The developmental anatomy of pes valgo planus.
Pes planus or flatfoot becomes a medical problem only when symptoms develop. The mere absence of a well-formed medial longitudinal arch does not necessarily imply pathology. Many apparently "flat feet" demonstrate congruent joints, and the extremities function normally. The size and shape, as well as the angles of declination for the talus or astragulers and the calcaneus or os calcis, are most often determined at the moment of fertilization by the genes of the patients. The zygote or fertilized ovum is a first totipotent. Cell division normally occurs as development proceeds, but the embryo is vulnerable to alterations of the cell cycle. Teratogenic substances can induce death or substantial structural modifications to the developing fetus. The post-World War II tragedy of the medical use of the drug thalidomide in pregnant mothers resulting in amelia is testimony as to how the lower extremity can be adversely affected. Early chromosomal aberrations including duplication, deletion, breakage, inversion, translocation, and mosaicism have been shown to be involved in faulty development of the foot, and there is no reason not to implicate pes valgo planus to these events. Intrauterine development apart from the genetic considerations just mentioned place the fetus under additional jeopardy. Even extraembryonic membranes can form strands of tissue that can entangle the delicate developing foot plate, and calcaneovalgus deformities could conceivably be established. The developing embryo and fetus first demonstrate a blastema that forms limb buds on the ventral caudal aspect. Anlage of the scleroblastema and myoblastema of the prospective leg and foot develop in the presence of nerve trunks. Such nerves are related to the lumbosacral plexus and they are thought to exert inductive developmental influences. Interference with any of these events may be implicated in pedal deformities such as pes valgo planus. This is also true of subsequent morphogenetic events involving embryonic rotations, osteogenesis, and myogenesis. Many pedal deformities have congenital basis and it is clear that pes valgo planus is one of them. Post-natal structural changes further accentuate underlying etiologies. For example, the calcaneus normally exhibits a varus position at birth, but this feature diminishes until the cessation of bone growth. The adult talar neck-calcaneal angle is normally about 24 degrees, representing a 6-degrees reduction from that of 30 degrees, which is demonstrated at birth.(ABSTRACT TRUNCATED AT 400 WORDS)
McCarthy
D J
DJ
Podiatric Section, VA Medical Center, Baltimore, Maryland.
D002869:Chromosome Aberrations; D005314:Embryonic and Fetal Development; D005260:Female; D005413:Flatfoot / Q000196:embryology* / Q000235:genetics; D005528:Foot / Q000196:embryology; D006801:Humans; D009024:Morphogenesis; D011247:Pregnancy