Does local vancomycin powder impregnated with autogenous bone graft and bone substitute decrease the risk of deep surgical site infection in degenerative lumbar spine fusion surgery?-An ambispective study.

BACKGROUND: Deep surgical site infection (DSSI) is one of the most challenging complications in lumbar fusion surgery. Few investigations examined the effect of vancomycin powder mixed with autogenic bone graft (ABG) and bone substitutes on preventing DSSI in degenerative lumbar fusion surgeries as well as any interference with bony fusion. The aim of the study was to investigate the effects of ABG along with bone substitutes as a local vancomycin delivery system on preventing DSSI in lumbar instrumented fusion and compared with those who did not use vancomycin powder. METHODS: From January, 2015 through December, 2015, a one-year prospective study using vancomycin powder mixed with ABG and bone substitute for degenerative lumbar fusion surgeries as vancomycin (V) group, 1 gm vancomycin for 2 and 3-level, and 2 gm for more than 3-level instrumentation. From December, 2013 through December 2014, patients received degenerative lumbar fusion surgeries without using vancomycin before the vancomycin protocol were retrospectively enrolled as non-vancomycin (NV) group. Vancomycin concentration was checked at post-operative days 1 and 3 for both the serum and drainage. Patients' demographic data, microbiology reports, fusion status and functional outcomes were evaluated. RESULTS: One hundred and ten patients were enrolled prospectively in the V group, and 86 for the NV group. After an average 41 months follow-up (range, 36-54), 3 patients (3.48%) developed postoperative DSSIs in the NV group, thereby requiring revision surgeries and parenteral antibiotics treatment versus no DSSIs (0%, 0/100) in the V group. (p = 0.048). The postoperative serum vancomycin levels were undetectable and no vancomycin related side effects was encountered. The mean vancomycin concentration of drainage at postoperative days 1 and 3 were 517.96 ± 174.4 and 220.14 ± 102.3 µg/mL, respectively. At final follow-up, there was no statistical difference observed in terms of clinical and radiologic outcomes. CONCLUSIONS: Our vancomycin protocol may reduce the incidence of DSSI in degenerative lumbar fusion surgery without affecting bony fusion. LEVEL OF EVIDENCE: Level III ambispective comparative study.

Postoperative spinal orthosis may not be necessary for minimally invasive lumbar spine fusion surgery: a prospective randomized controlled trial.

BACKGROUND: With the progress and success in minimally invasive surgery of transforaminal lumbar interbody fusion (MIS TLIF), the musculoskeletal injury was minimized. However, the role of postoperative orthosis in MIS TLIF has not been established and there is little evidence supporting the routine use of orthosis in MIS TLIF. METHODS: This is a prospective randomized clinical study. 90 patients who underwent MIS TLIF were randomly divided into groups A (with postoperative spinal orthosis) and B (without postoperative spinal orthosis). Patients were followed up for an average of 12.6 months. Clinical outcome was assessed using the Oswestry disability index (ODI) and visual analogue scale (VAS). Fusion rate was classified with the BSF scale system at postoperative 6-month, and 12-month. RESULTS: Both groups had similar patient demographics. The use of postoperative spinal orthosis had no significant influence on instrumentation-related complications or radiological parameters at each follow-up. CONCLUSIONS: In this study, we conclude that postoperative spinal orthosis is not necessary for MIS TLIF. Patients without postoperative spinal orthosis had the same fusion rates and improvement of VAS and ODI scores.

Multilevel calcium pyrophosphate dihydrate deposition in cervical ligamentum flavum: clinical characteristics and imaging features.

