Surgical stabilization of the severe thoracolumbar spine fractures*

·Surgical stabilization of the severe thoracolumbar spine fractures

*

José Barberá Department of Neurosurgery. Hospital General Universitario. Valencia. Spain. Spinal Unit. Centro de Recuperación y Rehabilitación de Levante. Valencia. Spain

Introduction When setting up a study of the symptoms of thoracolumbar spine (TLS) injuries and the techniques for the stabilization thereof, three fundamental concepts should be taken into account: 1) the concept of spinal stability, 2) the distribution of stress over spinal structures and 3) the causal mechanism of the injuries.

Spinal stability. The concept of stable and unstable vertebrallesion tends to be an intuitive feeling on the part of the physician when dealing with a particular patient or, more specifically, when observing an X-ray or a neuroradiological image. Defining spinal stability is a complicated business being, as it is, a biometrical condition and therefore having different parameters in each individual. For this reason it is generally considered preferable to define Instability as this term implies in itself the existence of some abnormality. However, this concept also involves a great deal of individual variability in such factors as the elinical requirements necessary for the detection of the instability. Frimoyer, in 1991, 32 gives the following definition: «Segmental instability is a loss of spinal motion segment stiffness such that force application to that motion segment produces greater displacements than would be seen in a normal structure, resulting in a painful condition, the potential for progressive deformity and neurological structures at risk». White and Panjabi, in 1990,68 offer the following definition: «Clinical instability is the loss of the ability of the spine under physiologic load to maintain its pattern of displacement so that there is no initial or additional neurological deficit, no major deformity, and no incapacitating pain». From this two definitions we can extract the following salient points: I)Instability can be considered a pathological condition when it produces such symptoms as persistent local or irradiated pain, visible local or compensatory deformity, andJor a neurological deficit.

2) Instability occurs as a result of a deformity in the structure and morphology of the vertebra and lor the failure of ligaments which prevent the abnormal movement of the vertebrae against each other. But it is also necessary to distinguish acute and chronic instability. In the acute form, the causes of instability are produced rapidly, in a short space of time, and the resulting injuries are therefore mechanically far more extensive and serious. The symptoms and effects of acute instability are, virtually or potentially, much more critical. Such is the case with inmediate traumatic instability or that which arises as a result of a tumor growing into a vertebral body. Chronic instability is the result of more slowly developing and structurally less damaging processes, and ineludes the instability arisingafter a vertebral fracture healed with gross residual deformity, after infections or degenerative diseases, or after surgery or spondylolistesis.

Anatomy 01 load transmitting spinal structures. The thoracolumbar junction is a transitional zone between the thoracic spine, which has a notable kiphotic curve and has a very little mobility due to the restrictive effect of the ribs, an the lumbar spine, with an opposit-lordotic- curve and a high degree of mobility. As a result of this, the centre of gravity in he thoracic spine is anatomically further forward than it is in the lumbar spine, and the thoracolumbar segment, between the two of them, has to act as a pivot for the powerful, rigid dorsal lever when this moves relative to the lumbar spine 55,69. The TLS is, therefore, a transitional area which has a heavy-duty task to perform and is often subjected to important dynamic stresses which facilitate the incidence of injury. Fract~res of the TLS, along with those of the cervical spirre, are the most frequently occurring in the spine as a whole 50. A comparatively recent mechanical concept, of great importance in the identification of suitable surgical procedures for the treatment of vertebral fractures, is that the distribution of load along the spine takes place in a me-

* Paper read at the 2nd European Course in Neurosurgery -4th Cycle, EANS, Zaragoza, Spain. August, 25-30, 1991. 91

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Surgical stabilization of the severe thoracolumbar spine fractures

chanical arragement comprising three columns, in accordance with the theory propossed by Denis based on CT observations 17,18. The anterior column is formed by the anterior longitudinalligament, the anterior half of the vertebral body and the anterior part of the annulus fibrosus; the rniddle column is formed by the posterior longitudinalligament, the posterior half of the vertebral body and the posterior part of the annulus fibrosus, and the posterior column consists of the neural arch, the ligamentum flavum, the capsules of the facet joints and all the posterior ligamentous complex (Figure 1). The most important con-

"

Lateral rotations

Fig. 2- Diagram of the twe/ve potencial displacements of the vertebrae in the spinal motion unit, following White & Panjabi (1990).

Fig. 1- Diagram of the three loading columns following Denis

(1983). See texto

c1usion to be drawn from Denis'work, and one wich receives almost universal acceptance, is that he integrity of the rniddle column is essential for the stability of the spine, as opposed to the previously held belief that he integrity of the ligamentous complex was an essential element in stability 43,44. In fact, can be conc1uded that the instability will only occur when two or all three of the load distribution columns are affected, and finally, that if the middle column is damaged the fracture will be unstable. Based on theses observations Denis 17 proposes his anatornical c1assification of fractures in this area. Mechanism and classification oi TLS injuries. According to White and Panjabi's biomechanical analysis 68, there are twelve different forces -or moments of forcewhich can act upon the spine. Of these, six are translational movements: compression, distraction, anterior and posterior translation and left and right translation. The other six are rotational movements: flexion, extension, right and left lateralization and righ and left torsion (Figure 2). When any of these movements exceeds its normal range in response to the aplication of an excessive force, verte-

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bral related damage may occur. This could prove to be an excelent theoretical mechanical reference for the c1assification of traumatic spinal injuries. Nevertheless, it should be taken into account that these movements rarely take . place in isolation, each one usually being associated wih .one o more other movements in the same plain or in different plains. Thus, for exemple, vertical compression is usually associated with a component of flexion and lateralization; torsion with flexion, and so on. This was predicted by Holdsworth 43 when he proposed the first mechanistic scheme for the c1assification of fractures. Bearing in rnind the habitual association of these movements.Fergson and Allen 27 propose a mechanical c1assification of TLS fractures which distinguishes seven different types according to the predorninant vector of the acting force: vertical compression, compressive flexion, distractive flexion, lateral rotation, torsion, translation andcompressive extension. This mechanical c1assification has proved both straightforward and useful in our experience as it can almost be applied directly to X-ray pictures. More recently, the same authors 28 published an analytical study of each type of the fractures described, which identifies the most important vectors of force wich act upon each of Denis' columns and, from this analysis, they worked out an algoritrn to determine the type of stabilization forces required in each case. Bauer an Eiri~o 4 have completed the study, filling in the fine details of the analysis. The following observations are made on the basis of this work (Figure 3). Vertical Compression is the most frequent cause of injury in this region of the spine. It is due to an axial compression applied to the body in a symmetrical fashion, either from the feet or the buttocks, resulting in the invasion

