Abstract
Study Design.
Prospective case series.
Objective.
To study the natural course of adult spinal deformity (ASD) over a 10-year period and the determinants associated with postural malalignments.
Summary of Background Data.
ASD comprises a heterogeneous spectrum of abnormalities of the thoracolumbar spine throughout adulthood. Radiographic deterioration of sagittal alignment is a combination of decreased lumbar lordosis (LL), PI-related retroversion of the pelvic tilt (PT), anteriorizing sagittal vertical axis (SVA), and increased T1 pelvic angle (TPA).
Materials and Methods.
The full spine radiographs were taken to measure the SRS-Schwab sagittal modifiers PI-LL, PT, and SVA to measure the possible change in severity of deformity from the 204 volunteer participants (mean age 62.7 yr, 61% female), which were 32% of the 637 consecutive patients with prolonged back pain who originally joined the study in 2012–2013. Each participant completed the Scoliosis Research Society 22r (SRS-22r) questionnaire.
Results.
The mean change in the SRS-Schwab score was 0.4 units (baseline 1.1 vs. follow-up 1.5, P<0.001) implying deterioration of the spinal deformity. The SRS-Schwab score decreased (n=76, 37%), remained the same (n=102, 50%), or improved (n=26, 13%). Four predictive factors for a change of sagittal alignment were found, of which the poor score in the SRS-22r function domain (P=0.049) and severe pelvic tilt (PT greater than 30°, P=0.006) predicted the change.
Conclusion.
This study showed the variability in how sagittal alignment of the spine changes during the 10-year follow-up period. The ASD patients with poor self-assessed functional ability and disturbed pelvic position were associated with the risk of deterioration in spinopelvic alignment. The diversity in the natural course of ASD and the known risk factors highlight the need for tailored advice when planning preventive treatment procedures for ASD patients.
Level of Evidence.
Level III.
Key Words: degenerative spinal disorder, sagittal alignment, spinal malalignment, natural course, radiographical parameters, health-related quality of life, Scoliosis Research Society-Schwab classification, Scoliosis Research Society (SRS)-22r, Oswestry Disability Index, follow-up study
Adult spinal deformity (ASD) is a common medical disorder with a significant and measurable impact on health-related quality of life (HRQoL). ASD can have similar negative effects on an individual’s HRQoL as other chronic conditions such as diabetes and chronic lung disease.1 ASD consists of a heterogeneous spectrum of abnormalities of the lumbar or thoracolumbar spine throughout adulthood. Prevalence has been reported to be up to 30% in the general population and as high as 60% in the elderly population.2–4 ASD is a multifaceted disorder that may include structural changes such as scoliosis, sagittal malalignment, kyphosis, spondylolisthesis, rotatory subluxation, and axial plane deformity. Spinal malalignment can occur between two adjacent vertebrae, segmentally or within cervical, thoracic, and lumbar regions of the spine, or it can be located globally, spanning from the upper spine to the sacrum.4
ASD has multiple etiologies and it can develop over many years, or it can appear in adult life without any earlier precedence.3,5 Typical radiographic findings show that the deterioration of sagittal alignment is a combination of lumbar lordosis (LL), pelvic incidence (PI), PI-related retroversion of the pelvis (pelvic tilt, PT), anteriorizing sagittal vertical axis (SVA), and increased T1 pelvic angle (TPA).6 As people age, they may start to lean forward which results in more positive sagittal alignment changes with asymptomatic individuals.7 SVA, PT, and PI-LL mismatch were the parameters that had the strongest direct correlation with disability and poor quality of life in both operated and nonoperated patients with ASD.2 Although these research findings are important in helping us to understand the deterioration of sagittal spinal and spinopelvic alignment and their related risk factors, they do not provide information on the natural course of spinopelvic changes in adults in the long term.
The Scoliosis Research Society (SRS)-Schwab ASD classification consists of both coronal (frontal) and sagittal (lateral) modifiers, and the classification is validated for evaluating ASD.8 In particular, sagittal malalignment and loss of a sagittal balance are detrimental for everyday life, as they are related to physical and social performance and HRQol.9–11
In the present study, we explored prospectively the possible change of the sagittal alignment of the spine over the past 10 years using the SRS-Schwab sagittal modifiers PI-LL, PT, and SVA. We also measured TPA to evaluate the global, sagittal alignment of the spine. In addition, we sought to identify factors that might be associated with changes in the sagittal posture of the spine.
