CHAPTER 6
Back
EPIDEMIOLOGY OF BACK PAIN
BACK PAIN IN THE GENERAL POPULATION
Prevalence and common causes
• Up to 80% (14%–85% lifetime prevalence, depending on definition) in the Western world (1)
• Second most common (MC) reason for physician visit (after upper respiratory problems)
Male = female, peak incidence between the ages of 30 and 50
• MC cause of work-related disability <45 years and the most expensive cause of work-related disability
• Isolated low back pain (LBP): 85% have nonspecific (no specific pathoanatomical) diagnoses
Risk factors
• Aging (degenerative changes), heavy lifting and twisting, bodily vibration, obesity, and poor conditioning
BACK PAIN IN CHILDREN
• Spondylolysis: 50%
• Mechanical LBP: 25%
• Discogenic: 10%
BACK PAIN IN ATHLETES
Prevalence
• Common cause of pain in young athletes, (2) 1% to 30%, MC cause of missed playing time in professional athletes
• Sprains: MC cause of back pain (3)
• Spondylolysis: peak in ages from 6 to 10 years, prevalence: 4%, repeated hyperextension motions such as gymnastics and diving
• Unclear etiologies: only 15% have precise pathoanatomical diagnosis
• MC: strain/sprain, disc herniation, spinal stenosis, sacroiliac dysfunction, and fracture (compression, sacral stress)
Sports-related rates of LBP
• Higher rates in gymnastics, diving, weightlifting, golf, American football, rowing, and others (ice hockey, rugby, basketball, and racquet sports)
Higher in contact sports: football (30% have significant back pain, highest in linemen), ice hockey, basketball, wrestling, and rugby
Noncontact sports: 29% professional golfers, 22.5% of spondylolysis in track and field, weightlifters, racquet sports, gymnasts, and divers
• Rare in runners
Risk factors: Hamstring flexibility (spondylolysis), prior back pain (six times higher), improper technique, or poor equipment
Common causes of LBP in mature athletes
• Prevalence of back pain among former elite athletes of all sports is lower than that in nonathletes
BACK PAIN AT WORK (4)
Prevalence
• 14% to 80% in people of working age, depending on the case definition
Risk factors
• Manual work: materials handling, frequent bending or twisting, whole body vibration, carpenter, bus driver, and others
• Physical hard work: different definitions exist, but in general include agricultural, construction, mechanics, fishing, and soldering
• Job dissatisfaction and job control
Work-related factors for lumbar disc disease
• Heavy lifting, frequent bending and twisting
Predictors for disability after LBP at work
• Heavy physical demand, ability to modify work, social support, short job tenure, job satisfaction, and fear of re-injury (5)
SPORTS WITH HIGHER PREVALENCE | COMMON PATHOLOGIES | SUGGESTED MECHANISM |
Wrestling, gymnastics Dance and ballet, soccer American football Volleyball, throwing sports Racquet sports | Spondylolysis Spondylo-listhesis | Repetitive flexion/extension Hyperextension |
Weightlifting American football | Scheuermann’s disease | Repetitive loading with flexion |
Dancers, gymnasts, and swimmers | Scoliosis |
|
Weightlifting American football Endplate fracture in skeletally immature athletes | Fracture/compression fracture | Axial loading |
Hockey | Spinous process fracture | Resisted muscle contraction Direct trauma |
DIFFERENTIAL DIAGNOSIS
Differential diagnosis based on the location and radiation of pain (Flowchart 6.1) (1,6)
WORKING DEFINITION OF LOW BACK
• Below the 12th rib to the iliac crest (vs buttock: below the iliac crest to the gluteal fold); Figure 6.1
• Patients and clinicians use different definition, description based on anatomic landmark helps to facilitate communication between the patient and clinician
FIGURE 6.1
Surface anatomy of low back.
M, muscle; N, nerve; PSIS, posterior superior iliac spine.
Source: Adapted from Ref. (7). Franklyn-Miller A, Falvey E, McCrory P. The gluteal triangle: a clini-cal patho-anatomical approach to the diagnosis of gluteal pain in athletes. Br J Sports Med. 2009;43(6):460–466.