BACKGROUND: Involvement in cervical ligamentum flavum is a rare manifestation of the calcium pyrophosphate dihydrate deposition disease. Only few cases of this condition have been reported. We revealed eighteen cases of CPPD in cervical ligamentum flavum that diagnosed at a single medical center. In our case series, clinical characteristics and magnetic resonance imaging findings of patients are described. METHODS: We retrospectively reviewed the medical charts and imaging studies of the eighteen patients with pseudogout attack of the cervical ligamentum flavum. In addition, we discussed the differences between this disease and ossification of ligamentum flavum in image manifestations. RESULTS: There were fourteen men and four women aged between 59 and 87 years. Diabetes mellitus and hypertension were the most common comorbidities. Myelopathy and neck pain were presented in most patients. C4-5 and C5-6 were attacked most frequently, and multiple- rather than single-level involvement could be observed in our series. "Acute on chronic phenomenon" was a specific magnetic resonance image finding in patients whose symptom durations were between 2 to 5 months. Compared to ossification of ligamentum flavum, calcium pyrophosphate dihydrate crystal deposition had different image signs, including morphology, side of the involved ligament, no continuity with the lamina, acute on chronic phenomenon, and presence of retro-odontoid mass. CONCLUSIONS: Nodular calcifications in cervical ligamentum flavum raise highly suspicion for calcium pyrophosphate dihydrate deposition and must be diagnosed by histological examination and polarized light microscopy. This disease is different from ossification of ligamentum flavum, and it could be recognized by specific image features.

Functional outcomes and survival after surgical stabilization for inoperable non-small-cell lung cancer with spinal metastasis of the thoracic and lumbar spines: a retrospective comparison between epidermal growth factor receptor-tyrosine kinase inhibitor and platinum-based chemotherapy groups.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To compare the surgical results between targeted therapy and post-operative chemotherapy for patients with spinal metastasis of inoperable non-small-cell lung cancer (NSCLC). SETTING: Single-center study at an academic orthopedic department in Taiwan. METHODS: Sixty-five patients were treated surgically for spinal metastasis of inoperable NSCLC with long posterior instrumentation with or without posterior decompression according to the patient's neurologic status. Post-operative radiotherapy of the spinal lesion and targeted therapy or chemotherapy were done following surgery after the surgical wound healed. Post-operative clinical outcomes and survival were evaluated and compared between these two groups. The overall survival represented survival from the date of diagnosis to death. RESULTS: Thirty-five patients were grouped as the targeted therapy group and 30 patients as the chemotherapy group. The overall median survival times were 12.0 and 10.0 months in the targeted therapy and chemotherapy groups, respectively. Sixty-two patients were able to walk with or without an aid postoperatively. There was no significant difference observed between these two groups in terms of pain relief, neurologic improvement, ambulatory improvement, and survival. CONCLUSIONS: Surgical stabilization with or without laminectomy improved functional outcomes in patients with inoperable non-small-cell lung cancer, and post-operative functional outcomes were similar between chemotherapy and targeted therapy groups. A longer survival was observed with targeted therapy for the patients whose NSCLC was diagnosed before spinal metastasis, however, the longer survival was not statistically significant.

Differences in the interbody bone graft area and fusion rate between minimally invasive and traditional open transforaminal lumbar interbody fusion: a retrospective short-term image analysis.

PURPOSE: We aimed to quantify the interbody bone graft area following transforaminal lumbar interbody fusion (TLIF) using traditional open and minimally invasive surgeries (MIS) and investigate their correlations with rates of fusion, complications, and clinical outcomes. METHODS: Patients undergoing TLIF of 1 or 2 levels between October 2015 and December 2016 were retrospectively included. Fusion and bone graft areas were assessed with computed tomography (CT) at 6 months postoperatively. The bone graft area ratio was defined as the bone graft area divided by the average endplate area. The distributions of bone graft area within the discs were also recorded. Clinical outcomes were assessed using the visual analog scale (VAS) and Oswestry Disability Index (ODI) questionnaires. RESULTS: In total, 77 disc levels in 57 patients were analyzed. The fusion rate was 79.1% in the open group and 82.4% in the MIS group (p = 0.718). Clinical outcomes of both groups improved significantly. Changes in VAS and ODI scores at 12 months postoperatively were comparable between groups. Bone graft area ratio was not significantly different between the two groups (open, 38 ± 10.8%; MIS, 38.1 ± 9.0%, p = 0.977). Analysis of bone graft distribution revealed that the contralateral-dorsal part of the disc had the lowest bone graft area. The bone graft area ratio was significantly higher in the solid union group (39.2 ± 10.4%) than in the non-solid union group (33.5 ± 6.4%, p = 0.048). CONCLUSIONS: The fusion rates, bone graft area ratios, clinical outcomes, and complications were similar between MIS and open TLIF. These slides can be retrieved under Electronic Supplementary Material.