MATERIALS AND METHODS
This is a 10-year prospective case series study to assess the natural course of ASD and the factors associated with the change of sagittal alignment of the spine. The participants were a consecutive series of patients who were admitted to a spine clinic due to prolonged back pain originally in 2012–2013. The follow-up data was collected between October 2022 and January 2023. The present follow-up study was approved by the Research Ethics Committee of the Central Finland Healthcare District (approval number 4U/2022). All participants gave their written informed consent before enrollment according to the Declaration of Helsinki.
The original study group comprised both men and women over age 18 who visited a spine clinic due to prolonged back pain between 2012 and 2013 in Central Hospital of Central Finland, Jyväskylä. The exclusion criteria were age under 18 years, missing or nondiagnostic radiographs, pregnancy, malignancy, neuromuscular disease, surgery of more than one intervertebral disc level, or any surgeries more extensive than this, as well as acute fracture. A total of 637 patients were eligible for the study.9 They were contacted via post 10 years after the baseline measurements and asked to participate in the follow-up study.
The baseline measurements were performed between 2012 and 2013. The radiographs were obtained to measure SRS Schwab sagittal modifiers PI-LL, PT, and SVA to evaluate the severity of spinal deformity.8,10 We also measured TPA to evaluate the participant’s global postural balance. As a part of the study, the participants completed the following questionnaires: Oswestry Disability Index 2.0 (ODI),12 Scoliosis Research Society questionnaire version 30 (SRS-30),13 the 36-item Health Survey Questionnaire (SF-36),14 Frequency Intensity Time index by KASARI (FIT), the DEPS depression test, and Visual Analog Scale (VAS) for back and leg pain.
A total of 221 individuals indicated their willingness to participate in the follow-up study. Seventeen participants were excluded from the study due to exclusion criteria, which were cognitive impairment to understand and fill in questionnaires, pregnancy or any other reason that might prevent participation in full-spine imaging or any major spine surgeries performed within the past 10 years. A robotic twin arm system with slot scanning technology (Siemens Multitom Rax with True2Scale imaging option, Siemens Healthineers, Erlangen, Germany) was used as the imaging device for the full-spine radiographs. In addition, the three to four-view tilting technique (Siemens Ysio Max, Erlangen, Germany) was utilized with very obese participants or participants with severe thoracic kyphosis whose imaging needed a wider field of view. Full spine radiographs were taken to measure the SRS-Schwab sagittal modifiers PI-LL, PT, and SVA to assess potential changes in the spine’s sagittal alignment. TPA was measured to evaluate the global, sagittal alignment of the spine. Participants completed the same questionnaires as in the baseline stage: SRS-22r, ODI, SF-36, KASARI FIT, DEPS, and VAS for back and leg pain. At follow-up, the SRS-30 was replaced by the SRS-22r questionnaire as it is the only version approved by the Scoliosis Research Society and it has been validated by Kyrölä et al. 13 with the same group of patients during baseline measurements.
Statistical Analyses
The data are presented as means with SD, and as counts with percentage. Statistical comparison of unpaired and paired groups was made by t test, permutation test, and χ2 test, when appropriate. The linearity across the groups was tested by using the Cochran-Armitage trend test or Cuzick test depending on the distribution of the outcome. Multivariate logistic regression analysis was used to estimate odds ratios (OR) and 95% CI for change in sagittal spine alignment. The α-level was set at P <0.05, and all analyses were performed using STATA 17.0 (StataCorp LP, College Station, TX).
RESULTS
Of the 637 subjects originally recruited for the study, 204 (32%) volunteered for the follow-up study. At the 10-year follow-up, their mean age was 62.7 (SD=13.4) years and 124 (61%) of them were female. The characteristics of the subjects who participated both in baseline and follow-up measurements are shown in Table 1. At the baseline, the average age of all 637 participants was 54.8 (SD=15.3) and 358 (56.2%) of them were female.
TABLE 1.
Characteristics of the Individuals Who Participated Both in Baseline and 10-Year Follow-up Measurement
| Variables | Baseline, N=204 | Follow-up, N=204 |
|---|---|---|
| Female, n (%) | 118 (57.8) | 118 (57.8) |
| Age (y), mean (SD) | 53.4 (13.4) | 62.7 (13.4) |
| Married, common-law married, n (%) | 152 (74.5) | 152 (74.5) |
| Years of education, mean (SD) | 13.2 (3.6) | 13.4 (3.7) |
| BMI (kg/m2), mean (SD) | 27.3 (4.6) | 27.7 (4.8) |
| Smokers, n (%) | 34 (16.7) | 27 (13.2) |
| Available for work, n (%) | 128 (62.7) | 81 (39.8) |
| Physical activity (Kasari FIT index)*, mean (SD) | 37.2 (21.8) | 21.3 (17.7) |
| Back pain VAS, mean (SD) | 61.4 (26.2) | 41.5 (28.6) |
| Leg pain VAS, mean (SD) | 55.7 (30.7) | 41.8 (29.0) |
| Diagnoses at baseline, n (%) | ||
| Scoliosis | 8 (3.9) | |
| Spondylolisthesis | 33 (16.2) | |
| Neural compression | 95 (46.6) | |
| Degenerative spine without neural compression† | 68 (33.3) | |
| Previous spine surgery at baseline, n (%) | 14 (6.9) | |
Range 0 to 100, values are means ± SD or the number of subjects.
