MIS lateral spine surgery: a systematic literature review of complications, outcomes, and economics.

Eur Spine J DOI 10.1007/s00586-015-3886-1

REVIEW ARTICLE

MIS lateral spine surgery: a systematic literature review of complications, outcomes, and economics Jeff A. Lehmen1 • Edward J. Gerber1

Received: 9 March 2015 / Revised: 18 March 2015 / Accepted: 19 March 2015 Springer-Verlag Berlin Heidelberg 2015

Abstract Background Over the past decade, the minimally disruptive lateral transpsoas approach for lumbar interbody fusion (MI-LIF) is increasingly being used as an alternative to conventional surgical approaches. The purpose of this review was to evaluate four primary questions as they relate to MI-LIF: (1) Is there an anatomical justification for MI-LIF at L4–5? (2) What are the complication and outcome profiles of MI-LIF and are they acceptable with respect to conventional approaches? (3) Given technical and neuromonitoring differences between various MI-LIF procedures, are there any published clinical differences? And, (4) are modern minimally disruptive procedures (e.g., MI-LIF) economically viable? Methods Through a MEDLINE and Google Scholar search, a total of 237 articles that discussed MI-LIF were identified. Of those, topical areas included anatomy (22), biomechanics/testing (17), technical descriptions (11), case reports (40), complications (30), clinical and radiographic outcomes (43), deformity (23), trauma or thoracic applications (10), and review articles (41). Results In answer to the questions posed, (1) there is a high strength of evidence showing MI-LIF to be anatomically justified at all levels of the lumbar spine from L1–2 to L4–5. The evidence also supports the use of advanced neuromonitoring modalities. (2) There is moderate strength evidence in support of reproducible and reasonable complication, side effect, and outcome profiles following MI-LIF which may be technique dependent. (3) & Jeff A. Lehmen [email protected] 1

Spine Midwest, Inc., 200 St. Mary’s Plaza, Suite 301, Jefferson City, MO 65101, USA

There is low-strength evidence that shows elevated neural complication rates in non-traditional (e.g., shallow-docking approaches and/or those without specialized neuromonitoring) MI-LIF, and (4) there is low- to moderatestrength evidence that modern minimally disruptive surgical approaches are cost-effective. Conclusions There is considerable published evidence to support MI-LIF in spinal fusion and advanced applications, though the results of some reports, especially concerning complications, vary greatly depending on technique and instrumentation used. Additional cost-effectiveness analyses would assist in fully understanding the long-term implications of MI-LIF. Keywords XLIF DLIF Literature review Complications Outcomes

Introduction The minimally disruptive lateral transpsoas approach to the lumbar spine for interbody fusion (MI-LIF) was developed in the late 1990s and early 2000s by Luiz Pimenta [1] and was first published in the literature in 2006 as extreme lateral interbody fusion (XLIF, NuVasive, Inc. San Diego, CA) [2]. The approach was developed as an alternative to both anterior and posterior interbody access channels, obviating the need for an access surgeon and vascular/visceral retraction compared to anterior approaches [3–6] and without bony dissection, muscular denervation, and elevated infection risks of posterior approaches [7, 8]. The MI-LIF approach allows for a thorough discectomy from the lateral border of the anterior spine through an approximately 90 off midline, retroperitoneal, transpsoas corridor, which leaves the anterior and posterior

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longitudinal ligaments (A/PLL) intact. This is followed by placement of a large-aperture interbody spacer (similar to an anterior lumbar interbody fusion (ALIF) spacer) which spans the cortical bone of the ring apophysis. Various supplemental internal fixation options can be used for fixation without patient repositioning, including lateral plating, unilateral pedicle screws, bilateral transpedicular facet screws, spinous process plating, and, in certain circumstances, bilateral pedicle screws. Anatomically, passage to the lateral disc space through the psoas muscle requires blunt dissection into the retroperitoneal space to the lateral border of the psoas muscle, and then guided passage through the psoas muscle adjacent to the lumbar plexus. As such, advanced neuromonitoring techniques are recommended to monitor the approach to the disc space with respect to the location of neural anatomy. The MI-LIF procedure can generally be used cranially to the T4–5 level (restricted by the scapula) and caudally to L4–5 (restricted by the position of the iliac crest), though in some instances L5–S1 is accessible with a lateral approach. Since the development of XLIF, several other lateral approach instrumentation have been developed, including direct lateral interbody fusion (DLIF, Medtronic Sofamor Danek, Memphis, TN), lateral lumbar interbody fusion (LLIF, Globus Medical, Inc. Audubon, PA), the VEO system [9] (Baxano Surgical, Inc. Raleigh, NC, USA), MIS lateral system (DepuySynthes, Inc. Raynham, MA), and non-retracted transpsoas approaches (shallow docking) [10].While broad similarities exist between these MI-LIF approaches, there are some important differences between platforms, most notably the recommended use of neurophysiologic monitoring (e.g., automated [2], interpretative (technician), or none [9]). Therefore, this report will use the term MI-LIF to generically refer to lateral transpsoas approaches and will refer to specific transpsoas platforms only in describing individual articles that make the differentiation. There are several aspects of the MI-LIF procedure which have been studied extensively, and a few smaller literature reviews, but there has yet to be a broad literature review covering multiple topical areas, which precipitates the current work. The areas covered in this review include anatomical understandings of the lateral approach, safety and outcome profiles, different lateral approach-type comparisons, and economics. The purpose of this review was to evaluate four primary questions as they relate to MILIF: (1) Is there an anatomical justification for MI-LIF at L4–5? (2) What are the complication and outcome profiles of MI-LIF and are they acceptable with respect to conventional approaches? (3) Given technical and neuromonitoring differences between various MI-LIF procedures, are there any published clinical differences? And, (4) are modern minimally disruptive procedures (e.g., MI-LIF) economically viable?

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Methods A search of peer-reviewed, human-subject journals through MEDLINE and Google Scholar databases from 1995 to February 27th, 2015 was conducted using search terms including ‘‘extreme,’’ ‘‘lateral,’’ ‘‘direct,’’ ‘‘transpsoas,’’ ‘‘XLIF,’’ ‘‘DLIF,’’ and/or ‘‘LLIF,’’ and ‘‘lumbar,’’ ‘‘fusion,’’ ‘‘spin*,’’ without ‘‘(citation),’’ ‘‘posterolateral’’ or ‘‘cervical.’’ Any full-length article that described MI-LIF was included in the current study in an attempt to collect all currently available peer-reviewed articles. Each article from the primary search was assessed individually across titles and abstract for inclusion within the previously described parameters. A secondary review which included full article review was undertaken to further discriminate the primary findings. The authors attempted to pool outcome variables where reasonable homogeneity in patient population and technique were apparent. Study design, level of evidence, and sample size (including weighting) were similarly considered. A qualitative analysis was performed for the answer to each question posed with respect to the available literature across three domains including quality, quantity, and consistency of support for the answer [11]. From there, ratings of high, moderate, low, and very low were assigned to the conclusion from each question (by author JAL), based on guidelines from the GRADE working group [12]. High strength of conclusions are made based on literature that has quality (level of evidence [13] I–III findings, depending on study type and conclusions drawn), quantity, and consistency in support of the conclusion drawn. Further research in areas of high recommendation would have a low likelihood of changing findings. Moderate conclusions always come from quality findings, though may lack either consistency or quantity, but not both. The confidence in such conclusions has the potential to be changed by additional, higher quality research. Low-strength research conclusions lack quality, but have both consistency and quantity or they lack quantity and consistency but have quality. These findings are likely to have their confidence altered by additional, high-quality research. Finally, very low quality conclusions lack all three areas or have just quantity or consistent findings, without quality. For these conclusions, effect estimates are very uncertain [14].

Results A total of 2910 articles were identified through the primary search. Following adjudication, 237 articles were determined to meet inclusion in the current review (Fig. 1). Distribution of evidence quality (levels of evidence [13]) of the lateral-approach specific articles included 27 Level 1

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studies (of which 26 were non-clinical), 3 Level 2 studies, 30 Level 3 studies, 155 Level 4 studies, and 22 Level 5 studies. Of these 237 articles, 22 were MI-LIF-specific studies of lateral anatomy relevant to the surgical approach [15–36], 17 were biomechanical or non-interventional testing studies [37–53], 11 technical descriptions [2, 9, 10, 54–61], 40 case reports [62–101], 30 reports specifically examining complications [102–131], 43 studies assess clinical and/or radiographic outcomes in degenerative conditions [132–174], 23 specifically examining treatment and outcomes of deformity with MI-LIF [175–198], 10 articles reviewing traumatic or thoracic indications[218– 227], and 41 review articles without original data [198– 217, 228–248].

