Be aware of 3 important things:
1) Besides the average universal average, the value may differ greatly between people, for example, generally, the shorther you are, the higher the ratio is (that is, the tibia is relatively shorter; this may became a further "advantage" for tibial lenghtening versus femurs when evaluating both).
2) The value is diferent between diferent populations and countries, sometimes a lot.
3) Manual measurements are useless. The accurate measures can only be obtained by an Rx to full legs.