Abstract
Studies comparing the biomechanical properties of different meniscal repair systems are limited, and most have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Loading to failure using high radially orientated loads may, therefore, not be the most physiologically relevant in-vitro test for repair of circumferential tears, and determining increases in gapping across repair sites under cyclical loading at lower loads may be of greater importance. This study aimed to determine the load to failure for 4 different meniscal repair techniques, and to assess gapping across repairs under cyclical loading.
Bovine menisci were divided vertically, 5mm from the peripheral edge to simulate a circumferential tear, and then repaired using 1 of 4 techniques: vertical loop sutures using 2-0 PDS, bioabsorbable Meniscal Arrows (Atlantech), T-Fix Suture Bars (Acufex) or Meniscal Fasteners (Mitek). 9 specimens were tested in each group using an Instron 5565 materials testing machine with Merlin control software to determine load to failure. A further 9 specimens in each group were tested by cyclical loading between 5N and 10N at 20mm/min for 25 cycles. Gapping across the repairs under cyclical loading was measured using a digital micrometer and a Differential Voltage Reluctance Transducer.
The peak load to failure values for each repair method did not appear to fit a Gaussian distribution, but were skewed to the left due to some samples failing at lower loads than the main cluster. Results were analysed using the Kruskal-Wallis test, with Dunn’s multiple comparison post test. The results for gapping across the repairs from the cyclical testing all appeared to fit the Gaussian distribution, and these were analysed by Analysis of Variance, with Tukey’s multiple comparison post test. All analysis was performed using Prism (Graph-pad) Software.
The mean loads to failure for each of the repair groups were: Sutures 72.7 N, T-Fix 49.1 N, Fasteners 40.8 N, and Arrows 34.2 N. The load to failure was significantly greater with the Suture group compared to the Arrows (p< 0.01) or the Fasteners (p< 0.05). The mean gapping across the repairs for each of the repair groups after 25 loading cycles were: Sutures 3.29mm, Arrows 2.18mm,Fasteners 3.99mm,andT-Fix 3.47mm.The mean gapping was significantly less for the Arrows compared to the Sutures (p< 0.05), the Fasteners (p< 0.01), or the T-Fix (p< 0.05).
The results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold under lower loads, with the least gapping across repairs under cyclical loading by this testing protocol.
Abstracts prepared by Dr P E Watkins, Hodgkin Building, Guys Campus, King’s College London.
