Magnetic Resonance Imaging (MRI) is a very useful study, but it is often overused as well. It is well known that there are many false positives and false negatives. Often physicians who are not orthopedic surgeons order expensive ($1500) scans when a simple x-ray would tell an orthopedic surgeon what the problem is. Most general physicians are not used to interpreting x-rays on their own. In this instance the MRI is just wasted money. In my opinion, musculoskeletal MRI s should only be ordered by orthopedic surgeons after they have evaluated the patient (cost $300). This would result in large health care savings.

Many people believe that you cannot have an MRI if you have implanted metal. This is not true. Most implanted metals are not ferromagnetic and are not affected by the MRI magnets. The exceptions are metal fragments that get into the body accidentally, including shrapnel as well as cardiac pacemakers. Hopefully MRI compatible pacemakers will soon become available.

If an MRI is taken around an orthopedic implant there is no danger to the patient. The metals we use: stainless steel, cobalt chrome, and titanium are not magnetic. The problem with scanning around an implant is that artifact is created around the implant on the diagnostic image. This artifact makes the image difficult to interpret. New software to eliminate this artifact have been developed and are called metal suppression or metal artifact reduction sequences (MARS). Not all radiologists are familiar with these, and useless scans around implants are still occasionally performed. The radiologists that I use are well versed in these techniques, but sometimes patients who don’t live here need to get scans done near their home. I suggest finding a larger center that employs a musculoskeletal radiology subspecialist who is likely to perform the scan correctly.

In most cases of moderate to severe arthritis an x-ray is all that is needed to make the diagnosis. Hip dysplasia, various impingement deformities, and stage 3 and 4 necrosis are also best evaluated by simple x-rays. A hip MRI is a useful study to look for problems such as stage 1 and 2 osteonecrosis, hip abductor tears, and labral tears. An arthrogram MRI (dye is injected into the joint prior to the MRI) is better when we look for a labral tear.