Outcome for client-owned domestic rabbits undergoing limb amputation: 34 cases (2000–2009)

Nicole C. Northrup Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

Search for other papers by Nicole C. Northrup in
Current site
Google Scholar
PubMed
Close
 DVM
,
Grace Heather Wilson Barron Department of Clinical Sciences, School of Veterinary Medicine, St Matthew's University, Grand Cayman Island, British West Indies.

Search for other papers by Grace Heather Wilson Barron in
Current site
Google Scholar
PubMed
Close
 DVM
,
Charles F. Aldridge Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

Search for other papers by Charles F. Aldridge in
Current site
Google Scholar
PubMed
Close
 DVM
,
Lauren V. Powers Carolina Veterinary Specialists, 12117 Statesville Rd, Huntersville, NC 28078.

Search for other papers by Lauren V. Powers in
Current site
Google Scholar
PubMed
Close
 DVM
,
Cheryl B. Greenacre Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

Search for other papers by Cheryl B. Greenacre in
Current site
Google Scholar
PubMed
Close
 DVM
,
Jason D. Hutcheson For Pet's Sake, The Avian and Exotic Animal Hospital of Atlanta, 3761 N Druid Hills Rd, Atlanta, GA 30033.

Search for other papers by Jason D. Hutcheson in
Current site
Google Scholar
PubMed
Close
 DVM
, and
James K. Morrisey Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

Search for other papers by James K. Morrisey in
Current site
Google Scholar
PubMed
Close
 DVM

Abstract

Objective—To describe morbidity, function, outcome, and owner satisfaction associated with limb amputation in domestic rabbits.

Design—Retrospective case series.

Animals—34 client-owned domestic rabbits.

Procedures—Medical records of domestic rabbits undergoing limb amputation for any cause between 2000 and 2009 were reviewed. The Kaplan-Meier method was used to estimate survival rate and median survival time, and variables were analyzed for relationship to risk of morbidity resulting in euthanasia and to outcome (survival vs nonsurvival [death or euthanasia]). Owners were interviewed to determine satisfaction with outcome of the procedure.

Results—28 rabbits underwent pelvic limb amputation, and 6 underwent thoracic limb amputation. At the last follow-up, 18 rabbits were dead, 9 were alive, and 7 were lost to follow-up. Median overall survival time was 720 days (range, 4 to 3,250 days). Acute and delayed or chronic complications were observed in 22 of 34 and 19 of 32 rabbits, respectively, most commonly difficulty ambulating, hygiene issues, and pododermatitis (cutaneous ulcers at the hock). Six rabbits were euthanized because of complications at a median of 104 days (range, 4 to 399 days) after surgery. Risk of morbidity resulting in euthanasia increased with heavier body weight and concurrent disease affecting ambulation at the time of amputation. Weight, age, and pododermatitis at the time of amputation were significantly negatively associated with survival time. Thirty-one (91%) owners were satisfied with the outcome.

Conclusions and Clinical Relevance—Although limb amputation was tolerated by most rabbits and most owners were satisfied, complications resulted in death in 6 of 34 (18%) rabbits, and 19 of 32 (59%) developed chronic complications. Amputation in heavy rabbits or those with concurrent pododermatitis, musculoskeletal disease, or neurologic disease should be considered carefully. Because of the small sample size and retrospective nature of this study, results should be interpreted as exploratory and hypothesis generating.

Abstract

Objective—To describe morbidity, function, outcome, and owner satisfaction associated with limb amputation in domestic rabbits.

Design—Retrospective case series.

Animals—34 client-owned domestic rabbits.

Procedures—Medical records of domestic rabbits undergoing limb amputation for any cause between 2000 and 2009 were reviewed. The Kaplan-Meier method was used to estimate survival rate and median survival time, and variables were analyzed for relationship to risk of morbidity resulting in euthanasia and to outcome (survival vs nonsurvival [death or euthanasia]). Owners were interviewed to determine satisfaction with outcome of the procedure.

Results—28 rabbits underwent pelvic limb amputation, and 6 underwent thoracic limb amputation. At the last follow-up, 18 rabbits were dead, 9 were alive, and 7 were lost to follow-up. Median overall survival time was 720 days (range, 4 to 3,250 days). Acute and delayed or chronic complications were observed in 22 of 34 and 19 of 32 rabbits, respectively, most commonly difficulty ambulating, hygiene issues, and pododermatitis (cutaneous ulcers at the hock). Six rabbits were euthanized because of complications at a median of 104 days (range, 4 to 399 days) after surgery. Risk of morbidity resulting in euthanasia increased with heavier body weight and concurrent disease affecting ambulation at the time of amputation. Weight, age, and pododermatitis at the time of amputation were significantly negatively associated with survival time. Thirty-one (91%) owners were satisfied with the outcome.

