the rib hump inidiopathic scoliosis...64 the journal of bone and joint surgery the rib hump...
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64 THE JOURNAL OF BONE AND JOINT SURGERY
THE RIB HUMP IN IDIOPATHIC SCOLIOSIS
MEASUREMENT, ANALYSIS AND RESPONSE TO TREATMENT
T. THULBOURNE, BRIDGE OF EARN, SCOTLAND, and R. GILLESPIE, TORONTO, CANADA
Front the Hospitalfor Sick Children, Toronto, Ontario
This paper describes a simple method for the recording of rib deformity in idiopathic scoliosis. The
relationships have been recorded between the measured rib hump and rib depression deformities and I) the
rotation of the vertebral bodies (as measured by the method of Nash and Moe on the standing radiograph);
2) the degree of lateral curvature (as measured by the method of Cobb on the standing radiograph); and
3) the rib-vertebra angles and their differences (as described by Mehta). No clear linear relationships were
found. Many examples of irregular relationship were recorded, for example, marked spinal rotation with
minimal rib hump. The response of the rib deformities to treatment by Milwaukee brace in fifty-two patients
is described ; the hump is little changed but the depression on the opposite side may be considerably reduced.
Harrington instrumentation may have a similar effect.
In idiopathic scoliosis the most important compo-
nents of the deformity are the thoracic rib hump, the
lateral shift of the chest relative to the pelvis and the
asymmetry of the shoulders. The last two are easily
recorded photographically and radiographically and on
the whole are correctable by either bracing or operation.
The rib hump is the feature of the deformity most
resented by the patient, least understood by the surgeon
and most resistant to treatment.
Great ingenuity has been demonstrated in the de-
velopment of instruments to record the deformities of
scoliosis. These mechanical devices reached what was
probably a peak of complexity in 1913 when Layer-
miccoca described his pantoscoliosogr�fo and plasmo-
scoliosometro. With the general use of radiography,
however, increasing emphasis was placed on the radio-
graphic appearances. Although the rib deformity has
aroused interest because of its variable response to
treatment, few attempts have been made in recent years
to measure its extent accurately. The authors are aware
of only one modern instrument designed to chart this
feature, that described by Rippstein in 1967.
This paper presents a simple method of measuring
and recording the rib deformity and analyses its relation-
ship to lateral curvature, to rotation of the spine and to
the rib-vertebra angles. Finally, the response of the
deformity to treatment by the standard Milwaukee brace
and by standard Harrington instrumentation is described.
THE MEASURING DEVICE
The instrument consists of a series of movable strips
which can be locked in position by a lever on the frame
(Fig. I ). The central strip is marked and the frame
carries a spirit level. In clinical use the patient places her
hands together and flexes hips and spine until the hands
are between the extended knees at the level ofthe patellae.
The instrument is placed across the back, centred on the
spinous process of the apical vertebra and perpendicular
to the spine at this level. After ensuring from the spirit
level that the instrument is horizontal and that each
movable element is in contact with skin, the locking lever
is depressed and the resulting contour is transferred to
graph paper. By aligning the vertical elements of the
instrument with the lines on the graph paper, the profile
of the back is accurately reproduced as a chart. Serial
recordings afford a good visual impression of the pro-
gress of both rib hump and valley during treatment
(Fig. 2).
MATERIAL AND METHODS
Measurement of hump and relationship to radiographic
featuresUsing this device we measured the rib hump deformity infifty-two patients with untreated scoliosis. In order to producea numerical representation of the rib deformity, each chart
was reviewed and three figures, which can be read directly,were obtained (Fig. 3): H-the height of the hump; W-the
distance ofthe peak ofthe hump from the midline; and D-thedepression of the ribs at the same distance. In addition thegradients of the hump (H/W) and of the depression (D/W)were calculated. We believe that these gradients give a moreaccurate representation of the deformity than the heightsalone, because they eliminate the influence of the width ofthe patient’s back.
