Bearing Surfaces

 

Styker exeter polyS&N ceramic on polyCeramic on ceramic

 

Goal

 

To limit the generation of wear particles which can cause osteolysis and loosening

 

Wear Factors

 

Patient factors

- age, activity, time in situ

 

Acetabular component position

- avoid impingement and edge loading

- limit instability

- 40 - 50 degrees of abduction

- 10 - 15 degrees of anteversion

 

Implant factors

A. Surface material

- harder bearings have lower wear rates due to lower roughness

- i.e. ceramic, cobalt-chromium

B. Lubrication

- reduces contact and friction

- ceramic, cobalt-chromium hydrophilic

 

Options

 

Metal (Cobalt Chrome) on Cross-linked Polyethylene (XLPE)

Ceramic on Cross-linked Polyethylene (XLPE)

Ceramic on ceramic

Metal on metal

 

Australian Joint Registry 2023

 

20 year revision rate of 548,000 THA

 

  Metal on XLPE Ceramic on XLPE Ceramic on Ceramic

Metal on Metal

< 32 mm head

Metal on Metal

> 32 mm head

3 years 2.4 2.4 2.3 3.3 5.7
5 years 3.0 2.9 3.0 4.4 11.8
10 years 4.5 4.0 4.7 6.8 22.6
15 years 6.1 5.5 6.8 9.6 28.6
20 years 7.5 6.8 9.1 11.9 32

 

Polyethylene

THR Metal on PolyZimmer polyStyker exeter polyS&N cobalt chrome

Metal on poly THA                      Zimmer poly                                                   Stryker poly

 

Cross linked polyethylene

 

Highly cross linked

- gamma irradiated in a vaccuum

- decreases wear

 

Annealed / remelted

- heated below melting temperature to increase ductility

 

+/- Vitamin E

 

Results Australian Joint Registry 2023

 

At 20 years the cumulative revision of THA

- highly cross linked poly: 6.9%

- non cross linked poly: 17%

 

Ceramic

 

THR Ceramic on PolyS&N ceramic on polyS7N ConC

Ceramic on poly THA                   S&N oxinium on poly                                    S&N ceramic on ceramic
 

Types

 

Alumina ceramic

Zirconia ceramic

Oxidised zirconium / oxinium

 

Technique

 

Sintered in a furnace

Machine polished

 

Advantage

 

Extremely hard - resistant to wear

Hydrophilic - resist friction

 

Disadvantage

 

Squeaking

Ceramic fracture

 

Owen et al Bone Joint J 2014

- meta-analysis of 43 studies and 17,000 CoC THA

- incidence of squeaking of 4.2%

 

Hallan et al CORR 2020

- registry data of 31,00 CoP and 6,000 CoC THA

- risk of ceramic head or liner fracture 1/1000

- higher risk with CoC

 

Metal on Metal

 

MOMMoM2MoM

 

Advantage

 

Large heads

- 30 - 60 mm

- decreases dislocation

- ?improves ROM / function

 

Disadvantages

 

1. Increased ion levels

 

Cobalt and Chromium ions elevated in blood

Creatine cobalt and Creatinine chromium elevated in urine

 

2. Adverse Local Tissue Reactions

 

THR Metal on MetalMoM lysis

 

3. High revision rates / Prosthesis recall / Class actions

 

https://www.consumernotice.org/legal/hip-replacement-lawsuits/

 

Australian Joint Registry Revision Rates

 

 

Metal on Metal

> 32 mm

Metal on Metal

< 32 mm

Metal on Poly Ceramic on Poly
3 year 5.7 3.3 2.4 2,4
5 year 11.8 4.4 3.0 2.9
10 year 22.6 6.8 4.5 4.0
15 years 28.6 9.6 6.1 5.5
20 years 32 11.9 7.5 6.8

 

Adverse Local Tissue Reactions (ALTR)

 

Mechanism

 

Generation of biologically active, nanometer sized metal particles

- cause large inflammatory reaction

- pseudotumour (AKA aseptic lymphocyte-dominant vasculitis associated lesion ALVAL)

- can cause extensive soft tissue and bone loss

 

 

Diagnosis

 

Pain

High serum ion levels

Loosening on xray

Pseudotumour on MRI

 

Metallosis xrayMetallosis MRIMetallosis MRI 2

 

Metallosis xrayMetallosis MRIMetallosis MRI

 

Incidence

 

Madanat et al CORR 2016

- 288 Depuy ASR THA 6 years post surgery

- moderate or severe ATLR in 24% on MRI

 

Results of revision

 

Crawford et al J Arthroplasty 2019

- revision of 2023 metal on metal THA
- failure average 5 years post primary surgery

- acetabulum revised in 92% of cases

- reoperation in 14%

- re-revision in 8%

 

MOMMOM MOM revision