Carpus
Luxation(s)
Carpal hyperextension syndrome
Flexural deformity of the carpus
Carpal laxity syndrome
Trauma/fractures
Shearing injuries
Luxation(s)
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Luxations of a carpal joint or an individual carpal bone may result from an acute traumatic event or luxation of multiple bones may be a result of progressive OA or rheumatoid arthritis with ligamentous instability, leading to carpal instability.
History
Dogs may have a history of acute trauma and lameness, such as jumping from a height, or a more chronic insidious lameness that may be associated with erosive arthritis and subsequent luxation of a carpal joint or bone.
Clinical Findings
The affected area of the carpus has a firm swelling. Crepitus is generally present when the carpus is placed through a range of motion. In some cases, the affected bone or joint may be palpable, especially with acute injuries. More chronic conditions often have a great deal of fibrosis.
Diagnostics
Lateral and AP radiographs of the carpus are diagnostic. Radiographs of the contralateral normal limb may be useful to identify more subtle conditions.
Treatment Options
If a single bone is involved, reduction of the bone with stabilization of surrounding soft tissues or an implant may result in a successful outcome. If the luxation results from arthritic changes, carpal arthrodesis generally results in a more favorable outcome. However, if rheumatoid arthritis is the cause of the luxation, this condition affects multiple joints in a progressive fashion and eventually results in severe, crippling lameness.
Carpal hyperextension syndrome
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – Generally middle aged to older
Etiology - Carpal hyperextension injuries occur as a result of damage to the palmar fibrocartilage and the carpal ligaments, which usually occur as a result of jumping of falling from a height, placing all of the body weight on the limb. The antebrachiocarpal, middle carpal, carpometacarpal, or any combination of joints may be involved.
History
There is usually a history of some form of trauma, usually jumping down from a height. Dogs are acutely lame.
Clinical Findings
Affected dogs are lame and walk with overextension of the carpus; in severe cases, the carpus may touch the ground during weight-bearing.
Diagnostics
It is important to obtain stress radiographs to delineate which joint(s) is(are) involved because this information helps to guide the surgical treatment. Normal AP, lateral, and palmar stress views should be obtained. Similar views of the contralateral normal limb may provide valuable comparative information. Separation or collapse of carpometacarpal, middle carpal, or antebrachiocarpal joints, or displacement of individual carpal bones, may be seen on the stress views. Separation of the ulnar carpal bone from the row of distal carpal bones indicate damage to the middle carpal joint and/or carpometacarpal joints.
Treatment Options
Treatment usually involves surgical fusion (arthrodesis) of one or more of the joints. If the antebrachiocarpal joint is involved, fusion of all carpal joints (pancarpal arthrodesis) is performed. If the middle carpal or carpometacarpal joint(s) is(are) involved, a partial carpal arthrodesis is performed, sparing the antebrachiocarpal joint, which is the major motion joint of the carpus. The arthrodesis is performed by removing the articular cartilage, placing a bone graft to help speed bony union, and stabilizing the area with a bone plate. A coaptation device is placed after surgery until early bony union occurs to help reduce the stress on the implants. Treatment of a carpal hyperextension injury with a coaptation device alone is generally unsuccessful; a quicker return to function is achieved by fusing the offending joints.
Flexural deformity of the carpus
Signalment
Breeds – Generally medium to larger breeds. Doberman pinschers and Shar Pei dogs may have a higher predilection.
Gender – No clear gender predilection
Age – 6 to 20 weeks of age
Etiology - The underlying cause is unknown, but the flexor carpi ulnaris tendon is quite taught, and results in the characteristic posture of this condition. A disparity in growth between the bones and soft tissues is postulated as a cause.
History
Affected dogs seem to have a rapidly progressive development of a "knuckled over" posture of the carpus and foot.
Clinical Findings
Lameness is usually present, but the main finding is that of carpal flexion, lateral bowing of the carpus, and a taut flexor carpi ulnaris tendon where it attaches to the accessory carpal bone.
Diagnostics
The characteristic posture of the limb and the finding of a tight flexor carpi ulnaris tendon are generally diagnostic.
Treatment Options
Puppies generally recover with mild exercise on a surface with good footing, such as grass or carpet, and changing the diet to a large breed growth diet. Nonresponsive cases benefit from transection of the flexor carpi ulnaris tendon from the accessory carpal bone. There should be immediate correction of the condition if performed properly.
Carpal laxity syndrome
Signalment
Breeds –
Generally medium to larger breeds. German Shepherd dogs may have a higher predilection.
Gender – No clear gender predilection
Age – 8 to 12 weeks of age
Etiology - The underlying cause is unknown, but there may be underlying weakness of the flexor muscles or other supporting soft tissues.
History
Affected dogs stand with the carpus in a "dropped" position.
Clinical Findings
Dogs have a palmigrade stance. There is usually no pain on palpation. Some degree of limited mobility may be present, but it is generally not appreciated in puppies of this age.
Diagnostics
The signalment and physical exam findings are generally sufficient to diagnose this condition. In cases where there is a history of trauma, radiographs (including stress views of the carpus) may be taken.
Treatment Options
Mild exercises to encourage strengthening of the digital and carpal flexor muscles and walking on a surface with good footing are recommended. Walking in sand may be beneficial. Be certain that the dog is on a good diet.
Trauma/fractures
Signalment
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Trauma
History
Dogs have a history of trauma, such as jumping from a height or being hit by an automobile
Clinical Findings
Severe to non weight-bearing lameness. Swelling of the affected area is common, as is pain on direct palpation. Crepitus of the carpus during range of motion is common. Fragments may be palpable.
Diagnostics
Although A-P, lateral, and oblique view radiographs are very helpful, some fractures may be missed. A CT of the area gives a better 3-D perspective of injuries and may reveal additional fractures in the center of bones that may go undetected with conventional radiography.
Treatment Options
The recommended treatment depends on the type and severity of injuries. Individual small chip fractures may be treated conservatively if they are nonarticular; otherwise, they may be removed. Larger single fragments may be repaired with screws or K wires. Comminuted fractures may be best handled with a partial or pancarpal arthrodesis.
Shearing injuries
Breeds – No breed predilection
Gender – No gender predilection
Age – No age predilection
Etiology - Trauma, with the affected limb caught under a skidding tire. The medial aspect is generally affected.
History
Dogs have a history of being hit by an automobile
Clinical Findings
Severe to non weight-bearing lameness. The soft tissues are eroded to varying degrees, sometimes to the point of articular cartilage erosion. Swelling of the affected area is common, as is pain on direct palpation. Crepitus of the carpus during range of motion is common. Fragments may be palpable.
Diagnostics
Although A-P, lateral, and oblique view radiographs are very helpful, some fractures may be missed. A CT of the area gives a better 3-D perspective of injuries and may reveal additional fractures in the center of bones that may go undetected with conventional radiography.
Treatment Options
The recommended treatment depends on the severity of injuries. Soft tissue injuries must be managed with careful debridement and copious irrigation of the area. Appropriate bandaging and regular bandage changes are necessary usually for weeks. A transarticular external fixator may give appropriate stabilization, either temporarily or permanently depending on the extent of the injury and the response to this form of stabilization. When the wound is healthy with adequate granulation tissue formation, the carpal instability may be managed with a prosthetic collateral ligament repair, usually with screws or tissue anchors and suture. Skin grafting may be necessary in cases of severe soft tissue erosion. The bones should be covered with a healthy bed of granulation tissue prior to grafting. Complex extensive injuries with loss of articular cartilage may be best handled with a pancarpal arthrodesis.
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