Pedicle subtraction osteotomy in the lumbar spine: indications, technical aspects, results and complications

Two-Year Radiological Outcome of Adult Spinal Deformity Treated with Lumbar Pedicle Subtraction Osteotomy or Posterior Lumbar Interbody Fusion: A Propensity Score-Matched Analysis

OBJECTIVE

The purpose of this retrospective cohort study was to compare the 2-year radiological outcome and revision rates in patients with adult spinal deformity treated with either pedicle subtraction osteotomy (PSO) or posterior lumbar interbody fusion (PLIF), when PLIF was used to improve sagittal balance.

METHODS

In 2016, PLIF was introduced at our institution as an alternative method when restoring lumbar lordosis. We analyzed 2 cohorts of patients with adult spinal deformity undergoing either PSO in 2010-2015 or PLIF in 2016-2020, retrospectively. The rate of mechanical failure was analyzed using competing risk analysis.

RESULTS

We included 141 patients (111 PSO and 30 PLIF). After propensity score matching, 60 patients undergoing PSO and 30 patients undergoing PLIF were included. Baseline demographics were comparable between groups but radiographic parameters differed significantly on Sacral Slope; 23 ± 13 versus 28 ± 10, and segmental lordosis; 7 ± 14° versus. 14 ± 13° (P-value < 0.05) for PSO and PLIF, respectively. Postoperatively, PSO patients had a larger global lordosis; 54 ± 12 versus 48 ± 14 and segmental lordosis of 33 ± 10 versus 26 ± 10 (P-value < 0.05), than PLIF patients. Competing risk analysis showed a cumulative incidence of revision surgery of 38.3% (95% CI 28-43) versus 16.7 (95% CI 3-30), (P-value < 0.05) for PSO, and PLIF at 2-year follow-up.

CONCLUSIONS

A significantly lower revision rate was seen for patients undergoing PLIF compared with PSO at a 2-year follow-up. A satisfactory sagittal correction was obtained for both groups regardless of the procedure. Thus, PLIF could be a viable option in selected cases.

What factors are associated with a better restoration of pelvic version after adult spinal deformity surgery?

INTRODUCTION

Poor restoration of pelvic version after adult spinal deformity (ASD) surgery is associated with an increased risk of mechanical complications and worse quality of life. We studied the factors linked to the improvement of postoperative pelvic version.

MATERIALS AND METHODS

This is a retrospective analysis of a prospective multicenter ASD database. Selection criteria were: operated patients having preoperative severe pelvic retroversion as per GAP score (Relative Pelvic Version-RPV < - 15°); panlumbar fusions to the pelvis; 2-year follow-up. Group A comprised patients with any postoperative improvement of RPV score, and group B had no improvement. Groups were compared regarding baseline characteristics, surgical factors, and postoperative sagittal parameters. Parametric and non-parametric analyses were employed.

RESULTS

177 patients were studied, median age 67 years (61; 72.5), 83.6% female. Groups were homogeneous in baseline demographics, comorbidities, and preoperative sagittal parameters (p > 0.05). The difference in RPV improvement was 11.56º. Group A (137 patients) underwent a higher percentage of ALIF procedures (OR = 6.66; p = 0.049), and posterior osteotomies (OR = 4.96; p < 0.001) especially tricolumnar (OR = 2.31; p = 0.041). It also showed a lower percentage of TLIF procedures (OR = 0.45; p = 0.028), and posterior decompression (OR = 0.44; p = 0.024). Group A displayed better postoperative L4-S1 angle and relative lumbar lordosis (RLL), leading to improved sacral slope (and RPV), and global alignment (RSA). Group A patients had longer instrumentations (11.45 vs 10; p = 0.047) and hospitalization time (13 vs 11; p = 0.045). All postoperative sagittal parameters remained significantly better in group A through follow-up. However, differences between the groups narrowed over time.

CONCLUSIONS

ALIF procedures and posterior column osteotomies improved pelvic version postoperatively, and associated better L4-S1 and lumbar lordosis restoration, indirectly improving all other sagittal parameters. However, these improvements seemed to fade during the 2-year follow-up.

The Surgical Outcomes of Pedicle Subtraction Osteotomy per Different First Assistant: Retrospective Analysis of 312 Cases

INTRODUCTION

Pedicle subtraction osteotomies (PSOs) are complex spinal deformity surgeries that are associated with high complication rates. They are typically done by an experienced spine surgeon with another attending, resident, or physician assistant serving as the first assistant. The purpose of this study was to determine whether selecting a surgical team for single-level PSO based on case difficulty and fusion length could equalize intraoperative and perioperative outcomes among three groups: dual-attending (DA), attending and orthopaedic resident (RS), and attending and physician assistant (PA).

METHODS

This study was a retrospective cohort analysis of 312 patients undergoing single-level thoracic or lumbar PSO from January 2007 to December 2020 by a fellowship-trained orthopaedic spine surgeon. Demographic, intraoperative, and perioperative data within 30 days and 2 years of the index procedure were analyzed.

RESULTS

Patient demographics did not markedly differ between surgical groups. The mean cohort age was 64.5 years with BMI 31.9 kg/m 2 . Patients with the DA approach had a significantly longer surgical time (DA = 412 min vs. resident = 372 min vs. physician assistant = 323 min; P < 0.001). Patients within the DA group experienced a significantly lower rate of infection (DA = 2.1% [3/140] vs. RS = 7.9% [9/114] vs. PA = 1.7% [1/58], P = 0.043), surgical complication rate (DA = 26% [37/140] vs. RS = 41% [47/114] vs. PA = 33% [19/58], P < 0 .001), and readmission rate (DA = 6.4% [9/140] vs. RS = 12.3% [14/114] vs. PA = 19% [11/58] P = 0.030) within 30 days of surgery. No notable differences were observed among groups in 2-year complication, infection, readmission, or revision surgery rates.

CONCLUSIONS

These study results support the DA surgeon approach. Resident involvement, even in less complex cases, can still negatively affect perioperative outcomes. Additional selection criteria development is needed.

The "Sandwich" Extended Pedicle Subtraction Osteotomy for the Treatment of Fixed Sagittal Malalignment: Technical Description, Case Series, and Early Results With 2-Year Outcomes

BACKGROUND AND OBJECTIVES

Adult spinal deformity (ASD) with fixed sagittal malalignment (FSM) may require a pedicle subtraction osteotomy (PSO) for greater focal lordosis and restoration of global alignment. Despite growing trends in minimizing PSOs given their associated high risks, a considerable portion of patients with ASD still require a lumbar PSO most commonly because of iatrogenic flat back deformity. The purpose of this article is to describe a modified extended PSO technique with additional anterior column support coined the "sandwich" extended PSO (SE-PSO) to promote arthrodesis and report the outcomes in a consecutive case series.

METHODS

Patients with ASD treated with a lumbar SE-PSO at a single institution from 2015 to 2020 were analyzed. Complications, radiographic data, and patient-reported outcomes were compared preoperatively, at immediate postoperative follow-up, and at a 2-year postoperative follow-up (FU).

RESULTS

Fourteen patients who underwent revision operations for FSM were included. Improvements in segmental lordosis across the PSO site (14.8 ± 6.8 vs 39.9 ± 7.1, P < .0001), overall lumbar lordosis (14.6 ± 15.4 vs 44.6 ± 12.1, P < .0001), sacral slope (21.0 ± 10.5 31.1 ± 10.7, P = .0150), C7 sagittal vertical axis (140.1 ± 59.0 mm vs 35.9 ± 28.5, P < .0001), and spinopelvic mismatch (52.5 ± 21.3 vs 18.6 ± 14.1, P = .0001) were obtained in all patients. Eight patients experienced perioperative complications, with intraoperative durotomy being the most common (n = 7). Eight patients had a 2-year FU and demonstrated improvements in their segmental lordosis across the PSO site (14.3 ± 7.0 vs 41.3 ± 7.3, P = .0003), overall lumbar lordosis (8.7 ± 17.8 vs 46.1 ± 14.2, P = .0014), sacral slope (19.1 ± 12.8 vs 32.3 ± 12.5, P = .0479), C7 sagittal vertical axis (173.6 ± 54.4 mm vs 35.8 ± 30.0, P < .0001), and spinopelvic mismatch (63.0 ± 19.7 vs 21.1 ± 18.3, P < .0001), all of which were maintained at final FU (P > .05). At 2 years, a significant increase in Scoliosis Research Society-22r total score (2.5 ± 0.8 vs 3.6 ± 0.7, P = .0023 was reported. There were no reports of symptomatic pseudarthrosis or mechanical complications.

CONCLUSION

SE-PSO is an effective technique to correct FSM and is associated with low complications, improved patient-reported outcomes, and spinopelvic parameters that are maintained at 2 years.

Posterior-based Osteotomies for Deformity Correction

Posterior-based osteotomies are crucial to the restoration of lordosis in adult spinal deformity. Posterior-column osteotomies are suited for patients with an unfused anterior column and non-focal sagittal deformity requiring modest correction in lordosis. When performed on multiple levels, posterior-column osteotomy may provide significant harmonious correction in patients who require more extensive correction. Pedicle subtraction osteotomy and vertebral column resection are appropriate for patients with a fused anterior column and more severe deformity, particularly focal and/or multiplanar deformity. The power of pedicle subtraction osteotomy and vertebral column resection to provide greater correction and to address multiplanar deformity comes at the cost of higher complication rates than posterior-column osteotomy.

Lumbar Disc Degeneration Affects the Risk of Rod Fracture Following PSO; A Finite Element Study

STUDY DESIGN

Finite element (FE) study.

