Clinical outcomes of short rod technique in posterior lumbar interbody fusion surgery: a minimum of 2-year follow-up.

PURPOSE: We present for the first time a novel entry point of pedicle screws (Short Rod Technique, SRT), which can avoid superior facet violation and has been verified as a safe screw placement method. The purpose of this study is to determine the clinical outcomes of SRT in posterior lumbar interbody fusion (PLIF) surgery. METHODS: We retrospectively analyzed the clinical outcomes of 89 patients who received SRT and 109 patients who received PLIF surgery with regular entry points of pedicle screws with a minimum of 2 years of follow-ups. Patients were divided into three groups according to the number of fusion segments, and the clinical outcomes of the three groups were compared. RESULTS: The length of the wound and the length of rods were significantly shorter in the each SRT group. Less intraoperative blood loss was observed in the SRT group in patients with a single segment and two segments fusions, but not in three segments fusions. Fewer degenerations of the upper adjacent segment were observed in the SRT group in patients with a single segment and three segments fusions. In addition, less postoperative wound pain related to PLIF surgery was observed in the SRT group in patients with two and three segments fusions. CONCLUSION: SRT has been validated as an effective technique with good clinical outcomes, especially for reducing the occurrence of upper ASD in PLIF surgery with a single segment and three segments. The present study provides spinal surgeons with a novel method for performing PLIF surgery.

Risk analysis index predicts mortality and non-home discharge following posterior lumbar interbody fusion: a nationwide inpatient sample analysis of 429,380 patients (2019-2020).

PURPOSE: Frailty is an independent risk factor for adverse postoperative outcomes following spine surgery. The ability of the Risk Analysis Index (RAI) to predict adverse outcomes following posterior lumbar interbody fusion (PLIF) has not been studied extensively and may improve preoperative risk stratification. METHODS: Patients undergoing PLIF were queried from Nationwide Inpatient Sample (NIS) (2019-2020). The relationship between RAI-measured preoperative frailty and primary outcomes (mortality, non-home discharge (NHD)) and secondary outcomes (extended length of stay (eLOS), complication rates) was assessed via multivariate analyses. The discriminatory accuracy of the RAI for primary outcomes was measured in area under the receiver operating characteristic (AUROC) curve analysis. RESULTS: A total of 429,380 PLIF patients (mean age = 61y) were identified, with frailty cohorts stratified by standard RAI convention: 0-20 "robust" (R)(38.3%), 21-30 "normal" (N)(54.3%), 31-40 "frail" (F)(6.1%) and 41+ "very frail" (VF)(1.3%). The incidence of primary and secondary outcomes increased as frailty thresholds increased: mortality (R 0.1%, N 0.1%, F 0.4%, VF 1.3%; p < 0.001), NHD (R 6.5%, N 18.1%, F 36.9%, VF 42.0%; p < 0.001), eLOS (R 18.0%, N 21.9%, F 31.6%, VF 43.8%; p < 0.001) and complication rates (R 6.6%, N 8.8%, F 11.1%, VF 12.2%; p < 0.001). The RAI demonstrated acceptable discrimination for NHD (C-statistic: 0.706) and mortality (C-statistic: 0.676) in AUROC curve analysis. CONCLUSION: Increasing RAI-measured frailty is significantly associated with increased NHD, eLOS, complication rates, and mortality following PLIF. The RAI demonstrates acceptable discrimination for predicting NHD and mortality, and may be used to improve frailty-based risk assessment for spine surgeons.

Correlation between blood glucose level and poor wound healing after posterior lumbar interbody fusion in patients with type 2 diabetes.

