Objective To discuss the surgical treatment of thoracic ligamentum flavum ossificum and combined epidural adhesions, especially the management strategy of thoracic ligamentum flavum ossificum with posterior longitudinal ligament ossification, thoracic lordosis and combined epidural sac adhesions, optimize the selection method of responsible segment and observe the effect of surgical treatment. Methods The data of 78 patients with ossification of the thoracic ligamentum flavum treated by hemiarthrosis laminectomy in our hospital between January 2003 and December 2009 were reviewed. For patients with multisegmental and jumping ligamentum flavum ossification, the responsible segment was determined according to the degree of imaging compression, combined with clinical symptoms and signs; for multisegmental ligamentum flavum ossification combined with posterior longitudinal ligament ossification or thoracic kyphosis (>500), multisegmental internal arch fixation and correction of kyphosis were performed; for patients with combined dural sac adhesions, the dural sac on the caudal side of the adhesions was incised to release some cerebrospinal fluid, causing arachnoid In patients with combined dural sac adhesions, the dural sac on the caudal side was dissected to release some of the cerebrospinal fluid, resulting in separation of the arachnoid membrane from the dura mater, and the ossified or adherent dura mater was removed to preserve the integrity of the arachnoid membrane. The JOA score, Nurick classification and neurological recovery rate were used to evaluate the surgical efficacy before and after surgery. Results Fifty-three of 78 patients received more than six months of follow-up, with a follow-up rate of 67.9% and a mean follow-up time of 18 months (6 months-6 years). The mean preoperative JOA score was 4.3 and the postoperative score was 8.3 (5-11), with statistically significant differences (p<0.05). Postoperative neurological recovery rate: 18 cases were excellent, 20 cases were good, 10 cases were acceptable, and 5 cases were poor, with an excellent rate of 71.7% and a mean recovery rate of 65.8% (11-80%); the mean preoperative Nurick grade was 3.7 (grade 2-5), and the postoperative improvement was 2.3; the mean recovery rate of the 21 patients with high signal on MRI T2 image was 55.6%, which was lower than the mean recovery rate of this group of patients . Conclusion The hemiarthrosis laminectomy for thoracic ligamentous ossification is a safe and effective surgical method, and the simultaneous arch root fixation for posterior convexity correction in patients with posterior longitudinal ligament ossification or posterior convexity deformity helps the recovery of neurological function; dural resection after arachnoid atrophy can safely deal with the adhesions of the dural sac; according to the symptoms and signs, combined with CT and MRI examination results, the responsible segment is determined, which helps reduce the incidence of trauma and complications. Thoracic spinal stenosis is a common condition in spinal surgery, and ossification of the ligamentum flavum (OLF) is the most common cause of thoracic spinal stenosis [1], and surgical decompression is the only effective treatment for thoracic spinal cord compression due to OLF [2]. The unique pathological and anatomical structure of thoracic OLF leads to difficult surgery with higher risks and higher complication rates, especially when multisegmental OLF, or with ossification of the posterior longitudinal ligament, thoracic kyphosis and epidural adhesions, is more difficult to manage. In this paper, we report the use of hemiarthrosis laminectomy for the treatment of thoracic ligamentous ossification between January 2003 and December 2009 to address these difficulties in surgical treatment and to observe its surgical results. Data and methods I. General data This group included 78 patients with OLF of the thoracic spine diagnosed and treated surgically between January 2003 and December 2009. All patients were clearly diagnosed by medical history, physical examination, X-ray plain film, MRI combined with CT or CTM, and finally confirmed by surgery or pathology. A total of 53 patients were followed up for more than six months, with a follow-up rate of 67.9%. Among the 53 cases, there were 32 males and 21 females, aged 43-73 years, average 54.7 years, with the number of ossified ligamentum flavum segments ranging from 1 to 8, average 3.5, limited to the middle and upper thoracic vertebrae in 18 cases and involving the thoracolumbar segment in 35 cases. The main symptoms were slowly progressive numbness and weakness of both lower extremities, leading to difficulty in walking. Among them, 32 cases complained of numbness and weakness of lower extremities, 27 cases had difficulty walking, 21 cases had thoracic and back binding sensation, 19 cases had low back pain, 17 cases had urinary and bowel dysfunction, and 12 cases had intermittent claudication. Almost all patients had hypotonia and sensory disturbances below the plane of compression, 34 cases had typical signs of upper motor neuron paresis, increased muscle tone in both lower limbs, active reflexes, and positive pathological signs. joa score 1-9, mean 4.3. II. Imaging: According to their imaging typing [1], 9 cases (17.0%) were focal, 25 cases (47.2%) were continuous, and 19 cases (35.8%) were jumping type. According to the classification of segments involved in ossification of the ligamentum flavum, there were 9 cases of single segment, 10 cases of 2 segments, 13 cases of 3 segments, 11 cases of 4 segments, 7 cases of 6 segments, 3 cases of 8 segments, and the most frequent segment was T10-11 (21 cases). 