Full-Endoscopic Posterior Lumbar Interbody Fusion: A Review and Technical Note.

Remarkable innovations in spinal endoscopic surgery have broadened its applications over the past 20 years. Full-endoscopic fusions have been widely reported, and several full-endoscopic approaches for interbody fusion have been published. In general, full-endoscopic lumbar interbody fusion (LIF) is called Endo-LIF, and facet-preserving Endo-LIF through the transforaminal route is called trans-Kambin's triangle LIF, which has a relatively longer history than facet-sacrificing Endo-LIF via the posterolateral route. Both approaches can reduce intraoperative and postoperative bleeding. However, there is a higher risk of subsidence and exit nerve root injury. There is no direct decompression in either of the interbody fusions, and additional decompression is required if there is severe lumbar bony canal stenosis. However, the posterior interlaminar approach, which is a well-known standard in full-endoscopic spine surgery, has rarely been applied in the field of endoscopic lumbar fusion surgery. Full-endoscopic posterior LIF (FE-PLIF) via an interlaminar approach can accomplish direct decompression of bony canal stenosis and safe interbody fusion. FE-PLIF via an interlaminar approach demonstrated a longer operation time, less blood loss, and shorter hospitalization duration than minimally invasive transforaminal LIF. FE-PLIF, which can accomplish direct decompression for bony spinal canal stenosis, is superior to other Endo-LIFs. However, FE-PLIF requires technical dexterity to improve efficiency and reduce technical complexity.

Full-endoscopic versus microscopic spinal decompression for lumbar spinal stenosis: a systematic review & meta-analysis.

BACKGROUND CONTEXT: Symptomatic lumbar spinal stenosis is routinely treated with spinal decompression surgery, with an increasing trend towards minimally invasive techniques. Endoscopic decompression has emerged as a technique which minimizes approach-related morbidity while achieving similar clinical outcomes to conventional open or microscopic approaches. PURPOSE: To assess the safety and efficacy of endoscopic versus microscopic decompression for treatment of lumbar spinal stenosis. STUDY DESIGN: Systematic review and meta-analysis. METHODS: A systematic review on randomized and nonrandomized studies comparing endoscopic versus microscopic decompression was conducted, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Treatment effects were computed using pairwise random-effects meta-analysis. Risk of bias was assessed using the Cochrane Risk-of-bias and ROBINS-I tools for randomized and nonrandomized trials respectively. Quality of the overall body of evidence was appraised using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. RESULTS: A total of 19 primary references comprising 1,997 patients and 2,132 spinal levels were included. Endoscopic decompression was associated with significantly reduced intraoperative blood-loss (weighted mean differences [WMD]=-33.29 mL, 95% CI:-51.80 to -14.78, p=.0032), shorter duration of hospital stay (WMD=-1.79 days, 95% CI: -2.63 to 0.95, p=.001), rates of incidental durotomy (RR = 0.63, 95% CI: 0.43 to 0.91, p=.0184) and surgical site infections (RR=0.23, 95% CI: 0.10 to-0.51, p=.001), and a nonsignificant trend towards less back pain, leg pain, and better functional outcomes compared to its microscopic counterpart up to 2-year follow up. CONCLUSIONS: Endoscopic and microscopic decompression are safe and effective techniques for treatment of symptomatic lumbar spinal stenosis. Prospective studies of larger power considering medium to long-term outcomes and rates of iatrogenic instability are warranted to compare potential alignment changes and destabilization from either techniques.

Narrative Review of Uniportal Posterior Endoscopic Cervical Foraminotomy.

