An Experimental Study on the Biomechanical Effectiveness of Bone Cement-Augmented Pedicle Screw Fixation with Various Types of Fenestrations.

OBJECTIVE: To analyze the effects of the number and shape of fenestrations on the mechanical strength of pedicle screws and the effects of bone cement augmentation (BCA) on the pull-out strength (POS) of screws used in conventional BCA. METHODS: For the control group, a conventional screw was defined as C1, a screw with cannulated end-holes was defined as C2, a C2 screw with six pinholes was defined as C3, and the control group type was set. Among the experimental screws, T1 was designed using symmetrically placed thru-hole type fenestrations with an elliptical shape, while T2 was designed with half-moon (HM)-shaped asymmetrical fenestrations. T3 and T4 were designed with single HM-shaped fenestrations covering three pitches and five pitches, respectively. T5 and T6 were designed with 0.6-mm and 1-mm wider fenestrations than T3. BCA was performed by injecting 3 mL of commercial bone cement in the screw, and mechanical strength and POS tests were performed according to ASTM F1717 and ASTM F543 standards. Synthetic bone (model #1522-505) made of polyurethane foam was used as a model of osteoporotic bone, and radiographic examinations were performed using computed tomography and fluoroscopy. RESULTS: In the fatigue test, at 75% ultimate load, fractures occurred 7781 and 9189 times; at 50%, they occurred 36122 and 82067 times; and at 25%, no fractures occurred. The mean ultimate load for each screw type was 219.1±52.39 N for T1, 234.74±15.9 N for T2, 220.70±59.23 N for T3, 216.45±32.4 N for T4, 181.55±54.78 N for T5, and 216.47±29.25 N for T6. In comparison with C1, T1, T2, T3, T4, and T6 showed significantly different ultimate load values (p<0.05). However, when the values for C2 and the fenestrated screws were evaluated with an unpaired t test, the ultimate load value of C2 significantly differed only from that of T2 (p=0.025). The ultimate load value of C3 differed significantly from those of T1 and T2 (C3 vs. T1 : p=0.048; C3 vs. T2 : p<0.001). Linear correlation analysis revealed a significant correlation between the fenestration area and the volume of bone cement (Pearson's correlation coefficient r=0.288, p=0.036). The bone cement volume and ultimate load significantly correlated with each other in linear correlation analysis (r=0.403, p=0.003). CONCLUSION: Fenestration yielded a superior ultimate load in comparison with standard BCA using a conventional screw. In T2 screws with asymmetrical two-way fenestrations showed the maximal increase in ultimate load. The fenestrated screws can be expected to show a stable position for the formation of the cement mass.

The differential effect of cervical kyphosis correction surgery on global sagittal alignment and health-related quality of life according to head- and trunk-balanced subtype.

OBJECTIVE: No reports have investigated how cervical reconstructive surgery affects global sagittal alignment (GSA), including the lower extremities, and health-related quality of life (HRQOL). The study was aimed at elucidating the effects of cervical reconstruction on GSA and HRQOL. METHODS: Twenty-three patients who underwent reconstructive surgery for cervical kyphosis were divided into a head-balanced group (n = 13) and a trunk-balanced group (n = 10) according to the values of the C7 plumb line, T1 slope (T1S), and pelvic incidence minus lumbar lordosis (PI-LL). Head-balanced patients are those with a negative C7 sagittal vertical axis (SVA), a larger LL than PI, and a low T1S. Trunk-balanced patients are those with a positive SVAC7, a normal PI-LL, and a normal to high T1S. Various sagittal Cobb angles, SVA, and lower-extremity alignment parameters were measured before and after surgery using whole-body stereoradiography. RESULTS: Cervical malalignment was corrected to achieve cervical sagittal balance and occiput-trunk (OT) concordance (center of gravity [COG]-C7 SVA < 30 mm). Significant changes in the upper cervical spine and thoracolumbar spine were observed in the head-balanced group, but no significant change in lumbopelvic alignment was observed in the trunk-balanced group. Lower-extremity alignment did not change substantially in either group. HRQOL scores improved significantly after surgery in both groups. SVACOG-C7 and SVAC2-7 were negatively and positively correlated with the 36-Item Short-Form Health Survey physical component score and Neck Disability Index, respectively. The visual analog scale for back pain, Oswestry Disability Index, and PI-LL mismatch improved significantly in the head-balanced group after cervical reconstruction surgery. CONCLUSIONS: Patients with cervical kyphosis exhibited compensatory changes in the upper cervical spine and thoracolumbar spine, instead of in the lower extremities. These compensatory mechanisms resolved reciprocally in a different fashion in the head- and trunk-balanced groups. HRQOL scores improved significantly with GSA restoration and OT concordance following cervical reconstruction.