16 cases were combined with spinal cervical spondylosis or ossification of the posterior longitudinal ligament of the cervical spine (Ossification of the Posterior Longitudinal Ligament (OPLL), 14 cases combined with thoracic OPLL, and 8 cases combined with thoracic disc herniation. Lateral radiographs revealed a high-density shadow from the vertebral plate and articular eminence within the intervertebral foramen in 36 cases, and the posterior convexity angle of the thoracic spine was >500 in 8 cases; CT scans showed unilateral ossification in 18 cases and bilateral ossification in 35 cases; sagittal MRI showed T2 image high signal in the spinal cord of the compressed segment in 21 cases, and their JOA score was 3.5 on average. In the 14 patients with combined OPLL of the thoracic spine, among which 8 patients with OPLL of multiple segments causing anterior compression at the same time, multi-segmental internal arch fixation was performed to reduce the thoracic spine with the help of fixation. Among the 8 patients with multi-segment OPLL causing simultaneous anterior compression, multi-segment internal fixation was performed to reduce the physiological kyphosis of the thoracic spine with the help of fixation to indirectly relieve the anterior compression; among the 8 patients with thoracic kyphosis >500, multi-segment arch root fixation was performed in 5 cases to correct the kyphotic deformity and reduce the tension on the spinal cord with the help of anterior spinal space opening; in 6 cases with combined single-segment OPLL and 8 cases with thoracic disc herniation, lateral anterior decompression of this single-segment was performed; in 34 patients with combined dural sac adhesions, 10 cases were sharply peeled off and thinning and floating [4]12 Among the 16 patients with combined spinal cervical spondylosis or cervical OPLL, 6 cases underwent posterior cervical enlarged hemivertebral decompression in the first stage, 6 cases underwent posterior cervical enlarged hemivertebral decompression in the second stage, and 4 cases did not undergo 4 cases were not treated surgically. 2. Surgical technique: local anesthesia was chosen in the early cases, and general anesthesia was chosen in the later cases, with intraoperative somatosensory evoked potential monitoring. The patient was positioned prone, with a posterior median incision, and after revealing the accurate positioning by C-arm, the resection was started from the lower end of the stenotic segment, and in the mid-axis of the articular eminence on both sides, the groove was opened in the bilateral articular eminence with a pneumatic mill (shown in Figure 1), with a groove width of 3-4 mm, and the drill bit could be slightly tilted to the midline to reach the lateral side of the dura, not to the lateral person, so as not to enter the vertebral arch root, and the bone grooves on both sides were opened through to the spinal canal, and the cephalocaudal lateral ligament was transected, and the whole The bone plate including the medial half of both sides of the articular eminence with the whole plate, fixed lifting the whole plate, nerve stripping subvertebral plate under the separation of the dural sac, removal of the whole plate. When adhesions between the vertebral plate and the dural sac are found, methods such as sharp stripping and thinning and floating should be used, but when the adhesions are large or when there is ossification of the dural sac, the dural sac and the arachnoid membrane should be incised at the dural sac far from the side of the adhesions, about 1 cm in size, and some of the cerebrospinal fluid should be released, and the arachnoid membrane should then be atrophied, the adhesions or ossified dura should be removed, and care should be taken to protect the arachnoid membrane from breaking, and the caudal dural sac incision should be closed with continuous locking sutures. When correction of kyphosis is required: multi-segmental thoracic pedicle screws are implanted across the segments, and after performing a whole hemiarthrosis laminectomy, it is still necessary to remove part of the synovial process, operating similarly to the Smith-Peterson osteotomy [5], in order to facilitate closure of the posterior attachments and propping up of the anterior intervertebral space, thus partially correcting the kyphosis in order to correct the tension of the spinal cord and release the anterior compression. Fourth, assessment and statistical methods: preoperative and postoperative symptoms of thoracic spinal cord compression were assessed by JOA score and Nurick’s walking dysfunction classification. 11 was used to score JOA as normal, and the degree of postoperative neurological recovery was assessed by the postoperative recovery rate calculated by JOA score [6]: recovery rate = (postoperative JOA score – preoperative JOA score) / (11 – preoperative JOA score) × 100%. Nurick’s ambulatory dysfunction was graded by [7]: grade 1, walking and work unimpeded; grade 2, abnormal gait but does not affect work; grade 3, abnormal gait unable to work; grade 4, walking with the help of aids only; grade 5, wheelchair dependent or bedridden with paralysis. Stata 8.0 statistical software was applied for data analysis, and the preoperative and postoperative JOA scores were compared by paired t-test with a check level of α of 0.05. Results The surgeries were successfully completed, and the mean follow-up time after surgery was 18 months (6 months-6 years). 