What is the difference in morphologic features of the lumbar vertebrae between Caucasian and Taiwanese subjects? A CT-based study: implications of pedicle screw placement via Roy-Camille or Weinstein method.

BACKGROUND: Safe placement of pedicle screws without jeopardizing neurovascular structures medially and anteriorly is important during spine surgery. Inferior breach of pedicle is also dangerous due to low margin of error. Lumbar morphology and identical pedicle orientation at L1 to L5 shown on CT scan of young Taiwanese patients (90 patients) were analyzed and compared with findings reported for Caucasian subjects. METHODS: Previously reported techniques were employed to quantitatively elucidate the parameters regarding lumbar morphology and identical pedicle orientation at each vertebra. The parameters for pedicle angle (PA), pedicle diameter (PD), pedicle axis distance (PAD), midline axis distance (MAD), transverse pedicle axis distance (TPAD) and transverse intertangential angle (TITA) were measured. RESULTS: Taiwanese subjects had different PA, PD, PAD, MAD at L1 to L5 and TITA at L3 to L5 compared with Caucasian subjects. L5 had the most convergent pedicle axis, the widest PD and the shortest antero-posterior axis morphology. CONCLUSIONS: This study provides detailed information for identifying pedicle orientation during pedicle screw placement and elucidate racial differences in lumbar morphology and pedicle orientation between Taiwanese and Caucasian populations.

Intra-articular Injection of Tranexamic Acid Reduced Postoperative Hemarthrosis in Arthroscopic Anterior Cruciate Ligament Reconstruction: A Prospective Randomized Study.

PURPOSE: To evaluate the effect of intra-articular injection of tranexamic acid (TXA) in patients receiving arthroscopic anterior cruciate ligament reconstruction (ACLR). METHODS: A total of 304 patients were included in this study, which was performed between August 2017 and April 2018. Single-bundle reconstructions using autologous hamstring tendon grafts were performed in all patients. Patients were randomized into 2 groups: Group 1 patients (TXA group) received the index procedure with a 10-mL intra-articular injection of TXA (100 mg/mL). Group 2 patients (control group) received the index procedure without TXA injections. An intra-articular suction drain was placed in the joint and clamped for 2 hours after the procedure. The volume of drainage was recorded 24 hours after surgery. Clinical evaluations using the International Knee Documentation Committee functional score, range of motion, and a visual analog scale pain score were performed on day 3 and at week 4 postoperatively. RESULTS: Twenty-four hours after surgery, a significant decrease in the amount of drainage was observed in patients receiving intra-articular injections (TXA group, 56.1 ± 34.1 mL; control group, 80.1 ± 48 mL; P < .05). On day 3 and at week 4, significantly reduced pain scores were reported in the TXA group. However, at week 4, clinical function scores did not show significant differences between the 2 groups. CONCLUSIONS: Intra-articular injection of TXA could significantly reduce postoperative intra-articular bleeding in the first 24 hours in patients receiving arthroscopic ACLR. TXA injection may also decrease pain and the grade of hemarthrosis in the early postoperative period. No systemic side effects or need for aspiration was noted during the follow-up period. Therefore, intra-articular injection of TXA could be considered an effective and relatively safe solution to reduce postoperative bleeding and pain in ACLR patients. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Comparison of Tunnel Enlargement and Clinical Outcome Between Bioabsorbable Interference Screws and Cortical Button-Post Fixation in Arthroscopic Double-Bundle Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized Study With a Minimum Follow-Up of 2 Years.

