MECHANICAL
FUNCTION
AS AN INFLUENCE
STRUCTURE
AND FORM
OF BONE
L. E. LANYON
From
Rosette
in eight
the
Department
strain
gauges
skeletally
mature
and
of Anatomy,
were
attached
female
sheep.
walking
it was deformed
long axis, and the caudal
University
to the cranial
The
sheep’s
BRISTOL,
of Bristol,
and caudal
radius
was consistently
larger
cortex
not
difference
reflect
this
but
in younger
of the mechanical
Any
factors
attempt
on
tion
on
to
bone
the
assess
structure
Strain
gauge
is useful
in
respect,
be made
of the
there
right
any
amount
degrees
to them.
strain
the compression
reported
to
an animal’s
is deformed
its surface
two directions,
in one of which
the strain
shear
strain
which
A single
strain
gauge
is greatest
can
in the
strain
its response
In
there
react
any
is a
at 45
only
direction
it is possible
at
is
to
in which
neither
to infer
the principal
strain
direction
nor to discriminate
between
changes
in the amount,
or direction,
of deformation.
Single gauges
therefore
are of limited
practical
use unless
the
predominant
and
the
objects
gauges
of
changes
gauge
in
strains
can
be
Hitherto
from
These
it.
Because
vivo
is to
in different
Strain
gauge,
one
of the
the
activities,
ascertain
of
three
directions
at one
and
constant,
various
consist
other.
and
point
by
magnitude
and
direction
calculated
for
any
separate
and
stacked
can
then
analysis
of
instant
of
the
be
these
principal
only
report
gauge
analysis
from
an isolated
implantation
(Lanyon,
Hampson,
L. E. Lanyon,
D. G. Baggott,
B.V.Sc.,
B.V.Sc.,
has
been
a long
Goodship
Ph.D.,
process
reports
aspect.
The thickness
of osteonal
remodelling
concerned
1970; Cochran
readings
were
here
series
of strain
sheep’s
radius.
were
with
long
bones
1972; Barnes
and
from single gauges.
taken
gauges
during
(Lanyon
Pinder
The
1974)
results
locomotion
implanted
MATERIALS
Sheep
along
the
from
shaft
a
of the
throughout
published
bone,
on
a human
and
Shah
and
merely
gauge,
tibial
1975).
used
METHODS
as experimental
animals
because
they
have
swabbed
dry and wiped quickly
with ether before the
its underside
covered
with adhesive,
was pressed
into
position.
The
gauges
copper
wires
metre
radial
flange
where
PTFE
which
insulated
to
emerged
from
flange
was
securely
bone
screw
(27
a
of
that
were
AND
been found
to be most suitable
for this type of investigation.
In the sheep the radius
is the main weight-bearing
bone of the
foreleg.
It has a slight cranially
convex
curvature.
The ulna,
although
well developed
in the region
of the elbow
joint
and
olecranon,
has a small
shaft
which
is fused
to the caudolateral
aspect
of the radius
(Figs.
1 and 2).
The rosette gauges used were similar
to those
previously
described
(Lanyon
1973), but there were a number
of small
departures
from previous
procedure.
In this series no surface
activator
was used on the bone surface
before
attachment
of
the gauge.
After
removal
of the periosteum
the site was
Gauges
of
one
on the cranial
the
(7/008
in this
series
millimetre,
thickness,
they
were
PTFE
25 millimetres
joined
more
0l4
connected
insulated
long)
millimetre
attached
to
millimetres
(7J012
radial
skin
wires
epoxy
surface
which
resin
millimetre,
The
bone
diameter)
thin
milli-
thickness)
incision.
the
005
to an epoxy
substantial
a remote
by
to
resin
by
a small
penetrated
one
cortex.
cycle.
deformation
rosette
in
during
used.
each
the
along
gauges
aligned
from
recordings
aligned
is known
direction
are
the
direction
strain
strain
elements
above
recorded
436
are
using
gauges
rosette
one
strain
During
elastically
other
pure
tension.
principal
directions
From
Smith
strain
the
surfaces
recordings
during
as bone
or tension
it is aligned.
curvature.
to the larger deformation.
