Purpose: The aim of this study was to compare the initial fixation strength of tendon grafts between different sizes of bioabsorbable interference screws (BioScrew; Linvatec, Largo, FL) with bioabsorbable bead (EndoPearl; Linvatec) augmentation through biomechanical analysis of a porcine femoral bone model.
Methods: Forty pairs of porcine femurs and porcine flexor digitorum profundus tendons were divided into control and study groups. In the control group 8 x 30-mm BioScrews alone (n = 10) were inserted, whereas different sizes of BioScrews, measuring 7 x 30 mm (n = 10), 8 x 30 mm (n = 10), and 9 x 30 mm (n = 10), with 8-mm EndoPearl augmentation were inserted individually for fixation of tendon grafts in the study groups. All specimens were cyclically loaded with axial forces between 50 and 250 N at 1 Hz for 3,000 cycles and then incrementally loaded to failure at a rate of 150 mm/min.
Results: BioScrews with EndoPearl augmentation had a significantly higher failure load than BioScrews alone (8-mm BioScrew alone v 8-mm BioScrew and EndoPearl, P < .05). There were no significant differences in the ultimate failure load (8 mm v 7 mm and 9 mm, P = .201 and P = .871, respectively), stiffness (8 mm v 7 mm and 9 mm, P = .789 and P = .823, respectively), displacement (8 mm v 7 mm and 9 mm, P = .695 and P = .781, respectively), and bone mineral density (P = .728 for all comparisons) except insertion torque (8 mm v 7 mm and 9 mm, P = .045 and P = .518, respectively) between study groups. Less tendon laceration by the screw thread was noted in the group in which smaller-sized BioScrews were used.
Conclusions: When EndoPearl augmentation was used, smaller-sized BioScrews (BioScrew size 1 mm smaller than bone tunnel) offered equivalent graft fixation strength to BioScrews of similar or larger sizes.
Clinical relevance: Smaller-sized BioScrews can be chosen if EndoPearl augmentation has been used, and EndoPearl augmentation may reduce the risk of tendon rupture while BioScrews are inserted.