Distal Fusion Research Articles

Is It Enough to Stop Distal Fusion at L3 in Mild to Moderate Lenke 5C Adolescent Idiopathic Scoliosis Patients?

There has been no definitive conclusion on the selection of the lowest instrumented vertebra (LIV) in Lenke 5C adolescent idiopathic scoliosis (AIS) patients. The purpose of this study was to evaluate whether it is enough to stop distal fusion at L3 in mild to moderate Lenke 5C AIS patients with posterior selective lumbar fusion, Ponte osteotomies and segmental direct vertebra rotation and to analyze the risk factors for postoperative complications in patients selecting L3 as the LIV. A retrospective review was conducted on 106 Lenke 5C AIS patients who underwent corrective surgery in our institution from 2010 to 2021, with a minimum 2-year follow-up. The LIV was L3 or L4. According to the LIV, patients were initially divided into Group I (the LIV was L3) and Group II (the LIV was L4). Then, Group I was further divided into a complication group and a non-complication group. Demographics, radiological parameters, postoperative complications, and clinical outcomes were recorded. Univariate analysis and multivariate logistic analysis were used to identify the risk factors for postoperative complications in patients with L3 as the LIV. There were no significant differences in the demographics, radiological parameters, postoperative complications, or clinical outcomes between Group I and Group II (p > 0.05), and the outcomes were satisfactory in both groups. The main postoperative complications were distal adding-on (11 cases), coronal imbalance (16 cases), proximal junctional kyphosis (2 cases), and internal fixation failure (4 cases). Logistic regression analysis revealed that age and postoperative C7-CSVL were independent predictors of postoperative complications when selecting L3 as the LIV. Terminating the distal fusion level at L3 was practical for mild to moderate Lenke 5C AIS patients. For patients selecting L3 as the LIV, younger patients should be cautious, and maintaining postoperative coronal balance is necessary for avoiding postoperative complications.

The structure of wing in the earliest Permopsocida

Permopsocids are small acercarian insects with mouthparts specialized for sucking. They are closely related to Hemiptera and Thysanoptera. The earliest known representatives are from the Early Permian. Here evidence is presented that the Permopsocida occurred even earlier in Pennsylvanian (Moscovian) deposits in the Piesberg quarry near Osnabrück (Lower Saxony, Germany). This material is assigned to the Permian family Psocidiidae; Carbonopsocus mercuryi gen. et sp. nov., based on the wing venation diagnosed by the unique branching pattern of the main veins, the shape of the areola postica being longer than wide, the angular shape of the pterostigma, the ir crossvein directed proximally mid of pterostigma (apomorphy) and the vannus formed by the three veins of PCu, A1 and A2. The shape of the veins, with a Y-vein formed by the distal fusion of PCu with A1, could be a putative symplesiomorphy of the Psocodea with Permopsocida and Hemiptera. C. mercuryi gen. et sp. nov. is the first appearance date for Permopsocida and roots the Acercaria tree. In addition, another specimen of Dichentomum cf. arroyo (Psocidiidae) from Carrizo Arroyo is presented and figured, confirming the presence of the genus Dichentomum near the Carboniferous-Permian boundary and linking it to the Artinskian species from Elmo in Kansas, USA.

Incidence and Predictive Factors of New Onset Postoperative Sacroiliac Joint Pain After Posterior Lumbar Fusion Surgery for Degenerative Lumbar Disease.

To explore the incidence and predictive factors of new onset postoperative sacroiliac joint pain (PSJP) after posterior lumbar fusion surgery for degenerative lumbar disease. Three hundred and sixty-seven patient medical records from January 2020 to December 2021 were retrieved. The patients were divided into two groups: PSJP group and N-PSJP (non-postoperative sacroiliac joint pain group). To investigate potential risk factors for PSJP, HU value (Hounsfield unit value) was assessed on CT scans. ImageJ software was used to assess the fat and muscle of the lumbar multifidus muscle (LMM) in the axial MRI image, the red area was marked as fat and the rest were muscles to calculate the ratio of fatty infiltration. Patient characteristics, surgical variables and radiographic parameters were analyzed statistically. Twenty of 367 patients were diagnosed with PJSP at postoperative follow-up. Patients with PSJP presented with significantly higher HU value. For surgical variables, PSJP patients received more operations including distal fusion level at sacrum than the N-PSJP group. For radiographic parameters, most of the patients in the PSJP group had more severe fatty atrophic muscle in the LMM compared to the N-PSJP group. There was no statistically significant difference between the two groups in preoperative and postoperative lumbar lordosis (LL), angle of lumbar lordosis of fixed lumbar vertebrae (FV-LL), pelvic incidence (PI), sacrum slope (SS). The bivariate logistic regression model revealed preoperative fat infiltration rate of the LMM, and higher HU value were independently associated with PSJP. PSJP for degenerative lumbar disease was 5.4%, the predictive factors included preoperative severe infiltration of LMM, distal fusion level at sacrum and higher HU value.

