Still nowadays, innumerable standard of breed ennoble the angle of 45º, as ideal, to the inclination of the scapula to the horizontal, seeking the improvement of the reach from the footsteps of the hindquarters during the movement.
Persist, however, a basic mistake of postulation of the problem in all the studies already elaborated about the ideal structure to the movement: studying movement considering the dog in stay (stopped). By this it get lost innumerable data that could relieve at the study of the biodynamics of the movement.
Here, I intend to include several movements, up to now omitted, that are the one from the own scapula during the exercise from the movement.
The scapula is the contact of the forequarter with the trunk and the only one that isn’t joined by articulations. On humans, the scapula is articulated with the clavicle which is articulated with the thoracic box at the breastbone manubrium. On dogs, the clavicle is atrophic or, until nonexistent, but the tendency is the total disappearance.
Our chest, has an elliptic format, whose its bigger axis is
between the shoulders, while on quadruped species, exactly to be quadruped the bigger axle
is between the vertebral spine and the breastbone.
On humans the scapula works at the back, on canines, it is a flat and curved bone
perfectly accommodated to the format of the laterals faces of the chest.
This muscular complex, named by thoracic belt sustains, without fixing, the scapula on its
position, making a very singular articulation, mioartrosis or muscular articulation.
The scapula, with its special format, flat and accommodated to the thorax, has a spine in its external face disposed along of its bigger length and that divide(s) it in two half, practically equals, of big surfaces to insertion and architecture of a biomechanics complex system of suspenders and cushioning muscles, which distribution have origin in 3 main directions:
Neck, back / ribs and forequarters.
This format flat and accommodated to the thorax, allows its work with the trunk, free,
without articulations, in slide movements at the muscular contractions and relaxing.
At the articulation with the humerus, its most reinforced part, the scapula works as a capital of Greek column, that sustains much more than the half of the dog corporal weight.
To the maximum use of the effort, the scapula backbone would do, as the majority of the
standard of breed, an angle of 45º to the horizontal, angle which would offer to the
humerus the bigger width of the pendular movement of the forequarters, to the front, and
as a immediate consequence a bigger width of the step.
The ideal value of 45º is debatable, once that are very rare the specimen which
horizontal-scapula angular have this value, and the one that presents it, don’t
demonstrate good performance at the movement.
We have to observe that the horsy existed before the cynophily, which first standards of
breed were composed by hypists, with equine parameters, which, were elaborated under the
light of the human anatomy.
The equine structures that worked out, were studied to animal species of big size, with an approached weight of 500 to 600 kilos. The most heavy canine species reach about 10% of this value.
At the canine species, the cynology observed that the specimen of better perfomance at the trot, used to present a value about 50º to 60º to the horizontal-scapula angular.
The Dog in Stay
The angle, which the scapula does with the horizontal, has a little importance to the dog in stay, if the objective is the improvement of the reach to the front, from the forequarters, during the movement.
In fact, all the theory presented by McDowell Lyons, had considered, to his hypothesis the dog in stay.
The comparative illustrations from Lyons, between the scapulas that are inclined to
45º and 60º to lecture about the efficiency of the reach of the step from forequarters,
never considered the possible movement from the scapula.
Lyons commit the absurd of affirm that the fact of the scapula be inclined to 45º
increase its size providing a bigger area to the insertion of the muscles, instead of to
compare two scapulas of the same size, varying, only the angle of inclination.
The second big geometric mistake happened when Lyons tried to analyze, separately, the scapulars movement mounting his hypothesis with the only one objective of to prove that the angle of 45º was "very superior to the 60º".
1. 45º correspond to the diagonal of the square.
2. 60º , geometrically, correspond to the diagonal of a rectangle and to the
hypotenuse of the two rectangle triangles formed, therefore, 15% bigger than the diagonal
of a square inscribe ( trigonometry).
3. A free analysis would supposes two different inclinations, 45º and 60º to the same
scapula, instead of to affirm that 60º confer a smaller arch, declaring the bigger
geometric absurd.