Cervical radiculopathy is a common and disabling cervical condition characterized by symptoms including axial neck pain, radicular pain, weakness, and numbness in one or both arms. Common causes include herniated discs and foraminal stenosis, often accompanied by varying degrees of degenerative disc disease and uncovertebral joint hypertrophy. In the treatment of cervical radiculopathy, there is an increasing preference for posterior foraminotomy over anterior cervical discectomy and fusion due to the avoidance of fusion-related complications. As endoscopic spine surgery techniques continue to evolve, there is a rising interest in posterior endoscopic cervical foraminotomy and posterior endoscopic cervical discectomy as effective treatments for cervical radiculopathy. Because these procedures can performed through a single subcentimeter incision with minimal soft tissue damage, they can often be carried out as ambulatory procedures. In this narrative review, we examined current literature addressing the indications, surgical techniques, outcomes, and potential complications associated with posterior cervical endoscopic approaches.

Technical feasibility of combined uniportal unilateral laminotomy with bilateral decompression and interlaminar lumbar discectomy surgery for cauda equina syndrome due to lower lumbar disc herniation.

Background: Traditionally, open wide laminectomy and discectomy have been advocated for the treatment of cauda equina syndrome caused by lumbar disc herniation. We aimed to evaluate the technical feasibility of uniportal interlaminar endoscopy in treating cauda equina syndrome. Methods: Nine patients with cauda equina syndrome underwent uniportal endoscopic decompression and discectomy from December 2020 to December 2022. Data were collected retrospectively. Patients diagnosed with cauda equina syndrome were operated on within 6 hours of presentation to the hospital. The visual analogue score (VAS), Oswestry disability index (ODI), and bladder/bowel score were used to measure the outcome. Results: Analysis showed that VAS scores for leg pain and back pain significantly decreased from preoperative scores of 8.22±0.79 and 4.67±1.76 to postoperative day 1 scores of 0.67±0.67 and 2.56±1.42 (p<.05). The ODI scores improved from preoperative 52.33±11.93 to postoperative (day 1) 14±6.80. Eight patients had early recovery (1 week) of bladder and bowel functions, and one had delayed recovery at 8 months. None of the patients had a residual bowel/bladder deficit. Macnab's criteria outcomes were excellent in all patients at the final follow-up. Conclusions: Uniportal endoscopic lumbar endoscopic unilateral laminotomy with bilateral decompression and subsequent interlaminar endoscopic lumbar discectomy is a safe and effective minimally invasive course of treatment for cauda equina syndrome as an alternative to open laminectomy in our cohort of patients.

Optical Bistability in Nanosilicon with Record Low Q-Factor.

We demonstrated optical bistability in an amorphous silicon Mie resonator with a size of ∼100 nm and Q-factor as low as ∼4 by utilizing photothermal and thermo-optical effects. We not only experimentally confirmed the steep intensity transition and the hysteresis in the scattering response from silicon nanocuboids but also established a physical model to numerically explain the underlying mechanism based on temperature-dependent competition between photothermal heating and heat dissipation. The transition between the bistable states offered particularly steep superlinearity of scattering intensity, reaching an effective nonlinearity order of ∼100th power over excitation intensity, leading to the potential of advanced optical switching devices and super-resolution microscopy.

Uniportal Thoracic Endoscopic Unilateral Laminotomy with Bilateral Decompression of Thoracic Ossification of Ligamentum Flavum: A Systematic Review of Current Literature.

BACKGROUND: Thoracic ossification of ligamentum flavum (TOLF) is a rare disease that often results in worsening neurologic sequelae if left untreated. Although the gold standard treatment for TOLF is open posterior laminectomy, it is often accompanied by high rates of complications and perioperative morbidity. There have been studies looking into feasibility of endoscopic posterior decompression for TOLF, citing potential for lower perioperative morbidity and achieving similar functional outcomes to its open laminectomy counterparts. We provide an up-to-date systematic review of clinical outcomes after endoscopic posterior decompression for TOLF from the latest assemblage of evidence. METHODS: A systematic review of the technique was conducted from May 2000 to May 2023. Articles were selected based on PRISMA guidelines. Eligibility of studies was independently by 2 reviewers, with disagreements resolved by a third author. RESULTS: Nineteen primary references comprising 337 patients with TOLF who underwent endoscopic posterior decompression were included in the systematic review. Mean follow-up time across all studies ranged from 8.9 to 65.3 months. Mean age ranged from 51.2 to 63 years, with mean intraoperative blood loss ranging from 15 to 62 mL. There is significant improvement in visual analog scale (VAS) score, VAS back, VAS leg, modified Japanese Orthopaedic Association score, and Oswestry Disability Index compared with preoperative recorded values across all studies, with low rates of complications reported. CONCLUSIONS: Endoscopic posterior spinal decompression is a safe and effective technique for treatment of TOLF, with a low rate of complications and improvement in pain and function.

