Introduction: The usefulness of lateral lumbar interbody fusion (LLIF), represented by OLIF and XLIF, has been reported in correction surgery for adult spinal deformity (ASD). However, LLIF is associated with the risk of specific and potentially fatal complications, such as major vascular injuries and damage to the ureter and intestine. The microendoscopic extraforaminal lumbar interbody fusion (ME-LIF) using the MED technique offers several advantages over minimally invasive lumbar interbody fusion using FESS or BESS via the trans-Kambin approach, as well as LLIF. In this report, we describe our experience of performing a three-level ME-LIF (L2/3/4/5) with tandem operation for two ASD patients.

Patients and Methods: The ages of the two patients at the surgery were 80 and 75 years, respectively. In both cases, tandem ME-LIF was performed at L2/3/4/5 using the SYNCHA^® 18-mm tubular retractor, followed by posterior fixation with percutaneous pedicle screws. An expandable boomerang cage was used for the interbody fusion. For these two cases, we investigated the following: 1) Operation time; 2) Intraoperative blood loss; 3) Period of hospital stay; 4) Changes in pre- and postoperative Cobb angle and lumbar lordosis (LL) on plain X-rays; 5) Postoperative PI-LL mismatch on plain X-rays; 6) Changes in pre- and postoperative intervertebral disc height and slippage at each level on plain CT; 7) Bony fusion rate; and 8) Perioperative complications.

Results: The operation time was 231 and 173 min, the intraoperative blood loss was 195 and 116 mL, the period of hospital stay was 16 and 17 days, respectively. Postoperative imaging examinations revealed satisfactory correction of ASD in both cases. No perioperative complications were observed, and bony fusion was achieved across all intervertebral segments in both cases at six months postoperatively.

Conclusion: Multi-level tandem ME-LIF using the MED technique has the potential to be a minimally invasive, safe, and effective corrective surgical procedure for ASD, and further advancements are anticipated.

Introduction: We investigated the efficacy and limitations of tandem lumber spine operation using FESS and ME surgery for multiple lumbar lesions.

Methods: 9 cases (6 men and 3 women, mean age 65 years) who underwent tandem operation were selected at our hospital between April 2019 and March 2024. We investigated the operation procedures, operation time, shortened operation time by tandem procedure, amount of bleeding, and surgical outcomes up to 3 months after operation.

Results: The operation details were FED-PL and MED in 1 case, FED-PL and MEL in 1 case, FED-PL and ME-MILD (1 level) in 3 cases, and FED-PL and ME-MILD (2 levels) in 4 cases. The mean operating time was 139 minutes (FED-PL: 72.0 minutes, MED: 79.0 minutes, MEL: 80.0 minutes, ME-MILD: 135.7 minutes), and the mean shortened time was 57.6 minutes. The mean amount of bleeding was a little for FED-PL, 9.0 g for MED, 2.0 g for MEL, and 40.4 g for ME-MILD. The postoperative total JOA score improved from 13.8 point to 18.6 point to 20.7 point preoperatively, at discharge, and 3 months postoperatively.

Conclusions: If the cases are matched, it was useful for multiple lumbar lesions with lateral and spinal canal lesions.

Introduction: Foraminal re-stenosis after FPCF has been observed over time, but no reports have addressed this issue. This study investigated the occurrence of foraminal re-stenosis following FPCF and its clinical significance.

Materials and Methods: Among 634 patients who underwent FPCF at our institution between January 2014 and May 2023, 115 patients with postoperative CT images available more than one year after surgery were analyzed. The reduction rates of foraminal dimensions in coronal, sagittal, and 3D views were assessed. The influence of age, sex, BMI, diabetes, and ossification of the posterior longitudinal ligament (OPLL) was evaluated.

Results: The reduction rates of the resection dimensions were 32.6% for the upper facet, 32.7% for the lower facet, 35.1% for the sagittal resection height, and 55.1% for the 3D bony foramen area. These reduction rates were not correlated with age or BMI, nor were they associated with gender, diabetes, or the presence of ossification of the posterior longitudinal ligament. Reoperations at the same level were performed in 12 cases (10.4%), including anterior cervical decompression and fusion in 9 cases (7.8%) and cervical laminoplasty in 3 cases (2.6%). Moreover, no statistically significant differences in the reduction rates were observed between patients with and without reoperation (p>0.05).

