The Spine Journal - (2013) -

Perspective

Lumbar lordosis

Ella Been, PT, PhDa,b,*, Leonid Kalichman, PT, PhDc

aPhysical Therapy Department, Zefat Academic College, Safed, IsraelbDepartment of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

cDepartment of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences,

Ben-Gurion University of the Negev, Beer Sheva, Israel

Received 3 October 2011; revised 22 June 2013; accepted 21 July 2013

Abstract Lumbar lordosis is a key postural component th

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Sackler Faculty of M

þ972-3-6408287.

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at has interested both clinicians and researchers formany years. Despite its wide use in assessing postural abnormalities, there remain many unan-swered questions regarding lumbar lordosis measurements. Therefore, in this article we revieweddifferent factors associated with the lordosis angle based on existing literature and determined nor-mal values of lordosis. We reviewed more than 120 articles that measure and describe the differentfactors associated with the lumbar lordosis angle. Because of a variety of factors influencing theevaluation of lumbar lordosis such as how to position the patient and the number of vertebrae in-cluded in the calculation, we recommend establishing a uniform method of evaluating the lordosisangle. Based on our review, it seems that the optimal position for radiologic measurement of lor-dosis is standing with arms supported while shoulders are flexed at a 30� angle. There is evidencethat many factors, such as age, gender, body mass index, ethnicity, and sport, may affect the lordosisangle, making it difficult to determine uniform normal values. Normal lordosis should be deter-mined based on the specific characteristics of each individual; we therefore presented normal lor-dosis values for different groups/populations. There is also evidence that the lumbar lordosis angleis positively and significantly associated with spondylolysis and isthmic spondylolisthesis. How-ever, no association has been found with other spinal degenerative features. Inconclusive evidenceexists for association between lordosis and low back pain. Additional studies are needed to evaluatethese associations. The optimal lordotic range remains unknown and may be related to a variety ofindividual factors such as weight, activity, muscular strength, and flexibility of the spine and lowerextremities. � 2013 Elsevier Inc. All rights reserved.

Keywords: Spine; Posture; Lordosis; Spinal pathology; Spinal measurements

Introduction

Research studies have shown an increasing recognitionof the functional and clinical importance of lumbar lordosis[1–5]. It is a key feature in maintaining sagittal balance. Sag-ittal balance or ‘‘neutral upright sagittal spinal alignment’’ isa postural goal of surgical, ergonomic, and physiotherapeu-tic intervention. However, a wide variety of thoracic andlumbar spinal curves may correspond with the acceptedcriterion of sagittal balance (50 mm of C7–S1 sagittal devi-ation in asymptomatic adults while standing) [6,7], making

status: Not applicable.

: EB: Nothing to disclose. LK: Nothing to disclose.

uthor. Department of Anatomy and Anthropology,

edicine, Tel Aviv University, Tel Aviv, Israel. Tel.:

eenella@post.tau.ac.il (E. Been)

nt matter � 2013 Elsevier Inc. All rights reserved.

16/j.spinee.2013.07.464

it difficult for surgeons, researchers, therapists, and patientsto know if they are examining or achieving the same posturalgoal [8].

In this topical review, we determined, based on existingliterature, normal and abnormal parameters of lumbar lordo-sis and examine the different factors associated with the lor-dosis angle. To accomplish this, we searched PubMed,PEDro, EMBASE, and Google scholar databases (incep-tion–2012) for the key words ‘‘spine’’, ‘‘spinal’’, ‘‘lordosis’’,‘‘lumbar’’, ‘‘posture’’, ‘‘pathology’’, ‘‘measurements’’, andcombinations of key words. All relevant articles in Englishwere reviewed. Pertinent secondary references were also re-trieved.We are aware that this traditional approach to reviewshas much more potential for bias than systematic reviews ormeta-analyses; however, we have endeavored to be inclusiveand openminded.We also consulted experts in spinal surgeryand radiology to produce this review on lumbar lordosis.

Fig. 1. Measurements of lumbar lordosis Cobb’s angle (LA), vertebral

body (B) and intervertebral disc (D) wedging, and facet joint angle (F).

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Anatomy of lumbar lordosis

Lumbar lordosis is the inward (ventral) curvature of thelumbar spine formed by the wedging of lumbar vertebralbodies and the intervertebral disks [9,10] (Fig. 1). Dorsalwedging of the vertebral bodies and disks (anterior part lon-ger than posterior) increases the lordosis angle, whereasmore ventral wedging of these structures (anterior partshorter than posterior) reduces the lordosis angle (Fig. 1).Lumbar lordosis is similarly influenced by the shape ofthe vertebral bodies and the shape of the intervertebraldiscs, because each account for nearly 50% of the variabil-ity seen in lordotic angles of adults [11,12]. Each of the fivelumbar segments (vertebral body and the adjacent disc)contribute to the lordosis. The last lumbar segment (L5)contributes almost 40% to overall lordosis. The first seg-ment (L1) contributes only 5% [13]. The lordosis angle alsocorrelates with the orientation of the inferior articular pro-cesses—greater lordosis correlates with more dorsally (hor-izontally) inclined inferior articular (facet) processes inrelation to the vertebral bodies [14] (Fig. 1).

A close correlation exists between the lordosis angle (thecommon measure of lumbar lordosis) and other posturalvariables. Many researchers have found a high correlationbetween the lumbar lordosis angle and pelvic and thoracicorientation in space. Greater lordosis angles correlate witha more horizontally inclined sacrum (increased sacralslope, more vertical sacral endplate), increased pelvic inci-dence, and increased pelvic tilt [15,16]. Most researchersfound that greater lordosis usually correlates with higherthoracic kyphosis, but cases of increased lordosis with re-duced thoracic kyphosis have also been reported [15–17].Small lordosis angles usually correlate with a more verticalsacrum, small pelvic tilt, pelvic incidence, and reduced tho-racic kyphosis; however, cases of reduced lumbar lordosiswith increased thoracic kyphosis have also been detailed[15–17].

Ontogenetic development of the lumbar lordosis

Although many authors believe that the spine of the hu-man fetus shows only one kyphotic curvature from cranialto caudal [18,19], studies have shown that the fetal spinehas lordotic curvature at the lumbosacral junction [20,21].Choufani et al. [20] in a magnetic resonance imaging(MRI) study of 45 fetuses aged 23 to 40 weeks gestationdemonstrated that all fetuses had lordotic lumbar curvaturewith a mean radius of 18.7 mm. This lordosis was uncorre-lated with gestational age, which means that it was not re-lated to growth and, according to the authors, might havebeen genetically determined.

Few researchers have examined the lordosis angle inearly childhood, with Reichmann and Lewin [21], beinga notable exception. They found that lordosis angles in-creased during the first 3 years of life, claiming that atthe age of 3, the child’s spine reaches an adult-like lordosis

angle. Other researchers, however, found that the lordosisangle continues to increase during later childhood and pu-berty [22,23] even until the age of 20 [6] (Table 1). For ex-ample, Cil et al. [22] demonstrated an increase of thelordosis angle from 44.3� at 3 to 6 years to 54.6� at 13 to15 years.

