Gross post‐mortem and histological features in 27 horses with confirmed lumbosacral region pain and five control horses: A descriptive cadaveric study

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 fourth to fifth and ankylosis of the fifth to sixth lumbar articular process joints, left-right asymmetry of caudocranial position of the fourth to fifth 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 preclinical 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.

Complications following diagnostic and therapeutic sacroiliac joint region injections in horses: A study describing clinicians' experiences

“…15,16 However, a recent post-mortem study of horses with a positive response to periarticular injection of mepivacaine reported both sacroiliac joint and lumbosacral pathology. 17 In addition, there were gross abnormalities of the sciatic and obturator nerves, not observed in control horses, and higher histological scores in the lumbosacral plexus and the cranial gluteal nerve, sciatic and obturator nerves compared with control horses. These results indicate the potential extent of diffusion of local anaesthetic solution.…”

Age and sex correlate with bony changes and anatomic variations of the lumbosacroiliac region of the vertebral column in a mixed population of horses

“…9,10 In addition, some anatomic variations of the lumbosacral segment may alter the normal biomechanics of the area, predisposing to an early development of abnormal changes or inability to work correctly, resulting in poor performance. 11 While there are some necropsy studies 12,13 of the thoracolumbar region of the vertebral column in horses, only a few have focused on the lumbosacroiliac region and are mostly based on Thoroughbred racehorse specimens. [3][4][5]14 The aim of the study reported here was to describe the incidence of anatomic variations and abnormal changes of the lumbosacroiliac region in a mixed population of horses (ie, variable breeds, ages, and size).…”

“…In total, 38 specimens were included in this study, similar to previous anatomic studies in this field. 3,5,11,14 The breeds consisted of warmblood (n = 13), Thoroughbred (4), Anglo-Arabian (4), Arab (3), Standardbred (3), and others (11). There were 25 females and 13 males, ranging in age between 5 and 30 years (mean, 16 years; SD, 6.5 years) and weighing between 284 and 620 kg (mean, 489 kg; SD, 65 kg).…”

Response to comments on Complications following diagnostic and therapeutic sacroiliac joint region injections in horses: A study describing clinicians' experiences

“…In recent years there has been considerable global research effort to improve understanding of the functional biomechanics of the sacroiliac joint and related pelvic musculature, [3][4][5][6] and to document the pathological conditions that may contribute to pain and dysfunction through diagnostic imaging [7][8][9] and post mortem studies. 10,11 The pitfalls of over diagnosis by skeletal scintigraphy have been highlighted. 7,12 In his letter, Mr Gray stated that 'The February article displays a misunderstanding of the significance of the sacroiliac joint in equine lameness; the prevalence of which has been exaggerated; and the part it plays in lameness has never been proven'.…”

“…7,15,16 We strongly believe in the value of diagnostic anaesthesia of the sacroiliac joint region in horses showing suggestive clinical signs, acknowledging that, just like many other local anaesthetic techniques, it is not entirely specific. 7,9,11,15 Nonetheless, it greatly helps to localise the source of pain causing a gait abnormality and/or poor performance. Others may feel averse to diagnostic anaesthesia, mostly because of experience of or perceived risk of complications and make their diagnosis based on response to medication and/or diagnostic imaging.…”