Posterior Tibial Tendon Dysfunction (PTTD)

The tendon undergoes degenerative change rather than inflammatory tendinitis. Failure then spreads outwards: from the tendon to the static restraints, from the restraints to bony deformity, and from deformity to arthritis.

The tendon. Degeneration begins in a zone of hypovascularity 2-6cm proximal to the navicular insertion, the watershed between the musculotendinous blood supply proximally and the osseous supply from the navicular distally. Repetitive eccentric loading during stance causes fibre microtears, myxoid degeneration, collagen disorganisation and loss of type I collagen, which is replaced by type III. The tendon then elongates, failing under physiological loads, and progresses from tendinosis to partial or complete rupture. With it go dynamic arch support and control of hindfoot eversion.

The spring ligament. As the PTT fails, load shifts to the spring ligament. Its superomedial band elongates and its plantar bands attenuate or rupture, so the talar head loses its static support, plantarflexes and displaces medially.

The bony deformity.

• Hindfoot valgus - the calcaneus everts with loss of PTT inversion, unopposed peroneal eversion and the lateral vector (valgus thrust) of the Achilles tendon
• Peritalar subluxation - talonavicular uncovering (forefoot abduction), subtalar subluxation (hindfoot valgus) and calcaneocuboid impingement
• Forefoot supination - a compensatory forefoot varus relative to the hindfoot valgus, with first ray plantarflexion and lateral column overload

The joints. Chronic malalignment produces rigid arthritis of the subtalar, talonavicular and calcaneocuboid joints, the transition from flexible Stage II to rigid Stage III. Late in the disease the deltoid ligament becomes insufficient, and medial ankle instability, valgus talar tilt in the mortise and lateral tibiotalar impingement mark Stage IV.

The mechanical cost.

• The windlass mechanism is lost: the plantar fascia can no longer tighten the arch with dorsiflexion
• Calcaneal eversion shortens the Achilles moment arm and reduces its mechanical advantage
• The calcaneocuboid joint bears more load, overloading the lateral column (sinus tarsi pain)
• Lateral forefoot pressures rise, with a risk of ulceration in diabetics

The tendon. Tibialis posterior arises from the interosseous border of the posterior tibia, the interosseous membrane and, with a small contribution, the proximal fibula. It runs in the posterior compartment of the leg, passes behind the medial malleolus beneath the flexor retinaculum, curves beneath the sustentaculum tali and fans out to insert. Branches of the posterior tibial artery supply the musculotendinous junction and navicular osseous vessels supply the distal tendon, leaving between them the watershed in which degeneration begins.

The insertion. The primary insertion is the plantar-medial surface of the navicular tuberosity, but the tendon inserts as a broad fan that supports the entire medial and plantar arch. Secondary slips reach:

• all three cuneiforms (medial, intermediate and lateral)
• the bases of metatarsals 2-4
• the cuboid (occasional slips)
• the fibrocartilage of the spring ligament, giving functional support, and through the spring ligament, indirectly, the calcaneus

The breadth of the insertion explains why PTT dysfunction produces a multiplanar deformity (sagittal collapse, coronal valgus, transverse abduction), and why reconstruction often requires more than one procedure.

Function. Its primary actions are hindfoot inversion and adduction; its secondary actions are ankle plantarflexion and medial arch support. It is the dynamic stabiliser of the arch, controlling pronation during stance.

The spring ligament (plantar calcaneonavicular ligament) is the primary static support of the talar head. It prevents talar plantarflexion and medial displacement and forms a fibrocartilaginous articulation with the talar head. It has three bands:

1. Superomedial (strongest) - sustentaculum tali to navicular
2. Medioplantar oblique - middle calcaneus to navicular
3. Inferior plantar longitudinal - plantar calcaneus to navicular

In PTTD it attenuates secondarily after the tendon fails, the superomedial band most commonly. Its damage is graded by the Bluman classification (see Classification).

The other restraints. Static support comes from the plantar fascia (windlass mechanism, arch support), the long plantar ligament (lateral column stabilisation), the interosseous talocalcaneal ligament (subtalar stability) and the deltoid ligament (medial ankle stability, which fails in Stage IV). The dynamic supports are:

• Tibialis posterior - the primary arch stabiliser
• Flexor digitorum longus - the transfer donor, and a secondary arch support
• Flexor hallucis longus - secondary arch support
• Tibialis anterior - counterbalances tibialis posterior
• Peroneus longus - plantarflexes the first ray and supports the lateral column
• Gastrocnemius-soleus - the Achilles loads the hindfoot, and equinus increases valgus

Zones of PTT pathology. The tendon is divided into four zones for surgical planning:

• Zone 1 - myotendinous junction to medial malleolus; pathology is rare
• Zone 2 - behind the medial malleolus; tenosynovitis, stenosing tenosynovitis
• Zone 3 - inframalleolar to the navicular insertion; the most common zone of degeneration
• Zone 4 - the navicular insertion; insertional tendinopathy, avulsion

Stage I: tendinitis without deformity. The tendon is inflamed or degenerate but still works, and the foot's architecture is normal. The patient has medial ankle pain along the course of the PTT and fusiform swelling of tenosynovitis behind the medial malleolus. They can perform a single heel raise with heel inversion, the arch height is normal, and weight-bearing radiographs show normal arch parameters.

