Early outcomes of minimally invasive anterior longitudinal ligament release for correction of sagittal imbalance in patients with adult spinal deformity

Anterior Column Release: With Great Lordosis Comes Great Risk of Complications-A Case Series

STUDY DESIGN

Retrospective review.

OBJECTIVE

We sought to characterize complications associated with anterior column release (ACR).

SUMMARY OF BACKGROUND DATA

Correction of positive sagittal imbalance was traditionally completed with anterior column grafts or posterior osteotomies. ACR is a minimally invasive technique for addressing sagittal plane deformity by restoring lumbar lordosis.

METHODS

We conducted a retrospective review of consecutive patients who underwent ACR in a prospectively kept database at a tertiary care academic center from January 2012 to December 2018. The prespecified complications were hardware failure (rod fracture, hardware loosening, or screw fracture), proximal junctional kyphosis, ipsilateral thigh numbness, ipsilateral femoral nerve weakness, arterial injury requiring blood transfusion, bowel injury, and abdominal pseudohernia.

RESULTS

Thirty-eight patients were identified. Thirty-five patients had ACR at L3-4, 1 had ACR at L4-5, and 1 patient had ACR at L2-3 and L3-4. Eighteen patients (47.4%) had one of the prespecified complications (10 patients had multiple). Ten patients developed hardware failure (26.3%); 8 patients (21.1%) had rod fracture, 4 (10.5%) had screw fracture, and 1 (2.6%) had screw loosening. At discharge, rates of ipsilateral thigh numbness (37.8%) and hip flexor (37.8%)/quadriceps weakness (29.7%) were the highest. At follow-up, 6 patients (16.2%) had ipsilateral anterolateral thigh numbness, 5 (13.5%) suffered from ipsilateral hip flexion weakness, and 3 patients (5.4%) from ipsilateral quadriceps weakness. Arterial injury occurred in 1 patient (2.7%). Abdominal pseudohernia occurred in 1 patient (2.7%). There were no bowel injuries observed.

CONCLUSIONS

ACR is associated with a higher than initially anticipated risk of neurological complications, hardware failure, and proximal junctional kyphosis.

Pelvic Incidence as a Predictor of Proximal Junctional Failure in Patients Undergoing Anterior Column Realignment with Anterior Longitudinal Ligament Release to Restore Lordosis in Adult Spinal Deformity: A Retrospective Cohort Study

OBJECTIVE

To identify variables that may contribute to the development of proximal junctional failure (PJF) in patients with long lumbo-sacral and thoraco-lumbo-pelvic constructs undergoing anterior column realignment (ACR) with anterior longitudinal ligament release (ALLR).

METHODS

Data of patients with adult spinal deformity who underwent ACR with ALLR at L3-4 were collected retrospectively from medical records and a prospectively maintained spine research database between 2016 and 2022.

RESULTS

Eleven (41%) developed PJF at a mean of 24 ± 21 months from the index surgery. The cohort was then divided into 2 groups for analysis, 13 subjects in the high pelvic incidence (PI) group (defined as PI ≥ 55°) and 14 subjects in the low PI group (defined as PI < 55°). Visual Analog Scale for back pain and Oswestry Disability Index decreased from 9.5 to 2.1 and 61 to 10 in the high PI group, and from 8.9 to 2.4 and 60.9 to 10.3 in the low PI group, respectively. PI (P = 0.004), sacral slope (P = 0.005), and postoperative PI-lumbar lordosis mismatch (P = 0.02) were found to be significant predictors of PJF. The receiver operator curve revealed a cutoff PI value ≤ 53° (95% confidence interval: 52°-64°), below which the risk of PJF becomes significantly higher in patients undergoing ACR with ALLR at L3-4.

CONCLUSIONS

PI may be a predictor of PJF and highly correlates with ACR-ALLR levels. In patients undergoing L3-4 ACR-ALLR, a PI value of ≤53° is associated with a significantly elevated risk of PJF. Preoperative planning of ACR-ALLR level based on normal sagittal alignment in otherwise healthy individuals may mitigate the risk of PJF development in patients with adult spinal deformity treated with ACR-ALLR.

Top-ten most-cited articles on anterior column release in the context of minimally invasive lumbar interbody fusion

Introduction

Lateral anterior column release (ACR) is a minimally invasive option for the correction of sagittal plane deformity. To assemble a homogeneous picture of published research on ACR, an advanced bibliometric analysis was conducted to compile the top-ten most-cited articles on the topic of ACR.

Methods

A keyword search using the Thomson Reuters Web of Knowledge was conducted to identify articles discussing the role of lateral ACR. The articles were then ranked based on the total number of citations to identify the ten most-cited articles published. A subjective appraisal of the findings of these articles was conducted to provide a ranked literature review and to examine trends in the study of ACR between 2012 and 2019.

Results

The earliest published article on ACR was in 2012 by Deukmedjian et al. Three articles were in vitro biomechanical assessments of ACR, and seven articles were on outcome analyses, which were either case series or case controlled. The most-cited article was a biomechanical study authored by Uribe et al. The article with the highest rate of citations/year was authored by Manwaring et al. Uribe and the European Spine Journal were the most frequently cited author and journal, respectively.

Conclusions

The lateral ACR approach has enjoyed significant scholarly attention since its advent. Higher-level analyses with robust control groups, larger sample sizes, and long-term follow-up are necessary to improve our understanding of this approach.

A Modified Anterior Column Realignment With Partial Anterior Longitudinal Ligament Release in Oblique Lateral Interbody Fusion

STUDY DESIGN

Retrospective radiological analysis.

OBJECTIVE

To demonstrate the radiological outcome after a modified anterior column realignment (mACR) with partial anterior longitudinal ligament (ALL) release in oblique lateral interbody fusion (OLIF).

SUMMARY OF BACKGROUND DATA

Anterior column realignment (ACR) remains a powerful sagittal correction technique in minimally invasive adult spinal deformity surgery and is often combined with posterior column osteotomy (PCO) to achieve more lordosis. OLIF is ideal for ACR because the anterior-to-psoas corridor typically involves the anterolateral half of the disk.

METHODS

This study included 112 operated disk levels of 101 consecutive patients who underwent OLIF between L2-L3 and L4-L5 using a 12° lateral cage. The mACR was performed at 73 (65.2%) levels with 30% to 50% sectioning of the ALL. Each operated level was grouped according to the mACR and additional PCO as: (1) no mACR, OLIF only (n=39); (2) mACR with no PCO (n=18); (3) mACR with grade 1 PCO (n=27); (4) mACR with grade 2 PCO (n=22); or (5) mACR with grade 3 PCO (n=6).

RESULTS

At the last follow-up, the mean disk lordotic angles were 10.9±2.9°, 12.6±3.0°, 13.3±3.9°, 16.7±3.2°, and 16.8±2.4° in the no mACR, mACR with no PCO, mACR with grade 1 PCO, mACR with grade 2 PCO, and mACR with grade 3 PCO groups, respectively ( P <0.001). The mean increases in disk lordotic angle were 5.8±4.1°, 12.1±6.1°, 13.5±8.7°, 15.8±6.7°, and 17.9±6.2° in each group, respectively ( P <0.001).

CONCLUSIONS

ACR can be performed with partial ALL release under direct vision in OLIF without deep dissection into the ventral disk space. The mACR in OLIF is a simple, safe, and effective technique for anterior column lengthening.

LEVEL OF EVIDENCE

4.

Radiographic and MRI evidence of indirect neural decompression after the anterior column realignment procedure for adult spinal deformity

OBJECTIVE

The anterior column realignment (ACR) procedure, which consists of sectioning the anterior longitudinal ligament/annulus and placing a hyperlordotic interbody cage, has emerged as a minimally invasive surgery (MIS) for achieving aggressive segmental lordosis enhancement to address adult spinal deformity (ASD). Although accumulated evidence has revealed indirect neural decompression after lateral lumbar interbody fusion (LLIF), whether ACR serves equally well for neural decompression remains to be proven. The current study intended to clarify this ambiguous issue.

METHODS

A series of 36 ASD patients with spinopelvic mismatch, defined as pelvic incidence (PI) minus lumbar lordosis (LL) > 10°, underwent a combination of ACR, LLIF, and percutaneous pedicle screw (PPS) fixation. This "MIS triad" procedure was applied over short segments with mean fusion length of 3.3 levels, and most patients underwent single-level ACR. The authors analyzed full-length standing radiographs, CT and MRI scans, and Oswestry Disability Index (ODI) scores in patients with minimum 1 year of follow-up (mean [range] 20.3 [12-39] months).