Dynamic Stabilization Surgery in Patients with Spinal Stenosis: Long-term Outcomes and the Future.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: The purpose of this study was to analyze the long-term results for patients with lumbar spinal stenosis (LSS) treated with dynamic stabilization (DS) and to consider how we can improve the results. SUMMARY OF BACKGROUND DATA: Few studies have reported long-term outcomes of DS surgery for LSS with or without spondylolisthesis. METHODS: A single-center, single-surgeon consecutive series of LSS patients who underwent DS surgery with at least 5 years of follow-up were retrospectively reviewed. Twenty-seven patients were included in the LSS group and 38 patients in the spondylolisthesis group. Patient characteristics, operative data, radiographic parameters, clinical outcomes, and complications were analyzed at baseline and follow-up. RESULTS: In the LSS group, all radiographic parameters (e.g., disc height, segmental lordosis, segmental range of motion [ROM] at the index level and proximal adjacent level, global lordosis, and global ROM) were maintained well until the last follow-up. In the spondylolisthesis group, global lordosis decreased from 36.5°â€Š±â€Š8.2° to 32.6°â€Š±â€Š6.0° at the last follow-up (P = 0.039), and global ROM decreased from 22.1°â€Š±â€Š6.9° to 18.8°â€Š±â€Š7.1° at the last follow-up (P = 0.012). In both groups, back pain, leg pain, and Oswestry Disability Index scores showed significant and sustained improvements. Screw loosening occurred in three patients (11.1%) in the LSS group and five patients (13.2%) in the spondylolisthesis group. Symptomatic adjacent segment degeneration (ASD) occurred in two patients (7.4%) in the LSS group and three patients (7.9%) in the spondylolisthesis group. CONCLUSION: Decompression and DS surgery for LSS with or without spondylolisthesis showed favorable long-term surgical outcomes with an acceptable rate of complications and ASD. However, an improved physiological DS system should be developed.Level of Evidence: 4.

Comparison of Spinal Canal Expansion Following Cervical Laminoplasty Based on the Preoperative Lamina Angle : A Simulation Study.

OBJECTIVE: Expansion in the spinal canal area (SCA) after laminoplasty is one of the critical factors to relieve the preoperative symptoms. No previous study has compared the increases in SCA achieved by open-door laminoplasty (ODL) and double door laminoplasty (DDL) according to the preoperative lamina angle (LA). This study was designed to clarify the relationship between the laminoplasty opening angle (OA)/laminoplasty opening size (OS) and increases in the SCA following ODL and DDL according to the preoperative LA using a simulation model. METHODS: The simulation model was constructed and validated by comparing the clinical data of 64 patients who had undergone C3-C6 laminoplasty (43 patients with ODL and 21 patients with DDL). SCA expansion was predicted with a verified simulation model at various preoperative LAs (from 28° to 32°) with different OAs (40° to 44°) and OSs (10 mm to 14 mm) recruited from patient data. RESULTS: The constructed simulation model was validated by comparing clinical data and revealed a very high degree of correlation (r=0.935, p<0.001). In this validated model, at the same OA, the increase in SCA was higher following ODL than following DDL in the usual LA (p<0.05). At the same OS, the increase in SCA was slightly larger following DDL than following ODL, but the difference was not significant (p>0.05). The difference was significant when the preoperative LA was narrower or much wider. CONCLUSION: Based on clinical data, a simulation model was constructed and verified that could predict increases in the SCA following ODL and DDL. When applying this model, prediction in SCA increase using the OS parameter was more practical and compatible with clinical data. Both laminoplasties achieved enough SCA, and there was no significant difference between them in the usual range.

Durability and Failure Types of S2-Alar-Iliac Screws: An Analysis of 312 Consecutive Screws.

