Two level pedicle substraction osteotomies for the treatment of severe fixed sagittal plane deformity: computer software-assisted preoperative planning and assessing

Development and Validation of Deep Learning Preoperative Planning Software for Automatic Lumbosacral Screw Selection Using Computed Tomography

Achieving precise pedicle screw placement in posterior lumbar interbody fusion (PLIF) is essential but difficult due to the intricacies of manual preoperative planning with CT scans. We analyzed CT data from 316 PLIF patients, using Mimics software for manual planning by two surgeons. A deep learning model was trained on 228 patients and validated on 88 patients, assessing planning efficiency and accuracy. Automatic planning successfully segmented and placed screws in all 316 cases, significantly outperforming manual planning in speed. The Dice coefficient for segmentation accuracy was 0.95. The difference in mean pedicle transverse angle (PTA) and pedicle sagittal angle (PSA) for automatic planning screws compared to manual planning screws was 1.63 ± 0.83° and 1.39 ± 1.03°, respectively, and these differences were either statistically comparable or not significantly different compared to the variability of manual planning screws. The average Dice coefficient of implanted screws was 0.63 ± 0.08, and the consistency between automatic screws and manual reference screws was higher than that of internal screws (Dice 0.62 ± 0.09). Compared with manual screws, automatic screws were shorter (46.58 ± 3.09 mm) and thinner (6.24 ± 0.35 mm), and the difference was statistically significant. In qualitative validation, 97.7% of the automatic planning screws were rated Gertzbein-Robbins (GR) Class A and 97.3% of the automatic planning screws were rated Badu Class 0. Deep learning software automates lumbosacral pedicle screw planning, enhancing surgical efficiency and accuracy.

Analysis of the reliability of KEOPS version 2 for the measurement of coronal and sagittal parameters in spinal deformity

BACKGROUND

The purpose of the study is to evaluate the updated version of this software in patients with various spinal deformity.

METHODS

Sixty patients were included in this study and were divided into three categories: 20 patients with AIS, 20 patients with ASD, and 20 patients having undergone corrective surgery for spinal deformity. The measurements were performed by two senior and two junior orthopedic surgery residents, and were done at two points in time separated by a 3-week interval with the cases being randomized every time to reduce the risk of memory bias. Measured parameters included coronal, sagittal, global alignment parameters, and pelvic parameters.

RESULTS

When assessing the inter- and intra-observer reliability across all the groups of patients, none of the coefficients was smaller than 0.8 with a very high level of agreement. The standard error ranged from 0.7° to 1.5° demonstrating a high level of accuracy. Fairly similar results were seen when the groups were divided into the three categories except for the post-operative groups where a strong and not perfect level of agreement was reported.

CONCLUSION

This is the first study to assess the reproducibility of the new version of KEOPS, showing a very high agreement in all measurements. In the post-operative group, although it showed a strong agreement, the lower performance can be explained by the presence of surgical material making it harder to identify the anatomical landmarks accurately. Nevertheless, we can recommend the usage of this software in a clinical setting.

Multilevel Pedicle Subtraction Osteotomy for Correction of Thoracolumbar Kyphosis in Ankylosing Spondylitis: Clinical Effect and Biomechanical Evaluation

OBJECTIVE

To compare the clinical outcomes and biomechanical characteristics of 1-, 2-, and 3-level pedicle subtraction osteotomy (PSO), and establish selection criteria based on preoperative radiographic parameters.

METHODS

Patients undergone PSO to treat ankylosing spondylitis from February 2009 to May 2019 in Sun Yat-sen Memorial Hospital of Sun Yat-sen University were enrolled. According to the quantity of osteotomy performed, the participants were divided into group A (1-level PSO, n = 24), group B (2-level PSO, n = 19), and group C (3-level PSO, n = 11). Clinical outcomes were assessed before surgery and at the final follow-up. Comparisons of the radiographic parameters and quality-of-life indicators were performed among and within these groups, and the selection criteria were established by regression. Finite element analysis was conducted to compare the biomechanical characteristics of the spine treated with different quantity of osteotomies under different working conditions.

