The EndoPearl device increases fixation strength and eliminates construct slippage of hamstring tendon grafts with interference screw fixation

The EndoPearl (Linvatec, Largo, FL), a biodegradable device to augment the femoral interference screw fixation of hamstring tendon grafts has been dev eloped. The first objective of this study was to compare the initial fixati on strength of quadrupled hamstring tendons and biodegradable interference screw fixation with and without the application of the EndoPearl device. Th e second objective was to determine the influence of the EndoPearl device o n the fatigue behavior under incremental cyclic loading conditions in a sim ulation of critical fixation conditions. Type of Study: Biomechanical study . Methods: Fresh human hamstring tendons were harvested and,grafts were fix ed with biodegradable poly-L-lactide interference screws. Twenty proximal c alf tibias were used to compare the initial fixation strength of the study and the control group. Ln the study group, the EndoPearl device was secured to the graft using two No, 5 Ethibond sutures (Ethicon, Somerville, NJ). S pecimens were loaded until failure in a materials testing machine. For cycl ic testing, human hamstring tendons and 20 distal porcine femurs were used. Critical graft fixation conditions were simulated by increasing tunnel dia meter 2 mm over the graft diameter. Grafts were loaded progressively in inc rements of 100 N until failure; 100 cycles were applied per load increment. Results: Graft fixation with the additional EndoPearl device had a signifi cantly higher maximum load to failure (658.9 +/- 118.1 N v 385.9 +/- 185.6 N, P = .003) and stiffness (41.7 +/- 11 N/mm v 25.7 +/-: 8.5 N/mm), Graft f ixation with the EndoPearl device sustained a significant higher total numb er of cycles (388.5 +/- 125.6) compared with the control group (152.8 +/- 1 44.9, P = .002). Conclusions: We demonstrated that the augmentation of a ha mstring tendon graft with the EndoPearl device increases interference screw fixation strength significantly. Under dynamic loading conditions, specime ns of the study group sustained substantially higher loads and a larger num ber of cycles, which indicates a greater resistance to graft slippage. The application of the EndoPearl device may also allow for a secure soft-tissue graft fixation with interference screws in cases of critical fixation cond itions.