BACKGROUND: S2-alar-iliac (S2AI) screws improve stability across the lumbosacral junction in spinopelvic fixation procedures by crossing the cortical surfaces of the sacroiliac joint (SIJ), thereby increasing the biomechanical strength of the instrumentation. OBJECTIVE: To investigate the durability and failure types of S2AI screws after spinopelvic reconstruction surgery. METHODS: A single-center, single-surgeon consecutive series of patients who underwent spinopelvic fixation using bilateral S2AI screws with a ≥1-yr follow-up and at least 1 postoperative computed tomographic scan were retrospectively reviewed. Patient characteristics, radiographic parameters, operative data, clinical outcomes, and complications were analyzed. RESULTS: In total, 312 S2AI screws in 156 patients were evaluated (mean follow-up, 26.1 mo; range 12-71 mo). There were no significant differences in screw diameter, length, or insertion angle between right-side and left-side screws. Visual analogue scale scores for back pain, ambulatory status, and Oswestry Disability Index scores significantly improved. A total of 10 patients (3.2%) experienced SIJ pain after S2AI screw installation. SIJ pain improved in 8 of them following SIJ block. In total, 7 screws (2.2%) showed partial periscrew lucency. Set screw dislodgement occurred in 7 screws (2.2%). Screw fracture occurred in 6 screws (1.9%): 5 neck fractures and 1 shaft fracture. A total of 5 patients (1.6%) underwent revision surgery for S2AI screw failure. Distal device (L4-pelvis region) breakage occurred in 5 patients. CONCLUSION: The radiographic and clinical outcomes of S2AI screw fixation were acceptable. However, S2AI screw fixation has several drawbacks, including screw fracture and dislodgement of the set screw. SIJ irritation symptoms after S2AI screw fixation occurred with considerable frequency.

Surgical Outcomes and Complications Following All Posterior Approach for Spinal Deformity Associated with Neurofibromatosis Type-1.

OBJECTIVES: The purpose of this study was to evaluate surgical outcomes and complications of spinal deformity associated with neurofibromatosis type-1 (NF-1). METHODS: From 2012 to 2018, patients suffering from spinal deformity associated with NF-1 who underwent surgical correction were identified. Demographic data and radiographic measures were retrospectively reviewed. Pre- and postoperative whole spine radiograph images were used to determine both coronal and sagittal Cobb angles. All of patients underwent 3-dimentional computed tomographic scan and magnetic resonance imaging scan to confirm dystrophic features. For evaluation of clinical outcomes, we surveyed the pre- and postoperative scoliosis research society-22r (SRS-22r) score. RESULTS: Seven patients with spinal deformity associated with NF-1 were enrolled in this study. The mean age of patients was 29.5±1.2 years old. The mean follow-up period was 2.8±1.4 years. The apex of the deformity was located in cervicothoracic (n=1), thoracic (n=4), and lumbar region (n=2). Most patients have poor bone quality and decreased bone mineral density with average T-score of -3.5±1.0. All patients underwent surgical correction via posterior approach. The pre- and postoperative mean coronal and sagittal Cobb angle was 61.6±22.6° and 34.6±38.1°, 56.8±18.5° and 40.2±9.1°, respectively. Mean correction rate of coronal and sagittal angle was 44.7% and 23.1%. Ultimate follow-up SRS-22r score (average score, 3.9±0.4) improved comparing to preoperative score (average score, 3.3±0.9). Only one patient received revision surgery due to rod fracture. No serious complication occurred, such as neurological deficit, and viscerovascular injury. CONCLUSION: The surgical correction of patients having spinal deformity associated with NF-1 is challenging, however the radiographic and clinical outcomes are satisfactory. The all posterior approach can be a safe and effective surgical option for patients having dystrophic curves associated with NF-1.

Trends in Incidence and Treatment of Herniated Lumbar Disc in Republic of Korea : A Nationwide Database Study.

OBJECTIVE: This study aimed to determine the incidence and analyze trends of the herniated lumbar disc (HLD) based on a national database in the Republic of Korea (ROK) from January 2008 to December 2016. METHODS: This study was a retrospective analysis of data obtained from the national health-claim database provided by the National Health Insurance Service for 2008-2016 using the International Classification of Diseases. The crude incidence and age-standardized incidence of HLD were calculated, and additional analysis was conducted according to age and sex. Changes in trends in treatment methods and some treatments were analyzed using the Korean Classification of Diseases procedure codes. RESULTS: The number of patients diagnosed with HLD was 472245 in 2008 and increased to 537577 in 2012; however, it decreased to 478697 in 2016. The pattern of crude incidence and the standardized incidence were also similar. Overall, the incidence of HLD increased annually for the 30s, 40s, 50s, and 70s until 2012 and then decreased. However, the incidence of HLD for the 80s continued to increase. The crude incidence of HLD in female patients exceeded that of male patients in their middle age (30s or 40s) and was 1.5-1.6 times higher than in male patients in their 60s. The total number of open discectomy (OD) increased from 71598 in 2008 to 93942 in 2012 and then decreased to 85846 in 2016. The rate of younger patients (the 20s, 30s, and 40s) who underwent OD was decreased, and the rate of younger patients who underwent percutaneous endoscopic lumbar discectomy was increased. However, the rate of older patients (the 70s and 80s) who underwent OD was continuously increased. CONCLUSION: This nationwide data on HLD from 2008 to 2016 in the ROK demonstrated that the crude incidence and the standardized incidence increased until 2012 and then decreased. The annual crude incidence was different according to age and sex. These findings may be considered when deciding future health policy, especially in countries with a similar national health insurance system (or with plans to adopt).

