Does the Global Alignment and Proportion score predict mechanical complications in circumferential minimally invasive surgery for adult spinal deformity?

David GendelbergDepartment of Orthopaedics, University of California, San Francisco–Orthopaedic Trauma Institute, San Francisco;

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Arya RaoDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Andrew ChungDepartment of Orthopaedics, Sonoran Spine Institute, Tempe, Arizona;

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Jose H. Jimenez-AlmonteDepartment of Orthopaedics, Central Florida Bone and Joint Institute, Orange City, Florida

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Anita AnandDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Jerry RobinsonDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Bardia KhandehrooDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Babak KhandehrooDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Sheila KahwatyDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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Neel AnandDepartment of Orthopaedics, Cedars-Sinai Medical Center, Los Angeles, California;

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OBJECTIVE

The Global Alignment and Proportion (GAP) score was developed to serve as a tool to predict mechanical complication probability in patients undergoing surgery for adult spinal deformity (ASD), serving as an aid for setting surgical goals to decrease the prevalence of mechanical complications in ASD surgery. However, it was developed using ASD patients for whom open surgical techniques were used for correction. Therefore, the purpose of this study was to assess the applicability of the score for patients undergoing circumferential minimally invasive surgery (cMIS) for correction of ASD.

METHODS

Study participants were patients undergoing cMIS ASD surgery without the use of osteotomies with a minimum of four levels fused and 2 years of follow-up. Postoperative GAP scores were calculated for all patients, and the association with mechanical failure was analyzed.

RESULTS

The authors identified 182 patients who underwent cMIS correction of ASD. Mechanical complications were found in 11.1% of patients with proportioned spinopelvic states, 20.5% of patients with moderately disproportioned spinopelvic states, and 18.8% of patients with severely disproportioned spinopelvic states. Analysis with a chi-square test showed a significant difference between the cMIS and original GAP study cohorts in the moderately disproportioned and severely disproportioned spinopelvic states, but not in the proportioned spinopelvic states.

CONCLUSIONS

For patients stratified into proportioned, moderately disproportioned, and severely disproportioned spinopelvic states, the GAP score predicted 6%, 47%, and 95% mechanical complication rates, respectively. The mechanical complication rate in patients undergoing cMIS ASD correction did not correlate with the calculated GAP spinopelvic state.

ABBREVIATIONS

ASD = adult spinal deformity; cMIS = circumferential MIS; DJF = distal junctional failure; DJK = distal junctional kyphosis; GAP = Global Alignment and Proportion; ILL = ideal LL; LDI = lordosis distribution index; LIV = lower instrumented vertebra; LL = lumbar lordosis; LLIF = lateral lumbar interbody fusion; MIS = minimally invasive surgery; PI = pelvic incidence; PI-LL = PI minus LL; PJF = proximal junctional failure; PJK = proximal junctional kyphosis; RLL = relative LL; RPV = relative pelvic version; RSA = relative spinopelvic alignment; UIV = upper instrumented vertebra.

OBJECTIVE

The Global Alignment and Proportion (GAP) score was developed to serve as a tool to predict mechanical complication probability in patients undergoing surgery for adult spinal deformity (ASD), serving as an aid for setting surgical goals to decrease the prevalence of mechanical complications in ASD surgery. However, it was developed using ASD patients for whom open surgical techniques were used for correction. Therefore, the purpose of this study was to assess the applicability of the score for patients undergoing circumferential minimally invasive surgery (cMIS) for correction of ASD.

METHODS

Study participants were patients undergoing cMIS ASD surgery without the use of osteotomies with a minimum of four levels fused and 2 years of follow-up. Postoperative GAP scores were calculated for all patients, and the association with mechanical failure was analyzed.

RESULTS

The authors identified 182 patients who underwent cMIS correction of ASD. Mechanical complications were found in 11.1% of patients with proportioned spinopelvic states, 20.5% of patients with moderately disproportioned spinopelvic states, and 18.8% of patients with severely disproportioned spinopelvic states. Analysis with a chi-square test showed a significant difference between the cMIS and original GAP study cohorts in the moderately disproportioned and severely disproportioned spinopelvic states, but not in the proportioned spinopelvic states.

