What is the Difference in Morphologic Features of the Thoracic Pedicle Between Patients With Adolescent Idiopathic Scoliosis and Healthy Subjects? A CT-based Case-control Study

Analysis of accuracy of pedicle screw placement in dysplastic pedicles in adolescent idiopathic scoliosis using the pedicle expansion technique with CT-based navigation

BACKGROUND

This study aimed to study the accuracy of pedicle screw (PS) insertion into dysplastic pedicles in adolescent idiopathic scoliosis (AIS) comparing cannulated screw using the pedicle expansion technique (PET) versus conventional technique.

METHODS

Forty-two AIS patients with 766 PSs were evaluated. In total, 236 screws were inserted into dysplastic pedicles: 138 and 98 screws were inserted using the PET (PET group) and standard technique (conventional group), respectively. Both methods used CT-based navigation to determine the insertion point. In the PET, a rigid ball tip feeler was tapped with a mallet to create an insertion route, a guide wire was passed through the tap, the pedicle was enlarged, and then a cannulated PS with a diameter of 4.35 mm was inserted. Postoperative CT was used to compare the accuracy of PS insertion.

RESULTS

In total, 23/236 (9.7%) perforations occurred. Regarding overall perforation, there were six (4.3%) and 17 (17.3%) cases in the PET and conventional group, respectively (P = 0.008). In terms of medial perforation, the PET group (n = 2, 1.4%) was significantly better than the conventional group (n = 7, 7.1%) (P = 0.021). In terms of lateral perforation, the PET group (n = 4, 2.9%) was significantly better than conventional group (n = 10, 10.2%) (P = 0.030). Only grade 1 perforation had occurred in the PET group, whereas grades 2 and 3 perforation occurred in the conventional group.

CONCLUSION

Use of the PET with CT-based navigation significantly increased the accuracy and safety of PS insertion in dysplastic pedicles in AIS.

Are the Spinal Changes in the Course of Scoliogeny Primary but Secondary?

In this opinion article, there is an analysis and discussion regarding the effects of growth on the spinal and rib cage deformities, the role of the rib cage in scoliogeny, the lateral spinal profile in adolescent idiopathic scoliosis (AIS), the genetics and epigenetics of AIS, and the interesting and novel field investigating the sleep impact at nighttime on AIS in relation to the sequence of the scoliogenetic changes in scoliotics. The expressed opinions are mainly based on the published peer-reviewed research of the author and his team of co-authors. Based on the analysis noted above, it can be postulated that the vertebral growth changes in the spine during initial idiopathic scoliosis (IS) development are not primary-intrinsic but secondary changes. The primary cause starting the deformity is not located within the vertebral bodies. Instead, the deformations seen in the vertebral bodies are the secondary effects of asymmetrical loads exerted upon them, due to muscular loads, growth, and gravity.

Freehand power-assisted pedicle screw placement in scoliotic patients: results on 5522 consecutive pedicle screws

Pedicle screws is the current gold standard in spine surgery, achieving a solid tricolumnar fixation which is unreachable by wires and hooks. The freehand technique is the most widely adopted for pedicle screws placing. While freehand technique has been classically performed with manual tools, there has been a recent trend toward the use of power tools. However, placing a pedicle screw remains a technically demanding procedure with significant risk of complications. The aim of this article is to retrospectively evaluate safety and accuracy of free-hand power-assisted pedicle screw placement in a cohort of patients who underwent correction and fusion surgery for scoliosis (both idiopathic and non-idiopathic) in our department. A retrospective review of all patients with scoliosis who underwent surgery and received a postoperative CT scan in our department in a 9-year period was undertaken. Screw density, number and location of pedicle screws were measured using pre and postoperative full-length standing and lateral supine side-bending radiographs. Then, postoperative CT scan was used to assess the accuracy of screw placement according to Gertzbein-Robbins scale. Malpositioned screws were divided according to their displacement direction. Finally, intra and postoperative neurological complications and the need for revision of misplaced screws were recorded. A total of 205 patients were included, with a follow-up of 64.9 ± 38.67 months. All constructs were high density (average density 1.97 ± 0.04), and the average number of fusion levels was 13.72 ± 1.97. A total of 5522 screws were placed: 5308 (96.12%) were grade A, 141 (2.5%) grade B, 73 (1.32%) grade C. Neither grade D nor grade E trajectories were found. The absolute accuracy (grade A) rate was 96.12% (5308/5522) and the effective accuracy (within the safe zone, grade A + B) was 98.6% (5449/5522). Of the 73 misplaced screws (grade C), 59 were lateral (80.80%), 8 anterior (10.95%) and 6 medial (8.22%); 58 were in convexity, while 15 were in concavity (the difference was not statistically significant, p = 0.33). Intraoperatively, neither neurological nor vascular complications were recorded. Postoperatively, 4 screws needed revision (0.072% of the total): Power-assisted pedicle screw placing may be a safe an accurate technique in the scoliosis surgery, both of idiopathic and non-idiopathic etiology. Further, and higher quality, research is necessary in order to better assess the results of this relatively emerging technique.

