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In the Western world, the incidence of spinal fractures is estimated to be about 64 per 100,000 inhabitants. As a consequence of such fractures, a posttraumatic deformity may occur, regardless of the primary treatment. The most likely form of posttraumatic deformity is a kyphosis. To prevent such deformities, the clinician has to understand the following factors1:

• Biomechanical aspects of the intact spine

• Compensatory mechanisms of the spine and pelvis following structural changes of the spinal shape

• Therapeutic principles of thoracolumbar fractures (stability, reduction options, stable surgical concepts, neuroprotection, avoidance of complications, evaluation of progressive subsidence)

There are several possible causes of posttraumatic deformities:

• Persistent instability following conservative or surgical treatment

• Misinterpretation of the primary injury and consecutive inadequate primary treatment

• Complications during further treatment (e.g., implant failure, infection)

The development of posttraumatic deformities is generally characterized by sagittal imbalance with ongoing or progressive pain, and in some cases in association with neurologic compromises. Kyphotic deformities with a Cobb angle greater than 30 degrees typically cause severe pain.²

Managing posttraumatic deformities requires comprehensive knowledge of the factors and causes listed above and of the surgical treatment options for deformities, especially the different osteotomy techniques.

The results of surgical interventions for posttraumatic deformities are generally very good, if coronal and sagittal balance can be achieved. Depending on the extent of the required surgical treatment, several complications can potentially arise, and it is important to discuss these possibilities with the patient when planning such surgeries. The treatment decisions regarding posttraumatic deformities are made on an individual case-by-case basis.

Definition

There is currently no precise definition of posttraumatic deformity. The Spine Study Trauma Group defines it as a painful kyphotic angulation of the posttraumatic spine,³ but this definition lacks a precise threshold angle for symptomatic posttraumatic deformity.

In the cervical and lumbar spine, every singleor multilevel kyphosis has to be defined as a deformity. In the thoracic spine, the definition of a localized kyphotic deformity specifies an angle exceeding 30 degrees.4,5 Patients with such a deformity are at a statistically increased risk for chronic continued pain in the kyphotic region.²

According to the Scoliosis Research Society (2006), the line between a normal curvature and a pathological kyphosis should be drawn as follows:

• High thoracic region (T1–T5): ≥ 20 degrees

• Thoracic region (T5–T10): ≥ 50 degrees

• Thoracolumbar region (T10–L2): ≥ 20 degrees

• Lumbar region (T12–S1): ≥ 40 degrees

Exceeding of these segmental or global values does not automatically indicate the need for surgical treatment. Normal and reference values of the different parts of the spine as well as the pelvis are summed up in Fig. 11.1.

Epidemiology

The posttraumatic deformity can affect every part of the spine. Typically it is found in the thoracolumbar and cervicothoracic junctions. Because the proportion of primary fractures affecting T12, L1, and L2 is 59%,⁶ the majority of posttraumatic deformities are also found here. The incidence is difficult to quantify, as a general definition is lacking. The improvements in emergency medical services and primary care have led to a lower mortality rate of polytraumatized patients. Ironically, these improvements have also resulted in greater numbers of posttraumatic deformities, which pose a great challenge to attending surgeons.⁵ Patients with flexion-distraction injuries and bursttype fractures have an especially high risk of developing a posttraumatic deformity.⁶

Fig. 11.1 Spinopelvic measurements and references data. (From Koller H, Zenner J, Ferraris L, Meier O. Sagittale Balance und posttraumatische Fehlstellung der Brustund Lendenwirbelsäule. Teil 1. Orthop Unfallchir 2009;4:277–290. Reprinted with permission.)

