Risk Factors for Adjacent Segment Disease in Short Segment Lumbar Interbody Fusion

Operative Neurosurgery 25:136–141, 2023

Adjacent segment disease (ASD) is a common problem after lumbar spinal fusions. Ways to reduce the rates of ASD are highly sought after to reduce the need for reoperation.

OBJECTIVE: To find predisposing factors of ASD after lumbar interbody fusions, especially in mismatch of pelvic incidence and lumbar lordosis (PI-LL).

METHODS: We conducted a retrospective cohort study of all patients undergoing lumbar interbody fusions of less than 4 levels from June 2015 to July 2020 with at least 1 year of follow-up and in those who had obtained postoperative standing X-rays.

RESULTS: We found 243 patients who fit inclusion and exclusion criteria. Fourteen patients (5.8%) developed ASD, at a median of 24 months. Postoperative lumbar lordosis was significantly higher in the non-ASD cohort (median 46.4°± 1.4°vs 36.9°± 3.6°, P < .001), pelvic tilt was significantly lower in the non-ASD cohort (16.0°± 0.66°vs 20.3°± 2.4°, P = .002), PI-LL mismatch was significantly lower in the non-ASD cohort (5.28°± 1.0°vs 17.1°± 2.0°, P < .001), and age-appropriate PI-LL mismatch was less common in the non-ASD cohort (34 patients [14.8%] vs 13 [92.9%] of patients with high mismatch, P < .001). Using multivariate analysis, greater PI-LL mismatch was predictive of ASD (95% odds ratio CI = 1.393-2.458, P < .001) and age-appropriate PI-LL mismatch was predictive of ASD (95% odds ratio CI = 10.8-970.4, P < .001).

CONCLUSION: Higher PI-LL mismatch, both age-independent and when adjusted for age, after lumbar interbody fusion was predictive for developing ASD. In lumbar degenerative disease, correction of spinopelvic parameters should be a main goal of surgical correction.

Comparison of local and regional radiographic outcomes in minimally invasive and open TLIF

J Neurosurg Spine 37:384–394, 2022

Local and regional radiographic outcomes following minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) versus open TLIF remain unclear. The purpose of this study was to provide a comprehensive assessment of local and regional radiographic parameters following MI-TLIF and open TLIF. The authors hypothesized that open TLIF provides greater segmental and global lordosis correction than MI-TLIF.

METHODS A single-center retrospective cohort study of consecutive patients undergoing MI- or open TLIF for grade I degenerative spondylolisthesis was performed. One-to-one nearest-neighbor propensity score matching (PSM) was used to match patients who underwent open TLIF to those who underwent MI-TLIF. Sagittal segmental radiographic measures included segmental lordosis (SL), anterior disc height (ADH), posterior disc height (PDH), foraminal height (FH), percent spondylolisthesis, and cage position. Lumbopelvic radiographic parameters included overall lumbar lordosis (LL), pelvic incidence (PI)–lumbar lordosis (PI-LL) mismatch, sacral slope (SS), and pelvic tilt (PT). Change in segmental or overall lordosis after surgery was considered “lordosing” if the change was > 0° and “kyphosing” if it was ≤ 0°. Student t-tests or Wilcoxon rank-sum tests were used to compare outcomes between MI-TLIF and open-TLIF groups.

