Endplate-specific fusion rate 1 year after surgery for two-level anterior cervical discectomy and fusion(ACDF).

STUDY DESIGN: This is a retrospective study. OBJECTIVE: Implant nonfusion is an important prognostic factor for patients after anterior cervical discectomy and fusion (ACDF). This study aimed to investigate endplate-specific pseudarthrosis after ACDF, to determine if the rate of fusion is inferior in the lower endplate, and to identify any differences in clinical and radiological results. Research comparing each endplate on which the endplate affects nonfusion is limited. METHODS: We analyzed 71 patients with 142 total spinal levels who underwent double-level ACDF (C4-5-6 and C5-6-7) with an allograft and plate at our hospital between January 2012 and December 2018. Fusion grades were assessed using computed tomography and the Bridwell fusion grade system at 1 year postoperatively. Radiological parameters were obtained from lateral cervical radiographs collected preoperatively and at 1 month and 1 year after surgery. RESULTS: There was no difference in fusion between the C4-5-6 and C5-6-7 ACDF procedures, but the fusion rate and Bridwell fusion grade at the caudal surgery level were lower than those at the cranial surgery level (93 vs. 79%, p < 0.001). The lower endplate of the caudal fusion level showed the most common pseudarthrosis (18 of 71 [25%]). There was no difference in radiological parameters and clinical outcomes between the fusion and pseudarthrosis groups. CONCLUSION: In double-level ACDF procedures, the nonfusion rate was higher at the caudal fusion levels, especially at the lower endplates of the caudal fusion levels.

The timing of fusion surgery for clival chordoma with occipito-cervical joint instability: before or after tumor resection?

Clival chordoma with occipito-cervical (OC) joint invasion can result in preoperative and postoperative instability. The authors investigate the appropriate timing of OC fusion to prevent instability-, fusion-, and surgery time-related morbidity. Twenty-two consecutive patients underwent surgery for clival chordoma from December 2008 to September 2014. OC fusion was performed for patients with OC joint invasion and instability due to preoperative destruction of the occipital condyle or extensive postoperative condylectomy. The data in relation to OC joint instability, fusion, and surgery time were analyzed retrospectively and compared between OC fusion before and after tumor resection. Of the 22 patients, 8 with tumor invasion of the OC joint underwent OC fusion. OC fusion was performed after tumor resection in one-stage for four patients and before tumor resection in two-stage for four patients. There was OC joint instability from tumor destruction of the occipital condyle in seven patients (87.5%). Patients with OC fusion after tumor resection encountered complications such as surgery site wound dehiscence, encephalitis, and cardiac arrest with consequent mortality in one patient. These complications were avoided in subsequent patients where OC fusion was performed before tumor resection. There were no differences in the extent of tumor resection between OC fusion before and after tumor resection. Two-stage OC fusion before tumor resection can reduce instability-, fusion-, and surgery time-related morbidity and achieve feasible tumor resection when OC joint instability is expected. The extent of tumor invasion and brain stem compression should be considered when fusion precedes tumor resection.

Association of complete uncinate process removal on 2-year assessment of radiologic outcomes: subsidence and sagittal balance in patients receiving one-level anterior cervical discectomy and fusion.

