Accepted Manuscript Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody Fusion: Radiographic and Clinical Analysis Alan T. Villavicencio , MD, Benjamin J. Serxner , MD, Alexander Mason , MD, E. Lee Nelson , MD, Sharad Rajpal , MD, Nathan Faes , BA, Sigita Burneikiene , MD PII:
S1878-8750(14)01383-7
DOI:
10.1016/j.wneu.2014.12.012
Reference:
WNEU 2621
To appear in:
World Neurosurgery
Received Date: 28 May 2014 Revised Date:
15 August 2014
Accepted Date: 9 December 2014
Please cite this article as: Villavicencio AT, Serxner BJ, Mason A, Nelson EL, Rajpal S, Faes N, Burneikiene S, Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody Fusion: Radiographic and Clinical Analysis, World Neurosurgery (2015), doi: 10.1016/ j.wneu.2014.12.012. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Villavicencio et al, Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody
RI PT
Fusion: Radiographic and Clinical Analysis
Alan T. Villavicencio, MD1, 2; Benjamin J. Serxner, MD2; Alexander Mason, MD1, 2; E. Lee
1 Boulder
Neurosurgical Associates, Boulder, CO
Parker Neurological Institute, Boulder, CO
EP
Corresponding Author:
TE D
2 Justin
M AN U
SC
Nelson, MD1, 2; Sharad Rajpal, MD1; Nathan Faes, BA2; Sigita Burneikiene, MD1, 2
AC C
Sigita Burneikiene, MD
Boulder Neurosurgical Associates 4743 Arapahoe Avenue, Suite 202 Boulder, CO 80303
Phone: 303-938-5700 Fax: 303-998-0007 [email protected]
1
ACCEPTED MANUSCRIPT Villavicencio et al, ABSTRACT Objective Transforaminal lumbar interbody fusion with bilateral segmental pedicle screw fixation is
RI PT
a widely used and well-recognized technique that is performed to provide fixation and load-bearing capacity while restoring morphometric spine parameters and relieving
symptoms in patients with degenerative disc disease. A supplemental interspinous process
SC
fixation plate (ISFP) as an adjunct to unilateral PS fixation allows for reduced invasiveness of this technique as compared to bilateral PS placement. The biomechanical comparison
studied in clinical settings.
Methods
M AN U
results have been previously reported, but the significance of these findings has not been
TE D
A prospective cohort study with a supplemental retrospective chart review and radiographic analysis was performed. The patients were divided into two groups: surgeries that were performed using bilateral PS fixation (n=75) or unilateral PS fixation + ISFP
EP
(n=96). Lateral lumbar standing radiographs were used for pre- and postoperative
AC C
foraminal height (FH), disc height (DH), segmental (SSA) and lumbar sagittal alignment (LSA) measurements. Standardized questionnaires were used to compare postoperative clinical outcomes.
Results The estimated blood loss, duration of procedure and the length of hospital stay were significantly lower for one- and two-level procedures in the unilateral PS + ISFP patient
2
ACCEPTED MANUSCRIPT Villavicencio et al, group. A statistically significant mean DH increase was observed in both groups. Regardless of this, a statistically significant FH loss was detected in the bilateral PS patient group (from 17.1 to 16.3 mm; 4.7% loss; P=0.04) compared to FH height loss in the unilateral PS + ISFP
RI PT
patient group that was not statistically significant (from 19.0 to 18.4 mm; 3.2% loss; P=0.1). The analysis of SSA, LSA, clinical outcomes and fusion rates did not demonstrate any
SC
statistically significant differences.
Conclusions
M AN U
Significantly reduced surgical invasiveness was associated with unilateral PS + ISFP fixation, which represents the major advantage of this technique. Unilateral fixation was also associated with a slightly lower reduction in FH and was equally effective to bilateral
TE D
PS fixation in regards to fusion rates, clinical and other radiographic outcomes studied.
Keywords: Foraminal height; lumbar spine; pedicle screws; plate fixation; transforaminal
EP
lumbar interbody fusion.
AC C
Abbreviations: ALIF – anterior lumbar interbody fusion; DH - disc height; FH - foraminal height; ISFP - interspinous process fixation plate; LSA – lumbar sagittal alignment; MCS – mental component summary; PCS – physical component summary; PLIF – posterior lumbar interbody fusion; PS – pedicle screw; rhBMP-2 – recombinant human bone morphogenetic protein-2; SSA - segmental sagittal alignment; TLIF – transforaminal lumbar interbody fusion; VAS – visual analog scale; XLIF – extreme lateral interbody fusion.
3
ACCEPTED MANUSCRIPT Villavicencio et al, INTRODUCTION
Transforaminal lumbar interbody fusion (TLIF) with bilateral segmental pedicle screw
RI PT
fixation is a widely used and well-recognized technique that is performed to provide
fixation and load-bearing capacity while restoring morphometric spine parameters and relieving symptoms in patients with degenerative disc disease. TLIF allows a unilateral
SC
paraspinal approach, therefore is less invasive than other conventional posterior midline surgical techniques (2,10). In order to further minimize surgical exposure and iatrogenic
M AN U
morbidity, several technique modifications have been explored (3,4,20). One of them, unilateral pedicle screw fixation allows ipsilateral pedicle screw placement without the need to damage the contralateral muscles and soft tissues. Although several clinical reports demonstrated effectiveness of this technique (3,5,14,18,23,25,28), some biomechanical
TE D
studies noted off-axis rotational or coupled motions resulting from the construct asymmetry and inability to provide adequate rigidity, which could be detrimental to the promotion of fusion (1,7,8,21,22). A supplemental interspinous process fixation plate
EP
(ISFP) as an adjunct to unilateral PS fixation significantly improves stability in all planes
AC C
and may offer a good and less-invasive alternative to bilateral PS fixation based on a recent biomechanical study (15). The authors concluded that 2 methods of fixation that most closely reproduced the stability of the intact spine were bilateral pedicle screws and ISFP as an adjunct to unilateral pedicle screw fixation. The significance of these findings and the ability of this technique to achieve the same goals have not been studied in clinical settings.
4
ACCEPTED MANUSCRIPT Villavicencio et al, The main objectives of this study were to evaluate surgical, radiographic and clinical parameters in patients who underwent TLIF with bilateral or unilateral PS fixation with ISFP and to compare the effectiveness of these techniques in restoring disc height (DH),
RI PT
foraminal height (FH), lumbar lordosis, segmental sagittal alignment (SSA).
SC
METHODS
A prospective cohort study with a supplemental retrospective chart review and
M AN U
radiographic analysis was performed. This study analyzed all consecutive cases that met the following inclusion criteria: one- or two-level TLIF surgeries performed for painful degenerative disc disease at L3 – S1 levels in the setting of symptomatic spinal stenosis and/or lateral recess stenosis requiring surgical decompression to the extent that would
TE D
result in destabilizing the spine; unstable spondylolisthesis (≤ Grade II); no previous fusion surgeries; and availability of preoperative and postoperative (≥9 months) imaging studies. Patients were selected for surgery based on clinical symptoms, which included intractable
EP
low back pain and radiculopathy caused by spondylosis and/or disc herniation, foraminal
AC C
and/or central stenosis, and spondylolisthesis (Table 1). The surgeries included in this analysis were performed from May 2008 to November 2010. The patients were divided into the two groups for further analysis: surgeries that were performed using bilateral PS fixation (n = 75) or unilateral PS fixation + ISFP (n = 96) Figures 1 and 2 show spinal hardware constructs for comparison.
5
ACCEPTED MANUSCRIPT Villavicencio et al, Choice of unilateral or bilateral PS fixation was based on surgeon preference. All unilateral PS + ISFP fixation surgeries were performed by a first author (ATV) and bilateral fixation cases were performed by AM, and ELN, except for 13 out of 75 cases (ATV) where the
RI PT
unilateral screws were not felt to have adequate purchase with regards to the bone-screw interface. In this case, 13 intended unilateral cases were converted to bilateral PS fixation based on intraoperative findings with regards to screw purchase. In these cases bilateral
SC
screws were placed in lieu of unilateral pedicle screw fixation and a spinous process plate.
M AN U
Clinical outcome assessment and radiographic measurements were performed by authors SB and BJS, respectively, who were not involved in patient care.
TE D
Radiographic Outcome Measures and Analysis
Lateral lumbar standing radiographs were used for pre- and postoperative FH, DH, SSA and lumbar sagittal alignment (LSA) measurements. The FH was measured as the maximum
EP
distance between the inferior and superior margins of the adjacent level pedicles. The
AC C
intervertebral DH was measured at the anterior portion of the disc as the distance between the superior and inferior endplates. Lateral neutral radiographs were used (Figure 3) to measure lumbar lordosis in the sagittal plane using the Cobb method, where the Cobb angle was measured from the superior endplate of L1 to the superior endplate of S1 vertebral bodies. SSA was determined by measuring sagittal alignment of the fused segment(s).
