Significance of long corrective fusion to the ilium for physical function in patients with adult spinal deformity.

BACKGROUND: We aimed to investigate the impact of long corrective fusion to the ilium on the physical function in elderly patients with adult spinal deformity and its correlation with spinopelvic parameters and health-related quality of life outcomes. METHODS: We included 60 female patients who underwent long corrective fusion from T9 or T10 to the pelvis for adult spinal deformities (mean age of 69.8 years, range 55-78 years). The radiographic parameters, health-related quality of life outcomes using the Scoliosis Research Society Outcome Instrument-22 and physical function assessments were reviewed preoperatively and at 1-year postoperatively. RESULTS: All spinopelvic parameters, except for thoracolumbar kyphosis, and all domains of the Scoliosis Research Society Outcome Instrument-22 significantly improved at 1-year postoperatively (p < 0.0001). Physical function results, including those for one-leg standing time, timed up-and-go test, and 6-min walk tests, significantly improved at 1-year postoperatively (p < 0.005). Based on forward stepwise multivariate logistic regression, the predicted timed up-and-go test and 6-min walk test outcomes at 1-year postoperatively were as follows: timed up-and-go test, 7.8 + 0.47 × preoperative timed up-and-go test - 0.21 × 1-year postoperative grasping power +0.015 × 1-year postoperative C1 sagittal vertical axis (R2 = 0.6209, p < 0.0001); 6-min walk test, 309.2-9.1 × body mass index + 11.6 × 1-year postoperative grasping power + 3.3 × 1-year postoperative thoracolumbar kyphosis - 0.59 × 1-year postoperative C1 sagittal vertical axis (R2 = 0.4409, p < 0.0001). CONCLUSIONS: Corrective long fusion surgery for adult spinal deformity in normalizing sagittal alignment improves trunk balance and gait performance. Postoperative physical function depends on the preoperative physical performance status and skeletal muscle status; thus, preoperative interventions for improved physical function are recommended.

Relative position of sacral base in the pelvis and its correlation with spino-pelvic parameters.

PURPOSE: To investigate the relationship between relative location of the sacral base and spinal alignment in standing healthy adult volunteers. METHODS: One hundred seventy-two volunteers (men = 83, mean age = 39.3 years [20-70], women = 89, mean age = 39.6 years [20-62]) with no history of spinal disease were imaged using a low-dose biplanar slot-scanning 3D X-ray imaging system. A circle was drawn around three points: cranial vertex of the iliac crest (A), caudal vertex of the ischium (B), and anterior vertex of the pubis. Pelvic height (PH) was defined as the diameter (A-B). A tangent line perpendicular to PH (C) was drawn by passing through (A). Sacral height (SH) was defined as the distance between (C) and the center of the sacral base parallel to PH. Relative SH (rSH) was calculated as SH/PH × 100. RESULTS: Mean (SD) rSH was 18.3 ± 3.2 (men 20.0 ± 2.9, women 16.7 ± 2.6). rSH significantly positively correlated with thoracic kyphosis (r = 0.20, p < 0.05), lumbar lordosis (r = 0.28, p < 0.05), pelvic incidence (r = 0.28, p < 0.05), and sacral slope (r = 0.32, p < 0.0001), and significantly negatively correlated with pelvic thickness (r = - 0.66, p < 0.0001). rSH did not correlate with pelvic tilt. CONCLUSION: The center of the sacral base is normally located 3.8 ± 0.8 cm caudal to the cranial vertex of the iliac crest. The sacral base was located more caudally in men than in women, regardless of age. The more caudal the sacral base, the angle of the spino-pelvic parameters (TK, LL, PI, SS) progressively increases along with a decrease in the sacro-acetabular distance (Pth). Pelvic tilt did not correlate with the location of the sacrum.

Etiology and clinical manifestations of double-level versus single-level lumbar degenerative spondylolisthesis.