Conclusions and Clinical Relevance—Although limb amputation was tolerated by most rabbits and most owners were satisfied, complications resulted in death in 6 of 34 (18%) rabbits, and 19 of 32 (59%) developed chronic complications. Amputation in heavy rabbits or those with concurrent pododermatitis, musculoskeletal disease, or neurologic disease should be considered carefully. Because of the small sample size and retrospective nature of this study, results should be interpreted as exploratory and hypothesis generating.

Amputation of a limb is a commonly performed procedure in dogs and cats for treatment of neoplasia and irreparable traumatic conditions. Outcome is generally good for ability to walk and quality of life.1 This procedure is recommended for domestic rabbits (Oryctolagus cuniculus) with comparable conditions; however, there is little information describing outcome in this species. Even though the postoperative recovery of rabbits might be expected to be similar to what has been reported for dogs and cats, the unique hopping gait and conformation of this species prompted investigation of tolerance of limb amputation by rabbits. A PubMed search identified no studies describing outcome in clinical cases of rabbits undergoing amputation. The only case report2 involved a rabbit that died during amputation for humeral osteosarcoma. Most publications about limb amputations in rabbits described laboratory rabbits used as models for human disease. Rabbits were typically euthanized soon after surgery with no evaluation of recovery and return to function.3,4 The purpose of the study reported here was to retrospectively describe morbidity, survival rate, and survival time of client-owned domestic rabbits undergoing amputation of a thoracic or pelvic limb for any reason.

Materials and Methods

Case selection—Cases were solicited for this multi-institutional retrospective series from 50 veterinary practitioners known to work with rabbits and identified by searching medical records databases. Client-owned domestic rabbits undergoing limb amputation between 2000 and 2009 with follow-up information available describing postoperative ambulatory function, complications, and survival time were eligible for inclusion.

Medical records review—Medical records were reviewed by contributing veterinarians and data submitted by use of a standardized form. Data collected included patient signalment, body condition score (scale of 1 to 5), reason for amputation, limb amputated, concurrent diseases (with specific inquiry about orthopedic or neurologic disease), survival time (for nonsurvivors), and cause of death (including death or euthanasia). Information collected regarding the surgery and associated morbidity included procedure performed, date discharged, and descriptions of morbidity in general followed by questions about specific morbidities (whether observed [yes vs no], whether resolved [yes vs no], dates affected, and description) including difficulty ambulating or lameness, loss of ability to ambulate, pain, development of sores or ulcers, abnormal behavior, changes in appetite or gastrointestinal signs, incisional problems, and problems with other limbs. Morbidity was classified as acute if it occurred during the week following surgery and delayed or chronic if it was first observed or persisted ≥ 1 month after surgery. Because descriptions of morbidity were collected retrospectively from medical records and owner interviews, no grading scheme was applied. Additional follow-up information including owner satisfaction with outcome was obtained by telephone interviews of owners. Owner satisfaction was evaluated with a yes or no response and an open-ended request for comments.

Statistical analysis—The study endpoint was overall survival time, defined as the time from amputation until death from any cause. Median survival time of all rabbits was estimated by means of the Kaplan-Meier product limit method. Rabbits that were alive were censored on the date of last follow-up.

Variables for statistical analysis were chosen on the basis of suspected relationship to outcome. Risk factors evaluated for association with death and morbidity resulting in euthanasia included age, weight, body condition score, amputation of a thoracic or pelvic limb, concurrent disease at the time of amputation that affected ambulation (yes vs no), and pododermatitis at the time of amputation (yes vs no). Simple logistic regression was performed to test for relationships between risk factors and the probability of morbidity resulting in death. If quasiseparation of variables occurred, the Firth penalized maximum likelihood estimation method was used to reduce bias in logistic model parameter estimation. Multiple logistic regression was then performed to determine which risk factors significantly affected probability of morbidity. All risk factors were initially included in the model, and a stepwise selection procedure was used to select risk factors in the final model.

Cox proportional hazards regression was used to test for relationships of risk factors to probability of death. Cox proportional hazards multiple regression was also performed to test which risk factors significantly affected likelihood of death. All risk factors were initially included in the model, and a stepwise selection procedure was used to select risk factors in the final model.

