The impact of cage positioning on lumbar lordosis and disc space restoration following minimally invasive lateral lumbar interbody fusion

Tariq Ziad IssaDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Yunsoo LeeDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Mark J. LambrechtsDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Khoa S. TranDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Delano TrenchfieldDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Sydney BakerDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Sebastian FrasDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Goutham R. YallaDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Mark F. KurdDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Barrett I. WoodsDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Jeffrey A. RihnDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Jose A. CansecoDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Alan S. HilibrandDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Alexander R. VaccaroDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Christopher K. KeplerDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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Gregory D. SchroederDepartment of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania

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OBJECTIVE

The objective of this study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following a minimally invasive lateral lumbar interbody fusion (LLIF) procedure.

METHODS

A retrospective review was conducted of all patients who underwent one- or two-level LLIF. Preoperative, initial postoperative, and 6-month postoperative measurements of LL, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing the center point ratio (CPR) on immediate postoperative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes.

RESULTS

A total of 106 levels in 78 unique patients were included. Most procedures involved fusion of one level (n = 50, 64.1%), most commonly L3–4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively, and patients with anteriorly placed cages had greater overall lordosis correction postoperatively (mean 6.30°, p = 0.0338). At the 6-month follow-up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the change in posterior disc height postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255). There were no correlations between cage lordotic angle and outcomes. On multivariate regression, anterior cage placement predicted greater 6-month improvement in segmental lordosis, while posterior placement predicted greater 6-month improvement in posterior disc height. Percutaneous screw placement, cage lordotic angle, and cage height did not independently predict any radiographic outcomes.

CONCLUSIONS

LLIF procedures reliably improve LL and increase intervertebral disc space. Anterior cage placement improves the lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement in lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.

ABBREVIATIONS

CPR = center point ratio; LL = lumbar lordosis; LLIF = lateral lumbar interbody fusion; PLIF = posterior lumbar interbody fusion; TLIF = transforaminal lumbar interbody fusion.

OBJECTIVE

The objective of this study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following a minimally invasive lateral lumbar interbody fusion (LLIF) procedure.

METHODS

A retrospective review was conducted of all patients who underwent one- or two-level LLIF. Preoperative, initial postoperative, and 6-month postoperative measurements of LL, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing the center point ratio (CPR) on immediate postoperative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes.

RESULTS

A total of 106 levels in 78 unique patients were included. Most procedures involved fusion of one level (n = 50, 64.1%), most commonly L3–4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively, and patients with anteriorly placed cages had greater overall lordosis correction postoperatively (mean 6.30°, p = 0.0338). At the 6-month follow-up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the change in posterior disc height postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255). There were no correlations between cage lordotic angle and outcomes. On multivariate regression, anterior cage placement predicted greater 6-month improvement in segmental lordosis, while posterior placement predicted greater 6-month improvement in posterior disc height. Percutaneous screw placement, cage lordotic angle, and cage height did not independently predict any radiographic outcomes.

CONCLUSIONS

LLIF procedures reliably improve LL and increase intervertebral disc space. Anterior cage placement improves the lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement in lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.

Lumbar fusion, especially interbody fusion, can provide stability to painful and unstable motion segments, provide indirect decompression for foraminal stenosis, and improve spinal balance and deformity. Interbody placement allows for the correction of sagittal parameters including lordosis and restoration of disc height, both of which are frequently lost in the degenerative spine. Several techniques have achieved widespread acceptance for interbody fusion. Anterior lumbar fusion techniques offer significant and reliable benefits to lordotic correction that remain controversial in other approaches, such as transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF).1 TLIF procedures have been suggested to induce kyphosis or lordosis depending on various patient or surgical technique factors,26 while PLIFs are now less commonly performed.

Minimally invasive lateral lumbar interbody fusion (LLIF), another option for lumbar interbody fusions, offers the reliability of lordotic correction observed in anterior lumbar surgery while also supporting a minimally invasive approach that can reduce complications.4,7,8 These minimally invasive approaches have been reported by some investigators to be associated with decreased blood loss, lower postoperative readmissions, reduction in opioid use, and shorter length of hospital stay.4,911

There has been significant effort in the literature to better understand the sagittal correction provided by LLIFs, but no optimal technique or implant has been found. Cage geometry, including lordotic angle and implant size, and cage placement have both been suggested to play integral roles in radiographic outcomes.7,1216 However, recent studies have not demonstrated an association between degree of cage lordosis and correction of sagittal parameters following interbody fusion.13,14,17 The role of cage geometry and placement during LLIF procedures continues to remain unclear. Therefore, the primary objective of our study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following LLIF procedures, specifically evaluating cage geometry and positioning.

Methods

Patient Selection

After approval from the IRB, a retrospective cohort study was conducted on all patients older than 18 years of age who underwent an LLIF, using a Structured Query Language search. Patients were excluded if their surgery included a simultaneous osteotomy or a fusion of more than two levels, or if they underwent a subsequent spine surgery during the 6-month follow-up period. Patients were also excluded if their surgery was indicated for malignancy, infection, or trauma.

Patient Characteristics and Radiographic Parameters

Demographic parameters including age, sex, BMI, smoking status (current, former smoker, never), diabetes history, and history of prior spine surgery were collected via chart review. Surgical details that were recorded included the specific levels fused, interbody cage lordosis, cage dimensions, cage material, cage placement, whether the LLIF was a primary or revision surgery, and if posterior screws were placed via a percutaneous or open approach. Surgical outcomes included 90-day readmission and 90-day complication rates. Included complications were those defined as Clavien-Dindo grade 3 or 4 requiring invasive intervention or organ failure (e.g., reoperation, stroke, myocardial infarction, renal failure, and pulmonary embolism) and surgical complications associated with the procedure or approach (e.g., hardware fracture, dural tear, surgical site infection, arterial/venous injury, hematoma/seroma, and wound dehiscence).

