Fusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion

doi:10.1016/j.spinee.2007.03.013

The Spine Journal

Volume 8, Issue 4, July–August 2008, Pages 570-577

https://doi.org/10.1016/j.spinee.2007.03.013 Get rights and content

Abstract

Background

Plain radiographic assessment of posterolateral fusion has been reported as accurate in only two thirds of patients who were found to be healed at surgical exploration. Plain radiographic techniques for fusion assessment of interbody fusion with radiolucent cages are reported to be accurate. A helical computed tomography (CT) scan shows a high sensitivity for pseudarthrosis compared with plain radiography.

Purpose

To determine the accuracy of fusion assessment with plain X-ray films and helical CT scans by comparison to results of surgical exploration of fusion.

Study Design/Setting

The accuracy and interobserver agreement of plain X-ray films and thin-cut helical CT scans were compared with fusion assessment by surgical exploration in patients with posterior lumbar interbody fusion using a radiolucent carbon fiber reinforced polymer cage (CFRP) and iliac crest bone graft.

Patient Sample

A review of 90 patients who had surgical exploration of the lumbar fusion.

Outcome Measures

All patients had plain X-ray films including Ferguson anteroposterior parallel to the interbody space. Fifty-four patients had thin-section helical CT scans.

Methods

Fusion assessment by exploration was compared with blinded assessment by plain X-ray films and CT scans.

Results

Ninety patients had surgical exploration of 172 lumbar interbody and posterolateral fusion levels. At the time of exploration, fusion was determined to be successful in 87 of 90 patients and 168 of 172 (97%) fusion levels. X-ray assessment showed healed interbody fusions in 87% and posterolateral fusion healed in 75%. CT grading of the interbody fusion found healed interbody fusion in 77%, and the posterolateral fusion was fused in 68%. Plain X-ray films and CT scans had a sensitivity of 100% for pseudarthrosis and a negative predictive value of 100% for healed fusion. Specificity was almost 90% and was not significantly different between X-ray films and CT scans.

Conclusions

Fusion assessment with plain X-ray films and helical CT scans showed equal accuracy after posterior lumbar interbody fusion confirmed by surgical exploration. Our results indicate that when plain X-ray films show strong evidence of fusion or pseudarthrosis, the helical CT is unlikely to provide useful new information.

Introduction

Modern techniques combining posterolateral fusion (PLF) with interbody fusion (PLIF) using radiolucent interbody cages have increased the fusion rate to nearly 100% by plain radiographic assessment [1], [2], [3], [4], [5]. Nevertheless, 10% to 15% of patients may remain symptomatic. Accurate radiographic assessment of fusion success is important to identify patients who might benefit from further surgery. Physicians have continued to struggle with the correct interpretation of radiographic methods. To date, the “gold standard” of fusion determination has been surgical exploration [6], [7], [8]. Comparison of plain radiographic assessment of posterolateral fusion does not correlate with surgical exploration in a third or more of patients [6], [9], [10]. Plain radiographic techniques for fusion assessment of PLIF with radiolucent cages have been compared with surgical exploration and have been reported to be accurate [1], [2].

Improvement in computed tomography (CT) scanning has increased accuracy in fusion assessment. Early studies used only axial images, and, when compared with surgical exploration, they showed noncorrelation in up to 43% of cases [6]. More recently, thin-section 1 mm axial helical CT scans with sagittal and coronal reconstructions provide high-quality images with exquisite bone detail. Several helical CT studies have shown a high specificity for detection of pseudarthrosis compared with plain radiography particularly in evaluation of the interbody fusion [11], [12], [13], [14], [15], [16].

From a single surgical cohort, we have performed a retrospective chart and radiographic review of 90 consecutive patients who had surgical exploration of the fusion after posterior lumbar interbody fusion at one or more levels. Our purpose was to show the accuracy of plain X-ray films and helical CT scans in fusion assessment. To our knowledge, a comparison of plain X-ray films and helical CT scans to surgical exploration in evaluation of PLIF with radiolucent cages has not been previously reported.

