Facet dislocations in children are rare. This article presents the youngest case of a unilateral facet dislocation described in the pediatric population. A 9-year-old boy sustained a flexion/axial loading injury to his cervical spine while wrestling with his friends, causing a unilateral facet dislocation at C4/5. Prereduction magnetic resonance imaging (MRI) demonstrated the absence of a diskal herniation or cord impingement and an intact posterior ligamentous complex. Due to the patients young age, the decision was made to forgo a supervised awake closed reduction. Closed reduction was performed under general anesthesia with somatosensory-evoked potential and motor-evoked potential monitoring. Closed reduction was successfully achieved after Gardner-Wells tongs were applied and used to manually direct slow, steady in-line traction, along with slight flexion and posterior rotation of the dislocated side under direct fluoroscopy.
The patient was immediately awakened from anesthesia and was found to have an intact sensory examination. He was immobilized in a cervical collar for 12 weeks. At 2-year follow-up, he remained asymptomatic without recurrence and had painless full range of motion of the cervical spine. Radiographs revealed a normally aligned cervical spine.
Unilateral cervical facet dislocations and subluxations are the result of a distraction-flexion force applied to the spine along with a rotational component. These are not uncommon injuries in the adult spine; however, in the young pediatric population, cervical facet dislocations are rare.
Spinal trauma in the pediatric population is relatively uncommon, accounting for approximately 1% to 2% of pediatric trauma hospital admissions.1-3 Of these injuries, 60% to 80% involve the cervical spine.4-6 There is a bimodal distribution of cervical spinal injuries in children.7,8
The younger age group, children 0 to 9 years, is characterized by an immature spine that has increased physiological mobility. In this population, most spinal injuries result from an automobile accident or fall and involve the upper cervical spine 84% to 90% of the time.7,9 The older group, adolescents aged 10 years and older, is characterized by a more mature spine with anatomy more closely resembling that of an adult. This group is most typically injured in a motor vehicle accident or sporting/recreational activity, with 61% of cervical injuries occurring in the caudal cervical spine.4,9-11 Common injuries in this older patient population include compression fractures, tear-drop fractures, lateral mass fractures, spinous process fractures, and facet dislocations.12
The younger child with a subaxial spinal injury often has a neurologic injury in the absence of fracture that can be attributed to hypermobility of the spine and stretch of the spinal cord.13 Facet subluxation/dislocation in the absence of significant spinal fracture is a distinctly unusual finding in the younger child. This article describes 2-year follow-up of a 9 year-old boy who sustained a unilateral facet dislocation successfully treated at our facility with closed reduction and immobilization.
A 9-year-old professional wrestling enthusiast was pile-drived onto a bed by his playmate and sustained a flexion injury to his neck. The patient reported hearing a crack at the time of injury and was unable to continue wrestling secondary to neck pain. He presented approximately 24 hours after the injury reporting continued neck pain, but ambulating without assistance. He reported no numbness, tingling, or weakness in the arms or legs.
On examination, there was midline tenderness to palpation in the mid-cervical region. There was no spinous process step-off. There was paravertebral muscle spasm but no torticollis evident. His upper and lower extremities were neurologically intact. Active range of motion (ROM) of the neck was limited by pain, and passive ROM was limited to approximately 20° of flexion and 20° of extension. The remainder of his examination was unremarkable. Radiographs revealed retropharyngeal soft tissue swelling at the level of C4/5, C4/5 segmental kyphosis of 8°, anterolisthesis of C4 on C5 of 3 mm, and a positive bow tie sign indicative of a unilateral facet dislocation (Figure 1). Computed tomography (CT) scan confirmed a C4/5 unilateral facet dislocation without fracture (Figure 2). Magnetic resonance imaging (MRI) demonstrated no evidence of herniated nucleus pulposus or significant posterior ligamentous injury (Figure 3).