Unilateral interlaminar fenestration on the convex side provides a reliable access for intrathecal administration of nusinersen in spinal muscular atrophy: a retrospective study

BackgroundAs the first gene therapy for spinal muscular atrophy (SMA), nusinersen is supposed to be administrated via intrathecal injection regularly for a lifetime. However, for SMA patients with severe spinal deformities, bony fusion following posterior spinal instrumentation sets great obstacles for the application of nusinersen. Therefore, efforts have been devoted to the exploration of appropriate approach for nusinersen administration. This study aims to evaluate the safety and reliability of unilateral interlaminar fenestration on the convex side during spinal fusion surgery for intrathecal nusinersen injection in SMA.ResultsSMA patients receiving posterior spinal fusion and interlaminar fenestration in Peking Union Medical College Hospital from January 2020 to October 2021 were retrospectively analyzed. 13 patients were included. Of the 13 patients, 10 were classified into SMA type II and 3 into SMA type III. Distal fusion to pelvis was undertaken in 11 patients; while L5 was selected as the lowest instrumented vertebra in the other 2 patients. All patients received interlaminar fenestration on the convex side only with an area of about 15 mm × 20 mm. Fenestration at L2–L3 level was performed in 6 patients; while L3–L4 level was selected for windowing in the remaining 7 patients. 9 of the 13 patients received lumbar puncture and intrathecal nusinersen administration during the 1-year follow-up, with an accumulative total of 50 times. All injections were performed successfully under ultrasound guidance, with no one transferred to radiographic assistance. No severe complications occurred after injection.ConclusionsIn SMA with severe scoliosis planning to receive posterior spinal fusion, unilateral lumbar interlaminar fenestration on the convex side provides a feasible and reliable access for intrathecal nusinersen administration after surgery.

Distal fusion level, complications, and reoperations in individuals with cerebral palsy undergoing surgery for scoliosis.

To compare radiological outcome, complications and reoperations in individuals with cerebral palsy and scoliosis fused to the fifth lumbar vertebra (L5), the sacrum, or the ilia. 208 individuals were identified in the national quality registry Swespine. Lowest level of fusion was L5 in 58, the sacrum in 92, and the ilia in 58 individuals. A subanalysis on 58 matched pairs operated to L5 or the pelvis (sacrum = 42, ilia = 16) with similar pelvic obliquity (± 5°) was performed. The median (interquartile range) follow-up for the last radiograph was 1.7 (1.7) years and for reoperations 6.0 (5.9) years. Preoperatively, median Cobb angle of the major curve was 65° (23°) in the L5 group, 68° (28°) in the sacrum group, and 78° (25°) in the ilia group (p = 0.006). Preoperative median pelvic obliquity according to Maloney was 16° (19°), 21° (13°), and 27° (28°), respectively (p = 0.004). Immediate postoperative Cobb angles were 28° (18°), 28° (16°), and 32° (25°), respectively (p = 0.11). Immediate postoperative pelvic obliquity was 7° (10°), 7° (8°), and 8° (10°), respectively (p = 0.28). The median change in pelvic obliquity from the first to the last postoperative radiograph was - 5° (7°), - 3° (6°), - 3° (6°), respectively (p = 0.55). 7 (12%), 11 (12%), and 7 (12%) patients required at least one reoperation (p = 1.0), respectively. In the matched analysis, no significant differences in the radiological outcomes were found (all p ≥ 0.38). Maintained curve and pelvic obliquity correction with no significant difference in complication and reoperation rates were found irrespective of distal fusion level.

