Unfortunately, carpal hyperextension is a common injury among today’s canines due to their active lifestyles. Most patients may experience this injury after acute trauma such as jumping off a deck, a bridge, roofs, and, in extreme cases, cliffs. Other patients may experience carpal hyperextension secondary to a pathology such as Immune Mediated Polyarthropathy.
Bey, a 2-year-old border collie, experienced carpal hyperextension as a result of a contralateral limb amputation. In our experience, canine forelimb amputees commonly exhibit compensatory changes such as carpal varus and carpal hyperextension. In large part, this is due to dramatically increased forces acting against support structures of the remaining thoracic limb and abnormal limb positioning related to the loss of the contralateral limb. Bey’s right forelimb was amputated at 6 months of age due to a non-healing humeral fracture. Prior to his carpal orthosis, he was managed with a front-end cart and intermittent use of a neoprene carpal wrap.
Bey’s carpus continued to experience breakdown resulting in severe carpal valgus and carpal DJD in addition to the hyperextension. Bey presented to OrthoPets with pain, discomfort and exhaustion during ambulation. The goals of Bey’s orthosis were to provide carpal support, decrease pain and optimize function of his forelimb. Bey is very active and needed his remaining thoracic limb to keep up with his high energy level. Due to the degree of Bey’s instabilities, an articulating paw segment had to be included in the device to achieve the appropriate length of rigid support lever arm to offer the best support and stability to his carpus. This was required to lower the magnitude of force required to support the frontal plane valgus and sagittal plane hyperextension so that the skin can tolerate the supportive forces (3 Point Corrective System) applied to the skeleton through skin
The following are common reasons when a paw segment may be appropriate:
- The patients’ anatomy leaves a shortened lever arm
- A short manus
- The patient has severe instabilities and/or instabilities on more than one plane of motion
- Severe instabilities cause the patient to be completely reliant upon the support of the orthosis rather than being able to offer some complementary stability from musculoskeletal structures
- Multiple planes of instability cause the affected joint to be able to rotate or twist out of the 3 Point Corrective System locations of support requiring the orthosis to offer global support and mimic an arthrodesis salvage procedure approach
- The patient has missing or non-functional digits
- Restoring a normal ground reaction force vector alignment is critical to ensure that any form of support reduces abnormal forces acting against the limb while restoring normal forces through weight bearing
- There is SDF or DDF contracture
- SDF & DDF contracture causes digits to be positioned such that the main paw pad is unable to make contact with the ground. This causes an abnormal cranial shift of the total body force vector resulting in increased moment acting against the patients’ limb. Restoring normal vector alignment is the most critical first step in returning normal forces to the patient’s musculoskeletal system.
Bey has had his carpal orthosis for 4 months and, according to his owner, is like a puppy again. When the abnormal forces acting against a patient are supported and reduced through the orthosis, the patient is left with a normal weight-bearing environment leading to increased function, confidence, and comfort. Through the devotion of the owner and regular rehabilitation sessions, Bey is now spending his days running around his property and keeping the horses in check.