Dept. of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan. Brigham and Women s Hospital, Harvard Medical School, Boston, MA, USA.

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1 Microendoscopic Decompression for Lumbar Spinal Stenosis with Degenerative Spondylolisthesis: the influence of spondylolisthesis stage (disc height and static and dynamic translation) on clinical outcomes Akihito Minamide, MD, PhD 1 ; Andrew K. Simpson, MD, MHS 2 ; Munehito Yoshida, MD, PhD 1 ; Yukihiro Nakagawa, MD, PhD 1 ; Hiroshi Iwasaki, MD, PhD 1 ; Shunji Tsutsui, MD, PhD 1 ; Masanari Takami, MD, PhD 1 ; Keiji Nagata, MD, PhD 1 ; Yasutsugu Yukawa, MD, PhD 1 ; Hiroshi Yamada, MD, PhD 1 1 Dept. of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan 2 Brigham and Women s Hospital, Harvard Medical School, Boston, MA, USA.

2 Degenerative Lumbar Spondylolisthesis Generally, most patients with DS have grade I or II slippage according to the Meyerding classification system; few patients experience slippage of higher grades. Slippage does not continuously progress with spinal instability annually. DS develops as a result of degeneration of the lumbar spine. DS occurs with aging, and, finally, reacquires stabilization of the spine by the repair mechanism of osteoarthritic change. Therefore, it is proper to regard DS as a favorable self-limited disease.

3 Classification setting of pathological stages of DS Stage Disc height (DH) loss Slippage Pre-listhetic 1/3 0mm Early 1/3 < %slip 10% Advance 2/3 % slip 10% and/or dynamic slippage 3mm End > 2/3 dynamic slippage < 3mm

4 Microendoscopic Laminotomy (MEL) Pre-op. Post-op. Minamide A, et al. J Neurosurg Spine 2013: 19(6), The novel microendoscopic laminotomy (MEL) technique helps to preserve the facet joints, posterior ligament complex and soft tissues as much as possible.

5 Purpose was (1) to develop the pathological stages of DS based on natural history, (2) to determine how the subtypes of degenerative spondylolisthesis, based on pathologic stage, affect outcomes for microendoscopic decompression (MEL) surgery for DS with lumbar spinal stenosis (LSS).

6 Patients & Methods l Prospective cohort study, l Consecutive patients were enrolled if they had (1) single-level DS at L3/4 or L4/5, and (2) evidence of associated LSS. They had failure of conservative treatment for 3 months. l 218 pts. (male/female 91/127; mean age: 69.8 y.o) l They were divided into three groups (early, advance and end) based on pathological stage of DS. l Follow-up period: minimum 2 years postoperatively

7 Outcome Measures l Clinical outcome measures were assessed preoperatively and at final over-2-year postoperative visit. - Japanese Orthopaedic Association scoring system (JOA score, full score 29 pints) - Recovery rate of JOA score (Post-score - Pre-score/29 - Pre-score) x100 - VAS for low back pain (full score = 100 mm) Statistical Analysis: All parameter were analyzed by Student-test (p<0.05).

8 Results Characteristics and clinical outcomes of patients who underwent MEL for DS Patients Enrolled (n) 218 Final follow-up (n) 173 Mean follow-up period (years) 2.3 Gender (n) Men 96 Women 122 Mean age (range) (years) 69.7 (47-88) JOA score Preoperative (points) Final follow-up (points) Recovery rate (%)

9 Results Clinical outcomes after MEL in patients of each group Early Advanced End P value Patients (male/female) 15 (5/10) 145 (64/81) 13 (2/11) 0.11 Age JOA score (points) Preoperative 15.3± ± ±4.4* 0.04 Final follow-up 25.9±2.8* 22.7± ± Recovery rate (%) 77.7± ± ± Low back pain (VAS) Preoperative 61.3± ± ± Final follow-up ± ± ± % Slip Preoperative 7.9±3.0* 18.6± ±8.5 <.0001 Final follow-up 8.3±3.6* 19.0± ±8.2 <.0001

10 Results Graded recovery rate after MEL in each group Early (N=15) Advanced (N=145) End (N=13) P value Recovery rate Excellent 53.4% (8/15) 33.8% (49/145) 23.1% (3/13) 0.22 Good 33.3% (5/15) 29.0% (42/145) 61.5% (8/13) 0.07 Fair 13.3% (2/15) 22.7% (33/145) 15.4% (2/13) 0.58 Poor 0% (0/15) 14.5% (21/145)* 0% (0/13) 0.02

11 Results l Cases of additional surgeries following MEL in each group Early Advanced End Patients 6.7% (1/15) 11.0% (16/145) 0% (0/13) Fusion surgery Decompression surgery l Progress rate of pathological stage of DS Final follow-up Total Preoperation Early Advanced End Early (n) 11 4 (26.7%) 0 15 Advanced (n) (15.9%) 145 End (n) 13 13

12 Conclusions l Microendoscopic decompression is an effective treatment modality for patients with degenerative spondylolisthesis and concurrent stenosis, with only 5% of patients requiring additional fusion surgery at over-2-year follow up, and another 5% requiring revision decompression or adjacent segment decompression. l All but one of the patients requiring revision surgery were in the advanced stage DS group, indicating a greater than 10% anterolisthesis and/or >3mm of dynamic translation on flexionextension films. l These results suggest that microendoscopic decompression may represent the optimal first-line surgical treatment for the vast majority of patients with DS and LSS. Authors disclosure statement: The authors report no actual or potential conflict of interest in relation to this article.