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Background Cage subsidence (CS) was previously reported as one of the most common complications following oblique lumbar interbody fusion (OLIF). We aimed to assess the impacts of CS on surgical results following OLIF combined with anterolateral fixation, and determine its radiological characteristics as well as related risk factors. Methods Two hundred and forty-two patients who underwent OLIF at L4-5 and with a minimum 12 months follow-up were reviewed. Patients were divided into three groups according to the extent of disk height (DH) decrease during follow-up: no CS (DH decrease ≤ 2 mm), mild CS (2 mm < DH decrease ≤ 4 mm) and severe CS (DH decrease > 4 mm). The clinical and radiological results were compared between groups to evaluate radiological features, clinical effects and risk factors of CS. Results CS was identified in 79 (32.6%) patients, including 48 (19.8%) with mild CS and 31 (11.8%) with severe CS. CS was mainly identified within 1 month postoperatively, it did not progress after 3 months postoperatively, and more noted in the caudal endplate (44, 55.7%). In terms of clinical results, patients in the mild CS group were significantly worse than those in the no CS group, and patients in the severe CS group were significantly worse than those in the mild CS group. There was no significant difference in fusion rate between no CS (92.6%, 151/163) and mild CS (83.3%, 40/48) groups. However, significant lower fusion rate was observed in severe CS group (64.5%, 20/31) compared to no CS group. CS related risk factors included osteoporosis (OR = 5.976), DH overdistraction (OR = 1.175), flat disk space (OR = 3.309) and endplate injury (OR = 6.135). Conclusion CS following OLIF was an early postoperative complication. Higher magnitudes of CS were associated with worse clinical improvements and lower intervertebral fusion. Osteoporosis and endplate injury were significant risk factors for CS. Additionally, flat disk space and DH over-distraction were also correlated with an increased probability of CS.

Objective To compare the safety and accuracy of cortical bone trajectory screw placement between the robot-assisted and fluoroscopy-assisted approaches. Methods This retrospective study was conducted between November 2018 and June 2020, including 81 patients who underwent cortical bone trajectory (CBT) surgery for degenerative lumbar spine disease. CBT was performed by the same team of experienced surgeons. The patients were randomly divided into two groups—the fluoroscopy-assisted group (FA, 44 patients) and the robot-assisted group (RA, 37 patients). Robots for orthopedic surgery were used in the robot-assisted group , whereas conventional fluoroscopy-guided screw placement was used in the fluoroscopy-assisted group. The accuracy of screw placement and rate of superior facet joint violation were assessed using postoperative computed tomography (CT). The time of single screw placement, intraoperative blood loss, and radiation exposure to the surgical team were also recorded. The χ 2 test and Student’s t-test were used to analyze the significance of the variables ( P  < 0.05). Results A total of 376 screws were inserted in 81 patients, including 172 screws in the robot-assisted group and 204 pedicle screws in the fluoroscopy-assisted group. Screw placement accuracy was higher in the RA group (160, 93%) than in the FA group (169, 83%) ( P  = 0.003). The RA group had a lower violation of the superior facet joint than the FA group. The number of screws reaching grade 0 in the RA group (58, 78%) was more than that in the FA group (56, 64%) ( P  = 0.041). Screw placement time was longer in the FA group (7.25 ± 0.84 min) than in the RA group (5.58 ± 1.22 min, P  < 0.001). The FA group had more intraoperative bleeding (273.41 ± 118.20 ml) than the RA group (248.65 ± 97.53 ml, P  = 0.313). The radiation time of the FA group (0.43 ± 0.07 min) was longer than the RA group (0.37 ± 0.10 min, P  = 0.001). Furthermore, the overall learning curve tended to decrease. Conclusions Robot-assisted screw placement improves screw placement accuracy, shortens screw placement time, effectively improves surgical safety and efficiency, and reduces radiation exposure to the surgical team. In addition, the learning curve of robot-assisted screw placement is smooth and easy to operate.

