A symphysis is a joint in which the bones are joined by a disc of fibrocartilage. This study used ultrasound to look at the sympheses between the 5th and 6th lumbar vertebrae (L5/L6 symphysis), and between the 6th lumbar vertebra and the sacrum (the lumbosacral symphysis). The horses involved were being investigated for poor performance or unusual posture in their back. One of the aims of the study was to describe abnormalities seen on ultrasound in the L5/L6 symphysis, and to see whether problems in this area were linked to what’s called congenital sacralisation – a fusing of the last lumbar vertebra with the sacrum. The majority of these horses being investigated for poor performance showed changes at either the L5/L6 symphysis, the lumbosacral symphysis, or more commonly, both. However, the presence of lesions at the L5/L6 symphysis was not necessarily related to congenital sacralisation. The conclusion was that abnormalities of the L5/L6 and lumbosacral symphyses may cause pain and contribute to poor performance.
Boado, Ana & Nagy, Annamaria & Dyson, Sue. (2019). Ultrasonographic features associated with the lumbosacral or lumbar 5-6 symphyses in 64 horses with lumbosacral-sacroiliac joint region pain (2012-2018): Lumbar symphysis pathology. Equine Veterinary Education. 32. 10.1111/eve.13236. )
You can access the full article here.
The ultrasonographic appearance of the lumbosacral symphysis of horses with no history of hindlimb lameness or thoracolumbosacral pain has previously been documented. The aims of the study were to describe the signalment and clinical findings in horses with ultrasonographic lesions of the fifth and sixth lumbar (L) vertebrae and lumbosacral symphyses and to determine whether lesions of the L5-6 symphysis are only seen in horses with congenital sacralisation or other abnormalities of the lumbosacral symphysis. Horses in Group 1 (n = 25) underwent poor performance investigation and improved in ridden performance after infiltration of mepivacaine around the sacroiliac joints. Horses in Group 2 (n = 39) presented for investigation of changes in thoracolumbosacral shape or poor performance but did not undergo anaesthesia of the sacroiliac joint regions. The median ages were 10 and 19 years respectively for Groups 1 and 2. Mares (53.1%) were over-represented relative to the normal populations of the clinics. All horses had poor development of the thoracolumbar epaxial and pelvic muscles and prominence of the lumbar spinous processes and the tubera sacrale. Most horses (70%) had reduced range of movement of the thoracolumbosacral region. Ultrasonographic features included irregular vertebral end plates; heterogeneous echogenicity of the intervertebral disc ± ventral protrusion; and displacement of the ventral longitudinal ligament ± alteration in its echogenicity. In Group 1, abnormalities of the L5-6 symphysis were seen in 13 horses, of which 84.6% had congenital sacralisation or narrowing of the lumbosacral symphysis. In Group 2, the majority of horses had lesions of both the L5-6 and lumbosacral symphyses; only 9/39 horses (23.1%) had congenital fusion of either joint. Limitations include the lack of age-matched control horses. However, the purpose of the study was to raise awareness of lesions of the L5-6 and lumbosacral symphyses, which may contribute to pain and poor performance.
Dr Sue Dyson and I are in the process of writing a book for horse owners and riders on how to understand and use the Ridden Horse Pain Ethogram with your own horse. The book will be published by J A Allen, and available sometime In 2023. Sign up to my newsletter at www.thehorsephysio.co.uk for updates.
In the meantime, you can learn more about the Ridden Horse Pain Ethogram through listening to Dr Sue Dyson explaining here it on the Equine Veterinary Education, where you can also listen to her discussing many of the other studies that she has been involved in. You can also take an online course with Equitopia.
© Sue Palmer, The Horse Physio 2021
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