How cervical alignment and thoracic inlet angle affect on postoperative spinal cord alignment after laminoplasty?

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1 How cervical alignment and thoracic inlet angle affect on postoperative spinal cord alignment after laminoplasty? Shinya Kato, Hisanori Mihara Department of Orthopaedics Surgery, Yokohama Hodogaya Central Hospital Yokohama Minami Kyousai Hospital

2 Laminoplasty Majority of cervical myelopathy patients demonstrate cord compression lesion on the anterior, cervical laminoplasty (CLAP) attempts indirect decompression from posterior. Therefore, the spinal cord decompression status is affected by the total cervical alignment. According to Lee et.al, total cervical alignment was affected by thoracic inlet angle(tia). TIA was not changed by the position, like Pelvic Incidence (PI) in the pelvis

3 Purpose This study investigated how TIA and total cervical alignment ffected the spinal cord alignment (SCA) and neurological improvement following laminoplasty.

4 Subjects CLAP for Compressive Myelopathy since2004: 95patients Disease : CSM (65patients) : OPLL (30patients) Exclusion : Trauma, Tumor, Infection, Previous surgery continuous type of OPLL Age:67.1(36~85) Surgical Method: Midline Splitting, Open door ( Kurokawa:41 Hirabayashi:54)

5 .Clinical Evaluation Japanese Orthopedics Association (JOA) score recovery rate of JOA score (Hirabayashi method) Methods 2.thoracic inlet angle(tia) TIA the center of T1UEP the upper end of the sternum T1 upper end plate (T1UEP) a line vertical to the T1UEP Lee etc. J Spinal Disord Tech vol25, Num2: 2012 CTM(sagital)

6 3. Cervical Alignment 4. Formula C2-C7 Lordotic angle Lordosis is + In normal volunteers T1 slope= TIA C2-C7 angle= T1 slope (Lee, 2012) TIA (C2-C7 angle) 34.4

7 5.Postoperative spinal cord alignment (SCA) Lordosis: type L Straight: type S Local Kyphosis: type LK Kyphosis: type K Cord axis line: anterior border of the spinal cord between at C2 and at C7 Pass posterior of the cord Inside of the cord Partially anterior out of the cord Most anterior of the cord (Kawakami:2001 )

8 recovery rate of JOA score Results TIA (C2-C7 angle) ANOVA P<0.01 ANOVA P< patients type L type S type LK type K (9) (40) (31) (15)

9 TIA (C2-C7 angle) The average was 34.8 degrees Patients with under 34.8 degrees Patients with over 34.8 degrees 8/47 patients (17.0%) demonstrated postoperative SCA as type LK or type K 32/48 patients (66.7%) demonstrated postoperative SCA as type LK or type K

10 The mean TIA was 74.8 degrees, the mean C2-C7 angle was 12.5 degrees Group1: patients with both TIA over 74.8 degrees and C2-C7 angle under 12.5 degrees Group2: the other patients patients TIA (C2-C7 angle) type L,S: 32.7degrees(AVG) type LK,K: 44.5degrees(AVG) Group1 Group2 Recovery rate Group1:19/22 (86.4%) patients TIA 0.65-(C2-C7 angle) were over 44.5 degrees. Group2:8/73 (10.1%) patients TIA 0.65-(C2-C7 angle) were over 44.5 degrees. Patients with both large TIA and small C2-C7angle got large TIA (C2-C7 angle) and bad neurological recovery

11 Conclusions It is said that total cervical alignment is affected by TIA and neural decompression status was affected by total cervical alignment after laminoplasty. But ideal total cervical alignment after laminoplasty is unclear. In the present study the patients with TIA 0.65-(C2-C7 angle) under 38.4 degrees had good SCA after laminoplasty. So the ideal C2-C7 angle after laminoplasty was over TIA degrees. If patients had large TIA and small C2-C7 angle, there was a possibility of poor neurological recovery.

12 disclosure Shinya Kato, MD - n) None Hisanori Mihara, MD - b) DePuy Spine, Synthes b) Medtronic Sofamor Danek a) Research or institutional support received; b) Miscellaneous non-income support (e.g., equipment or services), commercially derived honoraria, or other non-research related funding (e.g., paid travel); c) Royalties; d) Stock or stock options held; e) Employee or Consultant; n) Nothing of value received