All hypothesis tests were 2 sided, and the significance level was P < 0.05. All statistical tests were performed with statistical software.a

Results

Thirty-four rabbits meeting the inclusion criteria for this study were identified at 11 participating institutions. Four cases were excluded owing to lack of follow-up information, and 1 was excluded because information regarding the surgical procedure was not available. Twenty-eight of 34 (82%) rabbits underwent pelvic limb amputation, and 6 (18%) underwent thoracic limb amputation. Median length of hospitalization was 2 days (range, 1 to 9 days). Patient characteristics and surgical procedure performed were summarized (Table 1).

Table 1—

Signalment, indication, and specific surgical procedure performed in 34 client-owned domestic rabbits (median age, 5.5 years [range, 2 months to 12 years]; median body weight, 2.1 kg [range, 0.4 to 4.5 kg]) that underwent limb amputation between 2000 and 2009.

VariableNo. of rabbits
Sex
 Sexually intact female5
 Spayed female15
 Sexually intact male5
 Castrated male9
Breed
 Dwarf or Dwarf mix5
 Rex4
 Mixed4
 New Zealand White or New Zealand White mix4
 Lop3
 Mini-Lop2
 Dutch1
 Holland Lop1
 Mini-Rex1
 Unknown9
Reason for amputation
 Fracture13
 Joint infection or abscess12
 Neoplasia4
 Strangulation injury to limb3
 Joint luxation1
 Self-trauma after declaw surgery1
Procedure performed
 Thoracic limb amputation6
 Transhumeral amputation3
 Interscapulothoracic amputation2
 Carpal disarticulation1
Pelvic limb amputation28
 Transfemoral amputation25
 Hip disarticulation2
 Transtibial amputation1

Neoplasia included fibrosarcoma, myxosarcoma, basal cell carcinoma, and unconfirmed probable neoplasia of muscle with secondary infection.

Morbidity and outcome for the cases in this study were summarized (Figure 1). Twenty-nine of 34 (85%) rabbits developed morbidity as a consequence of amputation. Acute morbidity (Table 2) was observed in 22 (65%) rabbits, with 12 (35%) having multiple adverse effects. For these rabbits, difficulty ambulating included balance disorder with falling to the side of the amputated leg and slipping (n = 5), problems supporting weight on 3 legs due to obesity or large size (2), and exacerbation of concurrent disease (3; osteoarthritis, myopathy, or undiagnosed weakness of a remaining limb). Gastrointestinal abnormalities included ileus (n = 5), decreased appetite (3), and soft feces (1). Incisional problems included infection (n = 3), dehiscence (1), mild bruising (3), serous discharge (1), and mild edema and erythema (2). Cutaneous ulceration occurred at the hock and was present before amputation in 3 rabbits. The 1 rabbit with a documented change in behavior became more aggressive at play, a change attributed to improved condition by the attending veterinarian and owner.

Figure 1—
Figure 1—

Flow diagram illustrating morbidity and outcome for 34 client-owned domestic rabbits undergoing limb amputation between 2000 and 2009. Alive = Rabbit was alive at last follow-up. Dead A = Rabbit was dead with death confirmed to be related to amputation. Dead T = Rabbit was dead because of tumor recurrence at amputation site. Dead O = Rabbit was dead with death confirmed to be unrelated to the amputation (ie, other cause). Dead U = Rabbit was dead because of unknown cause. Lost = Rabbit was lost to follow-up.

Citation: Journal of the American Veterinary Medical Association 244, 8; 10.2460/javma.244.8.950

Table 2—

Acute (occurring 0 to 7 days after surgery) and delayed or chronic (first observed or persisted ≥ 1 month after surgery) morbidity associated with limb amputation in the rabbits in Table 1.

VariableNo. of rabbits
Acute morbidity (n = 34)
 Total affected22
 Difficulty ambulating10
 Gastrointestinal abnormalities9
 Postoperative signs of pain8
 Incisional problems7
 Cutaneous ulceration5
 Behavior changes1
Delayed or chronic morbidity (n = 32)
 Total affected19
 Difficulty ambulating10
 Hygiene issues9
 Cutaneous ulceration6
 Abscessed surgical site1
 Chronic pain1
 Behavior changes1

Acute morbidity resolved in 17 of 22 (77%) affected rabbits. Medical records described resolution of pain in 1 to 2 days. Gastrointestinal stasis and decreased appetite resolved in 1 to 4 days. Patients with resolution of difficulties with ambulation were clinically normal in 1 to 3 days after surgery. Resolution of pododermatitis, incisional infections, or incisional abscesses took 1 to 8 weeks. Acute morbidity did not resolve in 5 rabbits (23%), including 4 with chronic abnormalities in ambulation or pododermatitis and 1 euthanized 4 days after surgery because of incisional infection and dehiscence, pododermatitis, and inability to ambulate. The decline in this rabbit's condition was exacerbated by presumptive concurrent myopathy.

