Increased incidence of pseudarthrosis after unilateral instrumented transforaminal lumbar interbody fusion in patients with lumbar spondylosis

Clinical article

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Object

Transforaminal lumbar interbody fusion (TLIF) with segmental pedicular instrumentation is a wellestablished procedure used to treat lumbar spondylosis with or without spondylolisthesis. Available biomechanical and clinical studies that compared unilateral and bilateral constructs have produced conflicting data regarding patient outcomes and hardware complications.

Methods

A prospective cohort study was undertaken by a group of neurosurgeons. They prospectively enrolled 80 patients into either bilateral or unilateral pedicle screw instrumentation groups (40 patients/group). Demographic data collected for each group included sex, age, body mass index, tobacco use, and Workers' Compensation/litigation status. Operative data included segments operated on, number of levels involved, estimated blood loss, length of hospital stay, and perioperative complications. Long-term outcomes (hardware malfunction, wound dehiscence, and pseudarthrosis) were recorded. For all patients, preoperative baseline and 6-month postoperative scores for Medical Outcomes 36-Item Short Form Health Survey (SF-36) outcomes were recorded.

Results

Patient follow-up times ranged from 37 to 63 months (mean 52 months). No patients were lost to follow-up. The patients who underwent unilateral pedicle screw instrumentation (unilateral cohort) were slightly younger than those who underwent bilateral pedicle screw instrumentation (bilateral cohort) (mean age 42 vs 47 years, respectively; p = 0.02). No other significant differences were detected between cohorts with regard to demographic data, mean number of lumbar levels operated on, or distribution of the levels operated on. Estimated blood loss was higher for patients in the bilateral cohort, but length of stay was similar for patients in both cohorts. The incidence of pseudarthrosis was significantly higher among patients in the unilateral cohort (7 patients [17.5%]) than among those in the bilateral cohort (1 patient [2.5%]) (p = 0.02). Wound dehiscence occurred for 1 patient in the unilateral cohort. Reoperation was offered to 8 patients in the unilateral cohort and 1 patient in the bilateral cohort (p = 0.03). The physical component scores of the Medical Outcomes SF-36 outcomes improved significantly for all patients (p < 0.001).

Conclusions

Transforaminal lumbar interbody fusion with either unilateral or bilateral segmental pedicular instrumentation is an effective treatment for lumbar spondylosis. Because patients with unilateral constructs were 7 times more likely to experience pseudarthrosis and require reoperation, TLIF with bilateral constructs might be the biomechanically superior technique.

Abbreviations used in this paper:HRQOL = health-related quality of life; MCS = mental component summary; ODI = Oswestry Disability Index; PCS = physical component summary; PLIF = posterior lumbar interbody fusion; rhBMP-2 = human bone morphogenetic protein; SF-36 = 36-Item Short Form Health Survey; TLIF = transforaminal lumbar interbody fusion.

Object

Transforaminal lumbar interbody fusion (TLIF) with segmental pedicular instrumentation is a wellestablished procedure used to treat lumbar spondylosis with or without spondylolisthesis. Available biomechanical and clinical studies that compared unilateral and bilateral constructs have produced conflicting data regarding patient outcomes and hardware complications.

Methods

A prospective cohort study was undertaken by a group of neurosurgeons. They prospectively enrolled 80 patients into either bilateral or unilateral pedicle screw instrumentation groups (40 patients/group). Demographic data collected for each group included sex, age, body mass index, tobacco use, and Workers' Compensation/litigation status. Operative data included segments operated on, number of levels involved, estimated blood loss, length of hospital stay, and perioperative complications. Long-term outcomes (hardware malfunction, wound dehiscence, and pseudarthrosis) were recorded. For all patients, preoperative baseline and 6-month postoperative scores for Medical Outcomes 36-Item Short Form Health Survey (SF-36) outcomes were recorded.

Results

Patient follow-up times ranged from 37 to 63 months (mean 52 months). No patients were lost to follow-up. The patients who underwent unilateral pedicle screw instrumentation (unilateral cohort) were slightly younger than those who underwent bilateral pedicle screw instrumentation (bilateral cohort) (mean age 42 vs 47 years, respectively; p = 0.02). No other significant differences were detected between cohorts with regard to demographic data, mean number of lumbar levels operated on, or distribution of the levels operated on. Estimated blood loss was higher for patients in the bilateral cohort, but length of stay was similar for patients in both cohorts. The incidence of pseudarthrosis was significantly higher among patients in the unilateral cohort (7 patients [17.5%]) than among those in the bilateral cohort (1 patient [2.5%]) (p = 0.02). Wound dehiscence occurred for 1 patient in the unilateral cohort. Reoperation was offered to 8 patients in the unilateral cohort and 1 patient in the bilateral cohort (p = 0.03). The physical component scores of the Medical Outcomes SF-36 outcomes improved significantly for all patients (p < 0.001).

Conclusions

Transforaminal lumbar interbody fusion with either unilateral or bilateral segmental pedicular instrumentation is an effective treatment for lumbar spondylosis. Because patients with unilateral constructs were 7 times more likely to experience pseudarthrosis and require reoperation, TLIF with bilateral constructs might be the biomechanically superior technique.

