34th Annual Scientific Meeting proceedings

This presentation provides an updated overview of the clinical relevance of radiographic abnormalities of the dorsal spinous processes (DSPs), commonly referred to impingements or “kissing spine” in sport horses. Unlike facet joint arthropathies or vertebral body pathologies, DSP lesions are among the most controversial in terms of diagnostic interpretation and relevance in the context of clinical significance. Moreover, the relationship between clinical signs and radiographic findings remains unclear [1-5].

Several studies have shown that radiographic findings of DSP impingement are extremely common in clinically sound sport horses [1,5-7]. In a very recent study, 100% of actively competing Warmblood horses used for show jumping had at least one radiographic abnormality, mostly mild in nature and not associated with decreased performance [5]. Interestingly, horses with higher performance levels showed a greater number of DSP changes, suggesting the effect of cumulative sport use rather than pathological adaptation [5]. However, the combination of radiographic and scintigraphic findings demonstrates a stronger association with clinical signs of back pain [8]. Their high prevalence in athletic horses demands a critical reassessment of diagnostic strategies.

It has been demonstrated that there are no significant differences in the amount and severity of the radiographic findings between yearling and adult Thoroughbred horses without back pain [9]. There was also no correlation between imaging findings and age and years of competition in jumping Warmbloods [5], supporting the idea that many changes are established at a young age. DSP impingement tends to develop around 11 months of age in Thoroughbreds, while other changes appear at approximately 13–15 months of age. Lesions that develop before four months of age, especially cyst-like ones, tend to resolve spontaneously. Our group has also observed a higher prevalence of DSP abnormalities in Thoroughbred foals born after May–June, which is possibly linked to environmental or developmental factors (unpublished data). The most frequently noted radiographic alterations, including narrowing, sclerosis, and radiolucency, were typically reported as more common in the mid- and caudal thoracic area under the saddle [5-6, 8-9]. Even though multiple grading systems were designed, all of them had some pitfalls, and a final cut-off value for increased odds of back pain was not identified [10].

From a physiotherapeutic perspective, the complexity of clinical back pain signs, the challenge of a correct diagnosis, and the need for multidimensional evaluation need to be emphasized. Radiology must be integrated with functional testing, dynamic palpation, pressure algometry, and behavioral pain indicators [11]. Diagnostic analgesia of the multifidus muscles may alter spinal biomechanics even in clinically sound horses, potentially complicating interpretation of the examination findings [11].

In summary, the clinical significance of radiographic changes in the DSPs should be evaluated within the context of each individual horse. Since radiographic evidence alone is insufficient for a comprehensive evaluation, an integrated, evidence-based approach that considers the horse’s physiology, history, biomechanics, genetics, discipline, and rider’s level and expectations is required.

References

1. Erichsen C, Eksell P, Holm KR, et al. (2004). Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems. Equine Vet J, 36(5):458–465.
2. Brunken G, de Besi N, Königsmann-Brunken D. (2006). Radiologische Untersuchungen an den Dornfortsätzen der Rückenwirbel. Der Praktische Tierarzt, 87:617-621.
3. Holmer M, Wollanke B, Stadtbäumer G. (2007). X-ray alterations on spinal processes of 295 warmblood horses without clinical findings. Pferdeheilkunde Equine Medicine, September:507-511.
4. van Zadelhoff C, Ehrle A, Merle R, et al., (2019). Thoracic processi spinosi findings agree among subjective, semiquantitative, and modified semiquantitative scintigraphic image evaluation methods and partially agree with clinical findings in horses with and without thoracolumbar pain. Vet Radiol Ultrasound, 60:210–218.
5. Kerbert MP, le Jeune SS, Philips KL, et al., (2025). Mild radiographic abnormalities of thoracolumbar spinous processes are not associated with decreased performance in 100 Warmblood jumping horses in active competition. J Equine Vet Sci, 147:105366.
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6. Walmsley JP, Pettersson H, Winberg F, et al., (2002). Impinging spinous processes in horses: diagnosis, treatment and outcome in 212 cases. Equine Vet J, 34(3):222–226.
7. Looijen MGP, Hanousek K, Maree JTM, et al., (2022). Inter- and intra-observer agreement for grading radiographs of thoracolumbar spinous processes in healthy horses during a pre-purchase examination. Vet Rec, 00e1065.
8. Zimmerman M, Dyson S, Murray R. (2012). Close, impinging and overriding spinous processes in the thoracolumbar spine: The relationship between radiological and scintigraphic findings and clinical signs. Equine Vet J, 44:178-184
9. Pressanto MC, Pepe M, Coomer RPC et al. (2023). Radiographic abnormalities of the thoracolumbar spinous processes do not differ between yearling and trained Thoroughbred horses without perceived back pain. J Am Vet Med Assoc, 261(6):844-851.
10. Looijen MGP and Morgan RE. (2024). Should radiographs of the thoracolumbar spine remain part of the pre-purchase examination? Equine Vet Educ, 36:438–448.
11. Harrison LM, Sole Guitart A, Ahern B, et al. (2024). Equine back pain is a diagnostic challenge: A physiotherapist’s perspective. J Equine Rehabil, 2:100017.