Are Metal-on-Metal hip implants safe?

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Health and 

Food Safety

Are Metal-on-Metal hip implants safe?

Stiff 

joints 

and 

aching bones – once, 

there was little to do 

but accept problems 

like these as part 

o f   a g e i n g .     B u t 

n o w ,     m o d e r n 

interventions like 

hip  implants  can 

help  give  people 

their mobility back.   

M e t a l - o n - M e t a l 

joint  implants,  one  specific  category  of 

implants,  may  solve  many  dysfunctions 

related to the hip. But, but do they come 

with risks?

The  European  Commission’s  Scientific 

Committee  on  Emerging  and  Newly 

Identified Health Risks (SCENIHR) responds 

to  this  question  in  its  Opinion  on  “The 

safety  of  Metal-on-Metal  (MoM)  joint 

replacements  with  a  particular  focus  on 

hip implants”, the main points of which are 

summarised in this fact sheet.



  WHaT  aRE  METal-ON-METal  HIp 

REplaCEMENTS?

Hip replacements can be total or partial, 

replacing all or only one of the two 

components of the hip joint – the ball and 

socket – that should glide together smoothly 

to make movement easy.

In a total hip replacement, the femoral head 

(the top of the thigh bone) and the damaged 

acetabulum (the socket) are removed and 

replaced with metal, plastic or ceramic 

components. 

In hip resurfacing arthroplasty, the femoral 

head is not removed. The damaged area 

is  trimmed  and  fitted  with  a  smooth  cap. 

Damaged bone and cartilage within the 

socket, however, are removed and replaced, 

like in total hip replacements.

In Metal-on-Metal hip implants, the 

replacement components in both the ball and 

the socket are made of metal. This type of 

implant can be used for both total and partial 

hip replacement surgery.



 WHy uSE METal?

Metal parts are long-lasting and are often 

used in younger patients to save them 

having to undergo revision operations later 

to replace less durable plastic parts.  Metal 

implant components tend to be larger as 

well, making them more durable and less 

likely to dislocate.



  WHaT  aRE  THE  CONCERNS  aBOuT 

METal-ON-METal HIp REplaCEMENTS?

When two components, as in an implant, 

continually rub against each other, there may 

be some resulting debris. In Metal-on-Metal 

hip implants, tiny metal particles may wear 

off  due  to  friction  and  build  up  over  time 

around the implant and even end up in blood 

and tissues.

Most patients who have Metal-on-Metal 

implants have no adverse effects, but some 

patients experience symptoms around 

the hip, like swelling.  A few others report 

problems located elsewhere than the hip 

area that may possibly be related to the 

release of metallic substances.



  WHaT  aRE  SCENIHR’S  CONCluSIONS 

aBOuT  THE  SafETy  Of  METal-ON-METal 

HIp REplaCEMENTS?

The SCENIHR concludes that large-head 

(large diameter) Metal-on-Metal hip 

implants, in particular, pose the highest risk 

of provoking undesirable reactions.

Because of the potential health risk posed by 

Metal-on-Metal hip implants, the decision to 

use them should be made on an individual 

basis, weighing the pros and cons and 

considering relevant factors such as 

age, gender, body size, physical fitness 

and lifestyle. 

All types of Metal-on-Metal implants 

should be avoided by high-risk patients 

including females of childbearing age, 

small-boned females and patients who 

are allergic to the relevant metals.

If Metal-on-Metal implants are judged 

to  best  fit  a  patient’s  needs,  the 

surgery should only be performed by a 

very experienced surgeon to minimize 

the risks.

For post-operative care, the SCENIHR 

endorses the strategy outlined in the 

European Consensus Statement, which 

recommends that all patients with 

implants have regular radiographic 

and clinical check-ups. In particular, 

routine checks should be conducted for 

any metal ions from large-head Metal-

on-Metal total hip replacements, and 

patients who have had hip resurfacing 

arthroplasty should have regular 

check-ups  at  least  during  the  first 

post-operative years.

This opinion is available at:

http://ec.europa.eu/health/scientific_

committees/emerging/opinions/index_

en.htm

This fact sheet is based on the 

Opinion of the independent  Scientific 

Committee on Emerging and Newly 

Identified  Health  Risks  (SCENIHR):  

“The safety of Metal-on-Metal joint 

replacements with a particular focus 

on hip implants".

September, 2014