6
ACCEPTED MANUSCRIPT Villavicencio et al, The mean preoperative and postoperative values were compared for the 2 groups of patients who underwent TLIFs using bilateral PS or unilateral PS + ISFP fixation.
RI PT
Radiographic fusion rates were assessed using either plain radiographs or CT scans (Table 1). Fusion was defined as an evidence of trabecular bone bridging on the CT scans and less than a 5-degree difference in angular motion between flexion and extension, and/or no
SC
radiolucency lines greater than 2 mm in thickness covering more than 50% of the superior
M AN U
or inferior surface of the grafts on the plain radiographs.
Clinical Outcome Measures and Analysis
Standardized questionnaires were used to compare postoperative clinical outcomes, which
TE D
included health-related quality of life or functional outcomes assessed with the HealthRelated Quality of Life Questionnaire (Short Form-36 [SF-36]). Two scores within the scoring algorithm were analyzed: the Physical Component Summary (PCS) and Mental
EP
Component Summary Score (MCS). The Oswestry Disability Index was used to evaluate the
AC C
impact of impairment on activities of daily living. The severity of low back and leg pain was evaluated and compared using pre-and postoperative VAS (Visual Analog Scale) scores. In addition, patients were asked to complete a self-reported Patient Satisfaction With Results survey. A sample of the patient satisfaction survey is presented in Figure 4. Answers were scored on a scale from 0 to 100. A total score was calculated for each patient by averaging the scores from all 3 responses and the means were compared between the patient groups.
7
ACCEPTED MANUSCRIPT Villavicencio et al, Surgical Procedure
The surgical technique for the bilateral TLIF approach has been previously described
RI PT
(26,27). TLIF with unilateral PS and ISFP (Aspen, LANX, Broomfield, CO) fixation is
performed through a small midline incision over the spinous processes at the index
level(s), which is carried down through the fascial layers and subperiosteal plane along the
SC
spinous process and down the lamina bilaterally. The contralateral lamina and facets are fully left intact and preserved for posterolateral bone graft after decortication without
M AN U
requiring exposure of the transverse processes, thus minimizing the amount of postoperative pain and risk to the neural elements. The facet joints are identified, carefully exposed and a far lateral transfacet decompression is performed on the TLIF side with a complete removal of the facet joints and unroofing of the nerve roots above and below.
TE D
Bilateral decompressions are performed when indicated but the facet joint is left intact on the contralateral side of the TLIF so that a posterolateral fusion can be performed on that side. On the TLIF side, the medial border of the pedicles is directly visualized, which allows
EP
for a much more medial starting point for placement of pedicle screws and avoids
AC C
extensive lateral dissection, de-innervation and associated postoperative pain. Computer volumetric stereotactic navigation is utilized to place pedicle screws unilaterally, followed by the rod placement and distraction. Under microscopic visualization an annulotomy and complete discectomy is performed without retraction of the nerve roots because the far lateral transfacet approach allows for the proper lateral to medial trajectory. The endplate preparation follows with special attention paid to preserve the structural integrity of the endplates and maximize the fusion surface area. Structural grafts are sized and inserted
8
ACCEPTED MANUSCRIPT Villavicencio et al, with locally harvested autograft from the facetectomy and bone morphogenetic protein (rhBMP-2). The ISFP device is clamped around the adjacent spinous processes after
RI PT
compression across the rod and locking caps are placed.
RESULTS
SC
A mean follow up time was 25.9 months (range, 9 – 71; median 22) and 28.3 months
(range, 9 -66; median 24) in the bilateral PS fixation and unilateral PS fixation + ISFP
M AN U
groups, respectively. The selected demographics and surgical characteristics are presented in Table 1. Comparing patient demographics, there were no statistically significant differences in regards to sex, age or previous surgeries. The estimated blood loss, duration of procedure (operating room time) and the length of hospital stay were significantly lower
TE D
for one- and two-level procedures in the unilateral PS + ISFP patient group compared to the bilateral PS patient group.
AC C
EP
Radiographic Outcomes
All patients in the study received rhBMP-2, with average doses of 5.2 mg (range, 4.2 – 12) and 4.8 mg (range 2.1 – 12) in the unilateral PS + ISFP and bilateral pedicle fixation groups, respectively. The overall fusion rate was 96.5%. Three patients in the bilateral PS and 3 patients in the unilateral PS + ISFP patient group out of a total of 171 patients had pseudoarthrosis.
9
ACCEPTED MANUSCRIPT Villavicencio et al, Disc and Foraminal Height
A highly statistically significant mean DH increase (Table 2) was observed in the unilateral
RI PT
PS + ISFP (from 9.2 to 11.2 mm; 21.7% increase; P < 0.0001) and bilateral PS (from 9.2 to 10.2 mm; 10.9% increase; P = 0.0004) patient groups. Regardless of this, a statistically significant FH loss was detected in the bilateral PS patient group (from 17.1 to 16.3 mm;
SC
4.7% loss; P = 0.04) compared to FH height loss in the unilateral PS + ISFP patient group that was not statistically significant (from 19.0 to 18.4 mm; 3.2% loss; P = 0.1).
M AN U
In addition, for the patients in the unilateral PS + ISFP group who had postoperative MRI studies performed, the mean FH on the access and PS fixation side (16.1 mm) was compared to the FH on the opposite side (17.6 mm) and this difference was 1.5 mm (9.3%),
TE D
which was not statistically significant (P = 0.3).
Sagittal and Segmental Alignment
EP
The analysis of segmental and sagittal alignment (Table 3) did not demonstrate any
AC C
statistically significant differences. The mean LSA postoperatively increased by 4.1% in the bilateral PS patient group, but this was not quite statistically significant.
Clinical Outcomes
Clinical outcomes are presented in Table 4. Although the patients in both groups postoperatively reported significantly lower low back and leg VAS scores compared with
10
ACCEPTED MANUSCRIPT Villavicencio et al, preoperative values, there were no statistically significant differences between the patient groups that underwent surgery using unilateral PS + ISFP or bilateral PS. There were also no statistically significant differences when the postoperative Oswestry disability, SF-36
RI PT
and satisfaction scores were compared between the patient groups. The preoperative
scores were not available for the comparison, but the disability range of 21- 40% on the Oswestry scale represents the moderate level of disability and the average Oswestry scores
SC
were 24.1% and 24.8% in the unilateral PS + ISFP and bilateral PS patient groups,
M AN U
respectively.
Similar assessments could be made for the SF-36 MCS and PCS scores. The average and standardized SF-36 component summary scores of 50 with a standard deviation of 10 points were established as a norm for the general US population in 1998. While the SF-36
TE D
PCS scores were similar in both patient groups and lower than the statistical norm, the average SF-36 MCS scores were 49.0 and 53.2 in the unilateral PS + ISFP and bilateral PS patient groups, respectively. Summarizing the clinical outcome data, there were no
AC C
measurements.
EP
statistically significant differences between the groups in any of the clinical outcome
DISCUSSION
The main surgical goals of TLIF are restoration of normal spinal anatomy and achieving proper biomechanics and stability. The structural grafts restore the disc and foraminal height and correction of the sagittal alignment is achieved by compressing the pedicle
11
ACCEPTED MANUSCRIPT Villavicencio et al, screw construct, thus reducing the posterior aspect of the spine. Pedicle screws are used extensively for internal fixation of the lumbar spine, however, this comes at the cost of increased rates of complications (13,17,24), damage to the paraspinal muscles, and
RI PT
increased radiation exposure (19). The ISFP device as an adjunct to the unilateral pedicle screw fixation provides a viable alternative to bilateral pedicle screw instrumentation and potentially minimizes the risk for neural injury, vascular damage or CSF leak, while still
SC
providing sufficient segmental stabilization. Biomechanical properties of the ISFP plate as an adjunct to anterior lumbar interbody fusion (ALIF) (16) or TLIF (15) have been
M AN U
previously studied. The studies reported that use of ISFP provides a statistically equivalent stability to bilateral pedicle screws when used in addition to ALIF or TLIF and unilateral PS. The foraminal height increase was also reported in these biomechanical studies; however,
TE D
it was associated with focal kyphosis.
Another advantage of the supplemental ISFP and unilateral PS technique is that one facet is left completely intact and contralateral musculature, ligaments and tendons are preserved.
EP
Minimized soft tissue trauma translates to less postoperative pain, earlier mobilization and
AC C
return to work. Our study demonstrated a highly significant reduction of the operative time, blood loss and duration of hospitalization in the unilateral PS + ISFP patient group. In fact, our study results demonstrated even less blood loss (mean of 79.5 mL) and shorter OR time (mean 128 min) in the one-level unilateral PS + ISFP patient group compared to a minimally invasive PLIF and unilateral pedicle screw fixation procedure performed through a tubular retractor, where the average of 215 mL blood loss and 146.8 min surgery time for one-level procedures was reported (5).
