Transforaminal Full-endoscopic Discectomy for Gas-containing Herniated Nucleus Pulposus at L5-S1 Under Local Anesthesia†:†A Case Report.

The vacuum phenomenon is often observed in degenerative disc disease, whereas gas-containing disc herniation is relatively rare. Full-endoscopic discectomy at the lumbar spine level via a transforaminal approach, which was established and subsequently refined over the last two decades, requires only an 8-mm skin incision and causes minimal damage to the paravertebral muscles. Foraminoplasty, performed with a high-speed drill, is a useful technique to enlarge the foramen, especially when applied at the L5-S1 level, where the trajectory is limited because of anatomical structures such as the iliac crest. Here, we report a case of gas-containing lumbar disc herniation at L5-S1 that was successfully treated by transforaminal full-endoscopic discectomy. The patient was a 62-year-old man with low back pain and pain in the plantar aspect of the right great toe. Magnetic resonance and computed tomography scans demonstrated gas-containing lumbar disc herniation at L5-S1 on the right. Following foraminoplasty, transforaminal full-endoscopic lumbar discectomy was successfully performed under local anesthesia. The patient's symptoms improved immediately after the surgery. Transforaminal full-endoscopic surgery can be effective and minimally invasive even when performed for gas-containing disc herniation. J. Med. Invest. 69 : 328-331, August, 2022.

Changes in Temperature Following Radiofrequency Thermal Ablation of the Nucleus Pulposus and Annulus Fibrosus: A Cadaveric Study.

BACKGROUND: Various minimally invasive procedures for treating discogenic pain have been reported in recent years. A Disc-FX® system can be used to perform nucleus pulposus (NP) removal, radiofrequency ablation, and annuloplasty under the guidance of x-ray fluoroscopy. However, when a probe tip with focused heat is placed on the intradiscal/subannular area to perform nucleo-annuloplasty using radiofrequency lesioning, thermal injury to the spinal cord or spinal nerves is a concern. OBJECTIVES: To assess the thermal profile generated by the Disc-FX ablation and modulation system in intervertebral discs from human cadaveric spine sections and evaluate the safety of its thermal dispersion function. STUDY DESIGN: A cadaveric study. METHODS: NP ablation and annulus fibrosus modulation were performed on a fresh human cadaveric lumbar spine intervertebral disc in a 36.5°C circulating water bath using radiofrequency. The 4 points from the center of the disc to one-third, two-thirds and the outer layer of the annulus were divided into 4 points, A-D, respectively, and radiofrequency lesions were performed on the 4 points. RESULTS: The temperature was increased upon irradiation. It fell slowly with the cessation of irradiation. The temperature was not significantly different between Turbo and Hemo mode at each point. The temperature was not significantly different among the 4 points at each mode. The average temperature of the ventral side of the dura mater was kept below 37°C. LIMITATIONS: The results of this study are limited due to the use of a cadaveric spine, which could not reflect the effect of soft tissue such as muscles and connective tissue around the disc. The position of the temperature measuring probe was relatively fixed. This cadaver demonstration was conducted at the L4-L5 level, which is mostly not restricted by the height of the iliac crest.  CONCLUSIONS: When performing NP ablation and annular modification, the epidural peripheral temperature should always be kept below 37°C. This preliminary in vitro research using human cadaveric discs showed that radiofrequency maintained the epidural space at a safe temperature during nucleo-annuloplasty.

Ultrasound Images under an Optimized Image Processing Algorithm in Guiding the Neurological Safety of Resection of Lumbar Disc Nucleus Pulposus in Spinal Surgery.