The prognosis with conservative treatment is good, but there is a risk of progression to Stage II if the biomechanical factors are not addressed.

Stage II: flexible flatfoot. The tendon has elongated or ruptured, the spring ligament has attenuated, and the peritalar subluxation is still flexible. Pain is medial and at the sinus tarsi. The hindfoot is in valgus with arch collapse and forefoot abduction, and the too many toes sign is positive.

The patient cannot perform a single heel raise, or performs it without heel inversion; and the deformity is passively correctable, reducing with hindfoot inversion. Weight-bearing radiographs show talonavicular uncovering and forefoot abduction on the AP view, and a decreased calcaneal pitch with an increased Meary's angle on the lateral.

Stage III: rigid flatfoot. Fixed peritalar arthritis of the subtalar, talonavicular and calcaneocuboid joints, with a ruptured tendon and a disrupted spring ligament. Pain is diffuse through the hindfoot and along the lateral column (calcaneocuboid impingement). The hindfoot valgus is fixed, the arch collapse rigid, and the deformity is not passively correctable; peritalar crepitus and sinus tarsi tenderness are found on examination. Weight-bearing radiographs show severe arch collapse and peritalar subluxation.

Stage IV: ankle valgus. Stage III pathology plus deltoid ligament insufficiency, with valgus talar tilt in the mortise and lateral tibiotalar impingement. To the Stage III features the patient adds ankle pain (medial gapping, lateral impingement), ankle valgus with talar tilt, medial ankle tenderness and ankle instability. It is end-stage disease, requiring extensive fusion.

Pain. Medial ankle and hindfoot pain along the course of the PTT, from the medial malleolus to the navicular. It aches, is exacerbated by activity, prolonged standing, uneven ground and stairs, and comes on insidiously over months to years. Acute onset is rare and suggests rupture after a steroid injection.

Swelling and deformity. Medial ankle swelling is worse with activity and better with rest; tenosynovitis gives a fusiform swelling behind the medial malleolus. The arch collapses gradually, the medial heel of the shoe breaks down and shoes become hard to fit, and the gait becomes antalgic with the foot externally rotated.

Function. Stairs are difficult, especially going down, and so is uneven ground. The patient cannot run or play sport, and prolonged standing is painful. Ask about the risk factors listed under Epidemiology, including medications and occupation.

Standing. The too many toes sign is pathognomonic. From behind, a normal foot shows the heel and 1-1.5 lateral toes; in PTTD forefoot abduction brings more than 2 into view, and the more toes visible, the greater the abduction. Normal hindfoot alignment is 5-7° of valgus; in PTTD it exceeds 10°, and side-to-side comparison is critical.

The arch and forefoot. The medial longitudinal arch is lost, the talar head is prominent medially, and the displaced talus can be felt as a medial ankle bulge; the lateral column is relatively short. The forefoot sits in relative supination, a forefoot varus compensating for the hindfoot valgus, with first ray plantarflexion and a callosity under the first metatarsal head.

Gait. Antalgic, with a shortened stance phase on the affected side, excessive external rotation of the foot progression angle and a valgus thrust on loading at heel strike.

Palpation. Tenderness runs along the PTT from behind the medial malleolus to the navicular insertion. Tenosynovitis gives fusiform or nodular thickening, and a palpable gap suggests rupture, which is rare. Over the bones:

• Navicular tuberosity - prominent with spring ligament failure
• Talar head - prominent medially and plantarly
• Sustentaculum tali - tender
• Sinus tarsi - pain from lateral hindfoot (calcaneocuboid) impingement

Single heel raise test - the gold standard. The patient stands on the affected leg and rises onto the forefoot while the examiner watches the hindfoot from behind. Normally the heel inverts, the arch reconstitutes and 10 or more repetitions are possible. In Stage I the patient can perform it, painfully, with normal inversion; in Stages II-IV they cannot perform it, or do so without heel inversion. Compare with the other side. It is the most sensitive clinical test: sensitivity is 100% for Stage II or greater and specificity 85%, as other causes of flatfoot may also fail the test.

Passive correction test - Stage II or Stage III. With the patient sitting or supine:

1. Invert the heel manually
2. Palpate the talonavicular joint while inverting
3. Assess whether the arch reconstitutes

In Stage II the deformity fully corrects and the talonavicular joint reduces. In Stage III it persists, the peritalar joints are rigid, and there is crepitus.

Coleman block test - forefoot- or hindfoot-driven. Stand the patient on a 1-inch block under the lateral foot, with the fifth metatarsal hanging off, and watch the hindfoot. If the valgus corrects, the deformity is forefoot-driven (a flexible forefoot varus); if it persists, it is hindfoot-driven, the PTTD pattern.

Flexibility. Compare hindfoot inversion and eversion with the other side. Forefoot supination is flexible if it corrects with the hindfoot held neutral, fixed if the forefoot varus persists; fixed varus is rare in PTTD. The first ray is hypermobile if its dorsiflexion-plantarflexion excursion exceeds 10mm, and this contributes to medial column instability.