To investigate the correlation of blood glucose level with poor wound healing (PWH) after posterior lumbar interbody fusion (PLIF) in patients with type 2 diabetes (T2D). From January 2016 to January 2023, a case-control study was conducted to analyse the clinical data of 400 patients with T2D who were treated by PLIF and internal fixation at our hospital. The following data were recorded: gender; age; body mass index (BMI); surgical stage; average perioperative blood glucose level; perioperative blood glucose variance; perioperative blood glucose coefficient of variation; glycated haemoglobin level; preoperative levels of total protein, albumin and haemoglobin; postoperative levels of total protein, albumin and haemoglobin; surgical time; intraoperative bleeding volume; operator; postoperative drainage volume; and postoperative drainage tube removal time of each group. The indicators for monitoring blood glucose variability (GV) included the SD of blood glucose level (SDBG), coefficient of variation (CV) and maximum amplitude of variation (LAGE) before and after surgery. According to the diagnostic criteria for PWH, patients with postoperative PWH were determined and assigned to two groups: Group A (good wound healing group; n = 330 patients) and Group B (poor wound healing group; n = 70 patients). The preoperative and postoperative blood GV indicators, namely SDBG, CV and LAGE, were compared between these two groups. We also determined the relationship between perioperative blood GV parameters and PWH after PLIF surgery and its predictive value through correlation analysis and receiver-operating characteristic curve. Of the 400 enrolled patients, 70 patients had PWH. Univariate analysis revealed significant differences between the two groups in the course of diabetes, mean fasting blood glucose (MFBG), SDBG, CV, LAGE, preoperative hypoglycaemic program, surgical segment, postoperative drainage time, incision length and other factors (p < 0.05). However, no significant differences were noted in factors such as gender, age, body mass index, hypertension, coronary heart disease, admission fasting blood glucose, preoperative haemoglobin A1c, surgical time, intraoperative bleeding volume, intraoperative blood transfusion volume and postoperative drainage volume (p > 0.05). The area under the curve (AUC) values of preoperative SDBG, CV and LAGE were 0.6657, 0.6432 and 0.6584, respectively. The cut-off values were 1.13 mmol/L, 6.97% and 0.75 mmol/L, respectively. The AUC values for postoperative SDBG, CV and LAGE were 0.5885, 0.6255 and 0.6261, respectively. The cut-off values were 1.94 mmol/L, 24.32% and 2.75 mmol/L, respectively. The multivariate ridge regression analysis showed that preoperative MFBG, SDBG, CV and LAGE; postoperative SDBG, CV and LAGE; postoperative long drainage time; and multiple surgical segments were independent risk factors for T2D patients to develop surgical site infection after PLIF (p < 0.05). The perioperative blood GV in patients with T2D is closely related to the occurrence of PWH after PLIF. Reducing blood GV may help to reduce the occurrence of PWH after PLIF.

Comparison of Fusion Rates among Various Demineralized Bone Matrices in Posterior Lumbar Interbody Fusion.

Background and Objectives: Posterior lumbar interbody fusion (PLIF) plays a crucial role in addressing various spinal disorders. The success of PLIF is contingent upon achieving bone fusion, as failure can lead to adverse clinical outcomes. Demineralized bone matrix (DBM) has emerged as a promising solution for promoting fusion due to its unique combination of osteoinductive and osteoconductive properties. This study aims to compare the effectiveness of three distinct DBMs (Exfuse®, Bongener®, and Bonfuse®) in achieving fusion rates in PLIF surgery. Materials and Methods: A retrospective review was conducted on 236 consecutive patients undergoing PLIF between September 2016 and February 2019. Patients over 50 years old with degenerative lumbar disease, receiving DBM, and following up for more than 12 months after surgery were included. Fusion was evaluated using the Bridwell grading system. Bridwell grades 1 and 2 were defined as 'fusion', while grades 3 and 4 were considered 'non-fusion.' Clinical outcomes were assessed using visual analog scale (VAS) scores for pain, the Oswestry disability index (ODI), and the European quality of life-5 (EQ-5D). Results: Fusion rates were 88.3% for Exfuse, 94.3% for Bongener, and 87.7% for Bonfuse, with no significant differences. All groups exhibited significant improvement in clinical outcomes at 12 months after surgery, but no significant differences were observed among the three groups. Conclusions: There were no significant differences in fusion rates and clinical outcomes among Exfuse, Bongener, and Bonfuse in PLIF surgery.

An analysis of clinical application effects of 3d-printed act titanium trabecular intervertebral fusion cage in posterior lumbar interbody fusion (PLIF).

Objective: To compare the clinical effects of applying a 3D-printed ACT titanium trabecular intervertebral fusion cage and a Polyetheretherketone (PEEK) cage in posterior lumbar interbody fusion (PLIF). Methods: This was a clinical comparative study. Forty patients with degenerative lumbar diseases admitted at The Second People's Hospital of Dalian from January 2020 to December 2021 were selected and divided into an observation group (3D cage) and a control group (PEEK cage) using the random number table method, with each group of 20 cases. The visual analogue scale (VAS) scores, Japanese Orthopaedic Association (JOA) scores, Cobb angles at fusion segments, intervertebral height and intervertebral fusion situations of the patients between the groups were compared. Results: No significant differences were found in their operation time, intraoperative blood losses and operation related complications(p>0.05). In terms of postoperative VAS and JOA scores in both groups, they are all significantly improved compared with those before the operation, and their differences are also statistically significant(p<0.05). However, no statistical significance exists in inter-group differences(p>0.05). Postoperative Cobb angles and intervertebral height of patients in both groups are considerably bettered compared with those before the operation. Their differences show statistical significance(p<0.05), while inter-group differences are proved to be not statistically significant(p>0.05). Conclusions: Applying a 3D-printed ACT titanium trabecular intervertebral fusion cage or PEEK cage in PLIF has the potential to improve clinical symptoms of patients with degenerative lumbar diseases, and restore the Cobb angle and intervertebral height. 3D-printed ACT titanium trabecular intervertebral fusion cage can accelerate intervertebral fusion without increasing operation related complications.