SurgicaJ stabilization of the severe thoracolumbar spine fractures

Fig. 3- The seven types of thoracolumbar spine fractures, fol/owing the classification of Ferguson & Al/en (1984). A Compressive Flexion B Vertical compression C Distractive-Flexion D Lateral rotation E Translation F Torsion G Compressive Extension.

of the vertebral body by the cephalic disco This invasion causes a circunferential centrifugal force that causes the explosion of vertebral body forrn inside, and so it is called burst fracture. All its walls being broken, the vertebral body loses height on all its surfaces and becomes wider in every transversal direction, the pedicles becorning separating from each other. Fragments from the posterior wall may invade the spinal canal and compress the dural seath. The compression of the larninae against each other may pinch the dura, breaking it an trapping one or more roots. If the rniddle column is fractured, the injury is unstable and is usually associated with the luxation of one or both posterior joints an the tearing of the posterior vertebralligament due to a flexion-torsion or rotational component. In the Compressive Flexion mechanism it is allways the anterior column which receives an intense compressive force causing it to fracture. In the most frequent forrn the reduction in height of the anterior wall of the vertebra is less than 50%, the posterior ligaments remain intact and the injury is stable and rarely involves neural complications. When the applied force is greater, the compression of the anterior column is also greater and reduction in height of the anterior wall is more than 50%. This is associated with a distractive force on the posterior column causing the tearing of ligaments which facilitates progressive angulation. In the more serious cases the rniddle column is also subject to distraction due to the damage of its ligaments, and this leads to the anterior dislocation of the superior vertebra. This is clearly an unstable injury with a risk of progressive neural complications. In Distractive Flexion fractures the rotational axis of the motion segment is displaced forwards in front of the vertebral body and, as a result of this, the three columns,

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specially the posterior one, are subjected to distractive forces. The fracture line may cross the entire vertebra, from back to front, breaking the posterior arch and the vertebral body, or it may cross the soft ligamentous tissues and the disc, or it may affect two vertebras, crossing the ligamentous system and continuing across one vertebral platforrn 17. In this last case there is usually anterior luxation with frequent neurogical complications due to strechting of the cord. Associated abdorninallesions are very common. The fracture is stable when in extension; the luxations, on the other hand, are highly unstable. With the Lateral Flexion mechanism there is a compressive force which acts upon one side of the vertebra, affecting the anterior and rniddle columns and causing lateral compaction. If the energy involved is very intense a distractive force is generated in the contralateral posterior column which may cause dislocation of the articular facets. In the first case the injury is stable, but if there is a failure of the posterior ligaments the deforrnity may progress to become symptomatic. Translational injury is caused by the forward, backward or lateral, displacement of the vertebra. This results in the tearing of all the holding ligaments, and if the displacement is large -more than 25% of the lenght of the vertebra- one can expect to find the luxation and fracture of the posterior joints as well. Neural complications are very frequent and severe, due to the extreme reduction of the spinal canal anteroposterior lenght caused by the luxation. These injuries are highly unstable. The Torsion mechanism produces compressive and shear forces to act upon the anterior column, combined with distraction and torsion acting in the opposite direction, upon the posterior column. This mechanism usually damages the rniddle colurnn at the level of the disc, which is tom, and also causes fracture of the articular apophyses. Torsion may sometimes cause a laterally displaced shear fracture producing abone slice at the inferior part of the vertebral body. This is one of the most unstable injuries of the TLS region, with frequent neural complications. Fractures due to a Distractive Extension mechanism are not frequent. This mechanism produces a distractive force which acts upon the anterior and rniddle columns, tearing the anterior longitudinal ligamento It is associated with compression of the posterior colurnn, which may become fractured at the level of the larninae~.If the patient is made to lie with the spine in flexion the injury is stable and will usually improve without complications, with the aid of a simple orthosis. Clínical and instrumental assesment of a TLS fracture.

The appropriate therapeutic procedure to adopt when faced by a TLS injury should be decided upon after a ca-

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Surgical stabilization of the severe thoracolumbar spine fractures

reful assesment of the data obtained in the routine study of the patient. The different steps of this study ar outlined below:

General clinical examination. As with any traumatism, in the spinal trauma it is important to find out the mechanism of the injury, either from the patient himself or from the withnesses of the accident, as this will help with the location of any vertebral damage. Traffic accidents, falls from a height, jumps and weights falling on the back, are frequent cause of TLS injury. The physical aggression causing a vertebral fracture is often serious and violent, and in many cases the associated injuries may put the patients's life at risk from the very start. If the patient is in a conscious state he will complain of pain in the spine and this is the signal for putting into effect the specific diagnostic procedures. The palpation of a gap between the spinous apophyses is a elear sign of luxation andJor injury of the posterior ligaments. However, this should not prevent the physician from carrying out a thorough general examination of the thorax and abdomen in order to identify any associated damage to internal organs, which frequently occurs in both cavities 49,48. The patient should also be examined for any peripheral fractures, particulary in the lower limbs -the femur and calcaneusas such injuries are often produced by the same mechanism as the spinal fracture. A blood sample should be taken immediately, in order to determine the basal status when any metabolic disturbances or internal bleeding resulting from occult injuries are suspected. In an unconscious patient with head injury, where there is no local pain to act as a reference, a spinal fracture should always be suspected if a radiological study of the entire spine does not demonstrate on the contrary.

Neurological examination. Neurological damage in fractures of the TLS segment is often complex and incomplete in relation to the myeloradicular anatomy at this level 15 (Figure 4). It often consists of a deficit from one or more roots of the cauda equina associated with partial or total damage to the conus terminalis with sphincter disorders. It is therefore very important to make an accurate assesment of the existing neurological damage as soon as posible, and record it in the most objective way possible, so as to have a reliable data base to work from. The initial examination report should therefore inelude the results of the skin sensitivy test, the musele balance for each root, the tone of the anal sphincter and the bulbocavernous reflex. The simplest and most frequently used recording system is the Frankel's functional scale 31, which is set out below: A: loss of motor and sensory functions B: sensory function conserved 94

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c: inefficient motor function conserved D: efficient motor function conserved E: complete recovery,normality Given the importance of the presence or ausence of sphincter disorders at this level, Bradford 10 proposes the division of group D in the following way: DI: efficient motor function conserved, but at a low level (3+) andJor intestinal or vesical sphincter paralysis. D2: efficient motor function conserved at a medium level (4+) andJor intestinal or vesical sphincter malfunction. D3: efficient motor function conserved at a high level (5+) with normaly voluntary sphincter function.

