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Plantar Plate Repair for Subluxed Metatarsophalangeal Joint


Indications

  • Lesser metatarsophalangeal (MTP) joint instability with toe deformity and metatarsalgia

  • Plantar plate rupture

  • Subluxated lesser MTP joint

Indications Pitfalls

  • Lesser MTP joint instability is a new concept that addresses all the components behind the old concept of “crossover toe.”

  • The toe can present subtle or gross instability with different tears of the plantar plate.

Indications Controversies

  • There are no comparative studies between the different treatments to address lesser MTP joint instability.

  • Lesser metatarsal osteotomy alone has a high percentage of floating toe, persistent pain, and functional impairment of the lesser toes after treatment.

Examination/Imaging

  • Clinical observation and physical examinations should be carefully performed and graded using the clinical staging system. This grading has a close relationship with intraoperative findings ( Table 17.1 ).

    TABLE 17.1
    Clinical Grading System
    Grade 0 Metatarsal phalangeal (MTP) joint alignment; pain with no deformity
    Plantar pain, thickening or swelling under MTP joint, reduced toe purchase, negative drawer test
    Grade 1 Mild misalignment, widening of web space, medial toe deviation
    MTP joint pain and swelling, loss of toe purchase, mild positive drawer test (<50% subluxable)
    Grade 2 Moderate misalignment; medial, lateral, dorsal, or dorsomedial deformity; hyperextension of toe
    MTP joint pain, reduced swelling, no toe purchase, moderate positive drawer test (>50% subluxable)
    Grade 3 Severe misalignment, dorsal or dorsomedial deformity, crossover toe, or flexible hammertoe
    MTP joint and toe pain, little swelling, no toe purchase, very positive drawer test (dislocatable MTP joint), and flexible hammertoe
    Grade 4 Dorsomedial or dorsal dislocation, severe deformity, fixed hammertoe
    MTP joint and toe pain, little or no swelling, no toe purchase, dislocated MTP joint, fixed hammertoe

  • Lesser MTP joint drawer test is one of the most important tests that help to grade the amount of instability ( Fig. 17.1 ): G0, stable joint; G1, mild instability (subluxable <50%); G2, moderate instability (subluxable >50%); G3, gross instability (dislocatable); and G4, dislocated joint.

    FIG. 17.1

  • Digital toe purchase is used to analyze the balance and function of the muscles across the lesser MTP joint ( Fig. 17.2 ).

    • With the patient standing, a narrow strip of paper (1 cm wide and 8 cm long) is placed beneath the affected toe, and the patient is asked to plantar flex the digit. If the patient is able to prevent the paper strip from being pulled out from beneath the digit, this is considered a positive test. When the patient is able to resist in some way to the pulling out of the paper strip but not so efficiently so that the paper can be removed, the result is considered reduced, and when the power exerted on the paper strip is so weak that it can be easily removed, the test is considered negative.

    FIG. 17.2

  • Anteroposterior weight-bearing comparative plain, lateral, and oblique radiographs are necessary to evaluate the MTP joint and exclude osseous pathology.

  • An anteroposterior weight-bearing radiograph can demonstrate second metatarsal pathologic protrusion, altered metatarsal parabola, splaying of the affected and adjacent toe, or a subluxated toe with overlapping of the proximal phalanx over the metatarsal head ( Fig. 17.3A ).

    FIG. 17.3

  • A lateral weight-bearing radiograph can demonstrate a toe elevation with the proximal phalanx lying dorsally at the metatarsal head ( Fig. 17.3B ).

  • Ultrasonography is a very good method to identify plantar plate tears. As always, the accuracy and specificity of this diagnostic tool depend on the experience of the examiner, and this could be an obstacle to its use.

  • Magnetic resonance imaging can present an eccentric pericapsular soft-tissue thickening ( STT ; Fig. 17.4 ), increase of lesser metatarsal supination ( Fig. 17.5 ), and rupture of the plantar plate ( arrows ) in sagittal and coronal images ( Fig. 17.6 ).

    FIG. 17.4

    FIG. 17.5

    FIG. 17.6

  • There are reproducible differences in the measurement of metatarsal axis rotation and second metatarsal protrusion and their relation with plantar plate tears. Lesser metatarsal supination >36° or second metatarsal protrusion >4 mm trends toward a correlation with plantar plate tear. Lesser metatarsal supination <24° is a strong negative predictor, and second metatarsal protrusion >4.5 mm is a strong positive predictor of plantar plate tear.

Treatment Options

  • Each type of plantar plate tear has a particular treatment.

  • The Anatomic Grading System is a classification that addresses plantar plate dysfunction and matches the Clinical Staging System. This anatomic grading helps in the surgical planning and management of an instable lesser MTP joint ( Fig. 17.7 ).

    • G0 represents plantar plate attenuation or discoloration, 23%.

    • G1 represents a transverse distal tear (adjacent to the insertion into the proximal phalanx), <50%; medial or lateral, 12%.

    • G2 represents a transverse distal tear (adjacent to the insertion into the proximal phalanx) complete or almost complete, 15%.

    • G3 represents combined transverse and longitudinal extensive tears; can assume the “7” shape, inverted “7” shape, or “T” shape, 33%.

    • G4 represents an extensive tear with a button hole (protrusion of the metatarsal head through the defect) resulting from the combination of transverse and longitudinal tears, 17%.

    FIG. 17.7

Positioning

  • The patient is placed supine on the operating table with a tourniquet applied at the shin or thigh level and inflated to 300 mmHg after exsanguination.

  • Surgery can be performed under regional block anesthesia and sedation.

Positioning Pearls

  • To avoid external rotation of the foot, one can use a small pad under the back.

  • We do recommend the use of a pad under the ankle and distal end of the leg to allow free movements around the forefoot during the surgical procedure.

  • The surgeon starts the procedure facing the dorsal aspect of the forefoot while the first assistant faces the sole of the foot. In some steps of the procedure, they will change their positions to make the surgical maneuvers feasible.

Positioning Equipment

  • Radiolucent table

  • Tourniquet

  • Silicone pads

Surgical Anatomy

  • Fig. 17.8 shows the anatomy of the lesser MTP joints in dorsomedial view.

    FIG. 17.8

  • Fig. 17.9 shows the anatomy of the lesser MTP joints in coronal view.

    FIG. 17.9

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