Discussion: Foraminal re-stenosis was observed after FPCF, but it did not affect clinical outcomes. Adequate bony decompression, including the removal of the perineural membrane, may have contributed to the lack of correlation between re-stenosis and reoperation rates.

Introduction: The selection criteria for full-endoscopic discectomy (FED) approaches, specifically transforaminal (TF) versus interlaminar (IL), for upper lumbar disc herniation (L2/3 level) remain unclear. This study aims to investigate the influence of cephalocaudal migration and facet joint angle on surgical approach selection for L2/3 disc herniation. It hypothesizes that both factors play a significant role in determining the optimal surgical approach.

Methods: A retrospective review was conducted on 85 patients who underwent FED for single-level L2/3 disc herniation between January 2013 and December 2023. Patients with radicular symptoms refractory to conservative treatment were included. Data collected included age, operative time, herniation level, cephalocaudal migration, and L2/3 facet joint angle. Patients were categorized into TF and IL groups for comparative analysis.

Results: The study cohort comprised 64 patients in the TF group and 21 patients in the IL group. The TF group demonstrated shorter operative times and predominantly included patients with intra- or extraforaminal herniations and cephalad migration. The IL group exclusively consisted of patients with caudal migration. In the TF group, cases with caudal migration beyond the lower half of the pedicle exhibited significantly longer operative times (85 min vs 45 min). Subgroup analysis of 33 patients with caudal migration revealed significantly larger facet joint angles in the TF group (61° vs 57°).

Conclusions: In FED for upper lumbar disc herniation, the cephalocaudal migration of the herniation and the facet joint angle influence the selection of the surgical approach.

Purpose: We investigated the usefulness of minimally invasive surgery using a spine surgery-assist robot for the treatment of Hangman's fractures.

Methods: We evaluated the surgical technique, fixation range, amount of bleeding, operating time, reference position, screw insertion accuracy, and bone fusion rate in five patients (three males and two females) who underwent robot-assisted surgery for Hangman's fractures. Bone fusion was assessed using postoperative CT. Screw deviation was classified according to the Gertzbein grading system: Grade 1: no deviation, Grade 2: deviation of ≤2 mm, Grade 3: deviation of 2-4 mm, and Grade 4: deviation of ≥4 mm. Grades 3 and 4 were considered clinically significant deviations.

Results: The mean age was 84.6 years, and the average follow-up period was 13.3 months. According to Levine's classification, one patient had Type I and four had Type II fractures. The mean operation time was 124.8 minutes, and the average intraoperative blood loss was 115.4 ml. One case was treated with transpedicular osteosynthesis and four with posterior fixation, all performed through a small skin incision using a posterolateral approach. The reference point for navigation was the Mayfield clamp in two cases, the C2 spinous process in one case, and the C7 spinous process in two cases. Screw insertion accuracy was 100%, and all cases achieved bone fusion.

Conclusion: This study demonstrates the feasibility and effectiveness of robot-assisted spinal surgery for Hangman's fractures. The use of a spine surgery-assist robot allowed for a minimally invasive procedure via a small skin incision with a posterolateral approach, achieving high screw insertion accuracy and successful bone fusion.

Lumbar spinal canal stenosis associated with lumbar degenerative spondylolisthesis (DS) can cause Stenosis at the Chevron region, which does not occur in "unaccompanied lumbar spinal stenosis" (NDS). The purpose of this study was to clarify the difference in Chevron stenosis between DS and NDS, and to specify the key points of decompression surgery for DS.

The subjects were 103 patients in the degenerative spondylolisthesis group (DS group) and 52 patients in the non-degenerative spondylolisthesis group (NDS group). B/A (Chevron-to-intervertebral disc stenosis ratio) was calculated from the distance from the caudal end of the L4 vertebral arch Chevron to the posterior wall of the L4 vertebral body (A) and the shortest distance to the L4/5 disc (B) on a standing lateral view of a myelogram. D/C (degree of cephalad disc bulging) was calculated from the L4 vertebral body height (C) and the distance of cephalad disc bulging (D). The correlation between the Chevron-to-intervertebral disc stenosis ratio and the degree of degenerative slip was examined.