Fig. 4- The different types ofnervous lession in TLS fractures.

They can present isolated or be associated between thern.

Plain radiographic examination oi the spine. Every patient suspected to be suffering from a spinal fracture should be subjected as quickly as possible to a plain X-ray examination. Taking extreme care wp~n moving and handling the patient, at least one frontal and one lateral Xray of suspected injured spinal region should be taken. The existance and position of the fracture having been identified, it is necessary to obtain X-rays of a high enough quality to be able to assess any vertebral displacements by comparing the alignement of the posterior walls of the vertebral bodies, the deformities directly related to the fracture of the body (compression and loss of hight),

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Surgical stabilization of the severe thoracolumbar spine fractures

the separation and loss of alignement of the spinal apophyses in the anteroposterior projection (which indicate rotation and ligamentous damage), and finally, in order to be able to classify the injury according to its mechanism. The diagnosis of injuries to the posterior arch and of luxations of the posterior joints is not allways possible with conventional radiography. If such an injury is suspected and the clinical condition of the patient permits it, and assurning the emergency unit possesses the necessary equipment, a tomographic exarnination of the area will be carried out. The existance of the suspected fracture having been confirmed, the entire lenght of the spine should then be subjected to a radiographical exarnination. The fact that statistically in more than 10% (between 5 and 30%) of spinal fracture cases there are other associated spinal injuries 50, at differents levels, is of sufficient importance to have to impose this diagnostic routine 49. The injuries most frequently associated with TLS fractures are placed at low cervical and lumbar spinal zones 7.13 0

CT examination. CT is the best diagnostic procedure to discover the existance of an injury to the middle column of the vertebra, and its use is therefore essential once a vertebral fracture has been identified using conventional radiographYoBy means of the transverse images the invasion of the spinal canal by fragments of the posterior wall of the broken vertebra can diagnoses, and the degree of stenosis can be assessed by measuring the saggital diameter of the canal and comparing its percentage-wise that of the neighbouring undamaged segments (figure 5). CT also

traumatismo Any patient with neurological injury, whate~ ver the degree of this, should receive a CT exarnination of the injured vertebral zoneo But, it should be remembered that, owing to the presence of roots at the level of the lumbar vertebrae, the information about the reduction in the anteroposterior diameter of the bony canal bears no direct relation to the presence of neurological complications 66. CT also provides information about associated visceral damageo Myelo-CT exarnination is useful in assessing the degree of compression of nervous structures by fragments of the posterior arch, and in identifying traumatic dural breakageso Its use is therefore appropriate in cases of rapid or progressive neurological deterioration, as it can also demonstrate the existence of a bruiseo The injection of the contrast medium can be carried out via a lateral puncture of the Cl-C2 gap, which does not necessitate dangerous movements of the patient. MR examination. MRI has not been used very often, In our opinion its use is appropriate in patients with neurological complications because it provides valuable information about the state of the cord --edema, ischerniaand it also permits the diagnosis of the cord section 61 Another important indication of MRI examination is in cases where the plain X-rays shows displacement of fragments of the posterior wall,in order to find out the state of the posterior longitudinalligament (Figure 6)0 If this ligament remains intact, any attempt of descompression by means of ligamentaxis is justifiable, and this will be 100ked into latero MRI is specially important in the assessment of pathological fractures resulting from tumors and in the diagnosis of traumatic disc injuries 5° Assessment oi instability. White and Panjabi 68 have constructed a table in which are listed a serie of objective parameters, obtained from the exarninations carried out according to the aforementioned diagnostic routine, which provides the basis for a reasonable suspicion of an unstable thoracolumbar injuryo The parameters considered and the core attributed to each one are shown in Table 1. 0

0

Fig. 5- el' scan of a burst of L-J showing the invasion of the spinal canal by the retropulsed body fragments.

provides important information about the condition of the posterior arch and about existence of dislocations in the posterior joints, which invariably indicate a high energy

Element Score Anterior elements destroyed or unable to function 2 Posterior elements destroyed or unable to function 2 Disruption of costovertebral articulations ...' 1 Radiographic criteria Sagittal plane displacement > 2.5 mm 2 Relative sagittal plane angulation >5° 2 Spinal cord or cauda equina damage 2 Dangerous loading anticipated 1

Table 1 Chek list for evaluation of instability. White y Panjabi, 1990.

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Surgical stabilization of the severe thoracolumbar spine fractures

Fig. 6- MRJ o[ a patient with a [racture 0[T-J2. The image shows the

impingement o[ the spinal canal by the bony [ragments o[ the vertebral body contained by the integrity o[ the posterior vertebral ligamento

In the author's opinion a total scoring of 5 or more points indicates instability. However, many clinicians do not agree with this form of assessment because,if one takes into account the concepts of instability which were discusses earlier and which receive general aceptance, any spinal injury capable of producing an immediate neurological deficit is, by definition, unstable 46.

Surgical indications and techniques in the treatment of TLS injuries The ideal aim of the treatment of spinal fractures should be to achieve and maintain the reduction of the vertebral deformities and displacements produced by the traumatism, while conserving the general morphology of the zone as well as neurological, segmentary and spinal function -improving this where possible- and to facilitate early recovery. Using conventional conservative methods these objectives can often be achieved in injuries to the

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TLS by means of postural reduction on a bed of plaster or any other rigid moulded material or by positioning cushions at the level of the fracture in order to conserve regionallordosis. The reduction is maintained for a period of up to twelve weeks of bed rest without load bearing in order to avoid the effect to axial compression by walking. Once stable reduction has been achived, the spine must be protected by an external support or by a plaster cast which permits walking and movement, and this should remain in place until consolidationof the fractured bone is achieved. This is the classic treatment, supported by many authors 5, 6,8.9.31.36,54,66 and well protocolized by Krompinger et al 51. But our purpose, now, is to consider the indications and techniques in the surgical treatment of these injuries. Indications for surgery in TLS injuries. The surgical treatment in TLS fractures could be considered in the presence of one or more of the following circumstances: a) Circumstances related to the development of neurological symptoms. The existance or appearance of progresive neurological deterioration in a spinal fracture patient, with evidence of nervous compression at the level of the fracture as shown by neuroradiological examination, is an indisputable indication for surgery. Fortunately this is not a frequent situation but, should it arise, inmediate surgery is imperative and the necessity to operate is absolute. There are other neurological circumstances in which surgical intervention may be advisable. Among these may be considered the detention of progressive neurological recovery at an early stage, when nervous compression has been demonstrated neuroradiologically and an incomplete neurologic injury exists. Clinical experience has shown that decompressive surgery, even at a late stage of the evolution, can improve the neurological deficit, especially when this is due to an exclusively radicular injury. b) Circumstances related to the fracture itself. The most frequent indication for surgery is the existence of a highly unstable fracture or dislocation which is likely to remain unstable even after the bone injury itself has consolited, due to the seriousness of the associated ligamentous damage. This is the case wih torsion and translation type fractures and any injury producing dislocation, whatever the mechanism involved. Burst fractures, involving the massive destructuration of the vertebral body can also be included in this group (Figure 7). Secondly there are those fractures which produce a deformity that could prove to be symptomatic in the medium or long run, due to residual changes in the anatomical relationship between the bony canal and nervous structures. This deformity may progress to produce what Jacobs 44 calls «chronic postraumatic instability», which occurs particularly "in those fractures involving a loss of more than 50% in the height of the anterior wall of the vertebral body.