PURPOSE: To investigate the tunnel enlargement rate and clinical function by comparing double-bundle anterior cruciate ligament reconstruction (ACLR) using different fixation devices. METHODS: Patients receiving primary arthroscopic double-bundle ACLR were screened and divided into 2 groups on the basis of the method of graft fixation: bioabsorbable interference screw (BS) group and cortical button (CB) group. Bone tunnel size was assessed digitally using magnetic resonance imaging, which was performed a minimum of 2 years postoperatively. Clinical evaluations were performed using the Knee Injury and Osteoarthritis Outcome Score, International Knee Documentation Committee score, and KT-1000 arthrometer 2 years postoperatively. RESULTS: Sixty patients receiving primary arthroscopic double-bundle ACLR were included. Overall, the BS group showed greater tunnel enlargement than the CB group, as well as a significantly increased rate of tunnel communication (P = .029). The average anteromedial tunnel enlargement rates for the BS and CB groups were 50% and 28%, respectively. The enlargement rate of the posterolateral (PL) femoral tunnel was similar in both groups. In the PL tibial tunnel, the CB group showed a significant increase in enlargement compared with the BS group (64% vs 45%, P = .0001). Both groups showed functional improvement in the Knee Injury and Osteoarthritis Outcome Score and International Knee Documentation Committee score. No significant difference in postoperative functional outcomes was found between the 2 groups. CONCLUSIONS: The BS group showed significantly greater tunnel enlargement in anteromedial tunnels and an increased tunnel communication rate compared with the CB group. On the other hand, the CB group showed greater tunnel enlargement in tibial PL tunnels. Tunnel communication was observed mostly on the tibial side in the BS patients. Equivalent clinical function outcomes were noted at 2 years after surgery in both groups of patients. LEVEL OF EVIDENCE: Level II, randomized controlled clinical trial.

Implantation of an empty polyetheretherketone cage in anterior cervical discectomy and fusion: a prospective randomised controlled study with 2 years follow-up.

PURPOSE: To compare the clinical outcomes, radiographic results and fusion rate of ACDF between empty PEEK cages and PEEK cages packed with ß-tricalcium phosphate. METHODS: Forty-five patients were prospectively enrolled with cervical degenerative disc disease who requiring ACDF with a PEEK cage. 23 patients were randomised to the study group (empty cages) and 22 patients were in the control group (cages filled with ß-tricalcium phosphate). Both patient groups were fixed with a cervical locking plate. A CT scan was performed 12 months postoperatively and 24 months if not confirmed fused at 12 months to evaluate the status of fusion. Clinical status was evaluated using the Japanese Orthopaedic Association (JOA) score, the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS). RESULTS: 46 levels (97.88%) in the study group and 44 levels (97.77%) in the control group were confirmed as fused at 24 months. There was no significant difference between the fusion rates observed in the study and control groups (p = 0.82). There was no significant difference in JOA, ODI, or VAS scores at 24 months follow-up. The results showed that the members of the non-fusion group tended to be older than the individuals in the fusion group at 12 months, but was not significant in statistics. CONCLUSIONS: Similar fusion rates and clinical outcomes were achieved when using ACDF with PEEK cages and instrumentation, regardless of whether the cage was filled with bone substitute at 24 months follow-up. Fusion rates improved over time and are comparable between both groups. These slides can be retrieved under Electronic Supplementary material.

The fates of pedicle screws and functional outcomes in a geriatric population following polymethylmethacrylate augmentation fixation for the osteoporotic thoracolumbar and lumbar burst fractures with mean ninety five month follow-up.

