Predictive model for distal junctional kyphosis after cervical deformity surgery

Accepted Manuscript Title: Predictive model for distal junctional kyphosis after cervical deformity surgery Author: Peter G. Passias, Dennis Vasquez-Montes, Gregory W. Poorman, Themistocles Protopsaltis, Samantha R. Horn, Cole A. Bortz, Frank Segreto, Bassel Diebo, Chris Ames, Justin Smith, Virginie LaFage, Renaud LaFage, Eric Klineberg, Chris Shaffrey, Shay Bess, Frank Schwab, ISSG PII: DOI: Reference:

S1529-9430(18)30190-6 https://doi.org/10.1016/j.spinee.2018.04.017 SPINEE 57658

To appear in:

The Spine Journal

Received date: Revised date: Accepted date:

28-8-2017 14-2-2018 20-4-2018

Please cite this article as: Peter G. Passias, Dennis Vasquez-Montes, Gregory W. Poorman, Themistocles Protopsaltis, Samantha R. Horn, Cole A. Bortz, Frank Segreto, Bassel Diebo, Chris Ames, Justin Smith, Virginie LaFage, Renaud LaFage, Eric Klineberg, Chris Shaffrey, Shay Bess, Frank Schwab, ISSG, Predictive model for distal junctional kyphosis after cervical deformity surgery, The Spine Journal (2018), https://doi.org/10.1016/j.spinee.2018.04.017. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

1

Predictive model for Distal Junctional Kyphosis After

2

Cervical Deformity Surgery

3 4 5

Peter G. Passias, MD1, Dennis Vasquez-Montes, MS1, Gregory W. Poorman, BA1, Themistocles

6

Protopsaltis, MD1, Samantha R. Horn, BA1, Cole A. Bortz, BA1, Frank Segreto, BS1, Bassel

7

Diebo, MD2, Chris Ames, MD3, Justin Smith, MD4, Virginie LaFage, PhD5, Renaud LaFage,

8

MS5, Eric Klineberg, MD6, Chris Shaffrey, MD4, Shay Bess, MD7, Frank Schwab MD5, ISSG8

9 10 11 12 13 14 15 16 17 18

1

Department of Orthopaedic Surgery, NYU Langone Orthopedic Hospital, New York, NY, USA; 2 Department of Orthopaedic Surgery, SUNY Health Sciences Center at Downstate, New York, NY, USA; 3Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA; 4Department of Neurosurgery, University of Virginia, Charlottesville, VA, USA; 5Department of Orthopaedic Surgery, Hospital for Special Surgery, New York City, NY, USA; 6 Department of Orthopaedic Surgery, Shriner’s Hospital for Children, Sacramento, CA, USA; 7 Department of Orthopaedic Surgery, Rocky Mountain Spine, Denver, CO, USA; 8Denver, CO, USA.

19 20 21 22 23 24 25 26 27 28 29 30 31

Corresponding author information: Peter G. Passias, MD New York Spine Institute NYU Medical Center – Langone Orthopedic Hospital, Department of Orthopaedic Surgery 301 East 17th St, New York, NY, 10003, USA. Tel.: (516) 357-8777 Fax: (516) 357- 0087 E-mail address: [email protected] 1 Page 1 of 25

1

Structured Abstract

2 3

Background Context: Distal Junctional Kyphosis (DJK) is a primary concern of surgeons

4

correcting cervical deformity. Identifying patients and procedures at higher risk for developing

5

this condition is paramount in improving patient selection and care.

6 7

Purpose: Develop a risk index for DJK development in the first year after surgery.

8 9 10

Study Design/Setting: Retrospective review of a prospective multicenter cervical deformity database.

11 12

Patient Sample: Patients over the age of 18 meeting one of the following deformities: cervical

13

kyphosis (C2-7 Cobb angle >10°), cervical scoliosis (coronal Cobb angle >10°), positive cervical

14

sagittal imbalance (C2-C7 sagittal vertical axis >4cm or T1-C6 >10 o), or horizontal gaze

15

impairment (chin-brow vertical angle >25o).

16 17

Outcome Measures: Development of DJK at any time before 1 year.

