SPINE Volume 39, Number 13, pp E782-E794 ©2014, Lippincott Williams & Wilkins
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life Among Adults From the General Population A Sex-Specific Association Fábio Araújo, MSc,*† Raquel Lucas, PhD,*† Nuno Alegrete, MD,‡§ Ana Azevedo, PhD,*†‡ and Henrique Barros, PhD*†
Study Design. A prospective radiographical study of sagittal standing posture among adults consecutively recruited from the general population. Objective. To analyze the relation of suboptimal sagittal standing posture with back pain and health-related quality of life in general adult males and females. Summary of Background Data. Clinical studies have shown the association of sagittal standing posture with pain and reduced quality of life, but this relation has not been assessed in the general adult population. Methods. As part of the EPIPorto population-based study of adults, 178 males and 311 females were evaluated. Age, education, and body mass index were recorded. Radiographical data collection consisted of 36-in. standing sagittal radiographs. Creation of 3 groups for individual spinopelvic parameters was performed (low, intermediate, or high), and 1 of 4 sagittal types of postural patterns attributed to each participant (Roussouly classification). Back pain prevalence and severity were assessed on the basis of self-reported data and health-related quality of life using 2 main components of the 36-Item Short Form Health Survey. Results. In males, differences in back pain severity were observed only among pelvic tilt/pelvic incidence ratio groups. Females presenting high pelvic incidence and sacral slope exhibited higher odds of severe back pain than those with intermediate values
From the *Institute of Public Health—University of Porto (ISPUP), Porto, Portugal; †Department of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Porto, Portugal; ‡Centro Hospitalar São João, Porto, Portugal; and §Department of Surgery, University of Porto Medical School, Porto, Portugal. Acknowledgment date: November 4, 2013. First revision date: January 16, 2014. Second revision date: February 18, 2014. Acceptance date: February 21, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). National Foundation for Science and Technology funds were received to support this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Fábio Araújo, MSc, Instituto de Saúde Pública da Universidade do Porto, Rua das Taipas, 135-139, 4050600 Porto, Portugal; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000347
E782
(adjusted odds ratios = 2.21 and 2.15; 95% confidence interval, 1.24–3.97 and 1.21–3.86; respectively). Sagittal vertical axis showed the largest differences in physical quality of life of females: high group had 8.8 lower score than the low group (P < 0.001), but this result lost statistical significance after adjustment for age, education, and body mass index. Conclusion. Sagittal standing posture was not consistently associated with quality of life measures in males. Increased pelvic incidence and sacral slope may be involved in causing severe back pain among females. Monitoring sagittal postural parameters has limited usefulness as a screening tool for causes of unspecific musculoskeletal symptoms in the general adult population. Key words: posture, spine, pelvis, back pain, quality of life, population survey. Level of Evidence: 3 Spine 2014;39:E782–E794
M
usculoskeletal spinal conditions are among the leading causes of pain and decreased quality of life in the general adult population.1,2 Aging trends lead to the expectation that the resultant burden on individuals, societies, and health systems will increase dramatically in the upcoming decades.2 Extreme nonneutral sagittal spinopelvic alignment was suggested to play a determinant role in the pathological development of spinal orthopedic conditions, such as spondylolisthesis3 and lumbar degenerative diseases,4 thereby contributing importantly for the global burden of musculoskeletal spinal conditions at a population level. Several clinical studies have consistently demonstrated associations of sagittal standing posture with pain, physical disability, and reduced quality of life in patients with5–8 or without5,6,9–12 previous spinal surgery. Specifically, an anterior displacement of sagittal balance and an increased pelvic tilt (PT) have emerged as the radiographical features most predictive of health-related quality of life measures among highly selected samples of patients.7,9 However, the relevance of sagittal standing posture on health-related quality of life has not been assessed in the general adult population, and although evaluations have been performed in samples less
www.spinejournal.com
June 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E782
08/05/14 9:39 PM
CLINICAL CASE SERIES severely impaired,13–18 these studies present important limitations, namely, the lack of an analysis of pelvic parameters,13–18 the use of a surface technique to evaluate standing posture,15,17,18 or the inclusion of samples clearly unrepresentative of the general population regarding age14–18 or symptoms presentation.13–18 Attempts during the last years to define a neutral range of sagittal spinopelvic postural parameters were made among asymptomatic adults without relevant orthopedic conditions.19 However, the wide variability observed within those normative samples precludes the use of reference alignment values to identify sagittal misalignment situations of clinical relevance. Therefore, it is thought that sagittal standing overall postural patterns should allow an improved comprehension of the effect of posture on quality of life measures comparatively to isolated parameters of standing alignment,20–22 but the meaning of sagittal postural patterns as determinants of quality of life in adults has not been evaluated. We hypothesized that presenting an extreme sagittal alignment organization is associated with worse health-related quality of life. By using individual sagittal spinopelvic parameters and standing postural patterns, our main aim was to analyze the relation of suboptimal sagittal standing posture with back pain severity and health-related quality of life in males and females from the general population.
