Cuboid Injuries.

Cuboid fractures are rare injuries. A number of different treatment methods have been proposed including plaster immobilization, open reduction, and internal fixation or external fixation. Bone grafting is commonly used to restore bony length. The majority of the current literature suggests that the loss of length of the lateral column and articular congruency are the two criteria opting for the surgical management of these fractures. Nevertheless, the exact indications and ideal management of these fractures are not established mainly due to the rarity of these injuries and the paucity of literature.

Introduction

Fractures that involve the midfoot are rare and have an annual incidence of approximately 3.6/100,000 fractures.12 From these, half involve the cuboid. Most commonly they are seen as isolated avulsion fractures, less frequently are combined with other midfoot fractures, dislocations or are associated with Lisfranc joint injuries.3 Cuboid fractures in isolation represent a diagnostic challenge and are frequently missed as the majority of cuboid injuries are relatively minor.4 The radiologic changes occurring in more serious injuries may also be subtle and easily overlooked. However, cuboid fractures have the potential to cause considerable deformity involving the foot arch, lateral column, and the function of the forefoot, and thus, a high index of suspicion is mandatory to prevent long term disability. This study aims to provide an overview of cuboid fractures and present their management.

Anatomy of the Cuboid

The cuboid is a wedge-shaped bone, and is a vital element of the lateral column; in fact, it is the only bone of the midfoot that supports the lateral column [Figures 1 and 2]. The importance of the cuboid stems from the fact that it is involved in all intrinsic movements of the foot.5 It articulates with the calcaneus (proximal facet), lateral cuneiform (medial facet), and 4th and 5th metatarsals (distal facets). An additional articulation with the navicular exists in 25% of the population. The dorsal calcaneal and medial cuboid tuberosities, together with a network of strong ligaments, support the calcaneocuboid joint during weight bearing.6 There is very little movement in the calcaneocuboid joint; all the movement of the lateral column occurs distally at the tarsometatarsal joints. The range of motion at the lateral tarsometatarsal joints is up to three times higher than that of the medial tarsometatarsal joints.7

Figure 1

Diagramatic representation of (a) 3 columns of the foot and the weight-bearing triangle (b) Lateral column shortening leads to abduction and overpronation of the forefoot

Figure 2

A line diagram showing anatomy of the cuboid

The peroneal sulcus is located at the plantar surface of the cuboid and runs plantar wards and medially toward the insertion of the tendon in the first metatarsal bone. The cuboid acts as a fulcrum during the contraction of the peroneus longus. The lateral plantar artery provides the blood supply to the cuboid.

Mechanism of Injury and Diagnosis

The vast majority of fractures involving the cuboid are minor avulsion fractures. These represent ligamentous or capsular avulsions. Direct trauma can result in a fracture, but this rarely results in a complex fracture configuration. Isolated fractures of the cuboid are uncommon and mostly documented in case reports. An isolated fracture can occur as the result of indirect compression with axial force applied to a plantar-flexed abducted foot crashing the cuboid between the calcaneal and the bases of the 4th and 5th metatarsals. This is often referred to as a “Nutcracker” fracture. Stress fractures can occur more often in young athletes.8 These are rare injuries that most commonly involve the lateral aspect of the cuboid.8 The “Nutcracker” fracture requires close attention as it can disrupt the mechanical alignment of the foot.9 Cuboid fractures are seen in conjunction with other complex injuries such as other hindfoot, midfoot or Lisfranc injuries.3 Painful subluxation of the cuboid (referred as a cuboid syndrome) is often reported in ballet dancers and athletes.101112 This condition is hypothesized to occur from a disruption of calcaneocuboid joint. It is characterized by lateral foot and ankle pain, reduced forefoot mobility with the weakness of forefoot push-off and peroneus longus spasm.12 Cuboid syndrome responds exceptionally well to conservative treatment and close manipulation of the cuboid can be diagnostic and therapeutic.1011

Dorsolateral foot pain associated with swelling and ecchymosis following injury should raise suspicion of a cuboid fracture.13 More severe injuries with or without concomitant trauma can even distort the normal anatomy. In young children, limping and antalgic gait with the inability to describe the nature and location of the pain is a common complaint. Cuboid fractures in children, especially of preschool age, are rare and probably unreported.1415 Englaro et al. in their study reported scintigraphic findings in the cuboid in nine out of the 56 children complaining of the midfoot pain of unknown etiology.14 It is interesting that of these nine children, only four had radiographs at the time of first hospital visit to the hospital. In place of scintigraphy, ultrasound can also be used in such cases to establish the presence of an occult fracture.16