Measurement of the lateral curvature was carried out onan antero-posterior radiograph of the erect spine by themethod ofCobb (1948). On the same radiograph the rotationof the apical vertebra was measured by the method of Nashand Moe (1969). Recognising that this method becomes
T. Thulbourne, F.R.C.S., Orthopaedic Department, Bridge of Earn Hospital, Bridge of Earn, Perthshire, Scotland.
Dr Robert Gillespie, F.R.C.S.(Ed.), F.R.C.S.(C), Suite 1028, 123 Edward Street, Toronto, Ontario, Canada. (Address for reprints).
:�.�
� ;�
1�.J;TI
�1
Fi-lu. I
Figure I-The measuring device in use.
CURVATURE (degrees) under 21 21-30 31-40 41-50 over 50
NUMBER OF PATIENTS 8 15 13 1 1 5
DEFORMITY Range 0-19 6-38 9-24 10-33 7-43(H . D millimetres) Mean 10 15 16 18 28
HUMP Range 0-022 003-022 007-025 002-036 010-044GRADIENT Mean 009 015 019 019 025
DEPRESSION Range 0-022 0-033 008-037 011-035 0-02-030GRADIENT Mean 016 016 022 024 020
ROTATION (degrees) under 10 10 15 20 over 20
NUMBER OF PATIENTS 13 8 12 13 6
DEFORMITY Range 0-25 7-18 9-31 7-33 10-43(H #{149}D millimetres) Mean 13 13 17 21 19
HUMP Range 0-022 003-022 007-036 007-033 003-044GRADIENT Mean 014 013 018 016 021
DEPRESSION Range 0-030 007-037 003-&33 002-034 013-035GRADIENT Mean 0-13 021 019 0-22 021
THE RIB HUMP IN IDIOPATHIC SCOLIOSIS 65
VOL. 58-B, No. I, FEBRUARY 1976
8
FIG. 2
Figure 2-Serial tracings of a rib cage deformity during treatment.
w
FIG. 3
w
Method of measuring the rib hump chart for analysis.H�hump height. W=distance of hump from midline.
D=rib depression.
TABLE I
LATERAL CURVATURE AND RIB DEFORMITY
TABLE II
VERTEBRAL ROTATION AT APEX OF TI-IORACIC CURVE AND RIB CAGE DEFORMITY
inaccurate beyond 20 degrees, as shown by Mehta (1973), werecorded the six cases with rotation of this severity as “over20 degrees”. The rib-vertebra angles at the apical vertebraewere measured by the method of Mehta (1972) and the R-Vangle differences (concave minus convex) were obtained. Anattempt was then made to determine if the rib cage deformityis directly related to any of these readings.
H/W
0.5
0.4
0.3
0.2
0.1
H+D (mm)
45
40#{149}
35
30
25
20
15’
l3�
5.
0.1
0.2
0.3 890.4
<21 � >50 ,w <21 � >50
LATERAL THORACIC CURVE
(DEGREES)
LATERAL THORACIC CURVE
(DEGREES)
FIG. 4
A histograph showing the relationship between rib deformityand lateral curvature.
H/W
<10 10 15 20 >20 <10 10 15 20 >20
ROTATION (DEGREES) ROTATION (DEGREES)
FIG. 5
A histograph showing the relationship between rib deformityand vertebral rotation.
The effect of bracing and of instrumentation on rib cage
deformityFor some time the authors had thought that Milwaukeebracing could reduce the rib hump. The introduction of amethod of serial recording of the deformity afforded anopportunity to test this opinion in thirty-seven patients overa period of one to two years. More recently we have beenable to observe the results of Harrington instrumentation andwe present the preliminary findings.
