Approach to the Posterior Tibial and Peroneal Tendons

What each side exposes. The medial approach opens the posterior tibial tendon (PTT) sheath behind the medial malleolus, giving access to the PTT, the flexor digitorum longus (FDL) tendon, and the contents of the tarsal tunnel. The lateral approach opens the peroneal tendon sheath behind the lateral malleolus, giving access to the peroneus longus and brevis, the retromalleolar groove, and the superior peroneal retinaculum (SPR). Why these approaches are chosen. The posterior tibial tendon runs in a sheath directly behind the medial malleolus, so direct access requires the medial route. The peroneal tendons run in a retromalleolar groove behind the lateral malleolus, and the lateral approach exposes them while protecting the sural nerve. Both approaches preserve the tendon sheaths so the retinacula can be repaired at closure — the key to preventing post-operative bowstringing and subluxation. Three approach variants. - Medial approach — behind the medial malleolus over the PTT sheath, for PTTD debridement, FDL harvest and transfer.

• Lateral approach — behind the lateral malleolus over the peroneal sheath, for peroneal repair, groove deepening and retinacular reconstruction.
• Combined — both medial and lateral incisions for complex bilateral tendon pathology or combined reconstruction. Indications — medial approach. - Posterior tibial tendon dysfunction (PTTD) stages I to II for debridement and repair.
• FDL harvest for tendon transfer in flatfoot reconstruction.
• Posterior tibial tendon transfer for foot drop or cavus correction.
• Tarsal tunnel release for tarsal tunnel syndrome.
• Excision of an accessory navicular or os tibiale externum. Indications — lateral approach. - Peroneal tendon tears or tendinopathy requiring repair.
• Peroneal tendon subluxation or dislocation requiring groove deepening.
• Superior peroneal retinacular reconstruction.
• Peroneus longus to brevis transfer for chronic tears.
• Harvest of peroneus longus for tendon grafting. Contraindications. Active infection over the proposed incision; severe soft tissue compromise requiring an alternative route; previous surgery with distorted anatomy (relative); and any situation where the neurovascular structures cannot be safely protected. Alternatives include endoscopic tendon sheath procedures for selected tendinopathies, percutaneous techniques for limited debridement, and combined medial and lateral incisions for complex reconstruction. Position and landmarks. The patient is positioned supine with an ipsilateral hip bump — internally rotate the leg for the medial approach, externally rotate it for the lateral approach. Apply a thigh tourniquet (inflated to 250 to 300 mmHg after exsanguination), flex the knee 20 to 30 degrees over a bolster, and place the foot at the end of a radiolucent table. Isolated lateral work can use the lateral decubitus position; simultaneous medial and lateral work is done prone. - Medial landmarks: medial malleolus tip; the PTT palpable behind and inferior to the malleolus with the foot in plantarflexion and inversion; the navicular tuberosity (the PTT insertion) 2 to 3 cm anterior and inferior to the malleolus; and the tarsal tunnel, running from 2 cm proximal to the medial malleolus distally to the abductor hallucis.
• Lateral landmarks: lateral malleolus tip; the peroneal tendons palpable in the retromalleolar groove with resisted eversion; the peroneal tubercle on the calcaneus separating longus and brevis; and the sural nerve, crossing 2 cm distal to the lateral malleolus tip in the subcutaneous tissue.
• Incisions: medial — a longitudinal incision 1 cm posterior to the medial malleolus, from 4 cm proximal to the tip to 3 cm distal toward the navicular (8 to 12 cm); lateral — a longitudinal incision 1 cm posterior to the lateral malleolus, from 4 cm proximal to the tip to 3 cm distal toward the peroneal tubercle (8 to 12 cm).

Work down through the layers behind each malleolus, opening the tendon sheath in line with the skin incision and protecting the adjacent neurovascular structures, then deliver the tendon for the planned procedure.

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Anatomy you must know first Bony anatomy. The medial malleolus carries the posterior groove for the posterior tibial tendon. The flexor retinaculum stretches from the medial malleolus to the calcaneus and forms the roof of the tarsal tunnel. Laterally, the lateral malleolus has a retromalleolar groove deepened by a fibrocartilaginous ridge that contains the peroneal tendons; the peroneal tubercle on the calcaneus separates the peroneus longus and brevis distally. Tendon anatomy — medial (posterior) compartment. - Posterior tibial tendon: inserts on the navicular, cuneiforms and metatarsal bases; the primary invertor and arch supporter.

• Flexor digitorum longus: lies deep and lateral to the PTT; harvested for transfer in PTTD.
• Flexor hallucis longus: the most lateral and deepest of the three; lies lateral to the neurovascular bundle. Tendon anatomy — lateral compartment. - Peroneus longus: superficial, crossing under the cuboid to reach the plantar foot.
• Peroneus brevis: deeper, inserting on the fifth metatarsal base.
• Both tendons share a common sheath proximal to the peroneal tubercle. Tarsal tunnel contents, from anterior to posterior — memorise this order, because safe medial dissection depends on it: 1. Tibialis posterior tendon.

