Pedicle screw-rod fixation: a feasible treatment for dogs with severe degenerative lumbosacral stenosis

Abstract

Background: Degenerative lumbosacral stenosis is a common problem in large breed dogs. For severe degenerative lumbosacral stenosis, conservative treatment is often not effective and surgical intervention remains as the last treatment option. The objective of this retrospective study was to assess the middle to long term outcome of treatment of severe degenerative lumbosacral stenosis with pedicle screw-rod fixation with or without evidence of radiological discospondylitis.

Results: Twelve client-owned dogs with severe degenerative lumbosacral stenosis underwent pedicle screw-rod fixation of the lumbosacral junction. During long term follow-up, dogs were monitored by clinical evaluation, diagnostic imaging, force plate analysis, and by using questionnaires to owners. Clinical evaluation, force plate data, and responses to questionnaires completed by the owners showed resolution (n = 8) or improvement (n = 4) of clinical signs after pedicle screw-rod fixation in 12 dogs. There were no implant failures, however, no interbody vertebral bone fusion of the lumbosacral junction was observed in the follow-up period. Four dogs developed mild recurrent low back pain that could easily be controlled by pain medication and an altered exercise regime.

Conclusions: Pedicle screw-rod fixation offers a surgical treatment option for large breed dogs with severe degenerative lumbosacral stenosis with or without evidence of radiological discospondylitis in which no other treatment is available. Pedicle screw-rod fixation alone does not result in interbody vertebral bone fusion between L7 and S1.

Fig. 1

a Sagittal T2-weighted MR image of a 5-year-old Labrador retriever (dog 1) with degenerative lumbosacral stenosis and acute onset of discospondylitis. There is a hyperintense signal (exudate) visible in the intervertebral disc space. b Sagittal T2-weighted MR image of dog 1 after three months of treatment with oral antibiotics. The inflammatory exudate has disappeared. c Immediate postoperative radiograph of dog 1 after pedicle screw-rod fixation (PSRF) showing osteolysis of the L7 and S1 endplates. d Radiograph of dog 1 at four years after PSRF. Spondylosis deformans has formed ventral to the LS junction

Fig. 2

a Transverse CT image of the lumbosacral (LS) junction of a 9-year-old Border collie (dog 9) with degenerative lumbosacral stenosis and discospondylitis. Spinal stenosis and severe intervertebral disc (IVD) bulging are visible and there is gas accumulation (vacuum phenomenon) present in the center of the L7-S1 IVD. b Transverse CT image at the level of S1 of a dog (dog 1) with pedicle screw-rod fixation, four years after implantation. No bony fusion between the L7 and S1 vertebrae was visible

Fig. 3

a Pre-operative radiograph of an 8-year-old German shepherd dog (dog 3) diagnosed with degenerative lumbosacral stenosis. There is non-bridging spondylosis deformans, end plate sclerosis, lumbosacral step formation and elongation of the sacral lamina underneath L7. b Radiograph showing dog 3 three years after pedicle screw-rod fixation with implants in correct position. At the level of L5-L6 and L6-L7, there is radiological evidence for adjacent segment pathology, seen by narrowing of the intervertebral foramen. No interbody fusion was present between L7 and S1

Fig. 4

P/T Fy- values of seven dogs (■ = dog 12; ▲ = dog 10; ♦ = dog 8; ● = dog 7; □ = dog 3; ○ = dog 2; ▼ = dog 1). The grey area marks reference values for the average P/T Fy- value ±1 SD previously determined for healthy dogs [19]