This study was aimed at investigating the effect of an optimized image processing algorithm in ultrasound images and the influence of resection of lumbar disc nucleus pulposus in spinal surgery under the guidance of ultrasound images on the neurological safety of patients. A total of 60 patients with lumbar disc herniation were selected and divided randomly into the control group and observation group. Patients from the control group were treated with resection of lumbar disc nucleus pulposus by an X-ray-guided foraminal microscope, and patients from the observation group underwent the ultrasound image-guided surgeries with an optimized image processing algorithm. Then, the treatment of patients from the two groups was compared. The results showed that the radiotherapy time in the control group was 120 ± 6.3 min and the radiotherapy dose was 129 ± 10.3 min/sec, while the radiotherapy time in the observation group was 4.5 ± 1.2 min and the radiotherapy dose was 22 ± 7.7 min/sec. The time and dose of radiotherapy in the observation group were significantly lower than those in the control group (P < 0.05). In the control group, the numbers of significant effective cases, effective cases, and ineffective cases were 8, 16, and 6, respectively, while those in the observation group were 12, 18, and 0, respectively. The comparison between the groups showed that the number of effective cases and the number of effective cases in the observation group were significantly higher than those in the control group, and the number of ineffective cases was significantly lower than that in the control group (P < 0.05). In conclusion, ultrasound-guided percutaneous foraminal lumbar discectomy could improve patients' clinical symptoms, promote clinical efficacy, and reduce postoperative pain symptoms, thereby accelerating the postoperative rehabilitation of patients. Moreover, it was extremely safe for the nerves.

Novel Silicone Rubber and Polyvinyl Alcohol (PVA) Compound as Nucleus Pulposus Replacement in Intervertebral Disc Herniation Surgery.

AIM: To identify a novel material with biomechanical properties identical to the nucleus pulposus in the lumbar vertebrae of goats for use in intervertebral disc herniation surgery. MATERIAL AND METHODS: In this laboratory-based experimental study, the silicone rubber material test group consisted of sample compositions 35PVA65SR, 30PVA70SR, and 40PVA60SR. Axial compression mechanical tests were conducted to assess the biomechanical properties of the resulting material in terms of stress, strain, load, and displacement. RESULTS: The mechanical compression test results revealed that the stress (MPa) and strain (%) values of the 40PVA60SR material were closest to the control group (p=1.00) with a load of 684 N in each group. The value of material displacement (mm) for 40PVA60SR was also the closest to control (p=1.00) with a loading of 684 N. CONCLUSION: The new material presents biomechanical properties closest to human nucleus pulposus and is promising in nucleus pulposus replacement therapy. Further clinical research is needed to evaluate other biomechanical properties and the bioavailability of the novel material.

Finite element models can reproduce the effect of nucleotomy on the multi-axial compliance of human intervertebral discs.

Finite element (FE) models can unravel the link between intervertebral disc (IVD) degeneration and its mechanical behaviour. Nucleotomy may provide the data required for model verification. Three human IVDs were scanned with MRI and tested in multiple loading scenarios, prior and post nucleotomy. The resulting data was used to generate, calibrate, and verify the FE models. Nucleotomy increased the experimental range of motion by 26%, a result reproduced by the FE simulation within a 5% error. This work demonstrates the ability of FE models to reproduce the mechanical compliance of human IVDs prior and post nucleotomy.

Early outcomes of transforaminal percutaneous endoscopic lumbar discectomy for high school athletes with herniated nucleus pulposus of the lumbar spine.

There are no reports in the literature on the clinical outcomes of percutaneous endoscopic lumbar discectomy (PELD) for high school athletes suffering from herniated nucleus pulposus (HNP) of the lumbar spine. PELD is a minimally invasive surgical procedure that can be performed under local anesthesia via an 8-mm skin incision. This study examined the outcomes of transforaminal PELD in high school athletes suffering from HNP. Subjects were 18 patients [14 males and four females; mean age 17 (15-18) years] who underwent PELD at our institutions. The events in which the patients competed were baseball (n = 6), softball (n = 2), rugby (n = 2), basketball (n = 2), table tennis (n = 2), American football (n = 1), wrestling (n = 1), track and field (n = 1), and dance (n = 1). All patients underwent PELD under local anesthesia. Back pain was assessed using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and a visual analog scale (VAS) before and after surgery. Time to return to competitive sport, complications, and rate of recurrence of herniation were examined. All factors assessed by the JOABPEQ were significantly improved after surgery. VAS score was also improved after surgery. Time to return to competitive sport was 7 weeks on average. The rate of return to play was 94.4%. There were no complications, such as dural tear, exiting nerve root injury, or hematoma. One patient had recurrence of HNP. PELD is a promising minimally invasive and effective procedure for high school athletes with HNP.