RESULTS

Three-level PSO improved the sagittal parameters more significantly, but resulted in longer operative time and greater blood loss (p < 0.05). Greater stress was found in the proximal screws and proximal junction area of the vertebra in the model simulating 1-level PSO. Larger stress of screws and vertebra was observed at the distal end in the model simulating 3-level PSO.

CONCLUSION

Multilevel PSO works better for larger deformity correction than single-level PSO by allowing greater sagittal parameter correction and obtaining a better distribution of stress in the hardware construct, although with longer operation time and greater blood loss. Three-level osteotomy is recommended for the patients with preoperative of global kyphosis > 85.95°, T1 pelvic angle > 62.3°, sagittal vertical alignment > 299.55 mm, and pelvic tilt+ chin-brow vertical angle > 109.6°.

Analysis of the outcome of bi-vertebral transpedicular wedge osteotomy for correcting severe kyphotic deformity in ankylosing spondylitis

To study the outcomes of bi-vertebral transpedicular wedge osteotomy in correcting severe kyphotic deformity in ankylosing spondylitis (AS). This retrospective study focused on all the patients who underwent thoracic and lumbar bi-vertebra transpedicular wedge osteotomy with pedicle screw internal fixation to treat their severe thoracolumbar kyphotic deformity of AS in our hospital from January 2014 to January 2020. The perioperative and operative data of each patient were collected and analyzed. A total of 21 male AS patients with severe kyphotic deformity were studied with a mean age of 42.2 ± 9.2 years. Intraoperatively, the mean operating time is 5.8 ± 1.6 hour with a mean blood loss of 725.5 ± 140.6 mL. The average postoperative correction of kyphosis reached 60.8o at 1 week after the surgery, which is significantly improved from preoperative presentation (P < .05), and stayed no significant change over the time during longer period of follow-ups (12-24 months) with the overall correction rate of 72.2%. Moreover, the postoperative changes in thoracic kyphosis (TK) angle, thoracolumbar kyphosis (TLK) angle, lumbar lordosis (LL) angle, maxilla-brow angle, as well as C2SVA and C7SVA sagittal balance were also significant, all of which enabled the patients to walk in upright position and sleep in the supine position with the improvements in other clinical symptoms. Bi-vertebral transpedicular wedge osteotomy of thoracic and lumbar vertebrae is a safe and effective method to restore the physiological curvature of the sagittal position of the spine and correct severe ankylosing deformity.

A novel technique of transpedicular opening-wedge osteotomy for treatment of rigid kyphosis in patients with ankylosing spondylitis

BACKGROUND

To investigate the effectiveness and feasibility of a novel vertebral osteotomy technique, transpedicular opening-wedge osteotomy (TOWO) was used to correct rigid thoracolumbar kyphotic deformities in patients with ankylosing spondylitis (AS).

METHODS

Eighteen AS patients underwent TOWO to correct rigid thoracolumbar kyphosis. Radiographic parameters were compared before surgery, 1 week after surgery and at the last follow-up. The SRS-22 questionnaire was given before surgery and at the last follow-up to evaluate clinical improvement. The operating time, estimated blood loss and complications were analyzed.

RESULTS

The mean operating time and estimated blood loss were 236 min and 595 ml, respectively. The mean preoperative sagittal vertical axis (SVA), thoracic kyphosis (TK), pelvic tilt (PT) and thoracolumbar kyphosis (TLK) were 158.97 mm, 51.24 mm, 43.63 mm and 41.74 mm, respectively, and decreased to 66.72 mm, 35.96 mm, 27.21 mm and 8.67 mm at the last follow-up. The mean preoperative lumbar lordosis (LL) and sacral slope (SS) were 8.30 ± 24.43 mm and 19.67 ± 9.40 mm, respectively, which increased to 38.23 mm and 28.13 mm at the last follow-up. The mean height of the anterior column of osteotomized vertebrae increased significantly from 25.17 mm preoperatively to 37.59 mm at the last follow, but the height of the middle column did not change significantly. SRS-22 scores were improved significantly at the last follow-up compared with preoperatively. Solid bone union was achieved in all patients after 12 months of follow-up, and no screw loosening, screw removal or rod breakage was noticed at the last follow-up.

