J Chiu. Treatment Of Lumbar Spinal Stenosis With Interspinous Process Decompression System (IPD) (X-Stop®). The Internet Journal of Minimally Invasive Spinal Technology. 2006 Volume 1 Number 1.
Lumbar spinal stenosis is most common reason for back surgery in patients over the age of 50 in America. With increased life expectancy, and the aging of baby boomers, many patients suffering from progressive lumbar spinal stenosis with symptomatic intermittent neurogenic claudication (NIC) have been limited to a choice between non-surgical therapies and more traumatic decompressive surgical procedure, with or without lumbar fusion. The interspinous process decompression system (IPD) (X-STOP®) implant was developed to provide a minimally invasive alternative therapeutic treatment of lumbar spinal stenosis.
The X-STOP® interspinous process decompression system, surgical indications, operative techniques, case illustrations, outcome and the potential complications and their avoidance are described and discussed herein.
With increase in life expectancy and the aging of Baby Boomers, more people are living to an age when Lumbar Spinal Stenosis (LSS) condition becomes symptomatic. LSS is one of the most common causes for spinal surgery in the elderly population over the age of 50 in the United States, and is a frequent manifestation of pathophysiological process of spinal degeneration that occurs with aging and often becomes symptomatic in the fifth and sixth decades of life (1,2,3,4,5,6,7,8,9,10,11,12) (Table 1). Approximately 2 million physician's offices visits were related to symptoms of LSS. It is estimated that more that 125,000 laminectomy procedures were performed for LSS. The financial impact of LSS in terms of health care dollars and lost work hours reaches billions of dollars each year in the US (1, 3, 5,6,7,8,9).
LSS presenting as disabling neurogenic intermittent claudication (NIC) and requiring surgical intervention, if not successful with conservative treatment of medication and exercise program. The pathophysiology of LSS is complex and multifactorial of progressive neural compression, as the result of spinal degeneration with narrowing of the spinal canal and neural foramina, secondary to the degeneration of the intervertebral disc, a loss of disc height, causing the effected spinal segment to adopt a position of hyperextension, leading to a bulging of annulus, hypertrophy of the facet, spondylolisthesis, and a thickening of interspinous ligament, in particular the ligamentum flavum (8,9,10,11,12,13,14,15,16,17,18) (Figure 1a-1d). The narrowing of the spinal canal and neural foramen leads to nerve root compression and ischemia, and neurogenic intermittent claudication (NIC) (17,18,19,20,21,22,23,24).
Typically the posture of the LSS patient is kyphotic while walking. Of course, extension of the spine often provokes symptoms while flexion relieves them (12,13,14,15). Typically, x-rays are taken to evaluate the alignment of the spine and extent of the degenerative bony changes. MRI scanning is helpful in defining and confirming nerve root impingement, disc bulging, ligamentum flavum hypertrophy, disc degeneration, and other soft tissue condition. Radiographic evidence of stenosis must be correlated with the patient's symptoms before diagnosis can be confirmed (4, 20, 23, 25,26,27).
The treatment of LSS begins with a regimen of non-surgical medical management (10,11,12, 16). While some patients respond to this treatment well, many do not and become candidates for the surgical intervention. More traumatic decompressive lumbar laminectomy is the most common surgical procedure with (for spinal instability) or without fusion (14, 19, 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46).
Interspinous process decompression (IPD) (X-STOP®) is a minimally invasive spinal surgery (MISS) in which an implant is placed between the adjacent spinal processes of the symptomatic disc level. The intraspinal process decompression system was developed for patients who have LSS with disabling neurogenic intermittent claudication, and who are able to relieve their symptoms when they bend forward or flex their spine. The IPD (X-STOP®) is designed (47,48,49,50,51,52,53,54) to limit pathological extension of the spinal segments and to maintain them in a neutral or slightly flexed position which may allow patients to resume their normal posture rather than flex the entire spine to gain symptomatic relief.
The reputation of fusion technology causes adverse consequence of fusion with loss of mobility, stiffness, and junctional disc (55,56) degeneration. The unique design of X-STOP® (IPD) allows it to be implanted with a straight forward approach without fixation to the bone or ligament, provides a physiologic spinal motion preservation system, as in other minimally invasive spinal surgery(57,58,59,60,61,61,62,63,64,65,66).
The advantages of using IPD or X-STOP® procedure over decompressive lumbar laminectomy are:
This minimally invasive spine surgery (MISS) usually can be performed on an outpatient basis
The procedure can usually be performed by using local anesthetics and IV conscious sedation. Patients with higher medical risks, which prohibit the use of general anesthesia, can be treated.
It usually requires little or no tissue or bone resection.
No significant blood loss
Most patients experience faster recover, ambulation and rapid relief of LSS symptoms.
The spinal canal is not compromised.
OR time is usually less than 60 minutes.
Much lower complication rate.
