Articles

What’s New In Hip Replacement?

David L. Roter MD.

Surgical replacement of the arthritic hip has been a generally successful treatment option for the last 50 years. The original procedure, developed by Sir John Charnley in the 1960’s has continued to evolve, both with respect to materials and surgical protocols.

Very few procedures in orthopaedics have been as predictably helpful in relieving pain and restoring function as total hip arthroplasty; however, as the application of this technology has been expanded to include younger and more active people, some problems have been noted, particularly component wear and implant loosening.  

The various orthopaedic implant manufacturers have expended enormous sums developing biomaterials which can survive many millions of cycles of high loads in a harsh biologic environment. Valuable lessons have been learned over the years as this technology has been put to the test by millions of patients, both in this country and abroad.

The original implant fixation method, using methyl methacrylate cement has had some problems in certain applications, prompting the development of biologicfixation designs, eliminating this source of potential loosening. We have now had more than 20 years of experience with this technology. Component wear, particularly in younger, active patients, has been an ongoing source of concern, prompting a great deal of research in improving the wear characteristics of polyethylene, the most common articulating surface in total hip sockets.

After years of development and clinical trials, particularly in Europe, we now have available alternate bearing surface options, including high technology metal on metal and ceramic on ceramic designs. Hopefully, these new materials will prove more durable in those patients with higher demands.

As advances have been made in implant design and materials, so too have surgical approaches and post-operative protocols improved over the years. Patients used to require a 2-week hospital stay, whereas most can now be discharged in 3 or 4 days. Surgical exposures have also been refined so that the old 10 or 12 inch incision has now shrunk to 4 or 5 inches in most cases with greater attention paid to preserving tissues and minimizing soft tissue damage, thereby improving post-operative recovery.

Recently, the concept of "minimally-invasive surgery" has been applied to hip replacement, although this is really a misnomer when you consider that the hip is one of the largest joints in the body and many of the replacement components are two to three inches in diameter.  Several centers in the country have been promoting two-incision approaches using several two to three inch incisions and relying on fluoroscopic guidance.  Early reports are quite mixed on results and complications.  In any event this procedure will never be truly "minimally invasive" like arthroscopic knee and shoulder procedures.  

The key concepts remain appropriate selection of components to match individual patient demands and to carefully position the implants so as to facilitate long-term service.  Fortunately, we have long passed the one-size-fits-all era, and now have a wealth of options at our disposal. 

As our population ages and joints continue to wear out it is indeed fortunate that we have a procedure that is so predictably successful in the vast majority of patients.  I have lost count of how many times I have heard people say "if I had only known how much better I would feel after this procedure I wouldn’t have waited so long."