Can Dynamic Spinal Stabilization Be an Alternative to Fusion Surgery in Adult Spinal Deformity Cases?

BACKGROUND: Rigid stabilization and fusion surgery are widely used for the correction of spinal sagittal and coronal imbalance (SCI). However, instrument failure, pseudoarthrosis, and adjacent segment disease are frequent complications of rigid stabilization and fusion surgery in elderly patients. In this study, we present the results of dynamic stabilization and 2-stage dynamic stabilization surgery for the treatment of spinal SCI. The advantages and disadvantages are discussed, especially as an alternative to fusion surgery. METHODS: In our study, spinal, sagittal, and coronal deformities were corrected with dynamic stabilization performed in a single session in patients with good bone quality (without osteopenia and osteoporosis), while 2-stage surgery was performed in patients with poor bone quality (first stage: percutaneous placement of screws; second stage: placement of dynamic rods and correction of spinal SCI 4-6 months after the first stage). One-stage dynamic spinal instrumentation was applied to 20 of 25 patients with spinal SCI, and 2-stage dynamic spinal instrumentation was applied to the remaining 5 patients. RESULTS: Spinal SCI was corrected with these stabilization systems. At 2-year follow-up, no significant loss was observed in the instrumentation system, while no significant loss of correction was observed in sagittal and coronal deformities. CONCLUSION: In adult patients with spinal SCI, single or 2-stage dynamic stabilization is a viable alternative to fusion surgery due to the very low rate of instrument failure. CLINICAL RELEVANCE: This study questions the use of dynamic stabilization systems for the treatment of adult degenerative deformities.

Use of Dynamic Spinal Instruments (Dynesys) in Adult Spinal Deformities According to Silva-Lenke and Berjano-Lamartina Classifications.

BACKGROUND: Adult spinal deformities (ASD) present complex challenges in spine surgery. The diverse nature of these deformities requires a comprehensive understanding of their classification and treatment options. Traditional approaches, such as fusion and rigid stabilization are associated with complications, including screw loosening, breakage, proximal junctional kyphosis (PJK), and pseudoarthrosis. Dynamic stabilization techniques have emerged as promising alternatives, to reduce these complications and preserve spinal motion. OBJECTIVE: This study investigated the effectiveness of dynamic stabilization using the Dynesys system in the surgical treatment of adult degenerative spinal deformities, with a particular emphasis on their classification. METHODS: ASDs were classified according to the Berjano-Lamartina (BL) and Silva-Lenke (SL) classifications. We analyzed the efficacy of the Dynesys system in enhancing sagittal balance, radiological parameters, and clinical outcomes in this context. RESULTS: Dynamic stabilization of patients with ASDs using the Dynesys system significantly improved the visual analog scale and Oswestry Disability Index scores and decreased the complication rates. Patients with BL types 2, 3, and 4 experienced a significant improvement in sagittal balance followed by sagittal vertical axis measurements (p = 0.045, p = 0.015, and p < 0.0001, respectively). CONCLUSION: The SL and BL classifications, which were originally developed for rigid spinal stabilization, can be applied in dynamic stabilization. Furthermore, dynamic stabilization using the Dynesys system can be used as an alternative to rigid stabilization in SL levels 2 and 3, and BL types 1, 2, and 3, and in some patients with type 4 ASDs.

Posterior video-assisted trans pedicular surgery for calcified midline thoracic disc herniation.

BACKGROUND: In the treatment of patients with calcified midline thoracic disc herniation (CMTDH), the posterior video-assisted transpedicular surgery (VATPS) technique is employed. Both anterior and posterior surgical approaches for treating CMTDH carry a significant risk of surgical complications and potential morbidity. This technical note introduces a surgical procedure that avoids the drawbacks associated with these approaches. METHODS: The VATPS technique presents a comprehensive approach for treating thoracic disc herniation, combining both microscopic and endoscopic stages. The microscopic phase entails a small thoracoscopic incision, muscle release, hemilaminotomy, facet joint resection, and vertebra removal, culminating in creating a corpectomy cavity for endoscope access. Careful separation of adhesions between the dura and ligaments marks this stage. Transitioning to the endoscopic phase, an endoscope is inserted into the cavity, allowing for precise visualization and separation of residual adhesions, removal of calcified disc fragments using specialized instruments, and ensuring complete discectomy. RESULTS: Fourteen patients underwent VATPS for CMTDH. During the procedure, evoked responses were reduced in one patient. However, no postoperative neurological deficits were observed. We also noted significant improvements in the Oswestry Disability Index (ODI) and the Visual Analog Scale (VAS) scores when comparing the preoperative and postoperative assessments. CONCLUSION: VATPS, a minimally invasive technique, offers excellent anterior visibility comparable to that of the anterolateral approach, all while avoiding the adverse effects associated with thoracotomies and the complications resulting from spinal cord encroachment often seen in the posterolateral approach. Moreover, it is a safer alternative to conventional endoscopic posterior thoracic surgery. The cavity formed within the vertebral corpus provides ample working space for the use of an endoscope.