Transforaminal lumbar interbody fusion (TLIF) has been increasing in popularity since its introduction by Harms and Rolinger in 1982.14,15 The TLIF procedure involves a far-lateral transforaminal approach to the disc space through the vertebral foramen combined with posterior instrumentation. This procedure promotes circumferential fusion based on the principle of load sharing and provides anterior column support and a posterior tension band. TLIF is designed to restore normal lumbar lordosis, widen the neural foramen, restore disc height, and relieve central stenosis.24 It is indicated for appropriately selected patients with a variety of lumbar spinal disorders, including degenerative disc disease, Grade I or Grade II spondylolisthesis, recurrent lumbar disc herniation, and complex lumbar stenosis.37

Transforaminal lumbar interbody fusion was conceptualized as a modified unilateral approach to posterior lumbar interbody fusion (PLIF). It has been repeatedly shown to be an effective method of spinal fusion associated with low risk for complications.13,21 Compared with the posterior approach, the transforaminal approach to the disc requires less thecal sac manipulation and decreases the chance of CSF leaks and nerve root damage. Thus, TLIF can be extended above L-3 (PLIF is contraindicated above L-3). In addition, with TLIF the interspinous ligament can be left intact, whereas with PLIF more tissue is disrupted. A 2001 study comparing TLIF and PLIF demonstrated that the number of complications and the amount of blood loss were less with TLIF than with PLIF and that outcomes were similar.17

Numerous posterior instrumentation methods have been used with the common goal of achieving maximal stability while minimizing tissue destruction and surgical risk. TLIF can be performed with bilateral pedicle screws and rods, with unilateral pedicle screws and a single rod, with unilateral screws and translaminar facet screws, and with unilateral screws and spinous process anchors. Some studies have reported unilateral instrumentation to be as effective as bilateral instrumentation.10 Other studies have demonstrated that bilateral pedicle screws offer more stability than unilateral screws.2,4,27 Because these conflicting reports have not clarified which construct most benefits the patient, we designed the present prospective cohort study. We compared rates of fusion, clinical outcomes, and complications among patients undergoing TLIF buttressed by either unilateral or bilateral pedicle screws.

Methods

Study Design

For this prospective cohort study, we consecutively enrolled 80 patients (40 men, 40 women) who underwent instrumented TLIF from October 2007 through November 2009. Indications for TLIF were degenerative disc disease and lumbar spondylosis. Exclusion criteria were infection, tumor, spondylolisthesis, or fracture. Patients were assigned to 1 of 2 groups (40 patients/group): bilateral pedicle screw instrumentation or unilateral pedicle screw instrumentation. In our clinical practice, 1 author (M.A.) preferred bilateral pedicle instrumentation, and another (F.M.) preferred unilateral pedicle instrumentation. The study was designed to prospectively enter patients into the study according to date of initial consultation until 40 patients were enrolled in each group. For patients initially seen when M.A. was on call, bilateral surgery was performed; and for those seen when F.M. was on call, unilateral surgery was performed. We have used this method of patient assignment previously.31 All surgeries were performed together by F.M. and M.A., thus ensuring equivalent technique. Plain radiographs were obtained 3 weeks, 3 months, 6 months, and 1 year postoperatively and biannually thereafter.

All patients eligible to participate in this study chose to do so, and no patients were lost to follow-up. Information about patient demographics and complications during the follow-up period was recorded and analyzed. For all patients, Medical Outcomes 36-Item Short Form Health Survey (SF-36) outcomes scores were recorded before surgery (baseline) and 6 months after surgery. This outcome measure is a patient-based, generic health status survey with 36 questions that assess patients' perceptions of 8 profiles of health-related quality of life (HRQOL) items (physical functioning, social functioning, physical role, emotional role, mental health, vitality, bodily pain, and general health) during the preceding 4 weeks. Each item is scored from 0 to 100 with a standardized mean of 50 and standard deviation of 10.35 The SF-36 is one of the most widely used health status instruments and is increasingly being used for measuring outcomes for patients with pain because it is sensitive to change and can differentiate between treatment responders and nonresponders.36 We used this validated instrument as an outcome measure in this study because we believe it is familiar to all medical practitioners and thus would increase the utility of our study. This study was approved by the Englewood Hospital and Medical Center Institutional Review Board.

Surgical Procedure

To ensure equivalent technique, 2 surgeons (F.M. and M.A.) performed all cases together. Carefully selected patients with spondylosis and degenerative disc disease underwent 1-level and 2-level TLIF. Under general anesthesia, patients were placed prone on the operating room table. A midline lumbar incision was created. Subperiosteal dissection of the lumbar paraspinal muscles was performed at all levels in which instrumentation was to be placed, but only unilaterally if instrumentation was placed unilaterally. An ipsilateral facetectomy and discectomy were performed at the level(s) of the pathology and on the side at which symptoms predominated. For all patients, the disc space was evacuated bilaterally through a unilateral approach. After the endplates were completely prepared, the anterior disc space was packed with autologous bone graft that had been locally obtained. One carbon fiber banana-shaped cage (DePuy-AcroMed, Inc.) per level was inserted into the disc space, anteriorly, and in the midline. Bone was also placed within the interbody cage. Intraoperative fluoroscopy was used to verify appropriate placement of the cage and screws. Unilateral or bilateral segmental pedicle screw fixation and fusion were performed with CD Horizon Legacy titanium screws (Medtronic Sofamor Danek) in the vertebrae adjacent to the TLIF(s). To ensure that the graft fit snugly into the disc space, compression was then applied to the screws above and below the level of the TLIF. All exposed transverse processes (that is, unilaterally in unilateral cases and bilaterally in bilateral cases) were decorticated by using a high-speed drill. The equivalent of an extra-small INFUSE sponge (Medtronic Sofamor Danek) (1.2 mg) was placed into the interbody cage, and the rest of the 12-mg sponge was placed on the decorticated transverse processes. No additional INFUSE sponge was placed in the disc space outside the cage. Of note, although the manner in which INFUSE was used in this study is off-label, such use is common. A subfascial drainage tube was placed, and routine multilayer wound closure was performed.

Clinical Follow-Up

After discharge from the hospital, patients returned to the office for follow-up visits at 2 weeks, 3 months, 6 months, and 1 year and biannually thereafter, unless more frequent visits were clinically indicated. Routine spine radiography was performed at each visit. If the patient's clinical course so indicated, more advanced imaging, such as CT, MRI, or myelography, was performed. At the 6-month follow-up visit, SF-36 scores were obtained. The nurse practitioners on our service prospectively recorded data on patient complications and adverse events during the follow-up period.

