The Selection of L5 Versus S1 in Long Fusions for Adult Idiopathic Scoliosis

Distal Junctional Failure After Fusion Stopping at L5 in Patients With Adult Spinal Deformity: Incidence, Risk Factors, and Radiographic Criteria

OBJECTIVE

To identify risk factors and establish radiographic criteria for distal junctional failure (DJF) in patients with adult spinal deformity (ASD), who underwent fusion surgery stopping at L5.

METHODS

This retrospective study was undertaken from January 2016 to December 2020. Patients with ASD who underwent fusion surgery (≥5 levels) stopping at L5 were analyzed. DJF was defined as symptomatic adjacent segment pathology at the lumbosacral junction necessitating consideration for revision surgery. Demographic data and radiographic measurements were compared between the DJF and non-DJF groups. Receiver operating characteristic curve analysis was performed to identify the radiographic cutoff value for DJF.

RESULTS

Among 76 patients, 16 (21.1%) experienced DJF. DJF was associated with older age, antidepressant/anxiolytic medication, longer level of fusions, and worse preoperative sagittal alignment. Antidepressant/anxiolytic medication (odds ratio, 5.60) and preoperative pelvic incidence (PI)-lumbar lordosis (LL) mismatch>40° (odds ratio, 5.87) were independent risk factors for DJF. Without both factors, the incidence of DJF has been greatly reduced (9.1%). Two radiographic criteria were determined for DJF: last distal junctional angle (DJA)>-5° and Δ last DJA-post DJA>5°. When both criteria were met, the sensitivity and specificity of the DJF were 93.3% and 91.7%, respectively.

CONCLUSION

Use of antidepressant/anxiolytic medication and preoperative PI-LL mismatch >40° were independent risk factors for DJF. DJF could be diagnosed using postoperative changes in the DJA. If both criteria were met, DJF could be strongly suggested.

Assessing the Fractional Curve for Proper Management of Adult Degenerative Scoliosis

Adult degenerative scoliosis (ADS) is a coronal plane deformity often accompanied by sagittal plane malalignment. Surgical correction may involve the major and/or distally-located fractional curves (FCs). Correction of the FC has been increasingly recognized as key to ameliorating radicular pain localized to the FC levels. The present study aims to summarize the literature on the rationale for FC correction in ADS. Three databases were systematically reviewed to identify all primary studies reporting the rationale for correcting the FC in ADS. Articles were included if they were English full-text studies with primary data from ADS ( ≥ 18 years old) patients. Seventy-four articles were identified, of which 12 were included after full-text review. Findings suggest FC correction with long-segment fusion terminating at L5 increases the risk of distal junctional degeneration as compared to constructs instrumenting the sacrum. Additionally, circumferential fusion offers greater FC correction, lower reoperation risk, and shorter construct length. Minimally invasive surgery (MIS) techniques may offer effective radiographic correction and improve leg pain associated with foraminal stenosis on the FC concavity, though experiences are limited. Open surgery may be necessary to achieve adequate correction of severe, highly rigid deformities. Current data support major curve correction in ASD where the FC concavity and truncal shift are concordant, suggesting that the FC contributes to the patient's overall deformity. Circumferential fusion and the use of kickstand rods can improve correction and enhance the stability and durability of long constructs. Last, MIS techniques show promise for milder deformities but require further investigation.

The Lumbosacral Fractional Curve in Adult Degenerative Scoliosis

Spine surgeons are often faced with a profoundly difficult challenge in surgically treating adult degenerative scoliosis. Deformity correction surgery is complicated by the difficulty in offering extensive surgical corrections to the elderly, complication-prone population it commonly affects. As spine surgeons attempt to offer minimally invasive solutions to this disease process, the need for fusion of the fractional curve at L4, L5, and S1 may be discounted. A treatment strategy to identify, address, and treat the fractional curve with either open or minimally invasive techniques can lead to improved patient outcomes and decrease revision rates in this complicated pathologic process.

Femoral head to lower lumbar neural foramen distance as a novel radiographic parameter to predict postoperative stretch neuropraxia

OBJECTIVE

Lumbosacral fractional curves in adult spinal deformity (ASD) patients often have sharp coronal curves resulting in significant pain and imbalance. Postoperative stretch neuropraxia after fractional curve correction can lead to discomfort and unsatisfactory outcomes. The goal of this study was to use radiographic measures to increase understanding of the relationship between postoperative stretch neuropraxia and fractional curve correction.