CONCLUSIONS

TOWO could achieve satisfactory kyphosis correction by opening the anterior column instead of vertebral body decancellation and posterior column closing, thus simplifying the osteotomy procedure and improving surgical efficacy.

Clinical and radiological outcomes of endoscopic foraminoplasty and decompression assisted with preoperative planning software for lumbar foraminal stenosis

PURPOSE

To assess the clinical and radiological outcomes of using endoscopic foraminoplasty and decompression assisted with a preoperative planning software in the treatment of lumbar foraminal stenosis.

METHODS

This retrospective study included 43 patients with lumbar foraminal stenosis (Jan 2018 and June 2019). These patients were divided into two groups. Patients in the conventional group (group A) underwent endoscopic lumbar foraminoplasty and decompression. Patients in the experimental group (group B) underwent the same surgery assisted with a preoperative software. The total operation time, puncture-channel establishment time, and the number of intraoperative fluoroscopic images taken were recorded. The Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) were administered preoperatively and postoperatively (at 1-month, 3-month, and 12-month follow-up). The modified MacNab criteria were used to assess the global outcome at 12-month follow-up.

RESULTS

Patients in group B had shorter operation time, puncture-channel establishment time, and less number of intraoperative fluoroscopic images taken, as compared with group A. The VAS and ODI scores were significantly lower than pre-operation for both groups at all follow-ups. No significant difference was observed between these two groups. Based on the modified MacNab criteria, the excellent-to-good rate was 86.4% in group A and 90.5% in group B, respectively. After the operation, no patients had residual osteophytes in group B, while two patients still had residual osteophytes and foraminal stenosis in group A.

CONCLUSION

For endoscopic surgery treating lumbar foraminal stenosis, using preoperative planning software could reduce the puncture-channel establishment time, operation time, and the number of intraoperative fluoroscopic images taken without affecting the clinical outcomes.

When Can One-level Pedicle Subtraction Osteotomy Obtain Satisfied Outcomes for Severe Thoracolumbar Kyphosis with Global Kyphosis ≥80° in Ankylosing Spondylitis: A Comparison with Two-level Pedicle Subtraction Osteotomy

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to make a thorough comparison of clinical and radiographic outcomes between ankylosing spondylitis (AS) patients with severe kyphosis who underwent one- or two-level pedicle subtraction osteotomy (PSO) and to determine the indications of one-level PSO.

SUMMARY OF BACKGROUND DATA

Traditionally, one-level PSO was considered being able to obtain 35° to 40° correction. However, in our practice, one-level PSO might achieve satisfied clinical and radiographic outcomes in AS patients with severe thoracolumbar kyphosis defined as global kyphosis (GK) ≥80°.

METHODS

Fifty-five AS-related severe thoracolumbar kyphosis patients undergoing one- or two-level PSO from January 2007 to November 2016 were reviewed. The radiographic parameters included thoracic kyphosis (TK), lumbar lordosis (LL), GK, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), and femoral obliquity angle (FOA). Clinical outcomes were evaluated by Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS).

RESULTS

The mean follow-up period was 39.7 ± 20.2 months (range, 24-120 months). Patients who underwent one-level PSO have significantly smaller preoperative GK, SVA, FOA, and larger preoperative LL and SS compared to those who underwent two-level PSO (P < 0.05). The optimal cutoff points of preoperative radiographic parameters for selecting one-level PSO were: GK <94°, SVA <18.0 cm, and LL <18°. No significant difference was observed between the two groups with regard to preoperative ODI and VAS (P > 0.05), and the improvement of ODI and VAS (P > 0.05). Significantly more operative time, blood loss, and fusion levels were found in two-level PSO group (P < 0.05).