Surgical Outcomes According to Dekyphosis in Patients with Ossification of the Posterior Longitudinal Ligament in the Thoracic Spine.

OBJECTIVE: Ossification of posterior longitudinal ligament (OPLL) in the thoracic spine may cause chronic compressive myelopathy that is usually progressive, and unfavorable by conservative treatment. Although surgical intervention is often needed, the standard surgical method has not been established. Recently, it has been reported that posterior decompression with dekyphosis is effective surgical technique for favorable clinical outcome. The purpose of this study was to evaluate the surgical outcomes in patients with thoracic OPLL according to dekyphosis procedure and to identify predictive factors for the surgical results. METHODS: A total of 25 patients with thoracic OPLL who underwent surgery for myelopathy from May 2004 to March 2017, were retrospectively reviewed. Patients with cervical myelopathy were excluded. We assessed the clinical outcomes according to various surgical approaches. The modified Japanese orthopedic association (JOA) scores for the thoracic spine (total, 11 points) and JOA recovery rates were used for investigating surgical outcomes. RESULTS: Of the 25 patients, 10 patients were male and the others were female. The mean JOA score was 6.7±2.3 points preoperatively and 8.8±1.8 points postoperatively, yielding a mean recovery rate of 53.8±31.0%. The mean patients' age at surgery was 52.4 years and mean follow-up period was 40.2 months. According to surgical approaches, seven patients underwent anterior approaches, 13 patients underwent posterior approaches, five patients underwent combined approaches. There was no significant difference of the surgical outcomes related with different surgical approaches. Age (≥55 years) and high signal intensity on preoperative magnetic resonance (MR) image in the thoracic spine were significant predictors of the lower recovery rate after surgery (p<0.05). Posterior decompression with dekyphosis procedure was related to the excellent surgical outcomes (p=0.047). Dekyphosis did not affect the complication rates. CONCLUSION: In this study, our result elucidated that old age (≥55 years) and presence of intramedullary high signal intensity on preoperative MR images were risk factors related to poor surgical outcomes. In the meanwhile, posterior decompression with dekyphosis affected favorable clinical outcome. Posterior approach with dekyphosis procedure can be a recommendable surgical option for favorable results.

Bicortical Screw Purchase at Upper Instrumented Vertebra (UIV) Can Cause UIV Fracture After Adult Spinal Deformity Surgery: A Finite Element Analysis Study.

OBJECTIVE: To examine the biomechanical stress distribution at the upper instrumented vertebra (UIV) according to unicortical- and bicortical purchase model by finite element analysis (FEA). METHODS: A T8 to Sacrum with implant finite element model was developed and validated. The pedicle screws were unicortically or bicortically inserted from T10 to L5, and each model was compared and the von Mises (VM) yield stress of T10 was calculated. According to the motion (flexion, extension, lateral bending, and axial rotation) of spine, boundary condition values were set as 15°, 15°, 10°, 4°. RESULTS: Although the 2 stress values did not show a significant difference between the unicortical- and bicortical purchase models in the flexion and extension, bicortical purchase model showed a larger stress distribution. However, the asymmetric behavior was significantly greater in the case of lateral bending (0.802 MPa vs. 0.489 MPa) and the rotation (5.545 MPa vs. 4.905 MPa). The greater stress was observed on the spinal body surface abutting the implanted screw. Although the maximum stress was observed around the implanted screw in the bicortical purchase model under axial loading, the VM stress of both models was not significantly different. CONCLUSION: Bicortical purchase model showed a larger stress distribution than the unicortical model, especially in the case of lateral bending and the rotation behavior. Our biomechanical simulation by FEA indicates that bicortical fixation at UIV can be a risk factor for early UIV compression fracture after adult spinal deformity surgery.

Radiographic and Clinical Outcomes Following Pedicle Subtraction Osteotomy : Minimum 2-Year Follow-Up Data.

