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Basset Hound
Elbow Dysplasia (ununited anconeal process)
Related terms: disunited anconeal process
Outline: In this condition, a protuberance of the ulna bone – the anconeal process - that forms part of the elbow joint, and which should during development fuse to the ulna, fails to do so and develops separately. This results in an ununited anconeal process (UAP). This condition is associated with dog breeds of a large body size but is also seen commonly in the Basset hound. The bone growth abnormality that causes the short legs of this breed may be a factor in its development. UAP leads to arthritis of the elbow joint which, unless successfully treated (which is difficult) is likely to cause lifelong pain and discomfort, which may be mild or more severe.
Summary of Information
(for more information click on the links below)
1. Brief description
An ununited anconeal process (UAP) is characterised by disease of a part of the ulna bone at the elbow joint. This process (protruberance) of the ulna bone fails to form properly and, because of this, the function of the elbow is affected and osteoarthritis develops.
Dogs with UAP develop osteoarthritis (degenerative joint disease) of the elbow, which causes pain. The disease is often present by 5-9 months of age but can show later. Affected dogs may be treated with rest and pain-killers, and treatment may need to be life-long. Various surgical procedures have been recommended to treat or alleviate the condition but there is no consensus as to which is best. Some procedures require major intervention, eg removal of sections of bone (Burton & Owen 2008a).
2. Intensity of welfare impact
UAP leads to pain and disability associated with the osteoarthritis of the elbow joint. This can be mild to severe.
3. Duration of welfare impact
The mild to severe welfare impacts that result from the osteoarthritis seen in this disease can be expected to start during the first few months of life and, without successful treatment, to continue for life. Treatment may help but keeping affected dogs free from pain and avoiding disabilities is often challenging.
4. Number of animals affected
We are unaware of any data on the proportion of Basset hounds affected by elbow dysplasia. It is known that they are predisposed to develop UAP and other forms of elbow dysplasia (eg fragmented medial coronoid process – see below) (Lafond et al 2002).
5. Diagnosis
The diagnosis is suspected when dogs show signs of forelimb lameness. Elbow dysplasia (a general term covering a number of developmental abnormalities of the joint) is confirmed and its cause, extent and severity determined by examinations including x-rays (van Ryssen & van Bree 1997), CT and MRI scans and exploratory surgery – often using an arthroscope.
6. Genetics
The genes involved have not been determined.
7. How do you know if an animal is a carrier or likely to become affected?
Affected dogs should not be used for breeding. Affected puppies can be born to unaffected parents (Hazelwinkel & Nap 2009). Determining carriers - those which carry and may pass on the gene(s) but which do not show signs of the disease themselves - is not currently possible.
8. Methods and prospects for elimination of the problem
A voluntary scheme to grade the elbows of dogs susceptible to elbow dysplasia has been in operation in the UK since 1998 although it has been suggested that breeder uptake has been relatively low (Sampson 2006). For this scheme, elbow condition is scored when dogs are over one year old.
In common with other complex, multi-gene diseases that are influenced also by environmental factors, efforts to reduce the prevalence of UAP are complicated by the lack of information about the underlying genetics. One approach is to breed from dogs that have a better breeding value (see below) than is average for the breed (Sampson 2006). This takes account of both the individual being evaluated and the prevalence of the disease in its relatives (Malm et al 2008).
For further details about this condition, please click on the following:
(these link to items down this page)
- Clinical and pathological effects
- Intensity of welfare impact
- Duration of welfare impact
- Number of animals affected
- Diagnosis
- Genetics
- How do you know if an animal is a carrier or likely to become affected?
- Methods and prospects for elimination of the problem
- Acknowledgements
- References
1. Clinical and pathological effects
Elbow dysplasia (ED) is a general term that encompasses five distinct anatomical problems that tend to result in malformation of the elbow joint, and that lead to early-onset osteoarthritis.
Ununited anconeal process (UAP) is one of these problems, and is the main focus here, but some of the other four conditions are referred to in the descriptions (below) of how UAP may develop. These conditions are:
Fragmented medial coronoid process (FMCP): The medial coronoid process is a piece of bone that should form part of the top of the ulna and of the elbow joint. In FMCP this fails, during development, to connect to the ulna.