Intraventricular Shunt Catheter Placement of Adult Normal Pressure Hydrocephalus Using an AxiEMTM Electromagnetic Neuronavigation System: A Single-Center Experience.

AIM: To prove the superiority of the electromagnetic (EM) neuronavigation technique to increase the accuracy of intraventicular shunt catheter placement, and to reduce accompanying complications. MATERIAL AND METHODS: A total of 21 patients with hydrocephalus [age range (years): 53-84] were studied. All of them had undergone thin-slice, navigation-compatible, computed tomography (CT) preoperatively. Shunt surgery was performed under the guidance of EM neuronavigation technology. All patients underwent follow-up CT the next day to evaluate catheter tip placement and were followed up at 1, 3, 6, and 12 months. RESULTS: All catheter tips were placed properly in front of the foramen of Monro in the desired position, except in one case in which the tip migrated to the perimesencephalic cistern and underwent reoperation in the early postoperative period. No complications due to infection and obstruction were observed in the medium- and long-term follow-ups. The complication rate due to the incorrect catheter positioning was 4.76% of the total cases. CONCLUSION: The placement of the ventricular catheter under EM-guided navigation technology reduces the proximal-end failure caused by malpositioning, obstruction, and infection.

Surface hardening of Ti-Al-V superalloy spinal implant by using the boronization method.

BACKGROUND: We compared the raw Ti-Al-V super alloy transpedicular implant screws with boronized and surface-hardened transpedicular implant screws. OBJECTIVE: To improve patients' postoperative prognosis with the production of harder and less fragile screws. METHODS: Surface hardening was achieved by applying green-body encapsulation of the specimen with elemental boron paste which is sintered at elevated temperatures to ensure the boron-metal diffusion. Boron transported into the Ti-Al-V super alloy matrix gradually while suppressing aluminum and a homogeneously boronized surface with a thickness of ∼15 microns was obtained. The uniform external shell was enriched with TiB2, which is one of the hardest ceramics. The Ti-Al-V core material, where boron penetration diminishes, shows cohesive transition and ensures intact core-surface structure. RESULTS: Scanning electron microscope images confirmed a complete homogeneous, uniform and non-laminating surface formation. Energy-dispersive X-ray monitored the elemental structural mapping and proved the replacement of the aluminum sites on the surface with boron ending up the TiB2. The procedure was 8.6 fold improved the hardness and the mechanical resistance of the tools. CONCLUSIONS: Surface-hardened, boronized pedicular screws can positively affect the prognosis. In vivo studies are needed to prove the safety of use.

Radiological and Clinical Follow-up of Alpha-D Cervical Disk Prosthesis.