Thirty-two rabbits lived long enough and had sufficient follow-up information to be evaluated for delayed or chronic morbidity. Nineteen of 32 (59%) developed delayed or chronic morbidity (Table 2), with 16 (50%) developing multiple complications. For these rabbits, difficulty ambulating included balance disorder with falling to side of amputated leg and slipping (n = 2), problems supporting weight on 3 legs due to obesity (1), and exacerbation of concurrent disease (7), including osteoarthritis (2), carpal valgus on side of amputated pelvic limb (1), healed limb fracture (1), undiagnosed paresis of remaining pelvic limb (2), and severe spondylosis (1). Hygiene issues included difficulty grooming the perineum (n = 8); difficulty grooming the face, ear, and eye on the side of the amputated leg (4); urine scald (3); and requiring a lower-sided litter box (1). Cutaneous ulcerations (pododermatitis lesions) occurred at the hock (n = 6). One rabbit developed an abscessed surgical site 2 months after surgery. A single rabbit was determined to have chronic signs of pain, attributed to exacerbation of osteoarthritis.

Morbidity observed at 1 month or later after surgery resolved in 3 of 19 (16%) rabbits: 2 developed pododermatitis 2 and 3 months after surgery, and 1 developed an abscess at the amputation site 2 months after surgery. Difficulties in ambulation did not resolve in any of the affected rabbits and contributed to the euthanasia of 3 at 79, 97, and 399 days after amputation. Pododermatitis contributed to the euthanasia of 3 rabbits due to persistent or recurrent lesions at 97, 110, and 199 days after surgery. Hygiene issues did not resolve in any rabbits affected ≥ 1 month after surgery. Inability to groom the perineum resulted in urine scald and contributed to the euthanasia of 1 rabbit 97 days after surgery. One rabbit with chronic difficulty ambulating, pododermatitis, and inability to groom resulting in urine scald was found dead 218 days after amputation. The cause of death was not determined.

Considering thoracic versus pelvic limb amputation and observed morbidity, 1 of 6 (17%) rabbits undergoing thoracic limb amputation and 9 of 28 (32%) rabbits undergoing pelvic limb amputation had difficulty ambulating that was persistent or resulted in euthanasia. Two thoracic limb amputees had difficulty grooming (the perineum [n = 1] and the ipsilateral eye and side of face [1]) and 7 pelvic limb amputees had difficulty grooming (the perineum [n = 6], the ipsilateral ear [2], and the need for a low-sided litterbox [1]). After amputation of a thoracic limb, 2 rabbits developed delayed pododermatitis. This condition resolved in both rabbits. After amputation of a pelvic limb, acute and chronic pododermatitis were observed in 5 and 4 rabbits, respectively, and contributed to the euthanasia of 4 rabbits. Six of 28 (21%) rabbits that underwent pelvic limb amputation developed morbidity resulting in euthanasia versus none of rabbits undergoing thoracic limb amputation; however, this difference was not significant (P = 0.42). There was also no significant (P = 0.77) difference in survival time based on limb amputated.

Overall, 6 of 34 (18%) rabbits were euthanized as a consequence of morbidity at a median of 104 days (range, 4 to 399 days) after surgery. On the basis of the multivariable model that included the risk factors concurrent disease affecting ambulation and weight, after adjusting for weight, the odds of euthanasia due to morbidity were significantly (P = 0.03) greater in rabbits with concurrent disease affecting ambulation at the time of amputation than unaffected rabbits (OR, 26.5; 95% CI, 1.5 to 472). In addition, after adjusting for having a concurrent disease that affected ambulation, the odds of euthanasia due to morbidity significantly (P = 0.04) increased with increasing body weight (OR, 4.2; 95% CI, 1.1 to 16.8) such that the predicted percentage of rabbits with concurrent disease euthanized for morbidity was 4%, 15%, 43%, and 77% for rabbits weighing 1, 2, 3, and 4 kg (2.2, 4.4, 6.6, and 8.8 lb), respectively. For rabbits without concurrent disease, the predicted percentage of affected rabbits was 1%, 3%, 13%, and 39% for rabbits weighing 1, 2, 3, and 4 kg (2.2, 4.4, 6.6, and 8.8 lb), respectively. Other variables examined were not significantly associated with risk of developing morbidity resulting in euthanasia in univariable analysis (Table 3).