2. Flexor digitorum longus tendon.
3. Posterior tibial artery and veins.
4. Tibial nerve (dividing into medial and lateral plantar nerves).
5. Flexor hallucis longus tendon. The neurovascular bundle therefore sits between FDL and FHL. Laterally, the sural nerve crosses 2 cm distal to the lateral malleolus tip and is sensory to the lateral foot; peroneal artery branches may lie deep to the tendons. There is no major motor nerve at risk in the lateral approach. ### Internervous plane There is no classical internervous plane on either side — the dissection is performed within the tendon sheath itself. - Medial: open the PTT sheath and incise the flexor retinaculum longitudinally. The tarsal tunnel neurovascular bundle lies between FDL and FHL; protect it by identifying that interval and retracting the bundle gently as the procedure demands.

• Lateral: open the common peroneal tendon sheath and incise the superior peroneal retinaculum. The sural nerve is the only structure at risk, protected by identifying it in the subcutaneous tissue 2 cm distal to the lateral malleolus.

Structures at risk, by side and layer.

Extensile options. - Medial, proximal: extend along the posteromedial border of the tibia; the interval stays between FDL and FHL with the neurovascular bundle protected — useful for proximal tendon pathology or combined procedures with tibial osteotomy.

• Medial, distal: extend toward the navicular and midfoot along the PTT to its insertion — useful for accessory navicular excision, distal tendon work or spring ligament repair.
• Medial, plantar: extend into the arch for knot of Henry access during FDL harvest.
• Lateral, proximal: extend along the peroneal compartment; the sural nerve is not at risk proximally — useful for proximal peroneal pathology.
• Lateral, distal: extend toward the peroneal tubercle and fifth metatarsal base, where longus and brevis separate — useful for distal peroneal work or peroneus longus harvest.
• Groove-deepening modification: elevate a posterior fibular periosteal flap, deepen the groove with a burr to a 5 to 6 mm depth, replace the flap, and repair the retinaculum over the tendons.
• Combined: for complex bilateral pathology, position the patient prone or stage lateral decubitus then supine, using separate incisions that each follow the principles above. Closure. Medial: irrigate, repair the PTT sheath with absorbable suture if opened, repair the flexor retinaculum with non-absorbable suture to prevent bowstringing, close subcutaneous tissue and skin, and apply a compressive dressing and posterior splint with the foot in slight plantarflexion and inversion. Lateral: irrigate, repair the SPR with non-absorbable suture or suture anchors to the fibular periosteum, test stability by ranging the ankle and subtalar joint, close in layers, and apply a compressive dressing and posterior splint with the foot in neutral or slight eversion. Post-operative protocol. Non-weight bearing in a splint or cast for 4 to 6 weeks depending on the procedure (longer for repair, shorter for debridement), transition to a walking boot with gradual weight bearing, and begin physical therapy for tendon strengthening and proprioception at 6 to 8 weeks. Follow up at 2 weeks for wound check and suture removal, 6 weeks for radiographs and weight-bearing progression, 12 weeks for functional review, and 6 months for strength testing and return to sport.

Through the medial approach: - Posterior tibial tendon debridement and repair for tendinopathy.

• Flexor digitorum longus transfer for PTTD reconstruction.
• Posterior tibial tendon transfer for foot drop.
• Tarsal tunnel decompression.
• Accessory navicular excision with tendon advancement.
• Spring ligament repair or reconstruction. Through the lateral approach: - Peroneal tendon debridement and repair.
• Peroneal groove deepening for recurrent subluxation.
• Superior peroneal retinacular reconstruction.
• Peroneus longus to brevis transfer.
• Peroneal tendon tenodesis for chronic tears.
• Harvest of peroneus longus for tendon grafting.

Guidelines, registries and global practice Tendon disorders of the hindfoot are managed worldwide according to principles that converge across examination systems. The medial approach for posterior tibial tendon dysfunction and the lateral approach for peroneal pathology are standard techniques taught in advanced orthopaedic practice and equivalent curricula. Side-by-side principles (where guidance converges).

Registry and population evidence. - PTTD affects approximately 3 to 5 percent of adults over 50 years, with higher prevalence in obese and diabetic populations.

• Peroneal tendon pathology is identified in 10 to 15 percent of patients with chronic lateral ankle instability.
• Long-term outcomes after FDL transfer and calcaneal osteotomy show 70 to 80 percent maintained correction at 10 years. Global practice variation. In high-resource settings, MRI, endoscopic assistance and dedicated tendon anchors are common. In resource-limited settings, the same anatomical principles apply using standard instruments, with careful attention to retinacular repair and neurovascular protection. Consent (globally applicable). Discuss sural nerve injury (3 to 5 percent, mostly transient), tarsal tunnel neurovascular injury (less than 2 percent), post-operative tendon subluxation if the retinaculum is not repaired (5 to 15 percent), wound infection (2 to 4 percent), and the possibility of revision surgery or arthrodesis if reconstruction fails.