New Insights Into the Phantom Complex for Small Animals
Dogs undergoing limb amputations can experience post-amputation pain and behavioral changes associated with a phantom complex.
Surgical limb amputations are commonly performed in small animals. In human medicine, a phantom complex (PC) has been defined as and consists of non-painful phantom limb sensation, stump pain (SP), and phantom limb pain (PLP). Unlike SP, which subsides, PLP can gradually worsen and become a chronic, neuropathic pain.
Phantom pain has not been extensively researched in veterinary medicine. In particular, veterinary limb amputation studies have primarily investigated the degree of adaptation and pet owner satisfaction. Also, assessing an animal’s abnormal pain sensations can be challenging because of animals’ inability to verbalize.
To address these knowledge gaps, an Italian research team conducted an online survey of pet owners whose dogs had undergone a limb amputation. The results were recently published in the Journal of Veterinary Behavior.
For this pilot study, the research team surveyed current and former dog owners whose dogs, regardless of reason, had 1 limb partially or completely amputated within the previous 3 months. According to human studies, 3 months is enough time to differentiate between simple postsurgical pain and PC-related pain in nonverbalizing patients.
The survey had 69 questions on pre- and post-amputation pain, pain-related behaviors, quality of life (QoL), and pet owner satisfaction. Statistical analysis was performed to identify associations with PC pain.
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Researchers collected 107 completed questionnaires. Just over half of the dogs were male and about 60% weighed more than 25 kg (about 55 pounds). Most dogs were adults at the time of amputation. Neoplasia (54%) and trauma (40%) were the most common reasons for amputation. Nearly 75% of amputations were complete and about 60% involved a thoracic limb.
Pain prevalence was roughly equal before (82%) and after amputation (85%). Slightly over half of dogs experienced pain more than 1 month before amputation and 14% of dogs had pain 1 to 6 months after amputation. Researchers identified ‘early onset of pre-amputation pain’ as a risk factor for increased post-amputation pain frequency.
Pet owners reported a transition from ‘waxing and waning’ or ‘persistent’ pain before amputation to ‘sudden and transient’ pain afterward, potentially due to abnormal circuitry following amputation and subsequent, sudden bursts of pain.
Most dogs received pre- or post-amputation medical treatment to relieve pain. However, as in people, there was no significant relationship between pre-surgical pain control and incidence of post-amputation pain.
Dogs reportedly became less playful and interactive during the first 3 to 6 months following amputation. From 3 months onward, some dogs exhibited behaviors potentially associated with the PC, including:
- Licking or scratching stump
- Muscular twitching in stump
Some behavioral changes like aggression or withdrawal reportedly occurred before and after amputation.
Although some dogs had mobility challenges after amputation, about 95% of dogs adapted well after the procedure. A high degree of adaptation was significantly associated with less post-amputation pain.
Pet Owner Satisfaction
Nearly 90% of the surveyed pet owners were happy with the decision to have their pets’ limbs amputated and felt their veterinarians informed them well about the procedure. Although about 60% of pet owners reported limited independence and social life in the first month after amputation, roughly the same percentage reported an improved relationship with their pet post-amputation.
The researchers acknowledged that this study’s survey was unvalidated. However, to date, validated pain scales and surveys for amputee dogs are not available, they noted.
They concluded that for veterinarians, “The ability to recognize behavioral signs that may indicate the presence of unpleasant sensations related to neuropathic pain would be of great interest” for pain prevention and treatment.
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.