Degenerative lumbosacral stenosis in dogs

Abstract

Degenerative lumbosacral stenosis (DLS) is now recognized as a significant cause of caudal lumbar pain and pelvic limb lameness in dogs. The condition includes lumbosacral intervertebral disc degeneration and protrusion, spondylosis deformans, sclerosis of the vertebral end plates, osteoarthrosis of articular facets, ventral sacral subluxation, and hypertrophy of the ligamentum flavum and joint capsules. The clinical signs are caudal lumbar pain, pelvic limb lameness, reluctance to jump, rise and climb stairs, and neurological signs. Diagnosis of DLS is based on the history, clinical signs, clinical examination, and imaging findings. The surgical treatment of dogs with DLS aims to relieve the compression on the cauda equina nerve roots. The first aim of this thesis was to determine the diagnostic value of advanced imaging techniques. The findings between computed tomography (CT), magnetic resonance imaging (MRI), and surgery were compared There was substantial to almost perfect agreement between the findings on CT and MRI for the degree and location of disc protrusion, the position of the dural sac, the presence of epidural fat, and swelling of nerve roots. There was slight to fair agreement between imaging and surgical findings for the degree and location of disc protrusion, and swelling of nerve roots. CT and MRI provided excellent discrimination of compressive tissues in the spinal canal. The second aim was to investigate the somatosensory function in dogs affected by DLS. Compressive lesions on the cauda equina at L7-S1 in dogs with DLS prolonged the mean latency of tibial nerve somatosensory evoked potentials in dogs with DLS compared with those in clinically normal dogs. The third aim was to objectively evaluate, using force plate analysis (FPA), the result of decompressive surgery in dogs with DLS. In 12 dogs, surgical treatment restored the propulsive forces of the pelvic limbs in a 6-month period after surgery. The long-term outcome of decompressive surgery in 35 dogs with DLS was assessed by FPA and questionnaires to owners. The propulsive forces of the pelvic limbs, and the ratio between the propulsive forces of the pelvic limbs and the thoracic limbs decreased significantly at 3 days after surgery, and increased during 6 months follow-up, but remained smaller than control values with long-term (? 1.5 years) follow up. In contrast, the results from the questionnaires showed significant improvement 6 months to 1.5 years after surgery compared to findings before surgery, and the majority of owners were satisfied. Biomechanical flexion-extension load forces were assessed in cadaveric lumbosacral specimens of healthy middle-sized dogs, before and after dorsal laminectomy with partial discectomy, and after pedicle screw-rod fixation. The flexion and extension load forces after dorsal laminectomy with partial discectomy, were not significantly different from those in the native lumbosacral spine specimen. After pedicle screw-rod fixation, the motions in the instrumented spine segment decreased significantly. Pedicle screw-rod fixation may be used to effectively stabilize the instable L7-S1 junction in dogs with DLS.