Osteochondrosis dissecans (OCD): In OCD an area of joint cartilage develops abnormally or becomes damaged leading to thickening, cracking and fragmentation of the cartilage.
Elbow incongruity (IC): Dogs with IC have malformed articular surfaces of the three bones that make up the elbow and because of this they do not fit together normally. It can affect the weight-bearing surfaces between the humerus and the radius and ulna and also the way in which the upper part of the ulna fits inside the lower end of the humerus (Schwarz 2000).
Ununited medial epicondyle (UME): This is an uncommon condition in which the medial epicondyle, part of the humerus, fails to unite with the humerus during development.
The elbow is a complex joint of three bones; the humerus (upper bone of the foreleg/arm bone), the ulna and the radius (lower foreleg/arm bones). At their upper ends, the radius and part of the ulna form a flattened surface that bears the load imposed by the humerus. The anconeal process is a bony protruberance that is normally part of the end of the ulna. Its main function is not weight bearing, rather it helps to stabilize the elbow joint, particularly when the leg is extended. The anconeal process articulates with the caudal (towards the tail of the dog) surface of the humerus and when the leg is extended (straightened) it fits into a hole at the lower end of the humerus called the humeral fossa.
Figure 1. The three bones of the elbow joint separated and in normal alignment. In a healthy canine elbow joint the ulna and radius form a flat surface for articulation with the humerus. (Image property of Phil Witte, to whom we are grateful for permission to reproduce it here).
Figure 2. A diagram of the upper end of the ulna illustrating the locations of the coronoid and anconeal processes. (Image property of Phil Witte, to whom we are grateful for permission to reproduce it here).
In most dogs, the anconeal process grows as part of the ulna and as such there is no possibility of it not “uniting”. But in breeds of large body size it is normal for the anconeal process to start as a separate small bone at birth, which, during development, should fuse on to the ulna. This usually occurs by 20 weeks of age. In UAP this fails to happen (Schwarz 2000). The cause of this is unclear but one possibility is that it is a consequence of the disproportionately greater growth of the radius in relation to the ulna such that the elbow joint is malformed and the anconeal process is subject to abnormal pressures that cause it to be pushed away from the ulna, thus preventing it from fusing (uniting). This is considered to be the cause of the problem in the Basset hound and it is associated with a further defect – valgus deformity (outward deviation) of the foot (Shell & Harasen 2007, Arthurs 2009).
UAP occurs particularly in chondrodysplastic breeds (Schwarz 2000, Innes 2006), those with the bone growth abnormality that causes the characteristic short legs of affected breeds (eg Dachshunds, Corgis and Basset hounds) (Parker et al 2009).
Figure 3. In particular dog breeds, the anconeal process initially forms separately. It should fuse with the ulna during development. If this process fails, the result is Ununited Anconeal Process (UAP).
Dogs with UAP develop osteoarthritis (degenerative joint disease) of the elbow. In osteoarthritis there are progressive changes to the cartilage of the affected joint, varying degrees of inflammation and ongoing damage to other joint structures - the joint capsule, the synovial fluid of the joint and the surrounding bone. These changes are often present by 4-6 months of age and lead to clinical signs later. Typical signs include: stiffness after rest, lameness (which can be worse after exercise) and reduced mobility of the joint, with the leg tending to be held twisted outwards (abducted and suppinated). Such signs are indistinguishable from those shown in other forms of elbow dysplasia and imaging of the joint is usually needed to make a definitive diagnosis (Schwarz 2000).
Figure 4a Figure 4b
Figures 4a and 4b. Osteoarthritic changes to the shape and structure of the elbow joint. The shaded areas on figure 4a (extended elbow) and 4b (flexed elbow) represent the changes to bone and cartilage as a result of UAP and other forms of elbow dysplasia. (Images property of the British Veterinary Association/ Kennel Club Elbow Dysplasia Scheme. We are grateful to the BVA for permission to reproduce them here).
Affected dogs may be treated with rest and pain-killers, and often treatment needs to be life-long. Various surgical procedures have been recommended but there is no clear consensus as to which is best. Some of these procedures involve major surgery, including removing whole sections of the ulna in order to shorten it (Burton & Owen 2008a).
