How To Treat Sesamoid Injuries

By Mark A. Caselli, DPM and Mohsen Khoshneviszadeh

Foot injuries are one of the most common injuries for athletes. Specifically, among all the joints and bones of the foot, the first metatarsophalangeal joint with its sesamoid complex is the most commonly affected. It is usually clear when an athletic injury involves the first metatarsophalangeal joint complex. However, identifying the specific injured structures and arriving at a precise diagnosis can be difficult. Acute or chronic injures to the sesamoid bones or their associated tendon and joint capsule apparatus may cause pain, limping and difficulty wearing shoes, all aggravated by even a simple activity like walking. The resultant clinical impact makes both acute (traumatic) and overuse injuries major causes of competitive and recreational athletic disability. Two hallucal sesamoids are situated under the first metatarsal head. The medial (tibial) sesamoid tends to be larger, oval-shaped and presents in a bipartite or multipartite form in 10 to 33 percent of feet. The lateral (fibular) sesamoid is smaller and rounder. Each sesamoid has an articular surface of hyaline cartilage, allowing it to articulate with the plantar aspect of the distal first metatarsal. While sesamoids elsewhere in the body occur variably, the hallucal sesamoids are virtually constant. These sesamoids function as an integral part of the first MPJ. The hallucal sesamoids play an important role in great toe function as they absorb weightbearing pressure, reduce friction and protect tendons. The functional complexity and anatomic location of these small bones make them vulnerable to injury from shear and loading forces. During running, more than half the weightbearing force travels through the great toe complex. Forces up to three times the athlete’s body weight may be transmitted across the sesamoids. The medial sesamoid bears most of this force and thus is more prone to injury than the lateral sesamoid. Injury to the hallucal sesamoids can cause incapacitating pain. Although you usually can diagnose traumatic injuries easily, you may overlook other pathologic conditions caused by overuse. Careful physical and radiographic examinations (including bone scans) may be necessary to determine the structures damaged, extent of damage and the optimal treatment plan. Sesamoidal injures are divided into acute and chronic injures. Acute injuries are traumatic fracture/dislocations of the sesamoids and sesamoidal apparatus caused by trauma to the first MPJ complex. Chronic injuries of the sesamoids can be divided into three groups: Stress fractures, osteochondritis and sesamoiditis. How To Detect And Treat Acute Injuries Fracture dislocation of the sesamoids and sesamoidal apparatus is relatively rare. It usually results from a high-impact force like a fall, an injury which the pathological force of hyperextension of the MPJ causes. The hallux is dorsiflexed, causing stretching of the plantar joint capsule. This causes distal distraction of the sesamoids due to their strong attachments to the plantar base of the proximal phalanx. As pathologic dorsiflexion continues, the capsule ruptures from its insertion at the plantar metatarsal neck. The hallux, with the sesamoids attached to the base of the proximal phalanx, dislocates dorsally to override the metatarsal head. The metatarsal head is then driven plantarly. The pathologic dorsiflexion may dislocate the sesamoids dorsally with the intersesamoidal ligament still intact. It also may result in either rupture of the intersesamoidal ligament or a transverse fracture of one of the sesamoids. Jahss classified two types of first MPJ dislocation. Type I is a dorsal dislocation of the proximal phalanx and sesamoids on the first metatarsal head with the intersesamoidal ligament still intact. You cannot reduce this type of dislocation by closed means because of the intact intersesamoidal ligament. However, you can often use closed means to reduce the two groups of Type II dislocations. Type IIA is a dorsal dislocation of the proximal phalanx and sesamoids on the first metatarsal head with rupture of the intersesamoidal ligament, which results in wide separation of the sesamoids. Type IIB shows a transverse fracture of one of the sesamoids. What About Sesamoid Stress Fractures? Stress fractures occur when an athlete applies abnormal repetitive stress to normal bone or applies normal repetitive stress to a weakened bone. Fractures are more common in long-distance runners.

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