Adult Degenerative Scoliosis

Summary of Key Points

Adult degenerative scoliosis (ADS) is a debilitating condition, with a spectrum of clinical presentations and spinal misalignment. There has a significant trend toward higher demand for management of ADS (both surgical and nonsurgical) in recent years.
A thorough history of main presenting complaints, onset and progression of the condition, and associated comorbidities, as well as a thorough neural examination and radiographic assessment, are important for the evaluation of degenerative scoliosis patients.
Assessment of regional and global alignment of the spine in the coronal, sagittal, and axial planes with appropriate radiological studies is important for both diagnosis of and operative planning for adult spinal deformity (ASD).
The Scoliosis Research Society–Schwab classification for ASD includes assessment of sagittal spinopelvic parameters. This classification correlates with health-related quality of life in patients with ASD and has excellent intraobserver and good interobserver reliability. New classifications should include more patient-specific variables (age, soft tissues, and comorbidities) that match the heterogeneous nature of this pathology.
Management of ADS starts with nonoperative treatment. Surgical correction of ASD has good outcomes in improving quality of life.
Preoperative surgical planning is critical in ASD surgery and should take a multidisciplinary approach, involving multiple subspecialties, to optimize outcomes.

Global demographics are facing a shift toward an older population because of improved medical care, increasing longevity, and declining natality. From 1950 to 2000 the population of people over 60 years tripled from 205 million to 606 million. ^, Changes in demographics have had a significant impact on the prevalence and burden of degenerative musculoskeletal diseases, specifically degenerative spinal disorders.

Aging of the spine involves a wide range of degenerative changes; intervertebral discs, facet joints, ligaments, muscle, and bone tissue changes related to cellular and extracellular modification. Degenerative changes in the lumbar spine characteristically begin in the end plate in the third decade of life, and progress to disc degeneration, followed by facet joint arthrosis, with progressive aging. The disc changes then lead to changes in loadbearing at the intervertebral level, including the facet joints, which triggers bone remodeling and progressive axial collapse, with a decline in ligamentous and musculature function. Generally, those changes happen in a synchronous pattern; the overall result is a progressive loss of height, sagittal plane kyphotic evolution, and reduction in spinal range of motion, without significant symptoms. However, when changes occur in an asymmetrical manner, a shift in mechanical loading of individual segments leads to further asymmetrical weightbearing by the discs and facets, as well as loss of muscle tone and mass. Asymmetric degeneration of spinal motion segments initiate a cascade-like process leading to spinal deformity, commonly with rotatory subluxation and spondylolisthesis, which are commonly associated with radicular or spinal stenosis symptoms.

Adult degenerative scoliosis (ADS) is an abnormal curvature of the spine affecting any of the three planes: sagittal, axial, or coronal. There are two principle types of patients: those with a previous deformity developed at early stages of life, and those with de novo deformity that develops during adulthood. De novo scoliosis is defined as a coronal Cobb angle greater than 10 degrees, as measured according to the Cobb method. The curve tends to progress 1 to 6 degrees per year (average is 3 degrees per year). De novo scoliosis has an even gender distribution and typically begins around the age of 50, with an average age of presentation of 70.5 years. ADS is highly prevalent, with a rate as high as 68% in individuals older than 65 years. ^,

The clinical presentation of patient with adult spinal deformity (ASD) characteristically involves heterogeneous symptoms that include back pain, radicular symptoms, and neurogenic claudication and weakness, as well as an inability to perform daily activities. Spinal deformity has a tremendous impact on quality of life that is commonly underestimated, yet can be more impactful than that of many chronic diseases, such as cancer, diabetes, and cardiac disease. As life expectancy increases in populations across the globe, and elderly people expect surgical interventions to improve pain, function, and life quality, management of ADS is more relevant than ever; and statistics show increasing trends in the surgical and nonsurgical management of spinal pathologies.

It is important to note that although the radiographic diagnosis of adult scoliosis is based on coronal-plane radiographs, it is predominantly the sagittal plane deformity that appears to drive symptoms. In response to this forward truncal inclination, patients will develop a set of compensatory mechanisms in an effort to maintain an erect posture. Once these compensatory measures reach their limit, the trunk falls forward, resulting in substantial energy expenditure for even the most basic activities.

Clinical Evaluation of the Adult Patient with Spinal Deformity

The most common complaints of patients seeking care for ADS are pain and disability. The majority of patients present with diffuse and axial low back pain. Other symptoms include loss of ambulatory endurance, leg weakness, and stooping forward with increasing truncal deformity.

A thorough history is necessary for evaluation of adult patients with degenerative scoliosis. A history of spinal pathologies such as adolescent idiopathic scoliosis, spondylodiscitis, trauma, or tumors should be investigated. It is important to understand the onset and progression of symptoms and what symptoms are most pressing for the patient. Red flags must be recognized, including weight loss, asthenia, nocturnal fever or sweating, neurological or sphincteric involvement, a history of associated neuromuscular diseases (i.e., Parkinson), or pain that is unresponsive to medications or nocturnal.

