Point-Counterpoint: Is The Flexor Digitorum Longus Tendon Transfer Effective For Stage 2 Adult-Acquired Flatfoot?

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Author(s): 
William T. DeCarbo, DPM, AACFAS; Lawrence A. DiDomenico, DPM, FACFAS, Ramy Fahim, DPM, AACFAS, and Zachary Thomas, DPM

Adult-acquired flatfoot deformity is characterized by a collapse of the medial longitudinal arch and loss of the mechanical advantage of the posterior medial soft tissue structures, including the posterior tibial tendon. Key initially described a chronic partial rupture of the posterior tibial tendon.1 Further literature confirmed an association with this pathology and in fact, “dysfunction” of this posterior tibial tendon with adult-acquired flatfoot deformity.

   Various authors have extensively reviewed conservative and surgical management of flatfoot deformity, but debate still exists in the surgical management of stage 2 deformities, especially in the presence of medial column instability and posterior tibial tendon dysfunction (PTTD).

   We will critically review and discuss a surgical technique that consists of procedures of various flatfoot reconstructions without performing a flexor digitorum longus tendon transfer. We believe if one addresses and evaluates the underlying pathology, there is no need to perform the flexor digitorum longus tendon transfer in most cases.

   After this reconstructive surgery, postoperative immobilization enables the posterior tibial tendon to heal and remodel without the need for further surgery. By eliminating the need for an additional procedure, one doesn’t have to address concerns about morbidity that are associated with a flexor digitorum longus tendon transfer.

   Furthermore, we do not believe that a much smaller flexor digitorum longus tendon can adequately replace the work of a much larger and stronger posterior tibial tendon. Additional benefits include less operative time, less anesthesia time, better cosmesis, reduction in postoperative edema, less chance of nerve injury and quicker postoperative rehabilitation.

A Guide To Flatfoot Classification

Johnson and Strom described stages 1-3, and Myerson described the fourth stage.2,3 Stage 1 is painful tenosynovitis of the posterior tibial tendon. Stage 2 consists of a flatfoot deformity with pain and dysfunction of the posterior tibial tendon. Patients maintain normal hindfoot motion during that stage and are able to perform the double limb heel rise test, but are unable to perform the single limb test. Stage 3 involves dysfunction of the posterior tibial tendon with signs of stiffness and arthrosis of the hindfoot.2 Finally, Stage 4 deformities are a progression of stage 3 with associated tibiotalar asymmetry as a result of the prolonged hindfoot valgus.3

   We should note that this classification system provides an organized and categorized system to define the stages of the deformity. However, the system lacks observer reliability as there exists a spectrum of underlying pathologies between the stages. For example, consider the role of the lateral column/midtarsal joint and the instability of the medial column in flatfoot deformity.

What The Literature Shows On Adjunctive Procedures With Posterior Tibial Tendon Augmentation

For the purposes of this article, we will focus on the operative management of stage 2 deformities and review the outcomes of various combination osteotomy procedures with augmented flexor digitorum longus tendon transfers.

   Medial calcaneal osteotomy and posterior tibial tendon augmentation. Surgeons commonly perform an osteotomy to protect the tendon transfer by improving the supinatory capacity of the gastroc soleus complex.4 Brodsky noted significant improvements in the postoperative gait analysis for patients undergoing medial calcaneal osteotomies in conjunction with flexor digitorum longus transfer to the navicular tuberosity.5 He specifically noted improvements in cadence, stride length and ankle push-off. Furthermore, studies by Myerson, Fayzi, Wacker, Guyton, Sammarco and Hockenbury and their respective colleagues demonstrated a high rate of successful results with short to intermediate follow-up.6-10 Those studies were mostly level IV case series but nonetheless demonstrated predictably good outcomes.

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