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`NUVASIVE 1073
`NuVasive, Inc. v. Warsaw Orthopedic, Inc.
`IPR2013-00206
`IPR2013-00208
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`424 Spine - Volume 28 - Number 5 - 2003
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`anterior margin of vertebral body
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`
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`psoas major muscle
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`posterior margin of vertebral body
`
`Figure 2. Zone definition of the localization of the lumbar plexus and nerve roots at each image. The area between the anterior edge of
`the vertebral body and the posterior edge of the vertebral body was divided into four zones. The most anterior zone was defined as zone
`I, the second anterior zone was zone II, the third anterior area was zone ”I, and the most posterior area was zone IV. The area posterior
`to the posterior edge of the vertebral body was defined as zone P, and the area anterior to the anterior edge of the vertebral body was
`defined as zone A.
`
`the safety zone of the psoas major muscle during retro—
`peritoneal endoscopic surgery using cadavers.
`
`I Materials and Methods
`
`Localization of the Lumbar Plexus and Nerve Roots.
`lumbar spines were removed from six embalmed human cae
`davers and immediately frozen at —80 C. From the “4.5
`vertebral body, each specimen was cut in parallel with the lum-
`bar disc space and the lumbar vertebra at the cranial third and
`caudal third of the each lumbar vertebral body (Figure 1). The
`distribution of the lumbar plexus and nerve roots in each axial
`section was photographed. Each image was captured into a
`computer. The relationship between the greater psoas muscle
`and the lumbar plexus was analyzed using computer images.
`The area between the anterior and posterior edges of the ver-
`ebral body was divided into zones 1, 11, ill, and 1V (Figure 2).
`"he area anterior to the anterior edge of the vertebral body was
`defined as zone A, and the area posterior to the posterior edge
`of the vertebral body was defined as zone P. The relationship
`between the localization of the lumbar plexus and nerve roots
`and each zone was examined.
`
`It-r
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`I Results
`
`The Relationship Between the Localization of the
`Lumbar Plexus and Nerve Roots and the
`Vertebral Body
`All parts of the lumbar plexus and nerve roots were
`found in zones IV and P at L2—L3 and above (Figure 3A).
`All of the lumbar plexus, except for the genitofemoral
`nerve, and all nerve roots were found in zone 11 and
`abdominally at L4-L5 and above (Figure 3B).
`A typical case is presented. The nerve tissue was found
`in zone lV and dorsally at 1.21.3 (Figure 4A). At l.3s (1.3
`superior) and caudally, the genitofemoral nerve was
`found in zone II on the right side and in zone III on the
`left side (Figure 4B). At L3i (L3 inferior) on both sides,
`the genitofemoral nerve was found in zone I (Figure 4C).
`At LS-S, the genitofemoral nerve was found in zone A;
`the L4 nerve root, l5 nerve root, femoral nerve, and
`obturator nerve were found in zones II, III, and IV (Fig—
`ure 4D). Intraobserver reliability was 0.87.
`
`The Relationship Between the Greater Psoas Muscle and
`the Genitofemoral Nerve. The positions where the genito-
`femoral nerve emerges on the abdominal surface of the psoas
`major muscle were analyzed using 24 embalmed cadavers. The
`three characteristics used to identify the genitofemoral nerves
`are piercing the psoas major muscle at its upper medial portion,
`piercing the fascia transversalis to enter the abdominal wall
`around the deep inguinal ring, and not having a lateral cutane-
`ous branch.
`
`The Relationship Between the Psoas Major Muscle
`and the Genitofemoral Nerve
`
`As for the level to which the genitofemoral nerve passes
`the psoas major muscle among the 24 examples (48
`sides) investigated in this study, L3—L4 had 15 sides and
`L4s had 14 sides. The level of the positions where all of
`the genitofeinoral nerve passed through the psoas Inaj or
`muscle was between L35 and L4i (95% confidence inter—
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`An Anatomic Study for Endoscopic Surgery - Mom at al 425
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`Figure 3. A, The number with which the lumbar plexus and the nerve roots by the 12 sides existed. B. The number with which the lumbar
`plexus and nerve roots, excluding the genitofemoral nerve, existed.
