Proximal Thoracic Research Articles

Three-dimensional finite element simulation of surgical correction for Lenke 2 type adolescent idiopathic scoliosis

Objective To simulate different anterior and posterior correction strategies using finite element model of Lenke 2 type adolescent idiopathic scoliosis(AIS),in an effort to seek the optimal surgical protocol.Methods The finite element model of Lenke 2 type AIS was established and used to simulate five surgical strategies.The effectiveness and shoulder balance parameters were compared among different surgical approaches.Results The coronary proximal thoracic(PT) Cobb angle and corrective rates of the five surgical strategies were 21.5(44.8%),26.5(32.1%),28.1(27.9%),34.1(12.5%),and 32(17.9%).The corrective rates for the main thoracic curves were not significantly different among the five strategies,and the physiological sagittal configuration was maintained.Postoperative radiographic shoulder balance parameters were increased for all five surgical protocols.Except for strategy A(posterior fusion from T2 to T11),other four strategy achieved the following outcomes: coracoid height difference9 mm,clavical angle2.5° and clavicular tilt angle difference4.5°.Conclusion Simulation of posterior correction and fusion to T2 including both thoracic curve can achieve excellent three-dimensional corrective results and balanced shoulders for Lenke 2 type AIS model with preoperative left elevated shoulder.Partial fusion of PT curves to T3 or T4 results in inferior corrective rate of PT curve and mild or moderate shoulder imbalance.Simulation of anterior or posterior selective main thoracic curve fusion has very low spontaneous PT corrective rate and can lead to deteriorated shoulder imbalance slight to moderate degrees.

Correction of Moderate (<70 Degrees) Lenke 1A and 2A Curve Patterns

Multiple reports have demonstrated the superiority of all-pedicle screw constructs, over hybrid and hook constructs, for severe sagittal and coronal deformities (>70 degrees) and have made anterior spinal releasing unnecessary for almost all spinal deformities. However, for lesser deformities, specifically coronal deformities <70 degrees, published studies have not been able to consistently demonstrate clinical superiority of all-pedicle screw constructs over hook or hybrid constructs. A prospective, multicenter database on AIS identified patients with <70 degrees main thoracic (MT) curves surgically treated with a posterior spinal fusion. Inclusion criteria were: Lenke 1A and 2A curve patterns, neurologically normal, primary surgery only, and at least 13 years of age at surgery or be Risser 3 or greater and a construct consisting of all-pedicle screws (PS) or hybrid instrumentation. Minimum follow-up was 2 years postoperative. Patients were excluded if surgeries included any releases (laminectomies, ligament releases, or osteotomies), which may increase curve flexibility. A total of 101 patients satisfied the criteria for inclusion: PS (n=53) and hybrid (n=48). Preoperative patient data, preoperative curve characteristics, and operative data were similar between the 2 groups. Postoperative thoracic coronal Cobb demonstrated PS had better proximal thoracic (PT) and MT correction, MT Cobb correction % and correction index than hybrid. Interestingly there were no differences in correction index/fixation point between the 2 groups, indicating PS constructs achieved better correction due, at least in part, to the greater number of spine fixation points. Lower instrumented vertebrae tilt and rotational correction was better in the PS group than hybrid. At 2-year follow-up PS had better absolute forced expiratory volume in 1 second values, trunk shift, and total scoliosis appearance questionnaire than hybrids. T5-T12 sagittal alignment was unchanged at 2-year follow-up for PS versus increased kyphosis in hybrids. All-pedicle screw systems had better coronal correction, lower instrumented vertebrae tilt, MT scoliometer measurements and scoliosis appearance questionnaire total measures than hybrid constructs. The improved coronal correction in the PS group is likely due, in part, to the higher number of spine fixation points than used in the hybrid groups.

Different Proximal Thoracic Curve Patterns Have Different Relative Positions of Esophagus to Spine in Adolescent Idiopathic Scoliosis

