Fluid collections in the osseous tunnel during the first year after anterior cruciate ligament repair using an autologous hamstring graft: natural history and clinical correlation.

Objective: To determine the natural history of fluid collections that occur within the osseous tunnel after autologous hamstring repair of the anterior cruciate ligament (ACL) and to correlate with clinical outcomes. Methods: Twenty-two patients were imaged within I year after autologous hamstring repair of the ACL and evaluated for the presence of fluid collections within the osseous tunnels. Eight patients with fluid collections were then re-evaluated with MRI within 6 to 9 months. Results: Fourteen of 22 (64%) of the initial MRI studies demonstrated fluid collections within one of the osseous tunnels. Eight of these 14 patients were available for follow-up imaging and clinical evaluation. Fluid collections resolved in 7 of the 8 patients, and in a single patient, the size of the fluid collection decreased. No patient developed ganglion formation or tunnel expansion, and all patients were clinically asymptomatic with no evidence of instability. Conclusion: Small fluid collections in the osseous tunnels are a common finding on MRI within the first year after ACL repair with an autologous hamstring graft. The fluid collections usually resolve over time and do not progress to ganglion formation or lead to tunnel expansion. They are not associated with clinical instability.