66 T. THULBOURNE AND R. GILLESPIE
THE JOURNAL OF BONE AND JOINT SURGERY
RESULTS
Rib deformity and lateral curvature-In order to assess
the influence of lateral curvature alone, without initially
considering the combined effect ofcurvature and rotation,
we allocated fifty-two patients to five groups according
to the severity of curve. Table I shows the range and
means, in each group, of the sums of the hump height
and depression (H+D) and of the two gradients (H/W
+ D/W).The pattern can be appreciated more readily in
histograph form (Fig. 4). As the severity of the lateral
curvature increased there was, as one would expect, a
general upward trend in both the total deformity and in
the hump gradient. This tendency was not so clearly
H/W
0-4
0-3
Q#{149}2
0�1
0
0�1
Q#{149}2
03
Q.4#{149}
D/WFIG. 6
A histograph in which each column represents a single patient.Charting the rib deformity in order of increasing rib humpgradient demonstrates no comparable progression of rib
depression gradient.
� shown in the gradient of the depression. Of more signifi-
cance, however, was the wide overlap in the different
groups. In patients with least curvature (under 21 de-
grees) there were humps of greater severity than the
means of all groups but the most curved. Conversely, in
those most curved (over 50 degrees) there were rib humps
even less than the mean of the group with the mildest
curves.
Rib deformity and vertebral rotation-When the fifty-two
patients were regrouped according to the degree of rota-
tion of the apical vertebra (Table II) and graphically
illustrated in the same manner as for lateral curvature
(Fig. 5), a similar result was obtained. The expected
trend ofincreasing deformity with increasing rotation was
present. Again there was extensive overlap ; some patients
with little rotation had marked rib humps and vice versa.
To assess the influence of vertebral rotation from
another aspect, consider the effect to be expected if a
TElL RIB HUMP lN IDIOPATHIC SCOLIOSIS 67
VOL. 58-B, No. I, FEBRUARY 1976
normal spine were rotated. The upward tilt on one side,
which produces in effect a rib hump, would be associated
with comparable depression on the other side. When,
however, each patient was charted in order of degree of
rib hump gradient (Fig. 6) it could be seen that the length
of the column below the axis, which represents the rib
depression gradient, was distributed in a random manner.
Thus the rib deformity cannot be a direct result of
vertebral rotation alone.
FiG. 7
Histographs showing the combined effect of lateral curvatureand vertebral rotation of 5 degrees or less.
FIG. 8
Histographs showing the combined effect of lateral curvature
and vertebral rotation of 20 degrees.
Rib deformity and combined lateral angulation and verte-
bral rotation-In attempting to determine if the deformity
is related to a combination of angulation and rotation,
we studied two groups of patients, with rotation of 5
degrees or less (Fig. 7) and of 20 degrees (Fig. 8).
The vertical axes represent, as before, the total rib
deformity (H+ D), and the hump and depression gradients
(H/W and D/W). In these two figures, each column
represents an individual patient, and the patients are
arranged in order of increasing lateral curvature. Within
groups of patients having the same degree of vertebral
rotation, the rib deformity was not significantly influenced
by the severity of the scoliosis. A similar analysis of the
remaining groups (10 and 15 degrees of rotation) revealed
a similar lack of correlation.
To illustrate this lack of correlation clinically, two
patients are presented. Figure 9 shows a girl aged fifteen
with a mild double curve. The thoracic curve, rather
unusual in being convex to the left, is the one producing
most of the clinical deformity and measures only 16
degrees from T.2 to T.9, with rotation of barely 5 degrees
at T.6. The lower curve, from T.8 to L.3, measures 22
degrees with no significant rotation. Figure 10 shows a
girl aged sixteen with severe scoliosis. The major curve,
from T.6 to T.l2, measures 50 degrees, with over 20
degrees of rotation at T.9. The upper curve, from T.2
to T.6, is 42 degrees, with 1 5 degrees of rotation at T.4.
As can be seen, the girl with the more deformed rib cage
is the one with the less marked spinal changes.