Radiological Follow-Up

Plain anteroposterior and lateral radiographs of the lumbar spine were obtained at 3 weeks, 3 months, 6 months, and 1 year and biannually thereafter. Radiographs were obtained at each postoperative visit. All radiographs were reviewed by one of the authors (A.S.). On anteroposterior and lateral radiographs, fusion was determined by the presence of newly formed trabeculated bone between 2 adjacent fusion segments. If fusion status was unclear, CT was ordered. With regard to the sensitivity and specificity of CT versus plain radiography, Fogel et al. confirmed by surgical exploration that accuracy of radiographs and helical CT scans equally predicted fusion after posterior lumbar interbody surgery. They concluded that when plain radiographs show strong evidence of fusion or pseudarthrosis, CT is unlikely to provide useful new information and might be indicated for unclear cases only.11 If progressive bony healing was not noted on radiographs after 1 year, a diagnosis of pseudarthrosis was made (Fig. 1).

Fig. 1
Fig. 1Pseudarthrosis. Reconstructed coronal CT images showing horizontal linear lucencies that traverse the fusion masses at L4–5 (arrows) through the disc space (upper) and intertransverse compartment (lower) in a patient who underwent L3–5 TLIF with unilateral instrumentation. Note the solid fusion at the L3–4 level and the halo surrounding the L-5 screw.

Data Analyses

Statistical analyses were performed by using SPSS for Windows, version 20.0 (SPSS, Inc.). Demographic data were analyzed by use of a chi-square test or a Fisher exact test for binomial values (for example, sex, tobacco use) and independent-sample t-tests or Wilcoxon ranksum tests for continuous variables. Surgical complications were compared by use of a Fisher exact test. Normal and independent conditions were met. Analyses of SF-36 outcomes were performed with paired t-tests for individual patients to compare outcomes before and after treatment and with independent t-tests with equal variances for intergroup comparisons. For all analyses, significance was accepted as p < 0.05.

Results

All patients eligible to participate in this study chose to do so. Mean patient age was 44.2 years (range 24–68 years). The patients in the unilateral pedicle screw group (unilateral cohort) were slightly younger than those in the bilateral pedicle screw group (bilateral cohort). No other significant differences were found for demographic data, mean number of lumbar levels operated on, distribution of the levels operated on, and mean preoperative SF-36 physical and mental health scores (Table 1). All patients had degenerative disc disease and lumbar spondylosis.

TABLE 1:

Patient demographics*

CharacteristicUnilateralBilateralp Value
no. of patients4040
sex (M/F)19:2121:190.82
mean age (yrs)41.646.90.02
body mass index25.227.60.07
tobacco use, no. (%)14 (35)8 (20)0.21
Workers' Comp/litigation, no. (%)12 (30)9 (22.5)0.61
baseline PCS2927.20.17
baseline MCS3940.80.62

Bilateral = pedicle screw instrumentation after TLIF; unilateral = unilateral pedicle screw instrumentation after TLIF; Workers' Comp = Workers' Compensation claim.

Estimated perioperative blood loss was greater for patients in the bilateral cohort than for those in the unilateral cohort (502 vs 396 ml, respectively; p < 0.001), but lengths of hospital stay were similar (median 4 days, p = 0.69). No differences between groups were found for incidence of nerve injury (0 patients), cage migration (0), screw breakage (0), or wound dehiscence (1 patient [1.25%]). No intraoperative complications occurred (Table 2).

TABLE 2:

Operative data*

VariableScrew Instrumentationp Value
Unilateral Bilateral
no. of patients4040
estimated blood loss (ml)396.3502.5<0.001
length of stay (days)3.753.830.69
neurological injury001.00
pseudarthrosis7 (17.5%)1 (2.5%)0.05
cage migration001.00
screw breakage001.00
wound dehiscence1 (2.5%)01.00
no. of levels operated on
 126170.07
 214230.07
specific levels operated on
 L2–3010.31
 L3–4111.00
 L4–5970.78
 L5–S11680.09
 L3–5221.00
 L4–S112210.07

Data indicate number of patients unless otherwise indicated.

The duration of patient follow-up ranged from 37 to 63 months (mean 52 months). No patients were lost to follow-up. Incidence of pseudarthrosis was significantly higher among patients undergoing unilateral instrumentation (7 [17.5%]) than among those undergoing bilateral instrumentation (1 [2.5%]) (p = 0.05). The relative risk for pseudarthrosis development after unilateral pedicle screw instrumentation was 7. Pseudarthrosis data are summarized in Table 3.

TABLE 3:

Pseudarthrosis data

Screw Fixation CohortProcedure Level(s)Pseudarthrosis Level
bilateral
L4–S1L5–S1
unilateral
L3–5L4–5
L4–5L4–5
L4–S1L4–5
L4–S1L5–S1
L4–S1L5–S1
L5–S1L5–S1
L5–S1L5–S1

All patients in whom pseudarthrosis developed were symptomatic and were offered reoperation. Of the 7 pseudarthrosis patients in the unilateral cohort, 5 agreed to reoperation and underwent augmentation of fusion and placement of bilateral pedicle screws. In addition, 1 patient in the unilateral cohort underwent reoperation for wound dehiscence. The only pseudarthrosis patient in the bilateral cohort refused further surgery. Thus, for an intent-to-treat analysis, 8 patients in the unilateral cohort were offered reoperation compared with 1 patient in the bilateral group (p = 0.03).

For all patients, scores for the physical component of the SF-36 improved significantly (p < 0.001). Score improvement for the mental health component of the SF-36 did not reach statistical significance after TLIF for the cohort as a whole (p = 0.08), although it did for those in the unilateral cohort (p = 0.03) (Table 4). However, according to multivariate analysis, improvements in mental component summary (MCS) or physical component summary (PCS) scores were not associated with unilateral or bilateral constructs.

