Abstract

Introduction

Studies evaluating neurogenic intermittent claudication (NIC) secondary to lumbar spinal stenosis (LSS) indicate that roughly 8% of adult population is affected by this pathology, 3 to 4% of patients who see a general physician have LSS and 13 to 14% of patients with low back pain who see a specialist have LSS1,2,3,4. The LSS surgery in over 65 patients have increased a lot over the past 20 years5,6,7. The characteristic symptoms of NIC, such back and leg pain, numbness and weakness are normally present and depending to patient's position, exacerbated with lumbar extension (standing, walking) and relieved by flexion (sitting, bending forward)8,9,10 . The primary level affected is L4-L5, followed by L3-L4, L5-S1, L2-L3 and L1-L211,12. Patients with stable symptoms are treated with conservative therapy (FANS, steroid oral drugs, physical therapy, epidural steroid injections). When this therapy fails, the only alternative solution is decompressive surgery, applied in open or mininvasive way (Stand Alone interspinous device). Decompression surgery is superior to conservative choice in terms of pain relief and patient satisfation but success rate of surgery vary widely (23-100%)13. Interspinous spacer devices have been recently used for cases of lumbar stenosis and spinal claudication. In vitro studies have demonstrated a reduction in facet joint forces by 68% and annulus pressures by 63%. MRI studies have demonstrated increased canal and neural foraminal area after implantation of these devices14,15,16. Previous studies by Zucherman17 et al. and Siddiqui18 et al. have demonstrated patient satisfaction rates of 71-73 %.

Materials And Methods

A total of 30 patients ( 16 males, 14 females ) affected by degenerative lumbar spinal stenosis and neurogenic intermittent claudication have been undergone to a percutaneously posterior decompression using an interspinous spacer device ( Aperius™ – Perc LID™ System; Khypon). The average age was 63.5 yrs. The levels of stenosis treated have been L4-L5 in 16 cases (53%), L3-L4 in 12 cases (40%) and L2-L3 in 2 cases (7%). The inclusion criteria have been symptomatic L1-L5 LSS with/without NIC with imaging (MRI or CT) correspondence resistant to conservative therapy for at least 6 months, symptoms exacerbated by walking or standing and relieved by flexion forward. One single level only treated. Exclusion criteria included degenerative spondylolisthesis >1, radiologically instability, intolerance to the material used in the implant (titanium alloy), scoliotic deformity with Cobb angle>25°, kyphosis requiring surgery, fracture of the affected level spinous and active infection/tumor of the spine. Previous surgery in general does not contraindicate the treatment. With the patient prone in slight flexion position, under local anesthesia and ev sedation, a small skin incision (less than 1,5cm) has made 6-10cm lateral to the midline at the affected level identified under C-arm control. The place for the implant is made through a percutaneous insertion of increasing size trocars (8-14mm); it's very important to avoid overdistraction; once decided the correct size, the final step consists in the implant positioning and progressive wings deployment under fluoroscopy control (figg. a,b,c,d,e).

Results

We carried out a multicentric retrospective study to assess the clinical outcomes following percutaneously posterior decompression using an interspinous spacer device ( Aperius™ – Perc LID™ System; Khypon) at an average follow up of 3 months.

The evaluation has been performed by applying pre and postop Visual Analogic Scale (VAS) and the Zurich Claudication Questionnaire (ZCQ) that permits to evaluate the Symptom severity (before and after surgery), the Physical function (before and after surgery) and Patient Satisfation (after surgery). Average stay in hospital was 2 days. The average VAS pain score improved from 8.2 to 2.8 (scale of 1 to 10). The ZCQ - Symptoms severity score and Physical passed from a preop value of 35% and 20% to a new of 76% and 69%, according with international literature results. The overall patient satisfaction rate was 88.5%. No complications has been detected at 2 months follow-up, no any other surgery has been employed.

Discussion

The use of the percutaneously interspinous spacer device Aperius™PercLID™is associated with minimum patient morbidity.

Experimental studies demonstrate that Aperius ™ percLID™ has several important biomechanical effects: limitation of extention with minimal effects on flexion, axial rotation and lateral flexion, an increasing of dimensions of spinal canal by reducing dural sac impingment, no postural change, a reloading on the disc in a more physiological pattern (load bearing structure in extention), and no effects at adjacent levels. The surgical technique is relatively simple; the use of local anesthesia permits to avoid risks due to general anesthesiologial procedures (bleeding, infections, CSF leakage...). It is a valuable addition to current treatment modalities. Respect to other interspinous devices, the Perc-LID™ System presents the following advantages:

1. Percutaneously procedure, through a 1 cm skin incision, preserving the thoracolumbar fascia and thus the SSL and permitting a reduction of operating time, risks and complications of open surgery ( bigger skin incision, bone removal, muscle damage, postsurgical scar...);

2. Stand Alone Decompression System with a reduction of re-operation rate, early decompression of the spinal canal with reduction of neurological damage risk;

3. Unilateral approach;

4. Postoperative physical therapy not requested

5. Fast functional recovery and return to daily activities;

6. Great patient's satisfaction and compliance

Surgical Technique

Figure 1a: patient position, local anesthesia and skin incision

Figure 1b: Percutaneous trocar insertion of incrising size (8-14mm)

Figure 1c: Implant positioning

Figure 1d: C-arm control of implant positioning and wings deployment

Figure 1e: Female, 69 yrs right L4-L5 foraminal stenosis preop axial MRI (above on the left) and postop CT reconstruction

Correspondence to

Pier Paolo M. Menchetti, M.D., F.R.C.S. (US) Villa Cherubini Clinic, Via Cherubini, 8 – 50132 Florence – Italy Fax : +39 055 2347266; e-mail: ppm.menchetti@libero.it

References