12
ACCEPTED MANUSCRIPT Villavicencio et al, The study directly compared the effectiveness of TLIF with unilateral PS + ISFP versus TLIF with bilateral PS in modifying radiographic parameters including DH, FH, segmental and sagittal alignment. The LSA and SSA analysis revealed very little change when the mean
RI PT
preoperative and postoperative values were compared, which addressed the concerns raised by biomechanical studies in regards to induction of kyphosis by the ISFP device (15). Although some authors report significant sagittal alignment corrections in patients
SC
undergoing TLIF procedures, the loss of lordosis is not uncommon (9), especially if
bilateral osteotomies (12) or multilevel procedures are performed (30). The surgical
M AN U
technique and intraoperative positioning play an important role, but such factors as inability to place the interbody graft anteriorly or failure to achieve increased lordosis due to the rigidity of the intact contralateral facets were also described in the literature (9).
TE D
A highly significant postoperative DH restoration in both patient groups was observed, which did not translate into the FH height increase. There was a statistically significant FH loss in the bilateral PS patient group. Interestingly, the mean FH loss was slightly lower and
EP
was not statistically significant for patients in the unilateral PS + ISFP group. Based on our
AC C
experience, less compression is applied for unilateral PS than bilateral PS and rod constructs, which is done to avoid an unbalanced placement of the construct. As a result, some of FH restoration gained during intervertebral distraction is preserved and the supplemental ISFP fixation provides additional stability and rigidity needed to prevent graft dislodgement and enhance the fusion. In summary, our results contradicted the biomechanical study, which reported a statistically significant FH increase in constructs that included the ISFP device (15).
13
ACCEPTED MANUSCRIPT Villavicencio et al,
Although some researchers have reported that TLIFs performed with bilateral PS fixation have resulted in significant increases in FH (6,29), there were other reports demonstrating
RI PT
a loss of FH (9), or even induced radiculopathy on the contralateral side (11). Hsieh et al. (9) reported a significant FH loss in a TLIF group when comparing the restoration of FH in TLIF and ALIF surgeries. The authors thought that compression applied across the
SC
posterior elements after the positioning of the interbody graft was responsible for
reduction of FH. Hunt et al. reported a case of contralateral radiculopathy in a patient
M AN U
undergoing TLIF, which according to the authors was caused by the distraction on the pedicle screws or the disc space on the ipsilateral site, resulting in compression of the contralateral foramen (11). They recommended distracting the rod or to consider performing bilateral foraminotomies if there is a preexisting stenosis, because restoration
TE D
of normal lordosis could unmask foraminal stenosis symptoms on the contralateral side. This issue would be particularly concerning in unilateral TLIF procedures, because the contralateral side is left intact. In our study, a 9.3% FH difference was found between the
EP
access and contralateral side on MRI in the unilateral PS + ISFP patient group, which is
AC C
quite high compared to the postoperative FH changes. The issue of asymmetrical FHs on the approach and contralateral side is not specific to the unilateral PS fixation, but rather to the TLIF approach itself. Tohmeh et al. reported significantly greater FH measurements on the contralateral side for the TLIF approach with bilateral PS fixation (Tohmeh A, Isaacs RE, Sembrano JN, SOLAS Degenerative Study Group. XLIF vs. MAS TLIF for the Treatment of Degenerative Spondylolisthesis: Interim Results from an Ongoing Prospective Multi-Center
14
ACCEPTED MANUSCRIPT Villavicencio et al, Comparative Study. Presented at SMISS 2013 Annual Conference). Further investigations are needed to confirm these statements and clinical significance of our findings.
RI PT
Trends in spinal fusion surgeries are progressing towards less-invasive approaches that can minimize risk while maintaining the efficacy of the procedure to obtain good clinical outcomes. Although both surgical techniques were highly effective in reducing back pain
SC
and radiculopathy symptoms with quite high patient satisfaction scores, there were no statistically significant differences when clinical outcomes were compared between
M AN U
patients who underwent TLIFs using bilateral PS and unilateral PS + ISFP.
CONCLUSIONS
TE D
Significantly reduced surgical invasiveness was associated with unilateral PS + ISFP fixation, which represents the major advantage of this technique. Unilateral fixation was also associated with a slightly lower reduction in FH and was equally effective to bilateral
AC C
EP
PS fixation in regards to fusion rates, clinical and other radiographic outcomes studied.
15
ACCEPTED MANUSCRIPT Villavicencio et al, FIGURE LEGENDS: Figure 1. Antero-posterior (A) and lateral (B) radiographs showing unilateral PS + ISFP
RI PT
fixation spinal construct.
Figure 2. Antero-posterior (A) and lateral (B) radiographs showing bilateral PS fixation
SC
spinal construct.
Figure 3. Anterior disc height and foraminal height were measured using lateral
M AN U
radiographs obtained in the neutral position (A). The Cobb method was used to measure segmental and lumbar sagittal alignment (B).
AC C
EP
TE D
Figure 4. Patient Satisfaction Survey.
16
ACCEPTED MANUSCRIPT Villavicencio et al, REFERENCES:
Chen SH, Lin SC, Tsai WC, Wang CW, Chao SH: Biomechanical comparison of
RI PT
1.
unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery--a finite element analysis. BMC Musculoskelet
2.
SC
Disord 13:72, 2012.
Cole CD, McCall TD, Schmidt MH, Dailey AT: Comparison of low back fusion
M AN U
techniques: transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) approaches. Curr Rev Musculoskelet Med 2:118-126, 2009. 3.
Deutsch H, Musacchio MJ, Jr.: Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation. Neurosurg Focus 20:E10, 2006. Dhall SS, Wang MY, Mummaneni PV: Clinical and radiographic comparison of mini-
TE D
4.
open transforaminal lumbar interbody fusion with open transforaminal lumbar
565, 2008.
Dong J, Rong L, Feng F, Liu B, Xu Y, Wang Q, Chen R, Xie P: Unilateral pedicle screw
AC C
5.
EP
interbody fusion in 42 patients with long-term follow-up. J Neurosurg Spine 9:560-
fixation through a tubular retractor via the Wiltse approach compared with conventional bilateral pedicle screw fixation for single-segment degenerative lumbar instability: a prospective randomized study. J Neurosurg Spine 20:53-59, 2014.
17
ACCEPTED MANUSCRIPT Villavicencio et al, 6.
Fujibayashi S, Neo M, Takemoto M, Ota M, Nakamura T: Paraspinal-approach transforaminal lumbar interbody fusion for the treatment of lumbar foraminal stenosis. J Neurosurg Spine 13:500-508, 2010. Goel VK, Lim TH, Gwon J, Chen JY, Winterbottom JM, Park JB, Weinstein JN, Ahn JY:
RI PT
7.
Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation. Spine (Phila Pa 1976) 16:S155-161, 1991.
Harris BM, Hilibrand AS, Savas PE, Pellegrino A, Vaccaro AR, Siegler S, Albert TJ:
SC
8.
Transforaminal lumbar interbody fusion: the effect of various instrumentation
M AN U
techniques on the flexibility of the lumbar spine. Spine (Phila Pa 1976) 29:E65-70, 2004. 9.
Hsieh PC, Koski TR, O'Shaughnessy BA, Sugrue P, Salehi S, Ondra S, Liu JC: Anterior lumbar interbody fusion in comparison with transforaminal lumbar interbody
TE D
fusion: implications for the restoration of foraminal height, local disc angle, lumbar lordosis, and sagittal balance. J Neurosurg Spine 7:379-386, 2007. 10.
Humphreys SC, Hodges SD, Patwardhan AG, Eck JC, Murphy RB, Covington LA:
EP
Comparison of posterior and transforaminal approaches to lumbar interbody fusion.
11.
AC C
Spine (Phila Pa 1976) 26:567-571, 2001. Hunt T, Shen FH, Shaffrey CI, Arlet V: Contralateral radiculopathy after
transforaminal lumbar interbody fusion. Eur Spine J 16 Suppl 3:311-314, 2007.
12.
Jagannathan J, Sansur CA, Oskouian RJ, Jr., Fu KM, Shaffrey CI: Radiographic
restoration of lumbar alignment after transforaminal lumbar interbody fusion. Neurosurgery 64:955-963; discussion 963-954, 2009.
18
ACCEPTED MANUSCRIPT Villavicencio et al, 13.
Jutte PC, Castelein RM: Complications of pedicle screws in lumbar and lumbosacral fusions in 105 consecutive primary operations. Eur Spine J 11:594-598, 2002.
14.
Kabins MB, Weinstein JN, Spratt KF, Found EM, Goel VK, Woody J, Sayre HA: Isolated
RI PT
L4-L5 fusions using the variable screw placement system: unilateral versus bilateral. J Spinal Disord 5:39-49, 1992. 15.
