Signalment

Age: 6 months (approximately)

Weight: 6 kg

Breed: Mixed

Sex: Male/Entire

Clinical signs

On presentation, Nong was responsive but slightly depressed with suspected mild dehydration. However, mucous membranes were pale pink and moist. Temperature was 37.8°C (100.04°F).

Nong’s right hind limb was severely injured, and removing the bandage revealed a large degloving injury. The tibial bone was partially visible on the lateral side. The wound had obviously been there for some time and was infected. A deep opening on the lateral aspect revealed a maggot infestation (myiasis). Whilst some granulation tissue had started to form, some necrotic tissue was also present, especially where the maggot infestation had taken hold. The foot pads and nails were completely missing. He was, of course, non-weight bearing on this leg, which was extremely painful and deformed.

A second wound was noted on his tail, likely from self-trauma; he had been biting the area due to the pain in his leg. This wound had started to heal, and granulation tissue was present. He was no longer biting this area but was licking it.

It is always important to fully assess the whole patient in the first instance, as it is easy to be distracted by the most obvious wound (in this case the hind limb) and miss another critical issue. In Nong’s case, fortunately no other abnormalities or injuries were detected, and assessment of the major body systems indicated he was otherwise considered stable.

Initial treatment

The next step was to fully assess, clean and debride the wound so that a decision could be made about how to treat the injury. Nong underwent a short anaesthesia, using Zoletil (tiletamine and zolazepam) and xylazine. Multimodal analgesia was provided in the form of tramadol and carprofen. He was placed on IV fluids (Acetated Ringer’s solution) to correct a mild hydration deficit.

The maggots were removed from the wound, followed by necrotic tissue debridement. The wound was then flushed with saline. Silver sulfadiazine cream (Flamazine) was applied to the surface, for topical antibacterial and antifungal action. The wound was dressed to protect the area and prevent contamination. He also received his next dose of amoxycillin clavulanic acid via subcutaneous injection.

The wound on his tail was examined: it was clean with a good bed of granulation tissue and could be left to heal by second intention. An Elizabethan collar was used to prevent further licking of the area.

Diagnostic tests

After initial treatment and assessment, a blood test was performed to evaluate whether Nong was experiencing systemic effects of the infection, or other systemic disease which could impact on surgical treatment.

Haematology results showed a moderate anaemia:

• reduced total red blood cells
• moderately low haematocrit (24%)
• reduced haemoglobin

Lymphocytosis was also noted. Platelets were normal and in adequate number, and no blood parasites were found.

Nong’s anaemia was the primary concern, and he was not well enough to undergo surgery yet. Any operation carries a risk of blood loss, so concurrent anaemia would have increased surgical risk. It is important that blood has an adequate oxygen-carrying capacity for a longer period of anaesthesia to be safe. It is also a factor in recovery and healing. His anaemia was likely due to previous haemorrhage at the time of trauma, and a prolonged period of inflammation/infection. The increase in lymphocytes could be physiological (age/stress), and/or relate to the prolonged period of inflammation and infection.

Further treatment

Stabilisation

Nong needed time for his anaemia to improve/ resolve, before he could undergo surgery safely. Therefore, a delayed approach was taken, and any further surgical treatment was postponed for a week.

He received ongoing medication:

Short term fluid therapy: IV fluid therapy had been started during initial assessment and was continued for several hours after the procedure. By then, he was eating and drinking well and was able to maintain oral hydration, so the drip was discontinued.

Antibiotic: amoxycillin clavulanic acid was continued orally.

Non-steroidal anti-inflammatory pain relief: carprofen continued orally.

Dressing changes were performed regularly over the course of a week, during which the wound was cleaned. Due to his temperament, sedation (Zoletil and xylazine) was required as well as ongoing pain relief.

Nong responded well to treatment, he gained weight, improved in demeanour, and the infection cleared well from the wound. Due to the severity of the trauma and the tissue deficit remaining, amputation was selected as the treatment most likely to have a successful outcome and a quick recovery.

Amputation

Amputation of the hind limb was performed seven days after initial presentation. Castration was performed at the same time for population control, and to avoid a repeat surgery. A mid-femoral method was chosen for amputation (see Discussion).

