I need to have a cervical MRI done and I wanted to know absolutely for
certain that it would be of no problem with my BHR.  I looked up the
description of the BHR in the Smith & Nephew Surgical Technique manual:

DEVICE DESCRIPTION
The BIRMINGHAM HIP Resurfacing (BHR) prosthesis is a metal-onmetal
hip resurfacing prosthesis. The device consists of a stemmed
femoral head resurfacing component designed for cemented
fixation, and a hemispherical acetabular cup designed for
cementless, press-fit, fixation. Both components are manufactured
from high carbon, as-cast, cobalt chrome (CoCr) alloy (ASTM F75
and ISO 5832-4).

I then researched the properties of the ASTM F75 Cobalt Chromium alloy.

From the ARCAM ASTM F75 CoCr Alloy Material Data Sheet:
ASTM F75 is a non-magnetic CoCrMo alloy exhibiting high strength,
corrosion resistance, and excellent wear resistance. It is widely used for orthopaedic
and dental implants.

I also contacted Dr. Palmer's assistant and was assured that it would be no problem. 
Calling Smith & Nephew was a total waste of time and I was shuffled around by people
that don't know the answers to other people that don't know them either.

The Smith & Nephew Birmingham Hip Resurfacing Patient Information booklet states:
If a physician prescribes an MRI scan for you, inform the physician that the Birmingham Hip
Resurfacing (BHR) System has not been evaluated for safety and compatibility in the MR
environment. The Birmingham Hip Resurfacing (BHR) System has not been tested for
heating or migration in the MR environment.

The latter statement is what had me worried to begin with.