Lumbar Spine Flexion and Extension Extremes of Motion in Women of Different Age and Racial Groups The WIN Study

The measurement of lumbar spine range of motion (ROM) is important clinically for physicians and rehabilitation specialists who treat low back pain. Current clinical measurement techniques include the use of inclinometers, goniometers, and tape measures with each of the techniques having its own set of limitations. For information obtained from any of these measurement techniques to be useful, normative data for lumbar spine ROM using the specific measurement technique are needed. However, adequate documentation of normative data for the lumbar spine is lacking in the literature. Most existing databases of normative data for lumbar spine ROM provide values obtained with measurement tools that are neither practical nor feasible for clinical use.1–4 The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) use spinal ROM measurements to estimate the level of impairment and subsequent compensation entitlement.5 The Guides specifically recommend the use of an inclinometer as the preferred device for measuring lumbar spine motion. However, normative values used by the Guides were not determined using an inclinometer3,6 and are based on a small sample size of 21 men and 20 women3 or a sample of mostly men (168 men and 4 women).6 Several investigators have demonstrated that mean values for lumbar spine ROM differ for gender2,3,7 and age.2–4,7 Despite this information, the baselines (the bottom of the impairment scale that reflects zero impairment) used to determine disability ratings do not take gender and age into account. Spieler et al,8 in a summary of criticisms of the fourth edition of the AMA Guides, argue that normative values used for baselines should include “known population variants” such as age, sex, and race. In addition to the lack of established normative data, there have been measurement issues associated with documentation of lumbar spine mobility. The term “range of motion” implies that 2 numbers are needed to define a motion, with the first number indicating where the motion begins and the second number indicating where the motion ends. This is consistent with the neutral zero method of notation9 that is widely used throughout the world and is supported by the American Academy of Orthopedic Surgeons and the American Medical Association.5,10,11 Lumbar ROM is most often recorded as a single number that represents the end point. It is implied that the start position is zero but several researchers have identified this practice as being problematic.7,12 The double inclinometer measurement of lumbar flexion and extension advocated by the AMA Guides uses initial resting posture as the zero reference from which flexion and extension are measured.7 Initial resting posture varies among individuals with a mean value of 31.7° of lordosis for women and 24.3° for men when using the γ-tangent method originally described by Loebl.13 Other sources have reported similar values of resting lordotic posture and similar differences between men and women.14 The problem with the practice of using initial resting posture as the zero reference is that as a person flexes forward, the lordosis must first be reversed. Because this reversal of lordosis is added to the lumbar ROM measurement when using the double inclinometer technique, excessive lordosis will artificially inflate the flexion ROM value.12 For lumbar extension measurements, an excessive amount of lordosis artificially deflates the extension ROM measurement since the underlying vertebrae are already in a position of extension.15,16 Sullivan et al7 argue that the true measure of lumbar ROM in the sagittal plane should not be dependent on the amount of lumbar lordosis present. The purpose of this study was to provide normative values of lumbar flexion and extension for a fairly large sample of women of different age and racial groups using inclinometric measurements that do not use lordosis as a zero reference point. Additionally, lumbar flexion and extension values were compared across age and racial groups and reliability for our inclinometer measurements was assessed.