National Registry Data Analysis on a Unique Highly-Crosslinked Polyethylene for Total Hip Arthroplasty

Background

Several types of highly-crosslinked polyethylene with different manufacturing processes and mechanical properties are commercially available, including HIGHCROSS (Medacta). The aim of this registry study is to ascertain the long-term safety of the HIGHCROSS liners in total hip arthroplasty and compare the revision rates with its contemporaries using real-world data to establish their safety and generalizability when used by multiple surgeons.

Methods

The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the Swiss National Joint Registry (SIRIS) were selected for the large number of users of Medacta implants and the availability of long-term results. Three reports from SIRIS and 4 reports from AOANJRR were examined to establish the overall and Kaplan-Meier (KM) cumulative revision rate.

Results

According to SIRIS, the HIGHCROSS liner was the most commonly used bearing surface with Medacta stems with overall revision rates for wear/osteolysis at 9.7 years of 0.04% and 0.03%, respectively, for AMIStem and Quadra. Based on AOANJRR, the KM cumulative revision rate for any reason of Medacta stems with HIGHCROSS liners was lower than that with ceramic liners at 3 years for MasterLoc and at 10 years for Quadra. The KM cumulative revision rate for any reasons of Medacta cementless cups with HIGHCROSS liners at 12 years was lower than the comparator made of all other implants and tribological couplings (1.6% vs 2.1%).

Conclusions

This real-world data proves that long-term HIGHCROSS survival rates are comparable to other modern bearing surfaces.

Introduction of innovations in joint arthroplasty: Recommendations from the 'EFORT implant and patient safety initiative'

With the implementation of the new MDR 2017/745 by the European Parliament, more robust clinical and pre-clinical data will be required due to a more stringent approval process. The EFORT Implant and Patient Safety Initiative WG1 'Introduction of Innovation', combined knowledge of orthopaedic surgeons, research institutes, orthopaedic device manufacturers, patient representatives and regulatory authorities to develop a comprehensive set of recommendations for the introduction of innovations in joint arthroplasty within the boundaries of MDR 2017/745. Recommendations have been developed to address key questions about pre-clinical and clinical requirements for the introduction of new implants and implant-related instrumentation with the participation of a steering group, invited by the EFORT Board in dialogue with representatives from European National Societies and Speciality Societies. Different degrees of novelty and innovation were described and agreed on in relation to when surgeons can start, using implants and implant-related instrumentation routinely. Before any clinical phase of a new implant, following the pre-market clinical investigation or the equivalent device PMCF pathway, it is a common understanding that all appropriate pre-clinical testing (regulatory mandatory and evident state of the art) - which has to be considered for a specific device - has been successfully completed. Once manufacturers receive the CE mark for a medical device, it can be used in patients routinely when a clinical investigation has been conducted to demonstrate the conformity of devices according to MDR Article 62 or full equivalence for the technical, biological and clinical characteristics has been demonstrated (MDR, Annex XIV, Part A, 3.) and a PMCF study has been initiated.

Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone

BACKGROUND

What is the right surface for an implant to achieve biological fixation? Surface technologies can play important roles in encouraging interactions between the implant surface and the host bone to achieve osseointegration. Preclinical animal models provide important insight into in vivo performance related to bone ongrowth and implant fixation.

METHODS

A large animal model was used to compare the in vivo response of HA and plasma-sprayed titanium coatings in a well-reported adult ovine model to evaluate bone ongrowth in terms of mechanical properties in cortical sites, and histology and histomorphometry in cortical and cancellous sites at 4 and 12 weeks.

RESULTS

Titanium plasma-sprayed surfaces outperformed the HA-coated samples in push-out testing in cortical sites while both surfaces supported new bone ongrowth and remodeling in cortical and cancellous sites.

CONCLUSIONS

While both HA and Ti plasma provided an osteoconductive surface for bone ongrowth, the Ti plasma provided a more robust bone-implant interface that ideally would be required for load transfer and implant stability in the longer term.

Accuracy of tibial cuts with patient-specific instrumentation is not influenced by the surgeon's level of experience

PURPOSE

It was hypothesized that surgeon's experience as well as bone density play a significant role in achieving accurate cuts with patient-specific instrumentation (PSI). The aim of this study was to compare the accuracy of the tibial cuts in different bone densities made by a highly experienced orthopedic surgeon on one hand and a less experienced orthopedic surgeon on the other.

METHODS

Tibial models from three different sawbone densities were developed for this study. Each surgeon performed 21 cuts. A coordinate measuring machine was used to analyse the cuts. The K-Cohen test was performed to evaluate the results. The analyzed parameters were guide positioning and deviation from the guide cut to the tibial cut, including varus/valgus angle, the tibial slope, cut height, planarity (mm²), and rugosity (mm).

RESULTS

There was a significant difference in the positioning of the tibial cut guide between the two surgeons for the tibial slope (p < 0.05), while no difference was observed for the varus/valgus angle (n.s.) and the cut height (n.s.). No significant difference in the tibial cut was observed between the surgeons for the tibial slope angle (n.s.), varus/valgus angle (n.s.), planarity (n.s.), and rugosity (n.s.). In the different bone types, no significant difference was observed for the tibial slope (n.s.) and varus/valgus angle (n.s.), while planarity and rugosity showed significant differences (p < 0.05). Our study showed no significant difference in the tibial cuts for the tibial slope, varus/valgus angle, planarity, and rugosity between the two surgeons.

CONCLUSIONS

In the present study, it could be demonstrated that accuracy of the cuts is ensured by PSI not depending on the surgeon's experience and the bone mineral density. This speaks to its clinical significance: PSI might be suited for less experienced surgeons to reduce outliers in total knee arthroplasty (TKA).

Ion release and chromosomal damage from total hip prostheses with metal-on-metal articulation

A prospective multicentric study was carried out in patients having metal-on-metal METASUL components (Sulzer Medica, Winterthur, Switzerland) in order to check the following null hypotheses: H1: The concentration of Co, Cr, Ni, and Mb in blood and urine is not modified by the implant of a hip prosthesis with METASUL components at 6 months. H2: The incidence of markers of chromosomal damage [sister chromatid exchanges (SCEs) and micronuclei (Mni)] in lymphocytes is not modified by the implant of METASUL components at 6 months. H3: The concentrations of Co, Cr, Ni, and Mb in blood and urine did not correlate with the incidence of the markers of chromosomal damage. The measurements showed a 2-fold increase of Co in blood, a 10-fold increase of Co in urine, a 1.5-fold increase of Cr in the blood, and a 3-fold increase of Cr in the urine at a follow-up of 6 months from the operation; there was also a significant increase in the Ni blood concentration at the 7 day checkup. The study cohort did not show any modification in the frequency of markers of chromosomal damage in the peripheral lymphocytes at any of the observation times. The amount of the SCEs and Mni recorded at all the observation times did not correlate with each other or with any of the ion levels measured in the blood and in the urine.