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Anatomy of Hereditary Bovine Syndactylism. II. Muscles, Tendons, and Ligaments1
Anatomy of Hereditary Bovine Syndactylism. II. Muscles, Tendons, and Ligaments 1 R. W. ADRIAN, H. W. LEIPOLD, KEITH HUSTON, D. M. TROTTER, and S. M. DENNIS Departments of Anatomy, Pathology, and Dairy and Poultry Science Kansas Agricultural Experiment Station, M,znhattan 66509
from + / + animals; and 3) syndactylous animals possessing the sy gene from other syndactylous animals. I n this paper, anomalies of the muscles, tendons, and ligaments are presented.
Abstract
Muscle, tendon, and ligament anomalies that distinguish externally 1) normal overlap s y / s y homozygotes from normal + / s y and + / + animals; 2) normal + / s y animals from + / + animals; and 3) syndactylous animals possessing the sy gene from other syndactylous animals were sought in the limbs from 35 syndactylons sy/sy, two normal overlap sy/sy, and six normal +/sy Holstein cattle. Tendons and ligaments were adapted to the single digit. Three digital extensor muscle tendons fused at the fetlock into a wide aponeurotic plate that received on each side a reinforcing branch from the deep suspensory ligament and inserted on the second and third phalanx. The tendons of the superficial and deep digital flexor muscles usually remained undivided and inserted normally on the single functional digit. A small branch often passed from the tendon of the superficial digital flexor muscle to the lateral dewclaw, the only anomaly of the front feet of normal overlap and of two of six + / s y animals. Other rarer muscle tendon branches to the dewclaw were found. The superficial p a r t of the suspensory ligament, besides joining the tubular portion of the superficial digital flexor muscle tendon, attached by a wide band to the proximal sesamoid bones. Branches of the deep suspensory ligament were fewer than normal.
Experimental Procedures
Limbs from 35 syndaetylous cattle, two normal overlap s y / s y bulls, and six normal + / s y cattle were removed at slaughter or necropsy by dismembering proximal to the carpal or tarsal joints. They were dissected either in fresh unfixed condition or after embalming with an attueous solution containing 12% formalin, 3.7% glycerin, and 0.5% acetic acid. Results and Discussion
As noted in the first p a p e r in this series (1), control of the incompletely penetrant, recessive U.S. Holstein form of syndactylism may be facilitated by knowledge of anatomic differences that distinguish externally 1) normal overlap s y / s y homozygotes from normal + / s y and + / + animals; 2) normal + / s y animals Received for publication April 9, 1969. 1 Contribution no. 14, Department of Anatomy; no. 118, Department of Pathology; and no. 729, Department of Dairy and Poultry Science. This research was part of the North Central Regional Dairy Cattle Breeding Project •C-2.
Among the 35 syndactylous animals, the external degree of syndactylism was as follows: eight with only right front foot syndactylous; 19, both front feet; four, both front feet and right rear; two, both front feet and left rear; one, right front foot and both rear; and one, four syndactylous feet. The arrangement of muscles, tendons, and ligaments was similar regardless of the number of affected feet; therefore, all syndactylous animals are described together. The two normal overlap s y / s y bulls and the six normal + / s y animals are described separately. Normal overlap sy/sy bulls. The muscles and tendons of the front feet of both bulls had normal positions and insertions. However, the superficial digital flexor tendon on both front feet gave rise to, at the middle of the metacarpus, a thin tendon about 10 cm long which inserted at the base of the lateral dewclaws. Both hind feet were normal. Syndactylous front feet. With few exceptions, muscles, tendons, and ligaments deviated similarly in all syndactylous front feet. The three separate digital extensor tendons passed normally over the carpal joint to the fetlock region. Here the tendons became wider and flatter and finally fused to form a broad, common aponeurotic plate that inserted mainly at the extensor surfaces of the second and third phalanges (Fig. 1). The dorsal digital synovial sheath was absent. On the right front foot
1432
BOVINE
SYNDAOTYLISM.