The mean Chevron-to-disc stenosis ratio was 59% and 93%, and the mean cephalad disc bulge was 13% and 3% in the DS and NDS groups, respectively, showing a significant difference. A negative correlation between the Chevron-to-intervertebral disc stenosis ratio and the degree of degenerative slip was also observed.

The results suggest that the key to decompression surgery for DS is to open the window up to the Chevron and sometimes perform a laminectomy.

Introduction: A rapidly growing elderly population with medical comorbidities requires traditional treatment algorithms for pyogenic spondylodiscitis in the lumbar and thoracic spines to be updated to incorporate recent advances in minimally invasive surgery (MIS). We previously reported the usefulness of our treatment algorithm developed for incorporating MIS with percutaneous pedicle screw (PPS) -rod fixation and transpsoas lateral interbody fusion (LIF) for this condition. More recently we have newly added an MIS option of "LIF at the affected intervertebral space with a titanium cage followed by PPS-rod fixation," to this algorithm. We wish to report our experience on this newly added treatment option.

Methods: The patients, who escaped both neurologic impairment and extensive bone destruction, had image-guided needle biopsy followed by conservative treatment with antibiotics and a spinal brace or a subsequent addition of non-fused PPS-rod fixation 2-3 levels rostral and caudal to the affected vertebrae.

We indicated this newly employed MIS combination to the patients either when conservative treatments had subsided active infection, if not eradicated, in 6 patients or when non-fused PPS-rod fixation at the infection-free vertebrae had failed to achieve fusion between the affected vertebrae in 2 patients.

Results: A total of 8 patients underwent this newly employed treatment option: at a single level of T11-12, L2-3, and L3-4 in 1 patient each; at 2 levels of L3-4 and L4-5 in 2 patients; and at a single level of L4-5 in 3 patients. Most of the patients had one or more comorbid diseases including diabetes mellitus, atrial fibrillation, malignant tumors, myasthenia gravis, and rheumatoid arthritis. Percutaneous imaged-guided needle biopsy, blood culture, and/or surgical sampling identified the causative bacteria in 3 of 8 patients. Immediately before surgery, the white blood cell counts fell into the normal range in all cases, but the CRP values failed to return to the normal range, averaging 1.35 mg/dl. In 5 of 8 patients, the postoperative CT scans revealed bone union at the affected intervertebral level without a relapse of infection.

Conclusion: We tend to feel hesitant to place the implant into an infected focus. However, the current study suggests that LIF with a titanium cage placement between the infected vertebrae followed by PPS-rod fixation provides a safe and effective treatment option in facilitating the healing process of infection and preventing deformity unless performed during the active phase of infection. Its clinical utility, however, awaits further confirmation with larger studies.

Objective: This study aimed to evaluate the indirect decompression effect of Unilateral Biportal Endoscopy-Assisted Extraforaminal Lumbar Interbody Fusion (UBE-ELIF) and to identify factors influencing postoperative outcomes.

Methods: We retrospectively analyzed 58 patients who underwent single-level UBE-ELIF for lumbar spinal stenosis or spondylolisthesis between May 2019 and February 2023. Surgical parameters, including operative time, blood loss, intervertebral height (anterior, middle, posterior), cross-sectional area of the spinal canal, ligamentum flavum thickness, disc bulging, Visual Analog Scale (VAS) scores, and cage subsidence were evaluated. The Wilcoxon signed-rank test and the Mann-Whitney U test were used for statistical analysis.

Results: The mean operative time was 174 minutes, and the mean blood loss was 32.4 g. Postoperatively, intervertebral height significantly increased (anterior: 7.0 mm to 10.0 mm; middle: 7.8 mm to 11.6 mm; posterior: 4.9 mm to 8.8 mm, all p < 0.05), and the cross-sectional area significantly expanded (80.8 mm² to 139.0 mm², p < 0.05). Ligamentum flavum thickness and disc bulging significantly decreased. VAS scores for low back pain, leg pain, and leg numbness significantly improved postoperatively. Cage subsidence occurred in 22 cases (38%), and in these cases, the expansion of the spinal canal area was significantly lower, and postoperative low back pain VAS was higher (p < 0.05).