OBJECTIVE: The purpose of this study was to report the results of pedicle subtraction osteotomy (PSO) for fixed sagittal imbalance with a minimum 2-year follow-up. Besides, authors evaluated the effect of adjunctive multi-level posterior column osteotomy (PCO) on achievement of additional lumbar lordosis (LL) during PSO. METHODS: A total of 31 consecutive patients undergoing PSO for fixed sagittal imbalance were enrolled and analyzed. Correction angle of osteotomized vertebra (PSO angle) and other radiographic parameters including pelvic incidence (PI), thoracic kyphosis, LL, and sagittal vertical axis (SVA) were evaluated. Clinical outcomes and surgical complications were also assessed. RESULTS: The mean age was 66.0±9.3 years with a mean follow-up period of 33.2±10.5 months. The mean number of fused segments was 9.6±3.5. The mean operative time and surgical bleeding were 475.9±160.5 minutes and 1406.1±932.1 mL, respectively. The preoperative SRS-22 score was 2.3±0.7 and improved to 3.2±0.8 at the final follow-up. The mean PI was 54.5±9.5°. LL was changed from 7.0±28.9° to -50.2±13.2°. The PSO angle was 33.7±13.5° (15.6±20.1° preoperatively, -16.1±19.4° postoperatively). The difference of correction angle of LL (57.3°) was greater about 23.6° than which of PSO angle (33.7°). SVA was improved from 189.5±93.0 mm, preoperatively to 12.4±40.8 mm, postoperatively. There occurred six, eight, and 14 cases of complications at intraoperative, early (<2 weeks) postoperative, and late (≥2 weeks) postoperative period, respectively. Additional operations were needed in nine patients due to the complications. CONCLUSION: PSO could provide satisfactory results for patients with fixed sagittal imbalance regarding clinical and radiographic outcomes. Additional correction of LL could be achieved with conduction of adjunctive multi-level PCOs during PSO.

Rod fracture after multiple-rod constructs for adult spinal deformity.

OBJECTIVE: This study investigated the incidence and risk factors of rod fracture (RF) after multiple-rod constructs (MRCs) for adult spinal deformity (ASD) surgery. METHODS: A single-center, single-surgeon consecutive series of adult patients who underwent posterior thoracolumbar fusion at 4 or more levels using MRCs after osteotomy with at least 1 year of follow-up were retrospectively reviewed. Patient characteristics, radiological parameters, operative data, and clinical outcomes (on the Scoliosis Research Society-22r questionnaire) were analyzed at baseline and follow-up. RESULTS: Seventy-six patients were enrolled in this study. RF occurred in 9 patients (11.8%), with all cases involving partial rod breakage. Seven patients (9.2%) underwent revision surgery. There were no significant differences in baseline demographic characteristics, radiological parameters, and surgical factors between the RF and non-RF groups. Multivariable analysis revealed that interbody fusion at the L5-S1 and L4-S1 levels could significantly reduce the occurrence of RF after MRCs for ASD (adjusted odds ratios 0.070 and 0.035, respectively). The RF group had significantly worse function score (mean 2.9 ± 0.8 vs 3.5 ± 0.7) and pain score (mean 2.8 ± 1.0 vs 3.5 ± 0.8) compared with the non-RF group at last visit. CONCLUSIONS: RF occurred in 11.8% of patients with MRCs after ASD surgery. Most RFs occurred at the lumbosacral junction or adjacent level (77%). Interbody fusion at the lumbosacral junction (L5-S1 or L4-S1 level) could significantly prevent the occurrence of RF after MRCs for ASD.

Anatomic Trajectory Screw Fixation at Upper Instrumented Vertebra Is a Substantial Risk Factor for Proximal Junctional Kyphosis.

BACKGROUND: This study aimed to investigate the risk of proximal junction kyphosis (PJK) and proximal junction failure (PJF) associated with screw trajectory (straightforward vs. mixed vs. anatomic) at upper instrumented vertebra (UIV). METHODS: A single-center, single-surgeon consecutive series of adult patients who underwent lumbar fusion for ≥4 levels (the UIV of the thoracolumbar spine, T9-L2, and the lower instrumented vertebra at the sacrum or pelvis) was retrospectively reviewed. Patients were divided into 3 groups according to UIV screw trajectory: group S, 2 straightforward screws; group M, 1 straightforward screw and 1 anatomic trajectory screw; and group A, 2 anatomic trajectory screws. RESULTS: A total of 83 patients were included in this study, including 51 in group S, 16 in group M, and 16 in group A. The incidence of PJK in group S (12 patients, 23.5%), group M (7 patients, 43.8%), and group A (9 patients, 56.3%) significantly increased in sequence by group (P = 0.044). Anatomic trajectory screw fixation increased the risk for PJF requiring revision surgery compared with straightforward screw fixation (3 patients [18.8%] vs. 1 patient [2.0%]; P = 0.040). Multivariable analysis identified that anatomic trajectory screw fixation was a significant risk factor for PJK (P = 0.008; adjusted odds ratio = 7.591; 95% confidence interval, 1.69-34.093). CONCLUSION: Anatomic trajectory screw fixation at the UIV is a substantial risk factor for PJK and PJF. To reduce PJK and PJF, straightforward screw fixation at the UIV is recommended in adult spinal deformity correction surgery.