In order to more succinctly review the evidence, each question posed will be addressed separately. Question 1: Is there an anatomical justification for MI-LIF, particularly at the L4–5 level? A summary of results from anatomical studies specific to MI-LIF are included in Tables 1 and 2. There is a large number (quantity) of high-quality articles reporting similar findings (consistency) that support a high strength conclusion that there is anatomical justification for the MI-LIF approach at all lumbar levels from L1–2 to L4–5. In these studies, all authors found at least the anterior half of the lateral disc space consistently free of neural trunks and

Fig. 1 Flow diagram of systematic review. MI-LIF minimally disruptive lateral interbody fusion, TDR total disc replacement

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roots. Articles that reported absolute measurements found between 22 and 31 mm of the lateral surface of the disc space anterior to the plexus free of motor nerves from L1–2 through L4–5 [25], and between 72 and 78 % of the lateral disc space free of motor nerves at L4–5 [16, 23, 28]. Question 1—representative articles Park et al. [27] studied 40 levels from L1–2 to L4–5 in 10 cadavers to assess the average absolute distance from the midpoint of the lateral disc space posteriorly to the anterior border of the lumbar plexus (trunk) and to the nerve roots. At L2–3, L3–4, and L4–5, the authors found, on average, 16.4, 14.9, and 10.6 mm of distance between the lateral midpoints of the discs to the nerve trunk. In all cases the nerve roots were dorsal to the trunks. Where lateral intervertebral cages range anywhere from 18 to 26 mm wide (anterior-posterior dimension) these results suggest that there is adequate space for cage placement anterior to the lumbar plexus at levels from L1–2 to L4–5 without requiring neural retraction (assuming the cage will occupy both the available space posterior to the lateral midline as well as the anterior half of the disc space). Another study by Benglis et al. [16] studied three cadavers at 12 levels from L1–2 through L4–5 to assess the distance from the posterior border of the lateral disc space to the anterior border of the lumbar plexus and calculated this as a percentage of the entire lateral disc space (100 %). At L1–2, L2–3, L3–4, and L4–5, the authors found, on average, the posterior 0, 11, 18, and 28 % of the lateral disc space was obstructed by the lumbar plexus, resulting in 100, 89, 82, and 72 % of the anterior portion of the lateral disc space free of motor nerves, at the respective levels. These data are closely corroborated in a study by Regev et al. [28] where similar measurements were made using 100 subjects (247 levels) on magnetic resonance imaging (MRI) and 89, 84, 84, and 74 % of the anterior disc space was found to be free of motor nerves (approximated by assessing the neural-adipose complex on the lateral posterior border of the disc space on axial MRI), using a 95 % confidence interval. Question 2: What are the safety (complication) and outcome profiles of MI-LIF and are they acceptable in comparison with conventional approaches? Safety There is considerable variation in the literature concerning reported rates of complication following MI-LIF [165, 229, 231]. As there are significant differences in indications for use, patient sample characteristics, levels treated,

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supplemental fixation used, techniques (XLIF vs. DLIF vs. other lateral) and neuromonitoring used (automated vs. technician), and terminology and classification of complications used, making unqualified conclusions about the safety of the approach becomes very challenging. The highest quality data available reports an overall perioperative complication rate of 5 % in the treatment of basic degenerative conditions with XLIF, including a 2.9 % rate of motor nerve injury [120]. This overall rate of complication and neural injury rate are corroborated by several studies that have similar inclusion criteria [102, 109, 118, 135, 136, 165]. Complication and side effect outliers tend to be in mixed indication samples (degenerative and deformity) with mixed procedures being performed (XLIF or DLIF or other lateral) [103, 151, 177, 187]. Several studies compared MI-LIF directly to conventional approaches and all showed significantly more favorable complication profiles for MI-LIF compared to conventional approaches [111, 117, 160]. Several studies also found that there were no incremental increases in morbidity treating patients predisposed to complications (elderly, obese) with MI-LIF [116, 117, 249]. In making a conclusion, high-quality evidence exists to support the safety of the MI-LIF approach with a large quantity of reports. However, there is a lack of consistency between reports, the reasons for which are multifactorial. This leads to a moderate-strength conclusion confirming that the MI-LIF approach is acceptable from a morbidity standpoint within the context of currently available approaches. A table of complication literature is included in Table 3. Question 2—safety—representative articles Several articles directly examine perioperative complications of MI-LIF. As previously mentioned, the highestquality evidence is from a prospective, multi-center, IRBapproved study of neural and general complications following XLIF at L3–4 and/or L4–5 by Tohmeh et al. [120]. In this study, 102 patients were treated with XLIF using the NV JJBTM/M5 (NuVasive, Inc.) neuromonitoring platform and were followed through the perioperative period to assess any postoperative complications or side effects and their resolution. Two (2 %) intraoperative complications were observed, both minor perforations of the peritoneum which did not require repair and which resolved without sequelae. Hip flexion weakness postoperatively was common (27.5 %), was considered to be a side effect of the approach, and was thought to be due to direct trauma to the psoas muscle during access to the lateral disc space and retraction during the procedure. The magnitude of weakness (most commonly Medical Research Council grade 4/5) and resolution (all in the early postoperative period) suggested muscular, rather than neural trauma, as the

I

I

I

I

I

I

I

I

I

I

I

I

I

Moro et al. [250]*

Park et al. [27]

Regev et al. [28]

Uribe et al. [31]

Davis et al. [19]

Benglis et al. [16]

Hu et al. [24]

Kepler et al. [25]

Guerin et al. [22]

Guerin et al. [23]

Lu et al. [26]

Yusof et al. [36]

Yusof et al. [36]

100

100

15

8

78

43

48

3

18

5

100

10

30

Subjects

200

200

120

60

304

172

192

12

54

20

247

40

120

Levels

In vivo

In vivo

Cadaver

Cadaver

In vivo

In vivo

In vivo

Cadaver

Cadaver

Cadaver

In vivo

Cadaver

Cadaver

Specimen

Degenerative

Degenerative

Normal

Normal

Normal

Normal

Normal

Normal

Normal

Normal

Normal

Normal

Normal

Population

MRI (mm)

MRI (mm)

Direct (zones)

Direct (zones)

MRI (%)

MRI (mm)

MRI (zones)

Direct (%)

Direct (zones)

Direct (mm)

MRI (95 % CI)

Direct (mm)

Direct (zones)

Measurement

mm from right-side anterior VB to plexus

mm from left-side anterior VB to plexus

Zones in thirds, plexus

I–IV safe zones, motor nerves

% of disc space from posterior border

mm from anterior VB to plexus

I–IV safe zones, nerves





Plexus distance from disc center

I–IV safe zones, nerves

Measurement definition

* Moro et al. included for historical reference

L4–5

L5–S1

–

–

–

–

11.1 %

30.8

–

0%

–

–

10.6 %

–

–

–

–

–

–

18.7 %

28.6

–

11 %

–

–

15.5 %

16.4

–

29.0

28.6

–

–

21.9 %

28.2

–

18 %

–

–

16.4 %

14.9

–

23.1

22.6

–

–

35.8 %

22.1

–

28 %

–

–

25.9 %

10.6

–

–

–

–

–

–

–

–

–

–

–

49.0 %

–

–

–

–

I–II

I–III

I–III

–

I–IV

I–IV

–

I–III

I–III

–

–

–

–

I–II

I–III

I–III

–

I–III

I–III

–

I–III

I–III

–

I–III

L2–3

–

–

I–II

I–III

I–III

–

I–II

I–III

–

I–III

I–III

–

I–II

L3–4

–

–

I–II

I–II

I–II

–

I–II

I–II

I–II

I–II

I–II

–

I–II

L4–5

–

–

–

–

–

–

–

–

–

–

I–II

–

None

L5–S1

L1–2

L3–4

L1–2

L2–3

Converted motor nerve safe zones

Motor nerve location

LOE level of evidence (I–V) [11], mm millimeters, MRI magnetic resonance imaging, CI confidence interval, VB vertebral body