CONCLUSION

One-level PSO might be appropriate for selected severe AS-related kyphosis patients with GK <94°, SVA <18.0 cm, and LL <18°. This finding might be beneficial for surgical decision-making in performing one-level PSO, a relatively less risky procedure, to reconstruct the ideal sagittal alignment in AS patients with severe thoracolumbar kyphosis.Level of Evidence: 2.

Surgical Treatment for Severe Fixed Hyperkyphosis in an Adult Patient Suffering From Ankylosing Spondylitis and Hereditary Hypophosphatemia With Vertebral Osteopetrosis

PURPOSE

Ankylosing spondylitis and hereditary hypophosphatemia with long-term high dose supplementation of phosphorous and calcitriol can both lead to severe structural abnormalities of the vertebrae. Impairment of spinal mobility and spinal deformity may ultimately necessitate surgical treatment. A severe fixed hyperkyphosis in a patient with ankylosing spondylitis is a surgically demanding condition, therefore, the indication for surgical treatment should be thoroughly considered and chosen individually.

METHODS

This is an uncommon case with a combination of a severe fixed hyperkyphosis with a Cobb-angle of 105 degrees between Th2 and L4 in an adult male patient suffering from ankylosing spondylitis and X-linked hypophosphatemia with surprisingly massive osteopetrosis. In this paper, the coexisting conditions of late-stage ankylosing spondylitis and long-term treated hereditary hypophosphatemia are highlighted. The surgical treatment with different techniques, complications, and results are well explained.

RESULTS

A normal gait and stand were achieved by a long posterior fusion with 3 pedicle subtraction osteotomies on L1, L3, and L5. The surgical correction was performed in 3 stages. Postoperative the patient was administered to a rehabilitation center for 3 months. The hyperkyphosis, the C7 plumbline, and the pelvic retroversion were corrected.

CONCLUSIONS

Surgical treatment of a severe fixed hyperkyphosis due to ankylosing spondylitis is technically demanding but can be successfully achieved if all surgical challenges and comorbidities are adequately addressed including intraoperative surprising findings like osteopetrotic bone in a patient with hereditary hypophosphatemia as in our case.

Two-Level Osteotomy for the Corrective Surgery of Severe Kyphosis From Ankylosing Spondylitis: A Retrospective Series

STUDY DESIGN

Retrospective study.

OBJECTIVE

To describe the treatment results of patients with severe ankylosing spondylitis (AS) kyphosis who underwent two-level osteotomy and correction surgery.

SUMMARY OF BACKGROUND DATA

The best solution for the fixed kyphotic deformity of AS is corrective osteotomy. Many osteotomy options are available: pedicle subtraction osteotomy (PSO), Smith-Peterson osteotomy (SPO), and vertical column resection (VCR). These procedures all provide multiplanar deformity correction. Nevertheless, when the AS deformity is severe, an additional osteotomy site to get more correction, achieve more ideal, and smooth curvature of the spine than single osteotomy.

METHODS

From May, 2008 to August, 2016, 19 patients of severe AS kyphosis underwent two-level spinal osteotomy and correction surgery. The patients had an average kyphosis angle greater than 90°. The radiological features and clinical evaluation, including Oswestry Disability Index (ODI), visual analog scale (VAS), and Scoliosis Research Society (SRS)-22 components were assessed before surgery and at follow-up. The patients underwent either one-level PSO combined with one-level SPO (n = 9) or two-level PSO (n = 10).