TABLE 4:

Summary of SF-36 data

Group (no. of patients)PreopPostop% Changep Value
both cohorts (80)
 PCS28.137.734.1<0.001
 MCS39.943.89.80.08
unilateral cohort (40)
 PCS2936.626.1<0.001
 MCS3945.717.20.03
bilateral cohort (40)
 PCS27.238.842.7<0.001
 MCS40.841.92.70.70

According to multivariate analysis, only male sex and unilateral constructs were significantly associated with pseudarthrosis. No correlations were found for age, body mass index, number of levels operated on, specific level operated on, or tobacco use (Table 5). Improved PCS scores were associated with lower body mass index and fewer levels operated on. Improvement was greater for patients with lower preoperative PCS scores (that is, those more debilitated by their disease process) than for those with higher preoperative PCS scores (that is, patients with fewer physical limitations preoperatively) (Table 6). Similarly, improvement was greater for patients with lower preoperative MCS scores than for those with higher preoperative MCS scores (Table 6). PCS score improvement was less among patients who were involved in litigation or who had filed Workers' Compensation claims, but this finding just missed statistical significance (p = 0.053).

TABLE 5:

Multivariate analysis for pseudarthrosis

Independent Variablestp Value
age−1.2490.216
body mass index0.3380.737
sex−3.0620.003
unilateral screw−2.1100.039
no. of levels (1 or 2)0.6860.495
tobacco use0.6710.504
level operated on
 L2–30.0190.985
 L3–41.0920.279
 L4–5−0.4060.686
 L5–S10.2550.800
TABLE 6:

Multivariate analysis for absolute improvement in PCS and MCS scores

Independent VariablesPCSMCS
tp Valuetp Value
age1.3340.1871.4060.164
sex−1.0300.3061.1320.262
body mass index−2.1140.038−0.1750.862
tobacco use0.2000.8420.8750.385
Workers' Comp/litigation−1.9710.0531.2450.217
no. of levels−2.5470.013−0.4660.643
unilateral1.4720.146−1.1680.247
pseudarthrosis−0.7020.485−0.9180.362
preop PCS−4.740<0.001−0.0870.931
preop MCS1.8090.075−9.013<0.001

Discussion

Posterior lumbar interbody fusion was described by Cloward in 1945.6 At that time, the procedure was not widely adopted because of a high rate of complications. The technique was later modified by Steffee and Sitkowski to include pedicle screw fixation, which resulted in increased rates of arthrodesis and decreased rates of graft extrusion.32,33 The TLIF procedure was designed by Harms and Rolinger to minimize nerve root retraction during placement of the interbody graft.1,14,15 This advance further diminished complications while maintaining a fusion rate of greater than 90%.

Alternative approaches that minimize muscle trauma continue to evolve. A minimally invasive TLIF procedure was designed in response to the substantial muscle disruption that occurs during open surgeries. At the time we designed this study, we did not have sufficient expertise in these methods. Other examples include the mini-open TLIF, TLIF with unilateral instrumentation alone, TLIF with unilateral screws and contralateral translaminar facet screws, and TLIF with unilateral screws and a spinous process anchor. Currently available biomechanical and clinical studies offer confounding results as to which surgical procedure is the best for maximizing fusion rates and clinical outcomes while minimizing patient complications.

Ideally, an operated segment should have enough rigidity to preclude implant loosening and cage displacement while maintaining adequate flexibility to prevent load transference and accelerated disease at adjacent levels.16 Some biomechanical studies have shown higher rates of fusion and improved strength of the fusion construct with more rigid internal fixation.18 However, 2 studies by McAfee et al.22,23 have shown that excessively stiff spinal instrumentation constructs can shield the fusion region from necessary strain, which could lead to osteopenia and failure of adequate fusion.

A biomechanical study by H. H. Chen at al.3 demonstrated that unilateral fixation was adequate for maintaining the stability of the lumbar spine. In contrast, Slucky et al.30 and S. H. Chen et al.4 demonstrated that although the unilateral pedicle screw construct with an interbody cage decreases overall bulk and dissection, it also allows for a significantly increased segmental range of motion and less stiffness and produces off-axis movement. Many authors recommend supplementing the unilateral construct with a contralateral facet screw, translaminar screw, or bilateral pedicle screw.4,27,29,30 These conflicting study findings preclude a consensus on the optimal environment in which to achieve arthrodesis.

More clinically oriented studies have not clarified the matter. In a study of 30 patients, Kotil et al. reported that a TLIF procedure without pedicle screw support would be sufficient for management of select patients after singlelevel decompression.20 In a prospective randomized trial of 80 patients comparing unilateral pedicle screw fixation with bilateral pedicle screw fixation for 1-level and 2-level TLIF, Xue et al. found comparable fusion rates and clinical outcomes between the 2 groups after a mean of 25.3 months of follow-up.38 In a prospective trial of 87 patients undergoing 1-segment or 2-segment lumbar fusion, Suk et al. demonstrated that unilateral pedicle screw fixation was as effective as bilateral instrumentation in terms of outcomes, fusion rates, and complications.34 Similar results have been found by Deutsch and Musacchio,9 Kabins et al.,19 and Fernández-Fairen et al.10

To the contrary, several authors have expressed doubts regarding unilateral pedicle screw stabilization in the lumbar spine. Goel et al.12 and Slucky et al.30 reported that results produced by unilateral pedicle screw constructs after TLIF were inferior to those produced by bilateral posterior constructs. Aoki et al. compared 25 patients who underwent unilateral pedicle screws/unilateral TLIF with 25 patients who underwent bilateral pedicle screws/bilateral TLIF.2 They reported that although complication and fusion rates were similar, outcomes (as measured on visual analog scales) were less favorable for patients who underwent unilateral TLIF with unilateral instrumentation.2 Sethi et al. reported that among a series of 19 patients, TLIF with unilateral pedicle screws supplemented by a contralateral translaminar facet screw resulted in excellent clinical outcomes and fusion rates.28

