Flexor Digitorum Longus Transfer for Posterior Tibial Tendon Dysfunction is the Standard of Care: Does the Evidence Support It?

Abstract

Category: Basic Sciences/Biologics; Hindfoot; Other Introduction/Purpose: Flexor digitorum longus (FDL) transfer, in conjunction with osseous procedures, is used routinely for the treatment of posterior tibial tendon dysfunction (PTTD). It is well established however that the relative power of the FDL tendon is significantly inferior than that of the native posterior tibial tendon. The purpose of this study is to systematically evaluate the evidence that supports or refutes the use of an FDL transfer in the surgical treatment of PTTD. Methods: A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta- Analysis. Using the terms 'flexor digitorum longus OR FDL AND posterior tibial tendon dysfunction OR PTTD OR adult acquired flatfoot OR AAFD' we searched the PubMed/Medline database. Both clinical and biomechanical studies were eligible for inclusion. Results: Forty-one studies met the inclusion criteria, including 31 clinical studies and 10 biomechanical in vitro studies. All 31 clinical studies consisted of Level IV evidence, and support the use of an FDL transfer. There was significant heterogeneity of the clinical evidence due to the variety of concomitant procedures. Of the 10 biomechanical in vitro studies, 2 support the use of an FDL transfer, although these did not assess the procedure in isolation. 8 biomechanical in vitro studies specifically assessing the effect on of an FDL transfer contradict its use for PTTD. Conclusion: There is poor quality clinical evidence to support the use of an FDL transfer for PTTD and the biomechanical literature refutes the use of the procedure. It remains unknown if the clinical improvement reported in the literature can be attributed to the FDL transfer or the concomitant osseous procedures. Additional studies are needed to assess the validity of the FDL transfer and whether alternatives are available to preserve the PTT muscle.