We set out to determine whether a minimally invasive approach for one-level instrumented posterior lumbar interbody fusion reduced undesirable changes in the multifidus muscle, compared to a conventional open approach. We also investigated associations between muscle injury during surgery (creatinine kinase levels), clinical outcome and changes in the multifidus at follow-up. We studied 59 patients treated by one team of surgeons at a single institution (minimally invasive approach in 28 and conventional open approach in 31, voluntarily chosen by patients). More than 1 year postoperatively, all the patients were followed up with the visual analogue scale (VAS) and Oswestry disability index (ODI), and 16 patients from each group were evaluated using MRI. This enabled the cross-sectional area (CSA) of lean multifidus muscle, and the T2 signal intensity ratio of multifidus to psoas muscle, to be compared at the operative and adjacent levels. The minimally invasive group had less postoperative back pain ( P  < 0.001) and lower postoperative ODI scores ( P  = 0.001). Multifidus atrophy was less in the minimally invasive group ( P  < 0.001), with mean reductions in CSA of 12.2% at the operative and 8.5% at the adjacent levels, compared to 36.8% and 29.3% in the conventional open group. The increase in the multifidus:psoas T2 signal intensity ratio was similarly less marked in the minimally invasive group where values increased by 10.6% at the operative and 8.3% at the adjacent levels, compared to 34.4 and 22.7% in the conventional open group ( P  < 0.001). These changes in multifidus CSA and T2 signal intensity ratio were significantly correlated with postoperative creatinine kinase levels, VAS scores and ODI scores ( P  < 0.01). The minimally invasive approach caused less change in multifidus, less postoperative back pain and functional disability than conventional open approach. Muscle damage during surgery was significantly correlated with long-term multifidus muscle atrophy and fatty infiltration. Furthermore these degenerative changes of multifidus were also significantly correlated with long-term clinical outcome.

PurposeTo provide an overview of the The Norwegian Degenerative spondylolisthesis and spinal stenosis (NORDSTEN)-study and the organizational structure, and to evaluate the study population.MethodsThe NORDSTEN is a multicentre study with 10 year follow-up, conducted at 18 public hospitals. NORDSTEN includes three studies: (1) The randomized spinal stenosis trial comparing the impact of three different decompression techniques; (2) the randomized degenerative spondylolisthesis trial investigating whether decompression surgery alone is as good as decompression with instrumented fusion; (3) the observational cohort tracking the natural course of LSS in patients without planned surgical treatment. A range of clinical and radiological data are collected at defined time points. To administer, guide, monitor and assist the surgical units and the researchers involved, the NORDSTEN national project organization was established.Corresponding clinical data from the Norwegian Registry for Spine Surgery (NORspine) were used to assess if the randomized NORDSTEN-population at baseline was representative for LSS patients treated in routine surgical practice.ResultsA total of 988 LSS patients with or without spondylolistheses were included from 2014 to 2018. The clinical trials did not find any difference in the efficacy of the surgical methods evaluated. The NORDSTEN patients were similar to those being consecutively operated at the same hospitals and reported to the NORspine during the same time period.ConclusionThe NORDSTEN study provides opportunity to investigate clinical course of LSS with or without surgical interventions. The NORDSTEN-study population were similar to LSS patients treated in routine surgical practice, supporting the external validity of previously published results.Trial registrationClinicalTrials.gov; NCT02007083 10/12/2013, NCT02051374 31/01/2014 and NCT03562936 20/06/2018.

The necessity of routinely placing closed suction wound drainage in spinal surgery has been questioned. This study aims to assess if closed suction wound drainage is necessary for posterior atlantoaxial fixation via intermuscular approach. The functional outcomes of these 40 patients who underwent posterior atlantoaxial fixation via intermuscular approach without drainage tube (Group A) were compared with that of a control group, which consisted of 68 randomly enrolled cases with posterior atlantoaxial fixation via intermuscular approach with drainage tube (Group B). Outcome assessments included American Spinal Injury Association (ASIA) scoring grade and Visual Analog Scale Score for Neck Pain (VASSNP). The postoperative analgesic consumption, the incidence of subcutaneous and surrounding ecchymosis and the time of ambulation were compared between two groups. Bone fusion was evaluated through computed tomography (CT) reconstruction. Postoperative paravertebral tissue edema was evaluated by the edema coefficient. The use of drainage tube had no significant influence on the postoperative analgesic consumption, wound ecchymosis, the time of ambulation and paravertebral tissue edema ( P  > 0.05). There were no statistically significant differences in the VASSNP and bone fusion rates during the follow-up period between the two groups ( P  > 0.05). All patients achieved ASIA grade E 3 months after surgery. No complications such as wound infection occurred in either group. Posterior atlantoaxial fixation via intermuscular approach does not necessitate postoperative drainage tube placement if there is no accidental vascular injury or excessive muscle bleeding occurs intraoperatively.

