Tendoscopy-Assisted Flexor Digitorum Longus Transfer and Spring Ligament Synthetic Suture Tape Reconstruction for Flexible Progressing Collapsing Foot Deformity
Keywords: Spring ligament; FDL; Posterior Tibial Tendon Dysfunction
Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex deformity that is predisposed to by failure of the spring ligament, resulting in peritalar subluxation. A medializing calcaneal osteotomy and flexor digitorum longus (FDL) tendon transfer are standard surgical procedures for a symptomatic flexible deformity. Endoscopic-assisted FDL transfer and a minimally invasive medializing calcaneal osteotomy (MIMCO), allow a fully MIS approach to address flat foot reconstruction. Concerns remain regarding low correction potential, without surgically addressing the attenuated spring ligament. Spring ligament augmentation with an internal brace provides benefits of high resistance to forefoot lateralization, reliably improved radiographic parameters, and patient-reported outcomes. We describe a tendoscopic-assisted FDL tendon transfer and a spring ligament synthetic suture tape reconstruction technique, used in conjunction with a MIMCO.
Methods: Commence with MIMCO. Once complete, position the patient into a supine position. Mark and place portals at the sustentaculum tali and 0.5cm under the navicular. View via proximal and work via distal portal. Identify FDL and divide its sheath distally until the knot of Henry is identified. Tack the FDL tendon with fiberwire using labral Scorpion suture passer. Secure the stitch, deliver the tendon outside the distal portal and cut it long. Whipstitch the FDL and pull it outside the proximal portal. Under fluoroscopy guidance introduce fibertape loaded 3.5 siwvelock into the sustentaculum tali. Establisch navicular tunnel 0.5mm larger than a measured tendon diameter. Pass FDL and the tape into the distal portal, feed to the Guide pin and pass through the navicular bone tunnel. Tighten the strands in inversion and secure with a SwiveLock, 0.25 - 0.5mm smaller than a drilled tunnel. Perform percutaneous triple hemisection of the Achilles tendon.
Results: This technique has proven itself to be safe in the cadaveric lab exercise and subsequent dissection demonstrating no damage to neurovascular structures in 5 specimens. It has been performed by a lead author in flexible PCFD with preserved clinical correction, radiographic parameters at 3 months follow up.
Conclusion: Tendoscopy-Assisted Flexor Digitorum Longus Transfer and Spring Ligament Synthetic Suture Tape Reconstruction for Flexible Progressing Collapsing Foot Deformity is a technically demanding procedure for advanced foot and ankle surgeons, which allows a completely minimally invasive approach to flexible progressive collapsing foot deformity reconstruction, with increased resistance to forefoot lateralization and the potential to more reliably improve and preserve radiographic parameters. The results of the larger sample size series are to be reported in the future.
