ADVANCES IN SPINAL SURGERY
From Cedars-Sinai Medical Center Institute for Spinal Disorders’ Sixth Annual Symposium on Current Concepts in
Spinal Disorders 2007
| DIAGNOSTIC, PROGNOSTIC, AND THERAPEUTIC NERVE BLOCKS —Howard L. Rosner, MD,
Medical Director, Cedars-Sinai Pain Center, Los Angeles, CA
|
| Purpose of injections: elucidate pain generator; predict treatment outcomes; reduce pain; understand purpose
before injection
|
| Components of pain: neuropathic; radicular; somatic; axial; all overlap; multiple sources of pain make diagnosis
difficult
|
| Anatomic pain generators in spine: anterior compartment (eg, vertebral body; endplates; intervertebral
discs; sympathetic chains); middle compartment (spinal cord; nerve roots; central canal; foramina); posterior
compartment (z-joint; supporting ligaments and musculature)
|
| Diagnostic procedures: nerve blocks intended to determine pain generator, eg, cervical radicular vs z-joint
problems; be specific—about diagnostic procedure being ordered; types of diagnostic procedures—medial
branch nerve block; selective nerve root block; discography; hardware injections; sympathetic chain
blocks; each assists in removing one component of pain; involve patient—in assessment of diagnosis immediately
after procedure; injection—local anesthetic most important component (higher concentrations
often used)
|
| Prognostic procedures: allow surgeon or patient to predict results of more definitive procedure; be
specific—tell patient and injector purpose of procedure; types of procedures—medial branch block to determine
whether fusion or medial branch rhizotomy appropriate; selective nerve root blocks; trigeminal
ganglion block (gives patient idea of how half-numb face would feel after trigeminal rhizotomy);
injection—very small doses of local anesthetic
|
| Therapeutic procedures: to relieve pain (either temporary or curative); be specific—about purpose of
procedure; types of procedures—intra-articular facet joint injections for inflammation; combine selective
nerve root blocks for radicular pain with therapeutic epidural injections; sympathetic chain blocks;
injection—steroid; botulinum toxin; alcohol; phenol; low concentration of local anesthetic
|
| UPDATE ON SPINAL CORD STIMULATION —Christopher J. Zarembinski, MD, Director, Acute Pain
Services, Cedars-Sinai Pain Center, Los Angeles, CA
|
| Possible mechanism of action: 1) allodynic animals have lower extracellular levels of γ-aminobutyric
acid (GABA); spinal cord stimulation may involve increased dorsal horn inhibitory action of GABA; intrathecal
baclofen (GABA agonist) produces augmentation of spinal cord stimulation; 2) intrathecal adenosine
receptor agonists also potentiate spinal cord stimulation; 3) suppression of sympathetic activity
via α-adrenal receptors; calcitonin-gene–related peptide induces vasodilation, which may explain redistribution
of coronary blood flow from regions of normal perfusion to areas of impaired myocardial perfusion
|
| Anatomy: paresthesias tend to diminish with thickening of dorsal cerebrospinal fluid (CSF) layer
|
| Terminology: cathode—negative charge; increases sodium permeability; anode—positive charge; shapes
field
|
| Indications for spinal cord stimulation: neuropathic pain with unilateral monoradicular distribution
(most likely to respond; radicular pain responds better than axial pain); peripheral vascular disease (ankle
brachial pressure index useful marker for following patients); phantom limb pain; stump pain; complex
regional pain syndromes; ischemic heart disease
|
| Outcome findings: reduced pain; decreased analgesic use (40%-80%); enhanced activities of daily living
(60% improvement); return to work (25% of patients); decrease in effectiveness over time (in 20%-
40% of patients)
|
 | Cost-effectiveness: paid for itself in ≈2 yr when effective
|
| Devices: new rechargeable implantable pulse generator (IPG); has longer life than primary cell IPG; 3-ft
programming range; neuronavigation (new software programs); main competitors—Advanced Neuromodulation
Systems (ANS); Medtronic; Precision device from Advanced Bionics (volume and weight
≈50% lower); spacing of leads—6 mm standard spacing; leads with 4-mm and 1.5-mm spacing now
available; narrower lead spacing produces deeper paresthesia; wide spacing produces shallow stimulation;
single-lead guarded array—cathode surrounded by anodes allows more focused direction of energy;
may lead to more effectiveness for axial pain; under development—magnetic resonance imaging (MRI)–
compatible hardware; antimicrobial coating; smaller batteries
|
| DISCOGRAPHY ISSUES AND PERSPECTIVES —Avrom Gart, MD, Director of Physical Medicine and
Rehabilitation, Cedars-Sinai Institute for Spinal Disorders, Los Angeles, CA
|
| Introduction: since discography depends on patient and person performing test, results can vary; provocative