MATERIALS AND METHODS This cross-sectional study was performed as part of a longitudinal evaluation of noninstitutionalized adult inhabitants of the city of Porto (EPIPorto study). The recruitment of the initial sample has been previously described.23 Briefly, the assembling of the cohort was conducted between 1999 and 2003 and comprised the assessment of 2485 individuals. Households were initially identified by random digit dialing of landline telephones, and in each household, a permanent resident 18 years of age or older was randomly selected for evaluation. No replacements were allowed if a refusal occurred (participation proportion of 70.0%). The ethics committee of Hospital de São João approved the study protocol. All participants gave written informed consent to participate in the study. Between 2005 and 2008, 1682 individuals (67.7%) were reevaluated and the first 518 consecutively assessed were eligible for the present study. Subjects were excluded if they had undergone instrumentation of the spine (n = 2) or hip arthroplasty (n = 10), and if they had a diagnosis of inflammatory spinal arthropathies (n = 17). The final sample included 489 subjects, namely, 311 females (63.6%). Age, complete years of formal education, and the measurement of weight and height were obtained for all participants. Body mass index was computed as the weight in kilograms divided by the square of the height in meters. Thirty-six-inch standing sagittal radiographs were obtained for each participant during free-standing posture in accordance with routine institutional protocol. All examiners were unaware of the hypothesis under study. Radiographical films were digitized using a Vidar scanner (Vidar Systems Corp., Herndon, VA) Spine
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
with 75 dpi resolution and 12 gray levels, and a spine-dedicated software with a precision of 0.1º in angles and 0.1 mm in distances (Sectra Imtec AB, Linköping, Sweden) was used to obtain spinopelvic measures as shown in Figure 1. Lumbar region was defined from the sacral plate up to the distal intervertebral space of the most tilted thoracolumbar vertebra—inflexion point24 identified by comparison of adjacent intervertebral angles. A physical therapist (coauthor F.A.) underwent intensive training at a major tertiary hospital under the supervision of a senior orthopedic surgeon specialized in vertebral conditions (coauthor N.A.) in order to standardize procedures. All radiographical parameters were recorded blindly with regard to the outcomes of the study (i.e., back pain and health-related quality of life). The zoom feature of the software was freely used during parameter measurement. Two ratios between parameters were additionally computed: lumbar lordosis (LL)/pelvic incidence (PI) and PT/PI. These ratios are valuable to relativize positional measures of alignment to the individual's constitutional PI.8,25 To define a neutral range of parameters, we used tertiles, that is, the cutoffs that divide the distributions into 3 equal parts. Males and females were independently categorized into 1 of the following 3 groups for each individual posture parameter: low, intermediate, or high. Roussouly et al24 have proposed 4 types of LL in adults, each of them representing a different overall spinopelvic postural pattern in the sagittal plane with type 3 reflecting a balanced and neutral sagittal standing posture. Based on sacral slope (SS)24 and the number of vertebrae in LL,26 sagittal postural pattern was determined for each participant. Types 1 and 2 have an SS smaller than 35.5°, whereas type 1 has up to 3 vertebrae in LL and type 2 has at least 4. The remaining 2 postural patterns have unique ranges of SS, between 35.5° and 44.4° (type 3), and higher or equal to 44.5° (type 4). It is expected that type-specific mechanical stresses predispose to distinctive clinical manifestations in different postural patterns,24,27 although only type 2 was confirmed to be intrinsically more frequent in patients with chronic low back pain.26 Prevalence of back pain not directly associated to trauma was assessed regarding the previous month (“During the past month have you had back pain?”). Participants also answered back pain severity questions: “In the last year have you sought a doctor because of your back pain, having been prescribed exams or treatment?”, “During the last year did you have more than 3 episodes of pain?”, and “During the last 6 months did the pain ever last longer than one week?”. A combined back pain severity variable was created: for each affirmative answer in back pain severity questions, a point was given and an additional point was attributed if the intensity of back pain in the previous month was higher than 50 mm in a visual analogue scale. Health-related quality of life was assessed using the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36).28 SF-36 has been previously translated29 and the adapted Portuguese version has been validated.30 Two summary health components were defined in the EPIPorto www.spinejournal.com
E783
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E783
08/05/14 9:39 PM
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
Figure 1. Measurement of pelvic (A) and spinal (B) sagittal radiographical parameters. Pelvic parameters: pelvic incidence—angle between perpendicular to the sacral plate at its midpoint and the line connecting the midpoint of the sacral plate to femoral head axis; sacral slope—angle between the horizontal and the sacral plate; and pelvic tilt—angle between the vertical and the line connecting the midpoint of the sacral plate to femoral head axis (pelvic retroversion is reflected by an increased pelvic tilt). Spinal parameters: lumbar lordosis—angle measured from the superior endplate of the vertebrae distally located to inflexion point and the sacral plate. Sagittal vertical axis—horizontal offset from the posterosuperior corner of S1 to the vertical line passing through the center of C7 vertebral body (negative when posterior to the posterosuperior corner of S1).
