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Transmission of pressures across the elbow joint.

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Transmission of Pressures Across the Elbow Joint
ALBERT A. HALLS AND ANTHONY TRAVILL’
Department of Anatomy, Creighton University School of Medicine,
Omaha, Nebraska
ABSTRACT
To ascertain the pathway (s) along which forces are conducted from
the hand to the humerus in the human cadaver specially designed pressure sensitive
transducers were introduced into the radio-capitular and ulnar-trochlear components
of the elbow joint. A constant force was applied to the hand, and changes in electrical
resistance and hence pressure across the elbow joint where recorded. It was observed
that 57% of the force applied crossed the radio-capitular joint while 43% crossed the
ulnar-trochlear joint. The pathway of this force transmission is discussed with particular reference to the involvement of the interosseous membrane.
Early in his anatomical training nearly
every medical student is taught “ex cathedra” that forces applied to the palm are
transmitted along a devious route from the
hand to the humerus by way of the radius,
interosseous membrane and ulnar-trochlear
joint. This explanation of force transmission first appears in the anatomical literature in a paper by Lopes (1860). He suggested that fractures of the distal end of the
radius are particularly prevalent because of
the structural relationship of the interosseous membrane to the two bones it connects.
Hennequin (1894) and others so supported
and embellished this concept that by the
beginning of the present century it had
become firmly entrenched in the French
anatomical teaching (Testut and Jacob,
’14). However, Destot and Gallois (1898)
had offered experimental evidence that
this was not so and that possibly the interosseous membrane acted onIy in a secondary role in the transmission of forces parallel to the axis of the forearm.
The view that the major function of the
interosseous membrane is one of force
transmission arises naturally from close
inspection of the ligament and an appreciation of the direction of its constituent
fibers. The constancy of the downward
and medially directed fibers led to a consideration of their potential as force transmitting instruments. The same observations have led others to ascribe different
functions to the membrane. Strasser (’17)
considered that the interosseous membrane
acts as a check ligament to restrain excessive supination. Hennequin (1894) had
ANAT. REC., 150: 243-248.
pointed out that Weitbrecht also held this
view, while Cruveilhier considered the
membrane acted as an aponeurosis for the
insertion of deep flexor and extensor muscles, and Sappey considered that the interosseous membrane’s sole function was to
prevent the separation of the radius and
the ulna.
There has been to date no direct experimental evidence to permit one to confirm
or deny whether forces applied to the hand
pass directly across the radio-capitular
joint or whether they are conducted to
the ulna and thence across the ulnartrochlear joint. Consequently we carried
out the present investigation in an attempt
to elucidate this problem.
MATERIAL AND METHODS
Seven human upper limbs were used for
this investigation after they had been dissected by students in the dissecting room.
They were separated from the body at the
gleno-humeral joint. Care was taken not
to disarrange the ligaments and capsule
about the elbow joint. Thus a fibro-osseous
specimen was prepared with metacarpal,
carpal, antebrachial, and brachial bony
and ligamentous elements left intact.
A scaffolding and platform were constructed so that the upper limb could be
supported and maintained in an upright
position with the hand uppermost (fig. 1).
To record forces transmitted across the
components of the elbow joint special
micro-transducers were designed. Both
1 Present address: Department of Anatomy, Queen’s
University, Kingston, Ontario, Canada.