The association of rod curvature with postoperative outcomes in patients undergoing posterior lumbar interbody fusion for spinal stenosis: a retrospective case-control study.

BACKGROUND: Restoration of sagittal balance is a crucial consideration in posterior lumbar interbody fusion (PLIF) surgery and adverse postoperative outcomes are associated with inadequate restoration of sagittal alignment. However, there remains a shortage of substantial evidence regarding the effect of rod curvature on both sagittal spinopelvic radiographic parameters and clinical outcomes. METHOD: A retrospective case-control study was conducted in this study. Patient demographics (age, gender, height, weight and BMI), surgical characteristics (number of fused levels, surgical time, blood loss and hospital stay) and radiographic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic incidence [PI], pelvic tilt [PT], PI-LL, Cobb angle of fused segments [Cobb], rod curvature [RC], Posterior tangent angle of fused segments [PTA] and RC-PTA) were analyzed. RESULTS: Patients in the abnormal group had older mean age and suffered more blood loss than those in the normal group. In addition, RC and RC-PTA were significantly lower in the abnormal group compared to the normal group. Multivariate regression analysis revealed that lower age (OR = 0.94; 95% CI: 0.89-0.99; P = 0.0187), lower PTA (OR = 0.91; 95% CI: 0.85-0.96; P = 0.0015) and higher RC (OR = 1.35; 95% CI: 1.20-1.51; P < 0.0001) were related to higher odds of better surgical outcomes. The receiver operating characteristic curve analysis showed that the ROC curve (AUC) for predicting outcomes of surgery by RC classifier was 0.851 (0.769-0.932). CONCLUSIONS: In patients who underwent PLIF surgery for lumbar spinal stenosis, those who had a satisfactory postoperative outcome tended to be younger, had lower blood loss, and higher values of RC and RC-PTA compared to those who had poor recovery and required revision surgery. Additionally, RC was found to be a reliable predictor of postoperative outcomes.

Biomechanical effect of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion: a finite element study.

BACKGROUND: Adjacent segment degeneration (ASD) is a common complication of lumbar interbody fusion; the paraspinal muscles significantly maintain spinal biomechanical stability. This study aims to investigate the biomechanical effects of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion (PLIF). METHODS: Data from a lumbosacral vertebral computed tomography scan of a healthy adult male volunteer were used to establish a normal lumbosacral vertebral finite element model and load the muscle force of the multifidus. A normal model, an L4/5 PLIF model (PFM) based on a preserved proximal multifidus, a total laminectomy PLIF model (TLPFM), and a hemi-laminectomy PLIF model based on a severed proximal multifidus were established, respectively. The range of motion (ROM) and maximum von Mises stress of the upper and lower adjacent segments were analyzed along with the total work of the multifidus muscle force. RESULTS: This model verified that the ROMs of all segments with four degrees of freedom were similar to those obtained in previous research data, which validated the model. PLIF resulted in an increased ROM and maximum von Mises stress in the upper and lower adjacent segments. The ROM and maximum von Mises stress in the TLPFM were most evident in the upper adjacent segment, except for lateral bending. The ROM of the lower adjacent segment increased most significantly in the PFM in flexion and extension and increased most significantly in the TLPFM in lateral bending and axial rotation, whereas the maximum von Mises stress of the lower adjacent segment increased the most in the TLPFM, except in flexion. The muscle force and work of the multifidus were the greatest in the TLPFM. CONCLUSIONS: PLIF increased the ROM and maximum von Mises stress in adjacent cranial segments. The preservation of the proximal multifidus muscle contributes to the maintenance of the physiological mechanical behavior of adjacent segments, thus preventing the occurrence and development of ASD.

Effect of Muscularity and Fatty Infiltration of Paraspinal Muscles on Outcome of Lumbar Interbody Fusion.

BACKGROUND: Lumbar paraspinal muscles play an important role in maintaining global spinal alignment and are associated with lower back pain; however, only a few studies on the effect of the paraspinal muscles on the surgical outcome exist. Therefore, this study aimed to analyze the association of preoperative muscularity and fatty infiltration (FI) of paraspinal muscles with the outcome of lumbar interbody fusion. METHODS: Postoperative clinical and radiographic outcomes were analyzed in 206 patients who underwent surgery for a degenerative lumbar disease. The preoperative diagnosis was spinal stenosis or low-grade spondylolisthesis, and the surgery performed was posterior lumbar interbody fusion or minimally invasive transforaminal lumbar interbody fusion. Indications for surgery were a complaint of severe radiating pain that did not improve with conservative treatment and neurological symptoms accompanied by lower extremity motor weakness. Patients with fractures, infections, tumors, or a history of lumbar surgery were excluded from this study. Clinical outcome measures included functional status, measured using the Oswestry disability index (ODI) and visual analog scale (VAS) score for lower back and leg pain. Other radiographic parameters included measures of spinal alignment, including lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, C7 sagittal vertical axis, and pelvic incidence-lumbar lordosis mismatch. Lumbar muscularity (LM) and FI were measured preoperatively using a lumbar magnetic resonance image (MRI). RESULTS: The high LM group showed more significant improvement in VAS score for lower back pain than the low LM group. In contrast, the VAS score for leg pain demonstrated no statistical significance. The high LM group showed more significant improvement in ODI postoperatively than the medium group. The severe FI group showed more significant improvement in ODI postoperatively, whereas the less severe FI group showed more significant improvement in the sagittal balance postoperatively. CONCLUSION: Patients with high LM and mild FI ratio observed on preoperative MRI demonstrated more favorable clinical and radiographic outcomes after lumbar interbody fusion. Therefore, preoperative paraspinal muscle condition should be considered when planning lumbar interbody fusion.

