Occipital condyle fractures

For occipital condyle fractures, the Anderson-Montesano [1] three part system described in 1988, a condensation of the Saternus [2] six part system, appears to have been most widely accepted. It is based on the primary mechanisms that cause occipital condyle fractures and presents a useful and relatively simple method for understanding injuries affecting this area. Its main weaknesses revolve around the difficulty in consistently identifying skull base fractures (type II injuries) that extend into the occipital condyle, and the methodological flaw of having been derived from a sample size of only six patients, from which a single type III avulsion fracture was used as the basis for a whole injury category. The main fracture subtypes try to differentiate between impaction fractures of the occipital condyle versus shear injuries that cause basilar skull fracture extending into the condyle versus alar ligament avulsion fractures. This classification system lacks clinical or prognostic relevance, especially with regard to type I and II injuries. The fact that type II I occipital condyle fractures are far less relevant than the severe occipito-cervical instability with which they are frequently associated serves to highlight the short-comings of focusing a classification system on individual bony elements rather than the upper cervical complex as a whole.

Occipito-cervical dissociation

Occipito-cervical dissociation remains a poorly understood and relatively inadequately studied clinical entity, partly because of the relatively small, yet increasing number of trauma victims who survive this type of injury. These dissociative injuries may involve the atlanto-occipital or atlanto-axial joints or a combination of the two, since the primary ligamentous stabilizers extend from the occiput to C2. However, the specific levels involved have not been used in a systematic fashion for classification purposes. For pure atlanto-occipital dissociation, Traynelis [3] recommended a classification system based on the direction of displacement, with the premise that prognosis was influenced by this injury variable and that distractive injuries in particular had a worse neurological outcome. However, this approach is likely to be of limited value as the direction of displacement at the occipito-cervical junction is likely to be more representative of forces being applied at the time of imaging rather than at the time of injury. The various directional subtypes, therefore, provide little information about the severity or prognosis of the injury, nor do they dictate to best course of treatment . The Harborview classification system [4] for occipito-cervical dissociation seeks to stratify injuries based on the severity of ligamentous instability in a manner that is analogous to ligamentous injury categories used for extremities in a three-tiered system. The challenge lies in repro-ducibly defining stage II injuries, which are occipito-cervical dissociations with borderline radiographic screening values. It does, however, point out the potential for incomplete and ra-diographically subtle disruptions, which remain a challenge to timely recognition of these injuries, as shown in multiple case reports over the years. Recent studies have suggested at least a 40% delay in diagnosis of these potentially life-threatening injuries, the majority of which are type II injuries that require a high index of suspicion and a critical radiographic evaluation to be diagnosed in a timely manner.

Atlas fractures

There have been few concerted efforts at categorizing atlas fractures. The basic questions pertain to predicting atlanto-axial stability and the fate of displaced intra-articular fractures. The classification suggested by Levine [5] allows for differentiation of problem fractures as opposed to injuries that normally follow an uncomplicated course. However, one of the key factors in determining outcomes of atlas fractures remains the integrity of the transverse atlantal ligament (TAL), which is unfortunately not specifically addressed in this classification system. Differentiating purely ligamentous TAL injuries from osseous injuries may impact treatment decisions as shown by Dickman [6] and others. The differentiation of unstable versus stable intra-articular fractures remains unclear as well. Intra-articular fractures of the atlas are poorly understood injuries that are not particularly well-described in the literature and may result in poor outcomes despite seeming to be intrinsically stable from a ligamentous standpoint. Because of the role of the atlas as a ‘washer’ that facilitates motion between the occiput and the axis, asymmetric injuries may lead to unacceptable alignment with loss of function of the upper cervical complex and a poor clinical outcome. Unfortunately, most currently used atlas fracture classification systems fail to address intraarticular fractures.

Odontoid fractures

Odontoid fractures probably feature the most well-known spine injury classification system, described by Anderson and D’Alonzo [7] in 1974. While simple and intuitively clear, it has several shortcomings. It features the rare type I injury that, much like the type III occipital condyle fracture, is likely to be less important from an osseous injury standpoint than from an associated occipito-cervical ligamentous instability standpoint. In addition, this classification system does not differentiate between the many variations of type II injuries in a manner that would help guide appropriate treatment for a given type II fracture pattern. Although Grauer [8], Hadley [9], and Aebi [10] have described sub classifications of type II fractures with the goal of preventing pitfalls in the management of these injuries, these features have generally not been integrated into a meaningful and more comprehensive odontoid fracture classification system. Because type II fractures consist of a wide range of injuries in terms of severity and treatment approach, other features of these fractures such as fracture orientation or degree of comminution are equally as important as fracture location in categorizing these injuries, determining the most appropriate treatment options and the anticipated prognosis.