Neurovascular examination. Palpate and document the dorsalis pedis and posterior tibial pulses, and measure the ankle-brachial index if peripheral vascular disease is suspected (diabetics, smokers). Test light touch and two-point discrimination to exclude neuropathy; power in tibialis posterior (inversion), the peroneals and the ankle dorsiflexors; and the Achilles reflex.

Tarsal tunnel syndrome coexists in 10% of patients with PTTD. Tap the posterior tibial nerve behind the medial malleolus: Tinel's sign is positive if it produces paraesthesiae in the plantar foot. Check sensation in the medial and lateral plantar nerve distributions.

Immobilisation (Stage I). A CAM walker boot for 4-6 weeks of strict immobilisation, fully weight-bearing in the boot, to reduce tendon inflammation, prevent microtrauma and allow healing. The patient then moves gradually into orthotics over 2 weeks.

Orthoses are the foundation of conservative treatment.

Shoe modifications.

• Medial heel wedge - a 4-6mm medial build-up controls hindfoot valgus and shifts the ground reaction force laterally
• Rocker-bottom sole - reduces forefoot stress and the eccentric load on the PTT, and assists toe-off
• Wide toe box - accommodates forefoot abduction and prevents lateral toe compression

Strengthening.

• Tibialis posterior - resisted inversion against a Theraband in sitting, single-leg stance (balance training, arch activation) and eccentric loading (controlled lowering from inversion). Evidence for tendon regeneration is limited; it may improve compensatory strength.
• Intrinsic foot muscles - toe curls (towel scrunches) and arch doming (the short foot exercise), to improve dynamic arch support
• Tibialis anterior - resisted dorsiflexion, to reduce the compensatory overload on the PTT, and heel walking for eccentric control
• Gastrocnemius-soleus - eccentric calf raises with progressive resistance

Stretching. Stretch the gastrocnemius with the knee extended and the soleus with the knee flexed, 30 seconds × 3, 2-3 times daily, to reduce hindfoot equinus and so the pronation moment. Gentle dorsiflexion with toe extension stretches the plantar fascia and reduces arch tension.

Gait retraining. Pronation is controlled by reducing the medial weight shift, shortening the stride and increasing cadence. A midfoot strike avoids a heel strike with valgus thrust, and the external foot progression angle is reduced.

The evidence. No RCT has shown physiotherapy to be effective for PTTD. It is best used as an adjunct to orthoses: it may prevent progression in Stage I and has a role in postoperative rehabilitation, but alone it is insufficient for established disease, Stage II or greater.

Analgesia. Pharmacological treatment is purely symptomatic and does not alter progression or reverse deformity.

• NSAIDs - for acute inflammation in Stage I: ibuprofen 400mg TDS or naproxen 500mg BD, as a short course of 2-4 weeks. Beware GI side effects, cardiovascular risk and renal impairment.
• Paracetamol - 1g QID regularly for chronic pain; preferred for long-term use
• Opioids - avoid in a chronic condition where they are not indicated; the exception is postoperative pain

Why no steroid. Steroid degrades collagen and weakens the tendon, risking complete rupture, and there is no evidence of benefit. Acute ruptures after injection have been reported.

Other modalities. Neither has good evidence:

• Shockwave therapy - limited, low-quality studies and unclear benefit; not routinely recommended
• Platelet-rich plasma - no high-quality RCTs for PTTD; experimental, not the standard of care

Indications. Stage I PTTD with MRI-confirmed tendinosis or partial tear, persistent pain limiting activities of daily living, and failure of 6 months of conservative treatment. There must be no architectural deformity, and the tendon must be structurally intact, with under 50% of its cross-section involved. Deformity means Stage II, which needs reconstruction; involvement over 50% needs augmentation with an FDL transfer. Isolated debridement is rarely performed, as most patients have progressed to Stage II by presentation.

Technique

Set-up. Supine, with a bump under the ipsilateral hip (15-20° of internal rotation) and a thigh tourniquet.

Approach. A longitudinal 8-10cm incision centred 1cm posterior to the medial malleolus, from 4cm proximal to the malleolus to the navicular insertion.

1. Identify and protect the saphenous vein and nerve, retracting them anteriorly
2. Incise the flexor retinaculum longitudinally, preserving its pulley function for later repair
3. Expose the PTT from the myotendinous junction to the navicular insertion
4. Inspect the entire tendon for pathology

Assess the tendon. Degeneration is typically in Zone 3, 2-6cm proximal to the navicular. Measure the percentage of the cross-section involved: over 50% is the decision point for augmentation with an FDL transfer (see the Stage IIA tab).

Debride. Make a longitudinal tenotomy along the degenerate segment and excise all degenerate tissue: macroscopically abnormal (yellow-brown discolouration), friable and myxoid, without normal striations. Preserve healthy margins; what remains should be intact, healthy tendon that maintains its structural integrity. Excise all inflamed synovium.

Close. Repair the flexor retinaculum to keep its pulley function, close subcutaneous tissue with absorbable sutures and the skin with monofilament non-absorbable or absorbable subcuticular sutures, and apply a below-knee plaster backslab.

