Recurrence of Cyclops Syndrome After Initial Arthrolysis: Characteristics and Risk Factors After ACL Reconstruction.

Background: Cyclops syndrome is a complication of anterior cruciate ligament (ACL) reconstruction (ACLR). Its recurrence (recyclops) after surgical treatment is poorly understood, with limited research on risk factors and characteristics.

Purpose/hypothesis: The purpose of this study is to determine the recurrence rate of cyclops syndrome after previous surgery and identify associated risk factors. It was hypothesized that the recyclops rate is significant and is associated with certain modifiable and nonmodifiable risk factors.

Study design: Cohort study; Level of evidence, 3.

Methods: This study included all patients who underwent knee arthrolysis for cyclops syndrome after ACLR at a sports surgery center between 2005 and 2022. The primary outcome was the rate of recurrent cyclops syndrome and its associated risk factors. Secondary outcomes included knee range of motion, measured using a goniometer, both preoperatively and 6 weeks postoperatively, with comparisons made between patients with primary and recurrent cyclops cases.

Results: During the study timeframe, 12,200 primary ACLRs were performed, from which a total of 359 patients with cyclops syndrome were found (2.9%), with a mean age of 25.34 ± 6.12 years and a male predominance of 57.38%. The recyclops rate was 6.9% (25 out of 359 patients). Risk factors identified in multivariate analysis were as follows: (1) age (patients >27 years, odds ratio [OR], 11.63 [95% CI, 3.41-39.73]; P < .001); (2) type of graft (quadrupled semitendinosus graft: OR, 5.09 [95% CI, 1.05-24.74]; P = .044); (3) bone-patellar tendon-bone grafts (OR, 26.01 [95% CI, 6.52-103.82]; P < .001); (4) absence of lateral extra-articular procedure (LEAP) (OR, 8.49 [95% CI, 1.64-43.97]; P = .011); and (5) time from ACL surgery to initial cyclops surgery of <7 months (OR, 13.62 [95% CI, 4.07-45.66]; P < .001). At 6 weeks postoperatively, the mean residual extension deficit, after initial arthrolysis, was significantly higher in the relapse group than in the no relapse group, with a median of 5° compared with 0° in the no relapse group (P < .001).

Conclusion: Recyclops syndrome occurred in 6.9% of patients after cyclops arthrolysis. Significant risk factors include age, type of graft, absence of LEAP, and shorter time from ACL surgery to initial cyclops surgery. Among patients who underwent operation for the first time for cyclops, those who had residual extension deficit at 6 weeks postoperatively were more likely to experience recyclops.