18 19

Methods: DJK was defined by both clinical diagnosis (by enrolling surgeon) and post-hoc

20

identification of development of an angle <-10 degrees from the end of fusion construct to the 2nd

21

distal vertebra, as well as a change in this angle by <-10 from baseline. Conditional Inference

22

Decision Trees were used to identify factors predictive of DJK incidence and the cut-off points at

23

which they have an effect. A conditional Variable-Importance table was constructed based on a

2 Page 2 of 25

1

non-replacement sampling set of 2000 Conditional Inference Trees. 12 influencing factors were

2

found, binary logistic regression for each variable at significant cut-offs indicated their effect

3

size.

4 5

Results: Statistical analysis included 101 surgical patients (average age: 60.1 years, 58.3%

6

female, BMI: 30.2) undergoing long cervical deformity correction (mean levels fused: 7.1,

7

osteotomy used: 49.5%, Approach: 46.5% Posterior, 17.8% Anterior, 35.7% Combined). In two

8

years after surgery 6% of patients were diagnosed with clinical DJK, however 23.8% of patients

9

met radiographic definition for DJK. Patients with neurologic symptoms were at risk for DJK

10

(OR:3.71 CI:0.11-0.63). However, no significant relationship was found between osteoporosis,

11

age, or ambulatory status with DJK incidence. Baseline radiographic malalignments were more

12

the most numerous and strong predictors for DJK: [1] C2-T1 Tilt >5.33 (OR:6.94 CI:2.99-

13

16.14), [2] Kyphosis <-50.6⁰ (OR:5.89 CI:0.07-0.43), [3] C2-C7 lordosis <-12⁰ (OR:5.7

14

CI:0.08-0.41), [4] T1 Slope minus Cervical Lordosis>36.4 (OR:5.6 CI:2.28-13.57), [5] C2-C7

15

SVA >56.3⁰ (OR:5.4 CI:2.20-13.23), and [6] C4_Tilt >56.7 (OR:5.0 CI:1.90-13.1).Clinically,

16

combined approaches (OR:2.67 CI:1.21-5.89) and usage of Smith Petersen osteotomy (OR:2.55

17

CI:1.02-6.34) were the most important predictors for DJK.

18 19

Conclusions: In a surgical cohort of cervical deformity patients, we found a 23.8% incidence of

20

DJK. Different procedures and patient malalignment predicted incidence of DJK up to 1-year.

21

Preoperative TS-CL, Cervical Kyphosis, SVA, and Cervical Lordosis all strongly predicted DJK

22

at specific cut-off points. Knowledge of these factors will potentially help direct future study and

23

strategy aimed at minimizing this potentially dramatic occurrence.

3 Page 3 of 25

1

Key Words: cervical; cervical deformity; deformity; distal junctional kyphosis; surgery

2

4 Page 4 of 25

1

Introduction

2

Adult cervical deformity is a severely debilitating disorder. Cervical deformity results in

3

significant compromises to patient health-related quality of life (HRQL).1–4 The most common

4

deformity in the cervical spine is kyphosis which may be associated with not only degenerative,

5

iatrogenic, and neuromuscular pathologies, but also myelopathy and post-laminectomy

6

syndrome.5 When untreated, this kyphosis may even progress to “chin-on-chest” deformities

7

which compromise vision, breathing, and swallowing. However, recent advances in spinal

8

deformity alignment techniques gives surgeons the tools to correct these high-risk pathologies.6,7

9 10

Although advances in alignment targets frequently allow for favorable short-term clinical results,

11

the durability of cervical deformity correction remains a challenge.8–10 Revision rates frequently

12

can exceed 20%. Junctional kyphosis is one of the most important risks surgeons consider in

13

planning surgical correction for cervical deformity.11 Distal junctional Kyphosis (DJK) is

14

radiographically defined as loss of alignment one or two levels distal to the lowest instrumented

15

vertebra. DJK results from fixation failure, adjacent level fracture, or spondylolisthesis and

16

results in pain, radiculopathy, myelopathy, and deformity.12 When DJK progresses, it can lead to

17

a radiographic finding of distal kyphosis as well as features of failure, termed distal junctional

18

failure.