2. Intensity of welfare impact
UAP causes pain and disability associated with osteoarthritis. This can vary from mild to severe. Welfare may also be affected as a result of the veterinary investigations and treatments of the disease. Restricted activity will often be recommended in order to prevent further joint damage and this reduced activity may constrain the dog’s capacity for normal life and behaviour.
3. Duration of welfare impact
The mild to severe pain and disability that result from the osteoarthritis seen in this disease can be expected to start during the first few months of life and, unless it can be successfully controlled, to continue for life. Treatment may help but keeping affected dogs free from pain and avoiding disabilities is often challenging.Return to top
4. Number of animals affected
The Basset hound is one of the breeds included in the British Veterinary Association/Kennel Club Elbow Dysplasia Scheme (Kennel Club 2010). Basset hounds have long been known to suffer from ED (Johnston & Cox 1970) and to be predisposed to UAP (LaFond et al 2002, Schwarz 2000, Innes 2006, Burton & Owen 2008b, Arthurs 2009), however, we are unaware of data on the proportion of the population that is affected.
5. Diagnosis
UAP can only be diagnosed in dogs older than about five months as it is normal for those breeds in which UAP occurs to have an ununited anconeal process prior to this (Schwarz 2000).
UAP will be suspected by a veterinary surgeon when presented with a Basset hound showing forelimb pain. Elbow disease and pain may be apparent. Determining the type of elbow disease, its extent and the degree of secondary osteoarthritis requires further diagnostic procedures, including radiography (x-rays) (Burton & Owen 2008b) or other imaging methods. In cases of UAP it is more difficult to detect other concurrent forms of elbow disease (Meyer-Lindenberg et al 2006).
6. Genetics
UAP is generally a disease of large dogs, as it is only in these that the anconeal process develops separately from the ulna. The genes involved in Basset hound UAP are unknown. The mutation that causes the bone growth abnormality resulting in their short legs has been determined (Parker et al 2009).
It is known in other breeds that the father and mother contribute equally to the likelihood of the development of elbow dysplasia (Maki et al 2002). There are genetic influences both on the presence or absence of UAP and on whether, and to what degree, osteoarthritis occurs in an individual with UAP (Clements et al 2006). Environmental factors also play a part in the development of the disease and its severity (Hazelwinkel & Nap 2009).
7. How do you know if an animal is a carrier or likely to become affected?
Affected dogs should not be used for breeding. Affected puppies can be produced from normal parents (Hazelwinkel & Nap 2009). Determining carriers - those which carry and may pass on the gene(s) but which do not show signs of the disease themselves - is not currently possible.
8. Methods and prospects for elimination of the problem
A voluntary scheme to grade the elbows of dogs susceptible to elbow dysplasia (all forms) has been in operation in the UK since 1998 although it has been suggested that breeder uptake has been relatively low (Sampson 2006). Details of the scheme can be found at: http://www.thekennelclub.org.uk/item/309.
In this scheme, elbows are scored once when the dog is over one year old. Radiographs taken by a local veterinary surgeon are forwarded to veterinary radiologists on the scheme panel for assessment. Each elbow is graded 0-3, with zero meaning that no evidence of elbow dysplasia was seen. If the two elbows have different grades, the higher of the grades is the one used to characterise the dog. The scheme recommends that dogs used for breeding should have grades of zero or one and that those with higher scores should not be used for breeding.
No evidence has yet been published as to whether this scheme is proving effective in reducing the prevalence of elbow dysplasia in the Basset hound. A comparable scheme that has been running in New Zealand since 1991 seems to have significantly reduced the severity in German Shepherd dogs, that have been screened prior to breeding for ED (Worth et al 2010) and a comparable scheme run in Sweden since 1990, appears to have reduced the prevalence of elbow dysplasia in Swedish Bernese Mountain dogs and Rottweilers (Swenson et al 1997, Malm et al 2008).
The bone growth abnormality of chondrodysplasia is part of the breed standard for Basset hounds and any influence of this abnormality on the development of UAP could only be decreased by radical alteration of the conformation of the breed.
