Accuracy and reliability of virtual femur measurement from CT scan

In the application of scientific human skeletal variation in medico-legal matters, virtual anthropology is the current technique performed to examine skeleton and its body parts. Hence, this study was conducted to assess the accuracy and reliability of virtual femur measurement through intra and inter-observer error analysis, and comparison was made between the virtual and conventional methods.

A total of 15 femora were examined with four parameters i.e. maximum length of femur (FeMl), diameter of femoral head (FeHd), transverse diameter of midshaft (FeMd) and condylar breadth (FeCb). Osteometric board and vernier calipers were employed for the conventional method, while CT reconstructed images and Osirix MD software was utilised for the virtual method.

Results exhibited that there were no significant differences in the measurements by conventional and virtual methods. There were also no significant differences in the measurements by the intra or inter-observer error analyses. The intraclass correlation coefficients (ICC) were more than 0.95 by both intra and inter-observer error analyses. Technical error of measurement had displayed values within the acceptable ranges (rTEM <0.08 for intra-observer, <2.25 for inter-observer), and coefficient of reliability (R) indicated small measurement errors (R > 0.95 for intra-observer, R > 0.92 for inter-observer). By parameters, FeMl showed the highest R value (0.99) with the least error in different methods and observers (rTEM = 0.02-0.41%). Bland and Altman plots revealed points scattered close to zero indicating perfect agreement by both virtual and conventional methods. The mean differences for FeMl, FeHd, FeMd and FeCb measurements were 0.01 cm, -0.01 cm, 0.02 cm and 0.01 cm, respectively.

This brought to suggest that bone measurement by virtual method was highly accurate and reliable as in the conventional method. It is recommended for implementation in the future anthropological studies especially in countries with limited skeletal collection.