The relevance
fixation
and to our understanding
of the
other
and
exist
of bohe
in the
these
of
half of the radius
convex
locomotion.
such
than
of the proximal
cranially
animals
only
mechanical
of informa-
actually
it allows
imposed
are at any point
on
angles
to each other,
varying
which
because
including
solid
pure
compression,
direction
other
of
by lack
instrumentation
deformation
activities,
When
influence
conditions
in vivo.
various
the
Science
of bone.
is hampered
mechanical
this
adaptability
Veterinary
to tension
aligned
along
the bone’s
The compressive
strain on the caudal
seemed further advanced
in the cortex which was customarily
subject
of these findings
is discussed
in relation
to the technique
of internal
basis
of
aspects
has a slight
( x 1 9) than the tensile
of the bone
of the
THE
ENGLAND
School
so that the cranial
surface
was subjected
surface
to compression
similarly
aligned.
aspect
did
D. G. BAGGOTT,
ON
a
was
shaft
In the
the
incision.
get
to
the
lame
animal
number
attached
shaft.
The
sufficient
be
were
radial
to the cranial
Both
sites
elevation
exposure
of the
for
four
was
sound,
of days
with
of
or
were
the
flexor
caudal
five
days
after
the
trotting
aspects
a
medial
necessary
caused
recordings
and
caudal
from
muscles
surface
however,
it walking
and
reached
the
operation.
were
to
animals
Once
taken
at different
on
speeds
M.R.C.V.S.
M.R.C.V.S.
f
Department
of Anatomy,
School
of Veterinary
THE
Science,
JOURNAL
Park
Row,
Bristol
BSI
OF
BONE
AND
JOINT
5LS,
England.
SURGERY
a
MECHANICAL
FUNCTION
AS AN INFLUENCE
ON THE STRUCTURE
AND
437
FORM OF BONE
both on the concrete
floor and on a moving
belt.
The strain
values during
these spells of locomotion
were calculated
for
at least ten consecutive
strides at the instant of peak deflection
on the gauge
trace showing
the greatest
deformation.
This
point did not necessarily
coincide
with the instant
when the
principal
strains
were greatest,
but it approximated
to it and
gave an indication
of the regularity
of the recordings.
A
“typical”
stride was chosen
from each series whose principal
strain
values
and strain
angle at this point
fell within
one
standard
deviation
of the mean.
This stride was then analysed
and the principal
strain
values
calculated
for 002-second
intervals.
As in previous
reports
zero strain was assumed
to
be the level of strain
recorded
during
the period
of slow strain
change
which
occurred
in the swing
phase
of the limb.
As
invariably
there
was error
in the exact
placing
of this line,
strain
levels
and
strain
angles
near
“zero”
strain
must
be
treated
with suspicion.
The
as lying parallel
to its medial
long axis of the bone was taken
and lateral sides in the midshaft
region.
the
During
intravenously
experimental
that some
so
the bone’s
remodelling
their attached
gauges
decalcified
100 micron
metre
intervals
sections
activity.
also
tetracycline
was given
could be obtained
of
After
death,
the
bones
with
were removed
and radiographed.
Untransverse
sections
were taken at centithe shaft. In the gauge region longitudinal
down
were
period
indication
taken
parallel
to the cortical
surface.
RESULTS
Gauges
were
aspect,
or
or
I
FIG.
Lateral
and
cranio-caudal
ulna of sheep 5 showing
the position
and
of the left radius
and
of the gauge attached
caudal
ten
to
surfaces.
were
taken
strides
II).
speed
to that
speed
above
regular
In general,
the animals
of the moving
belt but
would
adjust
their
they had a preferred
the
III).
of about
one
however,
is an
between
locomotion
The
Most
metre
animals
indication
or when
the speed
recordings
they
circumstances
even
Generally,
deformation
(Table
III).
being
of
when
but
a
alone,
comparability
size, and some
pareither push forward
were
reluctant
shape
under
the
increased
larger
speed
occasions.
required.
The size and
could
differ significantly
same.
less
strides
preferred
Belt
second.
on different
was
consecutive
of the
per
inadequate
enthusiastically
the
locomotion
between
animals
were of different
had moods
when they would
ticularly
tifiable
which
below
variability
(Table
speed
or caudal
of days and at least
for each recording
and
and
increased
to the cranial
on a number
were measured
consecutive
(Table
attached
both
aspects,
of the proximal
half of one
of eight skeletally
mature
ewes (Table
I).
