Imaging Guidelines for Suspected Scoliosis

Initial Radiographic Evaluation

• The American College of Radiology recommends obtaining upright postero‑anterior (PA) and lateral full‑spine radiographs to confirm a lateral curvature ≥ 10°, exclude congenital vertebral anomalies, and measure the Cobb angle for severity assessment. 1
• Standing PA and lateral radiographs that include the cervical, thoracic, and lumbar regions constitute the primary diagnostic modality for scoliosis. 2
• Radiographs should be used to stage skeletal maturity with the Risser classification, which guides prognosis and follow‑up intervals. 3

Age‑Specific Imaging Strategies

• For adolescent idiopathic scoliosis (ages 10‑18 yr), which accounts for roughly 75‑80 % of scoliosis cases, upright radiographs alone are generally sufficient for the initial work‑up. 4
• In congenital scoliosis, a combined approach of upright radiographs and magnetic resonance imaging (MRI) of the entire spine is advised to delineate both bony and neural abnormalities. 5
• For juvenile idiopathic scoliosis (ages 4‑9 yr), both radiographs and MRI are recommended because of the higher prevalence of intraspinal anomalies. 5

MRI Indications

• The American College of Radiology advises adding a non‑contrast MRI of the whole spine when any of the following risk factors are present:

  • Left‑sided thoracic curve pattern (atypical for idiopathic scoliosis) – 2
  • Absence of apical segment lordosis or hyper‑kyphosis – 2
  • Rapid curve progression (> 1° per month) – 3
  • Functionally disruptive pain – 3
  • Focal neurologic deficits on examination – 1
  • Male sex (idiopathic scoliosis is more common in females) – 3
  • Pes cavus foot deformity – 2

• MRI detects intraspinal anomalies in 2‑4 % of adolescents with idiopathic scoliosis; identified lesions include:

  • Chiari I malformation – 5
  • Cord syrinx / syringohydromyelia – 2
  • Tethered cord – 2
  • Rare intrinsic spinal cord tumors – 5

• In congenital scoliosis, intraspinal anomalies occur in 21‑43 % of patients, and a normal neurologic exam predicts a normal MRI with only ≈ 62 % accuracy; therefore, MRI is essential regardless of exam findings. 1

Computed Tomography (CT)

• CT is not routinely indicated for the initial assessment of idiopathic scoliosis. 6
• CT is valuable for:
  
  • Detailed bony anatomy evaluation in congenital scoliosis – 4
  • Characterizing the osseous septum in type I split‑cord malformations – 2
  • Pre‑surgical planning, which reduces pedicle‑screw misplacement from 15.3 % to 6.5 % when CT‑assisted navigation is used. – 2

Nuclear Medicine

• Tc‑99m bone scanning is not a primary imaging modality for scoliosis because it provides no information on the neural axis. 7

Clinical Examination Findings

• The presence of cutaneous stigmata—such as hemangiomas, nevi, dermal appendages, or sinus tracts—suggests underlying spinal dysraphism; when any are identified, MRI of the whole spine is mandatory. 8

Common Pitfalls to Avoid

• Do not rely solely on physical examination to exclude intraspinal anomalies in congenital scoliosis; MRI remains required even with normal neurologic findings. 2
• Avoid routine MRI in typical adolescent idiopathic scoliosis without risk factors, as it seldom alters surgical planning in neurologically intact patients. 6
• Supine radiographs should not be used for initial diagnosis; upright films are necessary to assess the true deformity under physiologic loading. 3
• Always assess skeletal maturity (Risser stage) because it determines the risk of curve progression and informs follow‑up intervals. 9

Cobb Angle Measurement Guidelines for Scoliosis

Definition and Measurement Technique

• The Cobb angle is measured on a standing postero‑anterior spinal radiograph by identifying the most tilted vertebrae at the superior and inferior limits of the curve, drawing lines along their endplates, and measuring the angle formed by the perpendiculars to those lines (or equivalently summing the tilt angles of the two end vertebrae). 10

Imaging Protocol

• For accurate Cobb angle assessment, obtain a standing PA full‑spine radiograph that captures the cervical, thoracic, and lumbar regions, ensuring the spine is imaged under physiologic loading. 10
• Use a PA projection rather than an anteroposterior projection to minimize breast radiation dose, and include the entire spine from cervical to lumbar levels in the image. 10

Skeletal Maturity Assessment

• Assess skeletal maturity on the same radiograph using the Risser classification, as maturity level influences curve progression risk and follow‑up scheduling. 10

Diagnostic Threshold

• A lateral curvature of 10° or greater on a standing PA radiograph defines scoliosis by convention. 10

American College of Radiology Guidelines for Imaging in Suspected Scoliosis

Initial Radiographic Protocol

• The ACR recommends obtaining standing postero‑anterior (PA) and lateral full‑spine radiographs as the primary imaging study for any patient with suspected scoliosis, covering the cervical, thoracic, and lumbar regions to confirm a lateral curvature ≥ 10°, measure the Cobb angle, evaluate skeletal maturity with the Risser index, and exclude congenital vertebral anomalies【11】.

Radiation Dose Optimization

• The ACR advises using a PA projection rather than an anteroposterior (AP) view to lower breast radiation exposure by increasing the distance between the breasts and the X‑ray source【11】.
• When available, low‑dose digital radiography or computed radiography techniques should be employed to further reduce patient dose【11】.

Follow‑up Imaging Frequency

• During active monitoring, follow‑up radiographs should be performed no more frequently than once every six months【12】.

MRI Indications and Use

• The ACR recommends adding a non‑contrast MRI of the entire spine when any of the following risk factors are present: left‑sided thoracic curve, absence of apical lordosis or presence of kyphosis, rapid curve progression > 1° per month, functionally disruptive pain, focal neurologic deficits, male sex, pes cavus foot deformity, or cutaneous stigmata suggestive of spinal dysraphism【11】.
• Intravenous gadolinium‑based contrast is not routinely required for scoliosis MRI; it should be reserved for cases where tumor or infection is suspected【11】【12】.

Computed Tomography (CT)

• CT is not indicated for the initial assessment of idiopathic scoliosis【11】.
• CT may be used for limited indications such as characterizing bony lesions (e.g., nidus of an osteoid osteoma) and should be performed with low‑dose protocols whenever possible【11】【12】.

Nuclear Medicine (Bone Scintigraphy)

• Tc‑99m bone scanning is not a primary imaging modality for scoliosis because it lacks neural‑axis information and has low specificity【11】【12】.
• Bone scintigraphy can be considered in painful scoliosis when primary bone tumors, spondylolysis, or infection are suspected, but MRI remains the preferred second‑line study【11】【12】.

Assessment of Skeletal Maturity

• The ACR emphasizes evaluating skeletal maturity using the Risser index on the initial radiographs, as this metric predicts curve progression risk and guides follow‑up intervals【11】【12】.

Imaging Pitfalls to Avoid

• Physical examination alone should not be used to exclude intraspinal anomalies in congenital scoliosis; MRI is mandatory even with a normal neurologic exam because exam accuracy is only ~62%【12】.
• Routine MRI is not recommended for typical adolescent idiopathic scoliosis without risk factors, since it rarely changes surgical planning in neurologically intact patients【11】.
• Lateral radiographs should not be obtained at every follow‑up visit; they are reserved for the initial evaluation and when clinical suspicion of sagittal balance change arises【11】.