CONCLUSIONS

For patients stratified into proportioned, moderately disproportioned, and severely disproportioned spinopelvic states, the GAP score predicted 6%, 47%, and 95% mechanical complication rates, respectively. The mechanical complication rate in patients undergoing cMIS ASD correction did not correlate with the calculated GAP spinopelvic state.

Adult spinal deformity (ASD) is a complex condition with a prevalence in elderly patients exceeding 60% that is known to dramatically affect health-related quality-of-life measures.1,2 While ASD is sometimes amenable to conservative management, operative intervention is often necessary. Achievement of global sagittal balance is a key goal in surgical correction of ASD, given that achieving sagittal balance is associated with lower rates of postoperative disability.3 However, given the vast heterogeneity in ASD presentation, the decision-making process for surgeons on how to achieve global balance can be challenging.4

Schwab et al. described the ideal sagittal parameters to produce a balanced spine and maximize health-related quality-of-life measures. They found that the ideal parameters for achieving satisfactory alignment and favorable quality-of-life outcomes were < 10° for pelvic incidence (PI) minus lumbar lordosis (LL) (PI-LL) mismatch, pelvic tilt < 20°, and a sagittal vertical axis < 4 cm.5 Although these parameters provided some structure to clinical decision-making surrounding surgical correction of ASD, Schwab et al. focused on quality-of-life measures as opposed to mechanical complication rates. Therefore, obtaining these parameters did not serve as a good predictor of the likelihood of surgical complications or need for revision surgery secondary to mechanical failure after ASD correction.

The Global Alignment and Proportion (GAP) score was created in order to address this shortcoming by creating a new PI-based proportional method of analyzing the sagittal plane that also predicts mechanical complications. Given that great variety in PI exists among the general population, it was necessary to establish sagittal parameter goals in proportion to an individual patient’s specific PI.68 The higher the GAP score, the higher the risk of mechanical complications. GAP score outcomes are further divided into three groups: proportioned, moderately disproportioned, and severely disproportioned, with 6%, 47%, and 95% postoperative mechanical failure rates, respectively.9

The GAP score was developed using outcomes of ASD cases treated with traditional open deformity surgical techniques. While open surgery is still a popular method for correction of ASD, circumferential minimally invasive surgery (cMIS) of the spine has also been shown to be an effective technique.1012 Now increasing in popularity in the treatment of spinal pathology, minimally invasive surgery (MIS) involves decreased blood loss, decreased postoperative pain, increased preservation of patient anatomy, and lower complication rates compared with open surgery.13 Given these differences between MIS and open surgery, we sought to determine whether the GAP score is a useful predictor of mechanical complication risk for patients undergoing ASD correction using cMIS.14,15

Methods

Patients

This study was a retrospective analysis of a prospectively collected data set of surgeries performed by a single surgeon at a single center. Institutional review board approval was obtained for the study. Inclusion criteria were patients older than 18 years of age who underwent cMIS for ASD, had 4 or more levels of posterior instrumentation, had ≥ 2 years of follow-up, and met any one of the following criteria: 1) coronal Cobb angle ≥ 20°, 2) sagittal vertical axis ≥ 5 cm, 3) pelvic tilt ≥ 25°, or 4) thoracic kyphosis ≥ 60°.

Outcome Data

We defined mechanical complications as proximal junctional kyphosis (PJK) or failure (PJF), distal junctional kyphosis (DJK) or failure (DJF), rod breakage, and implant-related complications. PJK was defined as an increase in kyphosis ≥ 10° between the upper instrumented vertebra (UIV) and UIV+2. PJF was defined as a fracture at the UIV or UIV+1, pullout of instrumentation, or sagittal subluxation. DJK and DJF were defined as an increase in kyphosis ≥ 10° between the lower instrumented vertebra (LIV) and LIV−1 and/or pullout of instrumentation at the LIV. Rod breakage was defined as single or double rods breaking. Implant complications included any other implant complication not previously mentioned, such as screw loosening, screw breakage, or pullout of an interbody graft, hook, or set screw. All these variables were defined in accordance with those used in the original GAP study.9