Table 3—

Results of simple logistic regression of risk factors for development of morbidity resulting in euthanasia in rabbits (n = 34) undergoing limb amputation.

FactorOR (95% CI)P value
Age1.25 (0.91–1.71)0.16
Weight3.42 (1.13–10.39)0.03
Body condition score5.84 (0.73–46.55)0.10
Limb amputated (thoracic vs pelvic)0.27 (0.01–6.74)0.42
Concurrent disease altering ambulation6.0 (0.88–40.87)0.07
at the time of amputation
Pododermatitis at the time of amputation 6.5 (0.7–60.14)

Significance set at P < 0.05.

At the time of last follow-up, 18 (53%) rabbits were dead, 9 (26%) were alive at a median of 1,379 days (range, 622 to 3,250 days), and 7 (21%) were lost to follow-up at a median of 376 days (range, 26 to 2,521 days). The median overall survival time for the rabbits in this study was 720 days (range, 4 to 3,250 days). Estimated 1- and 2-year survival rates were 62% and 42%, respectively. Of the 18 rabbits that were dead, 7 (39%) were euthanized for causes related to the amputation, including the 6 euthanized because of morbidity and 1 euthanized for recurrence of fibrosarcoma at the amputation site. Seven (39%) rabbits were euthanized for problems unrelated to amputation, including neoplasia (n = 3; metastatic nasal carcinoma, undiagnosed abdominal mass with effusion, and undiagnosed intrathoracic mass), degenerative bone disease leading to fracture of another limb (1), Actinomyces spp abscesses (1), confirmed Encephalitozoon cuniculi infection (1), and poor quality of life due to advanced age, spondylosis, loss of muscle mass, and a mammary mass (1). Three (17%) rabbits were found dead, and 1 (6%) collapsed and died of an unknown cause.

Univariable analysis demonstrated significant associations of age, weight, concurrent disease affecting ambulation at time of amputation, and concurrent pododermatitis at the time of amputation with risk of death (Table 4). In multivariable analysis, pododermatitis at the time of amputation (P = 0.006), weight (P = 0.02), and age (P = 0.002) remained significant risk factors. Hazard ratios for these risk factors were 31.2 (95% CI, 2.6 to 369), 2.2 (95% CI, 1.1 to 4.3), and 1.5 (95% CI, 1.2 to 1.8), respectively. Median survival times for rabbits with and without pododermatitis at the time of amputation were 93 days (range, 4 to 110 days) and 971 days (range, 46 to 3,250 days), respectively. The median survival time of rabbits weighing < 3 kg was 1,020 days (range, 4 to 3,250 days) and 126 days (range, 79 to 617 days) for rabbits > 3 kg. Median survival time was not reached in rabbits < 7 years of age, with a median follow-up time of 622 days (range, 4 to 3,250 days), and was 360 days (range, 97 to 1,020 days) for rabbits ≥ 7 years of age.

Table 4—

Results of univariable analysis of risk factors for death in rabbits (n = 34) undergoing limb amputation.

FactorHazard ratio (95% CI)P value
Age1.34 (1.14–1.58)< 0.001
Weight2.92 (1.73–4.93)< 0.001
Body condition score0.79 (0.34–1.87)0.59
Limb amputated (thoracic vs pelvic)0.83 (0.24–2.89)0.77
Concurrent condition altering ambulation at the time of amputation4.65 (1.56–13.83)0.006
Pododermatitis at the time of amputation24.34 (3.88–152.52)0.001

Risk factors were analyzed with Cox proportional hazards regression. Significance set at P < 0.05.

Thirty-one (91%) owners reported that they were satisfied with the outcome of amputation. Three (9%) owners were not satisfied. Their pet rabbits lived 4, 93, and 97 days after surgery. All 3 had concurrent conditions that contributed to poor recovery and euthanasia, specifically tetraparesis suspected to be due to presumptive myopathy, Actinomyces spp abscesses, and obesity.

