The Spine Journal
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Perspective
Lumbar lordosis Ella Been, PT, PhDa,b,*, Leonid Kalichman, PT, PhDc a Physical Therapy Department, Zefat Academic College, Safed, Israel Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel c Department of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel b
Received 3 October 2011; revised 22 June 2013; accepted 21 July 2013
Abstract
Lumbar lordosis is a key postural component that has interested both clinicians and researchers for many years. Despite its wide use in assessing postural abnormalities, there remain many unanswered questions regarding lumbar lordosis measurements. Therefore, in this article we reviewed different factors associated with the lordosis angle based on existing literature and determined normal values of lordosis. We reviewed more than 120 articles that measure and describe the different factors associated with the lumbar lordosis angle. Because of a variety of factors influencing the evaluation of lumbar lordosis such as how to position the patient and the number of vertebrae included in the calculation, we recommend establishing a uniform method of evaluating the lordosis angle. Based on our review, it seems that the optimal position for radiologic measurement of lordosis is standing with arms supported while shoulders are flexed at a 30 angle. There is evidence that many factors, such as age, gender, body mass index, ethnicity, and sport, may affect the lordosis angle, making it difficult to determine uniform normal values. Normal lordosis should be determined based on the specific characteristics of each individual; we therefore presented normal lordosis values for different groups/populations. There is also evidence that the lumbar lordosis angle is positively and significantly associated with spondylolysis and isthmic spondylolisthesis. However, no association has been found with other spinal degenerative features. Inconclusive evidence exists for association between lordosis and low back pain. Additional studies are needed to evaluate these associations. The optimal lordotic range remains unknown and may be related to a variety of individual factors such as weight, activity, muscular strength, and flexibility of the spine and lower extremities. Ó 2013 Elsevier Inc. All rights reserved.
Keywords:
Spine; Posture; Lordosis; Spinal pathology; Spinal measurements
Introduction Research studies have shown an increasing recognition of the functional and clinical importance of lumbar lordosis [1–5]. It is a key feature in maintaining sagittal balance. Sagittal balance or ‘‘neutral upright sagittal spinal alignment’’ is a postural goal of surgical, ergonomic, and physiotherapeutic intervention. However, a wide variety of thoracic and lumbar spinal curves may correspond with the accepted criterion of sagittal balance (50 mm of C7–S1 sagittal deviation in asymptomatic adults while standing) [6,7], making FDA device/drug status: Not applicable. Author disclosures: EB: Nothing to disclose. LK: Nothing to disclose. * Corresponding author. Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. Tel.: þ972-3-6408287. E-mail address:
[email protected] (E. Been) 1529-9430/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.spinee.2013.07.464
it difficult for surgeons, researchers, therapists, and patients to know if they are examining or achieving the same postural goal [8]. In this topical review, we determined, based on existing literature, normal and abnormal parameters of lumbar lordosis and examine the different factors associated with the lordosis angle. To accomplish this, we searched PubMed, PEDro, EMBASE, and Google scholar databases (inception–2012) for the key words ‘‘spine’’, ‘‘spinal’’, ‘‘lordosis’’, ‘‘lumbar’’, ‘‘posture’’, ‘‘pathology’’, ‘‘measurements’’, and combinations of key words. All relevant articles in English were reviewed. Pertinent secondary references were also retrieved. We are aware that this traditional approach to reviews has much more potential for bias than systematic reviews or meta-analyses; however, we have endeavored to be inclusive and open minded. We also consulted experts in spinal surgery and radiology to produce this review on lumbar lordosis.