cMIS Protocol

The cMIS protocol is a staged protocol, as described by Anand et al.16,17 Spinopelvic parameters and deformity were evaluated using 36-inch scoliosis series radiographs. In the first stage of surgery, MIS lateral lumbar interbody fusions (LLIFs) were performed at the predetermined levels. After this first stage, new standing lumbar and 36-inch scoliosis series radiographs were obtained, and new spinopelvic parameters were measured. The use of staging allowed for this period of reassessment and adjustment of the surgical plan as necessary. The second stage of surgery was performed 2–3 days after the first and was followed by multilevel percutaneous posterior instrumentation with aggressive rod contouring and reduction. No posterior column facetectomies or osteotomies were performed during this stage.

GAP Score Calculation

The GAP score may range from 0 to 13 points.9 A proportioned spinopelvic state is defined by a GAP score of 0–2, a moderately disproportioned state by a GAP score of 3–6, and a severely disproportioned spinopelvic state by a GAP score > 7. As in the original study, in the present study GAP scores were calculated by summing subgroup scores of 5 parameters: relative pelvic version (RPV), relative LL (RLL), lordosis distribution index (LDI), relative spinopelvic alignment (RSA), and the age factor. Each parameter was divided into four subgroups and points were assigned as defined in the original paper.9 PI, sacral slope, L1–S1 lordosis, L4–S1 lordosis, and global tilt were used to calculate parameters.

RPV was obtained by subtracting the ideal sacral slope (ISS) from the measured sacral slope. ISS is defined in terms of PI as ISS = (PI × 0.59) + 9. RPV < −15° was considered severe retroversion; −15° to −7.1°, moderate retroversion; −7° to 5°, aligned; and > 5°, anteversion. RLL was obtained by subtracting the ideal LL (ILL) from the measured LL; RLL is also defined in terms of PI and is given by RLL = (PI × 0.62) + 29. RLL < −25° is considered severe hypolordosis; −25° to −14.1°, moderate hypolordosis; −14° to 11°, aligned; and > 11°, hyperlordosis. LDI was obtained by dividing L4–S1 lordosis by L1–S1 lordosis and multiplying the resulting quotient by 100. An LDI < 40% is considered severe hypolordotic maldistribution; 40% to 49%, moderate hypolordotic maldistribution; 50% to 80%, aligned; and > 80%, hyperlordotic maldistribution. RSA was obtained by subtracting the ideal global tilt (IGT) from the measured global tilt and defined in terms of the PI, given by the expression IGT = (PI × 0.48) – 15. Age was divided into two subgroups: adults < 60 years and adults ≥ 60 years.9

Statistical Methods

In the analysis of the preoperative and postoperative deformity parameters, a Student t-test was performed, with p < 0.05 indicating significance.

In the analysis comparing the frequency of mechanical complication rates in the cMIS cohort with the original GAP study cohort, the chi-square test was performed for each of the spinopelvic states. The categorical variable was whether or not a mechanical complication had occurred. A p value < 0.05 was considered significant.

Results

In total, 381 patients who underwent cMIS ASD were reviewed, of whom 182 patients met our inclusion criteria. The parameters of the study population are presented in Table 1. The mean postoperative GAP score was 5 ± 4. Table 2 demonstrates the preoperative versus postoperative comparison of deformity parameters. Overall, significant change was found in the Cobb angle, sagittal vertical axis, PI-LL mismatch, LL, and pelvic tilt (Table 2). Overall, 24.73% (n = 45) of patients had a proportional spinopelvic state, 40.11% (n = 73) of patients had a moderately disproportioned spinopelvic state, and 35.16% (n = 64) had a severely disproportioned spinopelvic state according to the GAP score (Table 3). Of 182 patients, 32 (17.6%) patients had mechanical complications. Of those patients, 9 (4.9%) had PJK, 9 (4.9%) had PJF, 5 (2.7%) had rod fractures, and 9 (4.9%) had other implant-related complications (Table 4).

TABLE 1.