Clinical and Radiological Outcomes of a Comparative Study of Anterior Cervical Decompression and Fusion with Partial Pediculotomy, Partial Vertebrotomy (PPPV) Posterior Endoscopic Cervical Decompression (PECD) for Cervical Foraminal Pathology.

Background and Objectives: The purpose was to compaSre medium-term clinical and radiological outcomes of Partial Pediculotomy, Partial Vertebrotomy (PPPV) Posterior Endoscopic Cervical Decompression (PECD) surgery versus Anterior Cervical Discectomy and Fusion (ACDF) for patients with cervical disc herniations and foraminal pathologies. Materials and Methods: A prospective registry of patients who had undergone either PPPV PECD surgery or ACDF surgery for cervical disc herniation or foraminal pathologies under a single fellowship-trained spine surgeon was performed. The baseline characteristics and operative details including complications were recorded for all included patients. The clinical outcomes evaluated include VAS, MJOA, motor score, and NDI and MacNab's score. The radiological parameters in neutral-measured facet length, facet area, disc height, C2-C7 angle, neck tilt angle, T1 slope and thoracic inlet angle were also evaluated. Results: A total of 55 patients (29 PPPV PECD, 26 ACDF) were included, with mean follow-up periods of 21.9 and 32.3 months, respectively. Each cohort was noted to have a single case of surgical complication. Statistically significant changes of facet area (49.05 ± 14.50%) and facet length (52.71 ± 15.11%) were noted in the PPPV PECD group. At neutral alignment of the neck on a lateral X-ray, compared to ACDF, PPPV PECD had a statistically significant change in neck tilt angle (-11.68 ± 17.35°) and T1 slope angle (-11.69 ± 19.58°). Whilst both PPPV PECD and ACDF had significant improvements in VAS, MJOA and NDI postoperatively, PPPV PECD was found to be superior across all above scores at various follow-up timepoints compared to its ACDF counterparts. Conclusions: PPPV PECD surgery achieved a satisfactory radiological correction of neck alignment and significantly improved clinical outcomes at medium-term follow-up for our cohort of patients, highlighting its feasibility in treating patients with cervical disc herniations and foraminal pathologies.

Unilateral biportal endoscopic supralaminar, posterior spinous process sparing approach for en bloc cervical laminectomy in case of cervical osteochondroma causing myelopathy: A case report.

Background Context: Cervical osteochondroma is a rare cause of myelopathy. Traditional treatment is open laminectomy with or without fusion. There is limited literature on unilateral bi-portal endoscopic en-bloc resection of cervical osteochondroma. Study Design: We describe a case of a 39-year-old male diagnosed with cervical compressive myelopathy. The pathologic site is located on the ventral surface of C4 lamina. Herein we describe a step-by-step method of unilateral biportal endoscopy (UBE) en-bloc resection of extra-dural sublaminar osteochondroma for patient who had cervical myeloradiculopathy. Spinous process sparing osteotomy was performed to conserve the spinous process and supraspinous ligament.. Outcome Measures: The patient was successfully treated via UBE and the operative time was 50 minutes with no intra-operative complications. Patient symptoms improved in the immediate postoperative period and by 3 months he regained fine motor functions of hand. Conclusions: Unilateral biportal endoscopic en bloc cervical laminectomy can effectively decompress cervical spine and remove posterior benign cervical tumor. UBE preserves musculature and posterior ligamentous complex and thus reduces postoperative neck pain and postlaminectomy kyphosis.

