Preoperative 3D Modeling and Printing for Guiding Periacetabular Osteotomy.

INTRODUCTION: Achieving adequate acetabular correction in multiple planes is essential to the success of periacetabular osteotomy (PAO). Three-dimensional (3D) modeling and printing has the potential to improve preoperative planning by accurately guiding intraoperative correction. The authors therefore asked the following questions: (1) For a patient undergoing a PAO, does use of 3D modeling with intraoperative 3D-printed models create a reproducible surgical plan to obtain predetermined parameters of correction including lateral center edge angle (LCEA), anterior center edge angle (ACEA), Tonnis angle, and femoral head extrusion index (FHEI)? and (2) Can 3D computer modeling accurately predict when a normalized FHEI can be achieved without the need for a concomitant femoral-sided osteotomy? METHODS: A retrospective review was conducted on 42 consecutive patients that underwent a PAO. 3D modeling software was utilized to simulate a PAO in order to achieve normal LCEA, ACEA, Tonnis angle, and FHEI. If adequate FHEI was not achieved, a femoral osteotomy was simulated. 3D models were printed as intraoperative guides. Preoperative, simulated and postoperative radiographic ACEA, LCEA, Tonnis angle, and FHEI were measured and compared statistically. RESULTS: A total of 40 patients had a traditional PAO, and 2 had an anteverting-PAO. The simulated LCEA, ACEA, Tonnis angle, and FHEI were within a median difference of 3 degrees, 1 degrees, 1 degrees, and 0% of postoperative values, respectively, and showed no statistical difference. Of those that had a traditional PAO, all 34 patients were correctly predicted to need a traditional acetabular-sided correction alone and the other 6 were correctly predicted to need a concomitant femoral osteotomy for a correct prediction in 100% of patients. CONCLUSION: This study demonstrates that for PAO surgery, 3D modeling and printing allow the surgeon to accurately create a reproducible surgical plan to obtain predetermined postoperative hip coverage parameters. This new technology has the potential to improve preoperative/intraoperative decision making for hip dysplasia and other complex disorders of the hip.

Reliability of overcoverage parameters with varying morphologic pincer features: comparison of EOS® and radiography.

BACKGROUND: Multiple radiographic parameters used for diagnosis and quantification of morphologic pincer features have emerged, but the degree to which pelvic tilt or rotation affects conventional radiography and EOS(®) is unknown. QUESTION/PURPOSES: We asked: (1) What is the reliability of EOS(®) and conventional radiography at increasing sizes of morphologic pincer features with varying degrees of tilt and rotation? (2) What is the effect of tilt and rotation on acetabular overcoverage measurements? METHODS: Using a dry cadaveric pelvis, AP conventional radiographs and EOS(®) images were taken at intervals of increasing modeled pincer size with 0° to 15° varying tilt and rotation. Lateral center-edge angle, Sharp angle, Tönnis angle, crossover sign, and retroversion index were measured on all images. Statistical analysis was conducted. RESULTS: The intermodality intraclass correlation coefficients for conventional radiography and EOS(®) radiography across all pincer sizes, rotations, and tilts were excellent (0.93-0.98). Crossover sign was in perfect agreement in conventional radiography and EOS(®). Rotation of the hip away from the beam source and/or increased anterior tilt falsely increased all overcoverage parameters except for Tönnis angle. Rotation away from the beam of 10° or greater or anterior tilt of 5° or greater produced a false-positive crossover sign. CONCLUSIONS: EOS(®) radiography maintained excellent reliability in comparison to conventional radiography but both were equally vulnerable to the effects of tilt and rotation for quantification of hip parameters used in acetabular overcoverage assessment. A standardized pelvic radiograph ensuring that the pelvis is not excessively tilted or rotated should be used for assessing acetabular overcoverage parameters.

Lateral center-edge angle on conventional radiography and computed tomography.

