Overriding Spinous Processes “Kissing Spine”

“Kissing Spines”, which is a significant cause of alterations of gait and performance, is more easily diagnosed now because of the quality of mobile radiology and ultrasound equipment. The scientific name is Impingement of the Dorsal Spinous Processes (DSP) of the thoracolumbar spine. Visually, one sees that the adjacent vertebrae come in contact with each other. In humans, it is named Basstrup syndrome or Kissing Spine Syndrome.

Why: Lesion severity in the mid-caudal thoracic spine may be exacerbated by spinal lordosis when ridden. We also know that lesion severity increases with horse age and height (Clayton, Stubbs; Journal of Equine Veterinary Science, Dec. 2016)

Clinical Signs: A wide range of signs from asymptomatic to unrideable (bucking, refusing to be saddled, behavioral issues even on the ground, avoidance behavior, avoiding bit contact, traveling with heads up and backs dropped, unwilling to bend, difficulty picking up the correct lead, disconnected, cross cantering). These signs can also be associated with the likes of Lyme disease, tack issues, training, and rider, and stomach ulcers!

Most common location vertebral segments that are being impinged are between T10-18 (area of saddle), however we do see them between L1-L6 (behind saddle). We often see the lesions on lateral radiographs of the dorsal spinous processes. These overriding and kissing spines can be Graded from 0-3.

Bone Lesion Size
Periosteal Proliferation
Eburnation – Severity of Contact of DSPs
Grade 0
0 mm
No contact, smooth periosteum
No contact between DSPs
Grade 1
<2 mm
Mild
Mild with no lysis of bone
Grade 2
2-4 mm
Moderate
Moderate & moderate active bone remodeling
Grade 3
> 4 mm
Severe
Severe & marked bone remodeling

Abnormal findings can also be seen on the ventral aspect of the spinous processes and can involve the interspinal ligaments or be associated with osteoarthritis of the articular processes.

Ultrasound is also a valuable tool in evaluating the acute or subacute desmopathies of the supraspinous ligament (dorsoventral or transverse thickening, altered echogenicity, and alteration of longitudinal fiber pattern).

A Surgical desmotomy of the interspinous ligament (ISLD) also helps to relieve the tension on the afferent nociceptive receptors in the ligament insertion and relieve pain.
Controlled exercise program for spinal re-mobilization is key in helping these horses.

Treatment Options:

1. Physical therapy to restore normal range of motion and/or muscle patterns.
2. Deep needle Injections with corticosteroids and pitcher plant extract along the spinous processes.
3. Acupuncture and Chiropractic – First line of treatment OR supportive role
4. Muscle injections of Latissimus dorsi muscle or mesotherapy
5. Bisphosphonates – Decreases the bone destructive process of bone inflammation
6. Shockwave Therapy
7. Laser – Reducing inflammation of the bone, soft tissue, and nerves
8. Massage

Oftentimes, I am asked to provide chiropractic and/or acupuncture care on an uncomfortable back. This therapy can improve the comfort of the horse but a series of back x-rays have typically been proven valuable in determining our treatment protocol. Drs. Clayton and Stubbs have identified three areas of the thoracolumbar spine that appear to have the most severe lesions (Grade 3). These areas are

1. Cranial thoracic (T2-4)
2. Mid-thoracic to cranial lumbar (T11-L1))
3. Mid-lumbar (L4-5)

In conclusion, “kissing spine” of horses is common and that only a smaller percentage of these horses become clinically painful through their backs. Thoroughbred horses, horses used for dressage, horses 5 years of age or less, and horses with 5 or more vertebrae overriding are much more likely to develop back pain caused by the kissing spines (Turner, Overriding Spinous Processes (“Kissing Spines”) in Horses: Diagnosis, Treatment, and Outcome in 212 Cases, AAEP 2011).

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