Circumtibial Posterior Tibial Tendon Transfer to the Midfoot With Passage of the Tendon Under the Extensor Retinaculum

Drop foot is a common occurrence that may lead to active dorsiflexion restriction or weakness in dorsiflexion.1 Causes of drop foot include tibialis anterior tendon rupture, compressive peripheral nerve disorders, and lumbar radiculopathy.2 Treatments for foot drop include nonoperative management, such as an ankle-foot orthosis, primary nerve procedures, alternative tendon transfers, and fusion surgeries.3 The posterior tibial tendon transfer procedure has become a popular option for the correction of drop-foot in patients with tibialis anterior weakness and a functioning tibialis posterior.2,3 This transfer can be performed in a variety of techniques, including transsyndesmotic or circumtibial, with studies showing an improvement in ankle dorsiflexion, and Foot and Ankle Ability Measure (FAAM) scores.1,3,4 Additional procedures, including the Bridle procedure, capsulotomies, and Achilles tendon lengthening may be performed in addition to the posterior tibial tendon transfer. In this manuscript, we describe a modified version of the Ober procedure, with observed outcomes similar to those of the Bridle and nonmodified Ober techniques. The proposed technique is similar to the original technique described in 1933, involving running the posterior tibial tendon subcutaneously around the medial tibia to the dorsum of the foot. However, in this variation, we also route the posterior tibial tendon underneath the extensor retinaculum (Supplemental video 1, Supplemental Digital Content 1, https://links.lww.com/TIO/A95).5 The advantage offered by going underneath the extensor retinaculum is a decrease in tendon “tenting” observed on the anterior aspect of the ankle during active dorsiflexion. TECHNIQUE The patient is positioned supine on the operating table with a bump under the contralateral hip to externally rotate the operative leg, and bone foam is placed under the operative foot (Fig. 1A). A thigh tourniquet is applied on the operative side. After standard preparation and draping, the tourniquet is inflated.FIGURE 1: (A) Patient positioning; (B) Ankle manipulation for subtalar capsule release; (C) Release of the posterior tibialis tendon; (D) Exposed navicular; (E) Posterior tibialis tendon pulled through the channel under the extensor retinaculum; (F) Guide pin placement through the middle cuneiform.Before starting the case, a marking pen is then used to identify the bony landmarks of the medial malleolus and navicular tuberosity. A 3 cm longitudinal incision is made, centered over the insertion of the posterior tibial tendon on the navicular tuberosity, and advanced to the distal tip of the medial malleolus. Careful superficial dissection is carried out to expose the tibialis posterior tendon and its broad insertion on the navicular. The posterior tibial tendon is lifted off the navicular bone, as distal as possible, with sharp dissection using a 15-blade scalpel (Fig. 1B). The tendon is further dissected out of the surrounding fascial tissue and the fibrosed end of the tendon is excised. The tendon is then tubularized with #2 fiberwire suture. Next, a second 3 cm longitudinal incision is marked and made posterior to the medial malleolus directly over the tibialis posterior muscle belly. Dissection is carried out to visualize the tibialis posterior tendon and the muscle belly. The muscle and tendon are confirmed by giving a light tug on the tubularized tibialis posterior tendon. Once confirmed, the tendon is delivered circumtibially through the proximal incision, and the diameter of the tendon is measured using a sizing guide (Fig. 1C). The tendon is then wrapped in moist gauze. Under fluoroscopic guidance, a 2 cm longitudinal incision is made over the middle cuneiform, under fluoroscopic guidance with the foot in plantarflexion, and meticulous sharp dissection using a 15-blade scalpel is carried out to expose and elevate the overlying periosteum (Fig. 1D). Neurovascular structures are protected, including the saphenous vein. A curved Kocher forceps is passed from this incision medially and distally under the extensor retinaculum towards the posterior medial malleolar incision. The prongs are repeatedly opened as they are passed to perform blunt dissection and to make space for passing the tendon anterior to the syndesmosis