MIDTERM OUTCOMES OF REVISION TKA USING A SINGLE REVISION SYSTEM: INFECTED TKA VS. NON-INFECTED TKA

Introduction Even a number of studies have reported clinical outcomes after revision total knee arthroplasty (revision TKA), little information is still available on whether outcomes of patients undergoing a revision TKA as a second stage procedure because of infected TKA are poorer than those of the patients undergoing a single-stage revision TKA because of non-infectious causes. In addition, use of various revision prostheses in most previous studies may limit solid interpretation of the outcomes after revision TKA. This study sought to determine whether outcomes in patients undergoing revision TKA due to infected TKA would be different from those in patients undergoing revision TKA due to non-infectious causes. Materials and Methods We assessed 71 cases undergoing revision TKAs with use of a same revision system (Scorpio TS®, Stryker, Mahwah, NJ) from October 1999 to February 2012. All patients followed more than two years and mean follow-up period was 67 months (range: 24 – 168 months). Of them, thirty five patients underwent revisions due to infected TKA (group for infected TKA) while 36 patients due to non-infectious causes including loosening, wear, and/or instability (group for non-infected TKA). All patients in the group for infected TKA underwent two-stage revision surgeries while all patients in the group for non-infected TKA single stage revision surgeries. Comparative variables between two groups were preoperative range of motion (ROM) and American knee society (AKS) scores, postoperative ROM and AKS scores assessed at latest follow-up, amount of bone loss and requirement of stem assessed during the surgeries, and survival rate. Results Preoperatively, the group for infected TKA showed significantly poorer range of motion (102° vs. 112°, P = 0.011) and knee society knee scores (58 vs. 67 points, P = 0.02) than the group for non-infected TKA. During operation, stem for femoral component was more frequently used in the group for infected TKA than the group for non-infected TKA (71% vs. 42%, P = 0.009). Postoperatively, the group for infected TKA still showed significantly poorer range of motion (115° vs. 122°, P = 0.015) and trend of poorer knee society knee scores (83 vs. 89 points, P = 0.054). However, there were no significant differences in amounts of improvement of the ROM and AKS scores, and survival rate between the two groups. Conclusion The patients undergoing revision TKA as a two-stage procedure due to infected primary TKA showed significantly poorer pre- / postoperative range of motion and poorer preoperative clinical scores, and trend of poorer postoperative scores than those undergoing single stage revision TKA due to non-infectious causes. Nevertheless, the amounts of improvement of the clinical values and survival rate were not different between the two groups. Our findings suggest that even the group for infected TKA had inferior postoperative outcomes than the group for non-infected TKA, the inferior outcomes seems to stem from poorer preoperative outcomes of the group for infected TKA.