FLOWCHART 6.1
Differential diagnosis of back pain based on the location.
–, negative; +, positive; LBP, low back pain; N, nerve; SI, sacroiliac; syn., syndrome.
RADIATING BACK PAIN BELOW THE KNEE | OTHER LOW BACK PAIN |
Radiculopathy (from disc disease, spinal stenosis) • Sciatica: sensitive and specific for radiculopathy (8) • Mechanical (MC cause, >90%): discal disruption, spinal stenosis • Nonmechanical: DM, infectious, tumor etc Claudication • Neurogenic: spinal stenosis • Vascular: peripheral arterial disease Piriformis syndrome (buttock pain with radiating leg pain) | Localized (axial pain) • Facet joint disease (±referred pain) • Degenerative disc disease • Vertebral body fracture (±radiculopathy) Localized ± referred/radiating pain (proximal to knee) • Upper lumbar radiculopathy (to above the knee) • Myofascial pain disorder (± referred pain) • Sacroiliac joint dysfunction (± referred pain, occasionally distal to the knee) • Facet arthropathy • Cluneal neuropathy • Proximal hamstring tendinopathy (at the ischial tuberosity) |
DM, diabetes mellitus; MC, most common.
DIFFERENTIAL DIAGNOSIS BASED ON MODE OF ONSET
• Acute onset: disc disruption or inflammation, vascular process
• Gradual onset: degenerative spondylosis, spinal stenosis
Preceding events (with trauma or injury vs without clear event)
Unusual causes of LBP
LOCAL CAUSES | REFERRED FROM OUTSIDE THE SPINE (<5%) |
Neoplasia • Metastatic cancer • Multiple myeloma • Lymphoma and leukemia • Spinal cord tumor • Retroperitoneal tumor • Primary vertebral tumors Infection • Osteomyelitis, septic discitis, paraspinal abscess, epidural abscess Inflammatory arthropathy • Ankylosing spondylitis • Psoriatic spondylitis • Reiter syndrome • Inflammatory bowel disease Paget’s disease | Pelvic organ involvement • Prostatitis • Endometriosis • Chronic (pelvic) inflammatory disease Renal pathologies • Nephrolithiasis • Pyelonephritis • Perinephric abscess GI pathologies • Pancreatitis • Cholecystitis • Penetrating ulcer Abdominal aortic aneurysm/rupture (9) • More abdominal pain and back pain rather than isolated back pain |
FIGURE 6.2
Pain referral pattern from myofascial trigger point and painful facet joint.
CLASSIFICATION AND DIFFERENTIAL DIAGNOSIS OF SPINE DEFORMITY (10)
Scoliosis: frontal plane deformity ± rotation in axial plane
• Idiopathic: infantile <3 years; juvenile: 3 to 10 years; adolescent (MC): 10 years to maturation
• Degenerative or de novo scoliosis (11)
• Neuromuscular: neuropathic (cerebral palsy, syringomyelia, spinocerebellar degeneration, polio, spinal muscular atrophy, or myelomeningocele) or myopathic (muscular dystrophy, myotonic dystrophy, or arthrogryposis)
• Miscellaneous
Hyperkyphosis: sagittal malalignment; idiopathic, Scheuermann in young adults, and compression fracture in the elderly
Hyperlordosis: spondylolisthesis and back spasm
DIFFERENTIAL DIAGNOSIS OF SEVERE BACK SPASM (12)
• Infectious disease: tetanus
• Toxic disease: strychnine poisoning
• Neoplastic disease: mass-effect causing irritation to spinal nerves or paraspinal muscles
• Vascular disease: spinal arteriovenous malformations and intermittent venous congestion
• Genetic disease: hyperekplexia
• Autoimmune disease: stiff person syndrome, Isaacs’s syndrome, spinal multiple sclerosis, paraneoplasia, and myelitis