RESULTS

Compared with the preoperative values, the radiographic and MRI measurements of the latest postoperative studies changed as follows. Segmental disc angle more than quadrupled at the ACR level and LL nearly doubled. MRI examinations at the ACR level revealed a significant (p < 0.0001) increase in the area of the dural sac that was accompanied by significant (p < 0.0001) decreases in area and thickness of the ligamentum flavum and in thickness of the disc bulge. The corresponding CT scans demonstrated significant (all p < 0.0001) increases in disc height to 280% of the preoperative value at the anterior edge, 224% at the middle edge, and 209% at the posterior edge, as well as in pedicle-to-pedicle distance to 122%. Mean ODI significantly (p < 0.0001) decreased from 46.3 to 26.0.

CONCLUSIONS

The CT-based data showing vertebral column lengthening across the entire ACR segment with an increasingly greater degree anteriorly suggest that the corrective action of ACR relies on a lever mechanism, with the intact facet joints acting as the fulcrum. Whole-segment spine lengthening at the ACR level reduced the disc bulge anteriorly and the ligamentum flavum posteriorly, with eventual enlargement of the dural sac. ACR plays an important role in not only LL restoration but also stenotic spinal canal enlargement for ASD surgery.

Management of severe adult spinal deformity with circumferential minimally invasive surgical strategies without posterior column osteotomies: a 13-year experience

OBJECTIVE

To evaluate the mid- to long-term clinical outcomes of circumferential minimally invasive surgery (CMIS) without posterior column osteotomies for severe adult spine deformity (ASD) correction.

METHODS

All patients with a minimum of 2-year follow-up undergoing staged CMIS correction of ASD from January 2007 to July 2018 were identified. All included patients had fusion of 3 or more interbody levels that spanned the L5-S1 junction. Only patients with severe deformity, Coronal Cobb > 50° or at least one SRS-Schwab ++ sagittal modifier (SVA > 95 mm, or PI-LL > 20, or PT > 30) were included. All complications were noted.

RESULT

136 patients met inclusion criteria; mean age of patients was 63.6 years (21-85, SD 13.7). The mean follow-up was 82.8 months (24-159, SD 36.6). The mean number of levels fused was 7 (3-16, SD 3). A total of 40 (29.4%) major complications were noted at final follow-ups: 2 (1.4%) intra-operative, 12 (8.9%) peri-operative (≤ 6 weeks from index), 26 (19.1%) post-operative (> 6 weeks from index). There was a total of 53 (40.0%) minor complications. Seven (5.1%) patients who developed radiographic proximal junctional kyphosis. Three patients (2.2%) developed proximal junctional failure. There were 8 (5.9%) cases of pseudarthrosis. Five of these occurred in patients undergoing AxiaLIF. All patients experienced improvements in patient-perceived outcomes (VAS, TIS, ODI, and SRS-22) and radiographic parameters at last follow-up when compared to pre-op (p < 0.05).

CONCLUSION

Rates of complications with CMIS correction of severe ASD are lower than published rates of complications seen with open ASD correction. Specifically, the incidence of catastrophic complications is lower. Furthermore, CMIS is associated with significant improvements in clinical and functional outcomes, low rates of pseudarthrosis and proximal junctional kyphosis. Therefore, in the appropriately selected patient, CMIS may be an excellent alternative approach to addressing severe ASD.

Combined anterior-posterior versus all-posterior approaches for adult spinal deformity correction: a matched control study

PURPOSE

Anterior approaches are gaining popularity for adult spinal deformity (ASD) surgeries especially with the introduction of hyperlordotic cages and improvement in MIS techniques. Combined Approaches provide powerful segmental sagittal correction potential and increase the surface area available for fusion in ASD surgery, both of which would improve overall. This is the first study directly comparing surgical outcomes between combined anterior-posterior approaches and all-posterior approach in a matched ASD population.

METHODS

This is a retrospective matched control cohort analysis with substitution using a multicenter prospectively collected ASD data of patients with > 2 year FU. Matching criteria include: age, American Society of Anesthesiologists Score, Lumbar Cobb angle, sagittal deformity (Global tilt) and ODI.

RESULTS

In total, 1024 ASD patients were available for analysis. 29 Combined Approaches patients met inclusion criteria, and only 22 could be matched (1:2 ratio). Preoperative non-matched demographical, clinical, surgical and radiological parameters were comparable between both groups. Combined approaches had longer surgeries (548 mns vs 283) with more blood loss (2850 ml vs 1471) and needed longer ICU stays (74 h vs 27). Despite added morbidity, they had comparable complication rates but with significantly less readmissions (9.1% vs 38.1%) and reoperations (18.2% vs 43.2%) at 2 years. Combined Approaches achieved more individualised and harmonious deformity correction initially. At the 2 years control, Combined Approaches patients reported better outcomes as measured by COMI and SRS scores. This trend was maintained at 3 years.

CONCLUSION

Despite an increased initial surgical invasiveness, combined approaches seem to achieve more harmonious correction with superior sagittal deformity control; they need fewer revisions and have improved long-term functional outcomes when compared to all-posterior approaches for ASD deformity correction.

Patient outcomes after circumferential minimally invasive surgery compared with those of open correction for adult spinal deformity: initial analysis of prospectively collected data

OBJECTIVE

Circumferential minimally invasive spine surgery (cMIS) for adult scoliosis has become more advanced and powerful, but direct comparison with traditional open correction using prospectively collected data is limited. The authors performed a retrospective review of prospectively collected, multicenter adult spinal deformity data. The authors directly compared cMIS for adult scoliosis with open correction in propensity-matched cohorts using health-related quality-of-life (HRQOL) measures and surgical parameters.

METHODS

Data from a prospective, multicenter adult spinal deformity database were retrospectively reviewed. Inclusion criteria were age > 18 years, minimum 1-year follow-up, and one of the following characteristics: pelvic tilt (PT) > 25°, pelvic incidence minus lumbar lordosis (PI-LL) > 10°, Cobb angle > 20°, or sagittal vertical axis (SVA) > 5 cm. Patients were categorized as undergoing cMIS (percutaneous screws with minimally invasive anterior interbody fusion) or open correction (traditional open deformity correction). Propensity matching was used to create two equal groups and to control for age, BMI, preoperative PI-LL, pelvic incidence (PI), T1 pelvic angle (T1PA), SVA, PT, and number of posterior levels fused.

RESULTS

A total of 154 patients (77 underwent open procedures and 77 underwent cMIS) were included after matching for age, BMI, PI-LL (mean 15° vs 17°, respectively), PI (54° vs 54°), T1PA (21° vs 22°), and mean number of levels fused (6.3 vs 6). Patients who underwent three-column osteotomy were excluded. Follow-up was 1 year for all patients. Postoperative Oswestry Disability Index (ODI) (p = 0.50), Scoliosis Research Society-total (p = 0.45), and EQ-5D (p = 0.33) scores were not different between cMIS and open patients. Maximum Cobb angles were similar for open and cMIS patients at baseline (25.9° vs 26.3°, p = 0.85) and at 1 year postoperation (15.0° vs 17.5°, p = 0.17). In total, 58.3% of open patients and 64.4% of cMIS patients (p = 0.31) reached the minimal clinically important difference (MCID) in ODI at 1 year. At 1 year, no differences were observed in terms of PI-LL (p = 0.71), SVA (p = 0.46), PT (p = 0.9), or Cobb angle (p = 0.20). Open patients had greater estimated blood loss compared with cMIS patients (1.36 L vs 0.524 L, p < 0.05) and fewer levels of interbody fusion (1.87 vs 3.46, p < 0.05), but shorter operative times (356 minutes vs 452 minutes, p = 0.003). Revision surgery rates between the two cohorts were similar (p = 0.97).

CONCLUSIONS

When cMIS was compared with open adult scoliosis correction with propensity matching, HRQOL improvement, spinopelvic parameters, revision surgery rates, and proportions of patients who reached MCID were similar between cohorts. However, well-selected cMIS patients had less blood loss, comparable results, and longer operative times in comparison with open patients.

Comparison of Outcomes Between Single-level Lateral Lumbar Interbody Fusion and Transforaminal Lumbar Interbody Fusion: A Meta-analysis and Systematic Review

STUDY DESIGN

This is a meta-analysis and systematic review of the available literature.

OBJECTIVE

This study aims to compare the clinical and radiologic outcomes of single-level lateral lumbar interbody fusion (LLIF) with single-level transforaminal lumbar interbody fusion (TLIF).

SUMMARY OF BACKGROUND DATA

In the treatment of adult spinal deformity, LLIF allows interbody fusion while avoiding complications associated with an anterior or transforaminal approach, although the clinical outcomes of LLIF compared with other approaches have not been well established.