Rib deformity and rib-vertebra angles-These angles give
an indication of deformation in a coronal plane of the
ribs relative to the apical vertebra. The rib hump and
depression represent deviation of the ribs in a sagittal
plane, both as a result of vertebral rotation and of any
angulation relative to the vertebrae. Because we thought
there might be an interrelationship between these two
features, we regrouped the patients according to R-V
angle differences (concave side minus convex side). How-
ever, a familiar pattern emerged (Table 111, Fig. 1 1). A
slight upward trend in the severity of the deformity was
demonstrated, but again there was a wide overlap.
When one considers, independently, the effect of the
R-V angle of the convex side on the rib hump gradient
(Table 1V, Fig. 12), and of the R-V angle of the concave
side on the rib depression gradient (Table V, Fig. 13),
one sees a tendency for the rib hump to be more severe
if the ribs on that side are more depressed from the
horizontal, and for less marked rib depression as the ribs
on the concave side become more nearly horizontal. There
is, however, no evidence of a direct relationship.
The effect of bracing and instrumentation
The Milwaukee brace-The chart of one girl illustrates
the effect of Milwaukee bracing (Fig. 14). The tracings
made over a period of two years, from thirteen to fifteen,
demonstrated a common pattern of events. The positive
rib hump on the convex side remained fairly constant;
the rib depression, however, gradually became less notice-
able until finally it was actually reversed. Thus the total
deformity was much reduced. This change occurred
without change of the lateral curvature and with no
significant difference in vertebral rotation. The same
train of events, leading to an almost unchanged hump
but elevation of the depressed side, has been observed in
twenty-two of the thirty-seven cases.
Harrington insfrumentation-Although the nulnber of
cases is small, the pattern appears to be the same as that
with Milwaukee brace treatment. The tracings before and
after operation in three cases are given in Figure 15.
DISCUSSION AND CONCLUSIONS
In recent years there has been more emphasis on the
treatment of the rib hump deformity in scoliosis by such
means as resection of part of the prominent ribs or
osteotomy of the transverse process (Goldstein 1966,
:� 1FIG. 10
A severe curve of 50 degrees and over 20 degrees of rotation but with little rib cage deformity.
THE JOURNAL OF BONE AND JOINT SURGERY
68 T. THULBOURNE AND R. GILLESPIE
�w. .
p 4��’ � �
FIG. 9
A mild curve of 16 degrees and only 5 degrees of rotation but with a marked rib cage deformity.
D/W
0.4
0.3
0.2
0.1
D,,w8-V DIFFERENCE R-V DIFFERENCE
R-V DIFFERENCE (degrees) NEGATIVE 0-5 6-10 � 11-15 16-20 over 20
NUMBER OF PATIENTS 7 13 � 9 9 6 � 8
DEFORMITY Range 7-32 6-28 0-31 7-25 10-29 11-43(H-� D millimetres) Mean , 16 15 15 15 18 22
HUMP Range 003-030 0i0-0�2l 0-036 0-031 013-022 010-044GRADIENT Mean � 013 016 013 015 016 023
DEPRESSION Range 008-027 0-037 � 0-027 012-034 007-028 0-030GRADIENT Mean 021 � 017 018 023 022 018
THE RIB HUMP IN IDIOPATHIC SCOLIOSIS 69
VOL. 58-B, No. I, FEBRUARY 1976
FIG. II
Histographs showing the relationship of rib deformity to rib-vertebra angle difference.
H<60 60- 66- 71- >75 <7171- 76- 81- >85
65 70 75 75 80 85
CONVEX 8-V ANGLE CONCAVE 8-V ANGLE
(DEGREES) (DEGREES)
FIG. 12 FIG. 13
Figure 12-Histograph showing the re�ationship of theconvex R-V angle to the rib hump gradient. FigureI 3-Histograph showing the relationship between
concave R-V angle and rib depression gradient.
