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Home / Spine Non Trauma / Spine radiography and sagittal balance
Spine Non Trauma

Spine radiography and sagittal balance

Spine X-rays, lumbar AP views and measurements of spinal sagittal balance

22 questions 4 source pages 1 images

Images appear with the first question taken from each source page — tap a question to open it.

22 questions
Q1Which conditions are listed under 'Spine - non trauma'?▸
  • RA – C1/2 instability, subaxial involvement, cranial settling
  • AS – pseudoarthrosis; DISH
  • Cervical myelopathy, OPLL, PID, dural tear
  • Spinal stenosis, degenerative scoliosis, spondylolysis, sagittal balance
  • Vertebroplasty, TB spine, pyogenic spine, spine metastasis, failed back syndrome
Q2What spinal manifestations of RA are listed on this section?▸
  • C1/2 instability
  • Subaxial involvement
  • Cranial settling
Q3Which cervical spine conditions are listed?▸
  • Cervical myelopathy
  • OPLL
  • PID
  • Dural tear
Q4Which degenerative/structural topics are listed?▸
  • Spinal stenosis
  • Degenerative scoliosis
  • Spondylolysis
  • Sagittal balance
Q5Which infective, neoplastic and miscellaneous topics are listed?▸
  • Vertebroplasty
  • TB spine
  • Pyogenic spine
  • Spine metastasis
  • Failed back syndrome
Q6Describe the AP X-ray findings in ankylosing spondylitis.▸
  • Squaring of vertebrae with marginal syndesmophytes
  • Bamboo spine appearance; trolley-track and dagger sign
  • Bilateral SIJ ankylosed, hips okay, no discovertebral lesion
  • Frontal alignment good, no osteopenia; need lateral XR for facet joint ankylosis
Q7What are the history and examination findings in AS, and how is it diagnosed?▸
  • Hx: PMHx, FHx, morning stiffness, SOB, pain, other joint or heel pain
  • PE: gait, loss of lumbar lordosis with increased thoracic kyphosis, horizontal gaze, chin-brow vertical angle, wall-to-occiput, Schober's test, chest expansion
  • SIJ: Faber and Gaenslen tests; neurological exam of LL; listen to heart and lungs, look at eyes and nails
  • Diagnosis: modified New York criteria - at least 1 clinical + 1 radiological criterion
  • Clinical: inflammatory back pain >3 months improved by exercise/worse with rest, reduced spine ROM, reduced chest expansion
  • Radiological: unilateral grade 3-4 or bilateral grade 2-4 SIJ changes
Q8What are the differentials of multiple syndesmophytes and of SIJ sclerosis?▸
  • Multiple syndesmophytes/ossification: DISH - non-marginal syndesmophytes, disc and SIJ spared, more common in older patients (DM)
  • SIJ sclerosis: osteitis condensans ilii (young women, iliac side)
  • Fibrodysplasia ossificans progressiva
Q9What is ankylosing spondylitis and what is the role of HLA-B27?▸
  • A systemic seronegative arthritis mainly affecting the axial skeleton
  • More common in young male patients with family history (HLA-B27)
  • Presents with back pain not relieved by rest, spine/hip stiffness, stooped posture, fracture
  • HLA-B27 is an MHC presenting intracellular protein to T cells, initiating an immune response through TNF
  • Patho hypotheses: misfolding -> homodimer triggering a pro-inflammatory response; arthritogenic peptide presented to autoreactive cytotoxic T cells
Q10What are the discovertebral lesions in AS and the causes of pseudoarthrosis?▸
  • Romanus lesion (50%): erosion at the anterolateral corner with surrounding sclerosis, posterior column spared
  • Andersson lesion (4%): erosion at the mid-endplate (anterior + middle column), posterior column spared
  • Pseudoarthrosis: secondary to fracture/Andersson lesion with posterior column involvement - all 3 columns
  • Causes (D Fang): acute fracture through fused segment, stress fracture, escape fusion -> need circumferential fusion