Portuguese adult sample, one regarding physical and the other regarding mental health, a procedure shown to be valid and reproducible.31 Thirty males and 66 females were not included in this analysis because they did not have complete information on SF-36. Excluded males were less educated (median: 5.0 vs. 9.0; P = 0.004) and had slightly higher LL (mean: 64.6 vs. 60.4; P = 0.060) than those included, whereas females not included were older (mean: 63.1 vs. 57.9; P = 0.008) and less educated (median: 4.0 vs. 9.0; P = 0.001).
Statistical Analysis Given that sex is a known determinant of quality of life and that sex heterogeneity is recurrent in disease causation, we present all results separately for males and females. We used correlation analysis (Spearman coefficients) to assess the association of radiographical parameters with back pain variables and health-related quality of life. The χ2 test was used to compare back pain prevalence between sexes and posture-related groups. Mean differences in the 2 main components of SF-36 were compared through Student t test between sexes and analysis of variance between individual parameters categories, whereas Kruskall-Wallis tests were performed to compare types of postural patterns. Adjusted odds ratios and β coefficients with 95% confidence intervals (CI) were estimated by multiple binomial and multiple linear regressions, respectively. The associations of sagittal posture parameters and patterns with health-related outcomes were adjusted for age, education, and body mass index. E784
RESULTS Descriptive data are shown in Table 1. Comparatively to females, males had lower back pain prevalence and severity, and scored on average 4 points higher in physical and mental health–related quality of life (all comparisons P < 0.001). Table 2 shows that sagittal vertical axis (SVA) and PT/ PI ratio were correlated with physical health-related quality of life of females (ρ = −0.36 and 0.21, respectively, both P < 0.001), but stronger associations with quality of life were found regarding age, education, and body mass index (−0.42 ≤ ρ ≤ 0.62; P < 0.001). Severe back pain was significantly more frequent in males with low PT/PI ratio, but no differences were found for other sagittal radiographical parameters (Table 3). Females presenting high PI exhibited severe back pain more frequently (51% vs. 33% in the intermediate and 35% in the low PI group; P ≤ 0.018). In addition, females within the intermediate range of SS were less likely to have recent as well as severe back pain than the high SS group (34.9% vs. 52.0% and 31.2% vs. 48.0%, respectively; P ≤ 0.013). In males, a nonsignificant decreasing trend of physical quality of life was observed with increasing SVA (Table 4). In females, an inverse relation was found between SVA, PT, or PT/PI ratio and physical health-related quality of life. A direct association was found between LL/PI ratio and scores in the physical component of SF-36. Sagittal balance showed the largest differences: females with high SVA had 8.8 lower physical quality of life score than those with low SVA (P < 0.001).