PURPOSE: Polymethylmethacrylate (PMMA) augmentation is a common method to increase pullout strength fixed for osteoporotic spines. However, few papers evaluated whether these pedicle screws migrated with time and functional outcome in these geriatrics following PMMA-augmented pedicle screw fixation. METHODS: From March 2006 to September 2008, consecutive 64 patients were retrospectively enrolled. VAS and ODI were used to evaluate functional outcomes. Kyphotic angle at instrumented levels and horizontal and vertical distances (HD and VD) between screw tip and anterior and upper cortexes were evaluated. To avoid bias, we used horizontal and vertical migration index (HMI and VMI) to re-evaluate screw positions with normalization by the mean of superior and inferior endplates or anterior and posterior vertebral body height, respectively. RESULTS: Forty-six patients with 282 PMMA-augmented screws were analyzed with mean follow-up of 95 months. Nine patients were further excluded due to bed-ridden at latest follow-up. Twenty-six females and 11 males with mean T score of - 2.7 (range, - 2.6 to - 4.1) and mean age for operation of 77.6 ± 4.3 years (range, 65 to 86). The serial HD and kyphotic angle statistically progressed with time. The serial VD did not statistically change with time (p = 0.23), and neither HMI nor VMI (p = 0.772 and 0.631). Pre-operative DEXA results did not correlate with kyphotic angle. Most patients (80.4%) maintained similar functional outcomes at latest follow-up. The incidence of screws loosening was 2.7% of patients and 1.4% of screws, respectively. The overall incidences of systemic post-operative co-morbidities were 24.3% with overall 20.2 days for hospitalization. CONCLUSION: Most patients (80%) remained similar functional outcomes at latest follow-up in spite of kyphosis progression. The incidence of implant failure was not high, but the post-operative systemic co-morbidities were higher, which has to be informed before index surgery.

Is a drain tube necessary for minimally invasive lumbar spine fusion surgery?

PURPOSE: This study aimed to evaluate if closed suction wound drainage is necessary in minimally invasive surgery of transforaminal lumbar interbody fusion (MIS TLIF). METHODS: This is a prospective randomized clinical study. Fifty-six patients who underwent MIS TLIF were randomly divided into groups A (with a closed suction wound drainage) and B (without tube drainage). Surgical duration, intraoperative blood loss, timing of ambulation, length of hospital stay and complications were recorded. Patients were followed up for an average of 25.3 months. Clinical outcome was assessed using the Oswestry disability index and visual analogue scale (VAS). Fusion rate was classified with the Bridwell grading system, based on plain radiograph. RESULTS: Both groups had similar patient demographics. The use of drains had no significant influence on perioperative parameters including operative time, estimated blood loss, length of stay and complications. Patients in group B started ambulation 1 day earlier than patients in group A (p < 0.001). Clinical outcomes were comparable between group A and group B. CONCLUSION: A drain tube can lead to pain, anxiety and discomfort during the postoperative period. We conclude that drain tubes are not necessary for MIS TLIF. Patients without drains had the benefit of earlier ambulation than those with drains.

Pauci-immune glomerulonephritis in children: a clinicopathologic study of 21 patients.

BACKGROUND: Pauci-immune glomerulonephritis (GN) represents a severe form of glomerular injury and is the most common cause of crescentic GN in adults. To date, the clinicopathologic features of pauci-immune GN are not well characterized in the pediatric population. METHODS: Twenty-six biopsies from 21 pediatric patients with pauci-immune GN were identified retrospectively from the pathology archives of the University of Chicago (biopsy incidence 5 % among pediatric patients). RESULTS: There was distinct female predominance (2.5:1) among the patient cohort. Serologic studies identified anti-neutrophil cytoplasmic antibodies (ANCA) in 85 % of patients, and 80 % had systemic manifestations of vasculitis. The median estimated glomerular filtration rate (eGFR) at presentation was 43 ml/min/1.73 m(2). Based on a previously proposed classification of ANCA-associated GN, we identified a spectrum of injury, including crescentic (n = 9), focal (n = 7), mixed (n = 5) and sclerotic GN (n = 5). Necrotizing arteritis was identified in a minority of patients (n = 3). The majority of those patients for whom data were available had been treated with cyclophosphamide and corticosteroids, with or without rituximab. Of the 21 pediatric patients, 58 % had developed chronic kidney disease at follow-up (eGFR <90 ml/min/1.73 m(2)), of whom 85 % of those had crescentic, mixed or sclerotic GN. CONCLUSION: Pediatric patients with pauci-immune GN are similar to their adult counterparts in terms of clinical manifestations and histopathologic findings. Among the 21 patients in our study, those with focal GN had the best outcomes while patients with crescentic, mixed or sclerotic GN overwhelmingly had a poor long-term outcome for kidney function.