Is the morphology of the apical pedicles influenced by apical rotation or the coronal curve magnitude in adolescent idiopathic scoliosis?: a radiographic assessment

INTRODUCTION

Asymmetry in pedicle anatomy is most distinctly noted around the apex of the curve. The correlation of pedicle dysmorphia with apical vertebral rotation (AVR) and coronal Cobb angle (CCA) has not been studied.

OBJECTIVE

To establish whether pedicle dysmorphism is linked to curve magnitude CCA and the AVR in adolescent idiopathic scoliosis (AIS).

METHODOLOGY

Preoperative plain whole spine standing radiographs and non-contrast computed tomography (CT) scans of 25 AIS patients that were operated at a single centre from 2013 to 2019 were retrospectively reviewed by 3 independent co-investigators. CCA was noted on the standing radiograph, whereas the AVR was measured on the axial cuts of CT scan. Pedicle morphometric measurements were performed for apical and periapical pedicles. These included apical vertebra (when present), 2 vertebrae above (U1 and U2) and below (B1 and B2) the apex vertebra/disc. The pedicle morphometric measurements were performed on CT scans. We assessed the transverse pedicle diameter, transverse cancellous channel diameter, sagittal pedicle diameter, pedicle length and pedicle axis length. Correlation tests between various pedicle morphometric measurements, AVR and the curve magnitude (Cobb angle) was performed by the Pearson correlation test.

RESULTS

The apex of the major curve was in the thoracic spine in 20 patients, thoracolumbar in three patients and in the lumbar spine in two patients. The mean Cobb angle was 61.5 ± 9.3° and the mean AVR was 28.4 ± 17.8°. A positive correlation was noted with the AVR for U1 concave pedicle length (r = 0.45, p = 0.03), pedicle axis length of the U2 concave pedicle (r = 0.6, p = 0.04), transverse pedicle diameter of the convex apical vertebrae (r = 0.82, p = 0.00009) and the convex apical transverse pedicle diameter (r = 0.80, p = 0.002). A negative correlation with the AVR was noted for U2 convex pedicle length (r = - 0.51, p = 0009), transverse cancellous channel diameter of the U2 concave pedicle (r = - 0.42, p = 0.04) and apical concave pedicle (r = - 0.78, p = 0.002) and the sagittal pedicle diameter for the convex pedicle of U2 (r = - 0.45, p = 0.03) and apex(r = - 0.59, p = 0.04). The Cobb angle did not show a significant correlation with any of the pedicle measurements at any of the levels on the convex and the concave sides.

CONCLUSION

Pedicle asymmetry and dysmorphism demonstrate a morphometric association with the apical vertebral rotation than the curve magnitude. The pedicle length and the pedicle axis length increase on the concave apical and periapical region with increase in AVR. The transverse cancellous channel diameter significantly decreases on the concave apical region with the increase in AVR. The sagittal pedicle diameter decreases on the convex side with the increase in AVR.

Pedicle Dysplasia in Proximal Thoracic Adolescent Idiopathic Scoliosis Curves: What are We Missing and What are its Possible Surgical Implications? An Observational Retrospective Study on 104 Patients

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To assess if pedicle dysplasia is present in proximal thoracic (PT), both structural and nonstructural, compared to main thoracic (MT) curves; and to assess if it is predictive of radiographic outcomes at minimum 2 years of follow-up.