Selecting the Vertebra above Sagittal Stable Vertebra as the Distal Fusion Level in Scheuermann's Kyphosis: A Prospective Study with a Minimum of 2-Year Follow-Up.

The proper selection of the lower instrumented vertebra (LIV) remains controversial in the surgical treatment of Scheuermann's disease and there is a paucity of studies investigating the clinical outcomes of fusion surgery when selecting the vertebra one level proximal to the sagittal stable vertebra (SSV-1) as LIV. The purpose of this study is to investigate whether SSV-1 could be a valid LIV for Scheuermann kyphosis (SK) patients with different curve patterns. This was a prospective study on consecutive SK patients treated with posterior surgery between January 2018 and September 2020, in which the distal fusion level ended at SSV-1. The LIV was selected at SSV-1 only in patients with Risser >2 and with LIV translation less than 40 mm. All of the patients had a minimum of 2-year follow-up. Patients were further grouped based on the sagittal curve pattern as thoracic kyphosis (TK, n = 23) and thoracolumbar kyphosis (TLK, n = 13). Radiographic parameters including global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), LIV translation, pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured preoperatively, postoperatively, and at the latest follow-up. The intraoperative and postoperative complications were recorded. The Scoliosis Research Society (SRS)-22 scores were performed to evaluate clinical outcomes. A total of 36 patients were recruited in this study, with 23 in the TK group and 13 in the TLK group. In TK group, the GK was significantly decreased from 80.8° ± 10.1° to 45.4° ± 7.7° after surgery, and was maintained at 45.3° ± 8.6° at the final follow-up. While in the TLK group, GK was significantly decreased from 70.7° ± 9.2° to 39.1° ± 5.4° after surgery (p < 0.001) and to 39.3° ± 4.5° at the final follow-up. Meanwhile, despite presenting with different sagittal alignment, significant improvement was observed in LL, SVA, and LIV translation for both TK and TLK groups (p < 0.05). Self-reported scores of pain and self-image in TK group and scores of self-image and function in TLK group showed significant improvement at the final follow-up (all p < 0.05). Distal junctional kyphosis (DJK) was observed in two patients (8.7%) in TK group, and one patient (7.7%) in TLK group. No revision surgery was performed. Selecting SSV-1 as LIV can achieve satisfactory radiographic and clinical outcomes for SK patients with different curve patterns without increasing the risk of DJK. This selection strategy could be a favorable option for SK patients with Risser sign >2 and LIV translation less than 40 mm.

Distal fusion in Duchenne scoliosis: the relevance of preoperative pelvic obliquity. A case series study.

The aim of this study was to determine clinical and radiographic outcomes for Duchenne Muscular Dystrophy (DMD) patients who underwent posterior spinal fusion from T2/3 to L5 (without pelvic fixation), at this single centre. From January 2012 to January 2020, 29 consecutive DMD scoliosis patients underwent posterior spinal fusion using pedicle screws from T2/3 to L5 in a single center with a minimum of 3years follow-up (FU). Radiologic measurements and chart review were performed. Twenty nine patients aged 14 ± 1.5years were included. No patient was lost to FU. All patients had significant correction in Cobb angle, pelvic obliquity (PO) and lumbar lordosis (LL), without loss of correction at last FU. The mean values for preoperative, immediate postoperative and last FU were CA 62o, 15o and 17o, PO: 21o, 8o and 9o; and LL 10o, -41o and -41o respectively. Correction in CA was independent of any variable analysed including implant density, rod diameter, traction, or bone density. Regarding PO, it was inversely related to age and independent of all other variables. Factors associated with postoperative complications were age and respiratory function. It appears from our results that pelvic fixation might not always be required in DMD scoliosis surgery, when using pedicle screws with lowest instrumented vertebra at L5. However, larger preoperative PO values can be related with residual PO. It seems that probably related to the underlying condition, early surgery may decrease incidence of complications. IV.

Lowest instrumented vertebrae selection in posterior fusion of Lenke 3C/6C adolescent idiopathic scoliosis: L3 versus L4, when LEV is L4.

