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The objective of this study was to determine whether inadequate decompensation of spine and pelvis would lead to persistent compensatory action of lower extremity. Patients who underwent adult spinal deformity from January 2014 to December 2016 were included. Postoperatively, patients who showed persistent lower extremity compensation (femur obliquity angle/FOA ≥ 5°) were classified into compensated lower extremity (CLE) group and decompensated lower extremity (DLE) group with FOA 5°. Sagittal vertical axis (SVA), T1 spinopelvic inclination, TPA (T1 pelvic angle), thoracic kyphosis, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt, sacral slope and FOA were measured and compared between two groups. The lack of lumbar lordosis was assessed by PI-LL mismatch and multivariate analysis were used to investigate correlation in changes of parameters. 115 patients were classified into CLE group (23 patients) and DLE group (92 patients). Thoracic compensations were more prevalent in the CLE group while pelvic compensation was more prominent in the DLE group. Both postoperative TPA and PI-LL in the CLE group were greater than those in the DLE group while postoperative SVA was similar. At 1 year postoperatively, SVA was increased in the CB group with persistent lower extremity compensation. Changes in FOA had moderate correlation with changes in SVA and strong correlation with changes in TPA. In conclusion, postoperative persistent lower limb compensation can be interpreted into surgical undercorrection. TPA rather than SVA is a useful parameter to assess global alignment and compensatory action of the lower extremity.

BACKGROUND CONTEXT The impact of T1 slope (T1S) has emerged as a predictor of kyphotic alignment change after laminoplasty. Although it was reported that higher T1S had more pronounced lordotic curvature before surgery and higher loss of cervical lordosis (CL) after surgery, few studies have attempted to investigate these findings with the extent of laminoplasty. PURPOSE The goals of the present study were to investigate the impact of C3 involvement on the kyphosis following cervical laminoplasty in patients with high and low T1 slope. STUDY DESIGN/SETTING The data from ossification of the posterior longitudinal ligament (OPLL) patients who had undergone laminoplasty between January 2016 and January 2019 were retrospectively reviewed. PATIENT SAMPLE Patients were divided into two groups according to preoperative T1 slope, and subgroup analysis was done according to the C3 involvement in performing laminoplasty. OUTCOME MEASURES The involvement of C3 segment in performing laminopalsty, C1-2 angle, C0-2 angle, cervical lordosis and T1 slope was measured and compared. METHODS Univariate tests and multivariate logistic regression analysis were used to assess the statistical relationship between postoperative kyphosis and radiological and surgical variables. RESULTS Eighty-six patients were divided into two groups above and below preoperative T1S (20.0°). There were 33 patients (38.3%) in low T1S group and 53 patients (61.7%) in high T1S group. Twenty-three patients (26.7%) were performed with C3 involved laminoplasty. In multivariate logistic regression analysis, C3 involvement (OR; 9.671, 2.820-33.158, p= 0.000), high T1S (OR; 4.888,1.543-15.487, p= 0.007) and low T1S-CL (OR; 0.128, 0.037-0.449, p= 0.001) were significantly associated with postoperative kyphosis. In the subsequent subgroup analysis, C3 involvement was emerged as independent risk factor in high T1S group, increasing the odds of postoperative kyphosis by 27.315 -fold (1.560-478.282, p= 0.024). In high T1S group, the loss of CL was greater (p = 0.017) when C3 was involved whereas in low T1S group, the C3 involvement did not show the statistically significant difference in the change of CL (p = 0.190). CONCLUSIONS C3 involvement, low T1S-CL and high T1S increased the risk of postoperative kyphosis. Patients with high T1 slope tended to exbibit a greater loss of CL when the laminoplasty was performed extending to C3 segment. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Background We compared left and right vascular anatomy at the L5-S1 disc space and validated the anatomical feasibility of the right oblique approach for L5-S1 oblique lumbar interbody fusion. Methods Axial T2-weighted magnetic resonance imaging studies at the L5-S1 disc level were used to study 274 subjects (164 women and 110 men; average age, 62.97 years). The distance from the center of the L5-S1 disc to the medial wall of the left or right vessel was measured. Using the vessel position, 3 groups were established: medial, middle, and lateral. To describe the morphological configuration, the vessel type and the presence of perivascular adipose tissue (PVAT) around the vessels were identified on both sides. Results The vessels on the left L5-S1 disc space were located 12.47 mm from the midline and most subjects (209 subjects; 76.3%) were included in the medial or middle group. On the right side, the vessels were located more laterally (16.93 mm; P = 0.000) and most subjects (248 subjects; 90.5%) were in the middle or lateral group. On the left side, vessels were mostly veins (260 subjects; 94.9%) and 139 subjects (50.7%) had PVAT. On the right side, the vessels were mostly arteries (213 subjects; 77.7%) and 242 (88.3%) had PVAT. Conclusions The vessels on the right side of the L5-S1 disc were located more laterally, and most vessels on the right side were arteries accompanying PVAT, which might minimize vessel manipulation. These results indicate that the right side of the L5-S1 disc could provide feasible access for oblique lumbar interbody fusion at L5-S1.