Q11How are deformities in ankylosing spondylitis managed?▸
  • Aim: posture (horizontal gaze), visceral function, prevent complications (fracture, pseudoarthrosis)
  • Medical: physio, NSAIDs, TNF-alpha antagonists (infliximab, adalimumab, etanercept)
  • Preop: anaesthetic/airway, biologics, lung function test, echo, steroid coverage, PPI; osteotomy site usually lumbar (wider canal, end of conus, no ribs, large correction power)
  • Osteotomies: SPO, Ponte, PSO, VCR; cervical osteotomy for chin-on-chest at C7/T1, aim CBVA within 10 degrees; PSO closing wedge preferred over SPO opening wedge
  • Complications: neurologic injury, SMA, aortic rupture, non-union, residual deformity
  • Instrumentation: U3L3; C8 root decompression; C7 laminectomy + partial lateral mass resection +/- C6 and T1 partial laminectomy
Q12How does SIJ involvement progress radiologically in ankylosing spondylitis?▸
  • X-ray SIJ progression: erosion, sclerosis and ankylosis
  • Assess with the Ferguson view (~20 degrees cranial)
  • First radiological sign is squaring of the vertebrae
Q13What blood tests and further imaging are requested in suspected AS?▸
  • Bloods: CBC, ESR, CRP, HLA-B27
  • XR of the thoracic and cervical spine; whole spine sagittal alignment
  • Need lateral XR for facet joint ankylosis; watch for vertebral collapse (osteoporosis)
Q14What types of spinal osteotomy are used for AS deformity correction?▸
  • SPO: laminectomy + pars
  • Ponte: SPO + facets
  • PSO: posterior elements + pedicle
  • Vertebral column resection (VCR)
  • Site usually lumbar: wider canal, end of conus, no ribs, large correction power
Q15What are the key points of cervical spine osteotomy in AS?▸
  • Indications: chin-on-chest; residual upper cervical kyphosis causing downward gaze after lumbar osteotomy
  • Aim to correct CBVA to within 10 degrees
  • Level C7/T1: wide canal, mobile root (C8), vertebral artery not entering lateral mass
  • PSO closing wedge better than SPO opening wedge: instability; oesophageal stretching causing dysphagia
  • Instrumentation U3L3; C8 root decompression; C7 laminectomy + partial lateral mass resection +/- C6 and T1 partial laminectomy
Q16How is pelvic incidence (PI) measured?▸
  • Angle between a line from the centre of the sacrum to the femoral head and a line perpendicular to the S1 endplate through its midpoint
  • PI = PT + SS
Q17What is the relationship of pelvic incidence to spondylolisthesis?▸
  • Direct relationship to the severity of spondylolisthesis
  • High PI: more shearing across L5/S1 and less lumbar lordosis
  • Body tries to keep sagittal balance by increasing lumbar lordosis
Q18How does the body compensate when lumbar lordosis reduces?▸
  • Pelvis rotates posteriorly, reducing the sacral slope
  • When the sacrum is vertical, the knee flexes to further compensate
Q19How is sagittal vertical axis (SVA) measured?📷▸
Diagram showing measurements for spinal sagittal balance
Diagram showing measurements for spinal sagittal balance
  • On standing long film X-ray
  • Line from the centre of C7 vertebral body perpendicular to the ground; measure horizontal distance from the posterosuperior corner of S1
  • Normal = within 5cm
Q20What is the relationship between sacral slope, pelvic tilt and pelvic incidence?▸
  • Sacral slope + pelvic tilt (positional) = pelvic incidence (morphology)
Q21What are the target values for spinopelvic harmony?▸
  • Lumbar lordosis = PI +/- 9 degrees
  • PT < 25
  • SVA < 50mm
  • Spinal curvature (spinopelvic harmony / cone of economy)
Q22Why does sagittal imbalance matter?▸
  • Imbalance leads to pain and progressive deformity
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