19 20

In the lumbar spine proximal junctional kyphosis is well studied. Poor bone quality, over-

21

correction, and insufficient fusion construct are frequently cited as the most important factors

22

resulting in proximal junctional kyphosis.10 In the cervical spine, however, there is a dearth of

5 Page 5 of 25

1

literature on predictors and avoidance of DJK. Given the impact of DJK on patient outcomes,

2

understanding risk factors for DJK is important for surgical planning and mitigation of risk.

3 4

This study examines risk factors for development of DJK within one year after surgical

5

correction of cervical deformity. Specifically, a Random Forest statistical model employed on a

6

large, multi-center study group database may allow for valuable insights into DJK avoidance

7

generalizable to a plethora patient groups.

6 Page 6 of 25

1

Methods

2

Study population

3

Consecutive patients with adult cervical deformities were prospectively enrolled at one of

4

13 participating centers. Each institution obtained approval from their local Institutional Review

5

Board for patient enrollment. Inclusion criteria consisted of 18 years of age or older, presence of

6

cervical deformity and the undergoing of surgical treatment of their deformity. Cervical

7

deformity were defined as the presence of any of the following radiographic specifications

8

(Figure 1): cervical kyphosis (C2-7 sagittal Cobb angle  10); cervical scoliosis (C2-7 coronal

9

Cobb angle  10), C2-7 sagittal vertical axis (C2-7 SVA)  4 cm, or chin-brow vertical angle 

10

25. Patients with active spine neoplasm, spinal infection, or pregnancy were excluded from the

11

database. Surgical approach, techniques and instrumentation were conducted as prescribed by

12

the treating surgeon.

13 14 15

Data Collection and Radiographic Assessment Standardized data collection forms were used to record patient demographics, medical

16

comorbidities, surgical details, patient-reported outcome measures, and treatment complications

17

at baseline and follow-up points. Additionally, physician recorded neurological symptoms

18

(Unstable gait, corticospinal distribution motor deficit, hand muscle atrophy, hyperreflexia,

19

Hoffman sign, spasticity of lower limbs, upgoing plantar response) were also included. The

20

aforementioned clinical data was collected at 6 weeks, 3 months (8-16 weeks), and 1 year (9-23

21

months). All data was later consolidated at a single center for summary and analysis. The data

22

was then retrospectively reviewed.

23

7 Page 7 of 25

1

Radiographic assessment comprised standing long-cassette radiographs as well as cervical

2

anterior-posterior and lateral radiographs. Radiographs were obtained at baseline and each

3

clinical follow-up in accordance to study protocol. Radiographs were analyzed using validated

4

software (SpineView; ENSAM Laboratory of Biomechanics, Paris, France)23 at a central

5

location based on standard techniques.14, 24

6 7

Outcome Measures

8

DJK was defined as the development of < -10 from the end of fusion construct to the 2nd distal

9

vertebra, as well as a change in this angle by < -10 from baseline. Patients who met this criteria

10

at 3, 6, 12, or 24 months were included in the DJK group.

11 12

Data Analysis

13

R version 3.3.1 (2016-06-21) Copyright (C) 2016 The R Foundation for Statistical Computing,

14

was utilized conjointly with IBM SPSS Statistics for Windows, version 23.0 (IBM Corp.,

15

Armonk, N.Y., USA) for pre-processing and analysis of the data. Packages used in R include

16

“party” and “rpart”. First part of the analysis consisted of a Random Forest set of 2000

17

Conditional Inference Trees (sub-sampling without replacement) utilized to identify potential

18

factors that affect incidence of DJK as a previously defined dichotomous variable. A Variable-

19

Importance table (Gini Gain criterion) was generated via the varimp() function in the R “party”

20

package, said table outlined the importance of possible predictors of our target variable. A total

21

of 15 influencing factors were discovered and carried over to an IBM SPSS database where

22

logistic regressions were conducted to show their effect size as odd ratios, as well as, their

23

significance as possible predictors.

8 Page 8 of 25

1 2

Results

3

Baseline Characteristics

4

A cohort of 101 patients undergoing long cervical deformity correction (mean levels fused = 7.1,

5

osteotomy use = 49.5%, Approach = 46.5% Posterior only, 17.8% Anterior only, and 35.7%

6

Combined, Table 1). The most common UIVs were C2 and C3 and the most common LIV was

7

T2. The distribution of LIV for all patients is shown in Table 2. Patient population was 59.6%

8

female with a mean age = 60.1, BMI = 30.2, and a Charlson Comorbidity Index score of 0.747.

