Overview
Adult acquired flatfoot deformity, now termed progressive collapsing foot deformity (PCFD), is an acquired, asymmetric foot posture from peritalar instability, characterized on weight bearing by hindfoot valgus, midfoot abduction at the talonavicular joint and forefoot pronation. Posterior tibial tendon (PTT) insufficiency is a common cause, but spring ligament failure or medial column hypermobility can cause painful collapse with a functioning tendon. It differs from flexible flatfoot deformity, which is symmetric, has a functioning PTT, reflects the patient's morphology and is less symptomatic, though it can progress to tendon dysfunction. With progression the spring ligament fails, and the naviculocuneiform, first TMT and superficial deltoid (tibionavicular) structures may elongate. (Campbell)
Classification (Campbell)
Johnson and Strom (with Bluman and Myerson modifications)
Stage I: tenosynovitis with swelling, pain and sheath effusion; flexible hindfoot; single-leg heel rise possible.
Stage II: loss of PTT function, flexible deformity, cannot perform single-leg heel rise, mild sinus tarsi pain. IIA: under 30% talar head uncovering with minimal abduction. IIB: over 30% uncovering with severe abduction.
Stage III: rigid or semirigid valgus abduction deformity, possible degenerative changes, significant sinus tarsi pain.
Stage IV (Myerson): stage III plus incongruent valgus tilt of the ankle.
AOFAS PCFD classification (2020)
Stage 1 is flexible and stage 2 rigid. Classes, isolated or combined: A hindfoot valgus; B midfoot or forefoot abduction (decreased talar head coverage, sinus tarsi impingement); C forefoot varus or medial column instability (increased talus-first metatarsal angle, plantar gapping at the first TMT or naviculocuneiform joints); D peritalar subluxation (subtalar subluxation, subfibular impingement); E ankle instability (valgus tilt). Diagnostic accuracy improves with surgeon experience.
Clinical Assessment (Campbell)
Pain is the most common complaint, medial at first; with long-standing pronation it becomes lateral as the talus impinges in the sinus tarsi. Patients report fatigue, poor support and the foot "rolling out." Collapse is usually gradual.
Palpate the PTT behind the medial malleolus with the foot held in equinovarus; patients may substitute the tibialis anterior. A true single-limb heel rise with heel inversion is not possible without a functioning PTT; watch for the foot "jumping" into a locked position with external support.
"Too many toes," midfoot abduction and forefoot supination (varus) seen end-on with the hindfoot held neutral. Tendon transfer or a neutral subtalar fusion does not correct marked midfoot abduction.
Gait: failure to invert at terminal stance prevents locking of the midtarsal joints.
Gastrocnemius or gastrocsoleus contracture is frequent and worsens valgus; use the Silfverskiöld test. Treating the contracture is vital.
Imaging (Campbell)
Standing AP and lateral foot views (and ankle views). Lateral talus-first metatarsal angle (normally 0 to 10 degrees), hindfoot alignment angle and moment arm, calcaneal pitch, talonavicular coverage, AP talus-first metatarsal angle (normally about 0). MRI shows sheath effusion and tendon degeneration; weight-bearing CT shows peritalar subluxation and subfibular impingement.
Nonoperative Treatment (Campbell)
Tenosynovitis: rest, NSAIDs, walking boot or short leg cast with arch support. Avoid steroid injections around foot and ankle tendons because of rupture risk. Follow with calf and leg rehabilitation (graduated isometrics, gastrocsoleus stretching) and an orthosis with medial heel wedge and forefoot post. If this fails, perform tenosynovectomy (open or endoscopic), with an osseous procedure when the morphology warrants.
Flexible deformity: most patients obtain relief with a medially posted orthosis and an ankle-foot orthosis (double-upright AFO with medial T-strap, or a hinged polypropylene Richie brace). After 9 to 12 months many tolerate regular shoes with insoles. A structured program with an articulated AFO, high-repetition exercise and stretching allowed 83% to avoid surgery in one study.