BACKGROUND: The differences in etiology, clinical manifestation, and whole body standing alignment between single-level LDS (sLDS) and double-level LDS (dLDS) have not been sufficiently clarified. We hypothesized that the etiology and manifestations of dLDS differ from those of sLDS. This study aimed to test this hypothesis. METHODS: A total of 112 cases with sLDS, 25 cases with dLDS, and 50 healthy volunteers as a normal control were enrolled in the study. Following the data collection on demographic and Health-related quality of life (HRQOL) by ODI and SRS-22, radiologic measurement by EOS system and MRI examination including lumbar spinal stenosis (LSS), facet angle, and segmental instability defined by facet opening were performed. All the parameters were compared among the groups. Correlations among radiologic parameters and HRQOL were analyzed. Risk factors for sLDS and dLDS were investigated respectively using multivariate logistic analysis. RESULTS: Age is the most important etiologic factor of sLDS; whereas high PI, age, and sagittally oriented facet joints are the important factors for dLDS. HRQOL significantly correlates with sagittal alignment. HRQOL does not, however, significantly differ between patients with sLDS and dLDS. Although the mean value of %slip was higher in the dLDS group than in the sLDS group, the difference was not statistically significant. %slip positively correlated with the PI. The number of spinal stenoses (LSS) per patient is significantly higher in patients with dLDS than in patients with sLDS. The HRQOL does not, however, correlate with the number of LSS. CONCLUSIONS: Age is the most important etiologic factor of sLDS; whereas high PI, age, and sagittally oriented facet joints are the important factors for dLDS. HRQOL does not significantly differ between patients with sLDS and dLDS. Number of LSS is significantly higher in dLDS than in sLDS without statistical difference in terms of HRQOL outcome.

Correction surgery for adult spinal deformity improves not only spinopelvic alignment but also the three-dimensional alignment of the lower extremities.

BACKGROUND: It is well known that correction surgery for adult spinal deformity (ASD) improves sagittal and coronal spinopelvic alignment, but the surgery effect on lower extremities (LE) is not well clarified. The aim of this study was to test the hypothesis that LE alignment also improves following spinopelvic correction surgery for ASD as a function of compensatory mechanism, and to clarify an effect of the severity of knee osteoarthritis (OA) on the improvement. METHODS: We retrospectively evaluated spinopelvic alignment, hip knee ankle angle (HKA), knee flexion angle (KF), and severity of the knee OA in thirty-nine patients with ASD before, two weeks and three months after the surgery. The grade of knee OA was evaluated by Kellgren Lawrence grading, and classified grade 0 to 2 into mild, and 3, 4 into severe OA. All the values were compared by paired t test or Wilcoxon signed rank test with significant p value of <0.05. RESULTS: Following the surgery, not only spinopelvic, but also bilateral HKA and KF were significantly improved. HKA in mild OA side was more normalized compared to that in severe side. Although KF of both bilateral mild and bilateral severe OA groups improved, the improvement of mild group was more significant. CONCLUSION: The 3D alignment of LE improved following spinopelvic correction surgery. The improvement was inadequate in cases with severe knee OA.

Lumbar lordosis does not correlate with pelvic incidence in the cases with the lordosis apex located at L3 or above.

PURPOSE: To test the hypothesis that the relationship between PI and L1-S1 lumbar lordosis (LL) is always positive, even in cases with different lumbar sagittal profiles. METHODS: Standing whole-spine sagittal alignment was measured with EOS system in 100 healthy adults (46 men, 54 women, mean age 40.9 years). The apex of lumbar lordosis was defined as the most anterior lumbar vertebra or intervertebral disk from the gravity line determined by a force plate measurement. Subjects were stratified into three groups: the upper group with an apex between L1 and L3 (UppA, n = 19), the middle group with an apex from L3/4 to L4/5 (MidA, n = 67), and the lower group with an apex at L5 or below (LowA, n = 14). PI, PT, SS, thoracic kyphosis (TK), LL, SVA, T1 pelvic angle, and knee flexion angle were compared between the groups. The correlation between LL and PI in each group was also compared. RESULTS: PI and SS differed significantly between the three groups, and LL was significantly different between LowA and MidA and UppA. TK and KF did not differ significantly between groups. LL and PI were significantly positively correlated in the MidA and LowA groups, but not in the UppA group. CONCLUSION: Contrary to the hypothesis, the correlation coefficient between PI and LL was not significant in the cases with apex above L3, suggesting that the relationship between PI and LL is not always constant, and whole sagittal alignment should be taken into account. These slides can be retrieved under Electronic Supplementary Material.

Standing sagittal alignment of the whole axial skeleton with reference to the gravity line in humans.

