19 Posterior Tibial Tendon Transfer (Including Bridle’s Procedure) for Drop-Foot Abstract Drop-foot is a common problem that may result from anterior compartment syndrome, peroneal nerve palsy, incomplete sciatic nerve injuries, lumbar spinal disease, or other inherited or acquired neuromuscular diseases. If there is no potential for nerve recovery and bracing is unfeasible or poorly tolerated, then a posterior tibial tendon (PTT) transfer or Bridle’s tendon transfer may be considered. The ideal candidate, to ensure a successful clinical outcome, has a mobile nonarthritic ankle with maintained passive range of motion, minimal deformity, and at least 4/5 PTT strength. The PTT transfer technique has been modified multiple times over the years. The current technique, described here, includes a harvest of the tendon at its insertion on the navicular, and transfer from posterior to anterior through the interosseous membrane (IM). The tendon is secured to the middle or lateral cuneiform with a biotenodesis interference screw. The Bridle procedure, which has also evolved over the last few decades, includes the PTT transfer through the IM. It is then passed through the anterior tibial tendon (ATT) before reattachment in the middle cuneiform bone. The peroneal longus is transected proximally and transferred from the cuboid level to the anterior lower leg, just above the ankle, and secured to the ATT and PTT, completing a tritendon anastomosis. Compared to the PTT transfer alone, the Bridle procedure provides better coronal plane balance and stability and potentially greater dorsiflexion strength. With either of these tendon transfer procedures, patients can expect a brace-free lifestyle and near-normal ambulation on even ground. Assuming careful attention to technique is followed, complications are very uncommon and satisfaction rates are very high. Keywords: drop-foot, foot drop, posterior tibial tendon transfer, Bridle’s procedure, peroneal nerve palsy, anterior compartment syndrome • Peroneal nerve palsy. • Spinal cord injury (incomplete). • Sciatic nerve injuries (partial). • Anterior compartment deficiency. • Upper motor neuron disease (i.e., cerebral palsy). • Hereditary neurologic disorders (i.e., Charcot–Marie–Tooth). • Gait consistent with drop-foot (i.e., steppage). • Weak or absent active ankle dorsiflexion. • Ideally at least 4/5 posterior tibial tendon (PTT) strength (anything less will result in a tenodesis). • Intact peroneal longus (PL) tendon and anterior tibial tendon (ATT; for Bridle). • Normal ankle joint and well-maintained passive range of motion (ROM). • Gastroc-soleus motor strength of 4/5 or greater. • Standing ankle and foot radiographs. • Consider electromyogram (EMG) if clinical exam unclear (rarely necessary). • Physiotherapy if motor strength recovery a possibility. • Ankle-foot orthosis (AFO). • Weak or absent PTT strength (less than 4/5). • Absent anterior tibial or PL tendon (for Bridle). • Severely arthritic, deformed, and/or contracted ankle joint. • Incomplete nerve injury with likelihood of recovery. • Vascular insufficiency. The primary goal of the Bridle and PTT transfer procedures is to obtain a balanced foot and ankle that will permit brace-free ambulation. A successful transfer will ideally result in a normal gait pattern on even ground and at least 5 degrees of active ankle dorsiflexion, with limited plantarflexion. Running, wearing high heels, and walking on uneven ground may not be possible, and the patient should be counseled in this regard. These procedures have numerous advantages and relatively little downside. A brace-free lifestyle is almost universally well received given that bracing is expensive, cumbersome, and often uncomfortable. The patient is also afforded the maintenance of ankle and hindfoot motion, an obvious advantage over arthrodesis. The operation is relatively simple to perform for the experienced surgeon, and the results are very predictable. Complications are relatively rare and the recovery is straightforward. • Transferring a functional tendon (PTT 4/5 strength or greater). • “Powering” a mobile joint (preserved ankle joint with reasonable passive ROM). • Ensuring soft-tissue balance around the ankle (i.e., Achilles lengthening if necessary). • Correct any foot deformities at same time or in staged fashion (i.e., calcaneal osteotomy). • Establishing the right amount of tension on the transfer. • In-line tendon transfers with minimal soft-tissue friction (i.e., subcutaneous vs. below retinaculum). • Stable fixation to allow quicker and safer rehabilitation. The patient is positioned supine for the procedure, typically with a bump under the ipsilateral hip to ensure balanced access to the medial and lateral sides of the foot and ankle. Peripheral nerve blocks are usually avoided, particularly in the presence of an established neurologic deficit. General anesthesia and a thigh tourniquet are recommended. For peroneal neuropathy or other conditions only affecting the anterior compartment musculature, without hindfoot deformity or imbalance, a PTT transfer alone can be considered. The tendon, in its entirety, is transferred through the interosseous membrane (IM) to the middle cuneiform or lateral, as first described by Mayer.1 The