In structural thoracolumbar/lumbar (TL/L) curves, lowest instrumented vertebra is selected mostly as the lower end vertebra (LEV). To save more lumbar mobile segments, fusion may be stopped one level proximal. This study aimed to compare the radiologic and functional outcomes of Lenke type 3C and 6C adolescent idiopathic scoliosis patients according to distal fusion level. 109 patients with Lenke 3C and 6C AIS, which had L4 as LEV and underwent posterior fusion were retrospectively evaluated. Lowest instrumented vertebra (LIV) was selected intraoperatively either as L3 or L4 depending on the disc alignment below LIV. In 49 patiens LIV was L3, while 60 patients were fused to L4. Two groups were compared according to radiologic and clinical outcomes preoperatively and two years postoperatively. Operation times were recorded. Preoperative values of both groups were similar. Regarding postoperative radiographic values, only LIV disc angle was different between groups, which was significantly higher in L3 group at two years follow-up. Coronal or sagittal imbalance was not observed. Surgical times and postoperative clinical outcomes were also similar. In TL/L curves which have L4 as LEV, satisfactory results can be achieved with stopping the fusion at L3, if a proper disc alignment below LIV can be obtained intraoperatively. Higher amount of LIV disc angle in L3 group did not cause coronal and sagittal imbalance. Although clinical outcomes are similar with stopping at L3 or L4, fusion to L3 may be prefered to save one more mobile disc.

A remarkable new genus of Nevrorthidae (Neuroptera, Osmyloidea) from mid-Cretaceous Kachin amber of northern Myanmar

A remarkable new genus and species of Nevrorthidae, Sisyroneurorthus aspoeckorumgen. et sp. nov., is described from mid-Cretaceous Kachin amber of northern Myanmar. This new species is the second Mesozoic representative of Nevrorthidae. The distal fusion of ScP and RA in the forewing of this new genus is shared by most Sisyridae. Given the probable sister-group relationship between Nevrorthidae and Sisyridae, our study sheds light on the evolution and morphological diversity of Nevrorthidae in the Mesozoic era.

High Rates of Successful Return to Competitive Athletics After Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis Regardless of Distal Fusion Level: A Prospective Cohort Study.

Prospective cohort. To determine if distal spinal fusion level is associated with postoperative sport participation after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). The concept of "saving a level" during PSF for AIS refers to minimizing the distal extent of lumbar fusion to theoretically allow for increased postoperative spinal mobility and a more predictable return to athletic activity, as well as minimizing the risk of degenerative disc disease. There are few prospective studies evaluating the correlation between distal fusion level and timing of return to sports. Adolescent patients undergoing PSF for AIS between 2009 and 2019 were approached at their presurgical visit to participate in this prospective study. Participants were followed for a minimum of 2 years after surgery. Sports participation (classified by sport type and level of competitiveness) and radiographic data were collected at the initial visit. At each postoperative visit, it was noted whether patients returned to the same sport type and level of competitiveness. After an a priori power calculation was performed, a total of 106 participants were included in the analysis with a mean age of 14 ± 2 years. Distal fusion levels ranged from T11 to L4. There was no significant association between distal fusion level and return to the same level of sports participation ( P = 0.192). Of the participants, 93% returned to sports with no significant differences by distal fusion level ( P = 0.081). Distal fusion level demonstrated no difference in return to preoperative sport ( P = 0.486) or return to the same type of sport ( P = 0.247). This study found no association between distal fusion level and postoperative sports participation. Even though many patients may elect to change sports, nearly all patients returned to sports, and the majority of patients returned to the same level of sports competition or higher after PSF for AIS.

The Effect of Adolescent Idiopathic Scoliosis on Natural Delivery and Epidural Use in Pregnant Females: A Matched Cohort Study.

Retrospective matched cohort study. The aim of this study was to determine whether females with idiopathic scoliosis (IS), both with and without spine fusion, experience different rates of cesarean section (CS) and epidural anesthesia (EA) than females without scoliosis. IS is a common spine condition with a higher prevalence in females. It is unclear whether females with scoliosis, treated nonoperatively or operatively, have different rates of cesarean delivery or EA. Patients with IS who delivered in our integrated health care system during a 6-year period were identified (N = 1810). They were matched with a group without scoliosis who delivered during the same period (N = 1810). Rates and relative risk (RR) of CS and EA between cohorts and subgroups were calculated. The scoliosis cohort had significantly higher rates and RR of EA ( P = 0.002 and P = 0.004, respectively). Scoliosis patients treated nonoperatively had an 8% greater RR of EA ( P = 0.004) and had a significantly lower rate of CS (23.2% vs . 26%, P = 0.048) compared with the control group. Among only scoliosis patients, those treated with spine fusion had a 38% decreased RR of EA ( P < 0.001). Distal fusion level did not seem to influence the RR of EA or CS. Females with scoliosis were significantly more likely to receive EA at delivery compared with females without scoliosis. Rates and RR of cesarean delivery were not significantly lower among women with scoliosis, but females treated nonoperatively for scoliosis had a significantly lower CS rate than those without scoliosis. Females treated with spine fusion for scoliosis were far less likely to receive EA than both females without scoliosis and females with scoliosis treated nonoperatively.

