Instrumentation For Adolescent Idiopathic Scoliosis Research Articles

Effectiveness of cross-linking posterior segmental instrumentation in adolescent idiopathic scoliosis: a 2-year follow-up comparative study

Background contextSurgeons continue to debate the need for a cross-link (CL) in posterior spinal instrumentation constructs with segmental pedicle screws in adolescent idiopathic scoliosis (AIS). Advantage of CLs is increased stiffness of the construct, and disadvantages include added expense and risk of late operative-site pain and pseudarthrosis. PurposeTo compare the effectiveness of using CLs versus using no cross-links (NCLs) in posterior segmental instrumentation in AIS. Study designRetrospective comparative study, level of evidence 3. Patient sampleSeventy-five AIS patients less than 21 years of age, who underwent posterior spinal instrumentation with segmental pedicle screws (25 with CLs and 50 with NCLs) at a single institution with 2-year follow-up, are described. Outcome measuresPhysiologic measures include imaging: thoracic and lumbar Cobb angles, correction rate, apical vertebral translation (AVT), and apical vertebral rotation (AVR); self-report measures include Scoliosis Research Society (SRS) domain outcome scores. MethodsPreoperative (pre-op) and postoperative first erect, 1-year, and 2-year follow-up radiographs were measured. Instrumentation-related complications and normalized SRS scores were recorded. Independent sample t test, χ2 test, and repeated-measures analysis of variance were used for analyses. ResultsThe average age at surgery was 14 years, the mean pre-op Cobb angle was 57°, and the mean number of levels fused was 10.9. The groups were similar preoperatively with respect to age, sex, Lenke curve, Cobb angle, AVT, and Risser grade and were similar intraoperatively for levels fused and anchor density. There was no difference in AVR, Cobb angle, correction rate, or AVT between the groups (p>.05). Complications included one wound infection in the CL group and one painful scar in the NCL group. There were no differences in SRS domain scores. ConclusionWe observed no differences in maintenance of correction, SRS scores, and complications with or without cross-linking posterior segmental instrumentation in AIS patients over 2-year follow-up. Further follow-up is necessary.

Analysis of risk factors for loss of lumbar lordosis in patients who had surgical treatment with segmental instrumentation for adolescent idiopathic scoliosis

Iatrogenic flattening of lumbar lordosis in patients with adolescent idiopathic scoliosis (AIS) was a major downside of first generation instrumentation. Current instrumentation systems allow a three-dimensional scoliosis correction, but flattening of lumbar lordosis remains a significant problem which is associated with decreased health-related quality of life. This study sought to identify risk factors for loss of lumbar lordosis in patients who had surgical correction of AIS with the use of segmental instrumentation. Patients were included if they had surgical correction for AIS with segmental pedicle screw instrumentation Lenke type 1 or 2 and if they had a minimum follow-up of 24 months. Two groups were created, based on the average loss of lumbar lordosis. The two groups were then compared and multivariate analysis was performed to identify parameters that correlated to loss of lumbar lordosis. Four hundred and seventeen patients were analyzed for this study. The average loss of lumbar lordosis at 24 months follow-up was an increase of 10° lordosis for group 1 and a decrease of 15° for group 2. Risk factors for loss of lumbar lordosis included a high preoperative lumbar lordosis, surgical decrease of thoracic kyphosis, and the particular operating surgeon. The lowest instrumented vertebra or spinopelvic parameters were two of many parameters that did not seem to influence loss of lumbar lordosis. This study identified important risk factors for decrease of lumbar lordosis in patients who had surgical treatment for AIS with segmental pedicle screw instrumentation, including a high preoperative lumbar lordosis, surgical decrease of thoracic kyphosis, and factors attributable to a particular operating surgeon that were not quantified in this study.

