Lordosis Distribution Index in Short-Segment Lumbar Spine Fusion - Can Ideal Lordosis Reduce Revision Surgery and Iatrogenic Deformity?

Lumbar Apex Position as an Independent Risk Factor for Adjacent Segment Diseases in Patients Undergoing Short-Level Transforaminal Lumbar Interbody Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

To investigate whether lumbar apex position had an impact on the development of adjacent segment disease (ASD) following transforaminal lumbar interbody fusion (TLIF).

SUMMARY OF BACKGROUND DATA

Previous studies have demonstrated that solely concentrating on lumbar lordosis value is not suitable, and neglecting the significance of lumbar apex can lead to mechanical complications. However, the relationship between lumbar apex and ASD is still not well understood.

METHODS

In this retrospective study, 234 consecutive patients who underwent L3-5 or L4-5 TLIF for degenerative diseases were reviewed. The study evaluated the associations between sagittal parameters and pelvic incidence (PI). Patients were labeled "matched" when lumbar apex position aligned with the theoretical target, and "mismatched" when it did not. Multivariate analysis was applied to find the independent risk factors of ASD. In addition, a focused subanalysis was performed based on the lumbar apex position (ideal match, cranial from ideal, and caudal from ideal).

RESULTS

After an average follow-up period of 70.6 months, 68 cases were identified as having ASD. Postoperatively, 64.7% (44 of 68) of the patients with ASD exhibited a mismatched lumbar apex, compared with 41% (68 of 166) of those without ASD ( P < 0.001). PI correlated significantly with proximal lordosis (PL) and lordosis distribution index (LDI) but not with distal lordosis (DL). Multivariate analysis identified age, L3-5 fusion, postoperative DL, and postoperative mismatched lumbar apex as independent risk factors of ASD. Upon the subanalysis, it was discovered that there were unique compensatory strategies in the cranial and caudal groups, with notable variations in postoperative DL, PL, and LDI among three groups (all P value of <0.05).

CONCLUSION

Lumbar apex position significantly influenced the risk of ASD. To restore the lumbar apex to its ideal position, a proper value and distribution of DL should be attained.

LEVEL OF EVIDENCE

4.

Restoring L4-S1 Lordosis Shape in Severe Sagittal Deformity: Impact of Correction Techniques on Alignment and Complication Profile

BACKGROUND

Severe sagittal plane deformity with loss of L4-S1 lordosis is disabling and can be improved through various surgical techniques. However, data are limited on the differing ability of anterior lumbar interbody fusion (ALIF), pedicle subtraction osteotomy (PSO), and transforaminal lumbar interbody fusion (TLIF) to achieve alignment goals in severely malaligned patients.

METHODS

Severe adult spinal deformity patients with preoperative PI-LL >20°, L4-S1 lordosis <30°, and full body radiographs and PROMs at baseline and 6-week postoperative visit were included. Patients were grouped into ALIF (1-2 level ALIF at L4-S1), PSO (L4/L5 PSO), and TLIF (1-2 level TLIF at L4-S1). Comparative analyses were performed on demographics, radiographic spinopelvic parameters, complications, and PROMs.

RESULTS

Among the 96 included patients, 40 underwent ALIF, 27 underwent PSO, and 29 underwent TLIF. At baseline, cohorts had comparable age, sex, race, Edmonton frailty scores, and radiographic spinopelvic parameters (P > 0.05). However, PSO was performed more often in revision cases (P < 0.001). Following surgery, L4-S1 lordosis correction (P = 0.001) was comparable among ALIF and PSO patients and caudal lordotic apex migration (P = 0.044) was highest among ALIF patients. PSO patients had higher intraoperative estimated blood loss (P < 0.001) and motor deficits (P = 0.049), and in-hospital ICU admission (P = 0.022) and blood products given (P = 0.004), but were otherwise comparable in terms of length of stay, blood transfusion given, and postoperative admission to rehab. Likewise, 90-day postoperative complication profiles and 6-week PROMs were comparable as well.

CONCLUSIONS

ALIF can restore L4-S1 sagittal alignment as powerfully as PSO, with fewer intraoperative and in-hospital complications. When feasible, ALIF is a suitable alternative to PSO and likely superior to TLIF for correcting L4-S1 lordosis among patients with severe sagittal malalignment.

Evaluating the biomechanical effects of pedicle subtraction osteotomy at different lumbar levels: a finite element investigation

BACKGROUND

Pedicle subtraction osteotomy (PSO) is effective for correcting spinal malalignment but is associated with high complication rates. The biomechanical effect of different PSO levels remains unclear, and no finite element (FE) analysis has compared L2-, L3-, L4-, and L5-PSOs.