STUDY DESIGN This study was a technical case report. OBJECTIVES To introduce a new transforaminal percutaneous endoscopic lumbar discectomy (PELD) technique for the treatment of upper lumbar disc herniation using an extradiscal epiduroscopic approach. SUMMARY OF BACKGROUND DATA Although upper lumbar disc herniation accounts for only 1%-2% of all cases of lumbar disc herniation, the treatment is difficult and shows relatively poor outcomes compared with lower lumbar disc herniation. The anatomic characteristics of the upper lumbar spine are somewhat different from those of the lower lumbar spine. Thus, conventional transforaminal PELD may fail to remove the herniated disc. METHODS In the setting of extradiscal epiduroscopic PELD for upper lumbar disc herniation, the approach angle on the axial plane is ~30 degrees, which is less than that of the conventional transforaminal endoscopic discectomy and the working cannula is directly targeted to the herniated disc. Four patients who presented with back and/or leg pain due to disc herniation at L1-L2 or L2-L3 disc space were treated with extradiscal epiduroscopic PELD. RESULTS The patients experienced relief from symptoms and were discharged the next day. CONCLUSIONS Extradiscal epiduroscopic PELD is a promising treatment strategy for upper lumbar disc herniation, which may otherwise lead to a poor outcome.

Background To investigate changes of oblique corridor in patients with lumbar degenerative scoliosis and determine proper working angle with respect to the direction of vertebral axial rotation during the oblique lumbar interbody fusion procedure. Methods The distance of oblique corridor and the rotational angle of the left or right apex group were measured on axial T2 magnetic resonance images and then compared with those of the propensity score-matched control group. Results Fifty-five patients of the left apex group and 57 patients of the right apex group were compared with the equal number of patients of the propensity score-matched control group. The distance of oblique corridor in the left apex group was shorter than that in the control group at the levels of L1-2 and L2-3. In contrast, the distance of oblique corridor in the right apex group was longer than that of the control group at the level of L2-3. Patients of the left apex group showed the vertebral body rotating to the left side from L1-2 to L5-S1, whereas in the right apex group, the vertebral body rotated to the right side at the levels of L1-2, L2-3, and L3-4. Conclusions In the left apex group, the oblique corridor was decreased from psoas overlap, and coupled axial rotation to the left side might increase the risk of contralateral nerve root injury during orthogonally working. Thus, surgeons should pay attention to the state of coupled vertebral axial rotation of lumbar degenerative scoliosis for the oblique lumbar interbody fusion procedure.