Spinal Canal Remodeling and Indirect Decompression of Contralateral Foraminal Stenosis After Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion.

OBJECTIVE: There is a lack of literature on indirect decompression in uniportal endoscopic posterolateral transforaminal lumbar interbody fusion (EPTLIF). Our aim is to evaluate the dimensions of the spinal canal and contralateral foramen before and after EPTLIF. METHODS: This is a retrospective study of patients who underwent EPTLIF in a tertiary spine centre over a 2-year period. The cross-sectional area of the spinal canal and the contralateral foramen at the level of fusion were measured on magnetic resonance imaging scan at 1-day postoperation and at the final follow-up. Patients were grouped according to the decompression performed as per the clinician's judgement. RESULTS: One hundred fifty-two levels of fusion were performed in 120 patients. There was a statistically significant clinical improvement in visual analogue scale and Oswestry Disability Index scores postoperation. The measurements of the spinal canal area were 106.0 mm2, 138.8 mm2, and 195.5 mm2; while contralateral foraminal area were 73.2 mm2, 104.4 mm2, and 120.7 mm2 at preoperation, 1-day postoperation, and at the final follow-up, respectively (p < 0.001). For the subgroup analyses, spinal canal area measurements for the bilateral decompression cohort (n = 35) were 57.0 mm2, 123.9 mm2, and 191.8 mm2; for the ipsilateral decompression cohort (n = 42) were 89.3 mm2, 128.9 mm2, 183.3 mm2; and for the cohort without any decompression and only cage inserted (n = 75) were 138.3 mm2, 151.2 mm2, and 204.1 mm2 (p < 0.001). Contralateral foraminal area measurements were 73.3 mm2, 106.4 mm2 and 120.4 mm2 in the bilateral decompression cohort; 69.5 mm2, 99.0 mm2, 116.9 mm2 in the ipsilateral decompression cohort; and 75.1 mm2, 106.5 mm2, 122.9 mm2 in the cohort without any decompression (p < 0.001). CONCLUSION: Indirect decompression of both the spinal canal and the contralateral foramen can be achieved via EPTLIF. Decompression on an asymptomatic contralateral side is not necessary.

Ambulatory uniportal versus biportal endoscopic unilateral laminotomy with bilateral decompression for lumbar spinal stenosis-cohort study using a prospective registry.

BACKGROUND: Endoscopic spine surgery has been established as a practical, minimally invasive technique for decompression in patients with lumbar spinal stenosis. However, there remains a paucity of studies prospective cohort study comparing uniportal lumbar endoscopic unilateral laminotomy with bilateral decompression and unilateral biportal endoscopic unilateral laminotomy with bilateral decompression with open spinal decompression-both viable techniques with satisfactory clinical outcomes in the treatment of lumbar spinal stenosis. OBJECTIVE/AIM: To compare the efficacy of UPE and BPE lumbar decompression surgery for patients with lumbar spinal stenosis. METHODS: A prospective registry of patients who had undergone spinal decompression for lumbar stenosis via UPE or BPE under a single fellowship trained spine surgeon was studied. Baseline characteristics, initial clinical presentation, and operative details including complications were recorded for all included patients. Clinical outcomes, such as visual analogue scale and Oswestry Disability Index, were recorded at preoperative, immediate postoperative, 2-week, 3-, 6-, and 12-month follow-up periods. RESULTS: A total of 62 patients underwent endoscopic decompression surgery for lumbar spinal stenosis (29 UPE, 33 BPE). No significant baseline differences were found between uniportal and biportal decompression, when comparing operative duration (130 vs. 140 min; p = 0.30), intraoperative blood loss (5.4 vs. 6mLs; p = 0.05), and length of hospital stay (23.6 vs. 20.3 h; p = 0.35). Two patients (7%) who underwent uniportal endoscopic decompression required conversion to open surgery due to inadequate decompression. Intraoperative complication rates were significantly higher in the UPE group (13.4% vs. 0%, p < 0.05). VAS score (leg & back) and ODI improved significantly (p < 0.001) in both endoscopic decompression groups across all follow-up time points, with no appreciable statistical differences between both groups. CONCLUSION: UPE has the same efficacy as BPE in the treatment of lumbar spinal stenosis. While UPE surgery enjoys added aesthetic benefits of only one wound, BPE had potentially lower risks of intraoperative complication, inadequate decompression, and conversion to open surgery during early period of learning curve.

Prospective Cohort Study with a 2-Year Follow-up of Clinical Results, Fusion Rate, and Muscle Bulk for Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective cohort study. PURPOSE: Postoperative evaluation of the cross-sectional area of paraspinal muscle and clinical findings in patients who had interlaminar route uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion (EPTLIF) after 2 years. OVERVIEW OF LITERATURE: There are limited short-term follow-up studies on efficacy, safety, and physiological changes with a 2-year follow-up. There is no study on paraspinal muscle cross-sectional area change in patients who had undergone uniportal EPTLIF. METHODS: We evaluated patients who underwent EPTLIF with a minimum 24-month follow-up. Clinical parameters of the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) were measured at the preoperative, 1-week postoperative mark, postoperative 3-month mark, and final follow-up. Preoperative and 1-year postoperative magnetic resonance imaging measurement of preoperative and postoperative Kjaer grade, right and left psoas muscle mass area, and right and left paraspinal muscle mass area was performed. RESULTS: EPTLIF with a minimum 24-month follow-up of 35 levels was included. The complication rate was 6%, and the mean Bridwell's fusion grade was 1.37 (1-2). There was statistically significant improvement at 1 week, 3 months, and 2 years in VAS (4.11±1.23, 4.94±1.30, and 5.46±1.29) and in ODI (40.34±10.06, 46.69±9.14, and 49.63±8.68), respectively (p <0.05). Successful operation rate with excellent and good MacNab's criteria at 2 years was 97%. There was an increment of statistically significant bilateral psoas muscle cross-sectional area, right side (70.03±149.1 mm²) and left side (67.59±113.2 mm²) (p <0.05). CONCLUSIONS: Uniportal EPTLIF achieved good fusion and improved clinical outcomes with favorable paraspinal musculature bulk at the 2-year follow-up.

Remodeling of Epidural Fluid Hematoma after Uniportal Lumbar Endoscopic Unilateral Laminotomy with Bilateral Decompression: Comparative Clinical and Radiological Outcomes with a Minimum Follow-up of 2 Years.

STUDY DESIGN: Retrospective cohort study. PURPOSE: To evaluate the clinical and radiological effects of epidural fluid hematoma in the medium term after lumbar endoscopic decompression. OVERVIEW OF LITERATURE: There is limited literature comparing the effect of postoperative epidural fluid hematoma after uniportal endoscopic decompression. METHODS: Magnetic resonance imaging (MRI) and clinical evaluation were performed for patients with single-level uniportal endoscopic lumbar decompression with a minimum follow-up of 2 years. RESULTS: A total of 126 patients were recruited with a minimum follow-up of 26 months. The incidence of epidural fluid hematoma was 27%. Postoperative MRI revealed a significant improvement in the postoperative dura sac area at postoperative day 1 and at the upper endplate at 6 months in the hematoma cohort (39.69±15.72 and 26.89±16.58 mm2) as compared with the nonhematoma cohort (48.92±21.36 and 35.1±20.44 mm2), respectively (p <0.05); and at the lower endplate on postoperative 1 day in the hematoma cohort (51.18±24.69 mm2) compared to the nonhematoma cohort (63.91±27.92 mm2) (p <0.05). No significant difference was observed in the dura sac area at postoperative 1 year in both cohorts. The hematoma cohort had statistically significant higher postoperative 1-week Visual Analog Scale (VAS; 3.32±0.68) pain and Oswestry Disability Index (ODI; 32.65±5.56) scores than the nonhematoma cohort (2.99±0.50 and 30.02±4.84, respectively; p <0.05). No significant difference was found at the final follow-up VAS, ODI, and MRI dura sac area. CONCLUSIONS: Epidural fluid hematoma is a common early postoperative MRI finding in lumbar endoscopic unilateral laminotomy with bilateral decompression. Conservative management is the preferred treatment option for patients who do not have a neurological deficit. Symptoms last only a few days and are self-limiting. A common endpoint is a remodeled fluid hematoma and the subsequent expansion of the dura sac area.

Retrospective Case Control Study: Clinical and Computer Tomographic Fusion and Subsidence Evaluation for Single Level Uniportal Endoscopic Posterolateral Approach Transforaminal Lumbar Interbody Fusion Versus Microscopic Minimally Invasive Transforaminal Interbody Fusion.

STUDY DESIGN: Retrospective comparative study. OBJECTIVE: Assessment of difference in clinical and computer tomographic outcomes between the 2 cohorts. METHODS: Computer tomographic evaluation by Bridwell's grade, Kim's stage, Kim's subsidence grade and clinical evaluation by VAS, ODI and McNab's criteria on both cohorts. RESULTS: 33 levels of Endo-TLIF and 22 levels of TLIF were included, with a mean follow up of 14.3 (10-24) and 22.9 (13-30) months respectively. Both Endo-TLIF and TLIF achieved significant improvement of pain and ODI at post-operative 4 week, 3 months and at final follow up with VAS 4.39 ± 0.92, 5.27 ± 1.16 and 5.73 ± 1.21in Endo-TLIF and 4.55 ± 1.16, 5.05 ± 1.11 and 5.50 ± 1.20 in TLIF respectively and ODI at post-operative 1 week, 3 months and final follow up were 43.15 ± 6.57, 49.27 ± 8.24 and 51.73 ± 9.09 in Endo-TLIF and 41.73 ± 7.98, 46.18± 8.46 and 49.09 ± 8.98 in TLIF respectively, P < 0.05. Compared to TLIF, Endo-TLIF achieved better VAS with 0.727 ± 0.235 at 3 months and 0.727 ± 0.252 at final follow up and better ODI with 3.88 ± 1.50 at 3months and 3.42 ± 1.63 at final follow up, P < 0.05. At 6 months radiological evaluation comparison of the Endo-TLIF and TLIF showed significant with more favorable fusion rate in Endo-TLIF of -0.61 ± 0.12 at 6 months and -0.49 ± 0.12 at 1 year in Bridwell's grading and 0.70 ± 0.15 at 6 months and 0.56 ± 0.14 at 1 year in Kim's stage.There is less subsidence of 0.606 ± 0.18 at 6 months and -0.561 ± 0.20 at 1 year of Kim's subsidence grade, P < 0.05. CONCLUSION: Application of single level uniportal endoscopic posterolateral lumbar interbody fusion achieved better clinical outcomes and fusion rate with less subsidence than microscopic minimally invasive transforaminal lumbar interbody fusion in mid-term evaluation for our cohorts of patients.

Narrative Review of Pathophysiology and Endoscopic Management of Basivertebral and Sinuvertebral Neuropathy for Chronic Back Pain.

Chronic lower back pain is a leading cause of disability in musculoskeletal system. Degenerative disc disease is one of the main contributing factor of chronic back pain in the aging population in the world. It is postulated that sinuvertebral nerve and basivertebral nerve main mediator of the nociceptive response in degenerative disc disease as a result of neurotization of sinuvertebral and basivertebral nerve. A review in literature is done on the pathoanatomy, pathophysiology and pain generation pathway in degenerative disc disease and chronic back pain and management strategy is discussed in this review to aid understanding of sinuvertebral and basivertebral neuropathy treatment strategies.

Systematic Review of Current Literature on Clinical Outcomes of Uniportal Interlaminar Contralateral Endoscopic Lumbar Foraminotomy for Foraminal Stenosis.

BACKGROUND: Uniportal interlaminar contralateral endoscopic lumbar foraminotomy (ICELF) aims to achieve decompression of lumbar spinal stenosis in the contralateral lateral recess and foraminal and extraforaminal regions of the same segment. This technique is performed under normal saline irrigation using an endoscope with optical lens magnification close to the targeted stenotic segment and has the potential of lower incidence of exiting nerve root dorsal root ganglion irritation. METHODS: A systematic review of the ICELF technique was conducted from March 2000 to March 2022. Articles were selected with Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eligibility of studies was independently determined by 2 reviewers, and disagreements were resolved by a third author. RESULTS: Eight retrospective cohort studies comprising 194 patients with foraminal stenosis who underwent uniportal ICELF were selected for systematic review. Mean age range was 62-79 years, and surgical duration was 48-73.5 minutes. There was significant improvement in Oswestry Disability Index and visual analog scale leg pain score in the included studies. Four studies met the minimum clinically significant difference for leg pain, with visual analog scale improved >5 points and Oswestry Disability Index improved >8.2 points. Four studies reported a majority of the operated patients with good or excellent outcomes following surgery, with a low rate of complications in the studies selected. CONCLUSIONS: There is low-level evidence that ICELF when performed by an experienced spinal endoscopic surgeon is effective in providing pain relief and improved function with low rate of complications in select patients.

Spinal arachnoid cysts: A case series & systematic review of the literature.

Introduction: Spinal arachnoid cysts (SACs) are rare lesions with challenging and controversial management. Research question: We analyzed our experiences from a case series and provide a systematic review to determine 1) Demographic and clinical features of SACs, 2) Optimal imaging for diagnosis and operative planning, 3) Optimal management of SACs, and 4) Clinical outcomes following surgery. Materials and methods: A single-institution, ambispective analysis of patients with symptomatic SACs surgically managed between May 2005 and May 2019 was performed. Data were collected as per local ethics committee stipulations. A systematic review of SACs in adults was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and a preapproved protocol. Results: Our series consisted of 11 patients, M:F 8:3, mean age 47.8 years (range 18-73 years). Mean follow-up was 19 months (range 5-36 months). SACs were excised or marsupialised (7), fenestrated (3) or partially excised (1). Eight patients had expansile duroplasty, 3 primary dural closure. One patient had a cystoperitoneal shunt. All patients were AIS D preoperatively; 4 remained unchanged and 7 improved to AIS E at follow-up. Our systematic search retrieved 725 citations. Fourteen case series met the inclusion criteria. There was no evidence to support superiority of one surgical strategy over another. Surgery for symptomatic patients resulted in positive clinical outcomes. Discussion and conclusions: Symptomatic SACs require surgical intervention. Limited evidence suggests that decompressing the cord, breakdown of arachnoid adhesions, and establishing CSF flow by consideration of expansile duroplasty are important for positive outcomes.

A Flexible Ultrasound Array for Local Pulse Wave Velocity Monitoring.

Pulse wave velocity (PWV) measured at a specific artery location is called local PWV, which provides the elastic characteristics of arteries and indicates the degree of arterial stiffness. However, the large and cumbersome ultrasound probes require an appropriate sensor position and pressure maintenance, introducing usability constraints. In this paper, we developed a light (0.5 g) and thin (400 µm) flexible ultrasound array by encapsulating 1-3 composite piezoelectric transducers with a silicone elastomer. It can capture the distension waveforms of four arterial positions with a spacing of 10 mm and calculate the local PWV by multi-point fitting. This is illustrated by in vivo experiments, where the local PWV value of five normal subjects ranged from 3.07 to 4.82 m/s, in agreement with earlier studies. The beat-to-beat coefficient of variation (CV) is 12.0% ± 3.5%, showing high reliability. High reproducibility is shown by the results of two groups of independent measurements of three subjects (the error between the mean values is less than 0.3 m/s). These properties of the developed flexible ultrasound array enable the bandage-like application of local PWV monitoring to skin surfaces.