Study population

Value
Total no. of patients182
 Male53 (29.1%)
 Female129 (70.9%)
Age, yrs62 (21–84)
Follow-up, mos84 (24–169)
Total no. of levels fused1344
Mean (range) levels fused7 ± 3 (4–16)

Values are presented as number (%) of patients, mean (range), or mean ± SD (range) unless otherwise indicated.

TABLE 2.

Preoperative versus postoperative deformity parameters

PreopPostopp Value
Cobb angle, °33 ± 15.813.2 ± 9<0.05
SVA, cm68.2 ± 56.138.7 ± 32.3<0.05
PI-LL mismatch, °18.6 ± 13.911.4 ± 8.6<0.05
LL, °41.1 ± 17.749.1 ± 11.3<0.05
L4–S1 lordosis, °33.1 ± 11.232.6 ± 8.7>0.05
Pelvic tilt, °24 ± 9.323 ± 8.9<0.05
Sacral slope, °31.5 ± 1132.4 ± 8.7>0.05
PI, °55.3 ± 11.655.1 ± 11.1>0.05

SVA = sagittal vertical axis.

Values are presented as mean ± SD unless otherwise indicated. Boldface type indicates statistical significance.

TABLE 3.

cMIS versus original GAP study spinopelvic states

cMISOriginal GAP
Proportioned45 (24.73%)33 (44.59%)
Moderately disproportioned73 (40.11%)19 (25.68%)
Severely disproportioned64 (35.16%)22 (29.73%)
Total182 (100%)74 (100%)

Values are presented as number (%) of patients.

TABLE 4.

Complication breakdown

Total No. of PatientsNo. of Complications
PJKPJFScrew LooseningScrew FractureScrew PulloutRod FractureTotal
Proportioned451111015
Moderately disproportioned 7353311215
Severely disproportioned 6435200212
Total18299621532

We further observed that compared with the original study, cMIS patients with the same GAP score as the patients from the original GAP study experienced fewer mechanical complications overall. In our cohort, 17% (32 of 182) of the patients, compared with 43% (32 of 74) of the patients in the validation cohort of the original study, experienced mechanical failure (Fig. 1).

FIG. 1.
FIG. 1.

Rates of mechanical complications between studies according to GAP scores.

Mechanical complications were found in 11% (5 of 45) of patients with proportioned spinopelvic states, 19% (14 of 73) of patients with moderately disproportioned spinopelvic states, and 19% (12 of 64) of patients with severely disproportioned spinopelvic states compared with the original GAP score, with 6%, 47%, and 95% mechanical complication rates, respectively (Fig. 2).

FIG. 2.
FIG. 2.

Rates of mechanical complications between studies according to spinopelvic state.

The chi-square test was used to compare the frequency of mechanical complications in the cMIS cohort to that in the original GAP cohort. In the proportioned, moderately disproportioned, and severely disproportioned groups, the chi-square values were 0.59, 5.62, and 40.73, respectively, and the p values were 0.441, 0.018, and < 0.0001, respectively (Table 5).

TABLE 5.

Mechanical complications in cMIS versus original GAP study

Mechanical ComplicationChi-Square Valuep Value
YesNo
Proportioned0.590.441
 cMIS540
 Original231
Moderately disproportioned5.620.018
 cMIS1558
 Original910
Severely disproportioned40.73<0.0001
 cMIS1252
 Original211

Values are presented as number of patients unless otherwise indicated. Boldface type indicates statistical significance.

Discussion

The GAP score was created in order to produce a PI-based proportional method of analyzing the sagittal plane that also predicts mechanical complications. The original GAP score study patient population included ASD patients treated with open techniques. Therefore, the applicability of the results of that study to ASD treated with cMIS techniques was unclear. In our current study, we were unable to find a correlation between GAP score and mechanical complications in our cohort of patients who underwent ASD correction using cMIS techniques. Furthermore, it was found that the overall complication rates were lower in the cMIS cohort.