Comparative study on the selection of drainage methods in posterior lumbar interbody fusion.

OBJECTIVE: To compare and analyze the clinical effects of bilateral natural pressure drainage and negative pressure drainage after posterior lumbar interbody fusion (PLIF) to provide a reference for selecting drainage methods after lumbar surgery. METHODS: A retrospective cohort study, 281 patients who underwent single-segment PLIF in our hospital from January 2017 to December 2020 and met the inclusion and exclusion criteria were included in the study, including 132 males and 149 females, aged 22-85 years, with an average of (53.62 ± 11.23) years. According to different postoperative incision drainage methods determined by the random number table method before surgery, they were divided into the natural pressure drainage group and negative pressure drainage group, both of which were bilateral drainage. The general observation indexes and perioperative-related indexes were recorded and analyzed. RESULTS: There were 143 cases in the natural pressure drainage group and 138 cases in the negative pressure drainage group. There was no significant difference in age, gender, body mass index, disease type, blood pressure on the day of surgery, preoperative albumin, hemoglobin, platelet, prothrombin time, and intraoperative bleeding between the two groups (P > 0.05). The albumin on the first postoperative day in the natural pressure drainage group was higher than that in the negative pressure drainage group [(33.24 ± 3.52) vs. (32.17 ± 5.03), P < 0.05]; The hemoglobin on the first postoperative day in the natural pressure drainage group was higher than that in the negative pressure drainage group [(126.01 ± 15.03) vs. (115.19 ± 16.25), P < 0.01]; The drainage volume on the first postoperative day in the natural pressure drainage group was lower than that in the negative pressure drainage group [(93.25 ± 63.58) ml vs. (119.46 ± 54.48) ml, P < 0.01]; The total postoperative drainage volume in the natural pressure drainage group was lower than that in the negative pressure drainage group [(355.60 ± 189.69) ml vs. (434.37 ± 149.12) ml, P < 0.01]; The indwelling time of drainage tube in the natural pressure drainage group was lower than that in the negative pressure drainage group [(3.29 ± 1.17) d vs. (3.45 ± 0.97) d, P < 0.05]. There was no significant difference in platelet count on the first postoperative day, postoperative hospital stays, and complications (incision infection and hematoma) between the two groups (P > 0.05). CONCLUSION: Bilateral natural pressure drainage and negative pressure drainage can achieve good drainage effects after PLIF, but patients with natural pressure drainage have less loss of albumin and hemoglobin, less drainage volume, and shorter drainage tube indwelling time, which is worthy of clinical application.

Effectiveness of intraoperative table modification for achieving lumbar lordosis in multilevel lumbar fusion surgery: a propensity score-matched study.

BACKGROUND: In multilevel posterior lumbar interbody fusion (PLIF) with posterior screw fixation, obtaining sufficient lumbar lordosis (LL) is difficult, especially in patients with osteoporosis. We performed intraoperative table modification (TM) using gravitational dropping of the patient's lumbar spine, to improve restoration of LL. METHODS: We retrospectively reviewed the medical records of patients who underwent three- or four-level PLIF between 2005 and 2019. One hundred eleven patients were enrolled, with 96 patients receiving non-TM-PLIF and 15 patients receiving TM-PLIF. Radiological parameters, including segmental lordosis (SL), LL, sacral slope (SS), pelvic incidence, and pelvic tilt, were measured. Clinical outcomes were measured using a visual analogue scale (VAS) for the back and leg preoperatively and at the last follow-up. Additionally, the correlation between the bone mineral density (BMD) and the radiological parameters was calculated for TM-PLIF. We performed propensity score matching between the groups to control the baseline difference. RESULTS: We found a statistically better correction between immediate and last follow-up postoperative SL (p = 0.04), as well as between preoperative and last follow-up SL (p < 0.01) in the TM-PLIF group compared to that in the non-TM-PLIF group. VAS for the back and leg were not significantly different between the two groups. Additionally, the efficacy of lordosis correction in the TM-PLIF group showed a statistically significant negative correlation between BMD and the SS change both before and after the surgery (rho = -0.60, p = 0.02). CONCLUSION: Whilst further study is required to conclusively establish its efficacy, TM-PLIF (table modification using gravitational dropping) shows potential advantages for restoring and maintaining LL in multilevel lumbar fusion, particularly in cases with low BMD.