METHODS

In 62 ASD patients treated from 2015 to 2018, radiographic review was performed, including measurement of the distance between the lower lumbar neural foramen (L4 and L5) in the concavity and convexity of the lumbosacral fractional curve and the ipsilateral femoral heads (FHs; L4-FH and L5-FH) in pre- and postoperative anteroposterior spine radiographs. The largest absolute preoperative to postoperative change in distance between the lower lumbar neural foramen and the ipsilateral FH (ΔL4/L5-FH) was used for analysis. Chi-square analyses, independent and paired t-tests, and logistic regression were performed to study the relationship between L4/L5-FH and stretch neuropraxia for categorical and continuous variables, respectively.

RESULTS

Of the 62 patients, 13 (21.0%) had postoperative stretch neuropraxia. Patients without postoperative stretch neuropraxia had an average ΔL4-FH distance of 16.2 mm compared to patients with stretch neuropraxia, who had an average ΔL4-FH distance of 31.5 mm (p < 0.01). Patients without postoperative neuropraxia had an average ΔL5-FH distance of 11.1 mm compared to those with stretch neuropraxia, who had an average ΔL5-FH distance of 23.0 mm (p < 0.01). Chi-square analysis showed that patients had a 4.78-fold risk of developing stretch neuropraxia with ΔL4-FH > 20 mm (95% CI 1.3-17.3) and a 5.17-fold risk of developing stretch neuropraxia with ΔL5-FH > 15 mm (95% CI 1.4-18.7). Logistic regression analysis indicated that the odds of developing stretch neuropraxia were 15:1 with a ΔL4-FH > 20 mm (95% CI 3-78) and 21:1 with a ΔL5-FH > 15 mm (95% CI 4-113).

CONCLUSIONS

The novel ΔL4/L5-FH distances are strongly associated with postoperative stretch neuropraxia in ASD patients. A ΔL4-FH > 20 mm and ΔL5-FH > 15 mm significantly increase the odds for patients to develop postoperative stretch neuropraxia.

Can fusion to S1 maintain favorable surgical outcomes following one-level pedicle subtraction osteotomy in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis?

PURPOSE

To compare the surgical outcomes between ankylosing spondylitis (AS)-related thoracolumbar kyphosis patients with the lowest instrumented vertebra (LIV) at S1 or above following one-level pedicle subtraction osteotomy (PSO).

METHODS

One hundred and two AS patients undergoing one-level PSO with a minimum of 2-year follow-up were included. Twenty-two patients were in group S1 (LIV at S1), and eighty were in group non-S1 (LIV above S1). Radiographic parameters including lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI), and sagittal vertical axis (SVA) were measured. Oswestry Disability Index (ODI) and visual analog scale (VAS) were applied for clinical assessment.

RESULTS

In both S1 and non-S1 groups, the radiographic parameters and clinical outcomes were significantly improved after surgery (P  < 0.05). Patients undergoing distal fusion to S1 had significantly larger preoperative PI-LL mismatch, SVA, and smaller preoperative LL and SS compared to those in group non-S1 (P  < 0.05). No significant difference was found between the two groups regarding preoperative and final follow-up ODI and VAS (P  > 0.05), as well as the improvement in ODI and VAS (P  > 0.05). The incidence of overall complications and each type of complication including the implant failure was similar between group S1 and non-S1 (P  > 0.05).

CONCLUSION

Selecting S1 as the LIV without pelvic fixation following one-level PSO in thoracolumbar kyphosis caused by AS could achieve satisfactory surgical outcomes and might not increase the complications. Patients with relatively severe sagittal imbalance, loss of LL, PI-LL mismatch, and small SS might be the potential candidates for distal fusion to S1 following one-level PSO.

Comparison of long fusion terminating at L5 versus the sacrum in treating adult spinal deformity: a meta-analysis

Purpose

Choosing an optimal distal fusion level for adult spinal deformity (ASD) is still controversial. To compare the radiographic and clinical outcomes of distal fusion to L5 versus the sacrum in ASD, we conducted a meta-analysis.