Operative Principles for Flexible Deformity (Campbell)
Goals: pain relief and function through realignment, with motion preservation secondary to a stable, aligned foot.
Isolated FDL transfer has a high failure rate, so combine tendon reconstruction with bony correction.
MDCO (medial displacement calcaneal osteotomy) improves hindfoot alignment, heals predictably and avoids increased calcaneocuboid pressure. The 2020 consensus recommends it for isolated hindfoot valgus with adequate talonavicular coverage (under 40% uncoverage) and no significant forefoot supination, varus or abduction. Its correction is limited in stage IIB or class D deformity.
Lateral column lengthening (anterior calcaneal osteotomy, Z osteotomy or calcaneocuboid distraction arthrodesis) powerfully corrects abduction but has more complications (calcaneocuboid arthritis, sural neuritis, painful implants); MDCO is safer for mild abduction.
Medial column: spring ligament repair or reconstruction, Cotton osteotomy, or first TMT, naviculocuneiform or medial column arthrodesis (especially for class C instability).
Always address equinus (gastrocnemius recession or Achilles lengthening).
Technique 88.1: Synovectomy with Repair of Incomplete Tears (Campbell)
Rest the foot in gravity equinus. Incise from the inferior edge of the navicular tuberosity proximally 1 cm posterior to the medial malleolus, to 3 to 4 cm above the flexor retinaculum.
Identify the tendon distally and trace it to the muscle. Release the pulley behind the malleolus and the deep fascia.
Excise abnormal synovium sharply; inspect for longitudinal tears and fibrosis, and confirm the plantar slip is intact 1 cm distal to the tuberosity.
If insertion and plantar slip are intact, imbricate the tendon over 1.0 to 1.5 cm across the abnormal segment. Leave the retinaculum open and close.
Aftercare: splint until wound healing (2 weeks), weight bearing delayed 4 to 6 weeks depending on tendon quality, gentle tendon gliding in a removable boot; heavy patients may need a double-upright brace with T-strap for 3 months.
Technique 88.2: FDL Transfer to the Navicular (Campbell)
Incise from 3 to 4 cm above the medial malleolus tip, curving behind it, to 3 to 4 cm beyond the navicular tuberosity, so the PTT muscle-tendon unit can be assessed above the retinaculum.
Assess the PTT. If, freed and under slow tension, it regains length, suture it to the navicular undersurface after the transfer (rarely possible). Usually debride it and suture it under moderate tension to the transfer. If the PTT muscle is inelastic, does not contract with cautery and has lost color, do not use it; if it looks normal, resect the diseased segment and perform a side-to-side Pulvertaft weave.
Expose the FDL and FHL at the knot of Henry by dissecting along the superior border of abductor hallucis and retracting it plantarward. Branches of the medial plantar neurovascular bundle lie about 2 cm lateral to the distal navicular. The FHL crosses dorsal to the FDL.
Cut the FDL with the toes flexed; cross-connections preserve some lesser toe flexion. Rerouting through the PTT pulley is unnecessary.
Drill the navicular midportion dorsal to plantar with progressively larger bits (1/8 to 5/16 inch), ensuring enough medial bone remains to avoid fracture.
Weave a 0 or 2-0 nonabsorbable suture through the distal 1.0 to 1.5 cm, pass the tendon plantar to dorsal, take up slack, tighten further with the foot in equinovarus and suture to periosteum (or use an interference or biotenodesis screw). Advance and suture the PTT if possible.
Aftercare: bulky dressing and short leg splint in equinovarus; at 14 days change the splint, keep equinovarus for 4 to 6 weeks; then a walking cast or boot for 3 to 4 more weeks, physical therapy and a molded arch support.
Technique 88.7: Medial Displacement Calcaneal Osteotomy (Campbell)
Supine with a large ipsilateral hip bump or bean bag.