Preoperative, initial postoperative, 6-month postoperative, and Δ (postoperative minus preoperative) measurements were collected for each patient with intact imaging records using our PACS. Standing lateral lumbar radiographs were used for all measurements to ensure standard measurement techniques for each patient. The following pre- and postoperative measurements were recorded: LL, segmental lordosis, anterior disc height, and posterior disc height. LL was measured as the angle between the superior endplate of L1 and the superior endplate of S1. Segmental lordosis was defined as the angle between the superior endplate of the superior vertebra and the inferior endplate of the inferior vertebra. Anterior and posterior disc heights were measured as the distance between the inferior endplate of the superior vertebra and the superior endplate of the inferior vertebra both anteriorly and posteriorly, respectively. Cage placement was defined by measuring the center point ratio (CPR) on the initial postoperative standing lateral radiograph.17,18 CPR is the distance between the midpoint of the cage and the posterior edge of the superior endplate of the inferior vertebral body divided by the entire length of the superior endplate of the inferior vertebral body. In effect, cages with a greater CPR were placed more anteriorly, while those with a lower CPR were located more posteriorly; a CPR of 0.50 represented a cage placed exactly in the middle of the inferior vertebral body.

Statistical Analysis

After we collected radiographic parameters, patients were evaluated to determine if there were any significant predictors of postoperative change in segmental lordosis immediately and at the 6-month follow-up. The patient population was divided equally based on the median degree of immediate segmental lordosis correction, which was determined to be 3°. Patients were subsequently stratified into three subgroups based on the cage positioning CPR (anterior, central, or posterior). Because we expected clustering around more central values with fewer comparisons, we divided groups equally based on the cage positioning within our study population. For all these comparisons, continuous variables were assessed using either an independent t-test or Mann-Whitney U-test for parametric and nonparametric data, respectively. A Shapiro-Wilk score was calculated for each continuous variable to assess normality of distribution. All categorical variables were compared using a Pearson chi-square analysis or Fisher’s exact test. We then conducted a Spearman correlation coefficient analysis to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of Δ LL, Δ segmental lordosis, Δ anterior disc height, and Δ posterior disc height. All statistical tests were conducted using Stata SE (release 17, StataCorp). A p value < 0.05 was considered significant.

Results

Baseline Characteristics

A total of 106 levels in 78 unique patients met inclusion criteria (Table 1). Most of the cages were placed in male patients (62.3%), with a mean overall patient age of 65.2 years. Most procedures involved an LLIF at one level (n = 50, 64.1%), while 28 (35.9%) were two-level LLIF procedures. The most common levels fused were L3–4 (46.2%), followed by L2–3 (26.4%) and L4–5 (22.6%). The L1–2 vertebral level was the least commonly fused (4.7%). No stand-alone LLIF procedures were identified, and all patients had posterior instrumentation. Overall, 49.1% of all levels were associated with percutaneous screw placement via a minimally invasive or robotic approach, while 51.9% of screws at fused levels were placed via an open approach (Table 1). One complication and readmission was noted in our cohort, in which the same obese patient experienced wound dehiscence and required incision and drainage of their posterior incision site. The posterior fusion in this patient was performed via an open approach, and the surgery was a revision procedure.

TABLE 1.

Demographics on a per-level basis (n = 106 levels)

VariableValue
Mean age (SD), yrs65.2 (9.3)
Sex, n (%)
 Male66 (62.3)
 Female40 (37.7)
Mean BMI (SD)30.4 (6.0)
Diabetes history, n (%)21 (19.8)
Smoking history, n (%)
 Never smoker61 (57.6)
 Former smoker29 (27.4)
 Current smoker16 (15.1)
Revision surgery, n (%)31 (29.3)
No. of levels fused, n (%)
 1 level50 (47.2)
 2 levels56 (52.8)
Levels fused, n (%)
 L1–25 (4.7)
 L2–328 (26.4)
 L3–449 (46.2)
 L4–524 (22.6)
Percutaneous screws, n (%)52 (49.1)
Mean CLA (SD), °9.45 (2.3)
Mean cage height (SD), mm10.4 (2.1)
Cage material, n (%)
 PEEK40 (40.4)
 Titanium59 (59.6)

CLA = cage lordotic angle; PEEK = polyetheretherketone.

Immediate Postoperative Segmental Lordosis

We first divided our cohort by the median improvement in postoperative segmental lordosis, which was 3.0°. Fifty-two cages improved segmental lordosis by < 3°, while 54 provided > 3° of segmental lordosis. Only 8 patients experienced any loss of segmental lordosis postoperatively. Patients who experienced greater improvement in segmental lordosis after fusion were found to have worse preoperative segmental lordosis (mean 9.21° vs 13.18°, p = 0.0072) but similar overall LL (mean 34.9° vs 38.6°, p = 0.3617). There were no other differences in patient or operative characteristics based on initial postoperative improvement. Patients with greater segmental lordosis correction had a more anterior cage placement (mean CPR 0.586 vs 0.516, p = 0.0097), but no significant differences in overall cage dimensions, lordosis angle, or material (Table 2).

TABLE 2.

Association of patient factors with overall segmental correction in the immediate postoperative period

FactorΔ Segmental Lordosisp Value
<3.0°, n = 52>3.0°, n = 54
Mean age (SD), yrs66.6 (9.2)63.8 (9.2)0.1023
Sex, n0.515
 Male3432
 Female1822
Mean BMI (SD)30.3 (5.6)30.5 (6.4)0.9885
Diabetes history, n11100.734
Smoking history, n0.877
 Never smoker3031
 Former smoker1514
 Current smoker79
Primary vs revision15160.929
No. of levels fused, n0.552
 1 level2327
 2 levels2927
Percutaneous screws, n24280.557
Mean CLA (SD), °9.85 (2.1)9.06 (2.5)0.0997
Mean cage height (SD), mm10.4 (2.2)10.4 (2.0)0.7496
Cage material, n0.367
 PEEK2218
 Titanium2732
Mean CPR (SD)0.516 (0.12)0.586 (0.14)0.0097
Mean preop LL (SD), °38.60 (10.1)34.91 (15.1)0.3617
Mean preop segmental lordosis (SD), °13.18 (6.9)9.21 (8.0)0.0072

Boldface type indicates statistical significance.

Six-Month Postoperative Segmental Lordosis

On 6-month follow-up standing radiographs, 61 fused levels (57.5%) demonstrated > 3° postoperative improvement in segmental lordosis. Patients experiencing maintained improvement in segmental lordosis were more likely to be female (49.2% vs 22.2%, p = 0.005) and were more likely to have percutaneously placed posterior pedicle screws compared with open placement (57.4% vs 37.8%, p = 0.046). Patients with greater improvement in segmental lordosis were still more likely to have worse preoperative segmental lordosis (mean 9.11° vs 13.93°, p = 0.0012) and more likely to have anteriorly placed interbody cages (mean CPR 0.578 vs 0.519, p = 0.039; Table 3).

