http://upload.orthobullets.com/topic/7016/images/2nd MTP dislocation - courtesy Richardson_moved.jpg
http://upload.orthobullets.com/topic/7016/images/plantar plate.jpg
http://upload.orthobullets.com/topic/7016/images/mri plantar plate.jpg
http://upload.orthobullets.com/topic/7016/images/Weil procedure - courtesy Richardson_moved.jpg
  • Most frequent monoarticular synovitis of the MTP joints
  • Epidemiology
    • risk factors
      • elongated second metatarsal relative to the first metatarsal
        • Morton Foot
      • hallux valgus deformity
  • Pathoanatomy
    • synovitis causes the capsuloligamentous apparatus of the MTP joint to become stretched
      • stretching leads to instability
        • instability leads to deformity
    • attenuation of plantar plate
      • extension of MTP joint
      • sagittal plane deformity
      • associated with cross-over toe deformity  
    • MTP instability can lead to dorsal dislocation of MTP joint 
      • predisposition to hammer toe deformity
  • Cadaveric cross section of plantar plate  
  • MRI of plantar plate  
  • Symptoms
    • pain
    • warm joint
    • fullness of joint
  • Physical exam
    • pain and tenderness
      • may have pain in second web space
      • tenderness may be worse plantarly over plantar plate or over dorsal capsule
      • caused by inflammation or extrinsic pressure on interdigital nerve
      • pain with range of motion decreased with traction 
    • global swelling of MTP
    • motion
      • decreased plantar flexion
    • deformity & motion
      • deformity is often passively correctable in the predislocation stages
      • instability, if present, can be demonstrated with the dorsal drawer test
      • if able to dorsally sublux then attenuation of plantar plate present
      • as deformity progresses second toe may cross over adjacent toe in a varus or valgus deformity
        • disruption of a collateral ligament and the plantar plate
        • "cross over toe deformity"
  •  Radiographs
    • recommended views
      • weight-bearing AP and lateral views of foot
    • findings
      • widening or medial-lateral joint space imbalance of second MTP joint
      • dorsal subluxation of MTP joint
        • may appear like joint space narrowing or overlapping of the proximal phalanx on distal metatarsal head
      • varus or valgus deformity of toe
  • MRI
    • indications
      • if diagnosis unclear
      • quantify the extent of plantar plate or ligamentous disruption 
  • Morton's neuroma
    • may mimic Mortons neuroma
    • important to differentiate MTP synovitis from interdigital neuroma because a steroid injection into the interdigital space may weaken the capsuloligamentous structures at MTP joint leading to progressive deformity
  • Nonoperative
    • activity/shoe wear modifications, NSAIDs, external support of MTP joint
      • indications
        • first line treatment
      • technique
        • external support with crossover taping or Budin-type toe splint
        • nonoperative treatment should last 10 to 12 weeks
        • subsequently avoid shoes that aggravate symptoms
  • Operative
    • synovectomy
      • indications
        • no deformity
        • failure of nonoperative treatment
    • distal oblique shortening MT osteotomy (Weil procedure) 
      • indications
        • fixed deformity with long second metatarsal
      • technique
        • preserves joint
        • rebalances metatarsal cascade
        • relaxes plantar plate and rebalances alignment
    • FDL-to-EDL tendon transfer (Girdlestone-Taylor) or MTP capsular release with extensor tendon lengthening
      • indications
        • fixed deformity and NO long second metatarsal
        • sagittal deformity
  • Vascular compromise
    • if correcting a chronic dislocation the soft tissue, including vasculature, can contract
    • stretching of the vasculature can compromise flow
    • procedure may need to be reversed to save digit

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