Kyphectomy and interbody fixation using lag screws in a child with myelomeningocele kyphosis: a technical case report.

A 5-year-old boy had a thoracolumbar-level MMC that had been repaired at the day after birth and kyphotic deformity got worse as he grew. He complained of discomfort about not being able to take a supine posture and decided to perform surgery for kyphosis. In our case, surgical correction is offered to stop the deformity progression, manage the associated pain, and finally to gain sitting and supine posture. We report the surgical procedure with 4 levels of en bloc kyphectomy and using the lag screws. Especially when lag screws are used, several complications including posterior instrumentation failure, hardware prominence and wound break down can be solved by removing the implants after bone fusion has been achieved.

Effect of Vertebroplasty at the Upper Instrumented Vertebra and Upper Instrumented Vertebra +1 for Prevention of Proximal Junctional Failure in Adult Spinal Deformity Surgery: A Comparative Matched-Cohort Study.

BACKGROUND: This study aimed to compare radiographic outcomes of adult spinal deformity (ASD) surgery with or without 2-level prophylactic vertebroplasty (PVP) at the uppermost instrumented vertebra (UIV) and the vertebra 1 level proximal to the UIV. METHODS: This retrospective 1:2 matched-cohort comparative study enrolled 2 groups of patients undergoing ASD surgery, including 28 patients with PVP (PVP group) and 56 patients without PVP (non-PVP group), in 3 institutes between 2012 and 2015. The primary outcome measure was the incidence of proximal junctional kyphosis (PJK), proximal junctional failure (PJF), and proximal junctional fracture (PJFX). The secondary outcome measure were radiologic outcomes between PVP segments and non-PVP segments. RESULTS: Between the PVP group and non-PVP group, no significant differences were found in the incidence of PJK (13 [46.4%] vs. 26 [46.4%]; P = 1.000), PJF (11 [39.3%] vs. 18 [32.1%]; P = 0.516), and PJFX (11 [39.3%] vs. 18 [32.1%]; P = 0.516). The number of the PJFX segments was 16 and 33 in PVP segments and non-PVP segments, respectively. Until revision surgery or final follow-up, the PJFX had progressed in 24 non-PVP segments (82.7%), but not in PVP segments. The PJFX progression in all PVP segments stopped near the PVP mass at the final follow-up. Reoperation as a result of PJFX was performed in 1 patient (3.6%) and 8 patients (14.3%) in the PVP and non-PVP groups, respectively. CONCLUSIONS: PVP at UIV and vertebra 1 level proximal to the UIV cannot prevent PJK, PJF, and PJFX; however, it plays a positive role by delaying their progression. Furthermore, PVP tends to lower the reoperation rate after PJFX in ASD surgery.

Assessment of T1 Slope Minus Cervical Lordosis and C2-7 Sagittal Vertical Axis Criteria of a Cervical Spine Deformity Classification System Using Long-Term Follow-up Data After Multilevel Posterior Cervical Fusion Surgery.