OBJECTIVE

Pedicle subtraction osteotomy (PSO) is a surgical method to correct sagittal plane deformities. In this study, we aimed to investigate the biomechanical effects of lumbar disc degeneration on the instrumentation following PSO and assess the effects of using interbody spacers adjacent to the PSO level in a long instrumented spinal construct.

METHODS

A spinopelvic model (T10-pelvis) with PSO at the L3 level was used to generate 3 different simplified grades of degenerated lumbar discs (mild (Pfirrmann grade III), moderate (Pfirrmann grade IV), and severe (Pfirrmann grade V)). Instrumentation included eighteen pedicle screws and bilateral primary rods. To investigate the effect of interbody spacers, the model with normal disc height was modified to accommodate 2 interbody spacers adjacent to the PSO level through a lateral approach. For the models, the rods' stress distribution, PSO site force values, and the spine range of motion (ROM) were recorded.

RESULTS

The mildly, moderately, and severely degenerated models indicated approximately 10%, 26%, and 40% decrease in flexion/extension motion, respectively. Supplementing the instrumented spinopelvic PSO model using interbody spacers reduced the ROM by 22%, 21%, 4%, and 11% in flexion, extension, lateral bending, and axial rotation, respectively. The FE results illustrated lower von Mises stress on the rods and higher forces at the PSO site at higher degeneration grades and while using the interbody spacers.

CONCLUSIONS

Larger and less degenerated discs adjacent to the PSO site may warrant consideration for interbody cage instrumentation to decrease the risk of rod fracture and PSO site non-union.

Factors influencing complications after 3-columns spinal osteotomies for fixed sagittal imbalance from multiple etiologies: a multicentric cohort study about 286 cases in 273 patients

PURPOSE

Spinal osteotomies performed to treat fixed spinal deformities are technically demanding and associated with a high complications rate. The main purpose of this study was to analyze complications and their risk factors in spinal osteotomies performed for fixed sagittal imbalance from multiple etiologies.

METHODS

The study consisted of a blinded retrospective analysis of prospectively collected data from a large multicenter cohort of patients who underwent 3-columns (3C) spinal osteotomy, between January 2010 and January 2017. Clinical and radiological data were compared pre- and post-operatively. Complications and their risk factors were analyzed.

RESULTS

Two hundred eighty-six 3C osteotomies were performed in 273 patients. At 1 year follow-up, both clinical (VAS pain, ODI and SRS-22 scores) and radiological (SVA, SSA, loss of lordosis and pelvic version) parameters were significantly improved (p < 0.001). A total of 164 patients (59.2%) experienced at least 1 complication (277 complications). Complications-free survival rates were only 30% at 5 years. Most of those were mechanical (35.2%), followed by general (17.6%), surgical site infection (17.2%) and neurological (10.9%). Pre-operative neurological status [RR = 2.3 (1.32-4.00)], operative time (+ 19% of risk each additional hour) and combined surgery [RR = 1.76 (1.08-2.04)] were assessed as risk factors for overall complication (p < 0.05). The use of patient-specific rods appeared to be significantly associated with less overall complications [RR = 0.5 (0.29-0.89)] (p = 0.02).

CONCLUSION

Spinal 3C osteotomies were efficient to improve both clinical and radiological parameters despite high rates of complication. Efforts should be made to reduce operative time which appears to be the strongest predictive risk factor for complication.

Does the Level of Pedicle Subtraction Osteotomy Affect the Surgical Outcomes in Ankylosing Spondylitis-Related Thoracolumbar Kyphosis With the Same Curve Pattern?

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the effect of pedicle subtraction osteotomy (PSO) level on the surgical outcomes in ankylosing spondylitis-related thoracolumbar kyphosis with the same curve pattern.

METHODS

ankylosing spondylitis (AS) patients with thoracolumbar kyphosis, who underwent 1-level lumbar PSO between March 2006 and June 2017, were retrospectively reviewed. Criteria for curve-matched thoracolumbar kyphosis were: (1) have same level of preoperative apex (pre-apex); (2) have similar global kyphosis (GK, the angle between the superior/inferior endplate of the maximally tilted upper and lower end vertebra) (the difference of GK less than 15˚). The radiographic parameters measured were sagittal vertical axis (SVA, the horizontal distance between the C7 plumb line and the posterosuperior corner of the S1), GK, thoracic kyphosis (TK, the angle between the T5 superior endplate and the T12 inferior endplate), lumbar lordosis (LL, the angle between the L1 and S1 superior endplate), sacral slope (SS, the angle between the sacral endplate and the horizontal line), pelvic tilt (PT, the angle between the vertical and the line joining the midpoint of the sacral plate and hip axis), and pelvic incidence (PI, the angle between the line vertical to the superior margin of S1 and the line connecting the sacral plate midpoint with the hip joint axis). All of these parameters and health-related quality of life (HRQoL, evaluated by preoperative and the last follow-up questionnaires including ODI and VAS) scores were collected before surgery and at the last follow-up. According to their osteotomy level, patients were devided into 2 sub-groups (L1 group and L2 group), and differences of these mentioned parameters between 2 groups were compared.

RESULTS

26 curve-matched patients were recruited with a mean follow-up of 37.2 months. All patients improved significantly after surgery in HRQoL scores (VAS 1.6 vs 5.4, P < 0.001; ODI 11.9 vs 26.4, P < 0.001). Except for TK and PI, those radiographic parameters were also observed to be significantly changed after surgery. Compared to L2 group, PSO at L1 may have larger correction of TK (ΔTK -6.8 vs -0.3°, P = 0.164), PI (ΔPI -7.4 vs -0.7°, P = 0.364) and smaller correction of SVA (ΔSVA -105.3 vs -128.5 mm, P = 0.096), LL (ΔLL -31.1 vs -43.0°, P = 0.307) and SS (ΔSS 6.9 vs 12.2°, P = 0.279) but had no statistical significance.

CONCLUSION

The results of this investigation showed that in AS-related thoracolumbar kyphosis patients with the same curve pattern, the different levels of osteotomy had little effect on the improvement of surgical outcomes. However, osteotomy at L2 is more likely to obtain a larger correction of SVA compared to osteotomy at L1.

How do additional rods reduce loads on the primary rods in adult spinal instrumentation with pedicle subtraction osteotomy?

BACKGROUND

Additional auxiliary rods have been used in spinal instrumentation across pedicle subtraction osteotomy to reduce stresses in the primary rods. The auxiliary rods can be connected through dual-rod-screws, fixed-angle multi-rod connectors or variable-angle multi-rod connectors. The objective was to assess rod bending in conventional bilateral-rod construct vs. constructs with auxiliary rods.

METHODS

Computer models of two adult patients were developed to evaluate bending loads across a pedicle subtraction site in a control construct with bilateral rods vs. constructs with auxiliary rods bilaterally or unilaterally connected to the primary rods through either dual-rod-screws, fixed-angle multi-rod connectors, or variable-angle multi-rod connectors. Postoperative rod bending loads were computed and compared.

FINDINGS

Normalizing loads on the primary rods in the multi-rod constructs to the control construct, primary rod loads in multi-rod constructs were 17% to 48% lower than the control construct. Constructs with bilateral auxiliary rods through dual-rod-screws, fixed-angle multi-rod connectors, or variable-angle multi-rod connectors could result in similar primary rod bending loads. Bending loads on the auxiliary rods were higher or lower than those on the primary rods depending on how their curvatures matched the primary rods, and how they were locked onto the primary rods.

INTERPRETATION

Auxiliary rods noticeably reduced the bending loads on the primary rods compared with a standard bilateral-rod construct. Loads in the auxiliary rods were higher or lower than those in the primary rods depending on how their curvatures matched the primary rods, and how they were locked onto the primary rods.

Flexing a standard hinge-powered operating table for lumbosacral three-column osteotomy (3-CO) site closure in 84 consecutive patients

Three-column osteotomy (3-CO) is a powerful technique in adult deformity surgery, and pedicle subtraction osteotomy (PSO) is the workhorse to correct severe kyphotic spinal deformities. Aging of the population, increasing cases of iatrogenic flat back deformities and understanding the importance of sagittal balance have led to a dramatic increase of this surgical technique. Surgery, however, is demanding and associated with high complication rates so that every step of the procedure requires meticulous technique. Particularly, osteotomy closure is associated with risks like secondary fracture, translation, or iatrogenic stenosis. This step is traditionally performed by compression or a cantilever maneuver with sometimes excessive forces on the screws or instrumentation. Implant loosening or abrupt subluxation resulting in construct failure and/or neurological deficits can result. The aim of this prospective registry study was to assess the efficacy and safety of our surgical PSO technique as well as the osteotomy closure by flexing a hinge-powered OR table. In a series of 84 consecutive lumbosacral 3-CO, a standardized surgical technique with special focus on closure of the osteotomy was prospectively evaluated. The surgical steps with the patients positioned prone on a soft frame are detailed. Osteotomy closure was achieved by remote controlled bending of a standard OR table without compressive or cantilever forces in all 84 cases. This technique carries a number of advantages, particularly the reversibility and the slow speed of closure with minimum force. There was not a single mechanical intraoperative complication such as vertebral body fracture, subluxation, or adjacent implant loosening during osteotomy closure, compared to external cohorts using the cantilever technique (p = 0.130). The feasibility of controlled 3-CO closure by flexing a standard OR table is demonstrated. This technique enables a safe, gentle closure of the osteotomy site with minimal risk of implant failure or accidental neurological injury.

