Male predominance	Spondyloarthropathies Vertebral osteomyelitis Benign and malignant neoplasms Paget disease Retroperitoneal fibrosis Peptic ulcer disease Work-related mechanical disorders
Female predominance	Polymyalgia rheumatica Fibromyalgia Osteoporosis Parathyroid disease

Data from Klippel JH, Dieppe PA: Rheumatology, vol 1-2, ed 2, London, 1998, Mosby.

Other than the common cold, back pain is the most prevalent human affliction. As stated earlier, most patients have a mechanical cause (muscle strain or annular tear) for their back pain and do not have an underlying, serious, systemic medical illness.

Even if treatment involves only a localized part of the lumbar spine, in each case, the lumbar spine has to be considered as a functional unit consisting of bones, ligaments, intervertebral discs, muscles, and all other soft tissues. Because of their central location, spinal elements represent the focal point for the equilibrium of the body. Because of the many connections and relations, spinal changes influence some organs directly, and the functional equilibrium of the spine depends on the efficient performance of other organs.

TABLE 8-1 LUMBAR SPINE CROSS-REFERENCE TABLE BY ASSESSMENT PROCEDURE

TABLE 8-2 LUMBAR SPINE CROSS-REFERENCE TABLE BY SYNDROME OR TISSUE

Cord tumor	Bragard sign Lasègue test Milgram test Straight-leg-raising test
Denervation	Matchstick test Skin pinch test
Dural adhesions	Bechterew sitting test Fajersztajn test Lasègue test Straight-leg-raising test
Femoral nerve	Ely sign Femoral nerve traction test Hyperextension test Prone knee-bending test
Fracture	Minor sign Spinal percussion test
Hamstring spasm	Lewin standing test
Hip lesion	Ely sign Sign of the buttock
Intervertebral disc syndrome	Antalgia sign Bechterew sitting test Bilateral leg-lowering test Bragard sign Cox sign Double-leg-raise test Fajersztajn test Heel/toe walk test Kemp test Lasègue rebound test Lasègue test Lewin punch test Lewin snuff test Lewin supine test Matchstick test Milgram test Minor sign Neri sign Skin pinch test Spinal percussion test Straight-leg-raising test
Intervertebral foramen encroachment	Bechterew sitting test Bilateral leg-lowering test Lasègue test
L2–L3–L4	Femoral nerve traction test Hyperextension test Prone knee-bending test
Lower extremity joints	Quick test
Mechanical lower back	Bilateral leg-lowering test Demianoff sign Double-leg-raise test Kemp test Lasègue test Nachlas test Neri sign Schober test Sign of the buttock Skin pinch test Spinal percussion test
Meningitis	Kernig/Brudzinski sign
Myofascitis	Lewin supine test Skin pinch test
Sacroiliac lesion	Lasègue test Lewin supine test Mennell sign Minor sign Nachlas test Neri sign
Sciatica	Bechterew sitting test Bragard sign Deyerle sign Fajersztajn test Heel/toe walk test Lasègue sitting test Lasègue test Lewin snuff test Lewin standing test Lewin supine test Sicard sign Turyn sign Vanzetti sign
Spinal neuropathy	Bowstring sign Bragard sign Ely sign Femoral nerve traction test Heel/toe walk test Kemp test Lasègue differential sign Lasègue sitting test Sicard sign
Sprain	Double-leg-raise test Spinal percussion test
Subluxation	Bechterew sitting test Nachlas test

The spine contributes to many mutual relationships within the total body. With its equilibrium (statics), the spine exerts, influences, and receives forces (dynamics), all of which are interwoven with the far-reaching chain of motion (kinetics). In addition, the spine is able to exercise considerable influence on neighboring structures, as well as on remote organs. This influence is its action on nerves and blood vessels. To a considerable degree, this complicated system depends on the metabolism, the mineral metabolism of the bones, and the nutrition of the bradytrophic ligamentous and disc tissues. Improper function of the endocrine glands also affects the spine.

During fetal development, the spine may be exposed to many influences, such as drug-induced malformations, lack of oxygen, or radiation.

Occupational and daily-living stresses, as well as traumatic influences, may combine to have an unfavorable effect when coupled with the aging process, which has a marked effect on the disc apparatus and the bony substance. More resources for the diagnosis and treatment of spinal diseases are available today than previously.

Degeneration of posture during early years, lack of exercise, physical weakness, and degenerative changes in later life have taken on a serious social significance for the cultures of industrialized nations.