radii
Recordings
radiographs
its cranial
both
successfully
to
walking
speed
applied
to walk
at
of the strain
these unquanspeed
resulted
was
in
in the same
the
direction
Recordings
from
gauges
in all the animals
showed
that
on the cranial
aspect
of the radius
the principal
tension
was the larger
principal
strain
and at the time of
maximum
deformation
within
a few degrees
Radiograph
of a transverse
section
through
the left radius
of sheep 5. The elements of the gauge attached to the cranial
can just be seen (top) although
they became
detached
sectioning.
of
the
radius
The
degree
is more
of osteonal
extensive
still largely
VOL. 58-B,
No. 4, NOVEMBER
remodelling
than
in the
plexiform
1976
in the caudal
cranial
bone.
cortex
and
ulna
surface
during
cortex
which
caudal
side
principal
on this
strain
aspect,
axis.
is
principal
On
the
both
strains
of
on this aspect
it was
the bone’s
long axis.
principal
compression
was
aligned
On the
the
larger
and, at the time of maximum
deformation
it too was aligned
along
the bone’s
long
cranial
to
and
the
caudal
long
axis
sides
was
the
angle
fairly
of the
constant
438
E. LANYON
L.
AND
D. G. BAGGOTT
TABLE
THE
TYPE,
AND
AGE
WEIGHT
OF SHEEP
USED,
THE
LENGTH
FROM THEIR
Age
(years)
Breed
Animal
I
OF ITS RADII,
PROXIMAL
AND
1
Welsh
mountain
2
35
Left
142
Cranial
68
2
Welsh
mountain
2
36
Right
143
Cranial
70
3
Welsh
mountain
5 +
35
Right
148
Caudal
62
4
Welsh
mountain
25
43
Right
146
Cranial
53
Caudal
43
Cranial
47
Caudal
43
Cranial
71
Caudal
45
Cranial
45
Caudal
37
Cranial
50
Caudal
50
Cranial
68
Caudal
69
Cranial
70
Caudal
75
Welsh
5
mountain
2
146
140
Right
32
Left
6
Clun
7
the
main
of the
(Fig.
usually
3).
time
an inflection
producing
two
peaks,
sides
aspect
the larger
peak
generally
aspect
it came
second
(Fig.
by
the
not
cranial
second
different
lateral
constant
gauge
on
for these
peaks,
for the first,
and
second.
The
two
peaks
was
consistently
caudal
in the
aligned
along
the
which
could
be determined
coincided
one
at a maximum
microstrain*
II).
This
Strain
rate
rate
12 degrees
the long
7 similarly
curve.
by
first
each
part
of
at their
the
strain
between
60
in length
small
strain
curve
frames
was
and
to original
length
per
speed
imposed
149
x lO
(Table
and was
(00092-00294/second)
second
they
that the maximum
strain
with speed.
In the case
second)
second
at 254
In every
case
of the
radius
side
cranial
side.
gauge
region
secondary
younger
primary
had
was
the
also
been
than
bone
sections
caudal
cortex
2).
of the
1 is therefore
THE
into
both
in
labelling
in any
showed
cortices,
a large
second
(00254/
The
that
of strain.
OF
BONE
all
from
cranial
cortex
in the
with some
this
cortex
osteones.
was
there
some
the
in the
IV).
the animals
largely
of
plexiform,
animals
The
longitudinal.
was
new
A microstrain
AND
on
cortex
(Table
secondary
although
amount
JOURNAL
tension
consisted
cortices
per
on the caudal
the
of the bone
this difference
remodelled
direction
per
imposed
greater
(Fig.
osteones
Fluorescent
and has no units:
microstrain
animals
was predominantly
osteones.
In the older
osteonal
drift
not continue
to increase
4 (Table
III) it reached
the compression
of
that
the
side and 42 x lO microstrain
on the caudal
side.
The thickness
did not reflect
Examination
revealed
rate did
of sheep
x IO
on the cranial
(O’042/second)
at
high
speed
locomotion
on the
did achieve
there was a suggestion
comfortable
At the speeds
animal’s
preferred
the
the
was I 6
it was
in the
at sixty-four
second
varying
point
achieve
belt.
peak
a very
per
a maximum
for
indicated
The
second
The
walked
ofchange
to
5,
proximal
axis
per second
(0006-00149/second)
was estimated
over 002
second
is the ratio
sheep
angle
during
the first
and during
the second
with
per
case
the
by filming
metre
3).
shown
of
with
strain
axis.
(Fig. 3).