RESULTS

The height was increased after surgery in all patients (P < 0.05). The median follow-up was 24 months. The kyphosis angle improved from 92.0 ± 16.6° to 30.0 ± 17.2°. The chin-brow vertical angle improved from 37.6 ± 19.2° to -0.6 ± 2.5°. The sacral slope improved from 3.9 ± 11.8° to 21.7 ± 7.4°. Sagittal imbalance improved from 241.4 ± 115.3 mm to 74.6 ± 48.5 mm (P < 0.05). Lumbar lordosis improved from -3.9 ± 20.8° to 29.4 ± 14.1° (all P < 0.05). There were significant improvements in the ODI, VAS, and all components of SRS-22 (all P < 0.05). All patients with pseudarthrosis (n = 5) underwent PSO + SPO and achieved satisfactory results. Six complications were observed perioperatively, but without permanent sequelae.

CONCLUSION

Two-level osteotomy and correction procedure can achieve satisfactory results in severe AS kyphosis. PSO + SPO could be a good option for patients with pseudarthrosis because of relatively easier and faster operation.

LEVEL OF EVIDENCE

4.

Vertebral column decancellation in Pott's deformity: use of Surgimap Spine for preoperative surgical planning, retrospective review of 18 patients

Background

In the late stage of Spinal tuberculosis, the bony destruction and vertebral collapse often leads to significant kyphosis, presenting clinically as a painful gibbus deformity, with increased instability, vertebral body translations and increased risk of neurologic involvement. Vertebral column decancellation is thought to be suitable for most patients with severe rigid kyphosis. Surgimap Spine, could offer a pragmatic graphical method for the surgical planning of osteotomies. The aim of this study was to evaluate the efficacy of Vertebral column decancellation planned preoperatively with the computer software-assistance in the patients with Pott’s kyphosis.

Methods

Between May 2012 and May 2015, 18 patients with Pott’s kyphosis underwent the Vertebral column decancellation using Surgimap Spine for preoperative surgical planning. Preoperative and postoperative Konstam’s angle, sagittal vertical angle, lumbar lordosis, thoracic kyphosis, pelvic tilt and pelvic incidence were measured. Visual analog scale and American Spinal Injury Association were documented.

Results

The Konstam’s angles decreased from 88.1° (range, 70–105°) preoperatively to 18.5° (range, 7–31°) (P < 0.01). All patients reached the physiological limits at the final follow-up. The mean VAS score was reduced from preoperative 7.1 (range, 6–8) to 1.8 (range, 1–3, P < 0.01) and the ODI improved from 65.8% (range, 58–74%) to 20.2% (range, 12–38%, P < 0.01). At final follow-up, there was radiographic evidence of solid fusion at the osteotomy site and fixed segments in all patients. Neurological function improved from ASIA scale D to E in 5 patients. The patients were followed up for 30.4 months on average.

Conclusion

Vertebral column decancellation is an effective treatment option for severe Pott’s kyphosis. The surgical planning software Surgimap Spine can be a reliable and helpful tool that provides a simplified method to evaluate and analyze the spino-pelvic parameters and simulate the osteotomy procedure. According to individual character, the appropriate surgery strategy should be selected.

Osteotomies in ankylosing spondylitis: where, how many, and how much?

INTRODUCTION

This article presents the current concepts of correction of spinal deformity in ankylosing spondylitis (AS) patients. Untreated AS can be a debilitating disease. In a few patients, disease progression results in severe spinal deformity affecting not only the thoracolumbar, but also the cervical spine. Surgery for correction in AS patients has a long history. With the advent of modern instrumentation, standardization of surgical and anesthesiologic techniques, surgical safety and corrective results could be improved and experiences from lumbar osteotomies could be transferred to the cervical spine.

METHODS

This article presents the current concepts of correction of spinal deformity in AS patients. In particular, questions regarding the localization and number of osteotomies, the optimal surgical target angle as well as planning and prediction of postoperative alignment are discussed.

RESULTS

Insight into recent technical developments, current challenges with correction and geometric analysis of center of rotation (COR) in cervical 3-column osteotomies (3CO) will be presented.

