Análisis de los distintos modelos del espesor de la corteza en la frontera entre la Mesa

Distraction injuries occur in exion or exten-sion patterns. Hyperextenexten-sion injuries t ypically occur in patients w ith sti spines such as the elderly (spondylosis) or in patients w ith DISH or AS. Failure of the anterior and m iddle colum ns (EDI stage I) occurs w ith or w ithout posterior elem ent disruption and possible sublu xation/

dislocation (stage II) w ith central cord syn-drom es often associated. FDIs a ect prim arily posterior elem ents, w ith a broad array of inju-ries ranging from facet sublu xation (stage I), to

unilateral perch/dislocation (stage II), to stage III (≤ 50%) and stage IV (> 50%) bilateral dislocation w ith anterior cord syndrom es often associated.

There are m ultiple classi cation schem es for subaxial cer vical spine injuries. The lack of a un iform ly accepted classi cation system has greatly hindered both high-qualit y research and e orts to establish opt im al evidence-based treatm ent algorithm s. The evidence is lim ited to retrospective review s regarding distraction injuries. Earlier classi cations such as the Allen- Ferguson and the AO focus on m echanism of injur y (dist raction, com pression , rotation) ver-sus fracture m orphology (com pression, distrac-tion, rotat ion), m aking it di cult to incorporate spinal stabilit y and neurologic status and to determ ine the appropriate treatm ent. Cer vical spine instabilit y is best de ned, by W hite and Panjabi,¹² as the loss of the ability of the spine to m aintain, under physiological loads, its pattern of displacem ent so that there is n o initial or ad-ditional neurologic de cit, no m ajor deform it y, and no incapacitating pain. Subaxial instabilit y h as been characterized by 3.5-m m horizontal displacem ent or 11 degrees of adjacent verte-brae angulation on lateral radiographs. The Sub-axial Cer vical Spine Injur y Classi cation (SLIC) in tegrates fract ure m orphology (com pression, distraction, rotation), the diskoligam entous com -plex (DLC) integrit y (stabilit y), and neurologic stat us (intact, root, com plete, or incom plete in -juries).¹³ It has been show n to be reliable and valid, and to guide treatm ent appropriately^14,15 (Table 9.1). All three characteristics have sub-groups, assigning points to guide treatm ent;

patients w ith scores ≤ 3 are treated nonopera-tively, and patients w ith scores ≥ 5 are treated operatively. For patients w ith a score of 4, the treatm ent is guided by the surgeon’s experi-ence and preferexperi-ence as w ell as the patient’s co-m orbidities and other injuries.

Evaluation

The evaluation of a patient w ith spine traum a should follow the Advanced Traum a Life Sup -port (ATLS) protocol, w ith im m ediate at tention to a life-threatening air way com prom ise, ven-tilation (such as pneum othorax), and cardio-vascu lar inju r y. Su bsequ en t iden t i cat ion of

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addit ion al inju ries, par t icu larly n eu rologic or spinal injury, should be noted. A focused his-tory should include iden tifying the traum a m ech anism , determ ining the location of pain , and noting the presence of urinar y incont i-nence, spondyloarthropathy (AS or DISH), or a pacem aker or other m etallic foreign body that w ould contraindicate th e use of MRI. The his-tory sh ould also note if th e patient had under-gone earlier spine surger y. Patients w ith ASD often have m inim ally displaced, non displaced, or m issed fracture(s) that are often highly un -stable (long lever arm s from m ultifused seg-m ents) as a result of an extension -distraction m ech anism . Such a fract ure often is m issed in the initial clinical and radiographic evaluation, bu t in st abilit y, n eu rologic com p ression , an d sym ptom at ic ep idu ral h em atom a (especially in a patient w ith coagulopathy) can lead to high rates of neurologic decline.

The physical exam ination begins w ith com -plete exposure of the patient’s spine using a logroll techn ique. The dorsal spine is exam ined for ecchym osis, induration, or any other indi-cators of signi cant spine instabilit y. Com plete neurologic exam ination involves m otor m an -ual strength testing, sensor y pinprick and light

tou ch evalu at ion , an d re exes w ith a carefu l rectal exam ination (for voluntar y rectal tone, bulbocavernosus re ex, and anal w ink re ex) to assess sacral n er ve root function. The ASIA scale is the preferred n eurologic exam ination tool, as it provides a m ethod to characterize any residual function below the level of a spi-nal cord injury (SCI), w hich is de ned as the m ost caudal level w ith norm al m otor and sen -sor y fu n ct ion . Th e m ost im por tan t predictor of a favorable neurologic outcom e is retent ion of sacral (S4-S5) sensation 72 hours to 1 w eek after the injur y. Intact sacral pinprick sensa-tion suggests a favorable prognosis for recov-er y of bladdrecov-er fun ction. In con trast, priapism caused by loss of sym pathetic tone w ith unregulated parasym pathetic input suggests a com -plete SCI. Neu rologic stat u s can be u n cer tain in polytraum a patients w h o are intubated, ob-tunded, or unable to follow com m an ds. Serial neurologic exam s are m andator y, w ith docu-m entation of the neurologic exadocu-m ination as soon as possible.

