Lordosis distribution index for predicting mechanical complications after long-level fusion surgery: comparison of Global Alignment and Proportion score and Roussouly classification.

OBJECTIVE: Both the Global Alignment and Proportion (GAP) score and Roussouly classification account for the lordosis distribution index (LDI), but the LDI of the GAP score (G-LDI) is typically set to 50%-80%, while the LDI of the Roussouly classification (R-LDI) varies depending on the degree of pelvic incidence (PI). The objective of this study was to validate the ability of the G-LDI to predict mechanical complications and compare it with the predictive probability of R-LDI in patients with long-level fusion surgery. METHODS: A total of 171 patients were divided into two groups: 93 in the nonmechanical complication group (non-MC group) and 78 in the mechanical complication group (MC group). The mean age of the participants was 66.79 ± 8.56 years (range 34-83 years), and the mean follow-up period was 45.49 ± 16.20 months (range 24-62 months). The inclusion criteria for the study were patients who underwent > 4 levels of fusion and had > 2 years of follow-up. The predictive models for mechanical complications using the G-LDI and R-LDI were analyzed using binomial logistic regression and receiver operating characteristic analyses. RESULTS: There was a significant correlation between R-LDI and PI (r = -0.561, p < 0.001), while there was no correlation between G-LDI and PI (r = 0.132, p = 0.495). In reference to G-LDI, most patients in the non-MC group were classified as having alignment (72, 77.4%), while the MC group had an inhomogeneous composition (aligned: 34, 43.6%; hyperlordosis: 37, 47.4%). The agreement between the G-LDI and R-LDI was moderate (κ = 0.536, p < 0.001) to fair (κ = 0.383, p = 0.011) for patients with average or large PI, but poor (κ = -0.255, p = 0.245) for those with small PI. The areas under the curve for the G-LDI and R-LDI were 0.674 (95% CI, 0.592-0.757) and 0.745 (95% CI, 0.671-0.820), respectively. CONCLUSIONS: The R-LDI, which uses a PI-based proportional parameter, enables individual quantification of LL for all PI sizes and has been shown to have a higher accuracy in classifying cases and a stronger correlation with the risk of mechanical complications compared with G-LDI.

Evolution of sagittal spinal shape for the development of thoracic ossification of ligamentum flavum.

Thoracic ossification of the ligamentum flavum (TOLF) is a rare pathology for which limited research exists. While it is known that mechanical factors play a role in the development of TOLF, little is currently understood about the sagittal alignment and related mechanical stress involved in its development. This study aims to describe the sagittal alignment of patients with TOLF based on the pathologic evolution of the Roussouly classification. The current study evaluated the preoperative Roussouly type in consecutive patients who underwent posterior decompressive laminectomy with or without posterior screw fixation for TOLF between January 2015 and December 2021. The post-evolution sagittal alignments were analyzed using the classic Roussouly classification based on sacral slope (SS). To determine the pre-evolution Roussouly type, the patients were retrospectively classified using their individual PI and PT values. Lumbopelvic parameters and morphological index including inflection point (IP), lumbar apex (LA), and lordosis distribution index (LDI) were also evaluated. Forty-three patients (21 women and 22 men) were included; their mean age was 64.21 ±â€…11.01 years (range 43-81). The most affected level was T10-11 (48.83%). The mean PI was 50.81 ±â€…9.56°, the mean SS was 33.11 ±â€…8.61°and the mean PT was 17.69 ±â€…7.89°. According to the post-evolution Roussouly classification, type 2 shape was the most frequently observed type (n = 23, 53.5%) in the post-evolution classification while type 3 was the most common type observed in the pre-evolution classification (n = 22, 51.5% and P = .00). The level of IP and LA in type 3 moved caudally (around L2 and L4/5 level, respectively) and the LDI increased (77.98 ±â€…8.08%) than the normal standard value. The authors found that the majority of the patients had a false type 2 spine, which had evolved pathologically from Roussouly type 3 and exhibited increased LDI, a lowered level of IP, and a lowered level of LA. These changes of spinal shape, including the transition to long hypolordosis and increased length of the thoracic kyphosis, may have accentuated tensile stress at the lower thoracic spine and contributed to the development of TOLF.

Impact of C3 Involvement on Postoperative Kyphosis Following Cervical Laminoplasty: A Comparison Between High and Low T1 Slope.

BACKGROUND: The goal of the present study was to investigate the impact of C3 involvement on the postoperative kyphosis following cervical laminoplasty in patients with high and low T1S. METHODS: The data from ossification of the posterior longitudinal ligament patients who had undergone laminoplasty between January 2016 and December 2019 were retrospectively reviewed. Patients were divided into low-and high-T1S groups according to preoperative T1S, and the postoperative alignment change was compared between the groups. The relationships between postoperative cervical kyphosis and preoperative variables, including gender, C3 laminoplasty, T1S, cervical lordosis (CL), C2-7 Sagittal Vertical Axis, and T1S minus CL (T1S-CL) were investigated. RESULTS: Eighty-six patients were divided into 2 groups above and below median preoperative T1S (23.70). There were thirty-three patients (38.3%) in low-T1S group and fifty-three patients (61.7%) in high-T1S group. Twenty-three patients (26.7%) were performed with C3 involved laminoplasty. C3 laminoplasty (odds ratio [OR], 9.67; 2.82-33.16; P = 0.000), high T1S (OR, 4.89; 1.54-15.49; P = 0.007), and mismatched T1S-CL (OR, 5.96; 1.83-19.43; P = 0.003) were significantly associated with postoperative kyphosis. In high-T1S group, the loss of CL was significant (P = 0.017) when C3 laminoplasty was performed, whereas, in low-T1S group, the C3 laminoplasty did not show the statistically significant difference. (P = 0.194). CONCLUSIONS: C3 laminoplasty, mismatched T1S-CL, and high T1S were found to increase the risk of postoperative kyphosis following cervical laminoplasty. Patients with high T1 slope tended to exhibit a greater loss of CL when the laminoplasty was performed extending to C3 segment.