DIFFERENTIAL DIAGNOSES OF BOWEL AND BLADDER DYSFUNCTION RELATED TO SPINE PATHOLOGIES
Rare but highly morbid conditions such as cauda equina syndrome (CES) (2% of all disc herniation) or conus medullaris should be in differentials (requiring immediate referral to emergency room [ER])
| CONUS MEDULLARIS | CAUDA EQUINA SYNDROME (13) |
Pain | Not common Can be severe, bilateral, and symmetric in perineum or thigh | Severe back and radicular pain (83%–90%) |
Onset | Sudden and bilateral | Gradual and unilateral or acute |
Bladder/rectal dysfunction | Early and marked involvement | Less marked impairment Saddle anesthesia and vesicular (urinary retention or incontinence (~55%) >rectal dysfunction (decreased rectal tone) >erectile dysfunction |
Sexual function | Erection and ejaculation impaired | Late and less marked |
Sensory deficit | Saddle distribution, bilateral, symmetric, dissociation of sensation | Unilateral or asymmetric, sacral N distribution |
| Saddle distribution, may be unilateral and asymmetric, no dissociation of sensation | |
Motor loss | Symmetric, not marked, fasciculation | Asymmetric, more marked, atrophy, no fasciculation |
Reflex loss | Only Achilles reflex | Late and less marked |
N, nerve.
Other causes
• Iatrogenic from medications; antidepressant (TCA), opioids analgesics (urinary retention), muscle relaxants (retention), and sedatives
DIFFERENTIAL DIAGNOSIS OF CHEST WALL PAIN (FLOWCHART 6.2)
• If there are cardiovascular risk factors or if there is any suspicion, first evaluate cardiac causes and complete the cardiac workup with cardiology consultant
• Incidence of musculoskeletal causes of chest pain
13% to 20% of patients originally thought to be of cardiac origin
FLOWCHART 6.2
Differential diagnosis of chest wall pain.
MSK, musculoskeletal.
Differential diagnosis based on anatomical structures
ANATOMIC STRUCTURE | PATHOLOGIES | CHARACTERISTICS |
Nerve | Intercostal neuralgia (eg, herpes zoster) | Common, thoracic is the MC location, zoster sine herpes (without skin lesion) |
Thoracic spine root lesion (disc, tumor, infection) | Rarer causes: diabetes, sarcoidosis, tuberculosis, and syphilis | |
Spinal cord pathology | Myelopathy, dural AVM (lower thoracic), and root sleeves | |
Rib | Rib stress fracture | Posterolateral angle: MC location |
Slipping rib syndrome | 8th to 10th rib; pain under the rib cage and upper abdomen | |
Sternum | Sternal stress fracture | Anterior chest pain |
Manubrium stress fractures | ||
Painful xiphoid syndrome | ||
Joints | Costochondritis | Upper chest wall |
Tietze’s syndrome | 2nd and 3rd costochondral junction (upper chest wall) | |
Sternoclavicular arthritis | Anterior neck pain | |
Manubriosternal arthritis | ||
Costovertebral subluxation/arthritis | Posterior upper back pain | |
Sternocostal synchondrosis/subluxation | ||
Muscle | Intercostal muscle strain | MC followed by pectoralis M strain |
Epidemic myalgia | Group B coxsackie virus, intercostal and upper abdominal wall M (severe/sharp pain) | |
Precordial catch syndrome | Diagnosis of exclusion, left parasternal near cardiac apex, increased by deep breathing, no local tenderness | |
Referred pain (extrinsic causes) | Shoulder pathologies Pleuritis Cardiac conditions Esophageal dysfunction Renal: nephrolithiasis |
|
AVM, arteriovenous malformation; M, muscle; MC, most common.
