Fig 1.
Comparison between histological and MRI findings.
Endochondral ossification was assessed according to modified Streeter’s classification (1949) [22]. Representative histology was shown below. 1: Phase 1; 2: phase 2; 3: phase 3; 4: phase 4; 5: phase 5; OS: phase OS.
Fig 2.
Morphometry of the femur and evaluation of cartilage canals at the epiphysis.
(A) Morphometry of the femur. Method for the measurement of femur length, ossified shaft length (OSL), femoral neck anteversion (∠FNA), femoral neck shaft angle (∠FNS), and obliquity of the shaft (∠OBS). fh-a: midpoint of the femoral head as seen from above; fh-b: midpoint of the femoral head as seen from the back; fn-a: midpoint of the femoral neck as seen from above; fn-b: midpoint of the femoral neck as seen from the back; gt: midpoint of the greater trochanter as seen from above; if: intercondylar fossa as seen from the back; lc: bottom point of the lateral condyle; le: most lateral point of the lateral epicondyle as seen from above; mc: bottom point of the medial condyle; me: most lateral point of the medial epicondyle as seen from above; pm: midpoint of the proximal metaphysis just below the lesser trochanter as seen from the back. (B) Evaluation of cartilage canals at the epiphysis. Cartilage canal formation was evaluated by counting the number of cartilage canals and dividing them into three stages (-: 0, +: 1–4, ++: >5).
Table 1.
Landmarks and semi-landmarks for Procrustes analysis.
Fig 3.
Femur development between CS18 and CS23 (before ossification).
Representative longitudinal section images and 3-D reconstructed images. Longitudinal section images were acquired using PCX-CT between CS18 and CS21 and 7-T MR imaging between CS22 and CS23. fh: femoral head; gt: greater trochanter; If: intercondylar fossa; lt: lesser trochanter; yellow arrow: phase 4 according to Streeter’s classification. See also S1, S2, S3, S4, S5 and S6 Movies.
Fig 4.
Representative cross-sectional view of the right femur during the early fetal period on 7-T MR image.
The crown–rump length (CRL) of each fetus is indicated below the images. Yellow arrow: phase 4; red arrow: phase 5 according to Streeter’s classification. The region between the yellow arrows at the diaphysis corresponds to phase OS. The region outside the yellow arrows corresponds to phases 1–3.
Fig 5.
Representative 3-D reconstruction of the right femur from the embryonic period to the early fetal period.
(A) Gross view, (B) proximal epiphysis (posterior view), (C) distal epiphysis. Numbers represent the crown–rump length (mm). Ossified region is indicated as purple. ff: femoral head fovea; fh: femoral head; lt: lesser trochanter; tf: trochanteric fossa. See also S7, S8 and S9 Movies.
Fig 6.
Growth and endochondral ossification of the femur according to crown–rump length (CRL).
(A) Femur length and ossified shaft length (OSL) according to CRL. (B) OSL-to-femur length ratio according to CRL.
Table 2.
Evaluation of cartilage canals.
Fig 7.
Femur modeling during the fetal period.
(A) Distribution of crown–rump length (CRL) according to ossified shaft length (OSL). (B) Distribution of femoral neck anteversion (∠FNA) according to OSL. (C) Distribution of femoral neck shaft angle (∠FNS) according to OSL. (D) Distribution of obliquity of the shaft (∠OBS) according to OSL. In the box plots, the bars represent the sample range, the boxes represent the second and third quartiles, and the middle line represents the median.
Fig 8.
Reconstructed Procrustes shape coordinates for the proximal epiphysis.
FH-f: center of the femoral head fovea; GT-l: most lateral point of the greater trochanter; GT-t: top of the greater trochanter; LT-b: bottom end of the lesser trochanter; LT-t: top of the lesser trochanter; LT-u: upper end of the lesser trochanter; FH13: 13 semi-landmarks from the upper end to the lower end of the femoral head along the plane passing through the midpoint of the femoral head, femoral neck, and greater trochanter.