After surgery

• Weeks 0-4 - non-weight-bearing cast
• Weeks 4-6 - weight-bearing cast
• Then - CAM walker boot for 2 weeks with progressive weight-bearing, and a UCBL orthotic from week 8; physiotherapy for range of motion and strength
• Return - light activities at 3 months, full sport at 4-6 months; the orthotic is worn long-term

Outcomes

Good-to-excellent results in 70-80% at 2-5 years. Success is predicted by the absence of deformity, under 50% tendon involvement and appropriate patient selection. Failure is predicted by underlying biomechanical factors (flatfoot, hypermobility) left unaddressed, progression to Stage II deformity, and inadequate orthotic use after surgery. Wound problems occur in 5%, sural nerve injury in 2% and saphenous nerve injury in 5%, and 20-30% progress to Stage II over 5 years.

Indications. Flexible, passively correctable Stage IIA deformity, with talonavicular uncovering under 30% and no rigid arthritis. Surgery is offered after a failed 3-6 month trial of conservative treatment, for progressive deformity despite appropriate bracing, for functional impairment affecting quality of life, or when the patient wants the deformity corrected.

Goals. Stage II reconstruction must address every pathological component, and missing any risks failure:

• the tendon - an FDL transfer restores dynamic arch support
• the static restraints - repair of spring ligament pathology if present
• the bony malalignment - an MDCO corrects static hindfoot valgus (± lateral column lengthening in IIB)

Set-up. Supine, with a bump under the ipsilateral hip and a thigh tourniquet.

FDL transfer

Approach and harvest. A longitudinal 8-10cm medial incision 1cm posterior to the medial malleolus, from proximal to the malleolus to the navicular.

1. Open the flexor retinaculum
2. Identify the FDL, posterior to the PTT and adjacent to the FHL
3. Tag it with a non-absorbable suture
4. Divide it at the level of the master knot of Henry, distal to the crossing
5. Retrieve it distally through a plantar incision if needed

Prepare the PTT. Debride all degenerate tissue. A ruptured tendon has its ends prepared for weaving; an elongated one is prepared for side-to-side augmentation.

The transfer. Pass the FDL through the PTT in a Pulvertaft weave of 3-4 passes, set the tension with the foot in neutral (no hindfoot valgus, neutral arch), and secure it with non-absorbable sutures (#2 FiberWire). Passive ankle dorsiflexion should not over-tension the transfer.

Why FDL. It is the default donor for dynamic reconstruction of the medial arch:

• In phase - FDL and tibialis posterior both fire during stance, so the transferred tendon supports the arch in the correct phase without re-education or phase conversion
• Adjacent - it lies immediately posterior to the PTT in the same deep posterior compartment behind the medial malleolus, and is harvested through the same medial incision with little extra dissection
• Expendable - after division at the master knot of Henry, lesser-toe flexion is largely preserved through the tendinous interconnections between FDL and FHL distal to the knot, where FHL effectively takes over flexion of the lateral toes; it is sacrificed at little functional cost
• Weaker - it has only a fraction of the power of the native tibialis posterior, so a transfer alone cannot hold a flatfoot corrected. It is always combined with a bony realignment (MDCO, with lateral column lengthening when indicated): the osteotomy corrects and offloads the static deformity to protect the transfer, and the FDL adds dynamic reinforcement

The spring ligament. Grades 1-2 (attenuation, partial tear) are repaired directly with absorbable sutures. Grades 3-4 (complete rupture) require reconstruction, with allograft augmentation (dermal or fascia lata) or direct repair.

Medial displacement calcaneal osteotomy

Approach. An oblique 4-6cm incision inferior to the lateral malleolus, over the lateral calcaneus.

The cut.

1. Identify the sural nerve and protect it throughout
2. Expose the lateral calcaneus subperiosteally
3. With an oscillating saw, start 1-1.5cm posterior to the calcaneocuboid joint and cut obliquely from dorsal-posterior to plantar-anterior, at 45° to avoid breaching the plantar cortex
4. Complete the plantar cortex with an osteotome if needed

Displace and fix. Medialise the posterior fragment 10-15mm, using a lamina spreader to open the lateral gap and shift posteriorly, and restore neutral or slight varus hindfoot alignment. Fix with two 6.5mm partially threaded cannulated screws from plantar-posterior to dorsal-anterior, compressing the osteotomy and avoiding the calcaneocuboid joint, and check on lateral and axial calcaneal views. Repair the periosteum, close in layers and apply a backslab.

After surgery

• Weeks 0-6 - non-weight-bearing cast
• Then 4-6 weeks - weight-bearing cast
• Then - CAM walker boot for 2-4 weeks with progressive weight-bearing, and a UCBL orthotic long-term
• Physiotherapy - range of motion from week 12, strengthening from week 16, proprioception from week 20
• Return - unrestricted walking at 4-6 months, sport at 9-12 months

Outcomes

Good-to-excellent results in 85-90% at 5-10 years, and 80-90% of patients are satisfied. The talonavicular coverage angle improves from 25° to under 10°, calcaneal pitch from 10° to 18-20°, and hindfoot valgus corrects to neutral or slight varus.

Failure is predicted by an unrecognised Stage IIB (forefoot abduction over 30%, which needs lateral column lengthening), inadequate medial displacement of the MDCO, failure to address spring ligament pathology, or non-compliance with postoperative immobilisation. Wound problems occur in 5% and hardware irritation in 10%, which may require removal; sural nerve injury, calcaneal non-union and recurrence are covered under Complications.

