Histological and clinical analysis of knee cyclops lesions.

Background and aim: Cyclops Syndrome, first described by Jackson and Schaefer in 1990, is known as a complication of anterior cruciate ligament reconstruction (ACLR). However further researches have demonstrated that cyclops can be present even without symptoms and/or in absence of ACLR, simply configuring itself as a lesion in patients with rupture of the native ligament.

Methods: This is a retrospective cohort study in which we report our experience of 13 cyclops lesions found between 126 patients during a primary arthroscopic ACLR. Preoperative examination with tests of joint stability and range of movement measurement was performed and recorded. Accurate joint examination was performed during arthroscopy and the cyclops lesions found were removed and analyzed with haematoxylin-eosin coloration. Post-operative clinical examination was performed until 6 months of follow-up.

Results: Histological analysis showed proliferation of dense fibroelastic polypoid nodules with a macroscopically histological aspects of a "blue eye", hence the name Cyclops. At 6 months of follow-up after surgery, none of the patients reported pain at terminal extension or instability and they were all able to resume their previous activities.

Conclusions: Our study confirmed that surgical reconstruction of the ACL is not the only condition in which the Cyclops Syndrome develops; in fact our histological analysis indicate that the Cyclops lesions develop like a reactive fibroproliferative process following the rupture of the native ACL fibers, as scar reaction to the trauma: for this reason an accurate arthroscopic detection of these Cyclops lesions is crucial during primary ACL reconstruction in order to obtain the best surgical outcomes.