When should I have my hip resurfaced?

Hip arthritis causes a lot of pain and stiffness in the hip. The decision to have either a hip replacement or hip resurfacing is when the pain is bad enough and all conservative methods of treatment in terms of activity modification, weight reduction, and painkillers have failed. When one can no longer bear the pain or the quality of life is affected then that is the time to decide to have a hip replacement or a hip resurfacing.

Why should I choose hip resurfacing or traditional hip replacement?

This is a personal choice. What is required for hip resurfacing is a good bone stock. The people who live more sedentary type of lifestyle or are of older age, the bone is weak and if a hip resurfacing is done then the chances of failure in the first year due to hip fracture is high. However, if the person has very high level of activity and if wants to preserve this level of activity after hip surgery, then hip resurfacing is extremely good for them because after about six months to a year a person with resurfacing can resume all activities. Also in a younger person, hip resurfacing causes preservation of bone and if you were to have a re-do operation in future, then hip resurfacing gives an option of preservation of more bone and, hence, a re-do operation would be much easier. On the other hand, the patient for whom a total hip replacement can last the rest of his/her life would be a better candidate for traditional hip replacement.

What if the hip resurfacing wears out?

The hip resurfacing wears out usually because the femoral cap becomes loose from underlying bone. If this happens and the person is symptomatic then the metal socket is left alone because this is usually well fixed. The loose cap is revised to a traditional hip replacement with a metal pin into the thighbone and a large metal ball to match the socket and the patient ends up having a traditional hip replacement with metal-on-metal bearing.

What are the major benefits of hip resurfacing?

The major benefits of resurfacing compared to traditional hip replacement are preservation of bone, larger ball diameter, hence, risk of dislocation is less, and the hip joint feels more normal because majority of the bony anatomy is maintained around the hip joint. Also with the hip resurfacing, a person can resume all normal activities.

Should one be concerned about metal ions that are released in the blood?

This is very controversial with the present evidence available today. Many studies have been done and European studies have shown that long-term results that there is no risk of increased cancer in patients who have metal-on-metal prosthesis versus traditional metal-on-plastic prosthesis. So far they have been not linked to any increased in cancer or other diseases. At the present moment, we do not know the safe levels of this metal ions in the blood. Nor is it likely that we will be able to determine safe levels in the near future. It is advisable not to perform metal-on-metal hip resurfacing in patients on dialysis, kidney transplants, renal failure, metal allergy, or expected mothers.

Disadvantages of surface replacement

Due to the unique nature of surface replacement, there are certain disadvantages, which are specific to surface replacement, which are as follows:

1. Metal ion dispersal. The current generation of hip resurfacing is only available in one bearing surface, which is metal-on-metal. This means the surface of both the cup or the socket and the metal ball is made of high chromium cobalt carbide metal. Every time, a person walks on this, this sheds billion of particles over a course of a year. This gets dispersed through the body. The certain metal ions especially cobalt, chromium, and nickel are measured in the blood stream and there has been concern over the number of years that they can accumulate in the body and over a period of time they may cause cancer. However, long-term results especially from European studies have shown that they do not cause cancer. They can increase in levels in the blood, but we do not know what the toxic level is for these ions. One need to have a healthy kidney in order to filter these ions out and, hence, people who have malfunctioning kidneys or have kidney transplants or kidney failure should not have this operation for this reason.
   
   
2. Femur fracture. Because of the nature of the hip resurfacing, the femur head can break at the junction of the bone and the lower part of the metal surface. This risk is maximum in the first year and it is about 3-4%. To prevent this, crutches are used for about four to six weeks after the operation during the time of rehabilitation, which tends to decrease the chance of the fracture. This is because the fact that the bone takes sometime to adapt around the new prosthesis.
   
   
3. Nerve injury. Since surface replacement requires a lot of preservation of bone, hence, a larger incision has to be made in order to work around the bone in order to do the operation. This larger incision means that there is extra pressure on the nerve in the hip joint area, which at times can cause transient weakness in the muscles of the leg and the foot.
   
   
4. Heterotrophic ossification. During the time of the surgery a lot of bone debris is created at the hip side. This bone debris can get lodged in the muscle causing stiffness in the hip, a condition called heterotrophic ossification. This is more so in hip resurfacing than a traditional hip replacement. We take measures during the time of the surgery and after the surgery to reduce this and this may require either a period of anti-inflammatories medication or low-dose radiotherapy in the first two days after surgery. With radiotherapy, the risk of extra bone formation is less than 2%.
   
   
5. Level of activity after hip resurfacing. The traditional hip replacement especially with metal-on-plastic and ceramic-on-ceramic we tend to limit the activity on the hip and advise patients not to do impact exercise as this may accelerate the wear of the plastic liner or in terms of ceramic prosthesis can fracture it. In terms of hip resurfacing, it is not known whether such high activity in terms of running, jogging, etc. will cause any accelerated damage to the hip and the effect of this remains to be known.
   
   
6. Longevity of implant. The short-term results in terms of nine years in various studies have been encouraging. Have its early failure in the first year or so is by 2%-3% due to the fracture of the neck. In terms of more than nine years of results, it is not known whether it will be successful beyond that because it has not been implanted in the human body for so long. However, laboratory results and the current trend are very encouraging.