Mixed Reality-Based Navigation for Pedicle Screw Placement: A Preliminary Study Using a 3D-Printed Spine Model.

Background and objectives Mixed reality (MR) is one of the image processing technologies that allows the user to manipulate three-dimensional (3D) virtual images (hologram). The aim of this study was to evaluate the accuracy of MR-based pedicle screw (PS) placement using 3D spine models. Materials and methods Using the preoperative CT data of a patient with adolescent idiopathic scoliosis (AIS) who had undergone posterior spinal fusion in our hospital, a 3D-printed spine model was created. On the other hand, a 3D hologram of the same patient was automatically created using the preoperative CT data uploaded to the Holoeyes MD service website (Holoeyes Inc., Tokyo, Japan). Using a Magic Leap One® headset (Magic Leap Inc., Plantation, FL), the 3D hologram with lines of predetermined PS trajectories was superimposed onto the 3D-printed spine model and PS were inserted bilaterally along with the trajectory lines from T5 to L3. As a control, we used a readymade 3D spine model of AIS and inserted PS bilaterally with a freehand technique from T4 to L3. The rate of pedicle violation was compared between the MR-based and freehand techniques. Results A total of 22 and 24 PS were placed into the 3D-printed spine model of our patient and the readymade 3D spine model, respectively. The rate of pedicle violation was 4.5% (1/22 screws) in the MR-based technique and 29.2% (7/24 screws) in the freehand technique (P = 0.049). Conclusions We demonstrated a significantly lower rate of PS misplacement in the MR-based technique than in the freehand technique. Therefore, an MR-assisted system is a promising tool for PS placement in terms of feasibility, safety, and accuracy, warranting further studies including cadaveric and clinical studies.

Delayed paraparesis after posterior spinal fusion for congenital scoliosis: a case report.

INTRODUCTION: Although multimodal intraoperative neuromonitoring (IONM), which has high sensitivity and specificity, is typically performed during spinal deformity surgery, neurological status may deteriorate with delay after surgical maneuvers. Here, we report a rare case of delayed postoperative neurological deficit (DPND) that was not detected by IONM during posterior spinal fusion (PSF) for congenital scoliosis. CASE PRESENTATION: A 14-year-old male presented with congenital scoliosis associated with T3 and T10 hemivertebrae. Preoperative Cobb angle of proximal thoracic (PT) and main thoracic (MT) curves were 50° and 41°, respectively. PSF (T1-L1) without hemivertebrectomy was performed, and the curves were corrected to 31° and 21° in the PT and MT curves, respectively, without any abnormal findings in IONM, blood pressure, or hemoglobin level. However, postoperative neurological examination revealed complete loss of motor function. A revision surgery, release of the curve correction by removing the rods, was immediately performed and muscle strength completely recovered on the first postoperative day. Five days postoperatively, PSF was achieved with less curve correction (36° in the PT curve and 26° in the MT curve), without postoperative neurological deficits. DISCUSSION: Possible mechanisms of DPND in our patient are spinal cord ischemia due to spinal cord traction caused by scoliosis correction and spinal cord kinking by the pedicle at the concave side. Understanding the possible mechanisms of intra- and postoperative neural injury is essential for appropriate intervention in each situation. Additionally, IONM should be continued to at least skin closure to detect DPND observed in our patient.

Anatomical Pelvic Parameters Using the Anterior Pelvic Plane: Normative Values and Estimation of the Standing Sagittal Alignment in Healthy Volunteers.

Introduction: In this study, we aim to estimate the natural standing sagittal alignment in patients with adult spinal deformity (ASD), firstly by investigating the normative values of anatomical pelvic parameters based on the anterior pelvic plane (APP) in a healthy population, and to clarify the relationships between the anatomical and positional pelvic parameters in standing position. Methods: The images of biplanar slot-scanning full-body stereoradiography in 140 healthy Japanese volunteers (mean age, 39.5 years; 59.3% female) were examined. In addition to three-dimensional measurements including pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT), the APP angle (APPA; anterior tilting=positive) was measured as the angle between the APP and the vertical line using the two-dimensional lateral image. Anatomical SS and PT (aSS and aPT) were calculated as the angles of SS and PT in reference to APP. Results: The mean (range) values of APPA, aSS, and aPT were determined to be 0.7° (-16.8°/15.5°), 36.8° (18.3°/64.9°), and 13.2° (-0.6°/28.7°), respectively. Moreover, SS was found to be significantly correlated with PI and aSS, while PT was significantly correlated with PI, aSS, aPT, and body weight. Also, PT was significantly larger in females than in males. Multiple linear regression analysis deduced the following equations: SS=0.404×aSS+0.203×PI+12.463, PT=-0.391×aSS+0.774×PI+1.950×sex (male=0, female=1)-12.971, wherein aSS had the greatest effect for predicting SS among the included factors and PI had the greatest effect for predicting PT. In addition, no significant differences were noted between PT/PI and aPT/PI. Conclusions: As per the results of this study, significant correlations were noted among parameters and predicting models for positional parameters (SS and PT) using anatomical parameters (aSS and aPT) in a healthy population. This novel measurement concept based on the APP has been considered to be useful in estimating natural SS and PT in standing position using the anatomical pelvic parameters in patients with ASD.