LOE

References

Table 1 Summary of quantitative anatomical studies specific to MI-LIF

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123

123

IV

I

IV

IV

IV

IV

I

IV

IV

I

I

Dakwar et al. [17]

Banagan et al. [15]

Dakwar et al. [18]

Baaj et al. [33]

Menezes et al. [34]

Delasotta et al. [20]

Deukmedjian et al. [21]

Shirzadi et al. [29]

Voyadzis et al. [35]

Smith et al. [30]

Smith et al. [30]

–

–

3

1

10

1

94

5

9

8

6

Subjects

–

–

3

1

80

1

188

5 sides

18 sides

64

12 sides

Levels

Review

Review

In vivo

In vivo

In vivo

In vivo

In vivo

Cadaver

Cadaver

Cadaver

Cadaver

Specimen

–

Normal

Irregular

Irregular

Normal

Irregular

Normal

Normal

Normal

Normal

Normal

Population

Zone extrapolation

MRI and CR psoas muscle findings

MRI psoas muscle findings

L5–S1 lateral approach feasibility

Anatomy position in lateral decubitus

Variant vascular anatomy description

MRI % of nerves in zones by retractors

Anatomical description


Sympathetic chain from ALL


Measurement definition

351 series sample showing a 2.8 % transitional anatomy (and related difficulty in lateral approach) rate Found broad consistency between studies justifying MI-LIF from an anatomical perspective

Found that a ‘‘rising’’ psoas indicated a more difficult passage to the lateral disc space under neuromonitoring

Case description of potential for L5–S1 lateral approach

Vasculature travel significantly anteriorly from the lateral approach corridor in the lateral decubitus position.

Presentation of aberrant iliac artery case

Virtual overlay of 10 mm and 22 mm retractors to show interference with nerves based on retractor size

Describes attachments of diaphragm and considerations for deflection for lateral TLJ approaches

Describes attachments of diaphragm and considerations for deflection for lateral TLJ approaches

Sympathetic chain and average of 9.25 mm posterior from ALL; 25 % of k-wires pierced nerves

Describes origin and paths of subcostal, iliohypogastric, ilioinguinal, and lateral femoral cutaneous nerves

Summary

LOE level of evidence (I–V) [11], ALL anterior longitudinal ligament, TLJ thoracolumbar junction, MI-LIF minimally disruptive lateral interbody fusion

LOE

Author

Table 2 Summary of qualitative anatomical studies specific to MI-LIF

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XLIF

XLIF

Hyde and Seits [137]

Johnson et al. [138]

XLIF 22 mm wide

XLIF/cougar/SD

XLIF

XLIF

XLIF

PLIF

Nemani et al. [129]

Rodgers et al. [116]




Lykissas et al. [128]

Marchi et al. [113]

XLIF/cougar/SD ? auto/allograft

Lykissas [128]

XLIF/cougar/SD

XLIF/cougar/SD ? BMP

Lucio et al. [111]

XLIF 18 mm wide

Open PLIF

Lucio et al. [111]


X, TLIF

Lee et al. [110]

Marchi et al. [113]

XLIF

XLIF

Le et al. [109]

XLIF/cougar/SD

XLIF

Dakwar et al. [104]

XLIF

XLIF

Dakwar et al. [104]

Le et al. [108]

SD

Cheng et al. [124]

Kueper et al. [126]

XLIF

XLIF/cougar/SD

Al Maaieh et al. [122]

XLIF

XLIF/cougar/SD

Aichmair et al. [121]

Cheng et al. [124]

XLIF/cougar/SD


Cahill et al. [102]

DLIF

XLIF/cougar/SD

Moller et al. [114]

Aichmair [121]

X, D, AxiaLIF

X, DLIF

Cummock et al. [103]

XLIF/Cougar/SD

Pumberger et al. [115]

Knight et al. [106]

X, DLIF

XLIF, L5S1

Anand and Baron [198]

Isaacs et al. [182]

Procedure

References

III

III

III

III

IV

III

III

IV

III

III

III

III

III

IV

IV

IV

IV

IV

IV

IV

III

III

IV

III

III

III

III

III

III

III

III

II

IV

LOE

XLIF

Degen

Degen

Degen

BMI \ 30 PLIF

Degen

Degen/scoli

DDD

DDD

Degen/scoli

Degen/scoli

Degen/scoli

Degen

Degen

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

NR

Degen

Degen/scoli

Degen/scoli

Scoliosis

Scoliosis

Indication

1–8

1–3

1–4

1–4

1–4

1–2

1–2

1–5

2 pp

2 pp

2

2

1–3

1–4

1–4

1–5

1–3

1–4

1–4

3–6

1–4

1–4

1–3

2.3 pp

1–4

1–4

1–5

1.9 pp

1–3

1–3

1.9 pp

1–6

NR

Ant lvls

TL

TL

L

L

L1–5

L

L

T12–L5

T12–L5

T12–L5

L1–S1

L1–S1

L

L

L

T9–S1

L2–5

L1–5

L

TL

L1–L5

L1–L5

T12–L1

T11–L5

T12–L5

T12-L5

T12–L5

L

L2–L5

L1–L5

T12–L5

T8–S1

NR

Lvls

Treatment characteristics

BMI [ 30

18 mm

22 mm

BMP

Non-BMP

XLIF

PLIF

XLIF

SD

Control

Table 3 Summary of study characteristics and complication findings in published MI-LIF cohorts

PS

Mixed

Mixed

Mixed

None

None

None

Mixed

Mixed

Mixed

BP

BP

NR

Mixed

LP

Mixed

Mixed

Mixed

NR

NR

PS

PS

Mixed

Mixed

Mixed

Mixed

Mixed

NR

NR

PS

NR

Mixed

PS

Internal fixation

None

None

None

2

2

0–9

# of posterior levels

20

40

157

156

117

28

46

451

72

72

101

109

33

71

101

900

39

78

568

315

50

70

118

42/596

91

155

47

53

58

59

235

107

76

Total n

Periop

Periop

3 mo

3 mo

15.6 mo

12 mo

12 mo

15 mo

16.1 mo

18.5 mo

45 days

45 days

6 mo

12 mo

14.3 mo

Periop

6 mo

Periop

Periop

Periop

10 mo

10 mo

Periop

Periop

10.5 mo

16.5 mo

21.0 mo

21.2 mo

15 mo

10 mo

Periop

6 weeks

40 mo

Mean follow-up

146

81

75

298.8

291.9

156.5

163.2

221

392

297.0

257.6

265.5

161

255

178

277

ORT (min)

144

\50

\50

109.9

910.7

136

138

50–100

541

EBL (mL)

5.3

1.3

1.24

1.24

3.2

1.2

2.7

9.9

5

4.0

3.8

7.8

LOS (days)

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123

123

Complications and side effects

References

10 % miscellaneous complications

2011–2012 patients. Neural deficits reported as postop %—last follow-up %. Did not distinguish between motor deficits and HFW Data reported only for the 42 (7 %) patients with postoperative ileus


Al Maaieh et al. [122]

Transient thigh column = all neurologic deficits 1.5 % complex cases w/rhabdomyolysis 1.8 % with abdominal wall paresis 10 % radiographic subsidence, 2 dehiscence, 1 DVT

Cheng et al. [124]

Dakwar et al. [104]

Dakwar et al. [104]

Hyde and Seits [137]

0.56 % (5/900) vascular injury rate, four segmentals, one abdominal aorta. All recovered. 5.9 % lateral plating related complications

Kueper et al. [126]

Le et al. [108]


Transient thigh column = all neurologic deficits

Cheng et al. [124]

5.1

2009-2010 patients. Neural deficits reported as postop %—last follow-up %. Did not distinguish between motor deficits and HFW


4.2

2006–2008 patients. Neural deficits reported as postop %—last follow-up %. Did not distinguish between motor deficits and HFW

Aichmair [121]

Cahill et al. [102]

1 psoas hematoma, 1 segmental artery laceration

Moller et al. [114]

8.6

19.8

12.8

33

24.0

14.2

25.0–6.6

43.4–11.0

44.4–14.9

25

8.6

42.4

Knight et al. [106]

13.8

NR

Mixed

PS

Internal fixation


Transient/thigh sensory symptoms (%)

L3–4 and/or L4–5

L

L

Lvls

Cummock et al. [103]