Pseudarthrosis in adult spine deformity surgery: risk factors and treatment options

PURPOSE

Highlight risk factors for pseudarthrosis in long-segment spinal fusions, collect the approaches carried to address this complication.

METHODS

Patients with ASD and fusion of ≥ 4 levels with minimum follow-up (FU) of ≥ 2 years were included. Full-body X-rays were done preoperatively, < 3 months and ≥ 2 years. Oswestry disability index (ODI), Scoliosis Research Society-22 and SF36 assessed pre- and postoperatively. The relationship between demographic, surgical and radiological variables with the development of pseudarthrosis was evaluated.

RESULTS

Out of 524 patients included, 65 patients (12.4%) developed pseudarthrosis and 53 underwent revision surgery. Notably, 88% of pseudarthrosis cases are associated with fusion length (OR = 1.17, 95% CI = 1.05-1.292, p = 0.004), osteotomy requirement (OR = 0.28, 95% CI = 0.09-0.85, p = 0.025), pelvic fixation (OR = 0.34, 95% CI = 0.13-0.88, p = 0.026) and combined approaches (OR = 3.29, 95% CI = 1.09-9.91, p = 0.034). Sagittal alignment is not related to the rate of pseudarthrosis. Health related and quality of life scores were comparable at last FU between patients revised for pseudarthrosis and those that didn't require revision surgery (ODI = 28% no revision and 30% revision group).

CONCLUSIONS

Pseudarthrosis is not related to malalignment, but with the surgical techniques employed for its treatment. Anterior approaches with anterior support decrease the rate by 30%, while long fusions, osteotomies and pelvic fixation increase its rate.

Hybrid Anterior Column Realignment-Pedicle Subtraction Osteotomy for Severe Rigid Sagittal Deformity

OBJECTIVE

Recently, a hybrid anterior column realignment-pedicle subtraction osteotomy (ACR-PSO) approach has been conceived for patients with severe rigid sagittal deformity, the clinical and radiographic outcomes of which require further investigation compared with ACR only.

METHODS

A single-center, retrospective chart review identified patients undergoing a combination of hyperlordotic lateral lumbar interbody grafting (ACR) and concurrent Schwab grade 3 three-column osteotomy and propensity-matched patients undergoing ACR only in the same time frame. Anterior longitudinal ligament was directly released or partially sectioned in all patients. Chart data included demographics, Oswestry Disability Index scores, ACR and osteotomy locations, cage dimensions, fusion length, and complications. Radiographic measurements included lumbar lordosis, sagittal vertical axis, pelvic tilt (PT), and proximal junctional kyphosis.

RESULTS

Fourteen patients were enrolled in the ACR + PSO group and 36 in the ACR-only group. Mean ages were 68.5 and 63.9 years, 64% and 67% were female, average body mass index was 27.9 and 29.2, and cardiopulmonary comorbidities were 21% and 17%, respectively. There was no difference in complications (P = 0.347). The average follow-up for the ACR + PSO and ACR-only groups were 22 and 18 months, respectively. Excluding 2 mortalities, fusion occurred in all patients. Average change in lumbar lordosis measured -40.8 ± 9.2 degrees and -19.1 ± 15.7 degrees (P = 0.0006), and PT correction measured 10.5 ± 3.4 degrees and 27.3 ± 1.6 degrees (P < 0.0001), respectively.

CONCLUSIONS

For patients with severe rigid sagittal deformity, the hybrid ACR-PSO approach offers significant restoration of lumbar lordosis compared with ACR only, with similar complications but reduced PT correction.

Sagittal Deformity Correction in a Patient Suffering From Diffuse Idiopathic Skeletal Hyperostosis Who Previously Underwent a Total Hip and Bilateral Knee Replacement

Introduction

Physiological aging frequently leads to degenerative changes and spinal deformity. In patients with hypolordotic fusions or ankylosing illnesses such as diffuse idiopathic skeletal hyperostosis or ankylosing spondylitis, compensation mechanisms can be altered causing severe pain and disability. In addition, if a total hip replacement and/or knee replacement is performed, both pelvic and lower limbs compensation mechanisms could be damaged and prosthetic dislocation or impingement syndrome could be present. Pedicle subtraction osteotomy has proven to be the optimal correction technique for spinal deformation in patients suffering from a rigid spine.

Case Presentation

A 70-year-old male patient with diffuse idiopathic skeletal hyperostosis criteria and a rigid lumbar kyphosis, who previously underwent a total hip and knee replacement, had severe disability. We then performed corrective surgery by doing a pedicle subtraction osteotomy. The procedure and outcomes are presented here.

Conclusion

In symptomatic patients with sagittal imbalance and a rigid spine, pedicle subtraction osteotomy can indeed correct spinal deformity and re-establish sagittal balance.

[Battle: Indication for surgery in hip-spine syndrome-Hip or spine first? : The spine surgeon's view]

Pathologies of the hip, spine and the lower extremity are often concomitant due to their three-dimensional anatomic and physiological interrelation. The real challenge lies in defining which of the pathologies is most relevant for the patient in terms of clinical symptoms and which organ should be treated first. The purpose of this review article is two-fold: Firstly, to explain the treatment dilemma of hip-spine syndrome to the treating physician. Secondly, to highlight the significance of spinal pathology in this context.

Surgical site infection following surgery for spinal deformity: About 102 patients

INTRODUCTION

Complex spinal surgery is known to be at risk of complications. Surgical site infection is a serious complication in spine surgery and its frequency is significantly increased in adult spinal deformity correction. The aim of this study is to identify patients' characteristics and risk factors of surgical site infection (SSI) following an osteotomy.

METHODS

This is a single-center retrospective study of patients who underwent an osteotomy between January 2015 and December 2017. Surgical site infection diagnosis was based upon patient's clinical evidence of infection, biologic parameters, microbiological criteria and/or image findings.

RESULTS

In total, 102 patients were eligible and 70 were women (68.6%). Mean age was 65 years old (27-83 years) and mean body mass index (BMI) was 26.14kg.m^-2 (18.4-44.1). Eleven patients were in the SSI group and 91 in the No-SSI group. The mean Schwab grade was 1.5 (1-4) in the SSI group vs. 1.4 (1-5) in the No-SSI group (P=0.435). The mean operative time was on 201.9 minutes (67-377). Mean length of stay was 20.6 days (10-73) in the SSI group vs. 15 days (5-44) in the No-SSI group (P=0.041). Favorable outcome was found in 10 patients (90.9%) in the SSI group.

CONCLUSION

Correction surgery for adult spinal deformity with osteotomies carries a high risk of complications specially SSI. Identification of risk factors, prevention and medical management of SSI should be well assessed.

L5 pedicle subtraction osteotomy maintains good radiological and clinical outcomes in elderly patients with a rigid kyphosis deformity: a more than 2-year follow-up report

PURPOSE

L5 pedicle subtraction osteotomy (PSO) is a demanding technique; thus, PSOs are usually performed at the L3/L4 level to correct the lack of lumbar lordosis. Mid- to long-term improvements in clinical outcomes after L5 PSO are unknown. We aimed to determine the efficacy and safety of L5 PSO for rigid kyphosis deformities.

METHODS

We retrospectively reviewed the records of 57 patients with a rigid kyphosis deformity (mean age: 68 years) who underwent extensive corrective surgery incorporating PSO with a > 2-year follow-up. Radiographic parameters, postoperative complication rates, and the Oswestry Disability Index (ODI) scores were compared in the L5, L4, and L1-3 PSO groups preoperatively and at 1, 2, and 5 years postoperatively.

RESULTS

There were 12, 25, and 20 patients in the L5, L4, and L1-3 PSO groups, respectively. Significant between-group differences were found in preoperative L4-S1 lordosis (L5:L4:L1-3 PSO groups =  - 8.9°:8.9°:16.2°, P < 0.001). The surgeries improved the postoperative spinopelvic alignment (similar in all groups). There was no significant between-group difference in the postoperative complication rate; no irreversible complications occurred. In the L5 PSO group, there was one case of a common iliac vein injury. The ODI scores improved postoperatively in all groups; this was maintained for 5 years postoperatively.

CONCLUSION

L5 PSO for L4-5/L5 kyphosis deformities resulted in adequate correction and ODI improvement, which were maintained up to 5 years postoperatively. The surgical invasiveness, complication rates, and long-term prognosis associated with L5 PSO were similar to those of PSOs performed at other levels.

Individual Lordotic Cages Implantation and Radiographic Evaluation of Segmental and Lumbar Lordosis Correction for Patients with Adult Degenerative Scoliosis

Relevance. The development of minimally invasive surgery has led to the development of new methods for surgical treatment of the spine. Conventional surgical technique, such as vertebrotomy is accompanied by a several number of disadvantages (high blood loss, prolonged hospital stay, long intraoperative time, postoperative neurological deficit). An alternative to improve sagittal balance in the spine is to use custom-made hyperlordotic cages, which can also be used for indirect decompression of neural structures.

The objective is to compare the degree of segmental and total lumbar lordosis using hyperlordotic cages through ALIF and TLIF with posterior instrumentation.

Materials and Methods. A single-center retrospective cohort study using 96 patients treated from 2018 to 2019 about degenerative spinal deformities. Comparison of two groups: group 1 (A) consisted of 30 patients who were held anterior spinal fusion with individual lordotic cages from minimally invasive anterior approach (MISS ALIF) without posterior fixation. Group 2 (B) consisted of 33 patients whom were performed spinal fusion from the posterior approach (TLIF) with Smith-Peterson Osteotomy (SPO) and transpedicular fixation. Measuring segmental and lumbar lordosis, teleradiographs were used in a standing position. For an accurate assessment, the non-commercial available Surgimap software, © Nemaris, was used.