Implant can be removed easily.
Surgical Technique (,)
Meticulous and proper patient selection and proper surgical indication for X-STOP® (IPD) technique are of paramount importance in achieving good clinical results and in avoiding potential complications.
On physical examination, the patient should undergo a complete physical examination to rule out other disease processes with similar symptoms as LSS, especially vascular claudication of the legs. Radiological imaging studies should correlate with the patient's clinical signs to confirm the diagnosis of LSS.
The X-STOP® is contraindicated in patients with severe osteoporosis. It is manufactured from a titanium alloy and is MRI safe.
X-STOP® (IPD) procedure is indicated for patients (8,9):
Age 50 or older
Significant neurogenic intermittent claudication (NIC) with relief in flexion of lumbar spine
Secondary to evidence of LSS with x-ray, MRI scan and/or CT scan of thickened ligamentum flavum narrowed lateral recess and all central canal narrowing.
Not responding to at least six months of conservative treatment
No more than two levels of lumbar stenosis
Patient does not desire traditional lumbar surgery
Contraindications in the following situation
Spinal anatomy or disease that would prevent implantation of the device or cause the device to be unstable.
Known allergy to titanium or titanium alloy.
Significant scoliosis (greater than 25° of Cobb angle).
Active systemic infection or infection localized to site of the implantation.
Severe osteoporosis is more than 2.5 SD below the mean value of normal adult.
Cauda equina syndrome.
The X-STOP® System
The implant (IPD) (X-STOP®) (Figure 2a) is comprised of two components: A spacer implant assembly and a locking wing assembly with a fixed wing on the oval spacer, and a locking assembly of a wing and a locking screw.
The surgical instruments (Figure 2b):
Small curved dilator
Large curved dilator
Spacer insertion instrument
Wing insertion instrument
Hex head screwdriver
The surgeon may typically use monitored IV conscious mild sedation combined with local anesthesia, allowing a greater selection of higher anesthesia risk patients for this IPD procedure. In this manner, the anesthesiologist or the anesthetist can administer 2 g of Ancef and 8 mg dexamethasone IV at the start of the procedure. Local anesthesia of 1% Xylocaine mixed with 0.25% Marcaine is injected into subcutaneous tissue and paraspinal tissue. The patient should be sedated but remain awake and responsive to verbal commands (conscious sedation). Patients should not be disoriented.
The use of surface EEG monitoring provides added precision of anesthesia delivery, and offers an additional safeguard for patients undergoing this IPD procedure.
Operating Room Setup
Patient positioning (,)
Most of the time the patient is placed on a radiolucent table in the right lateral decubitus position (Figure 3) to allow flexion of the lumbar spine to have patient flex the spine to achieve spinal distraction, which is to be monitored radiographically with the digital C-arm fluoroscopy and image intensifier intraoperatively.
Operative Technique (,)
Skin incision and localization
After the surgical field is prepped and draped, a 4-8 cm. vertical midline lumbar incision (Figure 4a) is made over the proper spinal processes, under fluoroscopic guidance.
Using an 18 gauge spinal needle, the intraspinal process space for IPD insertion can be identified fluoroscopically (Figure 4b).
Of course, the skin and fascia are infiltrated on both sides of the supraspinous ligament, leaving 1.5 cm. of ligament width intact (Figure 4c). Also posterior rami nerves along the posterior aspect of facets joints and pars are infiltrated. A retractor is placed in after subperiosteal dissection of the tissue.
Creating the pilot hole
After incision of the lumbar fascia on either side of the spinal processes and supraspinous ligament, the dissection of the paraspinal muscle is performed, separating the bony spinal processes and lamina. The supraspinous ligament is preserved. With flexion position of the lumbar spine, the interspinous ligament is entered with a small curved dilator by paralleling the dilator to the spinous process until the facet is encountered, then rotating the instrument 90° and interspinous ligament with the tip of dilator into the lowest point of the interspinous ligament (Fig 5a, 5b). Fluoroscopy is used to confirm the position of the dilator (Figure 5c). A larger sized dilator is to follow to dilate the ligamentous opening further.
Application of the sizing distractor (Fig 6a-6c)
The sizing distractor is to be placed in the same opening as far anteriorly toward the lumbar lamina as possible for advancing of the distractor. A finger on the contralateral margin of the interspinous ligament to find the tip of the distractor as it passes through the opening. Once the distractor is in place, squeeze its handle gently and slowly until the resistance is encountered. As the handles are squeezed more and more, resistance should increase. When the supraspinous ligament becomes taut, optimal sizing has been achieved. Fluoroscopy is utilized for confirmation.
Selection of X-STOP® implant
With the handles open, the tip of the sizing distractor is shaping the opening of the spacer of X-STOP® implant. The measurement of the opening for the distractor ranges from 6 mm. to 14 mm. corresponding to the size of the X-STOP® implants available (Figure 7a – 7c). A locking nut at the base of the handle can be adjusted to fix the tips at specific size (Fig 7d).
