Do I Really Need My Pinky Toe?

Just the other day we saw this article in Popular Science written by Sally Zhang.  Sally obviously does not read our blog, but she got a lot of stuff right.

“If you’re born without a pinky toe or have an accident and it’s removed, you can completely do everything you wanted to do,” Dr. Anne Holly Johnson, instructor in orthopaedic surgery at Harvard Medical School, says.

Above you will see a photo of one of the gait guy’s feet.  It is quite clear from the photo that competent use of the pinky toe is not necessary for adequate, and possibly exceptionally skilled, foot function.  Here, check out this video of our foot in these 2 videos (here and here) for some advanced foot function (sans pinky toe). As you can see in the photo above, this 5th toe has likely never felt the ground, this is a fixed deformity.  Flexor and extensor function of the toe are intact, but it does not reach the ground and so assistance in gaining adequate purchase of the 5th metatarsal on the ground is absent. 

This brings us to a deeper question, what about the 5th metatarsal then? Is it necessary ?  Our answer even without deeper research is a solid “yes”. The foot tripod is severely compromised without the 5th metatarsal. The lateral stability of the foot is impaired without the 5th MET.  The natural locking of the calcaneocuboid joint mechanism will be impaired, the peroneal muscles that provide such critical lateral ankle and foot stability will have fascial planes and tendon attachments disengaged, the natural walking gait lateral to medial foot progression would be impaired, propulsion would be impaired and the list goes on and on. And, not even on the local foot/ankle level. Because, if you take out the function and stability of the lateral foot the hip is very likely to suffer lateral (frontal plane) stability deficits. Meaning, the gluteus medius and abdominal obliques will have more difficulty guarding frontal plane drift when in stance phase rendering all of the “cross over gait” risks (link) highly probable.  

So, not much exciting stuff here today. The presence of a functioning pinky toe does not appear to be critical but don’t take away its big brother neighbor, the 5th Metatarsal or trouble is just around the corner. Don’t believe us? Just ask anyone with a non-union fracture (Jones fracture) of the 5th metatarsal.

The answer goes back to the evolutionary history of humans, explains Dr. Anish Kadakia, assistant professor in orthopaedic surgery at Northwestern University. "Primates use their feet to grab, claw, to climb trees, but humans, we don’t need that function anymore,“ Kadakia says. "Clearly we’re not jumping up and down trees and using our feet to grab. We have toes embryologically, evolutionary for that particular reason because we descended from apes, but we don’t need them as people.”

The gait guys, working with 4 toes on each foot, one step ahead of evolution it seems.

Shawn and Ivo,

The gait guys

reference:

http://www.popsci.com/science/article/2013-05/fyi-do-i-really-need-my-pinky-toe?dom=tw&src=SOC