Plain radiographs (anteroposterior [AP], lateral, and medial oblique) are the baseline investigation. On the AP view, the medial and lateral columns can be adequately evaluated. The lateral view can be helpful in assessing the congruency of the calcaneocuboid joint. The oblique view best assesses the integrity of the tarsometatarsal joints. Imaging of the contralateral side can be performed for comparison when there is doubt. Stress and weight-bearing views can be obtained to rule out instability. Computed tomography scans can give further details of the fracture or better evaluate inter-osseous instability, while, in occult fractures, magnetic resonance imaging or scintigraphy can be used to visualize the fracture.

Classification of Cuboid Fractures

In clinical practice, cuboid fractures are most commonly classified according to the anatomic element involved. This often represents an arbitrary classification of a descriptive nature. Cuboid fractures can be described as stable or unstable, simple or comminuted, intraarticular or extraarticular, displaced or undisplaced or crush.

The Orthopedic Trauma Association has proposed a classification system dividing cuboid fractures (denoted as 76) into 3 main categories [Figure 3].1718 According to this classification, cuboid fractures can be extraarticular (Group A), involving either of the calcaneocuboid or metatarsocuboid joint (Group B) or represent complex injuries involving both major joint surfaces (Group C). This classification further subdivides these fractures according to their complexity, plane, and the part of the bone involved. Each group is denoted with numbers, and the higher the number, more significant is the nature of the injury. Group C fractures, in particular, represent significant crash injuries of the bone that involve the articular surfaces and can be either undisplaced (Type 1) or displaced (Type 2).

Figure 3

Orthopaedic Trauma Association classification of cuboid fractures

Despite the efforts to define the integrity and stability of the bone, a classification system that could guide surgeons in the appropriate management and predict the clinical outcome following these injuries does not exist.

Treatment

The principle behind the surgical intervention for cuboid fractures is to maintain the length of the lateral column and restore the congruency of the articular surfaces. As the majority of these injuries are simple extraarticular fractures, surgical treatment is rarely required. Similarly, these injuries in children are treated conservatively, unless they represent part of major foot trauma.

Cortical avulsion fractures can be allowed to weight bear as tolerated in a walking boot. Late instability is a risk with these injuries, and hence, these patients should be followed till they are asymptomatic. Undisplaced fractures of the cuboid can be managed with nonweight bearing for 4–6 weeks in a well-molded below knee cast. Followup at 2 weeks with weight bearing or stress X-rays can be obtained to exclude the presence of an occult fracture, ligamentous injury or subluxation. With the improvement in the pain on clinical examination, the patient can be allowed to gradually weight bear.

Surgical treatment is reserved for compressed and intraarticular fractures and aims to restore the articular congruency and length of the bone. Bone grafting is often required as cancellous bone impaction is a common finding with these fractures.19 The fixation can be achieved with the use of K-wires, 2.7 mm or 3.5 mm interfragmentary screws together with a mini-plate or the use of an external fixator.131920 The surgical incision is at the lateral border of the of the extensor Brevis muscle which will allow a good exposure of the dorsolateral aspect of the bone. A distractor or external fixator can be used to restore the length of the lateral column (proximal pin on the calcaneus and distal pin at the 5th or/and 4th metatarsal).21 The external fixator can be left in place for 6–8 weeks to facilitate healing and counteract the compressive forces exerted on the bone. In cases of cuboid subluxation or dislocation, the reduction can be achieved with the use of a threaded K-wire together with the use of an external fixator. The reduction can be maintained with either K-wires or screws running across the calcaneus and lateral cuneiform.

Postoperatively, the leg can be placed in a neutral cast for 6 weeks to minimize the compression forces exerted on the bone. Weight bearing should be avoided until bony and ligamentous stability is clinically evident. After 6 weeks, the leg can be placed in a walking boot, gradually building up the weight-bearing status. In cases where K-wires or an external fixator is used, these should be removed at 6–8 weeks.

