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Minimally Invasive Transforaminal Lumbar Interbody Fusion at L5-S1 through a Unilateral Approach: Technical Feasibility and Outcomes.

Choi WS, Kim JS, Ryu KS, Hur JW, Seong JH - Biomed Res Int (2016)

Bottom Line: The mean VAS scores for back and leg pain mean ODI scores improved significantly at the final follow-up.PSR was 88%.Conclusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, Seoul St. Mary's Hospital, Catholic University, Seoul 06591, Republic of Korea.

ABSTRACT
Background. Minimally invasive spinal transforaminal lumbar interbody fusion (MIS-TLIF) at L5-S1 is technically more demanding than it is at other levels because of the anatomical and biomechanical traits. Objective. To determine the clinical and radiological outcomes of MIS-TLIF for treatment of single-level spinal stenosis low-grade isthmic or degenerative spondylolisthesis at L5-S1. Methods. Radiological data and electronic medical records of patients who underwent MIS-TLIF between May 2012 and December 2014 were reviewed. Fusion rate, cage position, disc height (DH), disc angle (DA), disc slope angle, segmental lordotic angle (SLA), lumbar lordotic angle (LLA), and pelvic parameters were assessed. For functional assessment, the visual analogue scale (VAS), Oswestry disability index (ODI), and patient satisfaction rate (PSR) were utilized. Results. A total of 21 levels in 21 patients were studied. DH, DA, SLA, and LLA had increased from their preoperative measures at the final follow-up. Fusion rate was 86.7% (18/21) at 12 months' follow-up. The most common cage position was anteromedial (15/21). The mean VAS scores for back and leg pain mean ODI scores improved significantly at the final follow-up. PSR was 88%. Cage subsidence was observed in 33.3% (7/21). Conclusions. The clinical and radiologic outcomes after MIS-TLIF at L5-S1 in patients with spinal stenosis or spondylolisthesis are generally favorable.

No MeSH data available.


Related in: MedlinePlus

Because of the orientation of the L5-S1 disc space, the tubular retractor when placed in line with the disc space can often be slanted. Resultant unnatural posture of the surgeon can cause fatigue to the surgeon. To avoid this, we tilt the operating table caudally so the tubular retractor is almost perpendicular to the floor.
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fig7: Because of the orientation of the L5-S1 disc space, the tubular retractor when placed in line with the disc space can often be slanted. Resultant unnatural posture of the surgeon can cause fatigue to the surgeon. To avoid this, we tilt the operating table caudally so the tubular retractor is almost perpendicular to the floor.

Mentions: First, the DSA of L5-S1 is the greatest among all levels of the lumbar spine. In our single cohort group, the mean DSA was 30.5°, which is more than twice the mean L4-5 DSA that has been reported in previous published literature [15]. With the patient in the prone position on operating table, high DSA means that, in order obtain the ideal trajectory into the L5-S1 disk space, the tubular retractor has to be tilted more cranially than for other levels of the lumbar spine, and the surgeon's resulting posture could be uncomfortable, especially for inexperienced surgeons (Figure 7). Second, the L5-S1 disk space is conical in shape, with the posterior margin being narrower than anterior margin, compared with other lumbar levels [15, 33]. In our cohort, the preoperative DA was 8.8° and DH was 7.0 mm. In order to obtain maximal and tight contact between the interbody cage and the bony endplates, a tall cage with high lordotic angle should be used, but such tall cages are difficult to insert through the narrow posterior disc space. In order to overcome this difficulty, we drilled out the posterior edges of the caudal endplates of L5 and sometimes the posterior edges of the cranial endplates of S1, thereby widening the posterior disc space (Figure 8). There are reports that the cranial endplate is structurally weaker than the caudal endplate [34], so the cranial endplate of S1 was not drilled unless the posterior disc space was excessively narrow. Sometimes, the upper margins of S1 pedicles also had to be drilled. Because S1 pedicles usually have larger diameters than other levels, we believe that our drilling 2–4 mm of the upper part of S1 pedicles did not harm their integrity, and follow-up images did not show any evidence of S1 screw loosening in any of the patients. Extra care should still be taken to avoid unnecessary drilling of the endplates, as it could directly result in endplate violation during cage insertion or subsidence and migration afterwards. Third, the interpedicular distance between L5 and S1 is wide compared with other lumbar levels. When performing contralateral foraminal decompression through a unilateral facetolaminectomy corridor, the distance to the contralateral foramen is longer than it is in other lumbar levels. We tilted the tubular retractor laterally toward the surgeon and also tilted the operating table to the contralateral side to obtain a good working channel view. Then, gentle drilling of the inferior articular process and laminar was done using a high-speed diamond burr. To achieve adequate discectomy and endplate preparation of the contralateral side, we used angled curettes and angled box curettes that have longer reach to the contralateral side and are well suited for MIS-TLIF. Lastly, the dorsal root ganglion (DRG) has the largest diameter at L5, and the center of the DRG is also located at the lateral zone of the foramen at L5 [35]. This means that the entry site for cage insertion is often obscured by L5 DRG or L5 root, especially if it is enlarged or edematous. In order to avoid excessive retraction of nerve roots and resultant postoperative neurological deficit, the lower border of the L5 transverse process and upper border of S1 were gently drilled, widening the approach corridor to the disc space.


