The sports medicine practitioner is fascinated by the anatomy, physiology and pathology of the sesamoid bones. We now recognize their importance of sesamoid bones in relation to functional gait biomechanics (pathology such as hallux limitus); symptoms of pain (post-overuse or trauma); the particular sport in which the athlete participates (football, soccer, running, tennis and others); and the footwear athletes wear.
The sesamoid bones are isolated bones that lie within the flexor tendon. These bones have unique anatomical characteristics with the dorsal concavity and the plantar convexity. The tibial sesamoid is typically larger and longer, and lies more distally than the smaller, more rounded fibular sesamoid. Both sesamoids lie plantar and within each respective tendinous expansion of the medial and lateral heads of the flexor hallucis brevis muscle.1
The sesamoids act together as a fulcrum to increase the angle of application and improve the efficiency of the flexor hallucis longus tendon’s function. This also stabilizes the hallux. The sesamoids articulate dorsally with plantar facets on the first metatarsal head. These concave facets are separated by a crista or intersesamoid ridge, which separates the medial and lateral metatarsal facet. In one study, 3 to 10 percent of the feet evaluated had either a bipartite or multipartite sesamoid.2 The sesamoids have articular cartilage that lies within the tendon and is at risk for injury. The sesamoid provides both protection and shock absorption for both the joint and tendon.
Additionally, as a pulley, the sesamoids increase the musculotendinous mechanical advantage for the first metatarsophalangeal joint (MPJ), particularly during the propulsive phase of gait.3 In running, court sports and other high-impact sports, the high ground reactive forces act upon the first MPJ. Together via propulsion “push off” and pronatory “pivoting” of the hallux, the sesamoids act by assisting gait and providing additional flexor strength. Research has shown that forces three times body weight pass through the sesamoids during the weight shift of a normal gait cycle.4 Forces are greater plantar to the tibial sesamoid. This explains why the tibial sesamoid is involved in more injuries than the fibular sesamoid.
The arterial supply is critical for the sesamoid and is important in sesamoid injuries when it comes to healing and potential surgical outcomes. The blood supply arises from the medial plantar artery (25 percent), the plantar arch (25 percent) or from both sources (50 percent).5,6 Both sesamoids receive blood supply from proximal and plantar sources, but are less vascularized distally.
Understanding The Biomechanics Of The Sesamoids
In cases of hallux abductovalgus, a lateral shift of the tibial sesamoid will occur, creating a scenario in which the medial sesamoid is susceptible to increased forces plantar to the first metatarsal head. With the tibial sesamoid vulnerable to these excessive forces, subchondral erosion and/or stress fracture can occur. In cases of hallux limitus, with either a semi-rigid or rigid plantarflexed first ray, it is not unusual to see a condition such as sesamoiditis or injury to the sesamoid apparatus.
While weightbearing, the sesamoids are located just slightly posterior to the metatarsal head. As the MPJ dorsiflexes during gait, the sesamoids are distracted distally. This action provides for protection of the plantar surface of the first metatarsal head while acting as a shock absorber against forces on the medial aspect of the forefoot.
Sesamoid mobility is critically important since sesamoid arthrodesis can prevent hallux dorsiflexion.7 One can evaluate sesamoid mobility by loading the first ray while palpating the sesamoid apparatus and dorsiflexing the hallux. The sesamoid apparatus should glide smoothly over the metatarsal head.
When Sesamoid Injury Occurs
When injury to the sesamoids does occur, symptoms will include limited movement and pain upon dorsiflexion of the first MPJ. Routine radiographs with comparison views of the contralateral foot can often determine whether there is an actual fracture or if it is a bipartite or tripartite sesamoid. An axial or “sesamoidal” view radiograph can aid in determining whether there is deviation of the sesamoids. Additionally, the radiograph can also assist in identifying whether the tibial sesamoid is more plantigrade and, upon weightbearing, if the standing forces are greater than normal. Further investigative studies (i.e. bone scans and computed tomography (CT) scans) can help determine whether a fracture is present.3
In cases when injury or fracture has occurred and sesamoid dysfunction develops, restricted range of motion of the first MPJ may lead to a compensated gait pattern. The athlete may compensate by either an earlier or later propulsive phase of hallux during “toe-off” to minimize dorsiflexion of the hallux. When unrelenting pain and exhaustive conservative measures fail, postsurgical excision of the sesamoid may leave the hallux weakened in regard to plantarflexion or purchasing the ground during the toe-off phase of gait.
