Mechanisms and Incidence of Injury

A fall on the outstretched hand is the most common cause of a scaphoid fracture.2 ^– 8 Less commonly reported causes include punching and direct blows.9 Fractures may occur via one of two mechanisms: (1) Directly, a compression force may result in an impaction fracture at any point along the bone, whereas (2) indirectly, a forced wrist dorsiflexion may create a moment that typically results in a displaced distal third, waist, or proximal third scaphoid fracture.

Similarly to the adult population, the immature scaphoid is the most commonly fractured carpal bone6 ^– 8 ^, 10 ^– 13; however, in children, scaphoid fractures are relatively rarer because of the significant amount of cartilage present in the immature scaphoid, resulting in a cushioning effect protecting the bone.14 Scaphoid fractures represent 0.39% of all pediatric fractures,11 0.45% of pediatric upper extremity fractures,11 and 3% of pediatric fractures of the hand and wrist.12 In general, fractures start to appear at 6 years of age, and their frequency increases with time, reaching a peak at 15 years.12 ^, 15 ^– 17

Fracture Classification

The physical properties of the scaphoid are continuously evolving during its period of maturation (6 to 15 years). Therefore, the patient’s age, degree of ossification, and fracture location are important in classifying the fracture and determining treatment. Based on the child’s age and degree of ossification, D’Arienzo4 has proposed a classification system ( Fig. 25.1 ): In type A, the fracture line either involves the cartilage, or in addition may involve part of the ossific nucleus. This pattern occurs in children younger than 8 years. The diagnosis of type A fractures is a challenge and requires the use of advanced imaging modalities such as magnetic resonance imaging (MRI).2 ^– 4 ^, 6 ^, 8 ^, 18 Type B fractures are osteochondral and occur in patients aged 8 to 11 years. The type C fractures (the most common) occur in adolescents of 12 years of age or older, and because ossification of the scaphoid is almost complete, their behavior is similar to that of their adult counterpart.18

Pediatric scaphoid fractures may also be classified by anatomical location4 ^, 5 ^, 10 ^, 19 ( Fig. 25.2 ): (1) tuberosity, (2) transverse distal pole, (3) avulsion distal pole, (4) waist, and (5) proximal pole. The majority of pediatric scaphoid fractures occur commonly in the distal third of the bone (first three locations), 25% are waist fractures, whereas fractures of the proximal pole are extremely rare.2 ^– 8 ^, 11

In children, fractures of the scaphoid waist are more prone to nonunion and historically have taken longer to achieve union with immobilization.2 ^, 4 ^– 8 ^, 11 ^, 12 ^, 18 ^, 20 ^– 31

History and Physical Examination

Because symptoms may be vague or even absent, a high index of suspicion for a scaphoid injury is required when there is clinical evidence such as a fall on the outstretched hand, punching activity, and so forth. Pain in the anatomical snuffbox is the most common sign on examination, but there other findings, such as pain during range of motion, snuffbox swelling, and pain with axial loading, that may indicate injury to the scaphoid.3

Imaging

Standard radiographic evaluation should be the first imaging modality for suspected scaphoid injury and includes antero-posterior, lateral, oblique, and scaphoid views.32 The latter is particularly helpful in disclosing avulsion fractures.12 In the case of occult fractures, several soft tissue signs, such as exudation into the joint capsule recess, dorsal swelling of the wrist, and obliteration of a scaphoid fat stripe, may assist their detection; however, further imaging modalities will be required to ultimately confirm the diagnosis.33 The use of plain radiographs in children is not enough to rule out the presence of a fracture because the sensitivity of plain radiographs varies considerably (21% to 97%).2 ^, 3 ^, 34 Therefore, plain radiographs are useful in confirming the presence of a fracture and following healing. In addition, in cases where there is a discrepancy between bone age and chronological age, bone age radiographs may be appropriate in guiding treatment decisions.35

More advanced imaging modalities may be used in acute cases when radiographs look normal or equivocal. Computed tomography and bone scintigraphy have been proven to have high sensitivity and specificity in the adults36 ^– 38; however, those may be less desirable in children due to the radiation dose delivered and also due to the lack of studies reporting reliability and accuracy. Ultrasound imaging may be a valid alternative; however, it is operator dependent. In the adult population, the ranges are for sensitivity 50% to 78% and for specificity 89% to 91%.39 ^– 41

MRI is the most reliable modality for ultimate diagnosis in cases of suspected pediatric scaphoid fractures. In a series of 57 patients with mean age of 12 years, evaluated with radiography and MRI within 10 days of injury, Johnson et al34 found that the correct diagnosis could be established in 100% of patients using MRI ( Table 25.1 ). Importantly, 75% of the patients had a negative initial plain radiograph that was proven to be a fracture with MRI. In another series of 18 patients (age range 8 to 15 years), Cook et al33 found a 100% negative predictive value for MRI in the exclusion of a fracture.