www.spinejournal.com
June 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E784
08/05/14 9:39 PM
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
TABLE 1. Characteristics, Back Pain Variables, and Health-Related Quality of Life in All Participants
and Comparison Between Sexes
All Participants
Males
Females
P
59.5 (14.3)
60.5 (14.6)
59.0 (14.1)
0.285
8.0 (4.0–12.0)
9.0 (4.0–12.0)
7.0 (4.0–12.0)
0.069
27.0 (4.6)
26.0 (3.3)
27.5 (5.1)
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life Among Adults From the General Population A Sex-Specific Association Fábio Araújo, MSc,*† Raquel Lucas, PhD,*† Nuno Alegrete, MD,‡§ Ana Azevedo, PhD,*†‡ and Henrique Barros, PhD*†
Study Design. A prospective radiographical study of sagittal standing posture among adults consecutively recruited from the general population. Objective. To analyze the relation of suboptimal sagittal standing posture with back pain and health-related quality of life in general adult males and females. Summary of Background Data. Clinical studies have shown the association of sagittal standing posture with pain and reduced quality of life, but this relation has not been assessed in the general adult population. Methods. As part of the EPIPorto population-based study of adults, 178 males and 311 females were evaluated. Age, education, and body mass index were recorded. Radiographical data collection consisted of 36-in. standing sagittal radiographs. Creation of 3 groups for individual spinopelvic parameters was performed (low, intermediate, or high), and 1 of 4 sagittal types of postural patterns attributed to each participant (Roussouly classification). Back pain prevalence and severity were assessed on the basis of self-reported data and health-related quality of life using 2 main components of the 36-Item Short Form Health Survey. Results. In males, differences in back pain severity were observed only among pelvic tilt/pelvic incidence ratio groups. Females presenting high pelvic incidence and sacral slope exhibited higher odds of severe back pain than those with intermediate values
From the *Institute of Public Health—University of Porto (ISPUP), Porto, Portugal; †Department of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Porto, Portugal; ‡Centro Hospitalar São João, Porto, Portugal; and §Department of Surgery, University of Porto Medical School, Porto, Portugal. Acknowledgment date: November 4, 2013. First revision date: January 16, 2014. Second revision date: February 18, 2014. Acceptance date: February 21, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). National Foundation for Science and Technology funds were received to support this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Fábio Araújo, MSc, Instituto de Saúde Pública da Universidade do Porto, Rua das Taipas, 135-139, 4050600 Porto, Portugal; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000347
E782
(adjusted odds ratios = 2.21 and 2.15; 95% confidence interval, 1.24–3.97 and 1.21–3.86; respectively). Sagittal vertical axis showed the largest differences in physical quality of life of females: high group had 8.8 lower score than the low group (P < 0.001), but this result lost statistical significance after adjustment for age, education, and body mass index. Conclusion. Sagittal standing posture was not consistently associated with quality of life measures in males. Increased pelvic incidence and sacral slope may be involved in causing severe back pain among females. Monitoring sagittal postural parameters has limited usefulness as a screening tool for causes of unspecific musculoskeletal symptoms in the general adult population. Key words: posture, spine, pelvis, back pain, quality of life, population survey. Level of Evidence: 3 Spine 2014;39:E782–E794
M
usculoskeletal spinal conditions are among the leading causes of pain and decreased quality of life in the general adult population.1,2 Aging trends lead to the expectation that the resultant burden on individuals, societies, and health systems will increase dramatically in the upcoming decades.2 Extreme nonneutral sagittal spinopelvic alignment was suggested to play a determinant role in the pathological development of spinal orthopedic conditions, such as spondylolisthesis3 and lumbar degenerative diseases,4 thereby contributing importantly for the global burden of musculoskeletal spinal conditions at a population level. Several clinical studies have consistently demonstrated associations of sagittal standing posture with pain, physical disability, and reduced quality of life in patients with5–8 or without5,6,9–12 previous spinal surgery. Specifically, an anterior displacement of sagittal balance and an increased pelvic tilt (PT) have emerged as the radiographical features most predictive of health-related quality of life measures among highly selected samples of patients.7,9 However, the relevance of sagittal standing posture on health-related quality of life has not been assessed in the general adult population, and although evaluations have been performed in samples less
www.spinejournal.com
June 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E782
08/05/14 9:39 PM
CLINICAL CASE SERIES severely impaired,13–18 these studies present important limitations, namely, the lack of an analysis of pelvic parameters,13–18 the use of a surface technique to evaluate standing posture,15,17,18 or the inclusion of samples clearly unrepresentative of the general population regarding age14–18 or symptoms presentation.13–18 Attempts during the last years to define a neutral range of sagittal spinopelvic postural parameters were made among asymptomatic adults without relevant orthopedic conditions.19 However, the wide variability observed within those normative samples precludes the use of reference alignment values to identify sagittal misalignment situations of clinical relevance. Therefore, it is thought that sagittal standing overall postural patterns should allow an improved comprehension of the effect of posture on quality of life measures comparatively to isolated parameters of standing alignment,20–22 but the meaning of sagittal postural patterns as determinants of quality of life in adults has not been evaluated. We hypothesized that presenting an extreme sagittal alignment organization is associated with worse health-related quality of life. By using individual sagittal spinopelvic parameters and standing postural patterns, our main aim was to analyze the relation of suboptimal sagittal standing posture with back pain severity and health-related quality of life in males and females from the general population.