It can be concluded that lumbar lordosis begins to de-velop in fetuses. The major increase of the lordosis angleoccurs during the first 3 years of life and continues increas-ing at least until puberty. There are many gaps in the cur-rent knowledge regarding the ontogenetic development oflumbar lordosis. Additional studies are essential to fill inthis gap and to identify the factors that determine lordosisdevelopment. Ascertaining the normal values of lordosisin children is essential for early detection and treatmentof postural abnormalities.

Evaluation of lumbar lordosis

Number of evaluated vertebrae

One of the fundamental questions regarding lordosisevaluation is the number of vertebrae or segments (vertebraand adjacent intervertebral disk) measured. The most com-mon evaluation of lumbar lordosis uses the angle formed byall five lumbar segments (L1–L5). When employing Cobb’s

Table 1

Data available on lordosis angles in children

Research Method Position Age (y) Sample size Lordosis angle ( �)

Cil et al. [22] Cobb’s angle (superior end plate of L1 and S1) Standing 3–6 51 44.3611.0

7–9 37 51.7611.5

10–12 32 57.3610.6

13–15 31 54.669.8

Neuschwander et al. [124] Cobb’s angle (L1–S1) Standing 1162 8 60.263.1

Mac-Thiong et al. [7] Arc between L1 and L5 Standing 12.163.3 341 48611.7

Giglio and Volpon [6] Panthograph (spinous processes L1–L5) Standing 5 16 2269

10 30 3267

15 22 33611

20 17 38610

Willner and Johnson [23] Spinal panthograph Standing 8, boys 48 33.669.3

12, boys 63 3267.1

16, boys 74 33.668.6

8, girls 50 33.368.9

12, girls 64 34.868.5

16, girls 81 36.767.6

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method, the upper line is drawn at the superior endplateof L1, and the lower line at the superior endplate of thesacrum (S1; Fig. 1). However, some researchers measurelordosis starting as high as T10*, others finish at L3.Some researchers do not include the lower lumbar seg-ment (L5) or only do not include the last intervertebraldisk L5–S1 in their measurements. Significant differencesoccur between lordosis angles when different numbers ofvertebral segments are measured (Table 2). Therefore, webelieve that it is crucial to measure exactly the samenumber of segments to compare the different studies.We suggest that measurements should include the verte-bral bodies and intervertebral disks of L1–L5; in otherwords, measurements (Cobb’s method) should be per-formed between the superior endplate of the first lumbarvertebra and the superior endplate of the sacrum. Thelogic behind our suggestion is based on anatomic consid-erations, including all of the lumbar segments in the lum-bar lordosis measurements. In addition, this is the mostpopular measurement of lumbar lordosis used today[22,24–27]; functionally, the five lumbar segments sharea fundamental role in upright functions such as walkingand running [28].

Table 2

Lordosis angle (Cobb’s method) measured in a standing position using

different spinal levels

Measurement between

Modified after

Vialle et al. [10]

Modified after

Been et al. [11]

L1 superior end plate�S1 superior

end plate

58.5 51.3610.7

L1 inferior end plate�S1 superior

end plate

62 54.8

L2 superior end plate�S1 superior

end plate

57 49

L1 superior end plate�L5 superior

end plate

35 31.5

L1 superior end plate�L5 inferior

end plate

43611.2 39.6

Methods of measurement

Many methods are used to evaluate lumbar lordosis. Wedivided the methods into clinical and imaging evaluation.Clinical examination evaluates the degree of lordosis di-rectly on the individual’s body. Radiologic evaluation usestwo-dimensional radiographs, three-dimensional (3D) com-puted tomography and MRI. Each method of evaluation hasits advantages and disadvantages, but the major problem isthat it is difficult to compare the measurements when per-formed by different methodologies.

Clinical methods for evaluating lordosis angles includevarious 3D posture analysis systems and surface topographysystems [29,30]. Most of these methods use the spinous pro-cesses of the lumbar vertebrae to evaluate the degree of lor-dosis [6]. The main advantage of these measurements is thelack of radiation, thus allowing frequent evaluation of thespinal curves, and better monitoring of the changes in thelordosis angle. The reproducibility of clinical methods is rel-atively high (interobserver intraclass correlation coefficient[ICC] is 0.70–0.85, [31,32]); however, it is not as high aswith radiologic methods (interobserver ICC isO0.87 [33]).On the other hand, because clinical methods use surfaceanatomy to evaluate the lordosis angle, only moderate corre-lations with radiologic measurements were found. Compar-isons between the patients are also problematic because ofdifferent paraspinal muscle development, thickness of sub-cutaneous fat, and anatomic variations in spinous processeslength and orientation. Recently, a few articles have sug-gested the use of electronic or laser lordosis angle measure-ments. Letafatkar et al. [34] showed that using a flexibleplastic ruler and an AutoCAD (arc) for lordosis angle mea-surements is a reliable and valid method, and suggested thatthis method may replace radiography in evaluating lumbarlordosis. Celan et al. [35] measured the lordosis and kypho-sis angles using a laser triangulation method. Althoughthere are sophisticated 3D posture analysis systems such asOptotrak (Northern Digital Inc., Waterloo, Canada), Vicon

Fig. 2. Two possible lumbar lordosis curves with the same Cobb’s angle.

Fig. 3. Measurements of lumbar lordosis: anterior tangent, posterior tan-

gent, centroid, and best fit ellipse.

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(Vicon Motion Systems, Oxford, UK), Motion Analysis(Motion Analysis Corporation, Santa Rosa, CA, USA),and surface topography systems, these systems are notaccessible for most clinicians [36]. These sophisticated 3Dsystems enable researchers to evaluate the lordosis anglein different postures and settings. For example, Levineet al. [37] used motion analysis systems to examine thelordosis angles during walking and running.

Fortin et al. [36] presented a novel, promising techniquefor clinical posture assessment based on calculation of bodyangles and distances on photographs. This method has a rel-atively low cost, is easy to perform in a clinical setting, andthere is no exposure to radiation. Photograph acquisitionshowed good inter- and intrarater reliability (ICCO0.991),but only moderate validity (r50.48) compared with radio-graphic evaluation of lordosis [36]. We therefore concludethat utilizing clinical methods for evaluating lordosis anglescan be a useful tool for monitoring patients’ progress. How-ever, clinical methods in their present form are unsuitablefor research or clinical evaluation when absolute parame-ters of lumbar lordosis need to be measured.

