The maturation of grafted bone after posterior lumbar interbody fusion with an interbody carbon cage: a prospective five-year study

Factors important in bone union after posterior lumbar interbody fusion using the cortical bone trajectory technique

Background

The cortical bone trajectory (CBT) technique has developed as an alternative to the traditional pedicle screw fixation technique due to its minimum invasiveness for screw insertion and rigid fixation for posterior lumbar interbody fusion (PLIF). However, the factors contributing to bone union after CBT-PLIF is a controversial subject. The aim of this study was to investigate factors important to bone union after CBT-PLIF.

Methods

We analyzed 69 consecutive patients who underwent single-level CBT-PLIF from October 2011 to December 2016 and were followed for over two years. Bone union was evaluated using computed tomography (CT) and dynamic assessment in the radiograph within two years after CBT-PLIF. The following factors that may influence bone union were investigated: age, gender, bone mineral density (BMD), cage materials [polyether-ether-ketone (PEEK) or titanium (Ti)], vertebral-slip (neutral), translational motion (flexion/extension), angular motion (flexion/extension), screw depth into the vertebral body (% depth), interval of bilateral screw heads, and cage position.

Results

The bone union rate at the two-year follow-up was 88.4% (61/69). A univariate analysis revealed that variables with values of P<0.20 were age (P<0.01), gender (P=0.07), cage material (P=0.18), vertebral slip (neutral) (P=0.14), % depth (P=0.086), and cage position (P<0.01). Multiple logistic regression analyses revealed that factors related to bone union were young age (P<0.01), Ti cage (P<0.01), small vertebral slip (neutral) (P<0.01), high % depth (P<0.01), and anterior cage position (P<0.01).

Conclusions

For CBT-PLIF, deeper screw insertion into the vertebral body, anterior cage placement, and Ti cage usage may be important surgical techniques to achieve a successful bone union.

Changes in Sagittal Alignment Following Short-Level Lumbar Interbody Fusion: Comparison between Posterior and Lateral Lumbar Interbody Fusions

Study Design

Retrospective case-control study.

Purpose

We aimed to compare radiologic outcomes between posterior (PLIF) and lateral lumbar interbody fusion (LLIF) in short-level spinal fusion surgeries.

Overview of Literature

Although LLIF enables surgeons to insert large lordotic cages, it is unknown whether LLIF more effectively corrects local and global sagittal alignments compared with PLIF in short-level spinal fusion surgeries.

Methods

Radiographic data acquired from patients with lumbar interbody fusion (≤3 levels) using PLIF or LLIF for degenerative lumbar diseases were analyzed. The following radiographic parameters were evaluated preoperatively and at 2 years postoperatively: segmental lordotic angle, disk height, lumbar lordosis (LL), pelvic tilt (PT), C7 sagittal vertical axis, and thoracic kyphosis (TK).

Results

In total, 144 patients with PLIF (193 fused levels) and 101 with LLIF (159 fused levels) were included. Patients’ backgrounds and preoperative radiographic parameters for any level of fusion did not differ significantly between PLIF and LLIF procedures. The LLIF group exhibited significantly greater changes at 1-level fusion compared to the PLIF group in the parameters of segmental lordotic angle (5.1°±5.8° vs. 2.1°±5.0°, p<0.001), disk height (4.2±2.3 mm vs. 2.2±2.0 mm, p<0.001), LL (7.8°±7.6° vs. 3.9°±8.6°, p=0.004), and PI–LL (−6.9°±6.8° vs. −3.6°±10.1°, p=0.03). While, a similar trend was observed regarding 2-level fusion, significantly greater changes were only observed in LL (12.1°±11.1° vs. 4.2°±9.1°, p=0.047) and PI–LL (−11.2°±11.3° vs. −3.0°±9.3°, p=0.043), PT (−6.4°±4.9° vs. −2.5°±5.3°, p=0.049) and TK (7.8°±11.8° vs. −0.3°±9.7°, p=0.047) in the LLIF group at 3-level fusion.