TABLE 3.

Association of patient factors with overall segmental lordosis correction at 6 months postoperatively

VariableΔ Segmental Lordosisp Value
<3.0°, n = 45>3.0°, n = 61
Mean age (SD), yrs67.1 (8.3)63.8 (9.8)0.1375
Sex, n0.005
 Male3531
 Female1030
Mean BMI (SD)30.6 (5.7)30.2 (6.2)0.7484
Diabetes history, n8130.652
Smoking history, n0.491
 Never smoker2437
 Former smoker1514
 Current smoker610
Primary vs revision, n14170.717
No. of levels fused, n0.204
 1 level1832
 2 levels2729
Percutaneous screws, n17350.046
Mean CLA (SD), °9.88 (2.3)9.13 (2.4)0.1218
Mean cage height (SD), mm10.42 (1.8)10.39 (2.2)0.6972
Cage material, n0.990
 PEEK1723
 Titanium2534
Mean CPR (SD)0.519 (0.15)0.578 (0.13)0.039
Mean preop LL (SD), °37.84 (11.0)35.90 (14.3)0.8003
Mean preop segmental lordosis (SD), °13.93 (6.2)9.11 (8.1)0.0012

Boldface type indicates statistical significance.

Cage Placement and Segmental Lordosis

To evaluate the effect of cage placement on segmental lordosis, we then used the CPR to divide cage placement into anterior, central, and posterior. Patients were considered to have anteriorly placed cages at a CPR > 0.61 and posteriorly placed cages with a CPR < 0.485. All groups experienced improvement (as noted by positive Δ values) in overall LL, segmental lordosis, and anterior and posterior disc height both immediately postoperatively and at 6 months. Despite showing no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively. Patients with anteriorly placed cages also had greater overall lordosis correction postoperatively (mean 6.30°) compared with those with cages placed centrally (mean 3.71°) or posteriorly (mean 3.36°, p = 0.0338), but these differences disappeared at 6 months (mean 6.11° vs 5.17° vs 4.11°, p = 0.3408; Table 4).

TABLE 4.

Association of cage placement with radiographic parameters

ParameterAnterior, n = 35Central, n = 36Posterior, n = 35p Value
Mean overall LL (SD), °
 Preop34.77 (13.8)38.53 (11.8)36.81 (13.4)0.6234
 Postop41.07 (11.9)42.24 (13.2)40.18 (12.2)0.8220
 Δ postop6.30 (6.5)3.71 (5.0)3.36 (5.5)0.0338
 6 mos40.89 (12.2)43.70 (13.1)40.92 (12.5)0.6116
 Δ 6 mos6.11 (7.3)5.17 (5.9)4.11 (6.6)0.3408
Mean segmental lordosis (SD), °
 Preop11.21 (6.9)11.11 (8.0)11.15 (8.2)0.9986
 Postop16.02 (6.8)15.58 (7.9)13.62 (8.1)0.3788
 Δ postop4.81 (4.3)4.46 (4.6)2.47 (2.9)0.0315
 6 mos16.83 (7.1)15.68 (7.7)13.47 (7.9)0.1722
 Δ 6 mos5.62 (4.2)4.56 (4.8)2.32 (2.8)0.0024
Mean anterior disc height (SD), mm
 Preop8.71 (2.6)7.20 (3.3)8.15 (7.2)0.1439
 Postop15.33 (3.6)12.38 (2.8)12.67 (2.8)0.0004
 Δ postop6.63 (4.3)5.18 (4.0)4.5 (2.8)0.0602
 6 mos14.95 (2.7)12.73 (3.1)11.85 (3.2)0.0001
 Δ 6 mos6.24 (3.3)5.53 (4.1)3.69 (3.4)0.0122
Mean posterior disc height (SD), mm
 Preop4.71 (2.0)4.37 (1.7)4.61 (1.7)0.7154
 Postop6.51 (2.4)8.08 (2.8)9.52 (3.0)0.0001
 Δ postop1.80 (2.2)3.71 (2.8)4.91 (3.0)0.0001
 6 mos6.78 (2.1)7.87 (2.5)8.79 (3.3)0.0236
 Δ 6 mos2.06 (2.1)3.50 (2.4)4.18 (3.4)0.0255

Boldface type indicates statistical significance.

Postoperatively, patients with anteriorly placed cages had a greater mean anterior disc height (15.33 mm) compared with those placed centrally (12.38 mm) or posteriorly (12.67 mm, p = 0.0004), despite similar mean baseline anterior disc heights (p = 0.1439). At the 6-month follow-up, the overall mean anterior disc height was highest in cages placed anteriorly (p = 0.0122), and these patients experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). In contrast, cages placed more posteriorly increased the Δ posterior disc height both postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255; Table 4). Spearman correlation analysis found weak positive relationships between increasing (more anterior) CPR and Δ LL (correlation 0.1943, p = 0.046), Δ segmental lordosis (correlation 0.3053, p = 0.0015), and Δ anterior disc height (correlation 0.3494, p = 0.0002). More posterior cage placement was moderately correlated with a greater Δ posterior disc height (correlation 0.4603, p < 0.0001; Table 5).

TABLE 5.

Spearman correlation of CPR and radiographic parameters

Independent Variable (x)Dependent Variable (y)Spearman Correlationp ValueRelationship
LL
 CPRPreop LL, °−0.08230.4016No relationship
 CPRInitial postop LL−0.02780.7770No relationship
 CPRΔ initial LL0.19430.0460Weak positive
 CPR6-mo LL−0.05110.6209No relationship
 CPRΔ 6-mo LL0.10450.2865No relationship
Segmental lordosis
 CPRPreop segmental lordosis, °−0.01120.9089No relationship
 CPRInitial postop segmental lordosis0.11490.2409No relationship
 CPRΔ initial segmental lordosis0.22210.0221Weak positive
 CPR6-mo segmental lordosis0.14530.1373No relationship
 CPRΔ 6-mo segmental lordosis0.30530.0015Weak positive
Anterior disc height
 CPRPreop anterior disc height, mm0.11200.2530No relationship
 CPRInitial postop anterior disc height0.34940.0002Weak positive
 CPRΔ initial anterior height0.21780.0249Weak positive
 CPR6-mo anterior disc height 0.4132<0.0001Moderate positive
 CPRΔ 6-mo anterior height0.24070.0130Weak positive
Posterior disc height
 CPRPreop posterior disc height, mm0.07350.4539No relationship
 CPRInitial postop posterior disc height0.4399<0.0001Moderate negative
 CPRΔ initial posterior height0.4603<0.0001Moderate negative
 CPR6-mo posterior disc height0.30690.0014Weak negative
 CPRΔ 6-mo posterior height0.32100.0008Weak negative

Boldface type indicates statistical significance.

