The Caton-Deschamps Index (CDI) is a measure of patella height.
Exam: lateral radiograph of the knee with knee flexed from 10 to 80 degrees
Parameters:
(1) length of the articular surface of the patella (along posterior surface) in cm
(2) distance from the distal end of the articular facet of the patella to the anterior corner of the superior tibial epiphysis (running along the patellar tendon from the patella to the tibia) in cm
index =
= (length of articular surface) / (distance from patella to tibia)
Interpretation:
• The normal CDI is 0.6 to 1.2 (Rethlesen et al).
• The ratio is affected by the age of the patient in children and adolescents.
Age
Ratio
6-7 years
1.27 +/- 0.25
8-9 years
1.15 +/- 0.17
10-11 years
1.11 +/- 0.19
12-13 years
1.07 +/- 0.17
14-15 years
1.07 +/- 0.18
from Thevenin-Lemoine et al (2011)
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