Clean Run Magazine - April 2008 - 76

Focus on Canine Sports Medicine Jump Down Syndrome By Sherman O. Canapp Jr., DVM, MS, DACVS and Donald Hulse, DVM, DACVS “Jump down syndrome” or traumatic fragmented medial coronoid process is a condition in the elbow joint of dogs that appears to occur commonly in performance dogs. Unlike the classic condition of fragmented medial coronoid process (FMCP) affecting the elbow joints of skeletally immature large to giant breed dogs, jump down syndrome (JDS) appears to have no age or size limitations. Jump down syndrome (JDS) is not a topic that you will find in current veterinary literature. Clean Run is pleased to present the first report on the condition. The authors will be publishing a subsequent paper in Veterinary Surgery, the official publication of the American College of Veterinary Surgeons and European College of Veterinary Surgery. © LAURIE O’KEEFE Pathogenesis Humerus Coronoid Process Ulna Radius Figure 1. Normal anatomy of the canine ulna History and Clinical Signs Dogs with JDS may present with a history ranging from a subtle intermittent offloading of the forelimb to significant unilateral or bilateral forelimb lameness. This lameness is typically exacerbated with exercise and heavy activity. The onset of lameness is insidious. As lameness persists, it may increase in severity. Affected dogs often place the carpus in an exaggerated valgus position (turned out) when sitting or standing, and circle the foreleg outward and move the elbow away from the midline (circumduct the antebrachium and abduct the elbow) during the swing phase of the stride. The history of dogs with JDS typically includes a lack of response to rest and non-steroidal anti-inflammatory drugs (NSAIDs). Many dogs with JDS are mistakenly treated for shoulder pathology because the attending veterinarian elicits a pain response when the shoulder is extended. The authors believe the pain response actually arises from the elbow because when the veterinarian performs an extension maneuver of the shoulder, the elbow is usually simultaneously extended. Extension of the shoulder and elbow causes tension in the biceps/brachialis muscle complex. Tension in the biceps/brachialis exerts pressure on the medial coronoid and overlying inflamed joint capsule causing the pain response. Anatomy Long bones, like those that compose the elbow joint, have three parts: the marrow, which fills the interior, compact bone, which makes up the walls of the shaft of the bone, and trabecular bone, the spongyappearing bone that is located beneath the joints in long bones. The articular surfaces of bones are covered with a smooth cartilage that allows the bones to move against each other with a minimum of resistance. The specialized connective tissue that surrounds a joint, the joint capsule, not only provides mechanical support to the joint, but also has an interior surface that secretes a viscous fluid that lubricates the joints. The elbow joint is composed of three bones (radius, ulna, and humerus), which must all grow together and fit perfectly for the elbow joint to function properly. The radius is the main weight-bearing bone. The ulna serves more as a lever arm for the extensor muscles of the elbow joint. The normal elbow joint is characterized by a smooth transition from the ulnar articular (joint) surface to the radial surface. The medial coronoid process of the ulna sits level with or slightly below the surface of the radius as shown in Figure 1. The cause and pathogenesis of JDS are poorly understood. It is possible that abnormal repetitive loading, such as landing from a jump, hitting contacts or a flyball box, and so on, may lead to microfractures of the bone underneath the cartilage (subchondral fractures). Additionally, increased repetitive loading can arise from contraction of the biceps/ brachialis muscle complex. When the biceps/brachialis contracts, a force is generated that rotates the medial coronoid into the radius. These microcracks disturb the mechanical properties of bone, and if not repaired properly through normal body mechanisms, fatigue fractures develop. Additionally, loss of osteocytes (bone cells), indicated by decreased osteocyte densities, has been strongly associated with the presence of microdamage after fatigue loading. These studies imply that excess load may lead to fatigue microdamage of the subchondral trabecular bone and eventual fracture, which may play an important role in the pathogenesis of JDS. Dogs may be further predisposed to this condition if they have elbow dysplasia. Dogs with elbow dysplasia had asymmetric growth of the radius and ulna during development, resulting in elbow joint incongruity. Elbow incongruity such as radioulnar step defects, humeroulnar incongruence/conflict, and varus deformity of the humerus causes abnormal contact patterns in the elbow, specifically at the coronoid trochlear articulation, which is theorized to increase the load on the medial coronoid process (MCP). Regardless of the etiology, if left untreated as a continual lameness, secondary osteoarthritis may progress as noted by damage to the cartilage such as softening, fibrillation, fissuring, and erosions as well as additional subchondral bone microcracks and fragmentation. The free fragments contribute to frictional abrasion (“kissing lesions”) of the opposing surface including the medial aspect of the humeral condyle and radial head as seen in Figure 2. Clean Run | April 08 76

Table of Contents for the Digital Edition of Clean Run Magazine - April 2008

Clean Run Magazine - March 2008
Contents
Editorializing: Dog Friends Are the Best Friends
Tip of the Month
Everything You Always Wanted to Know About Agility…
Backyard Dogs
Starting Your Pup Off on the “Right” Foot for Jumping
Pre-Agility Skills: Laying the Foundation, Part 2
Handling Your Dog in Awesome Style: Direction Cues
Trainer’s Forum
Tent Ownership Dos and Don’ts
Foundation Fundamentals: Teaching Agility Cues
Skill of the Month
Say Yes to the Learning Curve: Starting as a Team, Part 1
Classes Gone Wild
Cece’s Gym Exercise of the Month: Powering Up the Rear Legs
Spy Kids: Rules for Access and Off-Leash Control
When Pigs Fly: How to Use Your Dog’s Natural Behaviors to Train Him
Shelter Champs: Reno
The Art of Electronic Timing
Power Paws Patterns: Number Four
Jump Down Syndrome Traumatic fragmented Medial
Conquering Ring Nerves: Want to Remember the Course? Focus!