RESULTS A total of 267 patients were included in the study, 114 (43%) who underwent MI-TLIF and 153 (57%) who underwent open TLIF, with an average follow-up of 56.6 weeks (SD 23.5 weeks). After PSM, there were 75 patients in each group. At the latest follow-up both MI- and open-TLIF patients experienced significant improvements in assessment scores obtained with the Oswestry Disability Index (ODI) and the numeric rating scale for low-back pain (NRS-BP), without significant differences between groups (p > 0.05). Both MI- and open-TLIF patients experienced significant improvements in SL, ADH, and percent corrected spondylolisthesis compared to baseline (p < 0.001). However, the MI-TLIF group experienced significantly larger magnitudes of correction with respect to these metrics (ΔSL 4.14° ± 4.35° vs 1.15° ± 3.88°, p < 0.001; ΔADH 4.25 ± 3.68 vs 1.41 ± 3.77 mm, p < 0.001; percent corrected spondylolisthesis: −10.82% ± 6.47% vs −5.87% ± 8.32%, p < 0.001). In the MI-TLIF group, LL improved in 44% (0.3° ± 8.5°) of the cases, compared to 48% (0.9° ± 6.4°) of the cases in the open-TLIF group (p > 0.05). Stratification by operative technique (unilateral vs bilateral facetectomy) and by interbody device (static vs expandable) did not yield statistically significant differences (p > 0.05).

CONCLUSIONS Both MI- and open-TLIF patients experienced significant improvements in patient-reported outcome (PRO) measures and local radiographic parameters, with neutral effects on regional alignment. Surprisingly, in our cohort, change in SL was significantly greater in MI-TLIF patients, perhaps reflecting the effect of operative techniques, technological innovations, and the preservation of the posterior tension band. Taking these results together, no significant overall differences in LL between groups were demonstrated, which suggests that MI-TLIF is comparable to open approaches in providing radiographic correction after surgery. These findings suggest that alignment targets can be achieved by either MI- or open-TLIF approaches, highlighting the importance of surgeon attention to these variables.

Radiographic and clinical outcomes in one- and two-level transforaminal lumbar interbody fusions: a comparison of bullet versus banana cages

J Neurosurg Spine 36:918–927, 2022

The aim of this study was to determine whether cage morphology influences clinical and radiographic outcomes following short-segment transforaminal lumbar interbody fusion (TLIF) procedures.

METHODS The authors retrospectively reviewed one- and two-level TLIFs at a single tertiary care center between August 2012 and November 2019 with a minimum 1-year radiographic and clinical follow-up. Two cohorts were compared based on interbody cage morphology: steerable “banana” cage or straight “bullet” cage. Patient-reported outcome measures (PROMs), radiographs, and complications were analyzed.

RESULTS A total of 135 patients with 177 interbody levels were identified; 45 patients had 52 straight cages and 90 patients had 125 steerable cages. Segmental lordosis increased with steerable cages, while it decreased with straight cages (+3.8 ± 4.6 vs −1.9 ± 4.3, p < 0.001). Conversely, the mean segmental lordosis of adjacent lumbar levels decreased in the former group, while it increased in the latter group (−0.52 ± 1.9 vs +0.52 ± 2.1, p = 0.004). This reciprocal relationship results in global sagittal parameters, including pelvic incidence minus lumbar lordosis and lumbar distribution index, which did not change after surgery with either cage morphology. Multivariate analysis confirmed that steerable cage morphology, anterior cage positioning, and less preoperative index-level segmental lordosis were associated with greater improvement in index-level segmental lordosis. PROMs were improved after surgery with both cage types, and the degree of improvement did not differ between cohorts (p > 0.05). Perioperative and radiographic complications were similar between cohorts (p > 0.05). Overall reoperation rates, as well as reoperation rates for adjacent-segment disease within 2 years of surgery, were not significantly different between cohorts.

CONCLUSIONS Steerable cages are more likely to lie within the anterior disc space, thus increasing index-level segmental lordosis, which is accompanied by a reciprocal change in segmental alignment at the adjacent lumbar levels. The converse relationship occurs for straight cages, with a kyphotic change at the index levels and reciprocal lordosis occurring at adjacent levels.

 

Does transforaminal lumbar interbody fusion induce lordosis or kyphosis?

J Neurosurg Spine 35:419–426, 2021

Conflicting reports exist about whether transforaminal lumbar interbody fusion (TLIF) induces lordosis or kyphosis, ranging from decreasing lordosis by 3.71° to increasing it by 18.8°. In this study, the authors’ aim was to identify factors that result in kyphosis or lordosis after TLIF.

