Summary

Meniscal repair with a suture interval spacing of 7mm and below demonstrates statistically significant lower gap formation and higher construct stiffness during cyclic loading than interval spacings greater than 7mm.

Abstract

Background

The probability of meniscal healing after meniscal repair is influenced by the resistance against gap formations during repetitive loading. Reduced gap formation is thought to enhance the healing potential, as the separation of meniscal edges facilitates the influx of synovial fluid, hindering the regenerative process and impeding meniscal healing. Correct suture placement is critical in achieving optimal fixation strength; however, no established guidelines exist regarding the optimal interval spacing between multiple meniscal sutures.This study aimed to investigate the impact of varying suture interval spacings on the biomechanical properties of longitudinal meniscal repairs.

Hypothesis

There exists a critical limit for meniscal suture spacing, beyond which gap formation during cyclic loading increases, while the stiffness of the repair construct decreases.

Study Design: Controlled laboratory study.

Methods

Complete longitudinal meniscal tears were created in 50 bovine menisci. All tears were repaired using two 2-0 braided sutures (Ultrabraid, Smith & Nephew) with vertical sutures applied via an inside-out technique. Five distinct suture spacings (3 mm, 5 mm, 7 mm, 9 mm, and 11 mm) were tested, with ten samples assigned to each spacing group. Sutures were tensioned with a final manual 35 N using a tensiometer. A custom-designed testing apparatus was created to enable uniform radial load application through a pulley system via an uniaxial universal testing machine. Each sample underwent 1000 loading cycles between 5-20 N at a crosshead speed of 75 mm/min. Meniscus repair gapping, defined as the increment in distance between the two optical markers, was continuously measured during cycling loading after 10, 100, 500, and 1000 cycles and during load-to-failure using a non-contact digital image correlation (DIC) system. Gap formation, cyclic stiffness, and load to produce a 1mm gap were measured.

Results

Meniscus repairs with suture distances of 3mm, 5mm, and 7mm demonstrated significantly smaller gap formation—on average, 36% less—compared to those with 9mm and 11mm. There were no significant differences in gap formation among the suture distances of 3mm, 5mm, and 7mm. Construct stiffness was significantly higher with suture interval spacings of 7mm and below, in contrast to 9mm and above (all p < .05). No significant difference in construct stiffness was observed among the 3mm, 5mm, and 7mm suture intervals. There was a trend indicating that higher loads were required to produce a 1mm gap in suture distances of 7mm and below, compared to 9mm and above. Suture breakage occurred in 76% of cases (38/50), suture cut-through in 22% (11/50), and a combination of both in 2% (1/50). Failure mode did not correlate with suture distance.

Conclusion

Meniscal repair with a suture interval spacing of 7mm and below demonstrates statistically significant lower gap formation and higher construct stiffness during cyclic loading than interval spacings greater than 7mm. Larger gapping may impede meniscus healing after meniscus repair. Based on this biomechanical data, a standard 3 cm longitudinal meniscus tear would require the placement of four to five sutures to achieve optimal fixation.