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


OBJECTIVE
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.


METHODS
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.


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


METHODS
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.
Fogel
Guy R
GR
South Texas Orthopedic and Spinal Surgery Associates, 9150 Huebner Road, San Antonio, TX 78240, USA. gfogel@satx.rr.com
Toohey
John S
JS
Neidre
Arvo
A
Brantigan
John W
JW
D000328:Adult; D000368:Aged; D002244:Carbon; D000077482:Carbon Fiber; D015194:Diffusion Chambers, Culture; D005260:Female; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000601:surgery; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016037:Single-Blind Method; D013123:Spinal Fusion / Q000145:classification* / Q000295:instrumentation / Q000706:statistics & numerical data; D036542:Tomography, Spiral Computed / Q000379:methods*; D016896:Treatment Outcome; D014965:X-Rays
D000077482:Carbon Fiber; D002244:Carbon