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THE ANATOMICAL RECORD 290:1568–1573 (2007)
New Method for Predicting the Lumbar Lordosis Angle in Skeletal Material ELLA BEEN,1,2* HAYUTA PESSAH,1 LAURENCE BEEN,3 ARIE TAWIL,4 AND SMADAR PELEG1 1 Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel 2 Department of Physical Therapy, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel 3 Spinal Private Practice, Raanana, Israel 4 Spinal Rehabilitation Clinic, Raanana, Israel
ABSTRACT Reconstructing the lordotic curvature of the lumbar spine in humans is essential for understanding their posture and locomotion. To date there is still no reliable method for predicting the lordotic curvature of disarticulated spines (in the absence of intervertebral disks). This article examines two possible methods for predicting the lordotic curvature of the lumbar spine. The first—the traditional method—is based on the degree of wedging of the vertebral bodies, and the second—the suggested new method—is based on a lateral view of the orientation of the inferior articular processes. We propose a linear regression model for predicting the lordotic curvature of the lumbar spine (lordosis angle) in disarticulated human spines. This model, derived directly from our new method, is a more reliable predictor of the lumbar lordosis angle in disarticulated spines. Anat Rec, 290:1568–1573, 2007. Ó 2007 Wiley-Liss, Inc.
Key words: articular process; vertebral spine; spinal curvature
The evolutionary adaptation of the human spine to the upright position includes the development of the spinal curvatures, alterations in the size and wedge angle of the lumbar vertebral bodies, and changes in the shape and orientation of the articular processes (Putz, 1985; Latimer and Ward, 1993; Schendel et al., 1993; Boszczyk et al., 2001). Today, there is growing recognition of the functional and clinical importance of the spinal curvatures. These curvatures allow the loads applied to the spinal column to be efficiently absorbed. As such, they have a great bearing on the maintenance of upright posture and the efficacy of bipedal walking (Gracovetsky and Iacono, 1987; Farfan, 1995; Vaz et al., 2002; Vialle et al., 2005). To date, there is no valid method for calculating the lordotic curvature of the lumbar spine (lumbar lordosis) in skeletal material, nor is there any way to calculate the lordotic curvature of disarticulated spines such as those found at archeological sites. The method used for estimating the lordotic curvature in archeological material is based on the wedging of the vertebral bodies (Cunningham’s index, or vertebral body wedge angle). Ó 2007 WILEY-LISS, INC.
This wedging results from the difference between the anterior and posterior heights of the vertebral body, measured from superior to inferior, and from its ventrodorsal length. The degree of wedging can only be used to estimate whether the lumbar spine is lordotic or kyphotic, but cannot be used to predict its degree of curvature (Cunningham, 1886; Digiovani et al., 1989; Scoles et al., 1991). The claim that vertebral body wedging relates to the lordotic curvature of the lumbar spine has found little support in the orthopedic literature. Most researchers measure the vertebral body and adjacent disk as one unit without considering the separate effect of vertebral *Correspondence to: Ella Been, Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel. Fax: 972-3-6408287. E-mail: beenella@ post.tau.ac.il Received 19 April 2007; Accepted 26 August 2007 DOI 10.1002/ar.20607 Published online 31 October 2007 in Wiley InterScience (www. interscience.wiley.com).
NEW METHOD FOR PREDICTING THE LUMBAR LORDOSIS ANGLE
body wedging (Harrison et al., 2001; Kimura et al., 2001; Vaz et al., 2002; Roussouly et al., 2005; Vialle et al., 2005). However, Cheng et al. (1998) found moderate to weak correlations between vertebral body wedging (Cunningham’s index) and the lumbar lordosis angle. The anterior pillar of the vertebral spine is composed of the vertebral bodies and intervertebral disks, and it is this anterior pillar that determines the lordotic curvature of the lumbar spine (Louis, 1985). It is reasonable to assume that the morphology of the posterior pillar, which is formed by the superior and inferior articular processes and the lamina, is influenced by the curvature exhibited by the lumbar spine. Our inspection of the inferior articular process of humans on the sagittal plane has revealed the correlation of that orientation with lordotic curvature (lumbar lordosis). To the best of our knowledge, this is the first time the interaction between the lordotic curvature of the lumbar spine and the orientation of the inferior articular process on the sagittal plane has been investigated. Such a correlation, if it exists, could be used as a reference for predicting the degree of lordotic curvature in disarticulated lumbar spines (i.e., in the absence of intervertebral disks). In this study, we propose a new method for predicting the lordotic curvatures of disarticulated spines. The goal of this study is threefold: first, to test the relationship between the lordotic curvature of the lumbar spine and vertebral body wedging; second, to test the relationship between the lordotic curvature and the inferior articular process angle; and third, to provide the best tool for predicting the lordotic curvature using only bony landmarks within the lumbar spine.
MATERIALS AND METHODS Lateral radiographs of the lumbar spine of 379 subjects (patients at spinal clinics, Raanana, Israel) were examined. All radiographs were part of a routine evaluation performed in the spinal clinics to assess posture and detect abnormality in the spinal column. (Patients attend the spinal clinics for a variety of musculoskeletal complaints, including, for example, neck and back pain, headaches, or numbness of the hand or arm.) Of the 379 radiographs, 106 (56 men and 50 women) were selected according to the following criteria: adult subjects (38 6 7.6 years of age, from 20 to 50 years old) with no history of spinal surgery and no radiographic abnormality (degeneration, scoliosis, spondylolysis/listhesis, reduced disk height, etc.) detected. In all cases, standard lateral lumbar radiographs were obtained with subjects standing in a comfortable position with knees straight and arms folded on the chest. All subjects signed an informed consent form, and the research was approved by the Helsinki committee of Tel-Aviv University. For each of the five lumbar vertebrae, three lines were drawn (Figs. 1, 2): along the superior endplate of the vertebral body (also on the first sacral vertebra); along the inferior endplate of the vertebral body; and along the anterior border of the inferior articular process. These lines were used to measure four angles: the lordosis angle (L1S1) between the superior endplate of L1 and the superior endplate of S1; the body wedge angle (B) between the superior and inferior endplates of a single vertebra; the total segmental angle (T) between the
Fig. 1.
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Lumbar lordosis angle (L,S) based on the cobb method.
superior endplate of one vertebra and the superior endplate of the successive vertebra; and the inferior articular process angle (AP) between the superior endplate and the anterior border of the inferior articular process of the same vertebra. Measurements B, T, and AP were taken for each of the five lumbar segments. The lordosis angle is shown in Figure 1, and the other three angles in Figure 2. All measurements were taken by the same investigator (E.B.) using a 25-cm Jamar goniometer with a 3608 scale in 18 increments. Measurements B, T, and AP were used to calculate ST, the sum of the lumbar L1–L5 segmental angles; SB, the sum of the lumbar L1–L5 body wedge angles; and SAP, the sum of the lumbar L1–L5 inferior articular process angles. Intraobserver reproducibility was assessed on the basis of five radiographs, remeasured by EB (reproducibility test: Intraobserver reproducibility was found to be high for the L1S1, B, and T angles [>99.7%, P < 0.001], and for the AP angles (