METHODS

We searched PubMed, Embase, and Scopus for 385 unique studies. On the basis of our exclusion criteria, 8 studies remained for our systematic review. Data were analyzed using Review Manager 5.3 using Mantel-Haenszel statistics and random effect models. This study identified self-reported Visual Analog Scale (VAS), Oswestry Disability Index, length of stay, blood loss, complication rate, and radiologic parameters (disk height, lumbar lordosis, segmental lordosis).

RESULTS

Our meta-analysis showed that LLIF contributed to decreased blood loss [mean difference (MD)=-67.62 mL, 95% confidence interval (CI): -104 to -30.90, P<0.001], superior restoration of segmental lordosis (MD=1.91 degrees, 95% CI: 0.71-3.10, P=0.002), lumbar lordosis (MD=1.95 degrees, 95% CI: 0.15-3.74, P=0.03), and disk height (MD=2.18 mm, 95% CI: 1.18-3.17, P<0.001) when compared with TLIF. However, current data suggests no significant difference in clinical outcomes between LLIF and TLIF based on overall complication rates (P=0.22), length of hospital stay (P=0.65), postoperative Oswestry Disability Index (P=0.13), postoperative VAS Back Pain (P=0.47) and VAS Leg Pain (P=0.16).

CONCLUSIONS

LLIF is an increasingly popular option for single-level anterior column reconstruction. When compared with single-level TLIF, single-level LLIF is associated with greater changes in lumbar lordosis and disk height. The single-level LLIF is a viable alternative to TLIF, demonstrating comparable clinical outcomes and better restoration of spinopelvic parameters.

LEVEL OF EVIDENCE

Level III.

Usefulness of anterior column release for segmental lordosis restoration in degenerative lumbar kyphosis

OBJECTIVE

Three-column osteotomies (3COs) for surgical correction of lumbar kyphosis show a strong correction capacity, but this procedure carries high morbidity rates. The anterior column release (ACR) technique was developed as a less invasive procedure. In this study the authors aimed to evaluate sagittal alignment restoration using ACR and to determine factors that affect the degree of correction.

METHODS

This study included 36 patients (68 cases) who underwent ACR of more than one level for adult spinal deformity. Parameters for regional sagittal alignment included segmental lordosis (SL). The parameters for global sagittal alignment included pelvic incidence, lumbar lordosis, sacral slope, pelvic tilt, and sagittal vertical axis (SVA). In addition, the interdiscal height (IDH) and difference of interdiscal angle (DIDA) were measured to evaluate the stiffness of the vertebra segment. The changes in SL were evaluated after ACR and the change of global sagittal alignment was also determined. Factors such as the location of the ACR level, IDH, DIDA, cage height, and additional posterior column osteotomy (PCO) were analyzed for correlation with the degree of SL correction.

RESULTS

Thirty-six patients were included in this study. A total of 68 levels were operated with the ACR (8 levels at L2-3, 27 levels at L3-4, and 33 levels at L4-5). ACR was performed for 1 level in 10 patients, 2 levels in 20, and 3 levels in 6 patients (mean 1.9 ± 0.7 levels per patient). Mean follow-up duration was 27.1 ± 4.2 months. The mean SL of the total segment was 0.4° ± 7.2° preoperatively and increased by 15.3° ± 5.5° at the last follow-up (p < 0.001); thus, the mean increase of SL was 14.9° ± 8.1° per one ACR. Global sagittal alignment was also improved following SL restoration with SVA from 101.9 mm to 31.4 mm. The degree of SL correction was correlated with the location of ACR level (p = 0.041) and was not correlated with IDH, DIDA, cage height and additional PCO.

CONCLUSIONS

This study demonstrated that the mean correction angle of SL was 14.9 per one ACR. The degree of disc space collapse and stiffness of segment did not affect the degree of correction by ACR.

Restoring spinopelvic harmony with lateral lumbar interbody fusion: is it a realistic goal?

Background

The importance of spinopelvic harmony [pelvic incidence (PI) = lumbar lordosis (LL) ±10 degrees] is well established in the literature. We aimed to determine whether lateral lumbar interbody fusion (LLIF) surgery in isolation is successful in restoring spinopelvic harmony, and whether the surgery maintained the relationship in those who present in a balanced state.

Methods

A retrospective radiographic analysis was performed on patients who underwent LLIF surgery, followed by posterior instrumented fusion, between January 2012 to August 2019 by a single surgeon (AD). Pre- and post-operative X-rays were reviewed by two authors using Surgimap spinal imaging 2.2.15.5. The LL, PI, and PI-LL mismatch, as well as a range of coronal and segmental sagittal radiographic parameters, were recorded.

Results

A total of 71 patients with 170 levels treated via LLIF were analysed. A mean pre-operative PI-LL of 14.3 degrees and post-operative value of 13.4 degrees was recorded (P=0.43). Of the 41 patients who were imbalanced pre-operatively, 13 (31.7%) were restored to a LL within 10 degrees of PI post-LLIF procedure. 30 patients presented in spinopelvic harmony, and 25 (83.3%) of those maintained that relationship following LLIF. Mean coronal global Cobb angles (13.7 degrees pre-operatively to 7.7 degrees post-operatively), segmental coronal Cobb angles (3.8 to 0.9 degrees), and anterior (5.2 to 9.8 mm) and posterior (3.2 to 6.7 mm) disc heights all improved significantly post-LLIF surgery (P<0.0001).

Conclusions

Although an effective treatment for coronal deformities and providing indirect decompression for degenerative lumbar disc disease, LLIF surgery alone is unlikely to result in correction of sagittal deformity and in particular spinopelvic harmony.

Anterior Column Realignment: Analysis of Neurological Risk and Radiographic Outcomes

BACKGROUND

Anterior column realignment (ACR) is a less invasive alternative to 3-column osteotomy for the correction of sagittal imbalance. We hypothesized that ACR would correct sagittal imbalance with an acceptable neurological risk.

OBJECTIVE

To assess long-term neurological and radiographic outcomes after ACR.

METHODS

Patients ≥18 yr who underwent ACR from 2005 to 2013 were eligible. Standing scoliosis radiographs were studied at preoperation, postoperation (≤6 wk), and at minimum 2 yr of follow-up. Clinical/radiographic data were collected through a retrospective chart review, with thoracic 1 spino-pelvic inclination (T1SPi) used as the angular surrogate for sagittal vertical axis.

RESULTS

A total of 26 patients had complete data, with a mean follow-up of 2.8 yr (1.8-7.4). Preoperative, sagittal parameters were lumbar lordosis (LL) of -16.1°, pelvic incidence (PI)-LL of 41.7°, T1SPi of 3.6°, and pelvis tilt (PT) of 32.4°. LL improved by 30.6° (P < .001) postoperation. Mean changes in PT (-8.3), sacral slope (8.9), T1SPi (-4.9), and PI-LL (-33.5) were all significant. The motion segment angle improved by 26.6°, from 5.2° to -21.4° (P < .001). Neurological complications occurred in 32% patients postoperation (n = 8; 1 patient with both sensory and motor). New thigh numbness/paresthesia developed in 3 (13%) patients postoperation; only 1 (4%) persisted at latest follow-up. A total of 6 (24%) patients developed a new lower extremity motor deficit postoperation, with 4 (8%) having persistent new weakness at last follow-up. Out of 8 patients with preoperative motor deficit, half saw improvement postoperation and 75% improved by last follow-up.

CONCLUSION

There was net motor improvement, with 24% of patients improving and 16% having persistent new weakness at latest follow-up; 60% were unchanged. Radiographic results demonstrate that ACR is a useful tool to treat severe sagittal plane deformity.

Overview of Minimally Invasive Spine Surgery

Minimally invasive spine surgery (MISS) has continued to evolve over the past few decades, with significant advancements in technology and technical skills. From endonasal cervical approaches to extreme lateral lumbar interbody fusions, MISS has showcased its usefulness across all practice areas of the spine, with unique points of access to avoid pertinent neurovascular structures. Adult spine deformity has also recognized the importance of minimally invasive techniques in its ability to limit complications and to provide adequate sagittal alignment correction and improvements in patients' functional status. Although MISS has continued to make significant progress clinically, consideration must also be given to its economic impact and the learning curve surgeons experience in adding these procedures to their armamentarium. This review examines current innovations in MISS, as well as the economic impact and future directions of the field.

Surgical Treatment of Flat Back Syndrome With Anterior Hyperlordotic Cages

BACKGROUND

Traditional correction for flat back syndrome is performed with a posterior-based surgery or combined approaches in revision cases.

OBJECTIVE

To evaluate outcome from anterior surgery with the use of hyperlordotic cages (HLCs) in patients with flat back syndrome.

METHODS

All patients operated with or without prior posterior lumbar surgery were studied. Pre- to postoperative sagittal alignment was analyzed. Radiographic parameters were analyzed including T1 pelvic angle (T1PA), sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), pelvic incidence and lumbar lordosis (PI-LL), and T4-12TK.

