Internal Fixation of the Sesamoid Bone of the Hallux

Symptomatic acute sesamoid fracture, fracture-delayed union or nonunion, and congenital bipartite sesamoid bone after failure of conservative treatment for at least 6–8 weeks

Acute sesamoid bone fracture or disruption of the synchondrosis between the sesamoid fragments of a bipartite sesamoid with a displacement >5 mm

Clinical examination

• Functional and structural assessment of the foot:

  • Risk factors for a sesamoid injury/stress include cavus foot, plantar-flexed foot, short or long first ray, and hallux valgus deformity

  • Swelling and tenderness over the symptomatic sesamoid

  • Pain on forced dorsiflexion of the great toe ( Fig. 21.1 )

    

Radiologic investigations

• Routine radiographs:

  • Weight-bearing dorsoposterior and lateral view of the foot such as anteroposterior, lateral, and Saltzman views of the ankle

  • Radiographs provide enough information to evaluate structural abnormalities in the ankle and foot, but limited information about the sesamoid bones. For a better visualization of the medial and lateral sesamoids, a medial oblique view and a lateral oblique view, respectively, can be acquired. An axial sesamoid view can provide a better assessment of both sesamoids with their metatarsal articulations and number of fragments ( Fig. 21.2 )

    

• Computed tomography

  • Very helpful to differentiate sesamoid acute and stress fractures from a delayed union; also useful to assess vitality of the fracture site in case of avascular necrosis. The differentiation between an acute sesamoid fracture and a bipartite sesamoid can also be achieved with a computed tomography scan. Contrary to the acute fracture with sharp edges, the bipartite sesamoid has blunt edges

• Isotope bone scan

  • Is not regularly performed but can help detect a sesamoid pathology. In 25% of the active population, there is an increased radionuclide uptake without sesamoid symptoms

• Magnetic resonance imaging

  • Provides additional information about the surrounding ligaments and tendons, for example, in a turf toe injury

Strapping

Immobilization in a cast for 6–8 weeks

Modification of activity

Electrical stimulation and low-intensity pulsed ultrasound in nonunion

• Healing rates similar to surgical procedures could be revealed in fresh fractures, arthrodesis, and nonunion fractures of long bones, such as the tibia

Bone grafting of nonunion

• In chronic sesamoid conditions with <3-mm fragment displacement

• Débridement and bone packing of the fracture site with autologous bone from the first metatarsal head

Complete or partial resection

• The total sesamoid excision results reasonable in pain management and return to activity. Although in 10–20% of the cases hallux valgus, hallux varus, hallux rigidus, and cock-up deformities are reported. Weakness of the great toe occurs in 50% of cases and the inability to stand on tip toe in up to 30% of cases

• Partial sesamoidectomy can be used for significant fragment separation or diastasis of bipartite sesamoids

• Percoutaneous fixation or open reduction and internal fixation

There are two sesamoids, medial (tibial) and lateral (fibular), and the length is 13.5 ± 3 mm. The medial sesamoid is elliptic, whereas the lateral one is more circular ( Fig. 21.3 ).

The sesamoid bones are contained within the tendons of the flexor hallucis brevis and form a portion of the plantar plate.

The plantar plate is the continuation of the flexor hallucis brevis tendon and connects the sesamoid bones to the plantar aspect of the distal phalanx.

There is an articulation between the dorsal facet of the sesamoids and the plantar facet of the metatarsal head. A crista divides this surface into two parts and provides intrinsic stability to the complex.

The flexor hallucis longus tendon runs between the sesamoids but has no connection to them.

The abductor and adductor hallucis tendons have fibrous insertions into the medial and lateral sesamoids, respectively.

The deep transverse metatarsal ligament attaches to the lateral sesamoid.

The blood supply to the sesamoids is tenuous and variable. Mostly, the perfusion enters from the proximal part, leading to a more tenuous blood supply of the distal part.

First and second digital nerves run close to the outer side of the medial and lateral sesamoids.