When
the animals
of about
*
long
peaks
radius
of sheep
;
stride
second
in this
than
degrees
right
aligned
principal
the deformation
proximal
lateral,
amount
two
was the larger
and sometimes
strain
angle was consistent
but
gauge
larger
; of the
the
the first peak
(Fig. 4). The
sometimes
the
always
The strain
294 x lO
same speed (Table
II).
In every case but one (7 left) the
rate during
release was greater
than that during
imposition.
With our facilities
it was not possible
for the sheep
on the
was
than O’05 second.
between
92 and
microstrain
than
On the caudal
This
maintained
for more
during
release
varied
rate
larger
came
cranial
180
in the prinone
the other.
first,
166
Left
rarely
Maximum
150
Left
62
on both
140
Right
58
4+
at the same
was
curves
crossbred
period
occur
There
strain
4+
crossbred
deformation
53
4
Leicester
did not
bone.
cipal
forest
Finn
8
deformation
OF THE GAUGES
Gauge site and distance from
proximal
end (millimetres)
Radius and length
(millimetres)
Weight
(kilograms)
Left
during
THE DISTANCE
ENDS
JOINT
no
overall
bone
was
is 1 x I0-.
SURGERY
MECHANICAL
FUNCTION
AS AN
INFLUENCE
ON
PRINCIPAL
ANGLE
LONG
AND STANDARD
DEViATION
OF THE
OF THE LARGER
OF THESE TO THE BONE’S
THE
S_
Animal
Radius
AND
TENSION
STRAIN,
PRINCIPAL
Axis, CALCULATED
AT THE PEAK
GtwmsT
VALUE*
Principal
Principal
tension
msec
STRUCTURE
FORM
439
OF BONE
II
TABLE
THE MEAN
THE
Principal
compression
strain
degrees,
COMPRESSION
STRAIN
AND THE
SHOWING
STRAIN,
ON THE GAUGE
Maximum
angle
strain
rate
proximal
Imposed
Released
69xl03
162x103
Cranial
1
Left
10
538±61
-
157±25
35±3
Lateral
2
Right
12
987±56
-
439±25
1 ± I
Lateral
107 x 10’
4
Right
1l
915±58
-
369±25
4
± 1
Medial
74 x 10
232
x l0
Left
1#{149}I
942±48
-
416±20
2
±05
Medial
88 x l0
175
x I0
Right
l’l
604±43
-
260±20
0
±1
98x10’
I06xI0
Left
l0
652±67
-
284±24
7
±2
5
6
Right
l0
1,123±67
-
621 40
7
Left
11
935±45
-
428±24
8
Left
12
569±40
-
272±25
3
Right
P0
437±30
5
Right
08
Left
6
0
188 x 10
60 x 10’
Lateral
92 x 10
7.7 x I0
±05
16
±2
Lateral
9
±2
Lateral
-1,119±67
3
±2
Medial
495±20
-1,098±40
1
±1
P0
221±15
-1,181±63
4
Right
10
718+18
7
Left
P2
8
Left
I2
4
Right
Left
207
105x10’
lOlxIO’
5.9 x 10
x 10
34
x 1ff’
Caudal
*At least ten consecutive
“typical”
formed
one
in regions
of
and
there
was
the
animal
had
been
lame
Medial
8lx10
171xl0’
±15
Medial
96xl0’
l13x10
-1,924+50
1 ±05
Lateral
131x10’
29’4x1&’
707±39
-1,771±52
1
±1
Lateral
149xl0
17’3xltV
321±11
-1,069±38
10
±1
Medial
116xl0
ll8xl0’
11
-1,461+58
at5
Medial
lIOxIff’
268xl0’
1#{149}1
-
at4
Lateral
ll5xlO’
ll0xI0
were measured
strains
The angles
for each speed indicated
disturbance
not
reactive
hypertrophy
some
on the
911±29
opposite
information
covered
if
leg.
structural
competence
significance
devoted
variety
to examining
of conditions.
manence
has
of the bony
that
not
in
of
reliable
has
vivo,
performed
encouraged
the
machine
than
laboratory
related
to
vivo,
ledge
then
more
many
regard
relevant
on
it
is
necessary,
these
No. 4, NOVEMBER
information
obtained
been
is under
it should
in
vivo
natural
activity
effort
same
tions
of
attention
to
mechanical
biological
and
1976
that
and
experiment
and
parameter.
