Approach to the Posterior Tibial and Peroneal Tendons

The medial approach to the posterior tibial tendon is performed through an incision placed 1 cm posterior to the medial malleolus, directly over the tendon sheath. The tarsal tunnel neurovascular bundle lies between the flexor digitorum longus and flexor hallucis longus and must be identified and protected. The posterior tibial tendon is exposed by incising its sheath longitudinally. This approach is used for debridement, repair, transfer or harvest of the posterior tibial tendon and flexor digitorum longus in flatfoot reconstruction.

The lateral approach to the peroneal tendons is performed through an incision placed 1 cm posterior to the lateral malleolus, directly over the peroneal tendon sheath. The sural nerve crosses 2 cm distal to the lateral malleolus tip and must be protected. The peroneal retinaculum is incised to expose the tendons. This approach is used for peroneal tendon repair, groove deepening and retinacular reconstruction. The retinaculum must be repaired at the end of the procedure to prevent subluxation.

Primary Indications for Medial Approach:

• Posterior tibial tendon dysfunction (PTTD) stages I-II for debridement and repair
• Flexor digitorum longus 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 accessory navicular or os tibiale externum

Primary Indications for 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

Why These Approaches Are Chosen:

The posterior tibial tendon runs in a sheath behind the medial malleolus. Direct access requires the medial approach. The peroneal tendons run in a retromalleolar groove behind the lateral malleolus. The lateral approach provides access while protecting the sural nerve. Both approaches allow preservation of tendon sheaths and retinacular repair.

Contraindications:

• Active infection over the proposed incision
• Severe soft tissue compromise requiring alternative routes
• Previous surgery with distorted anatomy (relative)
• Inability to protect the neurovascular structures

Alternative Approaches:

• Endoscopic tendon sheath procedures for selected tendinopathies
• Percutaneous techniques for limited debridement
• Combined medial and lateral for complex reconstruction

Bony Anatomy:

The medial malleolus provides the posterior groove for the posterior tibial tendon. The flexor retinaculum attaches from the medial malleolus to the calcaneus and sustains the tarsal tunnel. 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 navicular, cuneiforms and metatarsal bases. Primary inverter and arch supporter.
• Flexor digitorum longus: lies deep and lateral to PTT. Harvested for transfer in PTTD.
• Flexor hallucis longus: most lateral and deepest. Lies lateral to the neurovascular bundle.

Lateral (Lateral Compartment):

• Peroneus longus: superficial, crosses under cuboid to plantar foot.
• Peroneus brevis: deeper, inserts on fifth metatarsal base.
• Both tendons share a common sheath proximal to the peroneal tubercle.

Neurovascular Anatomy:

Medial (Tarsal Tunnel Contents from Anterior to Posterior):

• Tibialis posterior tendon
• Flexor digitorum longus tendon
• Posterior tibial artery and veins
• Tibial nerve (divides into medial and lateral plantar nerves)
• Flexor hallucis longus tendon

Lateral:

• Sural nerve: crosses 2 cm distal to lateral malleolus tip. Sensory to lateral foot.
• Peroneal artery branches: deep to tendons in some cases.
• No major motor nerves at risk in the lateral approach.

Medial Approach:

There is no classical internervous plane. The approach is performed within the tendon sheath of the posterior tibial tendon. The flexor retinaculum is incised longitudinally. The tarsal tunnel neurovascular bundle lies between FDL and FHL and is protected by identifying the interval between FDL and FHL and retracting the bundle laterally or medially depending on the procedure.

Lateral Approach:

There is no classical internervous plane. The approach is performed within the common peroneal tendon sheath. The superior peroneal retinaculum is incised. The sural nerve is the only structure at risk and is protected by identifying it in the subcutaneous tissue 2 cm distal to the lateral malleolus.

