Idiopathic Scoliosis: Adult Scoliosis 

Micheal Katsimihas, M.D. FRCSC
Christopher S. Bailey, M.D., FRCSC MSc(surg) 

London Health Science Centre, Division of Orthopaedics,
University of Western Ontario
London, ON

Epidemiology
Adult scoliosis can be defined as a spinal coronal plane deformity of greater than 10º that presents in a skeletally mature individual. A number of studies have reported the prevalence of adult scoliosis to be between two to 32% or even higher1.

 

Pathophysiology
Adult curves are typically pre-existing idiopathic scoliosis with secondary degenerative changes or de novo degenerative scoliosis, but can be iatrogenic, post-traumatic, congenital, post-paralytic, or secondary to infectious or neoplastic deformity. Although the etiology of scoliotic deformity remain incompletely understood, in adult degenerative scoliosis a coronal curvature, sagittal curvature, or combination of these deformities originates from a asymmetrical degeneration of lumbar inter-vertebral discs or facet joint degeneration and osteoporosis. These lead to loss of load support, changes in the local architecture and increasing deformity. Unlike pre-existing adolescent idiopathic scoliosis, which may progress at 0.5° to 1° per year, the degenerative nature of the curvature may cause rapid  progression (1° to 6° per year)2 .

Clinical Presentation
Unlike adolescent idiopathic scoliosis where pain is uncommon as a presenting complaint, patients with degenerative deformity frequently present with mechanical low back pain, radicular pain, neurogenic claudication, or truncal imbalance. Typical radiographic features include lumbar rotatory subluxation, asymmetrical disc tilt, and advanced disc degeneration. The saggital balance should be carefully analysed on lateral radiographs3.

Treatment
Most patients with degenerative scoliosis do not require surgical treatment, and are managed conservatively based on the patient's presenting symptoms i.e. analgesics for back pain, epidurals for neurogenic claudication. Bracing may sometimes help the symptoms, but it has no effect on curve progression4.

Lumbar and lumbosacral adult scoliosis are the most common curve locations to require surgical intervention. A posterior approach with single or multilevel posterior lumbar interbody fusion (PLIF), or transforaminal lumbar interbody fusion (TLIF) is typically utilized. It is recommended to perform a PLIF/TLIF at the L4-5 and L5-S1 levels to improve the saggital alignment and to augment the fusion potential. Restoration of saggital balance has been reported to be the primary parameter associated with outcome5.

When deciding on the last instrumented cephalad level, a general rule is to  cross the thoracolumbar junction transitional zone to reduce adjacent segment stresses and prevent junctional kyphosis from occurring above8.

Traditional Indications for Surgical Management

  1. Intractable axial or neurogenic pain.
  2. Prevention of curve progression; thoracic curves greater than 50° to 60°, lumbar greater than 40°, or short and sharp curves.
  3. Stabilisation of rapidly progressing curves.
  4. Symptomatic coronal or saggital imbalance with decompensation requiring re-alignment and stabilization2.

Surgical Controversies

a) Deciding the caudal level of the fusion: To fuse or not to fuse to the sacrum?
The advantages of stopping a long fusion at L5 are well recognized and include: retention of lumbosacral motion, decreased operating time, lower pseudarthrosis rate, decreased rate of re-operation, and decreased stresses at the SI joints. To stop at L5 requires a normal, well-hydrated L5-S1 disc, with good lumbar lordosis. The concern about stopping at L5 is that the L5-S1 disc may ultimately degenerate and can lead to a positive saggital shift (junctional kyphosis)6.

Indications for fusing to the sacrum include:

I. "Advanced" degeneration of the L5-S1 disc.
II. Spinal stenosis at L5-S1.
III. Spondylolisthesis at L5-S1.
IV. Oblique take-off of the L5-S1 segment greater than ten degrees.
V. Laminectomy at L5-S13.

b) Limited and focused versus extensive surgery:
Limited surgical intervention, which does not aim to address the deformity but rather specific symptom producing pathology (i.e. isolated foraminal stenosis with resulting radiculopathy), may be indicated under the following circumstances:

I. The deformity is stable and does not require stabilization.
II. The primary symptom(s) is/are not due to deformity itself.
III. The pathology can be addressed surgically without destabilising the curve.

There are two main categories for such surgery:

1. Limited decompression without fusion.
2. Decompression with short fusion7.

Complications
Medical complications are a major concern in adult spinal deformity surgery. The incidence ranges between 40% to 86%. Local complications include infection, pseudarthrosis/failure of instrumentation, neurological, and adjacent level degeneration/instability. Common medical complications include: pneumonia, atelectasis, ileus, delirium, and cerebrovascular incidents. With thoracic and thoracolumbar curves, the use of spinal cord monitoring has made spinal surgery much safer9.

References 

  1. Carter O.D., Haynes S.G. Prevalance rates for scoliosis in US adults: results from the first National Health and Nutrition Examination survey. Int J Epidemiol 1987;16:537-44
  2. Tribus C. Degenerative lumbar scoliosis:evaluation and management. J Am Acad Orthop Surg 2003;11:174-83
  3. Bridwell K.H. Selection of instrumentation and fusion levels for scoliosis: where to start and where to stop. J Neurosurg (Spine 1) 2004;1:1-8
  4. Chuah S.L., Kareem B.A., et al: The natural history of scoliosis: Curve progression of untreated curves of different aetiology, with early (mean 2 year) follow-up insurgically treated curves. Med J Malaysia 56 (suppl C):37-40, 2001.
  5. Glassman S.D., Bridwell K.H., Dimar J.R., et al. The impact of positive saggital balance in adult spinal deformity. Spine 2005;30:2024-49
  6. Edwards C.C. II, Bridwell K.H., Patel A. et al. Thoracolumbar deformity arthodesis to L5 in adults: the fate of the L5-S1 disc. Spine 2003;28:2122-31
  7. Weidenbaum, M. Considerations for focused Surgical Intervention in the presence of adult spinal deformity. Spine Volume 31, Number 19 Suppl, pp S139-S143 2006
  8. Kuklo, T.R. Principles for selecting fusion levels in adult spinal deformity with particular attention to lumbar curves and double major curves. Spine Vol. 31, Number 19 Suppl, pp S132-S138, 2006
  9. Baron, E.M, Albert, T.J. Medical complications of surgical treatment of adult spinal deformity and how to avoid them. Spine Vol. 31, Number 19, Suppl, ppS106-S118, 2006

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