Methods

Relevant studies on long fusion terminating at L5 or the sacrum in ASD were retrieved from the PubMed, Embase, Cochrane, and Google Scholar databases. Then, studies were manually selected for inclusion based on predefined criteria. The meta-analysis was performed by RevMan 5.3.

Results

Eleven retrospective studies with 1211 patients were included in meta-analysis. No significant difference was found in overall complication rate (95% CI 0.60 to 1.30) and revision rate (95% CI 0.59 to 1.99) between fusion to L5 group (L group) and fusion to the sacrum group (S group). Significant lower rate of pseudarthrosis and implant-related complications (95% CI 0.29 to 0.64) as well as proximal adjacent segment disease (95% CI 0.35 to 0.92) was found in L group. Patients in S group obtained a better correction of lumbar lordosis (95% CI − 7.85 to − 0.38) and less loss of sagittal balance (95% CI − 1.80 to − 0.50).

Conclusion

Our meta-analysis suggested that long fusion terminating at L5 or the sacrum was similar in scoliosis correction, overall complication rate, revision rate, and improvement in pain and disability. However, fusion to L5 had advantages in lower rate of pseudarthrosis, implant-related complications, and proximal adjacent segment disease, while fusion to the sacrum had advantages in the restoration of lumbar lordosis, maintenance of sagittal balance, and absence of distal adjacent segment disease.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

[Risk factors analysis of coronal imbalance after posterior long-level fixation and transforaminal lumbar interbody fusion for degenerative lumbar scoliosis]

OBJECTIVE

To explore the risk factors of coronal imbalance after posterior long-level fixation and fusion for degenerative lumbar scoliosis.

METHODS

Retrospectivly analyzed the clinical records of 41 patients with degenerative lumbar scoliosis who had received posterior long-level fixation and fusion with selective transforaminal lumbar interbody fusion (TLIF) accompanied by Ponte osteotomy between August 2011 and July 2016. Patients were divided into imbalance group (group A, 11 cases) and balance group (group B, 30 cases) according to state of coronal imbalance measured at last follow-up. The radiographic parameters at preoperation and last follow-up were measured, and the variance of preoperative and last follow-up parameters were calculated. The radiographic parameters included coronal Cobb angle, coronal balance distance (CBD), apical vertebral translation (AVT), apical vertebral rotation (AVR), Cobb angle of lumbar sacral curve (LSC), and L 5 tilt angle (L 5TA). Univariate analysis was performed for the factors including gender, age, preoperative T value of bone mineral density, number of instrumented vertebra, upper and lower instrumented vertebra, segments of TLIF, decompression, and Ponte osteotomy, as well as the continuous variables of preoperative imaging parameters with significant difference were converted into two-category variables, obtained the influence factors of postoperative coronal imbalance. Multivariate logistic regression analysis was performed to verify the risk factors from the preliminary screened influence factors and the variance of imaging parameters with significant difference between the two groups.

RESULTS

The follow-up time of groups A and B was (3.76±1.02) years and (3.56±1.03) years respectively, there was no significant difference between the two groups ( t=0.547, P=0.587). The coronal Cobb angle, AVT, LSC Cobb angle, and L 5TA in group A were significantly higher than those in group B before operation ( P<0.05), and all the imaging parameters in group A were significantly higher than those in group B at last follow-up ( P<0.05). There was no significant difference between the two groups in parameters including the variance of coronal Cobb angle, AVT, and LSC Cobb angle before and after operation ( P>0.05), and there were significant differences between the two groups in parameters including the variance of CBD, L 5TA, and AVR ( P<0.05). Univariate analysis showed that preoperative L 5TA was the influencing factor of postoperative coronal imbalance ( P<0.05). Multivariate logistic regression analysis showed that preoperative L 5TA≥15° was an independent risk factor of postoperative coronal imbalance, and variance of pre- and post-operative AVR was a protective factor.

CONCLUSION

Preoperative L 5TA≥15° is an independent risk factor for coronal imbalance in patients with degenerative lumbar scoliosis after posterior long-level fixation and fusion.

Stopping at Sacrum Versus Nonsacral Vertebra in Long Fusion Surgery for Adult Spinal Deformity: Meta-Analysis of Revision with Minimum 2-Year Follow-Up

OBJECTIVE

A pooled comparison was conducted on a revision to the sacrum (S) versus a nonsacral (NS) surgical strategy in adult spinal deformity (ASD).

