Abstract
Introduction
Mix and Match (M&M) describes the use of components from more than one manufacturer in a total hip replacement (THR) The NJR has records of over 90,000 instances where this practice, which is contrary to the advice of most manufacturers and regulators, has been followed.
Patients, Materials and Method
The NJR database 2003–13 was interrogated and the types of M&M were grouped using head size, bearing characteristics and use of cement.
Results
| Total Cohort | M&M | |
| HARD ON SOFT | ||
| Metal head on poly socket | 345,618 | 79,110 |
| Ceramic Head on a poly socket | 42,176 | 7,886 |
| HARD ON HARD | ||
| Metal on Metal (all types) | 31,609 | 2,131 |
| Ceramic on Ceramic | 87,156 | 3,861 |
In a large number of cases, the M&M metal on plastic groups outshone their non-mix and matched controls. M&M “Head on Stem” has been shown to give inferior results.
In the Ceramic on poly there is no significant difference in the performance between groups.
In the Hard on Hard Metal on Metal groups the results are generally poor with some M&M doing better and some worse.
In the case of ceramic on ceramic there is no significant difference so far.
There have been outlier reports to MHRA for both M&M and non M&M groups.
Discussion
This is the first time such a study, with such large numbers has ever been undertaken. The weakness of the study is the heavy reliance on “Revision” being the sole discriminator for failure, particularly in view of the sensitivity and potential incidence of under reporting of revision in NJR.
Conclusion
It is suggested that BHS endorses the use of M&M where the results show it to be advantageous to patients and in revisions when it is appropriate. Surgeons should be aware of the results in the groups where there has not been any advantage of M&M.