A computed tomography (CT) study. To evaluate the changed relative positions of esophagus in proximal thoracic (PT) curves of adolescent idiopathic scoliosis (AIS) patients and analyze the potential risks of esophageal injuries from thoracic pedicle screw (TPS) insertion. Translation and rotation of the vertebrae could lead to altered relative positions of surrounding vital structures in AIS patients. The changed positions of aorta and spinal cord in main thoracic (MT) curve have been comprehensively investigated; however, no studies have analyzed the relative position of esophagus in PT curve. Twenty patients with complete proximal thoracic (CPT group) curve, 22 patients with fractional proximal thoracic (FPT group) curve, and 14 normal patients with a straight spine (normal group) were included. Axial CT images from T2 to T5 at the midvertebral body level were obtained to evaluate esophagus-vertebral angle (EVA, defined as 0° when the esophagus was located directly lateral to the left, 90° when strictly anterior, and 180° when directly lateral to the right). The percentages of esophagus in the direction of screw passage were calculated to analyze potential risks of esophageal injuries during TPS insertion. EVA in the FPT group was significantly smaller than that in the normal group (P < 0.05), whereas EVA in the CPT group was significantly greater than that in the normal group (P < 0.05) at each level. The esophagus was located approximately anterior to the vertebral body in the normal group but shifted anterolaterally to the right in the CPT group and anterolaterally to the left in the FPT group. The esophagus was at a high risk of injury with right anterior penetrated TPS in the CPT group and was at a high risk of injury with left anterior penetrated TPS in the FPT group. Different anatomic patterns of PT curves could cause different altered positions of esophagus relative to spine and result in different potential risks of esophageal injuries during TPS insertion. Spine surgeons should choose appropriate pedicle screw length to avoid anterior cortical perforation in the PT region of AIS patients.

Correlation of Preoperative Deformity Magnitude and Pulmonary Function Tests in Adolescent Idiopathic Scoliosis

Clinical study correlating preoperative pulmonary function tests (PFTs) to radiographic measures of thoracic deformity severity in adolescent idiopathic scoliosis (AIS) patients. To determine (1) the incidence of clinically relevant (<65% predicted value) pulmonary impairment in AIS patients; (2) if patients with more severe deformity have greater impairment of PFTs than those with lesser deformity; (3) the effect, if any, of juvenile onset deformity (onset<age 10) on preoperative PFTs. Patients with late-onset (adolescent) spinal deformity are generally believed to have no respiratory morbidity except in severe curves exceeding 100°. A large multicenter database of surgically treated AIS patients with Lenke 1 to Lenke 4 curves was queried to report preoperative PFTs and correlate them with radiographic measures of coronal, sagittal, and axial plane deformities. Nineteen percent of 858 patients had <65% predicted forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) before surgery, and had larger main thoracic (MT) curves and greater axial rotation than those with predicted PFT values>65%. Patients with MT curves>70°, and especially >80°; proximal thoracic (PT) curves which were >30° or structural; or T5-T12 kyphosis<10° had significantly (P≤0.001) lower FEV1 or FVC compared to those with less deformity. Axial plane deformity did not correlate with PFT impairment. Juvenile-onset patients had greater PFT impairment than AIS patients, along with slightly larger MT curves. Patients who were braced before surgery had worse PFTs than those had no treatment before surgery. Preoperative PFTs are clinically impaired in 19% of AIS patients, and correlate significantly with the MT and sagittal plane deformity severity, and with PT curve severity to a lesser degree. PFTs do not correlate with degree of axial deformity. From a purely pulmonary standpoint, attention directed to coronal and sagittal plane deformity correction appears warranted, to address the specific deformities which are associated with PFT impairment.

Coronal deformity correction in adolescent idiopathic scoliosis patients using the fulcrum-bending radiograph: a prospective comparative analysis of the proximal thoracic, main thoracic, and thoracolumbar/lumbar curves

The aim of the prospective, comparative radiographic analysis was to determine the role of the fulcrum-bending radiograph (FBR) for the assessment of the proximal thoracic (PT), main thoracic (MT), and the thoracolumbar/lumbar (TL/L) curves in patients undergoing posterior spinal pedicle screw fixation and fusion for adolescent idiopathic scoliosis (AIS). The FBR demonstrated statistically better correction than other preoperative methods for the assessment of frontal plane correction of the MT curves. The fulcrum-bending correction index (FBCI) has been considered a superior method than the correction rate for comparing curve correction undergoing posterior spinal fusion because it accounts for the curve flexibility. However, their applicability to assess the PT and TL/L curves in AIS patients remains speculative. The relation between FBR and correction obtained by pedicle screws fixation is still unknown. Thirty-eight consecutive AIS patients who underwent pedicle screw fixation and posterior fusion were included in this study. The assessment of preoperative radiographs included standing posterior-anterior (PA), FBR, supine side-bending, and postoperative standing PA and lateral plain radiographs. The flexibility of the curve, as well as the FBCI, was calculated for all patients. Postoperatively, radiographs were assessed at immediate (i.e. 1 week), 3-month, 6-month, 12-month, and 2-year follow-up. Cobb angles were obtained from the PT, MT, and TL/L curves. The study consisted of 9 PT, 37 MT, and 12 TL/L curves, with a mean age of 15.1 years. The mean FBR flexibility of the PT, MT, and the TL/L curves was 42.6, 61.1, and 66.2%, respectively. The mean operative correction rates in the PT, MT, and TL/L curves were 43.4, 69.3, and 73.9%, respectively, and the mean FBCI was 103.8, 117.0, and 114.8%, respectively. Fulcrum-bending flexibility was positively correlated with the operative correction rate in PT, MT, and TL/L curves. Although the correction rate in MT and TL/L curves was higher than PT curves, the FBCI in PT, MT, and TL/L curves was not significantly different (p < 0.05). The FBR can be used to assist in the assessment of PT, MT, and TL/L curve corrections in AIS patients. When curve flexibility is taken into account by FBR, the ability of pedicle screws to correct PT, MT, and TL/L curves is the same.