discography provides diagnostic tool to help assess discs as potential pain generators in patients
with neck, middle, and lower back pain; needle placed inside disc to provoke pain; patient then asked
whether pain same as customary pain (concordance); correlation between anular disruption and concordance
based on level of anular disruption (eg, concordance lower with grade-1 anular disruption than
full-thickness anular fissure that leaks); compared to MRI—substances leaking out of disc onto nerve root
can cause radiculopathy and denervation without frank compression of disc
|
| Principles of discography: measures pressure—opening, distending, and closing pressures; pressure when
patient first feels pain; needle placement—extrapedicular approach with 22- or 25-gauge needle (use
smallest needle to minimize damage to nerve roots and disc); control necessary—study invalid without
control (negative) disc; report showing multiple levels of pain indicates need for psychologic assessment;
patient’s role—must be fully awake and cooperative; deep local anesthesia often preferable
|
| Aspects of discography: manometry—standard for measuring lumbar intradiscal pressure; not used in cervical
and thoracic regions; important not to overpressurize or use large volume; discography report—
should identify positive and negative levels, opening pressure, and control level; positive results followed
with computed tomography (CT; for more detailed anatomic analysis); causes of false positives—
injecting contrast too quickly, causing pressure spike; psychosocial distress; surgical outcomes—no significant
difference between discography and MRI
|
| FUNCTIONAL ANESTHETIC DISCOGRAPHY —Harvinder S. Sandhu, MD, Associate Professor of
Orthopaedic Surgery, Weill Cornell Medical College, and Director, Spine and Scoliosis Fellowship, Hospital
for Special Surgery, New York, NY
|
| Current diagnostic tools: most degenerative disc disease asymptomatic; goal to diagnose few symptomatic
discs; based today on x-rays, CT, MRI, and discography; MRI, CT, and x-ray can image degenerated
disc but not identify pain
|
| Discography: best tool for diagnosing painful degenerated disc; inherently flawed—depends on subjective
component; requires reliable, discerning, and honest patient (patient asked whether pain from discography
same as usual pain); unable to distinguish multiple causes for pain, eg, sacroiliac pain and disc pain;
data reveal almost 30% rate of misdiagnosis (often false positives); trial results demonstrate good surgery,
but pain often unresolved
|
| Functional anesthetic discography: rather than provoking pain, diagnosis made by relieving pain; rather
than lying down, patient stands and performs activities during test; provides access to disc over extended
period; patient able to reproduce postural pain, eg, swinging golf club; dual-lumen catheter with on-off
switch anchored in disc space; differentiates disc pain from other sources of pain; gives patient idea of
potential pain relief
|
| DISC REPAIR —Alexander R. Vaccaro, MD, Professor of Neurosurgery and Orthopaedic Surgery, Thomas
Jefferson University School of Medicine, and Co-Director, Regional Spinal Cord Injury Center of
Delaware Valley, Philadelphia, PA
|
| Introduction: “nothing costs more than a failed open spinal procedure”; 90% of costs in spine surgery expended
on 5% to 20% of patients with poor outcomes
|
| Recent focus on disc: attempt to understand nucleus pulposus and outer lining; center of disc—contains
few cells; rich in proteoglycans; has poor nutrition (no blood vasculature permeates disc in adults); notochordal
cells present until 10 yr of age replaced by nucleus pulposus cells and phenotypic chondrocyte-
like cells; outer portion of disc—fibroblasts form anulus fibrosus; thought to be source of much pain innervation;
lack of nutrition—makes disc immune privileged; may lead to degeneration of disc over time;
purpose of few cells in disc to make matrix and give it water-binding capacity
|
| Causes of degeneration: genetics primary cause; nutrition unable to penetrate center of disc (oxygen low;
glucose levels decline); cigarette smoking (smoking cessation relieves 20% of pain); certain activizes,
eg, riding in truck for long periods
|
| Treatment goals: to develop ability to inject agent into disc before instability develops; bone morphogenic
protein (BMP)-7 currently being injected into disc on investigative basis; BMP-7 intended to increase
water binding capacity and restore mechanical properties; aim to promote synthesis and negate
catabolism within disc
|
| Therapeutic options being investigated: include protein therapies (eg, BMP), gene therapies, and cell
therapies; gene therapy seeks to have body produce own proteins by replacing gene with therapeutic
gene (would increase production of metabolites and growth factors); speaker’s laboratory investigating
