SLR - June 2018 - Annie P. Stroze

Flexor Digitorum Longus Tendon Transfer to the Navicular: Tendon-to-Tendon Repair Is Stronger Compared with Interference Screw Fixation

Reference: Marsland, D. Stephen, JM. Calder, T. Amis, AA. Calder, JDF. Flexor Digitorum Longus Tendon Transfer to the Navicular: Tendon-to-Tendon Repair Is Stronger Compared with Interference Screw Fixation. Knee Surg Sports Traumatol Arthrosc. 2018 April 07.

Scientific Literature Review

Reviewed By: Annie P. Stroze, DPM
Residency Program: Wheaton Franciscan, St. Joseph’s, Milwaukee, WI

Podiatric Relevance:
The flexor digitorum longus tendon transfer (FDL) is commonly performed for Stage 2 flatfoot deformity correction. Current postoperative protocols recommend four to six weeks nonweightbearing and immobilization, and advances in surgical technique hope to decrease the time to return to activity. This article compares tendon transfer techniques involving tendon to tendon (TT) repair versus interference screw (ISF) fixation, investigating tendon displacement under cyclic loading in cadaveric foot models. The authors hypothesize that there is no difference in the load to failure.

Methods: This is a level three study. Twenty-four cadaveric limbs were used to perform 12 TT repairs and 12 ISF repairs. Standardized machine was used to load specimens at 150N for 1,000 cycles; load to failure and tendon displacement was measured. A statistical analysis was then performed using ANOVA and independent t-test, p<0.05.

Results: There was no difference in tendon displacement (less than 2 mm in both groups); however, there were two early failures in the ISF group and none in the TT group. This resulted in a greater load to failure in TT repair (459 +/- 96 N) versus ISF repair (327 +/- 76 N). All specimens with ISF failed at the bone-screw interface, and the TT group failed either at the bone tunnel (6), sutures (5) or midtendon rupture (1).

Conclusions: The authors then concluded that the traditional technique is stronger and ultimately more reliable. Authors as a result recommend early active range of motion and protected weightbearing following an FDL transfer. Based on the study presented, conclusions are limited by the fact that the study was performed on cadaveric specimens. Additionally, individual patient demographics should be considered, as well as length of time needed to perform each procedure. These considerations often carry equal weight and consideration when compared to strength of repair. More often than not, the FDL tendon transfer is not performed as an independent procedure and is supplemented by osseous procedures. Therefore, patients’ early rehabilitation is more greatly limited by time to bone healing. This study gives credit to the strength of TT repair and should make surgeons cognizant that more advanced hardware does not equate to stronger repairs.

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