MATERIALS AND METHODS This cross-sectional study was performed as part of a longitudinal evaluation of noninstitutionalized adult inhabitants of the city of Porto (EPIPorto study). The recruitment of the initial sample has been previously described.23 Briefly, the assembling of the cohort was conducted between 1999 and 2003 and comprised the assessment of 2485 individuals. Households were initially identified by random digit dialing of landline telephones, and in each household, a permanent resident 18 years of age or older was randomly selected for evaluation. No replacements were allowed if a refusal occurred (participation proportion of 70.0%). The ethics committee of Hospital de São João approved the study protocol. All participants gave written informed consent to participate in the study. Between 2005 and 2008, 1682 individuals (67.7%) were reevaluated and the first 518 consecutively assessed were eligible for the present study. Subjects were excluded if they had undergone instrumentation of the spine (n = 2) or hip arthroplasty (n = 10), and if they had a diagnosis of inflammatory spinal arthropathies (n = 17). The final sample included 489 subjects, namely, 311 females (63.6%). Age, complete years of formal education, and the measurement of weight and height were obtained for all participants. Body mass index was computed as the weight in kilograms divided by the square of the height in meters. Thirty-six-inch standing sagittal radiographs were obtained for each participant during free-standing posture in accordance with routine institutional protocol. All examiners were unaware of the hypothesis under study. Radiographical films were digitized using a Vidar scanner (Vidar Systems Corp., Herndon, VA) Spine
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
with 75 dpi resolution and 12 gray levels, and a spine-dedicated software with a precision of 0.1º in angles and 0.1 mm in distances (Sectra Imtec AB, Linköping, Sweden) was used to obtain spinopelvic measures as shown in Figure 1. Lumbar region was defined from the sacral plate up to the distal intervertebral space of the most tilted thoracolumbar vertebra—inflexion point24 identified by comparison of adjacent intervertebral angles. A physical therapist (coauthor F.A.) underwent intensive training at a major tertiary hospital under the supervision of a senior orthopedic surgeon specialized in vertebral conditions (coauthor N.A.) in order to standardize procedures. All radiographical parameters were recorded blindly with regard to the outcomes of the study (i.e., back pain and health-related quality of life). The zoom feature of the software was freely used during parameter measurement. Two ratios between parameters were additionally computed: lumbar lordosis (LL)/pelvic incidence (PI) and PT/PI. These ratios are valuable to relativize positional measures of alignment to the individual's constitutional PI.8,25 To define a neutral range of parameters, we used tertiles, that is, the cutoffs that divide the distributions into 3 equal parts. Males and females were independently categorized into 1 of the following 3 groups for each individual posture parameter: low, intermediate, or high. Roussouly et al24 have proposed 4 types of LL in adults, each of them representing a different overall spinopelvic postural pattern in the sagittal plane with type 3 reflecting a balanced and neutral sagittal standing posture. Based on sacral slope (SS)24 and the number of vertebrae in LL,26 sagittal postural pattern was determined for each participant. Types 1 and 2 have an SS smaller than 35.5°, whereas type 1 has up to 3 vertebrae in LL and type 2 has at least 4. The remaining 2 postural patterns have unique ranges of SS, between 35.5° and 44.4° (type 3), and higher or equal to 44.5° (type 4). It is expected that type-specific mechanical stresses predispose to distinctive clinical manifestations in different postural patterns,24,27 although only type 2 was confirmed to be intrinsically more frequent in patients with chronic low back pain.26 Prevalence of back pain not directly associated to trauma was assessed regarding the previous month (“During the past month have you had back pain?”). Participants also answered back pain severity questions: “In the last year have you sought a doctor because of your back pain, having been prescribed exams or treatment?”, “During the last year did you have more than 3 episodes of pain?”, and “During the last 6 months did the pain ever last longer than one week?”. A combined back pain severity variable was created: for each affirmative answer in back pain severity questions, a point was given and an additional point was attributed if the intensity of back pain in the previous month was higher than 50 mm in a visual analogue scale. Health-related quality of life was assessed using the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36).28 SF-36 has been previously translated29 and the adapted Portuguese version has been validated.30 Two summary health components were defined in the EPIPorto www.spinejournal.com
E783
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E783
08/05/14 9:39 PM
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
Figure 1. Measurement of pelvic (A) and spinal (B) sagittal radiographical parameters. Pelvic parameters: pelvic incidence—angle between perpendicular to the sacral plate at its midpoint and the line connecting the midpoint of the sacral plate to femoral head axis; sacral slope—angle between the horizontal and the sacral plate; and pelvic tilt—angle between the vertical and the line connecting the midpoint of the sacral plate to femoral head axis (pelvic retroversion is reflected by an increased pelvic tilt). Spinal parameters: lumbar lordosis—angle measured from the superior endplate of the vertebrae distally located to inflexion point and the sacral plate. Sagittal vertical axis—horizontal offset from the posterosuperior corner of S1 to the vertical line passing through the center of C7 vertebral body (negative when posterior to the posterosuperior corner of S1).