Risk of distal junctional kyphosis in scheuermann's kyphosis is decreased by selecting the LIV as two vertebrae distal to the first lordotic disc.

To determine whether (1) distal junctional kyphosis (DJK) is decreased by selecting the stable sagittal vertebra (SSV), versus the vertebra below the 1st lordotic disc (1stLD), as the lowest instrumented level (LIV); (2) DJK is decreased if the LIV is two versus one vertebrae distal to the 1stLD. A multi-institution prospective database was queried for SK patients who underwent posterior-only instrumentation and fusion with > 2year follow-up. DJK was defined as > 10° change in the distal junctional angle postoperative from the preoperative junctional angle. Statistical analysis was performed using ttest, chi-square test and logistic regression. Of 94 patients included, 38 (40%) developed radiographic DJK. 31 (39%) patients in whom the LIV was at or distal to the SSV developed DJK, whereas 7 (47%) in whom the LIV was proximal to the SSV developed DJK. 20 (59%) patients in whom the LIV was one vertebra below and 10 (22%) in whom the LIV was two vertebrae below the 1stLD developed DJK. Logistic regression demonstrated a significant increase in DJK development if the LIV was one vertebra below the 1stLD (OR = 3.2 (1.28-8.18)). There was not a significant relationship between DJK development and LIV position relative to the SSV. In SK surgery, LIV selection/fusion to two vertebrae below the 1stLD decreased the development of DJK. A significant relationship was not found between DJK development and location of distal fusion level in regards to the SSV, possibly due to the small number of patients who had LIV proximal to SSV.

Selection of the optimal distal fusion level for Scheuermann kyphosis with different curve patterns: when can we stop above the sagittal stable vertebra?

To investigate the optimal lowest instrumented vertebra (LIV) in the treatment of Scheuermann kyphosis (SK) with different curve patterns. Fifty-two SK patients who underwent posterior surgery between January 2010 and December 2017 with a minimum follow-up of 2years were retrospectively reviewed. Patients were divided into two groups based on the curve pattern: the Scheuermann thoracic kyphosis (STK group) or Scheuermann thoracolumbar kyphosis (STLK group). Based on the relationship between the sagittal stable vertebra (SSV) and LIV, both groups were further divided into the SSV group and SSV-1 group. Radiographic parameters, distal junctional kyphosis (DJK) incidence and SRS-22 questionnaire scores were evaluated. In STK and STLK groups, there were no significant differences in most pre- and postoperative radiographic assessments between SSV and SSV-1 subgroups. DJK incidence showed no significant differences between groups during follow-up (P > 0.05). LIV-PSVL was significantly more negative in the SSV-1 group than that in the SSV group (P < 0.001). Within the SSV-1 group, patients with DJK showed a more negative LIV-PSVL (P = 0.039). Moderate correlation was observed between preoperative LIV-PSVL and DJK with a Spearman coefficient of - 0.474 (P = 0.035). Receiver operative characteristic curve analysis showed that the threshold value of preoperative LIV-PSVL to predict DJK was - 37.35mm (area under the curve 0.882). Shorter fusion stopping at SSV-1 achieved comparable clinical outcomes and did not increase the risk of DJK for both STK and STLK patients. For patients whose preoperative LIV-PSVL < - 37.35mm, extending fusion to SSV is an acceptable solution to prevent DJK.

The Effect of Laminectomy with Instrumented Fusion Carried into the Thoracic Spine on the Sagittal Imbalance in Patients with Multilevel Ossification of the Posterior Longitudinal Ligament.