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digita~ flexor muscle remained undivided, received the superficial digital flexor muscle to form a tube around the single deep digital flexor tendon (Fig. 2). The single superficial digital flexor tendon inserted normally on the volar surface of the second phalanx. Occasionally, one or two fibrous bands attached their tubular part to the intersesamoidean or distal sesamoidean ligaments. The deep digital flexor tendon coursed and inserted normally on syndaetylous feet but it remained undivided. In two syndactylous left front feet it gave rise to a thin tendon to the base of the lateral dewclaws. The deep digital fascia formed three single annular ligaments for the digital flexor tendons. The suspensory ligament consisted of a superficial fibrous part and a deep part which was muscular in young specimens. The superficial part varied from a single fiat band to two
:FIG. 1. Dorsal view of a syndactylous leg after removal of skin, fascia, nerves, and veins. The tendons of the three digital extensor muscles form a thin aponeurotic plate in the fetlock area. of a cow with syndactylous front feet only, and on both front feet of a calf with all four feet syndactylous, the lateral digital extensor tendon branched off a small tendon to the base of the lateral dewclaws. Down to the distal third of the metacarpus, the superficial digital flexor tendon had the same anatomic features as in normal cattle. At this point, however, it branched off one and, occasionally, two thin tendons, 3 to 10 cm long, that inserted at the base of the lateral dewclaw, not only in syndactylous feet but also in normal left front feet of syndactylous cattle. In one case, that tendon was reconnected to the main tendon by two flat muscular bands 1 cm wide. The main tendon of the superficial
FIO. 2. Volar view of a syndactylous leg after removal of skin and fascia.. .]', DAIRY SOlENOE YOL. 52, NO. 9
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ADRIAS ET AL. s u s p e n s o r y l i g a m e n t gave off a b a n d to one of the r u d i m e n t a r y bones of the lateral dewclaw. The i n t e r s e s a m o i d e a n a n d the medial a n d Intern.1 sesamoidean l i g a m e n t s were normal. The
FIG. 3. Volar view of metacarpo-phalangeal joint. The suspensory ligament and the proximal sesamoid bones are reflected distally. Note two bra~lches of tlle deep suspensory ligament, three proximal sesamoid bones, and the distal metacarpal trochlea with two closely located sagittal ridges. bands, o r a single b a n d on e i t h e r the lateral or medial side. The superficial p a r t of the s u s p e n s o r y l i g a m e n t not only aided in the f o r m a t i o n of a tube f o r the deep digital flexor tendon, b u t also detached a considerable p o r tion to the superficial p r o x i m a l b o r d e r of the p r o x i m a l sesamoid bones. The deep p a r t of the s u s p e n s o r y l i g a m e n t did not always show a clear division into branches. AM a general rule, however, the n u m b e r of b r a n c h e s c o r r e s p o n d e d to the n u m b e r of p r o x i m a l sesamoid bones (Fig. 3). There was on each side a r a t h e r flat a n d wide connection to t h e a p o n e u r o t i c terminal p a r t of the digital extensor tendons. I n t h r e e cases the lateral b r a n c h of t h e deep J. DAIRY SCIENCE XTOb. 52, NO. 9
FIG. 4. ]~ifurcation of deep digital flexor tendon for the distance of 8 cm.
BO'VINE
SYNDACTYLIS~I.
middle distal sesamoidean ligaments were well developed and converged slightly distally. Between them there were sparse fibers of indistinct direction representing the deep distal sesamoidean ligaments. The collateral ligaments of the metacarpo-phalaageal and the phalangeal joints, and the ligaments of the distal sesamoid bone were normally developed for the single functional digit. The ligaments of the two dewclaws showed no deviation from the normal pattern. On the single toe there was no place for interdigital ligaments. On externally normal left front legs of syndactylous cattle, the superficial digital flexor muscle branched off a small thin tendon to the base of the lateral dewclaw. On one foot a snmll tendon from the lateral abaxial branch of the suspensory ligament connected to the first phalanx of the rudimentary fifth digit.
Syndactylous hind feet. On syndactylous pelvic limbs the arrangement of the extensor tendons corresponded to the description given for thoracic syndactylous limbs. Since the degree of fusion was less advanced on pelvic limbs, the structure of the flexor tendons a~d suspensory ligaments was nearly normal. The deep digital flexor tendon of one right pelvic limb bifurcated above the fetlock. Eight centimeters farther distally, the two branches fused again (Fig. 4). I n two cows the digital extensor tendons formed the aponeuropotic plate
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on the right syndactylous hind foot, as described above. However, the flexor tendons divided as in a normal pelvic leg. The rest of the ligaments corresponded to those of thoracic syndactylous limbs. Externally normal pelvic limbs of syndactylous animals showed some slight abnormalities. The tibialis posterior muscle and its tendon were absent on both limbs of four specimens and one on the right side. Not all limbs pernfitted study of this point, since some had been dismembered too far distally. The deep digital flexor tendon in one specimen detached on the medial side of a branch to the dewclaw plate. Both pelvic limbs of one specimen showed the pectinus muscle extending farther distally than nol~na]. The medial digital extensor tendon of another specimen consisted of two parts which fused below the tarsus. Normal + / s y cattle. The muscles, tendons, and ligaments of the six animals were essentially normal. I n two, once on both front legs and once on the right front leg only, the superficial digital flexor gave off a thin tendon to the base of the lateral dewclaw as described previously for syndactylous legs. References
(1)Leipold, tI. W., R. W. Adrian, Keith Ituston, D. 1~. Trotter, S. M. Dennis, and M. M. Guffy. 1969. Anatomy of hereditary bovine syd~cty]ism. I. O'steology. J. Dairy Sci., 52: 1422.
ft. DAIRY SOIENOE VOL. 52, NO. 9
from + / + animals; and 3) syndactylous animals possessing the sy gene from other syndactylous animals. I n this paper, anomalies of the muscles, tendons, and ligaments are presented.