Evaluation of cage lordotic angle found that an increasing degree of cage lordosis demonstrated no correlation with LL, segmental lordosis, or anterior or posterior disc height at any time point (Table 6).

TABLE 6.

Correlation of cage lordosis and radiographic parameters

Independent Variable (x)Dependent Variable (y)Spearman Correlationp ValueRelationship
LL
 CLAPreop LL, °−0.06010.5609None
 CLAInitial postop LL −0.14940.1463None
 CLAΔ initial LL −0.06680.5177None
 CLA6-mo LL −0.18070.0780None
 CLAΔ 6-mo LL −0.10920.2894None
Segmental lordosis
 CLAPreop segmental lordosis, °0.02390.8174None
 CLAInitial postop segmental lordosis−0.05350.6050None
 CLAΔ initial segmental lordosis−0.18010.0792None
 CLA6-mo segmental lordosis−0.01710.8687None
 CLAΔ 6-mo segmental lordosis−0.13460.1910None
Anterior disc height
 CLAPreop anterior disc height, mm−0.08360.4180None
 CLAInitial postop anterior disc height0.07110.4910None
 CLAΔ initial anterior height0.12690.2179None
 CLA6-mo anterior disc height 0.10370.3144None
 CLAΔ 6-mo anterior height0.13790.1803None
Posterior disc height
 CLAPreop posterior disc height, mm−0.09490.3575None
 CLAInitial postop posterior disc height−0.02340.8210None
 CLAΔ initial posterior height−0.02150.8350None
 CLA6-mo posterior disc height0.01320.8986None
 CLAΔ 6-mo posterior height0.04140.6889None

Multivariate Linear Regression

Multivariate linear regression showed that older age predicted less overall improvement in lordosis at 6 months (β = −0.20, p = 0.007), but CPR, cage lordotic angle, or number of levels fused did not affect lordosis. CPR independently predicted a greater 6-month improvement in segmental lordosis (β = 7.27, p = 0.015), while greater preoperative segmental lordosis predicted less improvement in segmental lordosis (β = −0.12, p = 0.030). Increasing CPR was associated with a decrease in posterior disc height (β = −8.43, p < 0.001) and an increase in anterior disc height (β = 4.68, p = 0.082), although its relationship to anterior disc height did not reach statistical significance. On multivariate regression, percutaneous screw placement, cage lordotic angle, and cage height did not predict any changes in radiographic outcomes (Table 7).

TABLE 7.

Multivariate linear regression of radiographic outcomes at 6 months

VariableBeta Coefficient95% CIp Value
Δ LL
 Levels fused2.42−0.53 to 5.370.107
 CPR0.52−8.73 to 9.780.911
 CLA−0.4−1.0 to 0.190.179
 Percutaneous screws1.94−1.00 to 4.890.194
 Sex (male)1.92−0.82 to 4.660.167
 Age−0.20−0.35 to −0.060.007
Δ segmental lordosis
 CPR7.271.43 to 13.120.015
 Cage height−0.25−0.69 to 0.180.253
 CLA−9.17−0.54 to 0.200.371
 Percutaneous screws0.79−1.00 to 2.590.383
 Preop segmental lordosis−0.12−0.23 to −0.010.030
 Age−0.09−0.17 to 0.0030.059
Δ anterior disc height
 CPR4.68−0.60 to 9.970.082
 CLA0.26−0.07 to 0.590.125
 Percutaneous screws0.88−0.67 to 2.430.263
Δ posterior disc height
 CPR−8.43−12.28 to −4.58<0.001
 CLA0.09−0.15 to 0.330.477
 Cage height−0.05−0.74 to 0.220.696
 Percutaneous screws0.44−0.74 to 1.610.461
 Sex (male)−1.08−2.19 to 0.02 0.054

Boldface type indicates statistical significance.

Discussion

Several contemporary surgical techniques, particularly anterior lumbar interbody fusion and minimally invasive LLIF, allow spine surgeons to offer significant lumbar lordotic improvement and indirect neural decompression. There are multiple considerations that affect surgical decisions in conjunction with many options for cage selection and placement technique, but no clear guidelines exist. For example, if a patient presents primarily with a kyphotic deformity, surgeons may fear that placing fewer lordotic cages may not help the deformity, or that posterior placement of the cage may worsen the deformity. But because persistent leg pain is associated with lower posterior disc height following interbody fusion,13 surgeons may instead feel a need to place the cage more posteriorly to provide indirect decompression.19 Our study aimed to help answer some of these uncertainties on postoperative radiographic outcomes.

In our evaluation of 106 levels fused via LLIF, we identified that all patients, on average, experienced greater improvement in sagittal parameters and disc space restoration, regardless of patient, surgical, or cage characteristics. Additionally, we identified that LLIFs were associated with a low complication and readmission rate. In TLIFs, another commonly utilized surgery for degenerative spinal conditions, both overall and segmental lordosis have been shown to inconsistently improve, with as many as 42.3% of patients exhibiting kyphotic alignment changes following the surgery.2 After a TLIF, fewer lordotic segments appear to be more likely to become more lordotic postoperatively, and highly lordotic segments may lose lordosis.2 However, in our study, only 7.5% of fused levels became kyphotic, consistent with the literature on the reliability of LLIFs.1,4,16,20,21 Moreover, cages placed more anteriorly provided greater improvements in overall lordosis, segmental lordosis, and anterior disc height, while those placed more posteriorly provided greater posterior disc space restoration, which may indicate better indirect decompression. These findings demonstrate that patient-specific factors will likely determine the ideal cage placement.