A rare but serious entity of posttraumatic deformities is aseptic osteonecrosis with vertebral body collapse, known as Kümmell’s disease. It is most probably caused by a posttraumatic vascular insufficiency and a secondary vertebral body collapse.7

Prevention

The success of the primary treatment of the injury is crucially important in avoiding posttraumatic deformities. When assessing a thoracolumbar injury with the goal of preventing a later deformity, the following issues have to be considered:

• Analysis of the fracture morphology and classification of the injury

• Assessment of the stability and of the risk of a later deformity

• Assessment of spinal comorbidities, such as osteoporosis, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH), Scheuermann disease, preexisting scoliosis and kyphosis, and advanced degenerative changes

• Selection of a primarily stable surgical procedure, thereby completely correcting the traumatic deformity

• Selection of the surgical technique and implant type with the lowest risk of a secondary correctional loss

Clinical Findings

The symptoms of posttraumatic deformities are not very specific and can be found in different emphasis. The accompanying pain can arise from any or all of the following:

• Local instability pain due to absent fracture healing, pseudarthrosis, or implant loosening. Such patients complain of pain localized in the area of the fracture depending on position, movement, and additional loaddependent pain. Some patients also describe pain peaks when lying on their back, as this leads to an “anti-kyphosing” position. Localized pressure pain, percussion pain, as well as pain in hyperextension are typical.

• Local decompensation accompanied by malalignment. The local deformity leads to an additional strain on the surrounding structures (joint capsules, facet joints, intervertebral disks). The pain is then found at the injury level or in the adjacent segments of the deformity. In these cases an adjacent instability has to be ruled out. Local pressure pain is typical.

• The failure of compensatory mechanisms. Often these patients describe referred pain due to the deformity. This pain is normally found in the caudal direction of the injury. Many patients project this pain into the region of the lower back, where the thoracolumbar fascia is adherent to or in the area of the iliosacral joints and buttocks. This pain is typically progressive as the day goes on. Patients often have pressure pain in their lower back, along the sacroiliac (SI) joints, as well as in their buttocks. Often there is no typical pain in the region of the primary injury.

To respond to patients’ reported complaints and to process the radiological findings, one must understand the compensatory mechanisms of the spinopelvic axis. The spinal column is made up of a row of motion segments that are connected to one another. Therefore, every malposition of the spinal column leads to the following typical compensatory mechanisms, except in paraplegic patients and patients with ankylosing spondylitis:

• Reduction of the thoracic kyphosis

• Hyperlordosis of the lumbar or cervical spine

• Retroversion of the pelvis

In cases of progressive posttraumatic deformities, neurologic deficits can develop. A kyphotic deformity is typically accompanied by central spinal canal stenosis, whereas a kyphoscoliosis produces foraminal stenosis. This scoliotic deformity results in radicular pain or neurologic deficits.

If the central stenosis is located in the thoracic spine or thoracolumbar junction, a resulting myelopathy or conus syndrome can be found. Neurologic deficits occur in 20% of patients.⁵ Gait disorders can be caused by either neurologic compromise or sagittal (or rarely coronal) imbalance. Pronounced thoracic deformities can also lead to restrictive ventilation disorders.

According to Booth et al,8 sagittal deformities can be differentiated as follows:

• Type 1: Segmental sagittal hyperkyphosis associated with segmental imbalance. The global balance is maintained via the compensation mechanisms. This typically occurs in posttraumatic deformities.

• Type 2: Global deformity associated with a global imbalance. The C7 plumb line falls more than 5 cm anterior to the lumbosacral disk (compensated imbalance). In some cases the plumb line falls anterior to the hip joints (decompensated imbalance). This can be seen in elderly patients after posttraumatic deformities.

Posttraumatic deformities are generally local deformities. These deformities are usually measured in the sagittal plane as changes of the superior-inferior endplate angle or as a Cobb angle in the coronal plane. The superiorinferior endplate (Fig. 11.1) angle is measured between the superior end plate of the first cranially noninjured vertebra and the inferior end plate of the first caudally noninjured vertebra.⁹ The angle is then compared with the norm values.¹⁰

These angles are also used to evaluate the changes that occur with conservative or surgical treatment, but are also useful in evaluating instabilities. Plain radiographs should always be taken with the patient in the standing position. The exception is the hypomochlion (hyperextension) radiograph, which is of great importance when evaluating posttraumatic deformities and the possible surgical treatment. These radiographs are taken with the patient in the supine position with a sandbag directly underneath the injured area. An abundant amount of pain medication has to be administered, and the patient has to relax in the supine position, to order to acquire an accurate radiograph of the possible flexibility. This picture is then compares with the standing radiograph to determine the presence of instability.

