1. Mini-invasive fenestration of the lumbar spine through a transspinous approach Pr Olivier GILLE Spinal Unit University Hospital Bordeaux France

2. Central stenosis The lamina The lamina –Its proximal part

3. lateral recess stenosis

4. foraminal stenosis

5. Lumbar fenestration described by Pr Senegas 1976 Alterations of erector spinae muscles following a posterior lumbar surgery

6. Assessment of erector spinae muscles Measurement of muscular strength with force measuring devices Measurement of muscular strength with force measuring devices Measurement of the electromyographic signal Measurement of the electromyographic signal Measurement of the cross-sectional area (CSA) of the muscles Measurement of the cross-sectional area (CSA) of the muscles –Ultrasound studies –CT scans –MRI Measurement of signal density (CT scans) or signal intensity (MRI) Measurement of signal density (CT scans) or signal intensity (MRI)

7. Assessment of muscles using MRI Measurement of muscle area on axial slides Measurement of muscle area on axial slides –Barker Spine. 2004 –Parkkola Spine. 1993 –Dangaria. Spine. 1998 muscle signal intensity muscle signal intensity –Visual assessment –Salminen. J Spinal Disord. 1993; Parkkola R, Spine. 1993 –Region of interest (ROI) in the muscle –Gejo Spine 1999 –Kim Spine 2005

8. Measurement of the muscle contractile component cross- section area (CCSA) Area measurement by surrounding the muscle Area measurement by surrounding the muscle signal intensity determination of the contractile tissue signal intensity determination of the contractile tissue –Using 4 ROI in plain muscular zone In collaboration with the biomechanics Laboratory of ENSAM, Paris

9. Measurement of the muscle contractile component cross- section area (CCSA)

10. Following a posterior surgery Pre operative MRI Post operative MRI

11. On proximal slide On proximal slide

12. TC TNC Postop Preop

13. CCSA NCCSA Pre operative MRI Post operative MRI Alterations of erector spinae muscles following a posterior lumbar surgery

14. Following a posterior lumbar surgery the contractile component of the erector spinae muscles decreases of 25% the contractile component of the erector spinae muscles decreases of 25% O.Gille, JM Vital. Erector spinae muscle changes on MRI following lumbar surgery through a posterior approach. Spine, 2008

15. LUMBAR SPINOUS PROCESS-SPLITING LAMINECTOMY WATANABE, 2006

16. CHIMNEY SUBLAMINAR DECOMPRESSION LIN, 2006

17. CHO : « Marmot technique », J. Neurosurgery Spine 2007

18. No high rate of improvement Long time surgery Technically difficult Long learning curve “Blind” surgery High risk of nerve root or dural tear

19. Step 1: Length spinous process measurement on preop MRI

20. Step 2: Spinous process osteotomy using a straight osteotom (3 mm security) Step 3: Osteotomy at the base of the spinous process performing with a curved osteotom. Step 5: The decompressive procedure can be continue as usual Step 4: Osteotomy of the distal part of the lamina using a curved osteotom L4 L5

21. Optical magnification Optical magnification Head light Head light Operative time < 30 mn Operative time < 30 mn No blood loss No blood loss

23. 15 patients 15 patients Lumbar canal stenosis Lumbar canal stenosis –One level preop and 3 months postop MRI preop and 3 months postop MRI –Quality of decompression –Assessment of muscle changes

24. Measurement of the cross-sectional area of the spinal canal (T2 sequence) PreopPostop

25. PreopPostop

26. Results Preop spinal canal area : 0.8 cm² Postop spinal canal area : 2.1 cm²

27. Measurement of the MULTIFIDUS AND LONGISSIMUS contractile component cross-section area (CCSA) (T1 sequence) PreopPostop

28. Measurement of the MULTIFIDUS AND LONGISSIMUS contractile component cross-section area (CCSA) (T1 sequence) PreopPostop

29. Results Following a transspinous approach : Following a transspinous approach : –the contractile component of the erector spinae muscles decrease less than 5% (Mean 4.8)

30. Conclusion Advantages of fenestration through transspinous approach: Technically simple Technically simple Minimal soft tissues injury Minimal soft tissues injury Short time surgery (< 30 mn) Short time surgery (< 30 mn) Excellent working space and visualization Excellent working space and visualization Less bleeding Less bleeding Less postoperative pain ? Less postoperative pain ? Limits: Difficulties for repairing a dural tear Difficulties for repairing a dural tear