9

7.3% of patients were smokers. Radiographically, patient presented at baseline with a mean

10

Pelvic tilt = 18.87, Pelvic Incidence - Lumbar Lordosis = 1.65, Thoracic Kyphosis=-38.05, C2-

11

C7 SVA =45.50, TS-CL = 37.61, and a McGregor Slope = 5.12. In up to 24 months after

12

surgery, 23.8% of patients developed DJK as defined by radiographic changes, 25% of these

13

cases were identified by clinical diagnoses.

14 15

Demographic predictors for DJK

16

Baseline demographic factors did not show a significant relationship in predicting incidence of

17

DJK, this included Age, BMI, Gender; additionally, Charlson Co-morbidity Index did not show

18

any significant relationship as well.

19 20

Clinical predictors for DJK

21

In respect to clinical variables, we found the presence of neurological symptoms to be the most

22

relevant predictor of DJK incidence (OR: 3.71, CI: 0.11 to 0.63; p-val = 0.012, Table 3).

23

9 Page 9 of 25

1

Surgical predictors for DJK

2

Operative variables revealed that a the use of a combined surgical approach as opposed to solely

3

anterior or posterior (OR: 2.67, CI: 1.21 to 5.89; p-val = 0.042), and usage of a Smith Peterson

4

Osteotomy (OR: 2.55, CI: 1.02 to 6.34; p-val = 0.092) also had a sizeable effect on DJK

5

incidence. Interestingly, the lack of use of intra-operative steroid also reached significance with a

6

comparable effect size (OR: 2.93, CI: 0.15 to 0.77; p-val = 0.029). Finally, level of the anterior

7

Upper Instrumented Vertebra approached significance (OR: 0.381, CI: 0.127 to 1.145; p-val =

8

0.149).

9

Levels fused and use of other osteotomy types were not found to affect incidence of DJK

10

significantly; as well as, the presence of osteoporosis or history of previous cervical surgery.

11 12

Radiographic predictors for DJK

13

Radiographic variables at baseline were the most numerous predictors of DJK incidence, the

14

majority of these predictors pertained structures in the cervical region - their effect size in

15

decreasing magnitude are as follows: C2-T1 Tilt > 5.33 increased incidence of DJK (OR: 6.94,

16

CI: 2.98 to 16.14; p-val = 0.000), C2-C7 lordosis < -12 increased incidence of DJK (OR: 5.70,

17

CI: 0.08 to 0.41; p-val = 0.001), T1 Slope minus Cervical Lordosis > 36.4 increased incidence of

18

DJK (OR: 5.57, CI: 2.28 to 13.57; p-val = 0.002), C2-C7 SVA > 56.3 increased incidence of

19

DJK (OR: 5.40, CI: 2.2 to 13.23; p-val = 0.002), C4 Tilt > 56.7 increased incidence of DJK (OR:

20

5.00, CI: 1.90 to 13.13; p-val = 0.006).

21 22

Other significant factors in the cervical region included T1-C2 Harrison angle >-4.17 (OR: 4.13,

23

CI: 0.11 to 0.54; p-val = 0.004), and T1-C2 angle > -13.6 (OR: 3.67, CI: 0.12 to 0.61; p-val =

10 Page 10 of 25

1

0.008). Additionally, Ames classification system cSVA Modifier > 1 (cSVA>8cm) also

2

increased incidence of DJK to a lesser but still significant extent (OR: 3.00, CI: 1.21 to 7.46; p-

3

val = 0.046).

4

In the thoracic region, Thoracic Kyphosis was found to have a sizeable significant effect on DJK

5

incidence at angles < -50.6 (OR: 4.58, CI: 0.09 to 0.51; p-val = 0.003). No other thoracic or

6

thoracolumbar measurement was found to be a significant predictor of DJK incidence.

