Contributors: Kelly Bowlt, Peter Poll
Species: Feline | Classification: Techniques
- Amputation of non-functional or seriously diseased digit.
- Digital amputation may be required for:
- Severely comminuted fractures.
- Intra-articular fractures.
- Chronic sprains, or recurrent luxations.
- Severe soft tissue injuries, eg degloving injuries, severed tendons.
- Marked degenerative joint disease causing pain which is unresponsive to medical management.
- Neoplasia Digit: neoplasia.
- Chronic bacterial or fungal infection, eg osteomyelitis Osteomyelitis, onychomycosis, which is unresponsive to medical management.
- Developmental or acquired digital malformation causing pain or lameness.
- 45 min.
- 30 min.
Even where every effort is taken to achieve meticulous hemostasis, a moderate amount of hemorrhage can be expected.
Criteria for choosing test
- Orthogonal radiographs of the affected foot should be taken to assess the degree of bony involvement and to plan the level of amputation.
- If neoplasia suspected, perform right and left inflated thoracic radiographs Radiography: thorax to rule out metastasis. Thoroughly palpate all lymph nodes and take a fine needle aspiration (FNA Fine-needle aspirate) or biopsy of enlarged nodes to aid in tumor staging. Results from a biopsy of the primary lesion will allow planning for appropriate surgical margins of excision.
- The removed portion should be sent in its entirety for histopathology. Bacterial or fungal culture should also be considered.
- Low grade persistent lameness may occur after amputation of the 3rd and/or 4th digits, which are the main weight bearing digits. Lameness may also occur if more than two digits are amputated. Preservation of the digital pad if possible will preserve post-operative function.
- Bone cutters, fine tooth hacksaw or oscillating saw.
- Tourniquet (some adhesive dressing, eg Vetwrap/CoFlex will be ideal).
- Fine mosquito hemostats or ideally the provision of monopolar/bipolar diathermy.
- Pre-anesthetic preparation:
- Fast animal for 12 hours prior to anesthesia to prevent regurgitation and subsequent reflux esophagitis or aspiration pneumonia. Water should be freely available.
- Consider serum biochemistry and electrolytes:
- In geriatric patients, ie over 8 years.
- If systemic disease, eg renal or hepatic, is suspected.
- If neoplasia is suspected or confirmed (ensure total or ionized calcium is included).
- Consider complete blood count Hematology: complete blood count (CBC) if infection is suspected.
- Premedication: acepromazine Acepromazine maleate or diazepam Diazepam /midazolam Midazolam in combination with an opioid (ideally a full µ-agonist, eg morphine or methadone) 30 mins before induction.
- Induction: propofol Propofol, alfaxalone Alfaxolone / Alfadolone, or thiopentone Thiopental.
- Local anesthesia: lidocaine Lidocaine (without adrenaline) and bupivicaine Bupivacaine combination can be used to administer a ring block, splash block, nerve block (eg radial/medial/ulnar block, brachial plexus block) or intravenous anesthesia, ie Bier block.
- Consider lumbrosacral epidural administration of opioids Anesthesia: epidural.
- A non-steroidal anti-inflammatory drug, eg meloxicam Meloxicam or carprofen Carprofen, should be provided intraoperatively if appropriate.
- Perioperative antibiosis could be administered if necessary.
- Position the animal in lateral or ventral recumbency.
- Completely clip the affected limb distal to the mid-antebrachiium or mid-tibial region, including all the toes.
- Secure a towel clamp onto a healthy nail and use a tie from the towel clamp to a hook or drip stand in order to elevate the limb from the surgical table and patient's body.
- Once the area is grossly clean, scrub the whole clipped region (including between the digits and pads) vigorously for at least 5 mins with a suitable preparation, eg chlorhexidine Chlorhexidine. A final liberal application of surgical spirit completes the preparation.
Whilst genuinely sterile conditions are virtually impossible in this region, they should be aimed for.
- Quarter drape the limb and release the aseptically prepared paw into the sterile field. Apply a tourniquet to the limb starting from the nail tipcs and working proximally. Cut the tourniquet distally to expose the digits.
- General anesthesia General anesthesia: overview.
Step 1 - Incision
- Make an elliptical skin incision around the digit at the level of the amputation beginning proximodorsally and ending distally on the palmar/plantar surface. If the level of amputation is distal, attempt to preserve the digital pad.
Step 2 - Bone exposure
- Transect the soft tissue down to expose bone using combination of blunt and sharp dissection to remove the extensor and flexor tendons, ligaments and joint capsule.
- Clamp the digital arteries and veins (on the dorsal and ventral aspect of the digits) with mosquito hemostats and use diathermy or ligate with suitable absorbable suture material, eg poliglecaprone 25.
- Once the bone has been exposed, use blunt dissection to undermine the soft tissue proximally. By pushing this soft tissue proximally when the bone is cut, this will ensure that there is plenty of soft tissue available to achieve a tension-free closure.
Step 3 - Disarticulation
- Disarticulate the joint proximal to the lesion by sharp transection and remove the condyle proximal to the amputation with ronguers. Alternatively, transect through the middle of phalynx with an oscillating saw, hacksaw or bone cutters.
- When the transection is performed through the metocarpophalangeal joint, the palmar sesamoid bones should also be removed.
Step 4 - Close wound
- Check for and address any further hemorrhage.
- Appose subcutaneous tissues over the end of the bone using absorbable material (eg polydiaxanone). Placement of the subcutaneous sutures should close any dead space and ensure that there is no tension in the overlying skin.
- Close the skin with simple interrupted sutures, eg nylon.
- The foot should be dressed with an appropriate primary layer, eg Primapore or Melolin, and generous amounts of padding applied. Ensure that there is light padding between the toes and under any dew claws.
- Tight bandages may cause swelling or ischemic necrosis.
- The dressing should be kept clean and dry and the owner should be isntructed how to examine the bandage daily.
- The dressing should be changed or removed after 3 days.
- The skin sutures should be removed after 7-10 days.
- Non-steroidal anti-inflammatory medication should be continued for 5-7 days post-operatively.
- Post-operative antibiotic administration may or may not be necessary depending on the reason for amputation.
- Restrict exercise for 3 weeks until wound is completely healed.
- Wound dehiscence.
- Persistent lameness.
- Generally good.
- Guarded when neoplasia is involved.
- Always send affected digit to histopathology and/or bacterial/fungal culture.
Reasons for Treatment Failure
- Skin tension.
- Infection or poor control of hemorrhage.
- Bandage too tight.
- Development of metastases.
Other sources of information
- Scott H W, McLaughlin R (2007) Digit Amputation. In: Feline Orthopaedics, Manson Publishing Ltd, London. pp 156-157.
- Probst C W, Millis D L (2003) Digit Amputation. In: Textbook of Small Animal Surgery, 3rd edn, pp 1987. Ed Slatter D, Saunders, Philadelphia.
- Hedlund C S (2002) Digit Amputation. In: Small Animal Surgery, 2nd edn, pp 206-207. Eds Fossum T W, Hedlund C S,Hulse D A, Johnson AL, Seim H B, Willard M D, Carroll G L, Mosby Inc, Missouri.