To retrospectively analyse the synchondrosis from the occipital bone to the whole cervical spine and determine the feasibility and validity of age estimation using computed tomography (CT) images.A total of 231 cervical spine or neck CT images of young children (7 years of age) were examined. Twelve ossification centres were assessed (occiput: n = 2; atlas: n = 2; axis, n = 6; whole sub-axial vertebra: n = 2), and the ossification process was graded as open (O, fully lucent), osseous bridging (B, partially ossified), and fusion (F, totally ossified). After the first analysis was completed, the resulting chronological chart was used to estimate the age of 10 new cases in order to confirm the usefulness of the chart.Infancy was easily estimated using the sub-axial or C2 posterior ossification centres, while the posterior occipital regions provided good estimation of age between 1-2 years. The most difficult period for accurate age estimation was between 2-4 years. However, the C2 anterior (neurocentral ossification) and C1 posterior regions did yield information to help determine the age around 3 years. The anterior occipital region was useful for age estimation between 4-5 years, and the C1-anterior region was potentially useful to help decide among the other parameters. The test for age estimation (TAE) had a very high ICC score (0.973) among the three observers.Segmentalised analysis can enhance the ability to estimate real age, at least by the year. The analysis of the occipital bone made a strong contribution to the usefulness of the chorological chart. An organised chronological chart can provide readily available information for age estimation, and the primary application of the above data (TAE) demonstrated the validity of this approach.

Purpose To evaluate a radiological and clinical difference between the curvilinear type cages compared to the straight type cages for the restoration of lumbopelvic sagittal alignment and its maintenance after transforaminal lumbar interbody fusion (TLIF) procedure. Methods 68 patients who underwent single-level TLIF using either the straight type or curvilinear type cage were retrospectively reviewed. Assessment of the lumbopelvic parameters and the height of disc space was performed before surgery as well as 2 days, 6 and 12 months after surgery. Clinical outcome was assessed using VAS and ODI. Results The curvilinear type cages were positioned more anteriorly than the straight type. Restoration of the segmental lordosis (SL) in the curvilinear group was significantly greater than the straight group and at 12 months of follow-up, the straight group showed greater decrease in the disc height than the curvilinear group. The straight group failed to show improvement of lumbar lordosis (LL), while the curvilinear group showed significant restoration of LL and could maintain it to the 6 months of follow-up. In both groups, pelvic tilt was significantly decreased and it lasted to 6 months in the straight group; whereas in the curvilinear group, it was maintained to the last follow-up of 12 months. There were no significant differences between the two groups in mean VAS and ODI score over the follow-up period. Conclusions This study demonstrates that the curvilinear type cage is superior to the straight type cage in improving the SL and maintaining both the restored lumbopelvic parameters and elevated disc height. These results could be attributable to the anterior position of the curvilinear cage which permits easy restoration of segmental lordosis and less sinking of cages.

The purpose of this study was to determine the feasibility and efficacy of bilateral decompression procedure via microscopic tubular crossing laminotomy (MTCL) for treating lumbar spinal stenosis (LSS). Seventeen patients with LSS underwent bilateral decompression via an MTCL procedure in which tubular retractor was placed. The mean age was 72 (range 59-84) years and there were 10 men and 7 women. All patients underwent pre- and postoperative dynamic lumbar x-ray, magnetic resonance (MR) image, and computed tomography. To verify the efficacy of this technique, pre- and postoperative cross-sectional area (CSA) of thecal sac, facet resection, and fatty infiltration (FI) of multifidus were measured. Clinical results were evaluated using Oswestry Disability Index (ODI), back and leg visual analog scale (VAS). The mean follow-up period was 17.5 months (range 12.1-21.2). 70.5% of MTCL was performed at the level of L4-5 and one case of dural violation (5.8%) was noted at the level of L5-S1. The mean preoperative CSA was 70.5 mm(2) (range 25.1-87.6) and it increased to 198.8 mm(2) (range 177.3-219.2) postoperatively (p = 0.00). The mean facet resection rate was 18.4% (range 9.9-26.9) and no radiological instability was noted postoperatively. MR image showed no increase in FI of the multifidus after 12 months of follow-up (p = 0.53). Preoperative clinical symptoms improved significantly at postoperative 6 months and 12 months of follow-up. These results indicate that an MTCL with use of tubular retractor system can be an effective procedure to achieve neural decompression for the treatment of LSS and it may be beneficial in preserving both facet joint and multifidus muscle.

