Percutaneous Full Endoscopic Decompression For Thoracic Spinal Stenosis

Background:Thoracic spinal stenosis(TSS)is a disease in which the thoracic spinal cord or nerve roots are compressed and injured,and is mainly due to the ossification of ligamentum flavum(OLF)and the ossification of posterior longitudinal ligament(OPLL).Decompression surgery is the only method to treat TSS.The traditional open decompression surgery for TSS is much difficult and has many complications,and the surgical results of it are much worse than cervical and lumbar spinal diseases.Since the treatment of TSS is challenging,minimally invasive surgery(MIS)may be promising.Percutaneous full spinal endoscopic surgery(PSE),which developed from percutaneous endoscopic lumbar discectomy(PELD),is the most promising MIS in spine surgeries.Using the transforaminal or interlaminar approaches,PSE could complete nervous decompression for the treatment of the ventral or dorsal lesions,and has been used to treat various types of lumbar disc herniation,lumbar spinal stenosis,and cervical radiculopathy,showing good clinical results and the high safety.Therefore,it is feasible and promising to investigate the application of PSE in the treatment of TSS.Purpose:1.To investigate the application of percutaneous full endoscopic posterior decompression(PEPD)for the treatment of thoracic OLF,summarize the technical note and the indications.2.To evaluate the surgical results and analyze the prognostic factors of PEPD through a retrospective series cases follow-up study;to improve the surgical techniques of PEPD by the visual trepan.3.To compare the surgical results between PEPD and the traditional posterior open laminectomy for the treatment of thoracic OLF through a retrospective case-control study.4.To investigate the application of percutaneous full endoscopic circumferential decompression(PECD)for the treatment of thoracic OPLL,and summarize the technical note.Methods:1.A total of 18 patients with thoracic OLF were collected retrospectively from April2016 to April 2017.All patients had single-segment OLF which were classified as non-fusion types in axial CT,and had no "track sign" or "comma sign" which predicted dural ossification(DO).PEPD were performed under local anesthesia,and guided by the technologies consist of the posterior interlaminar approach,“over-the-top”,and the "partial floating method".Pre-and postoperative imaging were compared to evaluate the decompression results.Pre-and postoperative neurological statuses were evaluated using the modified Japanese Orthopedic Association(m JOA)score,recovery rate(RR)calculated from m JOA score,Frankel grade,and American Spinal Injury Association(ASIA)sensory and motor score.Surgical complications were recorded during the follow up.2.A total of 30 patients with thoracic OLF treated by PEPD from April 2016 to January 2018 were collected retrospectively.Clinical data were collected from the medical and operative records.The surgical results were assessed by the RR calculated from m JOA score.Correlations between the RR and various factors were analyzed.The specially designed visual trepan was used to complete laminotomy in PEPD,and the surgical data between blind trepan and visual trepan were compared.3.A total of 55 patients with thoracic OLF were collected retrospectively from April2016 to October 2018.All patients had single-segment OLF which were classified as non-fusion types in axial CT,and had no signs predicting DO.Patients were divided into two groups according to the surgical method: the PEPD group(n=36),and the posterior open laminectomy group(n=19).Baseline data,imaging data,surgical data,pre-and postoperative m JOA scores,pre-and postoperative Frankel grades,the RR calculated from m JOA score,and the complication rates were assessed and compared between the two groups.4.2 patients with thoracic OPLL were collected retrospectively from April 2019 to September 2019.Both of them had focal lesions(≤ 2 levels),the non-continuous cylindrical type and big local ossification angle(LOA > 20°)according to sagittal CT images.One-stage unilateral PECD or two-stage bilateral PECD were performed under local anesthesia,and guided by the technologies consist of the transforaminal approach,foramino-laminaplasty,“box-shaped” resection,and the “Cave-in” technique.Pre-and postoperative imaging were compared to evaluate the decompression results.Pre-and postoperative neurological statuses were evaluated using m JOA,the RR calculated from m JOA score,and Frankel grade.Surgical complications were recorded during the follow up.Results:1.The average operation time of PEPD for the treatment of single-segment thoracic OLF was 172.2±30.4 min,the average estimated blood loss(EBL)was 36.4±7.6 ml,and the average hospital stay was 5.1 ± 2.1 days.Postoperative images showed that decompression was completed,and a dome-shaped laminotomy was performed through limited laminectomy and flavectomy.The average score of ASIA sensory and motor,m JOA,as well as the Frankel grade improved significantly after PEPD at an average follow-up of 17.4 months(P<0.001).The average RR was 48.4%.Dural tears occurred in2 patients without other complications.2.Among the 30 patients included,17 were males and 13 were females.The average age was 60.4±10.0 years,and the average duration of preoperative symptoms was 17.4±12.3 months.16 patients(53.3%)had a high intramedullary signal on T2-weighted MRI(T2HIS).Patients’ neurological status improved from a preoperative m JOA score of 6.0±1.3 to a postoperative m JOA score of 8.5±2.0(P<0.001)at an average follow-up of 21.3months.The average RR was 53.8%.Dural tears were the only observed complication,yielding an incidence of 6.7%(2/30).Multiple linear regression analysis showed that a longer duration of preoperative symptoms and the presence of T2 HIS were significantly associated with poor surgical results.The operation time and the number of intraoperative fluoroscopy in the modified PEPD using visual trepan are significantly less than the PEPD using blind trepan(P <0.001)3.36 OLF patients of PEPD group had an average RR of 54.6% at an average follow-up of 29.3 months.19 OLF patients of the laminectomy group had an average RR of 47.7% at an average follow-up of 21.8 months.There were no statistical differences between the two groups in terms of baseline data,imaging data,pre-and postoperative Frankel grade,pre-and postoperative m JOA score,and RR calculated from m JOA score(P> 0.05).The operation time of PEPD was longer than laminectomy(P<0.001),while the EBL,postoperative bed stay,hospital stay,and medical costs were less than laminectomy(P<0.001).2 patients had dural tears after PEPD,yielding a complication rate of 5.6%.After laminectomy,3 patients had dural tears,2 had cerebrospinal fluid leak,and 2 had transient neurological deterioration after surgery.The complication rate was 36.8% in laminectomy group,which was significantly higher than PEPD(P <0.01).4.Patient with single-segment lesions(T11-12)underwent one-stage unilateral PECD.The operation time was 110 minutes,and the EBL was 80 ml.The patient was in bed for only 1 day and discharged on the 4th day after PECD.Postoperative images showed that decompression was completed,and a unilateral culvert osteotomy was performed through the limited laminectomy,flavectomy and corpectomy.Patient’s neurological status improved from a preoperative Frankel C to a postoperative Frankel D,and the m JOA score from 5 to 9,yielding a RR of 66.7% at an follow-up of 8 months.Patients with two-segment lesions(T7-9)underwent two-stage bilateral PECD.The operation time were160 min and 150 min,and the EBL were 110 ml and 100 ml,respectively.Postoperative images showed that bilateral decompression was completed through the bilateral culvert osteotomy.Patients’ neurological status improved from a preoperative m JOA score of 6 to a postoperative m JOA score of 10,yielding a RR of 80.0% at an follow-up of 3 months.No perioperative complications occurred in either patient.Conclusions:1.PSE could perform surgical decompression under local anesthesia for the treatment of TSS caused by dorsal lesions.PEPD is safe and effective to treat single-segment thoracic OLF patients with non-fusion type and no signs of DO.2.The duration of preoperative symptoms and T2 HIS are independent prognostic factors of PEPD for thoracic OLF.The use of visual trepan could improve the efficiency of PEPD and reduce the intraoperative radiation exposure.3.When under the strict indications,PEPD could achieve the same surgical results as the posterior open laminectomy for thoracic OLF,and has the lower complication rates,the lower EBL,the shorter postoperative bed stay,the shorter hospital stay,and the less medical costs.4.PSE could perform surgical decompression under local anesthesia for the treatment of TSS caused by ventral lesions.PECD is feasible to treat middle-or lower-thoracic OPLL patients who have focal lesions(2 ≤ segments),non-continuous cylindrical type and big LOA(>20°).However,larger and longer follow-up studies are needed to further evaluate the surgical results and safety of PECD.