1. Radiographic Grading Criteria (Gorgas / Jeffcott System)
Radiographic evaluation focuses on the cranial thoracic to cranial lumbar vertebrae (T12 to L2), with peak incidence occurring under the saddle tree at T14–T17:
Interspinous space narrowed (<4 mm) without reactive bone remodeling or sclerosis.
Direct bony contact between adjacent spinous margins with mild cortical bone sclerosis.
Marked cortical sclerosis, radiolucent subchondral bone cysts, and peripheral enthesophytes.
Dorsal spinous processes visibly overlap, with severe structural distortion and pseudo-arthrosis.
2. Multimodal Conservative vs. Surgical Therapies
Stage 1: Ultrasound-Guided Injections: Injection of corticosteroids (triamcinolone acetonide) or orthobiologics (PRP, autologous conditioned serum / IRAP) directly into the affected interspinous spaces alleviates local enthesitis, restoring willingness to engage the abdominal sling.
Stage 2: Extracorporeal Shock Wave Therapy (ESWT): Focused radial shockwave delivered across the epaxial musculature and dorsal spinous processes reduces substance P release, providing documented analgesic relief for 4–8 weeks.
Stage 3: Interspinous Ligament Desmotomy (ISLD): For horses refractory to conservative therapy, standing endoscopic ligament transection provides permanent biomechanical relief without the prolonged 6-month recovery required by traditional ostectomy.
Kissing Spine Frequently Asked Questions
Why are radiographic signs of kissing spines sometimes present in clinically sound horses?
Up to 35% of high-performing Warmbloods and Thoroughbreds display mild to moderate radiographic impaction or sclerosis of dorsal spinous processes without exhibiting back pain or performance deficit. Radiographs show structural anatomy, not active inflammation. Therefore, diagnostic confirmation requires nuclear scintigraphy (bone scan showing focal radiopharmaceutical uptake) or a diagnostic ultrasound-guided local anesthetic block of the affected interspinous space that immediately eliminates clinical back stiffness under saddle.
What is the Interspinous Ligament Desmotomy (ISLD) surgical technique and its success rate?
Interspinous Ligament Desmotomy (developed by Coomer et al.) is a minimally invasive surgical procedure performed on standing, sedated horses under local anesthesia. A fine endoscopic blade transects the taut interspinous ligament connecting adjacent impinging dorsal spinous processes. By releasing tension, the spinal column relaxes into a biomechanically neutral position, alleviating mechanical nerve impingement with published return-to-competition success rates exceeding 80% to 85%.
How does saddle fit and rider balance influence the progression of kissing spine?
Saddles with narrow gullets that rest directly on the supraspinous ligament or bridges that concentrate pressure over the thoracic T13–T18 vertebrae force the horse to hollow its back. A hollowed thoracolumbar spine brings adjacent dorsal spinous processes into direct bony contact. Ensuring 3 to 4 fingers of wither clearance and full lateral spinal relief allows the horse to elevate its core and engage the abdominal sling, maintaining safe interspinous spacing.