Anterior cruciate ligament reconstruction carried after 12 months from injury would increase the incidence of medial meniscal tear in patient without initially concurrent meniscal tear.
The incidence of meniscal tears increases with delayed ACL reconstruction, which may occur with or after ACL injury. We determined the correlation between timing of surgery and incidence of meniscal tears in ACL-deficient knees with initially intact meniscus.
We retrospectively reviewed 387 patients who had undergone primary ACL reconstruction. Time of initial ACL injury to MRI examination and time to surgery were recorded. MRIs and intraoperative arthroscopic images were reviewed. The type of tear noted during surgery was categorized according to the modified ISAKOS classification. Patients were divided into early (surgery within 12 months of injury) and late (>12 months from injury) groups.
There were 216 and 257 patients with intact medial and lateral menisci, respectively, on post-injury MRI studies. The incidence of medial meniscus tears (MMT) was significantly higher than that of lateral meniscus tears (LMT) during ACL reconstruction (33.8% vs. 19.8%; p < 0.001). The incidence of MMT was higher in the late surgery group (53.7% vs. 29.1%; p = 0.004; odds ratio = 2.815). The incidence of LMT was slightly higher in the late surgery group (23.8% vs. 18.6%; p = 0.364). Patients who underwent ACL reconstruction within 3 months after injury (acute phase) had a significantly higher incidence of LMT than MMT (21.4% vs. 5.1%; p = 0.002).
For patients without concurrent meniscal injuries with the ACL tear, the incidence of MMT significantly increased if ACL reconstruction was performed >12 months after injury. During the acute phase, the incidence of LMT was higher than that of MMT. The medial meniscus was more prone to injury than the lateral meniscus in ACL-deficient knee. The lateral meniscus was prone to injury with or during the acute phase of ACL injury. ACL reconstruction should be performed early to reduce the risk of meniscal tears.