Several studies have evaluated the importance of cage characteristics across different interbody fusion techniques, primarily in TLIF procedures. A recent analysis of 126 single-level TLIFs demonstrated no association between cage lordosis or cage placement in sagittal parameters or disc height.17 Another study of 45 single-level TLIFs found that anterior cage placement contributed to greater posterior disc height but did not affect LL.13 This finding is counterintuitive and contrary to the findings of our study, as we found that cage positioning increases the height in the area wherein it is placed. Part of the reason for these contrasting findings may come from differences inherent to the approach. The lateral approach allows a surgeon to make a larger discectomy and insertion of large interbody grafts. An examination of 309 operative levels with degenerative spondylolisthesis found that patients undergoing anterior or lateral lumbar spine surgery experienced significantly greater improvement in lordosis than patients undergoing a TLIF.22 LLIF cages have a larger profile than TLIF cages, which allows them to increase disc space throughout the intravertebral space regardless of positioning, while simultaneously augmenting disc height at the site of placement. The larger interbody LLIF cages allow the devices to rest on the lateral margins of the ring apophysis, which may help provide a larger footprint to counteract the resistance of the anterior ligament. Conversely, the smaller TLIF cages may be unable to distract the disc space anteriorly due to tethering of the intact anterior longitudinal ligament.23

Cage positioning significantly impacted disc space restoration in our study. If cage height or lordosis were the primary factor for vertebral body distraction, then one could imagine that placing a hyperlordotic cage posteriorly would increase segmental lordosis by acting as a fulcrum for the superior vertebral body. However, based on radiographic review, anterior cage placement appeared to allow the anterior portion of the superior vertebra to sit atop the cage, while posterior cage placement led to a greater increase in disc height posteriorly than anteriorly. The reason for this finding may be partially because the tension of the anterior longitudinal ligament may resist this increased motion in posteriorly placed cages, limiting the effects of cage lordotic angle. Increasing CPR showed significant moderate negative correlations with Δ posterior disc height, suggesting that greater posterior disc height is associated with more posteriorly placed cages. This association remained significant with a large effect size independent of other patient factors, including age, BMI, cage height/lordosis, and percutaneous screw placement. Moreover, anterior cage placement resulted in significantly less improvement in posterior disc height. Increasing posterior disc height is particularly important because it consequently expands the foraminal space, which can relieve compression of the existing nerve root. However, LLIF cages still significantly increased disc height throughout the disc space regardless of where the cage was placed, suggesting that even anterior placement provides patients with some degree of neural decompression.

LLIF reliably increases lordosis for patients regardless of cage parameters. While patients with worse preoperative segmental lordosis experienced greater improvement in lordosis correction, patients with better baseline segmental lordosis still benefited from the additional lordosis provided via the LLIF approach. Open or mini-open anterior approaches may further expand lordosis, likely due to resection of the anterior longitudinal ligament that acts as a tether on the vertebral column.5 In the posterior and minimally invasive lateral approaches to the spine, the anterior longitudinal ligament remains intact and other surgical strategies are needed to further increase lordosis.24,25 Smith-Petersen and pedicle subtraction osteotomies allow for significant correction in overall lordosis following interbody fusion and may be indicated for severe spinal deformity correction. Patients undergoing PLIF or TLIF may also undergo bilateral facetectomies at the fused level, which may effectively act as an osteotomy in lordosis correction.18 These procedures may have greater effects on alignment than cage placement alone and frequently explain some of the findings in studies that suggest that TLIF and PLIF significantly increase overall lordosis.2,3,18,26 However, osteotomies may lead to increased blood loss, increased complications, prolonged hospital stay, and increased pseudarthrosis rates,2732 so the reliability of LLIF in lordosis correction may set the stage for an increase in utilization among those patients in need of smaller corrections in lumbar deformity.

We found strong associations for cages placed more anteriorly, with improved segmental and overall lordosis through 6 months of follow-up. While percutaneous screws appeared to contribute to sustained lordosis improvement at 6 months, percutaneous screws did not independently predict improvement in radiographic outcomes. Additionally, cage lordosis and cage height demonstrated no independent associations with lordosis improvement. Cage height has been speculated to contribute to increasing disc space height, which is intuitive, as a larger cage may increase disc space to match the height of the cage. Similarly, hyperlordotic cages are believed to incrementally increase the segmental angle after placement. In our study, cages had an average lordosis of 9.45° and height of 10.4 mm. Neither of these cage parameters impacted outcomes in patients immediately postoperatively. One prior study of 61 LLIF levels found that lordotic cages increased segmental lordosis more than parallel cages but did not affect foraminal disc height or overall LL.33 However, this study did not account for the different placements of each cage. Multiple other studies that also evaluated lordosis in LLIF and TLIF found that cage lordosis did not independently predict radiographic improvement.14,17 Moreover, surgeons should feel comfortable with cage choice without attempting to place progressively larger or more lordotic cages and instead focus on cage placement. Cages should be appropriately sized to a patient’s anatomy rather than to impact radiographic outcomes, which may significantly reduce vertebral endplate disruption and increase the chance of subsequent cage subsidence.12

Limitations of the Study

The results of this study must be interpreted in the context of its limitations, including those inherent to any retrospective study, which include missing data and bias in data availability. Second, the length of follow-up in our study precludes us from commenting on the effects of subsidence and long-term fusion rates. While these are clinically important, they may impact conclusions drawn as to the sagittal alignment and disc space changes from different cage parameters and surgical technique alone. Further long-term studies are needed to evaluate whether cage placement can affect cage subsidence. Despite these limitations, our study findings add significantly to the literature by showing that LLIF cages significantly improve radiographic parameters regardless of placement, but that placement can further positively augment certain findings with calculated placement techniques.

Conclusions

Surgeons should feel comfortable that a minimally invasive LLIF will contribute to improved lordosis and increased disc space height, regardless of where the cage is placed or the features of the cage that are utilized. During LLIF, anterior cage placement improves the lordosis angle greater than posterior placement, while posterior cage placement provides greater restoration in posterior disc space height. Cage placement should be guided by the primary purpose of surgery and whether the patient will benefit more from lordotic correction or indirect decompression.