Com plete disruption of neurologic function and neural im pulse tran sm ission in the torso and extrem ities can cause accid paralysis after SCI or can occur transiently during spinal shock.

Table 9.1 Subaxial Cervical Spine Injury Classif cation (SLIC) System

Finding

Distraction (e.g., facet perch, hyperextension)

  Rotation/translation (e.g., facet dislocation, unstable teardrop, or advanced staged  exion  compression injury)

Indeterminate (e.g., isolated interspinous widening, MRI signal change only) Disrupted (e.g., widening of disk space, facet perch, or dislocation)

0

 Continuous cord compression in setting of neurologic de cit (neurologic modi er)

0 1 2 3 +1

Source: Adapted from Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classi cation system. A  novel approach to recognize the importance of morphology, neurology, and integrit y of the disco-ligamentous complex.

Spine 2007;32:2365–2374

Distraction (AO Type-B Injuries)

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Spinal shock ends w ith the ret urn of the bulbo-cavernosus re ex, w hich indicates that the arc bet w een the pelvic a erent ner ves and sacral cord e erent nerves is once again functioning.

Hem odynam ic stat us should be carefully as-sessed to di erentiate neurogenic from hypo-volem ic shock. To treat neurogenic shock and m aintain m ean arterial pressure above 85 m m Hg, volum e resuscitation is follow ed by the use of vasopressors and chronotropic agents.

The use of corticosteroids for a closed acute traum atic SCI is controversial. High rates of m edical com plications, the lack of consistent evidence, and a record of inconsistent neuro-logic recover y have lim ited the abilit y to for-m ulate guidelines for the use of corticosteroids.

Additionally, elderly patients w ith m ultiple co-m orbidities, co-m orbidly obese pat ients, revision cases, polytraum a patients, and patients w ith suboptim al bone qualit y create m ore challeng-ing surgical environm ents. Patients w ith SCIs m ust be prom ptly identi ed to decom press and realign spinal elem ents w ith prevention of secondary SCI due to ischem ia.

Flexion an d exten sion dist ract ion inju ries are opt im ally m an aged by experien ced sp in al su rgeon s w h o are qu ali ed to p erform m u lt i-ple xat ion tech n iqu es an d bailou t strate-gies. In addition, optim al m an agem en t requires facilities w ith the appropriate support sta trained in traum a surger y, an esth esia, neuro-m on itoring, and interventional neuroradiol-ogy, and that have an intensive care unit (ICU) w hose sta is experienced in handling these t ypes of cases.

Imaging

Cer vical spine injuries require im m ediate eval-uation and coordination w ith m ultiple ser vices to adequately follow ATLS protocols. Once life- threatening injuries are diagnosed and stabi-lized, further cervical radiographic evaluation can proceed. Traditionally, anteroposterior (AP), lateral (Fig. 9.1), op en -m ou th odon toid, an d sw im m er’s lateral radiograp h ic view s w ere com m only ordered, but they have been largely replaced by initial cross-sectional im aging via m u lt idetector h elical com pu ted tom ography (CT) an d m agn et ic reson an ce im aging (MRI),

as injuries can often be m issed using only radiograph s. CT an d MRI are invalu able in iden -t ifying an d u n ders-t an ding osseou s frac-t u re pat terns, DLC and posterior ligam entous com -plex (PLC) integrit y, degree and location of neurologic com pression, anatom ic variants, hem atom a, and prior surger y (Figs. 9.2, 9.3, 9.4) Com plete radiographic evaluation in light of the clinical scen ario aids in form ulating a full treatm en t plan. CT angiography (CTA) or m agnetic resonance angiography (MRA) should be perform ed if a vertebral arterial injury is suspected an d in patients w ith C1 and C2 frac-tures requiring surgical treatm ent, patients w ith fract ure dislocations, and patients w ith frac-tures extending into th e foram en t ran sversar-ium given the higher rates of vertebral arter y injuries. CT m yelogram s are useful in evaluat-ing bony and n eural anatom y w hen MRIs are cont rain dicated, and can give excellent detail of neural struct ures.

Fig. 9.1 Lateral cervical radiograph demonstrating a C5–C6  exion-distraction injury with 50%  anterolis-thesis in a patient with bilateral facet dislocation.

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