Many radiologic methods have been used to evaluate thelordosis angle on two-dimensional radiographs. The Cobbmethod (or modified Cobb method) has become the goldstandard in measuring lumbar lordosis [33], using vertebralendplate lines to measure angles on sagittal radiographs.This method is very simple to perform, and has been provenhighly reliable [33]. The strongest limitation of the Cobbmethod is that, theoretically, two spinal curvatures of differ-ent magnitudes may result in the same Cobb angle (Fig. 2);therefore, other methods have been developed in attemptto overcome this problem. These methods use different

anatomic landmarks on the vertebral bodies to evaluate thelordosis angle. For example, the anterior and the posteriortangent methods use the anterior or posterior vertebral bodywall to determine the lordosis angle. The centroid methoduses the center of the vertebral body to measure the lordosisangle. Some methods, such as the best-fit ellipse, constructa circular geometrical model of the lumbar spine (Fig. 3).All of these methods were found to be reliable in evaluatinglordosis. A more detailed description of the different lordo-sis evaluation methods can be found in Vrtovec et al. [33]

Position of measurement

One of the fundamental variables in lordosis measure-ment is the position in which the measurements were taken,that is, standing, sitting, or lying down. Most lumbar lordo-sis studies use X-rays taken in the standing position, statingthat this is the most functionally relevant position [38,39].However, during the last two decades, more and more spi-nal clinical evaluations and research has been performedusing computed tomography and MRI technologies that al-low a much more detailed depiction of spinal anatomy andpathology. It is therefore important to understand how thesubject’s position influences the lordosis angle. Recently,several authors [40,41] reported that a horizontal MRI withthe patient supine and legs straight out (supine extended po-sition) was comparable with a vertical MRI, where the pa-tient stands. This is in agreement with earlier reports bySchmid et al. [42], who studied 12 young volunteers usinga positional MRI. All aforementioned authors concludedthat the supine extended position was a functionally rele-vant position and suggested that it could replace the uprightextended position (Table 3). On the other hand, lordosismeasured in the supine position, with bent hips and knees(psoas relaxed position), was found to be significantlysmaller than when in a standing or supine extended position[43]. In an open MRI study, lordosis showed a significantincrease of 6.3� (14%) from supine psoas relaxed positionto a true standing position.

Measuring the lordosis angle in sitting position

All researchers agree that the lordotic curvature in a sittingposition is significantly lower than in a standing position

Table 3

Average lordosis angle measured in different positions

Research N Modality

Lying with

extended legs

Lying in psoas

relaxed position* Standing Sitting

Hirasawa et al. [37] 29 MRI 53.269.2 53.3613.4 20.5612.7

Madsen et al. [38] 16 MRI 52 44 43.9y

Mauch et al. [40] 35 MRI 46.369.9 52.668.9

De Carvalho et al. [41] 8 X-ray 63615 20

* With flexed hips and knees.y Subjects were instructed to lean slightly backwards against the examination bench during the vertical magnetic resonance imaging (MRI) and to rest

their arms on the cross bar to secure immobility.

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[26,40,42,44,45] (Table 3). Furthermore, Hirasawa et al. [40]demonstrated significant differences in lordosis angles be-tween different sitting positions ranging from 3.1611.8 ina flexed sitting position to 46.2612.3 in an extended sittingposition. We therefore feel that the sitting position cannot re-place the standing position as the functionally relevant posi-tion. However, because sitting is one of the most commonpostures used in the modern world, the degree of lordosis ex-hibited during sitting may has its own significance.

The effect of arm position on lordosis measurements

Arm position in standing lateral radiographs may disturbsagittal balance and therefore alter the lordosis angle. Theneutral position (arms placed at the sides of the body) is im-practical because the arm bones overlay the spine and thusmay interfere with the measurements. Several studies havecompared different arm positions with a functional standingposition with arms at the sides [46,47], and found that armposition in standing lateral radiographs did not significantlyaffect the lordosis angle. Although no differences werefound between the different positions, both studies recom-mended the use of a standard position for repeated mea-surements of the lordosis angle. Marks et al. [39] usedmotion analysis laboratory and found that the lumbar anglemeasured from an X-ray taken in a standing position withthe hands supported and shoulders slightly flexed (30� flex-ion at the shoulder) was comparable with the measurementtaken in a functional standing position with arms at theside. They concluded that this seems to be the best wayto move the arms, anterior to the spine, with the least effecton overall sagittal balance.

The wide range of postures (standing, supine extended,and psoas-relaxed positions) and arm positions used tomeasure lumbar lordosis pose a problem when comparingdata and establishing normal values of lordosis. We believethat a uniform method of evaluating the lordosis angleshould be established to allow comparisons of clinicaland research measurements.

Based on our review, it seems that the optimal positionfor the radiologic measurement of lordosis is standing witharms supported while flexing the shoulder at a 30� angle. Ifstanding is not possible, the lordotic angle should be mea-sured in a supine position with straightened legs. In theclinical setting, there is a strong need to develop a method

that is reliable, comparable with radiographic measure-ments, easy to perform, and inexpensive.

Factors associated with lumbar lordosis

Age

The commonly held opinion is that lumbar lordosis ‘flat-tens’ out with spinal problems and subsequent age-relateddegenerative changes [48]. However, most studies did notfind an association between age and lordosis [27,48–51].Other studies claimed that lumbar lordosis increases withage [52] or decreases only after the sixth decade [53]. Onthe other hand, no association was found between ageand wedging of vertebral bodies and intervertebral discs[27]. Existing evidence, therefore, does not support thecommon opinion of lordosis flattening with age. However,the question of the lumbar lordosis angle changing with ageis not fully resolved and more research is needed to under-stand the effect of age on the lordosis angle.

Gender

One study evaluated lordosis in a supine position [27],whereas others used lateral standing X-rays [14,54–58],to show that the lumbar lordosis angle does not differ be-tween the genders. Middleditch and Oliver [59] found nodifference in the lumbar lordosis between males and fe-males until middle age. However, other studies found thatfemales have significantly greater lordosis angles (2�–5�)than males [10,48,50,60,61]. Stagnara et al. [62] suggestedthat females apparently had greater lumbar lordosis owingto their greater buttock size. Mosner et al. [63], who con-ducted a study of actual and apparent lumbar lordosis inCaucasian and African-American females, agree with Stag-nara’s view.

Height and weight

Most researchers agree that obesity, especially central(abdominal) obesity, increases the lordosis angle. Murrieet al. [48] found that lumbar lordosis was significantlygreater (p!.01) in individuals with a high body mass index(BMI). Guo et al. [64] found that a BMI exceeding 24 kg/m2 might increase the lumbar lordosis angle. Moore andDalley [65] suggested that a hyperlordotic lumbar spine

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found in obese individuals was owing to a compensatorybackward lean to improve balance. Recently, Smith et al.[66] reported a hyperlordotic or sway posture in children(3–14 years) with a high BMI. On the other hand, Naseriet al. [67], who examined 75 Iranian women, Mcllwraith[68], and Naido [49] found poor correlation between lum-bar lordosis and BMI.

Naido [49] found a significant association (p5.004) be-tween the height of the subjects and lumbar lordosis, whichis in agreement with Nourbakhsh et al.’s findings [69]. It ispossible that tall individuals have the increased loading inthe lumbar area, which causes increased lordosis [70].

Pregnancy

In two recent studies, the most significant increase inlumbar lordosis occurred in the late stages of pregnancy[65,71]. Nourbakhsh et al. [69] found that previous preg-nancies and the number of pregnancies were associatedwith the lumbar lordosis degree [69]. There are several pos-sible explanations for this phenomenon: a compensatorybackward lean to improve balance owing to increased ab-dominal weight [72]; the muscular imbalance caused byoverstretched weak abdominal muscles and strong backmuscles might contribute to increased lordosis found inwomen with a high number of pregnancies; and duringthe last trimester of pregnancy a significant increase in jointlaxity occurs [73,74]. It is possible that this hyperlaxity al-lows the increase of lumbar lordosis by softening the para-spinal ligaments. The new lordosis angle remains afterdelivery.