11 Page 11 of 25

1

Discussion

2

Advancing understanding of sagittal alignment, osteotomy techniques, and improved patient

3

safety has made realignment procedures for correction of cervical spinal more common.13

4

However, the incidence of junctional kyphosis has increased with modern instrumentation

5

techniques including all pedicle screw constructs.14 Distal junctional kyphosis can represent a

6

dramatic occurrence among cervical deformity corrective procedures, as the potential for

7

complete loss of initial correction and costly revision procedures can subsequently result, having

8

dramatic impact on patient experience and reported outcomes. To this end, we attempted to

9

model predictors of DJK 1-year post-correction in 101 patients undergoing cervical deformity

10

correction. The current analysis identified DJK radiographically in 23.8% of eligible patients up

11

to 2-years post-operation.

12 13

As it would be expected, excess preoperative thoracic and cervical kyphosis were predictive of

14

DJK. Random Forest analysis’ main utility lies in cutoff points at which DJK risk is most

15

elevated. The most clinically relevant cutoff points were: preoperative Thoracic Kyphosis

16

>50.6°, preoperative Cervical lordosis <-12°, preoperative Cervical SVA >56.3 mm, and

17

preoperative cervical lordosis minus T1 slope >36.4°. Patients with malalignment beyond these

18

thresholds were at a five to six times increased risk for DJK, likely due to increased shear stress

19

at the distal construct as the cervical kyphosis increases the slope of the transition segment.

20

These findings are analogous to those in lumbar spine deformity literature on incidence of

21

proximal junctional kyphosis. In a 2016 meta analysis detailing lumbar proximal junctional

22

kyphosis, Kim and Iyer described worse preoperative deformity measurements in SVA, thoracic

23

kyphosis, lumbar lordosis, sacral slope, and pelvic retroversion as leading to proximal junctional

12 Page 12 of 25

1

kyphosis.15 In both forms of junctional kyphosis, the major predictors described would add to the

2

shear stress on the construct from preoperative malalignment in the fused section of the spine.

3 4

In demographic analysis, age, gender, BMI, ambulatory status, and charlson comorbidity score

5

did not significantly increase risk of DJK. In osteoporosis patients, 3 DJK cases in 11 patients

6

(27% compared to 23% overall) similarly did not reach significance. Poor bone quality is

7

commonly cited as one of the most important factors contributing to junctional kyphosis, but

8

with only 11 patients, the current study cannot accurately determine the effect size of

9

osteoporosis on DJK. 6,10,16 Our lack of clear conclusions in typically high risk patients may also

10

be due to the comorbid nature of our cohort: patients were on average 60 years old, female,

11

obese, and had at least one comorbid factor.

12 13

In 2016 Glassman et al found neuromuscular comorbidities present in 76% of proximal

14

junctional kyphosis patients, and particularly cautioned surgeons of the risks of junctional failure

15

in patients with comorbidities that affect standing balance, regardless of alignment.10 Neurologic

16

comorbidities increased risk of DJK by 3.7 times. Parkinson’s, neuromuscular disease, and

17

cervical myelopathy patients may have difficulty rebalancing in unfused segments after

18

realignment for deformity correction, thereby putting additional stress on the fusion construct.

19

Additionally, in other instances of impaired neurologic feedback, the ability of the the patient to

20

achieve a sense of balance is limited at baseline, and adaptations to dramatic postural

21

realignments following corrective surgical procedures may further place additional kyphotic

22

pressure on the construct.

13 Page 13 of 25

1

Patients disproportionally experienced DJK at earlier followups at a logarithmic (checking with

2

dennis) rate. In these patients, 50% were identified 3 months after surgery and 75% in 6 months,

3

a higher incidence of junctional failure is to be expected at long-term followup.

4

Although patient selection plays an important role, fusion construct and procedure are decisive in

5

incidence of DJK. Selection of the lowest/highest instrumented vertebra, preemptive

6

vertebroplasty or kyphoplasty, and fusion construction are recommended in the literature as

7

means to minimize risk of junctional kyphosis1716. In the current study, combined approaches

8

(relative to single approach) and usage of smith-petersen osteotomies were predictive of

9

radiographic DJK. In a study on adolescent idiopathic scoliosis, Rhee et al found posterior,

10

relative to anterior, instrumentation more frequently associated with proximal junctional

11

kyphosis, and hypothesized its etiology in disruption of the posterior tension band18. Upper and

12

lower instrumented vertebra is typically viewed as the most significant decision a surgeon can

13

make in preventing junctional kyphosis. However, in the current analysis, lower instrumented

14

vertebra was not significantly associated with DJK. Fusions most frequently ended at T2.