METHODS

A retrospective review of surgically-treated Adolescent Idiopathic Scoliosis (AIS) patients with Lenke 1-2-3-4 curves was performed. On preoperative CT-scan, at the apical vertebra, pedicle width on the concavity (PWc) and on the convexity (PWv) and Pedicle Dysplasia Index (PDI, defined as PWc/PWv) were measured. Preoperative and last follow-up (at least 2 years) x-rays were reviewed.

RESULTS

104 patients meeting the inclusion criteria were divided into Structural-PT (S-PT) and Nonstructural-PT (NS-PT) groups based on Lenke criteria. PWc (P < .001). And PDI (P < .001 for S-PT, P = .004 for NS-PT) were significantly smaller in the PT than in MT curves for both groups. PT-PWc significantly correlated with follow-up PT Cobb for both groups (P < .001 and P = .015 respectively). PT-PDI significantly correlated with follow-up PT-Cobb (P < .001), CA (P < .040) and T1 tilt (P < .002), only for NS-PT group. NS-PT patients with PWc PT <1 mm had higher RSHD (P = .021) and T1 tilt (P = .025) at follow-up. NS-PT patients with PDI PT <.3 had higher RSHD (P < .001), CA (P = .002) and T1 tilt (P = .003) at follow-up.

CONCLUSION

S-PT and NS-PT curves show significant pedicle dysplasia on the concavity. Pedicle dysplasia significantly correlated with shoulder balance at follow-up, for NS-PT patterns. Patients with a PWc <1 mm or PDI <.30 are at particular risk of postoperative shoulder imbalance.

What is the prevalence and distribution of narrow dysplastic and fully corticalized pedicles in Asian adolescent idiopathic scoliosis patients with major main thoracic curves? A computed tomography scan analysis of 6,494 pedicles

BACKGROUND CONTEXT

Patients with adolescent idiopathic scoliosis (AIS) have higher prevalence of abnormal or dysplastic pedicles.

PURPOSE

To investigate the prevalence and distribution of narrow dysplastic and fully corticalized pedicles in Asian AIS patients with major main thoracic curves.

DESIGN

Retrospective study.

PATIENT SAMPLE

A total of 6,494 pedicles in 191 patients were measured and evaluated.

OUTCOME MEASURES

The primary outcomes measures were the pedicle width measurements (total transverse pedicle width, transverse cancellous width, total transverse cortical width) and classification of pedicles. Demographic data (age, gender, height, weight, body mass index), proximal thoracic Cobb angle, main thoracic Cobb angle and lumbar Cobb angle were also obtained.

METHODS

AIS patients with major (largest Cobb angle) main thoracic curves and had computed tomography (CT) scans prior to corrective spine surgery were reviewed. The pedicles were classified as Grade A: cancellous channel >4 mm; Grade B: cancellous channel 2 to 4 mm; Grade C: cancellous channel <2 mm or corticalized pedicle >4 mm; Grade D: corticalized pedicle ≤4 mm. Grades B, C, and D were dysplastic pedicles while grades C and D were narrow dysplastic pedicles.

RESULTS

The prevalence of dysplastic pedicles (grades B, C, and D) was 61.7%. There were 22.6% narrow dysplastic pedicles (grades C and D) and 4.1% fully corticalized pedicles (grade D). In the thoracolumbar region, there was a sharp transition from larger and less dysplastic pedicles at T11 and T12 to narrower and more dysplastic pedicles at L1 and L2 (narrow dysplastic pedicles at T11: 3.1%, T12: 3.1%, L1: 39.8% and L2: 23.6%). Higher prevalences of narrow dysplastic pedicles were located at right T3 to T5 (71.2%-83.7%) and left T7-T9 (51.3%-61.2%). Higher prevalences of fully corticalized pedicles were located at right T3 to T5 (20.9%-34.0%) and left T7 to T8 (11.0%-12.0%). These were the concave pedicles of proximal thoracic and main thoracic curves, respectively.