If
fragments
are
circumstances
to be
that
some
in
know-
comparable
so confine
others.
made
with
in
the
relevance
than
allowing
With
little
additional
that
less
obtain
of
which
The
may
strain
can
be
so it is important
restricted
direct
speeds,
state
the
condi-
strain
data.
fail to provide
of the specimen
results
comparisons
instrumentation
data can usually
be obtained,
and we hope that
of investigations
such as this will be to provide
work within
which
relevant
mechanical
testing
fragments
At
that
This
are to be compared,
the
as crosshead
on the mechanical
rather
the
as possible.
in vitro,
to
As
is the only one
these conditions.
situations
in vitro
be
such
conditions
technique
under
laboratory
Machine
data,
direct information
conditions
been
and
situations.
voluntary
control,
when
be in conscious
animals
specimens
should
the
for a
is negative.
two
compared
testing
if the in vivo
have
of a testing
we have
secondly
systhe
that
is limited
from
every
experiments
skeletal
mechanical
first,
are,
is of such
properties
under
a
its apparent
per-
to the capability
to an
in the
system
as near
has
the more
perishable
This, coupled
with
on
that
experiments
the specimen’s
of what
VOL. 58-B,
information
meant
with
effort
its mechanical
Unfortunately
realistic
testing
conditions
that
tems have obviously
demanded.
lack
skeleton
considerable
rates calculated
compression
to the gauge.
present
the strain
gauge
can yield direct information
DISCUSSION
obvious
strain
per second,
is collected
musculo-skeletal
it is studied
under
The
and the maximum
are in microstrain,
strain rates in microstrain
are in degrees to the bone’s long axis proximal
All
of periosteal
gauges
184x1O
strides
these.
by
113x10
to
the
one
between
strain
one result
a frameof skeletal
be conducted.
data
presented
here
suggest
a relatively
it
440
L. E. LANYON
EFFECT
THE
PRINCIPAL
OF SPEED
ON
COMPRESSION
THE CRANIAL
ASPECT
STRAIN
LEVELS.
STRAiN
OF THE
AND
RIGHT
THE
ANGLE
AND
TABLE
III
AND
STANDARD
MEAN
OF PRINCIPAL
RADIUS
D. G. BAGGOTT
TENSION
4 ON ONE
OF SHEEP
DEVIATION
STRAIN
DAY
WITH
TO THE
OF TI-IF
PRINCIPAL
BONE’S
LONG
THE ANIMAL
MOVING
Axis
Principal
Principal
tension
microstrain
compression
Principal
FROM
INDICATED*
strain
rate
angle
proximal
Imposed
Released
Medial
24 x 10
68 x l0
strain
degrees,
microstrain
STajiN,
RECORDED
AT THE SPEED
Maximum
Speed
rn/sec
TENSION
Cranial
± 25
041
760+
109
-
305 ±
50
325
082
841±
48
-
341±
22
575+l0
Medial
47x10’
109x10
110
974±
29
-
420±
14
51
Medial
99xl0
254xl0
1 46
1 ,023 ±
59
-
427
29
3#{149}75
± 1 1
Medial
136 x 10’
167
1,059±
68
-
432±
32
28
Medial
23l
1,205±
120
at
±
±08
± 1.5
252
x l0
x 10’
185 x 10
x l0
102 x 1ff’
Caudal
*At
5
Medial
80
041
-
082
-1,436±
49
I00xl0
210x10’
110
-1,601±
44
180x10’
300x10’
146
-1,637±
79
260xl0’
420xl0’
167
-1,700±
96
280xl0
324xl0’
least
stride
ten consecutive
in each
case.
strides
Tension
in n,.icrostrain/second.
maximum
strain
The
rates
are
were
measured
is expressed
given
angles
to
at each
positive,
are in degrees
the single operative
speed
; the maximum
compression
negative,
strain
all strains
rates
are
were calculated
in microstrain,
for a “typical”
and
strain
rate
is
proximal
to the gauge.
On the caudal
side the peak strains
and
gauge aligned at 5 degrees proximal
medial to the bone’s long axis.
20’
eE
DEGREES
C
10
MEDIAL
R
A
.----
N
A
E1
L
STRAIN
x
106
C
E2
A
U
D
A
L
SECS
.x0’1
eE
DEGREES
LATERAL
1
2
3
45
FIG.
Strain
axis
analysis
from the cranial
(OFt)
on the cranial
surface,
plotted
during
3
and caudal
aspects
and the principal
one stride with the animal
walking
of the radius of sheep 6. The principal
tension
(E1) and its angle to the bone’s long
compression
(E2) and its angle to the bone’s long axis (Ot:,) on the caudal surface are
at 1 rn/sec.
