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Yoshifumi Takahashi, Shinya Okuda, Yukitaka Nagamoto, Tomiya Matsumoto, Tsuyoshi Sugiura and Motoki Iwasaki

OBJECTIVE

Although the importance of spinopelvic sagittal balance and its implications for clinical outcomes of spinal fusion surgery have been described, to the authors’ knowledge there have been no reports of the relationship between spinopelvic alignment and clinical outcomes for 2-level posterior lumbar interbody fusion (PLIF). The purpose of this study was to elucidate the relationship between clinical outcomes and spinopelvic sagittal parameters after 2-level PLIF for 2-level degenerative spondylolisthesis (DS).

METHODS

This study was limited to patients who were treated with 2-level PLIF for 2-level DS at L3–4-5. Between 2005 and 2014, 33 patients who could be followed up for at least 2 years were included in this study. The average age at the time of surgery was 72 years, and the average follow-up period was 5.6 years. Based on clinical assessments, the Japanese Orthopaedic Association (JOA) score and recovery rate were evaluated. The patients were divided into 2 groups based on the recovery rate: the good outcome group (G group; n = 19), with recovery rate ≥ 50%, and the poor outcome group (P group; n = 14) with recovery rate < 50%. Spinopelvic parameters were measured using lateral standing radiographs of the whole spine as follows: sagittal vertical axis (SVA), thoracic kyphosis (TK), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), and segmental lordosis (SL) at L3–4-5. The clinical outcomes and radiological parameters were assessed preoperatively and at the final follow-up. Radiological parameters were compared between the 2 groups.

RESULTS

The mean JOA score improved significantly in all patients from 10.8 points before surgery to 19.6 points at the latest follow-up (mean recovery rate 47.7%). For radiological outcomes, no difference was observed from preoperative assessment to final follow-up in any of the spinopelvic parameters except SVA. Although no significant difference between the 2 groups was detected in any of the spinopelvic parameters, there were significant differences in the change in SL and LL (ΔSL 3.7° vs −2.1° and ΔLL 1.2° vs −5.6° for the G and P groups, respectively). In addition, the number of patients in the G group was significantly larger for the patients with ΔSL-plus than those with ΔSL-minus (p = 0.008).

CONCLUSIONS

The clinical outcomes of 2-level PLIF for 2-level DS limited at L3–4-5 appeared to be satisfactory. The results indicate that acquisition of increased SL in surgery might lead to better clinical outcomes.

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Yukitaka Nagamoto, Takahiro Ishii, Motoki Iwasaki, Hironobu Sakaura, Hisao Moritomo, Takahito Fujimori, Masafumi Kashii, Tsuyoshi Murase, Hideki Yoshikawa and Kazuomi Sugamoto

Object

The uncovertebral joints are peculiar but clinically important anatomical structures of the cervical vertebrae. In the aged or degenerative cervical spine, osteophytes arising from an uncovertebral joint can cause cervical radiculopathy, often necessitating decompression surgery. Although these joints are believed to bear some relationship to head rotation, how the uncovertebral joints work during head rotation remains unclear. The purpose of this study is to elucidate 3D motion of the uncovertebral joints during head rotation.

Methods

Study participants were 10 healthy volunteers who underwent 3D MRI of the cervical spine in 11 positions during head rotation: neutral (0°) and 15° increments to maximal head rotation on each side (left and right). Relative motions of the cervical spine were calculated by automatically superimposing a segmented 3D MR image of the vertebra in the neutral position over images of each position using the volume registration method. The 3D intervertebral motions of all 10 volunteers were standardized, and the 3D motion of uncovertebral joints was visualized on animations using data for the standardized motion. Inferred contact areas of uncovertebral joints were also calculated using a proximity mapping technique.

Results

The 3D animation of uncovertebral joints during head rotation showed that the joints alternate between contact and separation. Inferred contact areas of uncovertebral joints were situated directly lateral at the middle cervical spine and dorsolateral at the lower cervical spine. With increasing angle of rotation, inferred contact areas increased in the middle cervical spine, whereas areas in the lower cervical spine slightly decreased.

Conclusions

In this study, the 3D motions of uncovertebral joints during head rotation were depicted precisely for the first time.