Gait Analysis by the Severity of Gait Disturbance in Patients with Compressive Cervical Myelopathy.

Introduction: Gait disturbance due to compressive cervical myelopathy has been previously described. However, data on how gait disturbance varies with the degree of lower extremity motor impairment are limited. Therefore, we investigated the characteristics of gait analysis based on severity and determined how gait disturbance progresses in compressive cervical myelopathy. Methods: We enrolled 44 patients (32 men and 12 women; mean age, 65.0 years) out of 108 consecutive patients with compressive cervical myelopathy who underwent spinal cord decompression surgery in our hospital. The exclusion criteria were inability to gait and complications affecting gait. Twenty-two patients with Japanese Orthopaedic Association scores 1 or 2 for lower extremity motor functions were assigned to the severe group, and 22 patients who scored 3 or 4 were assigned to the moderate group. Gait analysis was performed preoperatively using a long thin-type sensor sheet, and 25 healthy volunteers were assigned to the control group. Results: Stride length, swing phase, and gait speed decreased whereas step angle, stance phase, and double support duration increased as myelopathy progressed. Step width was significantly larger in the severe group than in the moderate and control groups. The cutoff values based on severe myelopathy with the inability to ascend or descend stairs without support were 60% for the stride length percentage of body height and 100 cm/s for gait speed. Conclusions: Decreases in stride length, swing phase, and gait speed and increases in step angle, stance phase, and double support duration are compensatory changes as cervical myelopathy progresses. Step width is a compensatory change that is not significantly altered in moderate myelopathy but increases when gait becomes affected, such that the patient cannot ascend or descend stairs without support.

Characteristics of back pain in patients with adolescent idiopathic scoliosis: Considerations in candidates for corrective surgery.

BACKGROUND: Previous studies have demonstrated that the point prevalence of back pain ranges from 12 % to 33 % and that the lifetime prevalence of back pain ranges from 28 % to 51 % in adolescents. However, few studies on back pain in patients with Adolescent idiopathic scoliosis (AIS) have been conducted, and these studies had significant limitations, including a lack of comparative controls and detailed information about scoliotic deformity or pain location. This study aimed to determine whether adolescents with AIS experience back pain in specific regions. METHODS: This retrospective case-control study included 189 female adolescents with AIS who underwent corrective fusion from 2008 to 2020. Questionnaires on back pain and health-related quality of life (HRQOL) using the Scoliosis Research Society Outcomes Instrument-22 (SRS-22) were conducted preoperatively. The control group included 2909 general female adolescents. RESULTS: The mean Cobb angles in the main thoracic and thoracolumbar/lumbar curves were 51.4 ± 15.3° and 40.4 ± 12.9°. Back pain characteristics included higher point prevalence (25.9 %) and lifetime prevalence (64.6 %) compared to healthy controls. Adolescents with back pain showed lower scores in the pain and mental health domains of the SRS-22. Adolescents with major thoracic AIS showed more back pain in the upper and middle right back compared to adolescents with major thoracolumbar/lumbar AIS. CONCLUSION: The point and lifetime prevalence of back pain were definitely higher in patients with AIS, which affected their HRQOL. There was a relationship between pain around the right scapula and the right major thoracic curve with a rib hump deformity.

Usefulness and limitations of intraoperative pathological diagnosis using frozen sections for spinal cord tumors.

