A novel needleless graft-grasping suture (Ram Knot) for ACL reconstruction: a biomechanical study

Abstract Background This study describes the Ram Knot, a novel fully needleless graft-grasping suture technique for hamstring tendon autograft preparation in anterior cruciate ligament reconstruction (ACLR) comparing its biomechanical performance with the traditional whipstitch technique. Methods Porcine flexor tendons (n = 12) were standardised and randomly allocated to two groups: Ram Knot (RK) and whipstitch (WS) (n = 6 each). Specimens were subdivided into Single-Step Testing (SST) and Double-Step Testing (DST) protocols (n = 3 per subgroup). Biomechanical testing was performed using an Instron mechanical testing system and consisted of three phases: pre-tensioning (10–100 N), cyclic loading (200 cycles between 10–200 N), and load-to-failure testing. Outcome measures included ultimate failure load, elongation (E1–E3), stiffness, and failure mode. Results All specimens failed by suture rupture. There were no statistically significant differences in ultimate failure load or cyclic displacement between RK and WS groups. In SST conditions, WS demonstrated a higher mean failure load than RK (545.1 N vs 423.5 N), whereas in DST conditions RK demonstrated a higher mean failure load (382.5 N vs 359 N); these differences were not statistically significant. The RK demonstrated significantly greater stiffness (p = 0.004) and reduced elongation at failure (E3) (p = 0.007) compared with WS. Pre-tension elongation (E1) was also significantly lower in the RK group (p = 0.025). Qualitative analysis demonstrated minimal slippage of the primary loop in RK constructs, whereas WS constructs exhibited progressive tendon damage at the suture–tendon interface. Conclusion The Ram Knot demonstrates biomechanical performance comparable to the traditional whipstitch technique, with significantly increased stiffness and reduced elongation. In addition, it provides practical advantages including faster graft preparation, elimination of needle passes, and reduced tendon damage. These findings suggest that Ram Knot represents a mechanically reliable and efficient alternative for hamstring graft preparation in ACL reconstruction.