The results of hip and knee replacement surgery are generally regarded as positive for patients. Nonetheless, they are both major operations and have recognised complications. We present a review of relevant claims made to the National Health Service Litigation Authority. Between 1995 and 2010 there were 1004 claims to a value of £41.5 million following hip replacement surgery and 523 claims to a value of £21 million for knee replacement. The most common complaint after hip surgery was related to residual neurological deficit, whereas after knee replacement it was related to infection. Vascular complications resulted in the highest costs per case in each group.

Although there has been a large increase in the number of operations performed, there has not been a corresponding relative increase in litigation. The reasons for litigation have remained largely unchanged over time after hip replacement. In the case of knee replacement, although there has been a reduction in claims for infection, there has been an increase in claims for technical errors. There has also been a rise in claims for non-specified dissatisfaction. This information is of value to surgeons and can be used to minimise the potential mismatch between patient expectation, informed consent and outcome.

Cite this article: Bone Joint J 2013;95-B:122–6.

The product recall of Desmarquest Zirconia heads in 2001 was associated with specified batches of material. Despite of this fact, concerns raised over the stability of Zirconia led to a vast decrease in the use of Zirconia for hip prostheses. While there is evidence in the literature suggesting that Zirconia may become unstable, there remain many prostheses with Zirconia heads in use today. The purpose of this study was to report the condition observed in retrieved Zirconia heads not included in the product recall.

The bearing surfaces of seven retrieved 22mm diameter Zirconia on UHMWPE hip prostheses were investigated to determine whether any degradation of the Zirconia occurred in-vivo. All seven of the Zirconia heads were manufactured by Saint-Gobain Cerammiques Avancees Desmarquest and implantation time varied from 1 to 10 years. Components were analysed by Talysurf, Interferometer, SEM and XRD and compared to new components.

Talysurf of the components revealed an average surface roughness ranging from 0.004 to 0.007 micrometers Ra. This was only slightly rougher than new ceramic components which generally have an Ra of 0.003 micrometers. SEM of the surfaces did not reveal any difference between the retrieved components and new components. Further surface XRD of 4 of the 7 heads, as shown in Figure 1, showed very small percentages of monoclinic phase (28 degrees 2 theta) with predominantly tetragonal phase (30 degrees 2theta), similar to what is observed in new components. Figure 1: XRD of typical retrieved ZR head surface.

All seven retrieved heads demonstrated no evidence suggesting that degradation of the Zirconia had occurred in-vivo.

In vivo and in vitro studies of ceramic on ceramic (COC) bearings have demonstrated that swing phase microseparation followed by the impact of the femoral head on the superior acetabular insert rim leads to accelerated wear. However, resultant wear remained low. The wear of ceramic on polyethylene (COP) and metal on metal (MOM) couples under swing phase microseparation is unknown, this study aimed to compare the wear of these total hip replacements under standard and microseparation conditions.

A physiological hip simulator was used, loads and motions were applied to approximate in vivo conditions. Microseparation was achieved by displacing the femoral head inferiorly during swing phase, the head contacted the inferior cup rim and was laterally displaced. On heel strike the head contacted the superior cup rim prior to relocation. Components (as shown in table 1) were tested for 5 million cycles, at a frequency of 1 hertz in 25% (v/v) new born calf serum. Under standard conditions, wear of COC and MOM bearings was significantly lower than wear of COP couples. Under microseparation conditions the COC and MOM wear increased by 4 and 25 times respectively. Microseparation conditions reduced wear of COP couples by a factor of 4. Creep deformation and damage to the UHMWPE cup rim was observed, however, wear remained low. It is postulated that this reduction in polyethylene wear is due to the separation of the components in swing phase improving the entrapment of lubricant, hence wear is reduced via a squeeze film lubrication mechanism.