15

Reports increasingly cite the inclusion of the cervicothoracic junction, a site of complex

16

biomechanics due to transition from mobile to immobile vertebra, in the fusion construct as

17

important in avoiding mechanical failure.

18 19

Interestingly, DJK incidence did not correlate with reduced HRQL outcome scores. This agrees

20

with early research on junctional kyphosis, which identified the phenomenon with little concern

21

for its clinical relevance. However, this may be due to a limitation of our analysis, which did not

22

determine HRQLs at the time of DJK occurrence. Long-term followup is needed to determine

23

the incidence of global malalignment, neurogolocial symptoms, and junctional failure in these

14 Page 14 of 25

1

DJK patients, which have potential to reverse the radiographic achievements of initial surgery,

2

the clinical benefits achieved, and require extensive reoperations. Protracted analysis on DJK

3

patients’ incidence of these complications would also help determine a threshold for DJK’s

4

clinical relevance.

5 6

Limitations

7

The current analysis recognizes several limitations. First, there was no control group of untreated

8

cervical deformity patients that were followed over time, which limits conclusions on DJK’s

9

impact on outcomes. Second, many patients in this cohort had increased risk factors based on

10

comorbidities, with the average patient being over age 60, female, obese, and having at least one

11

comorbidity. This may have limited conclusions on the predictive value of demographic,

12

comorbidity , and age-related factors in the development of DJK. Additionally, we did not have

13

any MRI scans available to determine the effect of disc degeneration or ligamentous failure as a

14

cause of DJK development. Neurological abnormalities were not recorded with enough

15

granularity to make conclusions about the neurologic status of the patients beyond the specific

16

abnormality present, include severity and other factors.

17 18

Conclusions

19

In a surgical cohort of cervical deformity patients, we found a 23.8% incidence of DJK. With

20

regards determinants of occurrence, we found that certain radiographic factors were most

21

strongly related, and specific thresholds were able to be determined. Importantly, certain clinical

22

and mal-adaptive characteristics, such as baseline neurological comorbidities and surgical related

15 Page 15 of 25

1

factors were also highly related to development of distal junctional kyphosis, emphasizing the

2

importance of multiple contributors that can collectively place patients at risk.

3

16 Page 16 of 25

1

References

2 3

[1]

Passias PG, Soroceanu A, Smith J, et al. Postoperative cervical deformity in 215

4

thoracolumbar patients with adult spinal deformity: prevalence, risk factors, and impact on

5

patient-reported outcome and satisfaction at 2-year follow-up. Spine (Phila Pa 1976).

6

2015;40(5):283-291. doi:10.1097/BRS.0000000000000746.

7

[2]

Protopsaltis TS, Scheer JK, Terran JS, et al. How the neck affects the back: changes in

8

regional cervical sagittal alignment correlate to HRQOL improvement in adult

9

thoracolumbar deformity patients at 2-year follow-up. J Neurosurg Spine.

10 11

2015;23(2):153-158. doi:10.3171/2014.11.SPINE1441. [3]

Scheer JK, Passias PG, Sorocean AM, et al. Association between preoperative cervical

12

sagittal deformity and inferior outcomes at 2-year follow-up in patients with adult

13

thoracolumbar deformity: analysis of 182 patients. J Neurosurg Spine. 2016;24(1):108-

14

115. doi:10.3171/2015.3.SPINE141098.

15

[4]

Smith JS, Line B, Bess S, et al. The Health Impact of Adult Cervical Deformity in Patients

16

Presenting for Surgical Treatment: Comparison to United States Population Norms and

17

Chronic Disease States Based on the EuroQuol-5 Dimensions Questionnaire.

18

Neurosurgery. 2017;80(5):716-725. doi:10.1093/neuros/nyx028.

19

[5]

Shamji MF, Ames CP, Smith JS, Rhee JM, Chapman JR, Fehlings MG. Myelopathy and

20

Spinal Deformity. Spine (Phila Pa 1976). 2013;38(22):S147-S148.

21

doi:10.1097/BRS.0b013e3182a7f521.