After the procedure, a pressure bandage was applied in the first 24 hours to prevent swelling, e.g. haematoma. Nong continued oral amoxycillin clavulanic acid and carprofen, with the addition of tramadol (BID, SC) for the first three days. He was monitored closely to ensure pain was well-controlled. He was initially kept on strict cage rest and an Elizabeth collar was used to prevent wound interference.

Prognosis and case outcome

The prognosis for hind limb amputation is generally very good, providing the patient has no other severe orthopaedic or neurological disease affecting the remaining limbs, and recovery is not complicated by co-morbidities (see Discussion). Most dogs adapt to a good level of mobility within a month, with some ambulating within a week after the procedure (1, 2). Quality of life after the operation is also generally excellent, and there is evidence that the majority of dogs have the same demeanour and activity after the surgery, as they did before amputation (3). In cases of amputation due to aggressive neoplasia, prognosis is influenced more by risk of metastasis; median survival time for dogs with osteosarcoma, who are treated by amputation alone, is 3-4 months (4).

In Nong’s case, he recovered very well from the procedure. His body condition continued to improve. He weighed 7.35kg at his post-op check, an increase of 1.35kg compared to his arrival at the clinic. His tail wound also healed well.

Five days after the amputation a mild lameness was noted on his left fore limb, with mild swelling in his paw, and some pain on palpation. It was important to investigate, because amputation increases the loading on other limbs, and could exacerbate any other pathology in the musculoskeletal system. An x-ray was taken, but nothing abnormal was detected. The lameness resolved within a couple of days and did not recur.

Ten days after his amputation, Nong was ambulating easily and was signed-off ready for rehoming.

Discussion

Hind limb amputations are typically performed in cases where there is an inoperable neoplasia, or the limb has been severely traumatised beyond repair; in the free-roaming population this often associated with traumatic events such as a road traffic accident. Other reasons are included below.

Common reasons for limb amputation
Unresectable neoplasia
Severe fracture
Severe infections e.g. osteomyelitis, soft tissue infection
Vascular compromise e.g. ischaemic necrosis
Unmanageable osteoarthritis
Congenital deformity
Neurological issues e.g. peripheral neuropathies, paralysis

Amputation is often considered a treatment of choice, especially in resource-limited environments, because it is:

• generally safe
• carries a good prognosis
• facilitates a quick recovery
• is usually cost effective compared to other options.

Is the patient a suitable candidate for limb amputation?

Although amputation can be a very effective treatment, not all animals are suitable for this procedure. The patient’s health status and condition before the operation will impact on their ability to adapt and recover post-operatively. There are various factors to consider in each case.

Condition of the remaining limbs

In healthy, four-limbed dogs, weight is distributed 60% on the thoracic limbs (30% per limb), and 40% on the pelvic limbs (20% per limb) (5, 6). After hind limb amputation, the weight previously carried by the amputated limb must be redistributed. There is evidence that after the operation, dogs will bear around 73% of the weight on the thoracic limbs, and 26% on the remaining pelvic limb (5, 6).  Amputation of a limb is therefore contraindicated if there is severe orthopaedic or neurological disease in any of the remaining limbs, as they are unlikely to cope with the extra loading required.

A recent study suggested that the greatest increase in weight bearing after hind limb amputation is seen on the contralateral fore limb (7). Other work has demonstrated that diagonally contralateral limbs are important in four-limbed dogs, to counter rotational forces which occur during motions such as trotting (8). While any form of disease in the limbs should be a factor in considering amputation, it may be considered especially important if it occurs in the contralateral fore limb. It was interesting in Nong’s case, that lameness occurred post-operatively in the left fore limb. It’s possible that the increased weight-bearing after amputation led to increased stress on this limb, presenting as a transient, soft tissue injury. Fortunately, in Nong’s case this was short-term, and resolved quickly as he adapted to motion with three legs.

The altered pattern of weight bearing also affects other parts of the musculoskeletal system, affecting changes to centre of gravity and gait pattern (9, 6). To maintain balance, amputees have been noted to laterally bend the vertebral column, and place the remaining pelvic limb more centrally, as well as making other adaptations to movement including increased flexion/extension of the neck (5). There is also an increased burden on the muscles of the remaining limbs, which appear to undergo increased levels of activity after amputation (10).

