Four Bar Peg Leg

Lower limb amputees throughout recorded history have worn a peg leg, and it is still one of the most commonly used devices in many parts of the developing world. It is still provided in North America today for selected cases, primarily because the simplicity of the design can make it useful as a waterproof prosthesis for showering and marine activities.

I recently met a gentleman in New Mexico who had fashioned his own bent-knee peg leg from a discarded wooden crutch. He was born with a congenital anomaly that resulted in the analogue of a long transtibial amputation with an unstable knee joint. For many years, he was able to walk with a joints & corset style prosthesis, but over time his residual limb became increasingly unstable and ultimately contracted in 90 degrees of flexion.

From palpation, it appears that he may have had a Brown procedure to centralize the fibula under a short proximal tibial remnant. The literature suggests that many of these procedures did not result in a knee joint that was stable into adulthood, so it is rarely performed today.

I was asked to examine him to see if a more conventional prosthesis could offer more function than his do-it-yourself prosthesis. After an extensive discussion, it became clear that what he had evolved based on his experience was probably the most functional alternative for his needs. Despite the limited durability and ungainly gait of his wooden crutch peg, it allowed him to walk for short distances. More importantly, it could be quickly removed whenever the bent-knee configuration was a problem, such as whenever he needed to enter a confined space such as a car or restaurant booth. Without major surgery to try and correct the fixed contracture, which he did not want to risk, a more sophisticated prosthesis would provide few advantages.

This experience made me think of other amputees who also preferred a peg leg, most notably Bill Veeck, former owner of the Chicago White Sox, a transfemoral amputee who insisted on wearing a wooden knee-shin set-up that terminated in a rubber pod rather than a foot and included a built-in ashtray in the calf. For an excerpt from Veeck's autobiography, visit www.press.uchicago.edu.

While I was at Duke University, I had the opportunity to meet a fellow who had precisely the opposite problem from the gentleman from New Mexico. The North Carolina man had sustained a short transtibial amputation secondary to trauma, and it had unfortunately fused in full extension, preventing him from using a bent-knee prosthesis. He had tried a number of transtibial prostheses and various components but found that the anthropomorphic foot often got in the way and forced him to vault on the sound side to be sure to clear the toe in midswing. Eventually, he discarded the prosthetic ankle-foot mechanisms and replaced them with a wooden peg.


This gentleman presented with a short transtibial amputation that was fused in full extension, making walking and particularly sitting with a transtibial prosthesis awkward.
This gentleman presented with a short transtibial amputation that was fused in full extension, making walking and particularly sitting with a transtibial prosthesis awkward.

Having been trained as a carpenter, he hand-carved a cypress log and slipped it over the pylon protruding from the bottom of his socket. This proved more practical than a foot because he no longer had to worry about clearing the toe of a shoe in swing. But, the stiff-knee peg still made sitting difficult and kneeling impossible, due to the protruding shin segment.

We brainstormed many possible approaches together and ultimately settled on the incorporation of a locking polycentric knee, intended for use with knee disarticulation prostheses, between the socket and his peg. This allowed him to retain the advantages of a "footless" configuration for stiff-legged walking, but to unlock and flex the peg for sitting or kneeling.


Incorporating a locking four bar knee between the socket and peg allowed him to flex the peg underneath the socket, making sitting and kneeling possible.
Incorporating a locking four bar knee between the socket and peg allowed him to flex the peg underneath the socket, making sitting and kneeling possible.

So, even though rehab experts commonly think of peg legs as primitive solutions, this technology is still sometimes the most practical solution for special cases. As the New Mexico and North Carolina cases indicate, this is particularly true when the knee is fused, whether in extension or flexion.



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