Discussion

The objective of this study was to describe the outcome of domestic rabbits undergoing limb amputation. Of the 34 patients studied, 85% (29 rabbits) had acute or chronic postoperative morbidity. For most rabbits, recovery from immediate postoperative complications occurred during the week after amputation; however, chronic or delayed morbidity was observed in 19 (59%), most commonly difficulties in ambulating and grooming. In general, rabbits had long survival times after amputation (median, 720 days; range, 4 to 3,250 days); however, difficulty ambulating, pododermatitis, and amputation site abscesses resulted in euthanasia of 6 (18%) rabbits. Odds of life-threatening morbidity were greater for heavier rabbits and those with concurrent disease processes affecting ambulation at the time of amputation. Age, body weight, and pododermatitis at the time of amputation were associated with increased risk of death, further demonstrating the importance of case selection and management of concurrent medical problems.

The motivation for this study was the paucity of information describing outcome information limb amputation for rabbits. A search of the literature identified only limited studies3–7 involving laboratory rabbits and a single case report2 of a domestic rabbit with osteosarcoma that did not survive amputation. Only 2 studies5,7 provided outcome information. One report5 described 5 New Zealand White rabbits undergoing left thoracic limb amputation to create a model for end-neuroma formation. All rabbits were able to ambulate without difficulty, maintained their body weight, and did not develop stress-associated behaviors for 6 weeks following glenohumeral disarticulation.5 In another study,7 12 rabbits underwent transtibial amputation for investigation of circulation and bone healing at the amputation site and were euthanized at various intervals up to 12 weeks in duration. Reportedly, all rabbits withstood the operation quite well and after it, moved about freely in their cages. Although the investigators reported that none of the rabbits stood on the stump at rest or when walking, some developed infection or ulceration of the amputation site. In contrast with previous reports, the present study provides long-term follow-up of domestic rabbits undergoing limb amputation.

Anecdotal reports vary on whether the unique limb conformation and hopping gait of rabbits limit their ability to ambulate on 3 limbs and whether greater difficulty is associated with loss of a thoracic or pelvic limb. This study found that difficulty balancing on 3 limbs and slipping was common in the immediate postoperative period but resolved quickly or was mild in most rabbits. Persistent clinical gait abnormalities were primarily observed in rabbits with concurrent medical issues affecting movement (degenerative joint disease, undiagnosed paresis, pododermatitis, and obesity) or occurred later in rabbits that developed orthopedic or neurologic issues (spondylosis, fracture of another leg, degenerative joint disease, undiagnosed paresis, and carpal valgus). Difficulty ambulating contributed to the decision to euthanize 4 (12%) of the rabbits in this study. In addition, having a concurrent condition present at the time of amputation that affected ambulation was estimated to result in a 27-fold increase in odds of life-threatening morbidity. Consequently, it is clear that rabbits must be evaluated prior to amputation with thorough orthopedic and neurologic examinations. If musculoskeletal or neurologic abnormalities are identified, suitability of the rabbit for amputation should be considered and owners should be warned that amputation can exacerbate existing orthopedic or neurologic conditions.

Heavier body weight was associated with greater odds of life-threatening morbidity and poorer outcome, and the 1 obese rabbit in the study was euthanized 3 months after amputation because it could not support its body weight. The ORs calculated in this study predicted that 77% of 4-kg and 43% of 3-kg rabbits with concurrent disease and 39% of 4-kg and 13% of 3-kg rabbits without concurrent disease would develop life-threatening morbidity after amputation. Because this study included only 2 rabbits that weighed ≥ 4 kg and 7 that weighed ≥ 3 kg, it is possible that type I error resulted in overestimation of risk based on weight. However, on the basis of this preliminary information, body weight is a factor to be considered in case selection and merits investigation in further studies.

Ulcerative pododermatitis (referred to as sore hock) was a serious complication observed in this study. This is a common condition in rabbits.8 Trauma or pressure necrosis of the plantar surface of the metatarsus and, occasionally, the volar metacarpal area, results in ulceration and secondary infection. Housing on wire floors, obesity, poor sanitation, and breed predisposition increase the risk of this condition.8 The additional pressure on the remaining limbs of an amputee rabbit could increase risk of developing this condition or, if already present, exacerbate it. Pododermatitis resolved in only 1 of 3 rabbits affected at the time of amputation and developed in 5 additional rabbits. Ulceration and secondary infection contributed to the decision to euthanize 4 (12%) rabbits. This demonstrates the importance of taking measures to prevent pododermatitis, including maintaining amputee rabbits at healthy body weights and housing them on clean, soft bedding. If an amputee rabbit develops pododermatitis, early aggressive treatment is warranted. From a case selection standpoint, the presence of pododermatitis at the time of amputation negatively impacted survival rate, so amputation should be considered carefully in these cases and existing pododermatitis should be treated. If the rabbit's condition allows, delay of amputation might be appropriate for some rabbits with pododermatitis.