Axis fractures

Fractures of the axis have been divided into the broader categories of vertebral body fractures and the well-recognized “Hangman fractures”. The four tiers of Hangman fractures described by Effendi [11] and modified by Levine [12] are probably second to the odontoid fracture classification in their familiarity to physicians around the world. Levine separated the broader class of type II fractures into type II and type IIa subtypes based on the integrity of the C2-C3 disco-ligamentous complex. Type II fractures were considered more intrinsically stable and could therefore be managed in traction and converted to external immobilization, in contradistinction to the type IIa fractures in which a distractive injury of the C2-C3 disc and posterior osseo-ligamentous complex precludes the use of traction and dictates a more aggressive operative approach. An additional subtype was later added by Starr and Eismont [13] and is commonly referred to as the “atypical hangman variant ” w it h a much higher neurological injury rate. The fracture severity described by Francis [14] utilizes a relatively simple severity scale, but has found little resonance in publications. This classification system differentiates hangman fractures into categories I to V based on displacement and angulation. Unlike with Hangman fractures, there is no commonly used classification system for C2 body fractures. In 1996, Fujimu-ra [15] separated axis body fractures into four distinct entities with recommendations for operative management in fractures with severe mal-alignment of the atlanto-axial joint. However, these laudable efforts at further characterizing C2 body fractures have remained largely obscure.

SCALE DESCRIPTION

Fractures classified based on the anatomical location of the fracture line:

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  Type I—Apical (tip) fracture of the dens

  
  
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  Type II—Body fracture of the odontoid

  
  
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  Type III—Basilar fracture into the body of the axis

Interpretation:

Descriptive of fracture location. One type not necessarily more severe than the next.

SCALE ILLUSTRATION

METHODOLOGY

No predictive validity or reliability studies were identified.

Predictive validity

Reliability

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CONTENT

RATING

SCALE DESCRIPTION

Fractures classified based on morphology, anatomy, and mechanism of injury:

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  Type I—Impacted-type fracture

  
  
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  Type II—Basilar skull-type fracture

  
  
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  Type III—Avulsion-type fracture of the inferomedial aspect of the condyle

Interpretation:

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  Type I—Associated with an axial load injury, stable

  
  
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  Type II—Associated with direct trauma to the skull, stable

  
  
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  Type III—Associated with forced rotation and lateral bending, unstable

The higher the type, the greater the severity.

SCALE ILLUSTRATION

METHODOLOGY

No predictive validity or reliability studies were identified.

Predictive validity

CONTENT

RATING

SCALE DESCRIPTION

Fractures classified based on anatomical orientation and mechanism of injury:

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  Type 1—Coronally oriented vertical body fracture

  
  
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  Type 2—Sagitally oriented vertical body fracture

  
  
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  Type 3—Rostrally located horizontal body fracture

Interpretation:

Descriptive of fracture location. One type not necessarily more severe than the next.

SCALE ILLUSTRATION

METHODOLOGY

No predictive validity or reliability studies were identified.

Predictive validity

Reliability

CONTENT

RATING

SCALE DESCRIPTION

Classified based on morphological patterns of injuries to the bones and ligaments:

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  Type IA—Disrupt the ligament substance in its midportion

  
  
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  Type IB—Disrupt the ligament substance at its periosteal insertion

  
  
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  Type IIA—Disconnect the tubercle for insertion of the transverse ligament from the C1 lateral mass involving a comminuted C1 lateral mass

  
  
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  Type IIB—Avulsing the tubercle from an intact lateral mass

Interpretation:

Descriptive of fracture location. One type not necessarily more severe than the next.

SCALE ILLUSTRATION

METHODOLOGY

No predictive validity or reliability studies were identified.

Predictive validity

Reliability

CONTENT

RATING

SCALE DESCRIPTION

Classified based on the degree and type of displacement of the body of the axis and of the inferior facets of the axis as expressed by the state of the disc space and of the articular facets at C2/3:

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  Type I—Isolated hairline fractures of the ring of the axis with minimal displacement of the body of the axis with normal and stable disc space

  
  
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  Type II—Displacement of the anterior fragment with an abnormal disc below the axis.

  
  
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  Type III—Displacement of the anterior fragment with the body of the axis in the flexed position with the facet joints of C2/3 are also dislocated and locked

Interpretation:

The higher the type, the greater the severity.

SCALE ILLUSTRATION