Disclosures

Dr. Kurd reported personal fees from Stryker Spine, Durastat LLC, Spinal Elements, and Camber Spine outside the submitted work. Dr. Rihn reported personal fees from Globus Medical and stock ownership in Xtant Medical outside the submitted work. Dr. Hilibrand reported receiving royalties for intellectual property from Zimmer Biomet and CTL Amedica outside the submitted work. Dr. Vaccaro reported personal fees from Aesculap, Globus, Stryker Spine, and Medtronic; being an independent contractor for AO Spine; being a board member for the National Spine Health Foundation; and having stock options with Advanced Spinal Intellectual Properties, Atlas Spine, Avaz Surgical, Bonovo Orthopaedics, Computational Biodynamics, Cytonics, Deep Health, Dimension Orthotics LLC, Electrocore, Flagship Surgical, FlowPharma, Jushi, Innovative Surgical Design, NuVasive, Orthobullets, Paradigm Spine, Parvizi Surgical Innovation, Progressive Spinal Technologies, Replication Medica, Sentryx, Spine Medica, Spineology, Spine Wave, Stout Medical, Vertiflex, ViewFi Health, AVKN Patient Driven Care, Accellus, and Harvard Medtech outside the submitted work. Dr. Schroeder reported personal fees from consults for Zimmer, Stryker, Medtronic, Teledoc, Astura, ISD, Bioventus, NuVasive, Camber, and Surgalign; and being Editor in Chief of Clinical Spine Surgery outside the submitted work.

Author Contributions

Conception and design: Lee, Issa, Lambrechts, Tran, Kurd, Woods, Canseco, Vaccaro, Kepler, Schroeder. Acquisition of data: Issa, Tran, Trenchfield, Baker, Fras, Yalla, Kurd. Analysis and interpretation of data: Issa, Tran, Fras, Yalla, Woods, Canseco, Hilibrand, Kepler. Drafting the article: Issa, Lambrechts, Tran, Fras, Yalla, Canseco, Hilibrand. Critically revising the article: Lee, Issa, Tran, Kurd, Woods, Rihn, Canseco, Hilibrand, Vaccaro, Kepler, Schroeder. Reviewed submitted version of manuscript: Lee, Issa, Lambrechts, Tran, Trenchfield, Fras, Yalla, Kurd, Canseco, Hilibrand, Vaccaro, Kepler, Schroeder. Approved the final version of the manuscript on behalf of all authors: Lee. Statistical analysis: Issa, Tran. Administrative/technical/material support: Tran, Vaccaro, Schroeder. Study supervision: Lee, Lambrechts, Tran, Kurd, Canseco, Vaccaro, Kepler.

References

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    Rothrock RJ, McNeill IT, Yaeger K, Oermann EK, Cho SK, Caridi JM. Lumbar lordosis correction with interbody fusion: systematic literature review and analysis. World Neurosurg. 2018;118:2131.

    • Crossref
    • PubMed
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  • 2

    Liu J, Duan P, Mummaneni PV, et al. Does transforaminal lumbar interbody fusion induce lordosis or kyphosis? Radiographic evaluation with a minimum 2-year follow-up. J Neurosurg Spine. 2021;35(4):419426.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Jagannathan J, Sansur CA, Oskouian RJ Jr, Fu KM, Shaffrey CI. Radiographic restoration of lumbar alignment after transforaminal lumbar interbody fusion. Neurosurgery. 2009;64(5):955964.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Kono Y, Gen H, Sakuma Y, Koshika Y. Comparison of clinical and radiologic results of mini-open transforaminal lumbar interbody fusion and extreme lateral interbody fusion indirect decompression for degenerative lumbar spondylolisthesis. Asian Spine J. 2018;12(2):356364.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Hsieh PC, Koski TR, O’Shaughnessy BA, et al. Anterior lumbar interbody fusion in comparison with transforaminal lumbar interbody fusion: implications for the restoration of foraminal height, local disc angle, lumbar lordosis, and sagittal balance. J Neurosurg Spine. 2007;7(4):379386.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Gelfand Y, Benton J, De la Garza-Ramos R, Yanamadala V, Yassari R, Kinon MD. Effect of cage type on short-term radiographic outcomes in transforaminal lumbar interbody fusion. World Neurosurg. 2020;141:e953e958.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Ebata S, Ohba T, Haro H. Adequate cage placement for a satisfactory outcome after lumbar lateral interbody fusion with MRI and CT analysis. Spine Surg Relat Res. 2018;2(1):5359.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Billinghurst J, Akbarnia BA. Extreme lateral interbody fusion—XLIF. Curr Orthop Pract. 2009;20(3):238251.

  • 9

    Sembrano JN, Tohmeh A, Isaacs R. Two-year comparative outcomes of MIS lateral and MIS transforaminal interbody fusion in the treatment of degenerative spondylolisthesis: part I: clinical findings. Spine (Phila Pa 1976). 2016;41(suppl 8):S123-S132.

    • Search Google Scholar
    • Export Citation
  • 10

    Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976). 2007;32(5):537543.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11

    Acosta FL, Liu J, Slimack N, Moller D, Fessler R, Koski T. Changes in coronal and sagittal plane alignment following minimally invasive direct lateral interbody fusion for the treatment of degenerative lumbar disease in adults: a radiographic study. J Neurosurg Spine. 2011;15(1):9296.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12

    Park SJ, Lee CS, Chung SS, Kang SS, Park HJ, Kim SH. The ideal cage position for achieving both indirect neural decompression and segmental angle restoration in lateral lumbar interbody fusion (LLIF). Clin Spine Surg. 2017;30(6):E784E790.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13

    Kepler CK, Rihn JA, Radcliff KE, et al. Restoration of lordosis and disk height after single-level transforaminal lumbar interbody fusion. Orthop Surg. 2012;4(1):1520.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14

    Alimi M, Lang G, Navarro-Ramirez R, et al. The impact of cage dimensions, positioning, and side of approach in extreme lateral interbody fusion. Clin Spine Surg. 2018;31(1):E42E49.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Gambhir S, Wang T, Pelletier MH, Walsh WR, Ball JR. How does cage lordosis influence postoperative segmental lordosis in lumbar interbody fusion. World Neurosurg. 2019;126:e606e611.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16

    Bakare AA, Fessler DR, Wewel JT, Fontes RBV, Fessler RG, O’Toole JE. Changes in segmental and lumbar lordosis after lateral lumbar interbody fusion with different lordotic cage angulations. Int J Spine Surg. 2021;15(3):440448.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    DiMaria S, Karamian BA, Siegel N, et al. Does interbody cage lordosis and position affect radiographic outcomes after single-level transforaminal lumbar interbody fusion? Clin Spine Surg. 2022;35(9):E674E679.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Landham PR, Don AS, Robertson PA. Do position and size matter? An analysis of cage and placement variables for optimum lordosis in PLIF reconstruction. Eur Spine J. 2017;26(11):28432850.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Transfeldt EE, Topp R, Mehbod AA, Winter RB. Surgical outcomes of decompression, decompression with limited fusion, and decompression with full curve fusion for degenerative scoliosis with radiculopathy. Spine (Phila Pa 1976). 2010;35(20):18721875.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Uribe JS, Myhre SL, Youssef JA. Preservation or restoration of segmental and regional spinal lordosis using minimally invasive interbody fusion techniques in degenerative lumbar conditions: a literature review. Spine (Phila Pa 1976). 2016;41(suppl 8):S50-S58.