Sagittale Balance und Kompensationsmechanismen nach operativer Versorgung bei idiopathischer Skoliose mittels segmentaler Pedikelschraubeninstrumentation

Previous studies have demonstrated good ability to improve the sagittal profile with the use of segmental instrumentation for adolescent idiopathic scoliosis (AIS) by analysing the sagittal vertical axis (SVA). However, several authors recommend analysing the spinopelvic relation in addition to the SVA. While compensatory mechanisms may neutralise a positive SVA, these mechanisms are energy consuming and may lead to unphysiological biomechanics, which can negatively influence the quality of life. The purpose of this radiographic analysis was to analyse global sagittal balance and to identify potential compensatory mechanisms after segmental instrumentation for AIS. From a prospectively collected multicentre database, patients with segmental instrumentation for AIS and a minimum follow-up of 2 years were identified. An additional inclusion criterion was the ability to measure lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), and SVA on each X-ray (preoperative, 1st erect, and the 2-year follow-up visits). LL was analysed in relation to PI in order to identify iatrogenic changes. Changes in LL were correlated to changes in PT and SVA. 91 patients were included. On the 1st erect X-ray, LL significantly decreased from pre-op but the SVA remained stable due to a significant increase of PT. At two years follow-up, PT recurred to preoperative values, accompanied by a significant increase of SVA despite a compensatory hyperlordosis below the instrumentation. The temporary increase of PT on the 1st erect was significantly correlated to an iatrogenic decrease of LL. An iatrogenic decrease of LL was significantly correlated to an increase of SVA on the 1st erect and at 2 years follow-up. An iatrogenic decrease of LL after segmental instrumentation for AIS is initially compensated for by pelvic retroversion and later by a hyperlordosis below the instrumentation.

Comparative Analysis of Hook, Hybrid, and Pedicle Screw Instrumentation in the Posterior Treatment of Adolescent Idiopathic Scoliosis

Spinal instrumentation in adolescent idiopathic scoliosis (AIS) aims to correct spinal deformity and maintain long-term spinal stability until bony healing is ensured. The purpose of this study was to compare the minimum 2-year postoperative radiographic and clinical results of posterior spine correction and fusion with all-hook instrumentation versus hybrid segmental instrumentation versus pedicle screw instrumentation for AIS from a single institution. A total of 105 patients with AIS who underwent a posterior spinal fusion with segmental pedicle screw (35), hook (35), or hybrid (35) instrumentation were sorted and matched according to the following criteria: similar age at surgery, identical Lenke curve types, curve magnitude, and Risser grade. Patients were evaluated before, immediately after, and at 2 years after surgery for radiographic parameters, complications, and outcome, as well as on the basis of the Scoliosis Research Society (SRS) questionnaire. The age and Risser grade, major curve Cobb angle, apical vertebral rotation (AVR), apical vertebral translation (AVT), lowest instrumented vertebral tilt, global coronal and sagittal balance, lumbar lordosis, and thoracic kyphosis were determined as part of preoperative evaluation. All 3 groups showed significant differences between the preoperative and postoperative major curve Cobb angle, lowest instrumented vertebral tilt, AVT, and AVR. At the latest follow-up, lumbar lordosis, thoracic kyphosis, and global coronal and sagittal balance remained similar among the 3 groups. Major curve Cobb angle, AVT, and AVR were significantly different--the hook group's measurements were significantly higher than the other groups, but there was no difference between the pedicle screw and hybrid groups. Major curve correction rate was significantly different among all groups (screw=71.9%±13.8%, hybrid=61.4%±16.6%, hook=48.1%±19.7%) (P<0.001). The pedicle screw group had the least amount of correction loss but there was no statistically significant difference between groups (screw=2.6±6.7 degrees, hybrid=4.5±7.4 degrees, hook=4.4±6.2 degrees) (P=0.35). The hook group had the least amount of AVT correction, but the screw group and the hybrid groups were similar (pedicle=67.3%±15.5%, hybrid=57.5%±22.4%, hook=39.9%±32.5%) (P<0.001). Surgery time and blood loss were higher in the screw group. No differences in global SRS-22 scores were demonstrated between the patients treated with pedicle screw, hybrid, and hook constructs; however, the satisfaction domain was higher in the screw group at the latest follow-up. Pedicle screw and hybrid instrumentations offer significantly better spinal deformity correction than hook constructs in major curve coronal correction, AVT, and AVR. Patients with pedicle screw instrumentation had the greatest curve correction percentage, maintenance of this correction in the coronal and sagittal planes, and higher patient satisfaction by the SRS outcome scores. Global SRS-22 scores were similar at 2-year follow-up in all groups. Therapeutic level III retrospective comparative study.