BACKGROUND: Intraoperative pathological diagnosis has a major influence on the intra- and postoperative management of spinal cord tumors. Thus, the aim of this study was to assess the reliability of intraoperative pathological diagnosis for spinal cord lesions by comparing it with the final pathological diagnosis and to determine its usefulness and limitations. METHOD: Three-hundred and three consecutive patients (mean age, 53.9 years) with neoplastic spinal cord lesions who underwent initial surgery between 2000 and 2021 were included. The anatomical locations of the spinal cord tumors and the implementation rate of intraoperative pathological diagnosis in each tumor type were evaluated. As the primary outcome, we determined the concordance rates between the intraoperative pathological diagnosis and the final diagnosis. When the intraoperative pathological diagnosis and final diagnosis were the same, the diagnosis was defined as a "match." Otherwise, the diagnosis was defined as a "mismatch." RESULTS: The overall implementation rate of intraoperative pathological diagnosis was 53%, with implementation rates of 71%, 45%, 47%, and 50% for intramedullary, intradural extramedullary, extradural, and dumbbell tumors, respectively. The overall concordance rate was 87.6%, with concordance rates of 80%, 95%, 75%, and 90% for intramedullary, intradural extramedullary, extradural, and dumbbell tumors, respectively (p < 0.05). The diagnoses of ependymomas, low-grade astrocytomas, and high-grade astrocytomas was occasionally difficult among intramedullary tumors. Among intradural extramedullary tumors, differentiation between grade 1 meningioma and high-grade meningioma was difficult using intraoperative pathological diagnosis. CONCLUSIONS: Surgeons must recognize the lower accuracy of intraoperative pathological diagnosis for intramedullary and extradural lesions and make a final decision by considering the intraoperative gross findings, preoperative clinical course, and imaging.

Marriage and childbirth of patients who were surgically and non-surgically treated for adolescent idiopathic scoliosis: a survey at the age of 30 years or older.

PURPOSE: We aimed to investigate the marital status and childbirth in adolescent idiopathic scoliosis (AIS) patients. METHODS: This study included women who were treated surgically or non-surgically for AIS with a scoliosis magnitude ≥ 30° before surgery or at skeletal maturity and were followed up until age 30 years or older. Patients were divided into surgically treated (S-AIS, n = 55) and non-surgically treated AIS groups (N-AIS, n = 86). Data from the national fertility survey were used as control values. RESULTS: There were no significant differences in age at the final follow-up between the S- (40.7 years) and N-AIS (42.1 years) groups. The unmarried rate among all women and the nulliparous rate among married women in the S-AIS group (29.1% and 18.4%, respectively) were similar to those in the N-AIS group (26.7% and 16.1%, respectively). The mean number of children per married woman also did not differ between the S- and N-AIS groups (1.5 vs 1.4). Compared to the control group, after adjusting for age, the common odds ratio in the AIS group was 1.56 (p = 0.031) for unmarried status and 1.88 (p = 0.026) for nulliparity among married women. Moreover, the mean number of children per married woman was significantly lower in the AIS group than in the control group (1.3 vs 1.7, p < 0.001). CONCLUSION: Surgically and non-surgically treated women with AIS had a similar status with regard to marriage and childbirth, while women with AIS were more likely to be unmarried and nulliparous and to have fewer children compared to the nationwide population.

Evaluating flexibility and predicting curve correction using fulcrum-bending radiographs in Lenke type 2 adolescent idiopathic scoliosis.

BACKGROUND: Fulcrum-bending (FB) correction is considered to provide the best estimation of main thoracic (MT) curve flexibility and postoperative correction in surgical treatment for adolescent idiopathic scoliosis (AIS). However, few studies evaluated the usefulness of FB radiographs for proximal thoracic (PT) curve. We aimed to perform flexibility assessments using both active side-bending (SB) and FB radiographs and evaluate surgical outcomes after posterior spinal fusion (PSF) for Lenke type 2 AIS. METHODS: This study included 38 consecutive patients with Lenke type 2 AIS who underwent PSF using a pedicle screw construct with a minimum 2-year follow-up. Radiographic parameters, including correction rate, SB and FB flexibility, and FB correction index (FBCI: [correction rate/FB flexibility] × 100), were evaluated preoperatively, immediately after surgery, and at the 2-year follow-up. The clinical outcomes were preoperatively evaluated using the Scoliosis Research Outcomes Instrument-22 and at the follow-up. RESULTS: All scoliosis curves significantly improved and shoulder balance shifted toward left shoulder elevation (all comparisons, p < 0.0001). There were significant differences between the SB and FB corrections in the PT and MT curves (p < 0.0001). The magnitudes of the discrepancies between the SB and FB corrections in the PT and MT curves were 11.2° ± 5.2° and 11.6° ± 7.2°, respectively. FB correction did not differ from postoperative Cobb angles correction immediately after surgery or at the 2-year follow-up; the mean FBCIs in the PT and MT curves were 98.8% and 105.5%, respectively. The self-image domain SRS-22 scores had significantly increased at the 2-year follow-up (p < 0.0001). CONCLUSIONS: There were significant differences between the SB and FB corrections, and FB correction tended to approximate the postoperative curve correction (FBCI = 100%) for PT and MT curves in patients with Lenke type 2 AIS. FB flexibility is more reliable than SB flexibility in evaluating actual curve flexibility even for the PT curve.

