NAVLE Equine Surgery and Lameness 4

Question 1

A 7-year-old Thoroughbred presents with acute-onset, severe left forelimb lameness following a race. Radiographs reveal a complete, non-displaced sagittal fracture of the proximal phalanx. Intraoperative lag screw fixation is planned. Which cortex should the lag screw thread engage to achieve interfragmentary compression?

Accepted Answer

The far cortex only, with the near cortex overdrilled to gliding hole diameter

Answer

Lag screw technique requires overdrilling the near (glide) cortex to the outer thread diameter so it does not engage, while the thread bites only the far cortex. As the screw head seats against the near cortex, it pulls the far fragment toward the head, generating interfragmentary compression. Engaging both cortices or the near cortex alone negates the compression mechanism.

Question 2

During arthroscopic surgery of the tarsocrural joint in a horse, you identify an osteochondral fragment at the distal intermediate ridge of the tibia (DIRT lesion). Intraoperatively you notice the synovial membrane is markedly hypertrophied and there is significant fibrillation of the adjacent cartilage beyond the fragment margin. Which prognostic factor most significantly worsens the long-term athletic outcome after fragment removal in this scenario?

Accepted Answer

Presence of concurrent cartilage fibrillation extending beyond the lesion

Answer

While fragment size and age are considered, extensive cartilage fibrillation beyond the OCD lesion margin indicates generalized articular cartilage degeneration that will progress independently of fragment removal. This diffuse cartilage damage is the strongest negative prognostic indicator for return to full athletic function, as fragment removal alone cannot address the surrounding degenerative process.

Question 3

A 12-year-old Warmblood dressage horse presents with a 6-month history of progressive hindlimb ataxia and symmetric weakness. Cervical radiographs show dynamic stenosis at C3-C4. Myelography confirms spinal cord compression only during neck flexion. The owners request surgical intervention. Which procedure is most appropriate?

Accepted Answer

Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion)

Answer

Cervical vertebral interbody fusion using a Bagby basket (or modified basket/screw technique) is the surgical standard for dynamic cervical stenosis (Wobbler syndrome) in horses. It eliminates instability-driven compression by fusing the affected motion segment. Dorsal laminectomy is unsuitable because the compression in dynamic cases is typically ventral/lateral, and the equine cervical anatomy makes dorsal approach impractical for decompression.

Question 4

You perform a palmar digital nerve block (PDN block) in a horse with a 3/5 lameness. Lameness improves by only 30%. You then perform an abaxial sesamoid nerve block, and lameness improves by 70% from the original score. What is the most accurate interpretation of these sequential block results?

Accepted Answer

There is a pain source in the heel/caudal foot region AND a second source more proximal in the pastern or fetlock region

Answer

Sequential distal-to-proximal nerve blocks are additive. A 30% improvement with PDN (desensitizes caudal foot/heel) plus an additional 40% improvement with abaxial sesamoid block (adds the pastern/fetlock region) indicates two pain contributors: one in the heel/caudal foot and a second source in the region additionally desensitized by the abaxial block (pastern, proximal interphalangeal joint, palmar fetlock). Neither block alone accounted for the full lameness.

Question 5

A 4-year-old Quarter Horse undergoes emergency surgery for a right dorsal colon displacement (right dorsal displacement of the large colon). Intraoperatively, the pelvic flexure is exteriorized and the colon is repositioned. Postoperatively on day 3, the horse develops profuse watery diarrhea, hypoproteinemia, and peripheral edema. Repeat gastric reflux yields 8 liters. Which complication best explains this clinical picture?

Accepted Answer

Right dorsal colitis secondary to perioperative NSAID toxicity

Answer

Right dorsal colitis (RDC) is a well-recognized sequela of excessive NSAID administration (particularly phenylbutazone) in the perioperative period. It causes focal ulceration and inflammation of the right dorsal colon, leading to protein-losing enteropathy (hypoproteinemia, edema) and diarrhea. The concurrent large-volume gastric reflux results from ileus secondary to the colonic inflammation. While Salmonella is possible, the clinical context of recent intensive NSAID therapy for colic surgery makes RDC the most likely diagnosis.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Equine Surgery and Lameness 4