BACKGROUND We determined the optimal approach to perform lateral lumbar interbody fusion (LLIF) to treat lumbar degenerative scoliosis (LDS) by comparing the safe zone and psoas muscle on the concave and convex sides. METHODS Patients without scoliosis (N.=52) and those with levoscoliosis (N.=55) and dextroscoliosis (N.=53) were included. Vertebral anteroposterior diameter, overlap between the retroperitoneal vessels and the anterior edge of the vertebra, and overlap between the ventral nerve roots and the posterior edge of the vertebra were measured, and safe zones were calculated. The cross-sectional area (CSA) and fatty infiltration (FI) rate of the bilateral psoas muscle were measured, and the convex and concave sides were compared. RESULTS The ventral overlap on the convex side decreased at the L3-4 and L4-5 levels in the levoscoliosis group (P=0.05 and P=0.01, respectively) and at the L2-3 and L3-4 levels in the dextroscoliosis group (P=0.01 and P=0.03, respectively). The convex side at the L3-4 and L4-5 levels presented a greater safe zone in the levoscoliosis group (76.11% vs. 74.00% at L3-4, P=0.02; 69.37% vs. 63.16% at L4-5, P=0.00). The convex side at the L2-3, L3-4, and L4-5 levels in the dextroscoliosis group showed greater safe zones compared to those in the group without scoliosis (77.78% vs. 74.40% at L2-3, P=0.02; 72.15% vs. 69.87% at L3-4, P=0.03; and 58.45% vs. 54.39% L4-5 level, P=0.01). CSA of the psoas muscle on the concave side was significantly higher at the L2-3 and L3-4 levels (P=0.02 and 0.01, respectively). The psoas muscle on the concave side was significantly thicker (P=0.00 at all levels) with a higher FI rate. CONCLUSIONS The convex retroperitoneal vessels were positioned more anteriorly, whereas the ventral nerve roots lacked significant positional alterations, increasing the convex safe zone and providing optimal disc space access and less psoas muscle injury.

BACKGROUND To evaluate the validity of intraoperative somatosensory-evoked potential (SSEP) and motor-evoked potential (MEP) monitoring according to two different warning criteria for 6 months after intramedullary spinal ependymoma (IMSE) surgery. MATERIAL AND METHODS To evaluate the validity of intraoperative somatosensory-evoked potential (SSEP) and motor-evoked potential (MEP) monitoring according to two different warning criteria for 6 months after intramedullary spinal ependymoma (IMSE) surgery. RESULTS The success rates of SSEP and MEP monitoring were 84.9% and 83.7%, respectively. There was one indeterminate case in SSEP and six in MEP. All-or-none criterion in SSEP and MEP monitoring showed higher specificity, PPV, and DOR than 50% decline criterion during 6 months. During the follow up, 37 of 38 extremities (97.4%) and 21 of 29 extremities (72.4%) were observed the improvement of sensory and motor deficit, respectively. Seven indeterminate cases also showed good clinical outcomes. However, most patients remained some degree of neurologic deficit. CONCLUSION Many false positive and false negative results of SSEP and MEP monitoring occurred immediately postoperative period. All-or-none criterion was more beneficial for IMSE surgery than 50% decline criterion. This trend was maintained until 6 months after surgery.

Objective To investigate the sagittal sacropelvic morphology and balance of the patients with SIJ pain following lumbar fusion. Methods Among 452 patients who underwent posterior lumbar interbody fusion between June 2009 and January 2013, patients with postoperative SIJ pain, being responded to SIJ block were enrolled. For a control group, patients matched for sex, age group, the number of fused level and fusion to sacrum were randomly selected. Patients were assessed radiologic parameters including lumbar lordosis, pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). To evaluate the sagittal sacropelvic morphology and balance, the ratio of PT/PI, SS/PI and PT/SS were analyzed. Results A total of 28 patients with SIJ pain and 56 patients without SIJ pain were assessed. Postoperatively, SIJ pain group showed significantly greater PT (p=0.02) than non-SIJ pain group. Postoperatively, PT/PI and SS/PI in SIJ pain group was significantly greater and smaller than those in non-SIJ pain group respectively (p=0.03, 0.02, respectively) except for PT/SS (p=0.05). SIJ pain group did not show significant postoperative changes of PT/PI and SS/PI (p=0.09 and 0.08, respectively) while non-SIJ pain group showed significantly decrease of PT/PI (p=0.00) and increase of SS/PI (p=0.00). Conclusion This study presents different sagittal sacropelvic morphology and balance between the patients with/without SIJ pain following lumbar fusion surgery. The patients with SIJ pain showed retroversed pelvis and vertical sacrum while the patients without SIJ pain have similar morphologic features with asymptomatic populations in the literature.

