Selection of fusion levels in adults with spinal deformity: an update

doi:10.1016/j.spinee.2012.11.046

The Spine Journal

Volume 13, Issue 4, April 2013, Pages 464-474

https://doi.org/10.1016/j.spinee.2012.11.046 Get rights and content

Abstract

Background context

Adult spinal deformity (ASD) is commonly associated with disability and represents a challenging condition for physicians. Although surgical management has been reported as superior to conservative care, the choice of patient-specific optimal strategy has been poorly defined. A key question remains selection of fusion levels as this implies careful balance of risks and benefits.

Purpose

The aim of this review is to propose an update on current knowledge related to optimal fusion levels in the surgical treatment of ASD.

Study design

Literature review.

Methods

Based on a comprehensive literature search, recent studies focusing on the management of ASD were reviewed to establish current concepts on fusion levels in the management of symptomatic ASD.

Results

Despite numerous published studies, the management of ASD and specifically optimal fusion levels is incompletely defined. Described approaches carry benefits and risks. However, the need for detailed analysis and preoperative planning is confirmed as a prerequisite to obtaining realignment objectives and good outcomes.

Conclusions

The treatment of ASD is emerging as an important health-care issue of the 21st century because of prevalence and cost. Despite technical advances related to ASD surgery, complication rates remain elevated, particularly in the older population. Recent research, mostly driven by outcome measures, has improved our understanding of optimal treatment approaches to ASD. The development of a widely accepted classification system will help to share knowledge and improve our ability to treat these complex patients.

Introduction

Adult spinal deformities (ASDs) are complex pathologies associated with a broad range of clinical and radiological presentation. Precise prevalence is difficult to evaluate but has been reported to be as high as 60% in the general population older than 60 years [1]. Numerous studies have reported radiological and clinical outcomes related to ASD surgery, but clear therapeutic consensus is still not available. From previous results, however, it is possible to elaborate some algorithms for the management of ASD patients. According to some authors [2], therapeutic strategy for adult patients should be based on both clinical and radiographic evaluation (pain and disability). This differs from treatment for adolescent deformities where radiological findings typically guide treatment. Positive impact of ASD surgery outcomes has also been reported with an improvement of back and leg pain at 2-year follow-up when compared with nonoperative strategies [3], [4].

When a surgical treatment is indicated, one of the areas of ongoing debate remains the selection of end levels relating to fusion and instrumentation. At the distal end of the construct, although preserving levels will preserve mobility, it can also increase the risk for postoperative complications and revision surgeries. In addition to the concerns of distal fusion level, proximal extent of the fusion also requires specific attention because of the risks of instrumentation failure and proximal junctional kyphosis (PJK).

The aim of this work is to propose an update on the decision-making process for selection of fusion levels for ASD patients.

Section snippets

Radiographic evaluation of an ASD patient

To precisely evaluate a spinal deformity patient, satisfactory radiographs are needed. Standard imaging consists of 36'' full-cassette standing anteroposterior (AP) and lateral free-standing radiographs. Although complementary examinations, such as AP and lateral bending films, can sometimes be useful, specific attention must be paid to these two standard views to have a precise evaluation of spine alignment. Arms positioning must be taken into account according to the fact that different

Proximal fusion levels

There are many factors involved when choosing fusion levels in the ASD patient as compared with the AIS patient. The presence of additional spinal pathology such as foraminal and/or central stenosis, facet arthropathy, disc degeneration, olisthesis, and poor bone quality bring many additional considerations into play. The ongoing efforts to develop a widely accepted adult deformity classification system are testament to the difficulty and clinical variability that are inherent in treating the

Above L5: where to stop

There is the continued debate on stopping fusions at L5 or pelvis, which will be addressed in the next section. However, what caudal levels are appropriate cephalad to L5? Although some familiar arguments concerning the TL junction will be cited as reasons not to stop anywhere from T10 to L2, there are some data that suggest otherwise.