    • Search Google Scholar
    • Export Citation
  • 21

    Isaacs RE, Sembrano JN, Tohmeh AG. Two-year comparative outcomes of MIS lateral and MIS transforaminal interbody fusion in the treatment of degenerative spondylolisthesis: part II: radiographic findings. Spine (Phila Pa 1976).2016;41(suppl 8):S133-S144.

    • Search Google Scholar
    • Export Citation
  • 22

    Watkins RGI IV, Hanna R, Chang D, Watkins RGI III. Sagittal alignment after lumbar interbody fusion: comparing anterior, lateral, and transforaminal approaches. J Spinal Disord Tech. 2014;27(5):253256.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 23

    Ding Q, Tang X, Zhang R, Wu H, Liu C. Do radiographic results of transforaminal lumbar interbody fusion vary with cage position in patients with degenerative lumbar diseases? Orthop Surg. 2022;14(4):730741.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24

    Malham GM, Parker RM, Goss B, Blecher CM. Clinical results and limitations of indirect decompression in spinal stenosis with laterally implanted interbody cages: results from a prospective cohort study. Eur Spine J. 2015;24(3 suppl 3):339345.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25

    Malham GM, Parker RM, Goss B, Blecher CM, Ballok ZE. Indirect foraminal decompression is independent of metabolically active facet arthropathy in extreme lateral interbody fusion. Spine (Phila Pa 1976). 2014;39(22):E1303E1310.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26

    Tye EY, Alentado VJ, Mroz TE, Orr RD, Steinmetz MP. Comparison of clinical and radiographic outcomes in patients receiving single-level transforaminal lumbar interbody fusion with removal of unilateral or bilateral facet joints. Spine (Phila Pa 1976). 2016;41(17):E1039E1045.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27

    Dangelmajer S, Zadnik PL, Rodriguez ST, Gokaslan ZL, Sciubba DM. Minimally invasive spine surgery for adult degenerative lumbar scoliosis. Neurosurg Focus. 2014;36(5):E7.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28

    Qiao J, Xiao L, Sun X, et al. Vertebral subluxation during three-column osteotomy in surgical correction of adult spine deformity: incidence, risk factors, and complications. Eur Spine J. 2018;27(3):630635.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29

    Eskilsson K, Sharma D, Johansson C, Hedlund R. Pedicle subtraction osteotomy: a comprehensive analysis in 104 patients. Does the cause of deformity influence the outcome? J Neurosurg Spine. 2017;27(1):5662.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 30

    Ohba T, Ebata S, Ikegami S, Oba H, Haro H. Indications and limitations of minimally invasive lateral lumbar interbody fusion without osteotomy for adult spinal deformity. Eur Spine J. 2020;29(6):13621370.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31

    Kim YJ, Bridwell KH, Lenke LG, Cheh G, Baldus C. Results of lumbar pedicle subtraction osteotomies for fixed sagittal imbalance: a minimum 5-year follow-up study. Spine (Phila Pa 1976). 2007;32(20):21892197.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 32

    Yang BP, Ondra SL, Chen LA, Jung HS, Koski TR, Salehi SA. Clinical and radiographic outcomes of thoracic and lumbar pedicle subtraction osteotomy for fixed sagittal imbalance. J Neurosurg Spine. 2006;5(1):917.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 33

    Sembrano JN, Horazdovsky RD, Sharma AK, Yson SC, Santos ERG, Polly DWJ Jr. Do lordotic cages provide better segmental lordosis versus nonlordotic cages in lateral lumbar interbody fusion (LLIF)? Clin Spine Surg. 2017;30(4):E338E343.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand

Illustration from Chan et al. (E2). © Andrew K. Chan, published with permission.

  • 1

    Rothrock RJ, McNeill IT, Yaeger K, Oermann EK, Cho SK, Caridi JM. Lumbar lordosis correction with interbody fusion: systematic literature review and analysis. World Neurosurg. 2018;118:2131.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Liu J, Duan P, Mummaneni PV, et al. Does transforaminal lumbar interbody fusion induce lordosis or kyphosis? Radiographic evaluation with a minimum 2-year follow-up. J Neurosurg Spine. 2021;35(4):419426.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Jagannathan J, Sansur CA, Oskouian RJ Jr, Fu KM, Shaffrey CI. Radiographic restoration of lumbar alignment after transforaminal lumbar interbody fusion. Neurosurgery. 2009;64(5):955964.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Kono Y, Gen H, Sakuma Y, Koshika Y. Comparison of clinical and radiologic results of mini-open transforaminal lumbar interbody fusion and extreme lateral interbody fusion indirect decompression for degenerative lumbar spondylolisthesis. Asian Spine J. 2018;12(2):356364.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Hsieh PC, Koski TR, O’Shaughnessy BA, et al. Anterior lumbar interbody fusion in comparison with transforaminal lumbar interbody fusion: implications for the restoration of foraminal height, local disc angle, lumbar lordosis, and sagittal balance. J Neurosurg Spine. 2007;7(4):379386.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Gelfand Y, Benton J, De la Garza-Ramos R, Yanamadala V, Yassari R, Kinon MD. Effect of cage type on short-term radiographic outcomes in transforaminal lumbar interbody fusion. World Neurosurg. 2020;141:e953e958.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Ebata S, Ohba T, Haro H. Adequate cage placement for a satisfactory outcome after lumbar lateral interbody fusion with MRI and CT analysis. Spine Surg Relat Res. 2018;2(1):5359.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Billinghurst J, Akbarnia BA. Extreme lateral interbody fusion—XLIF. Curr Orthop Pract. 2009;20(3):238251.

