6 Fractures of the Spine
Overview of Spinal Fractures
Anatomic Features
The spinal column consists of individual bony vertebrae and intervertebral disks that connect each vertebra in the front of the spine. A healthy spine provides strength, is flexible, and allows movement in several planes. Body movement and weight-bearing changes can produce an alteration in the geometry of the spine. The vertebral column is made of 26 separate vertebrae, and can be divided into five sections: cervical, thoracic, lumbar, sacral, and coccygeal. Because the sacrum and coccyx are fused with five sacral vertebrae and four coccygeal vertebrae, respectively, some believe the vertebral column is actually made up of 33 vertebral bones. Each vertebra is composed of a body anteriorly and a neural arch posteriorly. The arch has two supporting pedicles and two arched laminae; it encloses an opening, the vertebral foramen, which helps to form the vertebral canal in which the spinal cord is housed. Seven processes arise from the vertebral arch: the central spinous process, two transverse processes, two superior facets, and two inferior facets. Three quarters of the length of the vertebral column is from the vertebral bodies and one quarter is from the thickness of the intervertebral disks.
Two important concepts have emerged during the study of the spine’s anatomic features. They are the two-column concept and three-column concept. In 1968, Kelly and Whitesides proposed a two-column concept that aided the assessment of angular deformation (▶ Fig. 6.1). The two columns, namely the anterior and posterior columns, are defined as involving the vertebral bodies and neural arches, respectively, and are delineated by the posterior longitudinal ligament. The anterior column is composed of the anterior longitudinal ligament, posterior longitudinal ligament, and vertebral body. The posterior column, otherwise known as the hollow column, is composed of the vertebral canal and the posterior ligamentous complex. Kelly and Whitesides highlighted the importance of the posterior ligamentous complex in the assessment of spinal stability. However, the two-column concept is limited in assessing posterior nerve root injury in spinal fractures, and has been gradually replaced by the three-column concept.
The three-column concept was introduced by Denis in 1983, and is more consistent with clinical observations regarding spinal stability than the two-column concept (▶ Fig. 6.2). It divides the spine into three columns: the anterior, middle, and posterior columns. Using this scheme, the anterior column is composed of the anterior half of the vertebral body, the intervertebral disk, and the anterior longitudinal ligament; the middle column includes the posterior part of vertebral body and the disk, and the posterior longitudinal ligament; and the posterior column includes the pedicles, the facet joints, and the supraspinous ligaments. In 1984, McAfee proposed that the demarcation lies between the anterior and middle columns at the junction of the anterior two-thirds and posterior one-third of the vertebral body, instead of the midpoint of the vertebral body as proposed by Denis. With McAfee’s scheme, fractures involving the middle column are unstable fractures. This concept is able to provide a better and more accurate assessment of spinal stability and neurological injury.
Fig. 6.1 Delineation illustration of two-column spine concept.
Fig. 6.2 Delineation illustration of three-column spine concept.
AO Classification and Coding System for Spinal Fractures
Based on AO classification, the spinal column is coded as number “5.” Cervical, thoracic, lumbar, and sacral fractures are assigned as numbers “51,” “52,” “53,” and “54,” respectively. Pelvic fractures always involve sacrococcygeal fractures; therefore, we put sacral and coccygeal fractures into the pelvic section during our statistical analysis.
Because the atlas (51.01) and axis (51.02) have different anatomic features and unique functions from the other cervical vertebrae, they require different methods of assessment regarding the stability and neurological injury resulting from fractures. As such, AO classification describes vertebral column fractures into four sections: atlas, axis, lower cervical, and thoracolumbar fractures. The atlas and axis constitute the upper cervical spine.
For AO classification of spinal fractures, number “5” is assigned for the spine; “51” for cervical spine, 51.01–51.07 for vertebrae C1–C7, respectively (▶ Fig. 6.3); “52” for thoracic spine, 52.01–52.12 for vertebrae T1–T12, respectively; and “53” for lumbar spine, 53.01–53.05 for L1–L5, respectively (▶ Fig. 6.4).