Background: Fusion surgery is applied to prevent segmental instability after surgery for cervical disk herniation. Motion-sparing surgeries have been developed to prevent adjacent segment disease after fusion surgery. Total disk replacement, one of these methods, has been applied in the cervical region for more than 20 years. We aimed to investigate the medium-term radiological and clinical outcomes of patients who had received Alpha-D disk prosthesis after cervical disk surgery, in terms of incidence of heterotopic ossification (HO) and other complications. Methods: We included 33 patients (17 women and 16 men) diagnosed with single-level cervical disk herniation and who had received prosthesis after anterior discectomy. The average follow-up period was 36 (18-78) months. The patients were followed up postoperatively at month 4, year 1, and annually thereafter. Patients, who had Alpha-D cervical disk prosthesis (CDP) (Medikon, Turkey), were monitored via radiological (standard and dynamic X-ray) and clinical (visual analog scale [VAS] and neck disability index [NDI]) modalities. Dynamic X-ray images were evaluated by an independent radiologist for HO and prosthesis movement. Results: Mean patient age was 40 ± 6.88 years. HO was observed in 7 (21.21%) patients, 6 of which were men. Significant intersex differences were noted for HO and movement rates (p = 0.039). Clinically, the mean preoperative and post-operative NDI levels were 35.4 ± 3.9 and 4 ± 2, respectively, whereas the mean pre- and post-operative VAS levels were 7 ± 1 and 1 ± 1, respectively. There was a clinically significant postoperative improvement in all the patients. However, there was no significant difference between the patients with and without HO in terms of age, operation level, and mean pre- and postoperative VAS, and postoperative NDI levels (p > 0.05). Despite the fact that there was a significant difference (p = 0.038) in favor of patients without HO in terms of mean preoperative NDI levels, this was not considered clinically significant. Conclusion: In the present study, all the patients demonstrated clinically significant improvement following CDP surgery. HO rate after CDP surgery was 21.21% in the medium term, and movement was preserved in 5 of the 7 patients with partial HO. The fact that the CDP design was based on the one-to-one reproduction of the movement segment in the cervical spine, might account for the underlying cause of success. However, these good results in the medium term may change in cases with long-term clinical follow-up.

A Combined Diagnosis and Treatment Algorithm for Spine Infection Management: A Single-Center Experience.

Background and objective Spinal infection (SI) is an infectious disease affecting the vertebral column, spinal cord, and adjacent structures. The infection can occur following interventions or spontaneously. The aim of this study was to highlight the importance of employing a methodological approach for the accurate and rapid diagnosis of SI and to share information on the most effective treatment method, which involves using a diagnostic-treatment algorithm that can help with SI management. Methodology This study included 50 patients diagnosed with SI between 2016 and 2020. The treatment follow-up period was limited to six months, and the study was conducted as a retrospective cohort analysis. The sample consisted of 22 female patients and 28 male patients, and the mean age of the patients was 50.2 years. All patients received diagnosis and treatment according to the algorithm described in this article. Results In the study group, 60% of patients had an infection in the lumbar spine, 4% in the thoracal spine, 12% in the cervical spine, and 8% in the sacral spine. Previously operated patients were diagnosed on the 30.16th day on average. A total of 19 patients (38%) had no history of undergoing surgery. Radiologically, the most common finding was spondylodiscitis/discitis (32%). Osteomyelitis was detected in one (2%) patient. Methicillin-sensitive Staphylococcus aureus (MSSA) was the most commonly isolated organism in culture results and was detected in 13 patients (26%). The culture results of 12 patients (24%) were negative. The number of patients with active SI who were unstable and stabilized at the time of diagnosis was 11 (22%), and stabilization materials were removed in two patients (4%). In the 6th month of control, the patients did not have any complaints, signs of an infection, or unstable vertebral column. Conclusions We conclude that the combined algorithm we recommend for the diagnosis and treatment of patients with SI can prevent negative deviation and is an effective treatment for this condition.

Preoperative Magnetic Resonance Imaging Abnormalities Predictive of Lumbar Herniation Recurrence After Surgical Repair.

OBJECTIVE: There are currently no standard criteria for evaluating the risk of recurrent disk herniation after surgical repair. This study investigated the predictive values of 5 presurgical imaging parameters: paraspinal muscle quality, annular tear size, Modic changes, modified Phirrmann disk degeneration grade, and presence of sacralization or fusion. METHODS: Between 2015 and 2018, 188 patients (89 female, 99 male, median age 50) receiving first corrective surgery for lumbar disk herniation were enrolled. Microdiskectomy was performed in 161 of these patients, and endoscopic translaminar diskectomy approach was performed in 27 patients. Clinical status was evaluated before surgery and 4, 12, and 24 months post surgery using a visual analog scale, Oswestry Disability Index, and Short Form 36. RESULTS: Recurrent disk herniation was observed in 21 of 188 patients. Seventeen of the recurrent disk herniations were seen in those who underwent microdiskectomy and 4 in those who underwent endoscopic translaminar diskectomy. There were significant differences in visual analog scale, Oswestry Disability Index, and Short Form 36 scores at 4, 12, and 24 months between patients with recurrence and the 167 no-recurrence patients. The median annular tear length was significantly greater in patients with recurrence than without recurrence. In addition, there were significant differences in recurrence rate according to Modic change type distribution, sacralization or fusion presence, Pfirmann disk; degeneration grade distribution, dichotomized annular tear size, dichotomized Modic change; and type and simplified 3-tier muscle degeneration classification distribution. CONCLUSIONS: Patients with poor clinical scores and recurrence exhibited additional radiologic abnormalities before surgery, such as poor paraspinal muscle quality, longer annular tears, higher Modic change type, higher modified Phirrmann disk degeneration grade, and sacralization or fusion. This risk evaluation protocol may prove valuable for patient selection, surgical planning, and choice of postoperative recovery regimen.