A Closer Look At The Classification Of Injuries To The Sesamoid Apparatus
There are four categories involved with injury to the sesamoid apparatus. The injuries can either be acute in nature, such as avulsion fractures, or of the chronic type involving repetitive stress to the sesamoids, or involving the medial or lateral support structures.
Sesamoiditis. This encompasses tendinitis of the flexor hallucis longus at the MPJ, sesamoid bursitis, synovitis of the MPJ, chondromalacia, and painful bi- or tripartite sesamoids.6 This condition usually is due to repetitive stress and compression upon the sesamoid as well as the first MPJ rather than an acute injury. This injury typically occurs in the cavus foot, with a plantarflexed semi- or rigid first ray, with functional or structural hallux limitus and when there is a high degree of forefoot varus.
Stress fractures of the sesamoid. These stress fractures occur in running, court sports and dancing due to high impact and compression. These fractures are characterized by pain, which may limit play or performance. Pain and inflammation from this injury may be severe enough to limit a player’s ability to compete.
A standard radiograph two to three weeks after the initial injury will reveal a stress fracture to the sesamoid bone. When there is suspicion of a stress fracture, it may not be readily apparent on plain film radiographs. In this case, a bone scan, CT scan and/or possibly a magnetic resonance image (MRI) may be necessary.
A clear diagnosis and early conservative management are essential with this particular injury. In the absence of an accurate diagnosis or sufficiently aggressive treatment, I have found the fracture may not go on to complete healing or may eventually progress to a delayed union at four months, non-union fracture at six months or osteochondrosis with possible avascular necrosis. The treatment plan may require additional months of immobilization or offloading as well as communication with the patient about adherence.
Proper treatment includes six weeks of below-knee casting followed by another six weeks of protection (i.e., a controlled ankle motion (CAM) walker boot, surgical shoe or running shoe). The use of prescription orthoses, particularly for the runner, is necessary to disperse pressure from the region of the sesamoid, often with a Morton’s extension (dancer’s pad). The orthotic will help prevent injury to the uninjured remaining sesamoid as well as further damage to the undersurface of the metatarsal head. It will also help in preventing compensation to the lateral aspect of the rearfoot and forefoot. In addition to offloading, other remedies may include the use of bone stimulation or platelet rich plasma in order to stimulate osteogenesis.
After exhausting all conservative measures after a prescribed period of time, surgical intervention may be indicated with the excision of the sesamoid non-union fracture. Intraoperative protection of the first MPJ support structures is essential. Again, the postoperative use of orthotics is imperative to provide for normal length of the flexor hallucis longus and brevis tendons, and assist in preventing the formation of hallux abductovalgus (after a tibial sesamoid excision).
Acute sesamoid fracture. This fracture occurs in dancers, basketball players, volleyball players and those playing other sports in which increased load from a height creates compression and stress to the sesamoid. One can recognize this injury on plain radiographs because of the sharply defined edges of the fragments with the contours being serrated.8,9 Additionally, evidence of a bony callus or attempted healing on serial radiographs is often visible. These fractures are more frequent in the tibial sesamoid and have a transverse compression appearance. An absence of similar radiographic findings in plain films of the contralateral limb is imperative to define the acute stress fracture.10 In this category, the avulsion fracture is the most common but it is not unusual to see fractures that are widely displaced. Surgical excision is the remedy for fractures that are widely displaced and do not respond to conservative care.
Osteochondritis dissecans. This condition can occur initially after trauma or after a repetitive stress injury and initial stress fracture. The most common cause of this injury is trauma. In the event of trauma, vascular disruption occurs. Once there is a fracture to the sesamoid bone, the blood supply is interrupted and can often lead to avascular necrosis. Due to the loss of integrity and functional support of the sesamoid, surgical excision is the most likely remedy.
Chondromalacia of the sesamoid. This happens as a result of continual synovitis. When chronic synovitis of the first MPJ occurs, fibrosis will develop, surrounding the sesamoid apparatus to the metatarsal head and the plantar capsule. This will lead to a “freezing” of the sesamoids. Consequently, the sesamoids will not be able to slide back and forth with motion of the flexor tendon. As a result, there will be a decreased range of motion of the joint, creating a functional hallux limitus and eventually a hallux rigidus. This can subsequently lead to a narrowing of the joint space and ultimately early degenerative joint disease.