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Anatomy of lumbar lordosis Lumbar lordosis is the inward (ventral) curvature of the lumbar spine formed by the wedging of lumbar vertebral bodies and the intervertebral disks [9,10] (Fig. 1). Dorsal wedging of the vertebral bodies and disks (anterior part longer than posterior) increases the lordosis angle, whereas more ventral wedging of these structures (anterior part shorter than posterior) reduces the lordosis angle (Fig. 1). Lumbar lordosis is similarly influenced by the shape of the vertebral bodies and the shape of the intervertebral discs, because each account for nearly 50% of the variability seen in lordotic angles of adults [11,12]. Each of the five lumbar segments (vertebral body and the adjacent disc) contribute to the lordosis. The last lumbar segment (L5) contributes almost 40% to overall lordosis. The first segment (L1) contributes only 5% [13]. The lordosis angle also correlates with the orientation of the inferior articular processes—greater lordosis correlates with more dorsally (horizontally) inclined inferior articular (facet) processes in relation to the vertebral bodies [14] (Fig. 1). A close correlation exists between the lordosis angle (the common measure of lumbar lordosis) and other postural variables. Many researchers have found a high correlation between the lumbar lordosis angle and pelvic and thoracic orientation in space. Greater lordosis angles correlate with a more horizontally inclined sacrum (increased sacral slope, more vertical sacral endplate), increased pelvic incidence, and increased pelvic tilt [15,16]. Most researchers found that greater lordosis usually correlates with higher thoracic kyphosis, but cases of increased lordosis with reduced thoracic kyphosis have also been reported [15–17]. Small lordosis angles usually correlate with a more vertical sacrum, small pelvic tilt, pelvic incidence, and reduced thoracic kyphosis; however, cases of reduced lumbar lordosis with increased thoracic kyphosis have also been detailed [15–17].
Ontogenetic development of the lumbar lordosis Although many authors believe that the spine of the human fetus shows only one kyphotic curvature from cranial to caudal [18,19], studies have shown that the fetal spine has 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 gestation demonstrated that all fetuses had lordotic lumbar curvature with a mean radius of 18.7 mm. This lordosis was uncorrelated with gestational age, which means that it was not related to growth and, according to the authors, might have been genetically determined. Few researchers have examined the lordosis angle in early childhood, with Reichmann and Lewin [21], being a notable exception. They found that lordosis angles increased during the first 3 years of life, claiming that at the age of 3, the child’s spine reaches an adult-like lordosis
Fig. 1. Measurements of lumbar lordosis Cobb’s angle (LA), vertebral body (B) and intervertebral disc (D) wedging, and facet joint angle (F).
angle. Other researchers, however, found that the lordosis angle continues to increase during later childhood and puberty [22,23] even until the age of 20 [6] (Table 1). For example, Cil et al. [22] demonstrated an increase of the lordosis angle from 44.3 at 3 to 6 years to 54.6 at 13 to 15 years. It can be concluded that lumbar lordosis begins to develop in fetuses. The major increase of the lordosis angle occurs during the first 3 years of life and continues increasing at least until puberty. There are many gaps in the current knowledge regarding the ontogenetic development of lumbar lordosis. Additional studies are essential to fill in this gap and to identify the factors that determine lordosis development. Ascertaining the normal values of lordosis in children is essential for early detection and treatment of postural abnormalities. Evaluation of lumbar lordosis Number of evaluated vertebrae One of the fundamental questions regarding lordosis evaluation is the number of vertebrae or segments (vertebra and adjacent intervertebral disk) measured. The most common evaluation of lumbar lordosis uses the angle formed by all five lumbar segments (L1–L5). When employing Cobb’s
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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
Neuschwander et al. [124] Mac-Thiong et al. [7] Giglio and Volpon [6]