Surgical stabilization of the severe thoracolumbar spine fractures

Fig. 7- Unstable fracture of L-l. This is an evident indicatian far surgical reductian and stabilizatian.

Thirdly, any fracture considered to be initially unstable, according to the criteria of White and Panjabi 68 discussed earlier, may obviously indicate the necessity for surgical intervention. It should be borne in mind, however, that many of these unstable fractures can be repaired by means ofthe appropriate conventional treatment, continued over an adequate period of time. Aside from this, but still within the context of surgical indications related to bone injury, are those fractures which threaten to produce potentially serious neurogical complications. This is the case of malignant tumors of the vertebral body 20. c) Sorne indications related to circumstances depending on the general condition of the patient may be considered. Firstly the existence of a complete neurogical injury which is known to be irreversible may be considered as an indication for surgery with the purpose of permiting early movement and facilitating the hygienic care are inmediate rehabilitation of the patient. Secondly surgical intervention may be used in those patients who are uncooperative, in whom conventional

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treatment could prove to be dangerous with the risk of further neurological complications, e. g. Patients with multiple injuries, the treatment of which may interfere with that of the spinal fracture, can be included whitin this group. Finally surgery may be considered when the therapeutic alternative is a conventional treatrnent predicted to involve a long period of immobility in bed. In such cases the purpose of surgery is to avoid the appearance of complications associated with prolonged inmobility, such as embolism pneumonia, bedsores, etc. Aims and timing 01surgery in TLS injuries. The aims of surgical tretament of spinal fractures are: decompression of the nerve tissue aml/or stabilization of unstable injuries when necessary. The theoretical principIe behind the concept of surgical decompression is the normalization of blood flow to the nervous tissue wich can be obstructed by the pressure exerted on the nervous vessels by bone or disc fragments, bruises or foreign bodies. Decompression does not allways involve the removal of compressive elements, but can often be achieved by simply reducing displacements and realigning the distorted spinal axis, thus freeing the trapped and ischemic nervous tissue. Structural anatomical cord injuries, with interruption to the nervous tissue caused by the direct impact of disc or bone fragments or the pressure produced by displacement at the moment of the traumatism can obviously not be treated by means of surgery. The stabilization of the injured segment has two purposes: a) To achieve, as far as posible, the anatomic reduction of the fractured site, thus eliminating all gross displacements, correcting angular deformities and restorating the primitive regional shape of the spine at that level. b) To fix corrected displacementsin a way that allows early mobilization of the patient with minimal external support. Decompression should be not considered the sole aim of surgery, because if this is intended to realign the distorted spinal axis it should be accompanied by certain fixation techniques which will hold the corrected spine solidly in place in order to avoid further displacements. Gn the oher hand, if the aim of surgery is to free the nerve tissue from bone or disc fragments or from a bruise which impinges upon it, the access to the interior of the spinal canal -whatever route is taken- will produce 'lll..additional instability which will have to be corrected. The conclussion to be drawn, therefore, is that decompression of radicular or spinal cord tissue should always be accompanied by the stabilization of the affected segments. The timing of operation depends on various conditions: Surgery must be performed as quickly as posible in cases involving neurological complication, assuming that this is caused by compressive ischemia on the ner-

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Surgical stabilization of the severe thoracolumbar spine fractures

vous tissue. This emergency surgery has the aim of shortening the ischemic time 4. In those cases in which surgery is choosen in order to avoid further complications, such as in the case of restless patients the operation should be performed whitin the first two or three days, that is to say in the first programmed surgical sesion. Finally,surgery may be performed later -from the third to the tenth day- in cases where there are no absolute indication 65. During this period of delay the patient's general condition can be improved, thus minimizing the operative risks such as blood loss. Operations performed after the first three weeks do nouft achieve easy reduction of displacements, and often requiere more agressive techniques such as osteotomies.

Surgical decompre$sion in TLS fractures. In this fractures, the compression of nerve tissue is generally caused by fragments of the posterior wall of the vertebral body which invade the spinal canal reducing the anteroposterior caliber -a condition typically associated with burst fracture. The common posterior vertebral ligament may or may not be torn, depending on the violence of vertebral displacements. If it is torn, the displaced bone fragments have easy access inside the spinal canal causing direct damage to the nerve tissue. If it remain intact, it retains the fragments, and neurological symptoms are more often produced by compression. Total paraplegia does not require decompression because it is ussually caused by direct injury to the nervous tissue wich is irreversible and, therefore, by avoiding decompression one also avoides aggrevating the instability 12. With that in mind, the indications for decompression are: Absolute: progressive neurological deterioration in the presence of demonstrated compresion. Relative; The cessation of spontaneous recovery at an early stage. Prophylactic: These are the special cases of impending vertebral pathological fractures in pati~nts with an already diagnosed malignant tumor. Decompression of the spinal canal can be carried out from three different approaches: posterior, posterolateral and anterior. The direct posterior approach involves the performance of a laminectomy. Nowadays virtually the only indication for this approache is in those cases in which there is a fracture of the posterior arch with fragments invading the canal from behind. Occasionally, laminectomy permits the repairing of a dural tear caused by the broken edges of the fractured laminae, or the freeing of roots trapped within the fracture lines of the posterior arch. It should be remenbered that at this level of the spine the cord and conus medullaris are still present,such that the manipulations necessary to re98