In a retrospective study of thoracic hyperkyphosis, the lowest instrumented vertebra (LIV) levels were compared. In 31 patients with a minimum follow-up of 2

Conclusion

Because of an increasing prevalence, ASD is emerging as a challenging health-care issue of the 21st century. Management of ASD patients and selection of fusion levels remain controversial. Technical environment for ASD surgery has evolved over the last years according to various factors, such as blood salvage, improved surgical technique, and instrumentation systems. However, complication rate remains substantial, particularly in the older population [71]. Recent researches, mostly driven by

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Cited by (27)

PreOperative Planning for Adult Spinal Deformity Goals: Level Selection and Alignment Goals
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Restore cervical sagittal alignment by cervical disc arthroplasty and systematic total bilateral uncuscectomy in severe spondylosis: A prospective study
2023, Brain and Spine
Severe spondylosis is common and represents contraindication to achieve cervical disc arthroplasty (CDA).
Is it possible to restore cervical sagittal alignment using an adequate prosthetic model and performing systematic bilateral total uncuscectomy (or uncinectomy), even in cases of severe spondylosis ?
We propose a prospective clinical and radiological study comparing the evolution of preoperative and postoperative cervical sagittal balance 1 year after the interposition of a prosthesis with mobile bearing and systematic total uncuscectomy. VAS for brachialgia and cervicalgia, NDI, Odom's criteria, C2–C7 Cobb angle, C2–C7 SVA, T1 slope, C2 slope, C1–C2 Cobb angle, and segmental Cobb angle were analyzed preoperatively and 1 year postoperatively.
73 patients for a total of 129 levels treated were analyzed. Patients showed significant improvements in VASb, VASc, NDI, and Odom's criteria one year after surgery without clinical differences in the severe spondylosis subgroup (41 patients for 77 levels treated). Our results showed an increase in the C2–C7 Cobb angle postoperatively and a better correlation between T1 slope and C2–C7 Cobb angle postoperatively than preoperatively. Postoperative radiological results were similar between the spondylosis and non-spondylosis subgroups. However preoperative C2–C7 Cobb angle and preoperative ROM were lower in the severe spondylosis subgroup.
This study showed the possibility of restoring cervical sagittal balance by performing cervical disc arthroplasty with systematic uncuscectomy, even in cases of severe spondylosis. Moreover, we propose a simplified mathematical formula to preoperatively evaluate the lack of angulation to restore sagittal cervical alignment.
Level selection for optimal adult spinal deformity correction: A narrative review
2022, Seminars in Spine Surgery
Citation Excerpt :
A key principle when selecting the upper instrumented vertebrae (UIV) of a patient with ASD is to fuse to the stable vertebra.37–40 The center sacral vertical line typically bisects the stable vertebra in the coronal plane, but sagittal plane considerations are also relevant.11 Prior work has advised extending the fusion past a coronally stable vertebra that is at the apex of the patient's normal thoracic kyphosis or of a focal pathologic kyphosis.
Adult spine deformity (ASD) is the loss of the normal sagittal and coronal alignment necessary to maintain the head over the hips. ASD increases energy expenditure to maintain normal balance and horizontal gaze, and can lead to chronic pain, fatigue, and significant functional disability. Selection of upper and lower instrumented levels for ASD constructs is critical to achieving and maintaining an optimal post-operative alignment. While classifications and recommendations have improved level selection strategies, decision-making still remains largely dependent on the individual surgeon. This work summarizes available literature on level selection for ASD constructs.
T9 versus T10 as the upper instrumented vertebra for correction of adult deformity—rationale and recommendations
2017, Spine Journal
Citation Excerpt :
Selection of fusion levels in adult spinal deformity is largely based on symptomatology, but may be influenced by the severity and morphology of the existing deformity [1,2].
Adult spinal deformity correction sometimes involves long posterior pedicle screw constructs extending from the lumbosacral spine to the thoracic vertebra. As fusion obliterates motion and places supraphysiological stress on adjacent spinal segments, it is crucial to ascertain the ideal upper instrumented vertebra (UIV) to minimize risk of proximal junctional failure (PJF). The T10 vertebra is often chosen to allow bridging of the thoracolumbar junction into the immobile thoracic vertebrae on the basis that it is the lowest immobile thoracic vertebra strut by the rib cage.
This study aimed to characterize the range of motion (ROM) of each vertebral segment from T7 to S1 to determine if T10 is truly the lowest immobile thoracic vertebra.
This is a prospective, comparative study.
Seventy-nine adults (mean age of 45.4 years) presenting with low back pain or lower limb radiculopathy or both, without previous spinal intervention, metastases, fractures, infection, or congenital deformities of the spine, were included in the study.
A ROM >5° across two vertebral segments as determined by the Cobb method from radiographs.
