Lumbosacral Disease involves degeneration of the lumbosacral junction and / or compression of the associated nerves
The LS joint is one of the highest-motion joints of the spine. As a result, it is uniquely predisposed to degenerative (wear-and-tear) diseases that are similar to the diseases causing lower back pain in humans. The lumbar spine is highly mobile whereas the sacrum is immobile, hence the LS junction is a transition zone and subsequent stress is placed on the joint and the LS intervertebral disc. Disc degeneration may arise leading to disc protrusion or tearing. Compression or impingement of nerves as they travel dorsal to a disc or exit the spinal cord at the nerve root foramina occurs as a result of the bulging disc, soft tissue proliferation, collapse of the foraminal area (foraminal stenosis) or new bone formation. This compression leads to discomfort, the canine equivalent of sciatica and with progression further compromise to nerve function.
The lumbosacral (LS) junction is the juncture of the last lumbar vertebra (L7) with the sacrum (where the spinal column meets the pelvis and back legs). At this junction, as between all vertebrae, are bony articular facets that articulate to form two small joints and an intervertebral disc – a cushion of gel-like cartilage – that acts as a shock absorber during physical activity. A nerve root exits the spinal cord at the foramen between L7 and the sacrum on either side which contributes to the sciatic nerve, the main nerve to the back legs, while other nerves (“the cauda equina”) continue to run within the spinal canal, encased by the vertebral bones, contributing to tail and urinary bladder function.