[Show abstract][Hide abstract] ABSTRACT: A clinicobiomechanical study.
To clarify the clinicobiomechanical characteristics of a segment with lumbar degenerative spondylolisthesis (LDS) using an original intraoperative measurement system.
Although radiographical evaluation of LDS is extensively performed, the diagnosis of segmental instability remains controversial. The intraoperative measurement system used in this study is the first clinically available system that performs cyclic flexion-extension displacement of the segment with all ligamentous structures intact and can determine both the stiffness (N/mm) and neutral zone (NZ, [mm/N]).
Forty-eight patients with LDS (males/females = 19/29, 68.5 yr; group D) were compared with 48 patients with lumbar spinal stenosis without LDS (males/females = 33/15, 64.8 yr, group N) in terms of symptoms, radiological, and biomechanical results. Instability was defined as a segment with NZ more than 2 mm. Symptoms (36-Item Short Form Health Survey), radiographical findings (radiographs, magnetic resonance images, computed tomographic scans), stiffness, NZ, and frequency of instability were also compared. Risk factors for instability were analyzed by multivariate logistic regression with a forward stepwise procedure.
None of the physical function categories or radiological findings of 36-Item Short Form Health Survey and low back pain (visual analogue scale) differed significantly between the groups. Although NZ was significantly greater in group D (1.97) than in group N (1.73) (P < 0.05), the frequency of instability did not differ significantly between groups. Facet opening (odds ratio, 11.0; P < 0.01) and facet type (odds ratio, 6.0; P < 0.05) were significant risk factors for instability.
Neither the symptoms nor the frequency of instability differed significantly between groups. The radiological findings of spondylolisthesis did not indicate instability, but facet opening and sagittally oriented facets were indicative of instability. The results of this study demonstrated that LDS is not always unstable in the measurement setting, suggesting that the instability of LDS can stabilize spontaneously during the natural course.
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE: To compare the diagnostic efficacy of recumbent magnetic resonance imaging (MRI), computed tomography myelography (CTM), and myelography, with regard to indications for surgery for lumbar stenosis. BACKGROUND DATA: In patients with lumbar spinal stenosis-like disorders, small compressions are sometimes observed in magnetic resonance images acquired in the recumbent position, leading to potential misdiagnosis. Few prospective studies have compared the diagnostic accuracy of MRI, myelography, and CTM. Therefore, it is not clear whether myelography is necessary or not. METHODS: Fifty-four patients fulfilled the criteria. All patients underwent MRI, myelography, and CTM. MRI was performed with the patient in a normal recumbent position, and CTM was performed with the patients in both a recumbent and extended positions. All patients underwent surgery for lumbar spinal stenosis. Findings from visual examinations (sagittal images of MR, axial images of MR, axial reconstruction images of CTM and myelograms) were defined as compression + or -. We analyzed the sensitivity of the different examinations for diagnosis and the relationship among the types of images. RESULTS: Sensitivity was as follows: CTM 94.4 %, myelography 87.0 %, and MRI 75.9 %. In myelography, the images of 37 patients were worsened by dynamic synthesis (Dyn+). Among patients without compression on MRI, 11 showed compression on myelography. Of these 11, 8 of these patients were Dyn+, and 2 patients showed compression on myelography, but not on CTM and were Dyn+. Thus, some compression can be revealed only with myelography. CTM was more sensitive than axial MRI and showed compression in 12 patients that was not detected by axial MRI. CONCLUSION: Myelography revealed stenosis that was not detected by MRI. CTM with extension is more sensitive for detecting stenosis than MRI. Recumbent MRI cannot replace myelography or CTM in terms of dynamic findings and sensitivity.
No preview · Article · Mar 2013 · European Journal of Orthopaedic Surgery & Traumatology
[Show abstract][Hide abstract] ABSTRACT: Object:
This study aimed to clarify changes in segmental instability following a unilateral approach for microendoscopic posterior decompression and muscle-preserving interlaminar decompression compared with traditional procedures and destabilized models.
An ex vivo experiment was performed using 30 fresh frozen porcine functional spinal units (FSUs). Each intact specimen was initially tested for flexion-extension, lateral bending, and torsion up to 1.5° using a material testing system at an angular velocity of 0.1°/second under a preload of 70 N. Microendoscopic posterior decompression, muscle-preserving interlaminar decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy were then performed, followed by mechanical testing with the same loading conditions, in 6 randomized FSUs from each group. Stiffness and neutral zone were standardized by dividing the experimental values by the baseline values and were then compared among groups.
