Elsevier

World Neurosurgery

Volume 109, January 2018, Pages e194-e202
World Neurosurgery

Original Article
Comparative Study of Cortical Bone Trajectory-Pedicle Screw (Cortical Screw) Versus Conventional Pedicle Screw in Single-Level Posterior Lumbar Interbody Fusion: A 2-Year Post Hoc Analysis from Prospectively Randomized Data

https://doi.org/10.1016/j.wneu.2017.09.137Get rights and content

Objective

The aim of this study was to report 2-year follow-up outcomes of posterior lumbar interbody fusion (PLIF) with cortical bone trajectory-pedicle screw (CS), in terms of fusion rates, clinical outcomes, surgical outcomes, and complications, and to compare these outcomes with outcomes for PLIF with conventional pedicle screw (PS).

Methods

We enrolled 79 patients and randomly assigned them to 2 groups (group A with PS, 39 patients; group B with CS, 40 patients), and finally 37 and 35 in group A and B were analyzed in the study. The primary outcome measure was the fusion rate, evaluated by dynamic radiographs and computed tomography scans. Secondary outcome measures included 1) patient satisfaction; 2) clinical outcomes measured with pain intensity using a visual analog scale, the Oswestry Disability Index, and 12-Item Short Form Health Survey; 3) radiologic outcomes; and 4) complications.

Results

At 2-year follow-up, the fusion rate was comparable between the PS and CS groups (35 of 37 patients in the PS group; 32 of 35 patients in the CS group; P > 0.99). The patient satisfaction rate at the 1-month follow-up was significantly greater in the CS group than in the PS group (P = 0.03); however, there was no significant difference between the groups at the 1-year and 2-year follow-ups. Clinical outcomes, radiologic outcomes, and related complications revealed no significant differences in both groups within 2 years postoperatively.

Conclusions

We suggest that CS in single-level PLIF may be an alternative to PS.

Introduction

Since the development of the pedicle screw (PS) technique, posterior instrumentation with PS has been an irreplaceable option in fusion surgery for lumbar pathologies.1, 2, 3 Surgeons have pointed out procedure-related limitations of PS, especially problems relating to a PS insertion point that is located laterally and close to the superior facet.4, 5, 6, 7, 8, 9 However, as the result of a lack of alternatives, PS continues to be used in posterior lumbar fusion surgery such as in posterior lumbar interbody fusion (PLIF).

A newer PS system using the cortical bone trajectory, also called the cortical bone trajectory-pedicle screw (CS) in the literature, has been introduced as an alternative to conventional PS and is becoming a popular technique.10 However, some concerns regarding the use of CS in lumbar fusion surgery also have been documented, as described herein. First, it can be technically demanding as the result of an unfamiliar entry point and trajectory for CS placement. However, previous studies have revealed that CS placement is the more favorable procedure for surgeons compared with PS placement, because of less skin incision and muscle dissection, a more medially located entry point, and a safer screw trajectory.11, 12, 13, 14, 15

Second, because of the shorter length and the smaller diameter of the CS, spine surgeons have concerns about the durability of the CS to endure mechanical stress and maintain screw strength compared with the PS. Several biomechanical studies have demonstrated that the insertional torque of CS was equivalent or greater than that of the PS and that the CS provided similar stiffness in flexion, extension, lateral bending, and axial rotation tests as the PS.16, 17, 18, 19, 20, 21, 22, 23 Finally, because of the limited number of clinical studies on the CS technique, surgeons are not completely convinced whether using CS in PLIF can produce similar clinical and radiologic outcomes in comparison with PS in PLIF.3, 11, 12, 13, 14, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 To our knowledge, only 1 prospective randomized study comparing CS and PS in PLIF has been reported,11 and it indicates similar fusion rates and clinical outcomes on 1-year follow-up. However, to the best of our knowledge, there have been no studies reporting comparative outcomes between CS and PS in PLIF over longer follow-up periods. Such studies are needed to establish the long-term efficacy and safety of CS as an alternative to PS in PLIF.

In our study, we aimed to describe the postoperative outcomes of CS in PLIF and compare them with outcomes of PLIF using PS over a 2-year follow-up period. Our study was a prospectively randomized double-arm parallel design focused on fusion rate, pain intensity, radiologic outcomes, clinical outcomes, and complications. To the best of our knowledge, this is the first study to report 2-year postoperative outcomes of PLIF using CS and compare them with the outcomes after PLIF with PS with a prospective randomized design.

Section snippets

Population

The institutional review board approved the current study. In the current study, we aimed to evaluate the 2-year outcomes of PLIF with CS versus PLIF with PS, using prospectively collected data of patients. Our previous study reported the postoperative outcomes of PLIF with CS versus PLIF with PS under a prospectively randomized noninferiority design over a 1-year follow-up.11 Thus, our current study design was a post-hoc comparative study to compare the postoperative outcomes of PLIF surgery

Patient Characteristics

Originally, 79 patients were randomly allocated to 2 groups (39 patients in group A with PS and 40 patients in group B with CS). During a 2-year follow-up, 7 patients were dropped out; the remaining 72 patients (37 in group A and 35 in group B) were analyzed for the present study (Figure 2). Patients were similar between the groups with respect to demographic characteristics such as age, sex, smoking status, height, weight, body mass index, and preoperative lumbar pathology (Table 1).

Primary Outcome Measure (Fusion Rate)

Based on

Discussion

CS has been reported to offer several advantages that may overcome the limitations of the PS. Because the CS has a caudomedial insertion point that is far from the superior facet joint in comparison with the PS, the CS may minimize the superior facet joint violation and be performed with less lateral muscle dissection and a shorter skin incision, possibly reducing surgery-related morbidity.11, 12, 13, 15, 24, 27, 29, 30, 31, 32, 33, 34 Moreover, its medial-to-lateral–directed trajectory may

Conclusions

The current study is the first to evaluate 2-year postoperative outcomes after single-level PLIF using PS or CS under a prospective, randomized, double-arm, noninferiority design. The fusion rate, which was the primary endpoint of the current study, revealed no significant difference between the 2 groups. Patient satisfaction was significantly greater in the CS group than in the PS group at the 1-month follow-up. However, there were no significant differences at the 1-year and 2-year follow-up

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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