Kaibara T, Karahalios DG, Porter RW, Kakarla UK, Reyes PM, Choi SK, Yaqoobi AS,
SC
Crawford NR: Biomechanics of a lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg 73:572-577, 2010.
Karahalios DG, Kaibara T, Porter RW, Kakarla UK, Reyes PM, Baaj AA, Yaqoobi AS,
M AN U
16.
Crawford NR: Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine 12:372-380, 2010. 17.
Kim MC, Chung HT, Cho JL, Kim DJ, Chung NS: Factors affecting the accurate
TE D
placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion. Eur Spine J 20:1635-1643, 2011. 18.
Moreland DB, Asch HL, Czajka GA, Overkamp JA, Sitzman DM: Posterior lumbar
EP
interbody fusion: comparison of single intervertebral cage and single side pedicle
AC C
screw fixation versus bilateral cages and screw fixation. Minim Invasive Neurosurg 52:132-136, 2009.
19.
Rampersaud YR, Foley KT, Shen AC, Williams S, Solomito M: Radiation exposure to
the spine surgeon during fluoroscopically assisted pedicle screw insertion. Spine (Phila Pa 1976) 25:2637-2645, 2000.
19
ACCEPTED MANUSCRIPT Villavicencio et al, 20.
Scheufler KM, Dohmen H, Vougioukas VI: Percutaneous transforaminal lumbar interbody fusion for the treatment of degenerative lumbar instability. Neurosurgery 60:203-212; discussion 212-203, 2007. Schleicher P, Beth P, Ottenbacher A, Pflugmacher R, Scholz M, Schnake KJ, Hass NP,
RI PT
21.
Kandziora F: Biomechanical evaluation of different asymmetrical posterior
fusion. J Neurosurg Spine 9:363-371, 2008. 22.
SC
stabilization methods for minimally invasive transforaminal lumbar interbody
Slucky AV, Brodke DS, Bachus KN, Droge JA, Braun JT: Less invasive posterior
analysis. Spine J 6:78-85, 2006. 23.
M AN U
fixation method following transforaminal lumbar interbody fusion: a biomechanical
Suk KS, Lee HM, Kim NH, Ha JW: Unilateral versus bilateral pedicle screw fixation in lumbar spinal fusion. Spine (Phila Pa 1976) 25:1843-1847, 2000 Suk SI, Kim WJ, Lee SM, Kim JH, Chung ER: Thoracic pedicle screw fixation in spinal
TE D
24.
deformities: are they really safe? Spine (Phila Pa 1976) 26:2049-2057, 2001. 25.
Tuttle J, Shakir A, Choudhri HF: Paramedian approach for transforaminal lumbar
EP
interbody fusion with unilateral pedicle screw fixation. Technical note and
26.
AC C
preliminary report on 47 cases. Neurosurg Focus 20:E5, 2006. Villavicencio AT, Burneikiene S, Bulsara KR, Thramann JJ: Perioperative
complications in transforaminal lumbar interbody fusion versus anterior-posterior reconstruction for lumbar disc degeneration and instability. J Spinal Disord Tech 19:92-97, 2006.
20
ACCEPTED MANUSCRIPT Villavicencio et al, 27.
Villavicencio AT, Burneikiene S, Nelson EL, Bulsara KR, Favors M, Thramann J: Safety of transforaminal lumbar interbody fusion and intervertebral recombinant human bone morphogenetic protein-2. J Neurosurg Spine 3:436-443, 2005. Xiaolong S, Lei W, Hailong Z, Xin G, Guangfei G, Shisheng H: Radiographic Analysis of
RI PT
28.
One-level Minimally Invasive Transforaminal Lumbar Interbody Fusion (MI-TLIF) With Unilateral Pedicle Screw Fixation for Lumbar Degenerative Diseases. J Spinal
29.
SC
Disord Tech, 2013.
Yan DL, Pei FX, Li J, Soo CL: Comparative study of PILF and TLIF treatment in adult
Yson SC, Santos ER, Sembrano JN, Polly DW, Jr.: Segmental lumbar sagittal correction after bilateral transforaminal lumbar interbody fusion. J Neurosurg Spine
EP
TE D
17:37-42, 2012.
AC C
30.
M AN U
degenerative spondylolisthesis. Eur Spine J 17:1311-1316, 2008.
21
ACCEPTED MANUSCRIPT
Bilateral PS
P
Patients (n)
96
75
-
Sex (M/F)
42/54
39/36
P = 0.4 *
Age
56.8 (20 – 91)
57.7 (27 – 81)
P = 0.7
Prev. surgeries
MCD/x1 = 11 (11.5%) MCD/x2 = 8 (8.3%) Laminectomy = 2 (2.1%)
MCD/x1 = 4 (5.3%) Foraminotomy = 1 (1.3%) Laminectomy = 9 (12.0%)
P = 0.7 *
Clinical Symptoms
Radiculopathy – 84 (87.5%) Radiculopathy – 64 (85.3%) P = 0.8* Stenosis – 48 (50.0%) Stenosis – 42 (56.0%) P = 0.5* Spondylolisthesis – 39 (40.6%) Spondylolisthesis – 36 (48.0%) P = 0.4*
TLIF Levels (n)
L3/L4 = 2 L4/L5 = 51 L5/S1 = 21 L3/L4 & L4/L5 = 14 L4/L5 & L5/S1 = 8
L4/L5 = 20 L5/S1 = 17 L3/L4 & L4/L5 = 7 L4/L5 & L5/S1 = 31
-
RhBMP-2 Dose (mg)
Total Dose: 5.2 (4.2 – 12.0)
Total Dose: 4.8 (2.1 – 12.0)
P = 0.169
EBL (mL)
One-Level: 79.5 (25 – 300) Two-Level: 217.9 (75 – 750)
One-Level: 196.5 (50 – 450) Two-Level: 337.5 (150 – 750)
P = 0.009 P < 0.0001
Surgery Time (min)
One-Level: 128 (71 – 225) Two-Level: 189 (149 – 221)
One-Level: 190 (90 – 240) Two-Level: 221 (180 – 266)
P < 0.0001 P = 0.03
One-Level: 3.0 (1 – 6) Two-Level: 3.4 (1 – 9)
P < 0.0001 P < 0.0001
CT Scans: 24% (18) X-rays: 76% (57)
P = 0.13*
SC
M AN U
TE D
EP
One-Level: 1.1 (0 - 6) Two-Level: 1.4 (0 – 3)
AC C
LOS (days)
Radiographic Fusion Assessment
RI PT
Unilateral PS + ISFP
CT Scans: 35% (34) X-rays: 65% (62)
Table 1. Selected Demographic, Clinical and Surgical Parameters. Values are presented as means (ranges) when appropriate. EBL, estimated blood loss; F, female; LOS, length of hospital stay; M, male. Student t tests were used for all calculations comparing the 2 groups except when noted (*), in which case χ2 tests were performed.
9.2 (2.0 – 17.0) 11.2 (5.3 – 18.0) < 0.0001
M AN U
Pre-Op Post-Op P value Foraminal Height (FH)
Bilateral PS
9.2 (2.8 – 17.5) 10.2 (1.4 – 18.8) 0.0004
SC
Unilateral PS + ISFP Disc Height (DH)
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
Pre-Op 19.0 (8.5 – 28.0) 17.1 (8.6 – 23.0) Post-Op 18.4 (10.0 – 33.0) 16.3 (7.8 – 23.4) P value 0.1 0.04 TABLE 2. Disc and foraminal height radiographic analysis. ISFP, interspinous process fixation plate; Pre-Op, preoperative; Post-Op, postoperative; PS, pedicle screws; Student t tests were used for all calculations comparing the 2 groups. The mean values are presented in mm.
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Bilateral PS Unilateral PS + ISFP Segmental Sagittal Alignment (SSA) Pre-Op 22.0 (8.2 – 51.8) 25.3 (4.5 – 44.5) Post-Op 22.1 (6.9 – 44.3) 25.4 (4.5 – 42.4) P value 0.9 0.9 Lumbar Sagittal Alignment (LSA) Pre-Op 51.1 (27.8 – 83.5) 50.9 (22.1 – 78) Post-Op 51.6 (25.3 – 83.5) 53.0 (29 – 78) P-value 0.6 0.08 TABLE 3. Change of segmental and sagittal alignment radiographic analysis. ISFP, interspinous process fixation plate; Pre-Op, preoperative; Post-Op, postoperative; PS, pedicle screws; Student t tests were used for all calculations. The mean values are presented in degrees and improvement percentage.