TABLE III
RIB-VERTEBRA ANGLE DIFFERENCE AND RIB CAGE DEFORMITY
TABLE IV
CONVEX R-V ANGLE AND RIB HUMP GRADIENT
CONVEX R-V ANGLE (degrees) � under 60 � 60-65 66-70 71-75 over 75
NUMBEROFPATIENTS 10 10 II 10 11
HUMP Range 0-044 0�02-036 009-025 0-02 1GRADIENT Mean 022 016 016 012
003-030012
TABLE V
CONCAVE R-V ANGLE AND RIB DEPRESSION GRADIENT
CONCAVE R-V ANGLE (degrees) under 71 � 71-75 , 76-80 81-85 over 85
NUMBEROFPATIENTS 13 II 8 8 12
DEPRESSION Range � 022-027 003-037 007-024 0-034GRADIENT Mean 017 020 019 020
0-#{216}�35021
1973), and the use of pressure pads within post-operative
casts (Cotrel and Morel 1964). This interest has increased
the need for a simple method of recording the deformity
rather than reliance on measurements of variations in
the height or slope of the back or on clinical photographs.
With a true outline of the back at its most deformed
level, one is better equipped to draw conclusions on the
effect of treatment. The authors believe that the instru-
ment described fulfils these requirements.
The severity of the rib cage deformity is widely
accepted as being a function of the degree of vertebral
rotation. Less accepted is the view that the rib changes
1-c.
FIG. 14
A series of rib hump graphs in a patient during treatment ina Milwaukee brace. Note the almost unchanged rib hump
but marked improvement in rib depression. FIG. 16
A diagram to show how rib hump and rib depression may beproduced by deformity of the posterior vertebral elements
without rotation of the vertebral body.
JUL
72
FE B74
MAY72
NOV
72
MAY
73T6-T11��5�
T6�T11:27’ \
FIG. 15
The improvement in rib depression but little change in ribhump shown in three patients after Harrington instrumen-
tation.
70 T. THULBOURNE AND R. GILLESPIE
THE JOURNAL OF BONE AND JOINT SURGERY
are always related to the lateral curve ; for example,
Goldstein (1973) stated that “some 75-degree lateral
thoracic curves have a milder and more correctable rib
�- -- ��1�26’
cage deformity than other patients with a 50- or 55-degree
curve”. We have been able to demonstrate, in this study
of fifty-two untreated cases, that the rib cage deformity
bears no direct relationship either to the degree of verte-
bral rotation or to the lateral angulation or to both.
Even the rib-vertebra angles and their differences, which
one might expect to bear some relationship to the de-
formity of those same ribs, give no indication of the
severity of the deformity.
As the rib hump and rib depression are not related
directly to any of the radiographic features normally
measured, there remains the question as to what is their
true causation. It is well known that in scoliosis the
posterior elements show a torsional deformity (Fig. 16),
with deviation of the spinous process towards the con-
cavity of the curve and asymmetry of pedicles, laminae
and transverse processes (Roaf 1960 ; James 1967 ; Enne-
king and Harrington 1969). This deformation occurs
independently of rotation. In our opinion, it is this
deformation which is the major factor contributing to
the altered shape of the rib cage, with vertebral angulation
and rotation contributing relatively little. Unfortunately,
the degree of variation in the shape of the posterior
elements cannot be assessed on a normal radiograph as
the alignment of the transverse processes is not given.
Admittedly the extra deviation of the spinous process
relative to the rotated vertebral body can be seen, but
this produces only indirect evidence. Axial tomography
(Gargano, Jacobson and Rosomoff 1974) could demon-
strate the true shape of the apical vertebrae but the
equipment for it is not available for our use at the present
time. Even if it were, we doubt whether the resulting
information would justify the large amount of extra
irradiation (equivalent to that of a myelogram) in a
growing girl who is already undergoing repeated radio-
graphic examinations.
