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Variations of the Lumbrical Muscles of the Hand.

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Variations of the Lumbrical Muscles of the Hand
S. S. BASU’ AND S. H A U R Y ’
Department of Anatomy, Yak University School of Medicine,
New Haven, Connecticut
The lumbrical muscles constitute an important part of the intrinsic musculature
of the hand. A most distinctive feature is
their origin from flexor tendons and insertions into extensor expansions. Although
several deviations from normal or variations of the lumbricales have been described in standard textbooks of gross
anatomy and other surgical or anatomical
publications, a review of the basic anatomy
of the lumbricales will be helpful. Usually they are 4 cylindrical muscles that
arise from the profundus tendons and approach the radial aspects of the metacarpophalangeal joints ventral to the
transverse metacarpal ligaments for their
insertion to the extensor expansion. The
first and second lumbricales are unipennate. The third and 4th lumbricales are
bipennate in origin and arise from adjacent tendons of deep flexor muscles. During the present investigation previously
undescribed variations of the lumbrical
origins or insertions were noted. This
paper describes the variations and presents data on the normal frequency as
well as the frequency of the more common
and previously described variations.
MATERIALS AND METHODS
The data for this report were obtained
from dissections of 36 adult cadavers ( 5
female and 31 male). Because both right
and left hands were observed, this study
included a total of 72 hands and 287 lumbrical muscles. The dissections were done
by students in the dissecting rooms and in
most instances completed by the investigators who examined each of the specimens and recorded on sketches the details
of the lumbrical musculature.
OBSERVATIONS
In 72 hands which were dissected the
following observations were made. Only
6 cadavers had in both hands origins, insertions and distributions of the lumbricales that are described in most anatomical
texts as being normal, that is, 4 lumbricales inserting in the radial side of the extensor expansion, the two lateral (radial)
lumbricales being unipennate and the two
medial bipennate (table 1 fig. 1), In addition to the 12 hands mentioned above, 9
other cadavers had a “normal” lumbrical
musculature of the right hand and 9 had
“normal” lumbricales in the left hand. A
total of 30 of the 72 hands were thus
“normar according to the usual textbook
description of the lumbricales.
The first lumbrical muscle consistently
conformed to the usual pattern both
in its origin and insertion. Sixteen of 72
(22.2% ) second lumbricales arose from
the profundus tendons adjacent to the
second and third digits (figs. 5, 7 and 8)
and two (2.8% ) had bifid insertions, on
adjacent sides of the second and third
digits (fig. 7). All the third lumbricales
showed the normal bipennate origin from
the profundus tendons adjacent to the
third and 4th digits. Fifteen of 72
(20.8% ) had bifid insertions to adjacent
sides of the third and 4th digits (fig. 7)
and 9 (12.5% ) were attached only to the
ulnar side of the third digit (figs. 2, 4).
The 4th lumbricales differed most extensively both in origin and insertion. Two
of 71 (2.8%) presented unipennate origins from the radial side of the profundus
tendon to the 5th digit (fig. 8 ) . In one
right hand the lumbrical muscle was missing (fig. 6). Eight of 71 (11.2%) 4th
lumbricales had bifid or split insertions
that attached to the adjacent sides of the
4th and 5th digits (fig. 5), and 4
(5.6% ) were inserted only to the ulnar
1 International Co-operation Administration FelIow (1958-1959). Permanent address: S. C. B.
Medical College, Cuttack, Orissa, India.
501
502
S . S . BASU AND S . HAZARY
TABLE 1
Frequency of "normal" and of variations of lumbrical musculature as revealed
by dissection of 72 hands
Left hand
Right hand
Types'
Normal
1
2
3
4
5
6
Bofh hands
Number
Per cent
Number
Per cent
Number
Per cent
15
20.8
9.7
1.4
13.9
4.2
2.8
1.4
5.5
2.8
15
9
1
5
6
0
0
4
2
20.8
12.5
30
16
2
15
9
2
1
8
4
41.7
7
1
10
3
2
1
4
2
7
8
1.4
6.9
8.3
-
5.5
2.8
22.2
2.8
20.8
12.5
2.8
1.4
11.2
5.6
- -
'Normal (see text).
1. Bipennate origin of the second lumbrical muscle.
2. Bifid insertion of the second lumbrical muscle.
3. B S d insertion of the third lumbrical muscle.
4. Insertion of the third lumbrical muscle on the ulnar side of the third digit.
5. Unipennate origin of the 4th lumbrical muscle.
6. Fourth lumbrical muscle missing.
7. Bifid insertion of the 4th lumbrical muscle.
8. Insertion of the 4th lumbrical muscle to the ulnar side of the fourth digit,
TABLE 2
Combination of variations of lumbrical muscles
as revealed by dissection of 72 hands
Types1
1 and4
1 and 3
1,2and 3
3 and 7
4 and 5
1 and 5
1 and 7
4 and 7
1 and2
4 and 8
1
Right side
Left side
1
2
1
2
I
1
0
0
0
0
0
2
0
0
0
0
1
1
1
1
Both
1
4
1
2
1
1
1
1
1
1
See table 1.
side of the 4th digit (fig. 3 ) . Different
combinations of variations in the lumbricales were aIso observed (table 2).
DISCUSSION
Standard textbooks of gross anatomy
and other relevant literature reveal that
the number of lumbrical mclscles vary
from two to 5 or 6 (Gray, '59). Braithwaite et al. ('48) have stated that additional or accessory lumbricales occur more
frequently than a reduction in number,
the third being the one most frequently
missing. Whereas Morris ('53) described
absence or doubling of the third and 4th
without stating the frequency. In the present series, except in one right hand in
which the 4th lumbricale was missing,
4 lumbricales were found in all hands
dissected.
