Photos of Embryological Foot Types

   Detailed Anatomical Model of the Talus





Etiology of the Primus Metatarus Supinatus foot type


     If the talar head 'fully unwinds' (during the 1st trimester of the developing embryo), there is no foot imbalance.  When the foot is placed in its anatomical neutral position, the big toe rests on the ground.
     If the talar head (red arrow) does not 'fully unwind', there is a foot imbalance (e.g., Primus Metatarsus Supinatus).  When the foot is placed in its anatomical neutral position, the big toe does not rest on the ground.
     In the Primus Metatarsus Supinatus foot, during mid-stance, as the body’s weight is transferred anteriorly towards the forefoot, the hallux (big toe) does not touch the ground (Pressure Plate Analysis).  This occurs because the first metatarsal is elevated and inverted.  In order for the hallux (big toe) to become weight bearing, the foot must abnormally pronate (e.g., roll inward and downward).  This abnormal, gravity induced pronation, allows the hallux to reach the ground and become weight bearing during mid to late stance phase.