Ethnicity

As early as the end of the 19th century, Cunningham[75] indicated that differences in lordosis angles were eth-nically related. Fahrni and Trueman [76] discovered smallerlordotic angles in a cadaver sample of Native Americanscompared with Caucasians. Patrick [77], using externalflexicurve measurements, found 20% higher lordosis anglesin a Nigerian population compared with Europeans. Hansonet al. [78] and recently Lonner et al. [79] found that lordosisangles in African-Americans averaged 4� greater than Cau-casians. Lonner et al.’s study was the largest study on thissubject. However, the authors used an adolescent scolioticpopulation; thus, the results may not be applicable to thegeneral population. On the other hand, many researchersfound a similarity in the degree of lordotic curvature be-tween populations. Mosner et al. [63] and Goldberg andChiarello [80] found similar lumbar lordosis angles in Cau-casians and African-Americans. Chen [81] compared thelordosis angles of 16 healthy Chinese men with that of Eu-ropeans and found no interracial differences. Mosner et al.[63] concluded that the clinician’s assumption that African-Americans have a greater lordosis than Caucasians is basedon an apparent increased lordosis owing to more prominentbuttocks.

Heritability

Although heritability and genetics of scoliosis has beenextensively studied [82], we found only one study that eval-uated the familial correlations of normal spinal curves [83],finding significant positive familial correlations in lumbarlordosis measurements. All sibling groups showed a greatercorrelation of lordosis measurement than unrelated con-trols. Same-sex siblings had a greater correlation than dif-ferent sex siblings.

Muscles and lumbar lordosis

It is widely accepted that abdominal and back muscula-tures affect pelvic inclination and lumbar lordosis while ina static, upright posture [84,85]. Many researchers[50,51,86,87] have suggested that lumbar lordosis and ab-dominal muscle function are related to each other. For ex-ample, the weakness of the abdominal muscle permits ananterior pelvic tilt and hyperlordotic posture [18,50,51].On the other hand, strong abdominal muscles can tilt thepelvis posteriorly and concurrently reduce lordosis. At thesame time, strong back muscles can tilt the pelvis anteri-orly, thus increasing lumbar lordosis. Some researchers ex-amined the association between abdominal muscle strengthand the lordosis angle, but found no conclusive evidence ofa relationship [51,85,88]. It is possible that, in the static po-sition, the equilibrium between trunk flexors and extensorsinfluenced the lumbar lordosis and not the strength of thespecific muscle group. Only Kim et al. [46] examined therelationship between trunk muscle strength (abdominalvs. back muscles) and lumbar lordosis and found that theratio of extensor torque to flexor torque was significantlyrelated to the lordotic angle (Pearson’s correlation coeffi-cient50.491; p!.01). Relatively strong spinal extensorsand weak spinal flexors were associated with high lumbarlordosis and vice versa. The researchers concluded that animbalance in trunk muscle strength can significantly influ-ence the lordotic curve of the lumbar spine and might bea risk factor for potential low back pain (LBP).

Hip muscles, such as the iliopsoas and hamstring, mightalso influence the degree of lordosis in a static upright pos-ture. These muscles are able to move the pelvis in the sag-ittal plane—anterior and posterior pelvic tilt. Posteriorpelvic tilt can result from contraction or tightness of thehamstring muscles, leading to a more horizontal sacral end-plate and hypolordosis (the smaller lordosis would be nec-essary to keep the line of gravity close to the acetabulum).Although theoretically the hip muscles can influence thedegree of lordosis, the evidence in the literature is inconclu-sive. Some authors found close correlation between tighthamstring muscles and hypolordosis [89], whereas othersfound no correlation between the two [67,90,91]. An ongo-ing debate exists as to the influence of the psoas major mus-cle on the lordotic curvature. Some researchers argue that itacts to flex the lumbar spine and therefore decrease the lor-dosis angle [92,93]. Others argue that it acts to increase the

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lordosis angle [94]. A third group of researchers claim thatthe role of the psoas major is to stabilize the lordotic lum-bar spine in an upright posture by adapting its contractionto the momentary degree of lordosis imposed by other fac-tors outside the lordosis, such as weight bearing [95,96].

Sport

Few researchers have examined the relationship betweenthe lordosis angle and sports activities. Wojtys et al. [58], re-porting on a sample of 2,270 children 8 to 18 years old,found that athletes have a greater lordosis angle than non-athletes, and that the greater lordosis angle was associatedwith greater cumulative training time. The nature of the re-lationship between sports activity and development of thelordosis angle is not fully known. Uetake and Ohtsuki[97] examined the lordosis angle in athletes according totheir sports and found that long distance runners andsprinters showed greater than average lordosis angles; rugbyand soccer players showed average lordosis angles, andswimmers and body builders showed lower than average lor-dosis angles. It has been reported that running is associatedwith increased lumbar lordosis and anterior pelvic tilt [98].Wodecki et al. [99] found increased lumbar lordosis in soc-cer players. Forster et al. [100] found high lordosis angles inhigh ability male rock climbers, whereas Nilsson et al. [101]reported less prominent lordosis in ballet dancers.

Occupation

Milosavljevic et al. [102] studied the effects of occupa-tion on sagittal spinal motion and posture. Their sampleconsisted of 64 sheep shearers and 64 nonshearers matchedby age and anthropometry findings. Results showed thatsheep shearers had hypolordosis of the lumbar spine anda flatter compensatory thoracic kyphotic curve comparedwith nonshearers. In a sample of 840 randomly selected Ira-nian subjects, Nourbakhsh et al. [69] reported no differencein the degree of lumbar lordosis angle between subjectswho utilized tables and chairs versus sitting on the floor,worked in standing versus sitting postures, or performedstrenuous versus light physical activity. Sarikaya et al.[103] assessed the incidence of LBP among Turkish coalminers (surface and underground) and investigated the rela-tionship between the angles of the lumbar spine and LBP.They found no differences between the lordosis angles ofthe two groups of miners. At the same time, they reporteda significant, negative correlation between lumbar lordosisand the number of years working as an underground miner.

Lumbar lordosis, spinal degeneration, and low backpain

Lumbar lordosis and spinal degeneration

Numerous studies have evaluated the association be-tween lumbar lordosis and spinal degeneration features

[2,4,24,54,104–107]. Most researchers agree that the lum-bar lordosis angle is positively and significantly associatedwith spondylolysis and isthmic spondylolisthesis[4,24,108–111]. A greater lordosis angle is thought to bea risk factor for developing spondylolysis and ventral slip-page of the affected vertebra.

Several investigators have argued that alterations in spi-nal balance and curvature are implicated in the developmentof early osteoarthritis and disc degeneration [112,113]. Tworecent studies explored the association between the degreeof lordosis and spinal osteoarthritis in Greek and Americanpopulations [27,106]. No significant association was foundbetween the lumbar angle and osteoarthritis in the lumbarspine in either study. Similar results were found by Linet al. [54] in a Chinese population. It is therefore suggestedthat lumbar lordosis is neither an outcome nor a contributorin the development of spinal osteoarthritis.