RESULTS

All 50 patients (mean age of 58 yr, 72% female with mean body mass index of 28) demonstrated significant radiographic alignment difference in their spinopelvic and global parameters from pre- to postoperative standing: LL (-37.04° vs -59.55°, P < .001), SS (35.12 vs 41.13, P < .001), PI-LL (23.55 vs 6.46), T4-12 TK (30.59 vs 41.67), PT (28.22 vs 22.13), SVA in mm (80.94 vs 37.39), and T1PA (28.70° vs 18.43°, P < .001). Using linear regression analysis, predicted pre- to postoperative change in standing LL corresponded to a pre- to postoperative changes in standing PI-LL mismatch, T1PA, TK, SS, PT, and SVA (R2 = 0.59, 0.38, 0.25, 0.16, 0.12, and 0.17, respectively). Five degrees of pre- to postoperative change in T1PA translates to -4.15° change in LL.

CONCLUSION

Anterior surgery with HLCs followed by posterior instrumentation is an effective technique to treat flat back syndrome. HLCs are effective to maximize LL up to 30°, which is equivalent in magnitude to a pedicle subtraction osteotomy, but associated with less blood loss, quicker recovery, lower complications, and good surgical outcome.

Development of Proximal Junctional Kyphosis After Minimally Invasive Lateral Anterior Column Realignment for Adult Spinal Deformity

BACKGROUND

Development of proximal junctional kyphosis (PJK) after correction of adult spinal deformity (ASD) undermines sagittal alignment. Minimally invasive anterior column realignment (ACR) is a powerful tool for correction of ASD; however, long-term PJK rates are unknown.

OBJECTIVE

To characterize PJK after utilization of ACR in ASD correction.

METHODS

A retrospective multi-institution cohort analysis per STROBE criteria was conducted of all patients who underwent lateral lumbar interbody fusion (LLIF) or ACR for ASD from 2010 to 2015. All patients obtained preoperative and follow-up upright radiographs, assessing spinal alignment and development of PJK. Patients without proper imaging or minimum 1-yr follow-up were excluded.

RESULTS

A total of 73 of 112 patients who underwent either LLIF or ACR for ASD met inclusion criteria. Mean follow-up was 22.8 mo. There was significant improvement of all spinopelvic parameters. Overall, PJK and proximal junctional failure (PJF) rates were 20.5% and 11%, respectively. The incidence of PJK increased with greater corrective surgery (0% LLIF, 30% ACR, 42.9% ACR + posterior column osteotomy (PCO); P < .001). PJF rates increased (0% LLIF, 11% ACR, 40% ACR + PCO; P = .005). Risk factors included location of the upper-instrumented vertebra at T10-L1 vs L2-L4 (P = .007), age (P = .029), severity of ASD, and overcorrection of sagittal imbalance.

CONCLUSION

The incidence of PJK after minimally invasive ACR is slightly lower than reported after open surgery but greater than in LLIF only and increases with PCO utilization. The PJK rate increases when crossing the TL junction, sagittal imbalance severity, and overcorrection. Elderly patients are at an increased risk, suggesting need for age appropriate correction goals.

Minimally Invasive Advances in Deformity

Adult spinal deformity is a major contributor to pain and disability. It is a degenerative disease with a rigid spine. Spinopelvic parameters have been identified that outline goals of operative intervention, as they have shown to significantly improve patient outcomes. Previously, this was accomplished with large, open fusions. Unfortunately, the adult spinal deformity population is often elderly with significant comorbidities. These extensive fusions have a high rate of morbidity and mortality. Technological advances have allowed minimally invasive approaches to be developed. These techniques have decreased operative morbidity without increasing health care spending.

Biomechanical in vitro comparison between anterior column realignment and pedicle subtraction osteotomy for severe sagittal imbalance correction

PURPOSE

To investigate the biomechanical effects of anterior column realignment (ACR) and pedicle subtraction osteotomy (PSO) on local lordosis correction, primary stability and rod strains.

METHODS

Seven cadaveric spine segments (T12-S1) underwent ACR at L1-L2. A stand-alone hyperlordotic cage was initially tested and then supplemented with posterior bilateral fixation. The same specimens already underwent a PSO at L4 stabilized by two rods, a supplemental central rod (three rods) and accessory rods (four rods) with and without adjacent interbody cages (La Barbera in Eur Spine J 27(9):2357-2366, 2018). In vitro flexibility tests were performed under pure moments in flexion/extension (FE), lateral bending (LB) and axial rotation (AR) to determine the range of motion (RoM), while measuring the rod strains with strain gauge rosettes.

RESULTS

Local lordosis correction with ACR (24.7° ± 3.7°) and PSO (25.1° ± 3.9°) was similar. Bilateral fixation significantly reduced the RoM (FE: 31%, LB: 2%, AR: 18%), providing a stability consistent with PSO constructs (p > 0.05); however, it demonstrates significantly higher rod strains compared to PSO constructs with lateral accessory rods and interbody cages in FE and AR (p < 0.05), while being comparable in FE or slightly higher in AR compared to PSO constructs with two and three rods.

CONCLUSION

Bilateral posterior fixation is highly recommended following ACR to provide adequate primary stability. However, primary rod strains in ACR were found comparable or higher than weak PSO construct associated with frequent rod failure; therefore, caution is recommended. These slides can be retrieved under Electronic Supplementary Material.

Anterior lumbar interbody fusions combined with posterior column osteotomy in patients who had sagittal imbalance associated with degenerative lumbar flat-back deformity: a retrospective case series

Anterior lumbar interbody fusion (ALIF) combined with posterior column osteotomy (PCO) may be effective to achieve ideal lumbar curve correction in lumbar flat-back deformity (LFD). We aimed to investigate the radiographic and clinical outcomes of patients with primary degenerative LFD treated with multi-level ALIFs combined with PCOs. Seventy patients with primary degenerative LFD who underwent corrective surgery were divided into three groups according to the 1-month postoperative pelvic incidence/lumbar lordosis (PI-LL) angles (≤ - 10°, from - 9° to 9°, and ≥ 10°). The spinopelvic parameters, including thoracic kyphosis, LL, pelvic tilt, T1 pelvic angle, and sagittal vertical axis, were analyzed at the preoperative, postoperative follow-up periods. The clinical outcomes, including the Oswestry disability index (ODI), visual analog scale (VAS), and Scoliosis Research Society (SRS)-22r, were also evaluated. Further, the paraspinal muscles were qualitatively and quantitatively examined, preoperatively. All spinopelvic parameters were corrected as close to the normal values at the 1-month postoperative period. The spinopelvic parameters in the PI-LL ≤ - 10° group were better corrected and maintained than those in the other groups. The ODI, VAS, and SRS-22r scores improved at the final follow-up in all groups. The PI-LL ≤ - 10° group showed better clinical outcomes than the other groups. In the paraspinal muscle examination, the mean lumbar muscularity value and fatty degeneration ratio were 236.7% and 20.7%, respectively. Multi-level ALIFs with PCOs in patients with LFD are effective in restoring sagittal balance and improving clinical symptoms. In addition, the postoperative LL angles should be larger than PI + 10° to achieve good overall outcomes in patients with severe degenerative back muscle.

Minimally Invasive Surgery for Mild-to-Moderate Adult Spinal Deformities: Impact on Intensive Care Unit and Hospital Stay

OBJECTIVE

To compare circumferential minimally invasive (cMIS) versus open surgeries for mild-to-moderate adult spinal deformity (ASD) with regard to intensive care unit (ICU) and hospital lengths of stay (LOS).

METHODS

A retrospective review of 2 multicenter ASD databases with 426 ASD (sagittal vertical axis <6 cm) surgery patients with 4 or more fusion levels and 2-year follow-up was conducted. ICU stay, LOS, and estimated blood loss (EBL) were compared between open and cMIS surgeries.

RESULTS

Propensity matching resulted in 88 patients (44 cMIS, 44 open). cMIS were older (61 vs. 53 years, P = 0.005). Mean levels fused were 6.5 in cMIS and 7.1 in open (P = 0.368). Preoperative lordosis was higher in open than in cMIS (42.7° vs. 40.9°, P = 0.016), and preoperative visual analog score back pain was greater in open than in cMIS (7 vs. 6.2, P = 0.033). Preoperative and postoperative spinopelvic parameters and coronal Cobb angles were not different. EBL was 534 cc in cMIS and 1211 cc in open (P < 0.001). Transfusions were less in cMIS (27.3% vs. 70.5%, P < 0.001). ICU stay was 0.6 days for cMIS and 1.2 days for open (P = 0.009). Hospital LOS was 7.9 days for cMIS versus 9.6 for open (P = 0.804).