PURPOSE

To assess the effects of PSO level on the spine's global range of motion, stresses on posterior instrumentation, load sharing with the anterior column, and proximal junctional stresses.

STUDY DESIGN

A computational biomechanical analysis.

METHODS

A validated 3D spinopelvic FE model (T10-Pelvis) was used to perform PSOs at L2, L3, L4 and L5. Each model was instrumented with a 4-rod configuration (primary rods + in-line satellite rods) from T11-Pelvis. Simulation included a 2-step analysis; (1) applying 300 N to thoracic, 400 N to lumbar, and 400 N to sacrum, and (2) applying a 7.5 Nm moment to the top endplate of the T10 vertebral body. Acetabulum surfaces were fixed in all degrees of freedom. The range of motion, spinopelvic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic incidence [PI], and pelvic tilt [PT]), PSO force, and von Mises stresses were measured. All models were compared with the L3-PSO model and percentage differences were captured.

RESULTS

Compared to the intact alignment: LL increased by 48%, 45%, 59%, and 56% in the L2-, L3-, L4-, and L5-PSO models; SS increased by 25%, 15%, and 11% while PT decreased by 76%, 53%, and 45% in L2-, L3-, and L4-PSOs (SS and PT approximated intact model in L5-PSO); Lumbar osteotomy did not affect the PI. Compared to L3-PSO: L2-, L4-, and L5-PSOs showed up to 32%, 34%, and 34% lower global ROM. The least T10-T11 ROM was observed in L5-PSO. The left and right SIJ ROM were approximately similar in each model. Amongst all, the L5-PSO model showed the least ROM at the SIJ. Compared to L3-PSO, the L2-, L4-, and L5-PSO models showed up to 67%, 61%, and 78% reduced stresses at the UIV, respectively. Minimum stress at UIV+ was observed in the L3-PSO model. The L2-and L3-PSOs showed the maximum PSO force. The L5-PSO model showed the lowest stresses on the primary rods in all motions.

CONCLUSION

Our FE investigation indicates that L5-PSO results in the greatest lumbar lordosis and lowest global, SIJ, and T10-T11 ROMs and stresses on the primary rods, suggesting potential mechanical benefits in reducing the risk of rod breakage. However, L4- and L5-PSOs led to the least force across the osteotomy site, which may increase the risk of pseudarthrosis. These findings provide biomechanical insights that may inform surgical planning, though further clinical investigation is essential to determine the optimal PSO level and validate these results.

CLINICAL SIGNIFICANCE

Understanding the biomechanical impact of PSO level is crucial for optimizing surgical outcomes and minimizing the risks of postoperative complications.

Reciprocal Changes in Sagittal Spinal Alignment After L5-S1 Anterior Lumbar Interbody Fusion

OBJECTIVE

Degenerative diseases of the lumbar spine decrease lumbar lordosis (LL). Anterior lumbar interbody fusion (ALIF) at the L5-S1 disc space improves segmental lordosis, LL, and sagittal balance. This study investigated reciprocal changes in spinopelvic alignment after L5-S1 ALIF.

METHODS

A retrospective chart review identified patients who underwent L5-S1 ALIF with or without posterior fixation at a single institution (November 1, 2016 to October 1, 2021). Changes in pelvic tilt, sacral slope, proximal LL (L1-L4), distal LL (L4-S1), total LL (L1-S1), segmental lordosis, pelvic incidence-LL mismatch, thoracic kyphosis, cervical lordosis, and sagittal vertical axis were measured on preoperative and postoperative radiographs.

RESULTS

Forty-eight patients were identified. Immediate postoperative radiographs were obtained at a mean (SD) of 17 (20) days after surgery; delayed radiographs were obtained 184 (82) days after surgery. After surgery, patients had significantly decreased pelvic tilt (15.71° [7.25°] vs. 17.52° [7.67°], P = 0.003) and proximal LL (11.86° [10.67°] vs. 16.03° [10.45°], P < 0.001) and increased sacral slope (39.49° [9.27°] vs. 36.31° [10.39°], P < 0.001), LL (55.35° [13.15°] vs. 51.63° [13.38°], P = 0.001), and distal LL (43.17° [9.33°] vs. 35.80° [8.02°], P < 0.001). Segmental lordosis increased significantly at L5-S1 and decreased significantly at L2-3, L3-4, and L4-5. Lordosis distribution index increased from 72.55 (19.53) to 81.38 (22.83) (P < 0.001).

CONCLUSIONS

L5-S1 ALIF was associated with increased L5-S1 segmental lordosis accompanied by pelvic anteversion and a reciprocal decrease in proximal LL. These changes may represent a reversal of compensatory mechanisms, suggesting an overall relaxation of spinopelvic alignment after L5-S1 ALIF.