Lumbar Foraminal Stenosis Classification That Guides Surgical Treatment.

BACKGROUND: There are numerous radiological and anatomical studies on lumbar foramina in the literature, but there are no distinctive studies about the relationship between treatment and the type of foraminal stenosis. This study was conducted to better evaluate foraminal stenosis and to plan treatment accordingly. METHODS: Foraminal stenosis was divided into 2 groups: stable and unstable stenosis. Both groups were also divided into 4 subgroups in relation to the cause and type of compression and based on the structure of the intervertebral disc. The visual analog scale for leg pain (VAS-LP) and Oswestry Disability Index (ODI) scores were investigated before and after surgery. RESULTS: A total of 115 patients (59 women and 56 men) underwent surgery for lumbar foraminal stenosis. The mean patient age was 56.1 years (range 17-80 years). The mean follow-up was 29 months (range 24-39 months). There were 36 patients (32%) with stable foraminal stenosis and 79 patients (68%) with unstable foraminal stenosis. The majority of the patients were identified as having unstable type 1 foraminal stenosis (45 of 115). The VAS-LP and ODI scores for each group decreased gradually during the follow-up periods and showed significant decrease during the last follow-up (P < 0.001). Interobserver and intraobserver agreement in the classification of foraminal stenosis was found to be nearly perfect. No patients experienced postoperative radiculopathy complication. Only 2 patients experienced superficial operation site infection and 1 showed deep wound infection. The patient who had a deep wound infection needed to repeat surgery for the infection. CONCLUSIONS: We introduced a novel classification system for lumbar foraminal stenosis. We aimed to guide appropriate treatment modality depending on the determined classification. This classification helps to determine the optimal treatment. In the light of our findings, the patients who were operated according to our classification experienced satisfactory clinical outcomes and low complication rates.

Lumbar Dynamic Stabilization With 2-Stage Surgery: Early Results.

BACKGROUND: Screw loosening, which is a major problem in dynamic systems, can be easily overcome with 2-stage surgery. In this article, the clinical and radiological results of patients undergoing dynamic stabilization with a Dynesys device in 2 stages are discussed. METHODS: A total of 10 male and 13 female adult patients were included in this single-center retrospective study conducted between 2018 and 2021. The mean age of the patients was 65.6 years. All of the patients had pain complaints that affected their daily lives. Bone density T scores were determined with the dual-energy x-ray absorptiometry method before patients were admitted for surgery. In the first surgery, Dynesys system pedicle screws were inserted. After 6 months of osteointegration, Dynesys system spacers and elastic bandages were placed. Preoperative, early postoperative, and late postoperative visual analog pain scale (VAS) scores and Oswestry Disability Index (ODI) scores were determined and statistically compared. RESULTS: Patients were followed for an average of 30 months. Complications and recurrence were not observed. Neurological deficits were not observed after patients recovered from anesthesia. Significant improvement was observed in the ODI and VAS parameters in the preoperative (ODI: 66.2%, VAS: 7.8), early postoperative (ODI: 20.3%, VAS: 2.4), and late postoperative (ODI: 6.8% and VAS: 1.1) periods. Symptomatic improvement was seen in all patients. No screw breakage or loosening was detected by radiological evaluation in any of the patients during the 2-year follow-up period. CONCLUSIONS: In our experience, the insufficiency of the proximal and distal end screws is eliminated when 2 stages of dynamic system stabilizations are completed after osteointegration of the screws.

Adjacent Segment Disease (ASD) in Incidental Segmental Fused Vertebra and Comparison With the Effect of Stabilization Systems on ASD.

