MTP Dislocations

Topic updated on 02/22/16 8:58pm
  • A condition characterized by multiplanar instability of MTP joint
    • often seen with "crossover toe"
    • dorsomedial subluxation
  • Pathoanatomic stages
    • plantar plate disrupted 
      • can be caused by
        • traumatic rupture 
        • chronic inflammation (more common)
    • lateral collateral ligament fails 
      • leads to medial deviation of the second toe
      • plantar plate, with its flexor tendon attachments, displace medially
      • medial displacement of the proximal phalanx relative to the metatarsal
    • medial structures become contracted
      • lumbrical and interosseous tendons, medial collateral ligament (MCL), and medial capsule become tight and contracted creating adduction force
    • plantar plate subsequently fails
      • hyperextension forces on the proximal phalanx result in dorsal instability
  • Associated conditions
    • MTP synovitis, deformity often accelerated by cortisone injection done for either misdiagnosed Morton's neuroma or into the MPJ for synovitis.
  • Plantar plate 
    • anatomy
      • broad, thick ligamentous structure that spans the plantar aspect of the MTP joint 
      • origin
        • on the metatarsal head via a thin synovial attachment, just proximal to the metatarsal articular surface
      • insertion
        • plantar base of the proximal phalanx
    • function
      • resists tensile loads in the sagittal plane (particularly in dorsiflexion of the joint)
      • cushion the joint and support weightbearing forces
  • Symptoms
    • pain
    • walking on “marble in the ball of their foot”
    • early instability (prior to deformity) may be confused with Morton's neuroma, deformity often follows cortisone injection for presumed neuroma
  • Physical exam
    • callus under the metatarsal head
    • dorsomedial deviation of the toe in relation to the metatarsal
    • hammertoe (flexion at the PIPJ, extension at the MPJ)
    • dorsal instability found on "drawer test "
      • grip toe (proximal phalanx) with one hand and the metatarsal head with the other and move toe dorsally
  • Radiographs
    • recommended views
      • weightbearing AP, oblique, and lateral
    • findings
      • AP shows dislocation of the proximal phalanx (medial more often than lateral)
      • weightbearing lateral shows hyperextension and dorsal dislocation of the proximal phalanx
  • MRI
    • indications
      • rule out other pathology
      • elucidate pathology of surrounding structures
    • used in early stages of MTP synovitis to evaluate plantar plate but not necessarily useful in dislocation
  • Nonoperative
    • taping, shoe modification, metatarsal pads, Budin splint, and NSAIDS
      • indications
        • first line of treatment
      • will not correct deformity
  • Operative
    • distal oblique shortening MT osteotomy (Weil procedure)  
      • indications
        • significant pain and loss of function
        • fixed deformity 
    • plantar plate repair
      • performed with metatarsal osteotomy
      • sutures passed through distal plantar plate and then through drill holes in proximal phalanx
    • flexor to extensor tendon transfer
      • FDL split and brought over top of proximal phalanx to stabilize joint
    • EDB transfer under intermetatarsal ligament
Surgical Techniques
  • Distal oblique shortening MT osteotomy (Weil procedure)
    • soft tissue balancing
      • dorsal and medial capsular release with lateral capsular reefing can be used in combination with Weil osteotomy
      • EDB tendon transfer after rerouting tendon through transverse intermetatarsal ligament results in a dynamic stabilizer of incompetent lateral structures
      • flexor digitorum longus (FDL)–to–extensor digitorum longus (EDL) tendon transfer (Girdlestone-Taylor procedure)
      • resection arthroplasty of the metatarsal head (DuVries)
      • plantar plate repair as above
    • osteotomy
      • intra-articular osteotomy that achieves longitudinal decompression through shortening and allows joint reduction.
      • metatarsal (MT) is exposed and the direction of shortening in the original Weil procedure runs mostly parallel to the plantar aspect of the foot. 
    • fixation
      • osteotomy is fixed by means of a screw running perpendicular to the osteotomy line.
  • Floating toe deformity
    • inability to flex MTP joint causing 2nd digit dorsiflexion deformity (ie. floating toe) 
    • most common complication 
  • Toe 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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Qbank (4 Questions)

(OBQ11.24) Floating-toe deformity is the most common complication of which of the following surgical procedures used to treat central metatarsalgia? Topic Review Topic

1. Dorsal soft-tissue release with pin fixation
2. Silicone implant arthroplasty
3. MTP joint excisional arthroplasty
4. Metatarsal shaft osteotomy (Helal procedure)
5. Metatarsal neck osteotomy (Weil procedure)

(OBQ09.61) A 57-year-old man plays 45 holes of golf per week and has foot pain during the toe-off phase of gait. He notes the foot pain started 3 months ago after walking up a hill and falling forward on some wet grass. Your exam shows skin callosities dorsally at the 2nd PIP joint and plantarly at the 2nd MT head. Radiographs show a hyperextension deformity of the 2nd proximal phalanx in relation to the metatarsal. All of the following are true about this patient's condition EXCEPT: Topic Review Topic

1. Symptomatic treatment initially includes extra depth shoes, metatarsal pads, and well-padded liners
2. The MTP drawer test will likely show laxity at the MTP joint in the dorsal-plantar plane
3. Repeated MTP dorsiflexion weakens the plantar aponeurosis, plantar plate, and capsular stabilizers
4. Plantar callosities result from dorsal displacement of the fatty cushion underneath the metatarsal head
5. Condition is a result of repetitive stresses causing microfractures with subsequent compromised blood supply to the metatarsal subchondral bone

(OBQ09.191) A 40-year-old man has metatarsalgia secondary to a chronically dislocated 2nd metatarsalphalangeal(MTP) joint. Nonoperative modalities including shoe modifications have failed to improved his symptoms. When comparing osteotomy B (Weil osteotomy) to osteotomy A (Helal osteotomy) as shown in Figure A, all of the following are true EXCEPT: Topic Review Topic
FIGURES: A          

1. Higher patient satisfaction rates
2. Lower incidence of recurrent metatarsalgia
3. Fewer transfer lesions
4. Higher percentage of radiographic reduction and maintenance of the MTP joint reduction
5. Increased rate of malunion or pseudoarthrosis

(OBQ04.107) A 70-year-old man complains of inability to wear normal shoes on his left foot due to a second and third toe deformities. Radiographs are shown in Figures A and B. He decides to undergo surgical treatment. After intra-operative extensor tendon lengthening and capsular release, the joints continue to subluxate. What is the next step to correct the deformities? Topic Review Topic
FIGURES: A   B        

1. Flexor tendon resection
2. Proximal phalangeal crescentic osteotomy
3. Metatarsophalangeal joint arthrodesis
4. Distraction osteogenesis of the metatarsal
5. Metatarsal shortening osteotomy



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