Lumbar flexion-extension and neutral erect radiographs were obtained in randomized order using a slot scanner. Segmental ROM was measured from T7–T8 to L5–S1 and analyzed for significant differences using t tests. Age, gender, radiographical indices such as standard spinopelvic parameters, sagittal vertical axis (SVA), C7–T12 SVA, T1 slope, thoracic kyphosis (TK), and lumbar lordosis (LL) were studied via multivariate analysis to identify predictive factors for >5° change in ROM at the various segmental levels. There were no sources of funding and no conflicts of interest associated with this study.
In the thoracolumbar spine, significant decreases in ROM when compared with the adjacent caudad segment occurs up to T9–T10, with mean total ROM of 1.98±1.47° (p<.001) seen in T9–T10, 2.19±1.67° (p<.001) in T10–T11, and 3.92±3.21°(p<.001) in T11–T12. The total ROM of T8–T9 (2.53±1.79°) was not significantly different from that of T9–T10 (p=.261). At the thoracolumbar junction, absence of scoliosis (OR 11.37, p=.020), high pelvic incidence (OR 1.14, p=.046), and low T1 slope (OR 1.45, p=.030) were predictive of ROM >5°.
Lumbar spine flexion-extension ROM decreases as it approaches the thoracolumbar junction. T10 is indeed the lowest immobile thoracic vertebra strut by the rib cage, and the last significant decrease in ROM is observed at T9–T10, in relation to T10–T11. However, because this also implies that a UIV of T10 would mean there is only one level of fixation above the relatively mobile segment, while respecting other factors that influence UIV selection, we propose the T9 vertebra as a more ideal UIV to fulfill the biomechanical concept of bridge fixation. However, this decision should still be taken on a case-by-case basis.
Instrumentation strategies to reduce the risks of proximal junctional kyphosis in adult scoliosis: A detailed biomechanical analysis
2015, Spine Deformity
Citation Excerpt :
Findings in this regard should be put in a broader context, because extending the instrumentation proximally will reduce the remaining spinal mobility and put higher biomechanical stresses on PJSS when performing daily activities such as flexion; this remains to be tested in future studies. Selection of the proximal fusion level with regard to PJK is still being debated and consensus based on biomechanical considerations has yet to be reached among spine surgeons [3,11]. Simulations using the design of experiment (DOE) approach also showed that the dissection of posterior intervertebral elements was positively correlated to mechanical stresses within the PJSS and PJ angle, increasing the risk of PJK, which had previously been postulated in clinical studies and those based on cadaveric experiments [8,30].
Biomechanical analysis of proximal junctional kyphosis (PJK) through numerical simulations.
Assessment of the effect of sagittal alignment, the upper instrumented vertebral level (UIV), and 4 other surgical variables on biomechanical indices related to the PJK risks.
Despite retrospective clinical studies, biomechanical analysis of individual parameters associated with PJK is lacking to support instrumentation strategies to reduce the PJK risks.
Instrumentations of 6 adult scoliosis cases with different operative strategies were simulated (1,152 simulations). Proximal junctional (PJ) angle and flexion loads were evaluated against the sagittal alignment and the proximal instrumentation level.
Instrumenting 1 more proximal vertebra allowed the PJ angle, proximal moment, and force to be reduced by 18%, 25%, and 16%, respectively. Shifting sagittal alignment by 20 mm posteriorly increased the PJ angle and proximal moment by 16% and 22%, and increased the equivalent posterior extensor force by 37%. Bilateral complete facetectomy, posterior ligaments resection, and the combination of the 2 resulted in an increase of the PJ angle (by 10%, 28%, and 53%, respectively), flexion forces (by 4%, 12%, and 22%, respectively), and proximal moments (by 16%, 44%, and 83%, respectively). Transverse process hooks at UIV compared with pedicle screws allowed 26% lower PJ angle and flexion loads. The use of proximal transition rods with proximal diameter reduced from 5.5 to 4 mm slightly reduced PJ angle, flexion force, and moment (less than 8%). The increase in sagittal rod curvature from 10° to 40° increased the PJ angle (from 6% to 19%), flexion force (from 3% to 10%), and moment (from 9% to 27%).
Simulated posteriorly shifted sagittal alignment was associated with higher PJK risks, whereas extending instrumentation proximally allowed a lower mechanical risk of PJK. Preserving PJ intervertebral elements and using a more flexible anchorage at UIV help reduce the biomechanical risks of PJK.
Degenerative lumbar scoliosis
2015, JBJS Reviews
Citation Excerpt :
In recent years, advances in operative techniques, including minimally invasive approaches, intraoperative navigation, implant design, and an enhanced ability to achieve fusion, have contributed to the overall safety and improved outcomes in adults undergoing surgery for deformity correction48,49,51,61,62,67,70-75,78. Another consideration for operative treatment is the number of levels to fuse, including the proximal and distal levels of the construct49,53,77,78,95. Overall recent trends in large published series have shown improvements in standard outcome metrics and the ability to achieve and maintain correction, even in the face of an increasingly elderly population with several comorbidities48,50,61,66,67,70,75,76.