243
244
ALBERT A. HALLS AND ANTHONY TRAVILL
of pressure. The effect of applying pressure is analogous to increasing the number
of resistances in parallel in an electric
circuit. The thickness of the completely
insulated transducer was 1.0 mm. The
micro-transducers were introduced between the articular surfaces of the radius
and capitulum and then the ulna and
trochlea through small incisions made in
the anterior aspect of the capsule of the
elbow joint. An electric circuit for recording changes of resistance in the transducers was completed by connecting in
series an ammeter and the galvanometer
of a pen writer. The power supply was
provided by a 45 volt battery. Each transducer was connected to such a circuit. The
scaffolding with the arm attached and the
transducers in situ was placed on a Toledo
beam scale (fig. 2 ) . Pressure was then
applied by one of us to the palm of the
extended hand so that the beam scale read
33 pounds (15 Kg). With each application of pressure to the hand recordings
were made by the pen writers and at the
same time readings of the ammeters were
noted. For each limb a series of five applications of pressure, each repeated five
times, was recorded. Between each application the system was allowed to come to
mechanical and electrical rest. The results
of 25 readings for each limb were averaged
and tabulated.
After the major investigation had been
completed three of the limbs were set in
turn on the scaffolding; and while pressure
was being applied to the hand the interosseous membrane of each limb was divided by a single swift downward stroke of
the scalpel. Changes in pressure across
the radio-capitular and ulnar-trochlear
joints were recorded.
OBSERVATIONS
Fig. 1 Scaffolding and platform with supported extremity.
sides of brass shim stock, 3 mils (0.125
mm) thick, were painted with a thin layer
of pressure sensitive paint (CELAB Clark
Electronic Laboratories). After drying for
24 hours this paint undergoes changes in
electrical resistance with the application
The changes of pressure across the
radio-capitular and ulnar-trochlear joints
following application of pressure to the
extended hand were recorded by the ammeters in circuit with the transducers. The
averages of these recordings are summarized in table 1.
In all limbs the changes of resistance,
hence pressure, across the radio-capitular
joint were greater than those across the
ulnar-trochlear joint. The average of the
245
PRESSURES ACROSS THE ELBOW JOINT
Fig. 2
Supported extremity with transducers i n situ mounted on beam scale.
TABLE 1
Ammeter readings and ratios following
applications of pressure across
the elbow joint
Av. ammeter readings
(milliamps)
Specimen
1
2
3
4
5
6
7
ulnar-
Radioc apitular
joint
Ratio
trochlear
joint
7.2
7.6
7.5
5.8
3.4
9.0
6.8
9.2
9.1
9.8
8.2
8.8
9.2
9.1
45:55
46:54
44:56
41 :59
28 : 72
50:50
42 : 58
Each average is that of 25 readings.
ammeter readings indicate that 57% of
the pressure applied to the hand was transmitted the length of the radius and across
the radio-capitular joint. While only 43%
was transmitted across the ulnar-trochlear
joint. Comparable results were obtained
for the ulnar-trochlear joint when its transducer was in position alone or accompanied
by the radio-capitular transducer in its
joint. Tracings taken while pressure was
being applied to the hand are shown in
figure 3. The coincident onset and decline
of pressure in both joints is also discernible.
When the interosseous membrane was
cut while force was being applied to the
hand there was recorded a minimal
amount of instability across the ulnartrochlear joint which rapidly settled down
ULNAR-TROC HLEAR
1
R A D I O - C APlTU L A R
Fig. 3 Traces showing changes of pressure
across components of elbow joint. Upright and
inverted arrows indicate application and release
of pressure respectively.
246
ALBERT A. HALLS AND ANTHONY TRAVILL
to its previous state. At this time there
was no evidence of any radio-capitular
pressure change (fig. 4 ) .
our recordings when the transducers are
within the joint.
The observations indicate that though
the articular surfaces are in point contact
UL N A R - T R O C H L E A R
at rest there is no detection of transmission
of forces until pressure is applied. When
pressure is applied to the hand we note
that 57% of the forces are transmitted
BEFORE
DURING
AFTER
through the radius to the humerus and
43% through the ulna. However, with the
l
_ 1 7 - J - l - n p
T L interosseous membrane cut, 43% of the
t
forces applied to the hand are still transmitted across the ulnar-trochlear joint.