Cobb’s angle (L1–S1) Arc between L1 and L5 Panthograph (spinous processes L1–L5)
Standing Standing Standing
Willner and Johnson [23]
Spinal panthograph
Standing
3–6 7–9 10–12 13–15 1162 12.163.3 5 10 15 20 8, boys 12, boys 16, boys 8, girls 12, girls 16, girls
51 37 32 31 8 341 16 30 22 17 48 63 74 50 64 81
44.3611.0 51.7611.5 57.3610.6 54.669.8 60.263.1 48611.7 2269 3267 33611 38610 33.669.3 3267.1 33.668.6 33.368.9 34.868.5 36.767.6
method, the upper line is drawn at the superior endplate of L1, and the lower line at the superior endplate of the sacrum (S1; Fig. 1). However, some researchers measure lordosis starting as high as T10*, others finish at L3. Some researchers do not include the lower lumbar segment (L5) or only do not include the last intervertebral disk L5–S1 in their measurements. Significant differences occur between lordosis angles when different numbers of vertebral segments are measured (Table 2). Therefore, we believe that it is crucial to measure exactly the same number of segments to compare the different studies. We suggest that measurements should include the vertebral bodies and intervertebral disks of L1–L5; in other words, measurements (Cobb’s method) should be performed between the superior endplate of the first lumbar vertebra and the superior endplate of the sacrum. The logic behind our suggestion is based on anatomic considerations, including all of the lumbar segments in the lumbar lordosis measurements. In addition, this is the most popular measurement of lumbar lordosis used today [22,24–27]; functionally, the five lumbar segments share a fundamental role in upright functions such as walking and running [28]. Table 2 Lordosis angle (Cobb’s method) measured in a standing position using different spinal levels Measurement between L1 superior end plateS1 superior end plate L1 inferior end plateS1 superior end plate L2 superior end plateS1 superior end plate L1 superior end plateL5 superior end plate L1 superior end plateL5 inferior end plate
Modified after Vialle et al. [10]
Modified after Been et al. [11]
58.5
51.3610.7
62
54.8
57
49
35
31.5
43611.2
39.6
Methods of measurement Many methods are used to evaluate lumbar lordosis. We divided the methods into clinical and imaging evaluation. Clinical examination evaluates the degree of lordosis directly on the individual’s body. Radiologic evaluation uses two-dimensional radiographs, three-dimensional (3D) computed tomography and MRI. Each method of evaluation has its advantages and disadvantages, but the major problem is that it is difficult to compare the measurements when performed by different methodologies. Clinical methods for evaluating lordosis angles include various 3D posture analysis systems and surface topography systems [29,30]. Most of these methods use the spinous processes of the lumbar vertebrae to evaluate the degree of lordosis [6]. The main advantage of these measurements is the lack of radiation, thus allowing frequent evaluation of the spinal curves, and better monitoring of the changes in the lordosis angle. The reproducibility of clinical methods is relatively high (interobserver intraclass correlation coefficient [ICC] is 0.70–0.85, [31,32]); however, it is not as high as with radiologic methods (interobserver ICC isO0.87 [33]). On the other hand, because clinical methods use surface anatomy to evaluate the lordosis angle, only moderate correlations with radiologic measurements were found. Comparisons between the patients are also problematic because of different paraspinal muscle development, thickness of subcutaneous fat, and anatomic variations in spinous processes length and orientation. Recently, a few articles have suggested the use of electronic or laser lordosis angle measurements. Letafatkar et al. [34] showed that using a flexible plastic ruler and an AutoCAD (arc) for lordosis angle measurements is a reliable and valid method, and suggested that this method may replace radiography in evaluating lumbar lordosis. Celan et al. [35] measured the lordosis and kyphosis angles using a laser triangulation method. Although there are sophisticated 3D posture analysis systems such as Optotrak (Northern Digital Inc., Waterloo, Canada), Vicon
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Fig. 3. Measurements of lumbar lordosis: anterior tangent, posterior tangent, centroid, and best fit ellipse.
Fig. 2. Two possible lumbar lordosis curves with the same Cobb’s angle.