RI PT
ACCEPTED MANUSCRIPT
Bilateral PS
P
Pre-Op VAS Back
6.5 (0 -10)
6.2 (0-10)
0.5
Post-Op VAS Back
2.4 (0 -10)
VAS/Back Improvement (%)
63.1%/ P
S1878-8750(14)01383-7
DOI:
10.1016/j.wneu.2014.12.012
Reference:
WNEU 2621
To appear in:
World Neurosurgery
Received Date: 28 May 2014 Revised Date:
15 August 2014
Accepted Date: 9 December 2014
Please cite this article as: Villavicencio AT, Serxner BJ, Mason A, Nelson EL, Rajpal S, Faes N, Burneikiene S, Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody Fusion: Radiographic and Clinical Analysis, World Neurosurgery (2015), doi: 10.1016/ j.wneu.2014.12.012. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Villavicencio et al, Unilateral and Bilateral Pedicle Screw Fixation in Transforaminal Lumbar Interbody
RI PT
Fusion: Radiographic and Clinical Analysis
Alan T. Villavicencio, MD1, 2; Benjamin J. Serxner, MD2; Alexander Mason, MD1, 2; E. Lee
1 Boulder
Neurosurgical Associates, Boulder, CO
Parker Neurological Institute, Boulder, CO
EP
Corresponding Author:
TE D
2 Justin
M AN U
SC
Nelson, MD1, 2; Sharad Rajpal, MD1; Nathan Faes, BA2; Sigita Burneikiene, MD1, 2
AC C
Sigita Burneikiene, MD
Boulder Neurosurgical Associates 4743 Arapahoe Avenue, Suite 202 Boulder, CO 80303
Phone: 303-938-5700 Fax: 303-998-0007 [email protected]
1
ACCEPTED MANUSCRIPT Villavicencio et al, ABSTRACT Objective Transforaminal lumbar interbody fusion with bilateral segmental pedicle screw fixation is
RI PT
a widely used and well-recognized technique that is performed to provide fixation and load-bearing capacity while restoring morphometric spine parameters and relieving
symptoms in patients with degenerative disc disease. A supplemental interspinous process
SC
fixation plate (ISFP) as an adjunct to unilateral PS fixation allows for reduced invasiveness of this technique as compared to bilateral PS placement. The biomechanical comparison
studied in clinical settings.
Methods
M AN U
results have been previously reported, but the significance of these findings has not been
TE D
A prospective cohort study with a supplemental retrospective chart review and radiographic analysis was performed. The patients were divided into two groups: surgeries that were performed using bilateral PS fixation (n=75) or unilateral PS fixation + ISFP
EP
(n=96). Lateral lumbar standing radiographs were used for pre- and postoperative
AC C
foraminal height (FH), disc height (DH), segmental (SSA) and lumbar sagittal alignment (LSA) measurements. Standardized questionnaires were used to compare postoperative clinical outcomes.
Results The estimated blood loss, duration of procedure and the length of hospital stay were significantly lower for one- and two-level procedures in the unilateral PS + ISFP patient
2
ACCEPTED MANUSCRIPT Villavicencio et al, group. A statistically significant mean DH increase was observed in both groups. Regardless of this, a statistically significant FH loss was detected in the bilateral PS patient group (from 17.1 to 16.3 mm; 4.7% loss; P=0.04) compared to FH height loss in the unilateral PS + ISFP
RI PT
patient group that was not statistically significant (from 19.0 to 18.4 mm; 3.2% loss; P=0.1). The analysis of SSA, LSA, clinical outcomes and fusion rates did not demonstrate any
SC
statistically significant differences.
Conclusions
M AN U
Significantly reduced surgical invasiveness was associated with unilateral PS + ISFP fixation, which represents the major advantage of this technique. Unilateral fixation was also associated with a slightly lower reduction in FH and was equally effective to bilateral
TE D
PS fixation in regards to fusion rates, clinical and other radiographic outcomes studied.
Keywords: Foraminal height; lumbar spine; pedicle screws; plate fixation; transforaminal
EP
lumbar interbody fusion.
AC C
Abbreviations: ALIF – anterior lumbar interbody fusion; DH - disc height; FH - foraminal height; ISFP - interspinous process fixation plate; LSA – lumbar sagittal alignment; MCS – mental component summary; PCS – physical component summary; PLIF – posterior lumbar interbody fusion; PS – pedicle screw; rhBMP-2 – recombinant human bone morphogenetic protein-2; SSA - segmental sagittal alignment; TLIF – transforaminal lumbar interbody fusion; VAS – visual analog scale; XLIF – extreme lateral interbody fusion.
3
ACCEPTED MANUSCRIPT Villavicencio et al, INTRODUCTION
Transforaminal lumbar interbody fusion (TLIF) with bilateral segmental pedicle screw
RI PT
fixation is a widely used and well-recognized technique that is performed to provide
fixation and load-bearing capacity while restoring morphometric spine parameters and relieving symptoms in patients with degenerative disc disease. TLIF allows a unilateral
SC
paraspinal approach, therefore is less invasive than other conventional posterior midline surgical techniques (2,10). In order to further minimize surgical exposure and iatrogenic
M AN U
morbidity, several technique modifications have been explored (3,4,20). One of them, unilateral pedicle screw fixation allows ipsilateral pedicle screw placement without the need to damage the contralateral muscles and soft tissues. Although several clinical reports demonstrated effectiveness of this technique (3,5,14,18,23,25,28), some biomechanical
TE D
studies noted off-axis rotational or coupled motions resulting from the construct asymmetry and inability to provide adequate rigidity, which could be detrimental to the promotion of fusion (1,7,8,21,22). A supplemental interspinous process fixation plate
EP
(ISFP) as an adjunct to unilateral PS fixation significantly improves stability in all planes
AC C
and may offer a good and less-invasive alternative to bilateral PS fixation based on a recent biomechanical study (15). The authors concluded that 2 methods of fixation that most closely reproduced the stability of the intact spine were bilateral pedicle screws and ISFP as an adjunct to unilateral pedicle screw fixation. The significance of these findings and the ability of this technique to achieve the same goals have not been studied in clinical settings.
4
ACCEPTED MANUSCRIPT Villavicencio et al, The main objectives of this study were to evaluate surgical, radiographic and clinical parameters in patients who underwent TLIF with bilateral or unilateral PS fixation with ISFP and to compare the effectiveness of these techniques in restoring disc height (DH),
RI PT
foraminal height (FH), lumbar lordosis, segmental sagittal alignment (SSA).
SC
METHODS
A prospective cohort study with a supplemental retrospective chart review and
M AN U
radiographic analysis was performed. This study analyzed all consecutive cases that met the following inclusion criteria: one- or two-level TLIF surgeries performed for painful degenerative disc disease at L3 – S1 levels in the setting of symptomatic spinal stenosis and/or lateral recess stenosis requiring surgical decompression to the extent that would
TE D
result in destabilizing the spine; unstable spondylolisthesis (≤ Grade II); no previous fusion surgeries; and availability of preoperative and postoperative (≥9 months) imaging studies. Patients were selected for surgery based on clinical symptoms, which included intractable
EP
low back pain and radiculopathy caused by spondylosis and/or disc herniation, foraminal
AC C
and/or central stenosis, and spondylolisthesis (Table 1). The surgeries included in this analysis were performed from May 2008 to November 2010. The patients were divided into the two groups for further analysis: surgeries that were performed using bilateral PS fixation (n = 75) or unilateral PS fixation + ISFP (n = 96) Figures 1 and 2 show spinal hardware constructs for comparison.
5
ACCEPTED MANUSCRIPT Villavicencio et al, Choice of unilateral or bilateral PS fixation was based on surgeon preference. All unilateral PS + ISFP fixation surgeries were performed by a first author (ATV) and bilateral fixation cases were performed by AM, and ELN, except for 13 out of 75 cases (ATV) where the
RI PT
unilateral screws were not felt to have adequate purchase with regards to the bone-screw interface. In this case, 13 intended unilateral cases were converted to bilateral PS fixation based on intraoperative findings with regards to screw purchase. In these cases bilateral
SC
screws were placed in lieu of unilateral pedicle screw fixation and a spinous process plate.
M AN U
Clinical outcome assessment and radiographic measurements were performed by authors SB and BJS, respectively, who were not involved in patient care.
TE D
Radiographic Outcome Measures and Analysis
Lateral lumbar standing radiographs were used for pre- and postoperative FH, DH, SSA and lumbar sagittal alignment (LSA) measurements. The FH was measured as the maximum
EP
distance between the inferior and superior margins of the adjacent level pedicles. The
AC C
intervertebral DH was measured at the anterior portion of the disc as the distance between the superior and inferior endplates. Lateral neutral radiographs were used (Figure 3) to measure lumbar lordosis in the sagittal plane using the Cobb method, where the Cobb angle was measured from the superior endplate of L1 to the superior endplate of S1 vertebral bodies. SSA was determined by measuring sagittal alignment of the fused segment(s).