Results. Segmental lordosis were superior to preoperative ones. In the intergroup comparison, the ALIF group showed an excellent increase in the enlarged lordosis segment (L3-L4 in 8 degrees; p = 0.0005, L4-L5 in 7 degrees; p = 0.0002, L5-S1 in 7 degrees; p = 0.0001). When conducting an intergroup comparison of total lumbar lordosis in the preoperative period, there was a statistically significant difference between them (p = 0.0043). At the same time, a greater degree of correction of lordosis is shown in ALIF compared to TLIF group (29,1 in comparison with 22,5; p = 0.00005).

Conclusion. The results of this study confirm that the using of custom-made lordotic cages can significantly increase segmental and total lumbar lordosis for patients with degenerative scoliosis in adults.

Multilevel extended posterior column osteotomy plus unilateral cage strutting for degenerative lumbar kyphoscoliosis

OBJECTIVE

To explore the surgical outcome of patients with degenerative lumbar kyphoscoliosis who underwent multilevel extended posterior column osteotomy (PCO) plus unilateral cage strutting (UCS).

METHODS

From Jan 2012 to Aug 2017, 23 patients with degenerative lumbar kyphoscoliosis who underwent multilevel extended PCO plus UCS technique (study group) and 13 patients who underwent asymmetrical pedicle subtraction osteotomy (PSO) technique (control group) were retrospectively reviewed; the radiological features, including coronal/sagittal deformity, and clinical evaluation including Oswestry Disability Index (ODI), visual analog scale (VAS), and Japanese Orthopedic Association (JOA) scores-lumbar were assessed before surgery and at follow-up.

RESULTS

All patients underwent the operation successfully. There was no difference in fusion level, blood loss, and follow-up duration between the two groups; the operation time and length of hospital stay were shorter in study group than that in control group. All patients achieved significant correction of both scoliotic and kyphotic deformity and maintained the correction at minimum of two year follow-up, without any difference in deformity correction and correction loss between the two groups. All patients got back pain and leg pain alleviation and neurological function improvement at two year follow-up, without any difference between the two groups. The incidence of complications was lower in study group than that in control group.

CONCLUSION

Multilevel extended PCO plus UCS procedure could achieve significant correction of scoliosis and kyphosis in the treatment of degenerative lumbar kyphoscoliosis, presenting less surgery time, lower incidence of complication, and shorter hospital stay when compared with the asymmetric PSO technique.

Pedicle Subtraction Osteotomy

Pedicle subtraction osteotomy (PSO) was originally performed in cases of ankylosing spondylitis. This procedure was invented because it was safer than trying to lengthen the anterior column via osteoclasis, which risked vascular injury and death^1-4. PSO involves the removal of the posterior elements and the use of a vertebral body wedge to shorten the spine posteriorly and achieve sagittal-plane correction^5,6. PSO has been used to correct sagittal-plane deformities not only in patients with ankylosing spondylitis but also in those with degenerative conditions or those who have previously undergone surgical procedures resulting in a loss of lumbar lordosis^7,8.

Description

The fixation points are placed with pedicle screws above and below the planned osteotomy level. The posterior elements are decompressed at the level of the osteotomy and at 1 level proximally. In addition to the use of straight and angled curets, a high-speed burr is used to decancellate the vertebral body. Pedicle osteotomes are used to remove the pedicle. Temporary rods are placed. The posterior wall of the body is then impacted into the vertebral body, and the temporary rods are loosened. To close the osteotomy, the bed is extended or the spine is pushed manually, resulting in correction of the lordosis. The temporary rods are tightened. The main rods, independent of the short rods, are used to connect multiple segments several levels above and below the osteotomy site to provide final stabilization.

Alternatives

The alternatives to PSO depend on the surgical history of the patients, as well as the flexibility and alignment of the spine. In a spine with mobile disc spaces, Smith-Petersen osteotomies can be performed posteriorly to shorten the posterior column over multiple segments to gain lordosis. A formal anterior or lateral approach can be performed to release the disc spaces and restore the disc height. A posterior release through the facet joints with segmental compression can achieve desired lumbar lordosis. A vertebral column resection can also be performed to achieve lordosis.

Rationale

PSO is ideal for patients who have undergone multiple spinal fusions and who have a very rigid, flat lumbar spine. A single posterior approach can be used to provide adequate correction of the flat lumbar spine up to 40°. Asymmetric PSO can also be performed to allow for correction in the coronal plane. Recently, PSO has been performed more frequently because of the improved osteotomy instrumentation, exposure to resection techniques, and improved positioning tables that allow correction of the osteotomy.

Biomechanical analysis of sagittal correction parameters for surgical instrumentation with pedicle subtraction osteotomy in adult spinal deformity

BACKGROUND

High complication rate has been documented in spinal instrumentation with pedicle subtraction osteotomy. The objective was to analyze the biomechanics of spinal instrumentation with pedicle subtraction osteotomy as functions of three instrumentation parameters.

METHODS

Patient-specific biomechanical computer models of 3 adult patients who were instrumented with pedicle subtraction osteotomy were used to simulate the actual instrumentations and alternative instrumentations derived by varying instrumentation parameters: pedicle subtraction osteotomy wedge angle and rod contouring angle, location of the osteotomy, and number of rods (2 vs. 4).

FINDINGS

A change of the sagittal correction by +7.5° (-7.5°) resulted in a change in the screw axial forces and rods bending loads around the osteotomy by +38% (-19%) and +28% (-11%), respectively. The bending moments in the rods were 31% lower at the osteotomy site when it was located at one level above, and 20% higher when it was located at a level below. Additional rods allowed the rod bending and screw axial loads to be reduced by 24% and 22%, respectively.

INTERPRETATION

The amount of sagittal correction was positively correlated with loads sustained by the screws and rods. Rods were subjected to higher bending loads at the pedicle subtraction osteotomy site when it was done at a lower level. A 4-rod construct is an effective way to reduce the risk of rod breakage by reducing the loads sustained by the rods.

State-of-the-Art Reviews: Safety in Complex Spine Surgery

The surgical correction of spinal deformities carries a high risk of perioperative morbidity. As the incidence of debilitating spinal deformities continues to increase, so too does our obligation to search for ways to enhance safety in our delivery of surgical care. Standardized work processes and other lean manufacturing methodologies have the potential to improve efficiency, safety, and hence value in our delivery of surgical care to patients with complex spine pathologies by reducing variability in our work processes. These principles can be applied to patient care from the initial preoperative assessment to long-term postoperative follow-up in the creation of comprehensive protocols that guide the management of these complex patients. Early evidence suggests that short-term outcomes can be improved by implementing packages of systems reform aimed at reducing variability in our work processes; however, contradicting evidence exists on the utility of several specific components of these systems-reform packages.

Does relocation of the apex after osteotomy affect surgical and clinical outcomes in patients with ankylosing spondylitis and thoracolumbar kyphosis?

OBJECTIVE

Relocation of the apex is often found in patients with ankylosing spondylitis (AS)-associated thoracolumbar/lumbar kyphosis after corrective surgery. This study evaluates the influence of different postoperative apex locations on surgical and clinical outcomes of osteotomy for patients with AS and thoracolumbar kyphosis.

METHODS

Sixty-two patients with a mean age of 34.6 ± 9.7 years (range 17-59 years) and a minimum of 2 years of follow-up, who underwent 1-level lumbar pedicle subtraction osteotomy for AS-related thoracolumbar kyphosis, were enrolled in the study, as well as 62 age-matched healthy individuals. Patients were divided into 2 groups according to the postoperative location of the apex (group 1, T8 or above; group 2, T9 or below). Demographic data, radiographic measurements (including 3 postoperative apex-related parameters), and clinical outcomes were compared between the 2 groups preoperatively, postoperatively, and at the last follow-up. Furthermore, a subgroup analysis was performed among patients with a postoperative apex located at T6-11 and postoperatively the entire AS cohort was compared with normal controls regarding the apex location of the thoracic spine.

RESULTS

In the majority of the enrolled patients, the apex location changed from T12-L2 preoperatively to T6-9 postoperatively. The sagittal vertical axis (SVA) differed significantly both postoperatively (25.7 vs 59.0 mm, p = 0.001) and at the last follow-up (34.6 vs 59.9 mm, p = 0.003) between the 2 groups, and the patients in group 1 had significantly smaller horizontal distance between the C7-vertical line and the apex (DCA) than the patients in group 2 (67.5 vs 103.7 mm, p = 0.001). Subgroup analysis demonstrated similar results, showing that the patients with a postoperative apex located at T8 or above had an average SVA < 47 mm. Notably, a significant correlation was found between postoperative SVA and DCA (r = 0.642, p = 0.001). Patients who underwent an osteotomy at L3 had limited apex relocation but larger SVA correction than those at L1 or L2. However, no significant difference was found in health-related quality of life between the 2 groups.

CONCLUSIONS

AS patients with an apex located at T8 or above after surgery tended to have better SVA correction (within 47 mm) than those who had a more caudally located apical vertebra. For ideal postoperative apex relocation, a higher (closer to or at the preoperative apex) level of osteotomy is more likely to obtain the surgical goal.

The prevalence of complications associated with lumbar and thoracic spinal deformity surgery in the elderly population: a meta-analysis

Background

The prevalence of spinal deformities increases with age, affecting between 30% and 68% of the elderly population (ages ≥65). The reported prevalence of complications associated with surgery for spinal deformities in this population ranges between 37% and 71%. Given the wide range of reported complication rates, the decision to perform surgery remains controversial.