DIFFERENTIAL DIAGNOSIS OF BUTTOCK PAIN
Anatomy-based differential diagnosis (see Figure 6.1)
Modified gluteal triangle: Triangle of spinous process of L5, ischial tuberosity, and laterally on the greater trochanter (see Figure 6.1) (7,157)
LOCATION | ANATOMIC STRUCTURE | PATHOLOGIES AND CHARACTERISTICS |
Superior | Iliac crest | Thoracodorsal fascia, quadratus lumborum M strain/myofascial pain syn |
Iliolumbar ligament | Iliolumbar lig sprain: mimics or coexists with SIJ pain (158), paraspinal region pain (above the SI dimple) | |
Gluteus medius | Myofascial pain syn: often poorly localized, trigger point, dry needling for diagnosis and Tx Gluteus medius strain/tear (muscle belly or near attachment to iliac crest) Pain worse in stance or running and tenderness | |
Fat pad | Epi-sacral painful fat pad syndrome (not all fat pads are painful) | |
Superficial cluneal N | Iatrogenic superficial cluneal nerve injury from bone graft or muscle injection Superior cluneal nerve entrapment syndrome (at traversing iliac crest) Maigne’s syndrome (thoracolumbar transition zone) with irritation of posterior rami T12 to L2 | |
In the triangle | SI joint | SI joint ligament sprain, joint dysfunction, arthritis Pain in the gluteal region (often lower back above iliac crest) ± referred pain (often thigh and rarely the leg) |
Piriformis | Piriformis syndrome (buttock pain ± referred pain or sciatica) | |
Obturator internus | Similar to piriformis syndrome; slightly lower than piriformis on the location of local tenderness, difficult to differentiate | |
Vessels | Circumflex femoral vein thrombosis Rare, tenderness and pain on resisted flexion without M weakness | |
Lat to triangle | Femoro-acetabular (hip) joint | Femoroacetabular impingement syn. Degenerative: restriction in daily living, pain on weight bearing +/- clicking or locking |
Femoral neck | Stress fracture Female, change in volume of training, osteopenia/osteoporosis (159) | |
Trochanteric bursa
Gluteus medius/minimus tendon Tensor fascia lata Iliotibial band (ITB) | Trochanteric tendinobursitis • Pain getting up off bed, tenderness superior and over the GT Gluteus medius (>minimus) tendinopathy/tear
TFL/ITB syndrome • Lateral thigh pain worsens with exercise ± snapping hip, sharp burning pain | |
Lateral femoral cutaneous N | Meralgia paresthetica • Anterolateral thigh pain/sensory symptoms (tingling, pins/needle sensation) | |
Med to triangle | SI joint | SI joint/ligament pain Sacroiliitis with/without spondyloarthropathy (AS) • Systemic symptoms (morning stiffness, improvement with mod. activity, diffuse buttock pain, other past medical history such as psoriasis etc.), asymmetric polyarthropathy involving large joints |
Sacrum | Sacral stress fracture • Vague incapacitating gluteal pain, pelvic anteversion, insufficiency versus fatigue fracture, and leg length discrepancy (risk factor) | |
Coccyx | Coccygodynia • Dull, achy pain on sitting, sitting to standing | |
Pubic ramus | Stress fracture of pubic ramus • Gradual onset, pain standing on one leg and hop, and deep buttock pain | |
Sup. (Inf.) gluteal A | Entrapment and endofibrosis • Claudicant gluteal pain on exercise relieved by rest, and smoking Aneurysm of inferior gluteal artery | |
Hamstring M/ischial tuberosity | High hamstring syndrome/tear, apophysitis/ischial tuberosity avulsion • Shooting pain following high-energy kick or change of direction Posterior compartment syndrome • Associated with avulsion fracture, sudden tearing pain gradually worsening over 24 hours in acute, more insidious in chronic | |
Obturator N | Medial thigh pain on exercise relieved by rest, adductor weakness, superficial dysesthesia, hyperesthesia on med thigh | |
Referred pain | Disc disease with radiculopathy Lumbar pathology (disc, facet) | LS radiculopathy • LBP radiating down to the leg (below knee) typically • Absence of LBP or leg pain (below knee) doesn’t rule out lower lumbar radiculopathy |
A, artery; AS, ankylosing spondylitis; ITB, Iliotibial band; LBP, low back pain; lig, ligament; LS, lumbosacral; M, muscle; N, nerve; SIJ, SI joint, sacroiliac joint; syn, syndrome; TFL, tensor facsia lata; Tx, treatment.