METHODS A single-center, retrospective study of open TLIF without osteotomy for spondylolisthesis with a minimum 2-year follow-up was undertaken. Preoperative and postoperative clinical and radiographic parameters and cage specifics were collected. TLIFs were considered to be “lordosing” if postoperative induction of lordosis was > 0° and “kyphosing” if postoperative induction of lordosis was ≤ 0°.

RESULTS A total of 137 patients with an average follow-up of 52.5 months (range 24–130 months) were included. The overall postoperative disc angle (DA) and segmental lordosis (SL) increased by 1.96° and 1.88° (p = 0.003 and p = 0.038), respectively, whereas overall lumbar lordosis remained unchanged (p = 0.133). Seventy-nine patients had lordosing TLIFs with a mean SL increase of 5.72° ± 3.97°, and 58 patients had kyphosing TLIFs with a mean decrease of 3.02° ± 2.98°. Multivariate analysis showed that a lower preoperative DA, lower preoperative SL, and anterior cage placement were correlated with the greatest increase in postoperative SL (p = 0.040, p < 0.001, and p = 0.035, respectively). There was no difference in demographics, cage type or height, or spinopelvic parameters between the groups (p > 0.05). Linear regression showed that the preoperative DA and SL correlated with SL after TLIF (R2 = 0.198, p < 0.001; and R2 = 0.2931, p < 0.001, respectively).

CONCLUSIONS Whether a TLIF induces kyphosis or lordosis depends on the preoperative DA, preoperative SL, and cage position. Less-lordotic segments became more lordotic postoperatively, and highly lordotic segments may lose lordosis after TLIF. Cages placed more anteriorly were associated with more lordosis.

Functional and radiological outcome of anterior retroperitoneal versus posterior transforaminal interbody fusion in the management of single-level lumbar degenerative disease

Neurosurg Focus 49 (3):E2, 2020

In this study the authors compared the anterior lumbar interbody fusion (ALIF) and posterior transforaminal lumbar interbody fusion (TLIF) techniques in a homogeneous group of patients affected by single-level L5–S1 degenerative disc disease (DDD) and postdiscectomy syndrome (PDS). The purpose of the study was to analyze perioperative, functional, and radiological data between the two techniques.

METHODS A retrospective analysis of patient data was performed between 2015 and 2018. Patients were clustered into two homogeneous groups (group 1 = ALIF, group 2 = TLIF) according to surgical procedure. A statistical analysis of clinical perioperative and radiological findings was performed to compare the two groups. A senior musculoskeletal radiologist retrospectively revised all radiological images.

RESULTS Seventy-two patients were comparable in terms of demographic features and surgical diagnosis and included in the study, involving 32 (44.4%) male and 40 (55.6%) female patients with an average age of 47.7 years. The mean follow-up duration was 49.7 months. Thirty-six patients (50%) were clustered in group 1, including 31 (86%) with DDD and 5 (14%) with PDS. Thirty-six patients (50%) were clustered in group 2, including 28 (78%) with DDD and 8 (22%) with PDS. A significant reduction in surgical time (107.4 vs 181.1 minutes) and blood loss (188.9 vs 387.1 ml) in group 1 (p < 0.0001) was observed. No significant differences in complications and reoperation rates between the two groups (p = 0.561) was observed. A significant improvement in functional outcome was observed in both groups (p < 0.001), but no significant difference between the two groups was found at the last follow-up. In group 1, a faster median time of return to work (2.4 vs 3.2 months) was recorded. A significant improvement in L5–S1 postoperative lordosis restoration was registered in the ALIF group (9.0 vs 5.0, p = 0.023).

