Plantar Plate Injury Of The Lesser Mtp Joints And Metatarsalgia

Metatarsalgia is a generic term applied to a spectrum of painful conditions in the region of the metatarsal heads resulting from chronic repetitive stress at the forefoot, most commonly affecting the second MTP joint. Differential diagnosis of metatarsalgia includes plantar plate injury, MTP joint synovitis, stress fracture, Freiberg's infraction (osteonecrosis of the metatarsal head), arthritis, interdigital (aka Morton's) neuroma, and synovial cyst formation.

The plantar plate of the lesser MTP joints primarily differs from that of the first MTP joint by the absence of the hallucal sesamoids. That means that the plantar plate articulates directly with the plantar surface of the lesser metatarsal head and functions without the benefit of the sesamoids to provide critical articular stability and shock absorption. Whereas turf toe represents a sports-related acute traumatic rupture of the plantar plate of the first MTP joint, rupture of the plantar plate of the lesser MTPjoints is typically a chronic acquired degenerative condition, developed over time as a result of increased loading [29].

The plantar plate is a firm, flexible fibrocartilaginous structure that has a mean length of 20 mm and average thickness of 2 mm at the second MTP joint [30]. Similar to the hallux, the plantar plate serves as the central attachment for ligamentous, capsular, and tendinous structures at the lesser MTP joint. It represents the distal insertion of the plantar fascia. The plantar third of the fibrocartilaginous plate blends with the deep transverse intermetatarsal

Ruptured Plantar PlateRuptured Plantar PlateRuptured Plantar PlateRuptured Plantar Plate

Fig. 15. Coronal (A) and sagittal (B) STIR images through the forefoot demonstrate soft tissue edema plantar to the first metatarsal head in the region of the sesamoids and plantar plate. Straight arrows (A) indicate the sesamoids; an arrowhead indicates the flexor hallucis longus tendon. Curved arrows (A, B) demonstrate defects in the plantar plate in the intersesamoidal region and at the capsular attachment. Sagittal (C] and axial STIR (D) images demonstrate associated soft tissue edema in the adductor hallucis musculature.

ligament, whereas the dorsal surface has a smooth, articular-like surface, gliding deep to the metatarsal head during ambulation.

Paired accessory collateral ligaments (ACL) course proximal-to-distal and dorsal-to-plantar originating at the dorsal tubercle of the lesser metatarsals to broadly insert on the medial and lateral margins of the plantar plate. Smaller, more obliquely oriented paired phalangeal collateral ligaments (PCL) also arise from the dorsal tubercle, but share a conjoint insertion along with the plantar plate at the medial and lateral base of the proximal phalanx [30]. The flexor tendon sheath is cradled within a central concavity at the deep surface of the plantar plate, anchored by a fibrous pulley [31]. The tendon sheath contains the flexor digitorum brevis (FDB) and the flexor digitorm longus (FDL) tendons. The FDB splits to straddle the FDL at the level of the proximal interpha-langeal (PIP) joint to insert bilaterally onto the base of the middle phalanx, whereas the FDL inserts onto the plantar base of the distal phalanx. Dorsally, the extensor hood and sling represent a fibroaponeurotic expansion extending bilaterally from the borders of the extensor digitorum longus (EDL) tendon sheath, with direct insertions onto the plantar plate, the deep transverse inter-metatarsal ligament, and base of the proximal phalanx [30].

MTP joint synovitis most commonly results from chronic excessive loading of the MTP joint [32]. At the lesser MTP joints, compressive and tensile forces of weight bearing and ambulation are greatest at the second ray and are increased in the context of hallux valgus or developmental elongation of the second metatarsal. Shoe gear with elevated heels and a narrow toe box increases axial loading, to the greatest degree at the second MTP joint. Chronic synovitis often stretches the joint capsule and contributes to MTP joint instability [33]. Degeneration and attritional change of the plantar plate and collateral ligaments may ensue.

MTP joint instability often accompanies plantar plate degeneration and rupture. Symptoms include pain and capsular and submetatarsal swelling. Pain is typically worst in the toe-off phase of ambulation, at which time the tensile forces across the degenerated plantar plate are maximal. Instability is detected and quantified by the Vertical Stress Test, which is simply performed by stabilizing the metatarsal head and forcibly displacing the proximal phalanx dor-sally. A positive test not only reveals instability, but elicits pain at the dorsal base of the proximal phalanx.

Plantar plate rupture most commonly occurs at the distal, lateral insertion onto the base of the proximal phalanx.

