Lordosis Recreation in Transforaminal and Posterior Lumbar Interbody Fusion: A Cadaveric Study of the Influence of Surgical Bone Resection and Cage Angle.

STUDY DESIGN: Controlled cadaveric study of surgical technique in transforaminal and posterior lumbar interbody fusion (TLIF and PLIF) OBJECTIVE.: To evaluate the contribution of surgical techniques and cage variables in lordosis recreation in posterior interbody fusion (TLIF/PLIF). SUMMARY OF BACKGROUND DATA: The major contributors to lumbar lordosis are the lordotic lower lumbar discs. The pathologies requiring treatment with segmental fusion are frequently hypolordotic or kyphotic. Current posterior based interbody techniques have a poor track record for recreating lordosis, although recreation of lordosis with optimum anatomical alignment is associated with better outcomes and reduced adjacent segment change needing revision. It is unclear whether surgical techniques or cage parameters contribute significantly to lordosis recreation. METHODS: Eight instrumented cadaveric motion segments were evaluated with pre and post experimental radiological assessment of lordosis. Each motion segment was instrumented with pedicle screw fixation to allow segmental stabilization. The surgical procedures were unilateral TLIF with an 18° lordotic and 27 mm length cage, unilateral TLIF (18°, 27 mm) with bilateral facetectomy, unilateral TLIF (18°, 27 mm) with posterior column osteotomy (PCO), PLIF with bilateral cages (18°, 22 mm), and PLIF with bilateral cages (24°, 22 mm). Cage insertion used and "insert and rotate" technique. RESULTS: Pooled results demonstrated a mean increase in lordosis of 2.2° with each procedural step (lordosis increase was serially 1.8°, 3.5°, 1.6°, 2.5°, and 1.6° through the procedures). TLIF and PLIF with PCO increased lordosis significantly compared with unilateral TLIF and TLIF with bilateral facetectomy. The major contributors to lordosis recreation were PCO, and PLIF with paired shorter cages rather than TLIF. CONCLUSION: This study demonstrates that the surgical approach to posterior interbody surgery influences lordosis gain and PCO optimizes lordosis gain in TLIF. The bilateral cages used in PLIF are shorter and associated with further gain in lordosis. This information has the potential to aid surgical planning when attempting to recreate lordosis to optimize outcomes. LEVEL OF EVIDENCE: N/A.

Aortic valve area on 64-MDCT correlates with transesophageal echocardiography in aortic stenosis.

OBJECTIVE: The purpose of our study was to compare aortic valve area and calcification between CT and echocardiography. MATERIALS AND METHODS: We performed retrospective evaluation of 80 consecutive patients with aortic stenosis (AS) who underwent ECG-gated 64-MDCT and transesophageal echocardiography (TEE). Valve planimetry was feasible in 80 patients with CT and in 63 patients with TEE; valve area by transthoracic echocardiography was available in 46 patients. Valve calcification grade on CT was compared with TEE. One cardiologist (echocardiography) and two radiologists (CT) independently and blindly reviewed the studies. Pearson's correlations, Spearman's rank correlations, paired Student's t tests, and weighted kappa tests were used. RESULTS: The median valve area on TEE was 0.7 +/- 0.9 cm(2). There was excellent correlation (n = 80; r = 0.91, p < 0.001) and no difference (0.06 +/- 0.26 cm(2), p = 0.06) between CT readers. There was strong correlation (n = 63; r = 0.84, p < 0.001) and no difference (-0.06 +/- 0.48 cm(2), p = 0.33) in valve area between CT and TEE, with a strong correlation (n = 46; r = 0.83, p < 0.001) and small overestimation (0.17 +/- 0.33 cm(2), p < 0.001) in valve area with CT versus transthoracic echocardiography. The sensitivity and specificity of CT to detect severe aortic stenosis compared with TEE were 92.1% (35/38) and 89.5% (17/19), respectively. Calcification grade had fair agreement between CT readers and TEE (kappa = 0.34 and 0.37, respectively). CONCLUSION: Aortic valve area on CT strongly correlates with echocardiography and has excellent sensitivity and specificity to detect severe stenosis. Valve calcification has fair agreement between studies. Valve area and calcification should be reported on CT angiography in patients with AS.