Axial Neck-Shoulder Pain After Posterior Correction and Fusion for Adolescent Idiopathic Scoliosis With Structural Thoracic Curve: Does Cranial Fusion Level Affect Neck Symptoms?

STUDY DESIGN: A retrospective cohort study using prospectively collected data. OBJECTIVES: To investigate the incidence and impact of fusion to the upper thoracic spine on neck-shoulder symptoms after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Axial neck-shoulder pain is established as a sequela of posterior cervical spine surgery and is mainly caused by the dissection of extensor muscles in the cervical and upper thoracic spine. MATERIALS AND METHODS: Sixty-three female patients with AIS who underwent PSF using segmental pedicle screw constructs for structural main thoracic curve with a minimum 2-year follow-up were included. Axial neck-shoulder pain was assessed using the visual analog scale and cervical spine function domain score of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire. The patients were divided into 2 groups, a higher group (underwent fusion up to T3 or above, n=27) and a lower group (underwent fusion up to T4 or below, n=36), and radiologic and clinical outcomes were compared. RESULTS: The incidence of axial neck-shoulder pain (visual analog scale ≥30) preoperatively and at the 2-year follow-up was 29 and 40%, respectively. The pain and mental health domains of the Scoliosis Research Society-22 and cervical spine function domain of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire were correlated with the severity of axial neck pain. In the comparison of clinical outcomes between the 2 groups, the pain domain score of the Scoliosis Research Society-22 in the lower group was significantly better than that in the higher group at the 2-year follow-up ( P <0.05). Other parameters showed no significant differences preoperatively or at the 2-year follow-up. CONCLUSION: Female patients with AIS had a relatively high incidence of axial neck-shoulder pain after PSF, which affected their health-related quality of life. Both groups showed similar clinical outcomes, and the cranial fusion level did not affect axial neck-shoulder pain and cervical spine function. LEVEL OF EVIDENCE: Level 3.

Impact of L4/5 Posterior Interbody Fusion With or Without Decompression on Spinopelvic Alignment and Health-related Quality-of-Life Outcomes.

STUDY DESIGN: This was a retrospective case control study. OBJECTIVE: The objective was to determine the impact of single-level interbody fusion at L4/5 with or without concomitant decompression on various spinopelvic parameters and health-related quality-of-life (HRQOL) outcomes. SUMMARY OF BACKGROUND DATA: Recently, focus has swayed from a regional concern to a global sagittal alignment, more comprehensive approach in multilevel, corrective fusion for adult spinal deformity. However, only a few comprehensive studies have investigated the relationships between the various related spinopelvic parameters and HRQOL outcomes using single-level interbody fusion. MATERIALS AND METHODS: In total, 119 patients with lumbar degenerative disorders (mean age, 68 y; 38 males and 81 females) who underwent L4/5 single-level posterior interbody fusion with a minimum 2-year follow-up were included. Participants were divided into 2 groups according to preoperative sagittal modifiers of the SRS-Schwab adult spinal deformity classification. The correlation between spinopelvic parameters and HRQOL outcomes was investigated. Negative or positive values indicated lordosis. HRQOL outcomes were assessed using visual analog scale scores, Japanese Orthopedic Association Back Pain Evaluation Questionnaires (JOABPEQ), and short form-36 (SF-36). RESULTS: L4/5 local lordosis increased from 6.4±4.4 degrees preoperatively to 11.3±4.5 degrees at 2 years postoperatively (P<0.0001). Further analysis of the results also showed a correlation between change in L4/5 local lordosis and change in lumbar lordosis (LL) (rs=0.229, P=0.0143). The high pelvic incidence-LL (≥20 degrees, n=28) and high sagittal vertical axis groups (≥5 cm, n=29) had lower scores in walking ability, social life domains of JOABPEQ, and physical component summary scores of SF-36 preoperatively, and 2 years postoperatively. Fusion status did not affect the HRQOL outcomes, except that concomitant decompression at the adjacent disk level yielded lower SF-36 physical component summary scores 2 years postoperatively. CONCLUSIONS: Improvement in L4/5 local lordosis possibly triggers a simultaneous sequence of change in total LL after posterior single-level fusion. HRQOL outcomes were negatively affected by both preoperative and postoperative pelvic incidence-LL mismatch and global sagittal malalignment. LEVEL OF EVIDENCE: Level III.