CONCLUSIONS

For patients with mild-to-moderate ASD, cMIS surgery had a significantly lower EBL and shorter ICU stay. Major and minor complication rates were lower in cMIS patients than open patients. Overall LOS was shorter in cMIS patients, but did not reach statistical significance.

The Radiologic and Clinical Outcomes of Oblique Lateral Interbody Fusion for Correction of Adult Degenerative Lumbar Deformity

BACKGROUND

Osteotomies aimed at correcting adult spinal deformity are associated with higher complications and perioperative morbidity. Recently, oblique lumbar interbody fusion (OLIF) was introduced for degenerative lumbar diseases. The aim of our study is to demonstrate the effectiveness of OLIF on the management of adult degenerative lumbar deformity (ADLD).

MATERIALS AND METHODS

Patients with ADLD who underwent deformity correction and decompression using OLIF and posterior instrumentation were enrolled. For radiologic evaluation, Cobb's angle (CA), sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI) were evaluated. Visual analog scale (VAS), Oswestry disability index (ODI), and perioperative parameters were recorded for clinical evaluation.

RESULTS

Fifteen patients with a mean age of 67 years (63-74 years) were enrolled prospectively and an average of 3 OLIFs (range 1-4) was performed. Posterior instrumentations were done at average of six levels (range 4-8). The mean operative blood loss was 863 ml (range 500-1400 ml) with a mean surgical duration of 7 h (range 3-11 h). SVA, TK, LL, CA, PT, and SS showed significant correction (P < 0.05) in immediate postoperative period and all parameters except TK were maintained at final followup. At the end of 24 months of average followup, 86% (13/15) showed fusion. VAS (leg pain), VAS (back pain), and ODI improved by 74% (range 40-100), 58% (range 20%-80%), and 69.5% (range 4%-90%), respectively. There were two major complications requiring revision (1 infection and 1 adjacent vertebral body fracture). Transient hip weakness present in two patients (13%) recovered within 6 weeks.

CONCLUSIONS

OLIF gives favorable short term clinical and radiological outcomes in patients of ADLD. It could potentially reduce the need for morbid pelvic fixation and posterior osteotomies in patients with degenerative lumbar deformity.

Curve Laterality for Lateral Lumbar Interbody Fusion in Adult Scoliosis Surgery: The Concave Versus Convex Controversy

BACKGROUND

Minimally invasive lateral lumbar interbody fusion (LLIF) is an effective adjunct in adult degenerative scoliosis (ADS) surgery. LLIF approaches performed from the concavity or convexity have inherent approach-related risks and benefits.

OBJECTIVE

To analyze LLIF approach-related complications and radiographic and clinical outcomes in patients with ADS.

METHODS

A multicenter retrospective review of a minimally invasive adult spinal deformity database was queried with a minimum of 2-yr follow-up. Patients were divided into 2 groups as determined by the side of the curve from which the LLIF was performed: concave or convex.

RESULTS

No differences between groups were noted in demographic, and preoperative or postoperative radiographic parameters (all P > .05). There were 8 total complications in the convex group (34.8%) and 21 complications in the concave group (52.5%; P = .17). A subgroup analysis was performed in 49 patients in whom L4-5 was in the primary curve and not in the fractional curve. In this subset of patients, there were 6 complications in the convex group (31.6%) compared to 19 in the concave group (63.3%; P < .05) and both groups experienced significant improvements in coronal Cobb angle, Oswestry Disability Index, and Visual Analog Scale score with no difference between groups.

CONCLUSION

Patients undergoing LLIF for ADS had no statistically significant clinical or operative complication rates regardless of a concave or convex approach to the curve. Clinical outcomes and coronal plane deformity improved regardless of approach side. However, in cases wherein L4-5 is in the primary curve, approaching the fractional curve at L4-5 from the concavity may be associated with a higher complication rate compared to a convex approach.

Treatment of the Fractional Curve of Adult Scoliosis With Circumferential Minimally Invasive Surgery Versus Traditional, Open Surgery: An Analysis of Surgical Outcomes

STUDY DESIGN

Retrospective, multicenter review of adult scoliosis patients with minimum 2-year follow-up.

OBJECTIVE

Because the fractional curve (FC) of adult scoliosis can cause radiculopathy, we evaluated patients treated with either circumferential minimally invasive surgery (cMIS) or open surgery.

METHODS

A multicenter retrospective adult deformity review was performed. Patients included: age >18 years with FC >10°, ≥3 levels of instrumentation, 2-year follow-up, and one of the following: coronal Cobb angle (CCA) > 20°, pelvic incidence and lumbar lordosis (PI-LL) > 10°, pelvic tilt (PT) > 20°, and sagittal vertical axis (SVA) > 5 cm.

RESULTS

The FC was treated in 118 patients, 79 open and 39 cMIS. The FCs had similar coronal Cobb angles preoperative (17° cMIS, 19.6° open) and postoperative (7° cMIS, 8.1° open), but open had more levels treated (12.1 vs 5.7). cMIS patients had greater reduction in VAS leg (6.4 to 1.8) than open (4.3 to 2.5). With propensity matching 40 patients for levels treated (cMIS: 6.6 levels, N = 20; open: 7.3 levels, N = 20), both groups had similar FC correction (18° in both preoperative, 6.9° in cMIS and 8.5° postoperative). Open had more posterior decompressions (80% vs 22.2%, P < .001). Both groups had similar preoperative (Visual Analogue Scale [VAS] leg 6.1 cMIS and 5.4 open) and postoperative (VAS leg 1.6 cMIS and 3.1 open) leg pain. All cMIS patients had interbody grafts; 35% of open did. There was no difference in change of primary CCA, PI-LL, LL, Oswestry Disability Index, or VAS Back.

CONCLUSION

Patients' FCs treated with cMIS had comparable reduction of leg pain compared with those treated with open surgery, despite significantly fewer cMIS patients undergoing direct decompression.

The comprehensive anatomical spinal osteotomy and anterior column realignment classification

OBJECTIVESpinal osteotomies and anterior column realignment (ACR) are procedures that allow preservation or restoration of spine lordosis. Variations of these techniques enable different degrees of segmental, regional, and global sagittal realignment. The authors propose a comprehensive anatomical classification system for ACR and its variants based on the level of technical complexity and invasiveness. This serves as a common language and platform to standardize clinical and radiographic outcomes for the utilization of ACR.METHODSThe proposed classification is based on 6 anatomical grades of ACR, including anterior longitudinal ligament (ALL) release, with varying degrees of posterior column release or osteotomies. Additionally, a surgical approach (anterior, lateral, or posterior) was added. Reliability of the classification was evaluated by an analysis of 16 clinical cases, rated twice by 14 different spine surgeons, and calculation of Fleiss kappa coefficients.RESULTSThe 6 grades of ACR are as follows: grade A, ALL release with hyperlordotic cage, intact posterior elements; grade 1 (ACR + Schwab grade 1), additional resection of the inferior facet and joint capsule; grade 2 (ACR + Schwab grade 2), additional resection of both superior and inferior facets, interspinous ligament, ligamentum flavum, lamina, and spinous process; grade 3 (ACR + Schwab grade 3), additional adjacent-level 3-column osteotomy including pedicle subtraction osteotomy; grade 4 (ACR + Schwab grade 4), 2-level distal 3-column osteotomy including pedicle subtraction osteotomy and disc space resection; and grade 5 (ACR + Schwab grade 5), complete or partial removal of a vertebral body and both adjacent discs with or without posterior element resection. Intraobserver and interobserver reliability were 97% and 98%, respectively, across the 14-reviewer cohort.CONCLUSIONSThe proposed anatomical realignment classification provides a consistent description of the various posterior and anterior column release/osteotomies. This reliability study confirmed that the classification is consistent and reproducible across a diverse group of spine surgeons.

Minimally Invasive Pedicle Subtraction Osteotomy

For patients with significant spinal deformity, the pedicle subtraction osteotomy provides a powerful means for correction, albeit with high morbidity. With the trend toward minimally invasive spine surgery, multiple less invasive techniques have been devised; however, there seems to be an upper limit to the degree of correction possible. The mini-open pedicle subtraction osteotomy addresses these limitations by minimizing the extent of soft tissue destruction needed to perform the osteotomy and by using the rod-cantilever technique to achieve maximum lordosis. Preliminary data are promising, with significant improvements in patient-reported clinical outcome measures as well as coronal and sagittal alignment.

Anterior Column Release/Realignment

Lateral anterior column release (ACR) is a powerful extension of the minimally invasive lateral lumbar interbody fusion procedure that incorporates division of the anterior longitudinal ligament to allow manipulation of the anterior and middle spinal columns. The resulting surgical control permits restoration of significant segmental lordosis that, when combined with varying posterior column releases, can achieve global sagittal realignment on par with traditional 3-column osteotomies. As a result, ACR is a factor in the growth of minimally invasive strategies for the correction of spinal deformities.