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ach the anterior face of the spinal canal,where the fragments causing the compression are to be found, can not be performed without great risk to the nervous elements which are already affected. At the same time, it has long been known 43 that laminectomies contribute towards the destabilization of the original injury, in that they interrupt all the osteoligamentous structures destabilization of the original injury, in that they interrupt all the osteoligamentous structures of the posterior colurnn. It can therefore be said that laminectomy is an intervention with very limited application in injuries of the TLS segment and, whenever it is performed, it should be accompanied by reliable system of stabilization and its associated instrumentation. When the integrity of the posterior vertebral ligament is conserved, in cases in which there are vertebral fragments invading the anterior face of the spinal canal, effective decompression can be achieved indirecly via a posterior approach without the need of a larninectomy. It is enough to use an instrumentation with sufficent distractive force to be able to hold the neighbouring vertebral bodies appart and disimpact the fragments, while tensing the posterior vertebralligament . In this way the tension of the ligament pushes the fragments forwards, returning them to their original position and elirninating the compresion of the nervous tissue. This operation is known as ligamentaxis 53 And is only of use when the posterior vertebral ligament is intact, as in the case of compression-flexion type fractures (Figure 12). The posterolateral approach provides acces to the spine via a parasagittal posterior incission, while sacrificing one or more costotransverse apophyses 30.33,52,60. By this approach the pedicle and the lateral part of the posterior vertebral wall are reached. By partial or total resection of the pedicle, the anterior wall of the spinal canal can be reached and the fragments of the vertebral body can be handled without the need to manipulate the dura and its contents. It is a much safer operation than a laminectomy, but provides a very deep and restricted field of action in which there is very limited freedom of movement. After decompression it is necessary to ensure stability with the appropriate posterior instrumentation, seeing as a pedicle has had to be elirninated. When the reduction in caliber of the spinal canal is greater than 50% the best procedure to use for decompression of the spinal cord is the anterior ap,pjoach 2,20 -popularized by Hogson and Stock when dealing with vertebral tuberculosis 41 which at this level of the spine requires a thoraco phreno laparotomy. Once the damaged segment has been reached, the resection of the posterior part of the vertebral body carried out, using the naked eye, and all the fragments invading the canal are removed. This approach is the safest for the cord and is the only one which allows a total controlled decompression 10.22. The vertebral resec-

Surgical stabilization of the severe thoracolumbar spine fractures

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tion malees stabilization obligatory. The resulting space in the vertebral body can be filled using a solid cortical bone graft, and the whole thing is then stabilized using anterior instrumentation, which should hold together at least the two vertebrae adjacent to the damaged one 2.22.47.50 (Figure 8). Occasionally, if the bone resection is substantial, it may be necessary to carry out a circumferential posterior fusion at a later stage 35.70. Finally, in patients with a malignant vertebral tumor who have already received conventional treatment and in whom the risk of an impending pathological fractures with neurological complications, or persistent pain, is reasonably certain a prophylactic surgical intervention 20 with resection of the vertebral body via the anterior approach and prosthetic replacement, rnight be appropriate if the patient in question has alife expectancy of more than 4 Ó 5 months 3. This approach is safer and more effective than a laminectomy and fixation via the posterior approach, which does not perrnit the decompression of the anterior wall of the spine.

Principies 01 the surgicai stabilization in the TLS injuries. Satisfactory stabilization requires arthrodesis -fusion and osseous union- between the unstable segments whose displacements have been duly corrected. Solid, stable bone union requires inmobilization in the corrective position during a long enough period for the biological process of bone reparation to be completed. The need for prolonged immobilization brings with it the need for supportive instrumentation, whose purpose is to maintain corrective position until the bone union is complete, while permitting the patient as much activity as possible, to sum up, the instrumentation should be capable of counteracting, efficientIy and consistentIy, the forces which caused the traumatic deformity and subsequent instability. Depending on the surgical requirements as dictated by the mechanical analysis of each type of fracture, as explained earlier, the direction of the forces necessary for the reduction of displacements and stabilization of the injury is different in each case.

Fig. 8 - A) Unstable fracture of L-I due to a mechanism of compressive flexion with anterior invasion of the spinal canal.

Fig. 8 - B) Anterior decompression and fusion with bone graft and

instrumentation.

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Surgical stabilization of the severe thoracolumbar spine fractures

In a Compressive fiexion type fracture, with more than 50% loss in height of the anterior wall, the posterior columns should be subjected to a constant force with a component of extension which is capable of recuperating lordosis without producing more compression. In the case of burst fractures there should be a component of distraction to release the fragments, while the extension reduces the anterior wedging. Vertical compression or burst fractures require stabilization with sustained distraction which permits, on the one hand, the release and alignement of fragments and, on the other hand, the aplication of tension to the common posterior vertebral ligament. The tension of the ligament pushes the fragments back into their original position. If the ligament is broken, theses fractures should be tackled by the anterior approach -the only procedure with which reduction can succesfully be achieved and the spinal canal freed and decompressed. If the invasion of the canal is less than 30% a spontaneous, progressive reabsorption of the invading fragments may occur 29. In Distractive fiexion type injuries a constant compressive force should be applied to the posterior arch to substitute for the broken ligaments and prevent the recurrence of displacements. In injuries caused by the Torsion fiexion mechanism reduction is achieved by applying a sustained force, who~ se major component is distraction, to the posterior column, with the aim of releasing and aligning the fragments. In Lateral fiexion type fractures, reduction is best obtained by the simultaneous application to the posterior arch of a distractive force on the side of the fiexion and a contralaterally applied compressive force. In Translation type injuries, whatever the direction of displacement, and in Distractive extension type injuries,manual reduction is generally simple. There is usually no fragmentation of the vertebral body, and the purpose of the instrumentation is, more than anything, to prevent the recurrence of displacements. For this purpose neutral fixation system, acting as tension band, is sufficient.

Stabilization techniques and instruments. As we have seen in previous paragraphs, the aim of stabilization is to achieve the reduction of displacements and a solid and permanent bone fusion which will conserve the correction achieved. This is achieved by the insertion of bone grafts along with prolonged inmobilization assited by a firm segmentary vertebral fixation system which permits patient mobility at the same time. Stabilization can be achieved by either an anterior or posterior approach, the latte generally being used, however, because it is less complicated. 100