The spine is an intricate and interesting mechanical structure. The spine’s functions are mechanical, and it is well suited for serving its basic mechanical roles. The materials used to execute the design are appropriate for enhancing these functions. The spine must transfer loads from the trunk to the pelvis, must allow for physiologic motion, and must protect the spinal cord from damage. When a proper appreciation of normal anatomy and mechanics has been gained, the pathophysiologic features of the diseased or deformed spine become clear.

The lumbar spine is designed to withstand loading and to provide truncal mobility. The primary plane of motion is during flexionextension, although axial rotation at the L5 level is significant. This rotation in the lower lumbar spine is particularly important, considering that the annulus fails and tears with torsional forces. Coupling in the lumbar spine is the opposite of cervical and thoracic spine coupling. The spinous processes move toward the concavity of the curve in physiologic lateral flexion.

Optimal spinal mobility in relation to age is difficult to pin down. The only generalization that can be made is that spinal mobility is probably greatest during adolescence and early adulthood. This tendency is significant when planning treatment and in determining prognoses.

The anatomic structures of the lumbosacral spine receive specific types of sensory innervation that are associated with distinct qualities of pain (Table 8-6).

TABLE 8-6 SUMMARY OF THE CHARACTERISTICS OF LOW BACK PAIN OF VARIOUS ORIGINS

ESSENTIAL ANATOMY

The lumbar spine consists of five lumbar vertebrae, numbered L1 to L5, followed by five fused sacral bodies that form the sacrum and the coccyx. The alignment of the lumbar spine generally has a lordotic contour. The normal lordosis is 30 to 50 degrees (apex L3) in a standing person.

ESSENTIAL MOTION ASSESSMENT

Range-of-motion findings are most helpful in pinpointing a vertebral structure that may be compromised in the lumbar spine. Pain at an early point in the extension of the lumbar spine suggests an inflamed posterior joint or pars disease. Painful lumbar flexion in the early-to-middle range connotes a faulty disc mechanism or muscular stain. Because the terminal range of flexion causes the facet joint capsule to stretch, a pain response at this point may indicate a posterior joint sprain.

Patients with acute spasm or significant trauma often have multidirectional complaints and severe limitation of motion in all planes. Therefore, range-of-motion testing may be initially inconclusive as to the severity of the injury.

To assess the contribution made to flexion by the lumbar spine, the examiner should mark the spine at the lumbosacral junction and then 10 cm above and 5 cm below this point. On forward flexion, the distance between the two upper marks should increase by approximately 4 cm, the distance between the lower two remaining unaltered (Figs. 8-1 to 8-4).

FIG. 8-1

FIG. 8-2 The patient flexes forward, and the angle of both inclinometers is recorded. The sacral inclination is subtracted from the T12 inclination to obtain the lumbar flexion angle.

FIG. 8-3 Extension is limited to 35 degrees in the lumbar spine. The patient extends the lumbar spine, and the angles of both instruments are recorded. The sacral inclination angle is subtracted from the T12 inclination angle to obtain the lumbar extension angle.

FIG. 8-4 Both instruments are zeroed at the superior aspect of the sacrum, in the coronal plane (A). The patient laterally flexes the lumbar spine to one side, and the inclinations of both instruments are recorded (B). The sacral angle is subtracted from the T12 angle to obtain the lumbar lateral flexion angle. The procedure is repeated for the range of motion to the opposite side. Lateral flexion of 20 degrees or less to either side is an impairment of the lumbar spine in the activities of daily living.

ESSENTIAL MUSCLE FUNCTION ASSESSMENT

The erector spinae consist of a minor portion (the spinalis) and two major portions (the longissimus and iliocostalis). The spinalis connects spinous processes, and the longissimus and iliocostalis connect homologous portions of the costal and transverse elements of the lumbar, thoracic, and cervical vertebrae and skull.

Useful in screening is muscle testing of the legs, which measures strength on a 5-point scale for extension and flexion (knee), abduction and adduction (hip), and eversion and inversion, as well as dorsiflexion and plantar flexion (foot) (Table 8-7).

TABLE 8-7 LUMBAR RADICULAR SYNDROMES

For patients in whom the objective findings do not match the subjective complaints, close observation helps identify the inconsistencies (Table 8-8). A finding of three or more of the five signs of the Waddell index is clinically significant. Isolated positive signs are ignored.