Predictive Value of Bolster Supine X-Ray for the Correction of Segmental Deformity After Thoracolumbar Fusion Surgery

BACKGROUND AND OBJECTIVES

Assessment of thoracolumbar spine flexibility is crucial for determining which osteotomy to perform (posterior column osteotomy or 3-column osteotomy) to restore sagittal balance. Although preoperative bolster supine X-rays have been used to evaluate spine flexibility, their correlation with postoperative spinopelvic parameters has not been reported. We aimed to evaluate the predictive value of bolster X-ray for correcting sagittal deformities after thoracolumbar fusion surgery.

METHODS

We retrospectively evaluated patients who underwent bolster supine radiography before posterior thoracolumbar fusion. Demographic data, operative records, and radiographic parameters were also recorded. The segmental Cobb angle, defined as the angle between the upper endplate of the uppermost and lower endplates of the lowest instrumented vertebrae, was compared between bolster and postoperative X-ray to evaluate the correlation between them. The predictive value of bolster X-ray for postoperative deformity correction was measured using intraclass correlation coefficients (ICC).

RESULTS

Forty-two patients were included. The preoperative segmental Cobb angle (-1.4 ± 22.4) was significantly lower than the bolster segmental Cobb angle (23.2 ± 18.7, P < .001) and postoperative segmental Cobb angle (27.9 ± 22.3, P < .001); however, no significant difference was observed between the bolster and postoperative segmental Cobb angles (P = .746). Bolster X-ray showed a very strong correlation with postoperative X-ray (r = 0.950, P < .001) for segmental Cobb angle. Bolster supine X-ray had good-to-excellent reliability for postoperative X-ray with an ICC of 0.913 (95% CI, 0.760-0.962, P < .001) for the segmental Cobb angle.

CONCLUSION

Bolster supine X-rays demonstrate good-to-excellent reliability with postoperative X-rays for segmental Cobb angles. These findings offer valuable insights into the selection of appropriate osteotomy techniques for clinical practice.

Modified S1 Pedicle Subtraction Osteotomy

STUDY DESIGN

Surgical technique video.

OBJECTIVE

To report a surgical technique to revise patients with previous fusions at L4-S1 leading to an iatrogenic flat back and sagittal imbalance using L5-S1 transforaminal interbody fusion combined with a small S1 corner osteotomy.

BACKGROUND

This is a case of a woman (51 y old) with a history of multiple lumbar surgeries, severe back pain, sagittal imbalance, and loss of lordosis.

METHODS

We describe a feasible revision technique in a complex patient with the goal of attaining optimal distribution of lumbar lordosis and sagittal balance through a modified S1 pedicle subtraction osteotomy, and the use of an interbody cage to enhance the fusion rate and facilitate closure of the 3-column osteotomy.

RESULTS

The preoperative patient lordosis angle of 31 degrees at L1-L4 and 16 degrees at L4-S1 became 12 degrees at L1-L4 and 44 degrees at L4-S1 postoperatively.

CONCLUSION

The combination of L5-S1 transforaminal interbody fusion and S1 corner osteotomy is a feasible technique for the restoration of lumbar lordosis in patients with previous fusion and consequent loss of lordosis.

Distal Lumbar Lordosis is Associated With Reoperation for Adjacent Segment Disease After Lumbar Fusion for Degenerative Conditions

STUDY DESIGN

A single centre retrospective review.

OBJECTIVE

Recent studies have suggested that distal lordosis (L4-S1, DL) remains constant across all pelvic incidence (PI) subgroups, whilst proximal lordosis (L1-L4, PL) varies. We sought to investigate the impact of post-operative DL on adjacent segment disease (ASD) requiring reoperation in patients undergoing lumbar fusion for degenerative conditions.

METHODS

Patients undergoing 1-3 level lumbar fusion with the two senior authors between 2007-16 were included. Demographic and radiographic data were recorded. Univariate, multivariate binary logistic regression, and Kaplan Meier survivorship analyses were performed.

RESULTS

335 patients were included in the final analysis. Most had single (67%) or two (31%) level fusions. The mean follow-up was 64-month. Fifty-seven patients (17%) underwent reoperation for ASD at an average of 78-month post-operatively (R group). The R group had a significantly lower mean post-operative DL (27.3 vs 31.1 deg, P < .001) and mean PI (55.5 vs 59.2 deg, P < .05). On univariate analysis, patients with a post-operative DL of <35 deg had higher odds of reoperation for ASD than those with a post-operative DL of ≥35 deg (OR 2.7, P = .016). In the multivariate model, post-operative DL, low/average PI, and spondylolisthesis were all significantly associated with reoperation for ASD.

