An Approach for Treatment of Complex Adult Spinal Deformity

Summary of Key Points

Decision-making in complex spinal problems can be made easier by a systematic approach to the problems.
“Problem, Goals, Tools, Plan” is one way to approach the problems.
The primary driver of a good clinical outcome in deformity surgery is a stable spine in neutral sagittal balance.
Pelvic parameters, in particular pelvic incidence, determine lumbar lordosis.
Numerous operative techniques are available, and each has a role.
Complication rates can be high, but outcomes are usually quite good.
Proximal junctional failure is still an unsolved problem.

Complex spinal deformity arises from a number of pathologies. In some cases it is the large-magnitude curves of idiopathic scoliosis or kyphosis. It may be the result of secondary deformity attributed to neuromuscular disease, congenital anomalies, infection, or trauma. The two major groups in terms of volume are decompensated deformities because of degenerative change in the preexisting curve, and iatrogenic deformity.

The range of normal for cervical lordosis, thoracic kyphosis, and lumbar lordosis is quite variable. Varying degrees of scoliosis can be tolerated, depending on a number of other factors. As a result, spinal balance appears to be more important in terms of symptoms and progression then the magnitude of scoliosis or kyphosis. A review by Kuntz et al. has shown that there is only a narrow range of spinal balance, and that this is highly conserved. The relationship between pelvic parameters, particularly pelvic incidence and sagittal balance, has received considerable interest in recent years. Clinically, spinal balance can be assessed by examining the head position of a standing patient in relation to the pelvis. In the lateral view a plumb line from the ear canal should pass through or behind the greater trochanter. In the anteroposterior (AP) view, a plumb line from the inion should pass between the posterior superior iliac spines. Radiographically on a long cassette film one can use either the C7 vertebral body or the odontoid as the starting point for a plumb line. Use of the odontoid as a marker allows assessment of cervical deformity in overall spinal balance. A plumb line from the odontoid should pass posterior to the center of rotation of the hip in the lateral plane and should fall between the medial borders of the S1 pedicle in the AP view. A plumb line from the C7 vertebral body should pass through the L5‒S1 disc space. Fig. 142.1 shows preoperative AP (see Fig. 142.1A ) and lateral (see Fig. 142.1B ) views of a patient with a decompensated kyphoscoliosis showing loss of both sagittal and coronal balance. Fig. 142.1C and D show postoperative views of the same patient showing restoration of balance.

In many patients with spinal deformity, particularly in adults, the clinical picture can be quite complex, and the decision-making process can seem daunting. When a patient with a complex deformity presents for evaluation, it is often difficult to know where to start. Having a systematic approach to assessment and treatment planning makes these complex patients easier to treat. A complex problem can be made easier to understand if it is broken down into its component parts. The author uses a four-part process to do this, and this chapter will use this framework to discuss the treatment of complex spinal deformity. The four components are: problems, goals, options, and plans.

Define the Problem

Although it sounds simplistic, it is important to begin the process by defining the problem. In contrast to adolescent idiopathic scoliosis, where the predominant focus had been on the magnitude and progression of the deformity, there are more factors to consider in adult deformity. One of the key clinical differences in adult deformity is that adults generally seek treatment for the symptoms of the deformity rather than the deformity itself. As a result the deformity is viewed within the context of the symptoms it produces. In addition, there are comorbidities to be considered. In many cases the patient will already have had other spinal procedures.

The first step is a detailed history. What is the main presenting problem? How does it affect the patient’s quality of life? How has the problem changed over time? If the effects on quality of life are relatively minimal, what is the likelihood of the problem progressing? In many patients nonoperative treatment may be a viable option even in the presence of very significant deformities. It is also important to understand the patient’s perception of the problem. In the author’s experience some patients present with few symptoms desiring aggressive treatment because of fear that progression of the problem will lead to paralysis or death. Others present seeking information or to establish a relationship with a practitioner in case the symptoms worsen.