Long-term Retrospective of the Kaneda Anterior Scoliosis System in Thoracic Adolescent Idiopathic Scoliosis

Currently, the Kaneda anterior scoliosis system (KASS) is reported to be acceptable for the treatment of adolescent idiopathic scoliosis (AIS), particularly thoracolumbar and lumbar deformities. Its use in thoracic AIS is not as established. Retrospective analysis of long-term results in patients treated with the KASS for thoracic AIS to determine specific factors associated with success or failure. We analyzed 16 consecutive patients who met the following criteria: thoracic AIS, anterior spinal fusion and KASS, and ≥24 months of follow-up or progression to failure, defined as the need for revision surgery or progression of the main thoracic curve (MTC) ≥50 degrees. Comparison of the MTC on the preoperative, postoperative, and final follow-up was the major evaluation criteria. On the basis of data analysis, patients were divided for comparison into 2 study groups: nonfailure group (n=11) and failure group (n=5). Statistical analysis was performed using paired and independent t tests. All curves were classified as Lenke 1 (n=14) and 2 (n=2). Mean age at surgery and levels fused were 14.6±2.7 years and 5±1 vertebrae, respectively. Mean follow-up was 4.2 years (range, 1.0 to 6.2 y). The failure group consisted of 5 patients that progressed to ≥50 degrees. In the nonfailure group, the mean MTC preoperative, postoperative, and at final follow-up were 52±8, 19±8, and 29±7 degrees, respectively. In the failure group, these measurements were 74±11, 35±8, and 56±12 degrees, respectively. This retrospective, long-term follow-up study found more KASS failures in thoracic AIS than previously reported. Even in the nonfailure group, 5 of the 11 patients progressed 10 degrees or more. Our results indicate an increased incidence of KASS failure with preoperative MTC curve ≥70 degrees. We consider an MTC≥70 degrees a likely contraindication for KASS instrumentation for thoracic AIS. Four of the 5 failures were fused short of the end vertebrae either proximally, distally, or both. Although short apical fusions were popular during the time these cases were done, fusion to the end vertebrae is an important principle for anterior fusions. Reaching the upper end vertebrae may be more difficult in these larger curves. We also recommend continued follow-up past 2 years as progression can occur after this time. Retrospective comparative study, level III.

Use and Outcomes of Wound Drain in Spinal Fusion for Adolescent Idiopathic Scoliosis

A multicenter retrospective analysis. To evaluate outcomes of closed-suction wound drainage after posterior spinal fusion with instrumentation for adolescent idiopathic scoliosis and to identify surgeon patterns of drain use in this cohort. There is little evidence on the use of drains in spinal surgery, particularly for repair of adolescent idiopathic scoliosis. Studies on hip and knee arthroplasty suggest no advantage to draining. There are few published reports on surgeon technique and rationale for drain use in spinal surgery. Patients were divided into drain and no drain cohorts and followed for 2 years. Primary outcome was complication rate. A separate survey was conducted from surgeons in the Spinal Deformity Study Group to evaluate drain practice patterns. There were 324 drained and 176 undrained patients. Complication rate did not differ between the drain and no drain cohorts in any of the 4 categories (wound infection, neural injury, other infection, and other complication) at any time (all P > 0.1). More drained patients received postoperative transfusions compared with those without a drain (43% vs. 22%, P < 0.001). Of the 50 surgeons in the group, 36 used drains. Half of these did so out of habit. Surgeons tended to place deep drains with bulb suction, without drain manipulation. Half removed drains on the basis of output, whereas half removed them after 1 to 3 days. More patients tended to receive wound drains than not receive wound drains. Drains did not impact complication rate and drained patients received more blood product. There are no universal criteria for draining and practice patterns vary widely.

Residual Thoracic Hypokyphosis After Posterior Spinal Fusion and Instrumentation in Adolescent Idiopathic Scoliosis