Indications. Flexible Stage IIB PTTD: talonavicular uncovering over 30% on the weight-bearing AP radiograph, with the lateral column relatively shortened. Medial procedures alone (MDCO and FDL transfer) will fail in IIB because the forefoot abduction persists, so lateral column lengthening is essential to prevent recurrence. There are two options: the Evans calcaneal lengthening osteotomy and the Cotton medial cuneiform opening-wedge osteotomy.

Evans osteotomy (preferred for most cases)

Indications. Stage IIB with significant forefoot abduction and an intact calcaneocuboid joint, free of arthritis.

Technique. Extend the MDCO incision anteriorly, protect the sural nerve and expose the anterior calcaneus.

1. Site the osteotomy 1-1.5cm posterior to the calcaneocuboid joint, perpendicular to the long axis of the calcaneus
2. Cut transversely through the lateral cortex into the medial cortex
3. Open the gap with a lamina spreader and distract 8-12mm, measured on fluoroscopy
4. Graft with tricortical iliac crest autograft (the gold standard) 8-12mm wide, or with femoral head or calcaneal allograft
5. Fix with a small fragment locking plate spanning the osteotomy, or a single screw with autogenous bone graft

Pitfalls. Lengthening over 12mm subluxes the calcaneocuboid joint, and under 8mm under-corrects. Lateral column overload causes sinus tarsi pain, which usually resolves.

Cotton osteotomy (alternative)

Indications. Stage IIB with a forefoot supination component, a hypermobile first ray, or calcaneocuboid arthritis contraindicating an Evans.

Technique. Through a 3-4cm medial incision over the medial cuneiform, make a transverse (dorsal to plantar) osteotomy in the body of the cuneiform, not the cuneiform-metatarsal joint. Open the wedge 4-6mm plantarly, graft with tricortical iliac crest or allograft, and fix with a dorsal small fragment plate, or with a staple or screws.

Trade-offs. It addresses first ray hypermobility and avoids the lateral column when the calcaneocuboid joint is arthritic. It does not address lateral column shortening directly, and risks first tarsometatarsal joint arthritis.

Subtalar arthroereisis (adjunct)

A small implant in the sinus tarsi mechanically limits excessive subtalar eversion and talar declination, blocking the hindfoot from collapsing into valgus while preserving subtalar motion. It limits motion; it does not fuse. The implants work in three ways:

• Self-locking wedge (interposition) - a spacer wedged into the sinus tarsi that physically blocks excessive eversion
• Axis-altering - shifts the position and axis of the subtalar joint
• Direct impact-blocking - a calcaneal-canal or sinus-tarsi device that abuts and limits the lateral process of the talus

Where it fits. Its best evidence and primary use are in the flexible, mobile flatfoot, particularly the paediatric flexible flatfoot. In adults it is an adjunct in young patients with a flexible, mobile Stage II deformity, addressing the dynamic deforming force while soft-tissue and bony correction is performed. It is not a standalone treatment for established adult PTTD with a degenerate or ruptured tendon, never substitutes for treating the tendon and spring ligament, and is never used in rigid Stage III disease.

Complications. Sinus tarsi pain is the commonest problem and the usual reason for implant removal, which is not uncommon. Others are under- or overcorrection, implant migration, and peroneal spasm or lateral hindfoot discomfort. Arthroereisis is more widely adopted in parts of Europe and used more selectively in other regions, reflecting concern over implant-related complications rather than a difference in the underlying biomechanics.

Sequence

The order matters: medial pathology first, then lateral correction, for a balanced reconstruction.

1. FDL transfer (medial approach) - restores dynamic support
2. Spring ligament repair, if needed
3. MDCO (lateral approach) - corrects hindfoot valgus
4. Lateral column lengthening (Evans or Cotton) - corrects forefoot abduction

After surgery

• Weeks 0-8 - non-weight-bearing cast, longer than for IIA because the lengthening must heal
• Weeks 8-12 - weight-bearing cast
• Then - CAM walker boot for 2-4 weeks, and a UCBL orthotic long-term
• Return - unrestricted walking at 6 months, sport at 12 months

Outcomes

Good-to-excellent results in 80-85% at 5 years. Talonavicular uncovering falls from over 40% to under 15%, and the forefoot abduction corrects. Lateral column pain affects 20-30% and usually resolves by 6-12 months. Foot stiffness is expected, and triple arthrodesis may be needed if it progresses. To the Stage IIA complications add:

• Evans non-union - 5-10%, higher than after MDCO alone
• Calcaneocuboid subluxation - 2-5%, from over-lengthening
• Lateral column overload syndrome - 10-20%, usually temporary

Indications. Rigid Stage III PTTD that is not passively correctable, with fixed peritalar arthritis of the subtalar, talonavicular and calcaneocuboid joints, symptomatic, limiting function and unresponsive to conservative treatment. Reconstruction is contraindicated: it will fail against rigid arthritis. Reconstruction is preferred for a flexible Stage II deformity, and neuropathy is a relative contraindication because of the Charcot risk.

