Posted by article repost - Part 2 on 4/6/2007, 3:17 pm, in reply to "A NEW LOOK AT THE PROBLEM OF HIP DYSPLASIA IN DOGS" The studied corpses of the animals had extremely strong capsules and powerful tendons at the femur/acetabulum joints, which were considerably stronger then in 10 dissected dogs belonging to the following popular breeds of European origin: Rottweilers, Black Russian Terrier, Great Dane and a few other breeds. 2. The group of small muscles of the pelvis in the form of a fan connecting the ishium, sacrum and ileum bones with the femur/acetabulum cavity and the large processus of the femur (mm. gemelli, m. obturatorius internus and m. obturatorius externus and m. piriformes) possesses a powerful aponeuroses making the pronation of the femur beyond the saggital plane impossible and securing its right place, when the muscles are in a relaxed state, preventing its head from shifting in a dorso-ventral direction. Investigations on the corpses of other dogs of cultured breeds had muscles and tendons listed above developed inferiorly. 3. The musculus pectineus, when exerting pressure on contraction, acts against the mm. gemelli and mm. abturatorii and applies force, shifting the femur in the ventro-cranial direction. 4. The small muscles of the pelvis, owing to their aponeuroses, relieve pressure on the femur-pelvic joint by passing it to the ishium bone and, in the event of falling on one of the pelvic bones, prevent pronation of the femur by passing the rotational force onto the pelvis. The results of this study allow the author of this article to propose the following hypothesis: 1. A too deep acetabular socket and its considerable inclusion of the femoral head (more then half of its radius) does not belong to the natural norm of the structural formation of the femur/pelvis joint in large canids, because it restricts the mobility of the joint and the general locomotion of the animal. 2. The insertion of the femoral head into the acetabular socket at roughly the depth of its radius (not deeper than that), on condition that a narrow and even joint space is preserved, should be considered natural and normal for large canids. According to the modern evaluation of x-ray data it is a transitional (limited) form or even a slight degree of displasia. 3. The head of the femur, in its natural form, is held in the acetabular socket not so much because of its depth, but rather because of the powerful development of aponeuroses of the small muscles of the pelvis (mm. gemelli, mm. obturatorii and m. piriformes) and the strength of the bone of the joint capsule. 4. Development of displasia at the femur/pelvis joint is caused initially by the underdevelopment or trauma of the small pelvic muscles. 5. The initial deterioration of the anterior external margin of the acetabular socket takes place during pronation of the femur under pressure at the base of the femoral head and even the femoral bone neck. Deterioration results in slack in the joint, when the leg is moved forward and finally the bone head hits the upper dome of the acetabular socket (in the caudo-dorsal direction), when the animal is on the ground with the leg stretched forward. 6. The underdevelopment of aponeuroses of the small muscles of the pelvis leads to the overloading of the acetabular joint, when the dog runs and jumps, because the stress cannot be distributed on the bone as well. One direct consequence of this is the stretching of the joint capsule and further deterioration of the upper dome of the acetabular socket; it becomes extended or it takes on an hourglass shape. 7. The deepening of the acetabular socket with the subsequent too deep submerging of the femoral head in it up to the point of forming a “closed” joint is a compensatory way of preventing hip displasia in cases of hereditary underdevelopment of the small muscles of the pelvis. 8. The most likely change in the structure of m. pectineus observed in cases with hip dysplasia is a result of the natural suppression of the function of this muscle by the dog; this muscle, under the conditions of the passive contrary action of the small muscles of the pelvis, can dislodge the head of the femur from its normal position. Thus, from the standpoint of functional anatomy, a myotomy of the m. pectineus is a justified method for the surgical correction of hip dysplasia in its initial stages of development. On the basis of the data we have, we can offer the following concept for the investigation of the causes displasia and measures for its control. To divide breeds of dogs according to the development of the small pelvic muscles and, in relation to the breeds by maintaining the natural norm of their development, to make use of other methods of evaluating hip dysplasia in which pelvic muscles lost their function of holding the acetabular joint in its proper place and preventing the pronation of the femoral bone. 3. To recommend that dog breeders should not use dogs with signs of pronation of femur (in the sitting position their patella are turned inward), even if they pass x-ray examination for hip dysplasia. 4. To recommend that dog breeders and owners of puppies belonging to breeds with normally developed acetabular joints should strictly limit the growth rate and condition of puppies as well as the physical load on them during the period from weaning to completion of the growth of bones in order to avoid the development of secondary hip dysplasia, because anatomically dogs of these breeds are predisposed to this problem. 5. To introduce into the practice of the zootechnical and exhibition appraisal of dogs with naturally normal development of the acetabular joints an examination in the sitting position to detect any signs of the pronation of the femur, especially by palpation of the triangle between the femur/pelvis joint, tail base and ishium bone. In cases of dogs sitting with close patellar joints or an “empty space” in the triangle described above, to lower its conformation rating. The following surgical corrections of hip dysplasia could be considered effective with the exception of cases of severe destructive changes in the joint. 1. In growing puppies with underdeveloped small muscles of the pelvis aponeuroses can be stimulated by the precise intramuscular injection of ligament tissue and bio stimulators, or by using different forms of plastic surgery. 2. In dogs with an already developed skeleton, besides the measures listed above, prosthetic replacement of the system of aponeuroses can be done by using a flexible fan-shaped plastic plate made out of lavsan or any other tough polymer fixed to the femoral bone head with the opposite side positioned along the ishium bone. Furthermore, the investigation of the role of the small muscles of the pelvis have confirmed the author’s earlier proposal about the absurdity of breeding certain types of dogs, such as the German Shepherd Dog and Black Russian Terrier, with deviations from a healthy body structure with extremely high anterior part of body and extremely bent lower thighs. The underdevelopment of muscles and tendons at the femur-pelvis joint along with an abnormally lowered direction of movement from the pelvis cause deformation of the joint in the most vulnerable ventro-cranial direction. It is precisely in this that can be seen the reason for the weak effect of selecting breeding stock dogs against hip dysplasia even in cases where such selection has been carried on for dozens of generations. The proposed concept still remains largely a theoretical construction and it requires further studies for experimental verification and clinical confirmation. Nevertheless, the author hopes that the obtained results will serve as orientation marks for further studies on a broader basis with the use of modern equipment. NOTE: English translation by Dr. Vladimir Beregovoy, curator for the Russian branch of the Primitive Aboriginal Dog Society (R-PADS).
216.249.9.25
Part 2
To investigate the condition of the group of small muscles of the dog’s pelvis of different breeds by using magnetic resonance tomography on live dogs. This method would be combined with a fine anatomical and functional analysis of the structures under consideration by working on canine corpses.
[Warren]
Message Thread:
« Back to thread