Treatment

Nonoperative treatment with cast immobilization is the cornerstone of management of the majority of pediatric scaphoid fractures. Operative treatment is usually indicated in patients near or at skeletal maturity with displaced fractures or in the case of nonunion (see next sections on pediatric scaphoid nonunions).

If, based on clinical and physical findings, the clinician suspects a pediatric scaphoid injury, the first step in the management should be cast immobilization, even when plain radiographs are negative. In the latter case, an MRI scan should be obtained to rule out any injury not visible on plain radiographs. If the MRI is negative, there is no further need for further treatment27 ^, 33 ^, 34; however, a brief (2- to 4-week) clinical follow-up period is recommended.35 In children, initial immobilization should include a long-arm thumb spica cast to ensure appropriate immobilization, whereas a short-arm thumb spica cast may be appropriate in cases of incomplete or avulsion fractures. In the patient presenting or diagnosed late, immobilization may be the first line of treatment because it has been shown that union may be achieved even in these late cases.2 ^, 3 ^, 6 ^, 8 ^, 22 ^, 31 ^, 42

Following the initial 2 weeks of immobilization, the long-arm thumb spica cast may be substituted with a short-arm thumb spica cast; however, because most of the scaphoid nonunions are complications of fractures of the scaphoid waist, it might be preferable to maintain the long-arm thumb spica cast in these cases. The duration of the period of immobilization is dictated by the presence of healing on plain radiographs, or MRI in equivocal cases, or in cases in which there are lesions not reliably visible on plain radiographs (pure chondral lesions or small osteochondral fractures). Table 25.2 presents duration of healing, based on fracture location, with nonoperative treatment of pediatric scaphoid fractures.4 ^, 5 ^, 7 ^, 8 ^, 12

Surgical Indications

As a general rule we advocate conservative treatment for acute scaphoid fractures in the pediatric patient. Fractures that fail to heal within 6 months should be considered as nonunions (see next section on nonunions). Acute displaced pediatric scaphoid fractures seem to be extremely rare; to our knowledge there is one case of a 9-year-old female with an acute displaced fracture of the scaphoid waist that was managed with open reduction and internal fixation using a Herbert screw, with excellent clinical and radiographic outcomes.43 Historically, in the patient who is close to skeletal maturity, based on physical closure and/or bone age radiographs, the literature indicates that cast immobilization may be effective.4 ^, 7 ^, 11 However, it is known that as skeletal maturity is reached, the fractures behave similarly to their adult counterparts, and therefore the approach to the adult may be indicated in these cases ( Table 25.3 ).

Incidence

In a large series of 371 pediatric scaphoid fractures Fabre et al2 reported 0.8% nonunion. However, the percentage of pediatric scaphoid fractures that reach nonunion stage is unknown, because some may heal spontaneously and therefore pass undetected.

Anatomical Distribution of the Nonunion in Children

In addition to the superior healing potential of the immature skeleton, the majority of pediatric scaphoid fractures involve either avulsions or distal third fractures, which result in a lower incidence of nonunions compared with the adult population.13 ^, 14 ^, 16 ^, 22 ^, 23 ^, 25 ^, 28 ^– 31 ^, 44 ^– 46 Therefore, the overwhelming majority of pediatric scaphoid nonunions involve the bone’s waist,2 ^, 3 ^, 7 ^– 9 ^, 11 ^, 14 ^, 18 ^, 22 ^– 30 ^, 47 whereas very rare cases involving the proximal9 ^, 20 ^, 48 ^, 49 or distal6 ^, 9 ^, 24 poles have also been reported ( Table 25.4 ).

Furthermore, in the adult, due to the retrograde intraosseous blood supply to the scaphoid, fractures and nonunions of the proximal pole of the scaphoid may be complicated by avascular necrosis (AVN).50 This appears to be a possible but exceptional complication in children.18 ^, 49 Larson et al18 treated by cast immobilization one scaphoid fracture of the proximal pole that resulted in nonunion with AVN. Waters and Stewart49 reported three cases of scaphoid nonunions complicated by AVN of the proximal pole in adolescent boys with a mean age of 14.5 years. The patients were treated with vascularized bone graft from the distal part of the radius with union and good function at 5 years. Two other cases of proximal pole nonunion in children were not complicated by AVN.9 ^, 20 ^, 48