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|Figure 1: Lateral radiograph of the injury demonstrating positive bow tie sign at C4 (outlined), making it possible to identify both facet joints, which are normally superimposed on each other. Other radiographic signs can include a sudden change in the spinous process alignment on AP radiographs (not shown). Figure 2: Sagittal CT image demonstrating unilateral facet dislocation. The white line demonstrates normal facet articulation, while the dashed line signifies facet dislocation with irregular articulation. Figure 3: Sagittal MRIs displaying no significant posterior ligamentous injury. |
Due to the patients young age and his perceived anxiety, he underwent closed reduction under general anesthesia. Somatosensory-evoked potential and motor-evoked potential monitoring was continuously performed once general anesthesia was induced. Gardner-Wells tongs were applied and used to manually direct slow, steady in-line traction, along with slight flexion and posterior rotation of the dislocated side under direct fluoroscopy. This was achieved while applying axial compression to the nondislocated side. Manual rotation of the head toward the dislocated side completed the reduction maneuver, and a subtle click was felt. Closed reduction was confirmed with continuous fluoroscopy without changes evident in somatosensory-evoked potential and motor-evoked potential monitoring.
The patient was immediately awakened from anesthesia and was found to have an intact sensory examination and 5/5 motor strength in all upper and lower extremity distributions. He was normoreflexive bilaterally, had no clonus, and had a negative Babinski and Hoffmans sign. Post-reduction radiographs confirmed a stable reduction and restoration of normal alignment of the cervical spine (Figure 4). The patient was subsequently discharged without incident.
|Figure 4: Postreduction lateral radiograph demonstrating restored alignment. |
The patient was placed in a rigid cervical collar for 12 weeks, over which time neck pain completely resolved. No formal physical therapy was required. At 12 weeks after injury, he had no tenderness to palpation and a painless full ROM. Flexion/extension radiographs at that time showed a stable reduction of C4/5 with no evidence of recurrence or instability.
At 2-year follow-up, he remained asymptomatic without recurrence. Regarding activity restrictions, the patient and his parents were informed that there is a paucity of reliable data to support recommendation to return to contact sports. Our recommendation was to avoid participation in contact sports, and the patient and his parents indicated that their desire was also to avoid contact sports. Examination at 2-year follow-up revealed painless full ROM of the cervical spine. Radiographs revealed a normally aligned cervical spine.
Unilateral cervical facet dislocations and subluxations are the result of a distraction-flexion force applied to the spine along with a rotational component.14,15 These are not uncommon injuries in the adult spine; however, in the young pediatric population, cervical facet dislocations are rare.
The pediatric cervical spine behaves differently than the adult spine for several reasons. The facet joints are initially more horizontal in the child, averaging 60° from the posterior vertebral wall at age 12 months, decreasing to 47° at age 6 years, and terminating at 45° as an adult.16-19 The more horizontal orientation of the facet joints allow more motion in the sagittal plane, which increases the incidence of neurological and ligamentous injury without bony fracture. C2/3 and C3/4 pseudosubluxation is commonly seen and is a normal finding in the child.20 The uncovertebral joints are not yet developed in the younger child, which also increases motion in the coronal plane. The childs head is proportionally larger than that of an adult, which results in an axis of rotation at the C2/3 level versus an adults axis of rotation at the C5/6 level. This, combined with poor head control in the young child and generalized ligamentous laxity, often contributes to a higher incidence of upper cervical spine injuries and a low incidence of lower spinal injuries.
Our patient did not present with torticollis, which is not a common presentation of a subaxial cervical spine unilateral facet dislocation. A common cause of pediatric torticollis, however, is atlantoaxial rotatory subluxation. This is due to the greater degree of rotation inherent to the upper cervical spine. Patients with this unilateral facet subluxation of C1 on C2 present with neck pain, headache, and a characteristic cock-robin positioning of rotating the head to one side with lateral flexion to the other. Etiology can include either trauma or infection. This condition needs to be evaluated with radiographic and CT imaging and differentiated from other causes of torticollis such as ophthalmologic problems, muscle tightening of the sternocleidomastoid, brain stem abnormalities, congenital vertebral abnormalities, and vertebral infections. This workup is crucial in differentiating this injury from a lower cervical spine facet dislocation, as the initial treatment for atlantoaxial rotatory subluxation is nonoperative.
