TOTAL HIP REPLACEMENT: INFECTION
Subfascial (deep) infection, whether acute or latent, is a serious complication in joint replacement surgery. It is important to identify the type of infection because prognosis and treatment differ. Also, because any implant can become a focus for infection, patients with a hip prosthesis should be given preventive antibiotics when undergoing dental, urinary, or gastrointestinal procedures.
Any unexplained wound or hip pain in the early post-operative period
should arouse suspicion. Acute infections are easiest to diagnose because they
manifest classic systemic and local signs of sepsis. Diagnosis of latent
infections is more difficult because clinical and radiographic signs are
similar to those seen in aseptic loosening of the prosthesis.
Strong indications of a suprafascial infection are pain at the
incision site, inflammation, and drainage in the first 2 weeks after surgery;
fever and leukocytosis may also be present. Daily surgical wound care is
therefore essential. Suprafascial infections respond well to drain- age and
debridement.
Symptoms of subfascial (deep) infections may include swelling of
the thigh, increased hip pain, and elevated leukocyte count with an increased
proportion of neutrophils. Accurate diagnosis depends on culture of aspirated
fluid to isolate the causative organism. Blood cultures are also indicated. If
the culture results are positive, surgical debridement and intravenous
administration of antibiotics should be instituted immediately.
Acute subfascial infections cause a variety of
signs and symptoms, depending on the organism’s virulence and the patient’s
immunologic status. Because long-term postoperative administration of
antibiotics can mask the appearance of symptoms, preventive intravenous
administration of antibiotics should not be continued for more than 48 hours
after surgery.
Acute deep infections must be treated aggressively with intravenous
administration of antibiotics and fluid replacement, as well as immediate open
debridement of the implant site. Because most nosocomial gram-positive cocci
have become resistant to penicillin, early treatment with a
penicillinase-resistant synthetic penicillin or cephalosporin is necessary
until the drug sensitivity of the organism is determined. If the infection is
controlled early enough, it may be possible to save the prosthesis. If the
infection is intractable or is due to antibiotic-resistant organisms, the
prosthesis must be removed. Secondary acute hematogenous infections can occur
after months or years, with or without septicemia and sudden onset of hip pain.
Latent infections do not usually become evident until at
least 12 weeks after surgery. They should be suspected if the patient is not
recovering normally. Delayed primary infections may be due to bacterial
contamination from a remote body source (mouth, urine, bowel), in the
perioperative period. There may be no fever or elevated leukocyte count,
although the erythrocyte sedimentation rate and C-reactive protein level are
usually elevated. In a long-standing infection, radiographs may show osteopenia
and a radiolucent zone around the implant. Results of bone scans are positive
for both infection and a loosened implant, but the pattern of
radioisotope uptake is sometimes specific enough to differentiate between the
two conditions.
Treatment. Removal of the prosthesis with a temporary
hip spacer is the treatment of choice. Intravenous administration of
antibiotics to establish adequate bactericidal levels as confirmed by tube
dilution sensitivity studies should be instituted for 4 to 6 weeks. Before
revision surgery, histologic examination of local tissue is
needed to ensure that the infection has been controlled.
Some organisms are so virulent and difficult to eradicate that a new
implant can never be placed for fear of recurrent infection. A Girdlestone
resection arthroplasty may be the only alternative procedure. Pain, severe limb
shortening, and concomitant gross instability of the hip are serious
disadvantages.