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From 1958 to the mid eighties the system most used for the stabilization of the spine was the Harrington instrumentation, originally designed for the correction of scoliotic curves 38,39. It represented the most importance innovation for the treatment of fractures in this area, achieving optimum results compared whit earlier techniques. The technique consists of postioning two rods, one on each side of the spinal apophyses, which are held in place at each end by sublaminar hooks. Depending on the orientation of the hooks, the Harrington instrumentation can be used to achieve either distraction or compression according to the nature of the deforrnity to be corrected and the casualmechanism of the fracture. The modification introduced by Jacobs, who uses closed hooks 46, and the use of sleeves on the rods, as introduced by Edwards 23, were undoubted improvements, giving the assembly a far higher degree of solidity. The instrumentation should be accompanied by the bony fusion of the damaged segment, either by intertransverse postero1ateral arthrodesis or by arthrodesis of the posterior joints. To achieve a stable reduction, the instrumental fixation should include two or three vertebrae above and below the damaged one, such that forces of t1exion can be satisfactorily counteracted. The purpose of this «long rod-short fuse» technique is to achieve a highly solid temporary fixation, capable of sustaining the reduction until the bone fusion is complete 14,21,62. When this occurs the instrumentation is removed in order to restore normal mobility to the non-arthrodesed segments 45. Another more recently developed technique consists in the application of two long rods, with an L-shaped bend at one end, which are attached to the vertebrae by means of segmentary sublarninar wires, as according to Luque 56, 57.The system can be improved by using the sublarninar segmentary wires with the Harrington rods 67. Nevertheless, the Harrington technique and the other similar ones have sorne disadvantages, of which the fo11owing are worth mentioning 4.20,50. 68: The instrumentation covers seven of more vertebral segments, which interferes with the mobility of the spine as a whole. This is a very serious limitation for the rehabilitation of paraplegics. Furthermore, after the fracture has mended an the instrumentation has been removed, there remain arthrosic alterations in the nonfused segments, which cause chronic pain in the medium and long runo There have ben may reports of neurological complications as a result of the invasion of spinaJsanal by the hooks or sublarninar wires. It is not uncommon for the hooks attached to the larninae at the upper end, to slide out of position, due to the t1exion of the proximal vertebra as a result of the distraction. This complication causes the immediate retum of the original displacement a the level of the fracture. In 1984, Dick developed a new set of instruments designed to use the pedicles as anchorage points 19,20, getting

Surgical stabilization of the severe tboracolumbar spine fractures

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his inspiration from the pioneering work of Roy-Camille and from Margel's idea of the vertebral fixator 58,59. The system was known generically as the Internal Vertebral Fixator and other fixators based on the same principIe of transpedicular attachement have since developed. Since 1989 we ourselves have used an internal vertebral fixator developed in Spain the Malaga fixator as support instrumentation for all cases of thoracolumbar, lumbar and lumbosacral vertebral fusiono Between January 1989 and december 1990 we have had occasion to use this procedure 27 times in the cases of TLS fracture requirig surgery which have come to our careo The first technical manoeuvre is the insertion of a wide-bored, short-threaded rod through each one of the pedieles of the vertebrae inmediately aboye and below the fraetured one (Figure 9). The anatomical references on the

are then connected, by means of the appropiated attachments, to a threaded bar which can be bent to adapt itself to the curvature of each segment of the spine. By manipulating the protruding segments of the rods located in the pedicles and with the help of external reduction manoeuvres, the surgeon can reduce the fracture (Figure 10). By using a surgical table which permits the dorsal flexion of the spine, and applying a counterpressure at the level of focus, practically anatomical reductions can be achieved. Once the distraction has been achieved, the rods are then connected to the attachments on the threaded bar

Fig. 9 - Technique of transpedicular instrumentation. A) Drilling the access to the pedicle and X-ray control of the position. Introduction of the pedicular screw. B) The pedicular screws are placed at the superior and inferior vertebrae immediate to the fractured one.

Fig. II - Compressive flexion fracture ofthe T-12 with anterior dislo-

63,63

Fig. 10 - Reduction of the fracture. The scheme follows that in the Figure. A) Fracture reduction (straigth arrows) is allowed by an extension force (curved arrows) applied to the pedicular screws previously attached to the rods. B) The position of reduction is mantained by fixing the pedicular screws to the rods by means ofconic nuts.

posterior arch for the identification of the points of entry into the pediele are specified in detail in the works of Louis 55 and Roy-Camille et al 63,64. The rods on each side

cation, reduced and fixed with posterior transpedicular instrumentation.

by means of conical nuts which give the assembly a high degree of stability. Finally, the attachments which connect the pedicular rods to the bars are fixed fmnly into the reducing postion by means of threaded nut on the bar itself

Fig. 12 - Ligamentaxis A) A distractive force (straigth arrows) is applied to the pedicular screws to pUl the posterior vertebralligament under tension. Then an extension force (curved arrows) is applied to reduce the fracture. B) The distracted posterior vertebralligament (straigth arrows) push the fragments forwards, (horizontal arrow) decompressing the vertebral canal. 'The position of reduction is mantained by fixing the pedicular screws to the rods.

101

Surgical stabilization of the severe thoracolumbar spine fractures

at either end of the attachment. These nuts are provided with a collar which closes on to the bar under pressure, preventing displacement of the attachments and holding the pedicular rods firmly in place (Figure 11). An important advantage of this instrumentation is that, depending on the type of fracture in question, either distraction or compression can be applied to the transpedicular screws by means of the nuts which hold the attachments to the bar (Figure 12). As with any other instrumentation, it should be accompanied by the bony fusion of the damaged verte-

Fig. 13 - Operative control X-ray taken during the transpedicular curettage of the vertebral body prior to introducing the bone chips graft following the Daniaux's technique.

bra to the two adjacent ones, either by intertransverse posterolateral arthrodesis or by arthrodesis of the posterior joints. The process can be completed by the introduction of autologous bone chips into the body of the fractured vertebra through an orificie driled by means of a screw through the pedicles of the vertebra in question, using the technique described by Daniaux 16 (Figure 13). This extra bone is especially useful in cases of burst fractures. The transpedicular instrumentation solves aH the problems and disadvantages associated with systems which use hooks and/or sublaminar wires. The instrumentation is much shorter, being limited to the vertebrae immediately aboye an below the damaged one, as opposed to the five or seven segments required by the Harrington technique. In this way the ideal aim of fusing the damaged joints, without damagin the unaffected joints of the superior and inferior segments, is achieved. Transpedicular atachment is the strongest type, and the only reliable kind for use in osteoporotic vertebrae 68. Moreover, it is the only form of attachment possible when a laminectomy has been performed 20. A study of clinical progress, when the transpedicular instrumentation has been removed, has shown there to be minimum deterioration in comparison with other systems 26. 102

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The techique demands a perfect knowledge of pedicular anatomy, of the topographicaI relationships of the pedicles, and of their reference points on the posterior arch. Otherwise there is a risk of damaging a spinaI nerve by incorrectly positioning a transpedicular screw.