ObjectiveTo determine if there is a difference in either the cervical alignment or the clinical outcomes in cervical ossification of the posterior longitudinal ligament (OPLL) patients who underwent laminectomy with instrumented fusion (LIF) ending at C6, C7, or proximal thoracic spine for the treatment of multilevel OPLL, and to find out the appropriate distal fusion level.MethodsThis was a single‐center retrospective study. In total, 36 patients with cervical OPLL who underwent three or more level LIF in our institution between January 2015 and January 2017 were enrolled. They were divided into three groups according to their distal ends: C6 (nine females and 11 males, 60.45 ± 9.68 years old), C7 (four females and six males, 61.60 ± 10.29 years old), and T‐group (two females and four males, 64.33 ± 8.12 years old). Radiographic (compression level, classification of OPLL, occupying rate, C2‐7 cobb angle, C2‐7 sagittal vertical axis, and fusion level) and clinical outcomes (NDI score, operative time, and blood loss) were compared. Predictors of postoperative sagittal imbalance were also identified according to if the postoperative C2‐7 SVA was greater than 40 mm. The sensitivity and specificity of preoperative parameters predicting postoperative cervical stability were evaluated via the receiver operating characteristic (ROC) curve.ResultsAll patients were followed up at least 1 year. The blood loss in T group was significantly more than C6 or C7 group. The length of fusion level became significantly longer when the caudal level extended to the thoracic spine. The age, preoperative SVA, and NDI score at follow‐up were significantly greater in the imbalance group. At the final follow‐up, the cervical lordosis tended to be straight and the C2‐7 SVA tended to be greater when the caudal level of fusion was extended to upper thoracic segment. Further ROC curve analysis suggested that patients’ age had a sensitivity of 75.00%, specificity of 79.17% for cervical stability, and the AUC was 0.844 (P < 0.01), with the cutoff value for age being 66.5 years old. For preoperative SVA, the sensitivity was 58.30%, and specificity was 91.70%, with the AUC of 0.778 (P < 0.01). The cutoff value for preoperative SVA was 30.4 mm.ConclusionAlthough posterior fusion terminating in the thoracic spine was not superior to the cervical spine for patients with multilevel OPLL, for elderly patients (>67 years) with great preoperative SVA (>30 mm), terminating at C6 was recommended to limit the invasion of cervical extensor muscles, provided the decompression was adequate.

Selecting proper distal fusion level in severe thoracolumbar kyphosis secondary to late osteoporotic vertebral compression fracture to limit distal complications

BackgroundSurgical treatment of severe thoracolumbar kyphosis (TLK) secondary to late osteoporotic vertebral compression fracture (OVCF) presents several challenges to spine surgeons. Proper selection of distal fusion level is an important issue in surgical planning to decrease the likelihood of distal mechanical complications. This study was designed to compare the clinical and radiographic outcomes in elderly patients suffering from severe TLK related with late OVCF between different distal fusion strategies and to recommend a superior distal fusion level for these patients. MethodsA total of 57 consecutive subjects with a minimum follow-up of two years were retrospectively reviewed. TLK was defined as the hyperkyphosis with an apex below T10. Severe TLK was defined as the Cobb angle of kyphosis ≥60°. Patients fused to sagittal stable vertebra (SSV) were assigned to Group SSV, while those fused to the vertebra above and below SSV were assigned to Groups SSV- and SSV+, respectively. Bone cement was used to enhance pedicle screw fixation. Clinical and radiographic results were collected and compared between different groups. ResultsDeformity corrections and living quality improvements at the latest follow-up were superior in Group SSV than Group SSV- with shorter fusion levels, while to the equal extent with Group SSV+ with longer fusion levels. 7 cases of distal complications were observed in Group SSV-. Negatively balanced lowest instrumented vertebra was revealed to be the independent factor predicting distal complications. Patients’ satisfaction of their surgical management was greater in Group SSV than Group SSV- (83.2 ± 4.4% vs. 70.5 ± 10.9%, P = 0.024), while comparable with Groups SSV + SSV+ (84.8 ± 5.7%). ConclusionsFusion to SSV with cement-augmented pedicle screws could limit the development of distal junctional mechanical complications after surgical treatment for severe TLK secondary to late OVCF in elderly patients, while achieves satisfactory deformity correction with the preservation of necessary lumbar motility.

Can We Stop Distally at LSTV-1 for Adolescent Idiopathic Scoliosis With Lenke 1A/2A Curves?