Mean standardized stiffness values for all loading modes tended to decrease in the order of muscle-preserving interlaminar decompression, microendoscopic posterior decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. In contrast, mean standardized neutral zone values tended to increase in the order of muscle-preserving interlaminar decompression, microendoscopic posterior decompression, bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. In flexion, values for standardized stiffness following microendoscopic posterior decompression and muscle-preserving interlaminar decompression were higher and standardized neutral zone following microendoscopic posterior decompression and muscle-preserving interlaminar decompression were lower than the values following left unilateral total facetectomy and bilateral total facetectomy while there was no significant difference among bilateral medial facetectomy, left unilateral total facetectomy, and bilateral total facetectomy. Values of standardized stiffness and standardized neutral zone in left torsion following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy were equally superior to values of the destabilization models (left unilateral total facetectomy and bilateral total facetectomy). Except for standardized stiffness in left bending, the values of the parameters for each bending tended to be the same as in the other loading modes.
The present biomechanical study showed that overall stability of the FSUs was maintained following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy compared with the destabilization models of left unilateral total facetectomy or bilateral total facetectomy. Comparison of the postoperative stability following microendoscopic posterior decompression, muscle-preserving interlaminar decompression, and bilateral medial facetectomy revealed that muscle-preserving interlaminar decompression tended to be superior, followed by microendoscopic posterior decompression and bilateral medial facetectomy.
No preview · Article · Mar 2013 · Journal of neurosurgery. Spine
[Show abstract][Hide abstract] ABSTRACT: We examined the reliability of radiological findings in predicting segmental instability in 112 patients (56 men, 56 women) with a mean age of 66.5 years (27 to 84) who had degenerative disease of the lumbar spine. They underwent intra-operative biomechanical evaluation using a new measurement system. Biomechanical instability was defined as a segment with a neutral zone > 2 mm/N. Risk factor analysis to predict instability was performed on radiographs (range of segmental movement, disc height), MRI (Thompson grade, Modic type), and on the axial CT appearance of the facet (type, opening, vacuum and the presence of osteophytes, subchondral erosion, cysts and sclerosis) using multivariate logistic regression analysis with a forward stepwise procedure. The facet type was classified as sagittally orientated, coronally orientated, anisotropic or wrapped. Stepwise multivariate regression analysis revealed that facet opening was the strongest predictor for instability (odds ratio 5.022, p = 0.009) followed by spondylolisthesis, MRI grade and subchondral sclerosis. Forward stepwise multivariate logistic regression indicated that spondylolisthesis, MRI grade, facet opening and subchondral sclerosis of the facet were risk factors. Symptoms evaluated by the Short-Form 36 and visual analogue scale showed that patients with an unstable segment were in significantly more pain than those without. Furthermore, the surgical procedures determined using the intra-operative measurement system were effective, suggesting that segmental instability influences the symptoms of lumbar degenerative disease.
No preview · Article · May 2011 · The Bone & Joint Journal
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was, using a novel intraoperative measurement (IOM) system, to test the hypothesis that an increased facet joint volume is evidence of spinal instability.
In 29 patients (male/female ratio 13:16; mean age 67.5 years, range 43-80 years)-17 with degenerative spondylolisthesis (DS) of the lumbar spine (Group DS) and 12 with canal stenosis (CS) of the lumbar spine (Group CS)-DICOM (Digital Imaging and Communications in Medicine) data derived from CT scans were transferred to a workstation. A 3D model of facet joint spaces was reconstructed and the average volume of the bilateral facets was calculated. Segmental properties-stiffness, absorption energy (AE), and neutral zone (NZ)-were measured using an IOM system, and values were compared between groups. Linear regression analyses were performed among biomechanical parameters and average volumes.
Stiffness and AE did not differ significantly between groups. The NZ was significantly greater in Group DS than in Group CS (p < 0.05) and significantly positively correlated with the average volume (R(2) = 0.141, p < 0.05). Stiffness tended to negatively correlate with average volume. Absorption energy did not correlate with average volume.
Biomechanical analyses using the IOM system verified that an increased facet joint volume is evidence of spinal instability, represented by NZ, in the degenerative lumbar spine.
