Functional results of septic arthritis after anterior cruciate ligament reconstruction treated by arthroscopic lavage with preservation of the graft: case-control study at 7 years follow-up.

Introduction: Septic arthritis is a rare but serious complication following anterior cruciate ligament reconstruction (ACLR). Arthroscopic lavage with graft retention and antibiotic therapy is considered to be the gold standard for the initial treatment of surgical site infections. The aim of this study was to compare long-term clinical and functional outcomes between patients with septic ACL reconstructions and those without septic complications.

Methods: This was a retrospective, single-center, multi-surgeon study. ACLR complicated by surgical site infection between 2010 and 2022 were matched 1:1 with ACLR without septic complications performed during the same period. Matching criteria included age, sex, body mass index, existence of meniscal and chondral lesions, graft type used, postoperative follow-up duration, and smoking status. At final follow-up, functional outcomes were assessed using IKDC, Lysholm, KOOS, and Tegner scores. Return to sport and level of return were also evaluated in each group.

Results: 17 septic ACLR were matched with non-septic ACLR. At a mean follow-up of 7 ± 3 years, no recurrent infections were observed; only one patient required a second lavage. There were no significant differences in the Lysholm, International Knee Documentation Committee (IKDC), or the Knee injury of Osteoarthritis Outcomes (KOOS) scores between septic and non-septic groups (Lysholm: 89.1 ± 10.4 vs 92.1 ± 8.5, p = 0.32; IKDC: 82.9 ± 12.6 vs 88.5 ± 11.2, p = 0.10; KOOS: 89.9 ± 9.9 vs 91.7 ± 9.7, p = 0.80). No significant difference was observed in activity level at final follow-up (Tegner: 4.9 ± 1.2 vs 5.5 ± 1.8, p = 0.18). However, time to return to sport was significantly longer in the septic ACLR group (10.2 ± 1.1 months vs 8.1 ± 2.1 months, p = 0.01). There was no significant difference in the level of return to sport (53% returned to the same level in the septic group vs 65% in the non-septic group, p = 0.49).

Conclusion: When treated early with arthroscopic lavage and antibiotic therapy without graft removal, septic arthritis following ACLR yields comparable functional outcomes to uncomplicated ACLR at 7-year follow-up. This approach allows good clinical recovery and limits long-term functional impact, but with a longer rehabilitation period before returning to sport. Arthroscopic lavage remains the first-line treatment in cases of septic arthritis after ACLR.

Level of evidence: IV Keywords: Anterior cruciate ligament, septic arthritis, arthroscopic lavage, clinical outcomes.