To evaluate the injury, a computed tomography (CT) scan is of the utmost importance. Intraas well as intervertebral pseudarthrosis and implant loosening can be ruled out on CT, and a bony fusion within the deformity can be diagnosed. If an osteotomy is planned, CT can provide the necessary details as well as the sagittal and coronal reconstructions. The CT scan should include the adjacent vertebrae to assist in planning the later implant position (maximum possible screw length and diameter). It is also useful to perform magnetic resonance imaging (MRI) to assess a local stenosis, to rule out intraspinal pathology (syrinx, myelomalacia), and to evaluate degenerative changes in the adjacent segments. Spinal canal stenosis or osteochondrosis is regularly found in older patients close to the injured levels, and it must be taken into account when planning the surgical treatment.

To plan the best possible treatment of a posttraumatic deformity, it is not enough to look at the local deformity.5 The spinal and pelvic compensatory mechanisms must also be carefully evaluated by performing a whole-spine radiograph in the standing patient in two planes. This radiograph should include the acoustic meatus as well as the proximal half of the femur to provide all the relevant information. To perform a comprehensive radiological evaluation, the following modalities should be included:

• Upright whole-spine radiographs

• CT scans including sagittal as well as coronal reconstructions

• MRI including a short tau inversion recovery (STIR) sequence

The following further examinations might be necessary, depending on the clinical case:

• Hypomochlion radiograph

• Functional radiographs (flexion/extension)

• Bending radiographs (to left/right side)

• Myelography or a postmyelography CT scan

• CT angiography and/or MR angiography

To further plan the therapy, the following measurements are performed using the radiological examinations (Fig. 11.1):

• Spinopelvic parameters (pelvic incidence, pelvic tilt, sacral slope)

• Sagittal vertical axis (SVA) = C7 plumb line

• Thoracic kyphosis (measured from the end plates of either T1 to T12 or T5 to T12)

• Thoracolumbar angle (measured from the end plates of T10 to L2)

• Lumbar lordosis (measured from the end plates of L1 to S1)

When looking at the radiological diagnostics, the following compensatory measurements should be looked out for¹¹:

• Cervical hyperlordosis (in cases of thoracic kyphosis)

• Thoracic hyperkyphosis or even lordosis (mainly in cases of cervical kyphosis as well as in cases of thoracolumbar kyphosis; it cannot be found in cases of global kyphosis)

• Lumbar hyperlordosis (as a reaction to an underlying hyperkyphosis of any kind)

• Pelvic retroversion (high pelvic tilt, low sacral slope)

• Flexion of the knees (as an additional compensatory mechanism, when the pelvic retroversion is at maximum)

All these factors must be taken into account when deciding on the treatment and planning the extent of the correction.

Treatment Goals

The goals of the treatment of posttraumatic deformities are an improvement in the quality of life and a reduction in pain. When temporary neurologic deficits are present, they also should be treated with surgery.

When selecting the appropriate surgery, the physical resilience of the patient must be taken into account. The surgical technique should correct the deformity into an adequate, ageappropriate physiological spinal form.⁵

Conservative Treatment

In cases of minor deformities with referred pain into the lumbosacral region, which worsens over the course of the day, conservative treatment, including muscular strengthening, especially of the core muscles, pain medication, and infiltrations, is a possible option. The pain medication is given according to the World Health Organization (WHO) schema, whereby strong opiates are regularly necessary. An additional local therapy of the muscular trigger points, the SI joint, and the contracting hamstring muscles can relieve the pain. In cases of additional instabilities, a three-point stabilizing orthosis can be useful. The additional use of walking aids, such as a walker, can further improve the mobility of the patient. The surgeon should explain to the patient that the expectations of the results of conservative treatment are limited, and may include imbalance with or without an additional instability.

