Objective: To evaluate the efficacy and safety of Smith-Petersen osteotomy (SPO) assisted by releasing disk space from posterior approach for thoracolumbar kyphosis. Methods: A review was conducted on 8 patients (3 males and 5 females) with thoracolumbar kyphosis were treated with SPO assisted by releasing disk space from posterior approach at Department of Orthopaedics, Peking University Third Hospital from June 2016 to September 2017. The age was 56.5 years (range:18-71 years). There were 3 cases of Scheuermanns kyphosis, 2 cases of degenerative kyphosis, 1 case of proximal junctional kyphosis (PJK) after lumbar surgery, and 2 cases of kyphosis after thoracolumbar laminectomy. The paired t test was used for statistical analysis in thoracolumbar kyphosis angle, osteotomy segment kyphosis angle, sagittal vertical value (SVA), visual analogue score (VAS), Oswestry dysfunction index (ODI) before and after surgery. Statistical difference was confirmed with P<0.05. Results: Osteotomy level included 2 cases in T_11-12, 3 cases in T₁₂-L₁, 3 cases in L_1-2. The average operation time was 339 min (range: 247-416 min), bleeding volume was 1 275 ml (range: 500-2 500 ml). The mean follow-up time was 16.5 months (range: 12-24 months). The average thoracolumbar kyphosis angle was 59.9° (range: 40°-73°) pre-operation, 9.5°(range:-5.1°-20°) post-operation and 13.5°(range:-1.3°-28°) at the latest follow-up. It made an average correction with 46.4°and corrective rate with 78.0%. The osteotomy segment kyphosis angle was 37.9° (range: 26°-46°) pre-operation, -1.3° (range:-11°-13°) post-operation making an 39.2° open-up angle, and 2.0° (range:-13.5°-13°) at the latest follow-up. Lumbar lordosis was 47.5° (range: 2°-76°) pre-operation, 41.2°(range:15°-62°) post-operation and 36.9°(range:15°-58°) at the latest follow-up. SVA was 54 mm(range:-34 mm-149 mm) pre-operation and 39 mm(range:-3 mm-119 mm) at the latest follow-up. VAS score of low back pain was 6.3(range:0-9) pre-operation and 3.0(range:0-6) at the latest follow-up. ODI score was 21.9(range: 0-42) pre-operation and 11.0(range: 0-26) at latest follow-up. Comparing to pre-operation value, there were statistical difference in the thoracolumbar kyphosis angle(t= 8.547, P=0.000), osteotomy segment kyphosis angle(t=9.739, P=0.000), VAS(t=3.077, P=0.018), ODI(t=5.800, P=0.001) at the latest follow-up. There was no neuropathic complication in all patients. Cerebrospinal fluid leakage occurred in 2 cases with spinal surgery history, and recovered after symptomatic treatment. Conclusions SPO assisted by releasing disk space from posterior approach could safely achieve effective correction of rigid thoracolumbar kyphosis deformity within 40°.