In an attempt to improve on previously reported fusion rates without need for large iliac crest harvest, many authors began adding human bone morphogenetic protein (rhBMP-2) to the TLIF operation.25 Although this usage is common, it is off-label. In a sample of 340,251 operations involving the implantation of BMP, usage was off-label for 85% of operations. Of those cases, the most commonly performed procedures were PLIF/TLIF (30%) followed by primary posterolateral spine fusion (20.4%). Among TLIF procedures performed in the United States in 2007, an estimated 44% involved use of BMP.26 Initial enthusiasm was tempered with small series and case reports of serious complications including heterotopic ossification within the epidural space or neuroforamina, postoperative radiculitis, and endplate osteolysis with interbody device subsidence.5 Published complication rates vary widely because of small sample sizes, variability in surgical technique, and no BMP dose guidelines. In the largest published retrospective review of prospectively collected data that we found, Crandall et al. reviewed 509 consecutive patients (872 discs) who underwent TLIF with rhBMP-2. Doses ranged from 2 to 12 mg (mean 7.3 mg); more recent cases tended to involve lower dosages. At an average of 5 years of follow-up, fusion was achieved in 864 (99.1%) of 872 levels and seroma formation occurred in 0.4% of patients, ectopic bone growth in 0.6%, radiculitis in 1%, and symptomatic osteolysis or cage subsidence in none.7,8 With such low rates, the study was inadequately powered to detect significant differences between dose groups.5 Overall, although small risks exist, the current widespread use of BMP for TLIF procedures seems safe when appropriate surgical techniques are used. Its use during spinal surgery should continue to evolve as more scientific data become available.

The series of 80 patients reported here demonstrates that TLIF with either unilateral or bilateral segmental pedicular instrumentation is an effective treatment for lumbar spondylosis. As measured by the SF-36, all patients experienced substantial physical improvement after TLIF. However, our results demonstrate that TLIF buttressed by bilateral instrumentation produces better results than TLIF with unilateral instrumentation. Among patients who underwent unilateral pedicle screw constructs, pseudarthrosis was 7 times more likely to develop and reoperation was more likely to be needed.

The conclusions of this study would be strengthened if we had conducted a prospectively randomized trial rather than a cohort study and if we had used a diseasespecific outcome tool (such as the Oswestry Disability Index [ODI]) in addition to the SF-36. In comparison with the 10-item ODI that was developed specifically for patients with low-back problems, the SF-36 is a multidimensional measure, is not diagnosis specific, and places more burden on respondents. The SF-36 does, however, offer more detailed information than the ODI, and, overall, the 2 measures share 74% variance.36 Although we tried to control for known major confounders that can influence outcomes and complication rates, such as smoking, age, body mass index, litigation status, and preoperative HRQOL scores, we obviously did not exhaust all other common comorbidities (for example, hypertension, diabetes, chronic steroid use, and osteoporosis). In addition, quantifying the amount of autologous bone harvested and used in fusion is difficult. The total volume of bone available for fusion differed because of variability in the requirement for decompression, character of spinal bone (for example, thick or thin lamina, wide or narrow lamina), and use of unilateral versus bilateral technique. This variability might contribute to different rates of fusion. Furthermore, there was no sample size calculation; our results indicate that we achieved the minimum sample size for fusion, but perhaps our sample size was inadequate for comparisons of HRQOL and complications. Although all efforts were made to encourage objective assessment of all radiographs for evidence of fusion, because internal fixation (unilateral or bilateral) was clearly visible on the films, true blinding could not be achieved and bias might have been introduced.

Conclusions

As surgical technology advances, surgical techniques continue to evolve. The optimal construct for the surgical treatment of carefully selected patients with lumbar spondylosis must be ascertained by rigorous study of incremental technique changes. The desire to minimize tissue disruption led to the current comparison of unilateral with bilateral transpedicular instrumentation in those patients undergoing TLIF. On the basis of the increased rates of pseudarthrosis and reoperations, we conclude that the unilateral technique is inferior to the bilateral technique. Not all authors agree with this conclusion. Conflicting reports in the peer-reviewed literature should lead to further study until a consensus is reached. As novel constructs are described, they should be similarly scrutinized.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Arginteanu, F Moore, A Steinberger. Acquisition of data: Arginteanu, Gologorsky, Skovrlj, M Moore. Analysis and interpretation of data: Arginteanu, Gologorsky. Drafting the article: Arginteanu, Gologorsky, Skovrlj, J Steinberger. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Arginteanu. Statistical analysis: Gologorsky.

This work was presented at the Advanced Spine Techniques (IMAST) Annual Meeting, Valencia, Spain, July 15–19, 2014.

References

  • 1Ames CPAcosta FL JrChi JIyengar JMuiru WAcaroglu E: Biomechanical comparison of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion performed at 1 and 2 levels. Spine (Phila Pa 1976) 30:E562E5662005

    • Search Google Scholar
    • Export Citation
  • 2Aoki YYamagata MIkeda YNakajima FOhtori SNakagawa K: A prospective randomized controlled study comparing transforaminal lumbar interbody fusion techniques for degenerative spondylolisthesis: unilateral pedicle screw and 1 cage versus bilateral pedicle screws and 2 cages. Clinical article. J Neurosurg Spine 17:1531592012

    • Search Google Scholar
    • Export Citation
  • 3Chen HHCheung HHWang WKLi ALi KC: Biomechanical analysis of unilateral fixation with interbody cages. Spine (Phila Pa 1976) 30:E92E962005

    • Search Google Scholar
    • Export Citation
  • 4Chen SHLin SCTsai WCWang CWChao SH: Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery—a finite element analysis. BMC Musculoskelet Disord 13:722012

    • Search Google Scholar
    • Export Citation
  • 5Chrastil JLow JBWhang PGPatel AA: Complications associated with the use of the recombinant human bone morphogenetic proteins for posterior interbody fusions of the lumbar spine. Spine (Phila Pa 1976) 38:E1020E10272013

    • Search Google Scholar
    • Export Citation
  • 6Cloward RB: The treatment of ruptured lumbar intervertebral discs by vertebral body fusion. I. Indications, operative technique, after care. J Neurosurg 10:1541681953

    • Search Google Scholar
    • Export Citation
  • 7Crandall DGRevella JPatterson JHuish EChang MMcLemore R: Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease—part 1: Large series diagnosis related outcomes and complications with 2-to 9-year follow-up. Spine (Phila Pa 1976) 38:112811362013