ANATOMY
BONE AND JOINT
Spine Complex (14)
Vertebra
• From anterior to posterior: body, pedicle, transverse process (at junction of pedicle and lamina), articular process (facets), lamina (including pars interarticularis), and spinous process (Figure 6.3)
• Characteristics of vertebral anatomy
Variation: sacralization of L5 (~17% of population) and lumbarization of S1 (4–6 lumbar vertebrae, less common than sacralization)
Vertebral body: taller anteriorly 
contribute to lordosis
Mamillary process; tubercles on the superior articular processes
L5: the largest vertebral body
Intervertebral disc
• Nucleus pulposus and annulus fibrosus (fibrocartilaginous lamina)
• Intervertebral disc accounts for one-fourth the length of the spinal column, partly responsible for physiologic lumbar lordosis
• Nucleus pulposus: gelatinous inner section containing water, proteoglycan, and collagen
• Annulus fibrosus: concentric layers of fibrous tissue and fibrocartilage
Vertebral canal (15)
• Space containing the spinal cord and nerve roots (caudal to L2)
• Spinal canal (central) bordered by
Anteriorly: posterior longitudinal ligament
Posteriorly: ligamentum flavum, lamina, and facet joints
Laterally: pedicles
ZONE | DESCRIPTION | PATHOLOGY CAUSING STENOSIS |
Entrance zone | Cephalad (superior) and medial aspects of lateral recess, which begins at lateral aspect of thecal sac and runs obliquely down and laterally toward intervertebral foramen. Same level of nerve root involved, L4 root under L4 superior articular process | Facet hypertrophy, particularly involving superior articular process Developmental problem (short pedicle) |
Midzone | Beneath pars interarticularis and just inferior to pedicle Bounded anteriorly by posterior aspect of vertebral body and posteriorly by pars; medial boundary is open to central spinal canal Contains dorsal ganglion and ventral root in extension of dura mater, more sensitive to the stenosis (decreased effective size) | Osteophyte under pars interarticularis Fibrocartilagenous or bursal hypertrophy at spondylolytic defect |
Exit zone | Formed by intervertebral foramen Lumbar nerve covered by perineurium | Hypertrophic facet arthritis or subluxation and osteophytic ridge along the superior margin of the disc |
FIGURE 6.3
Bony and soft-tissue anatomy with innervation in the lumbar spine (A and B) and location of lateral stenosis (C).
aCross-sectional view incorporates the level of the vertebral body (VB), and the periosteum (P) on the right and the intervertebral disc (IVD) on the left. all, anterior longitudinal ligaments; altlf, anterior layer of thoracolumbar fascia; dr, dorsal ramus; ds, dural sac; esa, erector spinal aponeurosis; grc, gray ramus communicans; i, intermediate branch; IL, iliocostal lumborum; l, lateral branch; LT, longissimus thoracic; m, medial branch; M, multidus; pll, posterior longitudinal ligament; pltlf, posterior layer of thoracolumbar fascia; QL, quadratus lumborum; st, sympathetic trunk; svn, sinuvertebral nerve; vr, ventral ramus; zj, zygapophyseal joint; PM, psoas muscle.
Source: Adapted from Ref. (18). Suri P, Rainville J, Kalichman L, Katz JN. Does this older adult with lower extremity pain have the clinical syndrome of lumbar spinal stenosis? JAMA. 2010;304(23):2628–2636.