Study Design Technical case report. Objective The authors report surgical experience of treating contained or noncontained lumbar disc herniation (LDH) at the L3–L4 and L4–L5 or L4–L5 and L5–S1 levels by transforaminal percutaneous endoscopic lumbar discectomy and annuloplasty (PELDA) through the single entry point. Summary of Background Data When there are concurrent LDHs involving lower two levels simultaneously, PELDA has not been performed. Methods Between March 2008 and May 2011, eight patients presented with back pain or radicular lower limb pain. Upon radiologic examination using magnetic resonance imaging, the patients were diagnosed with central or paramedian LDH at low spine levels (L3–L4 and L4–L5 or L4–L5 and L5–S1) consistent with their clinical presentations. We performed double PELDA at the affected two levels simultaneously through a single skin portal. Results The symptoms were relieved dramatically, and all patients were discharged the next day. There was no radiologic instability during the follow-up period. Conclusions Transforaminal PELDA to treat two levels of LDH through a single portal could be considered as one of the minimally invasive treatment modalities that avoids conventional open surgery.

The purpose of this retrospective study was to examine the association of facet tropism and progressive facet arthrosis (PFA) after lumbar total disc replacement (TDR) surgery using ProDisc-L.A total of 51 segments of 42 patients who had undergone lumbar TDR using ProDisc-L between October 2003 and July 2007 and completed minimum 36-month follow-up period were retrospectively reviewed. The changes of facet arthrosis were categorized as non-PFA and PFA group. Comparison between non-PFA and PFA group was made according to age, sex, mean follow-up duration, grade of preoperative facet arthrosis, coronal and sagittal prosthetic position and degree of facet tropism. Multiple logistic regression analysis was also performed to analyze the effect of facet tropism on the progression of facet arthrosis.The mean age at the surgery was 44.43 ± 11.09 years and there were 16 males and 26 females. The mean follow-up period was 53.18 ± 15.79 months. Non-PFA group was composed of 19 levels and PFA group was composed of 32 levels. Age at surgery, sex proportion, mean follow-up period, level of implant, grade of preoperative facet arthrosis and coronal and sagittal prosthetic position were not significantly different between two groups (p = 0.264, 0.433, 0.527, 0.232, 0.926, 0.849 and 0.369, respectively). However, PFA group showed significantly higher degree of facet tropism (7.37 ± 6.46°) than that of non-PFA group (3.51 ± 3.53°) and p value was 0.008. After adjustment for age, sex and coronal and sagittal prosthetic position, multiple logistic regression analysis revealed that facet tropism of more than 5° was the only significant independent predictor of progression of facet arthrosis (odds ratio 5.39, 95 % confidence interval 1.251-19.343, p = 0.023).The data demonstrate that significant higher degree of facet tropism was seen in PFA group compared with non-PFA group and facet tropism of more than 5° had a significant association with PFA after TDR using ProDisc-L.

