Digit amputation in small ruminants

Editor’s Note: The case images presented within this article were collected by the author as part of her surgical training as a resident at Cornell University.

Digit amputation should be considered as a treatment option for small ruminants facing treatment-resistant, painful foot conditions.¹ Goats and sheep, especially those without routine hoof care, are prone to injury because of solar trauma; infection can originate from these sites and result in bone or joint infection.

Commonly, breach of the hoof capsule can lead to septic pedal osteitis. Similarly, distal interphalangeal or proximal interphalangeal joint sepsis (Figure 1) can result from extension of sole disease, penetrating trauma, or severe interdigital dermatitis (Figure 2). Patients with these conditions that do not respond to local and systemic antibiotics, debridement, and drainage are considered to have failed first-line treatment. Notably, they often have persistent lameness and chronic pain. These patients are good candidates for unilateral digit amputation. This surgical option is also an appropriate choice for small ruminants with a distal phalangeal fracture or distal interphalangeal joint luxation whose clinical signs do not improve with immobilization.

Perioperative considerations for digit amputation include the commencement of systemic antimicrobial therapy and a nonsteroidal anti-inflammatory drug. Following point-of-care blood work, including packed cell volume/total solids and creatinine to confirm kidney function, either flunixin meglumine 1.1 mg/kg intravenously every 24 hours or meloxicam 1 mg/kg oral loading dose once, followed by 0.5 mg/kg orally every 24 hours, is recommended. Appropriate antibiotic choices include those with broad-spectrum coverage; for example, 22,000 IU/kg of procaine penicillin G subcutaneously or intramuscularly every 12 hours in combination with ceftiofur sodium 2.2 mg/kg subcutaneously every 24 hours. All small ruminants, whether kept as pets, or sanctuary animals or for milk and meat, are considered minor species by the FDA.² Therefore, withdrawal intervals for extralabel drug use should be followed per the Food Animal Residue Avoidance Databank.

The procedure may be performed in the sedated, laterally recumbent animal using locoregional anesthesia, or using the author’s preference: general anesthesia supplemented with locoregional anesthesia. Nerve blocks of this region are easily performed via either a lidocaine ring block just proximal to the fetlock or a Bier block. The Bier block is performed by placing an Esmarch tourniquet distal to the carpus or tarsus and using a 21-G butterfly needle to (blindly) inject lidocaine into the dorsal common digital vein, which is located on the midline just proximal to the dorsal interdigital cleft.³ The author recommends leaving this tourniquet in place for the duration of surgery.

Amputation is frequently performed through the distal aspect of the first phalanx or through the distal second phalanx.^1,3 Disarticulation through the interphalangeal joints risks inadvertent retention of cartilage or synovium that can result in persistent drainage.¹ The procedure is simple and rapidly performed, resulting in a wide resection with effective drainage if necessary, or the site can be easily primarily closed if appropriate, and the patient can return rapidly to weight-bearing on the contralateral digit. Caretakers should be made aware that postoperatively, the digit requires bandaging, wound care, and careful monitoring for pain control and delayed resolution of infection, if present.

The amputation site is chosen based on the extent of disease in the digit. The interdigital skin and tissues are incised sharply using a surgical blade, beginning axially and extending on a 45-degree angle abaxially and dorsally.⁴ This is performed at the level of the distal first phalanx for amputation at that level, or for amputation through the second phalanx or proximal interphalangeal joint, approximately 1 cm proximal to the coronary band. This allows an obstetrical wire to be seated in the incision, and an ostectomy is performed in the same plane. Throughout, visible large arteries should be ligated with absorbable monofilament suture.⁴ Using this method, all affected tissue is removed, leaving only healthy tissue prone to rapid healing, and promoting excellent drainage if the wound is deemed most suitable to heal by second intention. If the treated condition does not require continued drainage, the skin may be partially or completely primarily closed with nonabsorbable monofilament suture with removal planned for approximately 10 days later (Figure 3).

Postoperatively, a well-sealed bandage should be applied while the tourniquet is still in place. It is important that the bandage is not overbulked to maintain ground clearance and prevent inadvertent weight-bearing on the stump. The initial bandage may be left in place for 2 to 3 days and changed thereafter as needed for wound care. A palmar/plantar splint may be indicated in some patients to encourage weight-bearing in the immediate postoperative period (5-7 days). Discontinuation of systemic antibiotic therapy and pain control is based on the patient’s clinical signs, including resolution of infection if present (swelling, drainage, necrotic tissue), appropriate wound healing, lameness, willingness to weight-bear and ambulate, and general demeanor and pain level (attitude, appetite, rumination).

Goats and sheep undergoing digit amputation generally have a fair prognosis for return to comfort and herd activities. Patients can be expected to recover from the procedure (ie, wound healed, weight-bearing, and off medications) by 4 to 12 weeks postoperatively, depending on the primary condition and whether the wound was closed at the time of surgery or left to heal by second intention. Generally, lighter sheep and goat breeds have a better prognosis for long-term survival, as they tolerate digit loss more favorably than their heavier counterparts. Accelerated osteoarthritis and/or soft tissue breakdown in the remaining digit or the contralateral limb should be discussed as potential complications with clients, especially for animals anticipated to reach geriatric age.

In conclusion, digit amputation is an appropriate surgical option for sheep and goats with painful foot conditions that do not respond to first-line therapies. The procedure is safely, quickly, and easily performed, and perioperative care is routine. Patients can be expected to make a full recovery without major impact on their mobility, though long-term complications resulting in pain and disability in the contralateral limb may impair comfort and longevity. Digit amputation can be considered a life-sparing procedure for small ruminants and should be considered as a humane alternative to euthanasia.¹

References

1. Crilly JP, Reilly B, Scott P. Digit amputation in small ruminants. Livestock. 2022;27(2):90-94. doi:10.12968/live.2022.27.2.90
2. Martin KL, Clapham MO, Davis JL, et al. Extralabel drug use in small ruminants. J Am Vet Med Assoc. 2018;253(8):1001-1009. doi:10.2460/javma.253.8.1001
3. Anderson DE, Miesner MD. Surgical management of orthopedic and musculoskeletal diseases of feedlot calves. Vet Clin North Am Food Anim Pract. 2015;31(3):425-vii. doi:10.1016/j.cvfa.2015.05.012
4. Heppelmann M, Kofler J, Meyer H, Rehage J, Starke A. Advances in surgical treatment of septic arthritis of the distal interphalangeal joint in cattle: a review. Vet J. 2009;182(2):162-175. doi:10.1016/j.tvjl.2008.06.009