Re: where are the others?

May 11, 2004

Hi Alan,

Find below a cut / paste from an article written by the

British " National Institute for Clinical Excellence " or N.I.C.E.

It is from the article regarding Product apraisal. Full article at:

http://www.nice.org.uk/article.asp?a=30712

Hope it helps.

Richie

4.1 Clinical effectiveness

4.1.1 No randomised controlled trials of MoM hip resurfacing

arthroplasty were identified. Data were available for eight

observational studies, including three studies from the

manufacturers of these devices. Only four of these studies have been

published.

4.1.2 Most studies reported the percentage of patients who required

device revisions (MoM hip resurfacing devices to THR). However, only

a few studies explicitly provided information on time to device

failure, and so it is difficult to make comparisons between studies

of MoM devices and THRs. Comparisons were also made difficult as few

details were provided on the proportions of patients with specific

preoperative diagnoses and nearly all the studies examined the

outcome with more than one type of prosthesis.

4.1.3 Of the eight observational studies, the highest reported mean

age at the time of surgery was 51 years, suggesting that the

patients in all of these studies were relatively young compared with

patients who would normally receive a THR. The mean follow-up period

in seven of these studies was less than 5 years.

4.1.4 The numbers of patients included in the MoM hip resurfacing

studies ranged from 4 to 4424.

4.1.5 Few data were available on dislocation rates associated with

MoM devices. However, the manufacturers of the Birmingham Hip stated

that the rate of dislocation for this device in the year following

surgery was approximately 0.05%, based on 1 dislocation in over 1700

devices. Studies suggest that the rate of dislocation in the first

year following a conventional THR may be up to 5%.

4.1.6 The proportion of patients who required device revisions (from

MoM hip resurfacing to THR) was reported in all but one study and

ranged between 0% and 14.3%.

4.1.7 One study relating to the use of the currently available

Birmingham Hip reported 8 device failures at 4 years' follow-up. The

initial cohort consisted of 1400 patients but at the time of

preparing this guidance, 4 year data were available for only 21

patients. Including evidence on revision rates from the previous

version of this device increased the follow-up period from 4 years

to 7 years. Although only one device failure was reported over this

time, the 7 year study contained fewer patients (500) than the 4

year study as the analysis was restricted to patients aged less than

55 years rather than all patients who had received the Birmingham

Hip. At the time this guidance was prepared, 6 and 7 year data for

this analysis were available for 40 and 20 patients respectively.

4.1.8 No other survival statistics for MoM devices were available.

However, information from studies including the Swedish registry

data suggests that rates of conventional THR survival in people aged

less than 55 years are between 92% and 94% at 7 years.

4.1.9 Few complications were reported in any of the published

studies. Little information was available on functional outcomes

following MoM resurfacing and no data were available on the outcome

of revisions from MoM devices to primary THRs.

4.1.10 The Assessment Group was asked to include in its review a

number of alternatives to conventional THR and MoM hip resurfacing

arthroplasty, including 'watchful waiting'. However, the latter

option was only relevant to the extent that, if MoM devices offer

(or are believed to offer) lower revision rates in younger, active

patients, or better results after revision, patients and clinicians

may be inclined to refer individuals for earlier consideration of

hip surgery, effectively reducing the threshold for intervention.

> A note from a curious (and... some would say... suspiciously

twisted)

> mind: Is it possible that resurfacing is 100% successful with

ideal

> outcomes at all times? I ask because I don't think I've read

> anything since I joined the group that suggests anybody's resurf

has

> failed, or that it wasn't what they were told -- or hoped -- it

would

> be. It seems at times a little like Lake Woebegone, where all the

> children are above average.

>

> Possible I suppose that " the others " , the unsuccessful or unhappy

> ones just went away. Does Dave the rep know something he's

> not telling?

>

> Just Idly Curious...

> Alan

May 11, 2004