ONE STAGE REVISION OF INFECTED HIP REPLACEMENT USING UNCEMENTED SYSTEMS AND ANTIBIOTIC IMPREGNATED ALLOGRAFT BONE

Abstract

Infection of total hip replacement (THR) is a serious complication, usually necessitating complete removal of implants and thorough debridement of the site. Mostly implant removal is followed by several weeks of antibiotic therapy before a new prosthesis is inserted. One stage exchange using antibiotic containing cement did not gain widespread use because of several risks, although the possible clinical and economic advantages are evident. Uncemented revision techniques seem to provide better long term results, however in septic cases its use so far has been restricted to two stage procedures. Allograft bone impregnated with high loads of antibiotics using a special technique (antibiotic bone compound ABC) is likely to create markedly higher concentrations of antibiotics in its surrounding than cement.

Between 1998 and 2004 37 patients with infected THR were treated using a standardized protocol. Patients were 17 male and 20 female, their age at revision was 42–83 yrs with a mean of 68,5yrs. After removal of the implants a radical debridement and intensive pulsed lavage was performed. Bone deficiencies were filled with cancellous bone, impregnated with high loads of Vancomycin or (in cases with gramnegative cultures) a combination with Tobramycin (ABC). After impaction uncemented implants were anchored following the principles of press-fit fixation, all without cement; usually we preferred a rectangular diameter titanium stem and a hemispherical cup. Additional ABC was placed around eventually uncovered parts of the implants and impacted for good stability. Wounds were drained and closed immediately; rehabilitation was performed as after non-septic surgery. Cultures taken intraoperatively revealed growth of coag.neg.staph (19x), s.aureus (11x), MRSA (5x), enterococci (8x) and other grampositive pathogens (6x), respectively. In 8 hips gramnegative germs were found additionally. Patients were evaluated prospectively 2 weeks, 6 weeks, 3 months, 6 months and one year after surgery. After the first year evaluation was retrospective. Follow up included clinical and radiological examination and laboratory data (CRP, ESR, blood count, urea and creatinine).

Three hips required re-revision because of re-infection, the remaining 34 hips (92%) stayed infect free and stable throughout a follow up period between 2 and 8 years (mean 4,4yrs). No adverse side effects could be found. Incorporation of grafted bone followed the same patterns as known from unimpregnated grafts.

Infected THRs may be exchanged within a single procedure using antibiotic impregnated allograft bone, providing biological reconstruction of bone stock, stable insertion of an uncemented implant and control of infection. Since only one intervention is necessary rehabilitation of patients is improved and costs are markedly reduced. Improved long term results may be expected.