C-reactive protein to albumin ratio (CAR) in predicting surgical site infection (SSI) following instrumented posterior lumbar interbody fusion (PLIF).

Identification of novel markers would contribute to the individualised risk assessment and development of a risk prediction model. This study aimed to investigate the role of the C-reactive protein to albumin ratio (CAR) in predicting surgical site infection (SSI) following instrumented posterior lumbar interbody fusion (PLIF) of lumbar degenerative diseases. This study enrolled patients who underwent PLIF and instrumentation for treatment of lumbar degenerative diseases between 2015 and 2020. Electronic medical records were inquired for data collection, with follow-up register for identifying SSI cases. The optimal cut-off for CAR was determined by constructing the receiver operator characteristic (ROC) curve. Patients with high- or low-CAR value were compared using the univariate analyses, and the association between CAR and the risk of SSI was investigated using multivariate logistics regression analysis. A total of 905 patients were enrolled, twenty-nine (3.2%) had developed an SSI with 72.4% occurring during index hospitalisation, and 11 (1.2%) had deep and 18 (2.0%) superficial SSIs. An SSI was associated with additional 10.7 days of index total hospital stay (P = .001). The CAR was 0-5.43 (median, 0.05), and the optimal cut-off was 0.09 and area under the curve was 0.720 (P < .001). 336 (37.1%) patients had a CAR ≥0.09 and 22 (6.5%) developed an SSI, with a crude risk of 5.6 relative to those with a low CAR. The multivariate analyses showed CAR ≥0.09 was associated with 8.06-fold increased risk of SSI, together with diabetes (P = .018), while hypertension was identified as a protective factor (OR, 0.34; 95%CI, 0.11-1.00, P = .049). High CAR is found to significantly predict the incident SSI following instrumented PLIF of lumbar degenerative diseases, and can be considered as a useful index in practice only after it is verified by future high-level evidences.

Fat infiltration of paraspinal muscles as an independent risk for bone nonunion after posterior lumbar interbody fusion.

BACKGROUND: The prognosis value of paraspinal muscle degeneration on clinical outcomes has been revealed. However no study has investigated the effect of the fat infiltration (FI) of paraspinal muscles on bone nonunion after posterior lumbar interbody fusion (PLIF). METHODS: Three hundred fifty-one patients undergoing PLIF for lumbar spinal stenosis with 1-year follow-up were retrospectively identified. Patients were categorized into bone union (n = 301) and bone nonunion (n = 50) groups based on dynamic X-ray at 1-year follow-up. The relative total cross-sectional area (rTCSA) and FI of multifidus (MF) and erector spinae (ES), and the relative functional CSA (rFCSA) of psoas major (PS) were measured on preoperative magnetic resonance imaging. RESULTS: The nonunion group had a significantly higher MF FI and a higher ES FI and a smaller MF rTCSA than the union group (p = 0.001, 0.038, 0.026, respectively). Binary logistic regression revealed that MF FI (p = 0.029, odds ratio [OR] = 1.04), lumbosacral fusion (p = 0.026, OR = 2193) and length of fusion (p = 0.001, OR = 1.99) were independent factors of bone nonunion. In subgroup analysis, in one or two-level fusion group, the patients with nonunion had a higher MF FI and a higher ES FI than those of the patients with union (all p < 0.05). Similarly, in lumbosacral fusion group, the patients with nonunion had a higher MF FI and a higher ES FI than those of the patients with union (all p < 0.05). The logistic regressions showed that MF FI remained an independent factor of bone nonunion both in the patients with one or two-level fusion (p = 0.003, OR = 1.074) and in the patients with lumbosacral fusion (p = 0.006, OR = 1.073). CONCLUSIONS: Higher fatty degeneration was strongly associated with bone nonunion after PLIF. Surgeons should pay attention to the FI of paraspinal muscles when performing posterior surgery for patients, especially those who need short-segment fusion or to extend fusion to S1.

Comparison of percutaneous endoscopic and open posterior lumbar interbody fusion for the treatment of single-segmental lumbar degenerative diseases.

