Imaging of degenerative scoliosis: A review of current literature

S.Saipriya, J.Howard, C.J.Miranda, R. Siripurapu, A. Herwadkar

Department of Neuroradiology, Greater Manchester Neurosciences Centre,

Salford Royal NHS Foundation Trust, England UK

eEdE-213

No disclosures

Definiton

Primary degenerative scoliosis is a deformity developing in a previously straight spine, caused by progressive degeneration of the spine in middle age with progressive disc and facet degeneration.

This leads to generalised spondylosis and may result in instability that leads to vertebral rotation, lateral listhesis or spondylolisthesis.

Scoliosis is defined as a lateral spinal curvature with a Cobb angle of >10°.

Purpose (1)

Degenerative scoliosis is a type of adult scoliosis and has different etiologies.

There is an increase in prevelance of degenerative scoliosis in several countries with aging populations.

A thorough radiological evaluation is imperative for successful surgical management of adults with scoliosis.

We aim to depict the various imaging modalities with their relative utilities and also provide an update on the current research on degenerative scoliosis.

Aebi, M. "The adult scoliosis." European Spine Journal 14.10 (2005): 925-948.Ortiz, Orlando. Imaging of the Postoperative Spine, An Issue of Neuroimaging Clinics. Pages 69 - 74Vol. 24. No. 2. Elsevier Health Sciences, 2014.

Methods

We reviewed the imaging findings of patients treated with the intent of achieving spinal fusion presenting to our tertiary neurosciences and spinal centre over the past 7 years.

A literature review on assessing spinal fusion was carried out.

Background Several classification systems exist, there is no established

gold standard.

Adult scoliosis has been broadly divided into three major groups by Aebi M. et al-

Type I Primary or ‘de novo’ scoliosis

Type II Idiopathic adolescent scoliosis with progression in adult life

IIa : without secondary degenerative change

IIb: with secondary degenerative change

Type III Secondary adult curves- due to leg discrepancy, oblique pelvis, lumbosacral transitional anomaly, neuromuscular or congenital scoliosis, trauma, iatrogenic or due to metabolic disease. Grubb SA, Lipscomb HJ, Coonrad RW (1988) Degenerative adult onset scoliosis. Spine 13: 241 – 245

Grubb SA, Lipscomb HJ (1992) Diagnostic findings in painful adult scoliosis. Spine 17(5): 518 – 527

Risk factors for curve progression Faster progression with curve greater than 30º.

More than 30% rotation of apical vertebra.

6mm or greater lateral listhesis

L5-S1 disc degeneration

Osteoporosis

Background

Standard radiographs may provide us with clues regarding the primary or secondary nature of the curves.

Secondary degenerative scoliosis often tends to be expressed more strongly, less osteoporotic and longer than its primary counterpart.

Schwab et al presented a classification system based purely on the measurements of the endplate obliquity of L3 in the frontal plane.

Type 1 lordosis > 55°, L3 obliquity < 15°

Type 2 lordosis 35 – 55°, L3 obliquity 15 – 25°

Type 3 lordosis < 35°, L3 obliquity > 25° Schwab, F, el-Fegoun, AB, Gamez, L, Goodman, H, Farcy, JP (2005) A lumbar classification of scoliosis in the adult patient: preliminary approach. Spine 30: pp. 1670-1673

BackgroundPrimary degenerative adult scoliosis is most commonly seen in the lumbar spine and results from segmental degeneration.

Asymmetric degeneration of the disc/ facet joints results in asymmetric loading of the spinal segment resulting in deformity.

Asymmetric

degeneration

Asymmetric loading

Asymmetric deformity

The presence of the deformity then triggers further asymmetric loading resulting in a vicious circle.

Progressive degeneration and deformity often leads to central and foraminal stenosis.

Aebi, M. "The adult scoliosis." European Spine Journal 14.10 (2005): 925-948.

Clinical Manifestation

Back pain- most frequent clinical problem. Can be either localised, radicular, or due to secondary muscular

fatigue. Claudication/ radicular pain Neurological deficit Increasing deformity

Once the curve reaches a certain extent, progression automatically follows.

Cosmesis- although not as significant as in adolescent scoliosis, with improvements in quality of life into older age, this is becoming more important.

Concomitant osteoporosis aggravates the clinical picture.

Ellwitz, J, and Gupta M. "Adult Degenerative Scoliosis." Spine Surgery Basics. Springer Berlin Heidelberg, 2014. 247-258.

Diagnostic Work- up

Standard Radiographs

Whole spine X Rays: Indispensable. Frontal and lateral planes with the centre of the skull and pelvis

included. Spot views of the lumbar spine Oblique radiographs to assess facet joints and neural foramina Functional views including side bending, flexion and extension

films.

Aebi, M. "The adult scoliosis." European Spine Journal 14.10.2005: 925-948.Kim H, Kim HS, Moon ES, et al. Scoliosis imaging: What radiologists should know. RadioGraphics 2010 30:7, 1823-1842

Standard radiographs

• Spinal curvature (Cobb angle)• Asymmetric disc degeneration• Lateral listhesis• Rotation of vertebrae

Plain radiographs depicting measurement of the cobb angle.Maximal displacement of the apical vertebra is arrowed.

Standard Radiographs

Placement of the head over the pelvis results in less energy expenditure with movement, less stress in adjacent segments and correlates with less symptoms.

Sagittal balance is measured with a plumb line from the posterior aspect of the superior end plate of C7 (other authors use T3). If the line passes through the posterior aspect of the S1 endplate,

the alignment is neutral.