BACKGOUND: Recently, previous research proposed a cervical spine deformity (CSD) classification using a modified Delphi approach. However, C2-C7 sagittal vertical axis (SVA) and T1 slope minus C2-C7 lordosis (TS-CL) cut-off values for moderate and severe disability were based on expert opinion. OBJECTIVE: To investigate the validity of a CSD classification system. METHODS: From 2007 to 2012, 30 consecutive patients with a minimum 5-yr follow-up having 3- or more level posterior cervical fusion met inclusion criteria. The following radiographic parameters were measured: C0-C2 lordosis, C2-C7 lordosis, C2-C7 SVA, T1 slope, and TS-CL. Pearson correlation coefficients were calculated between pairs of radiographic measures and health-related quality of life. RESULTS: Average follow-up period was 7.3 yr. C2-C7 SVA positively correlated with neck disability index (NDI) scores (r = 0.554). Regression models predicted a threshold C2-C7 SVA value of 40.8 mm and 70.6 mm correlated with moderate and severe disability based on the NDI score, respectively. The TS-CL had positive correlation with C2-C7 SVA and NDI scores (r = 0.841 and r = 0.625, respectively). Regression analyses revealed that a C2-C7 SVA value of 40 mm and 70 mm corresponded to a TS-CL value of 20° and 25°, respectively. CONCLUSION: Regression models predicted a threshold C2-C7 SVA (value of 40.8 mm and 70.6 mm) and TS-CL (value of 20° and 25°) correlated with moderate and severe disability based on the NDI, respectively. The cut-off value C2-C7 SVA and TS-CL modifier of the CSD classification can be revised accordingly.

Clinical Efficacy of Intra-Operative Cell Salvage System in Major Spinal Deformity Surgery.

OBJECTIVE: The purpose of this study was to determine the efficacy of intra-operative cell salvage system (ICS) to decrease the need for allogeneic transfusions in patients undergoing major spinal deformity surgeries. METHODS: A total of 113 consecutive patients undergoing long level posterior spinal segmental instrumented fusion (≥5 levels) for spinal deformity correction were enrolled. Data including the osteotomy status, the number of fused segments, estimated blood loss, intra-operative transfusion amount by ICS (Cell Saver®, Haemonetics©, Baltimore, MA, USA) or allogeneic blood, postoperative transfusion amount, and operative time were collected and analyzed. RESULTS: The number of patients was 81 in ICS group and 32 in non-ICS group. There were no significant differences in demographic data and comorbidities between the groups. Autotransfusion by ICS system was performed in 53 patients out of 81 in the ICS group (65.4%) and the amount of transfused blood by ICS was 226.7 mL in ICS group. The mean intra-operative allogeneic blood transfusion requirement was significantly lower in the ICS group than non-ICS group (2.0 vs. 2.9 units, p=0.033). The regression coefficient of ICS use was -1.036. CONCLUSION: ICS use could decrease the need for intra-operative allogeneic blood transfusion. Specifically, the use of ICS may reduce about one unit amount of allogeneic transfusion in major spinal deformity surgery.

Total Deformity Angular Ratio as a Risk Factor for Complications after Posterior Vertebral Column Resection Surgery.

OBJECTIVE: The aim of the present study was to identify whether the deformity angular ratio (DAR) influences the occurrence of complications after posterior vertebral column resection (PVCR) and to establish the DAR cut-off value. METHODS: Thirty-six consecutive patients undergoing PVCR from December 2010 to October 2016 were reviewed. The relationships between the total, sagittal, and coronal DAR and complications were assessed using receiver operator characteristics curves. The patients were divided into two groups according to a reference value based on the cut-off value of DAR. Demographic, surgical, radiological, and clinical outcomes were compared between the groups. RESULTS: There were no significant differences in the patient demographic and surgical data between the groups. The cut-off values for the total DAR (T-DAR) and the sagittal DAR (S-DAR) were 20.2 and 16.4, respectively (p=0.018 and 0.010). Both values were significantly associated with complications (p=0.016 and 0.005). In the higher T-DAR group, total complications (12 vs. 21, p=0.042) and late-onset complications (3 vs. 9, p=0.036) were significantly correlated with the T-DAR. The number of patients experiencing complications (9 vs. 11, p=0.029) and the total number of complications (13 vs. 20, p=0.015) were significantly correlated with the S-DAR. Worsening intraoperative neurophysiologic monitoring was more frequent in the higher T-DAR group (2 vs. 4) than in the higher S-DAR group (3 vs. 3). There was no difference in neurological deterioration between the groups after surgery. CONCLUSION: Both the T-DAR and the S-DAR are risk factors for complications after PVCR. Those who had a T-DAR >20.2 or S-DAR >16.4 experienced a higher rate of complications after PVCR.

Factors for the acquisition of 10° angular change at the lumbar spine through posterior column osteotomy in adult spinal deformity surgery.