Human beings stand upright with the chain of balance beginning at the feet, progressing to the lower limbs (ankles, knees, hip joints, pelvis), each of the spinal segments, and then ending at the cranium to achieve horizontal gaze and balance using minimum muscle activity. The details of the alignment and balance of the chain, however, are not clearly understood, due to the lack of information regarding the three-dimensional (3D) orientation of all bony elements in relation to the gravity line (GL). We performed a clinical study to clarify the standing sagittal alignment of whole axial skeletons in reference to the GL using the EOS slot-scanning 3D X-ray imaging system with simultaneous force plate measurement in a healthy human population. The GL was defined as a vertical line drawn through the centre of vertical pressure measured by the force plate. The present study yielded a complete set of physiological alignment measurements of the standing axial skeleton from the database of 136 healthy subjects (a mean age of 39.7 years, 20-69 years; men: 40, women: 96). The mean offset of centre of the acoustic meati from the GL was 0.0 cm. The offset of the cervical and thoracic vertebrae was posterior to the GL with the apex of thoracic kyphosis at T7, 5.0 cm posterior to the GL. The sagittal alignment changed to lordosis at the level of L2. The apex of the lumbar lordosis was L4, 0.6 cm anterior to the GL, and the centre of the base of the sacrum (CBS) was just posterior to the GL. The hip axis (HA) was 1.4 cm anterior to the GL. The knee joint was 2.4 cm posterior and the ankle joint was 4.8 cm posterior to the GL. L4-, L5- and the CBS-offset in subjects in the age decades of 40s, 50s and 60s were significantly posterior to those of subjects in their 20s. The L5- and CBS-offset in subjects in their 50s and 60s were also significantly posterior to those in subjects in their 30s. HA was never posterior to the GL. In the global alignment, there was a positive correlation between offset of C7 vertebra from the sagittal vertical axis (a vertical line drawn through the posterior superior corner of the sacrum in the sagittal plane) and age, but no correlation was detected between the centre of the acoustic meati-GL offset and age. Cervical lordosis (CL), pelvic tilt (PT), pelvic incidence, hip extension, knee flexion and ankle dorsiflexion increased significantly with age. Our results revealed that aging induces trunk stooping, but the global alignment is compensated for by an increase in the CL, PT and knee flexion, with the main function of CL and PT to maintain a horizontal gaze in a healthy population.

Normative values of spino-pelvic sagittal alignment, balance, age, and health-related quality of life in a cohort of healthy adult subjects.

PURPOSE: To elucidate the normative values of whole body sagittal alignment and balance of a healthy population in the standing position; and to clarify the relationship among the alignment, balance, health-related quality of life (HRQOL), and age. METHODS: Healthy Japanese adult volunteers [n = 126, mean age 39.4 years (20-69), M/F = 30/96] with no history of spinal disease were enrolled in a cross-sectional cohort study. The Oswestry Disability Index (ODI) questionnaire was administered and subjects were scanned from the center of the acoustic meati (CAM) to the feet while standing on a force plate to determine the gravity line (GL), and the distance between CAM and GL (CAM-GL) was measured in the sagittal plane. Standard X-ray parameters were measured from the head to the lower extremities. ODI was compared among age groups stratified by decade. Correlations were investigated by simple linear regression analysis. Ideal lumbar lordosis was investigated using the least squares method. RESULTS: The present study yielded normative values for whole standing sagittal alignment including head and lower extremities in a cohort of 126 healthy adult volunteers, comparable to previous reports and thus a formula for ideal lumbar lordosis was deduced: LL = 32.9 + 0.60 × PI - 0.23 × age. There was a tendency of positive correlation between McGregor slope, thoracic kyphosis, PT, and age. SVA, T1 pelvic angle, sacrofemoral angle, knee flexion angle, and ankle flexion angle, but not CAM-GL, increased with age, suggesting that the spinopelvic alignment changes with age, but standing whole body alignment is compensated for to preserve a horizontal gaze. ODI tended to increase from the 40s in the domain of pain intensity, personal care, traveling, and total score. ODI weakly, but significantly positively correlated with age and PI-LL. CONCLUSION: Whole body standing alignment even in healthy subjects gradually deteriorates with age, but is compensated to preserve a horizontal gaze. HRQOL is also affected by aging and spinopelvic malalignment.

Can recumbent magnetic resonance imaging replace myelography or computed tomography myelography for detecting lumbar spinal stenosis?

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.

Biomechanical evaluation of segmental instability in degenerative lumbar spondylolisthesis.

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.

Evaluation of lumbar segmental instability in degenerative diseases by using a new intraoperative measurement system.

OBJECT: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Lumbar degenerative spondylolisthesis is not always unstable: clinicobiomechanical evidence.

STUDY DESIGN: A clinicobiomechanical study. OBJECTIVE: To clarify the clinicobiomechanical characteristics of a segment with lumbar degenerative spondylolisthesis (LDS) using an original intraoperative measurement system. SUMMARY OF BACKGROUND DATA: 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]). METHODS: 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. RESULTS: 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. CONCLUSION: 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. LEVEL OF EVIDENCE: N/A.

Biomechanical evaluation of destabilization following minimally invasive decompression for lumbar spinal canal stenosis.

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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Facet joint opening in lumbar degenerative diseases indicating segmental instability.

OBJECT: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Indications for cervical pedicle screw instrumentation in nontraumatic lesions.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: To evaluate clinical results of patients with nontraumatic cervical lesions treated by cervical pedicle screw (PS) fixation and to discuss the surgical indications. SUMMARY OF BACKGROUND DATA: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.