BACKGROUND: Many patients with cervical radiculopathy experience stenosis of the neural foramens due to cumulative osteophyte or uncovertebral joint hypertrophy. For cervical foraminal stenosis, complete uncinate process resection (UPR) is often conducted concurrently with anterior discectomy and fusion (ACDF). The aim of this study was to assess the clinical and radiological outcomes of ACDF with complete UPR versus ACDF without UPR. METHODS: In total, 105 patients who performed one-level ACDF with a cage-and-plate construct between 2011 and 2015 were retrospectively reviewed. Among them, 37 patients had ACDF with complete UPR, and 68 patients had ACDF without UPR. Radiologic outcomes of disc height, C2-C7 lordosis, T1 slope, C2-C7 sagittal vertical axis (SVA), center of the sella turcica-C7 SVA (St-SVA), spino-cranial angle (SCA), and fusion rate were evaluated on plain X-ray at pre-operation, immediately post-operation, and at 2-year follow-up. For statistically matched pairs analysis, ACDF with UPR group (24 patients) and ACDF without UPR (24 patients) were compared. RESULTS: All of the clinical parameters improved at the 2-year follow up (P < 0.0001). Improvement in visual analogue scale (VAS) scores for arm pain was significantly improved in the ACDF with complete UPR group immediately post-operation. All cervical sagittal parameters, including cervical lordosis, segmental angle, disc height, C2-C7 SVA, St-SVA, T1 slope, and SCA, except for preoperative St-SVA, SCA, and disc height of 2 years follow-up, were similar between the ACDF with complete UPR and ACDF without UPR groups. Differences in disc height, C2-C7 SVA, and SCA at 2-year follow up after preoperative examination, however, were statistically significant (p < 0.05). Subsidence occurred in 9 patients (ACDF with complete UPR: 8 cases [33%] versus ACDF without UPR: 1 cases [4%]; p < 0.05). CONCLUSIONS: Cervical sagittal alignment after ACDF with complete UPR is not significantly different from that achieved with ACDF without UPR. However, subsidence appears to occur more often after ACDF with complete UPR than after ACDF without UPR, although with little to no clinical impact. More precise and careful selection of patients is needed when deciding on additional complete UPR.

Residence could influence the surgical outcome after corrective surgery in adult spinal deformity: comparison study between urban and rural area in Korea.

PURPOSE: Numerous factors affect the surgical outcomes in patients with adult spinal deformity (ASD). However, no study has examined the relationship between residence and physical factors and surgical outcomes in patients with ASD. Here, we analysed the impact of residence and physical factors on the post-operative outcomes of patients with ASD residing in urban (U) and rural (R) environments. METHODS: We retrospectively reviewed data from patients who had undergone ASD surgery with sacropelvic fixation at a single institution between June 2011 and May 2017 with a minimum 1 year follow-up. We divided the patients into two groups (U and R). Preoperative demographic data were reviewed, and radiographic parameters were measured preoperatively, immediately postoperatively, at 1, 3, and 6 months, and at the final follow-up. The L4 axial paraspinal muscles were measured preoperatively using magnetic resonance imaging. RESULTS: There were 25 and 34 patients in the U and R groups, respectively. Both groups had similar preoperative demographic and radiological parameters. There were no differences between the groups in post-operative radiographic parameters, clinical outcomes, and complications, but proximal junctional kyphosis (PJK) was significantly higher in the R group. Additionally, muscle mass in the multifidus and erector spinae was lower in the R than in the U group. CONCLUSIONS: Patient residence influenced PJK in patients with ASD. Mass reduction in the trunk extensor muscle is an important and existing risk factor for PJK. Surgeons should be aware of this information for preoperative counselling, informed consent, and post-operative education of patients with ASD. These slides can be retrieved from Electronic Supplementary Material.

Preoperative radiographic clues for transdural disc herniation: could it be predictable?

BACKGROUND: Transdural disc herniation (TDH) is a rare event accounting for 0.3-1.5% of all disc herniation cases. Considering the risk of leakage of the cerebrospinal fluid from the dural defect after removal of TDH or incomplete removal, it is very important to recognize TDH before surgery. This study is a retrospective case analysis to analyze the imaging findings of seven cases and to construct a preoperative prediction model for TDH. METHODS: Retrospective radiographic examination was performed among patients operated for TDH in two institutions from 2008 to 2018. The radiographic images were analyzed according to the following eight signs: including absence of dural tent, complete block of spinal canal, hawk-beak sign, double-layered lesion, increased distance between the dura and cauda equina, rim enhancement, dural tent enhancement, and epidural gas. To clarify the predictive ability of these radiographic signs, consecutive 131 surgically confirmed epidural disc herniation (EDH) patients for the last 2 years were set as a control group for TDH. The sum of radiographic findings was compared between TDH and EDH patients to determine the cutoff value. RESULTS: There were 1 thoracic and 6 lumbar TDHs among 75 thoracic and 6674 lumbar disc herniation cases with an incidence of 1.33% and 0.09%, respectively. Dural tent (p = 0.000, odds ratio = 106.67), double-layered lesion (p = 0.000, odds ratio = 22.69), and distance between the dura and cauda equina (p = 0.007, odds ratio = 52.00) were statistically significantly different between TDH and EDH. According to the receiver operating characteristic curve, the cutoff value of 1.5 had 85.7% sensitivity and 90.8% specificity. CONCLUSION: Preoperative imaging can be useful for TDH diagnosis. It is safe to consider the possibility of TDH in patients with more than two findings in the preoperative images.