Lumbar Lordosis Correction With Interbody Hyperlordotic Cages: Initial Experience, Learning Curve, Technical Aspects, and Complication Incidence

Background

Analysis of the initial experience on learning curve, technical differences and perioperative or early postoperative complications using lumbar hyperlordotic anterior and lateral interbody cages for the correction of lumbar lordosis as compared with the usage of regular lordotic cages.

Methods

Initial 21 consecutive patients were treated with 13 hyperlordotic anterior lumbar interbody fusion (ALIF) cages and 8 hyperlordotic extreme lateral interbody fusion (XLIF) cages. The mean patient age was 64 years, and the mean lumbar hypolordosis was 23°.

Results

No significant procedure-related technical differences were found between the hyperlordotic and nonhyperlordotic ALIF cages. Slightly significant procedure-related technical differences were found between hyperlordotic and nonhyperlordotic XLIF cages. The complication type and occurrence were comparable.

Conclusions

Sagittal balance correction of lumbar lordosis using hyperlordotic ALIF and XLIF cages is a relatively safe surgical procedure with a short learning curve for those surgeons already familiar with anterior and lateral retroperitoneal procedures.

Patients with High Pelvic Tilt Achieve the Same Clinical Success as Those with Low Pelvic Tilt After Minimally Invasive Adult Deformity Surgery

BACKGROUND

Pelvic tilt (PT) is a compensatory mechanism for adult spinal deformity patients to mitigate sagittal imbalance. The association between preop PT and postop clinical and radiographic outcomes has not been well studied in patients undergoing minimally invasive adult deformity surgery.

OBJECTIVE

To evaluate clinical and radiographic outcomes in adult spinal deformity patients with high and low preoperative PT treated surgically using less invasive techniques.

METHODS

Retrospective case-control, institutional review board-approved study. A multicenter, minimally invasive surgery spinal deformity patient database was queried for 2-yr follow-up with complete radiographic and health-related quality of life (HRQOL) data. Hybrid surgery patients were excluded. Inclusion criteria were as follows: age > 18 and either coronal Cobb angle > 20, sagittal vertical axis > 5 cm, pelvic incidence-lumbar lordosis (PI-LL) > 10 or PT > 20. Patients were stratified by preop PT as per Schwab classification: low (PT< 20), mid (PT 20-30), or high (>30). Postoperative radiographic alignment parameters (PT, PI, LL, Cobb angle, sagittal vertical axis) and HRQOL data (Visual Analog Scale Back/Leg, Oswestry Disability Index) were evaluated and analyzed.

RESULTS

One hundred sixty-five patients had complete 2-yr outcomes data, and 64 patients met inclusion criteria (25 low, 21 mid, 18 high PT). High PT group had higher preop PI-LL mismatch (32.1 vs 4.7; P < .001). At last follow-up, 76.5% of patients in the high PT group had continued PI-LL mismatch compared to 34.8% in the low PT group (P < .006). There was a difference between groups in terms of postop changes of PT (-3.9 vs 1.9), LL (8.7 vs 0.5), and PI-LL (-9.5 vs 0.1). Postoperatively, HRQOL data (Oswestry Disability Index and Visual Analog Scale) were significantly improved in both groups (P < .001).

CONCLUSION

Adult deformity patients with high preoperative PT treated with minimally invasive surgical techniques had less radiographic success but equivalent clinical outcomes as patients with low PT.

Nonunion of Transpsoas Lateral Lumbar Interbody Fusion Using an Allograft: Clinical Assessment and Risk Factors

Introduction

This retrospective study was performed to evaluate the clinical influence of - and to identify the risk factors for nonunion of transpsoas lateral lumbar interbody fusion (LLIF) with use of allograft.

Methods

Sixty-three patients who underwent transpsoas LLIF (69.8 ± 8.9 years, 21 males and 42 females, 125 segments) were followed for a minimum 2 years postoperatively. For all LLIF segments, polyetheretherketone (PEEK) cages packed with allogenic bone were applied with supplemental bilateral pedicle screws (PSs). Bone bridge formation was evaluated by computed tomography (CT) 2 years postoperative, and a segment without any bridge formation was determined to be a nonunion. Sixty-one participants (96.8%) were classified into two groups for clinical evacuation: Group N that contained one or more nonunion segments and Group F that contained no nonunion segment. Visual analogue scales (VAS) scores and the effective rates of the five domains of the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) were compared between Groups N and F. The risk factors for nonunion were determined by univariate and multivariate analyses.

Results

Twenty segments (16%) were diagnosed as nonunion. There were no significant differences in all VAS scores, and the ratio of effective cases in all domains of JOABPEQ between Group N (n = 14) and F (n = 47). Multivariate analysis identified percutaneous PS (PPS) usage (odds ratio [OR]: 3.14, 95% confidence interval: 1.13-8.68, p = 0.028) as a positive risk factor for nonunion.

Conclusions

We should be aware of the higher nonunion rate in the LLIF segments supplemented with PPS, though nonunion does not affect significantly clinical outcomes at 2 years postoperative.

Minimally Invasive Spinal Surgery for Adult Spinal Deformity

The purpose of this review is to present the current techniques and outcomes of adult spine deformity (ASD) surgery using the minimally invasive spine surgery (MISS) approach. We performed a systemic search of PubMed for literature published through January 2018 with the following terms: "minimally invasive spine surgery," "adult spinal deformity," and "degenerative scoliosis." Of the 138 items that were found through this search, 57 English-language articles were selected for full-text review. According to the severity of the deformity and the symptoms, various types of MISS have been utilized, such as MISS decompression, circumferential MISS, and hybrid surgery. With proper indications, the MISS approach achieved satisfactory clinical and radiological outcomes for ASD, with reduced complication rates. Future studies should aim to define clear indications for the application of various surgical options.

Limitations and complications of minimally invasive spinal surgery in adult deformity

Minimally invasive spine (MIS) surgery has rapidly progressed from simple short segment fusions to large adult deformity corrections, with radiographic and clinical outcomes as good as those of open surgery. Anterior longitudinal ligament release (ALLR) and anterior column realignment (ACR) have been key advancements in the ability to correct deformity using MIS techniques. However, patient selection and appropriate preoperative workup is critical to obtain good outcomes and for complication avoidance. Despite favorable outcomes in spinal deformity surgery, MIS techniques are limited in (I) pronounced cervical or thoracic deformity; (II) patients with prior fusion mass; and (III) severe sagittal imbalance necessitating Schwab 5 osteotomy or higher. Guidelines for proper patient selection are needed to guide MIS spine surgeons in choosing the right candidate.

Complication rates associated with open versus percutaneous pedicle screw instrumentation among patients undergoing minimally invasive interbody fusion for adult spinal deformity

OBJECTIVE

High-quality studies that compare outcomes of open and minimally invasively placed pedicle screws for adult spinal deformity are needed. Therefore, the authors compared differences in complications from a circumferential minimally invasive spine (MIS) surgery and those from a hybrid surgery.

METHODS

A retrospective review of a multicenter database of patients with spinal deformity who were treated with an MIS surgery was performed. Database inclusion criteria included an age of ≥ 18 years and at least 1 of the following: a coronal Cobb angle of > 20°, a sagittal vertical axis of > 5 cm, a pelvic incidence–lumbar lordosis angle of > 10°, and/or a pelvic tilt of > 20°. Patients were propensity matched according to the levels instrumented.

RESULTS

In this database, a complete data set was available for 165 patients, and after those who underwent 3-column osteotomy were excluded, 137 patients were available for analysis; 76 patients remained after propensity matching (MIS surgery group 38 patients, hybrid surgery group 38 patients). The authors found no difference in demographics, number of levels instrumented, or preoperative and postoperative radiographic results. At least 1 complication was suffered by 55.3% of patients in the hybrid surgery group and 44.7% of those in the MIS surgery group (p = 0.359). Patients in the MIS surgery group had significantly fewer neurological, operative, and minor complications than those in the hybrid surgery group. The reoperation rates in both groups were similar. The most common complication category for the MIS surgery group was radiographic and for the hybrid surgery group was neurological. Patients in both groups experienced postoperative improvement in their Oswestry Disability Index and visual analog scale (VAS) back and leg pain scores (all p < 0.05); however, MIS surgery provided a greater reduction in leg pain according to VAS scores.

CONCLUSIONS

Overall complication rates in the MIS and hybrid surgery groups were similar. MIS surgery resulted in significantly fewer neurological, operative, and minor complications. Reoperation rates in the 2 groups were similar, and despite complications, the patients reported significant improvement in their pain and function.

