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MRI Web Clinic - March 2003
Turf Toe
by Mark H. Awh, M.D.
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Clinical History: Professional football player with a painful 1st metatarsophalangeal joint. What is your diagnosis" What are the pertinent findings?
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Answer
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Turf toe refers to a hyperextension injury at the 1st metatarsophalangeal (MTP) joint of the great toe, with resultant capsuloligamentous damage of varying severity. The term was originally coined to describe the characteristic injury found at the great toe of football players injured on artificial turf. The characteristic anatomical injury in turf toe involves the plantar plate and the plantar capsuloligamentous complex. The injury is graded based on the degree of injury to these plantar structures. With grade 1 injuries, stretching of the complex occurs. Grade 2 injuries refer to partial tears of the complex and Grade 3 injuries indicate a complete tear of the complex.
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A fat-suppressed proton-density weighted axial image following turf toe injury reveals characteristic edema within the plantar aspect of the 1st metatarsal head (white arrow) and within the plantar plate (black arrow). The medial and lateral sesamoids (arrowheads) remain in normal position.
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Striking edema is apparent within the 1st metatarsal head (arrow) on the corresponding fat-suppressed T2-weighted sagittal view. Fluid signal intensity indicates tearing (arrowhead) at the site of attachment of the plantar plate to the base of the proximal phalanx.
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Anatomy at the 1st Metatarsophalangeal Joint
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Detailed view of the 1st MTP joint from below. The abductor hallucis (ABH) and the adductor hallucis (ADH) muscles course adjacent to the medial and lateral sesamoids (S) respectively. The tendons of the flexor hallucis brevis (FHB) engulf the sesamoids, while the tendon of the flexor hallucis longus (FHL) runs between the sesamoids.
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Dorsal view of the 1st MTP joint with the metatarsal head removed reveals the smooth articular surfaces of the medial and lateral sesamoids, which are joined by the intersesamoidal ligament (arrowhead). The plantar plate (arrow) attaches the sesamoids to the base of the proximal phalanx.
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Imaging of Turf Toe
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Plain films in patients with turf toe are usually normal, though occasionally a capsular avulsion fracture is noted at the 1st metatarsal head or at the base of the proximal phalanx. MR is much more sensitive and is considered the gold standard for diagnosis of turf toe. A bone bruise is often present along the plantar aspect of the 1st metatarsal head, and is a characteristic sign in patients with turf toe. The soft-tissue injuries caused by the hyperextension event result in edema plantar to the 1st MTP joint. The associated signal abnormalities are best appreciated on T2-weighed images with fat-suppression or on STIR examinations. With plantar plate rupture, discontinuity may seen along the course of the plantar plate. Capsuloligamentous injuries in patients with grade 3 injuries vary widely. Sesamoid dislocation may be noted in severe cases, and require a complex injury to the stabilizing soft tissues at the joint.
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A T1-weighted sagittal image of a patient following severe turf toe injury reveals ill-defined soft-tissue thickening and edema (arrow) throughout the region of the plantar plate. The medial sesamoid (arrowhead) is dislocated and displaced proximally.
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Fluid fills the expected location of the medial sesamoid (black arrow) on a T2-weighted axial image obtained with fat-suppression. Edema is evident within the plantar aspect of the 1st metatarsal head (white arrow) and partial tearing is seen at the site where the abductor hallucis tendon would normally attach to the medial sesamoid (arrowhead).
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Injuries at the great toe that may mimic turf toe include occult fracture, sesamoiditis, and flexor hallucis longus tendinitis. MR's ability to accurately evaluate the osseous and soft tissue anatomy at the 1st MTP joint allows an accurate diagnosis to be made in such cases.
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Conclusion
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Injuries to the great toe are common in athletes. When one considers that 70-80% of the impact stress upon the foot is transmitted through the great toe, it is easy to understand why such injuries can be so debilitating. Turf toe is an increasingly common injury that involves the great toe, and the complex anatomy and range of injuries involved with this entity are often under-appreciated. In patients with suspected turf toe, MR provides accurate assessment and diagnosis of the osseous and soft-tissue abnormalities that may be present.
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