When comparing the cohort of cMIS patients to that of the original study, we found that despite the fact that the cMIS group had a higher percentage of patients in the severely disproportioned group (35.16% vs 29.73%) and a lower percentage of patients in the proportioned group (24.73% vs 44.59%), the cMIS group had a lower complication rate (Table 3, Figs. 13). Furthermore, the cMIS group had a longer average follow-up relative to the original GAP validation cohort (84 vs 27.9 months).9 One would expect that with longer follow-up there would be a higher likelihood of detecting complications, but this was not the case in the current study. A chi-square test performed to evaluate for a difference in mechanical complications based on GAP categories revealed a significant difference between the two cohorts in the moderately disproportioned and severely disproportioned groups (Table 5). These findings further support the notion that the GAP score in its current form may not be applicable to patients undergoing ASD correction using cMIS techniques.

FIG. 3.
FIG. 3.

Sagittal radiographs of a patient who had a severely disproportionate spinopelvic state with a 6-week postoperative GAP score of 12 and who did not experience a mechanical complication.

Bari et al. evaluated a cohort of 149 patients to see the applicability of the GAP score translated to their patients.18 These authors found no association between the GAP score and mechanical failure. However, their patient sample differed in the number of levels fused and patient characteristics compared with the original GAP study.

In a study by Baum et al., the investigators sought to validate the GAP score in their cohort of 67 patients.19 The findings of the study demonstrated mechanical complication rates of 31.3%, 34.3%, and 34.3% in the proportioned, moderately disproportioned, and severely disproportioned groups, respectively. Baum et al. concluded that in their cohort, GAP score designations did not correlate with mechanical complications. However, in addition to being a relatively smaller cohort, the majority of patients (55%) were idiopathic scoliosis patients, a percentage significantly higher than that reported for the original GAP study and not representative of the typical ASD patient population whose most common etiology is a degenerative deformity.

Kwan et al. attempted to externally validate the GAP score in a population of 272 patients, a larger patient group than that reported in the original GAP paper, who received open spinal surgery to correct complex spinal deformities.20 Using the same inclusion criteria as the original GAP study, Kwan et al. found that at a minimum follow-up of 2 years, a higher GAP score was not associated with increased risks of mechanical complications.

Some of the critiques of the original GAP study are that it was limited in scope and did not evaluate sufficient variables that may have affected mechanical complications, such as bone mineral density (BMD) and patient BMI. Noh et al. attempted to improve the predictive ability of the GAP score by incorporating BMD and BMI.21 In their study, they replicated the methods of the original GAP score study. These authors found a statistically significant difference in area under the curve when comparing their modified GAP score to the original score. However, the study cohort of Noh et al. consisted of patients who were not treated using MIS techniques.

All the studies conducted considered the predictive value of the GAP score for mechanical failure in patients who underwent open spinal surgery;9,1821 no current studies have assessed the applicability of the GAP score for patients who underwent MIS of the spine. In the present study, the patient sample differs from those of the other studies because it only includes cMIS patients. For this reason, although we included the same inclusion criteria and definitions of mechanical complications as the original GAP study, we do not claim to disprove the external validity of the original GAP score for all cases. We do not fully understand why the GAP score was not predictive of mechanical complication rates in the cMIS population or why this population had a lower complication rate. While these questions are very important, they are beyond the scope of this study. We only assert that the GAP score did not predict mechanical complication risk for cMIS patients.

Although the goals of both protocols are the same, cMIS and open spinal surgery differ vastly in their approaches and outcomes. cMIS involves smaller incisions, decreased blood loss, and more preservation of the patient anatomy, particularly the posterior tissues and musculature that help counteract kyphosing forces compared with open spinal surgery.22 Perhaps a modified GAP score could be not only used to account for the continuous nature of spinopelvic parameters but also further specified for cMIS patients. Further investigation is required to understand the basis of the difference in mechanical complication rates between cMIS and open surgery.

This study has a number of limitations. First, the retrospective nature of the study may introduce bias and confounding variables. In addition, the fact that this is a single-surgeon series introduces a potential confounding variable in terms of general reproducibility among other surgeons. Another limitation is the sample size, which may have caused the study to be underpowered. Although our sample size is well matched with the size of the study population in the original GAP study, a larger sample size may be necessary to elucidate the relationship between the GAP score and mechanical failure for cMIS patients given that cMIS patients seem to have fewer mechanical complications overall. Finally, it is possible that there are other variables that we did not account for that contribute to mechanical complications in cMIS patients.