BACKGROUND: Lateral center-edge angle (LCEA), originally described and validated on AP radiographs, has been used increasingly in CT-based studies, but it is unclear whether the measure is reliable and whether it correlates with that on AP radiographs. QUESTION/PURPOSES: We therefore determined: (1) the interobserver and intraobserver reliabilities of the LCEA measured on AP radiographs; (2) the interobserver and intraobserver reliabilities of the LCEA measured on CT scans; and (3) the intermodality correlation of the LCEA between CT and AP radiography. METHODS: We reviewed the AP radiographs and CT scans of 22 patients treated for slipped capital femoral epiphyses. CT scans were reoriented to a neutral pelvic tilt and inclination. Three evaluators measured the LCEA on the unaffected hip on the AP and CT coronal images that corresponded to the center of the acetabulum on the axial slice. RESULTS: We found an interobserver intraclass correlation (ICC) analysis of 0.84 for the AP radiographs and 0.88 for the CT scans. The intraobserver ICC for the AP radiographs was 0.96, and for the CT scans 0.98. The intermodality ICC for the CT scans and AP radiographs was 0.79, with a lower bound of 0.61 and an upper bound of 0.87. CONCLUSIONS: Our data suggest the LCEA measured on a CT scan is reliable and correlates with the LCEA on AP radiographs.

Is the acetabulum retroverted in slipped capital femoral epiphysis?

BACKGROUND: Recent biplanar radiographic studies have demonstrated acetabular retroversion and increased superolateral femoral head coverage in hips with slipped capital femoral epiphysis (SCFE), seemingly divergent from earlier CT-based studies suggesting normal acetabular version. QUESTION/PURPOSES: We therefore asked: Are there differences in (1) acetabular version at the superior » of the acetabular dome (AV(sup)), (2) acetabular version at the center of the femoral head (AV(cen)), and (3) superolateral femoral head coverage (lateral center-edge angle [LCEA]) among affected SCFE hips, unaffected hips, and normal controls? METHODS: We identified 32 patients with SCFE who underwent CT between 2007 and 2012. Twenty-three met our inclusion criteria. Seventy-six age- and sex-matched normal patients comprised the control group. Pelvic rotation, tilt, and inclination were corrected on each CT. AV(sup), AV(cen), and LCEA were measured. RESULTS: The mean AV(sup) of the affected hips (-1.71°) demonstrated retroversion compared to the unaffected hips and the control group; the mean AV(sup) of the unaffected hips was similar to that of the normal controls. Mean AVcen was similar among the three groups. The LCEA was higher in affected and unaffected SCFE hips than in the control group (34.3° versus 34.5° versus 28.9°, respectively), but we found no difference between affected and unaffected hips. CONCLUSIONS: Our data suggest an association of superior acetabular retroversion and increased superolateral femoral head coverage in SCFE. Whether this represents a primary abnormal morphology or a secondary pathologic response remains unclear. Further studies investigating the role of acetabular morphology in SCFE and its implications for development of symptomatic femoroacetabular impingement are warranted.

Does femoral rotation influence anteroposterior alpha angle, lateral center-edge angle, and medial proximal femoral angle? A pilot study.

BACKGROUND: Femoral rotation on AP radiographs affects several parameters used to assess morphologic features of the proximal femur but its effect on femoroacetabular impingement parameters remains unknown. QUESTION/PURPOSES: We therefore evaluated and characterized the potential effect of femoral rotation on (1) AP alpha angle, (2) lateral-center edge angle (LCEA), and (3) medial proximal femoral angle (MPFA) on AP hip radiographs. METHODS: We took seven AP hip radiographs at intervals of successive femoral rotation on a single dry, cadaveric specimen: 60°, 40°, and 20° internal rotation; 0° neutral/anatomic rotation; and 20°, 40°, and 50° external rotation. The AP alpha angle, LCEA, and MPFA were measured on all radiographs by two independent evaluators. RESULTS: Within the range of femoral rotation studied, the AP alpha angle ranged from 39° to 62°, the LCEA from 25° to 35°, and the MPFA from 70° to 115°. MPFA and AP alpha angle showed a linear relationship with femoral rotation. Each additional degree of internal rotation produced a reciprocal reduction of the MPFA by 0.36° and the AP alpha angle by 0.18° and vice versa in external rotation. The LCEA, especially within the internal rotation range, showed minimal variation. CONCLUSIONS: These changes in radiographic parameters emphasize the importance of femoral rotation and patient positioning. We recommend radiographs be evaluated for excessive femoral rotation or nonstandardized positioning before interpretation for diagnostic and treatment implications. It may be prudent to repeat radiographs in these circumstances or, when standardized positioning is not feasible, proceed toward advance imaging.