    • Search Google Scholar
    • Export Citation
  • 8Crandall DGRevella JPatterson JHuish EChang MMcLemore R: Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease—part 2: BMP dosage-related complications and long-term outcomes in 509 patients. Spine (Phila Pa 1976) 38:113711452013

    • Search Google Scholar
    • Export Citation
  • 9Deutsch HMusacchio MJ Jr: Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation. Neurosurg Focus 20:3E102006

    • Search Google Scholar
    • Export Citation
  • 10Fernández-Fairen MSala PRamírez HGil J: A prospective randomized study of unilateral versus bilateral instrumented posterolateral lumbar fusion in degenerative spondylolisthesis. Spine (Phila Pa 1976) 32:3954012007

    • Search Google Scholar
    • Export Citation
  • 11Fogel GRToohey JSNeidre ABrantigan JW: Fusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion. Spine J 8:5705772008

    • Search Google Scholar
    • Export Citation
  • 12Goel VKLim THGwon JChen JYWinterbottom JMPark JB: Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation. Spine (Phila Pa 1976) 16:3 SupplS155S1611991

    • Search Google Scholar
    • Export Citation
  • 13Hackenberg LHalm HBullmann VVieth VSchneider MLiljenqvist U: Transforaminal lumbar interbody fusion: a safe technique with satisfactory three to five year results. Eur Spine J 14:5515582005

    • Search Google Scholar
    • Export Citation
  • 14Harms JRolinger H: [A one-stager procedure in operative treatment of spondylolistheses: dorsal traction-reposition and anterior fusion (author's transl).]. Z Orthop Ihre Grenzgeb 120:3433471982. (Ger)

    • Search Google Scholar
    • Export Citation
  • 15Harms JGJeszenszky D: The unilateral transforaminal approach for posterior lumbar interbody fusion. Orthop Traumatol 6:88991998

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  • 16Harris BMHilibrand ASSavas PEPellegrino AVaccaro ARSiegler S: Transforaminal lumbar interbody fusion: the effect of various instrumentation techniques on the flexibility of the lumbar spine. Spine (Phila Pa 1976) 29:E65E702004

    • Search Google Scholar
    • Export Citation
  • 17Humphreys SCHodges SDPatwardhan AGEck JCMurphy RBCovington LA: Comparison of posterior and transforaminal approaches to lumbar interbody fusion. Spine (Phila Pa 1976) 26:5675712001

    • Search Google Scholar
    • Export Citation
  • 18Johnston CE IIAshman RBBaird AMAllard RN: Effect of spinal construct stiffness on early fusion mass incorporation. Experimental study. Spine (Phila Pa 1976) 15:9089121990

    • Search Google Scholar
    • Export Citation
  • 19Kabins MBWeinstein JNSpratt KFFound EMGoel VKWoody J: Isolated L4-L5 fusions using the variable screw placement system: unilateral versus bilateral. J Spinal Disord 5:39491992

    • Search Google Scholar
    • Export Citation
  • 20Kotil KAli Akçetin MSavaş Y: Clinical and radiologic outcomes of TLIF applications with or without pedicle screw: a double center prospective pilot comparative study. J Spinal Disord Tech 26:3593662013

    • Search Google Scholar
    • Export Citation
  • 21Lowe TGTahernia ADO'Brien MFSmith DA: Unilateral transforaminal posterior lumbar interbody fusion (TLIF): indications, technique, and 2-year results. J Spinal Disord Tech 15:31382002

    • Search Google Scholar
    • Export Citation
  • 22McAfee PCFarey IDSutterlin CEGurr KRWarden KECunningham BW: The effect of spinal implant rigidity on vertebral bone density. A canine model. Spine (Phila Pa 1976) 16:6 SupplS190S1971991

    • Search Google Scholar
    • Export Citation
  • 23McAfee PCFarey IDSutterlin CEGurr KRWarden KECunningham BW: 1989 Volvo Award in Basic Science. Device-related osteoporosis with spinal instrumentation. Spine (Phila Pa 1976) 14:9199261989

    • Search Google Scholar
    • Export Citation
  • 24Moskowitz A: Transforaminal lumbar interbody fusion. Orthop Clin North Am 33:3593662002

  • 25Mummaneni PVPan JHaid RWRodts GE: Contribution of recombinant human bone morphogenetic protein-2 to the rapid creation of interbody fusion when used in transforaminal lumbar interbody fusion: a preliminary report. J Neurosurg Spine 1:19232004

    • Search Google Scholar
    • Export Citation
  • 26Ong KLVillarraga MLLau ECarreon LYKurtz SMGlassman SD: Off-label use of bone morphogenetic proteins in the United States using administrative data. Spine (Phila Pa 1976) 35:179418002010

    • Search Google Scholar
    • Export Citation
  • 27Schleicher PBeth POttenbacher APflugmacher RScholz MSchnake KJ: Biomechanical evaluation of different asymmetrical posterior stabilization methods for minimally invasive transforaminal lumbar interbody fusion. Laboratory investigation. J Neurosurg Spine 9:3633712008

    • Search Google Scholar
    • Export Citation
  • 28Sethi ALee SVaidya R: Transforaminal lumbar interbody fusion using unilateral pedicle screws and a translaminar screw. Eur Spine J 18:4304342009

    • Search Google Scholar
    • Export Citation
  • 29Sethi AMuzumdar AMIngalhalikar AVaidya R: Biomechanical analysis of a novel posterior construct in a transforaminal lumbar interbody fusion model an in vitro study. Spine J 11:8638692011

    • Search Google Scholar
    • Export Citation
  • 30Slucky AVBrodke DSBachus KNDroge JABraun JT: Less invasive posterior fixation method following transforaminal lumbar interbody fusion: a biomechanical analysis. Spine J 6:78852006