Objectives:To investigate the risk factors of cage retropulsion(CR)after posterior lumbar inter-body fusion(PLIF).Methods:Retrospective analysis was made on 17 patients(13 males and 4 females,with an average age of 63.7±9.9 years)who underwent revision surgery due to CR after PLIF in our hospital from September 2017 to September 2021.And the patients were included into the CR group.Another 34 patients without CR were matched in a ratio of 2∶1 according to the same fusion and fixation segments,time of initial surgery(±1 year),gender,and age(±2 years),including 26 males and 8 females,with an average age of 65.2±10.2 years.They were included in the control group.In the CR group,the average number of fixed segments was 1.8±0.8,and the average number of fused segments was 1.5±0.6;The time of CR was 7(0.75-132)months after the first operation;15 patients had single segmental CR and 2 patients had two segmental CR.The lumbar lordosis(LL),pelvic tilt(PT),sacral slope(SS),and pelvic incidence(PI)were measured on full-spine X-ray before operation of the two groups of patients,the disc height(DH)of the diseased segment was mea-sured on lateral lumbar X-ray,and the intervertebral range of motion(ROM)was measured on flexion-exten-sion X-ray.The CT value of lumbar vertebrae was measured in CT examination before operation;The shape of disc was defined through MRI examination.The cage position was measured on X-ray immediately after operation(The ratio of the distance between the marker line of the posterior margin of the cage and the pos-terior upper margin of the lower vertebral body to the length of the upper endplate of the lower vertebra).The paired sample t-test was used for single factor analysis to analyze the data of the two groups,after which,the parameters with statistical significance were analyzed with logistic regression to determine the inde-pendent risk factors of CR.Results:The mean vertebral CT value in the CR group was lower than that in the control group(124.8±39.7 vs 147.7±38.2,P=0.011);The cage position in the CR group was more posterior than that in the control group(0.15±0.09 vs 0.31±0.07,P＜0.001).There was no significant difference between the two groups in LL(40.8°±12.9° vs 42.4°±7.5°,P=0.717),PT(19.6°±7.1° vs 17.1°±6.7°,P=0.356),SS(27.7°±6.5° vs 31.0°±4.3°,P=0.144),PI(44.3°±13.8° vs 44.7°±13.9°,P=0.926),DH(10.1±2.4mm vs 8.8±1.4mm,P=0.066),ROM(4.3°±2.8° vs 4.4°±2.2°,P=0.950),and Pear-shaped intervertebral discs(33.3％vs 21.4％,P=0.40).Logistic regression analysis showed that low vertebral CT value(osteoporosis)(OR=0.975,P=0.043)and cage po-sition(OR=28.393,P=0.003)were the independent risk factors.Conclusions:Osteoporosis and posterior placement of cage are the risk factors for CR after PLIF.

Objective To investigate the safety and effectiveness of posterior approach laminectomy combined with localized resection of ossified posterior longitudinal ligament and dekyphosis for multilevel ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine.Methods Thirty-one cases of thoracic multilevel OPLL was treated with this new technique between August of 2012 and August of 2016.Twenty-nine among the 31 cases were successfully followed up more than two years.Among these 29 cases,9 were male and the other 20 were female,with an average age of 48.5±7.1 years.The average segment number of OPLLwas 6.5±2.2 (range,3-11).The average segment number of laminectomy was 7.9±2.5 (range,4-13).There were 26 cases combined with ossification of the ligamentum flavum (OLF).Posterior approach laminectomy combined with localized resection of OPLL and dekyphosis for multilevel OPLL in the thoracic spine was applied to all cases.Firstly,en-bloc laminectomy was performed to all the segments of OPLL.Then the nearest segment of ossification to the kyphotic apex and the most stenotie level was selected and limitedly resected.Finally,wedge-shaped osteotomy was conducted to decrease the kyphosis.The outcomes including recovery rate of myelopathy and the radiological changes were recorded during the post-operative follow-up.Single group pre and post analysis was conducted by using paired t-test.Results Twenty-seven cases underwent one-level circumferential decompression,and the other two case underwent two-level localized resection of the ossified posterior longitudinal ligament.The average operation time was 245.2±75.1 min (range,131-423 min).The average blood loss was 1 307.9±1 457.7 ml(range,300-6 000 ml).The average follow-up time was 40.2± 14.9 months (range,25-69 months).The kyphotic angle of the stenotic segments decreased 11.4°±3.5° averagely after the surgery,from pre-operative 28.7°±9.6° to post-operative 17.3°±8.6°.The decreased kyphotic angle was 7.4°±3.1 ° at the final follow-up with an average kyphotic angel of 22.3°± 10.3°.The average length of the resected ossified posterior longitudinal ligament was 11.3±3.9 mm,and the average shortening length of the spinal column was 5.0±3.0 mm (range,0.4-13.8 mm).The pre-operative Japanese Orthopedic Association (JOA) score was 4.3±2.2 averagely (range,1-9),and the final JOA score increased to 9.3±2.3 (rang,3-11).The average recover rate was 85.7％ (range,-100％ to 100％),and the rate of excellent or good was 89.7％.Among the 29 cases,6 cases occurred post-operative transient deterioration and regained a satisfactory recovery eventually;one case occurred post-operative paraplegia and never recovered;19 cases occurred post-operative cerebrospinal fluid leakage and healed under conservative treatment.Conclusion For the thoracic multilevel OPLL,one-stage posterior approach laminectomy combined with localized resection of the ossified posterior longitudinal ligament and dekyphosis can significantly improve the outcomes of the myelopathy with low rate of post-operative paraplegia.Therefore,this new surgery technique is a safe and effective treatment for multilevel OPLL in thoracic spine.

