Mind you, the Troodon — a birdlike dinosaur — had partially opposable thumbs and Bambiraptor — a small, predatory dinosaur —could touch the outer two of its three digits together in an opposable grip. Fortunately, neither is around to demonstrate their dexterity.
Our hand today has two main functions (and that does not include letting other road users know you are upset at their driving). One is the ‘power grip’ which allowed us to hold axes and then develop tools, and the second is the ‘precision grip’, which needs the full range of thumb movement, allowing us to hold pens and led to written communication and eventually how to hold a scalpel.
Opposability of the thumb should not be confused with a precision grip as some animals possess semi-opposable thumbs yet are known to have extensive precision grips (Tufted Capuchins for example). Nevertheless, precision grips are usually only found in higher apes, and only in degrees significantly more restricted than in humans.
The hand is far more complex than you would imagine. It has 27 bones and there are four muscles in the forearm which act on just the thumb alone, plus another four muscles in the hand itself, pulling, pushing and rotating your thumb.
The hand has around 80 degrees of pronation (turning the palm to the floor), 40 degrees of abduction, and 50 degrees of flexion, and needs several muscles to be able to carry out these movements. Compared to the hand, the rest of the body is relatively much more simple.
Because of the complexity of the hand, this has led to specialization and we have a post graduate hand surgeon amongst our specialist orthopedic surgeons. Following trauma, we want to make sure you will always be able to order one beer or two! Familial hand conditions such as Dupuytrens Contracture also need a hand specialist to look at the degree of deformity.
For all information about our services go to www.bangkokpattayahospital.com
By Dr.Iain Corness