Infection after hip replacement may require second surgery

DEAR DR. ROACH: I had a hip replacement seven weeks ago. Three weeks ago, I went to physical therapy, where the therapist stretched my leg.

That evening, I was in severe pain. The surgeon checked my hip and said that the pain was muscular. Since that time, I have had severe pain, for which I was given Celebrex. The Celebrex totally relieves the pain for at least 12 hours. The surgeon wanted to make sure there was no infection so he sent me for an aspiration of the hip. The fluid that came out showed no pus. Upon testing, the preliminary result was borderline for neutrophils. I am awaiting the culture test. Please explain what “borderline” means, as I am quite nervous. – R.F.

ANSWER: A hip replacement surgery can dramatically improve the quality of life in people with severe arthritis. It is a procedure that is done often, and most of the time, things go well. But there are several possible complications, and one of the most feared is an infection inside the artificial hip joint. This happens in one to two per cent of people. The most common bacteria are Staph species, especially in the first three months after surgery.

Treatment is long-term antibiotics, usually coupled with a second surgery: often, the entire joint needs to be removed, and an antibiotic-impregnated spacer device is left in its place for four to six weeks. Because this is a major undertaking, the diagnosis needs to be clear.

Aspiration – that is, the removal of fluid from the joint – is done in the hip using ultrasound or X-ray guidance.

A small amount of fluid is removed and it can be seen to be pus immediately, due to the thick, cloudy fluid packed with white blood cells (mostly neutrophils, the type of white blood cell most concerned with bacterial infection) to fight off the infection. If it isn’t obviously pus, the number of white cells present can predict whether it’s likely to be infected. More than 1,000 white cells per microliter means about a 90 per cent chance of it being infected. If your cell count was lower, there is less than a 90 per cent risk of infection. This culture is the best way of proving that an infection is present, and the results can guide antibiotic treatment if necessary.

The symptoms of early infections can be very subtle, so your surgeon is being wisely cautious to evaluate you for infection, in my opinion.