CONCLUSION

This study provides preliminary support to an association between post-operative distal lumbar lordosis and risk of reoperation for ASD in patients undergoing fusions for degenerative conditions. Further multicentre prospective study is needed to independently confirm this association and identify the impact of restoration of physiological distal lumbar lordosis on long term patient outcomes.

Lumbar lordosis and sacral slope do not differ in two types of postoperative lumbar disc re-herniation: a cross-sectional observational study

BACKGROUND

To identify the differences of lumbar lordosis (LL) and sacral slope (SS) angles between two types of postoperative lumbar disc re-herniation, including the recurrence of same level and adjacent segment herniation (ASH).

METHODS

We searched the medical records of lumbar disc herniation (LDH) patients with re-herniation with complete imaging data (n = 58) from January 1, 2013 to December 30, 2020 in our hospital. After matching for age and sex, 58 patients with LDH without re-herniation from the same period operated by the same treatment group in our hospital were served as a control group. Re-herniation patients were divided into two groups, same-level recurrent lumbar disc herniation group (rLDHG) and adjacent segment herniation group with or without recurrence (ASHG). The preoperative, postoperative and one month after operation LL and SS were measured on standing radiographs and compared with the control group by using t-test, ANOVA, and rank-sum test. Next, we calculated the odds ratios (ORs) by unconditional logistic regression, progressively adjusted for other confounding factors.

RESULTS

Compared with the control group, the postoperative LL and SS were significantly lower in LDH patients with re-herniation. However, there were no differences in LL and SS between ASHG and rLDHG at any stage. After progressive adjustment for confounding factors, no matter what stage is, LL and SS remained unassociated with the two types of re-herniation.

CONCLUSIONS

Low postoperative LL and SS angles are associated with degeneration of the remaining disc. Low LL and SS may be independent risk factors for re-herniation but cannot determine type of recurrence (same or adjacent disc level).

Sagittal Alignment in the Degenerative Lumbar Spine: Surgical Planning

➤ Sagittal alignment of the spine has gained attention in the field of spinal deformity surgery for decades. However, emerging data support the importance of restoring segmental lumbar lordosis and lumbar spinal shape according to the pelvic morphology when surgically addressing degenerative lumbar pathologies such as degenerative disc disease and spondylolisthesis.➤ The distribution of caudal lordosis (L4-S1) and cranial lordosis (L1-L4) as a percentage of global lordosis varies by pelvic incidence (PI), with cephalad lordosis increasing its contribution to total lordosis as PI increases.➤ Spinal fusion may lead to iatrogenic deformity if performed without attention to lordosis magnitude and location in the lumbar spine.➤ A solid foundation of knowledge with regard to optimal spinal sagittal alignment is beneficial when performing lumbar spinal surgery, and thoughtful planning and execution of lumbar fusions with a focus on alignment may improve patient outcomes.

Long-term comparison of anterior (ALIF) versus transforaminal (TLIF) lumbar interbody fusion: a propensity score-matched register-based study

PURPOSE

Anterior (ALIF) and transforaminal (TLIF) lumbar interbody fusion have shown similar clinical outcomes at short- and medium-term follow-ups. Possible advantages of ALIF in the long run could be better disc height and lumbar lordosis and reduced risk of adjacent segment disease. We aimed to study if ALIF could be associated with superior clinical outcomes than TLIF at long-term follow-up.

METHODS

We analysed 535 patients treated with ALIF or TLIF of the L5-S1 spinal segment between 2007 and 2017 who completed long-term follow-up in a national spine registry database (NORspine). We defined treatment success after surgery as at least 30% improvement in Oswestry Disability Index (ODI) at long-term follow-up. Patients treated with ALIF and TLIF and who responded at long term were balanced by propensity score matching. The proportions of successfully treated patients within each group were compared by numbers and percentages with corresponding relative risk.

RESULTS

The mean (95%CI) age of the total study population was 50 (49-51) years, and 264 (49%) were females. The mean (95%CI) preoperative ODI score was 40 (39-42), and 174 (33%) had previous spine surgery. Propensity score matching left 120 patients in each treatment group. At a median (95%CI) of 92 (88-97) months after surgery, we found no difference in proportions successfully treated patients with ALIF versus TLIF (68 (58%) versus 77 (65%), RR (95%CI) = 0.88 (0.72 to1.08); p = 0.237).