Abstract BACKGROUND i-Factor™ Bone Graft (Cerapedics Inc, Westminster, Colorado) is a composite bone substitute material consisting of P-15 synthetic collagen fragment adsorbed onto anorganic bone mineral suspended in an inert biocompatible hydrogel carrier. A pivotal, noninferiority, US FDA Investigational Device Exemption study demonstrated the benefits of i-Factor™ compared to local autograft bone in single-level anterior cervical discectomy and fusion at 1-yr postoperative. OBJECTIVE To report 2-yr follow-up. METHODS Subjects randomly received either autograft (n = 154) or i-Factor™ (n = 165) in a cortical ring allograft and followed using radiological, clinical, and patient-reported outcomes. RESULTS At 2 yr, the fusion rate was 97.30% and 94.44% in i-Factor™ and autograft subjects, respectively (P = .2513), and neurological success rate was 94.87% (i-Factor™) and 93.79% (autograft; P = .7869). Neck Disability Index improved 28.30 (i-Factor™) and 26.95 (autograft; P = .1448); Visual Analog Scale arm pain improved 5.43 (i-Factor™) and 4.97 (autograft) (p = .2763); Visual Analog Scale neck pain improved 4.78 (i-Factor™) and 4.41 (autograft; P = .1652), Short Form-36 (SF-36v2) Physical Component Score improved 10.23 (i-Factor™) and 10.18 (autograft; P = .4507), and SF36v2 Mental Component Score improved 7.88 (i-FactorTM) and 7.53 (autograft; P = .9872). The composite endpoint of overall success (fusion, Neck Disability Index improvement >15, neurological success, and absence of re-operations) was greater in i-Factor™ subjects compared to autograft subjects (69.83% and 56.35%, respectively, P = .0302). Twelve (7.45%) i-Factor™ subjects and 16 (10.53%) autograft subjects underwent re-operation (P = .3411). There were no allergic reactions associated with i-Factor™. CONCLUSION Use of i-Factor™ in anterior cervical discectomy and fusion is effective and safe, and results in similar outcomes compared to local autograft bone at 2 yr following surgery.

PurposeThis study aimed to evaluate the mid-term efficacy and safety of Escherichia coli-derived bone morphogenetic protein-2 (E.BMP-2)/hydroxyapatite (HA) in lumbar posterolateral fusion (PLF). MethodsThis multicenter, evaluator-blinded, observational study utilized prospectively collected clinical data. We enrolled 74 patients who underwent lumbar PLF and had previously participated in the BA06-CP01 clinical study, which compared the short-term outcomes of E.BMP-2 with an auto-iliac bone graft (AIBG). Radiographs and CT scans were analyzed to evaluate fusion grade at 12, 24, and 36 months. Visual analog scale (VAS), Oswestry disability index (ODI), and Short Form-36 (SF-36) scores were measured preoperatively and at 36 months after surgery. All adverse events in this study were assessed for its relationship with E.BMP-2.ResultsThe fusion grade of the E.BMP-2 group (4.91 ± 0.41) was superior to that of the AIBG group (4.25 ± 1.26) in CT scans at 36 months after surgery (p = 0.007). Non-union cases were 4.3% in the E.BMP-2 and 16.7% in the AIBG. Both groups showed improvement in pain VAS, ODI, and SF-36 scores when compared to the baseline values, and there were no statistically significant differences between the two groups. No treatment-related serious adverse reactions were observed in either group. No neoplasm-related adverse events occurred in the E.BMP-2 group. ConclusionsThe fusion quality of E.BMP-2/HA was superior to that of AIBG. E.BMP-2/HA showed comparable mid-term outcomes to that of AIBG in terms of efficacy and safety in one-level lumbar PLF surgery.

The existence and importance of an accelerated adjacent segment disc degeneration (ASD) after lumbar fusion have previously not been demonstrated by RCTs. The objectives of this study were, to determine whether lumbar fusion in the long term accelerates degenerative changes in the adjacent disc and whether this affects the outcome, by using a prospective randomised design. A total of 111 patients, aged 18–55, with isthmic spondylolisthesis were randomised to exercise (EX, n  = 34) or posterolateral fusion (PLF, n  = 77), with ( n  = 37) or without pedicle screw instrumentation ( n  = 40). The minimum 10 years FU rate was 72%, with a mean FU time of 12.6 years (range 10–17 years). Three radiographic methods of ASD quantification were used, i.e. two digital radiographic measurement methods and the semi quantitative UCLA grading scale. One digital measurement method showed a mean disc height reduction by 2% in the EX group and by 15% in the PLF group ( p  = 0.0016), and the other showed 0.5 mm more disc height reduction in the PLF compared to the Ex group (ns). The UCLA grading scale showed normal discs in 100% of patients in the EX group, compared to 62% in the PLF group ( p  = 0.026). There were no significant differences between instrumented and non-instrumented patients. In patients with laminectomy we found a significantly higher incidence of ASD compared to non laminectomised patients (22/47 vs. 2/16 respectively, p  = 0.015). In the longitudinal analysis, the posterior and anterior disc heights were significantly reduced in the PLF group, whereas in the EX group only the posterior disc height was significantly reduced. Except for global outcome, which was significantly better for patients without ASD, the clinical outcome was not statistically different in patients with and without ASD. In conclusion, the long-term RCT shows that fusion accelerates degenerative changes at the adjacent level compared with natural history. The study suggests that not only fusion, but also laminectomy may be of pathogenetic importance. The clinical importance of ASD seems limited, with only the more severe forms affecting the outcome.

