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Sphericity Deviation Score

Sphericity Deviation Score. Hitesh Shah. SDS A quantitative outcome measure for LCPD that assesses the sphericity of the femoral head. Sphericity. Sphericity. Quantitative measure of sphericity. Late adult life. Quantitative measure of sphericity. Late adult life.

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Sphericity Deviation Score

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  1. Sphericity Deviation Score Hitesh Shah

  2. SDS • A quantitative outcome measure • for LCPD • that assesses the • sphericity of the femoral head

  3. Sphericity

  4. Sphericity

  5. Quantitative measure of sphericity Late adult life

  6. Quantitative measure of sphericity Late adult life • Two reference points are marked on the margins of the femoral head.

  7. Quantitative measure of sphericity At healing • Two reference points are marked on the margins of the femoral head. • If the growth plate is open the reference points are marked at the margins of the growth plate

  8. Quantitative measure of sphericity At healing • Two reference points are marked on the margins of the femoral head. • If the growth plate is open the reference points are marked at the margins of the growth plate

  9. Quantitative measure of sphericity Late adult life • A circle is drawn connecting these two points.....

  10. Quantitative measure of sphericity Late adult life • The size of the circle is adjusted to touch as many points on the articular margin as possible without extending outside the head

  11. Quantitative measure of sphericity Late adult life • Maximum inscribed circle - MIC

  12. Quantitative measure of sphericity Late adult life • Another concentric circle is drawn to just touch the outer limits of the articular margin without extending into the head

  13. Quantitative measure of sphericity Late adult life • Minimum circumscribed circle - MCC

  14. Sphericity deviation score Ellipsoid deformation = Or Roundness error (AP)= Roundness error (lat) =

  15. Sphericity deviation score Ellipsoid deformation Roundness error Lateral Roundness error AP

  16. Sphericity deviation score SDS= Roundness error AP + Roundness error lateral + Ellipsoid deformation

  17. Quantitative measure of sphericity • Three measures of deviation from sphericity are computed: • Roundness error in the AP view • Roundness error in the Lateral view • Degree of ellipsoid deformation

  18. Quantitative measure of sphericity Late adult life • Roundness error is the difference in the radii of the MCC and MIC.

  19. Diagrammatic representation

  20. Ellipsoid deformation is the difference in the radii of the femoral head in the AP and lateral views.

  21. Quantitative measure of sphericity • The • Roundness Error in AP view • Roundness Error in Lat view • Ellipsoid deformation are added to obtain the Sphericity Deviation Score

  22. Quantitative measure of sphericity • The • Roundness Error in AP view • Roundness Error in Lat view

  23. Quantitative measure of sphericity • Ellipsoid deformation

  24. Sphericity Deviation Score (SDS) • The Intra-Class Correlation coefficient for inter-observer reproducibility is very good: ICC: 0.91 (95% CI: 0.88, 0.93; p < 0.001)

  25. 100 80 60 40 20 0 SPHERICITY DEVIATION SCORE I II III IV V STULBERG CLASS

  26. 100 80 60 40 20 0 SPHERICITY DEVIATION SCORE I II III IV V STULBERG CLASS

  27. 100 80 60 40 20 0 SPHERICITY DEVIATION SCORE I II III IV V STULBERG CLASS

  28. 100 80 60 40 20 0 SPHERICITY DEVIATION SCORE I II III IV V STULBERG CLASS

  29. 100 80 60 40 20 0 SPHERICITY DEVIATION SCORE I II III IV V STULBERG CLASS

  30. SDS at healing of the disease

  31. Roundness error AP = 0Roundness error Lat = 0Ellipsoid deformation = 0Sphericity Deviation Score 0

  32. Roundness error AP = 0Roundness error Lat = 0Ellipsoid deformation = 0Sphericity Deviation Score 0 Stulberg Class at skeletal maturity : Class I

  33. Roundness error AP = 18Roundness error Lat = 40Ellipsoid deformation = 10Sphericity Deviation Score 68

  34. Roundness error AP = 18Roundness error Lat = 40Ellipsoid deformation = 10Sphericity Deviation Score 68 Stulberg Class at skeletal maturity : Class IV

  35. SDS at healing & skeletal maturity 80 60 40 20 0 • Spearman Correlation: - 0.75 Sphericity Deviation Score at skeletal maturity 0 20 40 60 Sphericity Deviation Score at healing

  36. 100 80 60 40 20 0 Predicted probability of hip falling into Stulberg Class I or II at skeletal maturity 0 10 20 30 40 50 60 Sphericity Deviation Score at Healing of LCPD

  37. The Sphericity Deviation Score • It can be applied as soon as LCPD heals • Consequently

  38. The Sphericity Deviation Score • It can be applied as soon as LCPD heals • Consequently • The duration of future outcome studies can be reduced by at least 4 years • Mean age at onset of disease……. 8.01 years • Mean age at healing ……………… 11.67 years • Mean age at skeletal maturity……. 16.12 years

  39. The Sphericity Deviation Score • It can be applied as soon as LCPD heals • Consequently • The duration of future outcome studies can be reduced by at least 4 years • Mean age at onset of disease……. 8.01 years • Mean age at healing ……………… 11.67 years • Mean age at skeletal maturity……. 16.12 years

  40. The Sphericity Deviation Score • Is a continuous measure

  41. The Sphericity Deviation Score • Is a continuous measure • Consequently

  42. The Sphericity Deviation Score • Is a continuous measure • Consequently • The sample size needed for future studies can be reduced substantially

  43. Thank you

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