Force plate analysis before and after dorsal decompression for treatment of degenerative lumbosacral stenosis in dogs

OBJECTIVE: Using force plate analysis (FPA), determine ground reaction forces in dogs with degenerative lumbosacral stenosis (DLS) and evaluate the effects of lumbosacral decompressive surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Twelve dogs with DLS. METHODS: DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy+), peak propulsive (Fy-), and peak vertical (Fz+) forces of 8 consecutive strides were determined. The ratio between the total Fy- of the pelvic limbs and the total Fy- of the thoracic limbs (P/TFy-), reflecting the distribution of Fy-, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control). RESULTS: In dogs with DLS, the propulsive forces (Fy-) of the pelvic limbs were significantly smaller than those of controls. P/TFy- was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery. CONCLUSIONS: Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period. CLINICAL RELEVANCE: In dogs with DLS, FPA is an effective method in evaluating the response to surgical treatment. Normal propulsive force in the pelvic limbs was restored during 6 months after decompressive surgery.     

The effect of doxycycline on canine hip osteoarthritis: design of a 6-months clinical trial

Twenty-five dogs were included in a randomized, double-blind trial to assess the efficacy of doxycycline (DOX) orally administered twice a day at 4 mg/kg/day (n = 12) for the treatment of osteoarthritis of the hip. Chondroitin sulfate (CS; 525 mg/day) was used as a positive control (n = 13). Dogs were re-examined monthly for 6 months after initiation of treatment. The assessment protocol included clinical score, radiographic findings and serum osteoarthritis biomarkers. Dogs treated with DOX showed statistically significant improvements (p < 0.05) in lameness, joint mobility, pain on palpation, weight-bearing and overall score at 2, 6, 4, 4 and 4 months, respectively, after treatment. Biomarker levels of CS-WF6 epitope and hyaluronan were significantly increased and decreased (p < 0.05) at 2 and 3 months after treatment compared to pretreatment. These results showed that DOX had a positive therapeutic effect in dogs with osteoarthritis.     

Review and retrospective analysis of degenerative lumbosacral stenosis in 156 dogs treated by dorsal laminectomy.

The medical records of 156 dogs with degenerative lumbosacral stenosis (DLS) that underwent decompressive surgery were reviewed for signalment, history, clinical signs, imaging and surgical findings. The German Shepherd Dog (GSD) was most commonly affected (40/156, 25.6%). Pelvic limb lameness, caudal lumbar pain and pain evoked by lumbosacral pressure were the most frequent clinical findings. Radiography showed lumbosacral step formation in 78.8% (93/118) of the dogs which was associated with elongation of the sacral lamina in 18.6% (22/118). Compression of the cauda equina was diagnosed by imaging (epidurography, CT, or MRI) in 94.2% (147/156) of the dogs. Loss of the bright nucleus pulposus signal of the L7-S1 disc was found on T2-weighted MR images in 73.5% (25/34) of the dogs. The facet joint angle at L7-S1 was significantly smaller, and the tropism greater in GSD than in the other dog breeds. The smaller facet joint angle and higher incidence of tropism seen in the GSD may predispose this breed to DLS. Epidurography, CT, and MRI allow adequate visualization of cauda equina compression. During surgery, disc protrusion was found in 70.5% (110/156) of the dogs. Overall improvement after surgery was recorded in the medical records in 79.0% (83/105) of the dogs. Of the 38 owners that responded to questionnaires up to five years after surgery, 29 (76%) perceived an improvement.     

Agreement between computed tomography, magnetic resonance imaging, and surgical findings in dogs with degenerative lumbosacral stenosis

OBJECTIVE: To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis. DESIGN: Observational study. ANIMALS: 35 dogs with degenerative lumbosacral stenosis. PROCEDURES: Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots. RESULTS: A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.     

