Knee arthrodesis using a custom modular intramedullary nail in failed, infected knee arthroplasties: A concise follow-up note of 31 cases at a median of 13 years post-arthrodesis

Abstract

Introduction: Knee arthrodesis utilizes an arthrodesis nail as a salvage technique for infected total knee arthroplasty (TKA), especially when the extensor mechanism is damaged, or the skin is compromised. This implant helps to minimize or prevent leg length discrepancy, while allowing immediate weight bearing without requiring bone fusion. However, there is a risk of infection. Surgical revisions were required in 19% of patients at 50 months' follow-up in our team's initial 31-patient case series. Since there is little long-term outcome data, we reviewed this same group of patients after a mean of 13 years to determine: (1) the implant's long-term survival, (2) the functional outcomes, (3) the microbiological changes in revision cases.

Hypothesis: The long-term survival of knee arthrodesis using an arthrodesis nail for failed infected TKA is acceptable.

Material and methods: Thirty-one patients operated on between January 2005 and December 2008 were retrospectively included in the initial study. The functional outcomes consisted of pain on a visual analog scale (VAS), neuropathic pain (DN4) and the Oxford Knee Score. All surgical revisions were documented with repeat microbiology samples.

Results: The median follow-up time was 13.1 years [11.5-13.5]. No mechanical failure (implant failure or aseptic loosening) was observed. Eight patients were re-operated on due to new infections. The nail had to be removed in five of these patients. None of the patients required an amputation. Among the eight patients who were re-operated on, only two (25%) had been re-operated on since the initial study and underwent a two-stage arthrodesis revision. At 10 years, the cumulative incidence of surgical revision at the knee was 26% [95% CI: 12%-43%] and 16% [95% CI: 5.7%-31%] for an implant change. Six (75%) of the re-operated patients had their revision within the first 72 months of the initial TKA, while 4 (50%) had it within the first 26 months. Among the 15 patients who were still alive, the median Oxford Knee Score was 17/48 [12-28]. At the final assessment, the median pain level was 0 [0-5], although 4 of the 10 analyzable patients (of the 15 living patients, 3 had a cognitive impairment and 2 refused to participate) had neuropathic pain and pain on VAS of 3/10. The microbiologic findings were the same during the surgical revision in five of the eight re-operated patients (62%); however, one patient who had a Staphylococcus aureus infection had acquired a resistance to methicillin. In one patient, only one of the two bacteria identified initially was still present (methicillin-susceptible Coagulase-negative staphylococci [CNS]) and while in two patients, the infectious agent changed completely (shift from Gram-negative bacilli to methicillin-susceptible CNS, and the opposite for the other patient).

Discussion: Knee arthrodesis with a custom modular intramedullary nail is a viable limb salvage option in failed infected TKA cases with long-term survival, and it is comparable to other arthrodesis techniques. In most cases, recurrence of the infection occurred in the short term (<72 months). Later recurrences of the infection (>72 months) were rarer and were found in only two of our patients (6%). There were no mechanical failures.

Level of evidence: IV; Retrospective cohort study.

Keywords: Arthrodesis; Infection; Knee; Total knee arthroplasty.