Minimally Invasive Total Hip Replacement

Minimally Invasive or Mini-incision Hip Replacement

There are several varieties of “minimally invasive” or “mini-incision” hip replacements being done. Some are the same as the normal operation, just through the use of specialized instruments the OS is able to work using a smaller incision, some do the normal procedure with an incision as small as 5 inches long. Another other type is done with instruments marketed by Zimmer Orthopedics, Inc. This involves two two-inch incisions and the procedure is done using flouroscopy. In this procedure the femoral head is broken into several peices so it can be removed through the smaller opening. The hardware is essentially the same as that used for other procedures, but the surgeon might be limited in his selection (as to what will fit and can be reamed for using the Zimmer tools). Zimmer aims to have the patient leave within 24 hrs and is marketing this as a cost-saving feature. Of course noone likes to spend any more time in the hospital than they have to, but it is still a major operation involving many of the same risks as the standard procedure, but there is some reason for concern that the patient would not be actively monitored for signs of these risks (infections, deep venous thrombosis, etc). Zimmer seems to claim in their press releases that the typical hip replacement takes up to 12 weeks to recover and up to two weeks in the hospital. If you are healthy to begin with, the recovery for the standard procedure is not any where as bad as they make it out to be. Hospital stays of 3-4 days can be done and you can be walking in 3-4 weeks in some cases. That walking time should be dictated in part by the bone ingrowth time that is a process similar to having a broken bone heal — it takes time and there is really no way it can be hurried by making the incision shorter.

The minimally invasive procedure offer advantages in the damage to the surrounding muscle is lessened so the muscle recovery is generally faster. Some methods are done without dislocation of the hip, so the tendon releases (subsequently repaired) are not needed and this may reduce the short-term risk of dislocation typically associated with the healing of the hip capsule and surrounding tendons.

Here are some questions you might want to ask if considering MIS:

• The longevity of a device and the prevention of dislocation is dependent in part on the proper alignment of the parts. Can the parts be accurately aligned and installed using the two-dimensional view provided by the flouroscope?
• If the procedure being used requires breaking the femoral head, that would generate additional bone debris, can this be completely lavaged from the site without visual aide? Any leftover debris might cause premature wear of plastic parts.
• For the young patient (younger than 65): Can the procedure be used with the hard bearing surfaces (metal-on-metal or ceramic-on-ceramic) that are likely to last longer than the typical metal on plastic bearings?
• For the active patient: Will the device used need to have a smaller than normal head? Although its not the only factor, a smaller than normal head might increase the risk of future dislocation.
• What criteria are used to determine weight bearing and discharge from the hospital. Will the patient be adequately supervised for signs of infection and deep venous thrombosis after discharge?

Minimally Invasive Hip Replacement Links

• Wright Medical PATH Minimally Invasive Technique
• Search PubMed for Minimally Invasive Hip Arthroplasty