CONCLUSIONS According to these results, interbody fusion is effective in the surgical management of discogenic pain. Even if clinical benefits were achieved earlier in the ALIF group (better scores and faster return to work), both procedures improved functional outcomes at last follow-up. The ALIF group showed significant reduction of blood loss, shorter surgical time, and better segmental lordosis restoration when compared to the TLIF group. No significant differences in postoperative complications were observed between the groups. Based on these results, the ALIF technique enhances radiological outcome improvement in spinopelvic parameters when compared to TLIF in the management of adult patients with L5–S1 DDD.

Outcomes of Minimally Invasive Transforaminal Lumbar Interbody Fusion With Expandable Lordotic Devices

Neurosurgery, Volume 86, Issue 2, February 2020, Pages E147–E155

Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is a well-accepted procedure for the treatment of degenerative lumbar disease. However, its ability to restore lumbar lordosis has been limited. Development of expandable lordotic interbody devices has challenged this limitation, furthering the scope ofminimally invasive surgery.

OBJECTIVE: To evaluate the radiographic and clinical effects of expandable lordotic interbody devices placed through an MIS-TLIF approach.

METHODS: We conducted a retrospective review of 32 1-level and 18 2-level MIS-TLIFs performed using lordotic expandable interbody devices. Lumbar radiographic measurements, Oswestry Disability Index scores (ODI), and Visual Analogue Scale scores (VAS)were obtained at preoperative, 6 wk follow up, and last follow up time points. Last follow up occurred at a mean of 11.5 ± 7.6 mo (mean ± SD).

RESULTS: At 6-wk follow-up, segmental lordosis, disc height, and foraminal height increased by an average of 3.4◦, 6.4 mm, and 4.4 mm, respectively. Only the 2-level group showed a significant increase in lumbar lordosis of 5.8◦. No significant changes occurred in sacral slope, pelvic tilt, or pelvic incidence. Average ODI and VAS decreased by −12.0 and −4.5, respectively. Postoperative lumbar lordosis inversely correlated with preoperative lordosis in patients with an initial Pelvic Incidence to Lumbar Lordosis mismatch (PI-LL) of >10◦, (r=−0.5, P = .009).

CONCLUSION: When applied across 2-levels, MIS-TLIF using expandable lordotic interbody devices produced a significant increase in lumbar lordosis. Preoperative lumbar lordosis was found to be a predictor of postoperative lumbar lordotic change in patients with sagittal imbalance.

Global Spinal Alignment in Cervical Kyphotic Deformity: The Importance of Head Position and Thoracolumbar Alignment in the Compensatory Mechanism

Neurosurgery 82:686–694, 2018

Previous studies have evaluated cervical kyphosis (C-kypho) using cervical curvature or chin-brow vertical angle, but the relationship between C-kypho and global spinal alignment is currently unknown.

OBJECTIVE: To elucidate global spinal alignment and compensatory mechanisms in primary symptomatic C-kypho using full-spine radiography.

METHODS: In this retrospectivemulticenter study, symptomatic primary C-kypho patients (Cerv group; n=103) and adult thoracolumbar deformity patients (TL group; n=119) were compared.We subanalyzed Cerv subgroups according to sagittal vertical axis (SVA) values of C7 (SVAC7 positive or negative [C7P or C7N]). Various Cobb angles (◦) and SVAs (mm) were evaluated.

RESULTS: SVAC7 values were –20.2 and 63.6 mm in the Cerv group and TL group, respectively (P < .0001). Various statistically significant compensatory curvatures were observed in the Cerv group, namely larger lumbar lordosis (LL) and thoracic kyphosis. The C7N group had significantly lower SVACOG (center of gravity of the head) and SVAC7 (32.9 and –49.5 mm) values than the C7P group (115.9 and 45.1 mm). Sagittal curvatures were also different in T4-12, T10-L2, LL4-S, and LL. The value of pelvic incidence (PI)-LL was different (C7N vs C7P; –2.2◦ vs 9.9◦; P < .0003). Compensatory sagittal curvatures were associated with potential for shifting of SVAC7 posteriorly to adjust head position. PI-LL affected these compensatory mechanisms. CONCLUSION: Compensation in symptomatic primary C-kypho was via posterior shifting of SVAC7, small T1 slope, and large LL. However, even in C-kypho patients, lumbar degeneration might affect global spinal alignment. Thus, global spinal alignment with cervical kyphosis is characterized as head balanced or trunk balanced.