A retrospective study. To determine in which case one level proximal to last substantially touching vertebra (LSTV-1) could be a valid lowest instrumented vertebra (LIV), in which case distal fusion should extend to last substantially touching vertebra (LSTV), and to identify risk factors for distal adding-on. Posterior thoracic fusion to save more lumbar mobile segments has become the mainstay of operative treatment for adolescent idiopathic scoliosis (AIS) with Lenke 1A/2A curves. Although previous studies have recommended selecting the LSTV as LIV, good outcomes could still be achieved in some cases when LSTV-1 was selected as LIV. Ninety-four patients were included in the study with a minimum of 2-year follow-up after posterior thoracic instrumentation, in which LSTV-1 was selected as LIV. Patients were identified with distal adding-on between first erect radiographs and 2-year follow-up based on previously defined parameters. Factors associated with the incidence of adding-on were analyzed. The mean follow-up duration was 37.7 ± 15.8 months. Forty patients (42.6%) with LSTV-1 selected as LIV achieved good outcomes at the last follow-up. Several preoperative risk factors significantly associated with distal adding-on were identified, including lower Risser (P = 0.001), longer thoracic curve length (P = 0.005), larger rotation and deviation of LSTV-1 (P < 0.001), and preoperative coronal imbalance (P = 0.013). Skeletally immature patients with long thoracic curve, preoperative coronal imbalance, large rotation, and deviation of LSTV-1 are at increased risk of distal adding-on when selecting LSTV-1 as LIV. Under this condition, distal fusion level should extend to LSTV; while in other case, LSTV-1 could be a valid LIV.Level of Evidence: 4.

P101. Pseudarthrosis and rod fracture at the distal levels of a long construct are associated with proximal junctional kyphosis after ASD surgery

<h3>BACKGROUND CONTEXT</h3> More distal fusion levels and overall stiffness of a long fusion construct for ASD may result in larger range of motion and stress at the proximal junctional level. Stability of distal fixation, inferred by the presence or absence of pseudarthrosis and rod fracture, may affect proximal junctional stresses and contribute to proximal junctional kyphosis (PJK) and associated revision surgery.To date, very few studies have evaluated the relationship between achieving solid fusion at the base of a long construct and rate of PJK. <h3>PURPOSE</h3> To assess the relationship between lumbosacral rod fracture and pseudarthrosis and development of proximal junctional kyphosis (PJK) after long construct ASD surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospectively collected single center database. <h3>PATIENT SAMPLE</h3> We performed a review of 942 patients who underwent ASD surgery (Age: 55 ± 23 y; mFI: .41 ± .67; Levels fused: 10.1 ± 4.2; Revision: 22.3%; 3CO: 12.3%). <h3>OUTCOME MEASURES</h3> We assessed the rate of PJK at minimum 2-year follow-up, as well as the rate of pseudarthrosis or rod fracture at the lower lumbar levels or lumbosacral junction, and the association between these complications. <h3>METHODS</h3> A total of 942 patients were divided into PJK and non-PJK groups using whole spine standing radiographs. The incidences of PJK, and lumbar or lumbosacral pseudarthrosis were defined. The relationship between these complications was assessed. <h3>RESULTS</h3> The cohort had sagittal malalignment as demonstrated by PT 23.7 ± 12.4°, TPA 22.5 ± 26.2°, and SVA 77.8 ± 70 mm. The PJK and non-PJK groups comprised 350 and 592 cases respectively. Mean follow-up time was 48.9 months. There was no significant difference in baseline SVA, T1 pelvic angle, change in sagittal alignment postoperatively, and surgical invasiveness index between the two groups. There were 11.1% of patients who developed PJK had a pseudarthrosis at the lower lumbar levels or lumbosacral junction, versus 6.4% of those who did not develop PJK (p=0.011). Patients who developed PJK had a significantly higher rate of rod fracture in the lower lumbar levels or lumbosacral junction (15.4%) versus those who did not develop PJK (7.3%) (p<0.0001). Pseudarthrosis (OR: 1.963, 95% CI: 1.14-3.38, p=0.015) and rod fracture at the lower lumbar levels or lumbosacral junction (OR: 2.27, 95% CI: 1.41-3.64, p=0.001) were predictors of PJK at final follow-up by regression analysis. <h3>CONCLUSIONS</h3> Pseudarthrosis and rod fracture at the lower lumbar levels or lumbosacral junction were predictive of development of PJK at final follow-up. This may indicate that distal stability of a long construct has a significant impact on stresses at the proximal junction. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Presence of the ground sloth Valgipes bucklandi (Xenarthra, Folivora, Scelidotheriinae) in southern Uruguay during the Late Pleistocene: Ecological and biogeographical implications