In a recent study [27], intervertebral disc narrowing wasnot found to be associated with the lordosis angle, which isin accord with Lebkowski et al. [105], who did not find di-minished lordosis in patients with lumbar degenerative diskdisease. Additional studies are needed to confirm thesefindings, which may have potential implications in diagnos-ing disc pathology and disc replacement surgery.

Lumbar lordosis and low back pain

The question of whether patients who suffer from LBPhave different lordosis angles than nonsufferers is not clear-cut. It has been claimed that flattening or loss of normallumbar lordosis is an important clinical sign of back prob-lems [114,115]; the patient is thought to keep the spinestraight to reduce pain. This view has been challenged byseveral radiologic studies suggesting that patients withchronic LBP have either no difference [48,52,116,117] orincreased lumbar lordosis compared with controls [118].These dissimilar results may be explained by different eti-ologies of LBP in the studies.

Lumbar lordosis and general health

Christensen and Hartvigsen [119] conducted a systematiccritical literature review of epidemiologic (cross-sectional,case-control, cohort) studies to determine whether sagittalspinal curves were associated with general health. Theyconcluded that there is no evidence of an association be-tween sagittal spinal curves and health, including spinalpain.

Lumbar lordosis reconstruction

Lumbar lordosis is formed by the sum of bodies and discwedge angles. When the intervertebral discs are gone orwhen the vertebral bodies are compressed, the lordoticangle might change. Loss of lordosis can also occur afterinstrumented spinal fusion, ‘‘flat-back syndrome’’ [120].

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The loss of normal lordosis often results in sagittal spinalimbalance, persistent back pain, and increased muscle fa-tigue [120,121]; therefore, there is a need for accurate re-construction of the lordotic curvature. Because the normalrange of lordosis is so wide (30�–80� using the Cobbmethod), it is difficult to determine the normal/optimal lor-dosis angle for an individual. The current knowledge baseis insufficient for accurate reconstruction of the lordoticcurvature, which is very important for spinal surgery[122]. Recent results showed that facet inclination can ac-curately predict lordosis [14] in the adult human popula-tion. Additional studies are needed to confirm thesefindings, which in turn might be an important tool in spinalsurgery. Another possible way to speculate what the nor-mal/optimal lordosis will be is based on pelvic morphology,especially pelvic incidence. Boulay et al. [123] found thata low value of pelvic incidence, 44� or less, was associatedwith decreases in the sacral slope, thus flattening the lordo-sis. A high value of pelvic incidence, 62� or more, increasesthe sacral slope, thus the lordosis is more pronounced. Be-cause pelvic incidence does not vary with age and otherpostural changes, and because it is highly correlated withlumbar lordosis in a healthy adult population, it may bean important tool for lordotic reconstruction. RecentlyChang et al. [121] reconstructed the lordotic curvature in94 patients with sagittal imbalance owing to lumbar kypho-sis. The authors used the center of gravity and line of grav-ity to align the pelvis, and based on pelvic alignmentreconstructed the lordotic curvature.

Conclusions

Lumbar lordosis is an important postural feature of sag-ittal spinal balance. However, many controversies related toits evaluation and associated factors exist. First, the numberof evaluated vertebrae varies among researchers. We sug-gest using a uniform measurement method (Cobb’smethod) to measure between the superior endplate of thefirst lumbar vertebra to the superior endplate of the first sa-cral vertebra. Second, the position of lordosis evaluation:the most functional and common method are X-rays takenin a standing position. We believe that this position shouldbe the position of choice when studying lordosis. However,recently more and more studies have begun to use com-puted tomography or MRI to study spinal pathologies. Amajority of studies showed that lordosis of the patient whilein a supine position with legs straight (supine extended po-sition) is comparable with one measured when the patientwas standing. Therefore, this position should also be ac-knowledged in future studies. Third, there is still inconclu-sive evidence regarding the association of the lordosis anglewith age, gender, ethnicity, occupation, and leisure physicalactivity. Additional studies are needed to confirm the pres-ence/absence of such associations. Fourth, the lumbar lor-dosis angle is positively and significantly associated withspondylolysis and isthmic spondylolisthesis, but no

associations have been found with other spinal degenerativefeatures. Inconclusive evidence exists as to an associationbetween lumbar lordosis and LBP. We believe that addi-tional studies are needed to evaluate these associations,which can help in the understanding of pathophysiologyunderlying spinal disorders and LBP, assist in recognizingindividuals at risk for spinal disorders and LBP, and inthe development of prevention and treatment strategies. Inconclusion, the optimal lordotic range remains unknownand may be related to a variety of individual factors suchas weight, activity, muscular strength and flexibility ofthe spine and lower extremities.

Acknowledgments

The authors thank Dr Hayuta Pessah for the illustrationsand Mrs Phyllis Kornspan for her editorial assistance.

References

[1] Adams MA, Mannion AF, Dolan P. Personal risk factors for first-

time low back pain. Spine 1999;24:2497–505.

[2] Berlemann U, Jeszenszky DJ, Buhler DW, Harms J. The role of

lumbar lordosis, vertebral end-plate inclination, disc height, and

facet orientation in degenerative spondylolisthesis. J Spinal Disord

1999;12:68–73.

[3] Booth KC, Bridwell KH, Lenke LG, et al. Complications and pre-

dictive factors for the successful treatment of flatback deformity

(fixed sagittal imbalance). Spine 1999;24:1712–20.

[4] Chen IR, Wei TS. Disc height and lumbar index as independent pre-

dictors of degenerative spondylolisthesis in middle-aged women

with low back pain. Spine 2009;34:1402–9.

[5] Jang JS, Lee SH, Min JH, Maeng DH. Influence of lumbar lordosis

restoration on thoracic curve and sagittal position in lumbar degen-

erative kyphosis patients. Spine 2009;34:280–4.

[6] Giglio CA, Volpon JB. Development and evaluation of thoracic ky-

phosis and lumbar lordosis during growth. J Child Orthop 2007;1:

187–93.

[7] Mac-Thiong JM, Labelle H, Berthonnaud E, et al. Sagittal spinopel-

vic balance in normal children and adolescents. Eur Spine J

2007;16:227–34.

[8] Claus AP, Hides JA, Moseley GL, Hodges PW. Different ways to

balance the spine: subtle changes in sagittal spinal curves affect re-

gional muscle activity. Spine 2009;34:E208–14.

[9] Vaz G, Roussouly P, Berthonnaud E, Dimnet J. Sagittal morphology

and equilibrium of pelvis and spine. Eur Spine J 2002;11:80–7.

[10] Vialle R, Levassor N, Rillardon L, et al. Radiographic analysis of

the sagittal alignment and balance of the spine in asymptomatic sub-

jects. J Bone Joint Surg Am 2005;87:260–7.

[11] Been E, Barash A, Pessah H, Peleg S. A new look at the geometry of

the lumbar spine. Spine 2010;35:E1014–7.

