Cyclops syndrome was defined as a loss of knee extension after anterior cruciate ligament reconstruction (ACL-R) due to the progressive development of a fibrovascular nodule (defined as cyclops lesions) anteriorly along the ACL graft.
Although the majority of cyclops lesions were asymptomatic, even minor degrees of knee extension loss might be predictive of developing knee osteoarthritis in the long term. With respect to cyclops syndrome, recent study indicated that extension deficit in the early postoperative period was the most important risk factor. In contrast, few studies have investigated risk factors for the development of cyclops lesions because most studies have not examined cyclops lesions using MRI or second-look arthroscopy in all their cases after ACL-R, and those studies had a small number of cases.
The purpose of this study was to evaluate the presence of cyclops lesions using magnetic resonance image (MRI) at 6 and 12 months after ACL-R, and to investigate the associated risk factors of cyclops lesions and syndrome.
A retrospective analysis of patients who underwent ACL-R using bone-patellar tendon-bone (BTPB) or hamstring tendon (HT) autograft from June 2008 to December 2017 was conducted. Graft selection (BPTB autograft or HT autograft) was chosen under consideration of the patient’s preference after detailed explanation of the strengths and weaknesses of each graft with the operating surgeon. The patient with cyclops syndrome was defined as having symptomatic extension deficit (greater than 5 degrees compared to the contralateral knee) at 3 months or more after ACL-R and a cyclops lesion on post-operative MRI.
Predictor variables (age, sex, body mass index [BMI], time from injury to ACL-R, pre-injury Tegner activity score, graft, meniscal and cartilage injury, and notch width index on MRI for the presence of cyclops lesions and syndrome were analyzed with multivariate logistic regression.
Four hundred and fifty-five patients (225 males and 230 females) were enrolled. The average age was 28.0 years old. BPTB autograft was used in 199 patients and HT autograft in 256 patients, respectively. One hundred and four patients (22.9%) had cyclops lesions, and all cyclops lesions were detected on MRI at 6 months post-operatively. Additionally, 20 patients (4.4%) had symptomatic cases of cyclops syndrome.
The risk factors for the presence of cyclops lesions were graft (BPTB) (odds ratio [OR], 2.85; 95% confidence interval [CI], 1.75-4.63; P<0.001) and female sex (OR, 2.03; 95%CI, 1.27-3.25; P=0.003). The presence of cyclops syndrome increased with graft (BPTB) (OR, 18.0; 95% CI, 3.67-88.3; P<0.001), female sex (OR, 3.27; 95% CI, 1.07-10.0; P=0.038), and increased BMI (OR, 1.21; 95% CI, 1.05-1.39; P=0.008).
All cyclops lesions were detected 6 months after ACL-R, and the majority of them were asymptomatic. BPTB autograft and female sex were the significant risk factors for the presence of cyclops lesions and syndrome. Increased BMI was also associated with cyclops syndrome.