CONCLUSIONS

This propensity score-matched national spine register study of patients treated with ALIF versus TLIF of the lumbosacral junction found no differences in proportions of successfully treated patients at long-term follow-up.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Limited Intervention in Adult Scoliosis-A Systematic Review

BACKGROUND/OBJECTIVES

Adult scoliosis is traditionally treated with long-segment fusion, which provides strong radiographic correction and significant improvements in health-related quality of life but comes at a high morbidity cost. This systematic review seeks to examine the literature behind limited interventions in adult scoliosis patients and examine the best approaches to treatment.

METHODS

This is a MEDLINE- and PubMed-based literature search that ultimately included 49 articles with a total of 21,836 subjects.

RESULTS

Our search found that long-segment interventions had strong radiographic corrections but also resulted in high perioperative morbidity. Limited interventions were best suited to patients with compensated deformity, with decompression best for neurologic symptoms and fusion needed to treat neurological symptoms secondary to up-down stenosis and to provide stability across unstable segments. Decompression can consist of discectomy, laminotomy, and/or foraminotomy, all of which are shown to provide symptomatic relief of neurologic pain. Short-segment fusion has been shown to provide improvements in patient outcomes, albeit with higher rates of adjacent segment disease and concerns for correctional loss. Interbody devices can provide decompression without posterior element manipulation. Future directions include short-segment fusion in uncompensated deformity and dynamic stabilization constructs.

CONCLUSIONS

Limited interventions can provide symptomatic relief to adult spine deformity patients, with indications mostly in patients with balanced deformities and neurological pain.

Validation of Roussouly classification in predicting the occurrence of adjacent segment disease after short-level lumbar fusion surgery

BACKGROUND

Recent studies demonstrated that restoring sagittal alignment to the original Roussouly type can remarkably reduce complication rates after adult spinal deformity surgery. However, there is still no data proving the benefit of maintaining ideal Roussouly shape in the lumbar degenerative diseases and its association with the development of adjacent segment disease (ASD). Thus, this study was performed to validate the usefulness of Roussouly classification to predict the occurrence of ASD after lumbar fusion surgery.

MATERIALS AND METHODS

This study retrospectively reviewed 234 consecutive patients with lumbar degenerative diseases who underwent 1- or 2-level fusion surgery. Demographic and radiographic data were compared between ASD and non-ASD groups. The patients were classified by both "theoretical" [based on pelvic incidence (PI)] and "current" (based on sacral slope) Roussouly types. The patients were defined as "matched" if their "current" shapes matched the "theoretical" types and otherwise as "mismatched". The logistic regression analysis was performed to identify the factors associated with ASD. Finally, clinical data and spinopelvic parameters of "theoretical" and "current" types were compared.

RESULTS

With a mean follow-up duration of 70.6 months, evidence of ASD was found in the 68 cases. Postoperatively, ASD group had more "current" shapes classified as type 1 or 2 and fewer as type 3 than the non-ASD group (p < 0.001), but the distribution of "theoretical" types was similar between groups. Moreover, 80.9% (55/68) of patients with ASD were mismatched, while 48.2% (80/166) of patients without ASD were mismatched (p < 0.001). A multivariate analysis identified age [odds ratio (OR) = 1.058)], 2-level fusion (OR = 2.9830), postoperative distal lordosis (DL, OR = 0.949) and mismatched Roussouly type (OR = 4.629) as independent risk factors of ASD. Among the four "theoretical" types, type 2 had the lowest lumbar lordosis, DL, and segmental lordosis. When considering the "current" types, current type 2 was associated with higher rates of 2-level fusion, worse DL, and greater pelvic tilt compared with other current types.

CONCLUSIONS

DL loss and mismatched Roussouly type were significant risk factors of ASD. To decrease the incidence of ASD, an appropriate value of DL should be achieved to restore sagittal alignment back to the ideal Roussouly type.

LEVEL OF EVIDENCE

Level 4.

Postoperative lordosis distribution index, patient reported outcome measures, and revision surgery following transforaminal lumbar interbody fusion

Objective

Lordosis Distribution Index (LDI) is a new radiographic parameter associated with postoperative residual symptoms in patients undergoing Transforaminal Lumbar Interbody Fusion (TLIF). Recently, it has been applied on patients undergoing instrumented spine surgery, however not correlated to Patient Related Outcome Measures (PROMs). This study investigates whether the obtained the postoperative LDI after TLIF surgery correlates with the clinical outcome measured with PROMs.

Methods

This study was based on prospectively obtained data in patients undergoing TLIF throughout 2017 at a Danish university hospital. Medical records and the DaneSpine Database were accessed to obtain preoperative, operative and follow-up data. Primary outcome was Oswestry Disability Index (ODI) 12 months postoperatively. Secondary outcomes included revision rate and additional PROMs.