[12] Cheng XG, Sun Y, Boonen S, et al. Measurements of vertebral shape

by radiographic morphometry: sex differences and relationships

with vertebral level and lumbar lordosis. Skeletal Radiol 1998;27:

380–4.

[13] Been E, Barash A, Marom A, Kramer PA. Vertebral bodies or discs:

which contributes more to human-like lumbar lordosis? Clin Orthop

Relat Res 2010;468:1822–9.

[14] Been E, Pessah H, Been L, et al. New method for predicting the

lumbar lordosis angle in skeletal material. Anat Rec 2007;290:

1568–73.

[15] Roussouly P, Nnadi C. Sagittal plane deformity: an overview of in-

terpretation and management. Eur Spine J 2010;19:1824–36.

9E. Been and L. Kalichman / The Spine Journal - (2013) -

[16] Schwab F, Patel A, Ungar B, et al. Adult spinal deformity-

postoperative standing imbalance: how much can you tolerate? An

overview of key parameters in assessing alignment and planning

corrective surgery. Spine 2010;35:2224–31.

[17] Ostrowska B, Rozek-Mroz K, Giemza C. Body posture in elderly,

physically active males. Aging Male 2003;6:222–9.

[18] Abitbol MM. Evolution of the lumbosacral angle. Am J Phys

Anthropol 1987;72:361–72.

[19] Dimeglio A, Bonnel F. Le rachis en croissance. Paris, France:

Springer-Verlag, 1990.

[20] Choufani E, Jouve JL, Pomero V, et al. Lumbosacral lordosis in fetal

spine: genetic or mechanic parameter. Eur Spine J 2009;18:1342–8.

[21] Reichmann S, Lewin T. The development of the lumbar lordosis. A

post mortem study on excised lumbar spines. Arch Orthop Unfall-

chir 1971;69:275–85.

[22] Cil A, Yazici M, Uzumcugil A, et al. The evolution of sagittal seg-

mental alignment of the spine during childhood. Spine 2005;30:

93–100.

[23] Willner S, Johnson B. Thoracic kyphosis and lumbar lordosis during

the growth period in children. Acta Paediatr Scand 1983;72:873–8.

[24] Schuller S, Charles YP, Steib JP. Sagittal spinopelvic alignment and

body mass index in patients with degenerative spondylolisthesis.

Eur Spine J 2011;20:713–9.

[25] Suzuki H, Endo K, Kobayashi H, et al. Total sagittal spinal align-

ment in patients with lumbar canal stenosis accompanied by inter-

mittent claudication. Spine 2010;35:E344–6.

[26] Andreasen ML, Langhoff L, Jensen TS, Albert HB. Reproduction of

the lumbar lordosis: a comparison of standing radiographs versus

supine magnetic resonance imaging obtained with straightened

lower extremities. J Manipulative Physiol Ther 2007;30:26–30.

[27] Kalichman L, Li L, Hunter DJ, Been E. Association between com-

puted tomography–evaluated lumbar lordosis and features of spinal

degeneration, evaluated in supine position. Spine J 2011;11:308–15.

[28] Gracovetsky SA, Zeman V, Carbone AR. Relationship between lor-

dosis and the position of the centre of reaction of the spinal disc.

J Biomed Eng 1987;9:237–48.

[29] Pazos V, Cheriet F, Danserau J, et al. Reliability of trunk shape mea-

surements based on 3-D surface reconstructions. Eur Spine J

2007;16:1882–91.

[30] Zabjek KF, Leroux MA, Coillard C, et al. Evaluation of segmental

postural characteristics during quiet standing in control and idio-

pathic scoliosis patients. Clin Biomech 2005;20:483–90.

[31] Penha PJ, Casarotto RA, Sacco ICN, et al. Qualitative postural anal-

ysis between boys and girls of 7 and 10 years of age. Revista Bra-

sileira de Fisioterapia 2008;12:386–91.

[32] Poussa MS, Heliovaara MM, Seitsamo JT, et al. Development of

spinal posture in a cohort of children from the age of 11 to 22 years.

Eur Spine J 2005;14:738–42.

[33] Vrtovec T, Pernus F, Likar B. A review of methods for quantitative

evaluation of spinal curvature. Eur Spine J 2009;18:593–607.

[34] Letafatkar A, Amirsasan R, Abdolvahabi Z, Hadadnezhad M. Reli-

ability and validity of the AutoCAD software method in lumbar lor-

dosis measurement. J Chiropr Med 2011;10:240–7.

[35] Celan D, Palfy M, Bracun D, et al. Measurement of spinal sagittal

curvatures using the laser triangulation method. Coll Antropol

2012;36:179–86.

[36] Fortin C, Feldman DE, Cheriet F, Labelle H. Validity of a quantita-

tive clinical measurement tool of trunk posture in idiopathic scolio-

sis. Spine 2010;35:E988–94.

[37] Levine D, Colston MA, Whittle MW, et al. Sagittal lumbar spine po-

sition during standing, walking, and running at various gradients.

J Athl Train 2007;42:29–34.

[38] Danielson B, Willen J. Axially loaded magnetic resonance image of

the lumbar spine in asymptomatic individuals. Spine 2001;26:2601–6.

[39] Marks M, Stanford C, Newton P. Which lateral radiographic posi-

tioning technique provides the most reliable and functional repre-

sentation of a patient’s sagittal balance? Spine 2009;34:949–54.

[40] Hirasawa Y, Bashir WA, Smith FW, et al. Postural changes of the

dural sac in the lumbar spines of asymptomatic individuals using

positional stand-up magnetic resonance imaging. Spine 2007;32:

E136–40.

[41] Madsen R, Jensen TS, Pope M, et al. The effect of body position and

axial load on spinal canal morphology: an MRI study of central spi-

nal stenosis. Spine 2008;33:61–7.

[42] Schmid MR, Stucki G, Duewell S, et al. Changes in cross-sectional

measurementsof the spinal canal and intervertebral foraminaas a func-

tion of body position: in vivo studies on an open-configuration MR

system. AJR Am J Roentgenol 1999;172:1095–102.

[43] Mauch F, Jung C, Huth J, Bauer G. Changes in the lumbar spine of

athletes from supine to the true-standing position in magnetic reso-

nance imaging. Spine 2010;35:1002–7.

[44] De Carvalho DE, Soave D, Ross K, Callaghan JP. Lumbar spine and

pelvic posture between standing and sitting: a radiologic investiga-

tion including reliability and repeatability of the lumbar lordosis

measure. J Manipulative Physiol Ther 2010;33:48–55.

[45] Karadimas EJ, Siddiqui M, Smith FW, Wardlaw D. Positional MRI

changes in supine versus sitting postures in patients with degenera-

tive lumbar spine. J Spinal Disord Tech 2006;19:495–500.

[46] Kim MS, Chung SW, Hwang C, et al. A radiographic analysis of

sagittal spinal alignment for the standardization of standing lateral

position. J Korean Orthop Assoc 2005;40:861–7.

[47] Vedantam R, Lenke LG, Bridwell KH, et al. The effect of vari-

ation in arm position on sagittal spinal alignment. Spine 2000;25:

2204–9.

[48] Murrie VL, Dixon AK, Hollingworth W, et al. Lumbar lordosis:

study of patients with and without low back pain. Clin Anat

2003;16:144–7.