12.1

1–2

1–4

1–4

Ant lvls

ORT and EBL for single stage surgeries only. LOS includes staged surgeries

Degen/scoli

Degen/scoli

Degen

Indication


28.7

15.9

II

Control

Pumberger et al. [115]

Isaacs et al. [182]

Anand and Baron [198]

XLIF

Tohmeh et al. [120]

IV

IV

LOE

Other/comment (%)

XLIF/cougar/SD

Major (%)

XLIF


Taher et al. [130]

Minor (%)

Procedure

References

Table 3 continued

36

19.3–2.2

24.3–2.6

22.2–4.3

36

23.7

13.1

268.8

5.1

1.7

0

6.8

4.9 1.7

LOS (days)

28.0

24.3

22.4

24.3

Total comps (%)

EBL (mL)

Reops (%)

ORT (min)

Motor neural (%)

Periop

Periop

12 mo

Mean follow-up

HFW (%)

102

244

600

Total n

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45.8–40.3

19.7

Transient/thigh sensory symptoms (%)

51.4–48.6

54.9

HFW (%)

0.7

1.3

Motor neural (%)

Reops (%)

Total comps (%)

2.9 2.9

LOE level of evidence (I–V)[11], ant anterior, Lvls levels, ORT operating room time, EBL estimated blood loss, LOS length of hospital stay, Reops reoperations, Comps complications, VAS visual analog scale, ODI Oswestry disability index, XLIF extreme lateral interbody fusion, DLIF direct lateral interbody fusion, SD possible shallow docking technique used, Scoli degenerative scoliosis, BPS bilateral pedicle screws, mo months, LP anterolateral plates, PLF posterolateral fusion, TLIF minimally invasive transforaminal interbody fusion, Degen mixed degenerative conditions (e.g., spondylolisthesis, DDD, adjacent segment disease, etc…), DDD degenerative disc disease, PLIF open posterior interbody fusion, sig significantly, BMI body mass index, yrs years, PS pedicle screws (uni- or bi-lateral); ASD, adjacent segment disease. Studies listed in adjacent rows with a border indicate two cohorts from the same study

Tohmeh et al. [120]

27.5

60 6.2


Taher et al. [130]

7.5

Rodgers et al. [117] 1.8

6.4 10.8


1.9

17.6

17.4 10.7


Assessed contralateral motor deficits

8.7 10.7

23.9–3.2

10.1

52 % any grade of subsidence 24 % any grade of subsidence

Marchi et al. [113]

Marchi et al. [113]

38–9.3

38.9–23.6

0.6

Neural deficits reported as postop %—last follow-up %. Did not distinguish between motor deficits and HFW


48.6–27.8

Nemani et al. [129]

Autograft/allograft patients. Neural deficits reported as postop %— last follow-up %. Did not distinguish between motor deficits and HFW



BMP patients. Neural deficits reported as postop %—last follow-up %. Did not distinguish between motor deficits and HFW.

Lykissas [128]

6

Hip flexion strength was less on the operative side, mostly resolved by 2 weeks postoperative

Other/comment (%)

14

Major (%)

Lucio et al. [111]

2

Minor (%)

Complications and side effects

Lucio et al. [111]

Lee et al. [110]

Le et al. [109]

References

Table 3 continued

Eur Spine J

123

Eur Spine J

cause. New upper medial thigh sensory loss was noted in 17.6 % of patients, most commonly a grade of 1/2 and, similar to hip flexion weakness, all resolved in the study within the perioperative period. Three (2.9 %) new distal motor deficits were observed: one 4/5 grade tibialis anterior deficit which resolved by 6 months, one 3/5 grade quadriceps weakness which resolved by 6 months, and one 4/5 grade quadriceps weakness which resolved by 6 weeks postoperatively. While this report highlights resolution of these deficits, other reports have shown continuing deficits (motor and sensor) at longer follow-up ([12 months), so any implication of non-permanence in all cases is not made [103]. A second study from prospectively collected registry data by Rodgers et al. [118] found a 6.2 % overall complication rate in 600 consecutive XLIF patients through 6 weeks postoperative. This rate included a 4.3 % rate of in-hospital complications (surgical and medical), 0.7 % rate of new distal motor deficits, and 1.8 % reoperation rate. Similar to the Tohmeh et al. [120] paper, hip flexion weakness and mild upper medial thigh sensory loss were common, but considered side effects of the approach. If sensory changes were severe or persistent, they we classified as complications. Outcomes Many reports (quantity) provide clinical and radiographic outcome information concerning MI-LIF, including several 2-year or longer follow up [132–175]. When separating outcomes by indication (degenerative vs. deformity), there is general consistency within the groups when considering some heterogeneity in specific treatment paradigms (types of fixation used, baseline patient characteristics), though some inconsistency remains in the magnitude of clinical improvement in some papers [151, 177]. There are several examples of higher quality evidence papers, with comparative groups and/or high compliance in long-term follow-up, in support of favorable long-term outcomes [143, 151–153, 156, 160]. With this in mind, the lack of consistency in the literature provides support for only a moderate-strength conclusion to be made that outcomes following MI-LIF are well documented and at least equivalent to those found in conventional procedures [160]. Reports of outcomes of individual cohorts from the literature review are reported in Table 4. Question 2—outcomes—representative articles In a prospective study by Kotwal et al. [143] 141 consecutive patients underwent MI-LIF (95 % XLIF), for a variety of degenerative conditions, including scoliosis, and 84 % (118) were available for 2-year follow-up and

123

included in the analysis. Mean patient age was 62.1 years, 59 % were females, and mean body mass index (BMI) was 27.6 kg/m2. In 118 patients, 237 levels were treated (mean 2.0 per patient). Four patients exhibited postoperative ileus, pulmonary insufficiency in two, arrhythmia in two, gastric ulcer in one, urinary retention in one, and delayed wound healing in one, all of which were treated conservatively to resolution. This resulted in a 9.3 % complication rate. Anterior thigh pain was observed in 36 % of patients, with 17 % experiencing hip flexion weakness and 11 % experiencing anterior thigh numbness. All resolved except for one patient with persistent anterior thigh pain at the last follow-up. Three patients were revised for pseudoarthrosis and one for adjacent segment degeneration (3.3 % reoperation rate through 2-year postoperative). In these 141 patients, mean postoperative follow up was 27.5 months. At last follow up, compared to baseline, pain improved and average of 53 % (8.7–4.1), disability improved 43 % (from 30.0 to 17.1), and quality of life (SF-12) physical component summary (PCS) improved 41 % from 27.0 to 38.1. Cobb angle from preoperative to last follow-up improved from 24.8 to 13.6. All comparisons from baseline were statistically significantly improved. Similar findings were reported by Rodgers et al. [153] in a study of 238 patients who underwent XLIF and who were followed for 2 years postoperatively. The authors found an average postoperative hemoglobin change of -1.4 g and a mean hospital stay of 1.2 days. Complications occurred in 6.7 % of patients, including 36 secondary reoperations or additional spine procedures. From preoperative to last follow-up, disc height increased from 6.2 to 9.0 mm, listheses were improved from 4.7 to 0.9 mm, pain improved 63 % from 8.6 to 3.2, and modified Lenke fusion assessments found an average value of 1.1 (fusion classified as either a 1 or 2), with 89.8 % of patients reaching a Lenke score of 1 and 98.9 % reaching a Lenke score of either 1 or 2. Outcome satisfaction was achieved in 87.3 % of patients and 91.4 % stated that they would still have chosen to undergo the procedure had their outcome been known in advance. Question 3: Given technical and neuromonitoring differences between various MI-LIF procedures, are there any published clinical differences? The majority of MI-LIF literature reports experience with and outcomes of XLIF (traditional lateral), as this procedure was the first developed and implemented lateral transpsoas approach for interbody fusion [2]. With the development of alternative MI-LIF approaches to the traditional lateral approach that use different transpsoas techniques and neuromonitoring [10], some early reports have emerged. In this review, there was a paucity of examples of literature strictly reviewing non-traditional

XLIF

Ahmadian et al. [133]

XLIF XLIF XLIF

Marchi et al. [147]

Marchi et al. [113]

Oliveira et al. [150] XLIF

XLIF

Marchi et al. [146]

Ozgur et al. [151]

XLIF

Malham et al. [145]

XLIF

XLIF

Le et al. [144]

Oliveira et al. [172]

XLIF XLIF

Kotwal et al. [143]