Does minimally invasive fusion technique influence surgical outcomes in isthmic spondylolisthesis?

OBJECTIVE: To compare the clinical and radiographic results between open transforaminal interbody fusion (TLIF-O) and minimally invasive TLIF (TLIF-M) for single-level low grade isthmic spondylolisthesis (IS). METHODS: This study enrolled 45 patients who underwent single-level TLIF with low grade IS. The patients were divided into two groups according to operative method: TLIF-M (20 patients) and TLIF-O (25 patients). TLIF-O group was matched with TLIF-M. RESULTS: At one-year postoperatively, there were no significant differences in any radiologic parameters between the two groups. Perioperative results such as blood loss, operation time, and hospital stay were superior in TLIF-M than in TLIF-O. Fusion was achieved in 17 of 20 patients (85.0%) in TLIF-M and 23 of 25 (92.0%) patients in TLIF-O. Back Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores of TLIF-O were significantly lower than TLIF-M at one (back VAS, ODI) and six months (ODI) postoperatively. CONCLUSIONS: TLIF-M and TLIF-O produced similar clinical and radiological outcomes, including reduction of spondylolisthesis and disc space height restoration at one-year follow-up for single-level low grade IS. However, considering perioperative outcomes, back pain, and quality of life, TLIF-M might be a better option for single-level low grade IS compared to TLIF-O.

Ossification foci act as stabilizers in continuous-type ossification of the posterior longitudinal ligament: a comparative study between laminectomy and laminoplasty.

BACKGROUND: In multilevel ossification of the posterior longitudinal ligament (OPLL), laminectomy is an effective surgical technique; however, there is a possibility of kyphotic alignment change after surgery. Nevertheless, in the continuous type of OPLL, the ossification foci are connected and may act as stabilizers preventing alignment change. We here compare the surgical outcome of laminectomy and laminoplasty in continuous-type OPLL of the cervical spine. METHODS: Seventy-three patients who underwent cervical laminectomy or laminoplasty for continuous-type OPLL from 2004 to 2014 were enrolled. The clinical outcomes were assessed by using the neck disability index, visual analogue scale, and Japanese Orthopedic Association scoring systems. Radiological evaluation with plain lateral radiographs was performed to observe alignment changes. RESULTS: The perioperative clinical outcome with laminectomy did not differ significantly from that of laminoplasty. Kyphotic change was observed in 3 of 35 patients with laminectomy and 3 of 38 patients with laminoplasty. Although loss of lordosis was observed in both groups, the C2-7 Cobb angle, sagittal vertical axis (SVA), and T1 slope did not demonstrate significant statistical differences between laminectomy and laminoplasty. Moreover, the C2-7 SVA in the C7-included laminectomy group (33.9 ± 13.4) became greater than that in the C7-excluded laminectomy group (24.8 ± 11.3) at the final follow-up (p = 0.049). CONCLUSIONS: In continuous-type OPLL, the surgical outcome did not show any significant difference between laminectomy and laminoplasty. Laminectomy alone is also a good choice in continuous-type OPLL, similar to laminoplasty.

A retrospective observational study on the treatment outcomes of 26 patients with spinal cord astrocytoma including two cases of malignant transformation.

PURPOSE: To determine the biologic behavior and prognostic factors of spinal cord astrocytoma, we reviewed surgical and clinical outcomes. Due to the rarity of spinal cord astrocytoma, there is a lack of research regarding this type of tumor and malignant transformation. METHODS: We retrospectively reviewed the data from all patients on whom we performed spinal cord tumor removal between 1983 and 2014. Twenty-six patients were pathologically confirmed to have spinal cord astrocytoma or glioblastoma. Surgical extent and disease progression were confirmed by the surgeon based on operative findings, postoperative MRI, and outpatient department (OPD) follow-up. RESULTS: Pain or neurological deficit was the chief complaint for all patients. With MRI studies, there is a tendency for high-grade astrocytomas to show as enhanced and heterogeneous images. Two of the low-grade astrocytomas showed malignant transformation over the course of 4 and 11 months, respectively. The overall survival (OS) for low-grade astrocytoma was 28-480 months (mean 156.38 months); the OS for high-grade astrocytoma was 1-36 months (mean 12.00 months). CONCLUSIONS: Two of 12 low-grade cases showed malignant transformations at 4 and 11 months, respectively, based on pathological confirmation. With spinal cord astrocytomas, enhanced MRI results appeared similar to those of a malignant lesion. We suggest close observation and image correlation of low-grade astrocytomas, even when pathologically confirmed as low-grade. In this review, we found that histologic grade is the most important prognostic factor, although it is not always concordant with biologic behaviors.