and under the extensor retinaculum. After passing through the incision on the posterior aspect of the medial malleolus, the Kocher forceps are used to grab the suture ends from the tubularized posterior tibialis tendon, and the tendon is advanced through the incision over the middle cuneiform (Fig. 1E). The tubularized tendon is then threaded over the middle cuneiform using the channel created through blunt dissection anterior to the syndesmosis. Next, a guide pin with an eye for suture is drilled into the middle cuneiform under fluoroscopic guidance and passed distally to exit through the plantar surface of the foot (Fig. 2F). Once the position is confirmed, a cannulated reamer of the size measured to the tendon diameter previously is used to drill across the middle cuneiform. The tubularized tendon is passed through the eye of the guide pin and delivered plantarly. The tubularized tendon is pulled distally until the tibialis posterior tendon passes into the reamed tunnel by 1 to 2 cm. The tendon is then fixed in the middle cuneiform with a biotenodesis screw while maintaining the ankle in neutral to 5 degrees of dorsiflexion (Figs. 2G and H). Due to poor bone quality in this patient, the fixation of the tendon into the bone was augmented with a suture anchor into the middle cuneiform with the threads of the suture tied into the tendon stump. Final images are checked under fluoroscopy.FIGURE 2: (G) Placement of the biotenodesis screw; (H) Fixated posterior tibialis tendon; (I) Post-operative imaging to confirm biotenodesis screw placement; (J) Closed incision.The wounds are irrigated with saline and closure is performed with 2-0 Monocryl for deep fascia, 4-0 Monocryl for the subcutaneous layer, and 3-0 nylon for the skin (Fig. 2J). The foot is maintained in neutral dorsiflexion and the patient is placed in a short leg splint (Fig. 2I). Patient remains nonweight bearing for 6 weeks, at which point they may begin physical therapy. Expected Outcomes To our knowledge, this is the first technique describing a circumtibial posterior tibial tendon transfer involving placement of the posterior tibial tendon underneath the extensor retinaculum. A transosseous or traditional subcutaneous tendon path could be used for the same procedure. However, going underneath the extensor retinaculum minimizes tendon tenting, a common cosmetic complaint among patients. Performed correctly, this procedure allows for improved ankle dorsiflexion, and functionality similar to that offered by the alternative procedures. In an unpublished series of 14 patients with a mean follow-up time of 5.96 months, who underwent a posterior tibial tendon transfer using the described technique, all patients experienced an improvement in their symptoms (Table 1). Complications included one instance of a peroneal tendon tear and one recurrence of foot drop. The recurrence of foot drop was due to a subsequent injury not present before nor caused by the surgery. TABLE 1 - Outcomes of Circumtibial Posterior Tibial Tendon Transfer Patient Sex Age BMI Follow-up (mo) Complication 1 F 29 49.85 0.5 0 2 F 61 47.8 1 0 3 M 44 48.65 1 0 4 F 57 19.7 3 0 5 M 43 26.61 6 0 6 M 59 24.41 6 0 7 M 68 23.37 6 0 8 F 58 32.49 6 0 9 F 63 25.1 6 1* 10 F 62 31.39 1 0 11 F 70 26.64 6 0 12 F 72 33.59 12 1* 13 M 76 32.92 11 0 14 F 58 22.08 12 0 *Complications include one instance of a peroneal tendon tear and one recurrence of foot drop. Complications There are no unique complications specific to the proposed technique. Potential complications include damage to the surrounding neurovascular structures and decreased ankle plantarflexion. In addition, transfers of the posterior tibial tendon may lead to flattening of the arch of the foot. This was not a concern in our patient as they exhibited a common peroneal nerve palsy with weakness of the peroneals. Careful dissection with identification and protection of the sural nerve, anterior tibial artery, and deep peroneal nerve can lessen the risk of damage and postoperative complications. Harvesting of the posterior tibialis tendon as distally as possible can help prevent loss of plantarflexion and allow for proper insertion into the midfoot. Furthermore, in older populations, this technique may be difficult as obtaining an adequate length of “healthy” posterior tibial tendon is dependent on the quality of the posterior tibial tendon secondary to tendon pathology.