2.1 Anatomy

The navicular is an important part of the Chopart joint, which is composed of the articular surfaces of the talar head and navicular medially, and the distal calcaneus and cuboid laterally ( Fig 6.10.2-1 ). It is the keystone of the medial longitudinal arch of the foot and has five articulations:

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  Talar head proximally (talonavicular joint)

  
  
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  Three cuneiforms distally (naviculocunieform joint)

  
  
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  Cuboid laterally (cubonavicular joint)

The medial and plantar aspects of the navicular are supported by soft tissues including the plantar calcaneonavicular ligament (spring ligament), the medial calcaneonavicular ligament (ligamentum neglectum), and especially by the insertion of the strongest of the five arms of the tibialis posterior tendon. Laterally, it is supported by the lateral calcaneonavicular ligament and the dorsal cubonavicular ligament. The dorsal joint capsule is reinforced by the dorsal talonavicular ligament, parts of the deltoid ligament, and the “neglected” ligament. The quadrilateral part of the navicular is stabilized by the navicular arm of the bifurcate ligament and the cubolateral navicular ligament. Pathomechanically, the tibialis posterior tendon may avulse the tuberosity in eversion trauma, or it can become entrapped in fracture dislocations making reduction difficult. Because of its central position in the foot, injuries to the navicular are often associated with injuries to the rest of the Chopart joint and/or Lisfranc joint. These must be excluded by clinical and x-ray examination and computed tomographic (CT) scan.

2.2 Fracture patterns and treatment

There are three types of navicular fractures: cortical avulsions, fractures of the tuberosity, and fractures of the body ( Fig 6.10.2-2 ) [1, 2]. Stress fractures of the body are occasionally seen in athletes.

Cortical avulsion fractures are the result of a twisting injury rupturing the strong talonavicular capsule and the most anterior fibers of the deltoid ligament: a bone fragment is avulsed ( Fig 6.10.2-3 ). It is important to clinically assess if these are a part of a more complex midfoot injury. Functional treatment consists of early weight bearing in a short leg cast or boot for 6 weeks. If the fragment includes more than 20% of the articular surface, or if there is significant instability seen on a stress x-ray, it should be stabilized with small screws.

Tuberosity fractures are caused by an eversion injury, with the tibialis posterior tendon avulsing the navicular tuberosity. If seen together with a crush fracture of the cuboid, this injury may indicate an occult dislocation or subluxation of the midtarsal joint. Without displacement, a short leg walking cast or boot for 6 weeks is the appropriate treatment. With displacement (> 2 mm), the fracture is reduced and stabilized with a screw or small tension band wire ( Fig 6.10.2-4 ).

Body fractures are usually associated with other midtarsal injuries, which must be diagnosed and treated. Undisplaced fractures are treated using a well-molded short leg cast for 6 weeks.

Displaced fractures of the navicular are treated operatively with screws, a plate, or a small temporary external fixator.

Bone defects in case of crush fractures should be filled with an autograft ( Fig 6.10.2-5 ). Multifragmentary fractures should be stabilized, and mini-fragment plates are a good option. The fracture is often associated with complex midfoot instability and adding an external fixator or a plate that bridges across the midfoot joints may stabilize the whole foot [3]. Accurate restoration of length and alignment of the medial column of the foot is important for good late function [3].

Stress fractures usually need compression by two or three 4.0 mm cancellous bone screws and a short leg walking cast for 6 weeks.

3.1 Anatomy

The cuboid is the lateral of the two midfoot bones and is an essential component of the lateral column of the foot ( Fig 6.10.2-6 ). It articulates:

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  Proximally with the calcaneus (calcaneocuboidal joint)

  
  
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  Medially with the navicular (cubonavicular joint)

  
  
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  Medially with the lateral cuneiform (cubocuneiform joint)

  
  
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  Distally with the bases of the fourth and fifth metatarsal (cubometatarsal joint)

3.2 Fracture patterns and treatment

The most common significant injury to the cuboid bone occurs because of the “nutcracker” mechanism [4].

There are often associated injuries [5] as the whole midfoot is forced into abduction and the cuboid is crushed between the calcaneus and metatarsals. This is comparable to the “nutcracker” fracture of the navicular in forced adduction injuries [6, 7].

If there is minimal impaction, nonoperative management with a below-knee cast for 6 weeks is appropriate. However, if there is significant loss of length or abduction deformity of the lateral column of the foot, it is likely that the long-term outcome will be pain and dysfunction in the calcaneocuboid joint and/or the peroneus longus tendon. Management should include early anatomical reconstruction of the joint surfaces ( Fig 6.10.2-7 ) as well as restoration of the length of the lateral column by open reduction and internal fixation. Plates that bridge across the joints of the lateral column or external fixators can be used to offload the construct and maintain length of the column.

In compression fractures of the cuboid bone, the intact joint surface of the calcaneus proximally or those of the fourth and fifth metatarsal base are used as a mold. Using a little distractor for reduction ( Fig 6.10.2-8 ), filling the defects with bone graft, and placing a locked plate on the lateral cuboid or a bridge plate from the calcaneus to the fourth metatarsal protects the reconstruction of the joint and effectively restores the lateral column length.

4.1 Anatomy

The Lisfranc area, which describes the transition between the forefoot and midfoot, is formed by the articulations of the metatarsals with the cuneiforms and the cuboid. Proper alignment and stability of this group of joints is crucial for normal foot function.

The medial column of the midfoot includes the three cuneiforms and the medial three metatarsals. This column is less mobile than the lateral column and serves as a structural support.

The inherent stability of the tarsometatarsal joint is due to the bone anatomy of the keystone-like base of the second metatarsal and to the strong ligaments between each tarsometatarsal joint.

Generally, the plantar ligaments are stronger and the Lisfranc ligament is the largest and strongest of all. It originates from the plantar aspect of the medial cuneiform and inserts on the plantar aspect of the base of the second metatarsal and is the only link between the first and second metatarsal. The Lisfranc ligament “locks” the base of the second metatarsal in place, further limiting motion and providing stability to this keystone structure.

The lateral column, made up of the cuboid and the lateral two metatarsals, is more mobile than the medial column to allow walking on uneven ground. This flexibility is necessary for proper foot function. Posttraumatic instability is better tolerated here but stiffness causes significant problems.

In reconstructing the tarsometatarsal joint, it is critical to keep these anatomical characteristics in mind. Perfect anatomical reduction is crucial for excellent long-term results [5, 6].