CONCLUSION

There were 95.9% pedicles with cancellous channels (grades A, B, and C) can allow pedicle screw fixation and only 4.1% fully corticalized pedicles (grade D) that require an alternative method of fixation. For grade C pedicles (18.5%), pedicle screws can still be attempted with caution. Precautions should also be observed at the L1 and L2 levels as there was a transition to narrower pedicles.

Freehand Juxtapedicular Screws Placed in the Apical Concavity of Adult Idiopathic Scoliosis Patients: Technique, Computed Tomography Confirmation, and Radiographic Results

OBJECTIVE

The purpose of this study is to highlight our technique for freehand placement of juxtapedicular screws along with intraoperative computed tomography (CT) and radiographic results.

METHODS

Consecutive patients with adult idiopathic scoliosis undergoing primary surgery by the senior author were identified. All type D (absent/slit like channel) pedicles were identified on preoperative CT. Three-dimensional visualization software was used to measure screw angulation and purchase. Radiographs were measured by a fellowship trained spine surgeon. The freehand technique was used to place all screws in a juxtapedicular fashion without any fluoroscopic, radiographic, navigational or robotic assistance.

RESULTS

Seventy-three juxtapedicular screws were analyzed. The most common level was T7 (9 screws) on the left and T5 (12 screws) on the right. The average medial angulation was 20.7° (range, 7.1°-36.3°), lateral vertebral body purchase was 13.4 mm (range, 0-28.9 mm), and medial vertebral body purchase was 21.1 mm (range, 8.9-31.8 mm). More than half (53.4%) of the screws had bicortical purchase. Two screws were lateral on CT scan, defined by the screw axis lateral to the lateral vertebral body cortex. No screws were medial. There was a difference in medial angulation between screws with (n = 58) and without (n = 15) lateral body purchase (22.0 ± 4.9 vs. 15.5 ± 4.5, p < 0.001). Three of 73 screws were repositioned after intraoperative CT. There were no neurovascular complications. The mean coronal cobb corrections for main thoracic and lumbar curves were 83.0% and 80.5%, respectively, at an average of 17.5 months postoperative.

CONCLUSION

Freehand juxtapedicular screw placement is a safe technique for type D pedicles in adult idiopathic scoliosis patients.

Evaluating bone quality and asymmetrical aplasia of the thoracic vertebral body in Lenke 1A adolescent idiopathic scoliosis using hounsfield units

Study Design

Retrospective analysis.

Objective

To evaluate bone quality and investigate asymmetrical development of the thoracic vertebral body in adolescent idiopathic scoliosis (AIS) based on Hounsfield unit (HU) measurements obtained from computed-tomography (CT) scans.

Summary of Background Data

HU value demonstrated higher reliability and accuracy than the traditional method, indicating that they could be used to individually evaluate and effectively assess the bone quality of every vertebra in the CT films.

Methods

Total 30 AIS patients classified as Lenke Type 1A and 30 paired controls were included in this study. Regions of interest for HU value were measured on three horizontal images of the thoracic vertebrae. HU measurements of the whole vertebral body in each vertebra were obtained. Using HU value, we separately measured the concave and convex sides of each vertebral body in patients' group, as well as within the left and right sides in controls.

Results

In controls, the mean HU value of T1–T12 thoracic vertebral bodies was 240.03 ± 39.77, with no statistical differences among different levels. As for AIS patients, in the structural curve, the apical region had a significantly lower HU compared with the other regions, and asymmetrical change was found between the concave and convex sides, most significantly in the apical region. In the non-structural curve, the average HU value was 254.99 ± 44.48, and no significant difference was found either among the different levels of vertebrae or between the concave and convex sides.

Conclusions

Abnormal and asymmetrical changes in bone quality of the thoracic vertebral body in patients with Lenke 1A AIS were indicated. Low bone quality in the convex side of the structural curve indicated stronger internal fixation in surgery to correct the deformity.

Three-dimensional morphological analysis of the thoracic pedicle and related radiographic factors in adolescent idiopathic scoliosis

Background

This study aimed to investigate the laterality of the pedicle morphology at the apical vertebra (AV) level and identify the radiographic factors associated with the laterality ratio of the pedicle morphology at the AV level in patients with adolescent idiopathic scoliosis (AIS).