MRI-based lesion quality score assessing ossification of the posterior longitudinal ligament of the cervical spine.

BACKGROUND CONTEXT: No method currently exists for MRI-based determination of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine using objective criteria. PURPOSE: The purpose of this study was to develop an MRI-based score to determine whether a lesion represents a cervical OPLL lesion and to establish the objective diagnostic value. STUDY DESIGN: Retrospective cohort in a single medical institution. PATIENT SAMPLE: Thirty-five patients undergoing surgery for OPLL (Group A) and 99 patients undergoing cervical disc arthroplasty for soft disc herniation (Group B) between 2011 and 2020 were retrospectively included. All OPLL lesions on unenhanced MRI scan were correlated with a corresponding CT scan. Demographics were comparable between the two groups. OUTCOME MEASURES (PHYSIOLOGIC MEASURES): Using unenhanced magnetic resonance imaging (MRI), the T1- and T2- lesion quality (LQ) scores were calculated. Receiver operating characteristic (ROC) analysis was performed to calculate the area-under-the-curve (AUC) of both LQ scores as a predictor of the presence of OPLL. Computed tomography (CT)-based Hounsfield unit (HU) values of OPLL lesions were obtained and compared with both LQ scores. The LQ scores for MRI scanners from different manufacturers were compared using Student's t test to confirm the validity of the LQ score by scanner type. METHODS: The regions of interest for signal intensity (SI) were defined as the darkest site of the lesion and the cerebrospinal fluid (CSF) at the cerebellomedullary cistern. The T1 and T2 LQ scores were measured as the ratio of the SI at the darkest site of the lesion divided by the SI of the CSF. RESULTS: The T1 and T2 LQ scores in Group A were significantly lower than those in Group B (p<.001). ROC analysis determined that T1 and T2 LQ scores of 0.46 and 0.07, respectively, could distinguish the presence of OPLL with an accuracy of 0.93 and 0.89, respectively (p<.001). When the T1 LQ score of the lesion is <0.46, a diagnosis of OPLL may be suspected with 100% sensitivity and 92.3% specificity. The HU of the lesion had a moderate negative correlation with the T1 LQ score (r=-0.665, p<.0001). Both LQ scores were unaffected by manufacturer type. CONCLUSIONS: This study found a correlation between the MRI-based T1 LQ scores and CT-based HU value for identifying OPLL lesions. Additional studies will be needed to validate that the T1 LQ score from the unenhanced MRI scan can identify cervical OPLL.

Atypical mycobacterial spondylitis as a challenging differential diagnosis to metastatic disease of the spine: a case report.

Disseminated Mycobacterium avium complex (MAC) infection is rarely seen in patients without acquired immune deficiency syndrome. A disseminated MAC infection presenting with symptoms that mimic tumor metastasis had not previously been reported. Few disseminated MAC infections have been reported, and all image patterns in these cases indicated destructive lesions. We present a case involving a tumor-like disseminated MAC infection with spondylitis in a 68-year-old man whose symptoms started with severe lower back pain and fever. Treatment for malignancy was performed initially but soon stopped after tissue proving MAC infection. Symptoms then improved dramatically after a four-drug combined anti-nontuberculous mycobacteria treatment.