Abstract
Muscle, tendon, and ligament anomalies that distinguish externally 1) normal overlap s y / s y homozygotes from normal + / s y and + / + animals; 2) normal + / s y animals from + / + animals; and 3) syndactylous animals possessing the sy gene from other syndactylous animals were sought in the limbs from 35 syndactylons sy/sy, two normal overlap sy/sy, and six normal +/sy Holstein cattle. Tendons and ligaments were adapted to the single digit. Three digital extensor muscle tendons fused at the fetlock into a wide aponeurotic plate that received on each side a reinforcing branch from the deep suspensory ligament and inserted on the second and third phalanx. The tendons of the superficial and deep digital flexor muscles usually remained undivided and inserted normally on the single functional digit. A small branch often passed from the tendon of the superficial digital flexor muscle to the lateral dewclaw, the only anomaly of the front feet of normal overlap and of two of six + / s y animals. Other rarer muscle tendon branches to the dewclaw were found. The superficial p a r t of the suspensory ligament, besides joining the tubular portion of the superficial digital flexor muscle tendon, attached by a wide band to the proximal sesamoid bones. Branches of the deep suspensory ligament were fewer than normal.
Experimental Procedures
Limbs from 35 syndaetylous cattle, two normal overlap s y / s y bulls, and six normal + / s y cattle were removed at slaughter or necropsy by dismembering proximal to the carpal or tarsal joints. They were dissected either in fresh unfixed condition or after embalming with an attueous solution containing 12% formalin, 3.7% glycerin, and 0.5% acetic acid. Results and Discussion
As noted in the first p a p e r in this series (1), control of the incompletely penetrant, recessive U.S. Holstein form of syndactylism may be facilitated by knowledge of anatomic differences that distinguish externally 1) normal overlap s y / s y homozygotes from normal + / s y and + / + animals; 2) normal + / s y animals Received for publication April 9, 1969. 1 Contribution no. 14, Department of Anatomy; no. 118, Department of Pathology; and no. 729, Department of Dairy and Poultry Science. This research was part of the North Central Regional Dairy Cattle Breeding Project •C-2.
Among the 35 syndactylous animals, the external degree of syndactylism was as follows: eight with only right front foot syndactylous; 19, both front feet; four, both front feet and right rear; two, both front feet and left rear; one, right front foot and both rear; and one, four syndactylous feet. The arrangement of muscles, tendons, and ligaments was similar regardless of the number of affected feet; therefore, all syndactylous animals are described together. The two normal overlap s y / s y bulls and the six normal + / s y animals are described separately. Normal overlap sy/sy bulls. The muscles and tendons of the front feet of both bulls had normal positions and insertions. However, the superficial digital flexor tendon on both front feet gave rise to, at the middle of the metacarpus, a thin tendon about 10 cm long which inserted at the base of the lateral dewclaws. Both hind feet were normal. Syndactylous front feet. With few exceptions, muscles, tendons, and ligaments deviated similarly in all syndactylous front feet. The three separate digital extensor tendons passed normally over the carpal joint to the fetlock region. Here the tendons became wider and flatter and finally fused to form a broad, common aponeurotic plate that inserted mainly at the extensor surfaces of the second and third phalanges (Fig. 1). The dorsal digital synovial sheath was absent. On the right front foot
1432
BOVINE
SYNDAOTYLISM.
