Infection of total hip replacement can be immediately after the surgery, which what I call “acute” postoperative infections. There could be “delayed” deep infections which happen from three months to the next two years.
“Late” infections which typically happen after 2 years are called hematogenous (blood bourne) infections because these infections are most commonly because of bacteria seeding the joint and these bacteria have originated elsewhere from the hip joint.
Acute postoperative infections happen within the first three months of surgery and it’s important to distinguish whether these infections are superficial or deep. Superficial infections are outside the fascia and do not affect the inside of the joint. Deep infections are infections where the actual artificial joint is seeded with the bacteria.
The best way to differentiate a superficial from a deep infection is by doing aspiration of the hip joint and looking for cell count, culture sensitivity, Gram stain, etc. A cell count has to be differential- which means we look at individual white cells – lymphocytes etc. Aspirated cell count is an extremely useful test. The cell count for artificial joints that are infected are significantly lower than the counts associated with primary joint infection ie native joints getting infected.
Deep delayed infections occur after three months and could be from the surgery or could be from a hematogenous infection from elsewhere in the body including urinary tract infection or the nasal tract. Depending upon how the infection manifests, one option is to do irrigation and debridement (surgical cleaning) and exchanging of the head and the plastic and then treating the patient with IV antibiotics to achieve resolution of the infection.
Late hematogenous infection occur typically after two years and is from a source away from the hip joint. In these circumstances, the patient typically has to have a two stage reconstruction in which the joint has to be removed, antibiotic spacer has to be placed inside the hip joint, and after treatment with IV antibiotics, the antibiotic spacer is removed and the final hip revision is placed into position.
The advantage of the antibiotic spacers is that the antibiotic spacers eludes huge amount of antibiotics and kills the infection. Such high level of antibiotics is impossible to achieve through an IV dose because of possible toxicity to the body. The best way to treat late hematogenous infection is “staged reconstruction”. However, if the patient has significant medical problems with the extreme limitation of life expectancy, another option is to do removal of the implant which is called the “hanging hip” or “Girdlestone operation of the hip”.
There’s also been studies which show that a single-stage revision is an option for infected joint in which the infected joint is removed. Thorough debridement is done on the joint and a new hip joint is placed in position at the same time the infected joint is removed. Studies looking at a single stage revision for infected joint arthroplasty are fairly limited.