A retrospective review of clinical and radiographic data from a single-center, prospectively collected scoliosis database. To assess risk factors for persistent thoracic hypokyphosis after posterior spinal fusion and instrumentation (PSFI) for adolescent idiopathic scoliosis (AIS) and to compare clinical outcomes between patients with residual thoracic hypokyphosis and those with normal thoracic kyphosis after PSFI for AIS. AIS is characterized by thoracic hypokyphosis, which should be corrected at the time of surgical treatment. Risk factors for residual thoracic hypokyphosis and the clinical ramifications have not been studied. Radiographic and clinical assessments by using the Scoliosis Research Society-30 (SRS-30) and Spinal Appearance Questionnaire (SAQ) were done preoperatively and at 2 years. Patients were divided into 2 groups on the basis of a threshold of 20° of thoracic kyphosis measured between T5 and T12 at 2-year follow-up. Risk factors for being hypokyphotic at 2 years were male sex (21.69% vs. 12.21%, P = 0.084), preoperative kyphosis (11.4° vs. 22.8°, P < 0.0001), and smaller preoperative main thoracic coronal curves (58.4° vs. 62.0°, P = 0.004). A total of 71.5% of patients instrumented with 6.35-mm rods had normal thoracic kyphosis at 2 years compared with 47.0% instrumented with 5.5-mm rods (P = 0.0043). All-pedicle screw constructs remained hypokyphotic compared with hook-based constructs (P = 0.035). Logistic regression analysis demonstrated 2 parameters associated with persistent thoracic hypokyphosis at 2 years: preoperative hypokyphosis and larger rod diameter. Both groups had similar clinical results on the SRS-30 at 2-year follow-up (P > 0.05). There was a small but statistically significant correlation between sagittal Cobb angle and clinical deformity at 2 years based on the sagittal components of the SAQ. There are 2 risk factors that lead to thoracic hypokyphosis in AIS: preoperative hypokyphosis and use of a 5.5-mm-diameter rod. A larger-diameter rod should be considered when planning surgery for thoracic AIS, especially when there is preoperative hypokyphosis. Despite thoracic kyphosis measuring less than 20°, these patients did not have decreased clinical outcomes as measured by the SRS-30 or SAQ.

A Kohonen neural network description of scoliosis fused regions and their corresponding Lenke classification

Surgical instrumentation for adolescent idiopathic scoliosis (AIS) is a complex procedure where selection of the appropriate curve segment to fuse, i.e., fusion region, is a challenging decision in scoliosis surgery. Currently, the Lenke classification model is used for fusion region evaluation and surgical planning. Retrospective evaluation of Lenke classification and fusion region results was performed. Using a database of 1,776 surgically treated AIS cases, we investigated a topologically ordered self organizing Kohonen network, trained using Cobb angle measurements, to determine the relationship between the Lenke class and the fusion region selection. Specifically, the purpose was twofold (1) produce two spatially matched maps, one of Lenke classes and the other of fusion regions, and (2) associate these two maps to determine where the Lenke classes correlate with the fused spine regions. Topologically ordered maps obtained using a multi-center database of surgically treated AIS cases, show that the recommended fusion region agrees with the Lenke class except near boundaries between Lenke map classes. Overall agreement was 88%. The Lenke classification and fusion region agree in the majority of adolescent idiopathic scoliosis when reviewed retrospectively. The results indicate the need for spinal fixation instrumentation variation associated with the Lenke classification.

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

The objective of this computational study was to compare the biomechanical effects of different implant densities in terms of curve reduction and the force levels at the implant-vertebra interface and on the intervertebral elements. Eight cases were randomly picked among patients who have undergone a posterior spinal instrumentation for adolescent idiopathic scoliosis (AIS). For each case, two computer simulations were performed, one with the actual surgery implant pattern and another with the same fusion levels but an alternative implant pattern proposed by an experienced surgeon. The two implant patterns for each case were respectively put into higher and lower implant density group. The spinal correction and the force levels at bone-implant interface and on the intervertebral elements were analyzed and compared between the two groups. There were on average 13% more pedicle screws and 30% more bilaterally placed pedicle screws in the higher versus lower density group. The difference in the density of screws (92% vs. 79%) did not lead to significant difference in terms of the resulting main thoracic (MT) Cobb angle, and the MT apical axial vertebral rotation. The average and maximum implant-vertebra force levels were about 50 and 65%, respectively higher in the higher versus lower density group, but without consistent distribution patterns. The average intervertebral forces did not significantly differ between the two groups. With the same fusion levels, lower density screws allowed achieving similar deformity correction and it was more likely to have lower screw-vertebra loads.

Comparison of intraoperative supine and postoperative standing radiographs after posterior instrumentation for adolescent idiopathic scoliosis

The utility of intraoperative radiographs after posterior spinal segmental instrumentation for adolescent idiopathic scoliosis (AIS) is debatable. A retrospective review of 74 patients with moderately severe AIS revealed the main thoracic Cobb measurements of 57° preoperatively, 17° intraoperatively, 18° on initial postoperative, and 20° on final postoperative radiographs. On the basis of the extent and type of instrumentation (pedicle screws vs. hybrid construct), there was no clinically significant difference in curve magnitude between intraoperative and postoperative radiographs. After posterior segmental instrumentation for moderate AIS, frontal plane correction measured on intraoperative supine radiographs are comparable with similar measurements made on full-length postoperative standing radiographs.