Methods

Overall, 684 pedicles in 57 AIS patients aged 10–20 years, who underwent preoperative computed tomography (CT) and had Lenke type 1 or 2 with right convex main thoracic curves (MTC), were evaluated. Pedicle diameters of the MTC were assessed. We defined and compared the region containing two vertebrae adjacent to the AV (APEX±1) and the region containing two vertebrae adjacent to the neutral vertebra. We analyzed the pedicle diameter and laterality ratio of APEX±1 and performed multiple linear regression analysis to identify the radiographic factors associated with the laterality of the pedicle diameter.

Results

On the concave side of APEX±1, the pedicles of 15 patients (26.3%) did not accept a 4-mm-diameter pedicle screw (PS), even with 25% cortical bone width expansion. Laterality ratio differences in the pedicle diameters of the cortical bone width in APEX±1 were large in patients with more proximal AV level (p < 0.001) and smaller apical vertebral rotation (AVR) (p = 0.029).

Conclusions

Preoperative planning to accurately select and insert the PS in AIS should be based on the anatomical limitations in APEX±1, AV level, and AVR degree. In APEX±1, the correlation between AVR and the laterality ratio of the pedicle diameter may be useful for pathoetiological interpretation of the AIS deformity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05799-4.

Instability Severity Index Score Does Not Predict the Risk of Shoulder Dislocation after a First Episode Treated Conservatively

The first purpose of this study was to verify the association between Instability Severity Index Score (ISIS) and Recurrent Shoulder Dislocation (RSD) after a first episode treated conservatively. The second aim is to identify the risk factors associated with RSD after a primary acute shoulder anterior dislocation treated conservatively. A total of 111 patients with first traumatic anterior shoulder dislocation treated at a single trauma centre between January 2014 and March 2016 were enrolled. The main predictive variables of risk factors and the ISIS score were calculated. Among the 85 patients included, 26 cases of RSD were observed (30.6%). Considering the whole population, no significant association between ISIS and RSD were reported. Regarding other risk factors, high-risk working activities and rotator cuff injury had a significantly higher RSD risk. Sex, dominant limb, familiar history, hyperlaxity, contact or overhead sports, competitive sport, post-reduction physiokinesitherapy, return to sports activity time, Hill-Sachs lesion, bony Bankart lesion and great tuberosity fracture did not seem to influence the risk of RSD. No correlation between ISIS score and RSD in patients treated conservatively after a first episode of shoulder dislocation were reported. The only risk factors with a significant association to RSD were high-risk working activities and rotator cuff injury.

Does use of pre-operative low-dose CT-scan in adolescent idiopathic scoliosis improve accuracy in screw placement? Results of a retrospective study

PURPOSE

To evaluate the efficacy of pre-operative low-dose radiation computed tomography (CT) in optimizing screw placement in patients with adolescent idiopathic scoliosis (AIS).

METHODS

49 patients with AIS who required correction and posterior fusion between January 2018 and December 2019 were included in this retrospective study. All patients underwent surgery performed by the same team of experienced surgeons. Patients were divided in two groups. The study group received a pre-operative low-dose CT scan (CT group, n = 25), differently from the control group (CG, n = 24). Patients of both groups received a post-operative low-dose CT scan. The primary outcome measure was the accuracy of screw placement on the Gertzbein-Robbins scale (grades A and B were considered acceptable). Secondary outcome measures included a comparison of perioperative complications.

RESULTS

A total of 1045 screws were placed. In CT group (n = 25, screws = 528) and CG (n = 24, screws = 517), trajectories were grade A or B in 94.5% and 93.6% of screws, respectively. Two screws (one for each group) were removed because of intra-operative-evoked potentials alteration and one screw required revision after post-operative imaging. No correlation was found between the malpositioning rate and the proximity to the apex of the curve, conversely a significative peak of misplacements was observed at T3 (p < 0.01). No neurological and vascular complications related to screw placement were recorded. There was not intergroup difference neither in screw accuracy (Chi-Square, 2-tailed Fisher's exact, p = 0.63), nor in complications rate.

CONCLUSION

Pre-operative low-dose CT scan as surgical plan does not contribute in reducing pedicle screw misplacement rate.