Epidemiologic Features of Spinal Fractures in the China National Fracture Study
A total of 168 patients with 168 spinal fractures were investigated in the China National Fracture Study (CNFS). The fractures accounted for 9.53% of all patients with fractures and 9.17% of all types of fractures. The population-weighted incidence rate of spinal fractures was 29 per 100,000 population.
The epidemiologic features of spinal fractures in the CNFS are as follows:
• More males than females
• The highest risk age group is 15–64 years
• The thoracic and lumbar vertebral fracture is the most common spinal fractures
• Injuries occurred most commonly via falls
Fig. 6.3 AO codes for the spine.
Spinal Fractures by Sex in CNFS
See ▶ Table 6.1 and ▶ Fig. 6.5.
Sex | Number of patients | Percentage |
Male | 92 | 54.76 |
Female | 76 | 45.24 |
Total | 168 | 100.00 |
Fig. 6.5 Sex distribution of 168 patients with spinal fractures in the China National Fracture Study (CNFS).
Spinal Fractures by Age and Sex in CNFS
See ▶ Table 6.2 and ▶ Fig. 6.6.
Fig. 6.6 (a) Age distribution of 168 patients with spinal fractures in the China National Fracture Study (CNFS); (b) age and sex distribution of 168 patients with spinal fractures in the CNFS.
Spinal Fractures by Location in CNFS
See ▶ Table 6.3 and ▶ Fig. 6.7.
Fig. 6.7 Segment distribution of 168 patients with spinal fractures in the China National Fracture Study (CNFS).
Spinal Fractures by Causal Mechanisms in CNFS
See ▶ Table 6.4 and ▶ Fig. 6.8.
Fig. 6.8 Causal mechanisms of 168 patients with spinal fractures in the China National Fracture Study (CNFS).
Clinical Epidemiologic Features of Fractures of the Spinal Column
A total of 49,679 patients with 55,097 spinal column fractures were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All cases were reviewed and statistically studied, accounting for 11.97% of all patients with fractures and 12.76% of all types of fractures, respectively. Among these 49,679 patients, there were 517 children and 49,162 adults. Epidemiologic features of fractures of the spinal column are as follows:
• More males than females
• The high-risk age group is 56–60 years. The most affected male age group is 41–45 years, while females aged 56–60 years have the highest risk.
• Thoracolumbar fractures occur more frequently than cervical or sacrococcygeal fractures.
Spinal Column Fractures by Sex
See ▶ Table 6.5 and ▶ Fig. 6.9.
Table 6.5 Sex distribution of 49,679 patients with spinal column fractures
Sex | Number of patients | Percentage |
Male | 25,280 | 50.89 |
Female | 24,399 | 49.11 |
Total | 49,679 | 100.00 |
Fig. 6.9 Sex distribution of 49,679 patients with spinal column fractures.
Spinal Column Fractures by Age Group
See ▶ Table 6.6 and ▶ Fig. 6.10.
Fig. 6.10 (a) Age distribution of 49,679 patients with spinal column fractures and (b) age and sex distribution of 49,679 patients with spinal column fractures.
Spinal Column Fractures by Segment
See ▶ Table 6.7.
Cervical Fractures (Segment 51)
Anatomic Features
The first two vertebral bodies in the cervical spine are called the atlas and the axis. They are very special with respect to their unique anatomic features and functions; therefore, assessment of injuries to the atlas and axis is very different from those of other vertebrae. AO classification has special descriptions for fractures of the atlas and axis (▶ Fig. 6.11).