The degenerative spine includes spondylosis, disc generation, facet joint arthrosis, and other degenerative conditions without neural compression.
BMI indicates body mass index, VAS, visual analog scale (0–10).
The mean change in the SRS-Schwab score was 0.4 units (baseline 1.12 ± 1.39 vs. follow-up 1.51 ± 1.75, P <0.001) implying deterioration of the spinal deformity. During the 10-year follow-up, the SRS-Schwab score increased by 37% (n=76), remained the same at 50% (n=102), and decreased by 13% (n=26) of the participants (Fig. 1).
Figure 1.
Distribution of the SRS-Schwab scores of the individuals (N=204) who participated in the baseline measurements and the changes in their Schwab scores at the follow-up measurements 10 years later.
When examining the percentage of participants whose sagittal modifier scores remained the same between the baseline and follow-up measurement, the PT score remained the same in 74% (95% CI: 67–79), SVA score in 73% (95% CI: 66–79) and PI-LL score in 73% (95% CI: 66–79) of the participants (Table 2).
TABLE 2.
Deformity Classifications for Pelvic Tilt, Sagittal Vertical Axis, and Pelvic Incidence Minus Lumbar Lordosis During Baseline and 10-Year Follow-up Measurements
| Follow-up | Baseline deformity | Percent agreement | ||
|---|---|---|---|---|
| PT | 0 n=126 n (%) |
1 n=63 n (%) |
2 n=15 n (%) |
74 (67–79) |
| 0 | 102 (81) | 14 (22) | 1 (7) | |
| 1 | 24 (19) | 40 (63) | 6 (40) | |
| 2 | 0 (0) | 9 (14) | 8 (53) | |
| SVA | 0 n=142 |
1 n=54 |
2 n=8 |
73 (66–79) |
| 0 | 112 (79) | 8 (15) | 1 (12) | |
| 1 | 25 (18) | 31 (57) | 1 (12) | |
| 2 | 5 (4) | 15 (28) | 6 (76) | |
| PI-LL | 0 n=154 |
1 n=35 |
2 n=15 |
73 (66–79) |
| 0 | 127 (82) | 8 (23) | 1 (7) | |
| 1 | 24 (16) | 12 (34) | 4 (27) | |
| 2 | 3 (2) | 15 (43) | 5 (67) | |
Severity: 0=mild or none, 1=moderate, 2=severe.
PI-LL indicates pelvic incidence-lumbar lordosis; PT, pelvic tilt; SVA, Sagittal vertical axis.
During the 10-year follow-up, SVA declined the most in participants aged 18 to 40 years, with a 1391% change in the parameters, and those aged 61 to 99 years, with a 69% change. PT remained the same and PI-LL was worse with elderly participants (aged 62–99 yr) presenting 98% change in the parameters. Table 3 shows the changes in the spinopelvic parameters in different age groups during the 10-year follow-up.
TABLE 3.
Spinopelvic Parameters Showing Change at the 10-Year Follow-up
| Age, yr | Spinopelvic parameters | 2013 | 2023 |
|---|---|---|---|
| 18–40 | SVA | 1.14 (6.0) mm | 17 (20.0) mm |
| PT | 10.4 (13.0)° | 10 (12.0)° | |
| PI-LL | −7.9 (−6.0)° | −4.1 (−3)° | |
| 41–60 | SVA | 18.3 (17.0) mm | 25.2 (23.0) mm |
| PT | 15.7 (15.0)° | 16.4 (18.0)° | |
| PI-LL | −2.3 (−3) ° | 0.24 (0.0)° | |
| 61–99 | SVA | 34.1 (31.0) mm | 57.5 (44.0) mm |
| PT | 20.4 (19.0)° | 20.5 (19.5)° | |
| PI-LL | 5.3 (4.0)° | 10.5 (7)° |
Data presented in mean (median).