Meninges
Dura mater
• The most superficial, becomes epineurium at the dorsal root ganglion
• Ligaments of Hoffman: connect the dural mater and nerve root to the posterior longitudinal ligament
Arachnoid
• Lines dural sac
• Subarachnoid space ends at the dorsal root
Pia mater
• The deepest: forms filum terminale (anchors to the coccyx)
Chest Wall and Thoracic Spine (19)
Thoracic spine
• Upper 10 thoracic vertebrae: costal facet on the anterolateral surface of the transverse process articulating with rib
Costal facets: thoracic vertebral body, anterior to the pedicle articulating with ribs
• Smaller clearance between the spinal cord and bony spinal segments (9.2 mm in thoracic spine vs 11.3 mm in the cervical spine), spinal cord/canal ratio: 0.4 in thoracic spine versus 0.25 in cervical spine
• Primary movements: rotation (8°–9°) and lateral bending (6°)
Ribs (Figure 6.4)
• 1 to 7 ribs: anteriorly with sternum via costochondral cartilage; 8 to 10 ribs: costochondral cartilage with adjacent ribs; 11 to 12 ribs: floating ribs
• 2 to 10 ribs: articulates with vertebral bodies and transverse processes of two vertebrae via the costovertebral and costotransverse (with transverse process) joints
FIGURE 6.4
Anatomy for chest wall pain.
M, muscle.
Thoracic spinal nerves and intercostal nerve
• Ventral rami: no plexus (except T1), continues as intercostal nerves
• T1 (2): supply thorax wall and give branches to brachial plexus
T1: larger branch to brachial plexus, smaller to the 1st intercostal nerve
Intercostobrachial cutaneous nerve: axillary sensation (20)
• T3–6: thoracic wall
Below the intercostal vessels (vein, artery, and nerve), between pleura and posterior intercostal membranes or between internal and innermost intercostal muscle
Innervates intercostal muscle, subcostal muscle, serratus post, superior, transversus thoracic muscle
Cutaneous branches: lateral cutaneous and anterior cutaneous branches
Articular branches to the rib periosteum
Branches to the parietal pleura
• T7–11: abdomen and peritoneum
Rectus abdominis and anterior cutaneous branches on the abdominal wall
• T12: subcostal
Sacroiliac Joint (Figure 6.5)
• Five sacral vertebrae and four coccygeal vertebrae
• Large, auricular-shaped, diarthrodial synovial joint
FIGURE 6.5
Sacroiliac joint and ligament.
The potential for vertical shearing is present in ~30% of sacroiliac (SI) joints, due to the more acute angulation of the short, horizontal articular component
• Part synovial: anterior inferior 1/3, hyaline cartilage on sacrum side, fibroid cartilage on the iliac side
• Part syndesmosis
• Ligament
Sacroiliac ligament: primary stabilizer of SI joint
Anterior, posterior (sacrum to posterior superior iliac spine [PSIS], short and long) and interosseous
More extensive posteriorly, function as a connecting band between the sacrum and iliac because of an absent or rudimentary posterior capsule
Main function is to limit motion in all planes of movement
In women, the ligaments are weaker, allowing mobility necessary for parturition
Sacrotuberous ligament (21)
Iliac spine, sacrum to ischial tuberosity
Stabilize the sacroiliac joint, provide vertical stability
Insertion site for gluteus maximus proximally, distally merge with conjoint hamstring tendon (biceps femoris and semitendinosus)
Sacrospinous ligament
Ischial spine to sacrum and coccyx
Divides sciatic notch into greater and lesser sciatic foramina
• Innervation of SI joint (22)