Dogs are generally very resilient, and adapt quickly and functionally to the new movement pattern, but it is worth remembering that these changes in kinematics could exacerbate pre-existing areas of pain or weakness. There is currently no specific evidence on the degree of pre-existing lameness which would preclude amputation, so the decision should be based on the individual animal, including other factors below.

Body weight

Larger breed dogs (even those with a healthy body condition) have historically been considered as less suitable candidates for the procedure. It is difficult to evaluate whether this is true, as there is little, high-quality, published research on the issue. Most studies are unable to adequately separate size of dog (i.e. breed size) from their body condition (i.e. obesity) in analysis of the results. It is therefore challenging to independently evaluate the impact of dog size on prognosis. There is some evidence that providing the dog is otherwise healthy, larger breed dogs can cope well with amputation: Kirpenstein et al reported no significant association between weight of animal and how quickly they adapted post-operatively (1,6). On balance, there is probably not enough evidence to confidently answer whether larger breed dogs cope better or worse with amputation, but providing there are no other concerns with the patient, larger breed dogs need not be excluded from the procedure due to size alone.

There is clear evidence that amputation increases weight-bearing on the remaining limbs, and affects other areas of the body such as the spine, so it is unsurprising that very obese patients are generally considered to be undesirable candidates for amputation. An increase in body weight and Body Condition Score (BCS) has been shown to negatively influence quality of life after amputation (3). This is usually more relevant to owned pets, and is less likely to be a concern in free-roaming dogs, who generally have a lower BCS. It is not usually practical to implement a weight-loss programme prior to amputation, due to the urgency of the procedure. Therefore, alternatives to amputation should be considered in very obese patients, or a weight loss programme should be initiated once the patient has recovered and it is safe to do so.

Surgical considerations

General health status: patients should be well enough to undergo the operation, without significant comorbidities. The procedure carries a high risk of large fluid loss (including blood loss) (4). Dogs must be well-hydrated pre-operatively, and supported on IV fluids during the procedure if possible. It is sensible to consider the use of broad spectrum antibiotics before, during and after the procedure due to the risk of infection, particularly orthopaedic infection (4). Appropriate aseptic surgical technique should, of course, also be used.

Amputation level: amputation may be performed at various levels of the limb or pelvis. Deciding how much to remove will be influenced by location of the lesion, and the nature of the pathology. If amputating to remove neoplasia, wide margins are required. For instance, a tumour in the femur would require the entire bone to be removed through disarticulation of the coxofemoral joint (4). In some cases, amputation may need to extend to the pelvis and include hemipelvectomy.

In a trauma case like Nong, the decision is based on the extent of the injury. The damaged tissue must be removed completely, and the remaining tissue must be healthy, to ensure adequate healing. It was decided that a mid-femoral approach would be suitable in this case. This approach cuts the femur and associated tissues but leaves the proximal portion of the femur, the coxofemoral joint and pelvis intact.

This approach has the advantage of being less invasive than disarticulation, acetabulectomy or hemipelvectomy. Fewer blood vessels, nerves and muscles are transected and the tissues are generally easier to access. However, it does require an orthopaedic saw to cut the femur. If this equipment is not available, a coxofemoral disarticulation would have been considered as an alternative in this case.

Risks of the procedure

Amputation is a relatively low risk procedure, with a good prognosis, however there is little evidence evaluating the long-term effects over the course of the patient’s life. As discussed above, there may be risks to the musculoskeletal system due to increased load and a change in movement pattern.

Some behavioural changes have been reported post-operatively. These were reported in a minority of patients and there is currently not enough evidence to prove these definitively relate to the procedure, as pre-amputation pain and comorbidities are likely complicating factors. These include an increase in fear and anxiety and reduction in interacting with humans and other animals (1,2).