Effect of Spiral Nucleus Implant Parameters on the Compressive Biomechanics of Lumbar Intervertebral Disc.

OBJECTIVE: To determine the effect of spiral nucleus implant parameters on the biomechanical behavior of the lumbar intervertebral disc after nucleus replacement under compressive loading. METHODS: A finite element (FE) model of nucleus replacement in the L4-5 intervertebral disc was constructed. The effects of a spiral implant parameters, such as elasticity, size, and friction property, on the biomechanical behavior of the disc under a compressive load were determined. The effect of an implant with a sharp edge on disc biomechanics was also examined. The stress distribution and contact pressure on the endplate and AF, axial stiffness of disc, and annular bulge of the nucleus replacement models were investigated. RESULTS: Axial stiffness, annular bulge, and contact pressure were all insensitive to friction properties. Insertion of the spiral implant reversed the changes in the AF and endplates due to the removal of the nucleus. There was a positive correlation between axial stiffness and elasticity with implant size. Annular bulge was positively correlated with size but negatively correlated with elasticity. Compared with the base model, the implant with a sharp edge caused a decrease in disc axial stiffness but an increase in contact pressure on the AF in an annular bulge in the sagittal and coronal axis, respectively. CONCLUSIONS: A spiral implant may provide similar biomechanical behavior as a normal disc during compressive loading, with an optimal modulus of approximately 7 MPa. The spiral implant should fully conform to the nucleus cavity during replacement for the best biomechanical results.

Surgical Treatment of Lumbar Herniated Nucleus Pulposus Combined with Residual Bony Fragment of Apophyseal Ring Fracture in High-Level Athletes†:†A Report of Two Cases.

In this paper, we present 2 cases of herniated nucleus pulposus (HNP) combined with the residual bony fragment of apophyseal ring fracture. HNP typically exists at the narrow lateral recess formed by the bony fragment, and so it has been reported that symptoms may persist. Case 1 was a 22-year-old man, a high-level javelin thrower and Paralympic athlete. He had a history of persistent pain for 4 years due to HNP, and so we performed surgical removal. Case 2 was a 23-year-old male professional baseball player. He was referred to us only 17 days after the onset of pain and presented with muscle weakness, a feature which may prolong the clinical course in addition other features such as pain. Thus, we performed a comparatively quick intervention of surgical removal. In both cases, we had excellent clinical outcomes and better function and performance. In conclusion, in cases with HNP and apophyseal ring separation, surgical intervention in the comparatively early phase can be recommended, particularly if the patients desire quick return to their original level of activity. J. Med. Invest. 66 : 358-361, August, 2019.

Flow induced stability of pluronic hydrogels: Injectable and unencapsulated nucleus pulposus replacement.