(Vicon Motion Systems, Oxford, UK), Motion Analysis (Motion Analysis Corporation, Santa Rosa, CA, USA), and surface topography systems, these systems are not accessible for most clinicians [36]. These sophisticated 3D systems enable researchers to evaluate the lordosis angle in different postures and settings. For example, Levine et al. [37] used motion analysis systems to examine the lordosis angles during walking and running. Fortin et al. [36] presented a novel, promising technique for clinical posture assessment based on calculation of body angles and distances on photographs. This method has a relatively low cost, is easy to perform in a clinical setting, and there is no exposure to radiation. Photograph acquisition showed good inter- and intrarater reliability (ICCO0.991), but only moderate validity (r50.48) compared with radiographic evaluation of lordosis [36]. We therefore conclude that utilizing clinical methods for evaluating lordosis angles can be a useful tool for monitoring patients’ progress. However, clinical methods in their present form are unsuitable for research or clinical evaluation when absolute parameters of lumbar lordosis need to be measured. Many radiologic methods have been used to evaluate the lordosis angle on two-dimensional radiographs. The Cobb method (or modified Cobb method) has become the gold standard in measuring lumbar lordosis [33], using vertebral endplate lines to measure angles on sagittal radiographs. This method is very simple to perform, and has been proven highly reliable [33]. The strongest limitation of the Cobb method is that, theoretically, two spinal curvatures of different magnitudes may result in the same Cobb angle (Fig. 2); therefore, other methods have been developed in attempt to overcome this problem. These methods use different
anatomic landmarks on the vertebral bodies to evaluate the lordosis angle. For example, the anterior and the posterior tangent methods use the anterior or posterior vertebral body wall to determine the lordosis angle. The centroid method uses the center of the vertebral body to measure the lordosis angle. Some methods, such as the best-fit ellipse, construct a circular geometrical model of the lumbar spine (Fig. 3). All of these methods were found to be reliable in evaluating lordosis. A more detailed description of the different lordosis evaluation methods can be found in Vrtovec et al. [33] Position of measurement One of the fundamental variables in lordosis measurement is the position in which the measurements were taken, that is, standing, sitting, or lying down. Most lumbar lordosis studies use X-rays taken in the standing position, stating that this is the most functionally relevant position [38,39]. However, during the last two decades, more and more spinal clinical evaluations and research has been performed using computed tomography and MRI technologies that allow a much more detailed depiction of spinal anatomy and pathology. It is therefore important to understand how the subject’s position influences the lordosis angle. Recently, several authors [40,41] reported that a horizontal MRI with the patient supine and legs straight out (supine extended position) was comparable with a vertical MRI, where the patient stands. This is in agreement with earlier reports by Schmid et al. [42], who studied 12 young volunteers using a positional MRI. All aforementioned authors concluded that the supine extended position was a functionally relevant position and suggested that it could replace the upright extended position (Table 3). On the other hand, lordosis measured in the supine position, with bent hips and knees (psoas relaxed position), was found to be significantly smaller than when in a standing or supine extended position [43]. In an open MRI study, lordosis showed a significant increase of 6.3 (14%) from supine psoas relaxed position to a true standing position. Measuring the lordosis angle in sitting position All researchers agree that the lordotic curvature in a sitting position is significantly lower than in a standing position
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Table 3 Average lordosis angle measured in different positions Research
N
Modality
Hirasawa et al. [37] Madsen et al. [38] Mauch et al. [40] De Carvalho et al. [41]
29 16 35 8
MRI MRI MRI X-ray
Lying with extended legs 53.269.2 52
Lying in psoas relaxed position* 44 46.369.9
Standing
Sitting
53.3613.4 43.9y 52.668.9 63615
20.5612.7
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.