OBJECTIVEPosterior column osteotomy (PCO) has been known to provide an angular change (AC) of approximately 10° in sagittal plane deformity. However, whether PCO can actually obtain an AC of ≥ 10° depending on the particular level in the lumbar spine and which factors can effect a gain of ≥ 10° AC after PCO remain to be elucidated. The aim of this study was to identify the factors that effect a gain of ≥ 10° AC through PCO by comparing radiographic measurements between an AC group and a control group before and after adult spinal deformity (ASD) surgery.METHODSForty consecutive patients who underwent multilevel PCOs for ASD at a single institution between 2012 and 2016 were included in this study. PCO was performed in 142 disc space levels in the lumbar spine. The authors defined the disc space level that obtained ≥ 10° AC in the sagittal plane by PCO as the AC group and the remaining patients as controls. The modified Pfirrmann grade, surgical level, implementation of the transforaminal lumbar interbody fusion (TLIF), and radiographic measurements were compared between the groups.RESULTSThere were 67 levels in the AC group and 75 in the control group. Multivariate analysis identified the surgical level at L4-5 (OR 3.802, 95% CI 1.127-12.827, p = 0.031), performing TLIF with PCO (OR 3.303, 95% CI 1.258-8.674, p = 0.015), and a preoperative kyphotic disc space angle (OR 1.397, 95% CI 1.231-1.585, p < 0.001) as the factors that significantly effected ≥ 10° AC in the sagittal plane after PCO.CONCLUSIONSIn ASD surgery, PCO cannot always achieve ≥ 10° AC in the sagittal plane. The factors that effected ≥ 10° AC in PCO for ASD were surgical level at L4-5, performing TLIF with PCO, and the preoperative kyphotic disc space angle.

Failure to generate baseline muscle motor evoked potentials during spine surgery: Risk factors and association with the postoperative outcomes.

OBJECTIVE: To identify factors associated with the failure to generate baseline muscle motor evoked potentials (mMEPs) during spinal surgery, and to determine the association between baseline mMEP generation and postoperative outcomes. METHODS: A total of 345 patients who underwent spine surgery with intraoperative mMEP monitoring were included, and we retrospectively reviewed their demographic/clinical parameters, and mMEP recording results according to lesion locations. RESULTS: Multivariable logistic regression analysis revealed that preoperative Medical Research Council grade of the weakest muscle <3 was significantly associated with failure of baseline mMEP generation in both cervical and thoracic lesions. In addition, high intramedullary T2 signal intensity on spine MRI for cervical lesions and male sex for thoracic lesions were also significantly associated with baseline mMEP generation failure. Moreover, the failure of baseline mMEP generation was a significantly associated factor for poor functional outcome in patients with thoracic lesions. CONCLUSION: Sex, radiological abnormality, and preoperative functional status were associated with baseline mMEP generation failure during spine surgery with different patterns according to lesion location. Moreover, baseline mMEP generation failure in thoracic lesion could be associated with risk of postoperative deficits. SIGNIFICANCE: The risk of baseline mMEP recording failure could be evaluated based on preoperative clinical parameters.

Surgical and radiological outcomes after posterior vertebral column resection according to the surgeon's experience.

The purpose of this study was to estimate and analyze the radiological, surgical, and clinical results of posterior vertebral column resection (PVCR) according to the surgeon's experience. Although PVCR has been recognized as the most powerful surgical technique to correct severe spinal deformity, PVCR is a technically demanding procedure with a high complication rate. A retrospective review of the chart and radiographic data of 34 consecutive patients who received PVCR was carried out. According to the time period, the former and latter 17 patients were divided into group 1 and group 2, respectively. Patients' demographics, surgical, radiological/clinical outcomes, and complications were compared between the groups. The demographic data of the patients had no significant difference between the groups. The surgical time (492.5 ±â€Š164.8 vs 350.5 ±â€Š133.9 minutes, P = .010), estimated blood loss (1294.1 ±â€Š711.9 vs 974.1 ±â€Š905.9 mL, P = .045), and length of hospital stay (22.8 ±â€Š12.9 vs 13.4 ±â€Š3.9 days, P = .017) were significantly reduced in group 2. The correction of the PVCR site (40.5°â€Š±â€Š13.3° vs 41.2°â€Š±â€Š23.7°, P = .909), sagittal vertical axis (SVA, 81.9 ±â€Š7.2 mm vs 77.9 ±â€Š102.0 mm, P = .904) were not different between the groups. The total number of complications (22 vs 10, P = .031) and patients having complications (13 vs 7, P = .039) were lower in group 2. Additional surgery was significantly lower in group 2 (13 vs 3, P = .007). The clinical outcomes by revised Scoliosis Research Society-22 (SRS-22r) questionnaire were not different between the groups. Our series revealed that the complications after PVCR may reduce from 17 cases and surgical outcomes might be stabilized by 29 cases.