There is a paucity of literature describing facet dislocations in the pediatric population. However, in adults, unilateral facet dislocations can be a subtle finding on radiographs and are frequently overlooked. In the adult population, Rorabeck et al21 showed 11 of 26 patients had a delay of up to 2 weeks prior to diagnosis. Braakman and Vinken22 also demonstrated a delay of >2 weeks in 15 of 35 patients. Beyer and Cabanela23 had a delay in diagnosis of a mean 8 days in 12 of 36 patients. Characteristic radiographic findings include a rotation of the spinous processes above the level of the injury toward the side of the dislocation. The bow tie sign is seen on the lateral view when there is a rotation of the involved facet from its normally superimposed position with the contralateral facet to allow visualization of both facet joints. Young et al24 described using the spinolaminar line and the posterior border of the articular pillar as a diagnostic aid. An abrupt change of this distance at any given level is suggestive of a unilateral cervical facet dislocation. This was accurate in 23 of 27 (85%) patients.24 The bow tie sign was present in 33%, subluxation of 2 to 7 mm in 81%, and fanning of the spinous processes in 37% of patients.24
If undetected and untreated, unilateral facet dislocations can lead to permanent disability or instability in the adult.21,23,25 Closed reduction is the first-line treatment of injuries in the acute setting. Closed reduction is commonly performed on awake, cooperative adult patients who can be serially examined to detect any change in neurologic function. There is no literature describing this technique in children younger than 10 years. In our case, a prereduction MRI was performed to ensure that no disk herniation was present. General anesthesia was used for sedation; however, somatosensory-evoked potential and motor-evoked potential monitoring was used to aid in the detection of any neurologic changes. The patient was also immediately awakened at the conclusion of the reduction to confirm no changes in neurologic examination.
Traction is commonly applied with the use of Garder-Wells tongs or a halo-ring. Prior to application of either device, concomitant skull fracture must be ruled out with appropriate radiographs. As slight flexion, as well as traction, is required for the reduction, the initial placement of the Gardner-Wells tongs in adults is usually slightly more posterior than normal. Due to the proportionally larger head of a child, this posterior placement is not needed or recommended. Reduction is achieved by gripping the tongs much like holding onto a steering wheel. One can simultaneously apply axial compression to the nondislocated side while applying longitudinal distraction to the dislocated side. This unlocks the dislocated facet. Obtaining final reduction is completed by addressing the rotational component. This is performed by rotating the head toward the dislocated side. Sometimes a click can be heard or felt by the person performing the reduction as occurred in this case. Traction is slowly released and fluoroscopy used to confirm the reduction.
Open reduction and cervical fusion is recommended for those cases that fail closed reduction, involve neurologic deterioration, or demonstrate recurrence or instability. The role of operative and nonoperative management of facet dislocations is not well defined in the existing literature.
Complications of treatment of these injuries in the pediatric population are not well known. Evidence exists of delayed complications such as neck pain and stiffness with posterior cervical fusion for facet dislocations in up to 33% of cases in adults.26 Our patient experienced no complications. Follow-up radiographs at 12 weeks postinjury demonstrated no evidence of recurrence, instability, or neurologic deterioration; therefore, no posterior fusion was required. Radiographic follow-up at 2 years showed no evidence of instability. Clinically, the patient returned to all activities of daily living, including sports, with no residual neurologic deficits or evidence of neck pain or decreased ROM.
Unilateral facet dislocation is an unusual diagnosis in the younger child. To our knowledge, Burke and Berryman27 reported the youngest facet dislocation in a 10-year-old child, but it is unclear whether this was a unilateral or a bilateral facet dislocation and what the mechanism of injury was. Webb et al28 reported a C3-4 subluxation sustained during a trampoline accident in a 12-year-old boy who had initial quadriparesis, which completely resolved. A unilateral facet dislocation can be a subtle diagnosis to make if not clinically suspected; however, if missed, it can result in permanent disability. Closed reduction and nonoperative management was a successful treatment option for our young patient with a unilateral facet dislocation and intact posterior ligaments. To our knowledge, this unusual case of a unilateral facet dislocation in a 9-year-old is the youngest in the literature to date.
