Table Of ContentContemporary Perspectives in Neurosurgery
Series Editor: Robert N. N. Holtzman
Contemporary Perspectives in Neurosurgery
Series Editor: Robert N.N. Holtzman
SurgelY of the Spinal Cord: Potential for Regeneration and RecovelY,
Robert N.N. Holtzman and Bennett M. Stein, Editors
Spinal Instability, Robert N.N. Holtzman, Paul C. McCormick,
lean-Pierre C. Farcy, Editors
Endovascular Interventional Neuroradiology, Robert N.N. Holtzman and
Bennett M. Stein, Editors
Robert N.N. Holtzman Paul C. McCormick
Jean-Pierre C. Farcy
Editors
Heidi Winston
Associate Editor
Spinal Instability
With 181 Figures in 399 Parts
Springer-V edag
New York Berlin Heidelberg London Paris
Tokyo Hong Kong Barcelona Budapest
ROBERT N.N. HOLTZMAN, MD
Assistant Clinical Professor of Neurological Surgery, College of Physicians and
Surgeons of Columbia University; Associate Neurosurgeon, Lenox Hill Hospital,
New York, NY 10021, USA
PAUL C. MCCORMICK, MD
Assistant Professor of Clinical Neurological Surgery, College of Physicians and
Surgeons of Columbia University; Assistant Attending, Department of Neuro
logical Surgery, The New York Neurological Institute, New York, NY 10032,
USA
JEAN-PIERRE C. FARCY, MD
Associate Clinical Professor of Orthopedics, College of Physicians and Surgeons
of Columbia University; Associate Attending, Department of Orthopedics,
Columbia-Presbyterian Medical Center, New York, NY 10032, USA
HEIDI WINSTON
The Harry Winston Research Foundation, 718 Fifth Avenue, New York, NY
10019, USA
Library of Congress Cataloging-in-Publication Data
Stonwin Conference (8th: 1991: Stonwin Estate)
Spinal instabilitylRobert N.N. Holtzman, Paul C. McCormick, Jean
Pierre C. Farcy, editors, with Heidi Winston, associate editor;
Stonwin Medical Conference; [sponsored by) Harry Winston Medical
Foundation, Inc.
p. cm.-(Contemporary perspectives in neurosurgery)
Includes bibliographical references and index.
1. Spine-Instability-Congresses. I. Holtzman, Robert N.N.
II. McCormick, Paul. III. Farcy, Jean-Pierre C.
IV. Harry Winston Medical Foundation. V. Title. VI. Series.
[DNLM: 1. Joint Instability-surgery-congresses. 2. Laminectomy
congresses. 3. Spinal Cord Injuries-surgery-congresses.
4. Spinal Diseases-surgery-congresses. 5. Spinal Fusion
congresses. WE 725 S881s 1991)
RD771.I58S86 1991
617.3'75-dc20
DNLMJDLC 92-48680
© 1993 Springer-Verlag New York, Inc.
Softcover reprint of the hardcover 1st edition 1993
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987 6 5 4 3 2 1
ISBN -13: 978-1-4613-93 28-3 e-ISBN -13 :978-1-4613-9326-9
001: 10.1007/978-1-4613-9326-9
This volume is dedicated to
My twin sister, Elizabeth Holtzman, the present
comptroller of New York City
-RNNH-
My wife, Doris, and my son, Paul Jr.
-PCMcC-
My wife, Pommy, and my children, Frederick,
David, and Sarah
-J-PCF-
Guest of Honor:
John P. Kostuik, MD
President, North American Back Society
Professor of Orthopedic Surgery, Department of Orthopedic Surgery
Johns Hopkins Outpatient Center
Henry Fleishmann, MD
Foreword
The Eighth Stonwin Medical Conference provided a unique forum for
both orthopedic spine surgeons and spinal neurosurgeons who gathered
together in the music room of the Stonwin Estate under the portrait of
Edna Winston. There they exchanged views on the nature of spinal in
stability and the possible means of correcting that instability so as to
preserve spinal mechanical function and to protect the neural tissues
housed in its vertebral compartments.
The conference represented one of the first of such exchanges where
orthopedists and neurosurgeons have formally met to discuss spinal insta
bility and to consider the evolution of a new category of surgeon
the spine surgeon. It was both controversial and stimulating, and it will
serve as a basis for collaborative efforts in the near future.
This could not have happened without the generosity of Ronald H.
Winston, the son of Harry and Edna Winston, who has unswervingly
given support to the exchange of scientific and medical ideas, in part from
the influence of his maternal grandfather, Henry Fleishmann, a physician,
and in part from his own scientific interests. We are deeply indebted to
him for supporting and promoting these conferences as we believe they
represent efforts to explore in depth problems on the frontiers of medi
cine and surgery.
