Ultrasound‐guided aspiration of anterior cruciate ligament mucinous cysts in the posterior intercondylar notch: Technique and short‐term outcomes

Purpose To describe our technique of aspirating symptomatic anterior cruciate ligament (ACL) mucinous cysts in the posterior intercondylar notch with ultrasound guidance, and to detail short‐term patient outcomes. Methods We identified 13 patients from February 2008 to May 2020 who underwent ultrasound‐guided aspiration of symptomatic ACL mucinous cysts in the posterior intercondylar notch. Post‐procedural imaging was reviewed to evaluate the degree of cyst decompression. Needle size was noted. Post‐procedural symptomatology was also assessed. Results No or minimal fluid was initially aspirated in 11/13 (84.6%) patients. For the two patients in which the cysts were aspirated completely with initial needle placement, with no need for lavage, a 13‐gauge trocar was utilized. Of the remaining cysts, 10/11 were aspirated with an 18‐gauge needle and one with a 20‐gauge needle. Subsequent lavage was performed in 10 of the remaining 11 patients. After lavage, in eight there was a reduction of at least 50% volume by retrospective image interpretation; of 25% to 50% volume in one patient and of less than 25% volume in one patient. Five of the 13 patients reported immediate post‐procedural symptomatic relief. In the other patients, immediate efficacy or post‐procedural symptomatology was not documented. Conclusion Aspiration of symptomatic ACL mucinous cysts is a safe procedure and can provide symptomatic relief that may be temporary, but useful clinically. We recommend needles larger than 18 gauge for the best chance of successful aspiration.