Anatomical parameters of fifth lumbar vertebra in L5-S1 spondylolytic spondylolisthesis from a surgical point of view.

PURPOSE: We measured the length, width, height, and angles related to both Meyerding grading system and Marchetti-Bartolozzi classification in L5-S1 spondylolytic spondylolisthesis patients to investigate the anatomical characteristics of fifth lumbar pedicles. METHODS: Seventy patients with L5-S1 spondylolytic spondylolisthesis and general spinal disease were included. Patient attributes, Meyerding grading system and Marchetti-Bartolozzi classification of spondylolisthesis, length, width, height of L4 and L5 pedicle, and the angle between pedicle and vertebral midline were measured. The heights of L5 vertebral body, divided as anterior, mid, and posterior were also measured. RESULTS: The pedicle is elongated and the angle of the pedicle is wider in cases of L5-S1 spondylolysis. Vertebral body shape was more posteriorly wedged in L5-S1 spondylolysis. Pedicles were more narrow and shorter in L5-S1 spondylolysis. CONCLUSIONS: In L5-S1 spondylolytic spondylolisthesis, a longer screw is suitable for insertion of L5 pedicle and the screw should be inserted more medially compared to patients without spondylolysis.

Spine surgeon's kinematics during discectomy, part II: operating table height and visualization methods, including microscope.

PURPOSE: Surgeon spine angle during surgery was studied ergonomically and the kinematics of the surgeon's spine was related with musculoskeletal fatigue and pain. Spine angles varied depending on operation table height and visualization method, and in a previous paper we showed that the use of a loupe and a table height at the midpoint between the umbilicus and the sternum are optimal for reducing musculoskeletal loading. However, no studies have previously included a microscope as a possible visualization method. The objective of this study is to assess differences in surgeon spine angles depending on operating table height and visualization method, including microscope. MATERIALS AND METHODS: We enrolled 18 experienced spine surgeons for this study, who each performed a discectomy using a spine surgery simulator. Three different methods were used to visualize the surgical field (naked eye, loupe, microscope) and three different operating table heights (anterior superior iliac spine, umbilicus, the midpoint between the umbilicus and the sternum) were studied. Whole spine angles were compared for three different views during the discectomy simulation: midline, ipsilateral, and contralateral. A 16-camera optoelectronic motion analysis system was used, and 16 markers were placed from the head to the pelvis. Lumbar lordosis, thoracic kyphosis, cervical lordosis, and occipital angle were compared between the different operating table heights and visualization methods as well as a natural standing position. RESULTS: Whole spine angles differed significantly depending on visualization method. All parameters were closer to natural standing values when discectomy was performed with a microscope, and there were no differences between the naked eye and the loupe. Whole spine angles were also found to differ from the natural standing position depending on operating table height, and became closer to natural standing position values as the operating table height increased, independent of the visualization method. When using a microscope, lumbar lordosis, thoracic kyphosis, and cervical lordosis showed no differences according to table heights above the umbilicus. CONCLUSION: This study suggests that the use of a microscope and a table height above the umbilicus are optimal for reducing surgeon musculoskeletal fatigue.

Prognostic Factors of Spinal Intramedullary Hemangioblastoma : Analysis of Surgical Outcomes and Tumor Characteristics.

