Interference screw for fixation of FDL transfer in the treatment of adult acquired flat foot deformity stage II.

Introduction: Flexor digitorum longus transfer and medial displacement calcaneal osteotomy have shown favourable results in the treatment of adult acquired flat foot deformity stage 2. Little is known about the resorbable interference screw for tendon fixation and postoperative patient satisfaction though. Moreover possible changes of radiographic parameters at final follow-up, possible implant-associated complications and differences concerning clinical results at final follow-up to other studies using bone tunnel techniques for fixation of the FDL tendon were investigated.

Materials And Methods: 21 feet in 21 patients with a mean age of 51 years were evaluated pre- and postoperatively after a standardised operative procedure using MDCO and FDL transfer with interference screw fixation. Patients were evaluated with the American Orthopaedic Foot and Ankle Society Hindfoot Score and the Visual Analogue Scale at an average follow-up of 20 months. Hindfoot radiographic parameters were evaluated according to AOFAS guidelines. For statistical analysis SPSS v.15.0.1 was used.

Results: The average AOFAS Score (from 42 to 95 points) and VAS (from 0.5 to 8 points) both increased significantly (p < 0.001 each) from preoperative to final follow-up as well as the hindfoot valgus (from 10 to 4 degrees (p = 0.005)) and the lateral talo-first metatarsal angle (from 13.6 preoperative to 5.2° at follow-up). 88 percent of patients evaluated the postoperative result with "very good" or "good". Implant-associated complications could not be detected.

Conclusion: We conclude that interference screw fixation for FDL transfer is a safe and promising operative technique, allowing a smaller skin incision without disrupting the normal interconnections at the knot of Henry, while achieving very high patient satisfaction and improving postoperative function as well as relieving pain. This method is technically easy to perform, has a low complication risk and we, therefore, recommend this fixation technique in patients with adult acquired flatfoot deformity stage 2.