Great Toe Sesamoids

Stress fractures of the great toe sesamoids may lead to significant and prolonged disability in athletes, and represent as many as 40 % of all sesamoid disorders [82]. The tibial (medial) sesamoid is more likely to develop stress fracture than the fibular sesamoid [83-85]. The tibial sesamoid is larger and lies directly under the first metatarsal head, and is therefore subjected to more force than the fibular (lateral) sesamoid. The bone is subjected to tensile forces during forced dorsiflex-ion and abduction of the great toe during activities such as running or jumping due to the pull of the flexor hallucis brevis. This causes significant tension across the bone, which in combination to local pressure under the medial forefoot may lead to accumulative damage and stress fracture.

Diagnosis of sesamoid stress fracture may be difficult in some cases. The athlete usually presents with point tenderness under one of the sesamoids (usually tibial), often associated with swelling and pain with passive dorsiflexion. The posture of the foot must be examined, looking specifically for hallux valgus and cavovarus type deformities, as well as gastrocnemius or Achilles tendon contracture, any of which may lead to increased strain and compressive forces on the tibial sesamoid, respectively.

Imaging begins with plain radiographs, and the series should include AP, standard oblique images as well alternate oblique views and sesamoid - specific end-on view. Diagnosis is made difficult by the fact that 5-30 % of asymptomatic individuals have bipartite sesamoid [86]. Bipartate sesamoids typically demonstrate smoother margins than those with stress fractures, which may show jagged margins [84]. Since the rate of bilaterality may be as high as 80 % [87], both feet should be imaged. Unfortunately, stress fractures of a sesamoid bone may take many weeks to become evident on plain radiographs [88 ) . When plain radiographs are inconclusive, advance imaging such as nuclear medicine bone scan or MRI may be undertaken to confirm the diagnosis. CT scan is useful to determine the orientation of the fracture line, as well as to evaluate for any sclerotic changes of the fracture suggesting non-union (Fig. 9.8).

Non-operative treatment of sesamoid stress fractures should be the primary treatment, at least initially. Activity modification is immediately

Fig. 9.8 a Plain radiographs in a coUege level runner demonstrating a stress fracture of the tibial sesamoid. The patient elected non-operative treatment and continued to run. b Sagittal plane CT scan taken several months later shows evidence of sclerotic margins consistent with nonunion. The patient continued to decline surgery and an MRI

(c) taken 1 year later for a separate injury re-demonstrates the fracture line on T1 weighted coronal images. The patient is no longer able to run due to the pain and has developed lateral forefoot pain, likely secondary to an altered gait; however, he still declines to have operative intervention

Implemented, aiming to avoid all high impact activities that place stress on the medial forefoot, particularly those forcing the great toe into dorsi-flexion. Shoe orthoses with a rigid turf-toe plate and recessed area under the sesamoid may be useful. One should have a low threshold to place the athlete into a cast boot or even a non-weightbearing cast, which should be modified to prevent dorsi-flexion of the great toe. Unfortunately, these fractures often require extended periods of time for healing [83], and radiographs should be obtained

Regularly to assure that diastasis of the fracture is not occurring.

When conservative treatment fails, surgical intervention is required. Options include partial or complete sesamoidectomy, bone grafting and internal fixation. Tibial sesamoidectomy may result in a decrease of push-off strength by 10 %, and if the soft tissues are not adequately repaired, hallux valgus may result [1]. The abductor hallucis tendon may be transferred from the medial aspect of the MTP joint into the plantar structures, which may improve plantarflexion strength. This is done through a medial, extraarticular approach. When excising the tibial sesamoid, care must be taken not to damage the plantar medial sensory nerve and FHL tendon, and the defect in the flexor hallucis brevis tendon must be repaired. If even mild hallux valgus exists, consideration should be given to its correction to prevent progression due to the fact that the medial restraining structures may be weakened following this procedure.

Biedert and Hintermann [83] recommended excision of the proximal fractured fragment only, and reported that five of six athletes undergoing this procedure returned to full activity within 6 months. They recommended that the procedure be performed early in the course, as they had little success with non-operative treatment.

Bone grafting of sesamoid stress fracture has been described by Anderson and McBryde [89] for chronic stress fracture or non-union of the tibial sesamoid. This technique was performed in 21 athletes. All but two achieved successful union. The procedure is performed through a medial extra-articular approach, reflecting the flexor hal-lucis brevis tendon to expose the fracture, which must be repaired after the graft inserted. Bone graft may be obtained from the metatarsal head, and is inserted after the fracture is curetted back to healthy bone. Fixation is not typically used. The patient is kept non-weightbearing for at least 4 weeks with dorsiflexion prevented and then transitions to a protected weightbearing in a cast boot. When the athlete returns to sport, a rigid turf-toe plate is used in the shoe to decrease dorsi-flexion forces. This procedure is contraindicated if one fragment is very small, in which case partial excision would be treatment of choice. When significant arthritis is present between the sesamoid and metatarsal head, complete sesamoidectomy is recommended.

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