METHODS

Strictly following the PRISMA 2009 guidelines, the MEDLINE, EMBASE, and Cochrane Library databases were used to search for studies published in English up to March 2018 that addressed the S versus NS surgical approach for a long fusion to treat ASD. Data on total revisions and revision reasons were extracted from the included studies and were pooled analyzed.

RESULTS

Eight retrospective studies with a total of 1846 ASD patients (528 S and 1318 NS) were included. The total revision rate was 11.38% (S: 17.80% and NS: 8.80%), and implant failure, pseudarthrosis, adjacent segment degeneration, and proximal junctional kyphosis (PJK) were common reasons for revision. The pooled results indicated that the NS group had decreased incident rates of total revision (95% confidence interval [CI] 1.20-2.32, P = 0.002; I2 = 0%) and pseudarthrosis (95% CI 2.16-15.44, P = 0.0005; I2 = 0%) compared with the S group. No significant differences were observed in implant failure (95% CI 0.86-3.90, P = 0.12; I2 = 0%), adjacent segment degeneration (95% CI 0.08-1.25, P = 0.10; I2 = 0%), and PJK (95% CI 0.54-6.88, P = 0.35; I2 = 0%) between the 2 groups.

CONCLUSIONS

Revision in ASD patients is a serious problem with a total rate of 11.38%, and implant failure, pseudarthrosis, adjacent segment degeneration, and PJK are common reasons for revision. Stopping at the sacrum vertebra in long fusion surgery on ASD patients seems to increase the incidence rates of total revision and pseudarthrosis.

L5-S1 disc degeneration and the anatomic parameters of the iliac crest: imaging study

PURPOSE

To evaluate the relationship between height ratio of the iliac crest to L4 (HR), width ratio of the iliac crest to L4 (WR) and L5-S1 disc degeneration.

METHODS

On T2-weighted sagittal images of the 50 randomly selected patients, two observers graded L5-S1 discs and some other parameters were measured. Then, relative signal intensity (RSI) of the L5-S1 nucleus pulposus was calculated. On anteroposterior and lateral radiographs of the same 50 patients' lumbar spine, the parameters such as the height of the iliac crest were measured and then HR and WR were calculated. Finally, HR, WR and the percentage of the sROM of L5-S1 in L1-S1 segments of the other 51 randomly selected patients were calculated.

RESULTS

Positive correlations were found between HR, WR and RSI of the L5-S1 disc. Negative correlations were found between HR, WR and modified Pfirrmann scores of L5-S1 nucleus pulposus. A statistically significant negative correlation was found between HR and the percentage of sROM of L5-S1 in L1-S1 segments.

CONCLUSIONS

Low HR and (or) WR were the risk factors for L5-S1 disc degeneration. High HR could reduce the percentage of sROM of L5-S1 in L1-S1 segments and high HR and (or) WR could reduce the incidence of L5-S1 disc degeneration.

Changes in thoracic kyphosis negatively impact sagittal alignment after lumbar pedicle subtraction osteotomy: a comprehensive radiographic analysis

STUDY DESIGN

Consecutive, multicenter retrospective review.

OBJECTIVE

To evaluate if change in thoracic kyphosis (TK) has a positive or negative impact on spinopelvic alignment after lumbar pedicle subtraction osteotomy (PSO) with short fusions.

SUMMARY OF BACKGROUND DATA

In the setting of sagittal malalignment, the effect of large vertebral resections can now be anticipated in long fusions, but their impact on unfused segments (reciprocal changes [RC]) remains poorly understood.

METHODS

A total of 34 adult patients (mean age = 54 years; SD = 12) who underwent lumbar PSO with upper instrumented vertebra below T10 were included. Radiographic analysis included pre- and postassessment of TK, lumbar lordosis (LL), sagittal vertical axis (SVA), T1 spinopelvic inclination (T1SPI), pelvic tilt (PT), and pelvic incidence (PI). Final SVA and PT were analyzed to determine successful realignment. RC in the thoracic spine was designated favorable or unfavorable on the basis of impact on final SVA and PT.

