Abstract
Suture anchors have gained popularity in recent years, particularly owing to their ease of use for attaching soft tissues to bone and improved biomechanical properties. Three methods to reattach avulsed finger flexor tendons to the distal phalanx were biomechanically compared: a 1.8mm metal Mitek barbed suture anchor, twin 1.3mm PLA suture anchors (Microfix), or a pull-out suture over a button. The suture-anchor interface was tested by pulling the suture at 0, 45, 90° to the anchor's axis. The anchors were tested similarly in plastic foam bone substitute. Repairs of transected tendons in cadaveric fingers were loaded cyclically, then to failure.
The results were subject to statistical analysis using Student t test (p< 0.001) and 1-way ANOVA (p<0.0001). The suture failed prematurely if pulled across the axis of the anchor. Conversely, fixation in bone substitute was stronger when pulling at an angle from the axis. Cyclic loads caused significantly more gap formation in-vitro with twin 1.3mm anchors than the other methods; this method was significantly weaker. The 1.8mm anchor gave similar performance to the pull-out suture and button, while the twin 1.3mm anchors were weaker and vulnerable to gap formation even with passive motion alone.
A suture anchor embedded at between 45 and 90o to the direction of pull gave greater strength than if the pull was in-line. The absorbable 1.3 mm Microfix PLA anchors appeared to be a weak construct, even when twin 1.3 mm anchors were compared to a single metallic 1.8 mm Mitek anchor or the pull-out suture over button technique. All three methods are likely to be satisfactory for reattachment of finger flexor tendons if a low load or non-loading rehabilitation of the hand is planned; however the gap formation on cyclic loading with the Microfix is a concern even if patients are restricted to passive motion.