Uribe et al. [247] Kepler et al. [140]

Kepler [141]

XLIF X, TLIF XLIF


XLIF XLIF

Elowitz et al. [136]

Castellvi et al. [168]

Caputo et al. [179]

XLIF XLIF

Berjano et al. [135]

XLIF

PLF

Tormenti et al. [186]

XLIF

X, TLIF


Alimi et al. [167]

X, DLIF

Acosta et al. [132]


XLIF/cougar/SD

Sharma et al. [159] Tempel et al. [196] X,T,PLIF

XLIF/SD XLIF w open PSF

Wang and Mummaneni [187]

Sofianos et al. [119]

X, DLIF

Khajavi and Shen [192]


XLIF XLIF

Castro et al. [190]

IV

IV

IV

III

IV

IV

III

III

IV

III

IV IV

IV

IV

IV

IV

IV

IV

IV

IV

III

III

IV

IV

IV

IV IV

IV

IV

IV

IV

X,TLIF

PLF

XLIF

Caputo et al. [189]

IV

Degen/scoli

Degen/scoli

Degen

Degen/scoli

G I/II spondy

DDD

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli

Degen/scoli Degen

Degen/scoli

Degen

Scoliosis

Degen/scoli

Degen/scoli

Degen/scoli

degen/scoli

Spondy

Scoliosis

Scoliosis

Degen/scoli

Degen/scoli

Degen

Degen/scoli Scoliosis

Scoliosis

Scoliosis

Scoliosis

Scoliosis

Scoliosis

Scoliosis

X, D, AxLIF

Anand et al. [177]

IV

X, D, AxLIF

Anand et al. [176]

1–3

1.9

1

1–2

1

1–2

1–3

1–4

1–4

2.3 pp

1–6 1

1–2

1–3

1–6

2.4 pp

1–4

1–4

1/4

1

1–3

2–5

1.8 pp

1–4

1–4 1–4

1–5

1–5

1–7

2–7

2–6

1–6

Ant lvls

Indication

Control

Procedure

References

LOE


Study characteristics

Table 4 Summary of clinical and radiographic outcomes in published MI-LIF cohorts

T12–L5

T6–L5

L4–L5

L

L1–5

L2–5

L1–5 (T6–7)

L

L

L1–L5

T6–L5 L3–5

L

L1–L5

T10–L5

TL

T11–L5

T10–L5

T11–L5

L4–5

L2–S1

L1–L5

L1–5

L1–S1

L1–5 L1–5

T12–L5

T12–S1

TL

T10–L5

T12–S1

T12–S1

Lvls

BP

Mixed

None

None

None

None

Mixed

Mixed

Mixed

Mixed

Mixed LP

Mixed

PS

LP

BP

Mixed

Mixed

None

PS

BP

BP

PS

Mixed

NR

Mixed Mixed

BP

Mixed

None

BP

BP

BP

Internal fixation

0–5

None

None

None

None

2–7

None

4–11

6–12

None

3–7

2–8

3–8


62

14

15

46

52

22

30

140

118

29

22 13

39

25

25

44

93

90

59

31

4

8

36

45

30

43 26

23

21

35

30

12

28

Total n

24 mo

8 mo

2 yrs

12 mo

24 mo

24 mo

11.5 mo

9.6 mo

27.5 mo

6 mo

16.4 mo 6 mo

16 mo

25.6 weeks

11 mo

12 mo

12.1 mo

17.6 mo

14.6 mo

18.2 mo

11.5 mo

10.5 mo

21 mo

Periop

21 mo

12 mo 12 mo

12 mo

24 mo

24 mo

14.3 mo

22.4 mo

75 days

Mean follow-up

Eur Spine J

123

Control

123 XLIF



I

XLIF

Youssef et al. [165]

Degen/scoli

ASD

Degen

Degen/scoli

Degen Degen

G II Spondy

Degen/scoli

Degen/scoli

Degen

ASD

1

62 60.2 57.9 44.6


Tormenti et al. [186] Ahmadian et al. [133]

60

Sofianos et al. [119]

Acosta et al. [132]

47 71

Tempel et al. [196]

L

L1–5

L3–5

L1–5

L L

L2–5

L

L1–5

L

L

L1–L5

L4–5

L4–5

T8–S1

Lvls

50

43

82.1

ODI decrease (%)

38.7

51

21

1–3

1–2

1

1–3

1–2 1–2

1–3

1–4

1.1 pp

1–3

1–4

1–4

Sig Imp


100

Degen Degen

1–6 1

Sig imp

54.1

Wang and Mummaneni [187]

Sharma et al. [159]

68

32.4

57

59 100

Scoliosis Degen

VAS decrease (%)

ALIF XLIF

Khajavi and Shen [192]

88.2

100

Fusion (%)

III

IV

IV

IV

IV

BMP

SiCaP

Castro et al. [190]

Caputo et al. [189]

Anand et al. [177]

Anand et al. [176]

References

XLIF

Wang et al. [174]

IV

XLIF XLIF

Tohmeh et al. [161]

XLIF XLIF ALIF


Smith et al. [160] Smith et al. [160]

Voyadzis and Anaizi [163]

III III

XLIF


IV IV

XLIF XLIF


IV

IV


Outcomes

XLIF w SiCaP XLIF

Pimenta et al. [152]

I

II

XLIF, L5S1 XLIF w BMP

Phillips et al. [185]


Ant lvls

Indication

LOE

References

Procedure


Study characteristics

Table 4 continued

1–3

None

None

0–9


100

Outcome satisfaction (%)

Mixed

Mixed

Facet

Mixed

PS PS

PS

Mixed

Mixed

PS

Mixed

PS

None

None

Mixed

Internal fixation

82

21

10

40

115 87

63

238

50

66

100

100

15

15

82

Total n

86

Re-do (%)

15.7 mo

23.6 mo

8.2 mo

12 mo

24 mo 24 mo

12 mo

24 mo

12 mo

12 mo

6 mo

6 mo

36 mo

36 mo

24 mo

Mean follow-up

Eur Spine J

91 100

Marchi et al. [146] Marchi et al. [147]

Marchi et al. [113]


100


80

98.4 93.2



Voyadzis and Anaizi [163]

Tohmeh et al. [161]

Smith et al. [160] Smith et al. [160] 90.2

90

55

68 65

62.8 75



100

67.4

Rodgers et al. [155] 41

68.7


46

46

100


37 3.4 points

Ozgur et al. [151]

Phillips et al. [185]

69

57.1

59.2

Oliveira et al. [172] 91

93 86.5

Malham et al. [145] 70 60

38.7 63

85

Le et al. [144]

89

41

60 59

35

31

31

39

56

46.9

57 55

41

39.6 52.9

57.8 43

88

47.7

Kotwal et al. [143]

100

Kepler et al. [140]

61

70.2

44.2

33

54.9

47.3

38.6

ODI decrease (%)

Kepler [141]

95.5

Uribe et al. [247]

77.5


Caputo et al. [179] 73.3

70.4

Castellvi et al. [168]

Elowitz et al. [136]

61.4 44

Berjano et al. [135] 80

45.3

VAS decrease (%)

61.5

95

Fusion (%)

Outcomes

Alimi et al. [167]


References

Table 4 continued

92

89

89.4

85

92

95.5 % SCB

92 % success

84.8 % Macnab


86

93

89.4

85

71

Re-do (%)

Eur Spine J

123

123

LOE level of evidence (I–V)[11], ant anterior, Lvls levels, Reops reoperations, Comps complications, VAS visual analog scale, ODI Oswestry disability index, XLIF extreme lateral interbody fusion, DLIF direct lateral interbody fusion, SD possible shallow docking technique used, Scoli degenerative scoliosis, BPS bilateral pedicle screws, mo months, LP anterolateral plates, PLF posterolateral fusion, TLIF minimally invasive transforaminal interbody fusion, Degen mixed degenerative conditions (e.g., spondylolisthesis, DDD, adjacent segment disease, etc…), DDD degenerative disc disease, PLIF open posterior interbody fusion, sig significantly, BMI body mass index, yrs years, PS pedicle screws (uni- or bi-lateral), ASD adjacent segment disease. Studies listed in adjacent rows with a border indicate two cohorts from the same study

56 61

77 100 (pts w f/u) Youssef et al. [165]

Wang et al. [174]

Fusion (%)

References

Table 4 continued

Outcomes

VAS decrease (%)