RESULTS

Mean PSO resection was 26°. LL increased from 20° to 49° (P < 0.001). SVA improved from 14 to 4 cm (P < 0.001), and PT improved from 33° to 25° (P < 0.001). Mean increase in TK was 13° (P = 0.002) but was unchanged in 11 patients. Five patients had a favorable RC, and 18 patients had an unfavorable RC. Unfavorable RC was attributed to junctional failure in 6 of 18 patients. Significant differences in the unfavorable RC group included age and greater preoperative PT, PI, SVA, and T1SPI.

CONCLUSION

Significant postoperative alignment changes can occur through unfused thoracic spinal segments after lumbar PSO. Unfavorable RC may limit optimal correction and lead to clinical failures. Risk factors for unfavorable thoracic RC include older patients, larger preoperative PI and PT, and worse preoperative T1SPI and are not simply due to junctional failure. Care should be taken with selective lumbar fusion and PSO in older patients and in those with severe preoperative spinopelvic parameters.

Bilateral pars fractures complicating long fusion to L5 in a patient with rheumatoid arthritis

STUDY DESIGN

Case report.

OBJECTIVE

To report bilateral pars fractures at L5 complicating a long fusion for adult idiopathic scoliosis in a patient with rheumatoid arthritis.

SUMMARY OF BACKGROUND DATA

To our knowledge, there are no reports in the literature regarding bilateral pars fractures at the end instrumented vertebrae of a long fusion at the lumbosacral junction, nor reports that have evaluated long spinal deformity corrections in patients with rheumatoid arthritis. The question of ending a long fusion at L5 or S1 is controversial, and a review is presented.

METHODS

We present the patient's history, physical examination, and radiographic findings; describe the surgical treatment and long-term follow-up; and provide a literature review.

RESULTS

Bilateral pars fractures at the end instrumented vertebrae of a long construct (T4-L5) that we discovered were subsequently revised by extension of the fusion to the sacrum. Anterior structural support at L5-S1 was also provided. At the latest follow-up (46 months), the patient has had no recurrence of her symptoms. Her radiographs showed a stable construct without loss of alignment in the sagittal or coronal planes. Her rheumatoid arthritis continues to be treated with biologic, disease-modifying antirheumatic drugs.

CONCLUSION

To our knowledge, this is the first report of the treatment and long-term outcome of a patient with rheumatoid arthritis and bilateral pars fractures at the end instrumented vertebrae (L5) of a long deformity correction construct.

Critical length of fusion requiring additional fixation to prevent nonunion of the lumbosacral junction

STUDY DESIGN

A retrospective study.

OBJECTIVE

To determine the critical length of fusion that warrants additional stronger fixation in lumbosacral (L-S) fusion, and to analyze the risk factors of nonunion at the L-S junction.

SUMMARY OF BACKGROUND DATA

Long lever arm fusion down to S1 requires stronger fixation than short lever arm fusion. However, no published criteria are available about the critical length of fusion requiring stronger fixation to the ilium or S2 to obtain adequate stability for union at the L-S junction.

METHODS

A total of 327 adult patients with degenerative lumbar disease, who were treated with instrumented fusion, including the L-S junction, were included in this study. Mean patient age was 59.7 (20-79) years and the minimum follow-up was 12 months. Union rates were compared using univariate and multivariate logistic regression analysis. Length of fusion, age, sex, lumbar lordosis at preoperative, early postoperative and final follow-ups, BMD, smoking history, associated morbidities, fat content of paraspinal muscle, methods of fusion, and levels of intercristal line were examined as independent variables to identify factors that affect union rate at the L-S junction.

RESULTS

Of the 327 patients, 47 (14.4%) had nonunion at the L-S junction. Union rate of the L-S junction at the single level, and at 2, 3, 4, 5, and more than 5 levels were 96.6%, 92.9%, 87.4%, 64.7%, 66.7%, and 58.0%, respectively. A significant difference of union rate was found between less than 4 levels and 4 or more levels of fusion (P < 0.05). The factors found by multivariate analysis to significantly affect union rate at the L-S junction were fusion length and fat content of paraspinal muscle.

CONCLUSION

The risk of nonunion at the L-S junction was found to increase significantly for more than 3 levels of fusion. We advise that additional stronger fixation is needed in such cases.