Objective:To investigate the clinical efficacy of percutaneous kyphoplasty (PKP) assisted by intuitive visual navigation orthopaedic surgery robot in the treatment of osteoporotic vertebral compression fracture (OVCF).Methods:A retrospective analysis was conducted in Peking University Third Hospital from June 2021 to November 2022, 78 patients with OVCF were treated by the intuitive visual navigation orthopaedic surgery robot or freehand surgery with a "C" arm X-ray machine. According to the method of puncture, they were divided into robot group and freehand group. In the robot group, there were 36 cases, including 7 males and 29 females, aged 74.50±5.87 years, 32 cases of single vertebral fractures, 4 cases of double vertebral fractures, 1 case of T 8, 2 cases of T 10, 2 cases of T 11, 11 cases of T 12, 10 cases of L 1, 8 cases of L 2, 2 cases of L 3, 3 cases of L 4, and 1 case of L 5. Bone mineral density T value was -2.94±0.50; In the freehand group, there were 42 cases, including 9 males and 33 females, aged 72.86±8.84 years, 36 cases of single fracture and 6 cases of double fracture, 1 case of T 6, 2 cases of T 7, 3 cases of T 11, 9 cases of T 12, 8 cases of L 1, 9 cases of L 2, 5 cases of L 3, 6 cases of L 4, and 5 cases of L 5. Bone mineral density T value was -3.00±0.50. The effectiveness evaluation indexes of the two groups were compared, which included surgery duration, X-ray fluoroscopy times, hospitalization time, lumbar pain visual analogue scale (VAS), Oswestry disability index (ODI) and height of fractured anterior vertebrae (HFAV). Results:Both groups of patients successfully received surgical treatment. The mean operating time of the robot group was 33.44±2.50 min, which was significantly longer than that of the free hand group, which was 29.69±2.40 min ( t=6.491, P<0.001). Meanwhile, the intraoperative blood loss of the robot group was 3.54±0.89 ml, which was significantly less than that of the freehand group, which was 6.72±1.89 ml ( t=9.110, P<0.001). In terms of radiographic fluoroscopy times, the average of the robot group was 26.81±7.76 times, which was significantly less than the freehand group's 42.61±6.62 times ( t=9.294, P<0.001). The postoperative vertebral front edge height in the free hand group was 18.64±0.32 mm and in the robot group was 18.79±0.36 mm. The difference was not statistically significant ( t=2.673, P=0.067). All patients were followed up for 8.3±2.9 months (range, 6-13 months). The VAS scores of low back pain in the two groups at 1 day and 6 months after operation were significantly improved compared with those before operation ( P<0.05), and there was no significant difference between the two groups in VAS score after operation ( P>0.05). Six months after surgery, the ODI of the free hand group and the robot group were 11.67%±2.13% and 12.11%±2.33%, respectively. The ODI scores of the two groups were significantly lower at 6 months postoperative follow-up than that before surgery, and the postoperative follow-up at all had significant differences compared with that before surgery ( P<0.05), and there was no difference between the two groups in postoperative ODI scores ( P>0.05). No obvious bone cement leakage was found in all patients during operation. Conclusion:Compared with the traditional C-arm X-ray for PKP treatment of OVCF by free hand, intuitive visual navigation orthopedic robot can safely and effectively assist in the completion of the operation process, and has the advantages of less intraoperative blood loss, fewer fluoroscopy times.