Selective fusion in adolescent idiopathic scoliosis

Selective fusion in adolescent idiopathic scoliosis

The Reliability of Preoperative Supine Radiographs to Predict the Amount of Curve Flexibility in Adolescent Idiopathic Scoliosis

Retrospective review. To determine the reliability of supine long-cassette radiographs as compared with side-bending films in predicting curve flexibility in operative cases of adolescent idiopathic scoliosis (AIS). The value of side-bending films is important in the classification of AIS, as well as predicting curve flexibility. A total of 675 patients with a diagnosis of operative AIS were evaluated. All curves were classified by the Lenke classification. Coronal parameters included: proximal thoracic (PT), main thoracic (MT), and thoracolumbar/lumbar (TL/L) Cobb measurements; sagittal data including: T2-T5, T5-T12, and TL/L measurements. Curves were divided into Lenke Types 1 (N = 263), 2 (N = 118), 3 (N = 52), 4 (N = 31), 5 (N = 57), and 6 (N = 54). Lenke Types 1 to 4 (Group I-MT Major) were compared with Types 5 and 6 (Group II-TL/L Major). For Group I, MT supine films were highly predictive of MT side-bending while TL/L supine films were highly predictive of TL/L side-bending and standing films. An equation was derived to predict the value of the side-bending radiographs for each part of the curve. For Group II, MT supine films were highly predictive of MT side-bending and standing films. TL/L supine films were highly predictive of TL/L side-bending and standing films. Contingency table analysis for Group I resulted in the supine film providing a strong statistical ability to predict a nonstructural PT curve (sensitivity = 0.952, PPV = 0.864, NPV = 0.865) and also a nonstructural TL/L curve (sensitivity = 0.958, PPV = 0.916). Similarly, in Group II, we found a strong statistical ability to predict a nonstructural PT (sensitivity 1.00, PPV = 0.982, NPV = 1.00) and a nonstructural MT curve (sensitivity 0.789, specificity = 0.842, PPV = 0.833, NPV = 0.80). A single preoperative supine radiograph is highly predictive of side-bending radiographs and can be used as an adjunct to predicting curve type, flexibility, and structurality. Thus, this singular, reproducible, and non-effort-related radiograph can potentially replace the need for dual side-bending films.

Traction Versus Supine Side-bending Radiographs in Determining Flexibility

Prospective clinical, radiologic study of adolescent idiopathic scoliosis (AIS). We evaluated a Cobb angle in standing position, patient age, the level of the apex, and the number of involved vertebrae in patients with AIS to determine whether the corrective ability of traction or side-bending radiographs was superior. Side-bending and traction radiographs are used to evaluate curve flexibility during corrective surgery for AIS despite notable differences in the flexibilities of identical curves. Thus, interpretation for the differences among these techniques should be investigated. A total of 229 consecutive patients with AIS who were surgically treated were evaluated. Standing, supine side-bending, and traction radiographs were obtained before surgery. Curves were divided into main thoracic (MT) or thoracolumbar/lumbar (TL/L) curves, and proximal thoracic (PT) curves. We evaluated the Cobb angle in standing position, the level of the apex, the number of involved vertebrae, kyphosis angle of main thoracic curve, and patient age in patients with AIS to determine whether the corrective ability of traction or side-bending radiographs was superior. A total of 219 curves were observed in MT lesions. The traction flexibility rate (FR) was higher than the side-bending FR at angle of > or = 60 degrees (P = 0.02), in patients younger than 15 years (P = 0.02), in curves whose apex was located at T4-T8/T9 (P = 0.01), in curves whose involved vertebrae were 6 or 7 (P = 0.02), and at kyphosis angle between 10 degrees and 39 degrees (P = 0.02). In 96 TL/L curves, side-bending FR was higher at angle of < 60 degrees (P < 0.01). In 163 PT curves, traction FR was higher at angles of > or = 40 degrees (P = 0.02). In addition to a Cobb angle, patient age, the level of the apex, and the number of involved vertebrae also influence the conditions under which the corrective ability of traction radiographs is superior to that of side-bending radiographs.