Poloxamers, or pluronics, have been proposed as biomimetic substitutes for physiological gels. Concern regarding their ability to resist swelling under fluid flows has impeded their implementation. Using a combination of techniques including cryo-TEM and rapid X-ray imaging, we found that rapid flow rates stabilized the gels against dissolution. Energy balance calculations confirmed that disentanglement of individual micelles was not possible at time scales faster than the reptation time when the system response was that of a solid which dissipated the hydrodynamic force field via cooperative deformation. In-vivo tests were performed where the hydrogel was injected as a substitute for the nucleus pulposus following discectomy in dogs. The results indicated that the gel was still present after 3 months, and radiographs indicated that compression of the disc space was prevented despite the gel being exposed to constant perfusion. STATEMENT OF SIGNIFICANCE: This paper demonstrates a highly unexpected result and counter intuitive result, namely the inverse dependence of the dissociation rate of a physical hydrogel on the flow velocity of the liquid medium. Using cryo-electron microscopy we demonstrate that the gel responds like deformable solid in high flow rates, with minimal dissociation. Since these gels are thermoreversible, they were injected into dogs, where we show that they were a viable alternative to the nucleus pulposus, without dissolution in physiological fluid flows for at least three months.

Biomaterials for intervertebral disc regeneration: Current status and looming challenges.

A biomaterial-based strategy is employed to regenerate the degenerated intervertebral disc, which is considered a major generator of neck and back pain. Although encouraging enhancements in the anatomy and kinematics of the degenerative disc have been gained by biomaterials with various formulations in animals, the number of biomaterials tested in humans is rare. At present, most studies that involve the use of newly developed biomaterials focus on regeneration of the degenerative disc, but not pain relief. In this review, we summarise the current state of the art in the field of biomaterial-based regeneration or repair for the nucleus pulposus, annulus fibrosus, and total disc transplantation in animals and humans, and we then provide essential suggestions for the development and clinical translation of biomaterials for disc regeneration. It is important for researchers to consider the commonly neglected issues instead of concentrating solely on biomaterial development and fabrication.

Full Endoscopic Lumbar Discectomy using the Calcification Floating Technique for Symptomatic Partially Calcified Lumbar Herniated Nucleus Pulposus.

BACKGROUND: Partially calcified lumbar herniated nucleus pulposus (HNP) can cause severe radiating pain and neurologic symptoms requiring surgical treatment. As it is not safe to enforce conventional endoscopic lumbar discectomy using trephine or burr to remove the partially calcified disc, we report a calcification floating technique using a working channel for the treatment of these cases. METHODS: We retrospectively analyzed 31 patients who underwent full endoscopic discectomy using this technique for partially calcified lumbar HNP between April 2009 and June 2013. Calcification floating technique was performed by inserting the working channel around the partially calcified HNP and then rotating the working channel around it to remove the lesion. We analyzed the outcomes with a Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and complication rate. RESULTS: The mean follow-up period was 26.58 ± 11.2 months. The interlaminar approach was used in 15 cases, and the transforaminal approach was used in 16 cases. The mean VAS of 8.19 ± 0.65 before surgery was decreased to 1.29 ± 0.69 at the last follow-up. The mean ODI score before surgery was decreased at the last follow-up, from 41.32 ± 2.87 to 9.87 ± 3.47. Mean operative duration was 45 ± 12 minutes per level. None of the patients required revision surgery or developed any major complication. CONCLUSIONS: Calcification floating technique is a safe and effective method for the treatment of partially calcified lumbar HNP.

Posture control in patients with herniated nucleus pulposus in cervical and lumbosacral spine subjected to operative treatment.

BACKGROUND: Patients with lumbar degenerative disc disease suffer from impairments in deep trunk muscles, which may lead to poorer posture control. OBJECTIVE: The purpose of the study was to assess body balance during double limb stance in patients with herniated nucleus pulposus in cervical and lumbosacral spine, subjected to surgical treatment. METHODS: The qualified subjects included patients operated due to herniated nucleus pulposus in lumbosacral (L-S group) and in cervical area (C group) as well as healthy controls. Static balance was examined in double-limb stance, with eyes open and closed, on force platform. The patients were examined before the surgery, on the day they were discharged from the hospital ward and one month following the discharge from the ward. RESULTS: The findings show significant differences between the study group and the controls in the examined parameters before and after the surgery. It was observed significant differences in the length of centre of pressure path in the trial with eyes closed between the L-S and C groups. CONCLUSIONS: Both groups of patients with discopathy have significantly poorer posture control in comparison to healthy subjects. After operative treatment both groups of patients with discopathy presented with significantly decreased values in all the examined balance parameters.