Although opioids represent the mainstay of treating surgical pain, their use is associated with significant side effects. There is an urgent need to find new pain relievers with safer side effect profiles. One drug that has been receiving increasing attention is ketamine. By using the oral route of administration, ketamine could potentially be used by patients in a less resource-intensive manner with similar efficacy. This study aims to examine the role of oral ketamine in improving recovery after major spine surgery. A prospective, single-center, double blinded parallel arm, placebo controlled randomized feasibility trial. Toronto Western Hospital (TWH), UHN, Toronto, Canada. Adult patients (aged 18–75) undergoing multi-level lumbar spine decompression and fusion with planned overnight admission in hospital. Study treatment (oral ketamine 30 mg) or matching placebo for three days (nine doses total) or until hospital discharge. The primary outcome was the patient-reported Quality of Recovery-15 score (QoR-15). Secondary outcomes were opioid use, pain intensity, pain interference (PROMIS-pain interference questionnaire), mood (PHQ-9) and, side-effects (Generic Assessment of Side Effects Scale). Data from 35 patients were analyzed, of which 18 patients in the ketamine group and 17 patients in the placebo group. There were no significant differences identified in QoR-15 scores at postoperative days 1,3,7, and 30. There were also no significant differences found in pain intensity scale scores at postoperative days 1, 3, 7, and 30, and PROMIS and PHQ-9 scores at postoperative days 7 and 30. Significantly less oral opioids were used in the ketamine group compared to the placebo group on postoperative day 3 and by postoperative day 7. In addition, patients in the ketamine group spent significantly less days on oral opioids and trended to be discharged from hospital earlier. This pilot study demonstrated that low dose oral ketamine can be safely used as an adjunct in postoperative pain treatment to help reduce opioid consumption after major spine surgery. •Although opioids represent the mainstay of treating surgical pain, their use is associated with significant side effects.•Low dose oral ketamine can be safely used as an adjunct in postoperative pain treatment.•Ketamine can more effectively reduce symptoms of pain hypersensitivity, including allodynia and hyperalgesia.

Background To find out if three-dimensional printing (3DP) off-the-shelf (OTS) prosthesis is superior to titanium mesh cages in anterior cervical corpectomy and fusion (ACCF) when treating single-segment degenerative cervical spondylotic myelopathy (DCSM). Methods DCSM patients underwent ACCF from January 2016 to January 2019 in a single center were included. Patients were divided into the 3DP group (28) and the TMC group (23). The hospital stays, operation time, intraoperative blood loss, and the cost of hospitalization were compared. The Japanese Orthopedic Association (JOA) scores and Neck Disability Index (NDI) were recorded pre-operatively, 1 day, 3, 6, 12, and 24 months post-operatively. Radiological data was measured to evaluate fusion, subsidence, and cervical lordosis. Patients were sent with SF-36 to assess their health-related quality of life (HRQoL). Results The differences in operative time, intraoperative blood loss, and hospital stay were not statistically significant between groups ( p  > 0.05). Postoperative dysphagia occurred in 2 cases in the 3DP group and 3 cases in the TMC group, which all relieved one week later. The difference in improvement of JOA and NDI between the two groups was not statistically significant ( p  > 0.05). No hardware failure was found and bony fusion was achieved in all cases except one in the 3DP group. The difference in cervical lordosis (CL), fused segmental angle (FSA), mean vertebral height (MVH), and subsidence rates between groups at each follow-up time point was not statistically significant and the results of the SF-36 were similar ( p  > 0.05). The total cost was higher in the 3DP group with its higher graft cost ( p  < 0.05). Conclusion In treating single-segment DCSM with ACCF, both 3DP OTS prosthesis and TMC achieved satisfactory outcomes. However, the more costly 3DP OTS prosthesis was not able to reduce subsidence as it claimed.