[Comparison of therapeutic strategies for hip and knee prosthetic joint infection]

Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty. Several strategies have been developed to treat it. The purpose of our study was to compare therapeutic strategies for PJI treatment published in the literature.

We retrieved around 5,000 documents concerning this topic, published between January 1960 and November 2006, from the databases MEDLINE and EMBASE. Using a two-phase selection, 382 relevant articles were chosen, and full texts were obtained for 302 of them (79%). However, only 77 of them fulfilled the criteria for inclusion in our study. A total of 645 hips and 1,145 knees could be analyzed. A comparison was made of the following procedures: two-stage surgery, one- stage surgery, implant removal and long-term antibiotic therapy in hip PJI; two-stage surgery, debridement, arthrodesis and long-term antibiotic therapy in knee PJI. The criteria used to evaluate successful PJI treatment included the rate of recur- rent infection (primary outcome) and the rate of additional surgery (secondary outcome). The capability index (c), relative risk (RR), odds ratio and "number needed to treat" (NNT) were calculated for both outcomes under study.

1. The lowest rate of recurrent PJI was reported for two-stage reimplantation (hips, 7.4%; knees, 11%), then came one-stage reimplantation for hip PJI (9.2%) and arthrodesis for knee PJI (15.6%). 2. The lowest relative risk for the primary outcome of this study was found in two-stage reimplantation (RR=0.62 and 0.32 for hip and knee PJI, respectively, knee arthrodesis (RR=0.78) and one-stage hip reimplantation (RR=1.07). 3. The NNT was negative for two-stage reimplantation (NNT = -21.6 and -4.3 for hip and knee PJI, respectively). 4. Compared to long-term antibiotic therapy, knee debridement had a higher risk of recurrent infection (RR, 4.72 versus 1.20) as well as the risk of additional surgery (RR, 4.41 versus 1.31). However, when the capability index and NNT were used, knee debridement achieved better primary outcomes than antibiotic therapy (c=0.0317 versus 0.0000) and NNT (2.2 versus 26.3). 5. Relative risk for additional surgery was the lowest in two-stage reimplantation (RR=0.47 and 0.36 for hip and knee PJI, respectively), and the highest in long-term antibiotic therapy for hip PJI (RR=6.47).

The resultant ranking of therapeutic approaches to PJI, as found in our study, is not surprising; except for seemingly bet- ter outcomes achieved by long-term antibiotic therapy compared to surgical debridement in knee PJI. This, among others, shows the need to use more comprehensible statistical instruments, such as the capability index, that could provide a more reliable evaluation of therapeutic interventions.

A two-stage protocol for PJI treatment had the lowest risk for both PJI recurrence and need for additional surgery in comparison with all other strategies developed for PJI therapy. Therefore, it should be accepted as the method of choice. One-stage hip reimplantation is a less reliable approach in which it is inevitable to strictly respect the indication criteria. Other methods are either less reliable or associated with a high risk of repeat surgeries, or provide functionally unacceptable outcomes.