Objective: Spinal intramedullary hemangioblastoma is a rare and highly vascularized benign tumor. The characteristics of the tumor, its corresponding location, and surgical outcomes remain unknown. The purpose of this study was to identify risk factors and strategies for neurologic deterioration following hemangioblastoma surgery. Methods: A comprehensive retrospective analysis was undertaken to evaluate patients who underwent surgical intervention for intramedullary hemangioblastoma at our institution from 1993 to 2022. Patients with at least one year of follow-up data were included. The analysis covered patient demographics, pre- and post-operative Modified McCormick Scale (MMCS), tumor location, and tumor size. Results: This study included 25 cases. One-year after surgery, neurological deterioration was observed in 5 (20.0%) cases, and neurological improvement was found in 9 (36.0%) cases. Five cases were ventrally located, and twelve cases were dorsally located. Ventrally located cases were larger in tumor axial size (p = 0.029) than dorsal location tumors, resulting in poorer follow-up MMCS and a higher prevalence of von Hippel-Lindau syndrome (VHL) (p = 0.042). Three of them were confirmed to be supplied by the anterior spinal artery. In the case of dorsally located cases, there was no neurologic deterioration. Conclusion: In intramedullary spinal cord hemangioblastomas, cases located ventrally had a higher incidence of neurological deterioration following surgery than those located dorsally or in intramedullary extramedullary cases. Ventrally located hemangioblastomas were larger than those in other locations. They were mainly supplied by the anterior spinal artery in VHL patients.

A Propensity Score-Matched Cohort Study Comparing 3 Different Spine Pedicle Screw Fixation Methods: Freehand, Fluoroscopy-Guided, and Robot-Assisted Techniques.

OBJECTIVE: This study aimed to compare the accuracy of robotic spine surgery and conventional pedicle screw fixation in lumbar degenerative disease. We evaluated clinical and radiological outcomes to demonstrate the noninferiority of robotic surgery. METHODS: This study employed propensity score matching and included 3 groups: robot-assisted mini-open posterior lumbar interbody fusion (PLIF) (robotic surgery, RS), c-arm guided minimally invasive surgery transforaminal lumbar interbody fusion (C-arm guidance, CG), and freehand open PLIF (free of guidance, FG) (54 patients each). The mean follow-up period was 2.2 years. The preoperative spine condition was considered. Accuracy was evaluated using the Gertzbein-Robbins scale (GRS score) and Babu classification (Babu score). Radiological outcomes included adjacent segmental disease (ASD) and mechanical failure. Clinical outcomes were assessed based on the visual analogue scale, Oswestry Disability Index, 36-item Short Form health survey, and clinical ASD rate. RESULTS: Accuracy was higher in the RS group (p < 0.01) than in other groups. The GRS score was lower in the CG group, whereas the Babu score was lower in the FG group compared with the RS group. No significant differences were observed in radiological and clinical outcomes among the 3 groups. Regression analysis identified preoperative facet degeneration, GRS and Babu scores as significant variables for radiological and clinical ASD. Mechanical failure was influenced by the GRS score and patients' age. CONCLUSION: This study showed the superior accuracy of robotic spine surgery compared with conventional techniques. When combined with minimally invasive surgery, robotic surgery is advantageous with reduced ligament and muscle damage associated with traditional open procedures.

Factors Associated With Repeat Surgery in Cervical Ossification of the Posterior Longitudinal Ligaments: Minimum 8-year Follow-up Study.

STUDY DESIGN: Single-center retrospective study. OBJECTIVE: The objective of this study is to identify the factors leading to repeat surgery in patients with cervical ossification of the longitudinal ligament (OPLL) during a minimal 8-year follow-up after the initial surgery. SUMMARY OF BACKGROUND DATA: The long-term effects of cervical OPLL are well known, but it's not always clear how many patients need to have surgery again because their neurological symptoms get worse. METHODS: This study is included 117 patients who underwent surgery for cervical OPLL and had a follow-up of at least 8 years. OPLL type, surgical extent, surgical method, and sagittal radiological parameters were measured, and OPLL characteristics were analyzed. RESULTS: The average age of patients at the time of surgery was 53.2 years, with a male-to-female ratio of 78:39. The median follow-up duration was 122 months (96-170 mo). Out of the total, 20 cases (17.1%) necessitated repeat surgery, among which 8 cases required surgery at the same site as the initial operation. The highest rate of repeat surgery was observed in patients who underwent total laminectomy without fusion (TL), where 6 out of 21 patients (29%) needed a second surgery, and 5 of these (23%) involved the same surgical site. Patients who underwent repeat surgery at the same site exhibited a greater range of motion (ROM) one year postsurgery (16.4 ± 8.5° vs. 23.1 ± 12.7°, P =0.041). In addition, the ROM at 1 year was higher in patients who underwent TL compared with those who had laminoplasty. Furthermore, the recurrence rate for hill-shape OPLL was higher at 30.8% compared to 10% for plateau-shape OPLL ( P = 0.05). CONCLUSION: Larger cervical ROM 1 year after surgery is related to repeat surgery at the same level as previous surgery, especially in laminectomy without fusion surgery.