A number of complications can be seen following the treatment of cuboid fractures. Pain, stiffness, and instability, reduced length of the lateral column and degenerative arthritis can occur.19 Coalition with other midfoot bones can result in stiffness.19 A reduction in the length of the lateral column would require lengthening with the use of bone grafting. Arthritic changes in the calcaneocuboid joint can be treated with fusion. Lateral column tarso-metatarsal osteoarthritis can severely limit a patient's mobility and lifestyle.1921 Treating these degenerative changes with bony fusion often leads to the poor functional outcome; tendon or ceramic interposition arthroplasty could allow some movement and provide pain relief.2122 Other complications following these fractures include loss of foot arch, osteonecrosis, pronation deformity and wound complications following surgery. Nonunion of the cuboid is rare and only reported as isolated case reports.23

Surgical Fixation: Outcomes

The majority of the evidence reporting on the functional outcomes following cuboid fracture fixation comes from case reports [Table 1].19192023242526272829 The outcomes presented by these studies are favorable. In two small case series involving four patients each, the authors reported no complications and good function postoperatively.2327 Weber and Locher, analyzed the short outcomes of 12 patients treated surgically for cuboid fractures.19 The authors reported no complications but noted a residual articular step in two patients and early degenerative arthritis in four cases. Interestingly, residual disability was reported in nine patients, but complaints were associated with the extent of initial trauma and concomitant injuries. Yu et al. reported similar results in a case series of six patients.26 The authors reported fair results in four patients and good in two patients.

Table 1

Selected studies reporting outcome following cuboid fracture fixation

Discussion

The cuboid is a vital part of the lateral column, and fractures can disrupt the mechanical alignment and function of the whole foot. These injuries are merely found in isolation and are most often seen in complex midfoot injuries.3031 Sharma et al. have shown that the nutcracker fracture cannot occur in isolation but should be associated with other midfoot trauma, especially of the medial column.32 Regarding the surgical management of these injuries, there is a general agreement that the disruption of the articular surface and loss of lateral column length are the most important decisive factors that one should consider before making a decision on how to manage these injuries. It is largely unknown how much cuboid length loss is acceptable or what size articular step is significant. However, once the need for surgery is established, open reduction and internal fixation with the use of mini-plates, and screws is a well-accepted method of fixation. Alternatively, external fixator could be used to maintain the length and alignment with satisfactory results.21

Based on our experience, we feel that these injuries are nearly never isolated injuries. They occur in association with Lisfranc injuries or other complex midfoot injuries [Figure 4]. Our decision making process is based on two findings as follows: (a) loss of 2 mm of lateral column length and (b) articular incongruency of >1 mm. The main goal is to restore the length of the cuboid; once this is achieved some articular congruence will be present. It is of interest that following reduction; there is often a significant bone void which can be considered for bone grafting. We appreciate there are advocates favoring fixation of the cuboid bone with plates. Our experience has shown that screw purchase is usually poor. For this reason, following restoration of the cuboid length and articular congruency, we use a bridging plate from calcaneus to the 4th metatarsal. Such approach provides optimum mechanical support promoting fracture healing. We understand that there might be advocates of nonoperative management or primary fusion for displaced cuboid fractures. Nonetheless, we feel that dealing with these injuries early could minimize the long term consequences associated with these fractures.13031

Figure 4

(a) Computed tomography image, sagittal view of left foot demonstrating compression type injury of cuboid in association with other ipsilateral foot injuries. (b) Lateral radiograph; (c) anteroposterior radiograph; (d) Oblique radiograph of left foot at 12 month postoperative followup showing healing of 1st, 2nd, 3rd and 4th ray tarsometatarsal injuries that were reduced and stabilized with anatomical locking plates and screws

Overall, the management of cuboid fractures is largely based on personal experience and beliefs. No high level of evidence is currently available to allow any safe recommendations. Examining the available literature, it should be noted that the clinical outcomes from the larger series are not as favorable as the ones presented in case reports. We believe that bigger scale studies comparing the outcome of primary arthrodesis versus bridging plating or external fixation or open reduction and internal fixation for severely comminuted fractures are needed. Hopefully, with the accumulation of more evidence, we may be able to shed some light in this area and allow clinicians and patients to make well informed decisions.

Conclusion

Cuboid fractures are rare injuries. The published literature supports the view that surgical fixation should only be attempted in cases where disruption of the articular surface and loss of lateral column length occurs. Evidence of the long term functional outcomes and ideal management of these fractures is lacking.

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Conflicts of interest

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