Scott’s parabola and the rise and fall of metal-on-metal hip replacements

BMJ 2012; 345 doi: (Published 17 December 2012) Cite this as: BMJ 2012;345:e8306
  1. David Hamilton, research fellow1,
  2. Colin Howie, consultant orthopaedic surgeon2,
  3. Paul Gaston, consultant orthopaedic surgeon2,
  4. Hamish Simpson, professor of orthopaedics and trauma1
  1. 1Department of Orthopaedics, University of Edinburgh, Edinburgh EH16 4SB, UK
  2. 2Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
  1. Correspondence to: D Hamilton d.f.hamilton{at}

Though not our intention to trivialise something that affects 30 000 people and has resulted in the loss of public trust in the most successful of surgical interventions, we would like to suggest a retrospective view of events. It is that the unfortunate episode involving metal-on-metal (MoM) hip replacements has now passed, and, actually, the system worked.

The BMJ has been at the forefront in reporting and documenting the MoM saga: dodgy regulation, “pseudo-tumours,” etc. It would be a brave surgeon now to advocate the use of large diameter MoM bearings for total hip replacement, orthopaedic guidelines have been published (in the BMJ) regarding ongoing management of patients implanted with such devices, and steps are being taken “Beyond Compliance.”

We must react quicker next time to limit patient exposure to the unexpected failure of new technologies, and work is under way to ensure this does happen. However, the problem was quite contained. Although 31 171 stemmed MoM prostheses (implanted from 2003 to 2011) seems a large number, it represents only 8% of hip replacements performed over that time. MoM bearings were introduced with the best of intentions, promising greater implant longevity and the avoidance of complex revision surgery. There were unforeseen complications, and these particular prostheses quickly fell out of favour.

Scott’s description of the parabola of the rise and fall of surgical techniques, which appeared in the BMJ Christmas issue of 2001 (fig 1) reminds us that such a trajectory is not a new phenomenon. The most recent National Joint Registry report of large metal bearing use essentially traces the suggested parabola; though it perhaps it more accurately reflects a spike of use—rapid uptake followed by an exponential drop-off (fig 2), showing that, once the problems came to light, surgeons reacted quickly.


Fig 1 “Scott’s parabola” (reproduced from Scott JW. Scott’s parabola: the rise and fall of a surgical technique. BMJ 2001;323:1477)


Fig 2 Trends in use of metal-on-metal hip replacements by head size, 2003–11 (adapted from National Joint Registry ninth annual report, 2012)

Further use of this technology is not expected. We now await the completion of Scott’s parabola, where today’s surgeons regale their juniors with tales of MoM prostheses.


Cite this as: BMJ 2012;345:e8306