Within the subfamily Scelidotheriinae, Valgipes bucklandi represents one of the least known taxa due to its scarce records and material found so far. This Pleistocene ground sloth had been registered only in Brazil, within the Brazilian Intertropical Region (BIR) in the states of Bahia, Minas Gerais, Piauí, Rio Grande do Norte and, more recently, outside the BIR, in Mato Grosso do Sul. A particular feature of this sloth is the proximal and distal fusion of the tibia and fibula in adults. Here, we report a tibia-fibula assigned to V. bucklandi found in Arroyo del Vizcaíno (Canelones, Uruguay), a fossiliferous site that harbors a large amount of megamammal remains at an approximate age of 30 ka (29696–32009 cal yr B.P.). We performed stable isotopes analyses and ecological niche models (ENM) to study V. bucklandi distribution and climatic and dietary preferences, as well as to better understand its presence ~2000 km southward of its previous recorded occurrences. δ13C values were consistent with those of the BIR, indicating a similar preference for C3 plants, while the results of δ18O values could be related to colder and more humid environments, clearly different from those obtained from BIR specimens. Furthermore, the ENM results also showed colder and more humid environments for the AdV record, with the occurrence being in the margins of the predicted potential distribution of the taxa. This discovery expands the distribution of this taxa to southern colder climates, indicating a greater climatic tolerance. Moreover, our results support the existence of mixed faunas composed of Southern and Northern taxa coexisting in Southern Uruguay at the onset of the Last Glacial Maximum, and provide evidence of the existence of an open mosaic habitat with patches of mixed vegetation in the region.

Selection of the optimal distal fusion level for Scheuermann kyphosis with different curve patterns: When can we stop above the sagittal stable vertebra?

Selection of the optimal distal fusion level for Scheuermann kyphosis with different curve patterns: When can we stop above the sagittal stable vertebra?

Lumbar Adding-on of the Thoracic Spine After Selective Fusion in Adolescent Idiopathic Scoliosis Lenke Types 1 and 2 Patients: A Critical Appraisal.

Retrospective cohort study. This study aimed to identify risk factors that predict lumbar curve adding-on in patients who had selective thoracic fusion. Selective thoracic fusion offers deformity correction of Lenke 1 and 2 thoracic curves and maintains lumbar range of movement. However, some patients may develop postoperative lumbar adding-on. This study included patients 18 years or younger that underwent spinal instrumentation for Lenke 1 and 2 curves. A total of 161 patients were included (147 females, 14 males). The mean age was 14.0 ± 2.1 years: 103 patients were Lenke 1, and 58 patients were Lenke 2 curves. Ninety-seven patients underwent posterior approach surgery, whereas 64 via anterior approach. In the posterior approach group, 79(81.4%) patients underwent selective fusion. Ten patients (6.2%) had lumbar curve adding-on, with nine females and one male. There were seven Lenke 1 and three Lenke 2 patients. All 10 patients were lumbar modifier (a), with 5 hypokyphotic patients. Selective fusion was done in nine patients. Lumbar adding-on was seen most commonly between 6 months to 1 year postoperative period (five patients). Two patients had adding-on because of incorrect distal fusion level, six were due to 1A-R curve, one due to the inadvertent fusion from the excessive long rod at the subjacent level. In multivariate analysis, hypokyphotic patients were at higher risk of lumbar adding-on (odds ratio = 9.2). Patients with Risser classification 0, 1, 2, 3 were also at higher risk of lumbar adding-on (odds ratio =6.1). The incidence of lumbar curve adding-on was 6.2%. Patients who were hypokyphotic and skeletally immature are nine times and six times more likely to have lumbar adding-on, respectively. This article examines adding-on in patients who had either anterior or posterior approach scoliosis surgeries, with follow-up stretching up to 10 years. This offers the rare opportunity to examine the natural history of the adding-on phenomenon.Level of Evidence: 3.