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digita~ flexor muscle remained undivided, received the superficial digital flexor muscle to form a tube around the single deep digital flexor tendon (Fig. 2). The single superficial digital flexor tendon inserted normally on the volar surface of the second phalanx. Occasionally, one or two fibrous bands attached their tubular part to the intersesamoidean or distal sesamoidean ligaments. The deep digital flexor tendon coursed and inserted normally on syndaetylous feet but it remained undivided. In two syndactylous left front feet it gave rise to a thin tendon to the base of the lateral dewclaws. The deep digital fascia formed three single annular ligaments for the digital flexor tendons. The suspensory ligament consisted of a superficial fibrous part and a deep part which was muscular in young specimens. The superficial part varied from a single fiat band to two
:FIG. 1. Dorsal view of a syndactylous leg after removal of skin, fascia, nerves, and veins. The tendons of the three digital extensor muscles form a thin aponeurotic plate in the fetlock area. of a cow with syndactylous front feet only, and on both front feet of a calf with all four feet syndactylous, the lateral digital extensor tendon branched off a small tendon to the base of the lateral dewclaws. Down to the distal third of the metacarpus, the superficial digital flexor tendon had the same anatomic features as in normal cattle. At this point, however, it branched off one and, occasionally, two thin tendons, 3 to 10 cm long, that inserted at the base of the lateral dewclaw, not only in syndactylous feet but also in normal left front feet of syndactylous cattle. In one case, that tendon was reconnected to the main tendon by two flat muscular bands 1 cm wide. The main tendon of the superficial
FIO. 2. Volar view of a syndactylous leg after removal of skin and fascia.. .]', DAIRY SOlENOE YOL. 52, NO. 9
1434
ADRIAS ET AL. s u s p e n s o r y l i g a m e n t gave off a b a n d to one of the r u d i m e n t a r y bones of the lateral dewclaw. The i n t e r s e s a m o i d e a n a n d the medial a n d Intern.1 sesamoidean l i g a m e n t s were normal. The
FIG. 3. Volar view of metacarpo-phalangeal joint. The suspensory ligament and the proximal sesamoid bones are reflected distally. Note two bra~lches of tlle deep suspensory ligament, three proximal sesamoid bones, and the distal metacarpal trochlea with two closely located sagittal ridges. bands, o r a single b a n d on e i t h e r the lateral or medial side. The superficial p a r t of the s u s p e n s o r y l i g a m e n t not only aided in the f o r m a t i o n of a tube f o r the deep digital flexor tendon, b u t also detached a considerable p o r tion to the superficial p r o x i m a l b o r d e r of the p r o x i m a l sesamoid bones. The deep p a r t of the s u s p e n s o r y l i g a m e n t did not always show a clear division into branches. AM a general rule, however, the n u m b e r of b r a n c h e s c o r r e s p o n d e d to the n u m b e r of p r o x i m a l sesamoid bones (Fig. 3). There was on each side a r a t h e r flat a n d wide connection to t h e a p o n e u r o t i c terminal p a r t of the digital extensor tendons. I n t h r e e cases the lateral b r a n c h of t h e deep J. DAIRY SCIENCE XTOb. 52, NO. 9
FIG. 4. ]~ifurcation of deep digital flexor tendon for the distance of 8 cm.
BO'VINE
SYNDACTYLIS~I.
middle distal sesamoidean ligaments were well developed and converged slightly distally. Between them there were sparse fibers of indistinct direction representing the deep distal sesamoidean ligaments. The collateral ligaments of the metacarpo-phalaageal and the phalangeal joints, and the ligaments of the distal sesamoid bone were normally developed for the single functional digit. The ligaments of the two dewclaws showed no deviation from the normal pattern. On the single toe there was no place for interdigital ligaments. On externally normal left front legs of syndactylous cattle, the superficial digital flexor muscle branched off a small thin tendon to the base of the lateral dewclaw. On one foot a snmll tendon from the lateral abaxial branch of the suspensory ligament connected to the first phalanx of the rudimentary fifth digit.
Syndactylous hind feet. On syndactylous pelvic limbs the arrangement of the extensor tendons corresponded to the description given for thoracic syndactylous limbs. Since the degree of fusion was less advanced on pelvic limbs, the structure of the flexor tendons a~d suspensory ligaments was nearly normal. The deep digital flexor tendon of one right pelvic limb bifurcated above the fetlock. Eight centimeters farther distally, the two branches fused again (Fig. 4). I n two cows the digital extensor tendons formed the aponeuropotic plate
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1435
on the right syndactylous hind foot, as described above. However, the flexor tendons divided as in a normal pelvic leg. The rest of the ligaments corresponded to those of thoracic syndactylous limbs. Externally normal pelvic limbs of syndactylous animals showed some slight abnormalities. The tibialis posterior muscle and its tendon were absent on both limbs of four specimens and one on the right side. Not all limbs pernfitted study of this point, since some had been dismembered too far distally. The deep digital flexor tendon in one specimen detached on the medial side of a branch to the dewclaw plate. Both pelvic limbs of one specimen showed the pectinus muscle extending farther distally than nol~na]. The medial digital extensor tendon of another specimen consisted of two parts which fused below the tarsus. Normal + / s y cattle. The muscles, tendons, and ligaments of the six animals were essentially normal. I n two, once on both front legs and once on the right front leg only, the superficial digital flexor gave off a thin tendon to the base of the lateral dewclaw as described previously for syndactylous legs. References
(1)Leipold, tI. W., R. W. Adrian, Keith Ituston, D. 1~. Trotter, S. M. Dennis, and M. M. Guffy. 1969. Anatomy of hereditary bovine syd~cty]ism. I. O'steology. J. Dairy Sci., 52: 1422.
ft. DAIRY SOIENOE VOL. 52, NO. 9