BACKGROUND: Endoscopic lumbar interbody fusion has become an emerging technique. Some researchers have reported the technique of percutaneous endoscopic transforaminal lumbar interbody fusion. We propose percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF) as an alternative approach. The purpose of this study was to assess the clinical efficacy of PE-PLIF by comparing percutaneous endoscopic and open posterior lumbar interbody fusion (PLIF). METHODS: Thirty patients were enrolled in each group. Demographic data, perioperative data, and radiological parameters were collected prospectively. The clinical outcomes were evaluated by visual analog scale (VAS) and Oswestry Disability Index (ODI) scores. RESULTS: The background data were comparable between the two groups. The mean operation time was longer in the PE-PLIF group. The PE-PLIF group showed benefits in less blood loss and shorter hospital stay. VAS and ODI scores significantly improved in both groups. However, the VAS score of low-back pain was lower in the PE-PLIF group. The satisfaction rate was 96.7% in both groups. The radiological outcomes were similar in both groups. In the PE-PLIF group, the fusion rate was 93.3%, and the cage subsidence rate was 6.7%; in the open PLIF group, the fusion and cage subsidence rates were 96.7% and 16.7%. There were minor complications in one patient in the PE-PLIF group and two in the open PLIF group. CONCLUSIONS: The current study revealed that PE-PLIF is safe and effective compared with open PLIF. In addition, this minimally invasive technique may enhance postoperative recovery by reducing tissue damage and blood loss.

A study of screw placement to obtain the optimal pull-out resistance of lumbar pedicle screws-analysis of Hounsfield units measurements based on computed tomography.

OBJECTIVE: The screw path of lumbar pedicle screws in the vertebral body has certain variability. It is not clear whether the screw paths in different directions can obtain the same pull-out resistance. This study intends to use CT (Computed Tomography) to measure the Hounsfield unit (HU value) around the screw paths in different parts of the lumbar vertebral body to obtain the bone mineral density value of the corresponding parts which will provide some reference for the direction of lumbar pedicle screw placement. METHODS: This retrospective study included 200 patients with lumbar degenerative diseases selected randomly from the case base and the patient's basic information was recorded. L1-L5 vertebral body was divided equally into the upper, middle and lower 1/3, which was consistent with the three sagittal entry directions of the pedicle screw head tilt, parallel endplate and caudal tilt, and the HU values were measured by CT cross-sectional scanning to indirectly reflect the local bone density values. The paired t-test (randomized block experiment) was used to compare the HU values of the upper, middle and lower 1 / 3 parts, with P < 0.05 being considered statistically significant. RESULTS: Comparison of HU values in different parts of each vertebral body revealed that HU values in the middle 1/3 of the L1,L2 (163.88 ± 58.44 and 152.94 ± 59.45) and in the lower 1/3 of the L4 (149.86 ± 60.18) were higher than in the other two parts of the vertebral body of the same segment(P < 0.0001,P = 0.0069 and P = 0.0024, respectively); According to the results of each stratification, patients with younger age and better bone condition had higher HU values in the middle 1/3 of L1 and L2, and higher HU values in the lower 1/3 of L3, L4 and L5; With the increase of age, the decrease of bone condition and the difference of HU value in each vertebral body gradually decreased. CONCLUSION: Although further follow-up studies are needed, based on the analysis of the statistical results, we speculate that from the perspective of obtaining the best pull-out resistance of the lumbar pedicle screws, the placement direction of L1 and L2 in the sagittal position may be as parallel to the endplate as possible; L3, L4, and L5 may be as appropriate as possible to the tail tilt theoretically.

Should adjacent asymptomatic lumbar disc herniation of L5-S1 isthmic spondylolisthesis be simultaneously rectified? Evaluation of postoperative spino-pelvic sagittal balance and functional outcomes.

BACKGROUND: This study aimed to analyze the efficacy of the simultaneous rectification of adjacent asymptomatic lumbar disc herniation (asLDH) of L5-S1 isthmic spondylolisthesis (IS). METHODS: One hundred and forty-eight patients with L5-S1 IS, and simultaneous L4-5 asLDH, were recruited between January 2012 and December 2017, for this study. Group A: seventy-two patients received PLIF at L5-S1. Group B: seventy-six patients received PLIF at L4-S1. The radiographic outcomes were assessed via the lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT), PI-LL and slip degree (SD). The functional outcomes were evaluated via the visual analog scale (VAS), Oswestry disability index (ODI), and reoperation rate. The potential risk hazards for reoperation were identified using both uni- and multivariate logistic regression analyses. RESULTS: The postoperative LL, SL, PT, SS, SD, VAS, and ODI exhibited vast improvements (P < 0.05). Relative to Group A, Group B exhibited markedly better LL, SL, PT, PI-LL,VAS and ODI scores at the final follow-up (P < 0.05). Group B also achieved better SD values post surgery than Group A (P < 0.05). The reoperation rate was remarkably elevated in Group A, compared to Group B (P < 0.05). The multivariate logistic regression analysis showed the L4-5 asLDH grade was a stand-alone risk hazard for reoperation, whereas, pre-SL and pre-LL offered protection against reoperation (P < 0.05). CONCLUSIONS: L4-S1 PLIF is recommended to correct asLDH in L5-S1 IS patients, with high-grade disc herniation and abnormal sagittal alignment.