Aggressive treatment for the athlete may include icing, immobilization, physical therapy, topical and oral non-steroidal anti-inflammatory drugs (NSAIDs) and a prescription orthotic with a Morton’s extension. These modalities can be successful and help avoid the need for surgical intervention. By employing this early and proactive treatment plan, the athlete may be able to return to action with limited symptoms, restoration of normal gait and little or no sequelae.
Key Pointers On Turf Toe In Athletes
Turf toe is an injury of the soft tissue surrounding the first MPJ. The injury is most common when a foot that is fixed in equinus experiences an axial load. It usually occurs when the first MPJ extends beyond its normal range.
A turf toe will cause an immediate, sharp pain and swelling with limited range of motion of the joint. Turf toe may result in an injury to the soft tissue attached to the sesamoid or a fracture of the sesamoid. Sometimes, the athlete feels a “pop” at the moment of injury.
The typical scenario, which occurs often in football lineman, involves the fixation of the forefoot on the ground with dorsiflexed hyperextension of the first MPJ. Turf toe most frequently occurs in football players but it can occur in athletes in other sports (basketball, soccer, rugby, tennis, lacrosse). Research has shown that as many as 50 percent of athletes with turf toe injuries will have persistent symptoms after five years. This can result in possible long-term sequelae including hallux rigidus, hallux valgus, cocked hallux and failure to regain push-off strength. This usually correlates to a severe articular injury. Ultimately, this will impair the performance of the athlete and lead to compensation of the forefoot.
How Playing Surfaces Affect Turf Toe Incidence
The hardness of artificial turf is reportedly a factor in the increased incidence of turf toe injuries. Clanton and colleagues showed there was no significant change in the incidence of turf toe injuries documented on the different artificial surfaces between 1980 and 1986.8,10 Nigg and Segesser showed an increased incidence of first MPJ injuries and correlated this to the enhanced surface friction inherent to artificial surfaces.11 In the 1990s, a third-generation surface emerged that was composed of less dense fibrillated fibers that closely mimicked natural grass due to the addition of an infill of rubber, sand particles or both.
In a study of 80 professional football players, Rodeo and coworkers found that 45 percent experienced a turf toe injury.12 In this study, 83 percent of these players reported their initial turf toe injury occurred on artificial turf and 85 percent of injuries occurred secondary to a hyperextension injury.
Athletes prefer lightweight, flexible shoes, which afford little structural support. This can put the competitive athlete at considerable risk for hyperextension injury to the first MPJ, particularly on harder playing surfaces. Preseason screening of the athletes with a cursory biomechanical evaluation and gait analysis can help predict which players may be at risk for experiencing a turf toe injury. When it comes to those athletes with restricted dorsiflexion of the first MPJ and at the ankle joint, clinicians should emphasize a more supportive, stiffer shoe and a prescription orthotic to allow for enhanced propulsion and prevent injury.
Keys To The Classification Of Turf Toe Injuries
Grade 1 injuries are the least severe.13 These injuries typically are a minor stretch or strain without compromise to the soft tissue restraints. Clinically, a patient with a Grade 1 injury will present with localized plantar or medial tenderness, mild edema and no visible ecchymosis. The patient will be able to bear weight and there is little change in the range of motion or strength. Typically, radiographs will be normal and an MRI evaluation will demonstrate an intact capsular integrity with mild soft tissue edema.
Grade 2 injuries are more moderate in severity. They represent partial tears of the capsuloligamentous structures, most often the sesamoid phalangeal and MPJ ligaments. The medial collateral ligament of the MPJ is commonly involved. Clinically, patients will present with a more diffuse and intense tenderness as well as mild to moderate edema with ecchymosis on the plantar and medial surface of the first MPJ. These injuries typically have varying levels of disability. There is restricted range of motion of the MPJ with severe pain, and antalgic gait with weightbearing. Symptoms are typically progressive. Radiographs may appear normal with the sesamoid bones lying in the normal position. An MRI demonstrates moderate soft tissue edema extending through the plantar plate, indicating a partial thickness disruption.
Grade 3 injuries are the most severe type of turf toe injury. This stage describes severe acute injuries with plantar capsuloligamentous disruption or the lasting chronic effects of a capsuloligamentous injury. Clinically, patients will present with severe and diffuse tenderness. There is often marked swelling accompanied by moderate to severe ecchymosis to the MPJ with an acute injury. Pain is often so severe that patients are unable to bear weight, which is significant for the high performance athlete. Radiographs may demonstrate proximal migration of sesamoids, compression fractures, asymmetric lateral, medial or dorsal subluxation, or capsular avulsion fragments or capsular avulsion. Often, joint subluxation or deviation may also be apparent on radiographic stress views. In some cases, dislocation of the MPJ may occur.