Incise inferior and parallel to the peroneal tendons, posterior and inferior to the sural nerve, from the upper calcaneal border anterior to the retrocalcaneal space to the inferior border.
Reflect the periosteum and make a transverse saw cut in line with the incision, perpendicular to the lateral calcaneal border and angled about 45 degrees posteriorly to the plane of the foot.
Spread with a toothless lamina spreader to mobilize soft tissues, then translate the tuberosity about 10 mm medially, preventing proximal migration.
Fix with a cannulated screw from posteromedial-inferior toward the sinus tarsi. A minimally invasive MDCO is similarly effective with fewer wound and nerve complications.
Spring Ligament and Cotton Osteotomy (Campbell)
Spring ligament: results of direct repair are equivocal. Excise an 8- to 10-mm wedge of the superomedial calcaneonavicular ligament and plantar talonavicular capsule with the forefoot in neutral or slight adduction and repair with interrupted 2-0 nonabsorbable sutures; suture tape augmentation is popular but unproven. When unrepairable, reconstruct with allograft, PTT autograft or a peroneus longus transfer (Williams) through a calcaneal tunnel for plantar sag or a tibial tunnel for pure abduction.
Cotton osteotomy: corrects residual forefoot supination after hindfoot correction. Make a transverse dorsal-to-plantar cut through the mid medial cuneiform at the level of the second TMT joint, lever it open (usually a 5- to 6-mm tricortical iliac crest wedge) until the first metatarsal head lies at the level of the fifth, and fix with a cannulated screw or plate. Do not place the graft too far laterally (second cuneiform impingement).
Complications
Failure of isolated soft-tissue reconstruction, undercorrection or overcorrection, calcaneocuboid arthritis and nonunion after lateral column lengthening, sural neuritis, painful hardware, and wound problems. (Campbell)
Pediatric and Adolescent Flexible Flatfoot (Tachdjian)
Flexible flatfoot is usual in infants, common in children and within normal range in adults; a depressed arch occurs in about 23% of adults. About two thirds of flatfeet are flexible and hypermobile, about one fourth have an associated triceps surae contracture, and the rest are rigid (typically tarsal coalition).
Although described as "pronated," the forefoot is actually supinated relative to the hindfoot, which becomes evident when the hindfoot is corrected.
Diagnosis: the arch reconstitutes non-weight bearing and on tiptoe standing with heel inversion; these are required findings. If absent, consider tarsal coalition, inflammatory arthritis, congenital vertical talus (rigid rocker bottom), accessory navicular or neuromuscular causes. Test heel walking and dorsiflexion with the heel locked in inversion to detect Achilles contracture, which makes flexible flatfeet symptomatic.
Radiographs: the lateral talus-first metatarsal (Meary) angle is normally 0 degrees; sag can be talonavicular or naviculocuneiform. Plantar sag improves spontaneously until about age 8.
Natural history: the arch develops through the first decade regardless of shoes or inserts. In 3600 army recruits (Harris and Beath), arch height did not correlate with disability unless an Achilles contracture was present. Randomized studies show no effect of shoe modifications or inserts on arch development, and bunion development is independent of arch height.
Treatment: no treatment for asymptomatic flexible flatfoot; education and reassurance are the mainstays, and prophylactic orthoses or special shoes should be abandoned. Stretch a contracted heel cord with the heel inverted and knee straight. For symptomatic feet (medial arch pain, callosities, fatigue, lateral sinus tarsi or fibular impingement), arch supports or supportive running shoes may help.
The adult acquired deformity differs: it is asymmetric, progressive and related to posterior tibial tendon or spring ligament failure. (Campbell)
References
Grear BJ. Disorders of the tendons and fascia and adolescent and adult acquired flatfoot deformity. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 88.
Herring JA, ed. Disorders of the foot. In: Tachdjian's Pediatric Orthopaedics. Philadelphia: Elsevier. Chapter 19, Flexible flatfoot.