[49] Naido M. The evaluation of radiographic measurements of the lum-

bar spine in young to middle aged Indian females in Durban. Dur-

ban, South Africa: Durban University of Technology, 2008:111.

[50] Youdas JW, Garrett TR, Egan KS, Therneau TM. Lumbar lordosis

and pelvic inclination in adults with chronic low back pain. Phys

Ther 2000;80:261–75.

[51] Youdas JW, Garrett TR, Harmsen S, et al. Lumbar lordosis and pelvic

inclination of asymptomatic adults. Phys Ther 1996;76:1066–81.

[52] Tuzun C, Yorulmaz I, Cindas A, Vatan S. Low back pain and pos-

ture. Clin Rheumatol 1999;18:308–12.

[53] Amonoo-Kuofi HS. Changes in the lumbosacral angle, sacral incli-

nation and the curvature of the lumbar spine during aging. Acta

Anat 1992;145:373–7.

[54] Lin RM, Jou IM, Yu CY. Lumbar lordosis: normal adults. J Formos

Med Assoc 1992;91:329–33.

[55] Korovessis PG, Stamatakis MV, Baikousis AG. Reciprocal angula-

tion of vertebral bodies in the sagittal plane in an asymptomatic

Greek population. Spine 1998;23:700–4; discussion 704–5.

[56] Takao S, Sakai T, Sairyo K, et al. Radiographic comparison between

male and female patients with lumbar spondylolysis. J Med Invest

2010;57:133–7.

[57] Torgerson WR, Dotter WE. Comparative roentgenographic study of

the asymptomatic and symptomatic lumbar spine. J Bone Joint Surg

Am 1976;58:850–3.

[58] Wojtys EM, Ashton-Miller JA, Huston LJ, Moga PJ. The association

between athletic training time and the sagittal curvature of the im-

mature spine. Am J Sports Med 2000;28:490–8.

[59] Middleditch A, Oliver J. Functional anatomy of the spine. 2nd ed.

Oxford, UK: Butterworth-Heinemann, 2005.

[60] Fernand R, Fox DE. Evaluation of lumbar lordosis. A prospective

and retrospective study. Spine 1985;10:799–803.

[61] Gelb DE, Lenke LG, Bridwell KH, et al. An analysis of sagittal spi-

nal alignment in 100 asymptomatic middle and older aged volun-

teers. Spine 1995;20:1351–8.

[62] Stagnara P, De Mauroy JC, Dran G, et al. Reciprocal angulation of

vertebral bodies in a sagittal plane: approach to references for the

evaluation of kyphosis and lordosis. Spine 1982;7:335–42.

10 E. Been and L. Kalichman / The Spine Journal - (2013) -

[63] Mosner EA, Bryan JM, Stull MA, Shippee R. A comparison of ac-

tual and apparent lumbar lordosis in black and white adult females.

Spine 1989;14:310–4.

[64] Guo JM, Zhang GQ, Alimujiang. [Effect of BMI and WHR on lum-

bar lordosis and sacrum slant angle in middle and elderly women],

[in Chinese]. Zhongguo Gu Shang 2008;21:30–1.

[65] Moore KL, Dalley AF. Clinically oriented anatomy. 6th ed. Phila-

delphia, PA: Lippincott Williams & Wilkins, 2009.

[66] Smith AJ, O’Sullivan PB, Beales DJ, et al. Trajectories of childhood

body mass index are associated with adolescent sagittal standing

posture. Int J Pediatr Obes 2011;6:e97–106.

[67] Naseri N, Fakhari Z, Senobari M, et al. The relationship between

pelvic tilt and lumbar lordosis with muscle tightness, and muscle

strength in healthy female subjects. J Mod Rehabil 2010;3:

383–6.

[68] Mcllwraith B. Loss of the lumbar curve in the driving seat: a twenty

person study. Brit Ost J 1996;29:19–23.

[69] Nourbakhsh MR, Moussavi SJ, Salavati M. Effects of lifestyle and

work-related physical activity on the degree of lumbar lordosis and

chronic low back pain in a Middle East population. J Spinal Disord

2001;14:283–92.

[70] Pietila TA, Stendel R, Kombos T, et al. Lumbar disc herniation in

patients up to 25 years of age. Neurol Med Chir 2001;41:340–4.

[71] Whitcome KK, Shapiro LJ, Lieberman DE. Fetal load and the evo-

lution of lumbar lordosis in bipedal hominins. Nature 2007;450:

1075–8.

[72] Colliton J. Back pain and pregnancy: active management strategies.

Phys Sportsmed 1996;24:89–93.

[73] Calguneri M, Bird HA, Wright V. Changes in joint laxity occurring

during pregnancy. Ann Rheum Dis 1982;41:126–8.

[74] Marnach ML, Ramin KD, Ramsey PS, et al. Characterization of the

relationship between joint laxity and maternal hormones in preg-

nancy. Obstet Gynecol 2003;101:331–5.

[75] Cunningham DJ. The lumbar curve in man and apes. Nature

1886;33:378–9.

[76] Fahrni WH, Trueman GE. Comparative radiological study of the

spines of a primitive population with North Americans and Northern

Europeans. J Bone Joint Surg Br 1965;47:552–5.

[77] Patrick JM. Thoracic and lumbar spinal curvatures in Nigerian

adults. Ann Hum Biol 1976;3:383–6.

[78] Hanson P, Magnusson SP, Simonsen EB. Differences in sacral angu-

lation and lumbosacral curvature in black and white young men and

women. Acta Anat 1998;162:226–31.

[79] Lonner BS, Auerbach JD, Sponseller P, et al. Variations in pelvic

and other sagittal spinal parameters as a function of race in adoles-

cent idiopathic scoliosis. Spine 2010;35:E374–7.

[80] Goldberg C, Chiarello CM. Lumbar sagittal plane mobility and lor-

dosis in the well elderly as related to gender and activity level. Phys

Occup Ther Geriatr 2001;19:17–34.

[81] Chen YL. Geometric measurements of the lumbar spine in Chinese

men during trunk flexion. Spine 1999;24:666–9.

[82] Miller NH. Genetics of familial idiopathic scoliosis. Clin Orthop

Relat Res 2007;462:6–10.

[83] Dryden IL, Oxborrow N, Dickson R. Familial relationships of nor-

mal spine shape. Stat Med 2008;27:1993–2003.

[84] Jull GA, Janda V. Muscles and motor control in low-back pain: as-

sessment and management. In: Twomey LT, Taylor JR, eds. Physical

therapy of the low back. New York, NY: Churchill Livingstone,

1987:253–78.

[85] Walker ML, Rothstein JM, Finucane SD, Lamb RL. Relationships

between lumbar lordosis, pelvic tilt, and abdominal muscle perfor-

mance. Phys Ther 1987;67:512–6.

[86] Cailliet R. Low back pain syndrome. 5th ed. Philadelphia, PA: F. A.

Davis Company, 1995.

[87] Polly DW Jr, Kilkelly FX, McHale KA, et al. Measurement of lum-

bar lordosis. Evaluation of intraobserver, interobserver, and tech-

nique variability. Spine 1996;21:1530–5; discussion 1535–6.

