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Flexible Endoscopic Intradiscal Discectomy

FEID

What is a flexible Endoscopic Intradiscal Discectomy?

The flexible endoscopic intradiscal discectomy can be performed through a one or two sided approach depending on the complexity of the problem. However as technology advances so we are able to perform an increasing number of discectomies through a single (Uniportal) approach.

The flexible endoscopic intradiscal discectomy.is performed following discography. An Endoscope is railroaded down to the disc. The disc wall is opened and the endoscope is inserted in to the disc. A side firing laser probe is inserted through the endoscope and under vision the laser is used to ablate disc material using Holmium or KTP532 wavelengths.

When do we use a flexible endoscopic intradiscal discectomy?

We use the F.E.I.D. for those cases of more advanced disc degeneration or in cases suffering the complications of previous conventional surgery. It is used with:

  • A narrow based disc protrusion
  • A protrusion occupying less than 40% of the antero-posterior (radiographic) diameter of the spinal canal
  • A weight bearing lumbar disc height of 3 mm or more
  • Dynamic retrolisthesis of 4 mm or less
  • A contained disc (NOT to be used when treating Leaks)
  • A disc previously addressed by surgery with preserved height

Whereas we used this technique for extruded protrusions, we now use the Endoscopic Laser Decompression & Foraminoplasty to treat extrusions and cases with yet more advanced degeneration and often in tandem with the flexible endoscopic intradiscal discectomy.

Results to date are proving encouraging with a >85% success rate at review at 2 years in cases with a contained disc protrusion and previous surgery and greater success in those patients with discs unadulterated by prior surgery.

Reasons for Development

Experience with PMD provided experience with the posterolateral approach and manual intradiscal discectomy. LDD provided experience of the application of intradiscal laser energy. Both techniques had shown particular and specific shortcomings concerning LRS and recurrent protrusion.

LDD offered a treatment for broad based disc protrusions and radial tears providing the degree of settlement, olisthesis or retrolisthesis was limited. Extruded disc protrusions in which the annular wall was breached, narrow based centromedial and foraminal disc protrusions remained out with the effective realm of LDD.

The presence of LRS, narrow based protrusions, extrusions and sequestra, instability and midline (central) stenosis precluded LDD, yet minimalism had the theoretical advantages of reducing trauma, destabilisation and scarring, whilst providing outpatient surgery and rapid rehabilitation. To forge a way forward and improve the ability to address more taxing pathology, there was a need to visualise and clear the intradiscal space more precisely. Attention was focused on improving the treatment of narrow and broad based protrusions and extrusions because contemporary treatment concepts still focused upon the disc as the progenitor of symptoms by direct or indirect effects.

Parvis Kambin in Washington USA, added endoscopy to PMD initially as a supplementation of open posterior discectomy (Kambin and Schaffer 1989, Kambin 1993, Kambin 1991a, b, c, Kambin et al 1996, Kambin 1996, Hermantin et al 1999) with posterolateral endoscopy and eventually dispensing with the open procedure. The procedure was a bi-portal bilateral endoscopic technique termed Arthroscopic Microdiscectomy (AMD). Kambin's ethos was to avoid extensive intradiscal excavation for fear of debulking the disc and encouraging collapse of the disc. He preferred to limit disc excision to a posterior centromedial clearance "Quadrantectomy" but this treatment concept suffered the limitation of an intradiscal technique as with PMD. In addition, he eschewed the use of intradiscal lasing. He used a rod lens rigid round stem endoscope with a 6.5mm outside diameter. The approach was fluoroscopically controlled to the annulus and required considerable manipulation and displacement of the nerve to gain clear access to the disc.

The straight rigid punches and power reamers used in the AMD as with PMD were limited in their intradiscal access and excursion. The intradiscal pathway continues along the 450 approach angle. Clearance of the nucleus pulposus was proportional to the excursion of the jaws of the punch as deviation of the axis of the punch was very limited. AMD used a bi-portal technique, which allowed endoscopic monitoring of the intradiscal clearance and the use of rigid powered reamers to accelerate the clearance. Kambin subsequently developed an intradiscal "bridging punch" which consisted of a flexible tip that could be flexed within the disc space by means of internal wires. The aim of this device was to achieve a more coronal clearance within the posterior disc. He also developed a "Shoehorn" deflector to guide a 2mm flexible tipped grasper to towards the posterior quadrant but the guidance was unpredictable, the radius of the curve was long and the instruments were delicate and limited in efficacy.

Independently Hansjorg Leu and colleagues in Zurich (Schreiber et al 1989) were developing fibreoptic intradiscal laser discectomy using a (Clarus Inc, Minneapolis, USA) flexible endoscope and forward firing laser fibre. However, the depth and field of view were extremely limited and such lack of definition inhibited its appeal.

Endoscopic intradiscal discectomy was technically fraught by difficulties resulting from the limited access and sighting of the instruments inserted from the opposite portal. The reamers would have to be used under fluoroscopic control to gain contact with the contra-lateral instrument. Clearance commenced in the disc in advance of visualisation. After carrying out a limited number of AMDs it became evident that the procedure needed flexible endoscopy and flexible instrumentation to achieve clearance of the nucleus pulposus, posterior narrow based protrusions or extrusions, to harness the ablative and thermoplastic effects of the laser, to shrink or anneal the posterior wall.

The Olympus Corporation (Tokyo, Japan) modified a flexible fibreoptic Bronchoscope (Figure 20 on page 121) for this purpose. It had irrigation, a working channel capable of transmitting a 300µm forward firing fibre and it could be flexed in the distal 2cms. The depth and breadth of field were limited; the resolution was limited by the 20,000-bundle density and low light source power (150 Watt Halogen) and transmission.

Danek Inc. (Warsaw, Indiana, USA) had developed a robust flexible guide cannula with a working channel diameter of 2.8 mm that allowed passive 2.5mm flexible punches to be guided to the point of operation under vision and control.

Summary

Experience with FEID indicates that this technique can be used to perform an endoscopic discectomy but sustained outcome benefit is jeopardised by settlement, LRS, limited visualisation of the epidural space, narrow based protrusions, epidural scarring, retrolisthesis, olisthesis, extrusion and spondylolytic spondylolisthesis.

This experience suggests that Endoscopic Discectomy can be used to address broad based disc protrusions but that this should be reserved for patients where the index level has preserved disc height, less than 3mm retrolisthesis or olisthesis, no pre-existing LRS, narrow based protrusions, epidural scarring or spondylolytic spondylolisthesis. It can prove successful in cases of extrusion but is not reliable and is therefore not recommended for this or sequestra. The indications for FEID are again strictly limited by a failure to address the foraminal volume, contents and their interaction and an ability to explore the epidural space and extraforaminal zone.

A means of addressing these shortcomings needed to be evolved which provided direct visualisation of the foramen and which allowed pathology of its contents to be addressed.
 

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