Rib Hyperostosis as a Risk Factor for Poor Prognosis in Cervical Spine Injury Patients With Diffuse Idiopathic Skeletal Hyperostosis.

STUDY DESIGN: Retrospective multi-center study. OBJECTIVE: To identify the morphological features of costovertebral joints and ribs in surgically managed cervical injury patients with diffuse idiopathic skeletal hyperostosis (DISH) and to examine its impact on their vital prognosis. SUMMARY OF BACKGROUND DATA: Several reports have indicated that DISH is an independent risk factor for mortality after spinal fracture. The reason for the high mortality in cervical injury patients with DISH is unclear, although some reports have suggested a possible association between pulmonary complications and mortality. METHODS: From 1999 to 2017, a total of 50 DISH patients (44 males) with cervical spine injuries who underwent spinal surgery were enrolled (average age 74 yrs). Prognosis and clinical risk factor data were collected; the morphological features of the patients' costovertebral joints and ribs were evaluated with computed tomography. The influence of each proposed risk factor and thoracic morphological feature on mortality was tested with univariate and multivariate analyses. RESULTS: The survival rate at 5 years after surgery was 52.3%. Nineteen (38%) patients died, and the most common cause of death was pneumonia (68%). Costovertebral bone excrescences and rib hyperostosis were found to be thoracic pathognomonic signs; their frequencies were 94% and 82%, respectively, and these conditions occurred in an average of 7.0 joints and 4.7 bones, respectively. The results of the log-rank test showed a significant difference in age, injury severity score (ISS), costovertebral bone excrescences, and rib hyperostosis. The results of age-adjusted multivariate analysis indicated that age (hazard ratio [HR] = 8.65, 95% confidence interval [CI] = 1.10-68.28, P = 0.041) and rib hyperostosis (HR = 3.82, 95% CI = 1.38-10.57, P = 0.010) were associated with mortality. CONCLUSION: Reduced chest wall mobility associated with rib hyperostosis in cervical spine injury patients with DISH leads to a poor prognosis. LEVEL OF EVIDENCE: 3.

Quantitative radiographic analysis of foraminal re-stenosis after posterior cervical foraminotomy with laminoplasty.

Few studies have performed detailed radiographic evaluation of the cause of recurrent cervical radiculopathy. In this study, we aimed to perform quantitative analyses of foraminal re-stenosis after posterior cervical foraminotomy (PCF) concomitant with laminoplasty. Seventy-eight consecutive patients (50 males and 28 females, mean age of 62 years at surgery) with cervical spondylotic radiculomyelopathy who underwent PCF concomitant with open-door laminoplasty were included. A total of 133 foramina undergoing PCF were radiographically evaluated using the following parameters: disc height, focal range of motion at the corresponding disc level, foraminal diameter (FD) and facet joint width (FJW) in the axial view on computed tomography, and re-stenosis rate (RR) of foramina. RR was calculated as follows: (foraminal regrowth at 2 years after surgery)/(foraminal enlargement immediate postoperatively) × 100% (RR2y). FDs preoperatively, postoperatively, and at 2-year follow-up were 2.2, 6.6, and 4.6 mm, respectively, and FJWs were 14.5, 9.0, and 10.6 mm, respectively. Both parameters significantly increased at the 2-year follow-up (p < 0.001). The mean RR2y was 42% (range, -16 to 108%). On logistic regression analysis of risk factors for higher RR2y (>50%), only preoperative posterior disc height (PDH) (OR = 0.33; 95% CI = 0.193-0.563; p < 0.001) was identified. Receiver operating characteristic curve analysis showed that the cut-off value of RR2y 50% was 1-mm PDH (AUC 0.73, sensitivity 52%, specificity 86%, p value < 0.001). After posterior foraminotomy with laminoplasty, the enlarged foraminal space gradually decreased during the 2-year follow-up. Foraminal re-stenosis was mainly due to bone regrowth of the resected facet joint, which is caused by disc degeneration with loss of PDH.