Structures at Risk in Each Layer:

Position: Supine with ipsilateral hip bump

Pre-positioning Checklist:

• Tourniquet applied to thigh (optional but recommended)
• Radiolucent table if fluoroscopy needed for associated procedures
• Leg prepped from toes to mid-thigh
• Contralateral leg padded and protected
• Head and neck in neutral position

Positioning Details:

• Supine position with a bump under the ipsilateral hip to internally rotate the leg for medial approach or externally rotate for lateral approach
• Knee flexed 20-30 degrees over a bolster for comfort
• Foot positioned at end of table for easy access
• Tourniquet inflated to 250-300 mmHg after exsanguination

Alternative Positioning:

• Lateral decubitus for isolated lateral approach if combined with other lateral procedures
• Prone position if simultaneous medial and lateral approaches planned for complex reconstruction

Medial Approach Landmarks:

• Medial malleolus tip: palpable prominence
• Posterior tibial tendon: palpable behind and inferior to medial malleolus with foot in plantarflexion and inversion
• Navicular tuberosity: insertion point of PTT, 2-3 cm anterior and inferior to medial malleolus
• Tarsal tunnel: extends from 2 cm proximal to medial malleolus distally to abductor hallucis

Lateral Approach Landmarks:

• Lateral malleolus tip: palpable prominence
• Peroneal tendons: palpable in retromalleolar groove with resisted eversion
• Peroneal tubercle: palpable on lateral calcaneus, separates longus and brevis
• Sural nerve: crosses 2 cm distal to lateral malleolus tip in subcutaneous tissue

Incision Planning:

• Medial: longitudinal incision 1 cm posterior to medial malleolus, extending from 4 cm proximal to tip to 3 cm distal toward navicular. Length 8-12 cm.
• Lateral: longitudinal incision 1 cm posterior to lateral malleolus, extending from 4 cm proximal to tip to 3 cm distal toward peroneal tubercle. Length 8-12 cm.

Neurovascular Injury Management:

• If tibial nerve injured medially: primary repair if transected, microsurgical technique, document and follow up
• If sural nerve injured laterally: if transected, consider primary repair or leave in situ and counsel regarding neuroma risk
• Post-operative sensory loss: document, follow up, consider exploration if no recovery and symptomatic neuroma

Medial Approach Extensions:

• Proximal: Extend along posteromedial tibia for more proximal tendon exposure. Interval remains between FDL and FHL. Useful for combined procedures with tibial osteotomy.
• Distal: Extend to navicular and midfoot for tendon insertion procedures, accessory navicular excision, or spring ligament repair.
• Plantar: Extend into the arch for knot of Henry access during FDL harvest.

Lateral Approach Extensions:

• Proximal: Extend along peroneal compartment for more proximal tendon pathology. Sural nerve is not at risk.
• Distal: Extend to peroneal tubercle and fifth metatarsal base for distal tendon procedures or peroneus longus harvest.
• Groove Deepening Modification: Elevate a posterior fibular periosteal flap, deepen the groove with a burr to 5-6 mm depth, then replace the flap and repair the retinaculum over the tendons.

Combined Approaches:

For complex cases requiring both medial and lateral access (bilateral tendon pathology, combined reconstruction), position the patient prone or use staged lateral decubitus and supine positioning. Separate incisions are used. Each approach follows the principles described.

Intra-operative Complications:

Post-operative Complications:

Immediate Post-operative:

• Neurovascular check documenting tibial nerve and sural nerve function
• Wound inspection
• Posterior splint with foot in slight plantarflexion and inversion (medial) or neutral to slight eversion (lateral)
• Elevate limb above heart level
• DVT prophylaxis per protocol

Weight Bearing Protocol:

• Non-weight bearing for 4-6 weeks depending on procedure (tendon repair versus debridement)
• Transition to walking boot at 4-6 weeks with gradual weight bearing
• Full weight bearing by 8-10 weeks if healing appropriate

Range of Motion:

• Early toe range of motion as pain allows
• Ankle and subtalar range of motion begins at 4-6 weeks in boot
• Resistance exercises begin at 8-10 weeks
• Proprioception and balance training at 10-12 weeks

Follow-up Schedule:

• 2 weeks: Wound check, suture removal
• 6 weeks: Radiographs if bony work performed, assess healing, progress weight bearing
• 12 weeks: Clinical review, functional assessment, return to activity planning
• 6 months: Final review, strength testing, return to sport if applicable

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 FRCS, FRACS, EBOT, ABOS 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 retinaculum not repaired (5 to 15 percent), wound infection (2 to 4 percent), and the possibility of revision surgery or arthrodesis if reconstruction fails.