Horses with lumbosacral region pain

We don’t often discuss lameness originating from the pelvic region for a simple reason: it is hard to diagnose and even with a diagnosis difficult to treat effectively. In recent years regional anesthesia has been used to localize pain to the lumbosacral region especially the sacroiliac joint. If a region is localized, then often corticosteroids are injected in an attempt to treat inflammation that may be present. Ultrasound guided injections has made this practice more reliable as often these structures lie under many inches of soft tissue. In this study a good effort was made to differentiate horses with lameness originating from the lumbosacral (ls) region and lameness originating from further down the hind limb. These horses were available for examination on postmortem and abnormalities of the lumbosacral region catalogued. A large number of congenital abnormalities of the spine were identified in this region but significance unknown. It was noted there were more abnormalities in the ls lame group. Of interest is that more than a quarter of the ls lame group had degenerative changes to the nerves originating from lumbosacral region.

The report illustrates the complexity of diagnosing lameness from this region and has a significant finding of frequent neurodegenerative disease, a problem with a likely poor prognosis.
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Pathological findings in horses with lumbosacral region pain
Equine Vet J. 2021 Jun 12.
Authors
Laura Quiney 1 , Jennifer Stewart 2 , Jennifer Routh 1 , Sue Dyson 1
Affiliations

1 Centre for Equine Studies, Animal Health Trust, Lanwades Park, Newmarket, Suffolk, CB8 7UU, UK.
2 Centre for Preventative Medicine, Animal Health Trust, Lanwades Park, Newmarket, Suffolk, CB8 7UU, UK.

Abstract

Background: There is a lack of understanding of the pathological and/or physiological nature of lumbosacral region pain.

Objectives: To describe the gross variations of the osseous and soft tissues of the lumbosacral region and report the histological findings of sections of nerve tissue in affected and control horses.

Study design: Descriptive post-mortem case series.

Methods: All horses had undergone full clinical and gait assessment, including ridden exercise. Horses with a substantial response to infiltration of local anaesthetic solution around the sacroiliac joint regions were included in the affected group (n=27). Horses for which the source(s) of pain was confirmed by diagnostic anaesthesia to be distant to the lumbosacral region were included in the control group (n=5). The pelvic regions were isolated and the soft tissues were assessed grossly. Sections of the lumbosacral plexus and cranial gluteal, sciatic and obturator nerves were examined histologically. The osseous specimens were evaluated for anatomical variants and abnormalities. Data were analysed using descriptive statistics.

Results: Gross discolouration of the sciatic or obturator nerves was observed in 7 (26%) affected and no control horses. Grade 3/3 histological abnormality scores were assigned in 22% of nerve sections from affected horses compared with 3% from control horses. Several osseous variants (bifid sacral spinous processes, straight-shaped sacroiliac joint surface, short arrow-shaped sacral alae, left-right asymmetry of sacral alae, sacral curvature, absence of the 4th -5th and ankylosis of the 5th -6th lumbar articular process joints, left-right asymmetry of caudocranial position of the 4th -5th and lumbar-sacral articular process joints) and abnormalities (sacroiliac enthesopathy, extra ventral sacroiliac joint surface, lumbosacral symphyseal periarticular modelling, lumbosacral intertransverse joint pitting-lesions) were more frequently observed in affected horses.

Main limitations: Both control and affected horses may have had pre-clinical abnormalities.

Conclusions: Lumbosacral region pain may reflect the presence of a number of pathological changes. Neural pain may play an important role in some horses.

Keywords: horse; lumbar; nerve pathology; poor performance; sacroiliac enthesopathy; sacroiliac joint.