Are ceramic-on-ceramic bearings in total hip arthroplasty associated with reduced revision risk for late dislocation?

The influence of bearing surfaces on revisions due to dislocations in total hip arthroplasty

INTRODUCTION

Recurrent dislocations are still the most frequent reason for revision in total hip arthroplasty (THA). The impact of bearing surfaces on dislocations is still controversial. We hypothesized that: (1) bearing surfaces influence the revisions due to dislocations; (2) ceramic-on-ceramic reduced the revisions for dislocations in adjusted models; (3) Delta-on-Delta bearings reduced the revisions for dislocations in comparison to surfaces with cross-linked polyethylene.

MATERIALS AND METHODS

The regional arthroplasty registry was enquired about bearing surfaces and revisions for dislocations and instability. Unadjusted and adjusted rates were provided, including sex, age (<65 years or ≥65 years), head diameter (≤28 mm or >28 mm; <36 mm or ≥36 mm) as variables. 44,065 THAs were included.

RESULTS

The rate of revisions for dislocations was significantly lower in ceramic-on-ceramic and metal-on-metal bearings (unadjusted rates). After adjusting for age, sex, and head size (36 and 28 mm), hard-on-hard bearings were protective (p < 0.05): ceramic-on-ceramic had a lower risk of revisions due to dislocation than ceramic-on-polyethylene (HR 1.6, 95% CI 1.2-2.2 p = 0.0009). The rate of revisions for dislocation was similar in bearings with cross-linked polyethylene and Delta-on-Delta articulations, in unadjusted and adjusted models.

CONCLUSION

Bearings with conventional polyethylene were more predisposed to dislocations. Currently adopted bearings exerted no significant influence on revisions due to dislocations. These findings could be primarily related to wear, but due to the time distribution, soft tissue envelopes and surface tension may also play a role. Pre-clinical biomechanical evaluations and prospective matched cohort studies are required to draw definitive conclusions.

A bicentric approach evaluating the combination of a hemispheric cup with a novel ceramic head in total hip arthroplasty

Medical ceramics are frequently used biomaterials as a liner in total hip arthroplasty. Strong efforts have been made to improve material properties over the last decades. Alumina toughened zirconia ceramics seem to be promising alternatives to further reduce fracture rates and squeaking phenomena. To answer the question if alumina toughened zirconia ceramic liners in combination with a cementless, hemispheric cup are able to reduce squeaking phenomena and fracture rates, we initiated a bicentric, mid-term trial. Noise phenomena will be recorded using MONA Score (Melbourne Orthopaedic Noise Assessment). Functional outcome (Harris Hip Score, University of California-Los Angeles, Forgotten Joint Score, EQ-5D Score, Visual Analogue Scale) and radiographic parameters will serve as secondary parameters. The study has been set up for 5 years, with follow-ups after 6-14 weeks, 12, 24 and 60 months.

Does load-bearing materials influence hip capsule thickness in total hip replacement? An MRI case-matched study

BACKGROUND

Ceramic-on-ceramic (COC) total hip replacements (THR) have exhibited less instability and late dislocation. Hip capsule plays an important role in hip stability. Different surrounding soft tissue reactions have been observed according to the bearing material used but no study compared these data using MRI investigation. Therefore, we performed a retrospective case control study to compare hip capsule thicknesses according to the bearing materials in THR and in native hips.

HYPOTHESIS

Hip capsule is thicker after COC THR compared to ceramic- or metal-on-polyethylene (PE) bearings, or native hips.

MATERIALS AND METHOD

Magnetic resonance imaging (MRI) images, combined with a multi acquisition variable resonance image combination (MAVRIC) sequence, was used to measure the hip capsule thickness in 16 patients (29 hips) who had either COC (13 hips, median age at surgery: 64.8 years old, median follow-up at imaging: 2482 days), PE bearings (11 hips, median age at surgery: 48.4 years old (significantly different from COC THR), median follow-up at imaging: 1860 days (NS)), or a native hip with no implant (5 hips). Two independent radiologists measured capsular thicknesses in 4 different zones and were blinded regarding the bearing components. The imaged hips were classified into three groups: native, COC and PE.

RESULTS

The COC THR group had the thickest capsules (median 7.0mm, range 2.9-15.5mm). This result was statistically significant (p<0.0001) when compared to PE THR (median 4.9mm, range 2.2-10.5mm), and to native hips (median 4.1mm, range 2.7-6.9mm) measurements, respectively. Furthermore, painful hips had thinner capsules (4.6mm, range 2-10.5) compared to not painful hips (6.8mm, range 2.3-15.5) (p=0.0006).

DISCUSSION

This is the first in-vivo study measuring capsular thickness in THR with the objective of measuring variations according to the hip implant materials used. The results revealed a significantly thicker capsule for the COC bearing compared to either PE or native hips, and a thinner capsule in painful hips.

