28
EQUINE VETERINARY EDUCATION / AE / JANUARY 2017
8 weeks prior to referral, the stallion showed an acute onset, moderate (grade 3/5) left forelimb lameness and a small wound to the lateral aspect of the left carpus due to a kick injury. The first opinion veterinarian recognised involvement of the antebrachiocarpal joint and referred the animal to a private equine clinic, where, per owner report, the joint was lavaged 3 times and received several antimicrobial treatments both locally and systemically. Six weeks later the horse was discharged from the hospital. Due to consistent lameness and purulent exudate from the lateral wound one week post discharge the horse was admitted to the Equine Clinic of the Free University of Berlin for evaluation.
Clinical findings
On presentation, the stallion was bright, alert and responsive. The heart rate was 44 beats/min, the respiratory rate 16 breaths/min and the body temperature 37.6°C. Initial orthopaedic examination revealed moderate to severe left forelimb lameness (grade 4/5), extensive swelling of the left carpal region with severe pain on flexion of the carpal joint. On the lateral aspect of the antebrachiocarpal joint a fistula with purulent exudate was present (Fig 1). Ultrasound examination of the carpus showed severe distension of the antebrachiocarpal joint with multiple hyperechogenic masses within the joint. A 2 cm fistula from the skin communicating with the antebrachiocarpal joint was identified. In the subcutis at the opening of the fistula, a mixed echogenic mass consistent with abscessation was also imaged. Standard radiographic views of the carpus showed new bone formation on the dorsolateral and dorsomedial aspect of the distal radius, the ulnacarpal and the radiocarpal bones. Arthrocentesis of the antebrachiocarpal joint did not provide enough synovial fluid for analysis of the white blood cell count, but the total protein was significantly elevated (75 g/l). The joint was distended with 30 ml of sterile saline resulting in
leakage from the lateral wound, confirming the communication of the fistula with the antebrachiocarpal joint. Culture and sensitivity of the fistula revealed an infection with multiresistant Enterobacter cloacae (extended-spectrum b-lactamase), sensitive to amikacin and marbofloxacin.
Diagnosis
The diagnosis of a chronic, septic osteoarthritis of the left antebrachiocarpal joint in combination with a fistula and a subcutaneous abscess infected with Enterobacter cloacae (extended-spectrum b-lactamase) was made.
Treatment
Due to the chronicity of the septic arthritis, degree of lameness, and infection with multidrug resistant bacteria a poor prognosis for survival was given. Treatment was pursued as the horse was a valuable breeding stallion. On the day of admission, the horse was taken to surgery and placed in dorsal recumbency. Arthroscopy through the dorsal and palmar approach of the left antebrachiocarpal joint revealed severe inflammation of the synovial membrane, a mild cartilage defect on the proximal aspect of the intermediate carpal bone, and an approximately 1 cm diameter fistula at the lateral aspect of the joint communicating with the external wound. During arthroscopic joint lavage the abscess was opened and drained by removing the necrotic skin surrounding the fistula. All necrotic tissue was removed surgically and debridement continued using UAWT for 1 min/cm² by a second assistant surgeon during lavage. The joint was arthroscopically lavaged with a total of 20 l lactated Ringer’s solution (Ringer-Solution)3, debrided using a synovial resector (Storz powershaver SL)4 and following completion of the procedure an intra-articular injection of 1 g of amikacin sulfate (Amikacina Normon)5 was performed. Due to the loss of soft tissue, the horse was left with a skin defect on the lateral aspect of the radiocarpal joint, approximately 5 cm in diameter and 2 cm in depth communicating with the antebrachiocarpal joint (Fig 2) through an approximately 1 cm diameter defect within the joint capsule. The wound was covered with a sterile nonadhesive drape and the entire limb immobilised using a Robert Jones splint bandage. Post operative treatment included 0.6 mg/kg bwt meloxicam (Metacam)6 orally once daily and antimicrobial treatment consisted of 15 mg/kg bwt amoxicillin (Amoxisel)7 twice daily and 6.6 mg/kg bwt gentamicin sulfate (Gentacin)8 once daily. Due to the poor weightbearing of the horse and the increased risk of developing laminitis the contralateral limb was protected using frog support immediately after recovery from surgery. Two days post admission the culture and sensitivity revealed that the wound was infected with an extended-spectrum b- lactamase producing Enterobacter cloacae, sensitive only to amikacin and marbofloxacin and the antimicrobial was switched to 2 mg/kg bwt marbofloxacin (Marbocyl10%)9 intravenously once daily. At the first bandage change 2 days post operatively, the stallion was grade 5/5 lame on the affected limb without the bandage. The wound contained granulation tissue that was irregular, had a cobblestone
Fig 1: Lateral aspect of the left carpus at admission showed severe distention of the radiocarpal joint with discharge of pus from the fistula.
© 2015 EVJ Ltd
appearance and was covered in purulent exudate. The fistula into the antebrachiocarpal joint was visible (Fig 3). Arthrocentesis was performed and a small amount of synovial
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72