Biomechanical feasibility of semi-rigid stabilization and semi-rigid lumbar interbody fusion: a finite element study.

BACKGROUND: Semi-rigid lumbar fusion offers a compromise between pedicle screw-based rigid fixation and non-instrumented lumbar fusion. However, the use of semi-rigid interspinous stabilization (SIS) with interspinous spacer and ligamentoplasty and semi-rigid posterior instrumentation (SPI) to assist interbody cage as fusion constructs remained controversial. The purpose of this study is to investigate the biomechanical properties of semi-rigidly stabilized lumbar fusion using SIS or SPI and their effect on adjacent levels using finite element (FE) method. METHOD: Eight FE models were constructed to simulate the lumbosacral spine. In the non-fusion constructs, semi-rigid stabilization with (i) semi-rigid interspinous spacer and artificial ligaments (PD-SIS), and (ii) PI with semi-rigid rods were simulated (PD + SPI). For fusion constructs, the spinal models were implanted with (iii) PEEK cage only (Cage), (iv) PEEK cage and SIS (Cage+SIS), (v) PEEK cage and SPI (Cage+SPI), (vi) PEEK cage and rigid PI (Cage+PI). RESULT: The comparison of flexion-extension range of motion (ROM) in the operated level showed the difference between Cage+SIS, Cage+SPI, and Cage+PI was less than 0.05 degree. In axial rotation, ROM of Cage+SIS were greater than Cage+PI by 0.81 degree. In the infrajacent level, while Cage+PI increased the ROM by 24.1, 27,7, 25.9, and 10.3% and Cage+SPI increased the ROM by 26.1, 30.0, 27.1, and 10.8% in flexion, extension, lateral bending and axial rotation respectively, Cage+SIS only increased the ROM by 3.6, 2.8, and 11.2% in flexion, extension, and lateral bending and reduced the ROM by 1.5% in axial rotation. The comparison of the von Mises stress showed that SIS reduced the adjacent IVD stress by 9.0%. The simulation of the strain energy showed a difference between constructs less than 7.9%, but all constructs increased the strain energy in the infradjacent level. CONCLUSION: FE simulation showed semi-rigid fusion constructs including Cage+SIS and Cage+SPI can provide sufficient stabilization and flexion-extension ROM reduction at the fusion level. In addition, SIS-assisted fusion resulted in less hypermobility and less von Mises stress in the adjacent levels. However, SIS-assisted fusion had a disadvantage of less ROM reduction in lateral bending and axial rotation. Further clinical studies are warranted to investigate the clinical efficacy and safety of semi-rigid fusions.

Risk factors for adjacent segment disease requiring reoperation after posterior lumbar interbody fusion with screw fixation: focus on paraspinal muscle, facet joint, and disc degeneration.

PURPOSE: Adjacent segment disease (ASD) requiring revision surgery is the most serious complication that can occur in patients undergoing posterior lumbar interbody fusion (PLIF) surgery. This study aimed to determine the risk factors for surgical ASD requiring revision surgery after PLIF with screw fixation surgery. We especially focused on paraspinal muscle, facet joint, and disc degeneration. METHODS: Among the patients who underwent PLIF with screw fixation due to degenerative spinal disease from January 2010 to December 2019, patients who underwent revision surgery for the development of ASD were enrolled. To evaluate the risk factors for surgical ASD, we selected a control group. Each patient in the control group was matched by age, sex, fusion level, number of fused segments, secondary MRI follow-up interval, and follow-up duration with a patient in the surgical ASD group. The radiographic and demographic data were compared between the surgical ASD and control groups. RESULTS: There were statistically significant differences between the two groups in radiological parameters of preoperative facet degeneration, facet effusion, facet angle, and fatty degeneration of the multifidus muscle. Multivariable logistic regression analysis revealed that preoperative facet effusion (odds ratio [OR] 6.48), preoperative facet angle (OR 1.24), and progression of fatty degeneration in the multifidus muscle (OR 1.07) were significant risk factors for surgical ASD. CONCLUSIONS: Preexisting high-grade adjacent facet effusion, sagittally oriented facet joint angle, and progressive fatty degeneration of the multifidus muscle are associated with the development of surgical ASD after PLIF surgery.

Risk factors for cage subsidence and clinical outcomes after transforaminal and posterior lumbar interbody fusion.

