Successful treatment of suspected sciatic neuritis following canine total hip arthroplasty

Sciatic neuritis is characterized by neuropathic pain with or without neurological deficits. There have been no previous reports of significant neuropathic pain or sciatic neuritis following total hip arthroplasty (THA) in dogs. This case report describes a male neutered Samoyed dog, aged 21 months and weighing 26 kg, with severe pain after THA that underwent revision surgery 2 days after the initial surgery. During the 36 hours after the initial surgery, analgesia was well managed with preventive and multimodal analgesic approaches (methadone, meloxicam, medetomidine infusion, epidural injection of bupivacaine and morphine). After this, the level of pain increased substantially and was refractory to treatment (revision surgery, methadone, ketamine and medetomidine infusions, paracetamol and gabapentin). Neuropathic pain was suspected based on signs of allodynia (hypersensitivity to gentle palpation of the affected limb) and concern for paraesthesia (sporadic vocalization and attempts of self-mutilation). The dog had no neurological deficits, and there were no significant findings on revision surgery or serial radiography. Ultrasonography of the sciatic nerve revealed marked hyperechoic thickening of the epineurium, suggestive of neuritis. A single perineural injection with a mixture of methylprednisolone (0.6 mL, 4%, 1 mg kg^-1) and bupivacaine (3 mL, 0.5%, 0.6 mg kg^-1) was injected proximal to the affected sciatic nerve via a modified parasacral approach under ultrasound guidance. The level of pain rapidly subsided following perineural injection, allowing for reduction of systemic analgesic use and return of the dog to its owner. The remainder of the recovery period was uneventful with no recurrence of significant pain at the time of most recent follow-up, 153 days after initial surgery.