An MRI typically will demonstrate complete disruption of the plantar plate as well as any other associated injuries to the capsuloligamentous structures.11,13,14
Reviewing The Non-Surgical Treatment Options
Immobilization. Place the foot in a cast or removable walking cast. Crutches may prevent placing weight on the foot.
Oral medications. Nonsteroidal anti-inflammatory drugs such as ibuprofen are often helpful in reducing the pain and inflammation.
Physical therapy. The rehabilitation period following immobilization sometimes includes physical therapy, such as exercises (range of motion, strengthening, and conditioning) and ultrasound therapy.
Steroid injections. In some cases, one can inject cortisone into the joint to reduce pain and inflammation. Platelet rich plasma may also be helpful.
Orthotic devices. Clinicians may prescribe custom orthotic devices that fit into the shoe for long-term treatment of sesamoiditis to balance the pressure placed on the ball of the foot.
Padding, strapping or taping. One may place a pad in the shoe to cushion the inflamed sesamoid area. Alternately, the clinician may tape or strap the toe in a neutral position with the placement of a pad just proximal to the sesamoids to relieve that area of tension.
Sesamoid and turf toe injuries are significant athletic injuries that require proper diagnosis and early appropriate treatment, based on the severity of the injury. Often misdiagnosed or undertreated, these injuries can develop sequelae such as malunions or structural hallux rigidus. Various new conservative treatment options are available with the use of bone stimulation or platelet rich plasma. Biomechanical correction with functional orthoses and proper shoe gear can make the difference between an athlete competing on the field versus being on the sideline.
Dr. Ross is an Associate Professor at the Baylor College of Medicine in Houston. He is a Fellow of the American College of Foot and Ankle Surgeons, and a Diplomate of the American Board of Podiatric Surgery. Dr. Ross is a Past President of the American Academy of Podiatric Sports Medicine and a Fellow of the American College of Sports Medicine.
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- Jahss MD. The sesamoids of the hallux. Clin Orthop Rel Res. 1981; 157:88-97.
- Ross JA. Neale’s Disorders of the Foot, Sports Medicine and Injuries, Seventh Edition, Churchill Livingstone, New York, 2006, p. 354
- Drez D. Forefoot problems in runners. In Symposium on the Foot and Leg in Running Sports. CV Mosby, St. Louis, 1982, pp. 73-75.
- Helal B. The great toe sesamoid bones: the lost souls of Ushaia. Clin Orthop Rel Res. 1981; 157:82-7.
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- McGlamry ED. Hallucial sesamoids. J Am Podiatric Assoc. 1965; 55(10):693-699.
- Quirk R. Common foot and ankle injuries in dance. Orthop Clin N Am. 1994; 25(1):123-133.
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- Boike A, Schnirring-Judge M, McMillin S. Sesamoid disorders of the first metatarsophalangeal joint. Clin Podiatr Med Surg. 2011; 28(2):269-85.
- Nigg BM, Segesser B. The influence of playing surfaces on the load on the locomotor system and on football and tennis injuries. Sports Med. 1988;5(6):375–85
- Rodeo SA, O’Brien S, Warren RF, et al. Turf-toe: an analysis of metatarsophalangeal joint sprains in professional football players. Am J Sports Med. 1990;18(3):280-5.
- VanPelt MD, Saxena A, Allen MA. Sports Medicine and Arthroscopic Surgery of the Foot and Ankle, Springer-Verlag, London, 2013, p. 13.
- Clanton TO, Butler JE, Eggert A. Injuries to the metatarsophalangeal joints in athletes. Foot Ankle Int. 1986;7(3):162–76.
For further reading, see “How To Treat Turf Toe Injuries” in the September 2008 issue of Podiatry Today, “Why We Should Consider Arthroscopic Treatment For The Chronically Diseased Sesamoid” in the March 2014 issue, “How To Treat Sesamoid Injuries In Athletes” in the April 2004 issue or the DPM Blog “Treating A Possible Case Of Avascular Necrosis Of A Sesamoid Bone” at tinyurl.com/glub3ee .
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