Focal compression of the cervical spinal cord alone does not indicate high risk of neurological deterioration in patients with a diagnosis of mild degenerative cervical myelopathy.

Degenerative Cervical Myelopathy (DCM) is the functional derangement of the spinal cord resulting from vertebral column spondylotic degeneration. Typical neurological symptoms of DCM include gait imbalance, hand/arm numbness, and upper extremity dexterity loss. Greater spinal cord compression is believed to lead to a higher rate of neurological deterioration, although clinical experience suggests a more complex mechanism involving spinal canal diameter (SCD). In this study, we utilized machine learning clustering to understand the relationship between SCD and different patterns of cord compression (i.e. compression at one disc level, two disc levels, etc.) to identify patient groups at risk of neurological deterioration. 124 MRI scans from 51 non-operative DCM patients were assessed through manual scoring of cord compression and SCD measurements. Dimensionality reduction techniques and k-means clustering established patient groups that were then defined with their unique risk criteria. We found that the compression pattern is unimportant at SCD extremes (≤14.5 mm or > 15.75 mm). Otherwise, severe spinal cord compression at two disc levels increases deterioration likelihood. Notably, if SCD is normal and cord compression is not severe at multiple levels, deterioration likelihood is relatively reduced, even if the spinal cord is experiencing compression. We elucidated five patient groups with their associated risks of deterioration, according to both SCD range and cord compression pattern. Overall, SCD and focal cord compression alone do not reliably predict an increased risk of neurological deterioration. Instead, the specific combination of narrow SCD with multi-level focal cord compression increases the likelihood of neurological deterioration in mild DCM patients.

Advanced MRI metrics improve the prediction of baseline disease severity for individuals with degenerative cervical myelopathy.

BACKGROUND CONTEXT: Degenerative cervical myelopathy (DCM) is the most common form of atraumatic spinal cord injury globally. Degeneration of spinal discs, bony osteophyte growth and ligament pathology results in physical compression of the spinal cord contributing to damage of white matter tracts and grey matter cellular populations. This results in an insidious neurological and functional decline in patients which can lead to paralysis. Magnetic resonance imaging (MRI) confirms the diagnosis of DCM and is a prerequisite to surgical intervention, the only known treatment for this disorder. Unfortunately, there is a weak correlation between features of current commonly acquired MRI scans ("community MRI, cMRI") and the degree of disability experienced by a patient. PURPOSE: This study examines the predictive ability of current MRI sequences relative to "advanced MRI" (aMRI) metrics designed to detect evidence of spinal cord injury secondary to degenerative myelopathy. We hypothesize that the utilization of higher fidelity aMRI scans will increase the effectiveness of machine learning models predicting DCM severity and may ultimately lead to a more efficient protocol for identifying patients in need of surgical intervention. STUDY DESIGN/SETTING: Single institution analysis of imaging registry of patients with DCM. PATIENT SAMPLE: A total of 296 patients in the cMRI group and 228 patients in the aMRI group. OUTCOME MEASURES: Physiologic measures: accuracy of machine learning algorithms to detect severity of DCM assessed clinically based on the modified Japanese Orthopedic Association (mJOA) scale. METHODS: Patients enrolled in the Canadian Spine Outcomes Research Network registry with DCM were screened and 296 cervical spine MRIs acquired in cMRI were compared with 228 aMRI acquisitions. aMRI acquisitions consisted of diffusion tensor imaging, magnetization transfer, T2-weighted, and T2*-weighted images. The cMRI group consisted of only T2-weighted MRI scans. Various machine learning models were applied to both MRI groups to assess accuracy of prediction of baseline disease severity assessed clinically using the mJOA scale for cervical myelopathy. RESULTS: Through the utilization of Random Forest Classifiers, disease severity was predicted with 41.8% accuracy in cMRI scans and 73.3% in the aMRI scans. Across different predictive model variations tested, the aMRI scans consistently produced higher prediction accuracies compared to the cMRI counterparts. CONCLUSIONS: aMRI metrics perform better in machine learning models at predicting disease severity of patients with DCM. Continued work is needed to refine these models and address DCM severity class imbalance concerns, ultimately improving model confidence for clinical implementation.

L5-S1 Pseudoarthrosis Rate with ALIF Versus TLIF in Adult Spinal Deformity Surgeries: A Retrospective Analysis of 100 Patients.