Outcome of Ti/PEEK Versus PEEK Cages in Minimally Invasive Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective case-control study. OBJECTIVES: This study aims to present the clinical and radiographical outcomes of the titanium-polyetheretherketone (Ti/PEEK) composite cage compared to those of the standard PEEK cage in patients receiving minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). METHODS: Patients receiving 1 level MI-TLIF between October 2015 and October 2017 were included with a minimum of 2-year follow-up. The patients were segregated into 2 groups; Ti/PEEK group and PEEK group. Each patient was propensity-matched using preoperative age, sex, and body mass index. Early fusion rate was evaluated by computed tomography at postoperative 6 months. Clinical outcomes were assessed using the visual analog scale (VAS) and Oswestry Disability Index (ODI) scores. RESULTS: After matching, there were 27 patients included in each group. The demographics, diagnosis, and surgical details were not significantly different between the 2 groups. The 6-month rate was 88.9% in Ti/PEEK group. The fusion rate and cage subsidence rate had no difference between the 2 groups. The complication rate in the Ti/PEEK group was comparable to that in the PEEK group. There was no difference in VAS and ODI scores during a 2-year follow-up period. CONCLUSIONS: The use of Ti/PEEK composite cage was as safe and effective as the use of PEEK cage in MI-TLIF. The 6-month fusion rate was 88.9%. Our finding revealed comparable clinical results for surgeons using Ti/PEEK composite cages in MI-TLIF compared to those using the PEEK cage.

Shorter screw lengths in dynamic Dynesys fixation have less screw loosening: From clinical investigation to finite-element analysis.

BACKGROUND: The dynamic Dynesys Stabilization System preserves lumbar mobility at instrumented levels. This study investigated the effect of screw length on screw loosening (SL) after dynamic Dynesys fixation and screw displacement during lumbar motion, using clinical investigation and finite-element (FE) analysis. METHODS: Clinical data of 50 patients with degenerative spondylolisthesis treated with decompression and Dynesys fixation in 2011 were analyzed retrospectively. Horizontal sliding displacement and vertical displacement of screw tips at L4 were analyzed postoperatively using displacement-controlled FE analysis at the L4-L5 level with screw lengths 45 (long screw), 36 (median screw), and 27 (short screw), and 6.4 mm in diameter, under flexion, extension, lateral bending, and rotation. RESULTS: In 13 patients (13/50, 26%), 40 screws (40/266, 15%) were loose at mean follow-up of 101.3 ± 4.4 months. Radiographic SL at 35, 40, 45, and 50 mm were 7.7%, 10.7%, 12.1%, and 37.5%, respectively, regardless of the fixation level ( p = 0.009). FE analysis revealed that the long screw model with corresponding longer lever arm had maximal horizontal sliding displacement under all directions and maximal vertical displacement, except for lateral bending. CONCLUSION: Shorter screws in Dynesys fixation may help avoid dynamic SL. Clinically, 50 mm screws showed the greatest SL and median screw screws demonstrated the least displacement biomechanically.

CT Hounsfield unit is a reliable parameter for screws loosening or cages subsidence in minimally invasive transforaminal lumbar interbody fusion.

Retrospective cohort study. To validate computed tomography (CT) radiodensity in Hounsfield units (HU) as a prognostic marker for pedicle screw loosening or cage subsidence in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). The retrospective study involved 198 patients treated with MI-TLIF. Screw loosening (SL), cage subsidence (CS), and fusion status were assessed by plain radiographs. The risk factors of SL and CS were identified using logistic regression. A total of 258 levels and 930 screws were analyzed. During a 2-year follow-up, 16.2% and 24.7% of patients had CS and SL respectively. The cut-off value of L1 HU for predicting SL or CS was 117. The L1 HU < 117 and BMI ≥ 25 were two independent risk factors. The risk of SL or CS was 4.1 fold in patients L1 HU < 117 and 2.6 fold in patients with BMI ≥ 25. For patients concurrently having BMI ≥ 25 and pre-op L1 HU < 117, the risk was 4.3 fold. Fusion rate and clinical outcome were comparable in patients with SL or CS. L1 HU < 117 and BMI > 25 were two independent risk factors that can be screened preoperatively for preventing SL or CS and lead to better management of patients undergoing MI-TLIF.

The Impact of Cage and End plate-Related Factors on Cage Subsidence in Oblique Lateral Interbody Fusion.