[26,40,42,44,45] (Table 3). Furthermore, Hirasawa et al. [40] demonstrated significant differences in lordosis angles between different sitting positions ranging from 3.1611.8 in a flexed sitting position to 46.2612.3 in an extended sitting position. We therefore feel that the sitting position cannot replace the standing position as the functionally relevant position. However, because sitting is one of the most common postures used in the modern world, the degree of lordosis exhibited during sitting may has its own significance. The effect of arm position on lordosis measurements Arm position in standing lateral radiographs may disturb sagittal balance and therefore alter the lordosis angle. The neutral position (arms placed at the sides of the body) is impractical because the arm bones overlay the spine and thus may interfere with the measurements. Several studies have compared different arm positions with a functional standing position with arms at the sides [46,47], and found that arm position in standing lateral radiographs did not significantly affect the lordosis angle. Although no differences were found between the different positions, both studies recommended the use of a standard position for repeated measurements of the lordosis angle. Marks et al. [39] used motion analysis laboratory and found that the lumbar angle measured from an X-ray taken in a standing position with the hands supported and shoulders slightly flexed (30 flexion at the shoulder) was comparable with the measurement taken in a functional standing position with arms at the side. They concluded that this seems to be the best way to move the arms, anterior to the spine, with the least effect on overall sagittal balance. The wide range of postures (standing, supine extended, and psoas-relaxed positions) and arm positions used to measure lumbar lordosis pose a problem when comparing data and establishing normal values of lordosis. We believe that a uniform method of evaluating the lordosis angle should be established to allow comparisons of clinical and research measurements. Based on our review, it seems that the optimal position for the radiologic measurement of lordosis is standing with arms supported while flexing the shoulder at a 30 angle. If standing is not possible, the lordotic angle should be measured in a supine position with straightened legs. In the clinical setting, there is a strong need to develop a method
that is reliable, comparable with radiographic measurements, easy to perform, and inexpensive. Factors associated with lumbar lordosis Age The commonly held opinion is that lumbar lordosis ‘flattens’ out with spinal problems and subsequent age-related degenerative changes [48]. However, most studies did not find an association between age and lordosis [27,48–51]. Other studies claimed that lumbar lordosis increases with age [52] or decreases only after the sixth decade [53]. On the other hand, no association was found between age and wedging of vertebral bodies and intervertebral discs [27]. Existing evidence, therefore, does not support the common opinion of lordosis flattening with age. However, the question of the lumbar lordosis angle changing with age is not fully resolved and more research is needed to understand 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 between the genders. Middleditch and Oliver [59] found no difference in the lumbar lordosis between males and females until middle age. However, other studies found that females have significantly greater lordosis angles (2 –5 ) than males [10,48,50,60,61]. Stagnara et al. [62] suggested that females apparently had greater lumbar lordosis owing to their greater buttock size. Mosner et al. [63], who conducted a study of actual and apparent lumbar lordosis in Caucasian and African-American females, agree with Stagnara’s view. Height and weight Most researchers agree that obesity, especially central (abdominal) obesity, increases the lordosis angle. Murrie et al. [48] found that lumbar lordosis was significantly greater (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 and Dalley [65] suggested that a hyperlordotic lumbar spine
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found in obese individuals was owing to a compensatory backward 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, Naseri et al. [67], who examined 75 Iranian women, Mcllwraith [68], and Naido [49] found poor correlation between lumbar lordosis and BMI. Naido [49] found a significant association (p5.004) between the height of the subjects and lumbar lordosis, which is in agreement with Nourbakhsh et al.’s findings [69]. It is possible that tall individuals have the increased loading in the lumbar area, which causes increased lordosis [70]. Pregnancy In two recent studies, the most significant increase in lumbar lordosis occurred in the late stages of pregnancy [65,71]. Nourbakhsh et al. [69] found that previous pregnancies and the number of pregnancies were associated with the lumbar lordosis degree [69]. There are several possible explanations for this phenomenon: a compensatory backward lean to improve balance owing to increased abdominal weight [72]; the muscular imbalance caused by overstretched weak abdominal muscles and strong back muscles might contribute to increased lordosis found in women with a high number of pregnancies; and during the last trimester of pregnancy a significant increase in joint laxity occurs [73,74]. It is possible that this hyperlaxity allows the increase of lumbar lordosis by softening the paraspinal ligaments. The new lordosis angle remains after delivery. Ethnicity As early as the end of the 19th century, Cunningham [75] indicated that differences in lordosis angles were ethnically related. Fahrni and Trueman [76] discovered smaller lordotic angles in a cadaver sample of Native Americans compared with Caucasians. Patrick [77], using external flexicurve measurements, found 20% higher lordosis angles in a Nigerian population compared with Europeans. Hanson et al. [78] and recently Lonner et al. [79] found that lordosis angles in African-Americans averaged 4 greater than Caucasians. Lonner et al.’s study was the largest study on this subject. However, the authors used an adolescent scoliotic population; thus, the results may not be applicable to the general population. On the other hand, many researchers found a similarity in the degree of lordotic curvature between populations. Mosner et al. [63] and Goldberg and Chiarello [80] found similar lumbar lordosis angles in Caucasians and African-Americans. Chen [81] compared the lordosis angles of 16 healthy Chinese men with that of Europeans and found no interracial differences. Mosner et al. [63] concluded that the clinician’s assumption that AfricanAmericans have a greater lordosis than Caucasians is based on an apparent increased lordosis owing to more prominent buttocks.