    • Search Google Scholar
    • Export Citation
  • 31Smith AJArginteanu MMoore FSteinberger ACamins M: Increased incidence of cage migration and nonunion in instrumented transforaminal lumbar interbody fusion with bioabsorbable cages. Clinical article. J Neurosurg Spine 13:3883932010

    • Search Google Scholar
    • Export Citation
  • 32Steffee ADBiscup RSSitkowski DJ: Segmental spine plates with pedicle screw fixation. A new internal fixation device for disorders of the lumbar and thoracolumbar spine. Clin Orthop Relat Res (203) 45531986

    • Search Google Scholar
    • Export Citation
  • 33Steffee ADSitkowski DJTopham LS: Total vertebral body and pedicle arthroplasty. Clin Orthop Relat Res (203) 2032081986

  • 34Suk KSLee HMKim NHHa JW: Unilateral versus bilateral pedicle screw fixation in lumbar spinal fusion. Spine (Phila Pa 1976) 25:184318472000

    • Search Google Scholar
    • Export Citation
  • 35Ware JE JrSherbourne CD: The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 30:4734831992

    • Search Google Scholar
    • Export Citation
  • 36Wittink HTurk DCCarr DBSukiennik ARogers W: Comparison of the redundancy, reliability, and responsiveness to change among SF-36, Oswestry Disability Index, and Multidimensional Pain Inventory. Clin J Pain 20:1331422004

    • Search Google Scholar
    • Export Citation
  • 37Xiao YXChen QXLi FC: Unilateral transforaminal lumbar interbody fusion: a review of the technique, indications and graft materials. J Int Med Res 37:9089172009

    • Search Google Scholar
    • Export Citation
  • 38Xue HTu YCai M: Comparison of unilateral versus bilateral instrumented transforaminal lumbar interbody fusion in degenerative lumbar diseases. Spine J 12:2092152012

    • Search Google Scholar
    • Export Citation

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Article Information

Address correspondence to: Marc Arginteanu, M.D., 1158 5th Ave., New York, NY 10029. email: neurosurgery@excite.com.

Please include this information when citing this paper: published online August 1, 2014; DOI: 10.3171/2014.6.SPINE13488.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery
    Pseudarthrosis. Reconstructed coronal CT images showing horizontal linear lucencies that traverse the fusion masses at L4–5 (arrows) through the disc space (upper) and intertransverse compartment (lower) in a patient who underwent L3–5 TLIF with unilateral instrumentation. Note the solid fusion at the L3–4 level and the halo surrounding the L-5 screw.

References

  • 1Ames CPAcosta FL JrChi JIyengar JMuiru WAcaroglu E: Biomechanical comparison of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion performed at 1 and 2 levels. Spine (Phila Pa 1976) 30:E562E5662005

    • Search Google Scholar
    • Export Citation
  • 2Aoki YYamagata MIkeda YNakajima FOhtori SNakagawa K: A prospective randomized controlled study comparing transforaminal lumbar interbody fusion techniques for degenerative spondylolisthesis: unilateral pedicle screw and 1 cage versus bilateral pedicle screws and 2 cages. Clinical article. J Neurosurg Spine 17:1531592012

    • Search Google Scholar
    • Export Citation
  • 3Chen HHCheung HHWang WKLi ALi KC: Biomechanical analysis of unilateral fixation with interbody cages. Spine (Phila Pa 1976) 30:E92E962005

    • Search Google Scholar
    • Export Citation
  • 4Chen SHLin SCTsai WCWang CWChao SH: Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery—a finite element analysis. BMC Musculoskelet Disord 13:722012

    • Search Google Scholar
    • Export Citation
  • 5Chrastil JLow JBWhang PGPatel AA: Complications associated with the use of the recombinant human bone morphogenetic proteins for posterior interbody fusions of the lumbar spine. Spine (Phila Pa 1976) 38:E1020E10272013

    • Search Google Scholar
    • Export Citation
  • 6Cloward RB: The treatment of ruptured lumbar intervertebral discs by vertebral body fusion. I. Indications, operative technique, after care. J Neurosurg 10:1541681953

    • Search Google Scholar
    • Export Citation
  • 7Crandall DGRevella JPatterson JHuish EChang MMcLemore R: Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease—part 1: Large series diagnosis related outcomes and complications with 2-to 9-year follow-up. Spine (Phila Pa 1976) 38:112811362013

    • Search Google Scholar
    • Export Citation
  • 8Crandall DGRevella JPatterson JHuish EChang MMcLemore R: Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease—part 2: BMP dosage-related complications and long-term outcomes in 509 patients. Spine (Phila Pa 1976) 38:113711452013

    • Search Google Scholar
    • Export Citation
  • 9Deutsch HMusacchio MJ Jr: Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation. Neurosurg Focus 20:3E102006

    • Search Google Scholar
    • Export Citation
  • 10Fernández-Fairen MSala PRamírez HGil J: A prospective randomized study of unilateral versus bilateral instrumented posterolateral lumbar fusion in degenerative spondylolisthesis. Spine (Phila Pa 1976) 32:3954012007

    • Search Google Scholar
    • Export Citation
  • 11Fogel GRToohey JSNeidre ABrantigan JW: Fusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion. Spine J 8:5705772008

    • Search Google Scholar
    • Export Citation
  • 12Goel VKLim THGwon JChen JYWinterbottom JMPark JB: Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation. Spine (Phila Pa 1976) 16:3 SupplS155S1611991

    • Search Google Scholar
    • Export Citation
  • 13Hackenberg LHalm HBullmann VVieth VSchneider MLiljenqvist U: Transforaminal lumbar interbody fusion: a safe technique with satisfactory three to five year results. Eur Spine J 14:5515582005

    • Search Google Scholar
    • Export Citation
  • 14Harms JRolinger H: [A one-stager procedure in operative treatment of spondylolistheses: dorsal traction-reposition and anterior fusion (author's transl).]. Z Orthop Ihre Grenzgeb 120:3433471982. (Ger)