Conclusion: UBE-ELIF provided effective indirect decompression as a minimally invasive alternative without posterior bony resection. However, cage subsidence remains a concern, as it negatively affects postoperative spinal canal expansion and low back pain relief. Appropriate cage size selection and optimal placement strategies are essential to prevent subsidence and to enhance surgical outcomes.

Introduction: This study evaluated the clinical outcomes of Extraforaminal Lumbar Interbody Fusion (ELIF) using an expandable cage, focusing on indirect decompression without accessing the spinal canal.

Methods: A total of 21 patients with degenerative lumbar spondylolisthesis underwent single-level interbody fusion using an expandable cage via a unilateral approach. Patients were divided into two groups: ELIF (n=11) and TLIF (n=10). The following parameters were assessed preoperatively and at one year postoperatively: visual analog scale (VAS) scores for low back pain, leg pain, and leg numbness; percentage slip (%slip); disc height; and segmental lordosis angle.

Results: VAS improvement in the ELIF and TLIF groups was as follows: low back pain (2.2, 3.5), leg pain (2.9, 5.0), and leg numbness (2.7, 3.7). Improvements in %slip (11.6%, 8.7%), disc height (+4.7 mm, +5.4 mm), and segmental lordosis angle (+2.0°, +1.7°) were observed. No statistically significant differences were found between the two groups in any of the parameters.

Conclusion: ELIF achieved sufficient indirect decompression by increasing disc height, suggesting that direct decompression may not be necessary. This technique may serve as an effective and minimally invasive alternative for treating degenerative lumbar spondylolisthesis.

Introduction: It is important to preserve the multifidus because damage to it during lumbar surgery can cause muscle atrophy, leading to spinal instability and low-back pain. The findings of our study suggests that unilateral biportal endoscopy (UBE) may reduce multifidus muscle damage and improve postoperative outcomes in obese patients undergoing microsurgical procedures.

Methods: We studied 122 patients (69 in the UBE group and 53 in the microscopic surgery group) with a body mass index of 25 or more who underwent unilateral biportal endoscopic lumbar discectomy using the interlaminar approach. To investigate the effect of multifidus atrophy on postoperative outcomes, we measured the cross-sectional area (CSA) of the multifidus on magnetic resonance images before and after surgery and compared the rate of muscle atrophy, creatine kinase (CK) and C-reactive protein (CRP) levels, and Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and visual analog scale (VAS) scores before and after surgery. The group with muscle atrophy was defined as having a CSA change rate of −10% or less, and the group without muscle atrophy was defined as having a CSA change rate greater than that.

Results: The incidence of muscle atrophy (CSA change rate of −10% or less) on the affected side after surgery was 13.0% in the UBE group and 30.2% in the microscopic surgery group. The incidence rate was significantly lower in the UBE group. In the comparison between the groups with and without muscle atrophy, CK and CRP levels on the first day after surgery were significantly higher in the group with muscle atrophy. There were no significant differences in the efficacy of the JOABPEQ or VAS between the groups with and without muscle atrophy.

Conclusions: Our findings suggest that UBE can be less invasive than microscopic surgery and causes less damage to the multifidus.

Introduction: In this study, we focus on fatty degeneration of the multifidus muscle after transforaminal full endoscopic spine surgery (TF-FESS) in elderly patients and aim to examine the minimal invasiveness of TF-FESS.

Materials: We conducted 17 patients aged 80 years or older who underwent TF-FESS at our institution. We classified fatty degeneration of the multifidus muscle into five stages using plain MRI and evaluated the progression of degeneration 3 months after surgery. We compared the multifidus muscle on the TF-FESS operated side and the contralateral side in the same patient, and compared it with 20 patients who underwent spinous process splitting laminectomy at one intervertebral level during the same period.