Background Segmental translation after lumbar total disc replacement (TDR) with ProDisc-L® prosthesis frequently observed radiographic findings during follow-up period. However its precise pathomechanism and relation with facet arthrosis have not been investigated yet. This study was performed to evaluate possible factors that affect postoperative segmental translation and to identify its relation with facet joint degeneration after lumbar TDR using ProDisc-L® prosthesis. Methods Thirty-five consecutive patients, who underwent lumbar TDR using ProDisc-L®, completed minimum 24 months follow-up. Segmental translation was assessed postoperatively at 1 month and at least at 24 months by using dynamic plain radiograph. Segmental translation was assessed in relation to patient age, sex, change of functional spinal unit (FSU) height, segmental range of motion (ROM), global lumbar ROM, implanted level, relative prosthesis size and prosthesis position. The comparison of segmental translation between progressive facet arthrosis (PFA) group and non-PFA group was also made. Results The mean segmental translation was 0.49±0.49 mm at 1 month after surgery and showed significant increase to 0.83±0.78 mm at last follow-up (P=0.014). Change of FSU height, segmental ROM, global lumbar ROM, implanted level and relative size of prosthesis were the significant factors among the variables related to segmental translation that authors assessed (P=0.032, P=0.000, P=0.001, P=0.046 and P=0.042, respectively). There was no significant intergroup difference of mean segmental translation between PFA group and non-PFA group (P=0.586). Conclusions This study demonstrates that segmental translation after TDR using ProDisc-L® has significant relations with change of FSU height, segmental ROM, global lumbar ROM, implanted level and relative size of prosthesis. With the intergroup comparison, PFA group did not show significant higher segmental translation than non-PFA group.

Objective Cervical spondylosis and shoulder disorders share with neck and shoulder pain. Differentiating between the two can be challenging and patient with combined pathologies is less likely to have pain improvement even after successful cervical operation. We investigated clinical characteristics of the patients who were diagnosed as cervical spondylosis however, were turned out to have shoulder disorders or the patients whose pain was solely originated from shoulder. Methods Between January 2008 and October 2009, the patients presenting neck and shoulder pain with diagnosis of cervical spondylosis were enrolled. Among them, the patients who met following inclusion criteria were grouped into shoulder disorder group and the others were into cervical spondylosis group. Inclusion criteria were as follows. (1) To have residual or unresponsive neck and shoulder pain despite of optimal surgical treatment due to concomitant shoulder disorders. (2) When the operation was cancelled for the reason that shoulder and neck pain was proved to be related with unrecognized shoulder disorders. The authors retrospectively reviewed and compared clinical characteristics, level of pathology, diagnosis of cervical spondylosis and shoulder disorders. Results A total of 96 patients were enrolled in this study. Shoulder disorder group was composed of 15 patients (15.8%) and needed additional orthopedic treatment. Cervical spondylosis group was composed of 81 patients (84.2%). There was no significant differences in mean age, sex ratio and major diagnosis in both shoulder disorder and cervical spondylosis group (p=0.33, 0.78, and 0.68 respectively). However, the distribution of pathologic levels was found to be significantly different (p=0.03). In shoulder disorder group, the majority of lesions (15 of 19 levels, 78.9%) were located at the level of C4-5 (36.8%) and C5-6 (42.1%). On the other hand, in cervical spondylosis group, C5-6 (39.0%) and C6-7 (37.1%) were the most frequently observed level of lesions (80 of 105 levels, 16.1%). Conclusion It is very important for spine surgeons to perform a complete history taking and physical examination using the special tests, and to discover the underlying shoulder disorders causing of symptom in treatment of cervical spondylosis presenting neck and shoulder pain.

A 72-year-old man presented with gas-containing disc herniations resulting in dual nerve root (exiting and traversing root) compression at the single level manifesting as lower back pain with the right anterolateral thigh and medial calf pain and no response to 4 weeks of conservative treatment. Physical examination revealed positive Lasegue's sign at 40°, but the patient had no evidence of neurological deficit. Magnetic resonance imaging showed two separate disc herniations, a posterocentral herniated disc that had migrated inferiorly at the L3-4 level and compressed the L4 traversing root, and another that had compressed the L3 exiting root in the extraforaminal area at the same level. Coronal computed tomography demonstrated the presence of gas in the spinal canal and extraforaminal area at the L3-4 level, and the vacuum phenomenon was also noted at the L3-4 intervertebral disc. Microscopic discectomy was performed using midline and paramedian approaches, and the presence of gas was confirmed by bubbles after pouring saline into the area intraoperatively. Histological examination revealed fibrous tissue. The patient was discharged with complete relief of pain. This is a rare case of symptomatic gas-containing disc herniations causing dual compression of exiting and traversing roots at a single disc level.