Anterior lumbar sagittal alignment after anterior or lateral interbody fusion

PURPOSE

Anterior or lateral interbody fusion is a treatment option for lumbar disc disease. A segmental change occurs after such surgery. This study was designed to evaluate the changes in the lumbar regional alignment after a single or two-level standalone anterior or lateral interbody fusion (ALIF or LLIF).

METHODS

Data from patients referred to our institution between March 2013 and November 2015 for standalone ALIF or LLIF for low-grade isthmic spondylolisthesis or degenerative discopathy were retrospectively included in our analysis. Patients with a history of spinal fusion were excluded. Global and regional alignments were analyzed pre- and postoperatively. Pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA), lumbar lordosis (LL), index segmental lordosis (ISL) and L4S1 lordosis were compared. Three groups according to the pelvic incidence (PI) (low, normal and high) were separately analyzed then compared.

RESULTS

Forty-one women and 27 men (mean age was 46 years; range 25-66) were included. The mean follow-up was 10.8 (range 3-34 months). The patients were globally well balanced preoperatively and remained after surgery (SVA stagnated from 16.76±28.42mm to 15.97±28.20mm, P=0.75). PT and LL did not vary. L4S1 lordosis, and ISL were significantly increased respectively from 30.56±8.59 to 34.58±7.47 (P=0.0026) and from 5.94±5.25 to 12.99±5.87 (P<0.0001) at latest follow-up.

CONCLUSION

Despite effective changes in the segmental lordosis at the index levels, our findings suggest that one or two-levels standalone ALIF or LLIF had no effect on the global balance and the lumbar lordosis. The three groups behaved similarly, the regional lordosis was redistributed in a better harmony (L4S1/LL ratio went up from 55% to 61%, P=0.01).

STUDY TYPE

Retrospective study.

LEVEL OF EVIDENCE

4.

Biomechanical study of rod stress after pedicle subtraction osteotomy versus anterior column reconstruction: A finite element study

BACKGROUND

In an effort to minimize rod fractures and nonunion in pedicle subtraction osteotomy (PSO) constructs, surgeons have adopted multirod constructs and interbody cages. Anterior column realignment (ACR) with posterior column osteotomies is a minimally invasive alternative to PSO in sagittal balance correction, however, there is a paucity of evidence with respect to rod survival.

METHODS

Three-dimensional (3D) finite-element-model of a T12-sacrum spine segment was used to compare a 25° PSO at L3 and an ACR with a posterior column osteotomy and 30° hyperlordotic interbody cage at L3-4. The amount of overall T12-S1 lordosis correction was the same for each condition. Each simulation included cobalt chromium alloy primary rods with: (1) PSO; (2) PSO with an interbody cage (IB) at L2-3 (PSO+IB); (3) PSO with accessory (A) rods and IB at L2-3 (PSO+IB+A); (4) PSO with satellite (S) rods and IB at L2-3 (PSO+IB+2S); (5) ACR; 6) ACR with satellite rods (ACR + 2S). A 400 N follower preload was simulated for each condition.

RESULTS

PSO condition had the largest rod stress of 286 MPa in flexion. Adding interbody support reduced the rod stress by 15%. The 4-rod constructs further reduced rod stress, with the satellite rod condition facilitating the largest reduction. The rod stress in the ACR+2S was equivalent to the PSO+2S, with 50% reduction in rod stress.

CONCLUSION

The rod stress with an ACR was comparable to a PSO coupled with interbody support. These results suggest an ACR is a viable MIS alternative to a PSO without the need for a large posterior osteotomy.

The Influence of Lordotic cages on creating Sagittal Balance in the CMIS treatment of Adult Spinal Deformity

BACKGROUND

CMIS techniques are heavily dependent on placement of lateral interbody cages. Cages with an increased lordotic angle are being advocated to improve segmental lordosis and SVA. We assessed the segmental lordosis achieved with the individual cages. We further studied three variables and the effect each had on segmental lordosis: the lordosis angle of the cage, the position of the cage in the intervertebral space, and the level that it has been placed.

METHODS

This is a retrospective study of 66 consecutive patients who underwent lateral interbody fusion using lordotic cages as part of CMIS correction of scoliosis from June 2012 to January 2016. Standing radiographs at pre op and 6-week follow-up were reviewed to identify the position of the cage in the intervertebral space and the amount of segmental lordosis achieved.

RESULTS

A total of 224 cages were placed. The 6°, 10°, 12°, and 20° cages achieved a mean segmental lordosis of 9.00°, 13.09°, 13.23°, and 18.32°, respectively (P < .05). Additionally, cages placed in the anterior, middle, and posterior 3rd of the disk space produced 13.02°, 11.47°, and 8.23° of lordosis, respectively (P < .05). Stratifying by level, cages placed at T12-L1, L1-2, L2-3, L3-4, and L4-5 translated to mean segmental lordotic values of 8.43°, 10.02°, 11.38°, 12.91°, and 14.58°, respectively (P < .05).

CONCLUSIONS

The angle of the cage had an impact on segmental lordosis. Achieved segmental lordosis was notably more when the cage was placed in lower lumbar levels. Additionally, cages placed in the posterior 3rd of the intervertebral space had significantly worse segmental lordosis compared to those placed in the anterior or middle 3rd. Our study shows that an average delta change of 8.03° can be achieved with 12° cages and this when done at each subsequent level results in a progressive harmonious creation of lordosis. IRB approval was obtained for this study.

Comparison of a Newer Versus Older Protocol for Circumferential Minimally Invasive Surgical (CMIS) Correction of Adult Spinal Deformity (ASD)-Evolution Over a 10-Year Experience

STUDY DESIGN

Retrospective.

OBJECTIVES

Compare circumferential minimally invasive surgical (CMIS) correction outcomes of patients treated for adult spinal deformity (ASD) with a newer versus older protocol SUMMARY OF BACKGROUND DATA: CMIS techniques have become increasingly popular. Increasing experience and learning curve may help improve outcomes.

METHODS

A prospectively collected database was queried for all patients who underwent CMIS correction of ASD (Cobb angle >20° or sagittal vertical axis [SVA] >50 mm or pelvic incidence-lumbar lordosis mismatch >10) at 3+ levels. Those without a full-length radiograph or 2-year follow-up were excluded. Patients were compared based on treatment using our original or newer protocol.

RESULTS

The original protocol had 76 patients with an average age of 66.99 years (range 46-81, standard deviation [SD] 9.03), and the new protocol had 53 patients with average age of 65.85 years (range 48-85, SD 8.08). Preoperative and latest visual analog scale (VAS) scores in the original were 6.85 and 3.45 (p = .001) and in the new were 6.19 and 2.27 (p = .004). Delta-VAS scores were 3.27 and 4.27. The Oswestry disability index (ODI) reduced from 45.84 to 32.91 (p = .041) in the original and from 44.21 to 25.39 (p = .017) in the new. Average delta-ODIs were 22.25 and 24.01. Preoperative, latest, and delta-SF physical component scores for the original were 35.38, 42.42, and 10.06 and for the new, 30.89, 39.49, and 11.93. SF mental component scores were 50.96, 55.19, and 12.84 and 50.12, 52.99, and 8.85. The original and new protocols had latest Cobb angles of 11.54° and 11.12° (p = .789), delta-Cobb angles of 14.51° and 20.03° (p < .05), latest SVAs of 42.85 and 30.58 mm (p < .05) and latest PI-LL mismatch of 15.49 and 9.00 mm (p < .05). In the original and the new, the average preoperative SVAs that reliably achieved a postoperative SVA of 50 mm or less were 84 and 119 mm, respectively, and the maximum delta-SVAs were 89 and 120 mm. The new protocol had fewer surgical complications (p < .05).

CONCLUSION

Improvements in radiographic scores, functional outcomes, and limits of SVA correction and lower complication rates suggest that the new protocol may help improve outcomes. These findings may be a reflection of our 10-year experience and advances in the learning curve.

LEVEL OF EVIDENCE

Level IV.

Effects of intradiscal vacuum phenomenon on surgical outcome of lateral interbody fusion for degenerative lumbar disease

OBJECTIVE

The authors investigated whether the presence of intradiscal vacuum phenomenon (IVP) results in greater correction of disc height and restoration of segmental lordosis (SL).

METHODS

A retrospective chart review was performed on every patient at the University of South Florida's Department of Neurosurgery treated with lateral lumbar interbody fusion between 2011 and 2015. From these charts, preoperative plain radiographs and CT images were reviewed for the presence of IVP. Preoperative and postoperative posterior disc height (PDH), anterior disc height (ADH), and SL were measured at disc levels with IVP and compared with those at disc levels without IVP using the t-test. Linear regression was used to evaluate the factors that predict changes in PDH, ADH, and SL.