Goals. Correct the rigid valgus, restore a plantigrade foot and fuse the painful arthritic joints, while preserving ankle and midfoot motion.

Technique

Set-up. Supine or lateral, by surgeon preference, with a thigh tourniquet. The two-incision technique is the most common and preferred; a single lateral extensile approach is the alternative.

Lateral incision - subtalar and calcaneocuboid joints. An oblique 8-10cm incision from the tip of the fibula to the base of the fourth metatarsal.

1. Identify and protect the sural nerve
2. Expose the posterior facet of the subtalar joint, and the anterior and middle facets if present
3. Denude all cartilage with osteotomes and curettes
4. Fish-scale the subchondral bone without violating it excessively, to preserve bone stock
5. Expose the calcaneocuboid joint, denude its cartilage and fish-scale the subchondral bone

Medial incision - talonavicular joint. A 4-6cm incision over the joint. Expose it, denude the talar head and navicular, and fish-scale the subchondral bone.

Reduce, in order.

1. Talonavicular - plantarflex the forefoot relative to the hindfoot and adduct it, reducing the talar head into the navicular and correcting the uncovering
2. Subtalar - invert the hindfoot to neutral or slight varus, with the calcaneus aligned under the talus
3. Calcaneocuboid - restore lateral column alignment

Before fixing, check for a plantigrade foot, a neutral hindfoot (or 5° of valgus), corrected forefoot abduction and a neutral forefoot with no residual varus.

Fix.

• Talonavicular - two or three 4.0-4.5mm cannulated screws from the navicular into the talar neck or body, avoiding the posterior talar neurovascular bundle
• Subtalar - two 6.5-7.0mm cannulated screws from calcaneus to talus, avoiding the subtalar neurovascular bundle: one from the posterior calcaneus into the talar body, one from the anterior calcaneus into the talar neck
• Calcaneocuboid - one or two 4.5mm screws, or a small fragment plate for comminution or bone loss
• Alternatives - locking plates for osteoporosis, bone loss or revision; bone graft (iliac crest autograft, or femoral head allograft morsels) for significant gaps or osteoporosis

Close. In layers, with a drain removed at 24-48 hours and a below-knee backslab.

After surgery

• Non-weight-bearing cast - 8-12 weeks, until radiographic union
• Weight-bearing cast - 4 weeks, making 12-16 weeks in all
• Then - CAM walker boot for 2-4 weeks, then regular shoes with orthotics as tolerated
• Radiographs - every 4-6 weeks; union typically at 12-16 weeks
• Return - unrestricted walking at 6 months, low-impact activities at 9-12 months; no high-impact sport

Outcomes

Good-to-excellent results in 75-85% at 5-10 years; 70-80% of patients are satisfied and 80-85% achieve significant pain relief. Loss of hindfoot motion is expected, with compensatory ankle and midfoot motion, and gait is near-normal in accommodative footwear. Smoking, diabetes, obesity, neuropathy and non-union predict a poor outcome.

Union. The overall union rate is 85-90%, a non-union rate of 10-15%. By joint, non-union affects the talonavicular in 5% (lowest), the subtalar in 10% and the calcaneocuboid in 15% (highest).

Other complications. Sural nerve injury in 5%, hardware irritation in 10%, and adjacent-joint arthritis of the ankle and midfoot in 20-30% at 10 years. Malunion, wound problems, infection and complex regional pain syndrome are covered under Complications.

Indications. Stage IV PTTD: rigid flatfoot with deltoid insufficiency and valgus tilt of the ankle, progressive ankle valgus deformity, pain and dysfunction, in a patient fit for major surgery. It also salvages a failed triple arthrodesis with progressive ankle valgus. Neuropathy contraindicates it (high Charcot risk), as does a non-ambulatory patient. Deltoid reconstruction is rarely successful as an isolated procedure.

Goals. Correct the ankle valgus, fuse the ankle and hindfoot, restore plantigrade alignment and relieve pain.

Option 1: pantalar arthrodesis

Ankle arthrodesis combined with triple arthrodesis, through two or three incisions, with plate and screw fixation. It gives maximal deformity correction and addresses every pathological joint, at the cost of extensive surgery, a long recovery, a high non-union rate and complete loss of ankle and hindfoot motion.

Option 2: tibiotalocalcaneal fusion with an intramedullary nail

Set-up and approach. Supine with a thigh tourniquet, through an anterior ankle incision (ankle preparation), a lateral incision (subtalar access) and a plantar heel incision (nail entry).

Joint preparation. Denude all cartilage from the tibial plafond and talar dome, fish-scale the subchondral bone and correct the valgus. Denude the subtalar joint and correct the hindfoot valgus. The talonavicular joint is optional, included if the deformity is significant.

The nail.

1. Enter the plantar calcaneus 2-3cm anterior to the posterior calcaneal tuberosity
2. Pass the guidewire from the calcaneus across the subtalar joint and talus into the tibia
3. Ream sequentially over the guidewire
4. Insert a retrograde locked tibiotalocalcaneal nail
5. Lock proximally with interlocking screws in the tibia
6. Lock distally with calcaneal screws

Compress across the ankle and the subtalar joint, and confirm plantigrade alignment.