6
ACCEPTED MANUSCRIPT Villavicencio et al, The mean preoperative and postoperative values were compared for the 2 groups of patients who underwent TLIFs using bilateral PS or unilateral PS + ISFP fixation.
RI PT
Radiographic fusion rates were assessed using either plain radiographs or CT scans (Table 1). Fusion was defined as an evidence of trabecular bone bridging on the CT scans and less than a 5-degree difference in angular motion between flexion and extension, and/or no
SC
radiolucency lines greater than 2 mm in thickness covering more than 50% of the superior
M AN U
or inferior surface of the grafts on the plain radiographs.
Clinical Outcome Measures and Analysis
Standardized questionnaires were used to compare postoperative clinical outcomes, which
TE D
included health-related quality of life or functional outcomes assessed with the HealthRelated Quality of Life Questionnaire (Short Form-36 [SF-36]). Two scores within the scoring algorithm were analyzed: the Physical Component Summary (PCS) and Mental
EP
Component Summary Score (MCS). The Oswestry Disability Index was used to evaluate the
AC C
impact of impairment on activities of daily living. The severity of low back and leg pain was evaluated and compared using pre-and postoperative VAS (Visual Analog Scale) scores. In addition, patients were asked to complete a self-reported Patient Satisfaction With Results survey. A sample of the patient satisfaction survey is presented in Figure 4. Answers were scored on a scale from 0 to 100. A total score was calculated for each patient by averaging the scores from all 3 responses and the means were compared between the patient groups.
7
ACCEPTED MANUSCRIPT Villavicencio et al, Surgical Procedure
The surgical technique for the bilateral TLIF approach has been previously described
RI PT
(26,27). TLIF with unilateral PS and ISFP (Aspen, LANX, Broomfield, CO) fixation is
performed through a small midline incision over the spinous processes at the index
level(s), which is carried down through the fascial layers and subperiosteal plane along the
SC
spinous process and down the lamina bilaterally. The contralateral lamina and facets are fully left intact and preserved for posterolateral bone graft after decortication without
M AN U
requiring exposure of the transverse processes, thus minimizing the amount of postoperative pain and risk to the neural elements. The facet joints are identified, carefully exposed and a far lateral transfacet decompression is performed on the TLIF side with a complete removal of the facet joints and unroofing of the nerve roots above and below.
TE D
Bilateral decompressions are performed when indicated but the facet joint is left intact on the contralateral side of the TLIF so that a posterolateral fusion can be performed on that side. On the TLIF side, the medial border of the pedicles is directly visualized, which allows
EP
for a much more medial starting point for placement of pedicle screws and avoids
AC C
extensive lateral dissection, de-innervation and associated postoperative pain. Computer volumetric stereotactic navigation is utilized to place pedicle screws unilaterally, followed by the rod placement and distraction. Under microscopic visualization an annulotomy and complete discectomy is performed without retraction of the nerve roots because the far lateral transfacet approach allows for the proper lateral to medial trajectory. The endplate preparation follows with special attention paid to preserve the structural integrity of the endplates and maximize the fusion surface area. Structural grafts are sized and inserted
8
ACCEPTED MANUSCRIPT Villavicencio et al, with locally harvested autograft from the facetectomy and bone morphogenetic protein (rhBMP-2). The ISFP device is clamped around the adjacent spinous processes after
RI PT
compression across the rod and locking caps are placed.
RESULTS
SC
A mean follow up time was 25.9 months (range, 9 – 71; median 22) and 28.3 months
(range, 9 -66; median 24) in the bilateral PS fixation and unilateral PS fixation + ISFP
M AN U
groups, respectively. The selected demographics and surgical characteristics are presented in Table 1. Comparing patient demographics, there were no statistically significant differences in regards to sex, age or previous surgeries. The estimated blood loss, duration of procedure (operating room time) and the length of hospital stay were significantly lower
TE D
for one- and two-level procedures in the unilateral PS + ISFP patient group compared to the bilateral PS patient group.
AC C
EP
Radiographic Outcomes
All patients in the study received rhBMP-2, with average doses of 5.2 mg (range, 4.2 – 12) and 4.8 mg (range 2.1 – 12) in the unilateral PS + ISFP and bilateral pedicle fixation groups, respectively. The overall fusion rate was 96.5%. Three patients in the bilateral PS and 3 patients in the unilateral PS + ISFP patient group out of a total of 171 patients had pseudoarthrosis.
9
ACCEPTED MANUSCRIPT Villavicencio et al, Disc and Foraminal Height
A highly statistically significant mean DH increase (Table 2) was observed in the unilateral
RI PT
PS + ISFP (from 9.2 to 11.2 mm; 21.7% increase; P < 0.0001) and bilateral PS (from 9.2 to 10.2 mm; 10.9% increase; P = 0.0004) patient groups. Regardless of this, a statistically significant FH loss was detected in the bilateral PS patient group (from 17.1 to 16.3 mm;
SC
4.7% loss; P = 0.04) compared to FH height loss in the unilateral PS + ISFP patient group that was not statistically significant (from 19.0 to 18.4 mm; 3.2% loss; P = 0.1).
M AN U
In addition, for the patients in the unilateral PS + ISFP group who had postoperative MRI studies performed, the mean FH on the access and PS fixation side (16.1 mm) was compared to the FH on the opposite side (17.6 mm) and this difference was 1.5 mm (9.3%),
TE D
which was not statistically significant (P = 0.3).
Sagittal and Segmental Alignment
EP
The analysis of segmental and sagittal alignment (Table 3) did not demonstrate any
AC C
statistically significant differences. The mean LSA postoperatively increased by 4.1% in the bilateral PS patient group, but this was not quite statistically significant.
Clinical Outcomes
Clinical outcomes are presented in Table 4. Although the patients in both groups postoperatively reported significantly lower low back and leg VAS scores compared with
10
ACCEPTED MANUSCRIPT Villavicencio et al, preoperative values, there were no statistically significant differences between the patient groups that underwent surgery using unilateral PS + ISFP or bilateral PS. There were also no statistically significant differences when the postoperative Oswestry disability, SF-36
RI PT
and satisfaction scores were compared between the patient groups. The preoperative
scores were not available for the comparison, but the disability range of 21- 40% on the Oswestry scale represents the moderate level of disability and the average Oswestry scores
SC
were 24.1% and 24.8% in the unilateral PS + ISFP and bilateral PS patient groups,
M AN U
respectively.
Similar assessments could be made for the SF-36 MCS and PCS scores. The average and standardized SF-36 component summary scores of 50 with a standard deviation of 10 points were established as a norm for the general US population in 1998. While the SF-36
TE D
PCS scores were similar in both patient groups and lower than the statistical norm, the average SF-36 MCS scores were 49.0 and 53.2 in the unilateral PS + ISFP and bilateral PS patient groups, respectively. Summarizing the clinical outcome data, there were no
AC C
measurements.
EP
statistically significant differences between the groups in any of the clinical outcome
DISCUSSION
The main surgical goals of TLIF are restoration of normal spinal anatomy and achieving proper biomechanics and stability. The structural grafts restore the disc and foraminal height and correction of the sagittal alignment is achieved by compressing the pedicle
11
ACCEPTED MANUSCRIPT Villavicencio et al, screw construct, thus reducing the posterior aspect of the spine. Pedicle screws are used extensively for internal fixation of the lumbar spine, however, this comes at the cost of increased rates of complications (13,17,24), damage to the paraspinal muscles, and
RI PT
increased radiation exposure (19). The ISFP device as an adjunct to the unilateral pedicle screw fixation provides a viable alternative to bilateral pedicle screw instrumentation and potentially minimizes the risk for neural injury, vascular damage or CSF leak, while still
SC
providing sufficient segmental stabilization. Biomechanical properties of the ISFP plate as an adjunct to anterior lumbar interbody fusion (ALIF) (16) or TLIF (15) have been
M AN U
previously studied. The studies reported that use of ISFP provides a statistically equivalent stability to bilateral pedicle screws when used in addition to ALIF or TLIF and unilateral PS. The foraminal height increase was also reported in these biomechanical studies; however,
TE D
it was associated with focal kyphosis.
Another advantage of the supplemental ISFP and unilateral PS technique is that one facet is left completely intact and contralateral musculature, ligaments and tendons are preserved.
EP
Minimized soft tissue trauma translates to less postoperative pain, earlier mobilization and
AC C
return to work. Our study demonstrated a highly significant reduction of the operative time, blood loss and duration of hospitalization in the unilateral PS + ISFP patient group. In fact, our study results demonstrated even less blood loss (mean of 79.5 mL) and shorter OR time (mean 128 min) in the one-level unilateral PS + ISFP patient group compared to a minimally invasive PLIF and unilateral pedicle screw fixation procedure performed through a tubular retractor, where the average of 215 mL blood loss and 146.8 min surgery time for one-level procedures was reported (5).