LEVEL OF EVIDENCE

III, retrospective non-consecutive cohort study.

Pelvic motion the key to understanding spine-hip interaction

Pelvic motion acting as a hinge between the spine and hips is essential to maintain proper balance during bipedalism. Pelvic rotation is recruited as a compensation mechanism when spinal malalignment occurs.This pelvic rotation can affect functional acetabular orientation, and consequently functional cup positioning if a total hip arthroplasty (THA) is needed. Pelvic retroversion, frequently associated with degenerative spinal changes, implies an increase of acetabular version.Patients with flexible lumbar spines (spine users) protect the hip joint. Patients with stiff, degenerated or fused lumbar spines (hip users) demand higher hip mobility, placing the THA at risk.Pelvises in retroversion place the THA at risk for anterior dislocation when standing. In contrast, pelvises in anteversion or with low pelvic incidence (PI) can place THA at risk for posterior dislocation when sitting.Try to set the cup in an anatomic position. However, bear in mind that low PI pelvises may need more acetabular ante-inclination, and high PI pelvises more acetabular retroversion.If surgery is needed, start first by addressing the hip, except in patients with compensation (high pelvic retroversion), who may need spine surgery first to place the pelvis, and consequently the acetabulum, in a proper position. Cite this article: EFORT Open Rev 2020;5:522-533. DOI: 10.1302/2058-5241.5.200032.

Have newer bearing surfaces changed expectations regarding the longevity of total hip arthroplasty?

AIMS

The purpose of this study is to examine six types of bearing surfaces implanted at a single institution over three decades to determine whether the reasons for revision vary among the groups and how long it takes to identify differences in survival.

METHODS

We considered six cohorts that included a total of 1,707 primary hips done between 1982 and 2010. These included 223 conventional polyethylene sterilized with γ irradiation in air (CPE-GA), 114 conventional polyethylene sterilized with gas plasma (CPE-GP), 116 crosslinked polyethylene (XLPE), 1,083 metal-on-metal (MOM), 90 ceramic-on-ceramic (COC), and 81 surface arthroplasties (SAs). With the exception of the COC, all other groups used cobalt-chromium (CoCr) femoral heads. The mean follow-up was 10 (0.008 to 35) years. Descriptive statistics with revisions per 100 component years (re/100 yr) and survival analysis with revision for any reason as the endpoint were used to compare bearing surfaces.

RESULTS

XLPE liners demonstrated a lower cumulative incidence of revision at 15 years compared to the CPE-GA and CPE-GP groups owing to the absence of wear-related revisions (4% for XLPE vs 18%, p = 0.02, and 15%, p = 0.003, respectively). Revisions for adverse local tissue reactions occurred exclusively among the MOM (0.8 re/100 year) and SA groups (0.1 re/100 year). The revision rate for instability was lower among hips with 36 mm and larger head sizes compared to smaller head sizes (0.2% vs 2%, p < 0.001).

CONCLUSION

The introduction of XLPE has eliminated wear-related revisions through 15-year follow-up compared to CPE-GP and CPE-GA. Dislocation incidence has been reduced with the introduction of larger diameter heads but remains a persistent concern. The potential for adverse local tissue reactions with MOM requires continued follow-up. Cite this article: Bone Joint J 2020;102-B(7 Supple B):105-111.

How screw connections influence the primary stability of acetabular cups under consideration of different bone models

Introduction

Good osteointegration of implants requires sufficient primary stability. Aim of this study was to examine the influence of screw fixation on the primary stability of press-fit cups.

Methods

Two press-fit acetabular cups were tested with regard to the influence and number of screws and their primary stability.

Results

For the relatively thin-walled Allofit®-S cup, an influence of the number of screws on the different forms of movement could be demonstrated.

Conclusions

We see a clear influence of the cup wall thickness on the elastic deformability and accordingly on the primary stability of the examined cups.

In vitro examination of the primary stability of three press-fit acetabular cups under consideration of two different bearing couples

BACKROUND

For preclinical statements about the anchoring behavior of prostheses, the primary stability of the prosthesis is of special importance. It was the aim of this study to examine and compare the relevant relative micromotions of three different acetabulum prostheses by introducing three-dimensional torques.

METHODS

The cups were implanted under standard conditions into an anatomical artificial bone model. Three-dimensional torques were applied to the acetabular cups. Taking into account the resulting frictional moments of two different bearing couples, ceramic-on-ceramic and ceramic-on-polyethylene, the relative micromotions of the cups were recorded as maximum total micromotion, translational and rotational micromotion, and the primary stability values of the three cups were compared.

RESULTS

Relative micromotion of all cup models was always significantly smaller with the CoC bearing couples than with the CoP bearing couples (p < 0.001). The rotational micromotion was always lower (p < 0.001) than the translational micromotion, and the rotational as well as the translational micromotions were each always lower than the maximum total micromotion (p < 0.001, p < 0.010). The thinnest-walled cup system always showed the largest relative micromotions.

