LU M B A R S P I N E R O M BY ANTHONY LETT
This weekâ€™s focus is on the lumbar spine and its ranges of flexion and extension.
Although movements between individual vertebra are relatively small and include only gliding and cartilaginous joints, (in this kind of joint the cartilage directly unites one bony structure to another: bone â€“ cartilage â€“ bone) the summation of all of these small movements produces a considerable range of movement of the whole spine, more comparable to that seen in a triaxial/multiaxial joint. (Multiaxial joints are more commonly known as ball & socket joints. All movement is possible in this type of joint. Examples include the Hip and Shoulder joints.) Movements of the lumbar spine include flexion-extension in the sagittal plane, right/left lateral flexion primarily in the frontal plane and right/left rotation primarily in the transverse plane. Movements of the lumbar spine can be described as relative to the spine as a whole or relative to a given motion segment (segmental motion.) A motion segment is composed of two adjacent vertebra and their related soft tissue, including the disks. Segmental movement varies markedly throughout the spine but in general, movements of the vertebral column are freer in the cervical and lumbar region. In contrast, they are more limited (except for rotation) in the thoracic region due to their connection to the relatively rigid rib cage.
Extension of the lumbar spine The vertebral body Extension of the lumbar spine is an increase in the normal anterior curve. According to Kendall (Muscles, Testing and Function) â€œthe range of extension is highly variable making it difficult to establish a standard for the purpose of measurements.â€? Moreover, says Kendall, the variations often exist without complaints of pain or disability making it difficult to determine to what extent limited or excessive motion contributes to disability. Here is an example of extreme hypermobility of the spine which was the subject of an MRI study: https://www.facebook.com/rehabscientist/videos/560191101019568/
The conclusion of the study: The kinematic magnetic resonance investigation of the presented case did not reveal any evidence for abnormal segmental motion or subluxation in extreme body contortions and indicates that this excessive motion results from extreme spinal flexibility.
Biomechanics During extension, the body of the upper vertebrae tilts and moves posteriorly. Meanwhile, the disk becomes flatter posteriorly and thicker anteriorly and is transformed into a wedge with its base lying anteriorly. The nucleus is pushed anteriorly stretching the anterior fibers of the annulus and the anterior longitudinal ligament. On the other hand, the posterior longitudinal ligament is relaxed. See Image A IMAGE A
Image A provides a visual of lumbar spine extension and flexion including facet joints, ligaments and disk movement
The articular processes/facet/apophyseal joints IMAGE B
Extension of one motion segment between L2 and L3 for example occurs as the inferior articular facets of L2 slide inferiorly relative to the superior facets of L3.
Full extension increases the load and area of contact at the apophyseal or facet joints until they are tightly interlocked. The spinous processes may also touch each other. Hence, once muscle and fascial restrictions on the ventral side of the body are overcome, (which we often describe as restrictions of tension) extension is limited by the impact of the bony structures of the arch (described as compression) and by the stretching of the anterior longitudinal ligament (described as tension). These limitations will vary too because of the anatomical differences between people. See image C below from Paul Grilley. IMAGE C
Image C. Lumbar spine on the left has more space between spinous processes and will permit more extension if myofascial restrictions are overcome.
(An apophyseal joint is a point where two or more bones join in the spine. It is composed of a superior articular facet joint that faces up and an inferior articular facet that faces down. Apophyseal joints are hinge-like joints that allow the flexion, extension and torsion of the spine.) Full lumbar extension reduces the diameter of the intervertebral foramina by 11 degrees and the volume of the vertebral canal by 15 degrees (Neuman. Kinesiology of the Musculoskeletal System, PP 267.) For this reason, clinicians often suggest that a person with nerve root impingement limit hyperextension. Extension however, tends to migrate the annulus fibrosus anteriorly. Persons with a nuclear protrusion or prolapse may find that extension reduces the pain associated with pressure on the spine or nerve roots. This 30 second video provides a brief look at the facet joints including their capsular structure in motion. Don’t be lazy, click on it!