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: FDA device/drug status: Not applicable.

: Author disclosures: BB: Nothing to disclose. AMW: Nothing to disclose. AA: Nothing to disclose. VCL: Stock Ownership: Nemaris, Inc. (20% ownership); Board of Directors: Nemaris, Inc. (None); Grants: Scoliosis Research Society (C, Paid directly to institution/employer). FJS: Royalties: MSB (D); Stock Ownership: Nemaris, Inc. (37 shares, 37%); Consulting: MSD (F); Speaking/Teaching Arrangements: DePuy Spine (D); Trips/Travel: MSD (C); Board of Directors: Nemaris, LLC (None); Research Support (Staff/Materials): MSD (E); Grants: SRS (C). JAB: Relationships Outside the Three-Year Requirement: Synthes Spine (11/1990, Consulting, C).

: The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

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Review ArticleSelection of fusion levels in adults with spinal deformity: an update

Abstract

Background context

Purpose

Study design

Methods

Results

Conclusions

Introduction

Section snippets

Radiographic evaluation of an ASD patient

Proximal fusion levels

Above L5: where to stop

Conclusion

Spine J

Adult scoliosis: prevalence, SF-36, and nutritional parameters in an elderly volunteer population

Spine

Pain and disability determine treatment modality for older patients with adult scoliosis, while deformity guides treatment for younger patients

Spine

Operative versus nonoperative treatment of leg pain in adults with scoliosis: a retrospective review of a prospective multicenter database with two-year follow-up

Spine

Improvement of back pain with operative and nonoperative treatment in adults with scoliosis

Neurosurgery

Standing lateral radiographic positioning does not represent customary standing balance

Spine

The effect of variation in arm position on sagittal spinal alignment

Spine

Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis

J Bone Joint Surg Am

Principles for selecting fusion levels in adult spinal deformity with particular attention to lumbar curves and double major curves

Spine

Standing balance and sagittal plane spinal deformity: analysis of spinopelvic and gravity line parameters

Spine

Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity

Spine

Importance de la vertèbre pelvienne dans l'équilibre rachidien. Application à la chirurgie de la colonne vertébrale chez l'enfant et l'adolescent

A Barycentremetric study of the sagittal shape of spine and pelvis: the conditions required for an economic standing position

Ann Biomed Eng

Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves

Eur Spine J

Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters

J Spinal Disord Tech

Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis

Eur Spine J

The vertical projection of the sum of the ground reactive forces of a standing patient is not the same as the C7 plumb line: a radiographic study of the sagittal alignment of 153 asymptomatic volunteers

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Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position

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Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects

J Bone Joint Surg Am

Adult scoliosis: a quantitative radiographic and clinical analysis

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A clinical impact classification of scoliosis in the adult

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The impact of positive sagittal balance in adult spinal deformity

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A lumbar classification of scoliosis in the adult patient: preliminary approach

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Surgical rates and operative outcome analysis in thoracolumbar and lumbar major adult scoliosis: application of the new adult deformity classification

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Predicting outcome and complications in the surgical treatment of adult scoliosis

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The SRS classification for adult spinal deformity: building on the King/Moe and Lenke classification systems

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The problems and limitations of applying evidence-based medicine to primary surgical treatment of adult spinal deformity

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Selection of instrumentation and fusion levels for scoliosis: where to start and where to stop. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004

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Sagittal thoracic decompensation following long adult lumbar spinal instrumentation and fusion to L5 or S1: causes, prevalence, and risk factor analysis

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Is the T9, T11, or L1 the more reliable proximal level after adult lumbar or lumbosacral instrumented fusion to L5 or S1?

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Review Article
Selection of fusion levels in adults with spinal deformity: an update