Assessment of popliteal neurovascular safety during all-inside suturing of the posterior horn of the lateral meniscus using Upright MRIs of the knee joint

Abstract

Background: To examine the risk of injury to the popliteal neurovascular bundle (pNVB) during all-inside repair of the posterior horn of the lateral meniscus (PHLM) using Upright-MRIs.

Methods: Upright-MRIs of 61 knees in extension (ext) and 90°-flexion (flex) were included. Distance D from the PHLM to the pNVB was compared between extended and 90°-flexed position, subgroups with/without joint-effusion and evaluated according to demographics. Portal safety was assessed simulating suturing of the PHLM via four arthroscopy portals. Distance d (shortest space from the simulated suturing-device trajectory lines to the pNVB) was compared among portals in increasing distances from the posterior cruciate ligament (PCL).

Results: D is longer in flex (17.3 ± 6.0 mm) than in ext (11.3 ± 4.2 mm, p < 0.0001). MRIs with joint-effusion displayed longer values of D than scans without joint-effusion (flex: 20.4 ± 7.1 mm vs. 16.1 ± 5.2 mm, p = 0.012). Shorter distances are associated with female gender, lower body weight and lower BMI. At 0 mm from the PCL, the 1 cm-lateral portal was the safest (p < 0.0001) whereas at 3 mm/6mm/9mm/12 mm the 1 cm-medial portal showed the longest d values (p < 0.0001 each).

Conclusion: All-inside suturing of the PHLM is safer in 90°-flexion, in presence of intraarticular fluid and in male patients with increasing weight/BMI. Sutures of the PHLM at 0 mm from the PCL are safer from a 1 cm-lateral portal whereas for tears located ≥ 3 mm from the PCL a 1 cm-medial portal involves a lower neurovascular risk. Upright-MRI proves excellent for preoperative planning to minimize neurovascular risks.

Keywords: All-inside meniscus suture; Popliteal neurovascular bundle; Popliteal vessels; Upright MRI.