STUDY OF THE NORMAL TIBIA. 
f Abstract ] 
By Dr. Ares Hrdricka, New York City. 
REPRINTED FROM 
Proceedings of the Association of American Anatomists, 
Eleventh Annual Session, held in New York City, 
December 28-30, 1898. STUDY OF THE NORMAL TIBIA. 
[Abstract.] 
By Dr. Ares Hrdlicka, New York City. 
Observations and measurements were made on about 2,600 
tibiae, almost 2,000 of which were bones of whites, 80 the 
bones of negroes, and the remainder the bones of North and 
Central American Indians. 
The study of the bones of whites and negroes was carried 
on at the College of Physicians and Surgeons, New York, on 
the collection of Prof. George S. Huntington ; the Indian 
tibiae were principally studied at the American Museum of 
Natural History, New York, and partly at the National Mu- 
seum, Washington, and at the Peabody Museum, Boston. 
The objects of the study are : 1. Contribution to the knowl- 
edge of variations of the bones; 2. Study of correspondence 
of different variations of the various parts of the skeleton ; 
3. The tracing, so far as possible, of the causation and ten- 
dencies of variations found ; 4. The establishing of some 
standards, if possible, for comparisons. 
The study presents numerous difficulties, the principal of 
which is due to a deficiency of data about many of the bones. 
This difficulty has been largely foreseen and diminished in 
Prof. Huntington’s collection by a system of keeping records 
about the bones. A good system of records and provision for 
a proper identification of every individual specimen is, in the 
author’s opinion, the main requisite and the most valuable 
feature of every large osteological collection. (A simple 
scheme for such identification and record keeping will be 
given in the detailed publication.) 
Of the results of the study, in the main, only generalities 
are mentioned, the details, particularly those of the meas- 
urements, being left for print; the results are as follows : 
The tibia differs much in shape, but the innumerable little 
variations can be arranged in a number of distinct types. The 
principal, though not the only differences in the bone, occur 
in the shape of the shaft. They are best appreciated when 
we study the shaft in a transverse section, particularly at the 2 
middle of the bone. The lower third of the shaft of the tibia 
is not so well differentiated as the middle, while the shape of 
the upper third is, in over a half of the cases, more or less 
disturbed by the oblique ridge. 
There are six main types of the shape of the shaft at the 
middle of the tibia and one or another of these types was 
clearly recognizable in fifty-five per cent, of the bones of the 
whites, the remaining forty-five per cent, of the bones show- 
ing intermediary stages. In the majority of cases tibiae do 
not fully develop their type until after the complete union of 
their epiphyses. Negro bones show variety which may be 
due to some extent to admixture. Indian tibiae are much 
more homogeneous in their shape than either those of whites 
or of negroes, particularly the former. No marked difference 
was found in the shape of the tibiae of whites of different 
nationalities. 
The six types of the shape of the shaft of the tibia at the 
middle are as follows : i. Closely approaching a right equilate- 
ral triangle, found in 18.2 percent, of white tibiae. 2. Closely 
approaching a lateral triangle, the posterior surface not facing 
directly backward, as in the previous type, but backward and 
outward, found in 14.9 per cent, of white tibiae. 3. Shaft more 
or less triangular with the external surface markedly concave, 
in 9.1 per cent, of the tibiae of whites, very prevalent among 
Indians, almost absent among negroes. 4. Shaft quadrilateral, 
posterior surface being divided by a marked vertical ridge into 
two lateral surfaces, in 5.1 per cent, of whites, mainly in males. 
This shape is somewhat less frequent in negroes, but consider- 
ably more frequent in Indians. 5. Posterior border blunt or 
effaced, posterior half of the shaft oval, in 5.2 per cent, of 
whites, mainly in females. 6. Internal surface flat or slightly 
convex, external and posterior surfaces quite convex, exter- 
nal border may be effaced; almost absent in whites, never met 
with in Indians, frequent in negroes (10.9 percent). Trans- 
verse sections of this type are very similar to those of the tibia 
of the gorilla. A little over five per cent, of all the white bones 
examined showed these various types in a perfect form (demon- 
stration of whole bones and of sections). 
The signification of the various shapes is obscure, but the 
author will follow a large number of the individuals to whom 
the bones belonged, and try to learn their vocation to see 
whether possibly this may not have had some effect in favor- 3 
Ext. Surf. 
VI. 