In Cider
Agility Organization Update
Letter to the Editor
Course Diagram Keys
Clean Run Magazine - April 2008 - Clean Run Magazine - March 2008
Clean Run Magazine - April 2008 - 2
Clean Run Magazine - April 2008 - Contents
Clean Run Magazine - April 2008 - 4
Clean Run Magazine - April 2008 - Editorializing: Dog Friends Are the Best Friends
Clean Run Magazine - April 2008 - Tip of the Month
Clean Run Magazine - April 2008 - Everything You Always Wanted to Know About Agility…
Clean Run Magazine - April 2008 - Backyard Dogs
Clean Run Magazine - April 2008 - 9
Clean Run Magazine - April 2008 - 10
Clean Run Magazine - April 2008 - 11
Clean Run Magazine - April 2008 - 12
Clean Run Magazine - April 2008 - 13
Clean Run Magazine - April 2008 - Starting Your Pup Off on the “Right” Foot for Jumping
Clean Run Magazine - April 2008 - 15
Clean Run Magazine - April 2008 - 16
Clean Run Magazine - April 2008 - 17
Clean Run Magazine - April 2008 - Pre-Agility Skills: Laying the Foundation, Part 2
Clean Run Magazine - April 2008 - 19
Clean Run Magazine - April 2008 - 20
Clean Run Magazine - April 2008 - 21
Clean Run Magazine - April 2008 - 22
Clean Run Magazine - April 2008 - Handling Your Dog in Awesome Style: Direction Cues
Clean Run Magazine - April 2008 - 24
Clean Run Magazine - April 2008 - 25
Clean Run Magazine - April 2008 - 26
Clean Run Magazine - April 2008 - 27
Clean Run Magazine - April 2008 - 28
Clean Run Magazine - April 2008 - 29
Clean Run Magazine - April 2008 - Trainer’s Forum
Clean Run Magazine - April 2008 - 31
Clean Run Magazine - April 2008 - 32
Clean Run Magazine - April 2008 - 33
Clean Run Magazine - April 2008 - Tent Ownership Dos and Don’ts
Clean Run Magazine - April 2008 - 35
Clean Run Magazine - April 2008 - 36
Clean Run Magazine - April 2008 - 37
Clean Run Magazine - April 2008 - Foundation Fundamentals: Teaching Agility Cues
Clean Run Magazine - April 2008 - 39
Clean Run Magazine - April 2008 - 40
Clean Run Magazine - April 2008 - 41
Clean Run Magazine - April 2008 - Skill of the Month
Clean Run Magazine - April 2008 - 43
Clean Run Magazine - April 2008 - 44
Clean Run Magazine - April 2008 - Say Yes to the Learning Curve: Starting as a Team, Part 1
Clean Run Magazine - April 2008 - 46
Clean Run Magazine - April 2008 - 47
Clean Run Magazine - April 2008 - 48
Clean Run Magazine - April 2008 - 49
Clean Run Magazine - April 2008 - Classes Gone Wild
Clean Run Magazine - April 2008 - 51
Clean Run Magazine - April 2008 - 52
Clean Run Magazine - April 2008 - Cece’s Gym Exercise of the Month: Powering Up the Rear Legs
Clean Run Magazine - April 2008 - Spy Kids: Rules for Access and Off-Leash Control
Clean Run Magazine - April 2008 - 55
Clean Run Magazine - April 2008 - 56
Clean Run Magazine - April 2008 - 57
Clean Run Magazine - April 2008 - 58
Clean Run Magazine - April 2008 - When Pigs Fly: How to Use Your Dog’s Natural Behaviors to Train Him
Clean Run Magazine - April 2008 - 60
Clean Run Magazine - April 2008 - 61
Clean Run Magazine - April 2008 - 62
Clean Run Magazine - April 2008 - 63
Clean Run Magazine - April 2008 - 64
Clean Run Magazine - April 2008 - Shelter Champs: Reno
Clean Run Magazine - April 2008 - 66
Clean Run Magazine - April 2008 - 67
Clean Run Magazine - April 2008 - The Art of Electronic Timing
Clean Run Magazine - April 2008 - 69
Clean Run Magazine - April 2008 - 70
Clean Run Magazine - April 2008 - 71
Clean Run Magazine - April 2008 - 72
Clean Run Magazine - April 2008 - Power Paws Patterns: Number Four
Clean Run Magazine - April 2008 - 74
Clean Run Magazine - April 2008 - 75
Clean Run Magazine - April 2008 - Jump Down Syndrome Traumatic fragmented Medial
Clean Run Magazine - April 2008 - 77
Clean Run Magazine - April 2008 - 78
Clean Run Magazine - April 2008 - 79
Clean Run Magazine - April 2008 - Conquering Ring Nerves: Want to Remember the Course? Focus!
