One of my my favorite Gary Larson cartoons depicts two cows sitting on a sofa with a phone on the coffee table wildly ringing. One bovine says to the other, “Well, there it goes again. …and here we sit without opposable thumbs.”

The cartoonist had it right. An opposable thumb–one that can swing forward out of the plane of the palm and face (oppose) the other digits–provides a distinct functional advantage. In all of the animal realm, this feature is shared among humans and only some other primates. We can uniquely manipulate small objects (buttons, keys, paperclips) and artfully grasp larger ones (pickle jars, phone receivers).

A person with a missing thumb sees life’s opportunities and obstacles as if they were stationed far down the evolutionary tree. Hand surgeons have three main ways to help such people. Two weeks ago I described the method of lengthening the thumb remnant, and last week I outlined the technique of shortening the index finger and rotating it into the thumb position. I think of these as begging and borrowing, respectively.

The third technique, which I nickname stealing, works best when multiple digits may be missing from the same hand or the patient has need for a 5-digit hand. In either case, there is no thumb remnant to beg nor finger to borrow. Here the surgeon may resort to theft. The victim is the unsuspecting foot. And it turns out that the crime is merely a misdemeanor.

The shape of the big toe is almost identical to the thumb, so it is the favored mark, although its theft leaves an ugly crime scene. Stealing the second toe makes for a rather scrawny thumb but leaves a pleasantly contoured foot that can still wear flip-flops. The absence of either the first or second toe has minimal effect on the owner’s ability to walk, run, and even hang nine on the surfboard.

Toe-to-thumb transfer is a 6- to 12-hour operation requiring honed microsurgical skills. In the foot, nerves, arteries, veins, tendons, and bone supplying the donor toe are identified, freed from one another, and divided. The meticulously amputated toe is then attached to the hand, like tissue to like tissue. The bone ends are securely fixed to one another, usually with loops of wires or steel pins. Forearm muscles are sutured to the toe’s tendons in order to restore some motion, especially opposition. The blood vessels are 1/16th to 1/8th of an inch in diameter and are precisely sutured with nearly invisible suture material. This ensures that blood flows through but does not leak out. Over months, many nerve fibers regenerate and provide the new thumb with some sensation, certainly enough to answer the phone.

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