Radiologic analysis of femoral acetabular impingement: from radiography to MRI.

Femoral acetabular impingement is a set of morphologic abnormalities that are considered to be a major cause of degenerative disease in the hip joint. Early changes are already present in adolescence when it is the pediatric radiologist who must assess current damage with the aim of averting progression to more severe and debilitating osteoarthritis. A multimodality approach is used for diagnosis, that includes conventional radiography and CT to assess the osseous structures. MR arthrography is the primary advanced imaging modality for assessment of morphologic changes as well as injuries of the labrum and articular cartilage. Details of radiologic imaging are offered to guide the radiologist and provide an avenue for the accurate description of the osseous and articular alterations and injury.

Multiplanar CT assessment of femoral head displacement in slipped capital femoral epiphysis.

BACKGROUND: With recent changing approaches to the management of slipped capital femoral epiphysis (SCFE), the accurate radiographic assessment of maximum extent of displacement is crucial for planning surgical treatment. OBJECTIVE: To determine what plane best represents the maximum SCFE displacement as quantified by the head-neck angle difference (HNAD), whether HNAD can quantitatively differentiate the SCFE cohort from the normal cohort, based on CT, and how Southwick slip angle (SSA) compares to HNAD. MATERIALS AND METHODS: We reviewed 19 children with SCFE (23 affected hips) with preoperative CT scans and 27 age- and sex-matched children undergoing abdominal CT for non-orthopedic problems. Head-neck angle (HNA), the angle between the femoral epiphysis and the neck axis, was measured in three planes on each hip and the HNAD (affected - unaffected hip) was determined. SSA was measured on radiographs. RESULTS: The coronal HNAD (mean 8.7°) was less than both the axial-oblique (mean 30.7°) and sagittal (mean 37.4°) HNADs, which were also greater than the HNADs of the normal cohort. Grouping HNAD measurements by SSA severity classification did not consistently distinguish between SCFE severity levels. CONCLUSION: Axial-oblique and sagittal planes best represent the maximum SCFE displacement while biplanar radiograph may underestimate the extent of the displacement, thereby potentially altering the management between in situ pinning and capital realignment.

Anterior centre-edge angle on sagittal CT: a comparison of normal hips to dysplastic hips.

PURPOSE: The anterior centre-edge angle (ACEA) describes anterior acetabular coverage on false profile radiographs. Variability associated with pelvic tilt, radiographic projection, and identifying the true anterior edge, causes discrepancies in measuring an accurate ACEA. Computed tomography (CT) has the potential of improving the accuracy of ACEA. However, because the ACEA on sagittal CT has been shown to not be equivalent to ACEA on false profile radiographs, the normal range of ACEA on CT currently remains unknown and cannot reliably be used to determine over/under coverage. We therefore asked: what is the normal variation of ACEA corrected for pelvic tilt on sagittal CT and how does this compare to dysplastic hips? MATERIAL AND METHODS: A retrospective review was conducted on patients 10-35 who underwent CT for non-orthopedic related issues and patients with known hip dysplasia. The ACEA was measured on a sagittal slice corresponding to the centre of the femoral head on the axial slice and adjusted for pelvic tilt. A statistical comparison was then performed. RESULTS: A total of 320 normal patients and 22 patients with hip dysplasia were reviewed. The mean ACEA for all ages was 50° ± 8°, (range: 23-81º), with a larger mean ACEA for males (51°) than females (49°). The ACEA mean for dysplastic hips was 30° ± 11° with a statistically significant difference in mean from the normal hip group ( p < 0.0001). CONCLUSION: The ACEA can be reliably measured on sagittal CT and significantly differs from dysplastic hips. ACEA measurements above 66° or below 34° may represent anterior over and under coverage.

Postoperative Stiffness Requiring Manipulation Under Anesthesia Is Significantly Reduced After Simultaneous Versus Staged Bilateral Total Knee Arthroplasty.