Cervical spine sagittal alignment variations following posterior spinal fusion and instrumentation for adolescent idiopathic scoliosis

The aim of this study is to quantify the changes in the sagittal alignment of the cervical spine in patients with adolescent idiopathic scoliosis following posterior spinal fusion. Patients eligible for study inclusion included those with a diagnosis of mainly thoracic adolescent idiopathic scoliosis treated by means of posterior multisegmented hook and screw instrumentation. Pre and post-operative anterior-posterior and lateral radiographs of the entire spine were reviewed to assess the changes of cervical sagittal alignment. Thirty-two patients (3 boys, 29 girls) met the inclusion criteria for the study. The average pre-operative cervical sagittal alignment (CSA) was 4.0° ± 12.3° (range -30° to 40°) of lordosis. Postoperatively, the average CSA was 1.7° ± 11.4° (range -24° to 30°). After surgery, it was less than 20° in 27 patients (84.4%) and between 20° and 40° in 5 patients (15.6%). The results of the present study suggest that even if rod precontouring is performed and postoperative thoracic sagittal alignment is restored, improved or remains unchanged after significant correction of the deformity on the frontal plane, the inherent rigidity of the cervical spine limits changes in the CSA as the cervical spine becomes rigid over time.

Patient Self-Assessment of Appearance Is Improved More by All Pedicle Screw Than by Hybrid Constructs in Surgical Treatment of Adolescent Idiopathic Scoliosis

A multicenter prospective cohort study. To compare the effect of all pedicle screw versus hybrid constructs on patient self-assessment of appearance after posterior spinal fusion with instrumentation for adolescent idiopathic scoliosis (AIS). This will contribute to future cost-effective analyses on surgical management of AIS. For surgical management of AIS, the Spinal Appearance Questionnaire (SAQ) and the Scoliosis Research Society outcomes instrument (SRS-30) are reliable surveys of patient satisfaction, but neither tool has been used to assess outcome by implant type. Patients received either all pedicle screws or hybrid instrumentation. Self-assessment of appearance pre- and after surgery was measured by SAQ and SRS-30. Statistical significance was evaluated through P values (P < 0.01 in the SAQ, P < 0.05 in the SRS-30) and effect sizes. There were 93 patients in the all pedicle screw cohort and 61 in the hybrid cohort. There were no significant preoperative differences between the cohorts in the SAQ or SRS-30. All pedicle screw patients tended to see more improvement in shoulder level than hybrid patients in 2 separate SAQ questions (P = 0.025, Cohen's D = 0.20; P = 0.013, D = 0.24). The screw patients also tended to have better scores than hybrid patients in the category, "looking better in clothes" (P = 0.017, V = 0.24) at 2 years postoperative. All pedicle screw patients self-reported significant greater improvement than hybrid patients in the SRS-30 Appearance and Mental domains (P = 0.016, ES = 0.038; P = 0.005, ES = 0.051). There were no significant differences between cohorts in age, gender, baseline curve, or major curve magnitude. All pedicle screw constructs lead to better self-assessment of appearance in operative treatment of AIS, as determined by SAQ and SRS-30.

Preoperative Bracing Affects Postoperative Outcome of Posterior Spine Fusion With Instrumentation for Adolescent Idiopathic Scoliosis