Results

126 patients were included. 70 patients were classified with normolordosis (56 %), 42 hypolordosis (33 %) and 14 hyperlordosis (11 %). All groups experienced significant radiological changes undergoing surgery. Average reduction in ODI at 12 months postoperatively was -15.3 (±20.0). Minimally clinical important difference was achieved in 68 patients (54.0 %). No significant difference in PROMs between LDI-groups was observed in unadjusted or adjusted analyses. Revision surgery was performed in 8 patients with normolordosis (11.4 %), 7 hypolordosis (16.7 %) and 4 hyperlordosis (28.6 %).

Conclusions

We found no significant correlation between postoperative LDI subgroups of normolordotic, hypo- or hyperlordotic patients and the clinical outcome of posterolateral fusion and TLIF surgery. A trend towards lower rate of revision surgery in the normolordotic group compared to the hypo- and hyperlordotic group was observed.

L3-L4 Hyperlordosis and Decreased Lower Lumbar Lordosis Following Short-Segment L4-L5 Lumbar Fusion Surgery is Associated With L3-L4 Revision Surgery for Adjacent Segment Stenosis

STUDY DESIGN

Retrospective review of prospective cohort.

OBJECTIVES

Reoperation at L3-L4 for adjacent segment disease (ASD) is common after L4-L5 spine fusion. L4-S1 lower lumbar lordosis (LLL) accounts for the majority of global lumbar lordosis (GLL) and is modifiable during surgery. We sought to determine if a reduction in LLL leads to an increase in L3-L4 focal lumbar lordosis (L3-L4 FLL) and resulting risk of ASD at L3-L4.

METHODS

We reviewed the records of a prospective cohort with lumbar spinal stenosis who underwent L4-L5 or L4-L5-S1 fusion between 2006 and 2012. Radiographic parameters-GLL, LLL, L3-L4 FLL, upper lumbar lordosis, lordosis distribution index, pelvic tilt, and pelvic incidence-were extracted from preoperative and postoperative lumbar spine radiographs. Statistical comparisons were made between those who underwent revision for post-fusion adjacent level stenosis at L3-L4 (REVISION) and those who did not (NO REVISION).

RESULTS

Inclusion criteria were met by 104 patients. The REVISION cohort included 19 individuals. No significant differences in baseline demographics or operative details for the index procedure were found between groups. Postoperatively, when compared to the NO REVISION cohort, the REVISION cohort had a decrease in LLL (-2.6° vs + 1.5°, P = .011) and LDI (-5.1% vs + 1.3%, P = .039), and an increase in L3-L4 FLL (+2.6° vs -.6°, P = .001).

CONCLUSIONS

A reduction in LLL and compensatory increase in L3-L4 FLL after initial lower lumbar fusion surgery resulted in more reoperation at L3-L4 for post-fusion adjacent level spinal stenosis.

Single position L5-S1 lateral ALIF with simultaneous robotic posterior fixation is safe and improves regional alignment and lordosis distribution index

PURPOSE

Minimally invasive single position lateral ALIF at L5-S1 with simultaneous robot-assisted posterior fixation has technical and anatomic considerations that need further description.

METHODS

This is a retrospective case series of single position lateral ALIF at L5-S1 with robotic assisted fixation. End points included radiographic parameters, lordosis distribution index (LDI), complications, pedicle screw accuracy, and inpatient metrics.

RESULTS

There were 17 patients with mean age of 60.5 years. Eight patients underwent interbody fusion at L5-S1, five patients at L4-S1, two patients at L3-S1, and one patient at L2-S1 in single lateral position. Operative times for 1-level and 2-level cases were 193 min and 278 min, respectively. Mean EBL was 71 cc. Mean improvements in L5-S1 segmental lordosis were 11.7 ± 4.0°, L1-S1 lordosis of 4.8 ± 6.4°, sagittal vertical axis of - 0.1 ± 1.7 cm°, pelvic tilt of - 3.1 ± 5.9°, and pelvic incidence lumbar-lordosis mismatch of - 4.6 ± 6.4°. Six patients corrected into a normal LDI (50-80%) and no patients became imbalanced over a mean follow-up period of 14.4 months. Of 100 screws placed in lateral position with robotic assistance, there were three total breaches (two lateral grade 3, one medial grade 2) for a screw accuracy of 97.0%. There were no neurologic, vascular, bowel, or ureteral injuries, and no implant failure or reoperation.

CONCLUSION

Single position lateral ALIF at L5-S1 with simultaneous robotic placement of pedicle screws by a second surgeon is a safe and effective technique that improves global alignment and lordosis distribution index.

The Significance of Odontoid Incidence in Patients With Cervical Spondylotic Myelopathy

STUDY DESIGN

Observational study.