We believe that while the GAP score may serve as a strong predictive tool for mechanical complications in patients undergoing surgery for ASD, we did not find that its predictive value applied to our cohort who underwent cMIS for ASD. Therefore, we suggest that further studies be performed to investigate the reasons behind this outcome. Perhaps the development of a modified GAP score or a separate GAP score for MIS should be considered.

Conclusions

In this study, we found that the mechanical complication rate in patients undergoing cMIS ASD correction did not correlate with the calculated GAP score. This finding is in sharp contrast to results in patients who underwent open surgery for ASD, in whom the GAP score was correlated with mechanical complications.

Disclosures

Dr. N. Anand reports grants from Medtronic; personal fees from Medtronic, Elsevier, Spinal Balance, Spinal Simplicity, Viseon, and On-Point Surgical outside the submitted work; and a patent for Medtronic issued and patents for Medtronic and Globus Medical with royalties paid.

Author Contributions

Conception and design: Gendelberg, Rao, Chung, Jimenez-Almonte, Robinson, Kahwaty, N Anand. Acquisition of data: Gendelberg, Jimenez-Almonte, A Anand, Bardia Khandehroo, Babak Khandehroo. Analysis and interpretation of data: Gendelberg, Rao, Chung, Jimenez-Almonte, Bardia Khandehroo, Babak Khandehroo. Drafting the article: Gendelberg, Rao, Chung, Jimenez-Almonte, Robinson, A Anand. Critically revising the article: Gendelberg, Rao, Chung, Jimenez-Almonte, N Anand. Reviewed submitted version of manuscript: Gendelberg, Rao, Chung, Jimenez-Almonte, Robinson, Kahwaty. Approved the final version of the manuscript on behalf of all authors: Gendelberg. Statistical analysis: Gendelberg, Rao, Jimenez-Almonte, Babak Khandehroo. Administrative/technical/material support: Bardia Khandehroo, Babak Khandehroo. Study supervision: Babak Khandehroo, N Anand.

Supplemental Information

Videos

Video Abstract. https://vimeo.com/780340474.

Previous Presentations

An abstract of this paper was presented at the Society for Minimally Invasive Spinal Surgery Annual Forum 2021, Las Vegas, NV, October 29, 2021.

References

  • 1

    Schwab F, Dubey A, Pagala M, Gamez L, Farcy JP. Adult scoliosis: a health assessment analysis by SF-36. Spine (Phila Pa 1976). 2003;28(6):602606.

  • 2

    Pellisé F, Vila-Casademunt A, Ferrer M, et al. Impact on health related quality of life of adult spinal deformity (ASD) compared with other chronic conditions. Eur Spine J. 2015;24(1):311.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Le Huec JC, Faundez A, Dominguez D, Hoffmeyer P, Aunoble S. Evidence showing the relationship between sagittal balance and clinical outcomes in surgical treatment of degenerative spinal diseases: a literature review. Int Orthop. 2015;39(1):8795.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Acaroğlu RE, Dede Ö, Pellisé F, et al. Adult spinal deformity: a very heterogeneous population of patients with different needs. Acta Orthop Traumatol Turc. 2016;50(1):5762.

    • Search Google Scholar
    • Export Citation
  • 5

    Schwab F, Ungar B, Blondel B, et al. Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine (Phila Pa 1976). 2012;37(12):10771082.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Le Huec JC, Aunoble S, Philippe L, Nicolas P. Pelvic parameters: origin and significance. Eur Spine J. 2011;20(suppl 5):564571.