Stabilization after decompression. The indications for decompression of nervous tissue in TLS injuries have been discused in an earlier section. When decompression is carried out via a posterolateraI or posterior approach, the intervention is completed in just one operative session by including bony fusion, supported by transpedicular instrumentation. However, given the characteristics of this type of injury, the most satisfactory decompression is achieved via the anterior approach, resecting the posterior part of vertebral body and thus completely liberating the dural saco In this case, the space left by the removaI of bone is filled by a strong, autologous tricortical one graft taken from the iliac crest or from the whole peroneal dyaphisis, or from the bone bank if this is available. The bone graft itself does not provied stability or prevent rotations 68, but serves exclusively as a base or support for the biological bone regeneration which causes the damaged vertebral segment to regain its original morphology. Stability is achieved by using vertebral fixation instrumentation. For this purpose there are two posibilities: transpedicular fixation from a posterior approach or a anterior fixation. Transpedicular fixation from the posterior approach gives a high degree of stability to the assembly, but has the disadvantage of requiring two interventions -decompression from an anterior approach and fusion from a posterior approach- which can rarely be performed in a single operative session owing to the magnitude of both operations. For this reason, many authors follow the anterior decompression by an anterior fusion, in the same surgical intervention, using plates, rods or specific anterior instrumentations devices 2.22,47,50. For the eight cases of cord decompression from an anterior approach on which we ourselves have worked, we have also used the Malaga fixator in association with a bone graft. Plates are placed on the lateral face of each of the two vertebrae adjacent to the damaged one, and are held in place by one or two screws. The two plates are attached by means of a threaded rod on which there are four nuts, one on each side of the two plates. By tightening the two outer nuts a certain amount of compression is applied, which helps the bone graft engage with its supportive platforms thus stabilizing the system. This having been achieved, the coHars of each nut are compressed against the rod to prevent the nuts for loosening. The weak point of this assembly is rotation for which reason an orthesis should be applied for at least twelve weeks in the postoperative periodo

Surgical stabilization of the severe thoracolumbar spine fractures

In case of malignant vertebral tumors of the zone, with impending fracture, in order to avoid the prolonged use of a postoperative corset, we accompany vertebn;tl prosthetic substitution 3 by posterior instrumentation with compression and with a transverse tension device which provides greater stability and strenght in aH plains of movement. This technique is similar to that proposed by Gertzbein 3S for use with burst fractures after more than seven days of development

References and suggested readings 1. ABAD, l.; SEBASTIAN, C.; GELOSI, F.: Surgical treatment of serious vertebromedullar lesions with the new F. V. M. modular instrumentation.. SICOT XVII World Congress Montreal, september 9-14,1990 2. AEBI, M.; WEBB, J. K; : The spine in: Muller, M. E.; Algower, M.; Schneider, R; Willenegger, H. (eds), Manual of Internal Fixation. (3 rd ed). Berlin, Springer Verlag, 1991. 3. BARBERA, J.; Substitución protésica vertebral en los tumores malignos del raquis.. (Submitted to publication). 4. BAUER, R D.; ERRICO, T. J.: Thoracolumbar spine injuries. In: Errico, T. J.; Bauer, R. D.; Wauch, T. (eds), Spinal trauma. Philadephia, JB Lippincott Co, 1990. 5. BEDBROOK, G. M.; Spinal injuries with tetraplegia and paraplegia. J. Bone Joint. 1979; 61: 267-284. 6. BEDBROOK, G. M.; Fracture dislocations of the spine with and without paralysis: the case for conservatism and against operative techniques ..In: Leathe, K E.; Hoaglund, F. T.; Riseborough E. J. (eds). controversies in Orthopedic Surgery. Philadelphia, WB Saunders, 1982. 7. BENTLEY, G.; MCSWEENEY, T.: Multiple injuries. Br. J. Surg. 1968; 55: 565-570. 8. BRAAKMAN, R.; The value of more aggressive management in traumatic paraplegia Neurosurg. Rev. 1986; 9: 141-147. 9. BRAAKMAN, R; FONTlINE, W. P.; ZEEGERS, R.; STEENBEEK, J. R: TANGHE, H. L.: Neurological deficit in injuries of the thoracic and lumbar spine. Acta Neurochir 1991; 11: 11-17. 10. BRADFORD, D. S.; Mc BRIDE G.: Surgical management of thoracolumbar spine fractures with incomplete neurological deficito Clin. Orthop. 1987; 218: 201-216. 11. BRYANT, C. E.; SULLIVAN, J. A.: Management o thoracic and lumbar spine fractures with Harringtol! distraction rod supplemented with segmental wiring. Spine 1986; 8: 532-537. 12. BOHLMAN, H. H.: Current concept review: Treatment of fractures and dislocations of the thoracic and lumbar spine. J. Bone Joint Surg. 1985; 67: 165--169 13. CALENOFF, L: CHESAR, J. W.; ROGERS, L. F. ET AL: MultipIe level spinal injuries: Importance of early recognition. AJR 1978; 130: 665-669. 14. COTLER, J. M.; VERNACE, J. V.; MICHLASKI, J. A.: The use of Harrington rods in thoracolumbar fractures. Orthop. Clin. NorthAm. 1986; 17: 87-103. 15. DALL, B.; STAUFFER, E. S.: Neurologic injury and recovery patterns in burst fractures at the Tl2 or Ll motion segmento Clin,Orthop. 1988; 233: 171-176. 16. DANIAUX, H.: Technik und erste Ergebnisse der transpedikuHiren spongiosaplastk bei Kompressionsbrüchen in Lendewirbelsaulenbereich. Acta Chi. Austriaca, 1982; (supl. 43), 79-86.