Trade-offs. The nail is a strong construct with a lower non-union rate than plate fixation, is better in osteoporosis, and allows early weight-bearing, although that is controversial. It does not address the talonavicular or calcaneocuboid joints directly, requires the plantar heel incision, and has a learning curve.

After surgery

• Non-weight-bearing cast - 12 weeks
• Weight-bearing cast or boot - 4-6 weeks, making 16-18 weeks in all; some surgeons allow protected weight-bearing at 6 weeks with a nail (controversial)
• Return - unrestricted walking at 9-12 months; an AFO may be required long-term

Outcomes

Good results in 70-80% at 5 years, but only 60-70% of patients are satisfied, fewer than after triple arthrodesis because all motion is lost. Union is 85-90% with a nail and 75-85% with plates.

Complications.

• Non-union - 15-20%, higher than triple arthrodesis alone: ankle 10-15%, subtalar 10%
• Malunion - 10%, residual valgus
• Infection - 5-10%, from the large wound burden
• Wound healing problems - 10-15%
• Nerve injury - 5%
• Amputation - 2-5%, after severe complications, non-union or infection
• Midfoot arthritis - common, 30-40% at 10 years

Function. The patient loses all ankle and hindfoot motion, has an abnormal gait and difficulty on stairs and uneven ground, and has significant disability despite the fusion. It is end-stage disease with limited salvage options if it fails: revision fusion, bone graft augmentation, or below-knee amputation for recurrent infection, non-union or severe pain.

Sural nerve injury is the most common neurovascular injury, in 5-10% of lateral approaches (MDCO, lateral column lengthening, triple arthrodesis). Prevention is careful identification and protection throughout. A transection recognised at surgery is repaired primarily; postoperative neuropathic pain is treated with gabapentin and referral to a pain specialist.

Saphenous vein and nerve injury occurs in 5% of medial approaches (FDL transfer). Retract them anteriorly during dissection, avoid ligating the vein if possible, and manage a nerve injury as for the sural nerve.

The posterior tibial neurovascular bundle is at risk from aggressive retraction in the medial approach. Retract gently, with awareness of the anatomy; an injury needs vascular repair and nerve repair or reconstruction.

Calcaneal fracture during MDCO occurs in 2-5%, from aggressive osteotome use or osteoporotic bone. Prevention is an oscillating saw and gentle technique. Fix it at the time with additional screws or a plate, and extend non-weight-bearing afterwards.

Talar fracture is a risk of aggressive joint preparation in triple arthrodesis. Prepare carefully without excessive subchondral bone removal; a fracture is fixed, grafted and immobilised for longer.

Wound problems (first 6 weeks). Superficial dehiscence occurs in 5-10%, more often in diabetics, smokers and obese patients; malnutrition and steroid use add to the risk. Prevention is preoperative optimisation, careful tissue handling, closure without excessive tension, and avoiding haematoma, with a drain after a large dissection. Minor breakdown heals by secondary intention with local wound care; major breakdown needs debridement and delayed closure or flap coverage.

Deep infection occurs in 2-5%. Risk factors are diabetes, immunosuppression, prolonged surgery and haematoma, and it presents with fever, wound erythema and purulent drainage. Staphylococcus aureus is the most common organism, with MRSA and Gram-negatives.

• Early (under 3 weeks) - debridement and irrigation, retaining the hardware if stable
• Late (over 3 weeks) - debridement, consideration of hardware removal, and 6 weeks of IV antibiotics

Haematoma occurs in 5%. Prevention is meticulous haemostasis and a drain (removed at 24-48 hours); a small one is observed, a large or expanding one evacuated.

Cast complications. Prevention of pressure sores is adequate padding, cast checks and education; they are treated by removing the cast and caring for the wound. Compartment syndrome is rare (under 1%): pain out of proportion and pain on passive stretch demand emergency cast removal, assessment, and fasciotomy if confirmed.

Calcaneal osteotomy non-union occurs in 2-5%, with smoking, diabetes, inadequate fixation and infection as risk factors. It presents with persistent pain at the osteotomy or hardware failure, and radiographs (lucency, sclerosis, no bridging bone) and CT confirm it. A symptomatic non-union needs revision osteotomy, bone graft and rigid fixation; an asymptomatic one is observed.

Triple arthrodesis non-union (rates in the Stage III tab) is associated with smoking, diabetes, obesity, inadequate fixation and malnutrition. It presents with persistent pain and inability to weight-bear; CT is the gold standard for diagnosis. Treatment is revision fusion with bone graft (iliac crest autograft or BMP) and rigid plate-and-screw fixation, with the risk factors addressed: stop smoking, control diabetes.

Residual valgus occurs in 5-10%, from under-correction at surgery or inadequate medial displacement of the MDCO; prevention is intraoperative fluoroscopy and assessment of alignment. Mild valgus is managed with orthotics and observation, severe valgus with revision osteotomy.

Over-correction into varus occurs in 2-5%, from excessive medial displacement of the MDCO. It overloads the lateral foot, with fifth metatarsal pain and inversion instability, and is treated with orthotics (a lateral heel wedge) or revision osteotomy if severe.