STUDY DESIGN.: Multicenter, prospective clinical series. OBJECTIVE.: To investigate the effect of preoperative bracing on postoperative outcome of posterior spine fusion with instrumentation for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA.: Bracing is the standard of care for adolescent idiopathic scoliosis between 25° and 45°, yet the efficacy of bracing is questionable. It is important to evaluate the effect of bracing on outcomes in the adolescent idiopathic scoliosis population. METHODS.: We reviewed the outcomes of 281 before surgery braced and 328 before surgery nonbraced patients who underwent posterior spine fusion with instrumentation for adolescent idiopathic scoliosis before operation and at 2 years after operation using the Scoliosis Research Society instrument (SRS-30) and the Spinal Appearance Questionnaire. RESULTS.: At 2 years after operation, nonbraced patients demonstrated a greater improvement in the SRS-30 Pain domain score (0.23 vs. 0.08, P < 0.001), more improvement in back pain at rest (26.7% vs. 20.5%, P = 0.0009), and more improvement in back pain in the past 6 months (42.4% vs. 32.6%, P = 0.039) compared to braced patients. Also at 2 years after operation, nonbraced patients reported higher SRS-30 Activity domain scores (4.38 vs. 4.32, P = 0.031), Satisfaction domain scores (4.53 vs. 4.42, P = 0.007), and Total scores (4.27 vs. 4.35, P = 0.036) compared with braced patients. The 2-year Spinal Appearance Questionnaire scores showed that nonbraced patients reported a greater "decrease in importance" than braced patients in having "more even shoulders" (79.4% vs. 70.5%, P = 0.03), "more even hips" (74.6% vs. 71.6%, P = 0.042), and "more even ribs in back" (78.4% vs. 69.5%, P = 0.05). CONCLUSION.: Before surgery braced patients have more pain, lower activity levels, lower satisfaction, and lower total SRS-30 scores at 2 years after operation. Braced patients also have more "spine-specific" appearance concerns compared to nonbraced patients. These results suggest a negative impact of preoperative bracing on outcomes after posterior spinal fusion for adolescent idiopathic scoliosis. This "brace signature" should be taken into account when brace treatment is being considered.

Transverse plane pelvic rotation increase (TPPRI) following rotationally corrective instrumentation of adolescent idiopathic scoliosis double curves

BackgroundWe have occasionally observed clinically noticeable postoperative transverse plane pelvic rotation increase (TPPRI) in the direction of direct thoracolumbar/lumbar rotational corrective load applied during posterior instrumentation and arthrodesis for double (Lenke 3 and 6) adolescent idiopathic scoliosis (AIS) curves. Our purposes were to document this occurrence; identify its frequency, associated variables, and natural history; and determine its effect upon patient outcome.MethodsTransverse plane pelvic rotation (TPPR) can be quantified using the left/right hemipelvis width ratio as measured on standing posterior-anterior scoliosis radiographs. Descriptive statistics were done to determine means and standard deviations. Non-parametric statistical tests were used due to the small sample size and non-normally distributed data. Significance was set at P < 0.05.ResultsSeventeen of 21 (81%) consecutive patients with double curves (7 with Lenke 3 curves and 10 with Lenke 6) instrumented with lumbar pedicle screw anchors to achieve direct rotation had a complete sequence of measurable radiographs. While 10 of these 17 had no postoperative TPPRI, 7 did all in the direction of the rotationally corrective thoracolumbar instrumentation load. Two preoperative variables were associated with postoperative TPPRI: more tilt of the vertebra below the lower instrumented vertebra (-23° ± 3.1° vs. -29° ± 4.6°, P = 0.014) and concurrent anterior thoracolumbar discectomy and arthrodesis (5 of 10 vs. 7 of 7, P = 0.044). Patients with a larger thoracolumbar/lumbar angle of trunk inclination or larger lower instrumented vertebra plus one to sacrum fractional/hemicurve were more likely to have received additional anterior thoracolumbar discectomy and arthrodesis (c = 0.90 and c = 0.833, respectively).Postoperative TPPRI resolved in 5 of the 7 by intermediate follow-up at 12 months. Patient outcome was not adversely affected by postoperative TPPRI, whether or not it persisted.ConclusionsOur findings suggest that TPPRI is a decompensation caused by extension of the corrective thoracolumbar rotational load into the lumbosacral hemicurve below. As posterior instrumentation of adolescent idiopathic scoliosis becomes increasingly more effective in the transverse plane, postoperative TPPRI may become more widely noticed. This study provides some assurance that recompensation usually occurs, but that in either event TPPRI does not seem to affect clinical outcome.