RADIO- C A P I T U L A R
Why 100% of the forces are not transFig. 4 Traces showing changes of pressure
across components of elbow joint before, during mitted directly across the radio-capitular
and after cutting the interosseous membrane. joint is still not clear from our investigaArrows same as in figure 3.
tion. However, the ulna is still bound to
the radius at the proximal and distal radioDISCUSSION
ulnar joints. At either one or both of these
The proponents of the concept that joints forces initially applied to the hand
forces are transmitted in a retrograde man- may be transmitted to the ulna. Further
ner across the interosseous membrane base studies of force transmission at these joints
their views, presumably, on the necessity will be necessary to elucidate the interreof a significant space being present be- lationships.
To explain the frequent occurrence of
tween the articular surfaces of the head of
the radius and capitulum of the humerus. fractures of the distal end of the radius, in
Mason ('54) stated that in the cadaver as contradistinction to the normal occurrence
well as in the living there is a one-quarter of midshaft fractures of most other long
inch space between the cartilaginous sur- bones, previous investigators have based
faces of the elbow joint. Grant ('58) in their explanation on: (1) the presence of
his schematic diagram of the radius and a significant joint space between the head
ulna indicates the presence of a wider of the radius and the capitulum, and ( 2 )
space between the capitulum and the the force transmitting capability of the
interosseous membrane due to its obliquely
radius than between the trochlea and the
fibers. However, we feel confiulna. With such a space the radius would directed
dent, from these initial observations on the
be impelled, following the application of
of cadavera, that the interosseous
force to the hand, toward the humerus limbs
membrane does not play a major role in
unless restrained by the interosseous membrane. Such restraint would be followed the transmission of forces along the forearm.
naturally by the transmission of force
across the membrane and thus substantiACKNOWLEDGMENT
ate the concept. However, should the
The authors wish to thank Mr. Fred
space between the articular facets be non- Bantin B.S., who designed and built the
existent or filled with an extremely thin scaffolding and platform.
layer of synovial fluid, as is now generally
This investigation was supported in part
accepted (Barnett, Davies and MacConaill, by Public Health Service Research Grant
'6 1; Gardner, '64), then any possible move- NBO5154-01 from the National Institutes
ment provoked in the radius would be re- of Neurological Diseases and Blindness.
strained by the capitulum acting as a
buffer, and any forces would of necessity
LITERATURE CITED
be directly transmitted across the radio- Barnett, C. H., D. V. Davies and M. A. MacConaill
Such
a
capitular joint to the humerus.
1961 Synovial Joints, Their Structure and
condition is confirmed by our visual obMechanics. Springfield, Ill., Charles C Thomas,
g . 177.
servations on the limbs of cadavera and
PRESSURES ACROSS THE ELBOW JOINT
Destot, and Gallois 1898 Recherches physiologiques et expkrimentales sur les fractures de
rextrkmitk hfkrieure du radius (radiographie).
Revue de Chir. Pans, 18: 886-915.
Gardner, E. 1964 Personal Communication.
Grant, J. c. B. 1958 A Method of Anatomy,
Descriptive and Deductive.
and Wilkins Company, p. 124.
Hennequin, J. 1894 Considkrations sur le
mkcanisme, les symptomes et le traitement des
fractures de l'extrkmitk inf6rieure du radius
conskcutives aux chutes sur le poignet. Revue
de Chir. Paris, 14: 557-583.
247
Lopes, H. 1860 Des fractures du radius et du
role physiologique du ligament interosseux de
l'avant bras. Thesis, University of Paris, p. 30.
Mason, M. L. 1954 Observations on fractures
of the head of the radius with a review of one
hundred cases. Brit. J. Surg., 42: 123-132.
Strasser, H. 1917 Lehrbuch Muskel-und Gelenkmechanik. Band nT, Berlin, Julius Springer,
Pa 314-317Testut, L., and 0. Jacob 1914 Trait6 d'Anatomie Topographique. 3rd ed., Tome 11, Paris,
Octave Doin et Fils, p. 789.
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