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Charles Radcliffe, Father of Prosthetic Biomechanics
By Sherry Metzger, MS  Professor Charles Radcliffe, MS, ME, is a
world-renowned engineer lauded as the father of prosthetic
biomechanics. He began his distinguished career in the orthotics
and prosthetics field in 1948 while in the US Navy as an
engineering officer in World War II. He learned of a research
opportunity at the University of California in Berkeley while
working on laminated plastic aircraft components.
Radcliffe is largely responsible for such pioneering
contributions as the quadrilateral socket,
patellar-tendon-bearing (PTB) prosthesis, solid ankle cushion heel
(SACH) Foot and the four-bar prosthetic knee. In addition, he is
credited with providing the fundamental principles of the
biomechanics of prosthetic alignment and socket force transfer
throughout the amputee gait cycle. His legendary principles still
are taught to prosthetists and therapists to this day.
From 1947 to 1956, Radcliffe earned degrees in mechanical
engineering at the University of California in Berkeley. He was a
principal investigator in the Prosthetics Research Group of the
Biomechanics Laboratory at Berkeley for 35 years, when the study of
human locomotion and improved artificial limb designs were the
highest-funded projects. During this time he also lectured in the
Design Division of the Mechanical Engineering Department and was a
professor of mechanical engineering from 19561988. Currently
serving as professor emeritus of mechanical engineering, Radcliffe
is involved in continuing to improve the understanding of the
four-bar prosthetic knee design.
Quad Socket Development
His first major project as a graduate student, studying the
factors underlying alignment of transfemoral prostheses, led to the
development of the AK adjustable leg and the alignment duplication
jig. These advancements revealed the limitations of the wooden
sockets used at that time, which led to the development of the
quadrilateral socket. Introduced in 1954, the quad socket was the
primary socket used in transfemoral amputees for 20 years. Though
this socket has since been redesigned, the fundamental principles
of socket design introduced by Radcliffe still are relevant
today.
Clinical Theories
As a Fulbright Scholar in the 60s, Radcliffe studied in the
Bioengineering Unit of the University of Strathclyde in Glasgow,
Scotland, and at the Orthopaedic Hospital in Copenhagen, Denmark.
During that time he lectured in several European countries on the
proper fitting of lower-extremity prostheses. As one of the major
pioneers who studied in Europe, he returned to the US with a number
of ideas on how to enhance American socket design for transfemoral
and transtibial prostheses.
His clinical theories, particularly on alignment, still are
widely accepted in the field to this day. "Ninety-five percent of
the clinical theories followed on a day-to-day basis today can be
traced back to Radcliffe's work in the 60s," commented John
Michael, CPO, FAAOP, who began his career in 1976. Michael
continued, "Radcliffe made a broad range of contributions to
clinical thinking. He changed the face of lower-limb prosthetic
practice."
Before Radcliffe, there was no concept of the biomechanics of
walking; no one knew the "science" behind gait. Michael credits
Radcliffe with "developing a cohesive, scientific basis underlying
the alignment of lower-limb prosthetic components." One of
Radcliffe's greatest contributions was a biomechanical description
of walking. In its simplest form, the gait cycle is broken into
primarily two phases: stance and swing. The stance phase is the
time when the foot is in contact with the ground, while the swing
phase describes the foot off the ground and swinging forward. The
phases comprise various proportions of the gait cycle depending on
the speed of walking or running. Radcliffe applied basic principles
of the normal gait cycle to that of transtibial amputees and
transfemoral amputees to develop prostheses that would enable the
patient more control during the swing phase.
Technological Advances
In the 50s the Prosthetics Research Group developed the
patellar-tendon-bearing (PTB) below-knee prosthesis in an effort to
improve the fitting of transtibial sockets. Until then, wooden
sockets had to be carved and then reinforced by shrinking rawhide
over the wood. The PTB socket achieved significant weight bearing
on the patellar tendon, allowing pressure to vary according to the
pain threshold of different tissues in the residual limb. PTB
socket biomechanics were developed with respect to each of the
progressive phases of the gait cycle, accommodating softer
tissues.
In addition to transfemoral and transtibial socket designs,
Radcliffe also is credited with the development of the solid ankle
cushion heel (SACH) foot. Made of a flexible rubber shell
surrounding a wooden core, the heel compresses and the toes bend
when the amputee walks. An extension of his other work, a SACH foot
allowed amputees a more natural gait.
The polycentric pneumatic knee, also developed during this time,
is a mechanical knee with multiple axes and fluid control. The
versatility of this knee makes it suitable for a variety of
amputees from those looking for greater stability to those who
desire greater movement control. An individual's prosthetic needs
can be determined by observing his walking cycle and providing the
proper balance between stability and motion control for each
individual.
The most common type of polycentric knee is the four-bar
prosthetic knee. With four axes of rotation connected by four rigid
"bars," these knees provide greater toe clearance during the swing
phase of walking than do single-axis knees. Other advantages
include stance-phase stability and less bulging of the prosthetic
knee when the amputee is sitting down.
Radcliffe commented in the October 2003 issue of The O&P
EDGE, "Current pneumatic and hydraulic swing control devices
are more than adequate for all but very active amputees. There will
be a continued effort to incorporate microprocessors into the
control systems for artificial knees. Current designs are extremely
simple devices compared to the possibilities of the engineering
field of mechatronics. Engineers in school today are eager to
design components that will benefit amputees, and I am sure they
will create designs far better and less expensive than what is
available today." He predicted, "In the future there will be many
improvements in the inputs [from sensors measuring control] and
control strategies used."
Honored for O&P Contributions
The coupling of Radcliffe's prosthetic research and his
mechanical engineering educational background produced a legendary
pioneer with significant, wide-ranging contributions to the O&P
field that are still relevant more than 50 years later. In 1997,
Radcliffe received the Honorary Membership Award from the American
Academy of Orthotists and Prosthetists (the Academy) as a credit to
his high level of knowledge and dedication to the field. In
February of this year, he received a Lifetime Achievement Award at
the Hanger Educational Fair. Though he is honored by these
accolades, he humbly said, "Oh, I'm just one of many pioneers in
this field." He added with a laugh, "I just happen to be one of the
few survivors."
Sherry Metzger, MS is a freelance writer with degrees in anatomy and neurobiology. She is based in Westminster, Coloradok and may be reached at metzgerfive@hotmail.com 
Table Of Contents - March 2006
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