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Yukitaka Nagamoto, Motoki Iwasaki, Hironobu Sakaura, Tsuyoshi Sugiura, Takahito Fujimori, Yohei Matsuo, Masafumi Kashii, Tsuyoshi Murase, Hideki Yoshikawa and Kazuomi Sugamoto

OBJECT

Usually additional anchors into the ilium are necessary in long fusion to the sacrum for degenerative lumbar spine disorders (DLSDs), especially for adult spine deformity. Although the use of anchors is becoming quite common, surgeons must always keep in mind that the sacroiliac (SI) joint is mobile and they should be aware of the kinematic properties of the SI joint in patients with DLSDs, including adult spinal deformity. No previous study has clarified in vivo kinematic changes in the SI joint with respect to patient age, sex, or parturition status or the presence of DLSDs. The authors conducted a study to clarify the mobility and kinematic characteristics of the SI joint in patients with DLSDs in comparison with healthy volunteers by using in vivo 3D motion analysis with voxel-based registration, a highly accurate, noninvasive method.

METHODS

Thirteen healthy volunteers (the control group) and 20 patients with DLSDs (the DLSD group) underwent low-dose 3D CT of the lumbar spine and pelvis in 3 positions (neutral, maximal trunk flexion, and maximal trunk extension). SI joint motion was calculated by computer processing of the CT images (voxel-based registration). 3D motion of the SI joint was expressed as both 6 df by Euler angles and translations on the coordinate system and a helical axis of rotation. The correlation between joint motion and the cross-sectional area of the trunk muscles was also investigated.

RESULTS

SI joint motion during trunk flexion-extension was minute in healthy volunteers. The mean rotation angles during trunk flexion were 0.07° around the x axis, −0.02° around the y axis, and 0.16° around the z axis. The mean rotation angles during trunk extension were 0.38° around the x axis, −0.08° around the y axis, and 0.08° around the z axis. During trunk flexion-extension, the largest amount of motion occurred around the x axis. In patients with DLSDs, the mean rotation angles during trunk flexion were 0.57° around the x axis, 0.01° around the y axis, and 0.19° around the z axis. The mean rotation angles during trunk extension were 0.68° around the x axis, −0.11° around the y axis, and 0.05° around the z axis. Joint motion in patients with DLSDs was significantly greater, with greater individual difference, than in healthy volunteers. Among patients with DLSDs, women had significantly more motion than men did during trunk extension. SI joint motion was significantly negatively correlated with the cross-sectional area of the trunk muscles during both flexion and extension of the trunk.

CONCLUSIONS

The authors elucidated the mobility and kinematic characteristics of the SI joint in patients with DLSDs compared with healthy volunteers for the first time. This information is useful for spine surgeons because of the recent increase in spinopelvic fusion for the treatment of DLSDs.

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Takahito Fujimori, Motoki Iwasaki, Yukitaka Nagamoto, Takahiro Ishii, Hironobu Sakaura, Masafumi Kashii, Hideki Yoshikawa and Kazuomi Sugamoto

Object

Ossification of the posterior longitudinal ligament (OPLL) is a progressive disease that causes cervical myelopathy. Because 2D evaluation of ossification growth with plain lateral radiographs has limitations, the authors developed a unique technique to measure ossification progression and volume increase by using multidetector CT scanning.

Methods

The authors used serial thin-slice volume data obtained by multidetector CT scanning in 5 patients. The mean patient age was 63 years, and the mean follow-up duration was 3.1 years. First, a 3D model of OPLL was semiautomatically segmented at a specific threshold. Then, a preoperative model of OPLL was superimposed on a postoperative model using voxel-based registration of the vertebral bodies. Progression and volume increase were measured using a digital viewer that was developed by the authors. Progression was visualized using a color-coded contour on the surface of the OPLL model.

Results

All patients had progression of 0.5 mm or greater. The mean values concerning OPLL growth were as follows: maximum progression length, 4.7 mm; progression rate, 1.5 mm/year; volume increase, 1622 mm3; volume expansion rate, 37%; and volume increase rate, 484 mm3/year. The accuracy of superimposition by voxel-based registration, defined as closeness to the true value, was less than 0.31 mm. For intraobserver reproducibility of the volume measurement, the mean intraclass correlation coefficient, root mean square error, and coefficient of variation were 0.987, 16.0 mm3, and 1.7%, respectively.