Methods

A comprehensive search was conducted using PubMed, Embase, and Cochrane to identify studies reporting complications for spinal deformity surgery in the elderly population. Pooled prevalence estimates for individual complication types were calculated using the random-effects model.

Results

Of 5,586 articles, 14 met inclusion criteria. Fourteen complication types were reported, with at least 2 studies for each complication with the following pooled prevalence: reoperation (prevalence 19%; 95% CI, 9-36%; 107 patients); hardware failure (11%; 95% CI, 5-25%; 52 patients); infection (7%; 95% CI, 4-12%; 262 patients); pseudarthrosis (6%; 95% CI, 3-12%; 149 patients); radiculopathy (6%; 95% CI, 1-33%; 116 patients); cardiovascular event (5%; 95% CI, 1-32%; 121 patients); neurological deficit (5%; 95% CI, 2-15%; 248 patients); deep vein thrombosis (3%; 95% CI, 1-7%; 230 patients); pulmonary embolism (3%; 95% CI, 1-7%; 210 patients); pneumonia (3%; 95% CI, 1-11%; 210 patients); cerebrovascular or stroke event (2%; 95% CI, 0-9%; 85 patients); death (2%; 95% CI, 1-9%; 113 patients); myocardial infarction (2%; 95% CI, 1-6%; 210 patients); and postoperative hemorrhage (1%; 95% CI, 0-10%; 85 patients).

Conclusions

Most complication types following spinal deformity surgery in the elderly had prevalence point estimates of <6%, while all were at least ≤19%. Additional studies are needed to further explore composite prevalence estimates and prevalence associated with traditional surgical approaches as compared to minimally-invasive procedures in the elderly.

The prevalence of complications associated with lumbar and thoracic spinal deformity surgery in the elderly population: a meta-analysis

BACKGROUND

The prevalence of spinal deformities increases with age, affecting between 30% and 68% of the elderly population (ages ≥65). The reported prevalence of complications associated with surgery for spinal deformities in this population ranges between 37% and 71%. Given the wide range of reported complication rates, the decision to perform surgery remains controversial.

METHODS

A comprehensive search was conducted using PubMed, Embase, and Cochrane to identify studies reporting complications for spinal deformity surgery in the elderly population. Pooled prevalence estimates for individual complication types were calculated using the random-effects model.

RESULTS

Of 5,586 articles, 14 met inclusion criteria. Fourteen complication types were reported, with at least 2 studies for each complication with the following pooled prevalence: reoperation (prevalence 19%; 95% CI, 9-36%; 107 patients); hardware failure (11%; 95% CI, 5-25%; 52 patients); infection (7%; 95% CI, 4-12%; 262 patients); pseudarthrosis (6%; 95% CI, 3-12%; 149 patients); radiculopathy (6%; 95% CI, 1-33%; 116 patients); cardiovascular event (5%; 95% CI, 1-32%; 121 patients); neurological deficit (5%; 95% CI, 2-15%; 248 patients); deep vein thrombosis (3%; 95% CI, 1-7%; 230 patients); pulmonary embolism (3%; 95% CI, 1-7%; 210 patients); pneumonia (3%; 95% CI, 1-11%; 210 patients); cerebrovascular or stroke event (2%; 95% CI, 0-9%; 85 patients); death (2%; 95% CI, 1-9%; 113 patients); myocardial infarction (2%; 95% CI, 1-6%; 210 patients); and postoperative hemorrhage (1%; 95% CI, 0-10%; 85 patients).

CONCLUSIONS

Most complication types following spinal deformity surgery in the elderly had prevalence point estimates of <6%, while all were at least ≤19%. Additional studies are needed to further explore composite prevalence estimates and prevalence associated with traditional surgical approaches as compared to minimally-invasive procedures in the elderly.

Spinal Balance/Alignment - Clinical Relevance and Biomechanics

In the normal spine due to its curvature in various regions, C7 plumb line (C7PL) passes through the sacrum so that the head is centered over the pelvis-ball and socket hip joints and ankle joints. This configuration leads to the least muscular activities to maintain the spinal balance. For any reason like deformity, scoliosis, kyphosis, trauma, and/or surgery this optimal configuration gets disturbed requiring higher muscular activity to maintain the posture and balance. Several parameters like the thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), Hip- and leg position influence the sagittal balance and thus the optimal configuration of spinal alignment. Global sagittal imbalance is energy consuming and often painful compensatory mechanisms are developed, that in turn negatively influence the quality of life. This review looks at the clinical aspects of spinal imbalance, and the biomechanics of spinal balance as dictated by the deformities- ankylosing spondylitis, scoliosis and kyphosis; surgical corrections- pedicle subtraction osteotomies and long segment stabilizations and consequent postural complications like the proximal and distal junctional kyphosis. This review suggests several potential research topics as well.

Optimal satellite rod constructs to mitigate rod failure following pedicle subtraction osteotomy (PSO): a finite element study

BACKGROUND CONTEXT

Pedicle subtraction osteotomy (PSO) is a challenging restoration technique for sagittal imbalance and is associated with significant complications. One of the major complications is rod fracture and there exists a need for a biomechanical assessment of this complication for various instrumentation configurations.

PURPOSE

To evaluate and compare the global range of motion (ROM), rod stress distribution, and the forces on the pedicle subtraction site in various instrumentation configurations using finite element analysis.

STUDY DESIGN/SETTING

A computational biomechanical analysis.

METHODS

A previously validated osseoligamentous three-dimensional spinopelvic finite element model (T10-pelvis) was used to develop a 30° PSO at the L3 level. In addition to the standard bilateral cobalt chromium primary rod instrumentation of the PSO model, various multirod configurations including constructs with medially, laterally, and posteriorly affixed satellite rods and the short-rod technique were assessed in spinal physiological motions. T10-S1 global ROM, maximum von Mises stress on the rods and at the PSO level, factor of safety (yield stress of the rod material/maximum actual stress in the rod) and the load acting across the PSO site were compared between various instrumentation configurations. The higher the factor of safety the lesser the chances of rod failure.

RESULTS

Among all multirod constructs, posteriorly affixed satellite rod construct showed the greatest motion reduction compared to the standard bilateral rod configuration followed by medially and laterally affixed satellite rod constructs. Compared to the standard bilateral rod configuration, recessed short-rod technique resulted in 4% to 49% reduction in T10-S1 ROM recorded in extension and lateral bending motions, respectively, while the axial rotation motion increased by approximately 31%. Considering the maximum stress values on the rods, the recessed short-rod technique showed the greatest factor of safety (FOS = 4.1) followed by posteriorly (FOS = 3.9), medially (FOS = 3), laterally affixed satellite rod constructs (FOS = 2.8), and finally the standard bilateral rod construct (FOS = 2.7). By adding satellite rods, the maximum von Mises stress at the PSO level of the rods also reduced significantly and at this level resulted in the greatest FOS in the posteriorly affixed satellite rod construct. Compared to the standard bilateral rod construct, the load magnitude acting on the osteotomy site decreased by 11%, 16%, and 37% in the laterally, medially, and posteriorly affixed satellite rod constructs, respectively, and did not change with the short-rod technique.

CONCLUSIONS

Adding satellite rods increases the rigidity of the construct, which results in an increase in the stability and the reduction of the global ROM. Additionally, having satellite rods reduces the stress on the primary rods at the PSO level and shifts the stresses from this PSO region to areas adjacent to the side-by-side connectors. The data suggest a significant benefit in supplementing medial over lateral satellite rods at the PSO by reducing stress on the primary rods. Except the recessed short-rod technique, all other multirod constructs decrease the magnitude of the load acting across the osteotomy region, which could cause a delayed or non-union at the PSO site.

CLINICAL SIGNIFICANCE

The study evaluates the mechanical performance of various satellite rod instrumentation configurations following PSO to predict the risk factors for rod fracture and thereby mitigate the rate of clinically relevant failures.

[Surgical management of ankylosing spondylitis (Bechterew's disease)]

Ankylosing spondylitis is an inflammatory rheumatic disease that is often associated with back pain and restricted spinal movement. In the later stages of the disease, complete ossification of the entire spine and severe deformity can occur, often resulting in a marked reduction in quality of life and an increased risk of loss of independence due to diminished visual field. Patients with ankylosing spondylitis are at greater risk of spinal fractures. These are generally complex fractures associated with high morbidity and mortality; in addition, neurological deficits are not unusual. Conventional radiological diagnosis is often insufficient to establish a diagnosis. Conservative treatment of fractures of the spine in this patient group is unsatisfactory. Surgical procedures, if necessary combined with decompression, are often the preferred treatment of choice in the fractured or malaligned ankylosed spine. Rebalancing of the sagittal profile with normalization of the visual axis and an improvement of quality of life is achieved through corrective osteotomies. Despite the high rate of complications, long-term results following spinal surgery in patients with ankylosing spondylitis are good. Minimally invasive surgery is appropriate for a further reduction in the complication rate. Meticulous preoperative planning is essential in the treatment of patients with ankylosing spondylitis.

S1 Pedicle Subtraction Osteotomy in Sagittal Balance Correction. A Feasibility Study on Human Cadaveric Specimens

BACKGROUND

A cadaveric feasibility study was carried out. Osteotomies to correct fixed sagittal imbalance are usually performed at L₃/ L₄.

OBJECTIVE

To investigate the feasibility of S₁ pedicle subtraction osteotomy to correct spinal deformity and spinopelvic parameters, achieving better results with more limited exposure. The data obtained will allow a fixation construct specific for this osteotomy to be designed.