Conclusions

LLIF provides significantly better local sagittal alignment than PLIF in 1- or 2-level fusion cases and improves spinopelvic alignment and local alignment for 3-level fusion cases. Thus, LLIF was demonstrated to be a useful lumbar interbody fusion technique, constituting a powerful tool for achieving sagittal realignment with minimal surgical invasiveness.

Comparative Radiographic Outcomes of Lateral and Posterior Lumbar Interbody Fusion in the Treatment of Degenerative Lumbar Kyphosis

STUDY DESIGN

Retrospective case-control study.

PURPOSE

To compare surgical invasiveness and radiological outcomes between posterior lumbar interbody fusion (PLIF) and lateral lumbar interbody fusion (LLIF) for degenerative lumbar kyphosis.

OVERVIEW OF LITERATURE

LLIF is a minimally invasive interbody fusion technique; however, few reports compared the clinical outcomes of conventional PLIF and LLIF for degenerative lumbar kyphosis.

METHODS

Radiographic data for patients who have undergone lumbar interbody fusion (≥3 levels) using PLIF or LLIF for degenerative lumbar kyphosis (lumbar lordosis [LL] <20°) were retrospectively examined. The following radiographic parameters were retrospectively evaluated preoperatively and 2 years postoperatively: segmental lordotic angle, LL, pelvic tilt (PT), pelvic incidence (PI), C7 sagittal vertical axis, and T1 pelvic angle.

RESULTS

Nineteen consecutive cases with PLIF and 27 cases with LLIF were included. There were no significant differences in patients' backgrounds or preoperative radiographic parameters between the PLIF and the LLIF groups. The mean fusion level was 5.5±2.5 levels and 5.8±2.5 levels in the PLIF and LLIF groups, respectively (p=0.69). Although there was no significant difference in surgical times (p=0.58), the estimated blood loss was significantly greater in the PLIF group (p<0.001). Two years postoperatively, comparing the PLIF and LLIF groups, the segmental lordotic angle achieved (7.4°±7.6° and 10.6°±9.4°, respectively; p=0.03), LL (27.8°±13.9° and 39.2°±12.7°, respectively; p=0.006), PI-LL (19.8°±14.8° and 3.1°±17.5°, respectively; p=0.002), and PT (22.6°±7.1° and 14.2°±13.9°, respectively; p=0.02) were significantly better in the LLIF group.

CONCLUSIONS

LLIF provided significantly better sagittal alignment restoration in the context of degenerative lumbar kyphosis, with less blood loss.

The Assessment of Fusion Following Sacroiliac Joint Fusion Surgery

Sacroiliac joint fusions (SIJF) have been the subject of many research studies. The technical success of an SIJF is in part determined by whether osseous bridging occurs across the sacroiliac joint (SIJ). However, no validated SIJF assessment method has been described. Our objective was to document previously described SIJF assessment methods and define and validate a detailed assessment system for SIJF. Our results are only intended to establish computed tomography (CT)-based guidelines for SIJF to be used in a subsequent large clinical study to correlate them with clinical outcomes.

The SIJF literature was reviewed to document previous descriptions of SIJF assessments. A detailed system was then developed for assessing SIJF from CT exams. To provide data that can be used to address a range of research questions, the system included assessing bridging bone relative to the SIJ anatomy, bridging bone immediately adjacent to the threaded implants crossing the joint, as well as bridging bone close to but not immediately adjacent to the implants. The system was applied to assessing SIJF from thin-slice CT exams in 19 patients 12 months following surgery. Two experienced radiologists implemented the assessment system, and in the event of a disagreement, an adjudicator was used.

Most prior studies provide very little detail about how SIJF was assessed. Using the new assessment system, the agreement between the primary readers was substantial (0.67 using Gwet’s AC1 statistic). Bridging bone representing a fusion of the SIJ was identified in most patients both immediately adjacent to the threaded implants crossing the joint, as well as distant to the implants.

A detailed radiographic assessment system proved to be applicable to SIJF. The assessment system includes explicit language describing the location and extent of bridging bone across the SIJ. Standardization of the assessment of the SIJFs may allow for a more meaningful comparison of data between studies.