A complete physical examination is needed. Key components of the physical examination include an assessment of the patient’s gait, a musculoskeletal evaluation, and a thorough neurological examination. Precise identification of symptom drivers and pain generators is needed. ADS is a multifactorial process, and symptoms can have many potential causes. It is helpful to know if the pain is radicular or axial in nature. Axial pain is associated with the degree of radiographic lateral subluxation and sagittal malalignment. Discrete physical weakness should be identified. The examination should include visual inspection of the spine, evaluation of any waist and hip asymmetry, pelvic obliquity, leg-length discrepancy, shoulder asymmetry, and overall spinal alignment in the coronal and sagittal planes. Forward and lateral bending maneuvers help in assessment of structural curve components, and rigidity. Observation of compensation mechanism, such as flattened buttock, asymmetric knee flexion (for coronal deformity), and bilateral knee flexion (sagittal compensation) is essential.

In patients with significant thoracic components, pulmonary function may need to be addressed. Patients’ comorbidities should be evaluated, and the presence of osteoporosis or osteopenia should be ascertained. Surgical management of ADS is known to have high complication rates, and candidates for elective surgery are commonly “frail” or “severely frail.” Frailty increases individuals’ vulnerability to injury (or surgery), thus necessitating thorough preoperative evaluation and risk assessment. An ASD frailty index (ASD-FI) was developed according to a validated protocol using a multicenter database, and later externally validated. Forty variables are used to calculate the ASD-FI, including deficits documented by the physician (i.e., diabetes, liver disease, cancer) and patient-reported variables (i.e., bladder incontinence, difficulty walking). Each variable is reported as a binary value (e.g., presence vs. absence of osteoporosis). The mean score of all deficits is calculated, resulting in a score ranging from 0 to 1. Patients with scores of less than 0.3 are considered not frail; those with scores of 0.3–0.5 are considered frail; and those with scores of over 0.5 are considered severely frail. Higher patient fragility scores are associated with worse outcomes and a greater risk for major complications like junctional kyphosis, pseudoarthrosis, and deep wound infection. Therefore the ASD-FI can be used as a component of preoperative risk assessment and patient counseling on potential adverse outcomes or recovery course after surgery. ^,

The occurrence of tandem cervical spinal stenosis patients with lumbar pathology is reported in 5% to 25% of individuals, emphasizing the importance of evaluating for myelopathy. In ADS, symptoms of spinal stenosis are often not relieved by forward posture, unlike in patients with neurogenic claudication without a curve.

The functional status of patients should also be assessed; current methods rely on patient-reported questionnaires. The Thomas test with a leveled pelvis in the supine position can help to evaluate for hip flexion contractures. Signs of myelopathy, such as hyperreflexia, clonus, and an impaired gait, may be present in patients with severe thoracic or concomitant cervical disease.

The cosmetic appearance of the deformity may also be a considerable factor in the psychosocial wellbeing of the patient. The psychosocial aspects of these patients are an important element in the consideration of treatment options. Pain and disability can produce depression and impact overall mental status. On the other hand, untreated depression may lead to aggravated symptoms of pain, functional loss, and weakness. Failure to address this might result in a poor surgical outcome.

Diagnostic Imaging

Radiographic assessment is an essential part of the complete evaluation and management of ADS patients. Imaging modalities allow the evaluation of bony, neurological, muscular, and soft tissue components of the spine. Anatomical relationships and radiographic parameters guide the decision-making regarding management, monitoring of progression, and measured outcomes. The tools mostly used include conventional radiographs and advanced imaging techniques, such as magnetic resonance imaging (MRI), computed tomography (CT), myelograms, EOS full-body imaging, and rarely radionuclide studies (e.g., bone scan, gallium).

Conventional Radiography

Plain-film radiography is the most widely used modality because of its availability, low cost, and relatively good resolution. The evaluation of the ASD patient should include frontal and sagittal full-spine radiographs, including the pelvis. A comparison of the degree of deformity between weightbearing and nonweightbearing films (i.e., standing vs. supine) provides information on the stiffness of the deformity, and therefore will impact the surgical strategy. For the purpose of using plain x-rays for spinopelvic parameters measurement, patients should adopt a freestanding position, with elbows flexed at 45 degrees and fingers on the supraclavicular fossa.

Recently, the introduction of full-body low-dose stereoradiography (EOS) system has permitted the inclusion of horizontal gaze and lower-limb compensatory mechanisms, such as pelvic shift and knee flexion. While the EOS system also permits three-dimensional reconstruction of the spine and pelvis, there is only one published report of the use of this function in ASD, and therefore little is known regarding its clinical relevance.

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