METHODS

S₁ pedicle subtraction osteotomy was performed on 12 cadaveric specimens. Baseline and postprocedural computed tomography and biomechanical studies were performed. Data were analyzed with a fixation system SolidWorks model, and the redesigned fixation construct was described and analyzed with an ANSYS model.

RESULTS

S₁ pedicle subtraction osteotomy is technically feasible. The fixation can be achieved with L₄, L₅, and iliac screws connected with bars. The system can be reinforced with a polyetheretherketone cage placed anteriorly in the S₁ body osteotomy site, a cross-connecting bar, a double iliac screw, or an anterior interbody cage placed at the L₅-S₁ disc. The fixation strength is improved by angulating the iliac rod channel 10°, adding a semi-sphere to the locking screw contact surface and 2 fins to its saddle. The redesigned construct showed suitable stress and deformation levels, achieving the expected biomechanical requirements.

DISCUSSION

Compared with surgery on higher levels, S₁ pedicle subtraction osteotomy allows greater correction with shorter fixation, because the osteotomy is performed at a more caudal level, modifying the spinopelvic parameters.

CONCLUSIONS

S₁ pedicle subtraction osteotomy is technically feasible. Finite element analysis results indicate that it has appropriate biomechanical properties.

Approach Selection: Multiple Anterior Lumbar Interbody Fusion to Recreate Lumbar Lordosis Versus Pedicle Subtraction Osteotomy: When, Why, How?

Restoration of physiologic lumbar lordosis is a fundamental principle of spinal deformity surgery. Techniques using multilevel anterior lumbar interbody fusion or pedicle subtraction osteotomy (PSO) are described. Multilevel anterior lumbar interbody fusion provides a gradual multilevel correction and avoids the morbidity associated with PSO but necessitates familiarity with the anterior approach or an approach surgeon. PSO provides a large angular correction at a single level, requires only one approach, and allows for simultaneous multiplanar correction and open posterior decompression. This article provides guidance on the appropriate use of each technique for restoration of lumbar lordosis in patients with degenerative lumbar deformity.

Analysis of risk factors for sagittal translation after pedicle subtraction osteotomy in patients with ankylosing spondylitis

BACKGROUND CONTEXT

Sagittal translation, a potential complication of pedicle subtraction osteotomy (PSO), can result in neurologic damage. However, few studies have been conducted on sagittal translation and its risk factors after PSO in patients with ankylosing spondylitis (AS).

PURPOSE

We aimed to report cases of sagittal translation that developed after PSO in patients with AS with kyphotic deformity and to analyze risk factors for sagittal translation.

STUDY DESIGN

A retrospective case-control study was carried out.

PATIENT SAMPLE

This study included 53 patients (58 cases) with AS who underwent PSO to correct their kyphotic deformity.

OUTCOME MEASURES

The modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) was measured before the surgery. Radiological pelvic and sagittal parameters were also measured before and after surgery. Developments of sagittal translation were confirmed with intraoperative radiograph.

METHODS

The subjects were grouped according to the presence (ST group) and absence (non-ST group) of sagittal translation. The demographic and radiological parameters were compared between two groups. Through multivariate logistic regression analysis, the correlations between sagittal translation and relevant parameters were analyzed for risk factor evaluation.

RESULTS

Sagittal translation developed in 16 patients (30.2%) [16 cases (27.6%)]. The mean lumbar lordosis angle and sagittal vertical axis of both ST group and non-ST group were successfully corrected. In a comparison of two groups, the ST group (58.2±13.3) showed a significantly higher mSASSS than the non-ST group (33.9±11.9) (p<.001). The ST group (50.4°±7.8°, 16.9°±6.8°) also showed a significantly higher preoperative pelvic incidence and sacral slope than the non-ST group (45.3°±7.2°, 11.0°±7.7°) (p=.026, p=.011). No significant differences were observed between the two groups for the rest of radiological parameters. In multivariate analysis, only mSASSS was positively correlated with sagittal translation (odds ratio 1.16, p=.001).

CONCLUSION

The incidence of sagittal translation after PSO was closely related with severity of ankylosis in patients with AS. Therefore, surgeons must consider sagittal translation, which could induce neurologic complications, when PSO is performed for patients with AS with severe ankylosis.

Effect of Tranexamic Acid on Blood Loss, D-Dimer, and Fibrinogen Kinetics in Adult Spinal Deformity Surgery

BACKGROUND

Antifibrinolytics such as tranexamic acid reduce operative blood loss and blood product transfusion requirements in patients undergoing surgical correction of scoliosis. The factors involved in the unrelenting coagulopathy seen in scoliosis surgery are not well understood. One potential contributor is activation of the fibrinolytic system during a surgical procedure, likely related to clot dissolution and consumption of fibrinogen. The addition of tranexamic acid during a surgical procedure may mitigate the coagulopathy by impeding the derangement in D-dimer and fibrinogen kinetics.

METHODS

We retrospectively studied consecutive patients who had undergone surgical correction of adult spinal deformity between January 2010 and July 2016 at our institution. Intraoperative hemostatic data, surgical time, estimated blood loss, and transfusion records were analyzed for patients before and after the addition of tranexamic acid to our protocol. Each patient who received tranexamic acid and met inclusion criteria was cohort-matched with a patient who underwent a surgical procedure without tranexamic acid administration.

RESULTS

There were 17 patients in the tranexamic acid cohort, with a mean age of 60.7 years, and 17 patients in the control cohort, with a mean age of 60.9 years. Estimated blood loss (932 ± 539 mL compared with 1,800 ± 1,029 mL; p = 0.005) and packed red blood-cell transfusions (1.5 ± 1.6 units compared with 4.0 ± 2.1 units; p = 0.001) were significantly lower in the tranexamic acid cohort. In all single-stage surgical procedures that met inclusion criteria, the rise of D-dimer was attenuated from 8.3 ± 5.0 μg/mL in the control cohort to 3.3 ± 3.2 μg/mL for the tranexamic acid cohort (p < 0.001). The consumption of fibrinogen was 98.4 ± 42.6 mg/dL in the control cohort but was reduced in the tranexamic acid cohort to 60.6 ± 35.1 mg/dL (p = 0.004).

CONCLUSIONS

In patients undergoing spinal surgery, intravenous administration of tranexamic acid is effective at reducing intraoperative blood loss. Monitoring of D-dimer and fibrinogen during spinal surgery suggests that tranexamic acid impedes the fibrinolytic pathway by decreasing consumption of fibrinogen and clot dissolution as evidenced by the reduced formation of D-dimer.

LEVEL OF EVIDENCE

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

Three column osteotomy for adult spine deformity: comparison of outcomes and complications between kyphosis and kyphoscoliosis

BACKGROUND

To compare the surgical outcomes and complications between kyphosis and kyphoscoliosis when using three-column osteotomies.

METHODS

Adult spine deformity (ASD) patients with three column osteotomies from March 2005 to December 2014 in our center were retrospectively reviewed. Pre- and postoperative standing postero-anterior and lateral radiographs of the entire spine were obtained. Scoliosis Research Society-22 questionnaire [SRS-22] and Oswestry Disability Index [ODI] were administered preoperatively, postoperatively (surveys within 2 months after surgery), and at final follow-up. Patients were assigned to one of two groups according to pre-operative coronal curve magnitude: (1) if coronal curve <10°, patients were assigned to kyphosis group (K group); (2) if coronal curve >40°, patients were assigned to kyphoscoliosis group (S group).

RESULTS

33 ASD patients were assigned to the kyphosis group (K group), of which 26 received PSO (pedicle subtraction osteotomy) and 7 VCR (vertebral column resection). 76 patients were assigned to kyphoscoliosis group (S group), of which 50 received PSO and 26 VCR. Patients in the K group were significantly older than in the S group (42.8 vs. 33.7 years, p < .05). Significantly longer OT (operation time) and more EBL (estimated blood loss) were observed in the S group as compared to K group (OT: 282 vs. 205 min, p < .05; EBL: 1827 vs. 1214ml, p < .05). No significant difference was noted for number of fusion levels between the groups (12.4 vs. 12.7, p > .05). Pre-operative radiographic parameters demonstrated no difference of GK (global kyphosis) and SVA (sagittal vertical axis) between the two groups (GK: 74.7° vs 76.2°, p > .05; SVA:53.2 vs. 55.7mm, p > .05). K group had larger KF than S group (26% vs. 15%, p < .05). Overall complication rate was higher in S group than in K group (30.3% vs. 18.2%, p < .05). No difference of neurological complication rates between the two groups (9.1% vs. 10.5%, p > .05).

CONCLUSIONS

Kyphoscoliosis group had less KF, GK correction and more OT, EBL and surgical complications when receiving three column osteotomies.

L5 pedicle subtraction osteotomy: indication, surgical technique and specificities

PURPOSE

To evaluate the radiographic, functional outcomes, complications and surgical specificities of L5 pedicle subtraction osteotomy for fixed sagittal and coronal malalignment.

METHODS

A retrospective cohort of consecutive patients with prospectively collected data. Ten patients who underwent PSO at L5 were eligible for a 2-year minimum follow-up (average, 4.0 years). Patients were evaluated by standardized upright radiographs. Preoperative and postoperative radiographies, surgical data and complications were collected.

RESULTS

All surgeries were revision surgeries. The mean lumbar lordosis before surgery was - 22.5° (range, 8° to - 33°) and improved to - 58.5° (range, - 40° to - 79°). The sagittal vertical axis demonstrated a preoperative mean sagittal malalignment of 13.7 cm (range 3.5 to 20 cm), with correction to 4.6 cm postoperatively. Three patients required additional surgery at the latest follow-up for rod breakage.

