Occult Pediatric Scaphoid Injuries

Fractures of the scaphoid may not be evident on the initial radiographic examination. They may be diagnosed in a late stage from the radiographic signs of bone healing. The diagnosis and treatment of children presenting with residual pain, swelling and tenderness on palpation in the anatomical snuffbox following either scaphoid injuries or distal forearm fractures after 5, at least, weeks of immobilization represent a true diagnostic dilemma. The use of a limited MRI with fat-suppression may indicate bone bruises of the carpal bones and/or of the scaphoid in these children. Prolonged immobilization and protection, until complete resolution of the clinical symptoms and signs, is the only required treatment.


EDITORIAL
A spherical growth plate circumferentially surrounds the entire ossific centre of each individual carpal bone during development. This growth plate is protective and offers resistance to fracture until sometime in adolescence. Fractures of the carpal scaphoid are rare in children. They are usually incomplete, undisplaced and located in the distal third. Radiographic findings indicative of a scaphoid fracture may be evident 2 to 3 weeks following a wrist injury. Scaphoid, as well as carpal bones lack a periosteal covering. Therefore, a periosteal reaction is not seen at imaging of a healing fracture. Sclerosis and bone resorption are common radiographic findings in the late stage. Diagnosis of scaphoid injuries in children may be easily missed because of their rarity, their unspecific and discrete clinical symptoms and partly because of difficult radiographic diagnostics. Avascular necrosis and nonunion are exceedingly rare in fresh fractures treated in a scaphoid type forearm-thumb cast. Immobilization is mandatory in cases with a clinical, although nonradiological, diagnosis  .
Clinical examination and standard radiographic evaluation procedures are reliable in the diagnosis of fractures of the scaphoid, in children with wrist injuries who suffer from acute or persistent pain and tenderness on palpation in the anatomical snuffbox, when performed by experienced pediatric orthopaedic surgeons. Occult fractures cannot by definition be diagnosed by conventional radiographs. In clinically suspected scaphoid injuries second-line investigations, including ultrasound, computed tomography (CT), bone scintigraphy and magnetic resonance imaging (MRI), may be used for the differential diagnosis of nonradiographically evident fractures and bone bruises from soft tissue injuries [31][32][33][34][35][36][37][38][39][40][41][42][43] .
With the advent of fat-suppression MRI, a new category of injury has been recognized: the bone bruise or contusion. It appears as an area of high intra-osseous signal intensity, representing focal edema and hemorrhage, following a microtrabecular injury of bone marrow without a defined cortical fracture line. Isolated subcortical trabecular fractures can occur in any region of the developing skeleton. Such injuries were rarely detected in the past because they are not visible on conventional radiographs, CT or routine MRI.

Nikolaos K. Sferopoulos
Bone bruises remain painful on palpation, whereas occult fractures through the growth plate or metaphysis of the long bones have become asymptomatic after a reasonable period of immobilization in plaster. This may be due to either a reduction in intra-osseous pressure by evacuation of the hematoma from the fractured cortex or to an acceleration of the healing process encouraged by the activated periosteum. A prolonged period of immobilization and restricted use of the involved limb is mandatory during trabecular healing of bone bruises to avoid insufficiency fractures. The bruises as well as their clinical symptoms usually disappear within 12-16 weeks. According to forensic applications and problems pursuant to insurance law, MRI examination is only indicated when conventional radiographs are unremarkable, pain persists for an unusually long period of time and when a relevant therapeutic consequence can be expected from the MRI results [44][45][46][47][48][49][50][51][52][53] .
The incidence of bone bruising to the distal radius and wrist or ankle has been well documented in children. The use of a limited MRI, using fat-suppression, to evaluate a potential bone bruising is indicated in children, whose symptoms do not resolve after a sufficient period of immobilization, usually exceeding 5 weeks. In the past, the appearance of a fracture line on plain radiography was needed to diagnose a fracture. Thus, children with bone bruises might have been encouraged to use an injured extremity or to participate in sporting activities after or even before 5 weeks of immobilization [54,55] .
Bone bruising of the scaphoid may exhibit substantial variation in anatomical location and extent. It may also be associated with bone bruising of other carpal bones. It is a benign injury with predictable recovery and is unlikely to result in long-term morbidity in the form of nonunion. An elongated recovery period is mandatory, with appropriate immobilization and restricted use of the involved limb, during trabecular healing to avoid an insufficiency fracture [56,57] .
Children with residual clinical symptoms and signs of radiographically occult scaphoid injury, following 5, at least, weeks of immobilization, are divided in two groups. The former group includes patients that have already been immobilized for a potential scaphoid injury. Scaphoid injuries with residual pain, swelling and tenderness on palpation in the anatomical snuffbox, where  radiographic imaging remains normal and recovery is significantly prolonged, represent a true diagnostic dilemma (Figures 1, 2, 3). The latter group includes patients with distal forearm fractures that were treated conservatively. Residual scaphoid symptoms and signs following the treatment of distal forearm fractures also pose a diagnostic enigma (Figures 4, 5).

Figure 3
An 8-year-old girl with a radiographically occult scaphoid injury that was immobilized in plaster. A MRI was performed due to residual symptoms, following cast removal, 5 weeks post-injury. Short tau inversion recovery image showed bone bruising of the mid-portion of the scaphoid and fluid signal around most of the carpal bones. Two bone islands on the scaphoid and the capitate were found incidentally on the radiographs.

Figure 4
A 13-year-old boy with an undisplaced physeal fracture of the distal forearm bones that was treated conservatively. A MRI was performed due to radial-sided wrist pain, following cast removal, 5 weeks post-injury. Short tau inversion recovery images showed bone bruising of the mid-portion of the scaphoid and fluid signal of the distal radioulnar joint.

Figure 5
A 12-year-old boy was referred 2 weeks following a football injury (the ball forced the wrist into extension). The fracture was immobilized but reduction was not attempted. A MRI was performed due to radial-sided wrist pain, following cast removal, 5 weeks post-injury. Short tau inversion recovery images showed diffuse bone bruising of the carpal bones, including the scaphoid, with fluid signal between them. Further immobilization and protection was offered for a total period of 3 months post-injury. By that time the patient was symptom-free and radiographs indicated complete remodeling of the displaced fracture of the distal radius.
MRI with fat-suppression may indicate bone bruises of the carpal bones and/or of the scaphoid in both groups of patients. We have also consistently observed fluid collection in the joints of the carpal bones. No long-term morbidity occurred in any of our patients.
It could be argued that bone bruises would heal uneventfully without treatment and that MRI rarely adds information that influences the treatment of such patients and should, therefore, not be considered as a first-line examination. However, the use of a limited MRI with fat-suppression might be considered as a useful second-line investigation to answer or evaluate the cause of residual posttraumatic radial-sided wrist tenderness, justify prolonged immobilization and protection and ensure appropriate treatment of bone bruising of the scaphoid in children.