High-resolution MRI of the forefoot is the gold standard for imaging of plantar plate rupture and differentiating it from other possible causes of metatarsal-gia. Coronal (short axis) MR images through the forefoot demonstrate the plantar plate as a thick low signal band deep to the metatarsal head, thinnest centrally and thickest distally. A shallow groove at the central plantar surface accommodates the flexor tendon sheath (Fig. 16A). Collateral ligaments are seen as vertically oriented bands medially and laterally, inserting bilaterally onto the margins of the plantar plate and the base of the proximal phalanx (Fig. 16C,D). Oblique sagittal images are plotted off of an axial localizer along the axis of the second metatarsal shaft. In the normal, oblique sagittal imaging permits visualization of a distinct, narrow zone of high signal intensity representing hyaline cartilage undercutting the low signal fibrocartilage [34] near the distal insertion of the plantar plate, which should not measure more than 2.5 mm [29] (Fig. 16B). In plane visualization of the ACL and PCL is inconstant and fortuitous in the oblique sagittal plane. Whereas axial (long axis) imaging is not useful in detection of plantar plate or collateral ligament rupture, it permits qualitative evaluation of hallux valgus, second metatarsal protrusion, and identification of possible marrow signal abnormalities attendant to stress injury, osteonecrosis, and arthritis.

In the context of plantar plate degeneration or rupture there is pathologic elongation and marginal indistinctness of the high signal intensity zone at the distal insertion of the plantar plate [29] (Fig. 17A). With capsular insufficiency and its attendant plantar plate and ligamentous degeneration, there is progressive hyperextension of the toe at the MTP joint. Degenerative thickening or thinning and signal distortion of the plantar plate and/or collateral ligaments is best demonstrated in the coronal plane. A rupture, seen as a high signal

Lesser Metatarsal Surgery

Fig. 16. Coronal 2D-Gradient Recalled Echo (GRE) image (A) at the level of the second metatarsal head demonstrates the intact plantar plate (arrowheads) with the subjacent flexor digito-rum tendon (curved arrow). Sagittal 2D-GRE images demonstrate normal anatomy. (B) The plantar plate lies subjacent to the second metatarsal head (arrow); note the focal high signal zone representing undercutting of hyaline cartilage at the distal margin of the fibrocartilaginous plate (curved arrow). The arrowhead indicates the flexor digitorum tendon. (C) The phalangeal collateral ligament (arrow) is coursing obliquely from the dorsal tubercle of the second metatarsal to its conjoint insertion with the plantar plate at the base of the proximal phalanx (curved arrow). (D) The broader, more vertically oriented accessory collateral ligament (arrowhead).

Fig. 16. Coronal 2D-Gradient Recalled Echo (GRE) image (A) at the level of the second metatarsal head demonstrates the intact plantar plate (arrowheads) with the subjacent flexor digito-rum tendon (curved arrow). Sagittal 2D-GRE images demonstrate normal anatomy. (B) The plantar plate lies subjacent to the second metatarsal head (arrow); note the focal high signal zone representing undercutting of hyaline cartilage at the distal margin of the fibrocartilaginous plate (curved arrow). The arrowhead indicates the flexor digitorum tendon. (C) The phalangeal collateral ligament (arrow) is coursing obliquely from the dorsal tubercle of the second metatarsal to its conjoint insertion with the plantar plate at the base of the proximal phalanx (curved arrow). (D) The broader, more vertically oriented accessory collateral ligament (arrowhead).

defect on fluid-sensitive sequences, most commonly at the distal lateral conjoint insertion of the plantar plate and PCL at the base of the proximal phalanx (Fig. 17C), is often accompanied by medial displacement of the plantar plate with respect to the metatarsal head [29]. Partial tear may be associated with adjacent ganglion formation (Fig. 17D). Complete rupture may be associated with dorsal dislocation of the toe (Fig. 17B). Coronal fluid-sensitive sequences best demonstrate synovitis, submetatarsal soft tissue edema, and intermetatarsal bursitis, all of which are common in the setting of plantar plate degeneration.

Arthritis Joint Pain

Arthritis Joint Pain

Arthritis is a general term which is commonly associated with a number of painful conditions affecting the joints and bones. The term arthritis literally translates to joint inflammation.

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Responses

  • olive
    What is done for MTP plantar plate injury?
    7 years ago
  • Nasih Kifle
    WHAT IS DISTAL ATTACHMENT OF THE PLANTAR PLATE?
    7 years ago
  • asmara filmon
    What is a central defect plantar plate at phalangeal attachment?
    10 months ago

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