HENRY B. ROBERTS, JR.
Publishing and Editorial Consultant
Stonwin Medical Conference
ix
Preface
The definition of spinal instability centers on the interrelationships, dis
position, and alignment of the vertebrae in both static and dynamic
phases. The integrity of these relationships is structurally maintained by
the intervertebral cartilaginous joints-the discs with their annulus fibro
sis and nucleus pulposus; the zygapophyseal synovial joints; the anterior
and posterior spinal ligaments, and to a lesser extent, the intertransverse
ligaments, the interspinous ligaments, and the ligamentum flavum. A very
important role is played in inertial loading by the paraspinal musculature.
The spinal cord and its roots, ganglia, rami, and their individual invest
ing membranes generally become involved in the definition by signaling
vertebral instability with focal or radicular pain, muscular spasms, or
frank neurological symptoms. It is essential to consider these elements
along with radiographically documented abnormal motion or position to
derive a working definition of spinal instability.
The problem is that the definition is not perfectly stated for all in
stances. Therefore, judgments about instability are often made on a clinical
basis without definitive radiographic correlation. Viewing the spine dur
ing the aging process discloses a variety of radiographic appearances
that demonstrate vertebral motion but do not reflect true instability.
These include the escalator-like steps in a child's flexed cervical spine, the
more fixed dynamic lordotic and kyphotic curves in adulthood, and the
pseudospondolytic slip of the aged. When there is "clear-cut" abnormal
motion in pathological settings of tumor, infection, trauma, and the post
operative state seen on flexion-extension radiographs, which demonstrate
varying degrees of vertebral displacement from 1 to 3 mm, most spine
surgeons will concur on the presence of spinal instability and recommend
internal fixation and fusion. On the other hand, when a patient has back
pain with spinal stenosis or spondylolisthesis without radiographic evi
dence of abnormal translational or rotational motion, some spine surgeons
will claim that instability exists and will perform extensive fusions where
as others will not, rather opting for decompression of the roots and thecal
sac-keeping the fusion as a backup procedure and achieving equivalent
xi
xii Preface
clinical outcomes though perhaps more frequent residual low back pain in
the unfused group. Another approach now offered by Dr. Arthur White
is to encourage such patients to embark upon a specific spine stabilization
training program.
It is these less-explicit situations relating to a numerical value of per
missible vertebral motion, the presence or absence of pain with such mo
tion, and the strict radiographic documentation of abnormal motion that
in some instances necessitates examination under general anesthesia,
that demand our attention in arriving at a formal definition of spinal in
stability. Evolving technology in the form of real-time magnetic reso
nance imaging (MRI) capable of performing kinetic imaging of the spine
may ultimately be able to prove or disprove stability.
At the present time, fusion procedures and fusion technology are rapid
ly evolving. Despite the sophistication of the instrumentation, achieving a
solid fusion always requires bone grafts as well as metallic constructs via
highly complex combined anterior and posterior approaches. Primarily
because of this, some guidelines are offered by Dr. Michael Neuwirth,
namely, that the ultimate aim of internal fixation be to restore normal
function, not to eliminate it with fusion, and when fusion must be per
formed under present circumstances it should preserve normal bony and
neurologic anatomy while eliminating motion in the shortest segment
possible. Of great importance in this regard is further knowledge concern
ing the osteointegration of foreign materials to insure the best bony
metallic interface possible and the strongest adherence of a given implant
to bone.
The chapters of this volume address these matters in great detail.
Structural integrity of the spine depends on bone growth, bone repair,
and ligamentous integrity. Vertebral integrity may be dependent on a
glucocorticoid and prostaglandin availability as was suggested from the
recent work of the Columbia astronaut, Dr. Millie Hughes-Fulford.
Osteoporotic, weakened bone is subject to fracture and it is precisely this
susceptibility with ongoing microtrauma and incomplete healing that may
be strongly implicated in the progressive instability or pseudospondylo
listhesis of aging.
Initially the spine may be conceptualized as a structure with five basic
motions: forward flexion, backward extension, lateral flexion, rotation,
and elongation. Lesser motions include forward and backward wedging
of the intervertebral discs and the shearing slippage of one vertebra on
another. These basic motions are translated into static and dynamic axial
and transverse stability. Axial stability is provided in two columns at Cl
C2 and three columns from C2 to the sacrum according to Prof. Rene
Louis. The anterior column is formed by the vertebrae and discs and the
two posterior columns formed by the two zygapophyseal joints. Transverse
stability of one motion segment-level is provided by bony buttresses con
sisting of end plates and facets and ligamentous brakes. Further stabiliza-
