CHAPTER

1 INTRODUCTION

Anatomy

Lumbar spinal stenosis is a narrowing of the spinal canalleading toa reduction inspaceavailable forneural structures and their blood supply. The direct narrowing is dueto a constellation of pathologies including thickenedlamina, hypertrophied buckled ligamentum flavum,spondylolisthesis, disk bulge and facet arthrosis. In thedegenerative cascade as the disk becomes dehydrated,the disk space collapses. Loss of disk height leads toannular bulging and infolding ofthe ligamentum flavum.As the disk space collapses, the distance between thespinous processes in the posterior column, shortens.^Additionally, the posterior facet joints assume a largerload transfer as the disk degenerates leading to facetarthrosis (i.e. osteophyte complex, facet cysts). Thesedegenerative alterations reducethe area of the canal. Inthe subarticular zone, these changes lead to compressionofthe traversing nerve root. Compression canalso occurwithin the neuroforamen causing compression of theexiting nerve root. The anteroposterior diameter of theforamen is reduced by the bulging of annulus anteriorlyand the hypertrophic facets posteriorly. The foraminalheight is reduced by disk dehydration and loss of diskheight. This is effectively known as "up-down" stenosis.The foraminal zone can become further stenotic if thesegment has a listhesis, catering the normal concentrickeyhole configuration.

Joshua Abrams, James Zucherman

I SURGICAL INDICATIONS

Neurogenic intermittent claudication (NIC) is the mostcommon presenting symptom of spinal stenosis. Thisis a posture-dependent complaint that typically affectspatients greater than 50 years of age. F^tients presentwith pain or numbness extending into the buttocks,thighs and/or legs brought on by walking or standingin an erect posture. These postures place the spine inextension and with the aforementioned degenerativechanges lead to canal narrowing. Patients frequentlyreceive relief of their symptoms with a forward flexedposture, known as the "shopping cart sign." Penningand Wilmink^ reported on the phenomenon in which aflexed posture increases the spinal canal diameter andeffectively reduces the compression on the neural structures (Figs lA and B).

This presentation led to the genesis ofthe concept ofkeeping individual spinal segments In flexion and limitingthe amount of local extension at the site of greateststenosis. To achieve this, interspinous process devices(IPDs) are placed in between the spinous processes,which act as lever arms of the entire spinal motionsegment. Placement of IPDs leads to focal flexion of thespinal segment, keeping the ligamentum flavum tightand effectively increasing the spinal canal diameter.^Zucherman et al. demonstrated theplacement ofan IPDwhich is superior to non-operative treatment for NIC at1,2,and4years postoperatively.'̂ ^The only interspinous

Chapter-54 ♦ Interspinous Spacers

Pedicular planemagnetic re^nance imaging ofaspecimen in theexf^dedposition with and without the implant. The axial slices weretaken through the middle of the L3/4 intervertebral disk AIS an intact specimen in the extended position. Notice thenarrow subarticular diameter between the anterior facet and

anTsTO^nl specimen whhan X-STOP placed between the L3 and L4 spinous processesNotice the subarticular diameter in the implanted specimen(arrows). Cis of the intact specimen in the extended positionand DIS of the same specimen in the extended position withthe impbnt placed at L3/4. The foraminal area and width arenoticeably greater in the implanted specimen (arrows)Source: Adapted from Richards, et al. The treatment mechanism of an interspinous process implant for lumbar neuro-genic intermittent claudlcation. Spine 2005

Co^x {Interspinous U) DIAMImplant Walls

X-STOP/X-STOP'**Company Abbott spine Kyphon Inc.Launch 2002 (new)

2002Developer Senegas J St Francis Inc.FDA Status Approved forclinical trial Approvedfor clinical useComposition Blocker—PEEK Titanium alloy body and

Technique Removal ofsupraspinousligaments necessary

PEEK spacer (X-STOP''*)Preserves supraspinousligament

Implant

Paradigm spine

1994 (The U)

Samani J

Approved forclinical trial

Titanium alloy

Removal ofsupraspinousligaments necessary

FDA mdicates Food and Drug Administration; PEEK. PEEK, polyether ether ketone

Medtronic

2001

Taylor J

Approvedfor clinical trial

Sllicone core with polyestersleeve

Preserves supraspinousligament

Fig. 3; 'Relevant Features of the Interspinous DevicesSource: Kabtr et al. Lumbar Interspinous Spacers

C IcareT'^ processes takingCobb elevator is used to sweep the subcutaneous tissues mut M supraspinous ligament. The spinal