Results: Three months after TF-FESS, there was one case (5.9%) in which fatty degeneration of the multifidus muscle had progressed by one or more stages at the intervertebral level, and one case (9.1%) at the caudal intervertebral level. The results were exactly the same on the contralateral side. In patients after spinous process splitting laminectomy, fatty degeneration progression was significantly more frequent in 8 cases (40.0%) at the operated intervertebral level and in 9 cases (45.0%) at the caudal intervertebral level.

Conclusions: TF-FESS is an effective treatment option that can preserve the multifidus muscle.

Objective: While laminoplasty (LP) is established for cervical spondylotic myelopathy (CSM), cervical microendoscopic laminectomy (CMEL) has emerged as a minimally invasive alternative. We compared outcomes of CMEL and LP between young-old (≤74 years) and old-old (≥75 years) patients.

Methods: We analyzed 158 CSM patients treated between January 2017 and December 2021. The young-old group included 13 CMEL and 77 LP cases, while the old-old group had 20 CMEL and 48 LP cases. We evaluated operative time, blood loss, complications, hospital stay, SF-36 changes, treatment effectiveness rate (proportion achieving ≥2.5 points improvement in JOA score), and satisfaction using Numerical Rating Scale (NRS) at 2 years follow up.

Results: In the young-old group, CMEL showed advantages in blood loss (18.2 ml vs 109.2 ml), complications (0% vs 13%), and hospital stay (9.6 vs 13.9 days) compared to LP (p<0.05). However, treatment effectiveness was lower with CMEL (30.8% vs 70.1%). Satisfaction scores were similar (CMEL 8.0 vs LP 8.5). In the old-old group, CMEL demonstrated benefits in blood loss (32.0 ml vs 86.6 ml) and complications (5.0% vs 12.5%). Hospital stay was comparable (CMEL 13.3 vs LP 15.8 days). Treatment effectiveness showed no significant difference (CMEL 45.0% vs LP 56.3%), while satisfaction was higher with CMEL (8.6 vs 7.6) (p<0.05).

Conclusion: While CMEL showed lower invasiveness overall, its effectiveness was inferior to LP in young-old patients. In old-old patients, CMEL achieved comparable effectiveness with higher satisfaction. These findings suggest CMEL as a preferred option for old-old patients, leveraging its minimally invasive advantages, while LP may be more suitable for young-old patients who can better tolerate the procedure for potentially better outcomes.

Introduction: The lumbar discs are located more cranially than the interlaminae in the upper disc from L3/4. Upwardly migrated herniated masses from the middle and upper lumbar discs are thus located far more cranially than the interlaminae. With micro-endoscopic discectomy (MED) of the upwardly migrated hernia mass using the Inter-Laminar approach (IL method), the amount of bone resection required is extensive. Alternatively, herniated fragments were removed through the approximately 8.5×12.3 mm hole drilled in laminae (Trans-Laminar approach; TL method), or a direct approach can be used from the lateral margin of the superior laminae (Far Lateral approach; FL method). We performed MED using these three approaches (IL, TL, and FL methods). We report the use of these approaches, the details of techniques, and the postoperative results.

Materials: Subjects were 17 patients (1 woman, 16 men; mean age, 68 years) who underwent MED using each of the 3 methods after January 2015. The IL method was used in 7 cases, the TL method in 4 cases, and the FL method in 6 cases. The affected disc levels were L3/4 in 13 cases and L2/3 in 4. All patients complained of sever lumbar and lower limb pain with motor and sensory deficits.

Results: Three approaches were used according to the position of the herniated mass. No perioperative complications were encountered. Mean postoperative hospital stay was 9.3 days with the IL method, 5.8 days with the TL method, and 3.8 days with the FL method. The clinical results were satisfactory. The prolapsed hernia had disappeared on MRI, and no problems such as vertebral fracture were found on CT. The center of the prolapsed hernia is determined using the distance from the inferior border of the superior pedicle and the distance from the lateral side of the superior articular process. The IL method was used for hernias that tended to prolapse closer to the intervertebral disc level. The TL method was used for hernias that tended to prolapse more inward than outside the laminae, and the FL method was used for hernias that tended to prolapse closer to the outside.

