Capassos method revisited: Comparison against conventional measurement tools for idiopathic scoliosi

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Capassos method re-visited Comparison against
conventional measurement tools for idiopathic
scoliosis

• N S Harshavardhana1, Dabke HV1, Debnath UK1,
  Freeman BJC2
• 1Queens Medical Centre, Nottingham (England)
• 2Royal Adelaide Hospital, North Terrace Adelaide
  (Australia)

3rd International Congress on Early Onset
Scoliosis (EOS), Nov 2009 Istanbul, TK
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Capassos method re-visited Comparison against
conventional measurement tools for idiopathic
scoliosis

• Presenter N Harshavardhana No
  Relationships
• Co-Authors HV Dabke No Relationships
• UK Debnath No Relationships
• BJC Freeman No Relationships

• Grants/Research Support
• Consultant
• Stock/Shareholder
• Speakers Bureau
• Other Financial Support

3rd International Congress on Early Onset
Scoliosis (ICEOS) Istanbul, TURKEY 2009 Authors
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Background Errors

• 90 methods of measurement described to quantify
  scoliosis (Capasso et al 1992)
• Cobb angle inaccurate for geometric statistical
  reasons (Beekman et al 1979, Robinson et al 1983
  Bunnell et al 1988)
• Statistical assessment validation of Cobb vs.
  Ferguson methods (George et al 1961 Lusskin
  1962)

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Background Errors

• Errors in taking radiograph
• Errors intrinsic to measurement method
• Error due to anatomical deformity of vertebra(e)
• Errors in end vertebra(e) selection technique
• Greater reproducibility by Capassos method
• JBJS(Br) 1996, 78(2) Page 339

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And Textbook says.....
(Page 143)

• A new method for radiographic evaluation of
  deformity in scoliosis
• Ital J Orthop traumatol. 1981, Apr7(1),
  127-36

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Capasso angle

• Based on bi-univocal principle
• Geometrically more valid
• Considers Scoliosis to be arc
• of a circumference of a circle
• Believed to be a true reflection of
• angular values
• Magnitude of scoliosis (S) 4a
• Capasso angle (a)

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Objectives

• To evaluate the sensitivity of Capassos method
  (CM) against-
• i) Oxford cobbometer (OC)
• ii) Traditional protractor (TP) as measurement
  tool for Cobb le in scoliosis
• To determine intra inter-observer reliability
  of these 3 methods

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Methods

• Measurement of 24 digital AP radiographs of
  scoliosis (12 X 15)
• 3 independent blinded observers on 3 occasions
  1/52 apart
• 3 methods-
• Oxford cobbometer
• Traditional protractor
• Capassos method

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Methods
Intra inter-observer reliability agreement
between 3 methods analysed statistically using
SPSS v16 Index case 1 Cobb angle of 30 degrees
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Methods
Index case 2 with cobb angle of 65 degrees
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Methods
Index case 3 with cobb angle of 92 degrees
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Results

• Mean Cobb Angle readings
• X-Angle (OC) 42.4 (1391)
• Traditional Protractor (TP) 45 (1689)
• Capassosmethod (CM) 70.4 (20148)
• Disagreement between CM against OC TP
  significant (plt0.01)
• CM overestimates the magnitude of scoliosis esp.
  curves lt 30

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Inter-observer correlation
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Discussion
Surgical decision-making is also driven by the
magnitude of scoliosis (in addition to skeletal
maturity, clinical appearance other
factors) Which is the most accurate, consistent
and reliable method for picking-up curve
progression ? What is the normal Capasso le
beyond which one considers a curve to be
scoliosis ?
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Conclusion

• CM is less reliable than OC TP esp. for
  smaller curves (lt 300)
• How practical is the Capasso angle ?
• A simple 3D measurement system to accurately
  define the magnitude is needed as current methods
  have limitations

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Bibliography

• 1) Cobb JR Outline for the study of scoliosis
• AAOS Inst Course Lect 1948 Vol 5, Pg 261-75
• 2) Lusskin R Curves and angles - A comparsion
  of scoliosis Mx Clin Orthop 1962, Vol 123, Pg
  232-5
• 3) Sevastikoglou JA et al Evaluation of
  relaibility of radiological methods for
  registration of Scoliosis Acta Orth.
  Scandinavica 1969, Vol 40, Pg 608-13
• Dawson EC et al Radiographic evaluation of
  scoliosis introduction of scoliosis chariot
• Clin Orthop 1978, Vol 131, Pg 151-55