PRELIMINARY RESULTS OF MINIMALLY INVASIVE LUMBAR INTERBODY FUSION (MILIF) USING A NOVEL EXPANDABLE RETRACTOR SYSTEM Michael H. Winer, M.D. Scottsdale, Arizona 19th Annual IITS Meeting Phoenix, Arizona April 5-9, 2006

Traditional Open Surgery Extensive dissection of muscle /soft tissue Extensive dissection of muscle /soft tissue Wide retraction, prolonged pressure Wide retraction, prolonged pressure  Ischemia and denervation leading to muscle atrophy and pain  “Failed back syndrome” & “post laminectomy syndrome”

Goals of Minimally Invasive Surgery Minimize approach related morbidityMinimize approach related morbidity  Less retraction pressure  Reduced paraspinal muscle damage  Less pain & quicker recovery /return to normal activities Same or better results as traditional open surgerySame or better results as traditional open surgery  Adequate access to disc space  No increase in complication rate

Atavi System Flexible retractor with distal expanding skirt Flexible retractor with distal expanding skirt  Increases surgical working area while minimizing muscle disruption  Direct visualization, operating microscope or loupes  Decompression, fusion, instrumentation and interbody  Validation of ATAVI presented in prior studies

FlexPosure Manipulation Proximal tube pivots over the skirt.

Atavi System Allows surgeon to do most posterior procedures in a minimally invasive fashion Atavi System Allows surgeon to do most posterior procedures in a minimally invasive fashion Dynamic stabilization using the MIS ATAVI portal System Dynamic stabilization using the MIS ATAVI portal System Potential Applications: Nucleus replacement Potential Applications: Nucleus replacement

Reduced Intramuscular Pressure on the Paraspinal Muscles Figures 1a and 1b: Orientation of pressure transducer with minimally invasive retractor (top) and standard open retractor (bottom) Minimally invasive retractor (blue) and standard open retractor (red). Kee D. Kim, M.D.1, David Spenciner, P.E., Sc.M.2 1Department of Neurological Surgery, University of California, Davis, CA 2RIH Orthopaedic Foundation, Providence, RI IMP with the minimally invasive retractor was transient in nature and significantly lower. This may be due to the smaller footprint and more flexible walls of this device as compared with the standard open retractor.

Equivalent Access To Disc Space 6 cadavers underwent lumbar discectomy & endplate preparation 6 cadavers underwent lumbar discectomy & endplate preparation Disc material removed was collected & weighed Disc material removed was collected & weighed Lumbar spines harvested & axially transected through each disc level Lumbar spines harvested & axially transected through each disc level Endplate Surface Area Calculation Available Endplate Surface Area Prepared Endplate Surface Area Minimally Invasive Open P value * % Disc Material Removed Mean % Endplate Surface Area Exposed

T2 relaxation time ms (95% CI) Open Minimally Invasive Comparison of mean T2 relaxation times at level of fusion ms (+ 23.3) 47ms (+ 8.4) p = Decreased Paraspinal Muscle Damage 4 Atavi & 4 Open patients - single level posterolateral fusion & pedicle screw fixation 4 Atavi & 4 Open patients - single level posterolateral fusion & pedicle screw fixation MRI scans performed ~6 months (range 4-10) post surgery MRI scans performed ~6 months (range 4-10) post surgery

Decreased Paraspinal Muscle Damage Coronal T2w-FSE (left) & axial T2w- STIR images (right) 6 mths post open L4-5 fusion, showing severe edema in multifidus. Coronal T2w-FSE (left) & axial T2w- STIR images (right) 6 mths post open L4-5 fusion, showing severe edema in multifidus. Coronal T2w-FSE (left) & axial T2w- STIR (right) images 5 mths post MIS L3-4 fusion, showing mild edema in multifidus. Coronal T2w-FSE (left) & axial T2w- STIR (right) images 5 mths post MIS L3-4 fusion, showing mild edema in multifidus.

Minimally Invasive Lumbar Interbody Fusion (MiLIF) Preliminary Results of a Multi-Center Study

Methods Prospective, multi-center study Prospective, multi-center study Single-level MiLIF for Degenerative Disc Disease or Isthmic Spondylolisthesis Single-level MiLIF for Degenerative Disc Disease or Isthmic Spondylolisthesis Interbody fusions performed with structural allograft or synthetic interbody fusion device with pedicle screws and autologous bone graft Interbody fusions performed with structural allograft or synthetic interbody fusion device with pedicle screws and autologous bone graft Patients evaluated pre-operatively, 2 & 6 wks, 3, 6, and 12 months post-op Patients evaluated pre-operatively, 2 & 6 wks, 3, 6, and 12 months post-op  Oswestry, NRS (pain score) SF-36, Modified Prolo

Access spine using soft tissue dilation. Slide retractor over last dilator. Paramedial approach; incision ~4cm lateral to midline MiLIF Technique Remove dilator leaving retractor in place. Retractor expanded beneath skin.

Direct visualization of anatomic structures, use same bone landmarks for placement of pedicle screws and access of disc space as traditional approach. MiLIF Technique

Demographics Average age- 44 years (22-75) Average age- 44 years (22-75) Gender - 59% male Gender - 59% male Mean height in (60-75) Mean height in (60-75) Mean weight lbs ( ) Mean weight lbs ( ) Smokers - 23% Smokers - 23% Worker’s Compensation- 6% Worker’s Compensation- 6%

Demographics Diagnosis Diagnosis  DDD27 (50%)  Spondylolisthesis29 (54%) Level of fusion Level of fusion  L2-L31 (2%)  L3-L41 (2%)  L4-L515 (30%)  L5-S133 (66%)

Procedural Results Mean blood loss cc Mean blood loss cc Mean Surgical Time -219 min Mean Surgical Time -219 min Blood transfusions- 0 Blood transfusions- 0 Intra-operative complications- 0 Intra-operative complications- 0 Conversions to an open procedure- 0 Conversions to an open procedure- 0 Mean length of hospital stay- 2.7 days Mean length of hospital stay- 2.7 days

Results Statistically significant decrease in ODI & NRS from baseline to 6 week, 3, 6 & 12 month follow-ups (p < 0.05 calculated using one-tailed paired t-test)

Results Work Status Work Status  Average return to work was 39.5 days  93% returned to work by 3 months, 100% working by 6 month follow-up Modified Prolo Scale Modified Prolo Scale  98% considered success at 3 months NASS Patient Satisfaction Index NASS Patient Satisfaction Index  73% satisfied with outcome at 6 wks SF-36 SF-36  Statistically significantly improved by 6 month follow-up

Conclusions MiLIF is safe and effective treatment for degenerative disc disease and spondylolisthesis MiLIF is safe and effective treatment for degenerative disc disease and spondylolisthesis Early MiLIF outcome data compares favorably to retrospective open TLIF case series Early MiLIF outcome data compares favorably to retrospective open TLIF case series  150 cc less blood  Fewer complications  Hospital stay decreased by 2 days

Thank you ! The beginning Madeline, Sophie, Paige & Allison