Clean Run Magazine - April 2008 - 81
Clean Run Magazine - April 2008 - 82
Clean Run Magazine - April 2008 - In Cider
Clean Run Magazine - April 2008 - 84
Clean Run Magazine - April 2008 - 85
Clean Run Magazine - April 2008 - 86
Clean Run Magazine - April 2008 - Agility Organization Update
Clean Run Magazine - April 2008 - 88
Clean Run Magazine - April 2008 - 89
Clean Run Magazine - April 2008 - Course Diagram Keys
Clean Run Magazine - April 2008 - 91
Clean Run Magazine - April 2008 - 92
http://www.nxtbook.com/nxtbooks/cleanrun/1219
http://www.nxtbook.com/nxtbooks/cleanrun/1119
http://www.nxtbook.com/nxtbooks/cleanrun/1019
http://www.nxtbook.com/nxtbooks/cleanrun/0919
http://www.nxtbook.com/nxtbooks/cleanrun/0819
http://www.nxtbook.com/nxtbooks/cleanrun/0719
http://www.nxtbook.com/nxtbooks/cleanrun/0619
http://www.nxtbook.com/nxtbooks/cleanrun/0519
http://www.nxtbook.com/nxtbooks/cleanrun/0419
http://www.nxtbook.com/nxtbooks/cleanrun/0319
http://www.nxtbook.com/nxtbooks/cleanrun/0219
http://www.nxtbook.com/nxtbooks/cleanrun/0119
http://www.nxtbook.com/nxtbooks/cleanrun/1218
http://www.nxtbook.com/nxtbooks/cleanrun/1118
http://www.nxtbook.com/nxtbooks/cleanrun/1018
http://www.nxtbook.com/nxtbooks/cleanrun/0918
http://www.nxtbook.com/nxtbooks/cleanrun/0818
http://www.nxtbook.com/nxtbooks/cleanrun/0718
http://www.nxtbook.com/nxtbooks/cleanrun/0618
http://www.nxtbook.com/nxtbooks/cleanrun/0518
http://www.nxtbook.com/nxtbooks/cleanrun/0418
http://www.nxtbook.com/nxtbooks/cleanrun/0318
http://www.nxtbook.com/nxtbooks/cleanrun/0218
http://www.nxtbook.com/nxtbooks/cleanrun/0118
http://www.nxtbook.com/nxtbooks/cleanrun/1217
http://www.nxtbook.com/nxtbooks/cleanrun/1117
http://www.nxtbook.com/nxtbooks/cleanrun/1017
http://www.nxtbook.com/nxtbooks/cleanrun/0917
http://www.nxtbook.com/nxtbooks/cleanrun/0817
http://www.nxtbook.com/nxtbooks/cleanrun/0717
http://www.nxtbook.com/nxtbooks/cleanrun/0617
http://www.nxtbook.com/nxtbooks/cleanrun/0517
http://www.nxtbook.com/nxtbooks/cleanrun/0417
http://www.nxtbook.com/nxtbooks/cleanrun/0317
http://www.nxtbook.com/nxtbooks/cleanrun/0217
http://www.nxtbook.com/nxtbooks/cleanrun/0117
http://www.nxtbook.com/nxtbooks/cleanrun/1216
http://www.nxtbook.com/nxtbooks/cleanrun/1116
http://www.nxtbook.com/nxtbooks/cleanrun/1016
http://www.nxtbook.com/nxtbooks/cleanrun/0916
http://www.nxtbook.com/nxtbooks/cleanrun/0816
http://www.nxtbook.com/nxtbooks/cleanrun/0716
http://www.nxtbook.com/nxtbooks/cleanrun/0616
http://www.nxtbook.com/nxtbooks/cleanrun/0516
http://www.nxtbook.com/nxtbooks/cleanrun/0416
http://www.nxtbook.com/nxtbooks/cleanrun/0316
http://www.nxtbook.com/nxtbooks/cleanrun/0216
http://www.nxtbook.com/nxtbooks/cleanrun/0116
http://www.nxtbook.com/nxtbooks/cleanrun/1215