  • 7

    Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976). 1989;14(7):717721.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Polly DW Jr, Kilkelly FX, McHale KA, Asplund LM, Mulligan M, Chang AS. Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability. Spine (Phila Pa 1976). 1996;21(13):15301536.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9

    Yilgor C, Sogunmez N, Boissiere L, et al. Global Alignment and Proportion (GAP) score: development and validation of a new method of analyzing spinopelvic alignment to predict mechanical complications after adult spinal deformity surgery. J Bone Joint Surg Am. 2017;99(19):16611672.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10

    Anand N, Baron EM, Thaiyananthan G, Khalsa K, Goldstein TB. Minimally invasive multilevel percutaneous correction and fusion for adult lumbar degenerative scoliosis: a technique and feasibility study. J Spinal Disord Tech. 2008;21(7):459467.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11

    Anand N, Rosemann R, Khalsa B, Baron EM. Mid-term to long-term clinical and functional outcomes of minimally invasive correction and fusion for adults with scoliosis. Neurosurg Focus. 2010;28(3):E6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12

    Manwaring JC, Bach K, Ahmadian AA, Deukmedjian AR, Smith DA, Uribe JS. Management of sagittal balance in adult spinal deformity with minimally invasive anterolateral lumbar interbody fusion: a preliminary radiographic study. J Neurosurg Spine. 2014;20(5):515522.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13

    Anand N, Agrawal A, Burger EL, et al. The prevalence of the use of MIS techniques in the treatment of adult spinal deformity (ASD) amongst members of the Scoliosis Research Society (SRS) in 2016. Spine Deform. 2019;7(2):319324.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14

    Uribe JS, Deukmedjian AR, Mummaneni PV, et al. Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus. 2014;36(5):E15.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Haque RM, Mundis GM Jr, Ahmed Y, et al. Comparison of radiographic results after minimally invasive, hybrid, and open surgery for adult spinal deformity: a multicenter study of 184 patients. Neurosurg Focus. 2014;36(5):E13.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16

    Anand N, Kong C, Fessler RG. A staged protocol for circumferential minimally invasive surgical correction of adult spinal deformity. Neurosurgery. 2017;81(5):733739.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    Anand N, Cohen JE, Cohen RB, Khandehroo B, Kahwaty S, Baron E. 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. Spine Deform. 2017;5(3):213223.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Bari TJ, Ohrt-Nissen S, Hansen LV, Dahl B, Gehrchen M. Ability of the Global Alignment and Proportion score to predict mechanical failure following adult spinal deformity surgery—validation in 149 patients with two-year follow-up. Spine Deform. 2019;7(2):331337.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Baum GR, Ha AS, Cerpa M, et al. Does the Global Alignment and Proportion score overestimate mechanical complications after adult spinal deformity correction? J Neurosurg Spine. 2021;34(1):96102.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Kwan KYH, Lenke LG, Shaffrey CI, et al. Are higher Global Alignment and Proportion scores associated with increased risks of mechanical complications after adult spinal deformity surgery? An external validation. Clin Orthop Relat Res. 2021;479(2):312320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21

    Noh SH, Ha Y, Obeid I, et al. Modified Global Alignment and Proportion scoring with body mass index and bone mineral density (GAPB) for improving predictions of mechanical complications after adult spinal deformity surgery. Spine J. 2020;20(5):776784.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22

    Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976). 2007;32(5):537543.

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Illustration from Chan et al. (E2). © Andrew K. Chan, published with permission.

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    FIG. 1.

    Rates of mechanical complications between studies according to GAP scores.

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    FIG. 2.

    Rates of mechanical complications between studies according to spinopelvic state.

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    FIG. 3.

    Sagittal radiographs of a patient who had a severely disproportionate spinopelvic state with a 6-week postoperative GAP score of 12 and who did not experience a mechanical complication.

  • 1

    Schwab F, Dubey A, Pagala M, Gamez L, Farcy JP. Adult scoliosis: a health assessment analysis by SF-36. Spine (Phila Pa 1976). 2003;28(6):602606.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Pellisé F, Vila-Casademunt A, Ferrer M, et al. Impact on health related quality of life of adult spinal deformity (ASD) compared with other chronic conditions. Eur Spine J. 2015;24(1):311.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Le Huec JC, Faundez A, Dominguez D, Hoffmeyer P, Aunoble S. Evidence showing the relationship between sagittal balance and clinical outcomes in surgical treatment of degenerative spinal diseases: a literature review. Int Orthop. 2015;39(1):8795.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Acaroğlu RE, Dede Ö, Pellisé F, et al. Adult spinal deformity: a very heterogeneous population of patients with different needs. Acta Orthop Traumatol Turc. 2016;50(1):5762.