Conclusions

Ossification of the posterior longitudinal ligament progresses even after surgery. Three-dimensional evaluation with the aid of CT scans is a useful and reliable method for assessing that growth.

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Takahito Fujimori, Motoki Iwasaki, Shinya Okuda, Yukitaka Nagamoto, Hironobu Sakaura, Takenori Oda and Hideki Yoshikawa

Object

Surgical results in cervical myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) evaluated with a patient-based method have not yet been reported. The purpose of this study was to examine patient satisfaction with surgery for cervical myelopathy due to OPLL and to clarify factors related to satisfaction.

Methods

Clinical data in 103 patients (74 male and 29 female) who underwent surgery for cervical OPLL were retrospectively reviewed. The average age at surgery was 57 years, and the average follow-up period was 9.3 years. Outcomes were assessed using an original satisfaction questionnaire, the conventional Japanese Orthopaedic Association (JOA) scoring system, the JOA Cervical Myelopathy Evaluation Questionnaire, the 36-Item Short Form Health Survey, and the hospital anxiety and depression scale. Spearman rank correlation coefficients for 5-scale patient satisfaction against outcome measures were calculated to test relationships between variables. All variables were compared between the satisfied (responses of very satisfied or satisfied) and dissatisfied (responses of dissatisfied or very dissatisfied) groups. Parameters exhibiting a significant Spearman rank correlation or difference between the groups were entered in a stepwise logistic regression analysis model, with satisfaction as the dependent variable.

Results

Sixty-nine patients were included in the analysis. There was not a significant difference in clinical data between these 69 study patients and the other 34 patients. Fifty-five patients (80%) were satisfied with the results of the surgery, and 58 patients (84%) reported that their condition was improved by the surgery. All patients who reported being very improved were either very satisfied or satisfied with the results of surgery. Quality of life (QOL), physical function (PF), and role physical (RP) were significantly correlated with patient satisfaction. The dissatisfied group had significantly more severe pain; lower maximum conventional JOA scores; lower maximum recovery rates; worse lower-extremity function (LEF); reduced QOL; and lower PF, RP, and vitality scores. Stepwise logistic regression analysis showed that PF, QOL, LEF, and maximum recovery rate based on JOA score were correlated with satisfaction.

Conclusions

Eighty percent of patients were satisfied with the surgical results after treatment of cervical myelopathy due to OPLL. Surgery for cervical OPLL was effective, as evaluated by both doctor- and patient-based methods. Patient satisfaction was related to QOL, PF (especially LEF), and improvement.

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Takahito Fujimori, Motoki Iwasaki, Yukitaka Nagamoto, Masafumi Kashii, Takahiro Ishii, Hironobu Sakaura, Kazuomi Sugamoto and Hideki Yoshikawa

Object

In this paper, the authors' goals were to determine the extent of the effect of continuous-type ossification of the posterior longitudinal ligament (OPLL) of the cervical spine on intervertebral range of motion (ROM) and to examine the relationship between the 3D morphology of OPLL and intervertebral ROM.

Methods

The authors evaluated 5 intervertebral segments in each of 20 patients (11 men and 9 women) with continuous-type OPLL, for a total of 100 intervertebral segments, using functional CT in anteroposterior (AP) flexion and right and left axial rotation. Three-dimensional kinematics were evaluated using the voxel-based registration method. Ossification was classified on the basis of 3D kinematics and morphology.

Results

The authors found 49 ossifications that were obviously of the continuous type. They were divided into 2 types: 1) bridging (13 instances), with thick, continuous ossification of the anterior or posterior longitudinal ligament bridging intervertebral segments and with an ROM of 0.3° in AP flexion and 0.2° in rotation; and 2) nonbridging (36 instances), with a minute gap in the ossification itself or between the ossification and vertebra and with an ROM of 4.9° in AP flexion and 4.0° in rotation. There were 8 stalagmite-type ossifications in the nonbridging group that had the unique kinematics of restricted AP flexion and normal axial rotation.

Conclusions

The authors' findings indicate that most continuous-type ossifications that are categorized using the conventional radiographic classification system have mobile segments. The discrimination between bridging and nonbridging on CT scans can be a useful predictive index for dynamic factors.