Delayed Presentation of Tetraparesis Following Posterior Thoracolumbar Spinal Fusion and Instrumentation for Adolescent Idiopathic Scoliosis

Case report. We present a case of delayed tetraparesis in a patient after posterior spinal fusion for adolescent idiopathic scoliosis. The reported rate of neural complications after scoliosis surgery is low. Intraoperative neuromonitoring is used to detect and prevent spinal cord injury. Review of medical record. Delayed tetraparesis developed on the second postoperative day after unremarkable T3-L4 posterior fusion. MRI revealed evidence of cord ischemia at C4-C7. Angiogram revealed a hypervascular T4 body resulting in arteriovenous shunting into the epidural venous plexus. Venous congestive myelopathy due to arteriovenous shunting or unrecognized syrinx are presented as possible etiologies of this patient's spinal cord injury. A preoperative MRI may have helped discern the cause of this patient's spinal cord injury.

Thoracic Pedicle Screw Instrumentation

Retrospective review. The purpose of this study is to evaluate the learning curve and associated evolution in surgical technique with thoracic pedicle screw instrumentation in adolescent idiopathic scoliosis (AIS). Common treatment for AIS now includes posterior spinal fusion, using thoracic pedicle screws (TPS). It is critical to assess the efficacy, safety profile, and learning curve associated with this technique as its use becomes more widespread among inexperienced surgeons. Retrospective review of the senior author's first 96 TPS cases for Lenke Type I AIS curves. Multiple regression techniques were used to discern whether increasing case number (CN) was associated with improved perioperative and 2-year minimum radiographic and clinical outcomes. The 96 cases were divided into 4 equal quartiles of 24 cases/group (i.e., Q1-Q4) and compared using analysis of variance measures. A total of 1169 thoracic pedicle screws were placed in 96 patients. We found a significant correlation between CN and major curve correction at 2 years (P < 0.0001), inverse correlation between CN and length of stay (P = 0.02), and estimated blood loss (P = 0.03), but no differences in cell saver or complications. Univariate analysis revealed significant inverse correlations between increasing CN and transfusion rate (P = 0.02) and operative times (P = 0.0001). Total number of screws placed (Q1:9.4 vs. Q4:16.2, P < 0.0001) and number of screws/level (Q1:0.98 vs. Q4:1.64, P < 0.0001) increased linearly with increasing CN, whereas the average time for screw placement (Q1:24.2 vs. Q4:11.4 minutes, P < 0.0001) and ability to maintain T2-T12 kyphosis decreased (Q1:0.21 vs. Q4:-5.5 P = 0.02) with increasing CN. There is a significant learning curve associated with thoracic pedicle screw placement in AIS. We describe several technical steps that can be taken to increase the safety of screw placement at the beginning of the learning curve. Inexperienced surgeons should expect a gradual improvement over time in radiographic and clinical outcomes.

Radiographic Classification of Complications of Instrumentation in Adolescent Idiopathic Scoliosis

In spinal deformity surgery, techniques and implants must be assessed for their safety and efficacy. Regulatory bodies, third-party payors, and patients will increasingly scrutinize treatment methods based on the frequency of adverse events. We therefore developed a classification of adverse hardware-related events using plain radiographic criteria. We analyzed the adverse events in 466 patients surgically treated for adolescent idiopathic scoliosis for a Type 1 (Lenke et al.) curve. We used plain radiographic films to define complications as either serious radiographic adverse events or radiographic adverse events in four technique groups: posterior spinal fusion with hooks and/or hybrid systems, posterior spinal fusion using mostly pedicle screws, open anterior spinal fusion, and thoracoscopic anterior spinal fusion. We defined serious radiographic adverse events as those requiring subsequent surgery. The minimum followup was 2 years. We found a reoperation rate ranging from 4.5% (open anterior spinal fusion) to 8.8% (posterior spinal fusion with hooks); we found no difference in the incidence of serious radiographic adverse events between surgical techniques. Among serious radiographic adverse events, the most common problems were revision for lumbar progression, rod breakage, and proximal screw pullout in the anterior spinal fusions and instrumentation removal for pain and infection in the posterior spinal fusions. We propose a new radiographic system of adverse hardware-related events for patients with Type 1 adolescent idiopathic scoliosis. Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Computer simulation for the optimization of instrumentation strategies in adolescent idiopathic scoliosis

Recent studies reveal a large variability of instrumentation strategies in adolescent idiopathic scoliosis (AIS). Determination of the optimal configuration remains controversial. This study aims to develop a method to define the optimal surgical instrumentation strategy using a computer model implemented in a spine surgery simulator (S3). A total of 702 different strategies were simulated on a scoliotic patient using S3. Each configuration was assessed using objective functions that represented different correction objectives. Twelve geometric parameters were used in the three anatomic planes and mobility, and their relative weights were defined by a spine surgeon according to his objectives for correction of scoliosis. Six instrumentation parameters were manipulated in a uniform experimental design framework. An interpolation technique was used to build an approximation model from the simulation results and to locate instrumentation parameters minimizing the objective function. Small or no differences in the correction between the simulated optimal strategy and the real postoperative results of the instrumented segments were observed in the three planes. But the same overall correction was obtained by using fewer implants (only screws) and less instrumented levels. This study demonstrates the potential and feasibility of using a spine surgery simulator to optimize the planning of surgical instrumentation in AIS.