Posterior SI joint: the lateral branches of the L4–S3 (L3–S4) dorsal rami
Anterior SI joint: L2 (to L5)–S2 ventral rami depending on the study
The anterior SI joint is less innervated
Animal study indicates that the SI joints may have lower pain sensitivity than that of the lumbar facet joints
NERVE
Nerve Innervation of the Spine
Somatic nociception
• Sinuvertebral nerve (see Figure 6.3)
The posterior longitudinal ligament, posterior annulus, epidural venous plexus, and ventral dura
Sinuvertebral nerve 
the dorsal root ganglion 
the spinal cord and brain
• The dorsal ramus: medial, intermediate, and lateral branches
The medial branch of the dorsal ramus
The facet joint, lamina, spinous process, and posterior ligaments
Supplies the multifidus muscle
Mamilloaxillary ligament: can entrap dorsal rami 
denervation of paraspinal muscle
The intermediate and lateral branches supply lateral muscles and receive supply from the skin (eg, cluneal nerve)
Sympathetic nociception
• The anterior and posterior longitudinal ligaments, annulus, and vertebral body
• Anterior spinal sympathetic ramus (anteriorly)
• The sinuvertebral nerve and white ramus communicans (preganglionic) posteriorly 
Paraspinal sympathetic ganglion 
grey ramus communicans (postganglionic) 
dorsal root ganglion
Possible mechanism of pain from spinal stenosis
• Venous engorgement and arterial insufficiency
• Venous congestion and stagnation 
increase epidural and intrathecal pressures 
microcirculatory, neuroischemic insults
• Arterial insufficiency: arterial dilatation of the lumbar radicular vessels during lower limb exercise. Loss of reflexic dilatation in spinal stenosis
Lumbar Root and Lumbosacral (LS) Plexus (Figure 6.6)
Ventral root 
spinal nerve (with dorsal root) 
ventral ramus 
lumbosacral (LS) plexus (from spinal cord distally)
Biggest nerve root: L5 with smaller lateral foramen at L5–S1 
one of the reasons for high prevalence of L5 radiculopathy
FIGURE 6.6
Lumbosacral plexus.
N, nerve.
Source: Adapted from Ref. (23). Laughlin RS, Dyck PJ. Electrodiagnostic testing in lumbosacral plexopathies. Phys Med Rehabil Clin N Am. 2013;24(1):93–105.
| NERVE | NOTES |
Lumbar plexus |
| L1–3, part of L4. Course within the psoas muscle |
Iliohypogastric and ilioinguinal (L1) Genitofemoral (L1–2) Lateral femoral cutaneous (L2–3) | Check groin region (P 302) | |
Obturator N (ant. div., L2–4) | Through obturator foramen | |
| Ant. div., post div., innervates hip, knee, and medial thigh sensation | |
Femoral (post div., L2–4) | Lateral border of psoas major, runs between psoas and iliacus | |
Femoral triangle, lat. to vein and artery | ||
Branches: Ant. femoral cutaneous N and saphenous N | ||
Sacral plexus |
| L4,5 (lumbosacral trunk) and S1–4 |
In the deeper surface of the piriformis | ||
Posterior femoral cutaneous S–3 | Inf. cluneal and perineal branches | |
Accompanied by sciatic N | ||
Pudendal S2–4 | Ant div., course below piriformis, lesser sciatic foramen, pudendal canal | |
N to obturator internus L5–S1 | ||
N to quadratus femoris L5–S2 | ||
Superior gluteal L4–S1 | Above (cephalad) piriformis, innervates glut. med., min., TFL | |
Inferior gluteal L5–S2 | Below (caudad) piriformis, innervates gluteus maximus Sup and inferior gluteal N: post div. | |
Sciatic N L4–S3 | Tibial (medial/ant. div.) and peroneal (lat./post div.) |
Ant., anterior; div., division; glut med, gluteus medius; glut min, gluteus minimus; inf., inferior; lat., lateral; N, nerve; post, posterior; post div., posterior division.