No preview · Article · Jun 2010 · Journal of neurosurgery. Spine
[Show abstract][Hide abstract] ABSTRACT: Here we investigated the biomechanical properties of spinal segments in patients with degenerative lumbar spondylolisthesis (DLS) using a novel intraoperative measurement system. The measurement system comprised spinous process holders, a motion generator, a load cell, an optical displacement transducer, and a computer. Cyclic displacement of the holders produced flexion-extension of the segment with all ligamentous structures intact. Stiffness, absorption energy (AE), and neutral zone (NZ) were determined from the load-deformation data. Forty-one patients with DLS (M/F = 15/26, mean age 68.6 years; Group D) were studied. Adjacent segments with normal discs in six patients (M/F = 3/3, mean age 35 years) were included as a control group (Group N). Flexion stiffness was significantly lower in Group D than in Group N. The NZ, however, was significantly greater in Group D than in Group N. Thus, compared to normal segments, spinal segments with DLS had a lower flexion stiffness and a higher NZ. NZs in Group D were, however, widely distributed compared to those in Group N that showed NZ <2 mm/N in all cases, suggesting that the segment with DLS is not always unstable and that the segments with NZ >2 mm/N can be considered as unstable.
Preview · Article · Apr 2009 · European Spine Journal
[Show abstract][Hide abstract] ABSTRACT: Retrospective clinical study.
To evaluate clinical results of patients with nontraumatic cervical lesions treated by cervical pedicle screw (PS) fixation and to discuss the surgical indications.
PS fixation provides an outstanding stability for cervical lesions with instability. This technique, however, has a potential risk of vertebral artery, spinal cord, and nerve root injuries, which may be catastrophic.
Fifty-eight patients were divided into 2 groups: patients with cervical kyphosis with vertebral destructive lesions (group D, n = 38) and those without destructive lesions (group ND, n = 20). Clinical results of the 2 groups were compared. The results of decompression and PS fixation for cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL) in this series were also compared with those of previous laminoplasty alone in patients with CSM and OPLL.
Nape pain in group D improved in 86.7% of the patients. Overall neurologic status was improved in both groups. Bony fusion was confirmed in 100% of the cases that were alive in group D and 95% in group ND. Eight complications including 2 vertebral artery injuries occurred. The incidence of postoperative cervical complications in group ND was significantly higher than that in group D. Although PS fixation significantly corrected cervical kyphosis and maintained in both CSM and OPLL, operation time and intraoperative blood loss in cases treated by PS were significantly higher than those treated by laminoplasty alone. Improvement of nape pain and neurologic status did not differ with and without using PS fixation.
There is an indication of cervical PS fixation for destructive lesions because of a high fusion rate with improvement of nape pain. On the other hand, there is no indication in cases of typical CSM and OPLL if a potential risk of vertebral artery or nerve injury is taken into account.
[Show abstract][Hide abstract] ABSTRACT: In vivo quantitative measurement of lumbar segmental stability has not been established. The authors developed a new measurement system to determine intraoperative lumbar stability. The objective of this study was to clarify the biomechanical properties of degenerative lumbar segments by using the new method.
Twenty-two patients with a degenerative symptomatic segment were studied and their measurements compared with those obtained in normal or asymptomatic degenerative segments (Normal group). The measurement system produces cyclic flexion-extension through spinous process holders by using a computer-controlled motion generator with all ligamentous structures intact. The following biomechanical parameters were determined: stiffness, absorption energy (AE), and neutral zone (NZ). Discs with degeneration were divided into 2 groups based on magnetic resonance imaging grading: degeneration without collapse (Collapse[-]) and degeneration with collapse (Collapse[+]). Biomechanical parameters were compared among the groups. Relationships among the biomechanical parameters and age, diagnosis, or radiographic parameters were analyzed.
The mean stiffness value in the Normal group was significantly greater than that in Collapse(-) or Collapse(+) group. There was no significant difference in the average AE value among the Normal, Collapse(-), and Collapse(+) groups. The NZ in the Collapse(-) was significantly higher than in the Normal or Collapse(+) groups. Stiffness was negatively and NZ was positively correlated with age. Stiffness demonstrated a significant negative and NZ a significant positive relationship with disc height, however.
There were no significant differences in stiffness between spines in the Collapse(-) and Collapse(+) groups. The values of a more sensitive parameter, NZ, were higher in Collapse(-) than in Collapse(+) groups, demonstrating that degenerative segments with preserved disc height have a latent instability compared to segments with collapsed discs.
No preview · Article · Apr 2008 · Journal of Neurosurgery Spine