Objective Adjacent segment disease is a controversial process after spine stabilization. The two important factors discussed are natural aging and hypermobility in incidental segmental fusion anomalies; patients have two or more fused vertebrae from birth, which are the results of spinal movement restriction due to the fusion of some spinal units. This article's main purpose is to determine the degree of relationship of hypermobility and the aging process in the deterioration of the disks adjacent to fusion. Methods In this study, the degenerative process developed by hypermobility in the adjacent segment due to incidental segmental fusion was evaluated. The MRI images of 52 adjacent and nonadjacent disks of 45 patients in total were analyzed according to the Pfirrmann grading systems. The average Pfirrmann rating of the disks just above and below the fused segment and the distant first, second, and third non-neighboring levels were evaluated and calculated, respectively. Results The highest rate of incidental fusion is determined on the cervical area with 51.9%, followed by the thoracal area with 32.7%, and the lumbar area with 15.4%. Damage to the adjacent segment disks in cases with incidental fusion can still be seen at any age, with fusion, indicating that the hypermobility effect plays a more prominent role. The evidence of hypermobility without aging is that the segments adjacent to fusion undergo more degeneration than the distant disks. Conclusion Adjacent segment disease is under the influence of many factors. Our findings suggest that its incidence is increasing with the pathological processes initiated by hypermobility. It seems that, at least, it carries equal importance as compared to age. Fusion surgeries damage the adjacent segments under the influence of the passage of time beyond the physiological aging of the patient.

Kyphoplasty with Posterior Dynamic Stabilization in the Surgical Treatment of Unstable Thoracolumbar Osteoporotic Vertebral Compression Fractures.

AIM: To evaluate the role of posterior dynamic stabilization (PDS) with kyphoplasty (KP) in the surgical treatment of unstable osteoporotic compression fractures, which are common in the elderly population. MATERIAL AND METHODS: This study included 25 patients with osteoporotic compression fractures. KP with PDS was performed on all patients. Radiological evaluation was performed with magnetic resonance imaging, computed tomography, and plain radiographs. The vertebral kyphosis angle (VKA), local kyphosis angle (LKA), and percentage of collapse were calculated. Clinical evaluation was performed with the visual analog scale and the Oswestry Disability Index (ODI). The preoperative and postoperative clinical and radiological data were compared. RESULTS: The clinical and radiological parameters showed significant improvement following surgical treatment. The mean preoperative visual analog scale score of 7.78 decreased to 0.94 after 12 months. The mean preoperative ODI score of 70.33 decreased to 15.65 after 12 months. The mean preoperative VKA of 17.89° decreased to 9.22° after 12 months. The mean preoperative LKA of 9.61° decreased to 5.50° after 12 months. The mean preoperative percentage of collapse of 32.56% decreased to 19.00% after 12 months. There were no major complications. CONCLUSION: KP with the PDS method offered satisfactory outcomes in the surgical treatment of unstable osteoporotic compression fractures.

Changes in cervical sagittal alignment and the effects on cervical parameters in patients with cervical spondylotic myelopathy after laminoplasty.

OBJECTIVE: To monitor changes in cervical parameters before and after laminoplasty surgery. Cervical parameters and health-related quality-of-life (HRQOL) values that may be affected after laminoplasty were examined before and after surgery. The clinical and radiological course of these values was monitored, and their interaction with all spinal radiological parameters was revealed. MATERIALS AND METHODS: Nineteen patients who underwent clinical and radiological evaluation for 2 years were followed in this study. Neck disability index, visual analog scale, and short form 36 scores were determined to evaluate HRQOL. For radiological parameters, the C0-C2 angle, C2-C7 angle, cervical sagittal vertical axis, T1 slope angle, neck tilt (NT) and thoracic inlet angle were used. The results of the 4-month, 1 year and 2-year follow-ups were statistically evaluated. RESULTS: Both the HRQOL and cervical radiological parameters deteriorated in the first 4 months and returned to normal in the 2nd year. Statistically, all parameters were meaningful (P < 0.05), except for NT. CONCLUSION: Cervical parameters and HRQOL values, which deteriorated in the early period, recovered in the late period in the long-term follow-up of patients undergoing laminoplasty. The important point is that preoperative cervical parameters suitable for laminoplasty should be present, and spinopelvic parameters should be normal.

Should Iliac Wing Screws Be Included in Long Segment Dynamic Stabilization?