OBJECTIVE: Lumbosacral pseudoarthrosis is a common complication following adult spine deformity (ASD) surgery. This study assessed the reoperation rate for L5-S1 pseudoarthrosis in the ASD population. Compared with transforaminal lumbar interbody fusions (TLIFs), we hypothesized that anterior lumbar interbody fusion (ALIF) would result in lower rates of L5-S1 pseudarthrosis. METHODS: This is a single center study with patient data retrieved from a prospective ASD database. The patients had a long-segment fusion, ALIF or TLIF at the L5-S1 level with a 2-year follow-up and were divided into 2 groups (TLIF and ALIF). The study's primary outcome was to assess the difference in the reoperation rate for clinical pseudoarthrosis between the TLIF and the ALIF groups. The secondary outcomes measured the radiological pseudoarthrosis rate and identified risks for L5-S1 pseudoarthrosis development. RESULTS: A total of 100 patients were included; 49 patients (mean age, 62.9 years; 77.5% females) were in TLIF and 51 patients (mean age, 64.4 years; 70.6% females) were in the ALIF group. Baseline characteristics were similar in both groups. Thirteen (13%) patients with L5-S1 pseudoarthrosis required reoperation. Clinical pseudoarthrosis was higher in the TLIF group than in the ALIF group (12/49 vs. 1/51; P < 0.001). Univariate analysis demonstrated a higher risk of L5-S1 pseudoarthrosis with TLIF than ALIF (risk ratio, 12.4; 95% confidence interval: 1.68-92.4; P < 0.001). Multivariate analysis revealed 4.86 times the risk of L5-S1 clinical pseudoarthrosis with TLIF than with ALIF (risk ratio, 4.86; 95% confidence interval 0.57-47; P = 0.17), but this ratio did not reach statistical significance. CONCLUSIONS: No difference in reoperation risk for L5-S1 pseudarthrosis was observed based on the method of IF. rhBMP-2 was noted as a significant predictor.

Unexpected intraoperative positive culture (UIPC) in presumed aseptic revision spine surgery: a systematic review and meta-analysis.

BACKGROUND CONTEXT: Unexpected intraoperative positive culture (UIPC) has recently become increasingly common in revision spine surgery, being implicated as an etiological factor in revision spine surgery indications such as implant failure or pseudoarthrosis. PURPOSE: Utilizing the available literature, this study aimed to investigate the prevalence of UIPC, and its clinical importance in patients following presumed aseptic revision spine surgery. STUDY DESIGN: Meta-analysis and systematic review. METHODS: Multiple databases and reference articles were searched until May 2022. The primary outcome was the pooled rate of UIPC, and the secondary outcomes were the microbiological profile of UIPC, the risk factors of UIPC, and the clinical fate of UIPC. RESULTS: Twelve studies were eligible for meta-analysis, with a total of 1,108 patients. The pooled rate of UIPC was 24.3% (95% CI=15.8%-35.5%) in adult patients, and 43.2% (95% CI=32.9%-54.2%) in pediatric patients. The UIPC rate was higher when both conventional wound culture and sonication were used together compared to sonication alone or conventional wound culture alone. The rates were 28.9%, 23.6%, and 15.5 %, respectively. In adult and pediatric patients, the most commonly cultured organism was Cutibacterium acnes (42.5% vs 57.7%), followed by coagulase-negative Staphylococcus (39.9% vs 30.5%). Male patients had a higher rate of UIPC (OR= 2.6, 95% CI=1.84-3.72, p<.001), as did patients with a longer fusion construct (MD=0.76, 95% CI=0.27-1.25, p<.001). CONCLUSIONS: The pooled rate of UIPC in aseptic spine revision surgery was 24.3% and 43.2% in adult and pediatric patients respectively. The most common organisms were C. acnes and coagulase-negative Staphylococcus. The impact of UIPC on patients` clinical outcomes is not fully understood. We are not able to recommend routine culture in revision spine surgery, however, adding sonication may aid in the diagnosis of UIPC. There is not enough evidence to recommend specific treatment strategies at this time, and further studies are warranted.

IL-1Ra deficiency accelerates intervertebral disc degeneration in C57BL6J mice.