  • 9

    Sembrano JN, Tohmeh A, Isaacs R. Two-year comparative outcomes of MIS lateral and MIS transforaminal interbody fusion in the treatment of degenerative spondylolisthesis: part I: clinical findings. Spine (Phila Pa 1976). 2016;41(suppl 8):S123-S132.

    • Search Google Scholar
    • Export Citation
  • 10

    Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976). 2007;32(5):537543.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11

    Acosta FL, Liu J, Slimack N, Moller D, Fessler R, Koski T. Changes in coronal and sagittal plane alignment following minimally invasive direct lateral interbody fusion for the treatment of degenerative lumbar disease in adults: a radiographic study. J Neurosurg Spine. 2011;15(1):9296.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12

    Park SJ, Lee CS, Chung SS, Kang SS, Park HJ, Kim SH. The ideal cage position for achieving both indirect neural decompression and segmental angle restoration in lateral lumbar interbody fusion (LLIF). Clin Spine Surg. 2017;30(6):E784E790.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13

    Kepler CK, Rihn JA, Radcliff KE, et al. Restoration of lordosis and disk height after single-level transforaminal lumbar interbody fusion. Orthop Surg. 2012;4(1):1520.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14

    Alimi M, Lang G, Navarro-Ramirez R, et al. The impact of cage dimensions, positioning, and side of approach in extreme lateral interbody fusion. Clin Spine Surg. 2018;31(1):E42E49.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Gambhir S, Wang T, Pelletier MH, Walsh WR, Ball JR. How does cage lordosis influence postoperative segmental lordosis in lumbar interbody fusion. World Neurosurg. 2019;126:e606e611.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16

    Bakare AA, Fessler DR, Wewel JT, Fontes RBV, Fessler RG, O’Toole JE. Changes in segmental and lumbar lordosis after lateral lumbar interbody fusion with different lordotic cage angulations. Int J Spine Surg. 2021;15(3):440448.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    DiMaria S, Karamian BA, Siegel N, et al. Does interbody cage lordosis and position affect radiographic outcomes after single-level transforaminal lumbar interbody fusion? Clin Spine Surg. 2022;35(9):E674E679.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Landham PR, Don AS, Robertson PA. Do position and size matter? An analysis of cage and placement variables for optimum lordosis in PLIF reconstruction. Eur Spine J. 2017;26(11):28432850.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19

    Transfeldt EE, Topp R, Mehbod AA, Winter RB. Surgical outcomes of decompression, decompression with limited fusion, and decompression with full curve fusion for degenerative scoliosis with radiculopathy. Spine (Phila Pa 1976). 2010;35(20):18721875.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20

    Uribe JS, Myhre SL, Youssef JA. Preservation or restoration of segmental and regional spinal lordosis using minimally invasive interbody fusion techniques in degenerative lumbar conditions: a literature review. Spine (Phila Pa 1976). 2016;41(suppl 8):S50-S58.

    • Search Google Scholar
    • Export Citation
  • 21

    Isaacs RE, Sembrano JN, Tohmeh AG. Two-year comparative outcomes of MIS lateral and MIS transforaminal interbody fusion in the treatment of degenerative spondylolisthesis: part II: radiographic findings. Spine (Phila Pa 1976).2016;41(suppl 8):S133-S144.

    • Search Google Scholar
    • Export Citation
  • 22

    Watkins RGI IV, Hanna R, Chang D, Watkins RGI III. Sagittal alignment after lumbar interbody fusion: comparing anterior, lateral, and transforaminal approaches. J Spinal Disord Tech. 2014;27(5):253256.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 23

    Ding Q, Tang X, Zhang R, Wu H, Liu C. Do radiographic results of transforaminal lumbar interbody fusion vary with cage position in patients with degenerative lumbar diseases? Orthop Surg. 2022;14(4):730741.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24

    Malham GM, Parker RM, Goss B, Blecher CM. Clinical results and limitations of indirect decompression in spinal stenosis with laterally implanted interbody cages: results from a prospective cohort study. Eur Spine J. 2015;24(3 suppl 3):339345.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25

    Malham GM, Parker RM, Goss B, Blecher CM, Ballok ZE. Indirect foraminal decompression is independent of metabolically active facet arthropathy in extreme lateral interbody fusion. Spine (Phila Pa 1976). 2014;39(22):E1303E1310.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26

    Tye EY, Alentado VJ, Mroz TE, Orr RD, Steinmetz MP. Comparison of clinical and radiographic outcomes in patients receiving single-level transforaminal lumbar interbody fusion with removal of unilateral or bilateral facet joints. Spine (Phila Pa 1976). 2016;41(17):E1039E1045.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27

    Dangelmajer S, Zadnik PL, Rodriguez ST, Gokaslan ZL, Sciubba DM. Minimally invasive spine surgery for adult degenerative lumbar scoliosis. Neurosurg Focus. 2014;36(5):E7.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28

    Qiao J, Xiao L, Sun X, et al. Vertebral subluxation during three-column osteotomy in surgical correction of adult spine deformity: incidence, risk factors, and complications. Eur Spine J. 2018;27(3):630635.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29

    Eskilsson K, Sharma D, Johansson C, Hedlund R. Pedicle subtraction osteotomy: a comprehensive analysis in 104 patients. Does the cause of deformity influence the outcome? J Neurosurg Spine. 2017;27(1):5662.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 30

    Ohba T, Ebata S, Ikegami S, Oba H, Haro H. Indications and limitations of minimally invasive lateral lumbar interbody fusion without osteotomy for adult spinal deformity. Eur Spine J. 2020;29(6):13621370.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31

    Kim YJ, Bridwell KH, Lenke LG, Cheh G, Baldus C. Results of lumbar pedicle subtraction osteotomies for fixed sagittal imbalance: a minimum 5-year follow-up study. Spine (Phila Pa 1976). 2007;32(20):21892197.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 32

    Yang BP, Ondra SL, Chen LA, Jung HS, Koski TR, Salehi SA. Clinical and radiographic outcomes of thoracic and lumbar pedicle subtraction osteotomy for fixed sagittal imbalance. J Neurosurg Spine. 2006;5(1):917.

    • Crossref
    • Search Google Scholar
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    Sembrano JN, Horazdovsky RD, Sharma AK, Yson SC, Santos ERG, Polly DWJ Jr. Do lordotic cages provide better segmental lordosis versus nonlordotic cages in lateral lumbar interbody fusion (LLIF)? Clin Spine Surg. 2017;30(4):E338E343.

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