http://www.nxtbook.com/nxtbooks/cleanrun/1115
http://www.nxtbook.com/nxtbooks/cleanrun/1015
http://www.nxtbook.com/nxtbooks/cleanrun/0915
http://www.nxtbook.com/nxtbooks/cleanrun/0815
http://www.nxtbook.com/nxtbooks/cleanrun/0715
http://www.nxtbook.com/nxtbooks/cleanrun/0615
http://www.nxtbook.com/nxtbooks/cleanrun/0515
http://www.nxtbook.com/nxtbooks/cleanrun/0415
http://www.nxtbook.com/nxtbooks/cleanrun/0315
http://www.nxtbook.com/nxtbooks/cleanrun/0215
http://www.nxtbook.com/nxtbooks/cleanrun/0115
http://www.nxtbook.com/nxtbooks/cleanrun/1214
http://www.nxtbook.com/nxtbooks/cleanrun/1114
http://www.nxtbook.com/nxtbooks/cleanrun/1014
http://www.nxtbook.com/nxtbooks/cleanrun/0914
http://www.nxtbook.com/nxtbooks/cleanrun/0814
http://www.nxtbook.com/nxtbooks/cleanrun/0714
http://www.nxtbook.com/nxtbooks/cleanrun/0614
http://www.nxtbook.com/nxtbooks/cleanrun/0514
http://www.nxtbook.com/nxtbooks/cleanrun/0414
http://www.nxtbook.com/nxtbooks/cleanrun/0314
http://www.nxtbook.com/nxtbooks/cleanrun/0214
http://www.nxtbook.com/nxtbooks/cleanrun/0114
http://www.nxtbook.com/nxtbooks/cleanrun/1213
http://www.nxtbook.com/nxtbooks/cleanrun/1113
http://www.nxtbook.com/nxtbooks/cleanrun/1013
http://www.nxtbook.com/nxtbooks/cleanrun/0913
http://www.nxtbook.com/nxtbooks/cleanrun/0813
http://www.nxtbook.com/nxtbooks/cleanrun/0713
http://www.nxtbook.com/nxtbooks/cleanrun/0613
http://www.nxtbook.com/nxtbooks/cleanrun/0513
http://www.nxtbook.com/nxtbooks/cleanrun/0413
http://www.nxtbook.com/nxtbooks/cleanrun/0313
http://www.nxtbook.com/nxtbooks/cleanrun/0213
http://www.nxtbook.com/nxtbooks/cleanrun/0113
http://www.nxtbook.com/nxtbooks/cleanrun/1212
http://www.nxtbook.com/nxtbooks/cleanrun/1112
http://www.nxtbook.com/nxtbooks/cleanrun/1012
http://www.nxtbook.com/nxtbooks/cleanrun/0912
http://www.nxtbook.com/nxtbooks/cleanrun/0812
http://www.nxtbook.com/nxtbooks/cleanrun/0712
http://www.nxtbook.com/nxtbooks/cleanrun/0612
http://www.nxtbook.com/nxtbooks/cleanrun/0512
http://www.nxtbook.com/nxtbooks/cleanrun/0412
http://www.nxtbook.com/nxtbooks/cleanrun/0312
http://www.nxtbook.com/nxtbooks/cleanrun/0212
http://www.nxtbook.com/nxtbooks/cleanrun/0112
http://www.nxtbook.com/nxtbooks/cleanrun/1211
http://www.nxtbook.com/nxtbooks/cleanrun/1111
http://www.nxtbook.com/nxtbooks/cleanrun/1011
http://www.nxtbook.com/nxtbooks/cleanrun/0911
http://www.nxtbook.com/nxtbooks/cleanrun/0811
http://www.nxtbook.com/nxtbooks/cleanrun/0711
http://www.nxtbook.com/nxtbooks/cleanrun/0611
http://www.nxtbook.com/nxtbooks/cleanrun/0511
http://www.nxtbook.com/nxtbooks/cleanrun/0411
http://www.nxtbook.com/nxtbooks/cleanrun/0311
http://www.nxtbook.com/nxtbooks/cleanrun/0211
http://www.nxtbook.com/nxtbooks/cleanrun/0111
http://www.nxtbook.com/nxtbooks/cleanrun/1210
http://www.nxtbook.com/nxtbooks/cleanrun/1110