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Heritability Although heritability and genetics of scoliosis has been extensively studied [82], we found only one study that evaluated the familial correlations of normal spinal curves [83], finding significant positive familial correlations in lumbar lordosis measurements. All sibling groups showed a greater correlation of lordosis measurement than unrelated controls. Same-sex siblings had a greater correlation than different sex siblings. Muscles and lumbar lordosis It is widely accepted that abdominal and back musculatures affect pelvic inclination and lumbar lordosis while in a static, upright posture [84,85]. Many researchers [50,51,86,87] have suggested that lumbar lordosis and abdominal muscle function are related to each other. For example, the weakness of the abdominal muscle permits an anterior pelvic tilt and hyperlordotic posture [18,50,51]. On the other hand, strong abdominal muscles can tilt the pelvis posteriorly and concurrently reduce lordosis. At the same time, strong back muscles can tilt the pelvis anteriorly, thus increasing lumbar lordosis. Some researchers examined the association between abdominal muscle strength and the lordosis angle, but found no conclusive evidence of a relationship [51,85,88]. It is possible that, in the static position, the equilibrium between trunk flexors and extensors influenced the lumbar lordosis and not the strength of the specific muscle group. Only Kim et al. [46] examined the relationship between trunk muscle strength (abdominal vs. back muscles) and lumbar lordosis and found that the ratio of extensor torque to flexor torque was significantly related to the lordotic angle (Pearson’s correlation coefficient50.491; p!.01). Relatively strong spinal extensors and weak spinal flexors were associated with high lumbar lordosis and vice versa. The researchers concluded that an imbalance in trunk muscle strength can significantly influence the lordotic curve of the lumbar spine and might be a risk factor for potential low back pain (LBP). Hip muscles, such as the iliopsoas and hamstring, might also influence the degree of lordosis in a static upright posture. These muscles are able to move the pelvis in the sagittal plane—anterior and posterior pelvic tilt. Posterior pelvic tilt can result from contraction or tightness of the hamstring muscles, leading to a more horizontal sacral endplate and hypolordosis (the smaller lordosis would be necessary to keep the line of gravity close to the acetabulum). Although theoretically the hip muscles can influence the degree of lordosis, the evidence in the literature is inconclusive. Some authors found close correlation between tight hamstring muscles and hypolordosis [89], whereas others found no correlation between the two [67,90,91]. An ongoing debate exists as to the influence of the psoas major muscle on the lordotic curvature. Some researchers argue that it acts to flex the lumbar spine and therefore decrease the lordosis angle [92,93]. Others argue that it acts to increase the
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lordosis angle [94]. A third group of researchers claim that the role of the psoas major is to stabilize the lordotic lumbar spine in an upright posture by adapting its contraction to the momentary degree of lordosis imposed by other factors outside the lordosis, such as weight bearing [95,96]. Sport Few researchers have examined the relationship between the lordosis angle and sports activities. Wojtys et al. [58], reporting on a sample of 2,270 children 8 to 18 years old, found that athletes have a greater lordosis angle than nonathletes, and that the greater lordosis angle was associated with greater cumulative training time. The nature of the relationship between sports activity and development of the lordosis angle is not fully known. Uetake and Ohtsuki [97] examined the lordosis angle in athletes according to their sports and found that long distance runners and sprinters showed greater than average lordosis angles; rugby and soccer