Overriding spinous processes or “kissing spines” contribute to equine back pain. With this condition, the space between two thoracolumbar spinous processes narrows to less than 4 millimeters. Most often, kissing spines occur between T14 and L1. Not all affected horses experience pain under saddle. Clinical signs vary from horse to horse, ranging from reduced performance to pain on palpation to behavioral and/or gait alterations.
Researchers in Germany evaluated a survey of equine orthopedic specialists about diagnosis and treatment methods for overriding spinous processes.
Diagnostic Methods for Overriding Spinous Processes in Horses
In total, 353 orthopedic surgeons responded to the survey. Preliminary diagnostic methods include a full lameness workup, especially if a horse demonstrates hind-limb lameness. Most respondents observe a horse’s response to back palpation. Diagnostic imaging relies primarily on radiography and ultrasound; scintigraphy is more common in Australia and Asia. Thermography is the least used (4%) diagnostic tool.
Local Anesthesia Techniques
Seventy-three percent of respondents use local anesthesia to aid their diagnosis. Some respondents use sedation, while others do not. The anesthesia techniques vary:
- Placement of two needles abaxial to the interspinous space by 42% of veterinarians (this is the most common technique among specialists included in the survey).
- Placement of one needle in the midline between two spinous processes by 35%.
- Radiographic-assisted needle placement by 17% and ultrasonographic guidance by 38%. Of the respondents, 30% do not use imaging guidance for injection; in many cases this is due to experience from performing frequent injections.
Medications Administered
Medications administered include triamcinolone (TA), dexamethasone, and methylprednisolone. For TA, practitioners in the U.S. inject a maximum of 60 milligrams compared to a maximum of 30 milligrams in Europe. Methylprednisolone doses range from 40-200 milligrams depending on training. The maximum dose for dexamethasone (2%) is 30 milligrams in Europe and 10 milligrams in the United States.
The most common anesthetics among the surveyed specialists are mepivacaine 2% and lidocaine 2%. Homeopathic injectable substances include traumeel or Zeel and vitamins E or B12.
Adverse Effects Following Injection
The practitioners have seen adverse effects following local injection, including:
- Superficial skin irritation (36%) more often correlated with methylprednisolone and mepivacaine.
- Skin infection (8%).
- Increased pain sensation (18%).
- Neurologic deficits (6%).
Therapeutic Approaches
Therapeutic approaches also vary:
- Manual therapy (with specific exercises) recommended by 42% European and 25% American specialists.
- Controlled exercise recommended by 71% of Europeans and 41% of Americans.
- Surgical intervention is most often recommended by practitioners in the U.S. (18%) and Europe (7%), namely the U.K. and Ireland. The authors note that up to 92% of racing Thoroughbreds have kissing spines, and desmotomy tends to yield a good prognosis. Owners and veterinarians in regions with racehorses might be more inclined to pursue surgery.
- Most (69%) approach treatment using conservative management and only resort to surgery for horses nonresponsive to conservative therapy.
Conservative management relies on controlled exercise, manual therapy, and anti-inflammatory medication, including local injections with corticosteroids. In the U.S., 82% of veterinarians believe rehabilitation alone facilitates clinical improvement.
Surgical Treatment
Surgical treatment varies from desmotomy of the interspinous ligament (36%) to a combination of desmotomy and partial ostectomy (30%) to partial (23%) or total (1%) ostectomy. Specialists in the U.S. tend to pursue desmotomy (46%) or desmotomy combined with partial ostectomy (39%), whereas 28% of Europeans prefer partial ostectomy.
Take-Home Message
Treatment strategies for overriding dorsal spinous processes in horses depend on the specialist’s training background and geographic region. Variations also depend on the individual practitioner and professional specialization as to local injection technique, needle size, medication, and volume infused. Radiography and ultrasonography are not defining diagnostic methods. Therefore, most practitioners rely on diagnostic local anesthetic infusion between affected dorsal spinous processes.
Reference
TreB D, Lischer C, Merle R, Ehrle A. International survey of equine orthopedic specialists reveals diverse treatment strategies for horses with overriding spinous processes. Vet Record Jan 2024; DOI: 10.1002/vetr.3899
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