Its position
is shown
at the points
illustrated
with the instrumented
leg darkened.
THE
JOURNAL
OF
BONE
AND
JOINT
SURGERY
MECHANICAL
simple
loading
shaft.
The
strain
regime
effect
field
long
with
axis
on
pression
the amount
of the
is to
radial
produce
a
aligned
along
the
the principal
comthe concave
surface.
If such
at the same
time the strain
tension
on
compressed
resemble
being
half
a column
surface
aligned
AS AN INFLUENCE
proximal
principal
convex
is axially
pattern
could
of compression
and
the
bending
the
the
similarly
a column
on
of
FUNCTION
and
that seen
increased
of tension
in the radius,
the
on the concave
diminished
amount
surface
on the convex
1Lt
1
ON THE STRUCTURE
Although
physiological
sometimes
concepts
deformation
within
: CAUDAL
THESE
WERE
MEAN
Animal
CORTICAL
THICKNESSES
and radius
Strain
-
THE
Various
this
LARGER
DURING
IN THE
control
PRINCiPAL
STRAIN
WALKING
(TABLE
RELEVANT
GAUGE
ratio
Cranial
-
limits.
IV
OF
AT A MAXIMUM
twin
so
to which
they will
mass to maintain
whereby
TABLE
CRANIAL
input”
and
relationship,
Law, embodies
the
of skeletal
elements
acceptable
THE
RATIOS
441
“mechanical
the general
proposed
2
T?1:
BONE
the deformation
adjustment
of their
been
THE
2OOsI
OF
referred
to as Wolff’s
of strategic
placement
mechanisms
have
could
be achieved.
WHEN
.
FORM
the link between
control
is not clear
as best to withstand
be subjected,
and
this
one.
AND
Cortical
: Caudal
2)
thi ckness
Cranial
AND
AREAS
ratio
: Caudal
5
Right
1
19
I
l0
5
Left
1
l9
1
Il
6
Right
I
P7
1
12
7
Left
I
l9
I
08
8
Left
1
l9
0#{149}1-4
FIG.
Part of the original
recordings
gauge attached
to the cranial
taken
while
direction,
it was
walking
the gauge
at
zeros
4
from the three elements
of the rosette
aspect of the right radius of sheep 5
lI
rn/sec.
are arrowed.
size of each
peak
caused
the changes
mentioned
in the text.
Each
strain
cycle
that
marked
marked
Tension
is in
The variability
in principal
occurred
an
strain
maxima
during
one stride,
T was chosen
as the “typical”
stride (Table
first principal
strain
peak was the larger
in that marked
2 it was the second.
I the
upward
in the relative
II).
The
bone
of the two,
then
information
bones
have
supports
tension
the
mechanical
not
because
hypothesis
compression
on
plating,
it must
of
adapting
be the best
possible
withstand
to
do
this
manner.
in
Many
yet practically
the controlling
factors
mechanical
environment
or at a rate
strain
falls
It is reasonable
to suppose,
relevant
mechanical
related
to, if not
bone
strain
ties.
Assuming
main
activity
and
which
in
from
the intermittent
related
VOL.
to
58-B,
from
the
a
locomotion
that
deformation
relevant
it
assume
to
principles
that
bone
in a straight
line
averaged
over
normally
we have
1976
have
measured
stimulus.
to be the
adapted,
not
time
occur,
should
has
is
then
be
considered
within
to
the acceptable
at a resting
each
process
was
loop,
would
any
on
a
the
tissue
of the bone
circum-
adjustment
of a
of intermittent
subjected.
He
to intermittent
load
induced
con-
arranged
so as to neutralise
to overall
compression.
of “flexure
subjected
if
that
towards
this
bone
point
actively
of
form
from the amount
its surfaces
are
bone
subjected
cortices
are
be subjected
feedback
threshold,
amount
mechanical
suggested
rate,
If the customary
then the bone
the
in their
both
and
drift”
to overall
would
If
ensure
compression.