VtT

As

)U

Figs 5A to 1; DIAM technique. {A)The Interspinous space Is prepared by removing the Inlerspinous ligament; (B) Distractionis applied until the appropriate degree of tension Is achieved; (C) Aseries of trials are used to select the proper size implant;(D) To prepare the implant for insertion, the Implant Is loaded into the inserter. The wings of the Implant will fold as the inserterflanges are compressed; (E) Overdistraction may be applied to facilitate Insertion of the Implant. The DIAM-devlce is passedthrough the interspace until the jaws of the Inserter are in contact with the corresponding splnous processes. The contralateraltether Is also passed through the Interspace simultaneously; (F) The tethers are passed around the adjacent splnous processesand then through the loop on the side of the implant; (G) Acrimp tool secures the crimps while applylne longitudinal tension;(H and I) Final position of the implant.Source: Adapted from Medtronic Sofamor Danic DIAM Spinal Stabilization System Surgical Technique guide

m

Figs 6A to |: Wallis Technique. {A and B) The adequate size of the Implant Is determined by placing different trial spacers;(O Placement of the final implant can be facilitated by the interlaminar distractor; (D) The band is engaged in the slot at thetip of the band passer; (E) The bands are passed through the adjacent interspinous ligaments; (F) The bands should be flatagainst the spinous processes; (G) The bands are threaded through the clip; (H) The clip is rotated 360® counterclockwise andreduced into the spacer with the clipping forceps; (1) The bands are pulled taut and the final tighteners are turned clockwiseto completion; (J) The excess bands are removed.Source: Adapted from Wallis Posterior Dynamic Stabilization System; Surgical

'•ih-

2. Penning L, Wlimink JT Posture-dependent bilateralcompression of L4 or L5 nerve roots in facet hypertrophy. A dynamic CT-myelographic study.Spine. 1987;12:488-500.

3. ZuchermanJ, Simons P, TimothyJ. XSTOP interspinousimplant for lumbar spinal decompression. Brussels

4. Zucherman JI; Hsu KY, Harden CA, et al. A prospective randomized multi-center study for the treatment oflumbar spinal stenosis with the X-STOP interspinousimplant: 1-year results. Eur Spine J. 2004;13(1):22-31.

5. Zucherman JF, Hsu KY, Hartjen CA, et al. A multicenter,prospective, randomized trial eveduating the X-STOPinterspinous process decompression system for the treatment of neurogenic intermittent claudication: two-yearfollow-upresults. Spine. 2005;30:1351-8.

6. Kondrashov DG, Hzmnibal M, Hsu KY, et al. Interspinousprocess decompression with the X-STOP device forlumbarspinalstenosis: a 4-year follow-up study. J SpineilDisord Tech. 2006;19:323-7.

7. Richards JC, Majumdzur S, Lindsey DR et al. The treatment mechanism of an interspinous process implantfor lumbar neurogenic intermittent claudication. Spine.2005;30(7):744-9.

8. Kabir SM, Gupta SR, Casey AT. Lumbar interspinousspacers: a systematic review of clinical and biomechan-ical evidence. Spine. 2010;35(25):E1499-506.

Chapter-54 ♦ Interspinous Spacers

9. ChristieSD, Song JK, FesslerRG. Dynamic InterspinousProcess Technology. Spine. 2005;30:S73-8.

10. Lindsey OR Swanson KE, Fiichs R et eil. The effects ofan interspinous implant on the kinematics of the instrumented and adjacent levels in the lumbar spine. Spine.2003;28:2192-7.

-11—NandakumatA^-Clark-NAr PeehalJR eiaL-Th&increase-in dural sac area is maintained at 2 years after X-STOPimplantation for the treatment of spinal stenosis with nosignificant alteration in lumbar spine range of movement.The Spine Joumzil. 2010;10:762-8.

12. Kim DH, Tantorski M, Shaw J, et al. Occult spinousprocess fractures associated with interspinous processspacers. Spine Epub;2011.

13. Siddiqui M, Karadimas E, Nicol M, et al. Effects ofX-STOP device on sagitted lumbar spine kinematics inspinal stenosis. J Spinal Disord Tech. 2006;19:328-30.

Surgical Technique Guides: DIAM Spinal StabilizationSystem: Surgical Technique. May 2008 (Version H)P04-08. Medtronic Sofamor Danek.

Cofiex TM: Surgical Technique. Paradigm Spine.http://www.ossano.se/Produkter/Ryggimplantat/Coflex/Coflex_surgical_technique.pdfWallis Posterior Dynamic Stabilization System: SurgicalTechnique. 2mmer (AbbottSpine), [online] Available fromhttpy/www.zimmer.com/^b/enUS/pdf^sur^cal_techniques/Wallis_Suigicai_Techniquel.pdf [Accessed December, 2011].