How Does Scaphoid Bone Develop?
Initially, the scaphoid bone is composed of articular cartilage that covers epiphyseal cartilage extensively, which undergoes enchondral ossification gradually. The cartilaginous structure of the scaphoid enlarges in size prenatally and postnatally. The ossification of the cartilage begins at five years and ten months in boys and four years and six months in girls. Occasionally, multiple ossification centers can appear. The ossification is complete at 15 years in boys and 13 years and six months in girls.
What Are Scaphoid Fractures in Children?
The scaphoid is one of the eight wrists' (carpal) bones. The scaphoid bone is located between the thumb and bones of the arm. A scaphoid fracture is any break in the scaphoid bone and typically affects children between 12 and 15 years old. As the bone has an unusual blood supply, the healing of the bone becomes difficult. It is a rare carpal injury in young people, making up about 3 % of wrist fractures.
The low incidence of scaphoid fracture was possible because of a thick cartilage covering the ossification center that required considerable force to cause injury and fracture in children. Previously, the distal end of the scaphoid was thought to be more prone to fracture in children, but more recent research has shown that children's scaphoid fractures are altering in pattern and now resemble those in adults. The adults are commonly susceptible to waist fracture. The predominance of distal fractures earlier was because the scaphoid ossification happened from the distal to the proximal region.
How Is Scaphoid Fracture Classified?
Scaphoid fractures are classified based on location as:
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Distal fracture.
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Waist fracture.
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Proximal fracture.
Based on stages of ossification:
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Type I: It is a pure chondral injury seen in children below eight years. Diagnosis is through MRI (magnetic resonance imaging).
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Type II: Osteochondral fracture seen in children between 8 to 11 years.
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Type III: Seen in children older than 12 years when the scaphoid bone is completely ossified.
What Causes Scaphoid Fractures in Children?
When the child falls on their outstretched and pronated hand, compressive force or a direct blow that results in crush injury causes a scaphoid fracture. These changes in fracture characteristics are because the children and adolescents have grown in size with increased BMI (body mass index), and their activities have changed. The emergence of extreme sports like snowboarding and motocross and younger age groups participating in them enormously have caused high-energy injuries. All these have contributed to increased susceptibility for scaphoid fracture.
The scaphoid bone is fractured by more severe trauma in youngsters under ten years. It is because thick cartilage surrounds the bone’s ossification center, making the bone resilient, which requires an enormous force for fracture. Therefore, older children might have additional associated fractures, such as carpal or metacarpal fractures.
What Are the Signs and Symptoms of Scaphoid Fractures in Children?
The symptoms are:
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Pain in the thumb side of the wrist.
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Tenderness to palpation occurs on scaphoid tuberosity in distal fractures, but the pain occurs at the anatomic snuffbox in waist fractures.
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Swelling and bruising develop at the base of the thumb.
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Difficult to grip objects.
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Difficulty in moving wrist.
How Is Scaphoid Fracture in Children Diagnosed?
Scaphoid fractures are frequently diagnosed with an X-ray of the wrist. Healthcare providers will order a navicular view of the wrist if a scaphoid fracture is suspected. The scaphoid fracture may not be visible on an X-ray for several weeks. It is mainly because of non-specific clinical features with unclear radiological findings in acute settings. Almost 12.5 to 37 % of cases of scaphoid fracture take at least five weeks to be visible on radiographs. Additional imaging studies like CT (computed tomography) and MRI are needed to visualize scaphoid fractures.
Radiologists must recognize the pseudo-Terry Thomas sign to prevent incorrect X-ray interpretation. As the scaphoid bone ossifies from distal to proximal, the distance between the ossified lunate and scaphoid tends to decrease when the child reaches adolescence. Therefore, the space between the two bones tends to increase, with the average being 9 mm in 7-year-olds and 3 mm in 15-year-olds. Failure to recognize these normal variations leads to X-ray misinterpretation.
How Is Scaphoid Fracture in Children Treated?
Earlier scaphoid fractures involving distal bone did not need surgical care or extended follow-up. Changing fracture characteristics have warranted the need for altering treatment. Presently, scaphoid fracture treatment in pediatric patients depends on the fracture location, displacement, and acuity.
Almost 90 % of non-displaced fractures heal without operative treatment. Stabilizing the bone is the best way to enable bone to heal. The bone is stabilized with a cast for three months to achieve radiological and clinical bone union. Proximal scaphoid fractures need more extended stabilization with the cast to achieve bone union. The doctor might take an X-ray to analyze how the fracture is healing. Additionally, displaced, chronic fractures and fractures with osteonecrosis need more elongated stabilization periods.
If the fracture does not heal or the injury is severe, surgery is required to repair the scaphoid fracture. Surgery includes reduction and internal fixation, which involves administering general anesthesia to the child and a surgical cut to the bone. The scaphoid bone is positioned correctly, and a screw is positioned to hold the bone in position. The affected wrist is bandaged, and a splint is placed for the fracture to heal. Pins and wires are removed after the fracture heals. The union rate for acute fracture with surgical treatment is 97.6 %, but the healing time did not reduce. The vascular supply to the cartilaginous scaphoid bone may be less robust. After the cast is removed, the doctors will advise physiotherapy.
Since most scaphoid fractures in the pediatric population are diagnosed late, chronic fractures do not have the same success rate for treatment. Chronic fractures are 30 times less likely to achieve union from casting compared to acute fractures. However, surgical approaches for chronic fractures are successful with shorter healing times.
What Are the Complications of Scaphoid Fracture in Children?
A missed or late diagnosis could result in the following complications:
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Malunion.
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Nonunion.
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Avascular necrosis.
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Osteoarthritis due to scaphoid nonunion advanced collapse.
Conclusion
Scaphoid fractures in children are uncommon. A high degree of suspicion is needed in children with clinical signs and symptoms of scaphoid fracture. Radiologic imaging with several views is required for proper diagnosis. Most fractures are healed with cast placement, but few require surgery.