Nerves in the Buttock
Cutaneous nerves (24)
• Superior cluneal nerve: medial (L1), intermediate (L2), and lateral (L3) or T12-L2
Course
Pass through the psoas major, and paraspinal, posterior to the quadratus lumborum under the thoracodorsal fascia
Traverse iliac crest—distance from midline (at the level of PSIS): ~5, 6.5, and 7.3 cm for medial, intermediate, and lateral branches, respectively
– Injection points (5–8 cm from midline on the posterior iliac crest) for superior cluneal nerve
• Middle cluneal nerve: from posterior sacral foramen, S1–3, S1 most constant and S3 (in 45%)
Traverse the paraspinal muscle and tissue overlying the gluteus maximus
Less likely entrapped due to shorter length and course through multiple fasciae
• Inferior cluneal nerve (25): from posterior femoral cutaneous nerve from S1–3, comes off with perineal branch (horizontal course medially), reflects cranially between glut. maximus and hamstring muscle
Motor branches (check lumbar spine anatomy)
• Superior gluteal nerve: gluteus medius, minimus and tensor fascia lata
• Inferior gluteal nerve: gluteus maximus
• Nerve to obturator internus (L5–S1)
• Nerve to quadratus femoris (L5–S2)
Pudendal nerve (anterior rami of S2–4): (26)
• Course
Pass through greater sciatic foramen (with internal pudendal artery caudal to the piriformis muscle)
Posterior to sacrospinous ligament and between sacrospinous and sacrotuberous ligament through lesser sciatic notch and Alcock’s canal (the fascia tunnel formed by the duplication of internal obturator muscles, under the plane of the levator ani muscle, on the lateral wall of the ischiorectal fossa)
Common mechanism of injury: parturition, bicycle riding, blunt trauma, and penetrating injury
• Three terminal branches
The dorsal nerve of the penis, the inferior rectal nerve, and the perineal nerve
Sensation around the skin of penis (clitoris), perianal area, and the posterior surface of scrotum or labia majora
The external anal sphincter (inferior rectal nerve) and deep muscles of the urogenital triangle (perineal nerve)
ARTERY (27)
Aorta internal iliac artery posterior division (superficial gluteal artery) and anterior division (inferior gluteal artery)
• Superior gluteal artery travels through the greater sciatic foramen above (superior to) the piriformis, then divides into superficial and deep division. Supplies the iliacus, piriformis, and obturators
Superior gluteal artery in gluteal canal: osseous fibromuscular structure
The crest of greater sciatic notch (superiorly), inferior by the arcade of Bouisson (superior border of the piriformis)
• Inferior gluteal artery
Inferior gluteal artery: inferior to the piriformis, supplies gluteus maximus and branches to become sciatic artery (runs with sciatic nerve)
Aneurysm or pseudoaneurysm can affect the sciatic nerve
• Iliolumbar and lateral sacral artery
Distal aortic occlusion: impotence and buttock claudication
MUSCLE
Paraspinal muscle (Figure 6.3)
• Superficial group: ipsilateral rotation with ipsilateral contraction
Erector spinae: iliocostalis, longissimus, and spinalis (lateral to medial)
• Deeper group: deeper to erector spinae, contralateral rotation with ipsilateral contraction
Transversospinalis: multifidus (deep to semispinalis) and rotatores
Multifidus
Local postural muscle, length transducer, or position sensors by way of rich composition of muscle spindles that pass along two or three spinal levels
Segmental stabilizer
Monosegmental (single root) supplied muscle
• Clinical implications in LBP
Pain perception from hypertonic saline injection to paraspinal muscle (28)
Depth and lateral position may be the most critical descriptors to determine the source of acute lumbar muscular pain
Overlapping regions of pain may be explained by convergence of receptive fields, innervation of multifidus fascicles at multiple lumbar segments, and convergence of sensory input from different muscles to the same sensory cell bodies (animal study)
Changes in chronic LBP
– Have both impaired spinal proprioception and a decrease in paraspinal muscle cross-sectional area (29)
– Association between decreased paraspinal muscle density and the presence of lumbar spondylosis (30)
Extrinsic muscles
• Quadratus lumborum: flexes vertebral column laterally when acting separately. Together maintains posture. Assists in forced inspiration (31)
Cited as a common source of back pain (myofascial pain)
• Latissimus dorsi: adductor and extensor of the shoulder (glenohumeral joint), an extensor and lateral flexor of the back, and is purported to have a bracing effect on the sacroiliac joint, in concert with the gluteus maximus through its action on the posterior layer of thoracolumbar fascia (32)
• Serratus posterior inferior: spinous processes of T11–L2 to inferior borders of 8th–12th ribs, innervated by ventral rami of T9–12 spinal nerves, depresses ribs and counteracts inward pull of diaphragms (assist forced expiration and rotation/extension of the trunk)
Buttock muscles (see the following table)
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