Biomechanical flexion-extension forces in normal canine lumbosacral cadaver specimens before and after dorsal laminectomy-discectomy and pedicle screw-rod fixation

Objective— To determine biomechanical flexion–extension forces in cadaveric canine lumbosacral specimens, before and after dorsal laminectomy with partial discectomy, and after dorsal pedicle screw–rod fixation of L7 and S1.
Study Design— Biomechanical cadaver study.
Animals— Cadaveric spine specimens without lumbosacral pathology from mature, intact Labrador retrievers (n=12).
Methods— Lumbosacral spine segments were subjected to a constant bending moment from L6 to S1 in a hydraulic 4-point bending materials testing machine. Force and displacement were recorded during each loading cycle constituting 1 complete flexion–extension cycle of the spine. Each spine segment had 3 series of recordings of 5 loading cycles each: (1) intact spine, (2) after surgical destabilization by dorsal laminectomy and partial discectomy, and (3) after surgical stabilization using dorsal pedicle screw–rod fixation.
Results— After dorsal laminectomy and partial discectomy, the neutral zone and range of motion were not different from those in the native spine specimen. After pedicle screw–rod fixation, the neutral zone and range of motion of the instrumented specimen significantly ( P <.0001) decreased compared with the native specimen and the specimen after dorsal laminectomy.
Conclusion— Dorsal laminectomy and partial discectomy does not lead to significant spinal instability in flexion and extension whereas pedicle screw and rod fixation effectively stabilizes the lumbosacral spine.
Clinical Relevance— Dorsal laminectomy and partial discectomy does not lead to significant spinal instability. Pedicle screw–rod fixation of L7 and S1 may be used to stabilize an unstable L7–S1 junction in dogs with degenerative lumbosacral stenosis.     

Tibial nerve somatosensory evoked potentials in dogs with degenerative lumbosacral stenosis

OBJECTIVE: To determine somatosensory evoked potentials (SEPs) in dogs with degenerative lumbosacral stenosis (DLS) and in healthy dogs. STUDY DESIGN: Clinical and experimental study. ANIMALS: Dogs with DLS (n = 21) and 11 clinically normal dogs, age, and weight matched. METHODS: Under anesthesia, the tibial nerve was stimulated at the caudolateral aspect of the stifle, and lumbar SEP (LSEP) were recorded percutaneously from S1 to T13 at each interspinous space. Cortical SEP (CSEP) were recorded from the scalp. RESULTS: LSEP were identified as the N1-P1 (latency 3-6 ms) and N2-P2 (latency 7-13 ms) wave complexes in the recordings of dogs with DLS and control dogs. Latency of N1-P1 increased and that of N2-P2 decreased as the active recording electrode was moved cranially from S1 to T13. Compared with controls, latencies were significantly delayed in DLS dogs: .8 ms for N1-P1 and 1.7 ms for the N2-P2 complex. CSEP were not different between groups. CONCLUSIONS: Surface needle recording of tibial nerve SEP can be used to monitor somatosensory nerve function of pelvic limbs in dogs. In dogs with DLS, the latency of LSEP, but not of CSEP, is prolonged compared with normal dogs. CLINICAL RELEVANCE: In dogs with lumbosacral pain from DLS, the cauda equina compression is sufficient to affect LSEP at the lumbar level.     

Assessment of decompressive surgery in dogs with degenerative lumbosacral stenosis using force plate analysis and questionnaires

Objective— To evaluate the long-term outcome after decompressive surgery in dogs with degenerative lumbosacral stenosis (DLS), using force plate analysis (FPA) and owner questionnaires.
Study Design— Prospective clinical study.
Animals— Dogs with DLS (n=31) and 24 clinically normal Labrador Retrievers.
Methods— FPA was performed before surgery (31 dogs) and at 3 days, 6 weeks, 6 months (each, 31 dogs) and ≥1.5 years (12 dogs) after surgery. Peak vertical forces (Fz⁺), braking (Fy⁺), and propulsive forces (Fy⁻), and the corresponding impulses were determined. Questionnaires were completed by the owners before and at 6 months and ≥1.5 years after surgery.
Results— Fy⁻ of the pelvic limbs and the ratio pelvic/thoracic of Fy⁻ (P/TFy⁻) were significantly smaller in dogs with DLS than controls. Fy⁻ and P/TFy⁻ decreased significantly 3 days after surgery, and increased during 6 months follow-up, but with long-term follow-up the values remained the same and were smaller than controls. From questionnaires there was a significant improvement after surgery compared with function before surgery. Most owners were satisfied with outcome after surgery.
Conclusions— Propulsive forces of the pelvic limbs in dogs with DLS are impaired and are partially restored by decompressive surgery.
Clinical Relevance— Owner's questionnaires illustrate that decompressive surgery restores function as perceived by owners whereas FPA continues to show impaired propulsive forces for the pelvic limbs.