Anatomical Feasibility of Right Oblique Approach for L5-S1 Oblique Lumbar Interbody Fusion.

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.

Extradiscal Epiduroscopic Percutaneous Endoscopic Discectomy for Upper Lumbar Disc Herniation A Technical Note.

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.

Postoperative lower limb compensation in patient with adult spinal deformity.

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.

Vertebral Body Rotation in Patients with Lumbar Degenerative Scoliosis: Surgical Implication for Oblique Lumbar Interbody Fusion.

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.

MRI-based determination of convex or concave surgical approach for lateral lumbar interbody fusion in lumbar degenerative scoliosis: a retrospective radiographic comparative analysis.

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.

Bilateral Decompression via Microscopic TubularCrossing Laminotomy (MTCL) for Lumbar Spinal Stenosis: Technique and Early Surgical Result.

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.

Restoration of lumbopelvic sagittal alignment and its maintenance following transforaminal lumbar interbody fusion (TLIF): comparison between straight type versus curvilinear type cage.

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.

Solitary cervical neurenteric cyst in an adolescent patient.

Spinal neurenteric cysts are uncommon congenital lesions, furthermore solitary neurenteric cysts of the upper cervical spine are very rare. A 15-year-old boy having an intraspinal neurenteric cyst located at cervical spine presented with symptoms of neck pain and both shoulders pain for 2 months. Cervical spine magnetic resonance (MR) imaging demonstrated an intradural extramedullary cystic mass at the C1-3 level without enhancement after gadolinium injection. There was no associated malformation on the MR imaging, computed tomography, and radiography. Hemilaminectomy at the C1-3 levels was performed and the lesion was completely removed through a posterior approach. Histological examination showed the cystic wall lined with ciliated pseudostratified columnar epithelium containing mucinous contents. Neurenteric cyst should be considered in the diagnosis of spinal solitary cystic mass.

Prospective Comparison Study Between the Fluoroscopy-guided and Navigation Coupled With O-arm-guided Pedicle Screw Placement in the Thoracic and Lumbosacral Spines.

STUDY DESIGN: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Percutaneous endoscopic lumbar discectomy and annuloplasty for lumbar disc herniation at the low two contiguous levels: single-portal, double surgeries.

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.

Sagittal sacropelvic morphology and balance in patients with sacroiliac joint pain following lumbar fusion 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.

Comparative study of lumbopelvic sagittal alignment between patients with and without sacroiliac joint pain after lumbar interbody fusion.

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.

Association of facet tropism and progressive facet arthrosis after lumbar total disc replacement using ProDisc-L.

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Accuracy and Safety in Pedicle Screw Placement in the Thoracic and Lumbar Spines : Comparison Study between Conventional C-Arm Fluoroscopy and Navigation Coupled with O-Arm® Guided Methods.

OBJECTIVE: The authors performed a retrospective study to assess the accuracy and clinical benefits of a navigation coupled with O-arm® system guided method in the thoracic and lumbar spines by comparing with a C-arm fluoroscopy-guided method. METHODS: Under the navigation guidance, 106 pedicle screws inserted from T7 to S1 in 24 patients, and using the fluoroscopy guidance, 204 pedicle screws from T5 to S1 in 45 patients. The position of screws within the pedicle was classified into four groups, from grade 0 (no violation cortex) to 3 (more than 4 mm violation). The location of violated pedicle cortex was also assessed. Intra-operative parameters including time required for preparation of screwing procedure, times for screwing and the number of X-ray shot were assessed in each group. RESULTS: Grade 0 was observed in 186 (91.2%) screws of the fluoroscopy-guided group, and 99 (93.4%) of the navigation-guided group. Mean time required for inserting a screw was 3.8 minutes in the fluoroscopy-guided group, and 4.5 minutes in the navigation-guided group. Mean time required for preparation of screw placement was 4 minutes in the fluoroscopy-guided group, and 19 minutes in the navigation-guided group. The fluoroscopy-guided group required mean 8.9 times of X-ray shot for each screw placement. CONCLUSION: The screw placement under the navigation-guidance coupled with O-arm® system appears to be more accurate and safer than that under the fluoroscopy guidance, although the preparation and screwing time for the navigation-guided surgery is longer than that for the fluoroscopy-guided surgery.

Gas-containing disc herniations: dual nerve root compression at a single disc level.

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.

Direct pars repair surgery using two different surgical methods : pedicle screw with universal hook system and direct pars screw fixation in symptomatic lumbar spondylosis patients.

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.

Heterotopic ossification following cervical total disc replacement: iatrogenic or constitutional?

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 stand-alone 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, ACIF-cage 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.