`
`val; range, 92—100%) (Table 1). Intraobserver reliability
`was 0.82.
`
`I Discussion
`
`Safety Zone of the Lumbar Plexus and Nerve Hoots
`Nerve damage is one of the complications that should be
`avoided during retroperitoneal endoscopic surgery.
`From the results of this study, it was thought that the
`safety zone may be at L2—L3 and above. Between the
`cranial third of the L3 vertebral body and L4—L5 , only
`the genitofemoral nerve was located in the abdominal
`zone rather than the center of the vertebral body. If the
`possibility of damaging the genitofemoral nerve is not
`considered, the safety zone should be at L4—L5 and
`above. When spreading the psoas major muscle at L27L3
`and below, start from the abdominal edge of the verte—
`bra, because nerves are not located in the abdominal
`surface of the vertebra. The lumbar plexus and nerve
`roots were contained in the psoas major muscle. There—
`fore, split between the psoas major muscle and vertebral
`body without dissecting the psoas major muscle.
`T4581 is located on the caudal side from the abdomie
`nal aortic bifurcation. Therefore, during the method of
`
`spreading the psoas major muscle posteriorly for ex—
`treme lateral L561 lumbar disc herniation, there is a risk
`of iliac artery and vein damage. At L5—Sl, the space be—
`tween the psoas major muscle and the lumbar quadrate
`muscle is wide as compared with L4-L5 and above.
`Therefore, the lateral surface of the vertebral body can be
`reached from the gap of these muscles. The method of
`retracting the psoas major muscle anteriorly and reach—
`ing to the lateral surface of the vertebral body may be
`useful2 (Figure 5). However, according to the present
`study, it is the danger zone, where the lumbar plexus and
`nerve roots were included in the center of the vertebral
`body and dorsally, that is to be operated in the case of
`this approach. At L5—Sl, there is the L4 nerve root, L5
`nerve root, femoral nerve, and obturator nerve between
`the psoas major muscle and the lumbar quadrate muscle.
`Therefore, those nerve tissues must be checked and pro—
`tected with endoscope.
`
`The Possibility of Genitofemoral Nerve Damage
`The genitofemoral nerve forms the lumbar plexus to sup—
`ply the abdominal wall with the ilioinguinal nerve, ilio—
`hypogastricus nerve, and subcostalis nerve. The distribu—
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`426 Spine - Volume 28 - Number 5 - 2003
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`Figure 4. A. Cut image at L2-L3 (down shot) displays the L1 and L2 nerve roots that exist in zone IV. B. Cut image at L3s (down shot)
`displays the L1 and L2 nerve roots that exist in zones P and IV. X; shows the genitofemoral nerve that exists in zones II and Ill. c, Cut
`image at L3i Idown shot) displays the L1 and L2 nerve roots that exist in zone IV. Allows heads to show L3 nerve roots that exist in zone
`P. X; show genitofemoral nerves that exist in zone I. D, Cut image at L5-S (down shot) displays white frames that show the L4 and L5
`nerve roots that exist in zones II,
`III, and IV. Displays obturator nerves and femoral nerves that exist in zones II and I”. X; shows
`genitofemoral nerves that exist in zone A.