The atlas, a ring-shaped bone, is remarkable for having no “body.” It consists of anterior and posterior arches, and two lateral masses, from which two transverse processes project laterally and downward. Its superior articular facets articulate with the occipital condyles of the skull, and it forms the atlantoaxial joint with the dens of the axis. The two transverse processes of the atlas serve as an attachment site for muscles and ligaments, which assist in rotating the head. The foramen transversarium pierces the transverse processes of the atlas, and gives passage to the vertebral artery and vein. The anterior and posterior arches are thin, especially at their junction with the lateral mass, which is particularly susceptible to injury and, if damaged, may lead to fracture and dislocation.
The dens of the axis was originally part of the atlas, but became separated from the atlas during development; therefore, malformations commonly occur, such as absence of the dens of axis, hypoplasia or agenesis of the dens, occipital–atlas fusion, and atlas–axis fusion. These malformations may result in poor stability of the craniocervical region and compression of the spinal cord. The root of the dens is very thin, making it especially prone to injury. The resultant fracture and dislocation of the root would lead to a high risk of paraplegia or even death (▶ Fig. 6.11).
Fig. 6.11 Oblique posterior–superior views of atlas (a) and axis (b).
Fig. 6.12 Superior view of atlantoaxial ligaments.
There are important ligaments between the atlas and axis, connecting two or more bones, condrites, or other soft tissues. The atlantoaxial ligament complex provides stability to the atlantoaxial joint through its great range of motion, and prevents hyperflexion or hyperextension of the joint (▶ Fig. 6.12). The upper cervical ligament is important in stabilizing the upper cervical spine and preventing neurological injury. Loss of stability of the ligament can result in subluxation of C1–C2, and lead to lethal neurological injuries.
Each vertebra in the lower cervical spine (C3–C7) consists of a vertebral body, a vertebral arch, which is formed by a pair of pedicles, and a pair of laminae (▶ Fig. 6.13). Each vertebra also has seven processes, four articular, two transverse, and one spinous. By comparison, cervical vertebrae are smaller than thoracolumbar vertebrae. The lateral aspect of each vertebral body has a superior projection (uncinate process) that forms Luschka’s joints (uncovertebral joints) with a projection downward from the inferior surface of the vertebral body above. The transverse process is short and broad, with a wide groove for the existing spinal nerve on its upper surface. It gives attachment to a number of muscles. The bony protuberances at the end of the transverse processes are called the anterior and posterior tubercles, accordingly. The articular facets are inclined approximately 45 degrees from the horizontal plane. A characteristic feature of vertebrae C2 to C6 is a projection known as the bifid spinous process, whereas C7 has a prominent nonbifid spinous process that can be felt at the base of the neck.
AO Classification of Cervical Spinal Fractures
Based on AO classification, 51.01 (atlas) fractures can be divided into three types: A, unilateral neural arch fractures; B, burst fractures; and C, dislocation of the atlas–axis. And 51.02 (axis) fractures can also be grouped into three types: A, fractures through the isthmus, including neural arch (ring) fractures or Hangman’s fractures; B, dens fractures; and C, fractures through the isthmus plus a dens fracture. The AO classification for segment 51.03–51.07 (lower cervical spine) has three categories: A, compression fractures of the vertebral body; B, distraction injuries of the anterior and posterior elements; and C, rotational injuries with translation affecting the anterior and posterior elements (▶ Fig. 6.14).
Clinical Epidemiologic Features of Fractures of the Upper Cervical Spine (Segment 51.01–51.02)
A total of 1,341 adult fractures of the upper cervical column were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All were reviewed and statistically studied, accounting for 2.46% of all spinal column fractures in adults. Their epidemiologic features are as follows:
• More males than females
• The highest-risk age group is 41–50 years
• The most common type of fracture among segment 51.01 (atlas) fractures is type A
• The most common type of fracture among segment 51.02 (axis) fractures is type B
Fig. 6.13 Superior (a) and oblique lateral (b) views of anatomical features of the lower cervical spine.
Fig. 6.14 Algorithm.
Fractures of Segment 51.01–51.02 by Sex
See ▶ Table 6.8 and ▶ Fig. 6.15.