The
a local
stimulus
with
a constant
ensure
this to be equal
in amount
at
shaft.
it has
bone’s
In this experiment
activi-
does
drift
bending
reduce
to changes
(1973)
will
until
it occurred
in surface
speed
will
direction
form may result
strain
to which
considers
that a curved
that
falls
continues
or
bone’s
flexural
the
whatever
the
is, it will be
normal
tissue
bending
of
been
the strain
level.
and the overall
restore
Frost
cavity
either
the changes
would
functional
No. 4, NOVEMBER
we
is known
bone
which
which
what
moderate
a limb
manner
important
because
an animal’s
at
which
life are
them
but
so
responsive
stances.
or of which
aspect
of the
the definitive
influence.
upon,
locomotion
that
it
different
result
to
assuming
deform
consequent
However,
The
are also
level
remodelling
increase
and
so
by
is based.
of the basic
however,
on the
influence
and
has
determined
by other factors.
above
or below
this threshold
to
present
built
on an empirical
to certain
mechanical
nothing
involved
provides
some
fixation
in
of orthopaedic
management
are
knowledge
ofhow
bone will respond
circumstances,
internal
circumstances
is capable
that
surfaces
which
or compression
a bone’s
only
the
and
philosophy
band,
tension
confirms
present
If this
bone
remodels
Such
of bone
deformation.
range
In that
amount
be influenced
at least partly
by means
of a feedback
loop
which
is sensitive
to a customary
level of intermittent
been
shown
that
the sheep’s
radius
is bent
during
locomotion
and that the strain
is
consistently
larger and of a different
sign on the caudal
than
on
were
those
the
significant
bone
state
the
the
were
cranial
just
influence
related,
to be unstable
caudal
cortex
If the
surface.
suggested,
then
controlling
and
if intermittent
to which
adaptive
one
would
and
accompanied
or drift
of the
processes
strain
of
expected
this
have
by hypertrophy
whole
were
remodelling
bone
towards
of
the
442
caudal
facing
tween
concavity.
intermittent
Heft
1971),
becomes
If bone
does
and
compression
tension
then
this
distinction
irrelevant.
Bonfield
formation
of
230 x 10
formation
observed
bone
Reilly,
Bassett
and
Burstein
and
Gjelsvik
(1974)
one
piece
and
a constant
compression.
Therefore
level of intermittent
elasticity
of the
of bone
inversely
and
is not
in this
the
nor
and
part
this
cranial
proportional
modulus
stress
that
to
strain
being
sensitive
controlled
both
caudal
to their
trical
ones.
an incomplete
or the idea
threshold
view the
throughout
the bone
response
to intermittent
reaction
rather
than a local
that the customary
not
and
1968 ; Bassett
stoff
1974).
neither
two
phenomena
the
make
exerting
most
an
As
strain
achieved
between
the
strain
asymmetrical
to that
observed
Whatever
remodelling
space
which
be
controlling
processes
In
be
to
locomotion
(Lanyon
shearing
bone
is impossible
continuous
directions
the
along
avoid
sheep’s
surface.
radius
The
drafts
adhesive
while
here
drift
kindly
supplied
by the
M.
by
al-
The
periods
we
speeds
positive
As
the
or
imposition
surfaces
one
could
rates
at
faster
would
expect
that,
result
in the
corn-
more
positive
and
nature
and
predominance
should
negative
and
this
sign
have
could
strain
time,
depend
the
tension
side
of the
on the degree
of
rate
of charge
leakage,
the interval
of rapid
strain
change
within
each cycle,
it should
them
those
walking
during
potentials
the
to
voltage
the difference
the effect
of
be
strain
cycles in vivo.
strain
relationships
of
possible
to
mechanical
a satisfactory
calculate
the
ones.
Confirmamethod
of re-
in vivo.
have
been
series
of experiments
of the relationship
optimistic
to
would
between
that
anticipate
reveal
bone’s
principal
strain
influence
directed
tions
which
to be better
must
be
challenged,
if this
relationship
is
understood.
Mr A. E. Goodship,
Dr W. Hartman,
and the technicians
of the Department
under
sections
was by Mrs C. Goodall;
photography
was by Mr D. Telling.
The final copy
J. Gillard.
Ethicon
Medical
a
much
of the
mechanical
input
and its response
in terms
of modelling
and remodelling.