OBJECTIVE

To analyze the cervical sagittal parameters for standing Digital radiography (DR) and supine Magnetic resonance imaging (MRI), and to further clarify the relationship between odontoid incidence (OI) and cervical spondylotic myelopathy (CSM).

METHODS

52 CSM patients aged 54.46 ± 2.89 years underwent both standing DR and supine MRI scans of cervical spine between November 2021 and November 2022. OI, odontoid tilt (OT), C2 slope (C2S), T1 slope (T1S), C0-2 angle, C2-7 angle (cervical lordosis [CL]), and T1S-CL were measured in both DR and MRI images using Surgimap (Version 2.3.2.1). Pearson correlation and linear regression were used to compare these parameters between the two modalities.

RESULTS

Cervical sagittal parameters, including OI, OT, C2S, C0-2 angle, T1S, C2-7 angle (CL) and T1S-CL, showed no significant differences in the measurements between the two modalities. Based on the DR images, OI was related to OT (r = .386, P < .01), C2S (r = .505, P < .01), CL (r = -.412, P < .01), and T1S-CL (r = .320, P < .05), and OI was matched with CL (r2 = .170) and T1S-CL (r2 = .102). Based on MRI images, OI was related to OT (r = .433, P < .01), C2S (r = .516, P < .01), CL (r = -.355, P < .01), and T1S-CL (r = .271, P < .05), and OI matched with C2-7 (r2 = .126) and T1S-CL (r2 = .073).

CONCLUSION

OI is an independent parameter related to cervical anatomy and its measurement is unaffected by external factors. In patients with CSM, odontoid parameters may effectively describe the sagittal alignment of the cervical spine on DR and MRI images.

Spinal Canal Remodeling and Indirect Decompression of Contralateral Foraminal Stenosis After Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion

Objective: There is a lack of literature on indirect decompression in uniportal endoscopic posterolateral transforaminal lumbar interbody fusion (EPTLIF). Our aim is to evaluate the dimensions of the spinal canal and contralateral foramen before and after EPTLIF.Methods: This is a retrospective study of patients who underwent EPTLIF in a tertiary spine centre over a 2-year period. The cross-sectional area of the spinal canal and the contralateral foramen at the level of fusion were measured on magnetic resonance imaging scan at 1-day postoperation and at the final follow-up. Patients were grouped according to the decompression performed as per the clinician’s judgement.Results: One hundred fifty-two levels of fusion were performed in 120 patients. There was a statistically significant clinical improvement in visual analogue scale and Oswestry Disability Index scores postoperation. The measurements of the spinal canal area were 106.0 mm², 138.8 mm², and 195.5 mm²; while contralateral foraminal area were 73.2 mm², 104.4 mm², and 120.7 mm² at preoperation, 1-day postoperation, and at the final follow-up, respectively (p < 0.001). For the subgroup analyses, spinal canal area measurements for the bilateral decompression cohort (n = 35) were 57.0 mm², 123.9 mm², and 191.8 mm²; for the ipsilateral decompression cohort (n = 42) were 89.3 mm², 128.9 mm², 183.3 mm²; and for the cohort without any decompression and only cage inserted (n = 75) were 138.3 mm², 151.2 mm², and 204.1 mm² (p < 0.001). Contralateral foraminal area measurements were 73.3 mm², 106.4 mm² and 120.4 mm² in the bilateral decompression cohort; 69.5 mm², 99.0 mm², 116.9 mm² in the ipsilateral decompression cohort; and 75.1 mm², 106.5 mm², 122.9 mm² in the cohort without any decompression (p < 0.001).Conclusion: Indirect decompression of both the spinal canal and the contralateral foramen can be achieved via EPTLIF. Decompression on an asymptomatic contralateral side is not necessary.

Pelvic Incidence–Lumbar Lordosis Mismatch Is Predisposed to Adjacent Segment Degeneration After Single-Level Anterior Lumbar Interbody Fusion: A Retrospective Case-Control Study

Objective: Spinopelvic parameters play important roles in clinical outcomes and disability after short-segment fusion surgery for degenerative spine disease. This study aimed to investigate the relationship between preoperative or postoperative spinopelvic parameters and symptomatic adjacent segment degeneration (ASD) after single-level anterior lumbar interbody fusion (ALIF) surgery at the L4–5 segments.Methods: All patients who underwent single-level ALIF at the L4–5 level from January 2010 to December 2013 and were followed up for 5 years were analyzed. We collected the degree of degeneration at adjacent segments and preoperative and postoperative spinopelvic parameters. We compared the preoperative and postoperative parameters between patients with and without symptomatic ASD.Results: Sixty-one patients were included in our study, and 30 patients had symptomatic ASD. Degeneration at adjacent segments and preoperative spinopelvic parameters did not affect the occurrence of symptomatic ASD. Patients with symptomatic ASD had higher postoperative pelvic tilt (PT) and a mismatch between lumbar lordosis (LL) and pelvic incidence (PI) compared to those without. Postoperative PT > 15° and PI–LL mismatch > 10° were significant risk factors for symptomatic ASD.Conclusion: High PT and PI–LL mismatch were significant risk factors for symptomatic ASD after single-level ALIF surgery. Spine surgeons should consider achieving proper LL to insert the cage at the appropriate angle and prevent a PI–LL mismatch value > 10° after single-level fusion surgery.

