Osteoarthritis slowly develops in the weight-bearing joints, most commonly in the hip and knee, creating pain, stiffness, swelling and loss of function. There are many nonsurgical options such as: rest, weight loss, medication, physical therapy, steroid injections, and viscosupplementation injections. However, when conservative measures fail, surgical intervention, such as a joint replacement, becomes the next option. A total joint replacement uses a prosthesis to replace the end of the bone damaged from arthritis. These new metal and plastic surfaces in the joint allow pain free movement and function in the hip and knee. These procedures have been performed since the early 1970’s. The outcomes for active people continue to improve with advances in technology, prosthetic materials and new techniques. It will be the purpose of this column to present two new options in hip replacement surgery that may have promise for extending the life of the implant in younger, more active patients.
Surface replacement of the hip is an alternative to a traditional total hip replacement in which the thigh bone (femur) and the hip joint of the pelvis are preserved as much as possible while resurfacing only the ends of the bones. It is best used in younger and more active patients. Just as in the traditional total hip replacement surgery, this alternative procedure is indicated for osteoarthritis, avascular necrosis and traumatic arthritis of the hip joint. While the traditional replacement is very successful and allows the patient to return to pain-free activity, the implant can wear out or loosen over time. When this occurs, pain and loss of function return. In a traditional hip replacement the surgeon removes the head and neck of the femur resulting in significant bone loss. This may complicate a revision if necessary. The surface replacement preserves the bone by inserting a metal cap over the cup-shaped top of the hip joint. A short-stem prosthesis (as opposed to a long stem) is placed over the end of the hip ball-shaped bone. Two advantages of this technique are: preservation of the bone allows the use of a much larger ball size. This permits greater stability of the hip joint leading to a dislocation rate of 10 times less than traditional replacement. Secondly, the resurfaced hip, with less bone loss, has a greater success rate in the event of a revision. Therefore, younger, active patients, who may wear out the prosthesis sooner, will be less likely to dislocate and have a better outcome when they have a second hip implant. Previously, one would encourage patients to wait until they were older to have a replacement. In part, due to the fact that they would be less active and less likely to live long enough to outlast their new hip. Resurfacing changes the outlook.
As with the traditional hip replacement, the risks are small. Some include loss of blood, blood clots, and infections. To a lesser degree than traditional hip replacement, there is a risk of dislocation and implant wear or loosening. A risk unique to the surface replacement is due to the metal-on-metal bearings. While this may lessen wear and tear of the implant, it has been shown to cause metal ions to be dispersed through the body. It is measured in the bloodstream and has not been shown to cause cancer or other disease in humans. There is a 2% risk of fracture due to the preservation of more bone in the femur. However, if the patient maintains partial weight bearing status for 3-4 weeks after surgery for the bone to heal, this is rare. There is also a 1% chance of injury to the sciatic nerve due to increase work around the bone by the nerve. This may lead to transient weakness of the leg muscles. Stiffness may occur in some patients due to extra bone forming around the hip. Medications are used to limit this risk.
As with any new technology or procedure, it is unclear what the long term outcomes will be. The short term results at 4-6 years are very encouraging given the young age and increased activity level of the patient. However, it is too early to tell if this new technique is superior to the traditional total hip replacement long term.
Improvements in hip implant design and materials continue to be introduced. To decide which implant is best for you, discuss the details with your orthopedic surgeon. It will be dependent on your goals, activity level, general health, and age.
Sources: Rothman Institute, Philadelphia, PA, Hospital for Special Surgery, New York, NY. www.mayoclinic, www.health.harvard.edu, www.hss.org
Visit your doctor regularly and listen to your body.
Read Part 2 on hip resurfacing.
This article is not intended as a substitute for medical treatment. If you have questions related to your medical condition, please contact your family physician. For further inquires related to this topic email: firstname.lastname@example.org
Paul J. Mackarey PT, DHSc, OCS is a Doctor in Health Sciences specializing in orthopaedic and sports physical therapy. Dr. Mackarey is in private practice and is an affiliated faculty member at the University of Scranton, PT Dept.