Comorbidities are an important part of the history if one is considering surgery. In addition to cardiovascular and pulmonary conditions, nutritional status and risk factors for osteoporosis should be considered.

If the patient has had previous surgery, it is important to know what was done. It is also important to know why the surgery was performed and also what the short- and longer-term outcome of that surgery was. Previous investigations and operative reports are very valuable in the assessment if they can be obtained. In some cases, the deformity may be iatrogenic.

Physical examination should include a detailed neurological examination. Examination of spinal alignment and balance is important. Loss of sagittal and coronal balance is associated with increased symptoms and seems to have a higher risk of progression.

Imaging studies are an integral part of defining the problem. Conventional x-rays in the standing position, including the entire spine and pelvis, are the standard method of assessing deformity. Lateral bending films can assess the flexibility of the coronal deformity. Supine films (often done with a bolster under the apex of the deformity) can give an assessment of the flexibility of sagittal plane deformities. Magnetic resonance imaging (MRI) is the investigation of choice for assessing the status of the discs and the neural axis. Computed tomography (CT) provides excellent assessment of the bony anatomy, and the use of sagittal and coronal reformatting allows more detailed assessment of the bony architecture. If a patient has had previous surgeries, CT is a sensitive and specific method of assessing fusion status. Myelography with or without CT may make assessment of the neural axis easier in large deformities. Bone scan has historically been used for assessment of pseudoarthrosis but has been largely supplanted by CT in the author’s practice.

In those patients in whom surgery is being considered and comorbidities are present, general and specialty medical consultation for preoperative optimization should be utilized. Nutritional and bone health status are often overlooked in the workup and can have significant effects on outcome. Bone mineral density (BMD) testing can help to assess bone health, although the presence of degenerative changes in the spine may artificially increase the BMD of the spine. ^, Vitamin D testing and supplementation in the preoperative period should be considered, especially in regions or cultures where there is little direct sun exposure. ^, In large-magnitude thoracic deformities, pulmonary function testing should be done for risk assessment.

Goals

Once the problem has been defined, the next step is to decide on the goals of treatment. It is important to assess the patient’s goals for treatment, as well the practitioner’s goals. Are these goals achievable, and at what risk? Patients with minimal symptoms in daily life who have limits with high-level activities may be desiring a level of function that is just not achievable. Alternatively, for a patient with low demands and expectations, simpler nonoperative treatments may provide an appropriate quality of life without the risks associated with addressing the deformity.

Prevention of progression is a common goal in treatment of deformity. In adult deformity, progression is unpredictable for many conditions, and progression of symptoms may or may not correlate with progression of deformity. As a result, prevention of progression is not a common indication for treatment after skeletal maturity.

In general, the goals of surgical treatment are to relieve compression of neural elements, stabilize instabilities, and correct and maintain the correction of the deformity. These goals need to be accomplished with a view to minimizing risk in both the short and long term. One of the primary end results of deformity treatment should be restoration of sagittal and coronal balance. Outcome studies have shown weak, if any, correlation between correction of Cobb angle and outcome, but have shown clear correlation with spinal balance and outcome. ^, ^, More recent studies have shown the importance of restoring lumbar lordosis to equal pelvic incidence. Studies have identified a number of other radiographic parameters that correlate with outcome, and there is no clear consensus on which ones are the most useful.

Osteoporosis

Osteoporosis is common in patients with spinal deformity. It may be associated with vertebral fractures, leading to increased deformity. ^, It also may have an effect on outcome of surgery. ^, Although osteoporosis does not affect bone healing, it does affect the holding power of spinal instrumentation. For this reason, when considering surgery, assessment of osteoporosis is an important step. There is no quoted level of bone density beyond which surgery is not an option, however the risks of failure increase with higher degrees of bone loss. Preoperative optimization of bone health with vitamin D testing and supplementation as required and pretreatment with teraparatide have been advocated. Recent clinical studies have shown positive effect of teraparatide on fusion outcomes. ^,

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