Cyclic testing of pullout sutures and micro-Mitek suture anchors in flexor digitorum profundus tendon distal fixation

Purpose: Little data exist comparing the strength of traditional methods of fixation in a flexor digitorum profundus tendon with the use of a suture anchor. In vitro cyclic testing simulating a passive mobilization protocol was used to compare the repair of a flexor digitorum profundus tendon using a single micro-Mitek anchor (Mitek, Westwood, MA) or a modified Bunnell 2-strand pullout technique using a monofilament or a braided polyester suture. Methods: Twenty-four fresh-frozen cadaveric fingers were divided randomly into 4 repair groups (n = 6 each): a micro-Mitek with a 3-0 braided polyester suture or a 3-0 monofilament suture, or a modified Bunnell technique with a 3-0 braided polyester suture or a 3-0 monofilament suture. After repair the specimens were loaded cyclically from 2 to 15 N at 5 N/s, for a total of 500 cycles. Gap formation at the tendon-bone interface was assessed every 100 cycles. Samples were tested to failure at the completion of 500 cycles. Results: No specimens failed catastrophically during cyclic testing. A significantly greater gap formed using the monofilament sutures compared with the braided polyester sutures with both repair techniques. Load to failure in the modified Bunnell technique was superior to the micro-Mitek with both suture types. The modified Bunnell technique using a braided polyester suture was superior to the monofilament suture whereas the suture type did not alter the properties of the micro-Mitek repair. Conclusions: Significant gap formation with the use of a monofilament suture may be of concern. The use of a braided polyester suture when removal of the pullout suture is required as in the Bunnell technique also needs to be considered.