STUDY DESIGN

Retrospective comparative cohort study.

LEVEL OF EVIDENCE

III.

Correction of adolescent idiopathic scoliosis using a convex pedicle screw technique with low implant density

AIMS

The aim of this retrospective study was to compare the correction achieved using a convex pedicle screw technique and a low implant density achieved using periapical concave-sided screws and a high implant density. We hypothesized that there would be no difference in outcome between the two techniques.

METHODS

We retrospectively analyzed a series of 51 patients with a thoracic adolescent idiopathic scoliosis. There were 26 patients in the convex pedicle screw group who had screws implanted periapically (Group 2) and a control group of 25 patients with bilateral pedicle screws (Group 1). The patients' charts were reviewed and pre- and postoperative radiographs evaluated. Postoperative patient-reported outcome measures (PROMs) were recorded.

RESULTS

The number of implants (14.5 vs 17.1) and the implant density (1.5 vs 1.9) were significantly lower in Group 2 (p < 0.001). Operating time was 27 minutes shorter in Group 2 than in Group 1, with a mean of 217 minutes (SD 50.5; 120 to 346). The duration of surgery per instrumented vertebra was reduced by 19% in Group 2 (p = 0.011). No statistical difference was found in the postoperative Cobb angle, vertebral rotation, the relative correction achieved, or postoperative PROMs.

CONCLUSION

Despite a lower implant density and achieving correction through a convex rod, surgical correction of the Cobb angle and vertebral body rotation was similar in both groups. Periapical pedicle screws and primary correction on the concave side do not seem to be mandatory in order to achieve good surgical results in idiopathic thoracic scoliosis. The operating time was shorter in the group with lower implant density. In conclusion, the technique provided good results and has the potential to reduce complications and costs. Cite this article: Bone Joint J 2021;103-B(3):536-541.

Uniplanar Cannulated Pedicle Screws in the Correction of Lenke Type 1 Adolescent Idiopathic Scoliosis

OBJECTIVE

To report the clinical use of uniplanar cannulated pedicle screws for the correction of Lenke type 1 adolescent idiopathic scoliosis (AIS), and to evalute its safety and clinical outcomes.

METHODS

A total of 68 patients with Lenke type 1 AIS were retrospective analyzed, among which 38 patients were treated with uniplanar cannulated screws at the concave side of periapical levels and multiaxial screws at the other levels (group A). The remaining 30 patients were treated with all multiaxial screws (group B). The preoperative and postoperative radiographic parameters, axial vertebral rotation, and the safety of the pedicle screws were evaluated.

RESULTS

Preoperative data were comparable between the 2 groups. The postoperative proximal thoracic curve, main thoracic curve, thoracolumbar/lumbar curve, and apical vertebral rotation were significantly improved in both groups (P < 0.05). The coronal correction rates in group A and B were 83% and 81.9% (P = 0.723). The derotation rates in group A and B were 60.8% and 43.2% (P < 0.05). The rotation classification in the group A was also better than group B. The misplacement rate in group A and B was 7.9% and 11.8% (P < 0.05), and the total misplacement rate on the concave side (11.4%) was higher than that of convex side (8.4%). On the concave side, the misplacement rate in group A and B was 9.7% and 12.3%. On the convex side, the misplacement rate in group A and B was 5.9% and 11.1% (P < 0.05).

CONCLUSIONS

Collectively, uniplanar cannulated pedicle screws could effectively increase the accuracy of pedicle screws and facilitate the derotation of the apical vertebra compared with the multiaxial pedicle screws.

Non-Pedicular Fixation Techniques for the Treatment of Spinal Deformity: A Systematic Review

BACKGROUND

In recent years, the use of pedicle screws has become the gold standard for achieving stable, 3-column fixation of the spine. However, pedicle screw placement may not always be ideal, such as in adolescent idiopathic scoliosis, because of pedicle morphology. An understanding of the alternatives to pedicle screw fixation is therefore important in the treatment of patients with spinal deformity. The purpose of this article is to review the indications, advantages, disadvantages, and complications associated with non-pedicular fixation techniques of the thoracolumbar spine.