Insertion and securing of X-STOP® implant
The X-STOP® assembly is then removed from the sterilization container with a spacer insertion instrument as instructed for proper insertion into the opening of the interspinous process created. The X-STOP® implant must be placed in the cavity between the spinal processes as anteriorly as possible (Fig 8a-8d).
Posterior position of the implant is incorrect. Once the spacer assembly is secured in place, do not disengage the insertion instrument. Then attachment of the wing assembly is to be performed as instructed on the other side of the spinal processes. Do not disengage the spacer insertion instrument yet. The wing assembly should be adjusted to fit snugly against the lateral surface of the spinous processes. The hex head screwdriver is utilized to lock the screw of the wing with the wing adjusted as medially as possible (Fig 9a-9d). Once the locking screw is tightened to its pre-set torque, it clicks once followed by a second click. Fluoroscopy is used to confirm the position (Fig 10a, 10b). Then remove the hex head screwdriver first followed by removal of the spacer insertion instruments.
If necessary hemostasis is accomplished with bi-polar coagulation. The lumbar fascia and skin edges are closed with simple sutures.
Double Level X-STOP® implant surgery
Again, after separation of the soft tissue from the spinal process and lamina, the first X-STOP® should always be inserted at the caudal level and the second X-STOP® should be inserted at the upper level after the first insertion, with the same surgical technique described previously.
When two X-STOP® implants are placed at adjacent levels, usually there is a slight overlap of the superior and inferior implant wing with the shorter wing of the superior implant positioned posteriorly to the long tapered wing of the inferior implant. Rotation of the inferior implant wing would be effectively prevented. Again, fluoroscopy confirms the correct placement of the X-STOP's ® (Fig 11a, 11b).
Postoperative ambulation begins immediately after recovery and the patient is usually discharged one to two hours after the procedure. They may shower and drive a car the following day. Applying an ice pack is helpful. Non steroidal anti-inflammatory drugs (ANSAIDs) are prescribed and mild analgesics and muscle relaxants as needed. Patient returns to usual activities in 10 days to 2 weeks, provided heavy labor and prolonged sitting are not involved. Mild progressive exercise program can begin the day after the surgery.
Physiotherapy is recommended for the first several weeks following surgery to condition the patient and to allow the patient's spine to adjust to the presence of the X-STOP®. Gradual physical activity and build up are recommended for the first six weeks. Avoidance of hyperextension of the spine, no heavy lifting, no stair climbing, no sports such as swimming, golfing, tennis, racquetball, running or jogging. This will avoid damage to the spinal processes. Walking is appropriate as tolerated but not to exceed one hour in duration.
After two weeks, cycling as tolerated. Strenuous activities and swimming may be added at six months. Again, a stress fracture of the spinal process may occur if strenuous physical activity is resumed too soon postoperatively.
Case Illustrations and Outcome
X-STOP®, interspinous process decompression system (IPD) provides a conservative yet effective minimally invasive surgical treatment for the elderly patients suffering from lumbar spinal stenosis with neurogenic intermittent claudication (NIC). X-STOP® treatment is an outpatient surgical procedure, and offers an attractive alternative to both conservative care and more traumatic traditional decompressive lumbar spinal surgery with or without fusion. Patient's clinical outcome and satisfaction are achieved with this minimally invasive X-STOP® system.
The unique design of X-STOP® (IPD) allows it to be implanted with a straight forward approach without fixation to the bone or ligament, and preserves physiological spinal motion (7,8, 47,48,49,50,51,52,53,54). This procedure of X-STOP®/IPD for the treatment of lumbar spinal stenosis combined with transforaminal endoscopic lumbar discectomy/foraminoplasty with laser thermodiskoplasty (55,56,57,58,59,60,61,62,63,64,65,66), can provide further decompression of neural structure and lumbar nerve, and improves the decompressive surgical result(7,8).
Interspinous process decompression system (IPD) X-STOP® procedure for decompression of lumbar spinal stenosis is a minimally invasive, safe and effective treatment alternative to traditional more traumatic lumbar laminectomy and laminotomy procedures with or without fusion. It leads to excellent results, speedier recovery, and significant economic savings. When it is combined with endoscopic lumbar transforaminal discectomy/foraminoplasty (with laser thermodiskoplasty), it can provide further decompression of neural structure and lumbar nerve, and improves the spinal decompressive result. In addition, it also preserves the lumbar spinal motion.
John C. Chiu, M.D., D.Sc, F.R.C.S Department of Neurospine Surgery California Center for Minimally Invasive Spine Surgery California Spine Institute Medical Center 1001 Newbury Road Newbury Park, CA 91320 Telephone: (805) 375-7900 Fax: (805) 499-4137 Email: email@example.com