`
`tion and origin of these nerves have been sufl'iciently
`examined.5’8 The genitofemoral nerve mainly branches
`from the L1 and L2 nerve root, pierces through the psoas
`major muscle toward the anterior side from the posterior
`side, and subsequently descends in accordance with the
`abdominal surface of the psoas majorfl“ However, the
`authors paid no attention to the level of the genitofemo—
`ral nerve emerging on the surface of the psoas major
`muscle. From the results of this study, it was found that
`the level where the genitofemoral nerve passes the psoas
`major muscle ranges from the cranial third of the L3
`
`Table 1. The Positions Where the Genitofemoral Nerve
`Emerges on the Abdominal Surface of the Greater Psoas
`Muscle, Except for One Side, Which Has No
`Genitofemoral Nerve
`
`Genitofemoral Nerves That
`Had Pierced Through the
`Cut Level of Lumbar Spine Psoas Major Muscle (n)
`
`L35
`5
`L3i
`10
`L3-L4
`15
`L45
`l4
`
`L4i 3
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`vertebral body to the caudal third of the L4 vertebral
`body. That is, in the case of spreading the psoas major
`muscle, it is thought that at the more caudal level the
`genitofemoral nerve may be damaged. In fact, a case of
`transitory genitofemoral nerve paralysis after anterior
`fusion of the L37L4 vertebral body with the retroperitoi
`neal endoscope has been reported.9 On the other hand,
`
`
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`vertebral body
`
`ala of sacrum
`
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`Figure 5. Cut image at L5/Sl displays the course of the retroperi-
`toneoscopic lateral lumbar approach.
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`An Anatomic Study for Endoscopic Surgery - Mathews 427
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`entrapment neuralgia of the genitofernoral nerve is
`known as one of the complications of inguinal hernior—
`rhaphy. However, reports of having succeeded in remit?
`ting the symptoms (pain and paresthesia) without a seri—
`ous problem, even if neurectomy of the genitofemoral
`nerve is done as medical treatment of these complica—
`tions, have also been made.4 If such a conventional re—
`port is considered when the genitofemoral nerve is darn—
`aged, there is the possibility that a sensory disturbance
`will arise at the scrotum and medial thigh, which is the
`innervation area of the genitofemoral nerve. It is thought
`that genitofemoral nerve palsy rarely becomes a serious
`problem. However, before an operation accompanied by
`the spreading of the psoas major muscle at the L3 vertee
`bral body and below, the patient must be informed of the
`possibility of sensory disturbance by genitofemoral nerve
`damage, and it is considered necessary to obtain cornpre—
`hension beforehand.
`
`l Key Points
`
`0 The muscle should be split more anteriorly than
`the dorsal fourth of lumbar vertebral body from
`the cranial third of the IS vertebral body and above
`to prevent nerve injuries.
`0 When the psoas major muscle is split at the L3 or
`L4 vertebral body, there is a risk of injury to the
`genitofemoral nerve.
`
`Bale ren ces
`
`|\)
`
`1. Alsdel‘nll‘ c, Misl‘a M, Dujobny M, et al. Mlcl‘o anatomy of thotattt spine
`foramina and ligaments.
`In: Dickman (IA, Rosenthal DJ, Perin NI, eds.
`Thoracoscopic Spine Surgery. New York: Thiemc Medical Publishers, 1999;
`69 —78.
`. Derawa A, Yamane T, Milxami H, et al. Retroperitoneal laparoscopic lateral
`approach to the lumbar spine: a new approach, technique, and clinical trial.
`
`J Spinal Disord 2000;? 138—43.
`3. Foley KT, Smith MM. Microendoscopic disceixomy. Tech Neurosurg 1997;
`3:301—7.
`4. James RS, Bruce AH, Mark ES, et al. Diagnosis and treatment of genitofemr
`oral and ilioinguinal entrapment neuralgia. Surgery 1987;102:581—6.
`5. Kasai T. Pri la abdomenmuraj brangoi de la lumba plelxso. J Anat 1957,32:
`262—77.
`6. IVIarrin B, Lawrence HB, Susan his. The spinal nerves. In: Peter LW, ed.
`Gray’s Anatomy, 28th ed. London: Churchill Livingstone, 199311258792.
`\i
`. Mathews 1111, Evans M'i‘, Bolligan ii], et a1. Lapai‘oscoplc dlscectomy with
`anterior lumbar interbody fusion. Spine 1995;20:1797—802.
`8. Morikawa R. Course, distribution and their variety of the nerves derived
`from the lumbar plexus to supply the abdominal wall. J Anat 1971;46:
`3 12733.
`lVchfee PC, Regan JJ, Gels we, at a]. Minimally invasive anterior tempt-t
`itoneal approach to the lumbar spine. Spine 1998;23:1476—84.
