By Renata Trister DO
INTRODUCTION AND HISTORY
Julius Wolff (1836-1902) was a German surgeon and anatomist.
He postulated Wolff’s law (original title 1892: The law of transformation of
the bone), describing the relationship between bone geometry and
mechanical influences on bone. This work established the mechanism and
thus physical factors in evolutionary biology. He saw his work as an
extension of the theory of evolution by Charles Darwin (1809–1882).
Julius Wolff was born 1836 in the eastern part of Prussia/Germany. He was
a German surgeon and anatomist. His research in surgery focused on growth
and inner structure of bone. After decades of work Dr. Wolff published his
research titled “The Law of Transformation of Bone” in 1892. A lengthy
and thorough work – the main discovery of this work can be summarized in
the following passage:
“As a consequence of primary shape variations and continuous loading, or
even due to loading alone, bone changes its inner architecture according to
mathematical rules and, as a secondary effect and governed by the same
mathematical rules, also changes its shape.”
Simplified this “Wolff’s Law” says that structure and shape of bone
permanently adapt to the loading conditions. This law describes the
relationship between bone geometry and mechanical influences on bone.
Dr. Wolff saw his theory as an extension of the theory of evolution by
Charles Darwin (1809–1882). This classic work also established
orthopaedics as an independent discipline.
Human bone grows and strengthens under pressure, and weakens when
barely put to use.
This concept — that bone senses and adapts to its mechanical environment –
such as pressure or a lack of it — is an old observation. It’s the reason
astronauts return with reduced bone density after floating in microgravity.
And conversely, it explains why tennis players and fencers develop greater
bone mass in their dominant arms and legs. Although Dr. Wolff gets the
credit for discovering this principle other scientists and writers, such as
Galileo also made similar observations.
Today “Wolff’s law” has evolved and incorporates several concepts, some
of which Dr. wolf never discussed.
1. Optimization of strength with respect to weight. The architecture of
bone is influenced by mechanical forces. Strength is optimized with
respect to weight. Furthermore bone – similarly to structures made by
people – does not remain where it need not be.
2. Alignment of trabeculae with principle stress directions. This
discovery was made when an engineer visiting the lab of an anatomist
noticed the similarity between trabecular arrangement in neck of
femur and a street lamp bracket.
3. The final core principle of Wolff’s law states that self-regulation of
bone structure by cells responding to a mechanical stimulus. This is a
self-regulating biologic mechanism. Bone has the ability to adapt to
changes in its external environment.