BACKGROUND: For patients with symptomatic bilateral knee arthritis, it is unknown whether the risk of developing stiffness requiring manipulation under anesthesia postoperatively is higher or lower for those undergoing simultaneous bilateral total knee arthroplasty (TKA) compared with those having staged bilateral TKA. Therefore, we undertook this study to evaluate the risk of requiring manipulation under anesthesia in staged versus simultaneous bilateral TKA as well as patients undergoing unilateral TKA. METHODS: We utilized the California Patient Discharge Database, which is linked with the California Emergency Department, Ambulatory Surgery, and master death file databases. Using a literature-based estimate of the number of patients who failed to undergo the second stage of a staged bilateral TKA, replacement cases were randomly selected from patients who had unilateral TKA and were matched on 8 clinical characteristics of the patients who had staged bilateral TKA. Hierarchical multivariate logistic regression was performed to determine the risk-adjusted odds of manipulation in patients undergoing unilateral TKA, staged bilateral TKA, and simultaneous bilateral TKA using yearly hospital TKA volume as a random effect. Adjustment was made to allow fair comparison of the outcome at 90 and 180 days of follow-up after staged compared with simultaneous bilateral TKA. RESULTS: During the time period from 2005 through 2013, the cumulative incidence of manipulation within 90 days was 2.14% for unilateral TKA (4,398 events per 205,744 patients), 2.11% for staged bilateral TKA (724 events per 34,352 patients), and 1.62% for simultaneous bilateral TKA (195 events per 12,013 patients). At 180 days of complete follow-up, the cumulative incidence of manipulation was 3.07% after unilateral TKA (6,313 events per 205,649 patients), 2.89% after staged bilateral TKAs (957 events per 33,169 patients), and 2.29% after simultaneous bilateral TKA (267 events per 11,653 patients). With multivariate analyses used to adjust for relevant risk factors, the 90-day odds ratio (OR) of undergoing manipulation after simultaneous bilateral TKA was significantly lower than that for unilateral TKA (OR = 0.70; 95% confidence interval [CI], 0.57 to 0.86) and staged bilateral TKA (OR = 0.71; 95% CI, 0.57 to 0.90). Similarly, at 180 days, the odds of undergoing manipulation were significantly lower after simultaneous bilateral TKA than after both unilateral TKA (OR = 0.71; 95% CI, 0.59 to 0.84) and staged bilateral TKA (OR = 0.76; 95% CI, 0.63 to 0.93). The frequency of manipulation was significantly associated with younger age, fewer comorbidities, black race, and the absence of obesity. CONCLUSIONS: Although the ORs were small (close to 1), simultaneous bilateral TKA had a significantly decreased rate of stiffness requiring manipulation under anesthesia at 90 days and 180 days after knee replacement compared with that after staged bilateral TKA and unilateral TKA. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

When are CT angiograms indicated for patients with lower extremity fractures? A review of 275 extremities.

BACKGROUND: Computed tomography angiogram (CTA) is frequently utilized to detect vascular injuries even without examination findings indicating a vascular injury. We had the following hypotheses: (1) a CTA for lower extremity fractures with no clinical signs of a vascular injury is not indicated, and (2) fracture location and pattern would correlate with the risk of a vascular injury. METHODS: A retrospective review was conducted on patients who had an acute lower extremity fracture(s) and a CTA. Their charts were reviewed for multiple factors including the presence or absence of hard or soft signs of a vascular injury, soft tissue status, and fracture location/pattern. Every CTA radiology report was reviewed and any vascular intervention or amputation resulting from a vascular injury was recorded. Statistical analysis was performed. RESULTS: Of the 275 CTAs of fractured extremities reviewed, 80 (29%) had a positive CTA finding and 16 (6%) required treatment. A total of 109 (40%) of the extremities had no hard or soft signs; all had normal CTAs. Having at least one hard or soft sign was a significant risk factor for having a positive CTA. An open fracture, isolated proximal third fibula fracture, distal and shaft tibia fractures, and the presence of multiple fractures in one extremity were also associated with an increased risk for having a positive CTA. CONCLUSION: We found no evidence to support the routine use of CTAs to evaluate lower extremity fractures unless at least one hard or soft sign is present. The presence of an open fracture, distal tibia or tibial shaft fractures, multiple fractures in one extremity, and/or an isolated proximal third fibula fracture increases the risk of having a finding consistent with a vascular injury on a CTA. Only 6% of the cases required treatment, and all of them had diminished or absent distal pulses on presentation. LEVEL OF EVIDENCE: Diagnostic test, level III.

How to Use Fluoroscopic Imaging to Prevent Intraarticular Screw Perforation During Locked Plating of Proximal Humerus Fractures: A Cadaveric Study.