[88] Heino JG, Godges JJ, Carter CL. Relationship between hip exten-

sion range of motion and postural alignment. J Orthop Sports Phys

Ther 1990;12:243–7.

[89] McCarthy JJ, Betz RR. The relationship between tight hamstrings

and lumbar hypolordosis in children with cerebral palsy. Spine

2000;25:211–3.

[90] Avanzi O, Chih LY, Meves R, et al. Thoracic kyphosis and ham-

strings: an aesthetic-functional correlation. Acta Ortop Bras

2007;15:93–6.

[91] Hennessey L, Watson AW. Flexibility and posture assessment in re-

lation to hamstring injury. Br J Sports Med 1993;27:243–6.

[92] Hamilton WJ. Textbook of human anatomy. Baltimore, MD: Harper

& Row, 1972.

[93] Woodburne RT, Burke WE. Essentials of human anatomy. New

York, NY: Oxford University Press, 1988.

[94] Bogduk N, Pearcy M, Hadfield G. Anatomy and biomechanics of

the psoas major. Clin Biomech 1992;7:109–19.

[95] Nachemson A. The possible importance of the psoas muscle for sta-

bilization of the lumbar spine. Acta Orthop Scand 1968;39:47–57.

[96] Penning L. Psoas muscle and lumbar spine stability: a concept unit-

ing existing controversies. Critical review and hypothesis. Eur Spine

J 2000;9:577–85.

[97] Uetake T, Ohtsuki F. Sagittal configuration of spinal curvature line

in sportsmen using Moire technique. Okajimas Folia Anat Jpn

1993;70:91–103.

[98] Franz JR, Paylo KW, Dicharry J, et al. Changes in the coordination

of hip and pelvis kinematics with mode of locomotion. Gait Posture

2009;29:494–8.

[99] Wodecki P, Guigui P, Hanotel MC, et al. [Sagittal alignment of the

spine: comparison between soccer players and subjects without

sports activities], [in French]. Rev Chir Orthop Reparatrice Appar

Mot 2002;88:328–36.

[100] Forster R, Penka G, Bosl T, Schoffl VR. Climber’s back–form and

mobility of the thoracolumbar spine leading to postural adaptations

in male high ability rock climbers. Int J Sports Med 2009;30:53–9.

[101] Nilsson C, Wykman A, Leanderson J. Spinal sagittal mobility and

joint laxity in young ballet dancers. A comparative study between

first-year students at the Swedish Ballet School and a control group.

Knee Surg Sports Traumatol Arthrosc 1993;1:206–8.

[102] Milosavljevic S, Milburn PD, Knox BW. The influence of occupa-

tion on lumbar sagittal motion and posture. Ergonomics 2005;48:

657–67.

[103] Sarikaya S, Ozdolap S, Gumustass S, Koc U. Low back pain and

lumbar angles in Turkish coal miners. Am J Ind Med 2007;50:92–6.

[104] Harrison DD, Cailliet R, Janik TJ, et al. Elliptical modeling of the

sagittal lumbar lordosis and segmental rotation angles as a method

to discriminate between normal and low back pain subjects. J Spinal

Disord 1998;11:430–9.

[105] Lebkowski WJ, Lebkowska U, Niedzwiecka M, Dzieciol J. The ra-

diological symptoms of lumbar disc herniation and degenerative

changes of the lumbar intervertebral discs. Med Sci Monit

2004;10(3 Suppl):112–4.

[106] Papadakis M, Papadokostakis G, Kampanis N, et al. The association

of spinal osteoarthritis with lumbar lordosis. BMC Musculoskelet

Disord 2010;11:1.

[107] Rosenberg NJ. Degenerative spondylolisthesis. Predisposing factors.

J Bone Joint Surg Am 1975;57:467–74.

[108] Antoniades SB, Hammerberg KW, DeWald RL. Sagittal plane con-

figuration of the sacrum in spondylolisthesis. Spine 2000;25:

1085–91.

[109] Been E, Li L, Hunter DJ, Kalichman L. Geometry of the vertebral

bodies and the intervertebral discs in lumbar segments adjacent to

spondylolysis and spondylolisthesis: pilot study. Eur Spine J

2011;20:1159–65.

[110] Huang KY, Lin RM, Lee YL, Li JD. Factors affecting disability and

physical function in degenerative lumbar spondylolisthesis of L4-5:

evaluation with axially loaded MRI. Eur Spine J 2009;18:1851–7.

11E. Been and L. Kalichman / The Spine Journal - (2013) -

[111] Labelle H, Roussouly P, Chopin D, et al. Spino-pelvic alignment af-

ter surgical correction for developmental spondylolisthesis. Eur

Spine J 2008;17:1170–6.

[112] Umehara S, Zindrick MR, Patwardhan AG, et al. The biomechanical

effect of postoperative hypolordosis in instrumented lumbar fusion

on instrumented and adjacent spinal segments. Spine 2000;25:

1617–24.

[113] Kumar MN, Baklanov A, Chopin D. Correlation between sagittal

plane changes and adjacent segment degeneration following lumbar

spine fusion. Eur Spine J 2001;10:314–9.

[114] McRae R. Clinical orthopaedic examination. 4th ed. New York, NY:

Churchill Livingstone, 1997.

[115] Kenna CJ, Murtagh JE. Back pain and spinal manipulation. 2nd ed.

Oxford, UK: Butterworth-Heinemann, 1997.

[116] Hansson T, Bigos S, Beecher P, Wortley M. The lumbar lordosis in

acute and chronic low-back pain. Spine 1985;10:154–5.

[117] Nourbakhsh MR, Arab AM. Relationship between mechanical fac-

tors and incidence of low back pain. J Orthop Sports Phys Ther

2002;32:447–60.

[118] Christie HJ, Kumar S, Warren SA. Postural aberrations in low back

pain. Arch Phys Med Rehabil 1995;76:218–24.

[119] Christensen ST, Hartvigsen J. Spinal curves and health: a systematic

critical review of the epidemiological literature dealing with associ-

ations between sagittal spinal curves and health. J Manipulative

Physiol Ther 2008;31:690–714.

[120] Moskowitz A, Moe JH, Winter RB, Binner H. Long-term follow-up

of scoliosis fusion. J Bone Joint Surg Am 1980;62:364–76.

[121] Chang KW, Leng X, Zhao W, et al. Quality control of reconstructed

sagittal balance for sagittal imbalance. Spine 2011;36:E186–97.

[122] Lin RM, Lee RS, Huang YM, et al. Analysis of lumbosacral lordosis

using standing lateral radiographs through curve reconstruction. Bi-

omed Eng Appl Basis Commun 2002;14:149–56.

[123] Boulay C, Tardieu C, Hecquet J, et al. Sagittal alignment of spine

and pelvis regulated by pelvic incidence: standard values and pre-

diction of lordosis. Eur Spine J 2006;15:415–22.

[124] Neuschwander TB, Cultrone J, Marcia BR, et al. The effect of back-

packs on the lumbar spine in children: a standing magnetic reso-

nance imaging study. Spine 2010;35:83–8.