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Tsuyoshi Sugiura, Yukitaka Nagamoto, Motoki Iwasaki, Masafumi Kashii, Takashi Kaito, Tsuyoshi Murase, Tetsuya Tomita, Hideki Yoshikawa and Kazuomi Sugamoto

Object

The upper cervical spine is commonly involved in persons with rheumatoid arthritis (RA). Although 2D measurements have long been used in the evaluation of cervical lesions caused by RA, 2D measurements are limited in their effectiveness for detecting subtle and complex morphological and kinematic changes. The purpose of this study was to elucidate the 3D kinematics of the upper cervical spine in RA and the relationship between 3D morphological changes and decreased segmental rotational motion.

Methods

Twenty-five consecutive patients (2 men and 23 women, mean age 63.5 years, range 42–77 years) with RA (the RA group) and 10 patients (5 men and 5 women, mean age 69.9 years, range 57–82 years) with cervical spondylosis and no involvement of the upper cervical spine (the control group) underwent 3D CT of the cervical spine in 3 positions (neutral, 45° head rotation to the left, and 45° head rotation to the right). The segmental rotation angle from the occiput (Oc) to C-2 was calculated for each participant using a voxel-based registration method, and the 3D destruction of articular facets was quantified using the authors' own parameter, the articular facet index.

Results

The segmental rotation angle was significantly smaller at C1–2 and larger at Oc–C1 in the RA group compared with the control group. The degree of the destruction of the articular facet at C-1 and C-2 correlated with the segmental rotation angle.

Conclusions

In vivo 3D kinematics of the upper cervical spine during head rotation in patients with RA were accurately measured, allowing quantification of the degree of joint destruction for the first time. Joint destruction may play an important role in decreasing segmental motion of the upper cervical spine in RA.

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Yukitaka Nagamoto, Motoki Iwasaki, Tsuyoshi Sugiura, Takahito Fujimori, Yohei Matsuo, Masafumi Kashii, Hironobu Sakaura, Takahiro Ishii, Tsuyoshi Murase, Hideki Yoshikawa and Kazuomi Sugamoto

Object

Cervical laminoplasty is an effective procedure for decompressing the spinal cord at multiple levels, but restriction of neck motion is one of the well-known complications of the procedure. Although many authors have reported on cervical range of motion (ROM) after laminoplasty, they have focused mainly on 2D flexion and extension on lateral radiographs, not on 3D motion (including coupled motion) nor on precise intervertebral motion. The purpose of this study was to clarify the 3D kinematic changes in the cervical spine after laminoplasty performed to treat cervical spondylotic myelopathy.

Methods

Eleven consecutive patients (6 men and 5 women, mean age 68.1 years, age range 57–79 years) with cervical spondylotic myelopathy who had undergone laminoplasty were included in the study. All patients underwent 3D CT of the cervical spine in 5 positions (neutral, 45° head rotation left and right, maximum head flexion, and maximum head extension) using supporting devices. The scans were performed preoperatively and at 6 months after laminoplasty. Segmental ROM from Oc–C1 to C7–T1 was calculated both in flexion-extension and in rotation, using a voxel-based registration method.

Results

Mean C2–7 flexion-extension ROM, equivalent to cervical ROM in all previous studies, was 45.5° ± 7.1° preoperatively and 35.5° ± 8.2° postoperatively, which was a statistically significant 33% decrease. However, mean Oc–T1 flexion-extension ROM, which represented total cervical ROM, was 71.5° ± 8.3° preoperatively and 66.5° ± 8.3° postoperatively, an insignificant 7.0% decrease. In focusing on each motion segment, the authors observed a statistically significant 22.6% decrease in mean segmental ROM at the operated levels during flexion-extension and a statistically insignificant 10.2% decrease during rotation. The most significant decrease was observed at C2–3. Segmental ROM at C2–3 decreased 24.2% during flexion-extension and 21.8% during rotation. However, a statistically insignificant 37.2% increase was observed at the upper cervical spine (Oc–C2) during flexion-extension. The coupling pattern during rotation did not change significantly after laminoplasty.

Conclusions

In this first accurate documentation of 3D segmental kinematic changes after laminoplasty, Oc–T1 ROM, which represented total cervical ROM, did not change significantly during either flexion-extension or rotation by 6 months after laminoplasty despite a significant decrease in C2–7 flexion-extension ROM. This is thought to be partially because of a compensatory increase in segmental ROM at the upper cervical spine (Oc–C2).