Section snippets

Clinical study design

From February 1999 to October 2003, we performed PLIF using the Lumbar I/F Cage (DePuy Spine, Raynham, MA) with pedicle screw and plate fixation in our practice. Iliac crest bone autograft was used for the interbody fusion and local bone for the posterolateral fusion. Inclusion criteria included patients with disabling back pain because of degenerative disc disease at one or more lumbar levels and included patients with primary degenerative disc disease, failed discectomy, spondylolisthesis,

Results

Ninety patients had surgical exploration of 172 lumbar interbody and posterolateral fusion levels (Table 3). At the time of exploration, fusion was determined to be successful in 87 of 90 patients and 168 of 172 (97%) fusion levels (Fig. 1). Surgical exploration revealed four pseudarthroses (4/172, 2.3%). Two of the four pseudarthroses occurred at L5–S1, one at L4–5, and one at L1–2. Because all pseudarthrosis levels were relatively stable, the pedicle screws were left out and augmentation of

Discussion

The accuracy of distinguishing posterolateral fusion success from PLIF fusion success by surgical exploration is based on observations made over many years. Numerous authors have noted that a solid posterolateral fusion has flexibility of motion up to 4° or 5° [19], [20], [21], [22]. Unlike a posterolateral fusion, a successful interbody fusion creates a totally rigid motion segment [23], [24], [25]. Luk et al. [24] evaluated 52 cases of anterior lumbar interbody fusion 5 years after surgery

Conclusion

In a study of surgical exploration after PLIF and posterolateral fusion using a radiolucent interbody fusion device, X-ray and CT methods performed very similarly in evaluating lumbar fusion success with no significant differences in accuracy between the two methods. Both x-ray and helical CT scans predicted pseudarthrosis with 100% sensitivity and interbody and posterolateral fusion success with a 100% negative predictive value. Our results indicate that when plain films show strong evidence

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There are several complications associated with lumbar interbody fusion surgery however, pseudarthrosis (non-union) presents a multifaceted challenge in the postoperative management of the patient. Rates of pseudarthrosis range from 3 to 20 % in patients with healthy bone and 20 to 30 % in patients with osteoporosis. The current methods in post-operative follow-up - radiographs and CT, have high false positive rates and poor agreement between them. The aim of this study was to develop and test a proof-of-concept load-sensing interbody cage that may be used to monitor fusion progression. Piezoresistive pressure sensors were calibrated and embedded within a polyether ether ketone (PEEK) interbody cage. Silicone and poly (methyl methacrylate) (PMMA) were inserted in the graft regions to simulate early and solid fusion. The load-sensing cage was subjected to distributed and eccentric compressive loads up to 900 N between synthetic lumbar vertebral bodies. Under maximum load, the anterior sensors recorded a 56–58 % reduction in pressure in the full fusion state compared to early fusion. Lateral regions measured a 36–37 % stress reduction while the central location reduced by 45 %. The two graft states were distinguishable by sensor-recorded pressure at lower loads. The sensors more effectively detected left and right eccentric loads compared to anterior and posterior. Further, the load-sensing cage was able to detect changes in endplate stiffness. The proof-of-concept ‘smart’ cage could detect differences in fusion state, endplate stiffness, and loading conditions in this in vitro experimental setup.
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Lateral lumbar interbody fusion (LLIF) is a minimally invasive fusion procedure that may be performed with or without supplemental instrumentation. However, there is a paucity of evidence on the effect of supplemental instrumentation technique on perioperative morbidity and fusion rate in LLIF.
A single-institutional retrospective review of patients who underwent LLIF for lumbar spondylosis was conducted. Patients were grouped according to supplemental instrumentation technique: stand-alone LLIF, LLIF with laterally placed instrumentation, or LLIF with posterior percutaneous pedicle screw fixation (PPSF). Outcomes included fusion rates, peri-operative complication, and reoperation; estimated blood loss (EBL); surgery duration; length of stay; and length of follow-up.
82 patients underwent LLIF at 114 levels. 35 patients (42.7%) received supplemental lateral instrumentation, 30 (36.6%) received supplemental PPSF, and 17 (20.7%) underwent stand-alone LLIF. More patients in the lateral instrumentation group had prior lumbar fusion at adjacent levels (23/35, 65.71%) versus stand-alone (3/17, 17.6%) or PPSF (2/30, 6.67%) groups (p = 0.003). 4/17 patients (23.5%) with stand-alone LLIF and 4/35 patients (11.42%) with lateral instrumentation underwent reoperation, versus 0/30 with PPSF (p = 0.030). There was no difference in fusion rates between groups (p = 0.717). Operation duration was longer in patients with PPSF (p < 0.005) and length of follow-up was longer for PPSF than lateral instrumentation (p = 0.001). Choice of instrumentation group was a statistically significant predictor of reoperation.
While rates of complete radiographic fusion on imaging follow-up didn't differ, patients receiving PPSF were less likely than stand-alone or lateral instrumentation groups to require reoperation, though operative time was significantly longer. Further study of choice of supplemental instrumentation with LLIF is indicated.
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Most of the studies evaluating the effect of cross links on spinal stability are performed in vitro on porcine or human spine segments and there is limited data regarding clinical benefits of cross link augmentation in traumatic injuries. In this study we aimed to evaluate the effects of cross-links insertion between rods on the fusion rates and post-surgical patients’ satisfaction among patients with traumatic thoracolumbar fractures who underwent posterior spinal fixation with pedicle screws.
This study was conducted as a randomized clinical trial on 60 patients suffering from traumatic thoracolumbar vertebrae fractures. Patients were randomized into three groups: A (without any cross-link), B (One cross-link insertion) and C (two cross-links insertion). Six months after surgery outcomes were evaluated: fusion rates (plain X-ray and CT scan), Back pain (Visual Analog Scale) and patient satisfaction (fair, good, excellent).
In group A 13 (65%) patients had structured bone fusion, but in 7 (35%) patients bone fusion was not observed. In both groups B and C, 19 patients (95%) had bone fusion, but only in 1 patient (5%) fusion failed (p = 0.009). In group A, fair satisfaction has the highest rate (8 patients (40%)) compared to the other groups. The highest reported severity of back pain was observed in group A while the lowest reported intensity of back pain was related to group B (p = 0.001).
Adding cross link to posterior spinal fixations of patients with traumatic thoracolumbar fractures can be associated with better final fusion results and patients’ satisfaction. However it is necessary to design studies with greater sample sizes to confirm this theory.
Trial registration number: IRCT20120527009878N3.
La mayor parte de los estudios que evaluaron el efecto de los enlaces cruzados en la estabilidad de la columna vertebral se realizaron in vitro en segmentos de la columna vertebral porcina o humana, existen pocos datos sobre los beneficios del aumento de los enlaces cruzados en las lesiones traumáticas. El objetivo de este estudio era evaluar los efectos de la inserción de enlaces cruzados entre las varillas en las tasas de fusión y la satisfacción posoperatoria de los pacientes con fracturas traumáticas toracolumbares que se habían sometido a fijación vertebral posterior con tornillos pediculares.
Este estudio se realizó como un ensayo clínico aleatorizado de 60 pacientes que presentaban fracturas vertebrales toracolumbares traumáticas. Los pacientes se aleatorizaron en 3 grupos: A (sin ningún enlace cruzado), B (inserción de un enlace cruzado) y C (inserción de 2 enlaces cruzados). Se evaluaron los resultados 6 meses después de la intervención quirúrgica: tasas de fusión (radiografía simple y TC), dolor de espalda (escala analógica visual) y satisfacción del paciente (correcta, buena, excelente).
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View all citing articles on Scopus