http://www.nxtbook.com/nxtbooks/cleanrun/1010
http://www.nxtbook.com/nxtbooks/cleanrun/0910
http://www.nxtbook.com/nxtbooks/cleanrun/0810
http://www.nxtbook.com/nxtbooks/cleanrun/0710
http://www.nxtbook.com/nxtbooks/cleanrun/0610
http://www.nxtbook.com/nxtbooks/cleanrun/0510
http://www.nxtbook.com/nxtbooks/cleanrun/0410
http://www.nxtbook.com/nxtbooks/cleanrun/0310
http://www.nxtbook.com/nxtbooks/cleanrun/0210
http://www.nxtbook.com/nxtbooks/cleanrun/0110
http://www.nxtbook.com/nxtbooks/cleanrun/1209
http://www.nxtbook.com/nxtbooks/cleanrun/1109
http://www.nxtbook.com/nxtbooks/cleanrun/1009
http://www.nxtbook.com/nxtbooks/cleanrun/0909
http://www.nxtbook.com/nxtbooks/cleanrun/0809
http://www.nxtbook.com/nxtbooks/cleanrun/0709
http://www.nxtbook.com/nxtbooks/cleanrun/comp-demo
http://www.nxtbook.com/nxtbooks/cleanrun/0609
http://www.nxtbook.com/nxtbooks/cleanrun/0509
http://www.nxtbook.com/nxtbooks/cleanrun/0409
http://www.nxtbook.com/nxtbooks/cleanrun/0309
http://www.nxtbook.com/nxtbooks/cleanrun/0209
http://www.nxtbook.com/nxtbooks/cleanrun/0109
http://www.nxtbook.com/nxtbooks/cleanrun/1208
http://www.nxtbook.com/nxtbooks/cleanrun/1108
http://www.nxtbook.com/nxtbooks/cleanrun/1008
http://www.nxtbook.com/nxtbooks/cleanrun/0908
http://www.nxtbook.com/nxtbooks/cleanrun/0808
http://www.nxtbook.com/nxtbooks/cleanrun/0708
http://www.nxtbook.com/nxtbooks/cleanrun/0608
http://www.nxtbook.com/nxtbooks/cleanrun/0508
http://www.nxtbook.com/nxtbooks/cleanrun/0408
http://www.nxtbook.com/nxtbooks/cleanrun/0308
http://www.nxtbook.com/nxtbooks/cleanrun/0208
http://www.nxtbook.com/nxtbooks/cleanrun/0108
http://www.nxtbook.com/nxtbooks/cleanrun/1207
http://www.nxtbook.com/nxtbooks/cleanrun/1107
http://www.nxtbook.com/nxtbooks/cleanrun/1007
http://www.nxtbook.com/nxtbooks/cleanrun/0907
http://www.nxtbook.com/nxtbooks/cleanrun/0807
http://www.nxtbook.com/nxtbooks/cleanrun/0707
http://www.nxtbook.com/nxtbooks/cleanrun/0607
http://www.nxtbook.com/nxtbooks/cleanrun/0507
http://www.nxtbook.com/nxtbooks/cleanrun/0407
http://www.nxtbook.com/nxtbooks/cleanrun/0307
http://www.nxtbook.com/nxtbooks/cleanrun/0207
http://www.nxtbook.com/nxtbooks/cleanrun/0107
http://www.nxtbook.com/nxtbooks/cleanrun/1206
http://www.nxtbook.com/nxtbooks/cleanrun/1106
http://www.nxtbook.com/nxtbooks/cleanrun/1006
http://www.nxtbook.com/nxtbooks/cleanrun/0906
http://www.nxtbook.com/nxtbooks/cleanrun/0806
http://www.nxtbook.com/nxtbooks/cleanrun/0706
http://www.nxtbook.com/nxtbooks/cleanrun/0606
http://www.nxtbook.com/nxtbooks/cleanrun/0506
http://www.nxtbook.com/nxtbooks/cleanrun/0406
http://www.nxtbook.com/nxtbooks/cleanrun/0306
http://www.nxtbook.com/nxtbooks/cleanrun/0206
http://www.nxtbook.com/nxtbooks/cleanrun/0106
http://www.nxtbookMEDIA.com