Serial MRI and clinical assessment of cyclops lesions

'Clinical cyclops syndrome' is associated with pain and a palpable 'clunk' at terminal extension with the loss of full extension. The aims of this prospective controlled study were: (1) to assess whether the minimal debridement of the ACL stump and notch is associated with an increased incidence of clinical cyclops lesions, (2) to look at the incidence and natural history of 'MRI cyclops' lesions using serial MRI's and (3) to assess whether 'MRI cyclops' lesions are associated with the loss of extension.

Forty-eight patients were randomized for ACL reconstruction into standard (23) and minimal debridement (24) techniques. One patient was excluded from the study. All patients underwent MR scanning postoperatively at 2, 6 and 12 months, together with the clinical assessment using a KT-1000 arthrometer and International Knee Documentation Committee evaluation. All observations were made by investigators blinded to the surgical technique.

There was no statistical difference in the incidence of cyclops lesions between the two groups (n.s.). The overall incidence of cyclops lesions was 46.8% (22 of 47). The natural history is variable with some getting larger, smaller or remaining static in size. Of patients with cyclops lesions, 17 patients (77%) had cyclops lesions in the setting of full extension. Five patients (23%) had loss of extension at 12 months with no MRI cyclops detected at 2 months.

The natural history is variable; although once present, the majority of cyclops remain static or regress in size. The onset of cyclops lesions is usually between 6- and 12-month post-ACL reconstruction. Minimal debridement does not lead to an increased incidence of clinical cyclops lesions. The authors conclude that loss of extension is multi-factorial, and there is a discrepancy between what we term 'MRI cyclops' and true 'clinical cyclops'.

Case-control study, Level II.