PI-LL indicates pelvic incidence-lumbar lordosis; PT, pelvic tilt; SVA, Sagittal vertical axis.
The relationship between each deformity scores of PT, SVA, PI-LL, and the SRS-22r function domain at baseline is shown in Figure 2. The more SVA and PI-LL deformity scores increased (i.e., sagittal alignment worsened), the more the SRS function worsened (5=best, 1=worst). For participants with a PT of <20° (score 0) or between 20° and 30° (score 1), the level of SRS Function remained the same, but when PT was >30° (score 2), the level of SRS Function worsened.
Figure 2.
The relationship between the SRS-22r function domain and deformity scores of the sagittal modifiers of PT (pelvic tilt), SVA (sagittal vertical axis), and PI-LL (pelvic incidence – lumbar lordosis) at baseline. Sagittal modifiers, severity: 0=mild or none, 1=moderate, 2=severe.
In logistic regression analysis, significant predictors for change in sagittal spine alignment were age (OR: 1.04, 95% CI: 1.01–1.08), back pain (OR: 1.02, 95% CI: 1.00–1.03), SRS function (OR: 2.81, 95% CI: 1.35–5.85), and severe PT (OR: 5.3, 95% CI: 1.01–28.7). Table 4 presents that severe PT showed a 5.3-fold risk for change in sagittal spine alignment compared with mild PT, back pain (VAS back) showed a 1.02-fold risk for change in sagittal spine alignment compared with no pain in the back, and self-assessed poor functional ability (SRS-function) showed a 2.8-fold risk compared with good self-assessed functional ability.
TABLE 4.
Odds for Change in Sagittal Spinal Alignment
| Variable | OR | SEM | P [z] | 95% CI |
|---|---|---|---|---|
| Age | 1.04 | 0.017 | 0.008 | 1.01–1.08 |
| BMI | 0.95 | 0.04 | 0.188 | 0.87–1.03 |
| Years of education | 1.01 | 0.054 | 0.870 | 0.91–1.12 |
| Smoking | 2.12 | 1.12 | 0.155 | 0.75–5.9 |
| Duration of pain (months) | 1.00 | 0.00 | 0.338 | 1.00–1.01 |
| VAS back | 1.02 | 0.01 | 0.045 | 1.00–1.03 |
| VAS leg | 1.01 | 0.01 | 0.758 | 0.99–1.01 |
| Kasari index (0–10) | 1.01 | 0.01 | 0.194 | 0.97–1.01 |
| SRS pain 2013 | 1.48 | 0.48 | 0.230 | 0.78–2.79 |
| SRS function 2013 | 2.81 | 1.05 | 0.006 | 1.35–5.85 |
| SRS mental health 2013 | 0.74 | 0.20 | 0.262 | 0.43–1.26 |
| SRS self-image 2013 | 0.97 | 0.44 | 0.949 | 0.40–2.36 |
| PT moderate | 1.19 | 0.51 | 0.684 | 0.51–2.80 |
| PT severe | 5.32 | 4.51 | 0.049 | 1.01–28.1 |
| SVA moderate | 1.21 | 0.51 | 0.635 | 0.54–2.76 |
| SVA severe | 2.90 | 3.07 | 0.315 | 0.36–23.15 |
| PI-LL moderate | 2.21 | 1.15 | 0.132 | 0.79–6.13 |
| PI-LL severe | 0.99 | 0.86 | 0.991 | 0.18–5.49 |
Bold values indicate the significant values (P <0.05).
BMI indicates body mass index; OR, odds ratio; PI-LL, pelvic incidence-lumbar lordosis; PT, pelvic tilt; SRS, Scoliosis Research Society; SVA, sagittal vertical axis; VAS, Visual Analog Scale.
DISCUSSION
The main finding of the study was that on a scale from 0 to 6, the average SRS-Schwab score increased moderately by half a unit, indicating a deterioration of sagittal spinal alignment. Another clinically important finding was that poor self-assessed functional ability (SRS function/activity domain) and increased posterior pelvic tilt were associated with future sagittal posture deterioration among participants with varying degrees of spine deformities. The results of this study imply that especially people with ASD who perceive their functional ability to be poor and who have a pronounced pelvic tilt could benefit from long-term radiologic follow-up and tailored advice when planning preventive treatment procedures.
To our knowledge, this is the first study to investigate the natural course and predictors of adult spinal disorders in the sagittal plane with a 10-year follow-up study. Faraji et al. 15 studied coronal and sagittal alignment changes in a small sample of nonoperated ASD patients, mostly middle-aged women, at the follow-up after 5 years, but the study did not present determinants that may be associated with the possible changes.
