Objective:To introduce a new TIANJI robot assisted targeted puncture technique, and discuss the feasibility and clinical effect of transforaminal percutaneous endoscopic lumbar discectomy (tPELD) using this technique.Methods:The first 14 consecutive cases of single level lumbar disc herniation who underwent robot assisted tPELD procedure were retrospectively analyzed. The mean age was 46.3±16.0 years old (ranged from 16-72). After data transferred from C-arm to robot system and automatic registration, surgeons made plans of the trajectory on robot system based on intraoperative 3-dimensional images of lumbar spine. Move robotic arm to planned position, guide an accurate puncture pathway and establish working cannula. 25 consecutive patients who underwent conventional C-arm assisted tPELD surgery during the same period of time were assessed as the controlled group. The mean age was 45.5±13.7 years old (ranged from 16-68). All patients were followed up for 12 months. Clinical effect was assessed by visual analogue scale (VAS), Oswestry disability index (ODI) and Modified Macnab criteria. Intraoperative parameters and surgery-related complications were recorded.Results:The baseline data of age, surgical level, types of herniation, preoperative VAS scores and ODI had no significant difference between two groups ( P>0.05). In robot group, one case was converted to open microdiscectomy during operation due to technical failure. The other thirteen cases had successful robot assisted tPELD surgeries and were assessed accordingly. The new technique had good clinical outcomes. The immediate post-operative VAS score 2.85±1.79 and the last follow-up VAS score 1.50±1.04 were both significantly decreased than that before surgery 7.62±0.92 ( F=69.747, P<0.01); the last follow-up ODI 18.89%±12.16% was significantly reduced from the pre-operative ODI 71.19%±12.12% ( t=15.430, P<0.01). Between two groups, the immediate post-operative VAS score ( t=0.568, P=0.574), the last follow-up VAS score ( t=0.713, P=0.481), and last follow-up ODI had no significant difference ( t=0.171, P=0.865). The excellent or good rate of modified Macnab criteria at the last follow-up was 92.30% in robot group, comparing to 84.0% in controlled group. The fluoroscopic times during surgery of robot group 8.8±5.5 was significantly lowered the in controlled group 21.3±8.3 ( P<0.01). One case in robot group and two cases in controlled group had recurrence during follow-up period (recurrence rate 7.7% vs. 8.3%). However, there was no significant complications such as nerve root injury, dura injury or increased intracranial pressure in both groups. Conclusion:This study confirmed the feasibility of this new technique. Preliminary results indicated that TIANJI robot could help to build an easy, accurate and safe procedure of tPELD surgery.

Objective:To explore the factors affecting changes of disc angle (ΔDA) during oblique lateral interbody fusion (OLIF) and establish a predictive model of ΔDA.Methods:This retrospective study included 119 patients with 174 segments undergoing OLIF procedures between July 2017 and August 2019 in Beijing Jishuitan Hospital. 45 males and 74 females with an average age of 62.1±9.8 years (33-86 years) were included. The lordotic cages were all 6 degrees. Radiographic parameters included preoperative and postoperative disc angle (DA), disc height (DH), ΔDA on flexion-extension views (ΔDA-FE), cage location and cage inclination. Pearson correlation coefficient and machine-learning techniques were utilized to identify factors related to ΔDA. Based on machine leaning techniques, ten-fold cross-validation for model training and validation were used to develop a predictive linear model for ΔDA.Results:The average ΔDA was 3.9°±4.8° with preoperative disc angle (preoperative DA) of 5.3°±5.0°. The average change of posterior DH (ΔPDH) was 3.1±2.1 mm with preoperative posterior DH of 6.6±1.9 mm. The average change of anterior DH was 6.1±3.2 mm. Pearson correlation analysis showed a significant negative correlation between ΔDA and preoperative DA ( r=-0.713, P<0.001), cage location ( r=-0.183, P=0.016), and ΔDA-FE ( r=-0.153, P=0.044). PDH changes were significantly negatively correlated with preoperative PDH ( r=-0.444, P<0.001) and positively correlated with cage location ( r=0.218, P=0.004). ΔDA was 10.8°±3.2° for negative preoperative DA (indicating kyphotic), 5.0°±3.7° for preoperative DA between 0° and 6°, and 1.0°±4.1° for preoperative DA>6°. A predictive model was developed using ten-fold cross-validation, resulting in the formula ΔDA=7.9°-0.8×preoperative DA ( R=0.707, MAE=2.837). Conclusion:Disc angle changes in OLIF primarily depend on the preoperative disc angle, secondly on cage location. The predicting model based on machine-learning techniques using preoperative disc angle facilitates preoperative planning for OLIF procedures.

Objective To compare the clinical outcomes between oblique lumbar interbody fusion(OLIF)and transforaminal lumbar interbody fusion(TLIF)for patients with degenerative spondylolisthesis during 2-year follow-ups.Methods Patients with symptomatic degenerative spondylolisthesis who underwent OLIF(46 cases)and TLIF(45 cases)between July 2017 and September 2020 with 2-year follow-ups were retrospectively reviewed.One level or two-level lumbar fusion were included.The primary outcomes were Visual Analogue Scale(VAS)and Oswestry Disability Index(ODI)at 2 years after surgery.The secondary outcomes included radiographic parameters,fusion rate,cage subsidence rate,and permanent nerve injury rate.Results No significantly different changes were noted in VAS-back[2(2,3)vs.2(2,2),P=0.943],VAS-leg[2(2,2)vs.2(2,2),P=0.988],and ODI[17％(10％,22％)vs.14％(10％,22％),P=0.417]between the OLIF group and the TLIF group,respectively.Greater restoration of disc height and segmental lordosis were obtained in the OLIF group[mean,(11.9±1.5)mm and 15.7°±7.2°]than in the TLIF group[mean,(9.2±2.0)mm and 12.5°±5.9°]at postoperative 2-year(P＜0.001 and P=0.029).The subsidence rate was lower in the OLIF group than in the TLIF group[19.6％(9/46)vs.40.0％(16/40),P=0.037].The fusion rates at postoperative 2-year were 93.5％(43/46)in the OLIF group and 87.5％(35/40)in the TLIF group,having no significant difference(P=0.562).The rates of permanent nerve injury were similar between the two groups[4.3％(2/46)vs.6.7％(3/45),P=0.980]at postoperative 2-year.Conclusion Short segment OLIF doesn't show better clinical outcomes and fusion rate than TLIF for degenerative spondylolisthesis,except for greater disc height restoration,greater segmental lordosis,and lower subsidence rate at postoperative 2-year.