Conclusion: Micro-endoscopic herniectomy of the upwardly migrated hernia mass using All three methods in this report appeared minimally invasive and effective. Since the degree of tissue invasion is low and affected areas can be reached with pinpoint accuracy using X-P images, this operation fully utilizes the advantages of micro-endoscopy.

Introduction: Vertebroplasty for osteoporotic vertebral fractures (OVFs) of the lower lumbar spine has limitations as a standalone treatment. We report a case of anterior displacement of vertebral body stenting (VBS) after treatment for lower lumbar OVF, which was successfully managed with percutaneous pedicle screw fixation.

Case Report: A 68-year-old woman underwent VBS for a split-type OVF at L4. At 1.5 months postoperatively, anterior displacement of the VBS was observed with potential contact with major vessels. Additional percutaneous pedicle screw fixation from L2 to S1 was performed. Bone union was confirmed at 10 months, and the instrumentation was removed. At final follow-up, low back pain had improved significantly with good clinical outcome.

Conclusions: VBS alone for lower lumbar OVF requires careful consideration, especially in cases with poor prognostic factors. Percutaneous pedicle screw fixation can serve as an effective salvage strategy for the complication of cement displacement, preventing further migration and allowing for eventual bone healing.

Introduction: Lumbar spine decompression via unilateral biportal endoscopic spine surgery (UBE) is performed as unilateral laminotomy for bilateral decompression (ULBD). During ULBD, it is difficult to preserve the inferior articular process on the ipsilateral side of entry in the upper lumbar spine due to small facet joints. To apply UBE decompression to the upper lumbar spine, we developed biportal endoscopy-assisted bilateral contralateral laminoplasty (BE-BCL) technique, which provides contralateral decompression from the bilateral interlaminar. The techniques steps and indications are also discussed.

Technical Note: The surgery was performed by first entering from the left interlaminar osteotomy spino-laminar junction, identifying the midline of the yellow ligament, and performing an osteotomy of the contralateral lamina. On the right side, bony decompression of the contralateral side was performed, and the decompression was completed by resecting the yellow ligament on the left half from the right interlaminar region and the right half from the left interlaminar. When BE-BCL was performed in patients with facet joint angles of 20 degrees or less, the average joint preservation rate was 81%.

Conclusions: BE-BCL can prevent inferior articular process fractures even for sagittalized facet joints and can expand the indications for endoscopic lumbar decompression in the upper lumbar spine.

Introduction: Unilateral Biportal Endoscopy (UBE) has been rapidly adopted in Japan, following its success in Taiwan and South Korea. Unlike traditional spinal endoscopic procedures such as Microendoscopic Discectomy (MED) and Full Endoscopic Spine Surgery (FESS), UBE is distinguished by its biportal approach combined with continuous irrigation. While these features offer advantages, they also present unique technical challenges, particularly in irrigation management.

Technical Report: (1) Ensuring Outflow: Although FESS's outflow exits through the working portal of the cannula, UBE's outflow is influenced by factors such as subcutaneous fat thickness and incision width. Proper pathway preparation and irrigation pressure control are essential to maintain clear visualization. (2) Regulation of Irrigation Pressure: Higher pressure is beneficial in cases of bleeding, high-speed drilling, and adhesion dissection, while lower pressure suffices for most of the procedure, leading to reduction in fluid consumption. (3) Adhesion Dissection: The small diameter of the UBE endoscope allows superior visualization of the contralateral side. Utilizing irrigation pressure facilitates safe dissection of adhesions. (4) Dural Folding: Increased irrigation pressure may cause dural folding, making it resemble fibrous tissues other than dura mater. To prevent misidentification and accidental excision, irrigation should be temporarily stopped, or the dura should be probed for confirmation. (5) Use of High-Speed Drill: Bone debris size varies with burr speed, affecting visibility. Steel burrs with a 4 mm diameter should be operated at an optimal speed of approximately 20,000 rpm to prevent visual obstruction.

Conclusion: UBE presents distinct challenges compared to FESS, particularly due to variable outflow. The techniques discussed in this report aim to enhance the safety and precision of UBE procedures, making them valuable even for surgeons experienced in other endoscopic spinal surgeries.