Pelvic retroversion: a compensatory mechanism for lumbar stenosis

J Neurosurg Spine 27:137–144, 2017

The flexed posture of the proximal (L1–3) or distal (L4–S1) lumbar spine increases the diameter of the spinal canal and neuroforamina and can relieve symptoms of neurogenic claudication. Distal lumbar flexion can result in pelvic retroversion; therefore, in cases of flexible sagittal imbalance, pelvic retroversion may be compensatory for lumbar stenosis and not solely compensatory for the sagittal imbalance as previously thought. The authors investigate underlying causes for pelvic retroversion in patients with flexible sagittal imbalance.

METHODS One hundred thirty-eight patients with sagittal imbalance who underwent a total of 148 fusion procedures of the thoracolumbar spine were identified from a prospective clinical database. Radiographic parameters were obtained from images preoperatively, intraoperatively, and at 6-month and 2-year follow-up. A cohort of 24 patients with flexible sagittal imbalance was identified and individually matched with a control cohort of 23 patients with fixed deformities. Flexible deformities were defined as a 10° change in lumbar lordosis between weight-bearing and non–weight-bearing images. Pelvic retroversion was quantified as the ratio of pelvic tilt (PT) to pelvic incidence (PI).

RESULTS The average difference between lumbar lordosis on supine MR images and standing radiographs was 15° in the flexible cohort. Sixty-eight percent of the patients in the flexible cohort were diagnosed preoperatively with lumbar stenosis compared with only 22% in the fixed sagittal imbalance cohort (p = 0.0032). There was no difference between the flexible and fixed cohorts with regard to C-2 sagittal vertical axis (SVA) (p = 0.95) or C-7 SVA (p = 0.43). When assessing for postural compensation by pelvic retroversion in the stenotic patients and nonstenotic patients, the PT/PI ratio was found to be significantly greater in the patients with stenosis (p = 0.019).

CONCLUSIONS For flexible sagittal imbalance, preoperative attention should be given to the root cause of the sagittal misalignment, which could be compensation for lumbar stenosis. Pelvic retroversion can be compensatory for both the lumbar stenosis as well as for sagittal imbalance.

 

The Influence of Pelvic Incidence and Lumbar Lordosis Mismatch on Development of Symptomatic Adjacent Level Disease Following Single-Level Transforaminal Lumbar Interbody Fusion

Neurosurgery 80:880–886, 2017

Annual incidence of symptomatic adjacent level disease (ALD) following lumbar fusion surgery ranges from 0.6% to 3.9% per year. Sagittal malalignment may contribute to the development of ALD.

OBJECTIVE: To describe the relationship between pelvic incidence-lumbar lordosis (PI-LL) mismatch and the development of symptomatic ALD requiring revision surgery following single-level transforaminal lumbar interbody fusion for degenerative lumbar spondylosis and/or low-grade spondylolisthesis.

METHODS: All patients who underwent a single-level transforaminal lumbar interbody fusion at either L4/5 or L5/S1 between July 2006 and December 2012 were analyzed for pre- and postoperative spinopelvic parameters. Using univariate and logistic regression analysis,we compared the spinopelvic parameters of those patients who required revision surgery against those patients who did not develop symptomatic ALD. We calculated the predictive value of PI-LL mismatch.

