Summary

The remnant preservation technique may contribute to the remodeling of the graft into ligament-like tissue without increasing the incidence of cyclops lesions or cyclops syndrome.

Abstract

Background

During anterior cruciate ligament (ACL) reconstruction, remnant preservation has been reported to improve revascularization. However, its impact on the incidence of cyclops lesions and postoperative knee instability is still not well understood. This study aimed to evaluate the effects of remnant preservation on the incidence of cyclops lesions and postoperative knee instability during ACL reconstruction and second-look arthroscopy.

Methods

We retrospectively analyzed 164 patients (66 male, 98 female; average age 27.2 years) who underwent primary double-bundle ACL reconstruction using hamstring autograft tendon between June 2016 and April 2023, followed by second-look arthroscopy. Patients were divided into two groups based on remnant status at the end of ACL reconstruction: 119 in the remnant-preserved group (Group P) and 45 in the non-preserved group (Group N). Due to significant preoperative differences in anterior tibial translation (ATT), pivot shift grade, and meniscal injury, propensity score matching was used to adjust for these variables. We assessed the incidence of cyclops lesions and cyclops syndrome, side-to-side differences (SSD) in ATT, residual pivot shift rate, and quantitative measurement (side-to-side ratio (SSR) in acceleration (m/s2) and external rotational angular velocity (ERAV) (deg/s)) of pivot shift using inertial sensor. Graft quality was evaluated during second-look arthroscopy using scores for graft laceration and synovial coverage based on the previous report. Cyclops lesions were classified into four subgroups based on location: femoral side (type 1), midsubstance (type 2), tibial side (type 3), and anterior (type 4) of the ACL graft. Cyclops syndrome was defined as a cyclops lesion with extension limitation. Statistical analysis was performed using Student’s t-test, Mann-Whitney U test, and Fisher’s exact test, with significance set at P < .05.

Results

After propensity score matching, each group included 29 cases with no significant differences in patient characteristics. At the time of second-look arthroscopy, there were no significant differences in the incidence of the cyclops legion, the cyclops syndrome between the two groups. The graft scores, which assess graft quality at the time of second-look arthroscopy, were 5.0 points in Group P and 4.2 points in Group N, respectively (P = .064). No significant differences were observed in ATT, residual pivot shift rate, or quantitative measurement of pivot shift.

Discussion

The most important finding of this study was that there was no difference in the incidence of cyclops lesions, cyclops syndrome and postoperative knee instability between the remnant-preserved group and the non-preserved group. Additionally, there was no significant difference between the two groups regarding graft quality, as assessed by the graft scores; however, the remnant-preserved group tended to show higher graft scores compared to the non-preserved group. These findings suggested that the remnant preservation technique may contribute to the remodeling of the graft into ligament-like tissue without increasing the incidence of cyclops lesions or cyclops syndrome.

Conclusion

Remnant preservation during ACL reconstruction did not significantly affect the incidence of cyclops lesions or cyclops syndrome, nor postoperative knee instability. The remnant-preserved group showed a tendency for better graft quality; however, no significant difference was found between the two groups.