Clinical Outcomes of Hidden Lesions of the Medial Meniscus Treated With a Flexible All-Inside Device

Purpose Ramp lesions are characteristic injuries associated with anterior cruciate ligament (ACL) rupture and involve disruption of the meniscus-synovium interface near the posterior horn of the medial meniscus. Among these, tibiofibular side-only tears at the bursal attachment, so-called hidden lesions, are difficult to visualize from the standard anterior portal, making their diagnosis and treatment challenging. This study examined the outcomes of suturing hidden lesions using an all-inside technique with the FAST-FIX device from the anterior portal, with a focus on clinical results and the healing status assessed by postoperative second-look arthroscopy. Methods Forty patients with hidden lesions repaired using the FAST-FIX device (Smith & Nephew, Hertfordshire, UK) who underwent second-look arthroscopy from 2020 to 2023 were included. Until 2022, a non-flexible device (FAST-FIX 360), in which the shaft does not bend, was used (n = 21). After 2022, a flexible device (FAST-FIX FLEX), which allows bending of the needle and shaft, was used (n = 19). Meniscal healing was evaluated during second-look arthroscopy, and clinical outcomes were assessed using the Lysholm score and Knee Injury and Osteoarthritis Outcome Score (KOOS). Results With the non-flexible FAST-FIX 360, complete healing, partial healing, and re-tear were observed in 62%, 9%, and 29% of cases, respectively. In contrast, with the flexible FAST-FIX FLEX, complete healing, partial healing, and re-tear were observed in 74%, 21%, and 5% of cases, respectively. The flexible device demonstrated a significantly lower re-tear rate than the non-flexible device. Although the complete healing rate was higher in the flexible group, the difference was not statistically significant. Lysholm scores and KOOS did not differ significantly between the two groups. Discussion The anterior-portal repair of ramp lesions using all-inside devices results in modest healing rates due to the difficulty of penetrating the posterior horn. In the present study, incomplete healing occurred in 29% of cases using the non-flexible device, whereas the failure of healing with the flexible device was observed in only 1 of 19 cases. The flexibility of the device allows for better capture of the posteroinferior capsule and meniscotibial ligaments, facilitating a more secure repair. Therefore, the anterior-portal repair of hidden ramp lesions using a flexible all-inside device may achieve favorable healing outcomes.