12
ACCEPTED MANUSCRIPT Villavicencio et al, The study directly compared the effectiveness of TLIF with unilateral PS + ISFP versus TLIF with bilateral PS in modifying radiographic parameters including DH, FH, segmental and sagittal alignment. The LSA and SSA analysis revealed very little change when the mean
RI PT
preoperative and postoperative values were compared, which addressed the concerns raised by biomechanical studies in regards to induction of kyphosis by the ISFP device (15). Although some authors report significant sagittal alignment corrections in patients
SC
undergoing TLIF procedures, the loss of lordosis is not uncommon (9), especially if
bilateral osteotomies (12) or multilevel procedures are performed (30). The surgical
M AN U
technique and intraoperative positioning play an important role, but such factors as inability to place the interbody graft anteriorly or failure to achieve increased lordosis due to the rigidity of the intact contralateral facets were also described in the literature (9).
TE D
A highly significant postoperative DH restoration in both patient groups was observed, which did not translate into the FH height increase. There was a statistically significant FH loss in the bilateral PS patient group. Interestingly, the mean FH loss was slightly lower and
EP
was not statistically significant for patients in the unilateral PS + ISFP group. Based on our
AC C
experience, less compression is applied for unilateral PS than bilateral PS and rod constructs, which is done to avoid an unbalanced placement of the construct. As a result, some of FH restoration gained during intervertebral distraction is preserved and the supplemental ISFP fixation provides additional stability and rigidity needed to prevent graft dislodgement and enhance the fusion. In summary, our results contradicted the biomechanical study, which reported a statistically significant FH increase in constructs that included the ISFP device (15).
13
ACCEPTED MANUSCRIPT Villavicencio et al,
Although some researchers have reported that TLIFs performed with bilateral PS fixation have resulted in significant increases in FH (6,29), there were other reports demonstrating
RI PT
a loss of FH (9), or even induced radiculopathy on the contralateral side (11). Hsieh et al. (9) reported a significant FH loss in a TLIF group when comparing the restoration of FH in TLIF and ALIF surgeries. The authors thought that compression applied across the
SC
posterior elements after the positioning of the interbody graft was responsible for
reduction of FH. Hunt et al. reported a case of contralateral radiculopathy in a patient
M AN U
undergoing TLIF, which according to the authors was caused by the distraction on the pedicle screws or the disc space on the ipsilateral site, resulting in compression of the contralateral foramen (11). They recommended distracting the rod or to consider performing bilateral foraminotomies if there is a preexisting stenosis, because restoration
TE D
of normal lordosis could unmask foraminal stenosis symptoms on the contralateral side. This issue would be particularly concerning in unilateral TLIF procedures, because the contralateral side is left intact. In our study, a 9.3% FH difference was found between the
EP
access and contralateral side on MRI in the unilateral PS + ISFP patient group, which is
AC C
quite high compared to the postoperative FH changes. The issue of asymmetrical FHs on the approach and contralateral side is not specific to the unilateral PS fixation, but rather to the TLIF approach itself. Tohmeh et al. reported significantly greater FH measurements on the contralateral side for the TLIF approach with bilateral PS fixation (Tohmeh A, Isaacs RE, Sembrano JN, SOLAS Degenerative Study Group. XLIF vs. MAS TLIF for the Treatment of Degenerative Spondylolisthesis: Interim Results from an Ongoing Prospective Multi-Center
14
ACCEPTED MANUSCRIPT Villavicencio et al, Comparative Study. Presented at SMISS 2013 Annual Conference). Further investigations are needed to confirm these statements and clinical significance of our findings.
RI PT
Trends in spinal fusion surgeries are progressing towards less-invasive approaches that can minimize risk while maintaining the efficacy of the procedure to obtain good clinical outcomes. Although both surgical techniques were highly effective in reducing back pain
SC
and radiculopathy symptoms with quite high patient satisfaction scores, there were no statistically significant differences when clinical outcomes were compared between
M AN U
patients who underwent TLIFs using bilateral PS and unilateral PS + ISFP.
CONCLUSIONS
TE D
Significantly reduced surgical invasiveness was associated with unilateral PS + ISFP fixation, which represents the major advantage of this technique. Unilateral fixation was also associated with a slightly lower reduction in FH and was equally effective to bilateral
AC C
EP
PS fixation in regards to fusion rates, clinical and other radiographic outcomes studied.
15
ACCEPTED MANUSCRIPT Villavicencio et al, FIGURE LEGENDS: Figure 1. Antero-posterior (A) and lateral (B) radiographs showing unilateral PS + ISFP
RI PT
fixation spinal construct.
Figure 2. Antero-posterior (A) and lateral (B) radiographs showing bilateral PS fixation
SC
spinal construct.
Figure 3. Anterior disc height and foraminal height were measured using lateral
M AN U
radiographs obtained in the neutral position (A). The Cobb method was used to measure segmental and lumbar sagittal alignment (B).
AC C
EP
TE D
Figure 4. Patient Satisfaction Survey.
16
ACCEPTED MANUSCRIPT Villavicencio et al, REFERENCES:
Chen SH, Lin SC, Tsai WC, Wang CW, Chao SH: Biomechanical comparison of
RI PT
1.
unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery--a finite element analysis. BMC Musculoskelet
2.
SC
Disord 13:72, 2012.
Cole CD, McCall TD, Schmidt MH, Dailey AT: Comparison of low back fusion
M AN U
techniques: transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) approaches. Curr Rev Musculoskelet Med 2:118-126, 2009. 3.
Deutsch H, Musacchio MJ, Jr.: Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation. Neurosurg Focus 20:E10, 2006. Dhall SS, Wang MY, Mummaneni PV: Clinical and radiographic comparison of mini-
TE D
4.
open transforaminal lumbar interbody fusion with open transforaminal lumbar
565, 2008.
Dong J, Rong L, Feng F, Liu B, Xu Y, Wang Q, Chen R, Xie P: Unilateral pedicle screw
AC C
5.
EP
interbody fusion in 42 patients with long-term follow-up. J Neurosurg Spine 9:560-
fixation through a tubular retractor via the Wiltse approach compared with conventional bilateral pedicle screw fixation for single-segment degenerative lumbar instability: a prospective randomized study. J Neurosurg Spine 20:53-59, 2014.
17
ACCEPTED MANUSCRIPT Villavicencio et al, 6.
Fujibayashi S, Neo M, Takemoto M, Ota M, Nakamura T: Paraspinal-approach transforaminal lumbar interbody fusion for the treatment of lumbar foraminal stenosis. J Neurosurg Spine 13:500-508, 2010. Goel VK, Lim TH, Gwon J, Chen JY, Winterbottom JM, Park JB, Weinstein JN, Ahn JY:
RI PT
7.
Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation. Spine (Phila Pa 1976) 16:S155-161, 1991.
Harris BM, Hilibrand AS, Savas PE, Pellegrino A, Vaccaro AR, Siegler S, Albert TJ:
SC
8.
Transforaminal lumbar interbody fusion: the effect of various instrumentation
M AN U
techniques on the flexibility of the lumbar spine. Spine (Phila Pa 1976) 29:E65-70, 2004. 9.
Hsieh PC, Koski TR, O'Shaughnessy BA, Sugrue P, Salehi S, Ondra S, Liu JC: Anterior lumbar interbody fusion in comparison with transforaminal lumbar interbody
TE D
fusion: implications for the restoration of foraminal height, local disc angle, lumbar lordosis, and sagittal balance. J Neurosurg Spine 7:379-386, 2007. 10.
Humphreys SC, Hodges SD, Patwardhan AG, Eck JC, Murphy RB, Covington LA:
EP
Comparison of posterior and transforaminal approaches to lumbar interbody fusion.
11.
AC C
Spine (Phila Pa 1976) 26:567-571, 2001. Hunt T, Shen FH, Shaffrey CI, Arlet V: Contralateral radiculopathy after
transforaminal lumbar interbody fusion. Eur Spine J 16 Suppl 3:311-314, 2007.
12.
Jagannathan J, Sansur CA, Oskouian RJ, Jr., Fu KM, Shaffrey CI: Radiographic
restoration of lumbar alignment after transforaminal lumbar interbody fusion. Neurosurgery 64:955-963; discussion 963-954, 2009.
18
ACCEPTED MANUSCRIPT Villavicencio et al, 13.
Jutte PC, Castelein RM: Complications of pedicle screws in lumbar and lumbosacral fusions in 105 consecutive primary operations. Eur Spine J 11:594-598, 2002.
14.
Kabins MB, Weinstein JN, Spratt KF, Found EM, Goel VK, Woody J, Sayre HA: Isolated
RI PT
L4-L5 fusions using the variable screw placement system: unilateral versus bilateral. J Spinal Disord 5:39-49, 1992. 15.