players showed average lordosis angles, and swimmers and body builders showed lower than average lordosis angles. It has been reported that running is associated with increased lumbar lordosis and anterior pelvic tilt [98]. Wodecki et al. [99] found increased lumbar lordosis in soccer players. Forster et al. [100] found high lordosis angles in high 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 occupation on sagittal spinal motion and posture. Their sample consisted of 64 sheep shearers and 64 nonshearers matched by age and anthropometry findings. Results showed that sheep shearers had hypolordosis of the lumbar spine and a flatter compensatory thoracic kyphotic curve compared with nonshearers. In a sample of 840 randomly selected Iranian subjects, Nourbakhsh et al. [69] reported no difference in the degree of lumbar lordosis angle between subjects who utilized tables and chairs versus sitting on the floor, worked in standing versus sitting postures, or performed strenuous versus light physical activity. Sarikaya et al. [103] assessed the incidence of LBP among Turkish coal miners (surface and underground) and investigated the relationship between the angles of the lumbar spine and LBP. They found no differences between the lordosis angles of the two groups of miners. At the same time, they reported a significant, negative correlation between lumbar lordosis and the number of years working as an underground miner. Lumbar lordosis, spinal degeneration, and low back pain Lumbar lordosis and spinal degeneration Numerous studies have evaluated the association between lumbar lordosis and spinal degeneration features
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[2,4,24,54,104–107]. Most researchers agree that the lumbar lordosis angle is positively and significantly associated with spondylolysis and isthmic spondylolisthesis [4,24,108–111]. A greater lordosis angle is thought to be a risk factor for developing spondylolysis and ventral slippage of the affected vertebra. Several investigators have argued that alterations in spinal balance and curvature are implicated in the development of early osteoarthritis and disc degeneration [112,113]. Two recent studies explored the association between the degree of lordosis and spinal osteoarthritis in Greek and American populations [27,106]. No significant association was found between the lumbar angle and osteoarthritis in the lumbar spine in either study. Similar results were found by Lin et al. [54] in a Chinese population. It is therefore suggested that lumbar lordosis is neither an outcome nor a contributor in the development of spinal osteoarthritis. In a recent study [27], intervertebral disc narrowing was not found to be associated with the lordosis angle, which is in accord with Lebkowski et al. [105], who did not find diminished lordosis in patients with lumbar degenerative disk disease. Additional studies are needed to confirm these findings, which may have potential implications in diagnosing disc pathology and disc replacement surgery. Lumbar lordosis and low back pain The question of whether patients who suffer from LBP have different lordosis angles than nonsufferers is not clearcut. It has been claimed that flattening or loss of normal lumbar lordosis is an important clinical sign of back problems [114,115]; the patient is thought to keep the spine straight to reduce pain. This view has been challenged by several radiologic studies suggesting that patients with chronic LBP have either no difference [48,52,116,117] or increased lumbar lordosis compared with controls [118]. These dissimilar results may be explained by different etiologies of LBP in the studies. Lumbar lordosis and general health Christensen and Hartvigsen [119] conducted a systematic critical literature review of epidemiologic (cross-sectional, case-control, cohort) studies to determine whether sagittal spinal curves were associated with general health. They concluded that there is no evidence of an association between sagittal spinal curves and health, including spinal pain.