The Standing and Sitting Spino-Pelvic Sagittal Alignment in Patients with Instrumented Lumbar Fusion Might Correlate with Adjacent Segment Degeneration

OBJECTIVES

Sitting is a common weight-bearing posture, like standing, but there still lacks enough understanding of sagittal alignment in sitting position for patients after lumbar fusion. This study aimed to investigate the accommodation of fixed spine from standing to sitting position and its influence on unfused segments.

METHODS

Sixty-two patients after lumbar fusion (test group) and 40 healthy volunteers (control group) were recruited in this research. All subjects underwent lateral radiographs of entire spine in the standing and sitting positions. The spinopelvic parameters including sagittal vertical axis (SVA), T1 pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), and pelvic tilt (PT) were measured. The changes in parameters of patients between two positions were compared with control group, and patients were divided in different groups based on fusion level and their parameters were compared.

RESULTS

When changing from standing to sitting positions, a forward-moving SVA and TPA were observed in both patients and control groups, accompanied by the decrease in LL, TK and increase in PT, but the changes of patients were smaller in TPA, LL, and TK (6.5° ± 7.2° vs 9.7° ± 6.0°, 7.7° ± 8.3° vs 13.6° ± 8.5°, 2.2° ± 6.5° vs 5.4° ± 5.1°, respectively, p < 0.05). Increase of PT in the lumbosacral fixation group was lower than that in the control group (4.4° ± 9.1° vs 8.3° ± 7.1°, p < 0.05). Patients who had adjacent segments degeneration (ASD) showed more kyphosis in unfused lumbar segments than the other patients (16.4° ± 10.7° vs -1.0° ± 4.8°, p < 0.05) from standing to sitting.

CONCLUSIONS

The spine straightens in lumbar and thoracic curve, combined with forward-moving axis and pelvic retroversion when changing to the sitting position. However, these changes are relatively limited in patients after lumbar fusion, so the adjacent unfused lumbar segments compensate to stress during sitting and this may be related to ASD.

L5-S1 nonunion occurrence even after anterior column support combined with iliac screw fixation in long fusion for adult spinal deformity: CT-based analysis at 2-year follow-up

OBJECTIVE

Iliac screw fixation and anterior column support are highly recommended to prevent lumbosacral pseudarthrosis after long-level adult spinal deformity (ASD) surgery. Despite modern instrumentation techniques, a considerable number of patients still experience nonunion at the lumbosacral junction. However, most previous studies evaluating nonunion relied only on plain radiographs and only assessed when the implant failures occurred. Therefore, using CT, it is important to know the prevalence after iliac fixation and to evaluate risk factors for nonunion at L5-S1.

METHODS

Seventy-seven patients who underwent ≥ 4-level fusion to the sacrum using iliac screws for ASD and completed a 2-year postoperative CT scan were included in the present study. All L5-S1 segments were treated by interbody fusion. Lumbosacral fusion status was evaluated on 2-year postoperative CT scans using Brantigan, Steffee, and Fraser criteria. Risk factors for nonunion were analyzed using patient, surgical, and radiographic factors. The metal failure and its association with fusion status at L5-S1 were evaluated.

RESULTS

Of the 77 patients, 12 (15.6%) showed nonunion at the lumbosacral junction on the 2-year CT scans. Multivariate analysis using logistic regression revealed that only higher American Society of Anesthesiologists (ASA) grade was a risk factor for nonunion (OR 25.6, 95% CI 3.196-205.048, p = 0.002). There were no radiographic parameters associated with fusion status at L5-S1. Lumbosacral junction rod fracture occurred more frequently in patients with nonunion than in patients with fusion (33.3% vs 6.2%, p = 0.038).

CONCLUSIONS

Although iliac screw fixation and anterior column support have been performed to prevent lumbosacral nonunion during ASD surgery, 15.6% of patients still showed nonunion on 2-year postoperative CT scans. High ASA grade was a significant risk factor for nonunion. Rod fracture between L5 and S1 occurred more frequently in the nonunion group.