TABLE 8-8 NONORGANIC PHYSICAL SIGNS INDICATING ILLNESS BEHAVIOR

	Physical Disease/Normal Illness Behavior	Abnormal Illness Behavior
Symptoms
Pain	Anatomic distribution	Whole leg pain
		Tailbone pain
Numbness	Dermatomal	Whole leg numbness
Weakness	Myotomal	Whole leg giving way
Time pattern	Varies with time and activity	Never free of pain
Response to treatment	Variable benefit	Intolerance of treatments
		Emergency admissions to hospital
Signs
Tenderness	Anatomic distribution	Superficial
		Widespread nonanatomic
Axial loading	No lumbar pain	Lumbar pain
Simulated rotation	No lumbar pain	Lumbar pain
Straight leg raising	Limited on distraction	Improves with distraction
Sensory	Dermatomal	Regional
Motor	Myotomal	Regional, jerky, giving way

From Demeter SL, Andersson GBJ, Smith GM: Disability evaluation, St Louis, 1996, Mosby.

The iliacus arises from the iliac fossa and joins the psoas under the inguinal ligament. The iliacus then crosses the hip joint capsule and inserts into the lesser trochanter of the femur. These muscles flex the lumbar spine and bend it toward the same side. The quadratus lumborum, which lies lateral to the vertebral column, arises from the posterior part of the iliac crest and iliolumbar ligament and inserts into the twelfth rib and the tips of the transverse processes of the upper four lumbar vertebrae. This muscle fixes the diaphragm during inspiration and bends the trunk toward the same side when it acts alone (Figs. 8-5 to 8-7).

FIG. 8-5 The patient is lying prone on the examination table. The patient then extends the trunk.

FIG. 8-6 Lateral flexion of the trunk requires a combination of lateral flexion and hip abduction. The patient is side lying, with the head, upper trunk, pelvis, and lower extremities in a straight line. During the test, the patient laterally flexes the trunk away from the examination table.

FIG. 8-7 Raising the trunk obliquely forward combines trunk flexion and rotation. The patient is supine on the examination table, and the legs are supported by the examiner.

ESSENTIAL IMAGING

A variety of radiographic views can be taken when the lumbosacral region is evaluated. The standard views consist of the anteroposterior (AP), lateral, oblique, and either a frontal or a lateral lumbosacral spot.

ANTALGIA SIGN

Assessment for Posterolateral, Posteromedial, and Posterocentral Intervertebral Disc Protrusion

Comment

Two major types of low back abnormalities center on the intervertebral disc: acute impairment from herniated discs and chronic impairment from degenerative disc disease (Table 8-9).

TABLE 8-9 LUMBAR DISC SYNDROMES

	Lumbar Herniated Nucleus Pulposus	Degenerative Disc Disease
Physical examination findings	Back or leg pain Sciatic nerve tension signs: Positive straight leg raise less than 60 degrees Positive Bragard sign Positive bowstring sign Positive Bechterew test Painful arc of lumbar flexion, extension, or both True nerve root signs: Radiculopathy Motor or sensory deficit Paresthesias Diminished or absent deep-tendon reflexes Possible antalgia, muscle spasm, instability

Morning stiffness

Lumbopelvic hypomobility

Pain in lumbar flexion

History consistent with spinal degeneration

X-ray findings

Need to rule out organic abnormality

Hypolordosis secondary to muscle spasm

Possible loss of intervertebral disc height

Possible diagnosis of degenerative arthritis

Radiologic signs in acute exacerbation

Spur formation

Loss of intervertebral disc height

Discogenic spondylosis

Compatible findings on CT or MRI scans

CT, Computed tomography; MRI, magnetic resonance imaging.

Adapted from Brier SR: Primary care orthopedics, St Louis, 1999, Mosby.

ORTHOPEDIC GAMUT 8-2 DISC INJURIES

Definitions of disc injuries are as follows:

1. Disc protrusion is present when nuclear material does not extend beyond the annulus in a contained herniated nucleus pulposus.

2. Disc extrusion is a focal herniation contained by the posterior longitudinal ligament that extends into the spinal canal.

3. Sequestered disc is a free fragment that has broken off or through the annular peripheral fibers in the vertebral canal (prolapsed).

A disc may protrude lateral to a nerve root, medial to a nerve root, under a nerve root, or central to the nerve root.

PROCEDURE

• When the disc protrudes lateral to the nerve root, the patient assumes an antalgic lean away from the side of the disc lesion or pain (Fig. 8-8).

• When the disc protrudes medial to the nerve root, the patient assumes an antalgic lean into the side of the disc lesion or pain (Fig. 8-9).

• With a central disc lesion, the patient assumes a flexed posture of the lumbar spine, with or without leaning to either side (Fig. 8-10).

• With protrusion under the nerve root, the patient may not lean at all.

FIG. 8-8

FIG. 8-9

FIG. 8-10 With a central disc lesion, the patient assumes a flexed posture of the lumbar spine, with or without leaning to either side.

CLINICAL PEARL

If the antalgia is not readily apparent in a static posture, it will appear with forward flexion of the trunk. If a disc protrusion exists, even in the mildest degree, trunk flexion exerts enough pressure to irritate the inflamed muscle or to stretch neural structures over the bulging disc. The antalgia is manifested at this point. Patients with lower back pain might stiffen the trunk and pelvis and hyperextend the knees in an effort to decrease the number of degrees of freedom.

BECHTEREW SITTING TEST

Assessment for Sciatica, Intervertebral Disc Lesion, Vertebral Exostoses, Dural Sleeve Adhesions, Muscular Spasm, or Vertebral Subluxation

PROCEDURE

• While in a seated position, the patient attempts to extend each leg, one at a time.

• The examiner restricts the patient’s attempts at hip flexion with downward pressure on the thigh (Fig. 8-11).

• This extension is followed by an attempt to extend both legs.

• The test is positive if backache or sciatic pain is increased or if the maneuver is impossible.

• In disc involvement, extending both legs will usually increase the spinal and sciatic discomfort.

• A positive test indicates sciatica, a disc lesion, exostoses, adhesions, spasm, or subluxation.

FIG. 8-11

CLINICAL PEARL

Simple flattening or even reversing the lumbar curve is often not associated with radicular pain. The pain is localized in the lower lumbar spine, and any movement of the spine accentuates the pain. In these instances, the prime pathologic feature is sprain of an intervertebral joint rather than root irritation.

BILATERAL LEG-LOWERING TEST

Assessment for Mechanical Lumbosacral Lesion, Intervertebral Disc Lesion, or Vertebral Exostoses

PROCEDURE

• The patient lowers the straightened legs from a 90-degree angle to a 45-degree angle (Fig. 8-12).

• The test is positive if the legs drop or if the move produces pain.

• A positive test indicates lumbosacral involvement, disc lesions, or exostoses.

FIG. 8-12

CLINICAL PEARL

Because of the presence of the nociceptive nerve ending within the annulus fibrosus of the disc, annular tears can cause pain in the lower back, buttocks, sacroiliac region, and lower extremity. This pain can occur without nerve compression by a disc protrusion. Disc protrusion that does not compress the nerve root can cause an inflammatory response and secondary radiculitis by chemically induced inflammatory neural pain.

BOWSTRING SIGN

Assessment for Lumbar Nerve Root Compression

ORTHOPEDIC GAMUT 8-3 LUMBOSACRAL NERVE ROOTS

After leaving the dural sac, the lumbosacral nerve roots run caudally and laterally in the direction of departure from the spinal canal:

1. The fourth lumbar root (L4) leaves the dural sac slightly caudal of the intervertebral disc between the third and fourth lumbar vertebrae (third lumbar disc).

2. The fifth lumbar root (L5) leaves the dural sac near the level of the fourth lumbar disc.

3. The first sacral root (S1) leaves the dural sac medial of S1 and slightly below the level of the L5 disc.

ORTHOPEDIC GAMUT 8-4 WALLERIAN DEGENERATION SEQUENCE

• When axonal continuity is disrupted by mechanical compression or nerve trunk ischemia:

• Axons distal to the stump divide finely and begin to degenerate.

• At the same time, the myelin sheaths that have lost axons begin to break down.

• Wallerian degeneration occurs peripheral to the site of compression in the anterior root and central to this site (i.e., toward the spinal cord) in the posterior root when the cauda equina or nerve root is compressed by a herniated intervertebral disc or spinal canal stenosis.

• Nerve roots have a regenerative capacity similar to that of peripheral nerves.

• While regeneration of the anterior root approximates that of peripheral nerves, recovery of sensation presents problems in the posterior root because degeneration extends into the spinal cord.

PROCEDURE

• With the patient in the supine position, the examiner moves the patient’s leg until it is above the examiner’s shoulder.

• At this point, firm pressure should be exerted on the hamstring muscles (Fig. 8-13).

• If pain is not elicited, pressure is applied to the popliteal fossa.