transformation of mesenchymal stem cells into nucleus pulposus cells
|
| GROWTH FACTORS —Dr. Vaccaro
|
| Current status: growth differentiation factor (GDF)-5—originally called BMP-14 when released by
DePugh (name changed because term BMP patented); presently called radotermin by World Health Organization;
transforming growth factor-beta (TGF- β) super-family—all BMPs included; BMPs expressed in
early limb development; induces differentiation of cartilage, bone, tendon, and ligament; recombinant
production through bacterial fermentation; 9 BMPs now identified
|
| Commercial products: 2 studies looking at acute tibial fracture and nonunion, and interbody fusion with
GDF-5; Helos brand name for GDF-5 with collagen and hydroxyapatite coating now available to surgeons;
different companies have own carriers; BMP-2 available in noncompressible carrier; optimal
carrier—noncompressible, 3-dimensional, with appropriate porosity and interconnectivity; would allow
slow elution of growth factor over time; under investigation; current problem—BMP “goes places it
shouldn’t go”; eg, BMP permeated intertransverse ligament, causing ossification and significant disability
|
| Speaker’s study: using BMP-2 in transforaminal interbody fusion; hopes to avoid problem of substance
eluting over time into epidural space; results—interbody space heals predictably; posterolateral heals
poorly; response improves with increasing dose; with 1-mg dose, success rate ≈80% in posterolateral gutter;
performed better than allograft-to-bone
|
Suggested Reading
Boas RA: Nerve blocks in the diagnosis of low back pain. Neurosurg Clin N Am 2:807, 1991; Burkus JK et
al: Influence of rhBMP-2 on the healing patterns associated with allograft interbody constructs in comparison
with autograft. Spine 31:775, 2006; Burkus JK et al: Use of rhBMP-2 in combination with structural
cortical allografts: clinical and radiographic outcomes in anterior lumbar spinal surgery. J Bone Joint Surg
Am 87:1205, 2005; Collins HR: An evaluation of cervical and lumbar discography. Clin Orthop Relat
Res:133, 1975; Foletti A et al: Neurostimulation technology for the treatment of chronic pain: a focus on
spinal cord stimulation. Expert Rev Med Devices 4:201, 2007; Haque R et al: Spinal nerve root stimulation.
Neurosurg Focus 21:E4, 2006; Hidaka C et al: Gene therapy for spinal applications. Orthop Clin North Am
33:439, 2002; Huang RC et al: The current status of lumbar total disc replacement. Orthop Clin North Am
35:33, 2004; Jonsson B et al: Symptoms and signs in degeneration of the lumbar spine. A prospective,
consecutive study of 300 operated patients. J Bone Joint Surg Br 75:381, 1993; Khan SN et al: Bone morphogenetic
proteins: relevance in spine surgery. Orthop Clin North Am 33:447, 2002; Lee AW et al: Spinal
cord stimulation: indications and outcomes. Neurosurg Focus 21:E3, 2006; Mink JH et al: Spinal imaging
and intervention: 1998. Phys Med Rehabil Clin N Am 9:343, 1998; Sandhu HS et al: BMPs and gene therapy
for spinal fusion: summary statement. Spine 28:S85, 2003; Sandhu HS et al: Recombinant human bone
morphogenetic protein-2: use in spinal fusion applications. J Bone Joint Surg Am85, 2003; Sandhu HS:
Bone morphogenetic proteins and spinal surgery. Spine 28:S64, 2003; Suzuki A et al: A biodegradable delivery
system for antibiotics and recombinant human bone morphogenetic protein-2: A potential treatment
for infected bone defects. J Orthop Res 24:327, 2006.
Educational Objectives
| The goal of this program is to enable orthopaedists to implement recent advances in spinal surgery. After
hearing and assimilating this program, the surgeon will be better able to:
|
| 1. Identify components of disc pain and anatomic generators of spinal pain.
|
| 2. Select diagnostic, prognostic, and therapeutic procedures for lumbar disc pain.
|
| 3. Recognize indications for spinal cord stimulation.
|
| 4. Explain how functional anesthetic discography differs from provocative discography.
|
| 5. Incorporate new approaches for disc repair focusing on the center of the disc, including potential use
of growth factors and gene therapies.
|
Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty members to
disclose relevant financial relationships within the past 12 months that might create any personal conflicts
of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality
in health care and not a proprietary business or commercial interest. For this program, the following has
been disclosed: Dr. Rosner—Cephalon (Speakers’ Bureau); Pfizer (Speakers’ Bureau)
Acknowledgements
The speakers were recorded at Cedars-Sinai Medical Center Institute for Spinal Disorders’ Sixth Annual Symposium
on Current Concepts In Spinal Disorders 2007, held March 1-2, 2007, in Las Vegas, NV. The Audio-Digest
Foundation thanks the speakers and the meeting sponsor for their cooperation in the production of this program.
|