In common with other complex, multi-gene diseases that are influenced also by environmental factors, efforts to reduce the prevalence of UAP are complicated by the lack of information about the underlying genetics. One approach is to breed from dogs that have better estimated breeding values (EBV) than average for the breed (Sampson 2006). The EBV is a numerical prediction of the relative genetic value of a particular dog with regards to one or more genetic diseases and takes into account degree of inbreeding. EBVs are calculated using all available information on the dog including pedigree, health status and physical characteristics. For this type of health programme to work many breeders and owners need to submit their animals for monitoring and analysis.
Out-breeding Basset hounds with breeds known to have a much lower prevalence of UAP and elbow dysplasia (ED) would be likely to result in fewer dogs being born with a lifetime of painful joint problems before them.
9. Acknowledgements
UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section and to Stephanie Kaufman for assistance in illustrating it.
10. References
Arthurs G (2009) Canine Elbow Disease. In: Proceeding of British Small Animal Veterinary Congress 2009
Burton N and Owen M (2008a) Canine elbow dysplasia 2. Treatment and prognosis. In Practice 30: 552-557
Burton N and Owen M (2008b) Canine elbow dysplasia 1. Aetiopathogenesis and diagnosis. In Practice 30: 508-512
Clements DN, Carter SD, Innes JF and Ollier WER (2006) Genetic basis of secondary osteoarthritis in dogs with joint dysplasia. American Journal of Veterinary Research 67: 909-19
Hazelwinkel HAW and Nap RC (2009) Preamble. Proceedings of 24th Annual Meeting of International Elbow Working Group. pp 2
Innes JF (2006) Is elbow dysplasia a syndrome? Proceedings of the British Veterinary Orthopaedics Association Autumn Meeting 2006. 10-11
Johnston DE and Cox B (1970) The incidence in purebred dogs in Australia of abnormalities that may be inherited. Australian Veterinary Journal 46:465–474
Kennel Club (2010) The BVA /KC Elbow Dysplasia Scheme http://www.thekennelclub.org.uk/item/309 accessed 17th December 2010
LaFond E, Breur GJ and Austin CC (2002) Breed susceptibility for developmental orthopedic diseases in dogs. Journal of the American Animal Hospital Association 38: 467-77
Mäki K, Groen AF, Liinamo-E and Ojala M (2002) Genetic variances, trends and mode of inheritance for hip and elbow dysplasia in Finnish dog populations. Animal Science 75: 197-207
Malm S, Fikse WF, Danell B and Stanberg E (2008) Genetic variation and genetic trends in hip and elbow dysplasia in Swedish Rottweiler and Bernese Mountain dogs. Journal of Animal Breeding and Genetics 125: 403-12
Parker HG, VonHoldt BM, Quignon P, Marquilies EH et al (2009) An Expressed Fgf4Retogene Is Associated with Breed-Defining Chondrodysplasia in Domestic Dogs. Science 325: 995-998
Meyer-Lindenberg A, Fehr M and Nolte I (2006) Co-existence of ununited anconeal process and fragmented coronoid process of the ulna in the dog. Journal of Small Animal Medicine 47: 61-5
Sampson J (2006) What is required for breeding programmes or Molecular technologies to make impact on the prevalence and incidence of elbow dysplasia in dogs? Proceedings of the British Veterinary Orthopaedics Association Autumn Meeting 2006. 4-5
Schwarz PD (2000) Canine elbow dysplasia. In; Kirks Current Veterinary Therapy XIII editor J.D. Bonagura. WB Saunders, Philadelphia. pp 1004
Shell L and Harasen G (2007) Ununited anconeal process. VIN Associate. (on-line) http://www.vin.com/Members/Associate/Associate.plx?DiseaseId=447. accessed 17.12.2010
Swenson L, Audell L and Hedhammar A (1997) Prevalence and heritance of and selection for elbow dysplasia in Bernese mountain dogs in Sweden and benefit: cost analysis of a screening and control programme. Journal of the American Veterinary Medical Association 210: 215-221
van Ryssen B and van Bree H (1997) Arthroscopic findings in 100 dogs with elbow lameness. Veterinary Record 140: 360-362
Worth AJ, Bridges JP and Jones G (2010) Reduction in the incidence of elbow dysplasia in four breeds of dog as measured by the New Zealand Veterinary Association scoring scheme. New Zealand Veterinary Journal 190: 5
© UFAW 2012
Credit for main photo above:
By Cali1008 (Own work) [Public domain], via Wikimedia Com
