1. Templating – what is the evidence?
07 April 2019
Templating – what is the evidence?
Michael Whitehouse
Consultant Senior Lecturer
Bristol SpR Teaching, July 2017

2. Disclosures Member of Lot 2 statistical analysis team for NJR
07 April 2019
Disclosures
Member of Lot 2 statistical analysis team for NJR
Institutional Research funding/support
Stryker, DePuy, JRI, Ceramtec
Fellowship funding
Royal College of Surgeons of England, British Hip Society McMinn Scholarship, BOA/Zimmer travelling fellow
Institutional Teaching funding
Hearaeus, DePuy

3. How should we calibrate?
07 April 2019
How should we calibrate?
Spheres
Discs
Flexible frames
Adhesive markers
Coins
Assumed magnification

4. Mean hip height between 12 and 20cm above detector +/- 10cm
07 April 2019
Mean hip height between 12 and 20cm above detector +/- 10cm

5. 07 April 2019
Attempt to position marker in coronal plane of hip. Mean error of 7% (0-26%)

6. 07 April 2019
At level of the greater trochanter with no skin overlap visible on film best if marker used

7. 07 April 2019
But… if mean magnification known, presumed magnification accurate to within 0.5%

8. 07 April 2019
You do need to know and check your own departments magnification factor – it may be between 115 and 127%

9. 07 April 2019
Assumed magnification may be more accurate than calibration with markers

10. How should we calibrate?
07 April 2019
How should we calibrate?
If you use a marker, place it in coronal plane of hip
Reproducible and reliable positioning and films
If you use assumed magnification, know what your is, not someone else’s
Caution with importing images from other systems

11. What should we use to template?
07 April 2019
What should we use to template?
Acetate on film
Hard copy film printing
Acetate on digital
Need to get hold of/dig out acetate templates
Digital on digital
Licencing, number of terminals, web based

12. Digital on digital As accurate as acetate on film
07 April 2019
Digital on digital As accurate as acetate on film

13. Acetate on digital As accurate as digital, may be quicker and cheaper
07 April 2019
Acetate on digital As accurate as digital, may be quicker and cheaper

14. How accurate is templating?
07 April 2019
How accurate is templating?

15. How accurate is templating?
07 April 2019
How accurate is templating?
Most research suggests:
Correlation between observers of
To the correct size for 50-70%
To within one size for 70-90%
To within three sizes (!) in 100%

16. 07 April 2019
How accurate is templating? Accuracy can be improved with predictive models

17. What factors do we need to consider when templating?
07 April 2019
What factors do we need to consider when templating?

18. Adequacy of x-rays – as low as 6% if strict criteria applied
07 April 2019
Adequacy of x-rays – as low as 6% if strict criteria applied

19. 07 April 2019
BMI – does not effect accuracy of templating with marker in ”standard” position

20. Femoral offset Underestimated on AP pelvis > AP hip (⏆5mm)
07 April 2019
Femoral offset Underestimated on AP pelvis > AP hip (⏆5mm)

21. Femoral offset Accurately assessed on AP hips c.f. CT
07 April 2019
Femoral offset Accurately assessed on AP hips c.f. CT

22. Experience/Training Surprisingly little effect on templating
07 April 2019
Experience/Training Surprisingly little effect on templating

23. Beware common errors Inferior cup position & lateral cup position
07 April 2019
Beware common errors Inferior cup position & lateral cup position

24. 07 April 2019
Is 3D templating needed?

25. Probably not unless you want your patient to glow in the dark…
07 April 2019
Probably not unless you want your patient to glow in the dark…

26. Don’t forget, you need to template all of your plans….

27. Thank you