22 23

[6]

Caruso L, Barone G, Farneti A, Caraffa A. Pedicle subtraction osteotomy for the treatment of chin-on-chest deformity in a post-radiotherapy dropped head syndrome: A case report

17 Page 17 of 25

1

and review of literature. Eur Spine J. 2014;23:S634-S643. doi:10.1007/s00586-014-3544-

2

z.

3

[7]

Uchida K, Nakajima H, Sato R, et al. Cervical spondylotic myelopathy associated with

4

kyphosis or sagittal sigmoid alignment: outcome after anterior or posterior decompression.

5

J Neurosurg Spine. 2009;11(5):521-528. doi:10.3171/2009.2.SPINE08385.

6

[8]

Lafage R, Schwab F, Glassman S, et al. Age-adjusted Alignment Goals Have the Potential

7

to Reduce PJK. Spine (Phila Pa 1976). 2017;(917):1.

8

doi:10.1097/BRS.0000000000002146.

9

[9]

Smith JS, Ramchandran S, Lafage V, et al. Prospective Multicenter Assessment of Early

10

Complication Rates Associated With Adult Cervical Deformity Surgery in 78 Patients.

11

Neurosurgery. 2016;79(3):378-388. doi:10.1227/NEU.0000000000001129.

12

[10] Glassman SD, Coseo MP, Carreon LY. Sagittal balance is more than just alignment: why

13

PJK remains an unresolved problem. Scoliosis Spinal Disord. 2016;11(1):1.

14

doi:10.1186/s13013-016-0064-0.

15

[11] Scheer JK, Fakurnejad S, Lau D, et al. Results of the 2014 SRS Survey on PJK/PJF: A

16

Report on Variation of Select SRS Member Practice Patterns, Treatment Indications, and

17

Opinions on Classification Development. Spine (Phila Pa 1976). 2015;40(11):829-840.

18

doi:10.1097/BRS.0000000000000897.

19

[12] Lowe TG, Lenke L, Betz R, et al. Distal junctional kyphosis of adolescent idiopathic

20

thoracic curves following anterior or posterior instrumented fusion: incidence, risk factors,

21

and prevention. Spine (Phila Pa 1976). 2006;31(3):299-302.

22

doi:10.1097/01.brs.0000197221.23109.fc.

23

[13] Smith JS, Shaffrey CI, Bess S, et al. Recent and Emerging Advances in Spinal Deformity.

18 Page 18 of 25

1 2

Neurosurgery. 2017;80(3S):S70-S85. doi:10.1093/neuros/nyw048. [14] Kim HJ, Bridwell KH, Lenke LG, et al. Patients with proximal junctional kyphosis

3

requiring revision surgery have higher postoperative lumbar lordosis and larger sagittal

4

balance corrections. Spine (Phila Pa 1976). 2014;39(9):E576-80.

5

doi:10.1097/BRS.0000000000000246.

6 7 8 9 10

[15] Kim HJ, Iyer S. Proximal Junctional Kyphosis. J Am Acad Orthop Surg. 2016;24(5):318326. doi:10.5435/JAAOS-D-14-00393. [16] Cho SK, Shin JI, Kim YJ. Proximal junctional kyphosis following adult spinal deformity surgery. Eur Spine J. 2014;23(12):2726-2736. doi:10.1007/s00586-014-3531-4. [17] Denis F, Sun EC, Winter RB. Incidence and risk factors for proximal and distal junctional

11

kyphosis following surgical treatment for Scheuermann kyphosis: minimum five-year

12

follow-up. Spine (Phila Pa 1976). 2009;34(20):E729-34.

13

doi:10.1097/BRS.0b013e3181ae2ab2.

14

[18] Rhee JM, Bridwell KH, Won DS, Lenke LG, Chotigavanichaya C, Hanson DS. Sagittal

15

plane analysis of adolescent idiopathic scoliosis: the effect of anterior versus posterior

16

instrumentation. Spine (Phila Pa 1976). 2002;27(21):2350-2356.

17

doi:10.1097/01.BRS.0000030301.48250.3D.