Percutaneous Endoscopic Interlaminar Unilateral Ventral Dural Approach for Symptomatic Bilateral L5-S1 Herniated Nucleus Pulposus: Technical Note.

BACKGROUND: Percutaneous endoscopic lumbar diskectomy is a good treatment modality for lumbar disk herniation. However, when a patient complains of bilateral lower limb radicular pain with severe disk protrusion at the L5-S1 level, the transforaminal approach is often unable to resolve both lesions owing to anatomical limitations. It is also very difficult to resolve both lesions in an ipsilateral direction using the percutaneous interlaminar approach. We report our surgical technique and clinical results using a ventral dural approach of percutaneous endoscopic interlaminar lumbar diskectomy for L5-S1 herniated nucleus pulposus (HNP) in patients with bilateral radiculopathy due to a severe disk protrusion. METHODS: Twenty-seven patients with severe L5-S1 HNP complaining of back pain and bilateral lower limb pain were included in the study. The unilateral ventral dural approach of percutaneous full endoscopic interlaminar lumbar diskectomy technique was used. The visual analog scale (VAS) and Macnab criteria were used for clinical evaluation. All assessments were completed 1 day before surgery, 1 week after surgery, 6 months after surgery, and at final follow-up after surgery. RESULTS: The mean preoperative back and leg pain VAS scores decreased from 5.67 ± 0.78 and 7.81 ± 0.83 to 2.44 ± 0.58 and 2.26 ± 0.53 at 1 week, 1.78 ± 0.51 and 1.52 ± 0.58 at 6 months, and 1.56 ± 0.70 and 1.67 ± 0.96, respectively, at the final follow-up after surgery. With respect to the Macnab criteria, 51.85% of the results were excellent, 44.44% were good, and 3.70% were fair. Four cases recurred: three patients underwent conservative treatment and one patient operated with percutaneous endoscopic interlaminar lumbar diskectomy. CONCLUSION: According to the results of this study, the ventral dural approach of percutaneous full endoscopic interlaminar lumbar diskectomy in patients with L5-S1 HNP associated with bilateral lower limb pain due to a severely protruded HNP is a good option for a minimally invasive surgical approach.

Vertebral Augmentation can Induce Early Signs of Degeneration in the Adjacent Intervertebral Disc: Evidence from a Rabbit Model.

STUDY DESIGN: An experimental study. OBJECTIVE: The aim of this study was to determine the effect of polymethylmethacrylate (PMMA) augmentation on the adjacent disc. SUMMARY OF BACKGROUND DATA: Vertebral augmentation with PMMA reportedly may predispose the adjacent vertebra to fracture. The influence of PMMA augmentation on the adjacent disc, however, remains unclear. METHODS: Using a retroperitoneal approach, PMMA augmentation was performed for 23 rabbits. For each animal, at least one vertebra was augmented with 0.2 to 0.3 mL PMMA. The disc adjacent to the augmented vertebra and a proximal control disc were studied using magnetic resonance (MR) imaging, histological and molecular level evaluation at 1, 3, and 6 months postoperatively. Marrow contact channels in the endplate were quantified in histological slices and number of invalid channels (those without erythrocytes inside) was rated. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to determine disc cell apoptosis. RESULTS: On MR images, the signal and height of the adjacent disc did not change 6 months after vertebral augmentation. Histological scores of the adjacent disc increased over time, particularly for the nucleus pulposus. The adjacent disc had greater nucleus degeneration score than the control disc at 3 months (5.7 vs. 4.5, P < 0.01) and 6 months (6.9 vs. 4.4, P < 0.001). There were more invalid marrow contact channels in the endplate of augmented vertebra than the control (43.3% vs. 11.1%, P < 0.01). mRNA of ADAMTS-5, MMP-13, HIF-1α, and caspase-3 were significantly upregulated in the adjacent disc at 3 and 6 months (P < 0.05 for all). In addition, there were more TUNEL-positive cells in the adjacent disc than in the control disc (43.4% vs. 24.0%, P < 0.05) at 6 months postoperatively. CONCLUSION: Vertebral augmentation can induce early degenerative signs in the adjacent disc, which may be due to impaired nutrient supply to the disc. LEVEL OF EVIDENCE: N/A.