Immediate postoperative gastrointestinal abnormalities were common in our population of rabbits. Rabbits are particularly prone to ileus following stressors such as anesthesia and surgery.9 Gastrointestinal issues resolved in 1 to 2 days in all but 1 rabbit that had ileus for 4 days. Treatment with prokinetic drugs, fluid therapy, and soluble nutritional fiber is indicated for rabbits developing gastrointestinal signs.9

An unanticipated adverse effect of amputation identified in this study was difficulty grooming, reported in 9 cases (26%). Given that this is not a typical complication in dogs or cats, veterinarians and owners were not specifically asked about grooming, so this study likely underestimated its incidence. Rabbits had difficulties grooming the perineal region, which sometimes resulted in urine scald. In addition, difficulty grooming the eye and ear ipsilateral to the amputation resulted in chronic ocular discharge and wax accumulation in the ear canal in some rabbits. Owners reported that unless groomed by companion rabbits, these rabbits required routine ocular and aural cleaning by their owners. Difficulties grooming did not resolve but were tolerable for most rabbits and their owners. For 1 rabbit with multiple morbidities post amputation, however, consequent urine scald contributed to the owner's decision to euthanize.

Another unanticipated finding was the sudden death of 4 rabbits. This might be explained by underlying disease going undetected because rabbits did not manifest clinical signs. Another explanation might be that amputee rabbits were at increased risk of sudden death due to an unknown cause. Necropsy was performed in only 1 of these rabbits, and no cause of death was identified; therefore, we are unable to draw any conclusions about sudden death in amputee rabbits.

Whether a thoracic or pelvic limb was amputated did not affect survival rate or development of morbidity leading to euthanasia. However, only 6 rabbits underwent thoracic limb amputation, so this study had low power to detect a difference. Pododermatitis resolved in the 2 affected rabbits with amputated thoracic limbs, but resulted in the euthanasia of 4 rabbits with amputated pelvic limbs. It may be more difficult for rabbits with a single pelvic limb to heal lesions owing to less ability to transfer weight off of the affected pelvic limb. Additional investigation is required to elucidate differences in outcome on the basis of which limb is amputated in rabbits.

Most rabbits in this study underwent partial limb amputations. Currently, veterinary surgeons discourage partial limb amputation (with the exception of digit amputation) in small animals.1 The indication for partial limb amputation would be use of a prosthesis, which at this time is not widely available or generally beneficial to veterinary patients. The present study did not evaluate the effect of degree of amputation owing to the small number of cases treated with full limb amputation. It is possible that partial limb amputation resulted in unintended negative effects in some rabbits because more weight is left to carry, posture and gait are different, and pressure sores can occur at the amputation site.1

Because this study was retrospective, it was limited to the observations in medical records and the recollection of veterinarians and owners. Medical records may be incomplete, and veterinarian and owner recollections may be incomplete or biased. Lack of a uniform recheck schedule and loss of patients to follow-up contributed to incomplete follow-up information. Cases were heterogenous, with multiple variables contributing to outcome, and the small numbers of cases limited statistical analysis of prognostic variables. For example, type II error might explain why pododermatitis was significantly associated with risk of death but not with life-threatening morbidity and why concurrent disease affecting ambulation was associated with development of morbidity resulting in euthanasia but not risk of death. With additional cases and increased power to detect differences, more variables could be evaluated and other variables might be associated with outcome. Finally, since most rabbits died of unrelated causes, death probabilities likely underestimate survival rate after limb amputation. Despite these limitations, this study has value in providing preliminary information and generating questions for future studies.

In conclusion, whereas results of this study suggested that domestic rabbits can tolerate limb amputation well and most owners were satisfied, some rabbits developed life-threatening morbidity. Amputation in obese or large rabbits and those with concurrent musculoskeletal disease, neurologic disease, or pododermatitis should be considered carefully. Because of the small sample size, heterogenous population, and retrospective nature of the present study, P values and 95% CIs should be interpreted with caution, and results should be interpreted as exploratory and hypothesis generating.

ABBREVIATION

CI

Confidence interval

a.

SAS, version 9.41, SAS Institute Inc, Cary, NC.

References

  • 1. Séguin B, Weigel JP. Amputations. In: Tobias KM, Johnston SA, eds. Veterinary surgery: small animal. St Louis: Saunders, 2012;10291036.