FDA device/drug status: approved for this indication (Lumbar I/F Cage and the VSP Spinal Fixation System).

Dr. Brantigan has a financial interest in the Lumbar I/F Cage.

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Clinical StudyFusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion

Abstract

Background

Purpose

Study Design/Setting

Patient Sample

Outcome Measures

Methods

Results

Conclusions

Introduction

Section snippets

Clinical study design

Results

Discussion

Conclusion

Spine J

Orthop Clin North Am

J Biomed Eng

Lumbar interbody fusion using the Brantigan I/F cage for posterior lumbar interbody fusion and the variable pedicle screw placement system: two-year results from a Food and Drug Administration investigational device exemption clinical trial

Spine

Radiological changes in the bone fusion site after posterior lumbar interbody fusion using carbon cages impacted with laminar bone chips: follow-up study over more than 4 years

Spine

Is local bone viable as a source of bone graft in posterior lumbar interbody fusion?

Spine

Complications and surgical considerations in posterior lumbar interbody fusion with carbon fiber interbody cages and Steffee pedicle screws and plates

Orthopedics

Correlation of radiologic assessment of lumbar spine fusions with surgical exploration

Spine

Pseudarthrosis in the lumbosacral spine

J Bone Joint Surg Am

Can lumbar spine radiographs accurately determine fusion in postoperative patients? Correlation of routine radiographs with a second surgical look at lumbar fusions

Spine

Evaluation of lumbar spine fusion. Plain radiographs versus direct surgical exploration and observation

Spine

Three-dimensional computed tomography and multiplanar reformations in the assessment of pseudarthrosis in posterior lumbar fusion patients

Spine

Clinical and radiographic outcomes of anterior lumbar interbody fusion using recombinant human bone morphogenetic protein-2

Spine

Pseudarthrosis following lumbar fusion: detection by direct coronal CT scanning

Radiology

Radiologic assessment of interbody fusion using carbon fiber cages

Spine

Comparison of plain radiographs and CT scans in instrumented posterior lumbar interbody fusion

Orthopedics

Clinical Study
Fusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion