1.6

The thoracolumbar fascia An integrated functional view of the anatomyof the TLF and coupled structures

Q 2

Andry Vleeming

Introduction

To understand and treat low back pain, or even bet-ter, locomotion in vertebrates, models based on de-scriptive anatomy are generally used. This branchof anatomy was developed to answer the questionwhat structures does our body consist of, and to cat-egorize them. Categories like spine, pelvis, and legs,are primarily based on bone anatomy.

Functional anatomy of the locomotor system,which is strongly linked to biomechanics, attemptsto explain how bones, ligaments, andmuscles operateas a system. Consequently, use of categories likespine and pelvis can be misleading. From a biome-chanical and neurophysiological point of view theyare fully integrated. “Back muscles”, for instance,are categorized in descriptive anatomy as typicallyspinal. However, parts of these “back muscles” bridethe sacroiliac (SI) joints. As an example, in man themultifidus muscle shows an extensive attachment toboth the sacrum and the iliac crest (Vleeming &Stoeckart 2007).

With the use of descriptive anatomical models itis tempting to regard pain in the area of the SI jointsas a separate syndrome, not as part of low back pain.However, these joints are fully and crucially inte-grated in the spine–pelvis–leg mechanism (Snijderset al. 1993a). To function properly this mechanismneeds stability of the pelvis (external movement ofthe pelvis) and the SI joints and symphysis (internalmovement of the pelvis), for effective use of thethree levers connected to the pelvis: two legs andthe spine.

012, Elsevier Ltd.

Effective load transfer across the SI joints requiresspecific action of a variety of muscles, leading to suf-ficient compression of the SI joint, preventing shear(Snijders et al. 1993a, b). In increasing compressionthe biceps femoris and gluteusmaximusmuscles playa role (Vleeming et al. 1989a,b, 1992b 1996;DonTigny 1990; Vleeming 1990; Van Wingerdenet al. 1993). Both muscles are attached to the sacro-tuberous (and partially the sacrospinous) ligamentwhich functionally bridges the SI joint. Obviously,pain in the area of the SI joints is not necessarilya local problem; it can be symptomatic of a failedload transfer system (Snijders et al. 1993a, b).

The strong thoracolumbar fascia (TLF) (Tesh et al.1987) can be used for load transfer from the trunkto the legs (Mooney et al. 2001). The posterior(PLF) and middle layer (MLF) of this fascia are ofspecial interest because of the multiple connectionswith muscles. The main interest is whether muscle-induced tension of this fascia can assist in effectivelytransferring load between spine, pelvis, legs, and arms.

From an anatomical point of view the followingwas noticed:

In all preparations, the posterior layer of the thor-acolumbar fascia covers the back muscles from thesacral region through the thoracic region as far asthe fascia nuchae. At the level of L4–L5 and sacrumstrong connections exist between the superficial anddeep lamina. The transverse abdominal and internaloblique muscles are indirectly attached to the tho-racolumbar fascia through a dense raphe formed byfusion of the middle layer (Adams & Dolan 2007)of the thoracolumbar fascia and both laminas of the

P A R T O N E Anatomy of the Fascial Body

posterior layer. This “lateral raphe” (Bogduk &Macintosh 1984; Bogduk & Twomey 1987; DeRosa &Porterfield 2007) is localized lateral to the erectorspinae and cranial to the iliac crest.

Superficial lamina (Fig. 1.6.1)

The superficial lamina of the posterior layer of thethoracolumbar fascia is continuous with the latissi-mus dorsi, gluteus maximus, and partly the externaloblique muscle of the abdomen and the trapeziusmuscle. Cranial to the iliac crest, the lateral borderof the superficial lamina ismarkedby its junctionwith

D D

LR LRC C

B B

A A2 2

1 1

Fig. 1.6.1 • The superficial lamina. (A) Fascia of the gluteus

maximus. (B) Fascia of the gluteus medius. (C) Fascia of

external oblique. (D) Fascia of latissimus dorsi. (E) Cross-

hatched appearance of the superficial lamina due to

different fiber directions of latissimus dorsi and gluteus

maximus. 1. Posterior superior iliac spine. 2. Sacral crest.

LR, part of lateral raphe.Arrows (at left) indicate, fromcranial

tocaudal, thesiteanddirectionof the traction (50 N)given to

trapezius, cranial and caudal part of the latissimus dorsi,

gluteus medius and gluteus maximus, respectively. From

Vleeming et al., 2007, with permission.

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the latissimus dorsi muscle. Barker and Briggs (2007)reported that the superficial lamina also has an attach-ment of variable thickness to the lower border of therhomboid major muscle (Barker & Briggs 2007).

The fibers of the superficial lamina are orientatedfrom craniolateral to caudomedial. Only a few fibersof the superficial lamina are continuous with theaponeurosis of the external oblique and the trapezius.Most of the fibers of the superficial laminaderive fromtheaponeurosis of the latissimusdorsi andattach to thesupraspinal ligaments and spinous processus cranial toL4.Caudal toL4–L5, the superficial lamina is generallyloosely (or not at all) attached to midline structuressuch as supraspinal ligaments, spinous processes, andmedian sacral crest. In fact they cross to the contralat-eral side,where theyattachto the sacrum,posterior su-perior iliac spines, and iliaccrest.The levelatwhichthisphenomenon occurs varies: generally caudal to L4 butin some preparations already at L2–L3.

At sacral levels the superficial lamina is continuouswith the fascia of the gluteus maximus. These fibersare orientated from craniomedial to caudolateral.Most of these fibers attach to the median sacralcrest. However, at the level of L4–L5, and in somespecimens even as caudal as S1–S2, fibers cross themidline, attaching to the contralateral posteriorsuperior iliac spine and iliac crest. Some of thesefibers fuse with the lateral raphe and with fibersderived from the fascia of the latissimus dorsi. Dueto the different fiber directions of the latissimusdorsi and the gluteus maximus, the superficial laminahas a cross-hatched appearance at the level L4–L5,and in some preparations also at L5–S2.

Deep lamina (Fig. 1.6.2)

At lower lumbar andsacral levels the fibersof thedeeplamina are oriented from craniomedial to caudolat-eral. At sacral levels these fibers are fused with thoseof the superficial lamina. Since fibers of the deep lam-ina are continuous with the sacrotuberous ligamenthere, an indirect link exists between this ligamentand the superficial lamina. There is also a directconnection with some fibers of the deep lamina.

In the pelvic region the deep lamina is connectedto the posterior superior iliac spines, iliac crests, andthe long posterior sacroiliac ligament (O’Rahilly et al.1990). This ligament originates from the sacrum andattaches to the posterior superior iliac spines.

In the lumbar region fibers of the deep lamina de-rive from the interspinous ligaments. They attach to

F

G

F

E

G

B B

H H2 2

1 1

LRLR

Fig. 1.6.2 • The deep lamina. (B) Fascia of the gluteus

medius. (E) Connections between the deep lamina and the

fascia of the erector spinae. (F) Fascia of the internal

oblique. (G) Fascia of the serratus posterior inferior. (H)

Sacrotuberous ligament. 1. The posterior superior iliac

spine. 2. Sacral crest. LR, part of lateral raphe. Arrows (at

right) indicate, from cranial to caudal, traction to serratus

posterior inferior and internal oblique, respectively. From

Vleeming et al., 2007, with permission.

C H A P T E R 1 . 6The thoracolumbar fascia

the iliac crest and more cranially to the lateral raphe,to which the internal oblique is attached. In somespecimens, fibers of the deep lamina cross to the con-tralateral side between L5–S1. In the depression be-tween the median sacral crest and the posteriorsuperior and inferior iliac spines, fibers of the deeplamina fuse with the fascia of the erector. More cra-nial, in the lumbar region, the deep lamina becomesthinner and freely mobile over the back muscles. Inthe lower thoracic region fibers of the serratus poste-rior inferior muscle and its fascia fuse with fibers ofthe deep lamina.

Kinematics

The study presented here confirms some previousstudies and disagrees with others. The bilaminarstructure of the posterior layer of the thoracolumbar

fascia has been described by Fairbanks, andO’Brien (1980), Gracovetsky (1990), Macintoshand Bogduk (1986), Bogduk and Macintosh (1984),and Bogduk and Twomey (1987). They describethe orientation of the fibers of the superficial anddeep lamina as, respectively, caudomedial and caudo-lateral. The present study confirms the orientation ofthe laminae and their attachments. It is noteworthythat according to most studies (Fairbanks & O’Brien1980; Bogduk & Macintosh 1984; Bogduk & Twomy1987) the latissimus dorsi is mentioned as the signif-icant structure from which fibers of the superficiallamina originate. The gluteus maximus as origin forthe formation of the superficial fascia is ignored.Bogduk and Macintosh (1984) state that fiberslocated caudally from L3 decussate to the contra-lateral site, although it was not possible to trace theprecise origin of these fibers because of strong fusionto midline structures. The present study confirmsthe phenomenon of crossing fibers. The level of thecrossing varies from L2–S2. In contrast to the studyof Bogduk and Macintosh, no connections werefound between the serratus posterior inferior andthe superficial lamina: Its fascia is exclusivelyconnected to the deep lamina.

Bogduk and Macintosh (1984) and Bogduk andTwomeny (1987) describe the deep lamina as a struc-ture consisting of bands of collagen fibers extendingfrom the lumbar spinal processes to the iliac crestand lateral raphe. However, we can not confirm theexistence of bands of collagen fibers; we find a contin-uous layer. The authors pay no attention to the sacralpart of the deep lamina. As a consequence, theconnections with the sacrotuberous ligaments areomitted. Therefore the biomechanical model asproposed by Bogduk and Twomey (1987) is incom-plete. The bracing effect of the thoracolumbar fasciaon the lower lumbar spine and SI joints, essential forproper load transfer between spine and legs (Snijderset al. 1993a,b), canonly be adequatelydescribed if thecaudal part of the thoracolumbar fascia is included.

Overarching arguments aboutthe anatomy of the TLF

Another approach in looking at the thoracolumbarfascia in an integrated anatomical way is the anatom-ical work of Willard (2007). Willard shows that theTLF, including the myofascial sheath over the multi-fidus, is continuous with the supraspinous ligament,

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Mu

Fig. 1.6.3 • The attachment of the multifidus sheath

to the supraspinous ligament. The thoracolumbar fascia

(TLF) and multifidus sheath have been sectioned

longitudinally to reveal the multifidus muscle (Mu).

(A) The iliocostalis and longissimus muscles have

been removed. From Willard, In Vleeming et al., 2007, with

permission.

MLFL3

TrA

Fig. 1.6.4 • Middle layer of lumbar fascia (MLF). Note the

MLF is continuous with the transversus abdominis (TrA) via

inferolateral fibers and has thick attachments to the

transverse processes. MLF, middle layer of lumbar fasciae;

TrA, transversus abdominis. From Barker, In Vleeming et al.,

2007, with permission.

P A R T O N E Anatomy of the Fascial Body

ligament flavum, and facet joint capsule, with thedeeper ligaments as described here (Fig. 1.6.3).

Barker and Briggs (2007) summarize that themid-dle layer (MLF) of the TLF and the posterior layer(PLF) have a suitable morphology for generatingtransverse tension and are capable of transmitting ten-sile loads from attached muscles to all lumbarvertebrae. TheMLF, however, provides amore directroute and is indicated to transmit themajority of ten-sion of the transversus muscle (Fig. 1.6.4). Tension inboth layers (PLF and MLF) can influence features ofsegmental control in the sagittal plane and would bepredicted to have the greatest effects in thetransverse plane.

A biomechanical model of the SI joints was pro-posed (Snijders et al. 1993a,b). It was stated thatjoints with predominantly flat surfaces are wellsuited to transfer large moments of force but are vul-nerable to forces in the plane of the joint surfaces(Vleeming et al. 1990, 1992; Snijders et al. 1993a,b).Therefore flat joint surfaces go with restrictedjoint excursions. In a model (Vleeming 1990) of theSI joints based on anatomical and biomechanicalfindings, the principle of form and force closurewas discussed. Form closure refers to a stable situationwith closely fitting joint surfaces,wherenoextra forcesare needed to maintain the state of the system, given

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the actual load situation. In this situation no lateralforces are needed to counterbalance the effects ofthe vertical load. With force closure a lateral force isneeded.

The SI joint with its undulated form and sym-metrical ridges and depressions combined with com-pression and the generated friction is an example of ajoint (like any other joint) remaining stable through acombination of form and force closure (Vleeminget al. 1990). In case force closure is not sufficient,e.g., due to insufficient muscle action and hence in-sufficient ligament strain, form closure becomesimportant.

Pelvic instability (and peripartum pain) can bepartially and temporarily relieved by application ofa pelvic belt, a device fitting themodel of self-bracingof the SI joints (Snijders et al. 1976; Vleeming et al.1992). Force closure is increased by such a belt, lo-cated just cranially to the greater trochanter and cau-dally to the SI joints (Vleeming et al. 1992a,b;Snijders et al. 1993a). The belt can be used withsmall force, resembling the action of the laces of ashoe. As shown in this study, the coupled functionof gluteus maximus and contralateral latissimus dorsialso creates a force perpendicular to the SI joints(Mooney et al. 2001). The same is especially trueof the caudal fibers of the transversus and theinternal oblique muscle.

C H A P T E R 1 . 6The thoracolumbar fascia

Conclusion

In this chapter we have discussed the thoracolumbarfascia from a “fascial” point of view and its role intransferring forces between spine, pelvis, and legs,in relation to stabilization of the lower lumbar spineand SI joints.

The gluteus maximus and the latissimus dorsimerit special attention since they can conduct forcescontralaterally, via the posterior layer (Mooney et al.2001). We also discussed briefly the role of the MLFand especially the important effect of the transversesand internal oblique muscles on the MLF.

However, reality is more complex.Directly anterior to the deep layer of the PLF lies

the very strong erector spinae aponeurosis, overlyingboth the longissimus and the lumbar part of the ilio-costal muscle and the deeper-lying multifidus mus-cles. This aponeurosis blends together with themultifidus to the dorsal side of the sacrum and par-tially to the ilium. Contraction of both the erectormuscle and the multifidus will increase the tensionin the deep lamina, directly by pull, and indirectlyby dilating the complete posterior layer of the thor-acolumbar fascia, but also affecting the tension ofthe middle layer. If the transverses and the internaloblique fire earlier than other muscles in healthyindividuals, the “floor” (MLF) of the TLF envelopewill be tensed, also with a small effect on the PLF.In that case, erector and multifidus contractions will

VB

SP

TP

A

Fig. 1.6.5 • (A) Muscle contraction

resulting in increased tension to the

thoracolumbar fascia. EOA, external

oblique; ES, erector; IOA, internal

oblique; LD, latissimus dorsi; PM, psoas

major; QL, quadratus lumborum; SP,

spinous process; TA, transversus

abdominus; VB, vertebral body; TP,

transverse process. (B) Posterior view of

the musculature that attaches to the TLF.

Note the forces that are generated to the

fascia from the latissimus dorsi muscle

(1) from above, the gluteus maximus

(2) from below, and the internal oblique

muscle (3) and transversus abdominus

muscle from the front (4). From de Rosa and

Porterfield, In Vleeming et al., 2007, with

permission.

become more efficient because the slack of thefascial envelope is diminished.

For that reason we have to realize that withinthe envelope of the TLF (posterior, middle, andanterior layer) this strong aponeurotic fascia/tendonis present.

Furthermore, we have to realize that any externalmovement of the pelvis through the hip joints influ-ences the tension in the TLF, and also the relativeflexion or extension position of the trunk with orwithout lateroflexion and rotation. All these factorswill change the external and internal dynamics –force and pressure – of the fascial envelope (see alsoFig. 1.6.5).

Even more distant effects have to be considered.The fascia latae of the leg and especially the most

pronounced part, the iliotibial tract, can be expandedand tensioned by the large vastus lateralis muscle. Forexample, when a soccer player kicks the ball whilethe standing leg is flexed, both the vastus lateralisand gluteus maximus will be active. Both of thesemuscles influence each other’s function, because abig part of the gluteus maximus is directly connectedto the iliotibial tract of the fascia latae, which can alsobe dilated (“pumped up”) by the vastus.

We have discussed in this chapter that the gluteusmaximus couples the leg to the hipbones and tothe TLF. Therefore, the pathway of fascial transferis not restricted to the envelope of the three layersof the TLF.

ES

PM

QL

LD

IOAEOATA

1

3

2

4

B

41

A

B

Fig. 1.6.6 • Nutation and counternutation.

(A) Nutation winds up the sacrotuberous ligament.

(B) Counternutation winds up the long dorsal sacroiliac

ligament. From: Vleeming et al Movement, stability & lumbopelvic

pain, 2nd edition. Churchill Livingstone Elsevier, Edinburgh, 2007:

page 118, Fig. 8.6.

P A R T O N E Anatomy of the Fascial Body

Descriptive topographic anatomy likes to dissectand analyze structures topographically, while theyare actually functionally related. One has to realize,especially from a rehabilitation perspective, thatwithin the TLF envelope muscles are made of con-nective tissue of different kinds of tensile strength:“loose” connected tissue, tendons, aponeurosis, andfascia. So it is an illusion to consider the TLFa connective tissue envelope “filled” with muscletissue! It is a functionally coupled connective tissueunit filled with contractile elements.

In the beginning of this chapter we discussedforce closure of the spine and pelvis. Activation ofthe multifidus and the erector muscles and the sub-sequent tension through the erector spinae aponeu-rosis (all lying within the TLF envelope) develop astrong extension effect of the lower spine and anutation effect on the sacrum (Fig 1.6.6). Whenmoving from a lying to a standing or sitting positionthe sacrum nutates relative to the ilium and increasestension of the sacrospinous, sacrotuberous, andinterosseous ligaments, thereby further increasingforce closure of the sacroiliac joint.

Nutation is coupled to extension of the lumbarvertebra. Nutation of the SIJ means posterior rota-tion of the ilium relative to the sacrum. Extensionof the lumbar vertebrae coupled with posterior rota-tion of the ilium increases the tension in the iliolum-bar ligaments, coupling force closure of the SIJ to thelumbar spine.

Finally, also due to the coupling between thethoracolumbar fascia, muscles, and other large fascialsystems, one has to be very cautious in categorizingcertain muscles exclusively as belonging to the arm,spine or leg.

In transferring forces between spine, pelvis, and legs,the thoracolumbar fascia plays a crucial role, transfer-ring forces cranially, caudally, and also diagonally.

With all this in mind, we hopefully can appreciatehow to design a more suitable and realistic rehabilita-tion protocol for our lumbopelvic patients.

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