CONCLUSION

The article should encourage readers to improve surgical correction efficacy and provide a better understanding of correction geometry in 3CO for thoracolumbar and cervical spinal deformities.

Predictive Accuracy of Surgimap Surgical Planning for Sagittal Imbalance: A Cohort Study

MINI: Surgical planning in sagittal imbalance is recognized as a key step of treatment to ensure good clinical results. Surgimap is a reliable tool to predict satisfactory postoperative sagittal alignment. Setting by default pelvic tilt to 20° improves predictive value during surgical planning.

STUDY DESIGN

A cohort study.

OBJECTIVE

To evaluate the predictive value of surgical planning using Surgimap regarding postoperative sagittal alignment.

SUMMARY OF BACKGROUND DATA

Surgical planning in sagittal imbalance is recognized as a key step of treatment to ensure results.

METHODS

The study involved 40 nonconsecutive patients who underwent surgery for sagittal misalignment. Postoperative alignment measured by sagittal vertical axis (SVA) and pelvic tilt was considered the gold standard. Surgimap prediction of final alignment was considered the test. Planning and postoperative films were classified as properly and improperly aligned. Sensitivity, specificity, and positive and negative predictive values of Surgimap planning [using two different methods: direct simulation (method A) and simulation after correction of pelvic tilt to 20° (method B)] to detect postoperative improper alignment were calculated.

RESULTS

Seventeen (42.5%) of 40 patients had proper postoperative alignment. According to method A, a proper alignment was achieved in 13 patients [S = 76.5%, Sp = 73.9%, RR = 2.93 (95% confidence interval, CI 1.40; 6.12), P < 0.001]; According to method B, a proper alignment was achieved in 15 patients [S = 88.2%, Sp = 60.9%, RR = 2.25 (95% CI 1.32; 23.86), P < 0.001]. Kappa statistics indicate moderate agreement between actual postoperative alignment and computer prediction.

CONCLUSION

The ability of Surgimap to predict proper postoperative sagittal alignment was excellent in this cohort. Its ability to predict proper alignment was improved by correction of pelvic tilt to 20° during planning.

LEVEL OF EVIDENCE

2.

A Preliminary Algorithm Using Spine Measurement Software to Predict Sagittal Alignment Following Pedicle Subtraction Osteotomy

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To evaluate if spine measurement software can simulate sagittal alignment following pedicle subtraction osteotomy (PSO).

METHODS

We retrospectively reviewed consecutive adult spinal deformity patients who underwent lumbar PSO. Sagittal measurements were performed on preoperative lateral, standing radiographs. Sagittal measurements after simulated PSO were compared to actual postoperative measurements. A regression equation was developed using cases 1-7 to determine the amount of manual rotation required of each film to match the simulated sagittal vertical axis (SVA) to the actual postoperative SVA. The equation was then applied to cases 8-13.

RESULTS

For all 13 cases, the spine software accurately simulated lumbar lordosis, pelvic incidence lumbar lordosis mismatch, and T1 pelvic angle, with no significant differences between actual and simulated measurements. The pelvic tilt (PT), sacral slope (SS), thoracolumbar alignment (TL), thoracic kyphosis (TK), T9 spino-pelvic inclination (T9SPi), T1 spino-pelvic inclination (T1SPi), and SVA were inaccurately simulated. The PT, SS, T9SPi, T1SPi, and SVA all change with manual rotation of the film, and by using the regression equation developed with cases 1-7, we were able to improve the accuracy and decrease the variability of the simulated PT, SS, T9SPi, T1SPi, and SVA for cases 8-13.

CONCLUSIONS

Dedicated spine measurement software can accurately simulate certain sagittal measurements, such as LL, PI-LL, and TPA, following PSO. A number of measurements, including PT, SS, TL, TK, T9SPi, T1SPi, and SVA were inaccurately simulated. Our preliminary algorithm improved the accuracy and decreased the variability of certain measurements, but requires future prospective studies for further validation.