Clinical outcomes and considerations of the lumbar interbody fusion technique for lumbar disk disease in adolescents.

PURPOSE: The posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) techniques are commonly used surgical methods for wide indications such as degeneration or trauma. Although they are rarely required for lumbar disk disease in younger patients, there are a few children and adolescents who are indicated for PLIF or TLIF for other reasons, such as congenital severe stenosis with or without lumbar instability that requires wide decompression or severe bony spur that need to be removed. In such cases, different pathophysiology and outcomes are expected compared with adult patients. METHODS: We retrospectively reviewed data of 23 patients who underwent PLIF or TLIF surgery when less than 20 years old. Clinical and radiographic outcomes were assessed during a mean of 36.4 months follow-up period. The indications of lumbar interbody fusion, success of fusion, complications, and visual analog scale (VAS) were analyzed. RESULTS: Radiographs of all patients taken 6 months after the surgery showed fusion. Clinical outcome was also satisfactory, with improvement of VAS score from 7.7 preoperatively to 2.3 at 6 months after surgery. Only one patient had reoperation due to adjacent segment disease. CONCLUSIONS: For adolescent patients with severe bony spur, massive central disk rupture, or severe spondylolisthesis, lumbar interbody fusion surgery has good surgical outcome with few complications.

What are the associative factors of adjacent segment degeneration after anterior cervical spine surgery? Comparative study between anterior cervical fusion and arthroplasty with 5-year follow-up MRI and CT.

PURPOSE: It is well known that arthrodesis is associated with adjacent segment degeneration (ASD). However, previous studies were performed with simple radiography or CT. MRI is most sensitive in assessing the degenerative change of a disc, and this is the first study about ASD by radiography, CT and MRI. We sought to factors related to ASD at cervical spine by an MRI and CT, after anterior cervical spine surgery. MATERIALS AND METHODS: This is a retrospective cross-sectional study of cervical disc herniation. Patients of cervical disc herniation with only radiculopathy were treated with either arthroplasty (22 patients) or ACDF with cage alone (21 patients). These patients were required to undergo MRI, CT and radiography preoperatively, as well as radiography follow-up for 3 months and 1 year, and we conducted a cross-sectional study by MRI, CT and radiography including clinical evaluations 5 years after. Clinical outcomes were assessed using VAS and NDI. The fusion rate and ASD rate, and radiologic parameters (cervical lordosis, operated segmental height, C2-7 ROM, operated segmental ROM, upper segmental ROM and lower segmental ROM) were measured. RESULTS: The study groups were demographically similar, and substantial improvements in VAS (for arm) and NDI (for neck) scores were noted, and there were no significant differences between groups. Fusion rates were 95.2% in the fusion group and 4.5% in the arthroplasty group. ASD rates of the fusion and arthroplasty groups were 42.9 and 50%, respectively. Among the radiologic parameters, operated segmental height and operated segmental ROM significantly decreased, while the upper segmental ROM significantly increased in the fusion group. In a comparative study between patients with ASD and without ASD, the clinical results were found to be similar, although preexisting ASD and other segment degeneration were significantly higher in the ASD group. C2-7 ROM was significantly decreased in ASD group, and other radiologic parameters have no significant differences between groups. CONCLUSION: The ASD rate of 46.5% after ACDF or arthroplasty, and arthroplasty did not significantly lower the rate of ASD. ASD occurred in patients who had preexisting ASD and in patients who also had other segment degeneration. ASD may be associated with a natural history of cervical spondylosis rather than arthrodesis.

Unilateral versus bilateral percutaneous pedicle screw fixation in minimally invasive transforaminal lumbar interbody fusion.