OBJECTIVES: To identify cage and end plate factors of cage subsidence (CS) in patients who underwent oblique lateral interbody fusion (OLIF) and their association with patient-reported outcomes. METHODS: Sixty-one patients (43 women and 18 men), with a total of 69 segments (138 end plates) which underwent OLIF at a single academic institution between November 2018 and November 2020, were included. All the end plates were separated into CS and nonsubsidence groups. Cage-related parameters (cage height, cage width, cage insertion level, and cage position) and end plate-related parameters (position of end plate, Hounsfield unit value of the vertebra, end plate concave angle [ECA], end plate injury, and angular mismatch measured with cage/end plate angle [C/EA]) were compared and analyzed using logistic regression to predict CS. Receiver operating characteristic curve analysis was used to determine the cutoff points of the parameters. RESULTS: Postoperative CS was identified in 50 of the 138 end plates (36.2%). The CS group had significantly lower mean Hounsfield unit values of the vertebra, higher rate of end plate injury, lower ECA, and higher C/EA than the nonsubsidence group. ECA and C/EA were identified as independent risk factors for developing CS. The optimal cutoff points for ECA and C/EA were 176.9° and 5.4°, respectively. CONCLUSIONS: An ECA greater than 176.9° and a cage/end plate angular mismatch greater than 5.4° were found to be independent risk factors of postoperative CS after the OLIF procedure. These findings aid in preoperative decision-making and intraoperative technical guidance.

Reducing surgical site infections after spine surgery: the optimal amount of normal saline for intra-wound irrigation.

BACKGROUND CONTEXT: Surgical site infection (SSI) following lumbar surgery can increase healthcare costs and lead to poor clinical outcome. Irrigation of wounds with saline solution is widely accepted globally and safe for nearly all kinds of surgery. However, the efficacy of different volumes of wound irrigation has not been addressed in elective spine surgery. The role and the optimal amount of intraoperative wound saline irrigation in preventing SSI in clean spinal surgery remain unclear. PURPOSE: We aimed to investigate if insufficient intraoperative irrigation may be a risk factor for postoperative SSI. Additionally, we investigated the optimal amount of normal saline (NS) for irrigation to prevent postoperative SSI. STUDY DESIGN: This is a retrospective study of patients with degenerative spinal stenosis who were treated surgically. Patients were grouped according to the amount of intra-wound irrigation during surgery. PATIENT SAMPLE: We included 444 patients with degenerative lumbar spinal conditions who had undergone one to five level open spinal fusion surgeries from January 2015 through April 2020. OUTCOME MEASURES: The definition of superficial or deep SSI in this study was based on the Centers for Disease Control and Prevention criteria for SSI. The fusion status accessed was based on the Bridwell grading system at the final follow-up. Self-reported and clinical outcome measures include visual analog scale and Oswestry Disability Index. METHODS: A total of 193 patients underwent irrigation with a bulb syringe with manual method (B group) with 2,000 mL NS; 251 patients underwent interpulse battery-powered device irrigation (P group) with >6,000 mL NS. Based on our protocolized departmental guidelines, all patients received the same preoperative preparation and standard surgical steps and postoperative care plan. Patients' demographic and surgical parameters were recorded. The main outcome measures included superficial wound infection, deep infection and overall infection. RESULTS: The incidence of overall SSI was 4.66% in the B group and 1.59% in the P group. The univariate analysis revealed a significant correlation with DM and irrigation amount per hour during surgery but not age, BMI, smoking, operative duration, fusion level, or blood loss. We determined the optimal irrigation amount during surgery as 1,400 mL per hour based on the receiver operating characteristic (ROC) curve (sensitivity, 92.3%; specificity, 44.1%). This was statistically significant (p=.033) with an odds ratio of 9.284 (95% confidence interval 1.2-72.0). In the analysis of surgical factors, the infection group had a significantly lower irrigation amount during surgery. To summarize, patients with diabetes and those receiving less than 1,400 mL of NS/hour had a higher likelihood of developing SSI. CONCLUSIONS: We observed that diabetes and lower volume of intraoperative irrigation were both risk factors for postoperative SSI following degenerative lumbar spine surgery. To reduce SSI in lumbar spine surgery, intra-wound irrigation with more than 1,400 mL/h of NS was recommended.