OBJECTIVE: Intraarticular screw perforation is a common complication of open reduction and internal fixation of proximal humerus fractures. The purpose of this study was to (1) determine the sensitivity and specificity of the fluoroscopic images used to evaluate whether a screw tip has perforated into the glenohumeral joint, and (2) determine the specific fluoroscopic views that best evaluate screw position in the humeral head. METHODS: Twenty-two proximal humeri in 11 lightly embalmed cadavers were instrumented. The articular surface was divided into equal-sized rows (superior, central, inferior) and columns (anterior, middle, posterior). The screws in 10 humeri were inserted and so their tips were located 2 mm beneath the articular surface. Twelve humeri had screws placed such that their tips protruded 2 mm past the articular surface into the glenohumeral joint. Twenty-seven different C-arm views were obtained of each specimen/screw configuration. RESULTS: There were zero false-positives (100% specificity). The average sensitivity was 55% and varied greatly depending on the image view and the screw exit location (range, 0%-100%). The sensitivity for the inferior row of screws was the lowest (39.1%) and was particularly low for the posterior-inferior screw exit location (20.7%). CONCLUSIONS: Screws that are completely located within the bone of the proximal humerus will never appear on C-arm images as intraarticular. However, screws that are intraarticular may appear to be completely located within the bone of the proximal humerus on some C-arm images. A sensitivity of 100% for detecting intraarticular screws for 8 of the 9 screws' exit locations and 90% for the posterior-inferior screw can be achieved by imaging the proximal humerus in 25-degree internal rotation, neutral, and 25-degree external rotation with the C-arm in neutral cant at rainbow 25-degree roll over, neutral rainbow, and rainbow 25-degree roll back for a total of 9 images.

Intraoperative fluoroscopy, portable X-ray, and CT: patient and operating room personnel radiation exposure in spinal surgery.

BACKGROUND CONTEXT: Intraoperative imaging is essential in spinal surgery to both determine the correct level and place implants safely. Surgeons have a variety of options: C-arm fluoroscopy (C-arm), portable X-ray (XR) radiography, and portable cone-beam computed tomography (O-arm). Although these modalities have their respective advantages and disadvantages, direct comparison of radiation exposure to either the patient or the operating room (OR) staff has not been made. PURPOSE: To determine the amount of radiation exposure to patients and OR staff during spine surgery with C-arm, XR, and O-arm. STUDY DESIGN: An experimental model to assess radiation exposure to OR staff and phantom patient during spine surgery. METHODS: A plastic phantom was created to emulate patient volume and absorption scattering characteristics of a typical sized adult abdominal volume. Radiation exposure was measured with ion chamber dosimeters to determine entrance phantom and scatter exposures at common positions occupied by OR staff for C-arm, XR, and O-arm in typical image acquisition during spinal surgery. RESULTS: Single lateral (LAT)/posterior-anterior entrance patient radiation exposure for C-arm was on average 116/102 mR, single-exposure XR for LAT/anterior-posterior (AP) was 3,435/2,160 mR, and single-exposure O-arm for LAT/AP was 4,360/5,220 mR. O-arm surface exposure LAT/AP was equivalent to 38/41 C-arm and 1.5/2.4 XR exposures. The surgeon and surgeon assistant had higher levels of scatter radiation for C-arm, followed by O-arm and XR. For the LAT C-arm acquisition, a 7.7-fold increase in radiation exposure was measured on the X-ray tube side compared with the detector side. The anesthesiologist scatter radiation level for a single acquisition was highest for O-arm, followed by XR and C-arm. The radiologic technologist scatter radiation level was highest for XR, followed by O-arm and fluoroscopy. Overall radiation exposure to OR staff was less than 4.4 mR for a single acquisition in all modalities. CONCLUSIONS: Assessment of radiation risk to the patient and OR staff should be part of the decision for utilization of any specific imaging modality during spinal surgery. This study provides the surgeon with information to better weigh the risks and benefits of each imaging modality.

Idiopathic Cam Morphology Is Not Caused by Subclinical Slipped Capital Femoral Epiphysis: An MRI and CT Study.