Illustration of the six types of the shape of the shaft of the Tibia. (Partly schematic.) 
V. 
IV. 
Anter. Border. 
Post. Surf. 
III. 
II. 
I. 
Types : 
Int. Sur. 4 
ing the development of certain shapes. There are indications 
that even with such a knowledge we will be much at a loss to 
explain the different shapes. Some such indications are the 
occurrence of all the shapes in women, and that in proportions 
not differing greatly from those of men ; the weak bones differ 
quite as much as the strong bones, and there are found fully 
evolved types in young adults, in whom occupation or habits 
of life have not yet exerted much influence on the skeleton. 
The third type is found to be accentuated in some curved 
bones, but over thirty-five per cent, of curved bones did not 
show any concavity of the external surface to speak of. 
The shape of the anterior border or crest of the tibia was 
found to vary from an almost straight line to a marked double 
curved figure. The causes of the different forms could not be 
definitely traced, but the very curved crest seems to be at least 
partly due to muscular action. 
The measures of the tibia are all subject to numerous varia- 
tions, and they differ not only in different individuals, but also 
in the two bones of the same body. The tibia is in average 
both longer and stronger in the male. In numerous instances 
the left tibia is the longer. 
As to diametrical measurements, the author advocates that a 
preference be always given to those of the measured middle of 
the tibia over those at the height of the nutrient foramen. At 
this latter height many of the bones are influenced by the 
overgrowth of the oblique ridge ; the nutrient foramina are 
not situated at the same height in different bones, nor even 
in the bones of the two sides of the same body ; and occa- 
sionally the foramen will be double, all of which makes meas- 
ures taken at this height difficult of comparison and not fully 
reliable. 
The details of the measures cannot be given in an abstract. 
Advanced platycnemy (index below 60) is very rare in both 
the whites and the negroes, but is common in the Indians. In 
average the tibia is somewhat (two or three per cent.) more 
platycnemic at the height of the nutrient foramen than it is 
at the middle. The relative position of the external border 
can be measured. The articular surfaces of the male tibia are 
larger than those of the female. 
The head of the tibia as a whole is larger in the male both 
antero-posteriorly and laterally. The backward inclination of 
the head does not vary materially in the whites and the negroes, 5 
although in about oue-half per cent, in the white bones the 
inclination backward is plainly augmented. In Mexican In- 
dians, particularly in some tribes, a pronounced backward 
inclination of the head is common. 
The spine is, as a rule, double. Its length is not depend- 
ent on the length of the bone, and may differ on the two sides 
of the same body. The male spine is, on the average, slightly 
longer. 
The weight of the tibia differs greatly; it is much influ- 
enced by the age of the person. The weight and displacement 
of the bone being compared on a series of subjects, the fol- 
lowing results in general were obtained : The tibia is heaviest 
in proportion to its volume between 20 and 40 years of age. 
Above 40, and sometimes even before, the weight in propor- 
tion to the volume of the bone diminishes. This diminution 
is due to the beginning senile rarefaction ; it differs very much 
in different subjects, and is rarely the same on the two sides 
of the body. The rarefaction is much more regular and at 
all ages greater in the female. Bones of aged individuals 
may show as low as one-fourth of the relative weight found 
in young adults. 
The displacement of the tibia may be measured with shot 
or seeds, by a rough and unsatisfactory calculation from the 
various measures, or by rapidly immersing the bone in some 
heavy liquid which is not liable to be rapidly absorbed. The 
author used glycerine. 
There are chemical differences between the bones of young 
and old persons. The inorganic matter seems to decrease with 
age. 
The tibia is not subject to gross anomalies, but is very much 
subject to pathological conditions. An interesting, though 
perhaps not congenital, anomaly found, consisted of a well- 
defined, rounded, slightly convex, six mm. broad, articular 
facet on the tip of the malleolus of one tibia. 
The causes of the numerous variations of the tibia are ap- 
parently very multiple. Some indications point to the fact 
that they are partly due to hereditary influences and partly 
to acquisition. The effects of muscular action on the shape 
and size of the bones will require much additional investi- 
gation. 
The details as to the pathological conditions found will also 
be given later. 6 
Dr. Lamb agreed with the author in at least two points; 
first, that platycnemism is common in the bones of Indians 
in the Army Medical Museum and not in those of negroes; 
and, second, that for the reasons given by the author, the 
tibial index is more reliably measured below the opening of 
the nutrient foramen and oblique ridge.