    • Search Google Scholar
    • Export Citation
  • 2. Kondo H, Ishikawa M, Maeda H, et al. Spontaneous osteosarcoma in a rabbit (Oryctoloagus cuniculus). Vet Pathol 2007; 44:691694.

  • 3. Wang Q, Zhang J, Chen T, et al. DNA degradation in nuclei of muscle cells followed by ischemic injury in a rabbit amputation model. Microsurgery 2006; 26:391395.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Frogameni AD, Booth R, Mumaw LA, et al. Comparison of soft dressing and rigid dressing in the healing of amputated limbs of rabbits. Am J Phys Med Rehabil 1989; 68:234239.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Kim PS, Ko J, O'Shaughnessy KK, et al. Novel model for end-neuroma formation in the amputated rabbit forelimb. J Brachial Plex Peripher Nerve Inj 2010; 5:6. Available at: www.jbppni.com/content/5/1/6. Accessed Dec 27, 2013.

    • Search Google Scholar
    • Export Citation
  • 6. Shang J, Zhang XY, Bi ZG. Experimental study on the extent of injured blood vessels in an avulsion amputation model. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2000; 14:135138.

    • Search Google Scholar
    • Export Citation
  • 7. Hulth A & Olerud S. Studies on amputation stumps in rabbits. J Bone Joint Surg Br 1962; 44:431435.

  • 8. Gentz EJ, Carpenter JW. Neurologic and musculoskeletal disease. In: Hillyer EV, Quesenberry KE, eds. Ferrets, rabbits, and rodents. Philadelphia: WB Saunders Co, 1997;224225.

    • Search Google Scholar
    • Export Citation
  • 9. Jenkins JR. Gastrointestinal diseases. In: Quesenberry KE, Carpenter JW, eds. Ferrets, rabbits, and rodents. 2nd ed. Philadelphia: WB Saunders Co, 2004;163164.

    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Flow diagram illustrating morbidity and outcome for 34 client-owned domestic rabbits undergoing limb amputation between 2000 and 2009. Alive = Rabbit was alive at last follow-up. Dead A = Rabbit was dead with death confirmed to be related to amputation. Dead T = Rabbit was dead because of tumor recurrence at amputation site. Dead O = Rabbit was dead with death confirmed to be unrelated to the amputation (ie, other cause). Dead U = Rabbit was dead because of unknown cause. Lost = Rabbit was lost to follow-up.

  • 1. Séguin B, Weigel JP. Amputations. In: Tobias KM, Johnston SA, eds. Veterinary surgery: small animal. St Louis: Saunders, 2012;10291036.

    • Search Google Scholar
    • Export Citation
  • 2. Kondo H, Ishikawa M, Maeda H, et al. Spontaneous osteosarcoma in a rabbit (Oryctoloagus cuniculus). Vet Pathol 2007; 44:691694.

  • 3. Wang Q, Zhang J, Chen T, et al. DNA degradation in nuclei of muscle cells followed by ischemic injury in a rabbit amputation model. Microsurgery 2006; 26:391395.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Frogameni AD, Booth R, Mumaw LA, et al. Comparison of soft dressing and rigid dressing in the healing of amputated limbs of rabbits. Am J Phys Med Rehabil 1989; 68:234239.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Kim PS, Ko J, O'Shaughnessy KK, et al. Novel model for end-neuroma formation in the amputated rabbit forelimb. J Brachial Plex Peripher Nerve Inj 2010; 5:6. Available at: www.jbppni.com/content/5/1/6. Accessed Dec 27, 2013.

    • Search Google Scholar
    • Export Citation
  • 6. Shang J, Zhang XY, Bi ZG. Experimental study on the extent of injured blood vessels in an avulsion amputation model. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2000; 14:135138.

    • Search Google Scholar
    • Export Citation
  • 7. Hulth A & Olerud S. Studies on amputation stumps in rabbits. J Bone Joint Surg Br 1962; 44:431435.

  • 8. Gentz EJ, Carpenter JW. Neurologic and musculoskeletal disease. In: Hillyer EV, Quesenberry KE, eds. Ferrets, rabbits, and rodents. Philadelphia: WB Saunders Co, 1997;224225.

    • Search Google Scholar
    • Export Citation
  • 9. Jenkins JR. Gastrointestinal diseases. In: Quesenberry KE, Carpenter JW, eds. Ferrets, rabbits, and rodents. 2nd ed. Philadelphia: WB Saunders Co, 2004;163164.

    • Search Google Scholar
    • Export Citation

Advertisement