Surgical Treatment

Surgical treatment should be considered in patients with an intolerably low quality of life, excessive pain, and one or more of the following symptoms5:

• Persistent instability

• Growing neurologic or urologic impairment

• Progressive deformity with global decompensation

Early surgical treatment leads to better outcomes in the majority of cases.⁴ When the decision is made to perform surgical treatment, one must choose the appropriate surgical technique not only to address the local deformity but also to repair the instability.

But the global decompensation also must be addressed and corrected to achieve a satisfactory long-term result. The type of stabilization must be sufficiently rigid to counteract the biomechanical tendency toward a correctional loss and thereby enabling a stable healing. The surgical technique varies depending on the part of the spine to be addressed. The goals of surgical treatment of posttraumatic deformities are the following:

• Shortening of the posterior column

• Lengthening of the anterior column

• A combination of the two procedures

When deciding on the appropriate surgery, the following factors also must be taken into account:

• Rigidity of the deformity

• Localization (cervical, thoracic, thoracolumbar, or lumbar spine)

• Three-dimensional extent of the deformity

• Previous surgery

• Relevant comorbidities (osteoporosis, ankylosis, immune suppression, diabetes, dementia, cachexia)

• Patient’s physical resilience

• Patient’s suitability for prescription of narcotics

• Postoperative expectations of the patient

The selection of the surgical procedure is made by the experienced spine surgeon on an individual case-by-case basis in consultation with the anesthesiologist and with any other relevant specialist.

Surgical Planning

Even in cases of isolated local deformities, sagittal balance must be taken into account, as a well-balanced spine is the ultimate goal. The sagittal vertical axis should be brought within 5 cm of the posterior border of the superior end plate of S1. In elderly patients, the sagittal vertical axis may lie more than 5 cm in front of S1, but it should always lie behind the femoral heads. When striving for spinopelvic harmony, the pelvic tilt should be less than 20 degrees and the lumbar lordosis should be ± 9 degrees of the pelvic incidence. The sacral slope should normally be brought to lie at about 40 ± 10 degrees. Attaining these values results in a better clinical outcome.¹²

Preoperative planning should include consideration of the following factors:

• Extent of the correction, in degrees, necessary to obtain a well-balanced spine

• Patient’s existing compensatory mechanisms (residual mobile segments) on the one hand, and the existing restrictions of mobility (ankylosis, contractions, implants) on the other hand

• Necessity of a global or local correction of the kyphosis

• Type and number of necessary osteotomies

• Extent of stabilization required (fixation points), taking into account the adjacent curvatures

• Need for decompression of neurologic structures

• Previous surgery as well as additional local pathologies (e.g., scar tissue, pseudomeningocele, syrinx)

• Type of previously used, persisting implant

The surgical planning can be performed using paper printouts of the radiographs or special surgical planning software to assist the surgeon.

The surgery should generally incorporate the use of pedicle-screw–based instrumentations. If necessary, pedicle hooks or sublaminar clamps can be used. Directly adjacent to the osteotomy, the use of monoaxial screws has proven advantageous to facilitate a proper correction. The screw diameter should be at least 6 mm in the lumbar spine and at least 5 mm in the thoracic spine. In cases of additional osteoporosis, the cranial and caudal screw pairs can be augmented using polymethylmethacrylate (PMMA). Rigid rods such as 6-mm titanium or 5.5-mm cobaltchrome can help achieve a lasting correction.