ODI decrease (%)


Re-do (%)

Eur Spine J

lateral approaches. As such, an examination of those reports that used only traditional lateral approaches (traditional MI-LIF group) was compared to those reports that used either non-traditional lateral approaches or included patients treated with either traditional MI-LIF or non-traditional MI-LIF procedures (non-traditional MI-LIF group), where outcomes were not be separated between the groups. These literature cohorts were assessed through weighted averaging and results are included in Tables 5 and 6. In comparison to the primary outcomes related to the technique of the surgical procedures (complications and side effects), the traditional MI-LIF group showed an average new postoperative thigh sensory changes rate of 16.4 % in 1343 patients compared to 35.6 % in 1429 patients in the non-traditional MI-LIF group. Hip flexion weakness was similar between the traditional and nontraditional MI-LIF groups (20.9 vs. 20.7 %, respectively) while rates of new distal weaknesses were lower in the traditional MI-LIF group (1.6 vs. 5.1 %, respectively). Some reports did not separate out hip flexion and distal motor weakness, so when assessing all motor deficits (muscular and neural), the rate of occurrence in the traditional MI-LIF group was 12.1 % (1869 patients) compared to 22.1 % (1602 patients) in the non-traditional MI-LIF group. Of the studies that made up these results, higher quality evidence directly comparing perioperative outcomes between traditional MI-LIF and non-traditional MILIF was available and a large quantity of studies that were generally (though not completely) consistent with the quality findings lead to a moderate strength of conclusion that material differences exist between different MI-LIF approaches, with more favorable neural outcomes evident in traditional MI-LIF. Question 3—representative article Cheng et al. [124] directly compared perioperative adverse events, with an emphasis on neural and motor changes, between those patients treated with traditional MI-LIF, which included sequential dilation through the psoas muscle using evoked-EMG (XLIF) [2], and those treated using supra-psoas docking and directly visualized passage through the psoas muscle [shallow docking (SD)] at Stanford University Hospital [10]. In this, the authors analyzed 120 patients (70 traditional MI-LIF, 50 SD). Overall, the presence of new neurologic adverse events was higher in the SD group (24 %) compared to the traditional MI-LIF group (14.2 %) (p = 0.1751), and when examining neurologic outcomes in single level cases only (84/120), neurologic complications were almost three times more likely in the shallow docking compared to the traditional MI-LIF group (28.6 vs. 10.2 %, respectively) (p = 0.0302).

5781 (54)

7737 (67)

4869 (58)

2894 (22)

Mixed scoli (w degen/scoli)

Mixed degen (w degen/scoli)

Traditional lateral (XLIF) only

Non-traditional/mixed XLIF and non-XLIF lateral only

1179 (19)

970 (18)

1229 (8)

Mixed degen (w degen/ scoli)

Traditional lateral (XLIF) only

Non-traditional/ mixed XLIF and non-XLIF lateral only

20.5 % (0–54.9 %)

20.7 % (0–51.4 %)

20.9 % (0–54.9 %)

18.3 % (0–54.9 %)

21.1 % (1.2–54.9 %)

34 % (24–36 %)

14.7 % (0–23 %)

1568 (14)

390 (5)

1148 (9)

1515 (13)

864 (10)

–

651 (3)

2.6 % (0.0–9.5 %)

5.1 % (0–9.5 %)

1.6 % (0–6.7 %)

2.7 % (0–9.5 %)

3.9 % (0–9.5 %)

–

1.0 % (0–6.7 %)

3471 (35)

1602 (13)

1869 (22)

3311 (33)

2598 (25)

–

820 (9)

313.7 (136–910.7)

99.2 (26.5–230)

16.7 % (0–56.2 %) 4.2 % (0–23 %)

22.1 % (2.9–51.4 %)

12.1 % (0–56.2 %)

15.8 % (0–56.2 %)

20.3 % (0–56.2 %)

–

1114 (16)

910 (14) 292 (6)

198 (3)

1882 (21)

1966 (20)

869 (13)

114 (4)

1211

2080 (24)

n pts (n study arms)

263 (5)

1803 (26)

140.4 (26.5–910.7) 1774 (25)

164.1 (50–541)

78.7 (26.5–225) 227.5 (53–541)

7.0 % (1.7–10.1 %)

5.4 % (0–47 %)

5.3 % (0–47 %)

8.4 % (0–23 %)

10.6 % (4.3–23 %)

3.6 % (0.6–47 %)

214 (6)

2464 (31)

2398 (28)

1082 (21)

280 (9)

1596 (16)

27.3 % (0–43 %)

10.6 % (0–150 %)

10.2 % (0–43 %)

17.8 % (0–150 %)

27.5 % (0–150 %)

8.0 % (0–32 %)

12.0 % (0.0–150 %)

Total comps, % (range)

35.6 % (8.6–60.1 %)

16.4 % (0–75 %)

26.0 % (0–48.6 %)

28.8 %(1.2–75 %)

9.5 % (0–25 %) 33.1 % (12–75 %)

26.3 % (0–75 %)

Thigh SE, % (range)

2678 (37)


1429 (15)

1343 (25)

2602 (33)

2425 (30)

414 (11) 117 (6)

2772


5.6 % (0.0–47.0 %)

Reops, % (range)

6.9 (4–10)

2.5 (0.9–7.7)

2.7 (0.88–9.9)

3.9 (1.24–10)

1.6 (0.9–5.0) 5.2 (1.4–10)

3.0 (0.88–10)

LOS, days (range)

n number of patients or study arms with reported data and able to be calculated in the weighted average, f/u follow-up, ORT operating room time, EBL estimated blood loss, LOS length of postoperative hospital stay, SE side effects, HFW hip flexion weakness, reops reoperations, comps complications, VAS visual analog scale, ODI oswestry disability index, re-do patients indicated that they would have undergone the same procedure again if their outcome had been known in advance, Degen degenerative (non-deformity) spinal disease, Scoli scoliosis, degen/scoli mixed degenerative and scoliosis indications in the patient series, XLIF extreme lateral interbody fusion; traditional lateral (XLIF) only group: included reports that were of XLIF-lateral procedures only; non-traditional lateral (non-XLIF) only group: reports were included if they were either studies of non-XLIF lateral procedures or if there was a mixture of XLIF and non-XLIF lateral (e.g., shallow docking) procedures performed

128 (2)

2369 (23)

Mixed scoli (w degen/ scoli)

190 (7)

Degen

Scoliosis

1360 (22)

All studies


159.8 (26.5–910.7) 2066 (31)

EBL, mL (range)

All motor deficits (neural and HFW), % (range)

415 (8)

1054 (26)

1142 (26)

986 (20)

441 (13) 327 (8)

1469 (34)



262.2 (146–477)

143.2 (66–261)

198.9 (66–392)

225.8 (66–477)

113.5 (67–261) 223.1 (108–477)

202.5 (66–477)

ORT, mins (range)

Motor neural deficits, % (range)

1096 (14)

1104 (25)

1873 (31)

1639 (25)

519 (13) 327 (8)

2200 (39)



9.1 (1.5–40)

10.2 (1.5–36)

9.2 (1.5–36)

9.3 (1.5–40)

11.1 (1.5–36) 17.4 (1.5–40)

9.8 (1.5–40)

Mean f/u, months (range)

HFW, % (range)

1887 (24) 473 (12)

Degen Scoliosis


7763 (80)

All studies


Table 5 Weighted averages of study methods and side effect/complication outcomes from a systematic review of lateral transpsoas approach surgery, reported whole and in groups by surgical indication or procedure performed

Eur Spine J

123

123

106

615 (13)

801 (18)

856 (20)

Scoliosis

Mixed scoli (w degen/ scoli)

Mixed degen (w degen/ scoli)

Traditional lateral (XLIF) only 100 (100)

93.2 (80–100)

93.9 (85–100)

92.2 (80–100)

91.9 (80–100

96.7 (86.5–100)

93.6 (80–100)

Fusion, % (range)

129 (5)

1968 (36)

1919 (33)

1404 (25)

178 (8)

693 (16)

2097 (41)


58.8 (32.4–71)

60.0 (37–90)

60.1 (37–90)

56.4 (32.4–77.5)

57.9 (32–70)

67.1 (44.6–90)

60.0 (32.4–90)

VAS improvement, % (range)

64 (2)

1170 (27)

1099 (24)

