Objective: To understand the morphological details of the fibula, especially as it relates to the feasibility of retrograde intramedullary fibular nail use.

Materials and Methods: One-mm-thick slice Computed Tomography (CT) images of the left and right lower extremities of 40 patients were included in the study. Each CT image was reconstructed into a three-dimensional image using Mimic® 10.01 software. The authors measured the fibula in terms of total length, radius of curvature, fibular tip to isthmus distance, and inner diameter at the isthmus. Each parameter was analyzed and compared by sex, using the Mann-Whitney U test and the Wilcoxon sign rank test. All statistical analyses were performed in SPSS (Version 23.0, International Business Machines, Chicago, IL, USA).

Results: CT scans of 40 patients (21 female, mean age 59±15.91) were analyzed. The intraclass correlation coefficients between inter- and intra-observer were 0.743 to 0.921. The overall means and standard deviations were 342±21.2 mm for the total fibular length, 5.22±2.13 degree for radius of curvature, 87.03±14.27 mm for tip to isthmus distance, and 3.05±0.87 for isthmus inner diameter. Male participants had significant difference in measurements in terms of total fibular length as compared with female participants (p<0.001, male 356.25±18.84 mm, female 329.1±13.67). There was no statistically significant difference in radius of curvature, tip to isthmus distance, and isthmus inner diameter (p=0.912, 0.407, and 0.610, respectively). Comparison between left and right sides among participants of the same sex showed no statistically significant difference in any of the parameters in either sex (p=0.908 for total length, 0.583 for radius of curvature, 0.954 for tip-isthmus distance, and 0.908 for isthmus inner diameter in male participants, p=0.970, 0.554, 0.715, and 0.811 in female participants).

Conclusion: The retrograde fibular intramedullary nail can be safely used in the Thai population. There was no difference in regard to side or sex in terms of radius of curvature, tip to isthmus distance, and isthmus inner diameter. Appropriate pre-operative planning is necessary to achieve the safest and most adequate fixation.

Keywords: Fibula, Morphology, Anatomy, Three-dimensional, Mimic 10.01, Thai