Minimally Invasive Transforaminal Lumbar Interbody Fusion at L5-S1 through a Unilateral Approach: Technical Feasibility and Outcomes.

Choi WS, Kim JS, Ryu KS, Hur JW, Seong JH - Biomed Res Int (2016)

Because of the orientation of the L5-S1 disc space, the tubular retractor when placed in line with the disc space can often be slanted. Resultant unnatural posture of the surgeon can cause fatigue to the surgeon. To avoid this, we tilt the operating table caudally so the tubular retractor is almost perpendicular to the floor.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940521&req=5

fig7: Because of the orientation of the L5-S1 disc space, the tubular retractor when placed in line with the disc space can often be slanted. Resultant unnatural posture of the surgeon can cause fatigue to the surgeon. To avoid this, we tilt the operating table caudally so the tubular retractor is almost perpendicular to the floor.
Mentions: First, the DSA of L5-S1 is the greatest among all levels of the lumbar spine. In our single cohort group, the mean DSA was 30.5°, which is more than twice the mean L4-5 DSA that has been reported in previous published literature [15]. With the patient in the prone position on operating table, high DSA means that, in order obtain the ideal trajectory into the L5-S1 disk space, the tubular retractor has to be tilted more cranially than for other levels of the lumbar spine, and the surgeon's resulting posture could be uncomfortable, especially for inexperienced surgeons (Figure 7). Second, the L5-S1 disk space is conical in shape, with the posterior margin being narrower than anterior margin, compared with other lumbar levels [15, 33]. In our cohort, the preoperative DA was 8.8° and DH was 7.0 mm. In order to obtain maximal and tight contact between the interbody cage and the bony endplates, a tall cage with high lordotic angle should be used, but such tall cages are difficult to insert through the narrow posterior disc space. In order to overcome this difficulty, we drilled out the posterior edges of the caudal endplates of L5 and sometimes the posterior edges of the cranial endplates of S1, thereby widening the posterior disc space (Figure 8). There are reports that the cranial endplate is structurally weaker than the caudal endplate [34], so the cranial endplate of S1 was not drilled unless the posterior disc space was excessively narrow. Sometimes, the upper margins of S1 pedicles also had to be drilled. Because S1 pedicles usually have larger diameters than other levels, we believe that our drilling 2–4 mm of the upper part of S1 pedicles did not harm their integrity, and follow-up images did not show any evidence of S1 screw loosening in any of the patients. Extra care should still be taken to avoid unnecessary drilling of the endplates, as it could directly result in endplate violation during cage insertion or subsidence and migration afterwards. Third, the interpedicular distance between L5 and S1 is wide compared with other lumbar levels. When performing contralateral foraminal decompression through a unilateral facetolaminectomy corridor, the distance to the contralateral foramen is longer than it is in other lumbar levels. We tilted the tubular retractor laterally toward the surgeon and also tilted the operating table to the contralateral side to obtain a good working channel view. Then, gentle drilling of the inferior articular process and laminar was done using a high-speed diamond burr. To achieve adequate discectomy and endplate preparation of the contralateral side, we used angled curettes and angled box curettes that have longer reach to the contralateral side and are well suited for MIS-TLIF. Lastly, the dorsal root ganglion (DRG) has the largest diameter at L5, and the center of the DRG is also located at the lateral zone of the foramen at L5 [35]. This means that the entry site for cage insertion is often obscured by L5 DRG or L5 root, especially if it is enlarged or edematous. In order to avoid excessive retraction of nerve roots and resultant postoperative neurological deficit, the lower border of the L5 transverse process and upper border of S1 were gently drilled, widening the approach corridor to the disc space.

Bottom Line: The mean VAS scores for back and leg pain mean ODI scores improved significantly at the final follow-up.PSR was 88%.Conclusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, Seoul St. Mary's Hospital, Catholic University, Seoul 06591, Republic of Korea.

ABSTRACT
Background. Minimally invasive spinal transforaminal lumbar interbody fusion (MIS-TLIF) at L5-S1 is technically more demanding than it is at other levels because of the anatomical and biomechanical traits. Objective. To determine the clinical and radiological outcomes of MIS-TLIF for treatment of single-level spinal stenosis low-grade isthmic or degenerative spondylolisthesis at L5-S1. Methods. Radiological data and electronic medical records of patients who underwent MIS-TLIF between May 2012 and December 2014 were reviewed. Fusion rate, cage position, disc height (DH), disc angle (DA), disc slope angle, segmental lordotic angle (SLA), lumbar lordotic angle (LLA), and pelvic parameters were assessed. For functional assessment, the visual analogue scale (VAS), Oswestry disability index (ODI), and patient satisfaction rate (PSR) were utilized. Results. A total of 21 levels in 21 patients were studied. DH, DA, SLA, and LLA had increased from their preoperative measures at the final follow-up. Fusion rate was 86.7% (18/21) at 12 months' follow-up. The most common cage position was anteromedial (15/21). The mean VAS scores for back and leg pain mean ODI scores improved significantly at the final follow-up. PSR was 88%. Cage subsidence was observed in 33.3% (7/21). Conclusions. The clinical and radiologic outcomes after MIS-TLIF at L5-S1 in patients with spinal stenosis or spondylolisthesis are generally favorable.

No MeSH data available.


Related in: MedlinePlus