921 (19)

135 (5)

313 (10)

1234 (29)


64.6 (51–52.1)

47.5 (21–89)

48.4 (31–89)

46.0 (21–82.1)

48.2 (21–82)

55.1 (31–89)

48.4 (21–89)

ODI improvement, % (range)

–

491 (9)

388 (7)

362 (7)

103 (2)

129 (2)

491 (9)


–

89.2 (84.8–100)

89.6 (84.8–95.5)

89.3 (84.8–100)

88 (85–100)

89 (89–89.4)

89.3 (84.8–100)

Outcome satisfaction, % (range)

–

334 (6)

231 (4)

205 (4)

103 (2)

129 (2)

334 (6)


–

85.0 (71–93)

85 (71–93)

81.1 (71–86)

85 (85–86)

91 (89.4–93)

85 (71–93)

Re-do, % (range)

n number of patients or study arms with reported data and able to be calculated in the weighted average, f/u follow-up, ORT operating room time, EBL estimated blood loss, LOS length of postoperative hospital stay, SE side effects, HFW hip flexion weakness, reops reoperations, comps complications, VAS visual analog scale, ODI oswestry disability index, re-do patients indicated that they would have undergone the same procedure again if their outcome had been known in advance, degen degenerative (non-deformity) spinal disease, scoli scoliosis, degen/scoli mixed degenerative and scoliosis indications in the patient series, XLIF extreme lateral interbody fusion; traditional lateral (XLIF) only group: included reports that were of XLIF-lateral procedures only, non-traditional lateral (non-XLIF) only group: reports were included if they were either studies of non-XLIF lateral procedures or if there was a mixture of XLIF and non-XLIF lateral (e.g., shallow docking) procedures performed

51 (2)

292 (9)

Degen

Non-traditional lateral (non-XLIF) only

907 (22)

All studies


Table 6 Weighted averages of clinical and radiographic outcomes from a systematic review of lateral transpsoas approach surgery, reported whole and in groups by surgical indication or procedure performed

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Question 4: Are modern minimally disruptive procedures (e.g., MI-LIF) economically viable? There are only two articles which directly assess economics following MI-LIF [111, 160]. While they both represent higher quality studies (prospective registry data, comparative groups), they measure different variables and the authors of this work were, therefore, unable to assess consistency. Both manuscripts show significant cost savings using MI-LIF over conventional approaches during the perioperative period, measured through hospital operating costs or charges, but this low volume of work (quantity) with lack of comparability between (consistency) offsets their quality in assessing perioperative economics. Cost-effectiveness was assessed in neither, so only this limited economic scope can be considered. Due to these factors, there is low strength of evidence at this time to conclude that MI-LIF is an economically favorable approach to conventional approaches. Question 4—representative articles Two articles exist which describe the economics of MILIF. The first by Lucio et al. [111] compares clinical and economic outcomes of two-level minimally invasive (MIS) fusion (including XLIF in all patients at at least one level) with two-level open posterior lumbar interbody fusion (PLIF). Line-item actual hospital operating costs were examined to determine drivers of cost at different points within the perioperative period as well as the impact of performing procedures with similar surgical goals, through two different approaches. A total of 210 patients were included in the analysis (109 MIS and 101 open PLIF). Mean length of stay was 3.2 days for the open group and 1.2 days for the MIS group, and complications were significantly more frequent in the open group (14 vs. 6 %, respectively). Residual events (secondary medical interactions with the hospital outside of the acute perioperative period) were similarly more frequent in the open compared to MIS group (37 vs. 21 %). These clinical differences resulted in significant hospital operating cost savings, on average, of $2825 per patient (10.4 %), despite significantly higher up-front costs for MIS implants. A second study by Smith et al. [160] compared XLIF and anterior lumbar interbody fusion (ALIF) outcomes and economics and, similarly, found significantly fewer complications in the XLIF group which translated to 10 and 13.6 % cost savings (charges). At 2-year postoperative evaluation, outcomes between the two groups of patients were similar.

Discussion The purpose of this work was to compile and synthesize all currently available evidence on MI-LIF in an attempt to draw conclusions across four categories: (1) The anatomical justification for the approach, (2) an analysis of complication and outcome profiles following MI-LIF, (3) outcome variation between different lateral transpsoas approach procedures, and (4) an examination of current information regarding MIS economics. Question 1: Is there an anatomical justification for MI-LIF, particularly at L4–5? There is ongoing debate about the viability of the MI-LIF approach at the L4–5 level, primarily on location of the lumbar plexus with respect to the surgical corridor. This debate may be fueled by differences in MI-LIF systems and their respective trainings (e.g., integrated neuromonitoring), surgeon preference and comfort in adoption, and/or anecdotal reports perpetuating inconsistency. From a literature perspective, neural anatomy allows for a transpsoas approach to the lateral aspect of the spine from L1–2 through L4–5. A summary of the lateral approach anatomical literature by Smith et al. [30] was provided within an original examination of the effect of transitional anatomy at lower lumbar levels on the feasibility of the MI-LIF approach. In the literature review, when direct measurement studies were interpolated into zone categories (e.g., 75 % of anterior disc space free of motor nerves corresponded to zones I–III free of motor nerves), the authors found that there was broad agreement between the many high-quality studies available, finding that at least (and likely more when direct measurements instead of zones and soft-tissue retraction are considered), the anterior half of the lateral disc space is free of motor nerves. Those results are corroborated by the results in Table 1 in the current study. Additionally, while Moro et al. [250] separated the lateral disc space into quadrants to describe the location of relevant structures, the results of which have been replicated several times [19, 22, 24, 31], the results lack the specificity of the direct, finite measurements of many other anatomical studies of this region [16, 23, 25, 27, 28], where millimeters can make a difference in determining appropriate instrumentation dimensions. With respect to sensory nerves, the most relevant deep neural structure at risk is the genitofemoral nerve, which can generally be visually located as it emerges from the psoas muscle at the L3–4 disc space and it continues to travel inferiorly on the surface of the psoas muscle. A more posterior approach, anterior to motor nerves of the lumbar plexus, which can be monitored using electromyography

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(EMG), largely reduces the risk of docking on the genitofemoral nerve. Additionally, several studies examined vascular structures on axial MRI, suggesting that the anterior portion of the accessible zone to the lateral disc space is sometimes covered by, most commonly, right-sided vessels [20, 24, 28]. While this is certainly worth consideration, vascular structures are generally much more mobile than neural structures, as shown by Deukmedjian et al. [21] who showed that vascular structures migrate anteriorly significantly when in vivo subjects are placed in the lateral decubitus position, suggesting that this apparent risk from cadaveric or supine MRI studies (where vessels likely fall dorsally) may be overstated. Regardless, there are sensitive structures on the lateral aspect of the spine anterior to the trunks and root of the lumbar plexus. These anterior structures (genitofemoral nerve and vasculature) are less able to be monitored, whereas posterior structures are using EMG. Anterior docking and posterior retraction of the psoas muscle risks injury to the genitofemoral nerve and vasculature, as well as the lumbar plexus as the requirement for dorsal expansion of the retractor to access the disc space can compress the substance of the psoas muscle, and embedded plexus into the transverse process. A more posterior targeting, active mapping of the neural elements with EMG, and ventral-only retractor expansion may both avoid injuries to the lumbar plexus through more objective intraoperative awareness and through avoidance of sensitive anterior structures [120]. While all surgical procedures carry risk of injury and complications, several MI-LIF case reports describe specific complications which, while rare, highlight the potential risk for such events. Examples include urological injury, coronal plane vertebral body fractures, cage overhang, cage migration, incisional hernia, contralateral nerve injury, psoas hematoma, seroma, and abscess (ipsilateral or contralateral), arterial pseudoaneurysm, bowel injury, and iliac or great vessel injury [56, 65, 68, 69, 72, 74, 82, 83, 85, 86, 89, 94, 126, 186]. For many of these potential risks, they highlight the need for a deep understanding of peritoneal, vascular, and neural anatomy combined with attention to preoperative axial MRI and diligent intraoperative technique. MI-LIF is a detail-oriented approach, and pairing expected anatomy with preoperative planning and intraoperative assessment of actual anatomy aids in complication avoidance. Question 2: What are the safety (complication) and outcome profiles of MI-LIF and are they acceptable in comparison with conventional approaches? Neural complications have long been considered the primary concern in MI-LIF. High-quality evidence supports,

