Summary

Gold-standard inside-out meniscus repair results not only in subjective perceptions of healthy knee in around 85-90% of the operated cases, but also in good restoration of objectively measured functional parameters of strength and stability.

Abstract

Objective

To quantitatively measure strength and balance performance after inside-out repair of long meniscus tears in a biomechanical laboratory set-up and identify prognostic factors which may sharpen decision-making during meniscus surgery.

Methods

Since 2012, inside-out meniscus repair technique is consecutively implemented by a single surgeon for long tears requiring ≥3 sutures. At minimum 2-year follow-up, assessment of outcomes includes activity level scores, IKDC-subjective, and KOOS sub-scores. In men with uninjured contralateral limb, knee isokinetic extensor and flexor measures, time-to-stability and ground reaction forces at landing, and single-legged hop for distance are measured in a laboratory setup with calculation of their respective side-to-side symmetry indices (SI)[%]. Correlation coefficients are calculated between patient and injury demographics, and the clinical and biomechanical outcomes.

Results

Until August 2024, 95 patients which underwent repair of long meniscus tears (47 with concomitant ACLR) were reviewed. Of these, 12 were identified as "repair failure" (i.e., underwent re-arthroscopy for unhealed meniscus repairs), while the remaining 83 underwent clinical evaluation at minimum 2-year follow-up. Of these 83 patients (17 women), 41 men with unilateral injuries were eligible and available to undergo functional biomechanical evaluations. In the 83-patient group, IKDC-subjective at follow-up=91±8, KOOS-Symptoms=87±11, KOOS-Sports=79±19. Tegner level=6 [median] compared to 7 at pre-injury. In the 41-patient group who underwent the biomechanical functional assessment (31 cases of medial meniscus repair; 21 cases with concomitant ACLR), mean age at surgery=25 years (range, 15-55), mean follow-up=4 years (range, 2-8.5). Good recovery of isokinetic performance was demonstrated (SI flexors= 0-5%, SI extensors= 0-10%), although reduced performance in the operated compared to the uninjured leg was noticed for extensors torque and work measures (p<0.05). Excellent symmetry was observed in the single-legged hop for distance (SI<5%). SIs of time-to-stability and ground reaction force measures at landing were mean 15% and <5%, respectively. In patients with concomitant ACLR, time-to-stability was slightly longer compared to isolated meniscus repair subgroup (p=0.02). Age, time delay from injury to surgery, preinjury activity levels, or meniscus laterality were not associated with SIs of the biomechanical measures. Preinjury Tegner and Marx scores were powerful predictors of Tegner and Marx activity intensities at follow-up (r=0.5, p<0.01).

Conclusions

Gold-standard inside-out meniscus repair results not only in subjective perceptions of healthy knee in around 85-90% of the operated cases, but also in good restoration of objectively measured functional parameters of strength and stability. While further analysis in this clinical-biomechanical research will assist in identifying specific predictors of specific outcomes and in elaborating decision-making algorithms for meniscus repair, preliminary conclusions support that "Save the Meniscus" guiding principle should remain the surgeon's default. Thus, gold-standard inside-out repair for long meniscus tears with adequate tissue should be advocated while concerns related to tear chronicity, meniscus laterality, or patient age should be minimized in the decision-making process.