Comparison of transfer sites for flexor digitorum longus in a cadaveric adult acquired flatfoot model

Abstract

Posterior tibialis tendon (PTT) dysfunction (PTTD) is associated with adult acquired flatfoot deformity. PTTD is commonly treated with a flexor digitorum longus (FDL) tendon transfer (FDLTT) to the navicular (NAV), medial cuneiform (CUN), or distal residuum of the degraded PTT (rPTT). We assessed the kinetic and kinematic outcomes of these three attachment sites using cadaveric gait simulation. Three transfer locations (NAV, CUN, rPTT) were tested on seven prepared flatfoot models using a robotic gait simulator (RGS). The FDLTT procedures were simulated by pulling on the PTT with biomechanically realistic FDL forces (rPTT) or by pulling on the transected FDL tendon after fixation to the navicular or medial cuneiform (NAV and CUN, respectively). Plantar pressure and foot bone motion were quantified. Peak plantar pressure significantly decreased from the flatfoot condition at the first metatarsal (NAV) and hallux (CUN). No difference was found in the medial-lateral center of pressure. Kinematic findings showed minimal differences between flatfoot and FDLTT specimens. The three locations demonstrated only minimal differences from the flatfoot condition, with the NAV and CUN procedures resulting in decreased medial pressures. Functionally, all three surgical procedures performed similarly.

Passive engineering mechanism enhancement of a flexor digitorum longus tendon transfer procedure

“…In considering the generally non‐significant effects of standard FDL tendon transfer, our results are consistent with previous studies which concluded that the procedure appears to have only a minor effect on altering pedobarographic parameters in the absence of a concomitant bony procedure . Uniquely, PEM‐enhancement enabled expected pedobarographic and kinematic differences not seen by previous investigators . Additionally, these differences compare to those found by other studies which applied combined procedures to achieve desired changes …”

“…). In comparison to previous biomechanical flatfoot studies, our methods produced greater average changes across radiograph measures and showed comparable RGS validation metrics …”

“…). Using a biomechanical flatfoot model, we characterized the pedobarographic and kinematic effects of PEM‐enhancement during the stance phase of gait . As hypothesized, we found that PEM‐enhancement increased the force applied to the medial longitudinal arch and caused a lateral shift in peak plantar pressure and CoP, as well as joint adduction, inversion, and plantar flexion when compared to flatfoot and standard treatment.…”

“…Cutaneous incisions were closed via suture. Specimens were mounted to a mechanical test system (MTS Mini Bionix 858; Eden Prairie, MN) with a 40° heel wedge placed beneath the posteromedial aspect of the hindfoot to enhance calcaneal eversion . An approximately 90 N force was applied to the Achilles’ tendon using a clamp and directional pulley system to better reflect physiologic tendon loading during gait.…”

Design and validation of a foot–ankle dynamic simulator with a 6-degree-of-freedom parallel mechanism

“…The simulation of the stance phase was 2.7 s but the reproduced GRF was smaller than the actual value. [32][33][34][35][36][37][38] Besides that, the earliest passive simulator was designed in 2003 and there was no further development in the follow-up. 39,40 Another passive simulator, UMS, was designed in 2009 and applied to investigate the biomechanical behaviors of a diabetic foot.…”