The expression of Interleukin-1ß (IL-1ß) and its antagonist and Interleukin-1 receptor antagonist (IL-1Ra) are correlated with greater human intervertebral disc (IVD) degeneration, suggesting that elevated IL-1ß activity promotes disc degeneration. Many in vitro studies support such a mechanistic relationship, whereas few in vivo investigations have been reported. The present study tests the effect of increased IL-1ß activity on intervertebral disc in mice with an IL-1Ra gene deletion. IL-1Ra-/- mice and wild-type (WT) C57Bl6J mice were examined at 3 and 12 months of age. Caudal IVD segments were evaluated for disc degeneration by histopathology, functional testing, and inflammatory gene expression relevant to IL-1ß pathways. To test differences in injury response, pinprick annular puncture was performed on IL-1Ra-/- and WT mice and evaluated similarly. IL-1Ra-/- IVDs had significantly worse histopathology at 3 months compared to WT controls, but not at 12 months. IL-1Ra-/- IVDs exhibited significantly more viscous mechanical properties than WT IVDs. qPCR revealed downregulation of inflammatory genes at 3 and 12 months in IL-1Ra-/- IVDs, with concomitant downregulation of anabolic and catabolic genes. Annular puncture yielded no appreciable differences between 2-week and 6-week post-injured WT and IL1-Ra-/- IVDs in histopathology or biomechanics, but inflammatory gene expression was sharply downregulated in IL-1Ra-/- mice at 2 weeks, returning by 6 weeks post injury. In the present study, IL-1Ra deletion resulted in increased IVD histopathology, inferior biomechanics, and transiently decreased pro-inflammatory cytokine gene expression. The histopathology of IL-1Ra-/- IVDs on a C57BL/6J background is less severe than a previous report of IL1Ra-/- on a BALB/c background, yet both strains exhibit IVD degeneration, reinforcing a mechanistic role of IL-1ß signaling in IVD pathobiology. Despite a pro-inflammatory environment, the annular puncture was no worse in IL-1Ra-/- mice, suggesting that response to injury involves pathways other than inflammation. Overall, this study supports the hypothesis that IL-1ß-driven inflammation is important in IVD degeneration.

Mechanical Complications in Adult Spinal Deformity Surgery: Can Spinal Alignment Explain Everything?

STUDY DESIGN: Cohort study. OBJECTIVE: Our goal was to verify the validity of the global alignment and proportion (GAP) score, SRS-Schwab, and Roussouly theoretical apex of lordosis in predicting mechanical complications in adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: Achieving adequate sagittal alignment is critical to obtain favorable outcomes in ASD surgery. It has been proposed that mechanical complications are largely secondary to postoperative spinal alignment. METHODS: Retrospective review of consecutive primary ASD cases that underwent deformity correction in the same institution over a 5-year period. Association between the 6-week postoperative spinal alignment classification and occurrence of mechanical complications on the last follow-up was assessed using logistic regressions. The discriminant capacity was assessed using the receiver operating characteristic (ROC) curve analysis. RESULTS: 58.3% (N = 49/84) of patients presented with mechanical complications and 32.1% (N = 27/84) underwent revision surgery. GAP score did not show discriminant ability to predict complications (AUC = 0.53, 95% confidence interval [CI] = 0.40-0.66, P = 0.58). Conversely, the SRS-Schwab sagittal modifier score demonstrated a statistically significant (although modest) predictive value for mechanical complications (AUC = 0.67, 95% CI = 0.54-0.79, P = 0.008). There was a significant association between pelvic tilt (PT) (P = 0.03) and sagittal vertical axis (SVA) (P = 0.01) at 6 weeks postoperatively and the occurrence of later mechanical complications. There was no significant association between matched Roussouly theoretical apex of lordosis and final outcome (P = 0.47). CONCLUSION: The results point to the complexity of mechanical failure and the high likelihood that causative factors are multifactorial and not limited to alignment measures. GAP score should be used with caution as it may not explain or predict mechanical failure based on alignment in all populations as originally expected. Future studies should focus on etiology, surgical technique, and patient factors in order to generate a more universal score that can be applied to all populations.Level of Evidence: 4.

Lumbar Fusion Surgery for Patients With Back Pain and Degenerative Disc Disease: An Observational Study From the Canadian Spine Outcomes and Research Network.

