Updated: 3/1/2021

Posterior Tibial Tendon Insufficiency (PTTI)

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Introduction
  • Posterior tibial tendon insufficiency is the most common cause of adult-acquired flatfoot deformity
  • Epidemiology
    • demographics
      • more common in women
      • often presents in the sixth decade
    • risk factors
      • obesity
      • hypertension
      • diabetes
      • increased age
      • corticosteroid use
      • seronegative inflammatory disorders
  • Mechanism
    • exact etiology is unknown
      • acute injury (e.g., ankle fractures caused by pronation and external rotation) vs. long-standing tendon degeneration
  • Pathoanatomy
    • early disease
      • early tenosynovitis progresses to PTTI 
        • leads to loss of medial longitudinal arch dynamic stabilization  
    • late disease  
      • PTTI contributes to attritional failure of static hindfoot stabilizers and collapse of the medial longitudinal arch
        • spring ligament complex (e.g., superomedial calcaneonavicular ligament)  
        • plantar fascia
        • plantar ligaments
      • fixed degenerative joint changes occur at late stages
    • foot deformity
      • pes planus
      • hindfoot valgus
      • forefoot varus
      • forefoot abduction
  • Associated conditions
    • inflammatory arthropathy 
      • young males with mild pes planus may have one of the following conditions
    • tarsal coalition
      • young person with rigid pes planus and/or recurrent ankle sprains
Anatomy
  • Muscle
    • tibialis posterior 
      • originates from posterior fibula, tibia, and interosseous membrane
      • innervated by tibial nerve (L4-5)
  • Tendon
    • posterior tibial tendon (PTT) lies posterior to the medial malleolus before dividing into 3 limbs 
      • anterior limb
        • inserts onto navicular tuberosity and first cuneiform
      • middle limb
        • inserts onto second and third cuneiforms, cuboid, and metatarsals 2-4
      • posterior limb
        • inserts on sustentaculum tali anteriorly
  • Blood supply
    • branches of the posterior tibial artery supply the tendon distally
    • a watershed area of poor intrinsic blood supply exists between the navicular and distal medial malleolus (2-6 cm proximal to navicular insertion)
  • Biomechanics
    • PTT lies in an axis posterior to the tibiotalar joint and medial to the axis of the subtalar joint
      • functions as a primary dynamic support for the arch
      • acts as a hindfoot invertor
      • adducts and supinates the forefoot during stance phase of gait
      • acts as secondary plantar flexor of the ankle
    • major antagonist to PTT is peroneus brevis   
    • activation of PTT allows locking of the transverse tarsal joints creating a rigid lever arm for the toe-off phase of gait 
Classification 

 
Deformity
Physical exam
Radiographs
Stage I • Tenosynovitis
• No deformity
• (+) single-heel raise 
• Normal 
Stage IIA

Flatfoot deformity
• Flexible hindfoot
• Normal forefoot

(-) single-leg heel raise
• Mild sinus tarsi pain

Arch collapse deformity 
Stage IIB • Flatfoot deformity
• Flexible hindfoot
Forefoot abduction ("too many toes", >40% talonavicular uncoverage)
Stage III
q

• Flatfoot deformity
Rigid forefoot abduction
• Rigid hindfoot valgus

• (-) single-leg heel raise
• Severe sinus tarsi pain
• Arch collapse deformity
• 
Subtalar arthritis 
Stage IV • Flatfoot deformity
• Rigid forefoot abduction
• Rigid hindfoot valgus

• Deltoid ligament compromise
• (-) single-leg heel raise
• Severe sinus tarsi pain 
• Ankle pain
• Arch collapse deformity
• 
Subtalar arthritis
• 
Talar tilt in ankle mortise 
 