CONCLUSIONS

PSO of L5 can be a safe and effective technique to treat and correct fixed sagittal imbalance and provide biomechanical stability. The high complication rate mandates a careful assessment of the risk/benefit ratio of such a major surgery. Most patients are satisfied, particularly when sagittal balance is achieved.

Asymmetric pedicle subtractionosteotomy (aPSO) guided by a 3D-printed model to correct a combined fixed sagittal and coronal imbalance

Surgical correction of fixed thoracolumbar deformity is usually achieved by estimating the preoperatively planned correction angles during surgery and is therefore prone to inaccuracy. This is particularly problematic in biplanar deformities. To overcome these difficulties, 3D model for planning, preparation, and simulation of an asymmetric pedicle subtraction osteotomy (aPSO) was printed and used to realign coronal and sagittal balance in case of rigid degenerative kyphoscoliosis. A 59-year-old woman presented with severe back pain and spinal claudication and was diagnosed with a rigid kyphoscoliosis with multilevel spinal stenosis. Spino-pelvic parameters were measured preoperatively (pelvic incidence 47° [PI], lumbar lordosis 18° [LL]; pelvic tilt 42° [PT], T1 pelvic angle 40° [TPA], Cobb angle 33°, sagittal vertical axis 10.5 cm [SVA]). To aid the complex deformity in the sagittal and coronal plane, a 1:1 3D model of the spine was printed according to the preoperative computed tomography (CT). With the use of a rebalancing software, the spine was prepared in vitro as a model for intraoperative realignment and the correction was preoperatively simulated. Surgery was accomplished according to the preoperative software-guided plan. Asymmetric pedicle subtraction osteotomy (aPSO) of L3 identical to the 3D model was performed. Additionally, a Smith-Peterson osteotomy of L4/5 with transforaminal lumbar interbody fusion (TLIF) and laminectomy of L2-S1 with pedicle screw instrumentation TH12-S1 was accomplished. Postoperative radiological parameters revealed good success (LL 40°, SVA 6 cm, PT 19°, TPA 22°, and a Cobb angle of 8°). Improvement of the Oswestry disability index (ODI) of 42 to 18, the visual analog scale (VAS) of 8 to 1, and walking distance 100 to 8000 m compared to preoperatively resulted at 24 months follow-up. The precise coronal and sagittal correction of a rigid degenerative kyphoscoliosis presents a major challenge. Asymmetric PSO is able to realign the thoracolumbar spine in both the coronal and sagittal planes. The creation of an in vitro 3D-printed model of a patient's spinal deformity in combination with a software to calculate the correction angles facilitates preoperative planning and implementation of aPSO.

The Double-Transforaminal Lumbar Interbody Fusion: An Innovative One-Stage Surgical Technique for Posterior Kyphosis Correction

Posttraumatic deformities after vertebral fractures are challenging for orthopedic surgeons in the non-operative and operative field. Especially osteoporotic fractures may cause a hyperkyphosis resulting in segmental or global sagittal imbalance and chronic back pain. Different vertebral osteotomies are potent to restore sagittal profile but show a very high perioperative risk including neurological and soft tissue complications. In addition, some of these extensive operations require a two-step procedure including posterior and anterior approaches. Therefore, these established techniques may be contraindicated in elderly or multimorbide patients suffering from concomitant diseases. The authors describe the double transforaminal lumbar interbody fusion (TLIF) osteotomy (DTO) as an innovative one-stage and low-invasive surgical technique to correct a fixed posttraumatic kyphosis in the thoracolumbar junction. The procedure includes posterior release (laminectomy, facettectomy, nucleotomy) combined with two expandable TLIF implants (sandwich technique) and posterior instrumentation and is illustrated by a case of a multimorbide 78-year old female.

Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up

OBJECTIVE Although 3-column osteotomy (3CO) can provide powerful alignment correction in adult spinal deformity (ASD), these procedures are complex and associated with high complication rates. The authors' objective was to assess complications associated with ASD surgery that included 3CO based on a prospectively collected multicenter database. METHODS This study is a retrospective review of a prospectively collected multicenter consecutive case registry. ASD patients treated with 3CO and eligible for 2-year follow-up were identified from a prospectively collected multicenter ASD database. Early (≤ 6 weeks after surgery) and delayed (> 6 weeks after surgery) complications were collected using standardized forms and on-site coordinators. RESULTS Of 106 ASD patients treated with 3CO, 82 (77%; 68 treated with pedicle subtraction osteotomy [PSO] and 14 treated with vertebral column resection [VCR]) had 2-year follow-up (76% women, mean age 60.7 years, previous spine fusion in 80%). The mean number of posterior fusion levels was 12.9, and 17% also had an anterior fusion. A total of 76 early (44 minor, 32 major) and 66 delayed (13 minor, 53 major) complications were reported, with 41 patients (50.0%) and 45 patients (54.9%) affected, respectively. Overall, 64 patients (78.0%) had at least 1 complication, and 50 (61.0%) had at least 1 major complication. The most common complications were rod breakage (31.7%), dural tear (20.7%), radiculopathy (9.8%), motor deficit (9.8%), proximal junctional kyphosis (PJK, 9.8%), pleural effusion (8.5%), and deep wound infection (7.3%). Compared with patients who did not experience early or delayed complications, those who had these complications did not differ significantly with regard to age, sex, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists score, smoking status, history of previous spine surgery or spine fusion, or whether the 3CO performed was a PSO or VCR (p ≥ 0.06). Twenty-seven (33%) patients had 1-11 reoperations (total of 44 reoperations). The most common indications for reoperation were rod breakage (n = 14), deep wound infection (n = 15), and PJK (n = 6). The 24 patients who did not achieve 2-year follow-up had a mean of 0.85 years of follow-up, and the types of early and delayed complications encountered in these 24 patients were comparable to those encountered in the patients that achieved 2-year follow-up. CONCLUSIONS Among 82 ASD patients treated with 3CO, 64 (78.0%) had at least 1 early or delayed complication (57 minor, 85 major). The most common complications were instrumentation failure, dural tear, new neurological deficit, PJK, pleural effusion, and deep wound infection. None of the assessed demographic or surgical parameters were significantly associated with the occurrence of complications. These data may prove useful for surgical planning, patient counseling, and efforts to improve the safety and cost-effectiveness of these procedures.

[Surgical correction of post-vertebroplasty kyphosis by pedicle substraction osteotomy. Regarding three cases]

We report a case of three patients treated with pedicle subtraction osteotomy for post-vertebroplasty kyphosis. These patients were initially treated with a vertebroplasty for vertebral fracture (two cases) and spinal lymphoma (1 case). All of these patients worsened progressively on a clinical and radiographic level with progression of the spinal deformity in the form of kyphosis. The surgery consisted of transpedicular osteotomy instrumented at the level of the vertebra cemented with maximum removal of intra-corporeal cement. One of the three patients required a supplementary anterior approach to achieve good quality bone fusion. In all three cases the post-vertebroplasty kyphosis was able to be reduced by at least 50 % emphasizing the feasibility and relevance of the pedicle subtraction osteotomy in a context of cemented vertebra.

Treatment of kyphosis in ankylosing spondylitis by osteotomy through the gap of a pathological fracture: a retrospective study

Background

Surgical interventions are commonly advocated for correcting kyphotic deformities and relieving severe back pain in ankylosing spondylitis (AS) patients. The aim of this study was to evaluate the clinical outcome of osteotomy performed through the gap of a pathological fracture for the treatment of kyphosis in ankylosing spondylitis and to introduce the key points of this novel surgical approach.

Methods

From January 1, 2010, to December 31, 2014, 13 consecutive AS patients who were treated with osteotomy through the fracture gap were retrospectively reviewed. Patients underwent the radiographic assessment of sagittal balance parameters. Visual analog scale (VAS) scores were used to assess improvement in back pain.

Results

The average follow-up time was 2 years and 1 month. The median operation time was 280 min (range, 220–460 min). The mean blood loss was 1100 mL (range, 820–1300 mL). No major acute complications such as death or complete paralysis occurred. There were no neurologic complications or cerebrospinal fluid leaks in any patient. One patient had postoperative wound infection, which subsided after a switch of antibiotics. The global kyphosis Cobb angle of patients decreased from the preoperative 55.8° ± 11.0° to 23.2° ± 6.7° (P < 0.001) after surgery. The C7 plumb line was used to assess global balance; its relationship with the posterosuperior corner of the sacrum decreased from 166 ± 37 mm to 111 ± 20 mm (P < 0.001). The thoracolumbar kyphosis Cobb angle decreased from 51.0° ± 9.9° to 21.6° ± 11.0° (P < 0.001). VAS scores for back pain decreased from 7.2 ± 1.2 to 2.1 ± 1.1 (P < 0.001). Lumbar lordosis increased from 5.7° ± 23.2° to 10.5° ± 29.2° (P = 0.001).

Conclusions

Osteotomy through the pathological fracture gap is a safe and effective surgical procedure for kyphosis correction and improvement of back pain in AS patients with pathological fractures. A significant kyphosis correction and improvement of back pain can be achieved with this surgical procedure.