RESULTS: One hundred fifty-nine patients met the inclusion criteria. The results noted that, for a 1◦ increase in PI-LL mismatch (preop and postop), the odds of developing ALD requiring surgery increased by 1.3 and 1.4 fold, respectively, which were statistically significant increases. Based on our analysis, a PI-LL mismatch of >11◦ had a positive predictive value of 75% for the development of symptomatic ALD requiring revision surgery.

CONCLUSIONS: A high PI-LL mismatch is strongly associated with the development of symptomatic ALD requiring revision lumbar spine surgery. The development of ALD may represent a global disease process as opposed to a focal condition. Spine surgeons may wish to consider assessment of spinopelvic parameters in the evaluation of degenerative lumbar spine pathology.

 

Effect of lordosis angle change after lumbar/lumbosacral fusion on sacrum angular displacement

Sacrum angular displacement

Eur Spine J (2014) 23:2369–2374

To assess and characterize the sacrum angular displacements in response to lumbar lordosis after lumbar/ lumbosacral fusion.

Methods A finite element model of the lower lumbar spine-pelvis was established and used to simulate the posterior fusion at L3–L5 and L4–S1. The lordosis angle in the fusion segments was set to five different conditions with respect to the intact model: 10 less than intact, 5 less than intact, same as intact, 5 more than intact, and 10 more than intact. Variations of the sacrum angular displacements with lordosis changes were analyzed under loading setting of axial compression, flexion, extension, lateral bending, and axial rotation.

Results Compared with the intact lordosis, both increased and decreased lumbar lordosis angles caused the sacrum angular displacements to be increased. The lordosis angle increased by 10º induced the most substantial increase in sacrum angular displacements. In addition, the sacrum angular displacements of the L4–S1 fusion model at different lordosis angles were higher than those of the L3–L5 fusion model.

Conclusion The sacrum angular displacements occur as a result of the fusion surgery (L4–S1) and the changes in lumbar lordosis.

Surgical treatment of pathological loss of lumbar lordosis (flatback)

Flatback

J Neurosurg Spine 21:160–170, 2014

Increased sagittal vertical axis (SVA) correlates strongly with pain and disability for adults with spinal deformity. A subset of patients with sagittal spinopelvic malalignment (SSM) have flatback deformity (pelvic incidence–lumbar lordosis [PI-LL] mismatch > 10°) but remain sagittally compensated with normal SVA. Few data exist for SSM patients with flatback deformity and normal SVA. The authors’ objective was to compare baseline disability and treatment outcomes for patients with compensated (SVA < 5 cm and PI-LL mismatch > 10°) and decompensated (SVA > 5 cm) SSM.

Methods. The study was a multicenter, prospective analysis of adults with spinal deformity who consecutively underwent surgical treatment for SSM. Inclusion criteria included age older than 18 years, presence of adult spinal deformity with SSM, plan for surgical treatment, and minimum 1-year follow-up data. Patients with SSM were divided into 2 groups: those with compensated SSM (SVA < 5 cm and PI-LL mismatch > 10°) and those with decompensated SSM (SVA ≥ 5 cm). Baseline and 1-year follow-up radiographic and health-related quality of life (HRQOL) outcomes included Oswestry Disability Index, Short Form–36 scores, and Scoliosis Research Society–22 scores. Percentages of patients achieving minimal clinically important difference (MCID) were also assessed.

Results. A total of 125 patients (27 compensated and 98 decompensated) met inclusion criteria. Compared with patients in the compensated group, patients in the decompensated group were older (62.9 vs 55.1 years; p = 0.004) and had less scoliosis (43° vs 54°; p = 0.002), greater SVA (12.0 cm vs 1.7 cm; p < 0.001), greater PI-LL mismatch (26° vs 20°; p = 0.013), and poorer HRQOL scores (Oswestry Disability Index, Short Form-36 physical component score, Scoliosis Research Society-22 total; p ≤ 0.016). Although these baseline HRQOL differences between the groups reached statistical significance, only the mean difference in Short Form–36 physical component score reached threshold for MCID. Compared with baseline assessment, at 1 year after surgery improvement was noted for patients in both groups for mean SVA (compensated –1.1 cm, decompensated +4.8 cm; p ≤ 0.009), mean PI-LL mismatch (compensated 6°, decompensated 5°; p < 0.001), and all HRQOL measures assessed (p ≤ 0.005). No significant differences were found between the compensated and decompensated groups in the magnitude of HRQOL score improvement or in the percentages of patients achieving MCID for each of the outcome measures assessed.