• Pain in the lumbar region or radiculopathy is a positive sign for nerve root compression.

FIG. 8-13

CLINICAL PEARL

Nerve roots must change their lengths depending on the degree of flexion, extension, lateral flexion, and rotation of the lumbar spine. Lumbar nerve roots that are limited in motion by fibrosis of either intraspinal or extraspinal origin will create traction on the nerve root complex, causing ischemia and secondary neural dysfunction.

BRAGARD SIGN

Assessment for Sciatic Neuritis, Spinal Cord Tumor, Intervertebral Disc Lesions, and Spinal Nerve Irritation

PROCEDURE

• If the Lasègue test or the straight-leg-raising test is positive, the leg is lowered below the point of discomfort, and the foot is sharply dorsiflexed (Fig. 8-14).

• The sign is present if pain is increased.

• The presence of the sign is a finding associated with sciatic neuritis, spinal cord tumors, intervertebral disc lesions, and spinal nerve irritations.

FIG. 8-14

CLINICAL PEARL

Either the Bragard sign or the Hyndman sign (for neck flexion movement) must be accomplished as a finishing maneuver in any positive straight-leg-raising test. Pain that increases during neck flexion, ankle dorsiflexion, or both indicates an inflamed nerve root. Pain that does not increase with these maneuvers may indicate a problem in the hamstring area or in the lumbosacral or sacroiliac joints.

COX SIGN

Assessment for Prolapse of Intervertebral Disc Nucleus

Comment

Several maneuvers tighten the sciatic nerve and compress an inflamed nerve root against a herniated lumbar disc. With the straight-leg-raising tests, the L5 and S1 nerve roots move several millimeters at the level of the foramen. The L4 nerve root moves a smaller distance, and the proximal roots show little motion. The straight-leg-raising tests are most important and valuable for detecting lesions of the L5 and S1 nerve roots. Young patients with herniated discs have marked propensities for positive straight-leg-raising tests. Although the test itself is not pathognomonic, a negative test rules out the possibility of a herniated disc. After age 30, a negative straight-leg-raising test no longer precludes this diagnosis. Lumbosacral transitional vertebrae complicate this further (Table 8-10).

TABLE 8-10 CASTELLVI CLASSIFICATION OF LUMBOSACRAL TRANSITIONAL VERTEBRA

• Type I: dysplastic transverse process

• Type Ia (unilateral) height >19 mm

• Type Ib (bilateral) height >19 mm

• Type I is not considered a true lumbosacral transitional vertebra because no articulation with the sacrum is present

• Type II: incomplete lumbarization/sacralization

• Type IIa enlarged transverse process with unilateral pseudoarthrosis with the adjacent sacral ala

• Type IIb enlarged transverse process with bilateral pseudoarthrosis with the adjacent sacral ala

• Type III: complete lumbarization/sacralization

• Type IIIa enlarged transverse process that has unilateral complete fusion with the adjacent sacral ala

• Type IIIb enlarged transverse process that has bilateral complete fusion with the adjacent sacral ala

• Type IV: mixed (type IIa on one side and type IIIa on the other)

PROCEDURE

• Cox sign occurs during straight leg raising when the pelvis rises from the table instead of the hip flexing (Fig. 8-15).

• Cox sign is present when patients have a prolapse of the nucleus into the intervertebral foramen.

FIG. 8-15

CLINICAL PEARL

Cox sign is a consistent finding associated with disc prolapse. The sign is often overlooked in the patient’s pain presentation. A false-negative test result may occur if the examiner does not observe the movements of the buttocks on the affected side. The sign is present the moment hip flexion motion is locked and the buttock rises from the examination table.

DEMIANOFF SIGN

PROCEDURE

• While the patient is in the supine position, the examiner performs a straight-leg-raising test with either leg.

• The sign is present when this action produces a pain in the lumbar region.

• This pain prevents the patient from raising the leg high enough to form an angle between the examination table and the leg of 15 degrees or more (Fig. 8-16).

• The sign differentiates pain that originates in the sacrolumbalis muscles from lumbar pain of any other origin.

• A positive test demonstrates that the pain is caused by the stretching of the sacrolumbalis (iliocostalis lumborum).

FIG. 8-16

CLINICAL PEARL

Demianoff sign is clearly separate from Cox sign. Demianoff sign involves production of lower back pain, which prevents further raising of the leg. Sciatica is absent. Cox sign is present when the pelvis is locked, which prevents further elevation of the leg because of increasing sciatica.

