Is there a role for knee arthrodesis with modular endoprostheses for tumor and revision of failed endoprostheses?

Abstract BACKGROUND: Knee arthrodeses are performed to treat infection after arthroplasty and tumors requiring extensive soft tissue resection. Many techniques have been described, but most have important disadvantages. Currently, endoprosthetic arthrodesis implants are available, but little is known about them. QUESTIONS/PURPOSES: Our objective was to analyze a series of knee arthrodeses with a modular prosthetic system to evaluate (1) survivorship of the implant, (2) complications, (3) whether survivorship differed between arthrodeses done for primary tumor resection and revision reconstructions, and (4) whether survivorship differed based on the presence of previous infection or the use of a gastrocnemius flap. METHODS: We present 32 patients with modular knee arthrodeses; arthrodeses were performed in 25 patients with tumors and in seven patients without tumors. There were 14 implants done at the time of tumor resection and 18 for revision of failed implants. Survivorship and complications were analyzed with Kaplan-Meier curves. Log-rank test was used for comparison between primary and revision implants, not infected and previously infected implants, and use or nonuse of a gastrocnemius flap. RESULTS: Survivorship of arthrodeses with modular endoprostheses was 50% and 25% at 5 and 10 years, respectively. There were nine infections (29%) and one implant fracture (3%). Amputation as final surgery was required in 8 patients (six owing to infection and two to oncologic failures). There was no significant difference in survivorship between arthrodeses done for primary tumor resection and as a salvage procedure for failed implants. No differences were found between patients with and without prior infection or with and without a gastrocnemius flap. CONCLUSIONS: Survivorship of a modular arthrodesis implant was 50% at 5 years owing to a high complication rate. Infection is the most common cause of failure of oncologic and revision implants. Implant fracture is a rare occurrence. Modular segmental arthrodesis provides a stable construct for patients in whom limb preservation is possible but a hinged device is contraindicated as a result of major muscle resection. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence