Zoning Laminectomy For The Treatment Of Severe Thoracic Spinal Stenosis Caused By Ossification Of The Ligamentum Flavum

Background:Laminectomy is currently the most commonly used surgical method for the treatment of thoracic stenosis,but it still has disadvantages such as a high risk of nerve and dura mater injury,especially for patients with severe thoracic stenosis.Therefore,how to perform spinal decompression more safely and effectively to reduce the occurrence of spinal cord injury is the focus and difficulty that clinicians need to face in the operation of thoracic spinal stenosis.In this study,zoning laminectomy was used to treat severe thoracic spinal stenosis caused by ossification of the ligamentum flavum based on the anatomical characteristic of the ligament flavum and the pathological process of ossification.This technique determines the safe and dangerous area of the lamina,and further guides the decompression process by clarifying the safe resection range of the lamina,thus reducing the risk of intraoperative spinal cord and nerve injury.Objective:To discuss the safety and clinical effect of zoning laminectomy for severe thoracic ossification of ligamentum flavum.Methods:A retrospective analysis was performed on the clinical data of 47 patients with severe thoracic ossification of ligamentum flavum treated by zonal laminectomy in Zheng zhou Orthopaedics Hospital from September 2016 to August 2020.General information such as age,sex,course of the disease,and lesion level was recorded for all patients,as well as surgical data such as decompression level,operation time,hospital stay,blood loss,and postoperative complications.According to the anatomical and pathological characteristics of ligamentum flavum,the diseased segment was divided into different specific regions.Firstly,the head and tail laminas of the "first safety zone" were resected,and then detected the size of the ossification of ligamentum flavum and the boundary of the dura mater.Subsequently,the " transition zone " was excised and the inner edge of the "second safety zone" was explored and determined.Finally,complete dissociation and resection of the "danger zone".The laminectomy was performed in different regions and stages to achieve the goal of decompression.The Japanese Orthopedic Association(JOA)Score and Nurick grading were used to evaluate the preoperative and postoperative neurological function,and the overall JOA improvement rate was calculated to evaluate clinical outcomes.Results:All patients were followed up,and the time is(10-47)months,an average(27.5±8.5)months.In addition,the operation time was(102-341)minutes,with a mean of(164.5±59.8)minutes.Blood loss was(300-850)ml,with an average of(478.5±133.0)ml;The hospital stay was(5-11)days,mean(8.1±1.6)days.At the last follow-up,the sphincter function of all patients returned to normal,and the pain symptoms of the back or lower limbs were relieved to varying degrees.The symptoms of thoracic spinal myelopathy were not significantly improved in only 2 patients,while the symptoms of lower limb weakness and paresthesia were significantly improved in the remaining patients compared with before surgery.The patient’s JOA score increased from(4.7±1.3)before surgery to(7.0±1.1)at the 3 months after surgery and(9.0±1.1)at the last follow-up.The comparison of the JOA score at the three-time points before surgery,3 months after surgery,and the last follow-up were statistically significant(P<0.001).The average improvement rate of JOA at the last follow-up was(69.8±15.3)%,including excellent in 18 cases,good in 19 cases,fair in 10 cases,and poor in 0 cases.Nurick grade was improved by 1 grade in 6 cases,2 grades in 22 cases,3 grades in 16 cases,4grades in 1 case,and no improvement in 2 cases.Complications included dural defect in 12 cases(25.5%),cerebrospinal fluid leakage in 10 cases(21.3%),wound infection in 1 case(2.1%),and epidural hematoma in 1 case(2.1%).During the follow-up,there was no neurological deterioration and kyphosis.Conclusion:Zoning laminectomy determined the safe range of lamina,and emphasized that the decompression process was performed from the "safe zone" to the "dangerous zone".This method reduced intraoperative interference to the spinal cord and thus reduced the risk of spinal cord and nerve injury due to manipulation.Therefore,it is a safe and effective surgical method to choose.