Other previous studies have typically investigated sagittal alignment changes either immediately16 or from a few months to a few years after deformity corrective surgeries to monitor if the surgery achieved a successful correction.16–18 In the present study, there were only three individuals during the 10-year follow-up period who underwent extensive back surgery that might have an effect on posture. They were excluded from the analysis.
Other spine operations done before the baseline in the present study were decompressive or in situ short-segment infusion surgery, which is unlikely to have any effect on individuals' sagittal posture. The participants were heterogeneous in terms of age and severity of the sagittal malalignment, which may, in part, be related to the modest overall change in the SRS-Schwab score. The results of the present study increase our understanding of how sagittal spinal alignment is expected to change over a lengthy period of time in nonoperated ASD patients.
Regarding the individual sagittal modifiers of the present study, SVA deteriorated most with the youngest individuals, PT deteriorated most with the youngest and oldest individuals, whereas PI-LL deteriorated most with the oldest individuals. The findings, especially those among older participants, may be due to spinal degeneration where the biomechanical properties of intervertebral discs have changed over time, which can lead to changes in loadbearing at intervertebral facet joints and eventually causing progressive decline in spinal ligaments, deteriorating of trunk muscles and spinal deformity.19,20
Multiple studies have shown that patients with sagittal malalignment use a series of compensatory mechanisms to maintain an upright posture, such as producing pelvic retroversion, which is evident through increased PT, tilting the head and neck back to level the gaze, straightening the thoracic spine to reduce kyphosis and conducting hip extension, pelvic retroversion, and finally knee flexion.16,19–21 These compensatory mechanisms, along with sagittal imbalance, can eventually affect people’s experienced functional ability and increase pain in the lower back.22,23 In this study, the individuals whose sagittal alignment deteriorated over the 10-year period also reported a decline in self-assessed functional ability and back pain. Interestingly, self-image, smoking, physical activity, and body mass index were not related to worsened sagittal alignment, a finding which differs from previous studies in which those factors have been shown to be co-factors for prolonged back pain.24,25
The strength of this study was that our central hospital is the only tertiary spine clinic in the Central Finland region and the patient’s transfer to other hospitals is minimal, and it has standardized referral guidelines. A relatively large group of participants strengthen the value of the study when interpreting the results. Therefore, the results may be well generalized to patients with a previous history of ASD. The main limitation of the study may be selection bias, as almost two thirds of the original study population did not participate in the 10-year follow-up. Moreover, it may require a longer span of time to see if individuals develop spinal deformities with aging.
CONCLUSION
This study showed the variability in the sagittal alignment of spine change over a 10-year follow-up period. The ASD patients with poor self-assessed functional ability and disturbed pelvic position were associated with the risk of deterioration in spinopelvic alignment. The diversity in the natural course of ASD and the known risk factors highlight the need for tailored advice when planning preventive treatment procedures for ASD patients.
Key Points
Minor deterioration of sagittal alignment was found over a 10-year follow-up period in individuals with adult spinal deformity.
Four predictive factors for a change of sagittal spinal and spinopelvic alignment were found: age, back pain, severe pelvic tilt, and poor score in the SRS-22r function domain, of which poor SRS function (P=0.049) and severe pelvic tilt (P=0.006) were especially associated with the deterioration in alignment.
The individuals whose sagittal alignment worsened after 10 years showed decreased self-assessed functional ability and increased pain in the back.
Preventive treatment procedures should be considered for adult spinal deformity patients with poor functional ability and disturbed pelvic position.
ACKNOWLEDGMENTS
The authors thank all the participants for their important contributions to the study.
Footnotes
The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.
Research Ethics Committee of the Central Finland Healthcare District (approval number 4U/2022).
This research was funded by Finnish government research funding (VTR, University of Eastern Finland, B2204, B2205).
The authors report no conflicts of interest.
Contributor Information
Heidi Mannström, Email: heidi.mannstrom@gradia.fi.
Juhani Multanen, Email: juhani.multanen@xamk.fi.
Jari Ylinen, Email: jari.ylinen@ksshp.fi.
Arto Hautala, Email: arto.j.hautala@jyu.fi.
Arttu Peuna, Email: arttu.peuna@hyvaks.fi.
Lauri Karttunen, Email: lauri.u.karttunen@pshyvinvointialue.fi.
Liisa Pekkanen, Email: liisa.pekkanen@hyvaks.fi.
Kati Kyrölä, Email: kati.kyrola@hyvaks.fi.
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