29 cases had decompression segments involving the thoracolumbar segment (T10-L2), and the number of operated segments ranged from 1 to 8, with a mean of 4.2; 5 cases had cerebrospinal fluid leakage, and all were cured by One case of delayed healing due to fat liquefaction of the incision; one case of increased neurological symptoms, probably related to surgical stimulation, was treated with neuroprotective drugs and recovered in 3 months after surgery, and the remaining cases had different degrees of improvement in walking difficulties and numbness and weakness of the lower extremities; two cases of postoperative recurrence, one case of stenosis of the adjacent segment after decompression and a second operation to extend the decompression range, and one case of posterior convexity deformity of the thoracic spine, which was later treated with One case was caused by thoracic kyphosis, and the posterior correction of the kyphotic deformity was performed later (Figure 2). The mean preoperative JOA score was 4.3 and the postoperative score was 8.3 (5-11), and the difference was statistically significant (p<0.05). Postoperative neurological recovery rate: 18 cases were excellent, 20 cases were good, 10 cases were acceptable, and 5 cases were poor, with an excellent rate of 71.7% and a mean recovery rate of 65.8% (11-80%); the mean preoperative Nurick grade was 3.7 (grades 2-5), and the postoperative improvement was 2.3; 21 patients with high signal on MRI T2 image had a mean recovery rate of 55.6%, which was lower than the mean recovery rate of this group of patients The average reduction in thoracic kyphosis was about 160 (10-250) in 13 patients who had thoracic kyphosis correction, and the average neurological recovery rate was 63.7%. The pathogenesis of thoracic spinal stenosis due to thoracic OLF is not clear, and its clinical manifestations are complex and atypical. The combination of cervical OPLL, spinal cord cervical spondylosis, thoracic OPLL, thoracic kyphosis, and epidural adhesions often leads to delayed diagnosis, treatment difficulties, and many complications, thus affecting the effectiveness of its surgical treatment. I. Key points in the diagnosis of thoracic OLF The diagnosis of thoracic OLF is not difficult, but attention should be paid to clarifying the segment and site of ossification, determining the source of spinal cord compression (ligamentum flavum, intervertebral disc, articular eminence, etc.), observing the degree of spinal cord compression (changes in signal within the spinal cord), and clarifying whether it is combined with spinal cervical spondylosis, cervical OPLL, thoracic OPLL, diffuse idiopathic hypertrophy of bone (DISH), etc., in order to better determine the surgical treatment plan. to better determine the surgical treatment plan. Since OLF of the thoracic spine often has a multisegmental onset and not all segments require surgical management, how to determine the operative segment becomes the key to ensuring surgical results, reducing surgical trauma, and minimizing surgical complications. The establishment of the responsible segment relies on clinical symptoms and signs, and is compared with the patient's X-ray, CT and MRI imaging findings. We believe that the most important objective basis for determining the responsible segment is the sensory plane and motor plane, which means that which segment has symptoms and signs is the responsible segment. Liu Ning et al [8] showed that the degree of thoracic OLF spinal canal encroachment correlated with the degree of nerve damage, and we also applied the residual rate of spinal canal area as an aid to determine the responsible segment. In this study, we found that the group of patients with high signal in the spinal cord on MRI T2 images had higher preoperative JOA scores and lower recovery rates, and the change in high signal may reflect the degree of spinal cord compression, so it was used as an imaging basis for determining the responsible segment. For multi-segment OLF of the thoracic spine, when compression is present in both the upper and lower thoracic segments, and the clinical manifestations are symptoms of the lower thoracic segment, surgical treatment of the lower thoracic segment should be performed; however, when there are clinical manifestations of compression in the upper thoracic segment, and there are symptoms and signs of aggravation in the lower thoracic segment or imaging shows severe spinal cord compression, proximal decompression can be performed first, and the residual symptoms and recovery can be observed and second-stage surgical treatment can be performed. Second, the surgical treatment of thoracic OLF The decompression of thoracic OLF should choose hemiarthrosis laminectomy, which is determined by the pathological and anatomical characteristics of thoracic OLF. Pathological changes of thoracic OLF include thickening of the laminae of the thoracic spine, hyperplasia and coalescence of the articular processes, especially the hyperplasia of the superior articular processes into the vertebral canal, which compresses the lateral and posterior aspects of the spinal cord. The ossified ligamentum flavum and the vertebral plate often fuse into a whole bone plate, resulting in thickening of the vertebral plate, much sclerosis of the bone, loss