Study design A retrospective case-control study. Objective To elucidate the role of changes of lumbopelvic sagittal alignment in the pathogenesis of sacroiliac joint (SIJ) pain after posterior lumbar interbody fusion (PLIF) by comparing these values with the control, patients without SIJ pain. Summary of background data There has been no study specifically addressing the relation between lumbopelvic sagittal alignment and SIJ pain after PLIF. Methods Among 346 patients who underwent PLIF between June 2009 and April 2012, patients with postoperative SIJ pain who responded to SIJ block were enrolled. For a control group, patients who were matched for sex, age group, the number of fused level, and fusion to sacrum were randomly selected. The patients were assessed using clinical and radiological parameters including age, sex, diagnosis, bone mineral density, body mass index, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt, and sacral slope. Target LL (PI + 9°), achieved rate of LL (postoperative LL/target LL × 100), and LL-PI mismatch (Δ) were also calculated and compared between 2 groups. Results Twenty-three patients (9 males and 14 females) with SIJ pain and 46 patients (18 males and 28 females) without SIJ pain were assessed. Postoperatively, the SIJ pain group showed significantly greater pelvic tilt (19.88 ± 10.42°, P = 0.03), smaller achieved rate of LL (64.3%, P = 0.02), and substantial residual LL-PI mismatch (-14.45 ± 12.16°, P = 0.03) than the non-SIJ pain group (14.25 ± 7.68°, 73.2%, and -8.26 ± 9.12°, respectively). The degree of correlation between LL and PI in both the SIJ pain group and the non-SIJ pain group was positive preoperatively (r = 0.569; P = 0.003, r = 0.591; P = 0.000, respectively). Although correlation of the SIJ pain group remained positive postoperatively (r = 0.601, P = 0.002), it became strongly positive in the non-SIJ pain group (r = 0.856, P = 0.000). Conclusion This study indicates that lumbopelvic sagittal imbalance inferred from greater pelvic tilt and inadequately restored LL may play a central role in the development of SIJ pain after PLIF. Thus, it is important to restore lumbopelvic sagittal balance and to evaluate PI to determine the ideal LL that is needed to prevent postoperative SIJ pain. Level of evidence 3.

This is a prospective randomized comparison study between the fluoroscopy-guided and navigation coupled with O-arm-guided pedicle screw placement in the thoracic and lumbosacral spines.The objective of the study was to evaluate the accuracy and clinical benefits of a navigation coupled with O-arm-guided method in the thoracic and lumbar spines by comparing with a C-arm fluoroscopy-guided method.Under fluoroscopy guidance, 138 pedicle screws were inserted from T9 to S1 in 20 patients, and 124 pedicle screws were inserted from T9 to S1 in 20 patients using the navigation. The position of the screws within the pedicle was assessed from grade 0 (no violation cortex) to grade 3 (4 mm violation), and the location of the violated cortex was determined. Preparation time of each equipment setting, time for screwing, and the number of x-ray shots were evaluated.The number of screws observed as grade 0 was 121 (87.7%) in the fluoroscopy-guided group and 114 (91.9%) in the navigation-guided group. The lateral cortex was most commonly involved in the fluoroscopy-guided group (6 cases, 35.3%), and the medial cortex was most common in the navigation-guided group (4 cases, 40%). The mean time required for preparation for screw placement was 3.7 minutes in the fluoroscopy-guided group and 14.2 minutes in the navigation-guided group. Average screwing time was 3.6 minutes in the fluoroscopy-guided group and 4.3 minutes in the navigation-guided group. The mean number of x-ray shots for each screw placement in the fluoroscopy-guided group was 6.5. Postoperatively, 2 patients with misplacement of a screw under fluoroscopy guidance presented ipsilateral leg paresthesia, possibly related to the screw position.The present prospective study reveals that the pedicle screw placement guided by the navigation coupled with O-arm system was more accurate and safer than that under fluoroscopy guidance.