    • Search Google Scholar
    • Export Citation
  • 15Harms JGJeszenszky D: The unilateral transforaminal approach for posterior lumbar interbody fusion. Orthop Traumatol 6:88991998

    • Search Google Scholar
    • Export Citation
  • 16Harris BMHilibrand ASSavas PEPellegrino AVaccaro ARSiegler S: Transforaminal lumbar interbody fusion: the effect of various instrumentation techniques on the flexibility of the lumbar spine. Spine (Phila Pa 1976) 29:E65E702004

    • Search Google Scholar
    • Export Citation
  • 17Humphreys SCHodges SDPatwardhan AGEck JCMurphy RBCovington LA: Comparison of posterior and transforaminal approaches to lumbar interbody fusion. Spine (Phila Pa 1976) 26:5675712001

    • Search Google Scholar
    • Export Citation
  • 18Johnston CE IIAshman RBBaird AMAllard RN: Effect of spinal construct stiffness on early fusion mass incorporation. Experimental study. Spine (Phila Pa 1976) 15:9089121990

    • Search Google Scholar
    • Export Citation
  • 19Kabins MBWeinstein JNSpratt KFFound EMGoel VKWoody J: Isolated L4-L5 fusions using the variable screw placement system: unilateral versus bilateral. J Spinal Disord 5:39491992

    • Search Google Scholar
    • Export Citation
  • 20Kotil KAli Akçetin MSavaş Y: Clinical and radiologic outcomes of TLIF applications with or without pedicle screw: a double center prospective pilot comparative study. J Spinal Disord Tech 26:3593662013

    • Search Google Scholar
    • Export Citation
  • 21Lowe TGTahernia ADO'Brien MFSmith DA: Unilateral transforaminal posterior lumbar interbody fusion (TLIF): indications, technique, and 2-year results. J Spinal Disord Tech 15:31382002

    • Search Google Scholar
    • Export Citation
  • 22McAfee PCFarey IDSutterlin CEGurr KRWarden KECunningham BW: The effect of spinal implant rigidity on vertebral bone density. A canine model. Spine (Phila Pa 1976) 16:6 SupplS190S1971991

    • Search Google Scholar
    • Export Citation
  • 23McAfee PCFarey IDSutterlin CEGurr KRWarden KECunningham BW: 1989 Volvo Award in Basic Science. Device-related osteoporosis with spinal instrumentation. Spine (Phila Pa 1976) 14:9199261989

    • Search Google Scholar
    • Export Citation
  • 24Moskowitz A: Transforaminal lumbar interbody fusion. Orthop Clin North Am 33:3593662002

  • 25Mummaneni PVPan JHaid RWRodts GE: Contribution of recombinant human bone morphogenetic protein-2 to the rapid creation of interbody fusion when used in transforaminal lumbar interbody fusion: a preliminary report. J Neurosurg Spine 1:19232004

    • Search Google Scholar
    • Export Citation
  • 26Ong KLVillarraga MLLau ECarreon LYKurtz SMGlassman SD: Off-label use of bone morphogenetic proteins in the United States using administrative data. Spine (Phila Pa 1976) 35:179418002010

    • Search Google Scholar
    • Export Citation
  • 27Schleicher PBeth POttenbacher APflugmacher RScholz MSchnake KJ: Biomechanical evaluation of different asymmetrical posterior stabilization methods for minimally invasive transforaminal lumbar interbody fusion. Laboratory investigation. J Neurosurg Spine 9:3633712008

    • Search Google Scholar
    • Export Citation
  • 28Sethi ALee SVaidya R: Transforaminal lumbar interbody fusion using unilateral pedicle screws and a translaminar screw. Eur Spine J 18:4304342009

    • Search Google Scholar
    • Export Citation
  • 29Sethi AMuzumdar AMIngalhalikar AVaidya R: Biomechanical analysis of a novel posterior construct in a transforaminal lumbar interbody fusion model an in vitro study. Spine J 11:8638692011

    • Search Google Scholar
    • Export Citation
  • 30Slucky AVBrodke DSBachus KNDroge JABraun JT: Less invasive posterior fixation method following transforaminal lumbar interbody fusion: a biomechanical analysis. Spine J 6:78852006

    • Search Google Scholar
    • Export Citation
  • 31Smith AJArginteanu MMoore FSteinberger ACamins M: Increased incidence of cage migration and nonunion in instrumented transforaminal lumbar interbody fusion with bioabsorbable cages. Clinical article. J Neurosurg Spine 13:3883932010

    • Search Google Scholar
    • Export Citation
  • 32Steffee ADBiscup RSSitkowski DJ: Segmental spine plates with pedicle screw fixation. A new internal fixation device for disorders of the lumbar and thoracolumbar spine. Clin Orthop Relat Res (203) 45531986

    • Search Google Scholar
    • Export Citation
  • 33Steffee ADSitkowski DJTopham LS: Total vertebral body and pedicle arthroplasty. Clin Orthop Relat Res (203) 2032081986

  • 34Suk KSLee HMKim NHHa JW: Unilateral versus bilateral pedicle screw fixation in lumbar spinal fusion. Spine (Phila Pa 1976) 25:184318472000

    • Search Google Scholar
    • Export Citation
  • 35Ware JE JrSherbourne CD: The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 30:4734831992

    • Search Google Scholar
    • Export Citation
  • 36Wittink HTurk DCCarr DBSukiennik ARogers W: Comparison of the redundancy, reliability, and responsiveness to change among SF-36, Oswestry Disability Index, and Multidimensional Pain Inventory. Clin J Pain 20:1331422004

    • Search Google Scholar
    • Export Citation
  • 37Xiao YXChen QXLi FC: Unilateral transforaminal lumbar interbody fusion: a review of the technique, indications and graft materials. J Int Med Res 37:9089172009

    • Search Google Scholar
    • Export Citation
  • 38Xue HTu YCai M: Comparison of unilateral versus bilateral instrumented transforaminal lumbar interbody fusion in degenerative lumbar diseases. Spine J 12:2092152012

    • Search Google Scholar
    • Export Citation

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