Analysis of the correction results of the adolescent idiopathic scoliosis patients with a proximal thoracic curve

To analyze the correction results of the adolescent idiopathic scoliosis patients with a proximal thoracic (PT) curve. There were 13 cases of double thoracic curve (PUMC IIa) and 13 cases of triple curve (PUMC IIIa 11 cases, IIIb 2 case). The upper instrumented vertebra were at T(3) or above (fusion level including PT curve, Group A) in 18 cases, and at T(4) or T(5) (PT curve not fused, Group B) in 8 cases. Reviewing the medical records and radiographs of 26 adolescent idiopathic scoliosis patients with a proximal thoracic curve that underwent corrective surgery, the changes of the curve and the shoulder balance were analyzed. The coronal Cobb angles of the PT curve and the main thoracic (MT) curve before operation were 45.3 degrees and 61.2 degrees in group A, 35.6 degrees and 58.9 degrees in group B. After operation, they were corrected to 24.2 degrees and 20.1 degrees , 26.4 degrees and 20.3 degrees , respectively. The correction rates of the PT curve and MT curve were 48.2% and 68.7%, 24.5% and 66.3%, respectively. The correction rates of the PT curve of group A was significantly better than group B (P = 0.006), but for the MT curve, the difference was not significant (P = 0.694). The incidence of radiographic shoulder height (RSH) over than 10 mm (shoulder imbalance) after operation in group B was higher than group A significantly (P = 0.038). The incidence rate of shoulder imbalance after operation of the patients with a left higher shoulder or balance shoulder was significantly higher than that of the patients with a right higher shoulder (P = 0.015). Fusing the PT in patients with a left shoulder not lower than right side will make better coronal correction results of the PT curve and reduce the incidence of postoperative shoulder imbalance.

Monaxial Versus Multiaxial Thoracic Pedicle Screws in the Correction of Adolescent Idiopathic Scoliosis

Radiographic outcome analysis following thoracic fusion of Lenke Type I adolescent idiopathic scoliosis (AIS) curves with segmental pedicle screw fixation. To compare the correctional capacity of monaxial versus multiaxial pedicle screws in a matched cohort of AIS patients. Thoracic pedicle screws provide improved curve correction over hook and wire or hybrid constructs for AIS. Further, both monaxial and multiaxial screws are available, with each offering certain advantages over the other. However, different screw types have not been evaluated against each other. We retrospectively reviewed the preoperative and final postoperative follow-up radiographs of an age- and curve-matched cohort of 35 consecutive Lenke Type I AIS patients. Fifteen were treated with monaxial and 20 were treated with multiaxial pedicle screw constructs. All patients had a minimum 2-year follow-up. The average age at surgery was 14 years 4 months (range, 12-17 years) in the monaxial group and 13 years 8 months (12-16 years) in the multiaxial group. Evaluation included coronal proximal thoracic (PT), main thoracic (MT), and thoracolumbar/lumbar (TL/L) Cobb angles and flexibility indexes, regional sagittal curvature, the sagittal apical rib hump (RH) deformity, the apical vertebral body-rib ratio (AVB-R: ratio of linear measures from left and right apical body to lateral rib), and the apical rib spread distance (ARSD, difference of the sums of the intercostal distances at the five periapical segments measured at the lateral transverse process). There was no statistically significant difference with regard to the preoperative PT curves, MT curves, TL/L curves, flexibility indexes, regional sagittal curvature, AVB-R, or ARSD. The preoperative rib humps were significantly greater in the monaxial screw group (42.4 mm vs. 34.7 mm; P = 0.02). Postoperative follow-up averaged 59.9 months (range, 24-98 months) for the monaxial group and 38.0 months (range, 24-55 months) for the multiaxial group (P < 0.0001). An average of 7.7 vertebral levels were fused in the monaxial group compared with 7.2 levels in the multiaxial group (P = 0.39). After surgery, both constructs provided excellent instrumented correction of the MT curves (64.9% vs. 60.0% for the monaxial and multiaxial groups, respectively; P = 0.33), as well as good spontaneous correction of the PT (41.3% vs. 40.5%; P = 0.92) and TL/L curves (55.4% vs. 51.7%; P = 0.66). Monaxial screws demonstrated significantly greater absolute (13.9 mm vs. 25.2 mm; P < 0.0001) and relative (66.1% vs. 24.7%; P < 0.0001) correction of the apical RH. Additionally, AVB-R (77.9% vs. 54.1%; P = 0.0007) and ARSD (82.8% vs. 69.9%; P = 0.04) corrections were significantly greater in the monaxial group. There were no neurologic deficits or major complications in either group. Both monaxial and multiaxial thoracic pedicle screws provide excellent coronal deformity correction for thoracic fusion of main thoracic AIS. Monaxial screws provide superior derotation and restoration of thoracic symmetry as noted by significantly greater correction of the AVB-R, RH, and ARSD.