Biomechanical function of a balloon nucleus pulposus replacement system: A human cadaveric spine study.

With recent advances in motion-sparing techniques in spine surgery, disc nucleus replacement (DNR) has been introduced as a viable method to restore the biomechanical functions of the spine. Several methods of DNR have been proposed in the literature. However, the risk of device migration or extrusion is a major issue that should be addressed for a successful DNR. DNR using a balloon nucleus (BN) filled with pressurized fluid may be capable of reducing such risks while preserving the advantages of DNR. The objective of this study was to investigate the biomechanical functionalities of the human cadaveric lumbar motion segments with a custom made BN filled with saline at internal fluid pressure of 0.3 or 0.6 MPa in terms of axial and rotational flexibilities of the L4-L5 motion segment. Axial flexibility was quantified by the axial displacement resulting from an axial compressive force of 400 N while the rotational flexibility by the range of motions determined as the rotational angles in response to a pure moment of 6.0 Nm in flexion, extension, and right- and left-lateral bending directions. These tests were performed successively on the motion segment in the following conditions: intact, post nucleotomy, implanting BN with 0.3 MPa, and BN with 0.6 MPa. The nucleotomy was found to significantly increase both the axial and rotational flexibilities while the implantation of the BN reduced the axial and rotational flexibilities to those of the intact segment. The axial and rotational flexibilities of the segment with the BN with 0.3 MPa were greater than those of the segment with the BN with 0.6 MPa. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:167-173, 2018.

[The assessment of the impact of rehabilitation on the pain intensity level in patients with herniated nucleus pulposus of the intervertebral disc]. / Wplyw rehabilitacji na poziom natezenia dolegliwosci bólowych u chorych z zespolem bólowym kregoslupa po nieskutecznym zabiegu operacyjnym.

Back disorders are very common phenomena in modern society. One of the methods of spinal pain treatment is performing surgery. Unfortunately, this method is not one hundred percent effective. Some patients show no improvement after surgery, the pain persists and even increases. In these cases, it is reasonable to use the term Failed Back Surgery Syndrome (FBSS), i.e. back pain syndrome after unsuccessful spine surgery. AIM: The aim of the study is to assess the impact of rehabilitation on the pain intensity level in patients with FBSS. MATERIALS AND METHODS: The study was conducted in a group of 38 patients aged from 32 to 87 (mean age 61 years), including 20 women and 18 men. All patients were operated for spinal pain syndrome. Afterwards, they underwent rehabilitation because of persisting pain after the surgery. For the pain assessment was used The Visual- Analogue Scale and The Laitinen Modified Questionnaire Indicators of Pain. The results were statistically analyzed. RESULTS: The study showed the high efficacy of specialized rehabilitation in patients with FBSS. CONCLUSIONS: The rehabilitation in patients with FBSS has a significant analgesic effect. Rehabilitation should be a gold standard in patients with FBSS.

Functional compressive mechanics and tissue biocompatibility of an injectable SF/PU hydrogel for nucleus pulposus replacement.

