Table of Contents
We Are Not Alone
Research Paper II: Occupational Osteoarthritis
Who is an ISDI "Member"
Northern Inuits (sic), Again!
High Arctic Mushing: Part IV
The Inuit Dog: Its Provenance, Environment and History
Preserving "Bear" Dogs
Janice Howls: Extinction
IMHO: Little Minds, Little Worlds
Index of The Fan Hitch, Volume IV
|EDITOR'S NOTE: The length of the original paper made it necessary
to edit it for inclusion in the Fan Hitch. Therefore readers are reminded
that some data, statements in support of conclusions drawn, along
with the list of references, are not a part of what is presented
below. Nevertheless, this scientific paper offers insight into the invaluable
contribution of both the authors and the dogs. The Fan Hitch expresses
its profound gratitude to A.R.M. Bellars for sharing this research with
its readers. This paper is reproduced here by permission of the Natural
Environment Research Council (the parent body of the British Antarctic
Survey) who holds sole copyright. We are indebted to them for allowing
us to share it with you.
British Antarctic Survey Bulletin, Number 22, 1969, pp. 15-38
Veterinary Studies on the British Antarctic Survey's
By A.R.M. Bellars and M. F. Godsal
ABSTRACT: The results of the investigation into the problem of osteoarthritis in British Antarctic Survey sledge dogs are presented. Clinical, pathological and radiographical findings are described. The aetiology of the condition which shortens the working life of the majority of these dogs is discussed. The present evidence suggests that the pressure due to pulling loaded sledges is the main factor causing acceleration of the degenerative changes due to ageing, and movement, of the main limb joints. No evidence was found of an hereditary basis for the condition.
Dog-team drivers of the British Antarctic Survey have come to accept the fact that otherwise healthy Antarctic sledge dogs are usually incapable of further work by the time they are 8 years old. Since this is less than might be expected of a dog of the husky's size and weight under normal conditions, an investigation in to the possible causes of the decline of the ageing husky was started in 1963-1964.
This paper is intended to show the results of the investigation, undertaken during two austral summer tours of the survey's stations by the authors in 1963-64 (M.F.G.) and 1967-68 (A.R.M.B.)
In 1963-64 Godsal examined all the dogs at the stations, and destroyed 34 of them. Most of these dogs were incapable of further work, but some were destroyed because they were surplus to requirements. The main finding on post-mortem examination was erosions of the articular cartilage of the hip and shoulder joints. The results of this study led to the conclusion that no satisfactory hypothesis of the aetiology of the condition could be reached unless poor conformation of the affected joints was eliminated as a causal factor. Hip dysplasia, a disease thought to be hereditary, and known to affect certain breeds such as the Alsatian, Cocker Spaniel, Labrador Retriever and Alaskan Malamute, often gives rise to severe osteoarthritis of the hip. The condition is usually diagnosed by radiological examination of the hip, so that, although there was no other clinical evidence of hip dysplasia apart from the erosions, a portable x-ray unit was taken to Stonington Island in 1967-68. 29 Antarctic sledge dogs underwent radiological examination. In addition, slow-motion cine film was made of the dogs drawing a sledge to see if the unusual gait of the working husky might in itself be a factor in the slowing of the ageing dogs.
This paper also shows that osteoarthiris is the reason for the destruction for nearly 72 per cent of males and 52 per cent of females that survive beyond 5 years of age, excluding deaths due to accidents.
TABLE I: AGE DISTRIBUTION OF GRAHAM LAND
i. Aged less than 18 months
All other dogs between 18 months and 6 years were regarded as being in their prime and sound, and thus unlikely to reveal abnormalities.
The dogs tolerated being on their backs without sedation, and a satisfactory series of ventro-dorsal pictures was obtained.
Slow motion cine film was taken from the side, front and rear of a working team of sledge dogs. The results were analysed to see if the gait of the working husky could predispose to erosions of hip and shoulder articular cartilage.
Some experienced drivers turned the occurrence of osteoarthritis in their team to good advantage, finding that these older dogs seem to be aware of their capabilities and settle down more quickly at the start of a day's work than the young impulsive members of the team, transmitting to them the skill in pacing-out their energies for a long haul. However, once a dog has begun to suffer clinically from osteoarthritis, it is generally found that the affected dog will not last for another full season of work.