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17. DENIS, F. : The three co1umn spine and its significance in the c1assification of acute thoracolumbar spinal injuries. Spine 1983; 8: 817-831. 18. DENINS, F.: Spinal instability as defined by the three column spine concept in acute spinal trauma. Clin Orthop 1984; 1989: 65-76. 19. DICK, W.: Innere Fixation von Brust -und Lendenwirbelfrakturen. Ben, Hans Huber Publishers, 1984. 20. DICK, W.: Internal fixation of thoracic and lumbar spine fractures. Toronto, Hans Huber Publishers, 1989. 21. DICKSON, J. H., 1IARRINGTON, P. H., ERWIN, W. D.: Results of reduction and stabilization of the severely fractured thoracic and lumbar spine.. J. Bone Joint Surg. 1978; 60: 799805. 22. DUMM, H. K: Anterior spine stabilization and decompression for thoracolumbar fractures. Orthop. Clin. North Am. 1986; 17: 113-119. 23. EDWARDS, C. C.; LEVINE, A. M.: Early rod sleeve stabilization of the injured thoracic and lumbar spine. Orthop. Clin. North Am. 1986; 17: 121-145. 24. ERRIco, T. J.; BAUER, R. D.; WAUCH, T.: Spinal Trauma Philadelphia, JB Lippincott Co, 1991. 25. ERRIco, T. J.; O'NEIL, J.: Standar posterior techniques in the treatmetn of thoracic and lumbar spine fractures. In: Spinal trauma. TJ Errico, RE Beuer and T Wauch (eds) Philadelphia, JB Lippincott Co, 1991. 26. EYSEL, P.: MEININGo, G.; Comparative study of different dorsal stabilization techniques in recent throacolumbar spine fractures. Acta Neurochir. 1991; 109: 12-19. 27. FERGUSON, R L.; ALLEN, B. L.: A mechanistic c1assification of thoracolumbar spine fractures. Clin, Orthop. 1984; 189: 77-88. 28. FERGUSON, R L.; ALLEN, B. L.: An algorihtm for the treatment of unstable thoraco1umbar fractures. Orthop. Clin. North Am. 1986; 17: 105-112. 29. FIDLER, M. W.: Remodeling of the spina1 canal after burst fracture. A prospective study of two cases. J. Bone Joint Surg. 1988; 70: 730-732. 30. FLESH, J. M.; LEIDER, L. L.; ERICKSON, D. D. ET AL: Harrington instrumentation and spinal fusion for unstable fractures and fracture-dislocations of the thoracic and lumbar spine. J. Bone Joint Surg. 1977; 59: 143-153. 31. FRANKLE, H. L.; HANCOCK , D. O.; HYSLOP, G. ET AL: The value of postural reduction in the initial management of c10sed injuries of the spine with paraplegia and tetraplegia. Paraplegia 1969; 7: 179-192. 32. FRIMOYER, J. W.: Segmental instability: Overview and c1assfication. In Frimoyer, J. W, ed., The adult spine. PrincipIes and practice. New York, Raven Press, 1991. 33. GARFIN, S. R; MOWERY, C. S.; GUERM, J.; MARSHALL, L. F.: Confirmation of the posterolateral techniques to decompress and fuse the thoracolumbar spine burst fractures. Spine 1985; 10: 218-223 34. GELDERMAN, P. W.: The operative stabilization and grafting of thoracic and lumbar spinal fractures. Surg. Neurol. 1985; 23: 101-120. 35. GERTZBEIN, S. D.; COURT-BROUWN, C. M.; JACOBS, R R ET AL: Decompression and circunferential stabilization of unstable spinal fractures. 103

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36. GUTIMAN, L.: The conservative managemetn of closed injuries of the vertebral colurno resulting in damage to the spinal cord and spinal roots. In: Vinken, P. J.; Bruyn, G. W. (eds). Handbook of Clinical Neurology, vol. 25. Amsterdam, North Holland Publ. 1976. 37. HABER, T. R; FERMLY, W. T.; O'BRIEN, P.: Thoracic and lumbar fractures. Diagnosis and management. In: Bridwell, H. K; De Wald, RL. (eds).The textbook of spinal surgery. Philadelphia, Lippincott, 1991. 38. HARRINGTON, P. R: Treatment of scoliosis J. Bone Joint Surg. 1962; 44: 591-602. 39. HARRINGTON, P. R: Instrumentation in the spine instabilitY other than scoliosis. S. Afr. J. Surg. 1967; 5: 7-14. 40. HARR1NGTON, T.: Baker, B.: Multiple trauma associated with vertebral injury. Surg. Neurol. 1986; 26: 149-154 41. HODGSON, A. R; STOCK, F.E.: Anterior spinal fusiono A preliminary cornmunication on radical treatment of Pott's disease and Pott's paraplegia. 42. HOLDSWORTH, F. W.: Fractures, dislocations and fracture-dislocations of the spine. J. Bone Joint Surg. 1963; 45: 6-20. 43. HOLDSWORTH, F.W.: Fractures, dislocations and fracturedislocations of the spine. J. Bone Joint Surg. 1970; 52: 15241551. 44. JACüBS, R R; ASHER, M. A, SNIDER, R. K: Thoracolumbar spinal injuries. A comparative study of recumbency and operative treatment in 100 patients. Spine 1980; 5: 463-477. 45. JACOBS, R R; CASEY, M. P.: Surgical management of thoracolumbar spinal injuires: general principIes and controversial considerations. Clin Orthop. 1984; 1989: 22-35. 46. JACüBS, R R.; SCHLAEPFER, F.; MATHYS, R ET AL: A Looking hook spinal rod system for estabilization of fracture-dislocations and correction of deforrnities of the thoracolumbar spine: A biomechanic evaluation. Clin. Orthop. 1984; 1989: 168-177. 47. KANEDA, K: ABUMI, K; FUTIYAMA, M.: Burst fractures with neurologic deficit of the thoracolumbar - lumbar spine: Results of anterior decompression and stabilization with anterior instrumentation. Spine 1984; 9: 788-795. 48. KING, AG.: Spinal column trauma. In Anderson, L. D. ed. Instructional course lectures. vol. 35. Sto Louis, Mosby, 1986. 49. KORRES, D.; KATSAROS, A.; PANTAZOPOULOS, T. ET AL: Double or mu1tiple level fractures of the spine. Injury 1981; 13: 147-152. 50. KOUSTIK, J. P.; HULER, R J.; ESSE,S. 1.: STAUFFER, E. S.: Thoracolumbar spine fractures. In Frimoyer, J.W. (ed). The adult spine. PrincipIes and practice. New York, Raven Press, 1991. 51. KROMPINGER, W.J.; FREDERICKSON, B. E.; MINO, D.E.; YUAN, HA: Conservative treatment of fractures of the thoracic and lumbar spine. Orthop Clin North Am; 1986: 161-170. 52. LARSON, S. J.; HOLST, R. A; HEMMY, D. C.; SANCES, A.: Lateral extracavitary approach to traumatic lesions of the thoracic and lumbar spine. 53. LEVINE, A.; EDAWARDS, C. C.: Lumbar spine trauma.!n Camins, M., O'Leary, PI, eds. The lumbar spine. New York, Raven Press, 1987. 54. LINDAHL S. WILLEN, J. lRSTAM L: Unstable thoracolumbar fractures: A comparative radiologic stuyd of conservative treatment and Harrignton instrumentaion. Acta Radio (Diagn), 1985; 26: 66-77.

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Barberá,_ J.: Surgical stabilization of the severe thoracolumbar spine fractures. Neurocirugía 1992; 3: 91-104.