Table 6.8 Sex distribution of 1,341 upper cervical spine fractures in adults
Sex | Number of fractures | Percentage |
Male | 831 | 61.97 |
Female | 510 | 38.03 |
Total | 1,341 | 100.00 |
Fig. 6.15 Sex distribution of 1,341 upper cervical spine fractures in adults.
Fractures of Segment 51.01–51.02 by Age Group
See ▶ Table 6.9 and ▶ Fig. 6.16.
Fig. 6.16 (a) Age distribution of 1,341 upper cervical spine fractures in adults and (b) age and sex distribution of 1,341 upper cervical spine fractures in adults.
Fractures of Segment 51.01–51.02 by Fracture Type
Segment 51.01 (Atlas) Fractures by Fracture Type
See ▶ Table 6.10 and ▶ Fig. 6.17.
Fig. 6.17 (a) Fracture type distribution of 280 fractures of segment 51.01 in adults and (b) sex and fracture type distribution of 280 fractures of segment 51.01 in adults.
Segment 51.02 (Axis) Fractures by Fracture Type
See ▶ Table 6.11 and ▶ Fig. 6.18.
Fig. 6.18 (a) Fracture type distribution of 1,061 fractures of segment 51.02 in adults and (b) sex and fracture type distribution of 1,061 fractures of segment 51.02 in adults.
51.01-A Unilateral neural arch fracture 140 fractures M: 87 (62.14%) F: 53 (37.86%) 0.04% of total adult fractures 0.26% of adult spinal column fractures 3.86% of adult cervical column fractures | 51.01-A Unilateral neural arch fracture
|
51.01-B Burst fracture 48 fractures M: 28 (58.33%) F: 20 (41.67%) 0.01% of total adult fractures 0.09% of adult spinal column fractures 1.32% of adult cervical column fractures | 51.01-B Burst fracture
|
51.01-C Dislocation of atlas–axis 92 fractures M: 57 (61.96%) F: 35 (38.04%) 0.02% of total adult fractures 0.17% of adult spinal column fractures 2.54% of adult cervical column fractures | 51.01-C Dislocation of the atlas–axis
|
Segment 51.02 (axis) fracture | |
51.02-A Fractures through isthmus 200 fractures M: 137 (68.50%) F: 63 (31.50%) 0.05% of total adult fractures 0.37% of adult spinal column fractures 5.52% of adult cervical column fractures | 51.02-A Fractures through isthmus
|
51.02-B Odontoid fracture 766 fractures M: 466 (60.84%) F: 300 (39.16%) 0.20% of total adult fractures 1.40% of adult spinal column fractures 21.14% of adult cervical column fractures | 51.02-B Odontoid fracture
|
51.02-C Odontoid fracture plus fractures through isthmus 95 fractures M: 56 (58.95%) F: 39 (41.05%) 0.03% of total adult fractures 0.17% of adult spinal column fractures 2.62% of adult cervical column fractures | 51.02-C Odontoid fracture plus fractures through isthmus
|
Clinical Epidemiologic Features of Fractures of the Lower Cervical Spine (Segment 51.03–51.07)
A total of 2,282 adult fractures of the lower cervical column were treated in 83 hospitals of China over a 2-year period from 2010 to 2011. All were reviewed and statistically studied, accounting for 4.18% of all spinal column fractures in adults, and 0.61% of all types of fractures in adults. Their epidemiologic features are as follows:
• More males than females
• The highest-risk age group is 46–50 years. The most affected male age group is 41–45 years, while females aged 51–55 years have the highest risk.
• The most common type of fracture among lower cervical spine fractures is type A—the same for both males and females.
Fractures of Segment 51.03–51.07 by Sex
See ▶ Table 6.12 and ▶ Fig. 6.19.
Table 6.12 Sex distribution of 2,282 fractures of segment 51.03–51.07 in adults
Sex | Number of fractures | Percentage |
Male | 1,657 | 72.61 |
Female | 625 | 27.39 |
Total | 2,282 | 100.00 |
