Summary

Although outside-in meniscus repair appears to be disadvantageous in terms of adjusting meniscus tension during the repair, it shows no difference from the all-inside technique in terms of meniscus extrusion.

Abstract

Meniscus extrusion refers to the displacement of the meniscus tissue beyond the tibial plateau. Normally, the meniscus provides load distribution and stability in the knee joint, but when extrusion occurs, these functions may be impaired. Meniscus extrusions greater than 3 mm are generally considered pathological and can increase the risk of knee osteoarthritis. Extrusion is associated with meniscus tears, particularly root tears and degenerative changes. It is usually diagnosed through magnetic resonance imaging (MRI), which evaluates the position of the meniscus and its relationship to surrounding structures.
We hypothesize that meniscus extrusion would be greater in repairs performed using the inside-out technique compared to the all-inside technique, due to the fact that the sutures are tied manually and the tension of the meniscus cannot be directly adjusted during the knotting process in the inside-out technique.
All patients aged 18-35 who underwent meniscus repair were retrospectively identified from our patient records. Degenerative/chronic tears, root tears, non-vertical tears, and re-ruptures were excluded from the study. Patients in which both all-inside and outside-in techniques were applied to the same meniscus were also excluded from the study. The concurrent performance of other surgeries, such as anterior cruciate ligament reconstruction or osteochondral lesion treatment, during meniscus surgery was not considered an exclusion criterion. Patients who had an MRI of the same knee for follow-up or another reason at least one year after surgery were included. As result, a total of 217 patients who underwent meniscus repair using all-inside or outside-in techniques for acute-vertical tears were identified.
Of the patients, 145 were male and 72 were female. A total of 130 repairs were performed on the lateral meniscus and 87 on the medial meniscus. Along with meniscus repair, 103 patients underwent ACL reconstruction, 21 patients underwent osteochondral lesion fixation/mosaicplasty, and 8 patients underwent concurrent surgery due to a tibial plateau fracture. Meniscus repair was performed using the all-inside technique in 122 patients and the outside-in technique in 95 patients.
A 3 mm threshold has been accepted for both the medial and lateral meniscus, and extrusions greater than this value are considered pathological. Coronal slices in T2 sequences of knee MRIs taken at least one year after surgery were examined. Out of 122 patients who underwent all-inside repair, 85 (69%) showed no extrusion, while 37 (31%) had a pathological extrusion of more than 3 mm. In the outside-in repair group, 60 patients (63%) had no MRI findings suggestive of extrusion, while 35 patients (37%) were evaluated to have extrusion. When both groups were compared in terms of meniscus extrusion, no significant difference was found between the groups (p=0.3).
According to our data, there was no significant difference in meniscus extrusion between the two groups. This finding suggests that the rates of extrusion following meniscus repair may be similar regardless of the surgical technique used. Specifically, investigating the long-term clinical outcomes of different techniques may provide valuable insights into determining the optimal surgical approach that minimizes meniscus extrusion.