RESULTS

One hundred forty patients with 247 disc levels between L-1 and L-5 were treated with lateral lumbar interbody fusion. Among all disc levels treated, the mean PDH increased from 3.69 to 6.66 mm (p = 0.011), the mean ADH increased from 5.45 to 11.53 mm (p < 0.001), and the mean SL increased from 9.59° to 14.55° (p < 0.001). Significantly increased PDH was associated with the presence of IVP, addition of pedicle screws, and lack of cage subsidence; significantly increased ADH was associated with the presence of IVP, anterior longitudinal ligament (ALL) release, addition of pedicle screws, and lack of subsidence; and significantly increased SL was associated with the presence of IVP and ALL release.

CONCLUSIONS

IVP in patients with degenerative spinal disease remains grossly underreported. The data from the present study suggest that the presence of IVP results in increased restoration of disc height and SL.

The effect of anterior longitudinal ligament resection on lordosis correction during minimally invasive lateral lumbar interbody fusion: Biomechanical and radiographic feasibility of an integrated spacer/plate interbody reconstruction device

BACKGROUND

Lateral lumbar interbody fusion is powerful for correcting degenerative conditions, yet sagittal correction remains limited by anterior longitudinal ligament tethering. Although lordosis has been restored via ligament release, biomechanical consequences remain unknown. Investigators examined radiographic and biomechanical of ligament release for restoration of lumbar lordosis.

METHODS

Six fresh-frozen human cadaveric spines (L3-S1) were tested: (Miller et al., 1988) intact; (Battie et al., 1995) 8mm spacer with intact anterior longitudinal ligament; (Cho et al., 2013) 8mm spacer without intact ligament following ligament resection; (Galbusera et al., 2013) 13mm lateral lumbar interbody fusion; (Goldstein et al., 2001) integrated 13mm spacer. Focal lordosis and range of motion were assessed by applying pure moments in flexion-extension, lateral bending, and axial rotation.

FINDINGS

Cadaveric radiographs showed significant improvement in lordosis correction following ligament resection (P<0.05). The 8mm spacer with ligament construct provided greatest stability relative to intact (P>0.05) but did little to restore lordosis. Ligament release significantly destabilized the spine relative to intact in all modes and 8mm with ligament in lateral bending and axial rotation (P<0.05). Integrated lateral lumbar interbody fusion following ligament resection did not significantly differ from intact or from 8mm with ligament in all testing modes (P>0.05).

INTERPRETATION

Lordosis corrected by lateral lumbar interbody fusion can be improved by anterior longitudinal ligament resection, but significant construct instability and potential implant migration/dislodgment may result. This study shows that an added integrated lateral fixation system can significantly improve construct stability. Long-term multicenter studies are needed.

Utility of multilevel lateral interbody fusion of the thoracolumbar coronal curve apex in adult deformity surgery in combination with open posterior instrumentation and L5-S1 interbody fusion: a case-matched evaluation of 32 patients

OBJECTIVE The aim of this study was to evaluate the utility of supplementing long thoracolumbar posterior instrumented fusion (posterior spinal fusion, PSF) with lateral interbody fusion (LIF) of the lumbar/thoracolumbar coronal curve apex in adult spinal deformity (ASD). METHODS Two multicenter databases were evaluated. Adults who had undergone multilevel LIF of the coronal curve apex in addition to PSF with L5-S1 interbody fusion (LS+Apex group) were matched by number of posterior levels fused with patients who had undergone PSF with L5-S1 interbody fusion without LIF (LS-Only group). All patients had at least 2 years of follow-up. Percutaneous PSF and 3-column osteotomy (3CO) were excluded. Demographics, perioperative details, radiographic spinal deformity measurements, and HRQoL data were analyzed. RESULTS Thirty-two patients were matched (LS+Apex: 16; LS: 16) (6 men, 26 women; mean age 63 ± 10 years). Overall, the average values for measures of deformity were as follows: Cobb angle > 40°, sagittal vertical axis (SVA) > 6 cm, pelvic tilt (PT) > 25°, and mismatch between pelvic incidence (PI) and lumbar lordosis (LL) > 15°. There were no significant intergroup differences in preoperative radiographic parameters, although patients in the LS+Apex group had greater Cobb angles and less LL. Patients in the LS+Apex group had significantly more anterior levels fused (4.6 vs 1), longer operative times (859 vs 379 minutes), and longer length of stay (12 vs 7.5 days) (all p < 0.01). For patients in the LS+Apex group, Cobb angle, pelvic tilt (PT), lumbar lordosis (LL), PI-LL (lumbopelvic mismatch), Oswestry Disability Index (ODI) scores, and visual analog scale (VAS) scores for back and leg pain improved significantly (p < 0.05). For patients in the LS-Only group, there were significant improvements in Cobb angle, ODI score, and VAS scores for back and leg pain. The LS+Apex group had better correction of Cobb angles (56% vs 33%, p = 0.02), SVA (43% vs 5%, p = 0.46), LL (62% vs 13%, p = 0.35), and PI-LL (68% vs 33%, p = 0.32). Despite more LS+Apex patients having major complications (56% vs 13%; p = 0.02) and postoperative leg weakness (31% vs 6%, p = 0.07), there were no intergroup differences in 2-year outcomes. CONCLUSIONS Long open posterior instrumented fusion with or without multilevel LIF is used to treat a variety of coronal and sagittal adult thoracolumbar deformities. The addition of multilevel LIF to open PSF with L5-S1 interbody support in this small cohort was often used in more severe coronal and/or lumbopelvic sagittal deformities and offered better correction of major Cobb angles, lumbopelvic parameters, and SVA than posterior-only operations. As these advantages came at the expense of more major complications, more leg weakness, greater blood loss, and longer operative times and hospital stays without an improvement in 2-year outcomes, future investigations should aim to more clearly define deformities that warrant the addition of multilevel LIF to open PSF and L5-S1 interbody fusion.

Minimally invasive surgery in adult degenerative scoliosis: a systematic review and meta-analysis of decompression, anterior/lateral and posterior lumbar approaches

BACKGROUND

Minimally invasive approaches for the treatment of adult degenerative scoliosis have been increasingly implemented. However, little data exists regarding the safety and complication profiles of minimally invasive lumbar interbody fusion (LIF) for adult degenerative scoliosis. This study aimed to greater understand different minimally invasive surgical approaches for adult degenerative scoliosis with respect to clinical outcomes, changes in radiographic measurements, and complication profiles via meta-analytical techniques.

METHODS

A systematic search of six databases from inception to September 2015 was performed by two independent reviewers. Relevant studies were those that described the safety and/or effectiveness of minimally invasive anterior or lateral LIF (LLIF), transforaminal LIF (TLIF), and decompression only. Meta-analytical techniques and meta-regression were used to pool overall rates, and compare the different techniques. There was no financial funding or conflict of interest.

RESULTS

A total of 29 studies (1,228 patients) were included in this meta-analysis. Total pooled fusion rate was 95.9% (95% CI: 92.7-98.2%) for the anterior/lateral approach. The pooled construct or hardware-related complications was 4.3%, and was similar among anterior/lateral (4.4%) and posterior (5.2%) techniques. The total pooled pseudoarthrosis rate was 4.3% for the lateral approach. The overall pooled rate of motor deficit was 2.7% (95% CI: 1.7-4.0%). Subgroup meta-regression demonstrated that the anterior/lateral approach had the highest rate of motor deficits (3.6% LLIF vs. 0.7% TLIF vs. 0.5% decompression, P=0.004). The overall pooled rate of sensory deficit was 2.4%, highest for the anterior/lateral technique (3.3%) compared to TLIF (0.7%) and decompression (0.5%). The infection rate, dural tears/CSF leak, cardiac and pulmonary events were similar among the techniques, with a pooled value of 2.6%, 3.9%, 1.7%, and 1.4%, respectively. Similarly satisfactory radiological outcomes were obtained amongst the different approaches.

CONCLUSIONS

Minimally invasive spine technologies may be used for the surgical treatment of lumbar degenerative scoliosis with acceptable complication rates, functional and radiological outcome. Future studies, specifically multi-centered longitudinal, examining the adequacy of minimally invasive spine surgery is warranted to compare long-term outcomes with the traditional procedure.

Role of minimally invasive surgery for adult spinal deformity in preventing complications

With the aging population, there is a rising prevalence of degenerative spinal deformity and need of surgical care for these patients. Surgical treatment for adult spinal deformity (ASD) is often fraught with a high rate of complications. Minimally invasive surgery (MIS) has for the past decade been adopted by spine surgeons to treat ASD in the hopes of reducing access-related morbidity and perioperative complications. The benefits of MIS approach in general and recent development of MIS techniques to avoid long-term complications such as pseudoarthrosis or proximal junctional kyphosis are reviewed.

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.