Conclusions. Decompensated SSM patients with elevated SVA experience significant disability; however, the amount of disability in compensated SSM patients with flatback deformity caused by PI-LL mismatch but normal SVA is underappreciated. Surgical correction of SSM demonstrated similar radiographic and HRQOL score improvements for patients in both groups. Evaluation of SSM should extend beyond measuring SVA. Among patients with concordant pain and disability, PI-LL mismatch must be evaluated for SSM patients and can be considered a primary indication for surgery.

Radiological and clinical outcomes following extreme lateral interbody fusion

Radiological and clinical outcomes following extreme lateral interbody fusion

 J Neurosurg Spine 20:623–635, 2014

Extreme lateral interbody fusion (ELIF) is a popular technique for anterior fixation of the thoracolumbar spine. Clinical and radiological outcome studies are required to assess safety and efficacy. The aim of this study was to describe the functional and radiological impact of ELIF in a degenerative disc disease population with a longer follow-up and to assess the durability of this procedure.

Methods. Demographic and perioperative data for all patients who had undergone ELIF for degenerative lumbar disorders between 2007 and 2011 were collected. Trauma and tumor cases were excluded. For radiological outcome, the preoperative, immediate postoperative, and latest follow-up coronal Cobb angle, lumbar sagittal lordosis, bilateral foraminal heights, and disc heights were measured. Pelvic incidence (PI) and PI–lumbar lordosis (PI-LL) mismatch were assessed in scoliotic patients. Clinical outcome was evaluated using the Oswestry Disability Index (ODI) and visual analog scale (VAS), as well as the Macnab criteria.

Results. One hundred forty-five vertebral levels were surgically treated in 90 patients. Pedicle screw and rod constructs and lateral plates were used to stabilize fixation in 77% and 13% of cases, respectively. Ten percent of cases involved stand-alone cages. At an average radiological follow-up of 12.6 months, the coronal Cobb angle was 10.6° compared with 23.8° preoperatively (p < 0.0001). Lumbar sagittal lordosis increased by 5.3° postoperatively (p < 0.0001) and by 2.9° at the latest follow-up (p = 0.014). Foraminal height and disc height increased by 4 mm (p < 0.0001) and 3.3 mm (p < 0.0001), respectively, immediately after surgery and remained significantly improved at the last follow-up. Separate evaluation of scoliotic patients showed no statistically significant improvement in PI and PI-LL mismatch either immediately postoperatively or at the latest follow-up. Clinical evaluation at an average follow-up of 17.6 months revealed an improvement in the ODI and the VAS scores for back, buttock, and leg pain by 21.1% and 3.7, 3.6, and 3.7 points, respectively (p < 0.0001). According to the Macnab criteria, 84.8% of patients had an excellent, good, or fair functional outcome. New postoperative thigh numbness and weakness was detected in 4.4% and 2.2% of the patients, respectively, which resolved within the first 3 months after surgery in all but 1 case.

Conclusions. This study provides what is to the authors’ knowledge the most comprehensive set of radiological and clinical outcomes of ELIF in a fairly large population at a midterm follow-up. Extreme lateral interbody fusion showed good clinical outcomes with a low complication rate. The procedure allows for at least midterm clinically effective restoration of disc and foraminal heights. Improvement in coronal deformity and a small but significant increase in sagittal lordosis were observed. Nonetheless, no significant improvement in the PI-LL mismatch was achieved in scoliotic patients.