Pedicle Screw-only Constructs With Lumbar or Pelvic Fixation for Spinal Stabilization in Patients With Duchenne Muscular Dystrophy

Retrospective case study. We present a retrospective clinical study of 36 patients of Duchenne muscular dystrophy (DMD) treated for correction of scoliosis with pedicle screw-only constructs with the objective to analyze our technique, correction and maintenance of spinal and pelvic deformity, spinal fusion, the complications we encountered, and the adequacy of lumbar fixation. Pedicle screw constructs have shown better deformity correction and maintenance as compared with other methods of instrumentation in adolescent idiopathic scoliosis. There are very few reports of pedicle screw-only constructs for DMD patients. Thirty-six patients were followed up for an average period of 37.75 months (min 24 mo). All patients were instrumented from T2, T3, or T4 to L5 and all levels were instrumented. Pelvic fixation was performed only if the pelvic tilt was more than 15 degrees (10 patients). Cobb angle improved 65% (P<0.001) after surgery from a mean preoperative value of 71 degrees to an average postoperative value of 25.5 degrees. Balanced sitting posture was obtained in all patients. The lumbar lordosis improved significantly (P<0.0001) from an average preoperative value of -21.4 degrees to a mean immediate postoperative value of 23.7 degrees and to 19.5 degrees at final follow-up. In patients where pelvic fixation was performed, pelvic tilt improved 62% (P<0.0001) from an average of 25.8 degrees preoperatively to 9 degrees postoperatively to 11 degrees at final follow-up. In patients where pelvic fixation was not performed, the pelvic obliquity also improved from 10.5 degrees preoperatively to 5.8 degrees postoperatively (41.5% correction) and 8.5 degrees at final follow-up (4.2% correction). Pedicle screw-only constructs provide good stability allowing better correction and maintenance of coronal and lumbar deformities, obtaining good sitting balance, and mobilizing patients early after surgery. Longer follow-up is required to adequately comment on the need for pelvic stabilization.

Fuzzy-logic–assisted Surgical Planning in Adolescent Idiopathic Scoliosis

Selection of appropriate curve fusion levels for surgery in adolescent idiopathic scoliosis (AIS) is a complex and difficult task and, despite numerous publications, still remains a highly controversial topic. To evaluate a fuzzy-logic-based surgical planning tool by comparing the results suggested by the software with the average outcome recommended by a panel of 5 expert spinal deformity surgeons. It is hypothesized that, given the same information, the fuzzy-logic tool will perform as favorably as the surgeons. Proof-of-concept study evaluating the use of a fuzzy-logic-assisted surgical planning tool in AIS to select the appropriate spinal curve to be instrumented. A cohort of 30 AIS surgical cases with a main thoracic curve was used. Each case included standard measurements recorded from preoperative standing postero-anterior and lateral, supine side bending, and 1-year postoperative standing radiographs. Five experienced spinal deformity surgeons evaluated each case independently and gave their preferred levels of instrumentation and fusion. The cases were then presented to the fuzzy-logic tool to determine whether the high thoracic and/or lumbar curves were to be instrumented. For each case, a percentage value was obtained indicating inclusion/exclusion of the respective curves in the surgical instrumentation procedure. Kappa statistics was used to compare the model output and the average decision of the surgeons. Kappa values of 0.71 and 0.64 were obtained, respectively, for the proximal thoracic and lumbar curves models, thus suggesting a good agreement of the fusion recommendations made by the fuzzy-logic tool and the surgeons. Given the same information, the fuzzy-logic-assisted recommendation of the curve to be instrumented compared favorably with the collective decision of the surgeons. The findings thus suggest that a fuzzy-logic approach is helpful in assisting surgeons with the preoperative selection of curve instrumentation and fusion levels in AIS.