Portuguese adult sample, one regarding physical and the other regarding mental health, a procedure shown to be valid and reproducible.31 Thirty males and 66 females were not included in this analysis because they did not have complete information on SF-36. Excluded males were less educated (median: 5.0 vs. 9.0; P = 0.004) and had slightly higher LL (mean: 64.6 vs. 60.4; P = 0.060) than those included, whereas females not included were older (mean: 63.1 vs. 57.9; P = 0.008) and less educated (median: 4.0 vs. 9.0; P = 0.001).
Statistical Analysis Given that sex is a known determinant of quality of life and that sex heterogeneity is recurrent in disease causation, we present all results separately for males and females. We used correlation analysis (Spearman coefficients) to assess the association of radiographical parameters with back pain variables and health-related quality of life. The χ2 test was used to compare back pain prevalence between sexes and posture-related groups. Mean differences in the 2 main components of SF-36 were compared through Student t test between sexes and analysis of variance between individual parameters categories, whereas Kruskall-Wallis tests were performed to compare types of postural patterns. Adjusted odds ratios and β coefficients with 95% confidence intervals (CI) were estimated by multiple binomial and multiple linear regressions, respectively. The associations of sagittal posture parameters and patterns with health-related outcomes were adjusted for age, education, and body mass index. E784
RESULTS Descriptive data are shown in Table 1. Comparatively to females, males had lower back pain prevalence and severity, and scored on average 4 points higher in physical and mental health–related quality of life (all comparisons P < 0.001). Table 2 shows that sagittal vertical axis (SVA) and PT/ PI ratio were correlated with physical health-related quality of life of females (ρ = −0.36 and 0.21, respectively, both P < 0.001), but stronger associations with quality of life were found regarding age, education, and body mass index (−0.42 ≤ ρ ≤ 0.62; P < 0.001). Severe back pain was significantly more frequent in males with low PT/PI ratio, but no differences were found for other sagittal radiographical parameters (Table 3). Females presenting high PI exhibited severe back pain more frequently (51% vs. 33% in the intermediate and 35% in the low PI group; P ≤ 0.018). In addition, females within the intermediate range of SS were less likely to have recent as well as severe back pain than the high SS group (34.9% vs. 52.0% and 31.2% vs. 48.0%, respectively; P ≤ 0.013). In males, a nonsignificant decreasing trend of physical quality of life was observed with increasing SVA (Table 4). In females, an inverse relation was found between SVA, PT, or PT/PI ratio and physical health-related quality of life. A direct association was found between LL/PI ratio and scores in the physical component of SF-36. Sagittal balance showed the largest differences: females with high SVA had 8.8 lower physical quality of life score than those with low SVA (P < 0.001).
www.spinejournal.com
June 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131301_LR E784
08/05/14 9:39 PM
CLINICAL CASE SERIES
Sagittal Standing Posture, Back Pain, and Quality of Life • Araújo et al
TABLE 1. Characteristics, Back Pain Variables, and Health-Related Quality of Life in All Participants
and Comparison Between Sexes
All Participants
Males
Females
P
59.5 (14.3)
60.5 (14.6)
59.0 (14.1)
0.285
8.0 (4.0–12.0)
9.0 (4.0–12.0)
7.0 (4.0–12.0)
0.069
27.0 (4.6)
26.0 (3.3)
27.5 (5.1)
