Surgical Planning for Flexor Digitorum Longus Tendon Transfers: An Anatomic Study

Area of Science:

• Orthopedic Surgery
• Anatomy
• Biomechanical Engineering

Background:

• Posterior tibial tendon dysfunction (PTTD) frequently co-occurs with hindfoot valgus and equinus.
• Effective preoperative planning is crucial for selecting the appropriate surgical procedure and ensuring efficiency in PTTD treatment.
• The flexor digitorum longus (FDL) tendon transfer is a common surgical technique for PTTD, requiring careful consideration of the harvest site anatomy.

Purpose of the Study:

• To anatomically assess the harvest site of the flexor digitorum longus tendon, specifically at the master knot of Henry.
• To determine the optimal size of interference screw for graft fixation during FDL tendon transfer in PTTD surgery.
• To provide data that aids surgeons in preoperative planning for stage II flatfoot correction.

Main Methods:

• Dissection of 30 fresh-frozen below-the-knee cadavers.
• Standard anatomic approach for posterior tibial tendon debridement and FDL tendon transfer.
• Measurement of FDL tendon width at the master knot of Henry.

Main Results:

• Of 30 specimens, 67% (20) had an FDL tendon width of 5 mm, and 33% (10) had a width of 4 mm.
• A 5.0-mm interference screw is suitable for all specimens, representing the safest choice for graft fixation.
• A 4.0-mm interference screw would only be appropriate for 33% of the specimens studied.

Conclusions:

• The FDL tendon width at the master knot of Henry varies, with 5 mm being the most common measurement.
• A 5.0-mm interference screw is recommended for secure graft fixation in FDL tendon transfers for PTTD.
• This anatomical data enhances preoperative planning for surgeons performing flatfoot correction surgery.