METHODS

Comprehensive literature searches of PubMed, Scopus, and Web of Science databases were performed for 10 methods of non-pedicular fixation. Articles published between January 1, 1990, and June 1, 2019, were considered. Non-English-language articles and studies involving fixation of the cervical spine were excluded from our review.

RESULTS

After reviewing >1,600 titles and abstracts pertaining to non-pedicular fixation, a total of 213 articles met our inclusion criteria. Non-pedicular fixation may be preferred in certain cases of spinal deformity and may provide stronger fixation in osteoporotic bone. The use of non-pedicular fixation techniques is often limited by the inability to place multilevel constructs on intact posterior elements. Additionally, some methods of non-pedicular fixation, such as spinous process tethering, primarily have utility for the end of constructs to minimize junctional problems.

CONCLUSIONS

Pedicle screws remain the anchor of choice in spinal deformity surgery because of their ability to engage all 3 columns of the spine and provide safe correction in all 3 planes. Nevertheless, non-pedicular fixation may be useful in cases in which pedicle screw placement is extremely difficult.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Preoperative assessment of idiopathic scoliosis in adolescent and young adult with three-dimensional T2-weighted spin-echo MRI

PURPOSE

To compare tridimensional (3D) T2-weighted spin-echo MRI and CT for minimal pedicle width measurements in the preoperative assessment of adolescent idiopathic scoliosis (AIS) in adolescent and young patients.

MATERIALS AND METHODS

A total of 22 adolescents/young patients suffering from AIS were retrospectively included. There were 18 females and 4 males with a mean age of 15.3±2.3 (SD) years (range: 11-21years). Preoperative lumbar spine MRI and CT examinations of the 22 patients were reviewed by two independent readers who measured the minimal width of 259 pedicles. Inter-reader agreement for CT and MRI was assessed using intra-class correlation coefficient (ICC). Intra-reader agreement and relative differences in measurements between MRI and CT were also assessed for each reader.

RESULTS

Inter-reader agreement was excellent (ICC≥0.8) for both CT and MRI. Relative differences in measurements between CT and MRI was 10.3% for reader 1 and 9.4% for reader 2.

CONCLUSION

3D T2-weighted spin-echo MRI underestimates minimal pedicle width by only 9.4 - 10.3% compared to CT. 3D T2-weighted MRI appears as a valuable alternative to CT for preoperative measurements of vertebral pedicles in AIS.

Variability Analysis of Manual and Computer-Assisted Preoperative Thoracic Pedicle Screw Placement Planning

STUDY DESIGN

A comparison among preoperative pedicle screw placement plans, obtained from computed tomography (CT) images manually by two spine surgeons and automatically by a computer-assisted method.

OBJECTIVE

To analyze and compare the manual and computer-assisted approach to pedicle screw placement planning in terms of the inter- and intraobserver variability.

SUMMARY OF BACKGROUND DATA

Several methods for computer-assisted pedicle screw placement planning have been proposed; however, a systematic variability analysis against manual planning has not been performed yet.

METHODS

For 256 pedicle screws, preoperative placement plans were determined manually by two experienced spine surgeons, each independently performing two sets of measurements by using a dedicated software for surgery planning. For the same 256 pedicle screws, preoperative placement plans were also obtained automatically by a computer-assisted method that was based on modeling of the vertebral structures in 3D, which were used to determine the pedicle screw size and insertion trajectory by maximizing its fastening strength through the underlying bone mineral density.

RESULTS

A total of 1024 manually (2 observers × 2 sets × 256 screws) and 256 automatically (1 computer-assisted method × 256 screws) determined preoperative pedicle screw placement plans were obtained and compared in terms of the inter- and intraobserver variability. A large difference was observed for the pedicle screw sagittal inclination that was, in terms of the mean absolute difference and the corresponding standard deviation, equal to 18.3° ± 7.6° and 12.3° ± 6.5°, respectively for the intraobserver variability of the second observer and for the interobserver variability between the first observer and the computer-assisted method.

CONCLUSION

The interobserver variability among the observers and the computer-assisted method is within the intraobserver variability of each observer, which indicates on the potential use of the computer-assisted approach as a useful tool for spine surgery that can be adapted according to the preferences of the surgeon.

LEVEL OF EVIDENCE

3.