A study of the modification of the rib cage deformity
during treatment has produced an interesting, if unex-
pected, result. Ever since the introduction of the Mu-
waukee brace, opinions have differed widely as to its
effect on the rib hump. We are now able to state that
in most cases the true rib hump on the convex side of a
thoracic curve is little influenced, whereas the contra-
lateral rib depression can be markedly reduced, and in
THE RIB HUMP IN IDIOPATHIC SCOLIOSIS 71
VOL. 58-B, No. 1, FEBRUARY 1976
the most responsive cases even completely corrected.
Thus for patients where the rib depression contributes a
disproportionate part of the total deformity, one may
maintain a rather more optimistic view as to the ultimate
clinical appearance than can be held when the hump is
the more obvious feature. As this elevation of ribs may
occur without alteration of either curvature or rotation
and is on the side of the chest remote from any pressure
pad, it is difficult to picture what forces produce the
improvement. When treating a child in a Milwaukee
brace we place great emphasis on exercises both in and
out of the brace. One exercise which we regard as most
important is arching of the back in the brace, with the
breath held in deep inspiration. It is interesting to
speculate that this manoeuvre, originally intended to
control associated thoracic lordosis, might be forcing the
ribs on the concave side backwards and producing an
unexpected beneficial effect.
Because few cases are as yet fully documented, we
have been unable to prove conclusively that Harrington
instrumentation always produces the same favourable
effect on the rib cage deformity, but as in brace treatment,
we feel that the clinical appearance may be much im-
proved in patients with relatively severe rib depression.
It should be noted that our patients had a standard form
of instrumentation without osteotomy of the transverse
processes or special after-care aimed at reduction of the
rib hump. Perhaps such additional procedures merit
further consideration when the rib hump provides the
greater element of deformity.
REFERENCES
Cobb, J. R. (1948) Outline for the study of scoliosis. American Academy of Orthopaedic Surgeons. In Instructional Course Lectures,5, 261-275.
Cotrel, Y., and Morel, B. (1964) La technique de l’E.D.F. dans la correction des scolioses. Revue de Chirurgie orthop#{233}dique et r#{233}paratricede I’Appareil Moteur (Paris), 50, 59-75.
Enneking, W. F., and Harrington, P. (1969) Pathological changes in scoliosis. Journal of Bone and Joint Surgery, 51-A, 165-184.
Gargano, F. P., Jacobson, R., and Rosomoff, H. (1974) Transverse axial tomography of the spine. Neuroradiology, 6, 254-258.Goldstein, L. A. (1966) Surgical management of scoliosis. Journal ofBone and Joint Surgery, 48-A, 167-196.Goldstein, L. A. (1973) The surgical treatment of idiopathic scoliosis. Clinical Orthopaedics and Related Research, 93, 13 1-157.
James, J. L P. (1967) Scoliosis. Edinburgh and London : E. & S. Livingstone Ltd.
Laveriniccoca, A. (1913) Sulla scoliosometria-binostereoscopia-pantoscoliosografo-plasmascoliosometro. Atti di oriopedia e Iraurnato-logia, 8, 490-521.
Mehta, M. H. (1972) The rib-vertebra angle in the early diagnosis between resolving and progressive infantile scoliosis. Journal of Boneand Joint Surgery, 54-B, 230-243.
Mehta, M. H. (1973) Radiographic estimation of vertebral rotation in scoliosis. Journal ofBone andJoint Surgery, 55-B, 5 13-520Nash, C. L., Jun., and Moe, J. H. (1969) A study of vertebral rotation. Journal ofBone and Joint Surgery, 51-A, 223-229.
Rippstein, J� (1967) Deux nouveaux instruments pour l’examen clinique des scolioses. Acta orthopaedica Belgica, 33, 595-597.
Roaf, R. (1960) Vertebral growth and its mechanical control. Journal ofBone andJoint Surgery, 42-B, 40-59.