Alternatively, some authors also describe a line from the odontoid passing through the femoral heads but that may not be feasible depending on the coverage of the radiograph.

Ellwitz, J, and Gupta M. "Adult Degenerative Scoliosis." Spine Surgery Basics. Springer Berlin Heidelberg, 2014. 247-258.

Sagittal balance, C7-S1 plumb line

Negative balance Positive balanceBalanced

Standard Radiographs

Coronal balance is assessed by constructing a line that bisects the sacrum and extends upwards to pass through the centre of the C7 vertebral body and should normally bisect the head.

Any deviation from this would be termed as right or left decompensation.

Other parameters that may be useful and have shown correlation with pain scores are L3 or L4 tilt angle, listhesis, thoracolumbar kyphosis and loss or lumbar lordosis.

Cobb angle, plumb line, pelvic tilt and level of listhesis did not show any correlation with pain scores.

CT may be useful in some cases to assess complex 3 dimentional curves.

Ellwitz, J, and Gupta M. "Adult Degenerative Scoliosis." Spine Surgery Basics. Springer Berlin Heidelberg, 2014. 247-258.Schwab F, Smith V, Biserni M et al, Adult sco- liosis: a quantitative radiographic and clinical analysis. Spine 2002. 27(4):387–392

Coronal and sagittal plumb lines

Vertical line from C7 passes throughmid S1

Vertical line from C7 Passes through mid S1

Coronal imbalance

Right over balanced Balanced Left over balanced

Plain films – side bending views

Primary curve centered at L4Secondary curve at L2-3

Primary curve isnot corrected on bending.Secondary curve is corrected.

Determines if curveis fixed or otherwise.

Progressive worsening of scoliosis

2009 2011 2014Comparison with previous radiographs shows increasing curvature; increasing lateral listhesis of L3 over L4 and increasing spondylosis with progressive degeneration at L2-3 space

Role of CT Imaging (1)

• Spinal curvature• Asymmetric disc degeneration• Lateral listhesis• Tilt of vertebrae• Vertebral body rotation• Pelvic tilt

Role of CT imaging (2)

• Osseous elements of degeneration

• Osteophytic characterisation

• Bone density

• Pedicle size prior to surgery

• Instrumentation positioning

• Instrumentation failure

Role of CT imaging (3)

CT imaging demonstrates

Vacuum phenomenon

Multilevel disc degeneration

Rotation of vertebra

Exit foraminal narrowing

Role of CT imaging (4) Facetal arthropathy

Protruding facets narrow the lateral recesses,compress the traversing roots and contribute to canal stenosis.

CT 3D volume rendering

Allows for demonstration of - Rotation of vertebral bodies

Asymmetric disc degenerationPelvic tilt

Exit foraminal narrowing

Magnetic Resonance Imaging

Ideal for assessing neural compromise and disc degeneration.

If contraindicated, CT myelogram is a good alternative, and simultanously produces images for 3D reformatting.

Asymmetric disc degeneration at level of scoliosis

Many facets of degeneration

Lateral recess stenosis

Facetal arthropathyThickening of ligamentum flavum

Interspinous bursal thickening

Spinal stenosis

MR imaging depicting

• Narrowing of lower lumbar central canal

• Degenerative disc bulges

• Facetal arthropathy

• Ligamentum flavum thickening (arrow)

Coronal MR imaging

Demonstrates lateral listhesisExit foraminal narrowing on concave side (arrowed)Stretched nerves on convex side

Treatment

Must be tailored to individual patient.

Medication, facet joint injections,epidural blocks, root blocks, exercises and immobilization are non surgical options with limited success.

Surgical treatment options aim to achieve neural decompression, correction and stabilisation of the deformity and functional restoration.

Ellwitz, J, and Gupta M. "Adult Degenerative Scoliosis." Spine Surgery Basics. Springer Berlin Heidelberg, 2014. 247-258.Gupta M (2003) Degenerative scoliosis, options for sur- gical management. Orthop Clin North Am 34:269–279

Transpedicular instrumentation with disc cages

PretreatmentDisc cages (arrows)

Correct positioning of screws

Pedicular screws should not breach the medial margin before traversing the vertebral body; should be less than 2 mm beyond the anterior vertebral margin; without any lucency around the tip; and should be intact. On follow up, its position should be unaltered.

Lumbo-pelvic fixation

This technically demanding procedure is performed in patients with L5 S1 mobility, mainly to relieve pain.

Jones, Clifford B., Debra L. Sietsema, and Martin F. Hoffmann. "Can lumbopelvic fixation salvage unstable complex sacral fractures?." Clinical Orthopaedics and Related Research® 470.8 (2012): 2132-2141.

Fusion cages and bone graft to aid fusion Arrows denote fusion cages Speckled appearance of bone graft posteriorly

Fusion bony mass

…indicates succesful fusion.

Examples of failure of surgery for degenerative scoliosis

Failure of fusion due to screw loosening

No bone in disc space at L4-5

Lucency along the screws (loosening)

Mild anterior listhesis

Failure due to fracture below the prosthesis

Pretreatment Long segment fusion

Periprosthetic fracture

Conclusion

Adult degenerative scoliosis is an increasingly challenging day to day radiological demand

Imaging requires careful correlation between plain films, CT and MR scans

Plain films are useful in ascertaining balance, progress and as a followup post treatment

CT imaging is useful in demonstrating bony details, surgical planning and in ascertaining prosthesis

MR imaging will determine the effects on the neural structures and for reviewing post treatment complications

End