title: The EndoPearl device increases fixation strength and eliminates construct slippage of hamstring tendon grafts with interference screw fixation.
abstract: OBJECTIVE
  The EndoPearl (Linvatec, Largo, FL), a biodegradable device to augment the femoral interference screw fixation of hamstring tendon grafts has been developed. The first objective of this study was to compare the initial fixation strength of quadrupled hamstring tendons and biodegradable interference screw fixation with and without the application of the EndoPearl device. The second objective was to determine the influence of the EndoPearl device on the fatigue behavior under incremental cyclic loading conditions in a simulation of critical fixation conditions.
  
  
  METHODS
  Biomechanical study.
  
  
  METHODS
  Fresh human hamstring tendons were harvested and grafts were fixed with biodegradable poly-L-lactide interference screws. Twenty proximal calf tibias were used to compare the initial fixation strength of the study and the control group. In the study group, the EndoPearl device was secured to the graft using two No. 5 Ethibond sutures (Ethicon, Somerville, NJ). Specimens were loaded until failure in a materials testing machine. For cyclic testing, human hamstring tendons and 20 distal porcine femurs were used. Critical graft fixation conditions were simulated by increasing tunnel diameter 2 mm over the graft diameter. Grafts were loaded progressively in increments of 100 N until failure; 100 cycles were applied per load increment.
  
  
  RESULTS
  Graft fixation with the additional EndoPearl device had a significantly 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 fixation with the EndoPearl device sustained a significant higher total number of cycles (388.5 +/- 125.6) compared with the control group (152.8 +/- 144.9, P =.002).
  
  
  CONCLUSIONS
  We demonstrated that the augmentation of a hamstring tendon graft with the EndoPearl device increases interference screw fixation strength significantly. Under dynamic loading conditions, specimens of the study group sustained substantially higher loads and a larger number 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 conditions.
authors: Trauma and Reconstructive Surgery, Sports Traumatology and Arthroscopy Service, Charité, Campus Virchow-Clinic, Humboldt-University of Berlin, Germany. andreas.weiler@charite.de
authors: A
authors: A
authors: Weiler
authors: M
authors: M
authors: Richter
authors: G
authors: G
authors: Schmidmaier
authors: F
authors: F
authors: Kandziora
authors: N P
authors: NP
authors: Südkamp
mesh_terms: D020341:Absorbable Implants; D000328:Adult; D000818:Animals; D001863:Bone Screws; D002417:Cattle; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008875:Middle Aged; D010865:Pilot Projects; D011091:Polyesters; D011093:Polyethylene Terephthalates; D013537:Sutures; D013710:Tendons / Q000637:transplantation*; D016474:Weight-Bearing
chemical_list: C014534:Ethibond; D011091:Polyesters; D011093:Polyethylene Terephthalates; C033616:poly(lactide)