic bearings are associated with lower risk of infection compared with MoP bearings.
Noise in all bearings
In a study on noise emission from hip implants using a patient questionnaire, Robinson et al. found that this phenomenon is noted in hip implants with ceramic-on-ceramic as well as with metal-on-polyethylene bearings, although with different incidence. They concluded that noise apparently is an underreported phenomenon and recommend informing all patients of possible noise emission from their THA, irrespective of the bearing type.
Dislocations reduced with CoC
The revision rates for late dislocation are significantly lower with ceramic-on-ceramic bearings than with other bearing couples, when the bearing diameter is larger than 28mm. Pitto presented his analysis of the New Zealand register data at the 2016 congress of the Japanese Hip Society. He found the best outcome with 32mm CoC bearings and hypothesised as reason the prevention of inflammatory reactions to polyethylene and metal particles leading to fluid expansion and capsule dissociation.
Reasons for revision in THA
CoC can improve revision
Ceramic-on-ceramic bearings are possibly the best option for revision THA. For his study, Wirtz examined cumulative revision rates reported in several registers and clinical studies. In his presentation held at the 2016 AAOT Congress in Buenos Aires he pointed out that CoC bearings eliminate several revision causes, reduce the risk of re-infection and show superior results when compared to the alternatives.