Perioperative Complications of Pedicle Subtraction Osteotomy

Study Design Retrospective case series. Objective To describe the perioperative complications (0 to 90 days) associated with pedicle subtraction osteotomies (PSOs) performed at a tertiary spine center by two experienced spine surgeons who recently adopted the technique. Methods We reviewed all 65 patients (47 women and 18 men; mean age 60 years, range 24 to 80) who underwent a PSO at our institution. Descriptive data and analysis of complications were limited to the perioperative time (within 90 days of surgery). Data analyzed included operative time, length of stay (LOS), estimated blood loss (EBL), blood products, comorbidities, neurologic complications, and medical complications. Complications were rated as major and minor. Radiographic data was also analyzed. Results Ten patients (15.4%) had a major complication, and 15 (23%) had a minor complication. There were three perioperative deaths. The most common major complication was neurologic deficit (6.2%, 4/65), three with a permanent foot drop, and one with paraplegia secondary to postoperative hematoma. There were no differences between patients with and without a major complication in regard to age, gender, comorbidities, operative time, number of levels fused, and EBL (p > 0.05). Patients with a major complication had a longer intensive care unit stay (p = 0.04). There was no difference in the rate of major complications between the initial and later cases performed. Conclusion The major complication rate for pedicle subtraction osteotomy was 15% and the minor complication rate was 23%. The most common major complication was neurologic deficit in 6.2%. The complication rate did not change with increased surgeon experience.

Anterior hyperlordotic cages: early experience and radiographic results

OBJECTIVE The aim of this study was to evaluate the segmental correction obtained from 20° and 30° hyperlordotic cages (HLCs) used for anterior lumbar interbody fusion in staged anterior and posterior fusion in adults with degenerative spinal pathology and/or spinal deformities. METHODS The authors report a retrospective case series of 69 HLCs in 41 patients with adult degenerative spine disease and/or deformities who underwent staged anterior, followed by posterior, instrumentation and fusion. There were 29 females and 12 males with a mean age of 55 years (range 23-76 years). The average follow-up was 10 months (range 2-28 months). Radiographic measurements of segmental lordosis and standard sagittal parameters were obtained on pre- and postoperative radiographs. Implant subsidence was measured at the final postoperative follow-up. RESULTS For 30° HLCs, the mean segmental lordosis achieved was 29° (range 26°-34°), but in the presence of spondylolisthesis this was reduced to 19° (range 12°-21°) (p < 0.01). For 20° HLCs, the mean segmental lordosis achieved was 19° (range 16°-22°). The overall mean lumbar lordosis increased from 39° to 59° (p < 0.01). The mean sagittal vertical axis (SVA) reduced from 113 mm (range 38-320 mm) to 43 mm (range -13 to 112 mm). Six cages (9%) displayed a loss of segmental lordosis during follow-up. The mean loss of segmental lordosis was 4.5° (range 3°-10°). A total complication rate of 20% with a 4.1% transient neurological complication rate was observed. The mean blood loss per patient was 240 ml (range 50-900 ml). CONCLUSIONS HLCs provide a reliable and stable degree of segmental lordosis correction. A 30° HLC will produce correction of a similar magnitude to a pedicle subtraction osteotomy, but with a lower complication rate and less blood loss.

Use of Supplemental Short Pre-Contoured Accessory Rods and Cobalt Chrome Alloy Posterior Rods Reduces Primary Rod Strain and Range of Motion Across the Pedicle Subtraction Osteotomy Level: An In Vitro Biomechanical Study

STUDY DESIGN

In vitro cadaveric biomechanical study.

OBJECTIVE

To assess effects of 4-rod reconstruction, rod material, and anterior column support on motion and surface rod strain in a pedicle subtraction osteotomy model.

SUMMARY OF BACKGROUND DATA

Pedicle subtraction osteotomy (PSO) can correct significant sagittal deformity of the lumbar spine; however, revision rates are high. To reduce rod strain and the incidence of rod fracture, clinical use of multi-rod construction, cobalt chrome (CoCr) alloy rods, and interbody spacers adjacent to PSO has been proposed. Investigating both motion and rod strain is necessary to determine the biomechanical efficacy of these techniques.

METHODS

Five specimens (T12-S1) underwent PSO at L3 with pedicle screw stabilization at L1-S1. Pedicle subtraction was adjusted to achieve a final lordosis of 70°. Flexion-extension (FE), lateral bending, and axial rotation were applied. Linear strain gauges measured surface rod strain during FE on primary and accessory rods at PSO level. Testing evaluated (1) accessory rods (4-Rod) added at PSO level versus primary rods (2-Rod); (2) Ti versus CoCr rods; and (3) lateral interbody spacers (S) inserted adjacent to PSO. One-way and three-way analysis of variance was performed (P ≤ 0.05).

RESULTS

All constructs significantly reduced FE and lateral bending motion relative to intact (P < 0.001). The main effect of accessory rods in reducing FE motion was significant (P = 0.021). Accessory and CoCr rods reduced relative surface strain on the primary rod, irrespective of construct (P < 0.001). CoCr 4-Rod + S provided the greatest reduction in strain (76% decrease; P = 0.003).

CONCLUSION

Accessory and CoCr rods provided greatest reduction in motion and rod strain at PSO level. Interbody devices minimally affected motion-induced strain and might act primarily to maintain disc height. Clinicians must assess whether surface strain and motion reduction minimize the incidence of rod fracture.

LEVEL OF EVIDENCE

N/A.

Comparison of Clinical and Radiological Improvement Between the Modified Trephine and High-speed Drill as Main Osteotomy Instrument in Pedicle Subtraction Osteotomy

High-speed drill is the main osteotomy instrument in pedicle subtraction osteotomy (PSO) currently. Considering the long duration of surgery, the large amount of blood loss, and the high incidence of neurovascular injury, the osteotomy procedure is challenging. Use of trephine for the osteotomy displays high efficiency by shortening surgery time and reducing blood loss in anterior cervical corpectomy and fusion. However, the potential risk of neurological injury is high. We modified the trephine by adding locking instrument, when the serrated top of the trephine reaches the tip of the probe; the locking instrument on the probe restricts the trephine and improves security during the osteotomy procedure.The aim of this study was to compare the clinical and radiological improvement between the modified trephine and high-speed drill as main osteotomy instrument in PSO.From February 2009 to 2013, 50 patients with severe thoracolumbar kyphotic deformity caused by old compressive vertebrae were prospectively reviewed. All patients were randomly assigned to the experimental group (27 patients received PSO with modified trephine) and the control group (23 patients received PSO with high-speed drill). The clinical records were reviewed and compared for surgical time, operative blood loss, functional improvement (Oswestry Disability Index), and pain relief (visual analog scale). The radiological records were reviewed and compared for correction of kyphotic deformity postoperatively and correction loss at 2-year follow-up.All patients successfully finished the PSO procedure, and got satisfactory kyphotic deformity correction and overall function improvement. The surgery time was shorter in the experimental group than that in the control group (132.7 ± 12.6 vs 141.7 ± 16.7 min; P = 0.03). No significant difference was found in blood loss (882.9 ± 98.9 mL vs 902.2 ± 84.9 mL; P = 0.47) or correction of the kyphotic angle (33.4 ± 3.4° vs 32.1 ± 2.5°, P = 0.13) postoperatively between the 2 groups. At 24-month follow-up, no difference was discovered in loss of the correction (4.9 ± 1.6° vs 4.5 ± 1.6°; P = 0.42), change of Oswestry Disability Index (49.4 ± 6.2% vs 48.2 ± 4.2%; P = 0.44), or in back pain relief (6.2 ± 1.4 vs 6.4 ± 1.2 min; P = 0.51) between the 2 groups. No internal fixation related complication occurred and bony fusion was detected in lateral X-ray in all patients. In the control group, 2 patients had transient nerve root deficit, 14 patients at 3-month follow-up and 3 patients at 2-year follow-up experienced graft donor site morbidity, and pain killer medicine was always required.In conclusion, the modified trephine obviously shortens surgery time, and prevents graft donor site morbidity when compared to a high-speed drill. The learning curve for using the modified trephine in PSO procedure is short.

Insufficient restoration of lumbar lordosis and FBI index following pedicle subtraction osteotomy is an indicator of likely mechanical complication

PURPOSE

Pedicle subtraction osteotomies (PSO) enable correction of spinal deformities but remain difficult and are associated with high complication rates. This study aimed to prospectively review different post-operative complications and mechanical problems in patients who underwent PSO as treatment for sagittal imbalance as sequelae of degenerative disc disease or previous spinal fusion.

METHOD

This was a descriptive prospective single center study of 63 patients who underwent sagittal imbalance correction by PSO. Radiographic analysis of pre- and post-operative pelvic and spinal parameters was completed based on EOS images following 3D modeling. Global and sub-group analyses were completed based on the Roussouly classification. A systematic analysis of post-operative complications was conducted during hospital stay and at follow-up visits.

RESULTS

Complications included 15 cases (20.2%) of bilateral leg pain, with transient neurological deficit in 6 cases (9.5%), and 9 cases (12.5%) of early surgical site infections. Intra-operative complications included five tears of the dura mater and two cases of excessive blood loss (>5,000 mL). Two mortalities occurred from major intracerebral bleeds in the early post-operative period. Mechanical complications were principally non-union (9 cases) and junctional kyphosis (3 cases). All 19 post-operative complications (28.1%) were revised at an average of 2 years following surgery. All mechanical complications were found in the patients who had insufficient imbalance correction and this was mainly associated with high PI (>60°) or a moderate PI (45-60º) combined with excess FBI pre-operatively that remained >10° post-operatively.

CONCLUSION

Infection and neurologic complications following PSO are relatively common, and frequently reported in the literature. The principal cause of mechanical complications, such as non-union or junctional kyphosis, was insufficient sagittal correction, characterized by post-operative FBI >10°. The risks of insufficient correction are greater in patients with higher pelvic incidence and those patients who required very high correction.