Hardware. Irritation occurs in 10-15%, with palpable hardware, pain and skin irritation; remove it after union, a minimum of 12 months after surgery. Hardware failure occurs in 5%, from non-union, inadequate fixation or premature weight-bearing, and needs revision fixation with bone graft.

Recurrent deformity after Stage II reconstruction occurs in 10-15% at 5 years, with return of pain, deformity and functional limitation. The causes:

• unrecognised Stage IIB, with inadequate lateral column lengthening
• inadequate MDCO correction
• spring ligament failure
• progressive peritalar arthritis (Stage III)

A flexible recurrence is revised by reconstruction (repeat MDCO, adding lateral column lengthening if not done); rigid arthritis needs triple arthrodesis.

FDL transfer rupture or elongation occurs in 5%, from inadequate fixation or premature mobilisation, and presents as recurrent arch collapse. Revise the transfer or progress to triple arthrodesis.

Ankle arthritis after triple arthrodesis comes from the altered biomechanics and increased ankle stress, presenting with ankle pain, stiffness and reduced range of motion. Treat it conservatively with orthotics, NSAIDs and activity modification, or surgically with ankle arthrodesis or replacement (consider TTC fusion).

Midfoot arthritis after pantalar fusion follows the complete loss of ankle and hindfoot motion, which stresses the midfoot. It presents with midfoot pain and tarsometatarsal joint arthritis, and is treated with midfoot fusion or orthotics.

Complex regional pain syndrome occurs in 2-5%: pain out of proportion, allodynia, skin changes in colour and temperature, and oedema. Early recognition is critical. Treatment is physiotherapy (desensitisation), medication (gabapentin, pregabalin, ketamine), sympathetic nerve blocks and referral to a pain specialist.

Landmark Studies and Systematic Reviews

Guidelines, Registries and Global Practice

Global Epidemiology

PTTD is the most common cause of adult acquired flatfoot deformity (AAFD), driven by degenerative (not inflammatory) change in the tendon and progressing to fixed deformity if untreated (Bubra et al. 2015, J Family Med Prim Care; DOI). It predominantly affects women in the fifth-to-sixth decades, with obesity, hypertension and diabetes as the principal systemic associations. There is no national joint-replacement-style registry for flatfoot reconstruction; surgical-volume and outcome data derive from institutional series and the foot-and-ankle literature rather than population registries. Prevalence is anticipated to rise internationally as populations age and rates of overweight/obesity and diabetes increase.

Terminology Shift (Important for Modern Practice)

In 2020 an international expert consensus (Myerson, Deland and colleagues) recommended retiring the terms "PTTD" and "AAFD" in favour of "progressive collapsing foot deformity (PCFD)", replacing the linear Johnson & Strom/Myerson stages with a flexible/rigid classification across multiple deformity classes (A-E: hindfoot valgus, midfoot/forefoot abduction, forefoot varus, peritalar subluxation/dislocation, ankle valgus). The traditional Johnson & Strom (Myerson-modified) staging (Johnson & Strom 1989, Clin Orthop Relat Res; DOI not assigned, PMID 2912622) remains the dominant examination framework and is used throughout, but candidates should recognise PCFD nomenclature.

Side-by-Side Guidance and Practice Variation

There is no single high-level RCT-derived guideline; recommendations across AAOS/AOFAS (North America), BOFAS (UK), AO Foundation and EFORT-affiliated European practice converge on the same staging-driven algorithm, supported by the cohort-level evidence cited above.

Evidence Level

The evidence base is predominantly Level II-IV cohort and comparative series (e.g. Wacker/Saxby 2002; Ettinger 2019), with biomechanical/cadaveric support for soft-tissue reconstruction (Choi/Deland 2003) and expert-consensus classification work (Johnson & Strom 1989; PCFD consensus 2020). High-quality RCTs comparing reconstruction strategies are lacking, so recommendations are graded on expert consensus and cohort outcomes rather than Level I data.

Current Controversies and Ongoing Research

Controversy 1: Isolated MDCO vs MDCO + FDL Transfer for Stage IIA

Current consensus: MDCO + FDL transfer is the standard joint-sparing reconstruction, but isolated MDCO is acceptable in highly selected Stage IIA patients with minimal tendon pathology.

Controversy 2: Evans vs Cotton Osteotomy for Stage IIB

Current consensus: Evans preferred for most Stage IIB cases, Cotton reserved for patients with first ray hypermobility or calcaneocuboid arthritis.

Controversy 3: Early Weight-Bearing Post-Surgery

Traditional protocol: Non-weight-bearing 6-12 weeks

Accelerated protocol: Protected weight-bearing at 2-4 weeks in CAM boot

Evidence: Limited RCTs. Some studies suggest accelerated weight-bearing safe with rigid internal fixation (locking plates), but higher risk of hardware failure and non-union. Current consensus: Non-weight-bearing until radiographic evidence of healing.

Future Directions

Ongoing research:

• Biologic augmentation (PRP, stem cells) for Stage I tendon healing
• Patient-specific 3D-printed cutting guides for osteotomies (improved accuracy)
• Minimally invasive techniques for FDL transfer
• Ankle replacement (vs fusion) for Stage IV with good bone stock
• Long-term outcomes of spring ligament reconstruction (over 10 years)