Lumbar ROM IMAGE D
As usual, values for “normal” range of motion in the lumbar spine vary considerably. ROM also varies considerably depending on age also. Neumann (image D) assesses extension of the lumbar spine at an average of 15 degrees and flexion at 50 degrees for a total of 65 degrees.
Kapandji (image E) posits normal range of extension at 30 degrees and flexion at 40. That both leading researchers would arrive at such disparate figures is remarkable! Kapandji diagram illustrates how the lumbar spine flattens during flexion and increases its lordosis during extension. Limitations to lumbar extension include the anterior abdominal muscles and anterior ligaments of the spine including the anterior longitudinal and anterior surfaces of the disks.
Testing Back extension is often tested in the standing position. This can be useful as a gross evaluation, but is not very specific. Swinging forward or displacement at the hips is necessary for balance and adds an element of hip extension to the test. To calculate the result, you must subtract the hip extension from the back extension value. See Image F
Image F displays both spinal and hip extension
A simple test (see ROMA) is lying prone of the table or floor resting on forearms, elbow bent at right angles, arms close to the body (Image G) If the subject can extend the spine enough to prop up on the forearms with pelvis flat on the table (ASIS must stay on mat to avoid hip extension) the range is considered â€œgoodâ€? and around 30 degrees. (Kendall , Muscles, testing and function, pp 51)
ROMA score of two is depicted in image H. It is estimated to be around 50 degrees of extension as long as the ASIS remain on the table/floor
The ROMA score of 3 is estimated to be around 70 degrees of extension.
A Final word from Coulter Anatomy of Hatha Yoga (pp 274) IMAGE J
“Beginning with extremes, occasional circus performers—always women in images I’ve located—are able to extend their spines backward 180°, plastering their hips squarely against their upper backs. Images of 180° back bending can be seen in fig. 7.3 of Alter’s Science of Flexibility, as well as in a beautiful sequence of video frames 7–8 minutes into the tape of Cirque du Soleil’s Nouvelle Experience. Maximum hip hyperextension appears to be about 45°, which is seen in occasional women who can drop down into the wheel posture and then scamper around on their hands and feet looking like daddy-long-leg spiders in a hurry.
Both extremes—180° of back extension and 45° of hip hyperextension—are anomalous, and it is not advisable for anyone to attempt extending either the hips or the spine this much unless one’s profession requires it. Even highly flexible dancers, gymnasts, and hatha yogis rarely try to bend backward more than 90°, ordinarily combining 20° of extension at the hips with an additional 70° of extension in the lumbar region. In this case the right angle between their thighs and their chests is more than enough to permit them to touch their feet to their heads in advanced hatha yoga postures.” See images J and K.
Lumbar flexion Flexion of the lumbar spine decreases the normal anterior lumbar curve resulting in a straight position of the low back. The ability to flatten the lower back is considered normal flexion. You may notice that the discussion shifts to joints instead of muscles as we move to this region. It seems that joints play a greater role in permitting and preventing movement than tight muscles in the lumbar spine. Normal value for lumbar flexion is around 40-60 degrees. Most forward bending from the spine takes place between T12 and the sacrum. Coulter says up to 90 degrees of forward flexion is occasionally seen, but 30 to 80 degrees is more common. Hip and lumbar flexion usually occur together and are called lumbo-pelvic rhythm. However, it is often the case that hamstring tension does not permit the rhythmical combination of hip and lumbar flexion and the result can be strain on the intervertebral disks and posterior ligaments. (For a fuller discussion see Lett “Hack your Back”) A look at the video below provides a very good visual of the dangers. Click! Don’t be lazy!
Biomechanics During flexion at L3/L4 for example, the upper body of the L3 vertebra tilts and rotates slightly forward/anteriorly (Image L figure A arrow F) reducing the thickness of the vertebral disk anteriorly and increasing it posteriorly. The disk becomes wedge shaped and the nucleus pulposus is driven posteriorly. The posterior fibers of the annulus fibrosis are stretched.