To enable the anterior fusion, either cages or autologous tricortical bone grafts are suitable. Cages, which offer the highest primary stability, can be used as expandable models that facilitate contouring to the local conditions. Because the cage itself does not necessarily promote bony healing, it has to be filled or surrounded by bone graft.13 Tricortical bone graft is a feasible alternative. Depending on the local bone quality and the general rigidity of the construct, an additional anterior plate can be used.¹⁴

Choice of the Osteotomy Technique

Posterior osteotomies are generally used for shortening the posterior column, sometimes with an anterior distraction.

A facetectomy can achieve a correction of 3 to 5 degrees per segment, but only if the anterior column is flexible. It is advisable to perform an additional complete flavectomy and an interlaminar decompression to prevent a secondary spinal canal stenosis during the correction (pincer phenomenon).

A transversectomy or a Wilson and Ponte chevron osteotomy is a widely used technique. As early as 1949 Wilson and Turkell¹⁵ described the resection of the facet joints and the interlaminar structures for the therapy of Bechterew’s disease. Ponte et al¹⁶ then expanded the technique in 1984 to treat Scheuermann’s kyphosis. The combination of resecting the facets and all interlaminar structures (ligaments) along with an undercutting laminotomy achieves a correction potential of up to 10 degrees per segment.¹⁷

A further expansion of the general technique is a closing-opening wedge osteotomy (COWO), which was first report in 1945. It became popularly known in spine surgery as the so-called Smith-Petersen osteotomy (SPO).¹⁸ The terms SPO, Ponte osteotomy, and chevron osteotomy are now commonly used synonymously. The SPO incorporates the posterior resection and compression along with an anterior distraction. In cases of anteriorly mobile spinal segments, such as pseudarthrosis in posttraumatic deformities, corrections of 10 to 20 degrees can be obtained in each segment. In cases where an anterior defect arises due to the correction, an anterior support must be implemented.

The workhorse of posttraumatic deformity surgery is the pedicle subtraction osteotomy (PSO) with all of its variations.³ The general principle of this closing-wedge osteotomy (CWO) was described by Scudese and Calabro¹⁹ in 1963 and by Leong et al²⁰ in 1978. Thomasen²¹ reported the technique, which is typically used today, of a transpedicular cortical decancellation osteotomy in 1985. The eggshell osteotomy was reported by Heining²² in 1984.

Although the SPO is limited to a resection of the posterior portions of the spine, the PSO resects an additional anterior wedge out of the vertebral body from the posterior direction (Fig. 11.2). In doing so, a correction of 20 to 40 degrees is possible in a single segment.²³ The PSO was used primarily in the lumbar spine, but it eventually also made its way into the correction of marked thoracic kyphosis.²⁴

By performing a PSO, an average correction of 17 degrees per segment can be achieved in the thoracic spine. However, the amount of correction increases from the upper thoracic spine to the lower part.²⁵

With the PSO, the extensive posterior resection of the lamina along with the wide lateral resection, including the pedicles (Fig. 11.2a,b), is completed by an interosseous V-shaped resection within the vertebral body on both sides. The wedge-shaped resection is completed to the anterior cortex (Fig. 11.2c). Before closing the defect by posterior compression, the posterior wall of the vertebra is removed completely within the margins of the osteotomy. Generally, this is a critical point during the surgery, as it can lead to an impingement or damaging of the neural structures. A good closure of the anterior osteotomy should be achieved to get a solid bony fusion (Fig. 11.2d). In cases of an additional coronal deformity, the osteotomy can be performed asymmetrically. Within the thoracic spine the osteotomy has to be combined with an osteotomy of the corresponding ribs.

Posttraumatic deformities generally arise from the fractured vertebrae as well as the destroyed intervertebral disks. Several variations of the PSO were developed to treat these deformities, generally involving doing an osteotomy through the fractured vertebra, and often resecting the damaged disk along with the bone26,27 (Fig. 11.3). A special variation is the so-called corner osteotomy, in which a wedgeshaped piece of the posterior third of the cranial vertebra is resected to achieve a further lordosis.²⁸

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