technique involves four incisions. The first incision, utilized to harvest the PTT, is made along the medial hindfoot at the level of its insertion on the navicular bone. The dissection is started proximally and the PTT sheath is opened to expose the tendon. The dissection extends distally to the tendon insertion. To maximize tendon length, the PTT is harvested with a periosteal flap to the most distal extent of the navicular. The end of the harvested tendon is tagged with a 0–0 absorbable suture. The second incision, longitudinal, is made along the posteromedial border of the distal tibia, 4 to 5 cm proximal to the medial malleolus. The fascia is incised and the PTT is identified. A right-angled clamp is used to pull the distal part of the tendon out of the incision. The tendon is wrapped with a saline-soaked gauze to prevent desiccation. A third incision, longitudinal, is made along the anterior lower leg, 5 to 6 cm above the level of the ankle joint, just lateral to the tibial spine. The fascia is incised and dissection extends deep and directly along the lateral border of the tibia, medial to the anterior tibial tendon. A hemostat is used to carefully penetrate the IM, which is then opened proximally and distally 10 cm or more, in line with the skin incision. A right-angled clamp is then carefully passed from the medial lower leg incision, subperiosteally, to the anterior incision. To pass the PTT through the IM, it is easiest to first pass a looped suture with the right-angled clamp from medial to lateral between the incisions and through the IM. The looped suture can then be passed around the PTT and used to pull it through the IM out of the anterior incision. Lastly, a fourth longitudinal incision is made directly over the middle cuneiform. Fluoroscopy is used to identify the bone before the incision is made. Blunt dissection then proceeds carefully down to the middle cuneiform and a Bovie is used to mark the center of the bone. A biotenodesis screw set is used for the next step. The diameter of the PTT is measured and a drill hole of similar, or slightly larger, size is made from dorsal to plantar over a guide pin. The entire depth of the bone is drilled so that the tendon transfer can be appropriately tensioned without “bottoming out” in an incomplete osseous tunnel. The PTT is then passed subcutaneously with a long clamp from the incision over the IM to the distal wound over the middle cuneiform. The tendon is then passed through the middle cuneiform with a straight needle. The ankle is positioned in 5 degrees of dorsiflexion and the PTT is tensioned by pulling the attached suture from the bottom of the foot. If the Achilles is tight, a heel cord lengthening is performed before securing the tendon transfer. Finally, a biotenodesis screw (usually 5–6 mm in diameter) is placed from dorsal to plantar, securing the tendon in the osseous tunnel. The tendon can be oversewn to the surrounding periosteum for additional stability if necessary. The wounds are closed in routine layered fashion, followed by application of a well-padded short-leg splint with the ankle in maximal dorsiflexion. As reported by McCall et al, and later modified by Rodriguez, a Bridle procedure may also be considered to treat drop-foot, particularly if associated with hindfoot imbalance (i.e., cavovarus).2,3 It provides a more robust tenodesis affect and stronger medial to lateral balancing than the PTT transfer alone. In fact, it was designed for cases in which a too-far medial or too-far lateral transfer of the PTT alone may result in a coronal plane deformity. The Bridle procedure includes a slight modification of the PTT transfer (as described earlier) with the additional involvement of the PL tendon and ATT. The PTT is harvested, tagged, and passed around the IM exactly as described earlier. The ATT is split longitudinally just distal to the level where the PTT traverses the IM. The PTT is passed from posterior to anterior through the ATT (Fig. 19.1). After identification under fluoroscopy, a short longitudinal incision is made just lateral to the middle cuneiform (may consider transferring to the lateral cuneiform if there is significant varus and/or supination deformity). As described earlier, the PTT is passed subcutaneously to the cuneiform. An osseous tunnel is drilled into the center of the cuneiform and the PTT is passed, tensioned, and secured with a biotenodesis screw. A 4-cm longitudinal incision is made over the peroneal tendons, retrofibular, centered 8 cm proximal to the tip of the lateral malleolus (Fig. 19.2). The fascia is incised and the peroneal tendons are exposed. A side-to-side tenodesis between the longus and brevis tendons is performed with nonabsorbable suture. The PL tendon is transected just distal to the tenodesis and the tendon end is tagged.
19.1 Indications
19.1.1 Pathology
19.1.2 Clinical Evaluation
19.1.3 Radiographic Evaluation
19.1.4 Nonoperative Options
19.1.5 Contraindications
19.2 Goals of Surgical Procedure
19.3 Advantages of Surgical Procedure
19.4 Key Principles
19.5 Preoperative Preparation and Patient Positioning
19.6 Operative Technique
19.6.1 Isolated Posterior Tibial Tendon Transfer
19.6.2 Bridle’s Tendon Transfer
Musculoskeletal Key
Fastest Musculoskeletal Insight Engine