`10. Obenchain TG. Laparoscopic lumbar discectomy: case report. J Laparoene
`dosc Surg 1991;11145—9.
`()linger A, Hildebrandt U, Mutschler KW, et al. First clinical experience with
`an endoscopic retroperitoneal approach for anterior fusion of lumbar spine
`fractures from levels T12 to L5. Surg Endosc 1999;13:1215—9.
`12. Pait TG, Ture U, Arna utovic KI, et al. Surgical anatomy ofthc thoracic spine.
`In: Diclqnnn ca, Rosenihnl DJ, Perin NI, eds. Thorncoscnpic Spine Siugery.
`New Yorszhieme Medical Publishers. 199957767.
`1.}. Romanes (1|. The peripheral nervous system. In: Romans G], ed. (Jlfll‘llng’
`ham’s Textbook of Anatomy, 12th ed. Tront10xford University Press. 1981;
`739 —826.
`
`9.
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`11.
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`Point of View
`
`Hallett Holmes Mathews, MD
`From the Virginia Commonwealth University Medical College, and MidAtlantic Spine Specialists,
`Richmond, Virginia.
`
`As surgeons1 have become increasingly aware of surgical
`morbidity for anterior lumbar spine surgery, new tech—
`niques and approaches have been devised to access the
`anterior column of the lumbar spine less invasively and
`with less surgical morbidity. Transperitoneal endoscopic
`surgery has provided predictable access to the L5—Sl in—
`tervertebral space; however, I.4AI.5 and above has been
`less predictable in obtaining predictable access without
`the risk of significant intraoperative complications. The
`location of the great vessels anteriorly and their ana—
`
`
`Device status/drug statement: This report does not contain information
`about medical device(s)/drug(s).
`Conflict of interest: No funds were received in support of this work. No
`benefits in any form have been or will he received from a commercial
`party related directly or indirectly to the subject of this report.
`Address reprint requests to Hallett H. Mathews, I\4D7 MidAtlantie
`Spine Specialists, 7650 Parllam Road, Suite 200, Richmond, VA
`23294. E-mail: masshinalhews@aol.com
`
`tomic variations have provided less favorable access
`compared with a more lateral transpsoatic approach to
`the anterior vertebral column. The lumbar plexus repre—
`sents the most important structure in the psoas that
`could be injured, and the anatomic variations and loca—
`tions of these structures have yet to be clearly defined
`“An Anatomic Study of the Lumbar Plexus with Re—
`spect to Retroperitoneal Endoscopic Surgery” by Moro
`at al is an important anatomic study that describes the
`important relationship of the lumbar plexus to the
`greater psoas muscle when considering anterior lumbar
`surgical intervention. Whether using an endoscopic or
`minieopen technique, it is important to conceptualize the
`most common locations of lumbar plexus structures be—
`fore dissecting the psoas muscle to obtain access to the
`vertebral body or intervertebral disc space. Injuries to the
`genitofemoral nerve and other lumbar plexopathies have
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`428 Spine - Volume 28- Number 5 - 2003
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`been described when a more lateral approach is obtained
`for decompression or device implantation, as great vessel
`dissection is avoided anteriorly.
`Past morbidity of the anterior surgical approach to the
`lumbar spine has often dictated whether spinal surgeons
`would even use such an approach for the treatment of
`spinal disorders. It has become increasingly apparent
`that anterior techniques offer tremendous biomechanical
`and kinematic advantages during surgical reconstruction
`for Various spinal disorders. Part of the morbidity has
`been that of dissecting and mobilizing the great vessel at
`
`L4—L5 in both index and revision surgical techniques.
`The lateral transpsoatic approach is thought by many to
`be the least invasive endoscopically at 114715 and above;
`however, surgeons have not felt comfortable with dis—
`secting the psoas because of the presence of the lumbar
`plexus. This study has offered tremendous assistance in
`planning lateral access to the lumbar spine and also de—
`ciding whether this is the appropriate access for a specific
`surgical pathology. The authors have described very con—
`cise surgical anatomy, which will be helpful for all spine
`surgeons in the future who plan this approach.
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