DEYERLE SIGN

Assessment for Sciatic Nerve Irritation

Comment

Occasionally, L4 lesions may also cause similar symptoms and signs. The phase of degeneration or spondylosis often determines the level of intervention (Table 8-11).

TABLE 8-11 OVERVIEW OF SCHEME OF TREATMENT RELATIVE TO THE PHASE OF SPONDYLOSIS

Phase	Lesion	Treatment
Dysfunction	Facet joint Sacroiliac joint Myofascial syndromes Disc herniation

Mobilization, manipulation, injection

Contract stretching, injection

Epidural injection, discectomy

Unstable

Disc herniation

Segmental instability

Lateral stenosis

Central stenosis

Degenerative olisthesis

Isthmic olisthesis

Epidural injection, discectomy

Injection, fusion

Nerve root block, decompression, fusion

Epidural injection, decompression, fusion

Stabilization

Disc herniation

Lateral stenosis

Central stenosis

Degenerative olisthesis

Isthmic olisthesis

Epidural injection, discectomy

Nerve root block, decompression

Epidural injection, decompression

Epidural injection, decompression, rarely fusion

From Kirkaldy WH: Managing low back pain, ed 4, Philadelphia 1999, Churchill Livingstone.

PROCEDURE

• While the patient is seated, the affected leg is passively extended at the knee until pain is reproduced.

• The knee is then slightly flexed while strong pressure is applied by the examiner into the popliteal fossa (Fig. 8-17).

• The sign is present if this pressure increases radicular symptoms.

• The sign demonstrates irritation of the sciatic nerve above the knee.

• This irritation is caused by stretching the nerve over an abnormal mechanical obstruction.

FIG. 8-17

CLINICAL PEARL

Deyerle sign is a variation of the Lasègue sitting test. The sign demonstrates the effects of inflammation or partial denervation (neural compression) in the sciatic distribution. The pain response may be caused by myalgic hyperalgesia as a response to denervation hypersensitivity.

DOUBLE-LEG-RAISE TEST

ALSO KNOWN AS BILATERAL STRAIGHT-LEG-RAISING TEST

Assessment for Lumbosacral Joint Involvement

PROCEDURE

• While the patient is supine, the examiner performs a straightleg-raising test on each of the patient’s lower extremities, noting the angle at which the pain is produced.

• Next, both lower limbs are raised together.

• If pain is produced at an earlier angle by raising both legs together, the test is positive (Fig. 8-18).

• In the presence of disc disease with resulting vertebral instability, the double-leg-raising movement will cause pain in the lumbar area.

• The test is specific and highly accurate for lumbosacral joint involvement.

FIG. 8-18

CLINICAL PEARL

A typical cases of disc prolapse are common. A definite history of injury or strain is often lacking. The pain may begin gradually rather than suddenly, and the symptoms may be confined to the back and never radiate down the leg. On the other hand, the pain is sometimes felt predominantly in the limb and is scarcely perceptible in the back.

ELY SIGN

ELY HEEL-TO-BUTTOCK TEST

Assessment for Lumbar Radicular or Femoral Nerve Inflammation

Comment

The size of the lumbar vertebral canal ranges from 12 to 20 mm in its AP dimension at the mid sagittal plane and 18 to 27 mm in its transverse diameter. Stenosis has been defined as a narrowing below the lowest value of the range of normal (Table 8-12).

TABLE 8-12 DIMENSIONS OF THE LUMBAR VERTEBRAL FORAMINA (VERTEBRAL CANAL)^*

Dimension	Size (Range)^†
Anteroposterior (in midsagittal plane)	12–20 mm
Transverse (interpedicular distance)	18–27 mm

‡ A typical vertebral foramen is rather triangular (trefoil) in shape. However, the upper lumbar vertebral foramina are more rounded than the lower lumbar foramina. L1 is the most rounded, and each succeeding lumbar vertebra becomes increasingly triangular, with L5 the most dramatically trefoil of all. From Dommisse GF, Louw JA: Anatomy of the lumbar spine. In Floman Y, editor: Disorders of the lumbar spine, Rockville, Md, and Tel Aviv, Israel, 1990, Aspen and Freund Publishing House.

* Dimensions below the lowest value indicate spinal (vertebral) canal stenosis.

† Dimensions of lumbar vertebral foramina are usually smaller than those of the cervical region but larger than those of the thoracic region. From Cramer GD, Darby SA: Basic and clinical anatomy of the spine, spinal cord, and ANS, St Louis, 1995, Mosby.