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- Rachesky I, Boyce WT, Duncan B, Bjelland J, Sibley B. Clinical prediction of cervical spine injuries in children. Radiographic abnormalities. Am J Dis Child. 1987; 141(2):199-201.
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- Dickman CA, Rekate HL, Sonntag VK, Zabramski JM. Pediatric spinal trauma: vertebral column and spinal cord injuries in children. Pediatr Neurosci. 1989; 15(5):237-255; discussion 256.
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- McGrory BJ, Klassen RA, Chao EY, Staeheli JW, Weaver AL. Acute fractures and dislocations of the cervical spine in children and adolescents. J Bone Joint Surg Am. 1993; 75(7):988-955.
- Bohn D, Armstrong D, Becker L, Humphreys R. Cervical spine injuries in children. J Trauma. 1990; 30(4):463-469.
- Henrys P, Lyne ED, Lifton C, Salciccioli G. Clinical review of cervical spine injuries in children. Clin Orthop Relat Res. 1977; (129):172-176.
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- Allen BL Jr, Ferguson RL, Lehmann TR, OBrien RP. A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine (Phila Pa 1976). 1982; 7(1):1-27.
- Bauze RJ, Ardran GM. Experimental production of forward dislocation in the human cervical spine. J Bone Joint Surg Br. 1978; 60(2):239-245.
- Kumaresan S, Yoganandan N, Pintar FA, Maiman DJ, Kuppa S. Biomechanical study of pediatric human cervical spine: a finite element approach. J Biomech Eng. 2000; 122(1):60-71.
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- Fletcher G, Haughton VM, Ho KC, Yu SW. Age-related changes in the cervical facet joints: studies with cryomicrotomy, MR, and CT. AJR Am J Roentgenol. 1990; 154(4):817-820.
- Kuhns LR, Strouse PJ. Facet coverage in children on flexion lateral cervical radiographs. Spine (Phila Pa 1976). 1999; 24(4):339-341.
- Swischuk LE. Anterior displacement of C2 in children: physiologic or pathologic. Radiology. 1977; 122(3):759-763.
- Rorabeck CH, Rock MG, Hawkins RJ, Bourne RB. Unilateral facet dislocation of the cervical spine. An analysis of the results of treatment in 26 patients. Spine (Phila Pa 1976). 1987; 12(1):23-27.
- Braakman R, Vinken PJ. Unilateral facet interlocking in the lower cervical spine. J Bone Joint Surg Br. 1967; 49(2):249-257.
- Beyer CA, Cabanela ME. Unilateral facet dislocations and fracture-dislocations of the cervical spine: a review. Orthopedics. 1992; 15(3):311-315.
- Young JW, Resnik CS, DeCandido P, Mirvis SE. The laminar space in the diagnosis of rotational flexion injuries of the cervical spine. AJR Am J Roentgenol. 1989; 152(1):103-107.
- Cheshire DJ. The stability of the cervical spine following the conservative treatment of fractures and fracture-dislocations. Paraplegia. 1969; 7(3):193-203.
- OBrien PJ, Schweigel JF, Thompson WJ. Dislocations of the lower cervical spine. J Trauma. 1982; 22(8):710-714.
- Burke DC, Berryman D. The place of closed manipulation in the management of flexion-rotation dislocations of the cervical spine. J Bone Joint Surg Br. 1971; 53(2):165-182.
- Webb JK, Broughton RB, McSweeney T, Park WM. Hidden flexion injury of the cervical spine. J Bone Joint Surg Br. 1976; 58(3):322-327.
Drs Parada and Arrington are from Madigan Army Medical Center, Fort Lewis, Washington; Dr Kowalski is from Blanchfield Army Community Hospital, Fort Campbell, Kentucky; and Dr Molinari is from University of Rochester School of Medicine and Dentistry, Rochester, New York.
Drs Parada, Arrington, Kowalski, and Molinari have no relevant financial relationships to disclose.
Correspondence should be addressed to: Stephen A. Parada, MD, Madigan Army Medical Center, 9040A Fitzsimmons Dr, Joint Base Lewis McChord, WA 98431 (firstname.lastname@example.org).