OBJECT: Clinical results for unilateral pedicle screw fixation after lumbar interbody fusion have been reported to be as good as those for bilateral instrumentation. However, no studies have directly compared unilateral and bilateral percutaneous pedicle screw fixation after minimally invasive surgery (MIS) for transforaminal lumbar interbody fusion (TLIF). The purpose of this study was to determine whether unilateral percutaneous pedicle screw fixation is comparable with bilateral percutaneous pedicle screw fixation in 1-segment MIS TLIF. METHODS: This was a prospective randomized study of 53 patients who underwent unilateral or bilateral percutaneous pedicle screw fixation after MIS TLIF for 1-segment lumbar degenerative disc disease. Twenty-six patients were assigned to a unilateral percutaneous pedicle screw fixation group and 27 patients were assigned to a bilateral percutaneous pedicle screw fixation group. Operative time, blood loss, clinical outcomes (that is, Oswestry Disability Index [ODI] and visual analog scale [VAS] scores), complication rates, and fusion rates were assessed using CT scanning 2 years after surgical treatment. RESULTS: The 2 groups were similar in age, sex, preoperative diagnosis, and operated level, and they did not differ significantly in the length of follow-up (27.5 [Group 1] vs 28.9 [Group 2] months) or clinical results. Both groups showed substantial improvements in VAS and ODI scores 2 years after surgical treatment. The groups differed significantly in operative time (unilateral 84.2 minutes; bilateral 137.6 minutes), blood loss (unilateral 92.7 ml; bilateral, 232.0 ml), fusion rate (unilateral 84.6%; bilateral 96.3%), and postoperative scoliotic change (unilateral 23.1%; bilateral 3.7%). CONCLUSIONS: Unilateral and bilateral screw fixation after MIS TLIF produced similar clinical results. Although perioperative results were better with unilateral screw fixation, the long-term results were better with bilateral screw fixation, suggesting bilateral screw fixation is a better choice after MIS TLIF.

Association of VKORC1-1639G>A polymorphism with susceptibility to ossification of the posterior longitudinal ligament of the spine: a Korean study.

BACKGROUND: Abnormalities of bone metabolism may be involved in the pathogenesis of ossification of the posterior longitudinal ligament (OPLL) of the spine. Besides its hemostatic effect, vitamin K epoxide reductase complex subunit 1 (VKORC1) plays a pivotal role in bone mineralization. The aim of this study is to investigate whether single nucleotide polymorphisms (SNPs) of the VKORC1 gene are associated with the occurrence of OPLL in a Korean population. METHOD: A total of 98 patients with OPLL and 200 controls were genotyped for the VKORC1-1639G>A SNP (rs9923231) by polymerase chain reaction and restriction fragment length polymorphism analysis. All the patients (n = 98) in this study underwent surgery (60, posterior-only approach; 36, anterior-only approach; 2, combined anterior and posterior approach) during their admission. We analyzed this association separately according to the gender and OPLL subgroup: OPLL continuous group (continuous type plus mixed type) and OPLL segmental group (segmental and localized type). RESULTS: We found that the genotype VKORC1-1639G>A frequency was significantly associated with the occurrence of the OPLL in the female group (adjusted odds ratio = 5.22, 95 % confidence interval: 1.675 to 16.269, p = 0.004). However, there was no overall association between the OPLL susceptibility and VKORC1-1639G>A polymorphism. A subgroup analysis did not show any significant correlation between VKORC1-1639G>A polymorphism and subgroup of OPLL either. CONCLUSION: Our results suggest that the VKORC1-1639G>A SNP may increase susceptibility to OPLL in women. However, there was only a statistical association in the female group despite a number of stratified analyses. Therefore, the findings should be interpreted with caution, and further genetic study is needed to improve our understanding of the role of VKORC1 polymorphisms in determining the risk of OPLL occurrence.

Predictive risk factors for mechanical complications after multilevel posterior cervical instrumented fusion.