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overall, that MI-LIF has a complication profile superior to conventional interbody approaches and at least equivalent to alternative minimally disruptive approaches, on average [120] (Table 3). However, these data do not suggest that there is no risk of injury during these procedures. In fact, it is the contrary perspective. Given the anatomical understanding for the approach described in Tables 1 and 2, neural complication avoidance relies on preoperative planning paired with intraoperative adherence to neuromonitoring and diligent attention to technique. The issue of sensory changes and hip flexion weakness side effects postoperatively are artifacts of technique (position, extent, and duration of retraction), but also calls for the need for consistency in reporting and understanding within the literature [229, 247]. As far as the consideration, specifically, of designating mild transient hip flexion weakness and sensory changes as side effects, these authors believe it is analogous to back extension weakness and incisional pain (both of which are often more than mild) following open posterior fusion or PLIF. They are hardly, if ever, considered complications of the approach, as they are nearly universally encountered due to the exposure needed, but are real side effects that patients experience. It is within the understanding that all invasive medical interventions, by their nature, require access and some degree of effect based on that access that these and many other authors consider hip flexion weakness and mild, transient sensory changes to be common, expected, approach-related side effects, not complications of the approach. In assessing MI-LIF outcomes, there are many examples of mid- and long-term radiographic and clinical outcomes following MI-LIF [132–175], though with only one example of a direct comparison to conventional approaches, though that article is consistent with non-comparative findings and is at least equivalent to similar procedures (ALIF) at 2-year follow-up [160]. Question 3: Given technical and neuromonitoring differences between various MI-LIF procedures, are there any published clinical differences? The aggregate evidence shown here and early specific comparative reports of different approaches for MI-LIF suggest that these technical differences result in marked differences in outcome, specifically as they relate to neural complications and side effects [124] (Table 4). These differences manifest as elevated neural complication rates, on average, for non-traditional MI-LIF (e.g., those performed without specialized neurophysiologic monitoring, or any at all, those that advocate a more anterior passage through the psoas muscle, and/or those that advocate visual dissection through the psoas muscle to the lateral disc space) compared to traditional MI-LIF. As the procedure has regularly

Eur Spine J Table 7 Economics of MIS and open spine surgery

Instrumented fusion for spondylolisthesis

Exposure

2 yr $/QALY (k)

4 yr $/QALY (k)

SPORT results—Tosteson et al.

Open posterior

$116

$64

Rampersaud et al./Parker et al.

Open PLIF/TLIF

$109

$68

Rampersaud et al./Parker et al.

MIS PLIF/TLIF

$72

$38

yr year, QALY quality adjusted life year, SPORT spine patient outcomes research trial, PLIF posterior lumbar interbody fusion, MIS minimally invasive spine surgery, TLIF transforaminal lumbar interbody fusion, k number in thousands

been described as detail-oriented and passing adjacent to sensitive soft-tissue structures, it is not surprising that different outcomes have been realized following nuanced modifications to the described surgical procedure [2, 251]. This is not to advocate for one MI-LIF approach over another, but instead to put in context and describe differences between MI-LIF approaches with respect to literature validation and predicable and reproducible outcomes in a large body of evidence. Question 4: Is there currently evidence to support modern minimally disruptive approaches (including MI-LIF) from a cost-effectiveness perspective? Several studies of high-quality evidence exist describing the economics of spine surgery. Several large-scale prospective and/or randomized studies exist comparing surgical to non-surgical approaches [252, 253] as well as between MIS and conventional approaches [111, 160, 254, 255]. From a cost ($) per quality adjusted life year (QALY) ($/QALY) perspective, where $50 to $100 k per QALY for an intervention is considered ‘‘cost effective’’ in the US, several studies of conventional approaches for spinal fusion have been found to cost between $53.9 and $64.3 k per QALY [252, 253]. When considering MIS approaches, where complications often drive exponential increases in initial direct costs, there is a potential to substantially improve cost effectiveness should long-term clinical outcomes be at least equivalent, despite an up-front premium for MIS implants and instrumentation [111]. While there are several examples of MI-LIF economic analyses [111, 160], neither address long-term cost effectiveness. In other MIS approaches, direct cost-effectiveness comparisons with conventional approaches have been reported [254, 255]. These studies show a greater than 40 % improvement in cost effectiveness compared to conventional approaches (largely consistent with the previous conventional exposure cost effectiveness studies) through a 4-year postoperative assessment, and suggest the fulfillment of the promise of MIS approaches in general [230]. These reports, in their quality and corroboration with the MI-LIF economic reports, likely suggest low- to moderate-strength evidence favoring MIS economics, though additional studies are

needed. In the United States, where Medicare no longer pays for surgical site infections following spine surgery and penalties to hospitals are in place for hospital-acquired conditions, readmissions, and patient satisfaction, the economic viability of MIS approaches are even further supported at the local level, addressing a need for cost control and predictability for hospitals and hospital systems. An overview of open and MIS cost-effectiveness results is included in Table 7. In summary, these four MI-LIF topical areas—anatomy, outcomes, approach differences, and economics—have support within the literature from the 237 peer-reviewed papers that describe MI-LIF reviewed in this work. An anatomical justification for MI-LIF from L1–2 through L4–5 has many consistent examples of high-quality studies in corroboration. However, this anatomical justification should not be understood to obviate the need for diligent surgical technique and adherence to advanced neuromonitoring [247]. The principles of awareness of certain discoverable structures (plexus) and, conversely, to preoperative MRI assessment and intraoperative avoidance of less-easily discoverable structures (vasculature) are paramount to reproducibility, especially during the learning curve. Complication and clinical outcome findings are less consistent, but have a large body of evidence to support favorable findings on both counts within the context of current practice. These encompass the central tenets of MIS surgery compared to conventional approaches (improved morbidity with at least equivalence in outcome) and are moderately supported as true from the currently available literature. Next, emerging evidence supports that there are complication profile differences between different MI-LIF approaches and a thorough understanding of the literature is required to better understand these differences. Finally, and most importantly within the current healthcare environment, MIS and MI-LIF economic evidence and the resultant long-term implications are only recently emerging. What exists now is limited in scope, but these early reports support intuition—that benefits to patients in terms of decreased morbidity translates to surgical, hospital, and overall healthcare efficiency—and that such implications have the potential to echo between and support many parties involved in healthcare delivery.

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Eur Spine J Acknowledgments The authors thank Kyle Malone, MS at NuVasive, Inc. for his statistical and editorial support. 18. Conflict of interest interest.

None of the authors has any potential conflict of

19.

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Anterior lumbar spine surgery: a systematic review and meta-analysis of associated complications.

Systematic literature review to evaluate and characterize the health economics and outcomes research studies in India.

Does Patient Sex Affect the Rate of Mortality and Complications After Spine Surgery? A Systematic Review.

The Effects of Smoking and Smoking Cessation on Spine Surgery: A Systematic Review of the Literature.

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Complications associated with the initial learning curve of minimally invasive spine surgery: a systematic review.

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The Effects of Obesity on Spine Surgery: A Systematic Review of the Literature.

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Assessing the Economics of Dengue: Results from a Systematic Review of the Literature and Expert Survey.

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CORR Insights®: Does Patient Sex Affect the Rate of Mortality and Complications After Spine Surgery? A Systematic Review.

Pulmonary Complications following Thoracic Spinal Surgery: A Systematic Review.

Outcomes of salvage surgery for ileal pouch complications and dysfunctions. the experience of a referral centre and review of literature.

The influence of race and ethnicity on complications and mortality after orthopedic surgery: a systematic review of the literature.

A systematic review of utilities in hand surgery literature.

Complications in adolescent pregnancy: systematic review of the literature.

Psychosocial Outcomes in Orthognathic Surgery: A Review of the Literature.

Activity-Related Outcomes of Articular Cartilage Surgery: A Systematic Review.

Intrasite vancomycin powder for the prevention of surgical site infection in spine surgery: a systematic literature review.

Outcomes and Complications of Minimally Invasive Surgery of the Lumbar Spine in the Elderly.

Outcomes and complications of the midline anterior approach 3 years after lumbar spine surgery.

The Association Between Cervical Spine Manipulation and Carotid Artery Dissection: A Systematic Review of the Literature.

Cervical spine immobilization following blunt trauma: a systematic review of recent literature and proposed treatment algorithm.