BACKGROUND: Cam impingement as a known sequelae of slipped capital femoral epiphysis (SCFE) has led to speculation that subclinical SCFEs may be the causative factor in idiopathic cam morphology; alternatively, others have implicated an abnormal extension of the growth plate as a causative factor. HYPOTHESIS/PURPOSE: To investigate the growth plate tilt angle in 4 patient cohorts: normal patients, patients with idiopathic cam morphology (CamIP), patients with cam morphology secondary to known SCFE (CamSCFE), and patients with incidental findings of an asymptomatic cam (Camasymp). STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: A database of 192 computed tomography scans of abdomens/pelvises of patients (ages, 5-19 years) with no known orthopaedic issues, reformatted to neutral tilt, inclination, and rotation, were utilized for the normal cohort, the Camasymp cohort, and to create an age- and sex-matched control cohort. In addition, a retrospective review of all patients treated for femoroacetabular impingement (FAI) with preoperative advance imaging was conducted, and patients were separated to CamIP and CamSCFE cohorts. The alpha angle and tilt angle were measured on each hip. Statistical analysis was performed. RESULTS: The mean tilt angle among the normal patients was 12.1°, with 1.9% of the variation in tilt angle being explained by age; each additional year of age decreased the tilt angle by 0.27° (P = .008). The tilt angle for the CamSCFE cohort (mean, 44.5°) was found to be significantly greater than both the CamIP cohort (mean, 5.9°; P < .001) and the control cohort (mean, 12.8°; P < .001). The tilt angle for the CamIP cohort was found to be significantly less than the control cohort (P = .003). The alpha angle and tilt angle were positively correlated in the CamIP cohort, but no correlation was found in the other cohorts. The mean tilt angle of the 18 hips in the Camasymp cohort was 13.9° ± 11.5° (range, -12° to 37°), with 12 hips (67%) in the tilt angle range of CamIP cohort and 6 in the tilt angle range of CamSCFE. CONCLUSION: The proximal femoral growth plate normally has a posterior tilt that becomes more anterior through maturation. Idiopathic cam morphology has a drastically different growth plate tilt angle than cam morphology secondary to SCFE, suggesting that a majority of idiopathic cam morphology is not the result of subclinical SCFEs.

Multicenter Comparison of the Factors Important in Restoring Thoracic Kyphosis During Posterior Instrumentation for Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Multicenter review, prospectively collected data. OBJECTIVES: To determine factors predictive of postoperative correction of hypokyphosis when segmental posterior pedicle screw implants were used in treating thoracic adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Correcting hypokyphosis, which is common in patients with thoracic AIS, may be important in preventing junctional kyphosis, maintaining lumbar lordosis, and improving pulmonary function. METHODS: A multicenter, prospective database was reviewed for Lenke type 1-4 AIS patients with preoperative kyphosis of 5° to 20°, treated with posterior pedicle screws and 5.5-mm rods. Surgeons with a minimum of 20 patients identified were included. Patients were divided into 2 groups postoperatively based on first erect X-rays: those remaining hypokyphotic (HK) (T5-T12 less than 20° or an increase less than 5° in T5-T12 kyphosis) and those restored to normal kyphosis (NK) (T5-T12 greater than 20° with 5° or more increase). Regression analysis was done on 5 preoperative factors thought to influence the postoperative kyphosis: preoperative kyphosis, surgeon, rod material (standard, high-strength, and ultra-high-strength steel; titanium; and cobalt chromium), implant density, and use or no use of a posterior release (Ponte osteotomies). RESULTS: Of 280 patients included, 222 remained hypokyphotic and 53 achieved normal kyphosis. There were no differences in preoperative kyphosis (13.4° ± 5°, HK group vs. 14.5° ± 4°, NK group) and age (14.7, HK group vs. 14.6, NK group) between patients brought to greater than 20° (NK) and those who remained less than 20° (HK). Of the factors evaluated, the surgeon who performed the operation was the only significant predictor of restoration of normal kyphosis. Comparison of surgeons showed that the rate of normalizing kyphosis ranged from 6% to 42% (p = .001). There was no difference in the degree of preoperative kyphosis among surgeons. CONCLUSIONS: Restoration of thoracic kyphosis remains a challenge in posteriorly treated thoracic AIS patients. The surgeon was the only significant predictor of restoring normal kyphosis, which emphasizes the importance of intraoperative techniques.