Background In this article, clinical satisfaction and radiological results are discussed in a series of patients where the iliac wings participate in dynamic stabilization. Dynamic stabilization is an effective alternative surgical treatment method, especially in clinical pictures that go with pain due to minor instabilities. Practically the unique surgical instrument used in multilevel instabilities is the Dynesys system. The most important drawback of the Dynesys system is that the S1 screws become loose in time. In this article, our aim is to find solution to S1 insufficiency by extension of the system to the iliac wings. Methods Nineteen patients (eight females, 11 males) with a mean age of 54.16 were included in the study. Patients had multilevel (level 2 and above) instability, iliac wings were included in the stabilized segments, and Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) were used for patient follow-up. Results First year results showed a significant improvement in VAS and ODI. Regarding the complications, infection developed in one patient, loosening in the proximal iliac wing in one patient, and both S1 and iliac proximals in one patient, but no clinical findings were encountered. Conclusion When more than two levels of dynamic systems are used in chronic instability, especially in the elderly patients, S1 screws are loosened. In these patients, if the iliac bones are also included in stabilization, this problem is solved successfully. However unfortunately, Dynesys system does not have a screw suitable for the iliac bones.

Suppression of Aquaporin-4 By Antisense Oligonucleotides Reduces Brain Edema In Experimental Traumatic Brain Injury.

AIM: In this study, suppression of Aquaporin-4 (AQP4) synthesis via intracerebroventricular (i.c.v.) injection of antisense oligonucleotide after focal cortical contusion injury in mice was investigated. MATERIAL AND METHODS: 12-week female Swiss albino mice of 20-25 g were used to create a focal cortical contusion model by the weight drop method (35 grams blunt weight, 70 cm height) onto the parietal cortex after craniectomy. The sham group underwent craniectomy without trauma. In the control group, weight was dropped onto the parietal cortex immediately after Dulbecco\'s Modified Eagle Medium (DMEM) i.c.v. injection following craniectomy. In addition, 1 nM of aquaporin-4 (AQP4) antisense oligonucleotide (ASO) was injected via i.c.v route immediately after trauma (0 hours) and 4 hours after trauma. All animals underwent magnetic resonance (MR) imaging and were sacrificed at 24 h. Brain water content was determined using the wet/dry weight method. RESULTS: In the sham group, the average percentage of brain water content was 77.75% compared to the control group with 79.87%. The difference was statistically significant (*p=0.017). In the therapy group, the average was 78.81% and significantly reduced compared to the control group (*p=0.026) at 0 hours. In the 4-hour treatment group, the average of 79.11% was not statistically significant (p=0.39). MR imaging findings also showed a substantial reduction in brain edema in the 0-hour treatment group. However, the 4-hour treatment results, when compared with the control trauma group, did not show a significant difference. CONCLUSION: This study demonstrated that AQP4 antisense oligonucleotide therapy, when administered early after diffuse traumatic brain injury, leads to a significant reduction in brain edema.

Comparison of Two Minimally Invasive Techniques with Endoscopy and Microscopy for Extraforaminal Disc Herniations.

OBJECTIVE: Extraforaminal disc herniations are extraordinary herniations because they are located outside the foraminal bony borders and compress the root exiting at the corresponding level, whereas in median or paramedian herniations, the root 1 level below is compressed. Percutaneous endoscopic discectomy (PED) and microscopic extraforaminal discectomy (MEFD) are 2 popular contemporary techniques that have been performed extensively for these herniations since the 1970s. METHODS: In this study, we retrospectively analyzed 118 patients who underwent either PED (66 patients) or MEFD (52 patients). All the patients were clinically evaluated for neurologic examination findings, visual analog scale (VAS) scores for leg pain and Oswestry Disability Index (ODI) preoperatively and on the seventh postoperative day as well as 6 and 12 months after surgery. The complication rates and types of both techniques were discussed. RESULTS: The preoperative VAS score and ODI were all comparable. Improvements in VAS scores 6 months postoperatively and improvements in ODI at all follow-up periods were statistically significant in favor of PED. However, there was great discrepancy regarding the postsurgical complications in favor of MEFD. CONCLUSIONS: PED is more prone to complications because this technique is strictly dependent on the tubular system and the ideal anatomy of the Kambin triangle. Variations in or degeneration of the Kambin triangle can lead to devastating complications in the PED technique, but normal anatomic conditions are feasible in only approximately 20% of patients. The most important feature of this study was that both techniques were performed by the same experienced team, who developed their own concept.