Histologic Evaluation of Palmar Digital Nerves after Perineural Injection of 2% Ammonium Chloride in Miniature Horses

Neurolytic compounds are widely used by equine practitioners for the management of lameness, mostly related to the foot. The present study aimed to evaluate the neurotoxicity of 2% ammonium chloride (2% AC) applied adjacent to the palmar digital nerves in six miniature horses. The 2% AC and 0.9% saline solution were randomly injected into three and one palmar digital nerve of each horse, respectively. Nerve samples were collected by neurectomy performed under general anesthesia at 5, 12, 19, 35, 47, and 62 days after treatment, with one horse per day of surgery. The inflammatory reaction to perineural injection was evaluated by an increase of pastern superficial skin temperature through thermography 24 hours after treatments. Histological lesions were classified as absent, mild, moderate, and severe Wallerian degeneration. An increase of 2.43 ± 0.79°C and 1.69 ± 0.55°C was observed in the 2% AC and control groups, respectively (P > .05). Moreover, histologic lesions were observed after perineural injection of 2% AC (severe, n = 5/18; moderate, n = 4/18; mild, n = 5/18; and absent, n = 4/18) and saline solution (moderate, n = 3/6; mild, n = 1/6; and absent, n = 2/6) (P = .46). The 2% AC demonstrated to be as safe as 0.9% saline solution, producing mild to severe Wallerian degeneration for up to 62 days after injection with no interference in further neurectomy.

Recent advances in conservative and surgical treatment options of common equine foot problems

Foot problems are very common causes of lameness in horses. With the recent diagnostic advances to evaluate and treat foot pathology as well as to monitor response to therapy, it is now possible to more accurately evaluate the effectiveness of many of these treatments. This review details some of the recent advances of the most common conservative and surgical treatment options for foot problems in horses, including an overview of evidence on the efficacy to support the use of these treatment options and on factors that may affect prognosis.

Pain Management in Horses

There has been great progress in the understanding of basic neurobiologic mechanisms of pain, but this body of knowledge has not yet translated into new and improved analgesics. Progress has been made regarding pain assessment in horses, but more work is needed until sensitive and accurate pain assessment tools are available for use in clinical practice. This review summarizes and updates the knowledge concerning the cornerstones of pain medicine (understand, assess, prevent, and treat). It highlights the importance of understanding pain mechanisms and expressions to enable a rational approach to pain assessment, prevention, and management in the equine patient.

Effects of repetition within trials and frequency of trial sessions on quantitative parameters of vertical force peak in horses with naturally occurring lameness

OBJECTIVE To analyze the effects of vertical force peak (VFP) of repition within trials and between trial sessions in horses with naturally occurring appendicular lameness. ANIMALS 20 lame horses acclimated to trotting over a force plate. PROCEDURES Kinetic gait data were collected by use of a force plate regarding affected and contralateral limbs of lame horses that completed 5 valid repetitions in each of 5 sessions performed at 0, 3, 6, 12, and 24 hours, constituting 1 trial/horse. Data were compared within and among repetitions and sessions, and factors influencing VFP values were identified. RESULTS VFP values differed for lame limbs after 3 valid repetitions were performed within a session and when the interval between sessions was 3 hours. Direction of change reflected less lameness (greater VFP). Lamer horses (≥ grade 4/5) had this finding to a greater degree than did less lame horses. Results were similar for contralateral limbs regarding valid repetitions within a session; however, VFP decreased when the interval between sessions exceeded 6 hours. The coefficient of variation for VFP was ≤ 8% within sessions and ≤ 6% between sessions. The asymmetry index for VFP did not change throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Lameness profiles obtained through kinetic gait analysis of horses with naturally occurring lameness were most accurate when valid repetitions were limited to 3 and the interval between sessions within a trial was > 3 hours. Findings suggested that natural lameness may be as suitable as experimentally induced lameness for lameness research involving horses.

Alcohol neurolysis of digital nerves

Alcohol neurolysis is a well-established treatment in chronic pain management, often used in cases of intractable cancer-related pain that is refractory to other management therapies. We describe a 76-year-old woman with chronic toe neuritis who failed multiple treatments, including oral and topical analgesics, nerve blocks, and radiofrequency ablations. Alcohol neurolysis was performed via digit block of the toe resulting in 100% pain relief.