Various studies have reported a post-operative complication rate ranging between 12.5% to 20.9% (11, 3, 2, 12). The most common post-operative complications included infection and seroma, but these generally resolved with treatment. There is evidence that patients may be more likely to develop a surgical site infection if the reason for amputation is infection or traumatic injury (as opposed to neoplasia), and unsurprisingly, the rate is higher if the wound is not classified as clean (11). Although the risk of infection is slightly higher for amputation than other clean surgical procedures (11,12), the risks are generally easy to manage with effective pre- and post-operative care. For instance, a delayed approach in this case reduced the contamination and infection pre-operatively, and continued antibiotic therapy post-operatively ensured no infection occurred. Effective bandaging and a managed return to exercise also reduced the chance of a haematoma or seroma developing.

Key points

• Hind limb amputation generally carries a very good prognosis, with a quick recovery.
• Amputation can be a cost-effective, relatively low risk treatment option for severe limb disease.
• Good candidates for the procedure are systemically well, without other concurrent musculoskeletal disease, and with a healthy body condition.
• Surgical considerations include effective management of infection risk, and appropriate selection of amputation level.

References

1. Kirpensteijn J, van den Bos R, Endenburg N. Adaptation of dogs to the amputation of a limb and their owners' satisfaction with the procedure. Vet Rec. 1999 Jan 30;144(5):115-8. doi: 10.1136/vr.144.5.115.
2. Menchetti M, Gandini G, Gallucci A, Della Rocca G, Matiasek L, Matiasek K, Gentilini F, Rosati M, Approaching phantom complex after limb amputation in the canine species, Journal of Veterinary Behavior, Volume 22, 2017, Pages 24-28, doi: 10.1016/j.jveb.2017.09.010.
3. Dickerson VM, Coleman KD, Ogawa M, Saba CF, Cornell KK, Radlinsky MG, Schmiedt CW. (2015) Outcomes of dogs undergoing limb amputation, owner satisfaction with limb amputation procedures, and owner perceptions regarding postsurgical adaptation: 64 cases (2005-2012). Journal of the American Veterinary Medical Association. Oct 1;247(7):786-92. doi: 10.2460/javma.247.7.786.
4. Fossum, T W, ed. (2013). Small Animal Surgery. 4th ed. St. Louis, Elsevier Mosby.
5. Hogy SM, Worley DR, Jarvis SL, Hill AE, Reiser RF 2nd, Haussler KK. Kinematic and kinetic analysis of dogs during trotting after amputation of a pelvic limb. Am J Vet Res. 2013 Sep;74(9):1164-71. doi: 10.2460/ajvr.74.9.1164.
6. Kirpensteijn J, van den Bos R, van den Brom WE, Hazewinkel HA. Ground reaction force analysis of large breed dogs when walking after the amputation of a limb. Vet Rec. 2000 Feb 5;146(6):155-9. doi: 10.1136/vr.146.6.155.
7. Cole GL, Millis D. The effect of limb amputation on standing weight distribution in the remaining three limbs in dogs. Vet Comp Orthop Traumatol. 2017 Jan 16;30(1):59-61. doi: 10.3415/VCOT-16-05-0075. Epub 2016 Dec 15.
8. Lee DV, Bertram JE, Todhunter RJ. Acceleration and balance in trotting dogs. J Exp Biol. 1999 Dec;202(Pt 24):3565-73. doi: 10.1242/jeb.202.24.3565.
9. Goldner B, Fuchs A, Nolte I, Schilling N. Kinematic adaptations to tripedal locomotion in dogs. Vet J. 2015 May;204(2):192-200. doi: 10.1016/j.tvjl.2015.03.003. Epub 2015 Mar 6.
10. Fuchs A, Anders A, Nolte I, Schilling N. Limb and back muscle activity adaptations to tripedal locomotion in dogs. J Exp Zool A Ecol Genet Physiol. 2015 Oct;323(8):506-15. doi: 10.1002/jez.1936. Epub 2015 Jul 22.
11. Billas AR, Grimes JA, Hollenbeck DL, Dickerson VM, Wallace ML, Schmiedt CW. Incidence of and risk factors for surgical site infection following canine limb amputation. Vet Surg. 2022 Apr;51(3):418-425. doi: 10.1111/vsu.13762. Epub 2022 Jan 10.
12. Raske M, McClaran JK, Mariano A. Short-term wound complications and predictive variables for complication after limb amputation in dogs and cats. J Small Anim Pract. 2015 Apr;56(4):247-52. doi: 10.1111/jsap.12330. Epub 2015 Feb 19.