What we believe
it has done is to indicate
some
of the questions
which
require
answering
and assump-
trabecular
to the
especially
of histological
both
being
It would
nature
polarisation
similar
surfaces.
slow
over
potentials
limited
by Mrs
The work was partly financed
these
cellular
polarisation
intermittent
electrical
changes
from the
tion, however,
must await
ones
their
bone
which
presents
a
the arrangement
in the
to our colleagues,
The preparation
were prepared
induced
strain
directions
during
arrangement
oftissue
to
of some
the
moderate
bone
for
side
actual
cording
parallel
result
two
were
negative.
are the
tend to
for
of
and
a net
the
more
the
deformation
electrical
rates
at low
averaged
between
tissue
same
of
of bone
it and
ofintermittent
and the interval
between
consecutive
With
the necessary
data
on the
the
through
are the
orientation
Bassett
by-product
between
through
sensitivity
produce
pression
radius
involved,
advantageous
for cortical
However,
be the
was
bones
thickness
and
principal
1974). This
of osteones
could
are
bone
the structural
units
in the calcaneus
at least,
forces
Our thanks
are
due
Mr M. A. Coombs.
and many
cortical
character
of the
rate
release
when
remodelling
cortex
influences
cancellous
and these,
aligned
caudal
by which
or adapt
their
result
in the
tissue.
trabeculae
in the
and
Black and Korowhether
strain-
irrelevant
link
the concept
loading
observed
or to
bone
polarisation,
experiment.
Pawluk
seems to result at least in part from
charge
separation
and
leakage,
might
in this
its
or released
attractive.
the
or
vital
influence
irresistibly
during
similar
its size,
it is applied
Cochran,
the
are
of polarisa-
population.
However,
their strain dependent
relationship
coupled
with the known
susceptibility
of cells to elcctrical
at an optimal
level but that greater
strains
are tolerated
in some areas than in others.
The comparative
overstrain
in such areas
would
not then result
in hypertrophy
or
drift of the part of the cortex.
However,
the local price
for tolerating
such
increased
intermittent
deformation
osteonal
1964;
degree
of strain,
at which
an
elec-
as its mechanical
when deformed
the
amount
as
a bone’s
to
If
speeds
increased
Lavine
or the
these
of
at least,
rate
potentials
on
regions
deformation
remodelling,
to the
the principal
where
1971 ; Steinberg,
Busenkell,
It remains
to be determined
deformation,
charge
be
in sites
and
region
the
and
one.
In the latter case it is
overall
strain
is maintained
possible
in one
induced
or irrelevant
of each part of
to be constant,
strain
as a whole
at least
to
of
cortices,
a simple
stress
must
be modified.
might
be to consider
loop
is proportional
(Shamos
by
modifications
in the elastic
tion
direction,
ten-
of shear
directions
modelling
and,
that
in
amounts
properties
may be as significant
Bone becomes
electrically
polansed
Bar-
then
in the
for
and
cortices
would
have
customary
strain.
same
osteonal
shown
adapts
locally
the modulus
the
are not longitudinal.
When
considering
intermittent
influence
below
is similar
proportion,
reducing
To establish
whether
this arrangement
is coincior reflects
a causal
relationship
it will be necessary
strains
de-
strain
BA000TF
to examine
the
linear
(1974)
have
if bone
stress,
will be the
feedback
Such
Frankel
modulus
either
we are examining
of the functional
stimulus,
bone
consider
is limited
sion
their
between
if the anelastic
component
of deis ignored
then stress
in the range
we have
will be related
to strain
by the modulus
of
for
be
cortices
challenges
the assumpis locally
strain
depenis it stress
dependent?
(1974)
compact
two
G.
plane.
dental
(Likov#{225} and
the
D.
towards
be-
However,
-
elasticity.
gren,
Datta
AND
distinguish
the discrepancy
However,
and
not
between
amount
ofstrain
on the two surfaces
tion that any regulatory
feedback
dent.
If it is not strain
dependent
a
E. LANYON
L.
Ltd.,
Research
Edinburgh.
Council
and
partly
by the
Wellcome
THE
Trust,
JOURNAL
to both
of whom
OF BONE
AND
we are
JOINT
most
grateful.
SURGERY
MECHANICAL
FUNCTION
AS AN
INFLUENCE
ON
THE
STRUCTURE
AND
FORM
OF
443
BONE
REFERENCES
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D. N. (1974) In ho
A. (1974)
tendon
Mechanical
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bone
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Journal
of
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C. A. L. (1971)
Volume
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R. J., and Bassett,
C. A. L. (1968) Electro-mechanical
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L. E. (1974)
Experimental
support
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W. G. J., Goodship,
A. E., and Shah, J. S. (1975) Bone deformation
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strain
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A. H., and Frankel,
V. H. (1974) The elastic modulus
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VOL.
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58-B,
No. 4. NOVEMBER
1976