OBJECTIVE: Mechanical complications should be considered following the correction of multilevel posterior cervical instrumented fusion. This study aimed to investigate clinical data on the patients' pre- and postoperative cervical alignment in terms of the incidence of mechanical complications after multilevel posterior cervical instrumented fusion. METHODS: Between January 2008 and December 2018, 156 consecutive patients who underwent posterior cervical laminectomy and instrumented fusion surgery of 4 or more levels and were followed up for more than 2 years were included in this study. Age, sex, bone mineral density (BMD), BMI, mechanical complications, and pre- and postoperative radiographic factors were analyzed using multivariate logistic regression analysis to investigate the factors related to mechanical complications. RESULTS: Of the 156 patients, 114 were men and 42 were women; the mean age was 60.38 years (range 25-83 years), and the mean follow-up duration of follow-up was 37.56 months (range 24-128 months). Thirty-seven patients (23.7%) experienced mechanical complications, and 6 of them underwent revision surgery. The significant risk factors for mechanical complications were low BMD T-score (-1.36 vs -0.58, p = 0.001), a large number of fused vertebrae (5.08 vs 4.54, p = 0.003), a large preoperative C2-7 sagittal vertical axis (SVA; 32.28 vs 23.24 mm, p = 0.002), and low preoperative C2-7 lordosis (1.85° vs 8.83°, p = 0.001). The clinical outcomes demonstrated overall improvement in both groups; however, the neck visual analog scale, Neck Disability Index, and Japanese Orthopaedic Association scores after surgery were significantly worse in the mechanical complication group compared with the group without mechanical complications. CONCLUSIONS: Low BMD, a large number of fused vertebrae, a large preoperative C2-7 SVA, and low C2-7 lordosis were significant risk factors for mechanical complications after posterior cervical fusion surgery. The results of this study could be valuable for preoperative counseling, medical treatment, or surgical planning when multilevel posterior cervical instrumented fusion surgery is performed.

Risk factors for unplanned reoperation after corrective surgery for adult spinal deformity.

To determine the major risk factors for unplanned reoperations (UROs) following corrective surgery for adult spinal deformity (ASD) and their interactions, using machine learning-based prediction algorithms and game theory. Patients who underwent surgery for ASD, with a minimum of two-year follow-up, were retrospectively reviewed. In total, 210 patients were included and randomly allocated into training (70% of the sample size) and test (the remaining 30%) sets to develop the machine learning algorithm. Risk factors were included in the analysis, along with clinical characteristics and parameters acquired through diagnostic radiology. Overall, 152 patients without and 58 with a history of surgical revision following surgery for ASD were observed; the mean age was 68.9 years (SD 8.7) and 66.9 years (SD 6.6), respectively. On implementing a random forest model, the classification of URO events resulted in a balanced accuracy of 86.8%. Among machine learning-extracted risk factors, URO, proximal junction failure (PJF), and postoperative distance from the posterosuperior corner of C7 and the vertical axis from the centroid of C2 (SVA) were significant upon Kaplan-Meier survival analysis. The major risk factors for URO following surgery for ASD, i.e. postoperative SVA and PJF, and their interactions were identified using a machine learning algorithm and game theory. Clinical benefits will depend on patient risk profiles.

Clinical Effect of Transverse Process Hook with K-Means Clustering-Based Stratification of Computed Tomography Hounsfield Unit at Upper Instrumented Vertebra Level in Adult Spinal Deformity Patients.

OBJECTIVE: This study aimed to investigate the efficacy of transverse process (TP) hook system at the upper instrumented vertebra (UIV) for preventing screw pullout in adult spinal deformity surgery using the pedicle Hounsfield unit (HU) stratification based on K-means clustering. METHODS: We retrospectively reviewed 74 patients who underwent deformity correction surgery between 2011 and 2020 and were followed up for >12 months. Pre- and post-operative data were used to determine the incidence of screw pullout, UIV TP hook implementation, vertebral body HU, pedicle HU, and patient outcomes. Data was then statistically analyzed for assessment of efficacy and risk prediction using stratified HU at UIV level alongside the effect of the TP hook system. RESULTS: The screw pullout rate was 36.4% (27/74). Perioperative radiographic parameters were not significantly different between the pullout and non-pullout groups. The vertebral body HU and pedicle HU were significantly lower in the pullout group. K-means clustering stratified the vertebral body HU ≥205.3, <137.2, and pedicle HU ≥243.43, <156.03. The pullout rate significantly decreases in patients receiving the hook system when the pedicle HU was from ≥156.03 to < 243.43 (p<0.05), but the difference was not statistically significant in the vertebra HU stratified groups and when pedicle HU was ≥243.43 or <156.03. The postoperative clinical outcomes improved significantly with the implementation of the hook system. CONCLUSION: The UIV hook provides better clinical outcomes and can be considered a preventative strategy for screw-pullout in the certain pedicle HU range.