Lumbar lordosis reconstruction Lumbar lordosis is formed by the sum of bodies and disc wedge angles. When the intervertebral discs are gone or when the vertebral bodies are compressed, the lordotic angle might change. Loss of lordosis can also occur after instrumented spinal fusion, ‘‘flat-back syndrome’’ [120].
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The loss of normal lordosis often results in sagittal spinal imbalance, persistent back pain, and increased muscle fatigue [120,121]; therefore, there is a need for accurate reconstruction of the lordotic curvature. Because the normal range of lordosis is so wide (30 –80 using the Cobb method), it is difficult to determine the normal/optimal lordosis angle for an individual. The current knowledge base is insufficient for accurate reconstruction of the lordotic curvature, which is very important for spinal surgery [122]. Recent results showed that facet inclination can accurately predict lordosis [14] in the adult human population. Additional studies are needed to confirm these findings, which in turn might be an important tool in spinal surgery. Another possible way to speculate what the normal/optimal lordosis will be is based on pelvic morphology, especially pelvic incidence. Boulay et al. [123] found that a low value of pelvic incidence, 44 or less, was associated with decreases in the sacral slope, thus flattening the lordosis. A high value of pelvic incidence, 62 or more, increases the sacral slope, thus the lordosis is more pronounced. Because pelvic incidence does not vary with age and other postural changes, and because it is highly correlated with lumbar lordosis in a healthy adult population, it may be an important tool for lordotic reconstruction. Recently Chang et al. [121] reconstructed the lordotic curvature in 94 patients with sagittal imbalance owing to lumbar kyphosis. The authors used the center of gravity and line of gravity to align the pelvis, and based on pelvic alignment reconstructed the lordotic curvature. Conclusions Lumbar lordosis is an important postural feature of sagittal spinal balance. However, many controversies related to its evaluation and associated factors exist. First, the number of evaluated vertebrae varies among researchers. We suggest using a uniform measurement method (Cobb’s method) to measure between the superior endplate of the first lumbar vertebra to the superior endplate of the first sacral vertebra. Second, the position of lordosis evaluation: the most functional and common method are X-rays taken in a standing position. We believe that this position should be the position of choice when studying lordosis. However, recently more and more studies have begun to use computed tomography or MRI to study spinal pathologies. A majority of studies showed that lordosis of the patient while in a supine position with legs straight (supine extended position) is comparable with one measured when the patient was standing. Therefore, this position should also be acknowledged in future studies. Third, there is still inconclusive evidence regarding the association of the lordosis angle with age, gender, ethnicity, occupation, and leisure physical activity. Additional studies are needed to confirm the presence/absence of such associations. Fourth, the lumbar lordosis angle is positively and significantly associated with spondylolysis and isthmic spondylolisthesis, but no
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associations have been found with other spinal degenerative features. Inconclusive evidence exists as to an association between lumbar lordosis and LBP. We believe that additional studies are needed to evaluate these associations, which can help in the understanding of pathophysiology underlying spinal disorders and LBP, assist in recognizing individuals at risk for spinal disorders and LBP, and in the development of prevention and treatment strategies. In conclusion, the optimal lordotic range remains unknown and may be related to a variety of individual factors such as weight, activity, muscular strength and flexibility of the spine and lower extremities. Acknowledgments The authors thank Dr Hayuta Pessah for the illustrations and Mrs Phyllis Kornspan for her editorial assistance. References [1] Adams MA, Mannion AF, Dolan P. Personal risk factors for firsttime 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 predictive 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 predictors 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 degenerative kyphosis patients. Spine 2009;34:280–4. [6] Giglio CA, Volpon JB. Development and evaluation of thoracic kyphosis and lumbar lordosis during growth. J Child Orthop 2007;1: 187–93. [7] Mac-Thiong JM, Labelle H, Berthonnaud E, et al. Sagittal spinopelvic 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 regional 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 subjects. 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 interpretation and management. Eur Spine J 2010;19:1824–36.
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