Lumbricales have been described with
anomalous origins from any of the long
flexor tendons in either the forearm or the
hand, from the interosseous muscles, or
from other lumbricales; the third lumbricalis most frequently had an anomalous origin (Russel and Sunderland, '38). Lane
(1887) and du Bois-Reymond (1594) described unusual anomalous origins of extra
slips that joined lumbrical muscles of
otherwise normal origin. The first lumbricalis may arise from the opponens Follicis
or the metacarpal of the thumb (Morris,
'53). The present investigation revealed
anomalous origins of only 16 of 72 second
Iumbricales and two of 71 4th Iumbricales.
The most frequent anomalous insertion
involved splitting of the tendon and attachment to the adjacent digits or its attachment only on the ulnar side of a digit.
The first, second and 4th lumbricales attach along the radial side of the second,
third and 5th digits while the third
lumbricalis runs to the radial side of the
4th digit or spIits to attach to the adjacent
sides of the third and 4th digits (Spalteholz; Morris, '53). No abnormal insertion
of the first and second lumbricales were
observed in 32 hands by Eyler and Markee
('54), but 5 of 31 third lumbncales were
attached to both the third and 4th digits
VARIATIONS O F THE LUMBRICAL MUSCLES O F THE HAND
503
and two were attached to the ulnar side of known evolutionary or development prothe third digit; two of 29 4th lumbricales cesses.
were attached to both the 4th and the 5th
SUMMARY
digits and two were attached on the ulnar
1. Lumbrical muscles of 36 adult caside of the 4th digit.
davers (5 female and 31 male) or 72
The bifid attachment of the second hands were studied. In 6 cadavers
lumbricales to the adjacent sides of the (16.7% ) the lumbrical muscles in both
second and third digits (two in our series hands presented normal textbook pattern.
of 72) had not been described prior to In 18 other cadavers (50.0% ) either the
our study. Of 72 third lumbricales 15 right hand or the left had lumbricales that
were bifid and attached to the adjacent showed no abnormality. Thus, a total of
sides of the third and 4th digits and 9 were 30 hands (41.7%) were normal in the
attached to the ulnar side of the third origins, insertions, and distributions of
digit. Among the 71 4th lumbricales, 8 the lumbricales.
were bifid and attached to the adjacent
2. Eight different types of variations in
sides of the 4th and 5th digits, whereas 4 the lumbrical muscles were observed and
were inserted into the ulnar side of the their frequency of combinations of differ4th digit.
ent types of variations were recorded.
In the present study, only 6 cadavers
(16.7% ) had lumbrical muscles in both
ACKNOWLEDGMENTS
hands that presented the usual normal
Our
thanks
are due to Dr. William U.
pattern in their origins and insertions.
Gardner,
Chairman
of the Department of
When one hand, either the right or the
left was considered, in 15 cadavers Anatomy, Yale University School of Medi(41.7% ) the lumbricales showed no abnor- cine, for his advice and help in writing
mality. Two anomalies of the lumbricales this paper.
were observed in the right hand of 7
LITERATURE CITED
cadavers (19.4% ) and in the left hand of
G.D. Channell, F. T. Moore and J.
Braithwaite,
F.,
6 cadavers (16.7%). The right hand of
Whillis 1948 The applied anatomy of the
only one cadaver (2.8% ) had three varialumbrical and interosseous muscles of the hand.
tions of the lumbricales.
Guy’s Hosp. Rep., 97: 185-195.
The present investigation shows that du Bois-Reymond, R. 1894 Beschreibung einer
Anzahl Muskelvarietaten a n einem Individuum.
either the 4th or the 5th digit may have no
Anat. Anz., 9: 451.
lumbrical muscle attached to it. It may be Eyler, D. L., and J. E. Markee 1954 The anaassumed, therefore, that some deficiency
tomy and function of the intrinsic musculature
of the fingers. J. Bone Joint Surg., 36:A 1-9.
in the power of flexion of the metacarpoH. 1959 Anatomy of the Human Bodv,
phalangeal joints of those digits may exist Gray,
ed. C. M. Goss. Lea and F.ebiger, Philadelphia,
during life. The 30 hands with normal
p. 524.
lumbrical musculature were present in 24 Lane, W. A. 187 Abnormal muscIe of the hand.
J. Anat. Physiol., 21: 674.
of the 36 cadavers. Two or more varia- Morris,
H. 1953 Human Anatomy, ed. J. P.
tions of the lumbrical muscles were noted
Schaeffer. The Blakiston Co., Sect. V, p. 497.
in either the right or left of 12 cadavers; Russel, K. F., and S. Sunderland 1938 Abnormalities of the lumbrical muscles of the hand.
in one cadaver only and on the right side
J. Anat., 72: 30&307.
were multiple variations present (table 2). Spalteholz,
W. Hand-Atlas of Human Anatomy,
The patterns of the lumbrical muscula7th edition (in English). J. B. Lippincott Co.,
ture have permitted no association with
Philadelphia, p. 337.
PLATE 1
VARIATIONS OF THE LUMBRICAL MUSCLES OF THE HAND
S. S. Basu and S. Hazary
n
A
n
n
NORMAL
Diagrammatic presentation of normal lumbrical musculature and 8 types of variations
shown in different combinations actually obtained in cadavers.
Figs. 2-8
1 Normal.
2 Type 4.
504
See table 1 for description and frequency of the several different variations.
3
4
Type 8.
Types 4 and 7.
5
6
Types 1 and 7.
Type 6.
7 Types 1, 2 and 3.
8 Types 1 and 5.
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