Purpose: This biomechanical study compared the fixation characteristics of horizontally or vertically implanted FasT-Fix devices (Smith & Nephew, Endoscopy Division, Andover, MA) consisting of two 5-mm PLLA suture T-bar anchors with a pretied self-sliding knot (No. 0 nonabsorbable, USP, braided polyester suture material) and the RapidLoc device (Mitek Surgical Products, Westwood, MA) consisting of a PLLA T-bar anchor or "backstop," a connecting suture (No. 2 nonbiodegradable Ethibond; Ethicon, Somerville, NJ), and a PLLA grommet, for repairing posterior third lesions in human menisci.
Type of study: Controlled laboratory biomechanical study.
Methods: After repair of a vertical longitudinal meniscus lesion with either vertically or horizontally implanted FasT-Fix devices or RapidLoc devices, 3 groups of 6 specimens underwent cyclic loading (5 mm/minute, cycling between 5 and 50 N at 1 Hz for 500 cycles) before load to failure testing on a servo hydraulic device. One-way analysis of variance and Tukey HSD post hoc tests were used to evaluate group differences (P < .05).
Results: The vertical FasT-Fix device group (3.2 +/- 0.49 mm) had less displacement after cyclic testing than either the horizontal FasT-Fix (4.4 +/- 0.73 mm, P = .003) or the RapidLoc (4.6 +/- 0.22 mm, P = .002) device groups. The vertical FasT-Fix device group had greater stiffness during cyclic testing (14.4 +/- 2.1 N/mm) than the horizontal FasT-Fix (10.4 +/- 1.6 N/mm, P = .0001) or the RapidLoc (9.7 +/- 0.44 N/mm, P = .0001) device groups. During load to failure testing, the vertical FasT-Fix group (125.3 +/- 39 N) had 28% greater strength than the horizontal FasT-Fix device group (89.7 +/- 14 N, P = .02) and 30% greater strength than the RapidLoc device group (87.1 +/- 13 N, P = .028), whereas displacement and stiffness did not show statistically significant group differences.
Conclusions: The vertical FasT-Fix group had superior biomechanical characteristics for meniscal fixation during cyclic and load to failure testing compared with horizontal FasT-Fix or RapidLoc devices.
Clinical relevance: Although the RapidLoc devices provided fixation characteristics comparable to horizontally implanted FasT-Fix devices, vertically implanted FasT-Fix devices may provide superior all-inside fixation.