STUDY DESIGN: Uncontrolled retrospective observational study. OBJECTIVES: Surgery for patients with back pain and degenerative disc disease is controversial, and studies to date have yielded conflicting results. We evaluated the effects of lumbar fusion surgery for patients with this indication in the Canadian Spine Outcomes and Research Network (CSORN). METHODS: We analyzed data that were prospectively collected from consecutive patients at 11 centers between 2015 and 2019. Our primary outcome was change in patient-reported back pain at 12 months of follow-up, and our secondary outcomes were satisfaction, disability, health-related quality of life, and rates of adverse events. RESULTS: Among 84 patients, we observed a statistically significant improvement of back pain at 12 months that exceeded the threshold of Minimum Clinically Important Difference (MCID) (mean change -3.7 points, SD 2.6, p < 0.001, MCID = 1.2; 77% achieved MCID), and 81% reported being "somewhat" or "extremely" satisfied. We also observed improvements of Oswestry Disability Index (-17.3, SD 16.6), Short Form-12 Physical Component Summary (10.3, SD 9.6) and Short Form-12 Mental Component Summary (3.1, SD 8.3); all p < 0.001). The overall rate of adverse events was 19%. CONCLUSIONS: Among a highly selective group of patients undergoing lumbar fusion surgery for degenerative disc disease, most experienced a clinically significant improvement of back pain as well as significant improvements of disability and health-related quality of life, with high satisfaction at 1 year of follow-up. These findings suggest that surgery for this indication may provide some benefit, and that further research is warranted.

The cost effectiveness of minimally invasive spine surgery in the treatment of adult degenerative scoliosis: a comparison of transpsoas and open techniques.

INTRODUCTION: Surgical treatment improves quality of life in patients with adult degenerative scoliosis (ADS). However, open ADS surgeries are complex, large magnitude operations associated with a high rate of complications. The lateral transpsoas interbody fusion technique is a less invasive alternative to open ADS surgery, but less invasive techniques tend to be more expensive. The objective of this study was to evaluate the cost effectiveness of the transpsoas technique for patients with ADS over a 12-month time horizon from a public payer perspective. METHODS: A cost-effectiveness analysis was performed based on a consecutive case series of patients who underwent ADS surgeries between 2006 and 2012. Effectiveness was expressed as the difference in patient reported preoperative and 12-month postoperative health-related quality of life (HRQOL), which was measured in quality-adjusted life years. Health-care resource use was tabulated based on a clinical chart review on an item-by-item basis. Unit cost data were obtained from published provincial costs in Alberta, Canada. All costs were adjusted to 2015 Canadian dollars. The base case analysis included costs for the surgery, initial hospitalization, and treatment for complications over a 12-month follow-up period. The uncomplicated case analysis included costs for the surgery and initial hospitalization only. The joint uncertainty surrounding the cost and HRQOL differences was estimated using bootstrapping with 10,000 replicates. RESULTS: A total of 10 open technique and 12 transpsoas technique T11-pelvis fusions were included in the analysis. In the base case analysis, the transpsoas technique was less costly compared with the open technique, total cost of $83,513 (95% CI: $72,772-$94,253) versus $111,381 (95% CI: $36,340-$186,423), respectively (incremental cost $27,869), and was associated with 0.06 more quality-adjusted life years and/or patient. However, in the uncomplicated case, the open technique was less costly compared with the transpsoas technique ($47,795 [95% CI: $39,003-$56,586] vs $76,510 [95% CI: $72,273-$80,746]), respectively, with an incremental cost of $28,715. Based on the probabilistic analysis of 10,000 bootstrap iterations for the base case analysis, the transpsoas technique was more effective and less costly compared with the open technique 57% of time. One-way deterministic sensitivity analysis by adjusting bone-morphogenetic protein-2 dosage further improved cost effectiveness of the transpsoas technique by lowering overall costs. CONCLUSIONS: Transpsoas surgeries were associated with better outcomes in terms of HRQOL and lower costs over 1-year follow-up period compared with more invasive open technique. This study should be viewed as a pilot evaluation and should be replicated in a larger prospective multicenter controlled study.

Fractures After Removal of Spinal Instrumentation: Revisiting the Stress-Shielding Effect of Instrumentation in Spine Fusion.