of the epidural space, and thickening or even ossification of the dura mater to form a fasciculus restraining the spinal cord. In this group of cases, the decompression was chosen to remove the entire hemiarthrosis lamina. Compared with the traditional total laminectomy decompression, this decompression avoids the invasive decompression of the spinal canal at both sides of the groove and reaches the lateral side of the spinal cord, reducing the stimulation of the spinal cord by the positive posterior decompression, reducing the damage to the blood flow of the spinal cord, and effectively reducing the intraoperative medically induced injury. The resection of the medial hemiarthrosis can achieve complete decompression while preserving the stability of the spine. In this group of cases, no internal fixation was used except for patients with OLF of the thoracolumbar segment and combined OPLL, posterior convexity deformity, thoracic disc herniation and other anterior compressions requiring correction of thoracic lordosis and lateral anterior decompression. 1, with the management strategy of comorbidities Thoracic OLF combined with thoracic lordosis and continuous long segment OPLL and other anterior compression factors, the anterior surgery is traumatic and risky, and individual patients with continuous OPLL cannot be decompressed by the anterior surgery, for these patients we choose the posterior surgery treatment, while performing hemiarthrosis laminectomy, perform multi-segment pedicle screw fixation, remove part of the In these patients, we chose posterior surgery to reduce the pressure from the anterior side and the tension of the spinal cord by removing part of the articular process and correcting part of the thoracic kyphosis with the help of the closure of the posterior structures and the opening of the anterior intervertebral space, thus indirectly relieving the compression of the ventral side of the spinal cord. A total of 13 cases in this group underwent correction of thoracic kyphosis, and the average reduction of thoracic kyphosis was about 160 (10-250), with an average neurological recovery rate of 63.7% and no increase in neurological dysfunction. We believe that the loss of cerebrospinal fluid signal in the anterior spinal cord in the sagittal or axial position caused by thoracic kyphosis is an indication for correction of thoracic kyphosis, and for the anterior compression of the spinal cord caused by combined multisegmental OPLL, the hemiarthrosis laminectomy alone cannot achieve anterior decompression, and it is likely to cause thoracic kyphosis and aggravate anterior compression, so it is also one of the indications for correction of kyphosis by internal fixation of the pedicle. When combined with single-segment OPLL and thoracic disc herniation, after posterior decompression, lateral access to the spinal cord from the side with heavier compression is performed to remove the anterior OPLL and herniated disc, and unilateral synovectomy is required for internal fixation of the arch. 2, management strategy of epidural adhesions Epidural adhesions are very common in patients with thoracic OLF, with 34 cases (64.2%) in our group, and their preoperative diagnosis is difficult and often found intraoperatively, and improper management can easily cause spinal cord medical injury and cerebrospinal fluid leakage [9], and even subarachnoid infection. Intraoperative awareness of epidural adhesions should be sufficient, especially when lifting the whole bone plate should be careful and careful, pay attention to the changes of the dural sac, if the dural sac appears to be pulled or there is elastic resistance of the nerve stripper, the possibility of epidural adhesions should be considered, and it is important not to forcibly peel off. When epidural adhesions are found, the scope of epidural adhesions should be carefully explored, first try to perform blunt stripping, if it is difficult, sharp stripping should be abandoned and feasible, because some epidural adhesions are often serious or even part of the dura is ossified together with the ligamentum flavum, and sharp stripping is prone to dural tearing or cerebrospinal fluid leakage. In this group of cases, for the 12 patients with difficulty in sharp stripping, large bone masses with tight dural adhesions and difficulties in floating methods, a small opening can be made in the caudal dural sac to release part of the cerebrospinal fluid, causing atrophy of the arachnoid membrane, facilitating the separation of the arachnoid membrane and dura mater, and then part of the dura mater can be excised, preserving the integrity of the arachnoid membrane as much as possible during excision, followed by continuous locked-edge sutures of the caudal opening and covered with gelatin The sponge or bioprotein glue was used to reduce the incidence of cerebrospinal fluid leakage by reducing the irritation to the neural structures. Only 5 of the 53 patients in this group had cerebrospinal fluid leakage, and all of them healed with conservative treatment. In conclusion, the treatment of OLF in the thoracic spine should be individualized by assessing the patient's symptoms, signs and imaging examinations, analyzing and identifying the responsible segment in a comprehensive manner, selecting the most appropriate treatment method according to the combined pathological changes, reducing surgical trauma, minimizing surgical complications and promoting the recovery of neurological function.