Kaibara T, Karahalios DG, Porter RW, Kakarla UK, Reyes PM, Choi SK, Yaqoobi AS,
SC
Crawford NR: Biomechanics of a lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg 73:572-577, 2010.
Karahalios DG, Kaibara T, Porter RW, Kakarla UK, Reyes PM, Baaj AA, Yaqoobi AS,
M AN U
16.
Crawford NR: Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine 12:372-380, 2010. 17.
Kim MC, Chung HT, Cho JL, Kim DJ, Chung NS: Factors affecting the accurate
TE D
placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion. Eur Spine J 20:1635-1643, 2011. 18.
Moreland DB, Asch HL, Czajka GA, Overkamp JA, Sitzman DM: Posterior lumbar
EP
interbody fusion: comparison of single intervertebral cage and single side pedicle
AC C
screw fixation versus bilateral cages and screw fixation. Minim Invasive Neurosurg 52:132-136, 2009.
19.
Rampersaud YR, Foley KT, Shen AC, Williams S, Solomito M: Radiation exposure to
the spine surgeon during fluoroscopically assisted pedicle screw insertion. Spine (Phila Pa 1976) 25:2637-2645, 2000.
19
ACCEPTED MANUSCRIPT Villavicencio et al, 20.
Scheufler KM, Dohmen H, Vougioukas VI: Percutaneous transforaminal lumbar interbody fusion for the treatment of degenerative lumbar instability. Neurosurgery 60:203-212; discussion 212-203, 2007. Schleicher P, Beth P, Ottenbacher A, Pflugmacher R, Scholz M, Schnake KJ, Hass NP,
RI PT
21.
Kandziora F: Biomechanical evaluation of different asymmetrical posterior
fusion. J Neurosurg Spine 9:363-371, 2008. 22.
SC
stabilization methods for minimally invasive transforaminal lumbar interbody
Slucky AV, Brodke DS, Bachus KN, Droge JA, Braun JT: Less invasive posterior
analysis. Spine J 6:78-85, 2006. 23.
M AN U
fixation method following transforaminal lumbar interbody fusion: a biomechanical
Suk KS, Lee HM, Kim NH, Ha JW: Unilateral versus bilateral pedicle screw fixation in lumbar spinal fusion. Spine (Phila Pa 1976) 25:1843-1847, 2000 Suk SI, Kim WJ, Lee SM, Kim JH, Chung ER: Thoracic pedicle screw fixation in spinal
TE D
24.
deformities: are they really safe? Spine (Phila Pa 1976) 26:2049-2057, 2001. 25.
Tuttle J, Shakir A, Choudhri HF: Paramedian approach for transforaminal lumbar
EP
interbody fusion with unilateral pedicle screw fixation. Technical note and
26.
AC C
preliminary report on 47 cases. Neurosurg Focus 20:E5, 2006. Villavicencio AT, Burneikiene S, Bulsara KR, Thramann JJ: Perioperative
complications in transforaminal lumbar interbody fusion versus anterior-posterior reconstruction for lumbar disc degeneration and instability. J Spinal Disord Tech 19:92-97, 2006.
20
ACCEPTED MANUSCRIPT Villavicencio et al, 27.
Villavicencio AT, Burneikiene S, Nelson EL, Bulsara KR, Favors M, Thramann J: Safety of transforaminal lumbar interbody fusion and intervertebral recombinant human bone morphogenetic protein-2. J Neurosurg Spine 3:436-443, 2005. Xiaolong S, Lei W, Hailong Z, Xin G, Guangfei G, Shisheng H: Radiographic Analysis of
RI PT
28.
One-level Minimally Invasive Transforaminal Lumbar Interbody Fusion (MI-TLIF) With Unilateral Pedicle Screw Fixation for Lumbar Degenerative Diseases. J Spinal
29.
SC
Disord Tech, 2013.
Yan DL, Pei FX, Li J, Soo CL: Comparative study of PILF and TLIF treatment in adult
Yson SC, Santos ER, Sembrano JN, Polly DW, Jr.: Segmental lumbar sagittal correction after bilateral transforaminal lumbar interbody fusion. J Neurosurg Spine
EP
TE D
17:37-42, 2012.
AC C
30.
M AN U
degenerative spondylolisthesis. Eur Spine J 17:1311-1316, 2008.
21
ACCEPTED MANUSCRIPT
Bilateral PS
P
Patients (n)
96
75
-
Sex (M/F)
42/54
39/36
P = 0.4 *
Age
56.8 (20 – 91)
57.7 (27 – 81)
P = 0.7
Prev. surgeries
MCD/x1 = 11 (11.5%) MCD/x2 = 8 (8.3%) Laminectomy = 2 (2.1%)
MCD/x1 = 4 (5.3%) Foraminotomy = 1 (1.3%) Laminectomy = 9 (12.0%)
P = 0.7 *
Clinical Symptoms
Radiculopathy – 84 (87.5%) Radiculopathy – 64 (85.3%) P = 0.8* Stenosis – 48 (50.0%) Stenosis – 42 (56.0%) P = 0.5* Spondylolisthesis – 39 (40.6%) Spondylolisthesis – 36 (48.0%) P = 0.4*
TLIF Levels (n)
L3/L4 = 2 L4/L5 = 51 L5/S1 = 21 L3/L4 & L4/L5 = 14 L4/L5 & L5/S1 = 8
L4/L5 = 20 L5/S1 = 17 L3/L4 & L4/L5 = 7 L4/L5 & L5/S1 = 31
-
RhBMP-2 Dose (mg)
Total Dose: 5.2 (4.2 – 12.0)
Total Dose: 4.8 (2.1 – 12.0)
P = 0.169
EBL (mL)
One-Level: 79.5 (25 – 300) Two-Level: 217.9 (75 – 750)
One-Level: 196.5 (50 – 450) Two-Level: 337.5 (150 – 750)
P = 0.009 P < 0.0001
Surgery Time (min)
One-Level: 128 (71 – 225) Two-Level: 189 (149 – 221)
One-Level: 190 (90 – 240) Two-Level: 221 (180 – 266)
P < 0.0001 P = 0.03
One-Level: 3.0 (1 – 6) Two-Level: 3.4 (1 – 9)
P < 0.0001 P < 0.0001
CT Scans: 24% (18) X-rays: 76% (57)
P = 0.13*
SC
M AN U
TE D
EP
One-Level: 1.1 (0 - 6) Two-Level: 1.4 (0 – 3)
AC C
LOS (days)
Radiographic Fusion Assessment
RI PT
Unilateral PS + ISFP
CT Scans: 35% (34) X-rays: 65% (62)
Table 1. Selected Demographic, Clinical and Surgical Parameters. Values are presented as means (ranges) when appropriate. EBL, estimated blood loss; F, female; LOS, length of hospital stay; M, male. Student t tests were used for all calculations comparing the 2 groups except when noted (*), in which case χ2 tests were performed.
9.2 (2.0 – 17.0) 11.2 (5.3 – 18.0) < 0.0001
M AN U
Pre-Op Post-Op P value Foraminal Height (FH)
Bilateral PS
9.2 (2.8 – 17.5) 10.2 (1.4 – 18.8) 0.0004
SC
Unilateral PS + ISFP Disc Height (DH)
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
Pre-Op 19.0 (8.5 – 28.0) 17.1 (8.6 – 23.0) Post-Op 18.4 (10.0 – 33.0) 16.3 (7.8 – 23.4) P value 0.1 0.04 TABLE 2. Disc and foraminal height radiographic analysis. ISFP, interspinous process fixation plate; Pre-Op, preoperative; Post-Op, postoperative; PS, pedicle screws; Student t tests were used for all calculations comparing the 2 groups. The mean values are presented in mm.
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Bilateral PS Unilateral PS + ISFP Segmental Sagittal Alignment (SSA) Pre-Op 22.0 (8.2 – 51.8) 25.3 (4.5 – 44.5) Post-Op 22.1 (6.9 – 44.3) 25.4 (4.5 – 42.4) P value 0.9 0.9 Lumbar Sagittal Alignment (LSA) Pre-Op 51.1 (27.8 – 83.5) 50.9 (22.1 – 78) Post-Op 51.6 (25.3 – 83.5) 53.0 (29 – 78) P-value 0.6 0.08 TABLE 3. Change of segmental and sagittal alignment radiographic analysis. ISFP, interspinous process fixation plate; Pre-Op, preoperative; Post-Op, postoperative; PS, pedicle screws; Student t tests were used for all calculations. The mean values are presented in degrees and improvement percentage.
RI PT
ACCEPTED MANUSCRIPT
Bilateral PS
P
Pre-Op VAS Back
6.5 (0 -10)
6.2 (0-10)
0.5
Post-Op VAS Back
2.4 (0 -10)
VAS/Back Improvement (%)
63.1%/ P