BACKGROUND: Many practicing spine surgeons believe that instrumentation can be removed during revision surgery in successful posterolateral or anterior spinal fusions, confirmed by computed tomography and intraoperative exploration. The stress-shielding effect of spinal instrumentation was well described in the late 1980s and 1990s but has not received recent attention. Despite the paucity of recent literature, concepts underlying the biology and biomechanics of the spinal fusion mass remain particularly salient given the increasing incidence of revision spinal fusion surgery. The aim of this study was to highlight a potential complication of instrumentation removal owing to stress shielding of instrumentation on the spinal column and fusion mass. METHODS: A retrospective review was performed, and a small case series was described. RESULTS: In 3 cases, despite apparent solid fusion demonstrated on preoperative computed tomography and confirmed by intraoperative exploration, new fractures developed after removal of instrumentation. In these cases, fracture occurred at the transition zone between the newly rigid instrumented area and previous fusion. This highlights the relative weakness of the fusion and may be explained by the stress-shielding effect of instrumentation within the fusion mass. CONCLUSIONS: Spinal instrumentation revision requires careful consideration, and routine implant removal should not be performed. The presence of a solid fusion on computed tomography and/or at intraoperative exploration may not justify implant removal in these cases. In cases of extension of a fusion, use of a bridging connection to the new implants should be considered. The cases presented demonstrate the consequences of the stress-shielding effect of implants on the spine and fusion mass.

Hypotension in the Right Lateral Position Secondary to Inferior Vena Cava Abnormality.

Surgical positioning is accompanied by numerous anesthetic considerations, particularly its potential effects on the cardiovascular, respiratory, and nervous systems. Clinical studies have shown that lateral positioning does not affect hemodynamics; however, with the addition of trunk flexion, there is a decrease in cardiac output, which may be secondary to caval compression. In this report, we describe a unique case of hypotension that arose in a patient positioned only in the right lateral decubitus position with flexion and that was exacerbated by an abnormally narrow inferior vena cava.

Forces in spinal cannulation and breaches ex vivo.

BACKGROUND: Pedicle screw insertion, to stabilize or correct the spine, relies on creating a probe path with the correct trajectory to prevent unsafe breaching of the cortical wall. Safe pedicle cannulation is aided when the surgeon can feel the difference between a safe and unsafe path. Pedicle probe forces and torques are currently unknown. The purpose of this study was to investigate the forces and torques encountered while cannulating the pedicle tract in both correct and incorrect cannulations. METHODS: Two experienced surgeons used a standard lumbar probe modified to incorporate a 6 degree-of-freedom load cell to cannulate and breach the T12 to S1 vertebrae of six fresh frozen cadavers (3 males, 3 females, ages 65 to 92). A total of 76 pedicles were tested. FINDINGS: Cannulation axial forces averaged 48 N (standard deviation = 13 N), medial breach 129 N (standard deviation = 25 N), and lateral breach 86 N (standard deviation = 27 N). Cannulation values were significantly lower than the breach values in all 6 degrees of freedom (p < 0.001). There were significant differences between specimens, including males and females, and between degrees of freedom, but no significant right and left differences or by vertebral level. CONCLUSION: A large range of cannulation and breach forces and torques were measured due to variations in bone quality and geometry, as experienced clinically. This is the first time that the absolute and relative force and torque levels have been reported, to our knowledge.

Does preoperative DVT chemoprophylaxis in spinal surgery affect the incidence of thromboembolic complications and spinal epidural hematomas?

BACKGROUND: Deep venous thrombosis (DVT) and pulmonary embolus (PE) remain common surgical complications, often affecting patients without any prior warning. Postoperative spinal epidural hematomas (SEH) may have a devastating impact on a patient's recovery from a routine procedure. The effect of preoperative DVT prophylaxis administration on elective spinal patients has not previously been studied. STUDY DESIGN: Retrospective cohort analysis. OBJECTIVE: To correlate the incidence of preoperative DVT prophylaxis administration and the rate of postoperative DVT, PE, and SEH after elective spinal surgery. SUMMARY OF BACKGROUND DATA: Earlier studies have shown a postoperative DVT rate in elective spinal patients of between 0.3% and 31%, a PE rate of 0.2% to 0.9%, and a SEH rate of approximately 0.1%. METHODS: About 3870 patient notes, from 2004 to 2008 elective spinal procedures, were reviewed. DVT, PE, and SEH rates were compared between those patients receiving and not receiving preoperative DVT prophylaxis. RESULTS: The 36.9% of patients received preoperative DVT prophylaxis, and 19 patients suffered and DVT and/or PE. Nine of these had received preoperative prophylaxis, giving an odds ratio of 0.91. Sixteen patients suffered a SEH, and this gave an odds ratio of 1.33. The SEH's presented with a median postoperative time of 4 days. CONCLUSIONS: Preoperative DVT prophylaxis does not influence the rate of postoperative DVT or PE among elective spinal patients. It probably does not influence SEH rate, and it is noted that SEH may present quite late, in contrast to currently accepted time courses.

