Radiographic Risk Factors for Unfavourable Outcomes after

Percutaneous Interlaminar Endoscopic Lumbar Discectomy

at L4-5 LevelJong-chul Chung, MD, Eun-kyung Kim, RN, In-sun Jeong, RN,

Woo-sung Sun, MD, Byeong-wook Hwang, MD, PhD, Hyung-dong Kim, MD, PhD.

Department of Neurosurgery, Bumin Hospital, Busan, Korea

Backgrounds

• Endoscopic interlaminar approach is still more challenging above L4-5 level

• Endoscopic working sheath inserted in narrow interlaminar space can cause dysesthesia or motor weakness.

• This study investigated the radiographic variables related to the interlaminar working zone.

Radiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

Choi et al. 2006 Operative Neurosurgery

Materials : PEILD at L4-5 levelRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

• Fully endoscopic interlaminar approach– FHD Rigid scope (OD 6.3mm, WchD 3.7mm, OA 30º, WL 125mm, TL 205mm )– Ligamentum flavum splitted and spared– Except for cases with laminotomy

• Jan.2015 – Jul.2016• 34 patients (M:F = 23:11)• Mean age: 49.6 years (19-74)• Mean follow-up : 14.2 months (12-27)• Type of disc protrusion 6%

9%

26%

15%

44% sup.migration

huge rupture

inf.migration

central

paracentral

Methods : Plain radiographyRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

• ILH : Interlaminar space height on anteroposterior radiography• ILW : Interlaminar space width on anteroposterior radiography• ISDf : Interspinous distance of flexion lateral radiography • ISDe : Interspinous distance of extension lateral radiography• ISDd : distance difference between dynamic radiography

ISDf

ISDe

ISDd = IDSf - ISDe

FLEXION EXTENSION

ILH

ILW

AP

Methods : Computed tomographyRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

• SLA : Sublaminar angle of L4 level on sagittal CT image• ILDs : Interlaminar distance at ipsilateral lateral margin of dura on sagittal CT • ILDc : Interlaminar distance at ipsilateral lateral margin of dura on coronal CT

ILDc

ILDs

SLA

midlineparamedian

Results: OverallRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

• Pain score (VAS)

Ave VAS leg 7.7(6-10) → 2.2(1-5) Ave VAS back 3.9(0-8) → 2.1(0-5)

• Group I : Favorable outcome group• Group II : Unfavorable outcome group

– Persistent dysesthesia : 3 patients– Aggravated motor weakness : 2 patients

Group I Group II

Group I Group II

Results: IL height & widthRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

ILW

ILH

ILH

ILW

ILH (mm) 13.7±3.2 12.7±3.0ILW (mm) 23.1±3.7 20.5±6.3

※ P>.05

Results: IL height & widthRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

ISDf

ISDe

ISDd = IDSf - ISDe

FLEXION EXTENSION

ISDf ISDe ISDd

ISDd (mm) 9.4±4.3 3.3±2.5 P<.05 0.630 (95%CI, 0.933-0.996)

ISDf (mm) 14.4±4.9 9.1±3.2

ISDe (mm) 5.3±4.8 5.7±5.1

Results: IL distance, & SLARadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

ILDc

ILDs

SLA

midlineparamedian

ILDcILDsSLA

SLA ( º) 24.8±8.6 20.6±3.4

ILDc (mm) 9.2±2.9 5.4±3.1 P<.05 0.635 (95%CI, 0.408-0.989)

ILDs (mm) 10.3±2.9 7.7±4.2

DiscussionRadiographic risk factor for unfavorable outcome after PIELD at L4-5. Chung et al.

• L45 interalminar space can be widened in flexion position.

• ISDd, and ILDc were significant parameters for planning PIELD.

• In cases of narrower and unexpandable interlaminar space, laminotomy or laminoplasty by advanced endoscopic instruments should be required.

ISDf

ISDe

ISDd = IDSf - ISDe

FLEXION EXTENSION

ILDc

paramedian