50 Years Ago in CORR: The Skeletal Development of the Foot Ronan O’Rahilly MD, Ernest Gardner MD, and DJ Gray PhD CORR 1960;16:7–14

Excerpt

The foot, like other parts of the skeleton, develops in an exquisitely sequential manner. O’Rahilly, Gardner, and Gray described these sequences in CORR in 1960 [3]: (1) the formation of small limb buds in the embryo about four weeks postovulation; (2) thickening of an ectodermal ridge that disappears by five weeks postovulation; (3) the formation of mesodermal condensations along the previous ectodermal ridge; (4) chondrification of the mesodermal condensations beginning the fifth week; (5) segmentation of the chondrified tissue into individual anlagen (“canonical elements”) that will become the bones; (6) ossification of the anlagen by perichondral and endochondral ossification. The spatial distribution and timing of these events varies depending upon the particular bone and its location. The mesodermal condensation develops in a proximodistal sequence. Chondrification of the mesoderm begins during the fifth postovulatory week in the femur and is completed in all canonical elements of the foot by the seventh postovulatory week. O’Rahilly et al. note, “…therefore, the number and the arrangements of these elements is determined prior to this time. It follows that anomalies in which the number of the skeletal elements is increased arise very early in intra-uterine life and the causative factors must act before 7 weeks of development.” …