CONCLUSION

The results of our study can be interpreted as indicating that the low relative micromotions of all cups - irrespective of the use of CoC or CoP bearing couples - are within an acceptable range favoring secondary osseointegration of the implants. Furthermore, we were able to show that the cup wall thickness and the surface quality of the cup systems have an influence on the primary stability and the elastic deformability of the examined cup systems.

Effect of bearing friction torques on the primary stability of press-fit acetabular cups: A novel in vitro method

Aseptic loosening is the main reason for revision of total hip arthroplasty, and relative micromotions between cementless acetabular cups and bone play an important role regarding their comparatively high loosening rate. Therefore, the aim of the present study was to analyze the influence of resulting frictional torques on the primary stability of press-fit acetabular cups subjected to two different bearing partners. A cementless press-fit cup was implanted in bone-like foam. Primary stability of the cup was analyzed by determining spatial total, translational, and rotational interface micromotions by means of an eddy current sensor measuring system. Torque transmission into the cup was realized by three synchronous servomotors considering resultant friction torques based on constant friction for ceramic-on-ceramic (CoC: μ = 0.044; max. resultant torque: 1.5 Nm) and for ceramic-on-polyethylene (CoP: μ = 0.063; max. resultant torque: 1.9 Nm) bearing partners. Rotational micromotion of CoC was 8.99 ± 0.85 µm and of CoP 13.39 ± 1.43 µm. Translational micromotion of CoC was 29.93 ± 1.44 μm and of CoP 39.91 ± 2.25 μm. Maximum total relative micromotions were 37.10 ± 1.07 μm for CoC and 51.64 ± 2.18 μm for CoP. Micromotions resulting from CoC were statistically lower than those resulting from CoP (p < 0.05). The described 3D-measuring set-up offers a novel in vitro method of measuring primary stability of acetabular cups. We can therefore conclude, that primary stability of acetabular cup systems can be observed using either the lower friction curve (CoC) or the higher friction curve (CoP). In future studies different cup designs or cup fixation mechanisms may be tested and compared in vitro and assessed prior to implantation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2745-2753, 2018.

The Ideal Total Hip Replacement Bearing Surface in the Young Patient: A Prospective Randomized Trial Comparing Alumina Ceramic-On-Ceramic With Ceramic-On-Conventional Polyethylene: 15-Year Follow-Up

BACKGROUND

The optimum bearing surface for total hip arthroplasty remains debatable. We have previously published our outcome at 10 years and this represents the 15-year follow-up.

METHODS

A total of 58 hips (in 57 patients with a mean age of 42 years) were randomized to receive either ceramic-on-ceramic (CoC) or ceramic-on-polyethylene (CoP) total hip arthroplasty. We prospectively followed for survivorship, functional outcomes (using the Harris Hip Score and the St Michael's Hip Score [SMH]), and radiological outcomes.

RESULTS

At a minimum of 15 years, 3 patients had died, but not been revised. Seven were lost to follow-up. Five cases from the CoP group were revised (4 for polyethylene wear and osteolysis). Four from the CoC were revised; one each for head fracture, instability, infection, and trunnionosis. Both groups showed statistically significant improvements in Harris Hip Score scores and SMH functional scores, with no difference between the 2 bearings. For the CoP group, there was an improvement from 15.6 to 21.5 in the SMH and from 48.8 to 88.7 (P > .05); and for CoC, this improvement was 15.8 to 23.5 and 50.3 to 94.6 (P > .05), respectively. Mean wear rate of the polyethylene was 0.092 mm/y and for the CoC was 0.018 mm/y. Two patients in the CoC group had evidence of acetabular osteolysis vs 3 in the CoP. Six patients had femoral osteolysis in the CoC group and 12 in the CoP group.

CONCLUSION

Survivorship and function of the 2 bearing groups remains comparable; while the polyethylene wear and osteolysis may represent issues in the future.

Ceramic on ceramic arthroplasty of the hip

The leading indication for revision total hip arthroplasty (THA) remains aseptic loosening owing to wear. The younger, more active patients currently undergoing THA present unprecedented demands on the bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest rates of wear. The recent advances, especially involving alumina/zirconia composite ceramic, have led to substantial improvements and good results in vitro.

Alumina/zirconia composite ceramics are extremely hard, scratch resistant and biocompatible. They offer a low co-efficient of friction and superior lubrication and lower rates of wear compared with other bearings. The major disadvantage is the risk of fracture of the ceramic. The new composite ceramic has reduced the risk of fracture of the femoral head to 0.002%. The risk of fracture of the liner is slightly higher (0.02%).

Assuming that the components are introduced without impingement, CoC bearings have major advantages over other bearings. Owing to the superior hardness, they produce less third body wear and are less vulnerable to intra-operative damage.

The improved tribology means that CoC bearings are an excellent choice for young, active patients requiring THA.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):14–17.