Objective : The authors performed a retrospective study to assess the clinical and radiological outcome in symptomatic lumbar spondylolysis patients who underwent a direct pars repair surgery using two different surgical methods; pedicle screw with universal hook system (PSUH) and direct pars screw fixation (DPSF), and compared the results between two different treated groups. Methods : Forty-seven consecutive patients (PSUH; 23, DPSF; 15) with symptomatic lumbar spondylolysis who underwent a direct pars repair surgery were included. The average follow-up period was 37 months in the PSUH group, and 28 months in the DPSF group. The clinical outcome was measured using visual analogue pain scale (VAS) and Oswestry disability index (ODI). The length of operation time, the amount of blood loss, the duration of hospital stay, surgical complications, and fusion status were also assessed. Results : When compared to the DPSF group, the average preoperative VAS and ODI score of the PSUH group were less decreased at the last follow-up; (the PSUH group; back VAS : 4.9 vs. 3.0, leg VAS : 6.8 vs. 2.2, ODI : 50.6% vs. 24.6%, the DPSF group; back VAS : 5.7 vs. 1.1, leg VAS : 6.1 vs. 1.2, ODI : 57.4% vs. 18.2%). The average operation time was 174.9 minutes in the PSUH group, and 141.7 minutes in the DPSF group. The average blood loss during operation was 468.8 cc in the PSUH group, and 298.8 cc in the DPSF group. The average hospital stay after operation was 8.9 days in the PSUH group, and 7 days in the DPSF group. In the PSUH group, there was one case of a screw misplacement requiring revision surgery. In the DPSF group, one patient suffered from transient leg pain. The successful bone fusion rate was 78.3% in the PSUH group, and 93.3% in the DPSF group. Conclusion : The present study suggests that the technique using direct pars screw would be more effective than the method using pedicle screw with lamina hook system, in terms of decreased operation time, amount of blood loss, hospital stay, and increased fusion success rate, as well as better clinical outcome.

Objective: To elucidate etiological factors of heterotopic ossification (HO) by evaluating retrospectively if HO is a unique finding following cervical total disc replacement (CTDR) or a finding observable following an anterior cervical interbody fusion (ACIF). Methods: The authors had selected 87 patients who underwent anterior cervical surgery (TDR or ACIF), and could be followed up more than 24 months. A cervical TDR was performed using a Bryan disc or a ProDisc-C and an ACIF using a standalone cage or fibular allograft with a plate and screws system. The presence of HO was determined by observing plain radiography at the last follow up. The relation between HO occurrence and specific preoperative radio- logical findings (osteophyte and calcification of posterior longitudinal ligament (PLL)) at the index level was investigated. Results: Cervical TDR was performed in 40 patients (43 levels) and ACIF in 47 patients (54 levels). At the final radiographs, HO was demonstrated at 27 levels (TDR-Bryan; 8/18, TDR-Prodisc-C; 12/25, ACIF-cage alone; 7/29, and ACIF-plate screw; 0/25). Mean ROM at the last follow-up of each TDR subgroup were 7.8±4.7° in Bryan, 3.89±1.77° in Prodisc-C, and it did not correlated with the incidence of HO. Fusion status of ACIF groups was observed as 2 case of grade 1, 6 of grade 2, and 21 of grade 3 in cage alone subgroup, and no case of grade 1, 4 of grade 2, and 21 of grade 3 in plate screw subgroup. Fusion status in ACIF-cage alone subgroup was significantly related to the HO incidence. The preoperative osteophyte at the operated level observed in 27 levels, and HO was demonstrated in 12 levels (TDR-Bryan; 3/5, TDR-Prodisc-C; 2/3, ACIFcage alone; 7/11, and ACIF-plate screw; 0/8). Preoperative PLL calcification at the operated level was observed 22 levels, and HO was defined at 14 levels (TDR-Bryan; 5/5, TDR-Prodisc-C; 4/5, ACIF-cage alone; 5/7, and ACIF-plate screw; 0/5). The evidence of preoperative osteophyte and PLL calcification showed statistically significant relations to the occurrence of HO. Conclusion: HO was observed in both TDR and ACIF groups. HO was more frequently occurred in TDR group regardless of prosthesis type. In ACIF group, only cage alone subgroup showed HO, with relation to fusion status. Preoperative calcification of longitudinal ligaments and osteophyte were strongly related to the occurrence of HO.