Click link or image to play video: https://www.youtube.com/ watch?v=n78PS4zq3D8
At the same time the inferior articular processes of L3 glide upwards and tend to free themselves from the superior articular processes of the vertebra below-L4. (Image L figure A, black arrow) As a result, the capsule and ligaments of this facet joint are maximally stretched along with the other ligaments of the vertebral arch. See discussion below on ligaments.
Figure A: Lumbar Flexion
Figure B: Lumbar Extension
Nutation There is also a small capacity for movement between the sacrum and the pelvis at the sacroiliac joints. These movements are called nutation and counternutation, terminology coined by French orthopedist LA Kapandji. During flexion of the lumbar spine, the sacrum rotates in a sagittal plane within the pelvic bowel.
The promontory (top front border, see image M) of the sacrum rotates anteriorly and the coccyx posteriorly. During extension, the opposite occurs. It is important to differentiate these movements from anterior and posterior pelvic tilt, which are movements of the pelvis as a whole. IMAGE N
The role of Ligaments Flexion is greatest in the lower lumbar joints of L4 and L5 and decreases progressively toward L1/ L2. See Image and table image E. Note however that Kapandji (p.104 Physiology of the Joints, Vol 3) states that L3 and T12 are the most mobile and hinge like vertebrae. During flexion the superior band of the Iliolumbar ligament is tightened to prevent excessive movement.
During extension, this band is relaxed but the inferior band of the iliolumbar ligament is pulled taught to limit excessive movement. The mobility of the lumbosacral joint on the whole is limited by the strength of the iliolumbar ligaments. According to Kapandji they limit lateral flexion more than flexion and extension. (p.98) See Image O.
Overall, limitations to lumbar spinal flexion include the spinal muscles, thoracolumbar fascia, and several ligaments: Supraspinous, interspinous, facet capsular, ligamentum flavum, posterior longitudinal and posterior surfaces of the disks. See Image P for ligamentous images.
Testing According to Alter, most, if not all forward flexion occurs in the lumber spine (Science of flexibility, p. 270) Specifically, 5 to 10 % of flexion occurs between L1 and L4, 20 to 25% between L4 and L5 and 60 to 75% between L5 and S1. Calliet argues that total lumbar flexion is limited to the extent of reversal of the lumbar curve. The ROMA test offers several alternatives. First, eliminating the hamstrings by sitting, we observe the ability of the lumbar spine to flex. Watch for freedom and quality of movement and the overall shape of the lumbar region. Image Q would score a two or three.
The cat stretch offers another alternative, although it is more dependent on abdominal strength and co-ordination. However, it provides an opportunity to observe movement. Look at the quality of the movement. Is it free and fluid with a sense that there could be more movement available, or does it look stiff and forced? Curiously, the photo above is of a dancer who is very flexible generally (Image R). However, she would score a one due to her inability to flatten or reverse the lumbar curve.
In the two photos below, the degree of lumbar flexion is the same, and both score a two. The difference is the degree of pelvic rotation, a product of hamstring flexibility.
In this final example, the lumbar spine will not flatten and demonstrates marked resistance. The score is one. The images below (Kendall pp 46-47) demonstrate several examples of the messiness of testing the lumbar spine in flexion. You need to think about the role of the hamstrings, the shape of the lumbar curve, the quality of the movement and importantly, there is an intuitive element. What do you and the client feel?
And another final word from Coulter Unlike the outermost limits for backbending, the outside limits for forward bending are all within a normal range for anyone with very good general flexibility. Dancers, gymnasts, and hatha yogis, including both men and women, can often bend forward up to 120째 at the hips with the lumbar lordosis arched and the knees straight. These same people may also be able to bend an additional 90째 in the lumbar region, making a total of 210째. Since 180째 is all that is required to lay the torso down against the thighs in a sitting forward bend (fig. 6.12), their full capacity for forward bending is difficult to gauge. - Coulter, David. Anatomy of Hatha Yoga, PP 334.