Acute cervical fractures in ankylosing spondylitis: an opportunity to correct preexisting deformity.

STUDY DESIGN: A new technique for the management of traumatic cervical fracture in patients with chin-on-chest deformity in ankylosing spondylitis is presented. OBJECTIVE.: To present a new surgical technique for acute deformity correction through cervical fractures in the setting of kyphotic deformities. SUMMARY OF BACKGROUND DATA: Cervicothoracic kyphotic deformity in ankylosing spondylitis is currently treated with extension osteotomy in an elective setting. In elective extension osteotomies, the surgeon manipulates the head to generate osteoclasis, temporarily producing an unstable cervical fracture. Cervical fractures in ankylosing spondylitis are highly unstable and frequently associated with neurologic compromise. Most reports describe either no reduction and fixation in situ or reduction in preoperative traction followed by fixation. METHODS: A 60-year-old man with chronic ankylosing spondylitis and profound kyphotic deformity suffered a traumatic lower cervical spine fracture. He was treated with an acute cervical spine extension osteotomy through the fracture site using an anterior lengthening bar modification to a halo vest. The anterior lengthening bar allows controlled extension of the neck without manual manipulation by the surgeon. RESULTS: This patient presented with a chin-brow angle of approximately 90 degrees and was corrected to approximately 5 degrees to 8 degrees . No immediate or delayed complications were seen. After halo vest treatment for 3 months, an excellent postural correction was obtained. CONCLUSION: Surgical extension osteotomy in the lower cervical spine through the fracture site using the anterior lengthening bar-halo extension brace seems to be a safe method for correcting spine flexion deformity in ankylosing spondylitis after traumatic fracture.

Juvenile idiopathic scoliosis: the effectiveness of part-time bracing.

STUDY DESIGN: A retrospective review of 34 patients with juvenile idiopathic scoliosis (JIS) treated with a nighttime bending brace. OBJECTIVE: To determine the effectiveness of part-time bracing in JIS. SUMMARY OF BACKGROUND DATA: Although previous bracing studies have focused on adolescent idiopathic scoliosis, no authors have dealt specifically with part-time bracing for JIS. METHODS: Twenty-three patients included in the study met the following criteria: curves greater than 20 degrees and Risser zero at initiation of bracing, brace wear more than 12 months, completion of the bracing program and Risser sign greater than or equal to 4 at final follow-up. Patients were analyzed according to 3 groups: (1) success (progression equal or less than 5 degrees), (2) progression more than 5 degrees (but not requiring surgery and achieving curve stabilization at skeletal maturity), and (3) surgery (curve progressing to greater than 45 degrees ) with failure of bracing treatment during skeletal immaturity. RESULTS: Seven boys and 16 girls with a total of 37 curves were analyzed. The average age at referral and initiation of bracing was 8.3 and 10.3 years, respectively. Average curve magnitude at time of bracing was 30 degrees. Length of bracing averaged 3.7 years with follow-up after brace discontinuation of 2.5 years. Nine patients met the criteria for success, with 7 patients progressing and 7 patients eventually requiring spinal fusion. Of the 37 curves, 19 (51%) were successfully managed in the brace. The magnitude of curvature at initiation of bracing did not relate to a successful outcome, whereas success did correlate with higher radiographic in-brace correction. Given the longer course of treatment for JIS patients, part-time bracing offers potential psychosocial and compliance benefits. CONCLUSION: Part-time bracing in JIS is successful and is better than the natural history.

The selection of L5 versus S1 in long fusions for adult idiopathic scoliosis.

The treatment of adult spinal deformities often involves long thoracolumbar fusions into the lower lumbar spine, raising the debate of selecting L5 or S1 as the caudal extent of the fusion. The presence of significant deformity or degenerative pathologic findings at L5-S1 mandates fusion to the sacrum. Fusion to the sacrum is of larger magnitude than fusion to L5 and introduces a higher surgical complication rate. Advantages of ending the fusion at L5 include preservation of motion, avoiding the high complication rate associated with fusion to the sacrum, and possibly avoiding a second operation. Complications with fusion to L5 include possible loss of fixation and subsequent disc degeneration at L5-S1, however, leading to possible pain and loss of sagittal balance and the need for revision surgery. To date, the functional consequences of an open disc space beneath long constructs remain poorly defined, and there is no firm evidence in the literature guiding the surgeon's choice. The issues and evidence guiding the decision to fuse to L5 or S1 are examined in this article.