    • Search Google Scholar
    • Export Citation
  • 5

    Schwab F, Ungar B, Blondel B, et al. Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine (Phila Pa 1976). 2012;37(12):10771082.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Le Huec JC, Aunoble S, Philippe L, Nicolas P. Pelvic parameters: origin and significance. Eur Spine J. 2011;20(suppl 5):564571.

  • 7

    Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976). 1989;14(7):717721.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Polly DW Jr, Kilkelly FX, McHale KA, Asplund LM, Mulligan M, Chang AS. Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability. Spine (Phila Pa 1976). 1996;21(13):15301536.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9

    Yilgor C, Sogunmez N, Boissiere L, et al. Global Alignment and Proportion (GAP) score: development and validation of a new method of analyzing spinopelvic alignment to predict mechanical complications after adult spinal deformity surgery. J Bone Joint Surg Am. 2017;99(19):16611672.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10

    Anand N, Baron EM, Thaiyananthan G, Khalsa K, Goldstein TB. Minimally invasive multilevel percutaneous correction and fusion for adult lumbar degenerative scoliosis: a technique and feasibility study. J Spinal Disord Tech. 2008;21(7):459467.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11

    Anand N, Rosemann R, Khalsa B, Baron EM. Mid-term to long-term clinical and functional outcomes of minimally invasive correction and fusion for adults with scoliosis. Neurosurg Focus. 2010;28(3):E6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12

    Manwaring JC, Bach K, Ahmadian AA, Deukmedjian AR, Smith DA, Uribe JS. Management of sagittal balance in adult spinal deformity with minimally invasive anterolateral lumbar interbody fusion: a preliminary radiographic study. J Neurosurg Spine. 2014;20(5):515522.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13

    Anand N, Agrawal A, Burger EL, et al. The prevalence of the use of MIS techniques in the treatment of adult spinal deformity (ASD) amongst members of the Scoliosis Research Society (SRS) in 2016. Spine Deform. 2019;7(2):319324.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14

    Uribe JS, Deukmedjian AR, Mummaneni PV, et al. Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus. 2014;36(5):E15.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Haque RM, Mundis GM Jr, Ahmed Y, et al. Comparison of radiographic results after minimally invasive, hybrid, and open surgery for adult spinal deformity: a multicenter study of 184 patients. Neurosurg Focus. 2014;36(5):E13.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16

    Anand N, Kong C, Fessler RG. A staged protocol for circumferential minimally invasive surgical correction of adult spinal deformity. Neurosurgery. 2017;81(5):733739.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    Anand N, Cohen JE, Cohen RB, Khandehroo B, Kahwaty S, Baron E. 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. Spine Deform. 2017;5(3):213223.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Bari TJ, Ohrt-Nissen S, Hansen LV, Dahl B, Gehrchen M. Ability of the Global Alignment and Proportion score to predict mechanical failure following adult spinal deformity surgery—validation in 149 patients with two-year follow-up. Spine Deform. 2019;7(2):331337.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Baum GR, Ha AS, Cerpa M, et al. Does the Global Alignment and Proportion score overestimate mechanical complications after adult spinal deformity correction? J Neurosurg Spine. 2021;34(1):96102.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Kwan KYH, Lenke LG, Shaffrey CI, et al. Are higher Global Alignment and Proportion scores associated with increased risks of mechanical complications after adult spinal deformity surgery? An external validation. Clin Orthop Relat Res. 2021;479(2):312320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21

    Noh SH, Ha Y, Obeid I, et al. Modified Global Alignment and Proportion scoring with body mass index and bone mineral density (GAPB) for improving predictions of mechanical complications after adult spinal deformity surgery. Spine J. 2020;20(5):776784.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22

    Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976). 2007;32(5):537543.

    • Crossref
    • Search Google Scholar
    • Export Citation

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