BACKGROUND: Cage subsidence is a very common complication after lumbar interbody fusion. It may compromise vertebral interbody fusion through progressive spinal deformity and consequently cause compression of neural elements. Clinical relevance remains, however, unclear, with few studies on this subject and even less information regarding its correlation with clinical findings. The aim of this study was to identify risk factors for cage subsidence and clinical evaluation after transforaminal (TLIF) and posterior (PLIF) lumbar interbody fusion. METHODS: A retrospective study in patients submitted to TLIF and PLIF between 2008 and 2017 was conducted. RESULTS: A total of 165 patients were included (123 TLIF and 42 PLIF). Univariate analysis showed an increased risk of cage subsidence in spondylolisthesis comparing with degenerative disk disease (p = 0.007). A higher preoperative lumbar lordosis angle (p = 0.014) and cage placement in L2-L3 (p = 0.012) were associated with higher risk of subsidence. The posterior cage positioning on vertebral endplate was associated with a higher risk of subsidence (p = 0.028) and significant subsidence (p = 0.005), defined as cage migration > 50% of cage height. PLIF presented a higher risk when comparing with TLIF (p = 0.024). Hounsfield unit (HU) values < 135 (OR6; 95% CI [1.95-34]) and posterior positioning (OR7; 95% CI [1.7-27.3]) were independent risk factors for cage subsidence and significant subsidence, respectively, in multivariate analysis. There was a tendency for significant subsidence in degrees ≥ 2 of Meyerding spondylolisthesis (OR4; 95% CI [0.85-21.5]). Significant cage subsidence was not associated with worse clinical results. Other analyzed factors, such as age (p = 0.008), low bone mineral density (BMD) (p = 0.029) and type of surgery (TLIF) (p = 0.004), were associated with worse results. CONCLUSION: The present study shows that lower BMD and posterior cage positioning are relevant risk factors for lumbar cage subsidence. Low BMD is also a predictor of poor clinical results, so it must be properly evaluated and considered, through HU values measurement in CT scan, a feasible and reliable tool in perioperative planning.

Associated factors of patients with spinal stenosis who undergo reoperation after a posterior lumbar spinal fusion in a Hispanic-American population.

PURPOSE: The aim of this study was to evaluate the associated factors of patients with LSS who undergo reoperation after a PLSF in a Hispanic-American population. METHODS: A retrospective single-center review was performed from all non-age-related Hispanic-Americans with LSS who underwent one or two-level PLSF from 2008 to 2018. Baseline characteristics were analyzed between the reoperation and no-reoperation group using a bivariate and multivariate analyses. RESULTS: Out of 425 patients who underwent PLSF, 38 patients underwent reoperation. At a two-year follow-up, the reoperation rate was 6.1% (26/425), mostly due to pseudoarthrosis (39.5%), recurrent stenosis (26.3%), new condition (15.8%), infection (10.5%), hematoma (5.3%), and dural tear (2.6%). Patients who underwent reoperation were more likely to have a preoperative history of epidural steroid injection (ESI) (OR 5.18, P = 0.009), four or more comorbidities (OR 2.69, P = 0.028), and operated only with a posterolateral fusion without intervertebral fusion (OR 2.15, P = 0.032). Finally, the multivariable analysis showed that ESI was the only independent associated factor in patients who underwent reoperation after a PLSF in our group. CONCLUSION: Among this population who underwent surgery, a reoperation rate at two years of follow-up was less than ten percent. Our study did not find any associated factor inherent to Hispanic-Americans, as ethnic group, who were reoperated after LSS.

Efficacy and radiographic analysis of oblique lumbar interbody fusion in treating lumbar degenerative spondylolisthesis with sagittal imbalance.

The aim of this study was to evaluate the effectiveness of OLIF (oblique lumbar interbody fusion) in the treatment of lumbar degenerative spondylolisthesis with sagittal imbalance. Fifty-nine patients were included in our analysis. Included patients were divided into 2 groups according to the surgical techniques: PLIF (posterior lumbar interbody fusion) (n = 31) and OLIF + PSF (OLIF combined with posterior spinal fixation) (n = 28). Perioperative radiographic parameters, complications, and clinical outcome from each group were assessed and compared. The operation time for both groups was 165.1 min in the OLIF group and 182.1 min in the PLIF group (P < 0.05). The intraoperative blood loss was 190.6 ml in the OLIF group and 356.3 ml in the PLIF group (P < 0.05). The number of intraoperative and postoperative complications for both groups was 7 in the OLIF group and 11 in the PLIF group. Significant clinical improvement was observed in VAS scores and ODI when comparing preoperative evaluation and final follow-up. The preoperative SVA (the distance from the posterosuperior corner of S1body to the C7 plumb line), PI (pelvic incidence), LL (lumbar lordosis), PI-LL mismatch, DH (disc height), and lumbar Cobb angles of both groups were similar. The postoperative and final follow-up SVA, LL, PI-LL mismatch, and disc height were improved in both groups, and a statistical difference was found between both groups (P < 0.05). An improvement of SVA, LL, PI-LL mismatch, and disc height at the OLIF group was better than that found at the PLIF group. An improvement in radiographic and clinical outcomes for the OLIF group was better than that seen for the PLIF group. Then, OLIF had a more curative effect in lumbar degenerative spondylolisthesis with sagittal imbalance.