In spinal degenerative disease, an injectable liquid hydrogel can fill in defect entirely, lessen the danger of implant relocation and following loss of disc height, minimizing the operative trauma. Here, we propose an injectable in-situ chemically cross-linked hydrogel by a two-component reaction of liquid silk fibroin with liquid polyurethane at physiological temperature conditions. Confined compression tests and fatigue tests were reported to assess physical properties of the hydrogel. Impact of different diameter on the biomechanical behaviours was tested to evaluate the clinical potentiality of the hydrogel for replacing nucleus pulposus. Degradation behaviours in different solutions and animal experiments were also investigated to examine the tissue biocompatibility of the hydrogel. The hydrogel modulus was affected by the hydrogel geometrical (diameter) parameters. SF/PU composite hydrogel can survive a million cycles, unconstrained fatigue resistance. More importantly, in vivo biocompatibility using New Zealand white rabbits, showed good biocompatibility over a three-month period in culture. Particularly, they showed the significant clinical merit of providing stronger axial compressive stiffness on confined compression test. Based on the outcomes of the present research, the SF/PU composite hydrogel may provide significant advantages for use in future clinical application in replacing nucleus pulposus field.

The influence of artificial nucleus pulposus replacement on stress distribution in the cartilaginous endplate in a 3-dimensional finite element model of the lumbar intervertebral disc.

OBJECTIVE: This study aimed to investigate the effects involved with the artificial nucleus pulposus (NP) replacement on stress distribution of the cartilaginous endplate (CEP) in a 3-dimensional lumbar intervertebral disc (IVD) model using a finite element (FE) analysis. METHODS: A healthy male volunteer was recruited for the purposes of the study and a spiral computed tomography scan was subsequently conducted to obtain the data information in relation to the L4/5 motion segment. An FE model of the L4/5 motion segment constructed, on the basis of which degenerative IVD, IVD with NP removal, and IVD with NP replacement were in turn built. The stress distribution of the CEP and bulging of IVD were estimated using various motion states, including axial loading, forward flexion, backward extension, left axial rotation, and right axial rotation. RESULTS: Under different motion states, the vertebral stress was higher in the degenerative IVD, the IVD with NP removal, and the IVD with NP replacement, in comparison to that of the normal IVD. Furthermore, a higher vertebral stress was detected in the degenerative IVD than the IVD with NP removal and the IVD with NP replacement. An even distribution of vertebral stress was observed in the IVD model with an artificial NP replacement, while the vertebral stress and bulging displacement were lower than after NP removal. Our findings provided confirmation that stress of the CEP was consistent with the vertebral stress. CONCLUSION: This study provided evidence suggesting that NP replacement, vertebral stress, and bulging displacement are lower than that of degenerative IVD and IVD with NP removal under different motion states.

Structural Preservation Percutaneous Endoscopic Lumbar Interlaminar Discectomy for L5-S1 Herniated Nucleus Pulposus.

Objective. Structures such as ligamentum flavum, annulus, and lamina play an important role in the segmental function. We proposed the surgical technique for achieving the sufficient preservation of segmental structures, in spite of sufficient removal of pathologic disc in the L5-S1 using the ligamentum flavum splitting and sealing technique. Methods. We retrospectively analyzed 80 cases that underwent percutaneous endoscopic lumbar discectomy for L5-S1 herniated nucleus pulposus, using the ligamentum flavum splitting and sealing technique between January 2011 and June 2013. Outcomes were assessed using VAS (leg, back), MacNab's criteria, and the immediate postoperative MRI for all patients. Structural preservation was classified as complete, sufficient, and incomplete. Results. The surgical results are as follows: 65 cases were complete, 15 cases were sufficient, and 0 cases were incomplete. The VAS was decreased at the last follow-up (leg: from 7.91 ± 0.73 to 1.15 ± 0.62; back: from 5.15 ± 0.71 to 1.19 ± 0.75). A favorable outcome (excellent or good outcome by MacNab's criteria) was achieved in 77 patients (96.25%). During the follow-up period, 2 cases (2.5%) of recurrence have occurred. Conclusion. According to the result, we could obtain the favorable clinical and radiological outcomes while simultaneously removing pathologic discs using the ligamentum flavum splitting and annular fissure sealing technique.