4. To reinforce his absurd affirmative, without base on trigonometry, he shows that the scapula at 60º describe a smaller arch (F) than one with an angle of 45º when the scapula not even rotates around of a theoretical axis because it, according to Lyons isn’t fixed by articulations but by musculature.
At the moment in what, during the gait (and not in stay) the paw reach a position the most in front as possible, the scapula should assume the angle of 45º, and, to take this member back, the angle of the scapula, with the horizontal must approaches to the 90º. This is almost vertical.
To it happens, the angle of the scapula with the horizontal, when the dog is in stay must be around of 57º to 60º.
The scapular movement isn’t, reduced enough to be ignored.
Rotating on the theoretical axis (C), in the center of the bigger size of the backbone of the scapula.
At the movement of the member to the front, the scapula rotates, in the clockwise,
about 15º. At the movement to the back the scapula rotates, in anticlockwise, about 30º.
We still have to consider the fact of all the authors describe the scapula as doesn’t
being articulated with no one bone from the torso, but sustained by muscular complex,
complex that permits to the theoretical axis (C) an elliptic movement.
The crown of the scapula appears several times above the superior line during the movimentation.
To compute this elliptic movement, would complicate the calculation of the
scapuloumeral angulation taken when the dog is in stay.
However, it is exactly this, the movement that permits to the dog to realize the traction
force, on the apex of a climb on an obstacle ramp, to put it at the other side. The
muscles that realize this movement are the ones of insertion in the scapula.
The crown makes what we call withers and the end of the scapula, which glenoid cavity
articulate with the humerus, makes the end of the shoulder and the vertex of the
scapuloumeral angulation. On a well built shoulder, the distance from the crown of the
scapula to the end of the shoulder must be approximately the same to the distance from the
end of the shoulder to the elbow.
The Scapuloumeral Joint
We can’t mention the modification of the scapular angulation without doing an analysis of the scapuloumeral angulation with the values of a new situation of the scapula.
The bisector of the angle between the crest of the scapula and the axis of the humerus
must be horizontal.
To make possible it happens, the scapuloumeral angulation must be always the double of the
angle of the scapula with the horizontal.
In other words the angle that the humerus must does with the horizontal is identical to
the angle of the scapula.
The antique standard of the Rottweiler breed recommended an angle of 90º, to the
escapulo-umeral articulation, and of 45º the one of the scapula with the horizontal.
When they notice that the Rottweiler will never have a escapulo-umeral of 90º, even
because, if they got it, it will looks like a disabled, they changed it to 115º, but
forgot to evaluate again the escapulo-horizontal, that stayed on 45º.
The difference: 115º - 90º = 25º
Now, 45º + 115º = 160º, then, the humerus would make, with the vertical, an angle of, just 20º that is the difference with the add of two rectum angles: 180º : 180º - 160º = 20º
To Balance, again the system, the real angle with the horizontal must be substituted from 45º to, around of 57º or, even, around of 60º. The theory which says that the ideal scapula is on 45º with the horizontal, had been just surpassed, because all the calculations done until now about the ideal scapular angulation to a fluent movement with bigger reach of footstep were done considering the dog in Stay forgetting, completely, that:
So, with the scapula to 60º in stay, in its extreme position to the front, (-15º) the angle of the backbone of the scapula reaches the ideal angulation of 45º.
The German breeders are on the right way, they just have to correct the scapulo-horizontal angle (at the text, because indeed, the dogs already have them correctly, but it have been considering fault).
The conclusion that we do is that the best angulation to the scapula is the one of 45º WHEN ON MOVEMENT AND THE POSITION OF THE MEMBER, MAXIM TO THE FRONT.
AND, to be on this position, it is necessary that, sttoped the dog has a scapuloumeral angulation of 115º to 120º and a scapulohorizontal angulation of middle value 57º to 60º
Bruno Tausz