Of the 34 dogs that were destroyed, 26 were affected. Nine of these had osteoarthritis of the hips only, three had erosions of the head of the humerus only, and in the remaining 15 affected dogs both hips and shoulders were involved. In two dogs one elbow was arthritic and in one dog both elbows showed lesions. One dog was found to have osteoarthritis in one stifle joint. The youngest affected dog was a 3.5 year-old female. Study at post-mortem examination and later showed that there was no evidence of shallowness of the acetabulum in any of the dogs examined. Likewise, the heads of the femora and humeri showed normal conformation.
Results show that in the British Antarctic Survey sledge dog:
i. there is an increased tendency to osteoarthritis of the hip
and shoulder joints with increased age.
The post-mortem appearance of some of the joints makes it remarkable that the affected dogs were willing to pull a sledge at all.
Findings from the cine film
The results show that osteoarthritis of the hip and shoulder joints is the cause of decline of the majority of the Survey's older sledge dogs and that hip dysplasia does not occur in a representative selection of these dogs. This discussion assesses the possible factors that may be concerned in the aetiology of the condition, particularly the normal processes of ageing, the effects of pressure on weight-bearing joints, the loads that may be taken on the joints of sledge dogs and the effects of the Antarctic environment. The discussion also refutes the argument that osteoarthritis of the hip joint of the dog should immediately lead to a tentative diagnosis of hip dysplasia.
Trueta and Trias have not only emphasized the effect of weight-bearing on joint degeneration but have also pointed out that osteoarthritis is brought about by interference with the vitality of the chondrocytes, and that this is commonly achieved by wrongly distributed and intermittent pressure. Although weight-bearing areas show the development of degenerative changes, the work of Harrison and others showed that the primary change in articular cartilage took place in the non-weight-bearing areas and consisted mainly of hyperplasia of the cartilage, leading to chondromalacia. Thus it may be that the occurrence of osteoarthritis depends not so much on weight-bearing on so-called normal areas but on weight-bearing on areas of joint cartilage not normally subject to pressure. This may be due to anatomical anomalies of which the Antarctic sledge dog shows no signs, or to incorrect joint function causing undo compression on part of the articular cartilage and insufficient compression on the remainder. If, as has been suggested, the Antarctic sledge dog adopts an unusual posture while pulling, this abnormal gait will induce faulty joint function. In addition, the life of the dogs is such that hard-pulling efforts alternate with "lie-up" periods of bad weather, periods when the dog drivers are working in the field away from the team, and long spells of relative idleness at the scientific station. It is probable that this alternation between extreme effort and rest is an important factor leading to articular changes.
The effects of pressure and postural changes have been implicated in the possibility of ischaemia of articular structures. Articular cartilage itself is devoid of blood vessels except in the very young and the very old. It was suggested by Walmsley that the arterial supply to the head of the femur in man was reduced with age. However Harrison and others found a copious blood supply and free anastomosis even in old age, and Roberts found no evidence to support the view that osteoarthritis in the human hip is often due to ischaemia of the femoral head. Against this, Trueta and Trias found in the rabbit that after about 14 days of severe continuous pressure on the stifle joint there was irreversible interference with growth of the epiphysial cartilage due to compression damage and interruption of the blood supply. Hall showed in similar experiments in the young rat that articular surfaces of young animals were able to stand considerable compression without becoming necrotic and that this ability was retained even in maturity. Thus the evidence suggests that interference with the vascular epiphyseal cartilage is easier to achieve than interference with the relatively non-vascular articular cartilage. In this respect the intermittent high pressure on the main limb joints of the Antarctic husky could lead to changes in the epiphyseal cartilage, particularly in the growing animal. It is therefore most important that the musculo-skeletal system of the Antarctic dogs should be allowed to mature before they are expected to haul heavy loads.
In the British Antarctic Survey sledge dog, the stress and strains involved in pulling a loaded sledge in an adverse environment are the main factors causing exaggeration of degenerative changes in the hips and shoulders, here called osteoarthritis. It is suggested that the abnormal posture of the dogs while pulling causes incorrect distribution of great pressures on the joints, producing incorrect joint function. It is not known whether similar work-induced changes occur in other draught animals. It therefore appears that this condition could only be noticeably alleviated by changing the way of life of the dogs and thereby eliminating their usefulness.