18

19 Page 19 of 25

1

Figure Legend

2 3

Figure 1. Schematic of the measured sagittal alignment parameters for the cervical (left) and

4

global spinopelvic (right) spinal regions. cSVA= cervical sagittal vertical axis; C2-7 CL =

5

cervical lordosis; CBVA = chin-brow vertical angle; TK = thoracic kyphosis; LL = lumbar

6

lordosis; SVA = sagittal vertical axis; PT = pelvic tilt; PI = pelvic incidence.

7 8

Figure 2. Survival curve modeling incidence of DJK over time after cervical deformity surgery.

9 10

Figure 3. Survival curve modeling incidence of DJK at progressively lower instrumented

11

vertebra.

12 13

20 Page 20 of 25

1

Table 1. Demographics, comorbidities, and surgical data compared between patients who did and

2

did not experience DJK.

Variable Age (years) Sex (female) Body Mass Index (kg/m2) Current Smoker Charlson Comorbidity Index

DJK (n=24) 59.18 58% 31.60 8.70% 0.67

No DJK (n=77) 60.35 60% 29.72 6.85% 0.77

p value 0.653 0.886 0.355 0.766 0.687

HROQL Metric

NDI mJOA EQ-5D EQ-5D VAS NSR Back NSR Neck

49.73 13.45 0.73 70.03 5.05 6.91

47.42 13.58 0.73 136.08 5.29 6.71

0.559 0.857 0.923 0.249 0.731 0.711

Osteotomy

Partial Facet Complete Facet Smith-Petersen Opening Wedge Closing Wedge Vertebral Column Resection

4.55% 0.00% 36.36% 0.00% 18.18% 0.00%

6.67% 8.33% 18.33% 1.67% 20.00% 5.00%

0.722 0.162 0.086 0.542 0.854 0.285

Surgical

Levels fused Lower Instrumented Vertebrae Upper Instrumented Vertebrae Previous Cervical Surgery Operative time (minutes) Estimated Blood Loss (Ant) Operative time (Post) Estimated Blood Loss (Post)

6.54 2.50 9.04 64.29% 207.67 148.46 306.50 771.59

6.28 2.90 9.10 73.81% 241.41 220.39 302.98 760.78

0.690 0.173 0.939 0.777 0.449 0.483 0.923 0.955

Demographics

3 4 5 6

Abbreviations: DJK = distal junctional kyphosis; HRQOL = health-related quality of life; Ant = anterior surgical approach; Post = posterior surgical approach; NDI = Neck Disability Index; mJOA = modified Japanese Orthopedics Association scale; EQ-5D = EuroQol 5-Dimension health status; VAS = visual analogue scale; NSR = numeric rating scale

7 8

21 Page 21 of 25

1 2 3

Table 2. Results of Random Forest model describing the most significant factors predicting incidence of DJK. ‘Risk Factor’ column describes the cutoff observed for each ‘Condition’, and is described in magnitude by Odds Ratio.

Condition Preop Thoracic Kyphosis Preop C2-C7 Cobb angle Preop TS-CL Preop C2-C7 SVA Preop Pelvic Obliquity Neurologic comorbidities Preop T1-C2 Cobb angle Preop cSVA modifier group Intraop steroids Surgical Approach Smith Petersen Osteotomy 4 5

Risk Factor >50.6 <-12mm >36.4 >56.3mm >0.272 Any comorbidity <-13.6 >1 Any used Combined Any used

Significance

O.R.

0.001 0.001 0.002 0.002 0.004 0.012 0.008 0.046 0.029 0.042 0.092

5.9 5.7 5.6 5.4 4.2 3.7 3.7 3.0 0.3 2.7 2.5

90% C.I.for EXP(B) Lower Upper 2.4 14.7 2.5 13.3 2.3 13.6 2.2 13.2 1.9 9.3 1.6 8.7 1.6 8.2 1.2 7.5 0.2 0.8 1.2 5.9 1.0 6.3

O.R. = Odds Ratio; TS = T1 Slope; CL = Cervical Lordosis; SVA = Sagittal Vertical Axis; cSVA = Cervical Sagittal Vertical Axis

6 7

22 Page 22 of 25

1 2

Figure 1.tif

3

23 Page 23 of 25

1 2

Figure 2.tif

3

24 Page 24 of 25

1 2

Figure 3.tif

25 Page 25 of 25