Presentation
  • Symptoms
    • medial ankle/foot pain and weakness is seen early
    • progressive loss of arch
    • lateral ankle pain due to subfibular impingement is a late symptom
  • Physical exam
    • inspection & palpation
      • pes planus
        • collapse of the medial longitudinal arch 
      • hindfoot valgus deformity
        • flexible stage II
        • rigid stage III, IV
      • forefoot abduction (Stage IIB disease)
        • "too many toes" sign 
        • >40% talonavicular uncoverage
      • forefoot varus
        • place flexible heel in neutral position
        • observe the relationship of metatarsal heads
          • flexible = MT heads perpendicular to long axis of tibia and calcaneus
          • fixed = lateral border of foot is more plantar flexed than medial border
      •  tenderness just posterior to tip of medial malleolus
        • often associated with an equinus contracture q
    • range of motion
      • single-limb heel rise
        • unable to perform in stages II, III, and IV
      • PTT power
        • foot positioned in plantar and full inversion
        • unable to maintain foot position when examiner applies eversion force 
      • determine whether deformity is flexible or fixed   
        • flexible deformities are passively correctable to a plantigrade foot (stage II)
        • rigid deformities are not correctable (stages III and IV)
Imaging
  • Radiographs
    • recommended views
      • weight bearing AP and lateral foot 
      • ankle mortise
    • findings
      • AP foot 
        • increased talonavicular uncoverage
        • increased talo-first metatarsal angle (Simmon angle)
          • seen in stages II-IV
      • weight bearing lateral foot 
        • increased talo-first metatarsal angle (Meary angle)
          • angles >4° indicate pes planus 
          • seen in stages II-IV
        • decreased calcaneal pitch
          • normal angle is between 17-32°
          • indicates loss of arch height
        • decreased medial cuneiform-floor height
          • indicates loss of arch height
        • subtalar arthritis 
          • seen in stages III and IV
      • ankle mortise
        • talar tilt due to deltoid insufficiency
          • seen in stage IV
  • MRI
    • findings
      • variable amounts of tendon degeneration and arthritic changes in the talonavicular, subtalar, and tibiotalar joints 
  • Ultrasound
    • increasing role in the evaluation of pathology within the PTT
Differential
  • Pes planus secondary to 
    • midfoot pathology (osteoarthritis or chronic Lisfranc injury)
      • treat with midfoot fusion and a realignment procedure
    • incompetence of the spring ligament (primary static stabilizer of the talonavicular joint) in the absence of PTT pathology
      • treat with adjunctive spring ligament reconstruction in addition to standard flatfoot reconstruction
Treatment
  • Nonoperative
    • ankle foot orthosis
      • indications
        • initial treatment for stage II, III, and IV 
        • also for patients who are not operative candidates, sedentary/low demand (age > 60-70) 
      • technique
        • AFO family of braces (Arizona, molded, articulating) 
          • AFO found to be most effective q 
          • want medial orthotic post to support valgus collapse
          • Arizona brace is a molded leather gauntlet that provides stability to the tibiotalar joint, hindfoot, and longitudinal arch  
    • immobilization in walking cast/boot for 3-4 months 
      • indications
        • first line of treatment in stage I disease
    • custom-molded in-shoe orthosis  
      • indications
        • stage I patients after a period of immobilization
        • stage II patients q
      • technique
        • medial heel lift and longitudinal arch support 
          • medial forefoot post indicated if fixed forefoot varus is present q
          • UCBL with medial posting 
  • Operative
    • tenosynovectomy
      • indications
        • indicated in stage I disease if immobilization fails
    • FDL transfer, calcaneal osteotomy, TAL, ± forefoot correction osteotomy ± spring ligament repair ± lateral column lengthening ± medial column arthrodesis ± PTT debridement q q q    
      • indications
        • stage II disease
        • lateral column lengthening for talonavicular uncoverage
        • medial column arthrodesis if deformity is at naviculocuneiform joint
      • contraindications
        • hypermobility
        • neuromuscular conditions
        • severe subtalar arthritis
        • obesity (relative)
        • age >60-70 (relative)
    • first TMT joint arthrodesis, calcaneal osteotomy, TAL ± lateral column lengthening ± PTT debridement q 
      • indications
        • stage II disease with 1st TMT hypermobility, instability or arthritis 
    • isolated subtalar arthrodesis
      • indications
        • absence of fixed forefoot deformity
      • contraindications
        • fixed forefoot supination/varus
          • otherwise will overload lateral border of foot
        • joint hypermobility
    • hindfoot arthrodesis    
      • indications
        • stage III disease 
        • typically triple arthrodesis
        • stage II disease with severe subtalar arthritis
        • subtalar and talonavicular arthrodesis can be considered 
    • triple arthrodesis and TAL + deltoid ligament reconstruction
      • indications
        • stage IV disease with passively correctable ankle valgus
    • tibiotalocalcaneal arthrodesis
      • indications
        • stage IV disease with a rigid hindfoot, valgus angulation of the talus, and tibiotalar and subtalar arthritis
Surgical Techniques
  • FDL transfer
    • indications
      • FDL is synergistic with tibialis posterior and therefore transfer can augment function of deficient PT
      • Stage II disease
    • relative contraindications
      • rigidity of subtalar joint (<15 degrees of motion)
      • fixed forefoot varus deformity (>10-12 degrees)
    • technique
      • find FDL and FHL at knot of Henry
      • insert FDL into navicular near insertion of PT
      • vs. FHL transfer
        • FHL is more complicated to mobilize and has not shown improved results
        • in the midfoot, FHL runs under FDL q
  • Calcaneal osteotomy 
    • indicated to correct hindfoot valgus q
    • techniques include
      • medial displacement calcaneal osteotomy (MDCO) post
        • used in stage IIA (insignificant forefoot abduction)
      • Evans lateral column lengthening osteotomy post
        • used in stage IIB (significant forefoot abduction) 
        • may require additional MDCO to correct the deformity
        • overlengthening may be corrected by a first TMT fusion or medial cuneiform osteotomy
  • TAL or gastrocnemius recession
    • indicated for equinus contracture
  • Forefoot correction osteotomy 
    • indicated for fixed forefoot supination/varus (stage IIC)
    • techniques
      • plantarflexion (dorsal opening-wedge) medial cuneiform (Cotton) osteotomy q 
        • used with a stable medial column (navicular is colinear with first MT)
        • corrects residual forefoot varus after hindfoot correction is made surgically
      • medial column fusion (isolated first TMT fusion, isolated navicular fusion, or combined TMT and navicular fusions)
        • used with an unstable medial column (plantar sag at first TMT and/or naviculocuneiform joint)
  • Spring ligament repair
    • indicated with spring ligament rupture in some cases
  • PTT debridement
    • may also be required
  • Triple arthrodesis 
    • triple arthrodesis includes calcaneocuboid, talonavicular, subtalar joints   
    • additional medial column stabilization may be required

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