Medical Student Steadman Philippon Research Institute Gainesville, FL, United States
Disclosure(s): No financial relationships to disclose
Disclosure(s):
Taylor K. Calibo, MS: No financial relationships to disclose
Objectives: The purpose of this study was to isolate the effect of suture configuration on proximal hamstring repair by comparing the failure load, stiffness, and failure mode of Krackow, Mason-Allen, horizontal mattress, and simple suture configurations at the tendon-suture interface. We hypothesized that running-locking configurations (Krackow and Mason-Allen) would demonstrate higher load to failure compared to simpler techniques (horizontal mattress and simple suture). Methods: Twenty-four fresh frozen proximal hamstring units were prepared (mean age 64.5 years; range 42-75; 10 males, 14 females). The conjoined tendon was exposed and split at the fascial plane to create independent test units and randomized to simple, horizontal mattress, Krackow, or Mason-Allen configurations (n=6 per group). Sutures were placed 10 mm from the edge and secured to a 1 cm steel rod to standardize the tendon suture interface. Repair constructs were mounted in a custom fixture aligned to the tendon axis. After preconditioning at 10N for 60s and performing 100 cycles from 20 to 200N at 0.5 Hz, failure load was performed at a constant rate of displacement of 33 mm/min. Simple sutures demonstrated early failure during pre-conditioning and were therefore tested without cyclic preconditioning. Force-displacement data were sampled at 100 Hz. Linear stiffness was calculated as the slope of the linear region of the load displacement curve. Two observers recorded failure mode. Results: Ultimate failure load was higher for Krackow versus simple suture (283.0 +- 67.9 N vs 141.2 +- 44.6 N; p=0.002) and Mason-Allen versus simple suture (282.5 +- 102.8 N; p=0.002). Horizontal mattress also exceeded simple suture (239.7 +- 68.9 N; p=0.018). Linear stiffness did not differ among groups (simple 48.9 +- 22.5, horizontal mattress 72.9 +- 26.3, Krackow 59.7 +- 22.7, Mason-Allen 74.4 +- 28.4 N/mm; all p>0.05). The predominant failure mode was suture pull through at the tendon-suture interface (75% of specimens), followed by suture failure at the repair site (12.5%), midsubstance rupture (8.3%) and tendon failure (4.2%). Conclusions: This study evaluated the biomechanical performance of four common suture configurations at the proximal hamstring tendon-suture interface. In confirmation of the hypotheses, Mason-Allen and Krackow produced nearly a twofold increase in time-zero strength compared with simple sutures without compromising construct stiffness. Horizontal mattress sutures also demonstrated a greater mean failure load than simple sutures, though the ultimate failure load of the horizontal mattress configuration was not statistically different from the Mason-Allen or Krackow configurations. Lastly, the predominance of suture pull-through as the failure mode reinforces the tendon-suture interface as a key determinant of construct strength in hamstring repair. Limitations include a cadaveric time-zero design, absence of biologic healing and complete constructs and the use of older specimens. In this model, locking configurations double time zero strength without a stiffness penalty, which supports their use when early fixation strength matters, including high-demand patients, subacute tears with compromised tendon quality, or limited working length for purchase. These findings provide a biomechanical basis for future development and refinement of all-endoscopic locking techniques.
