Radiographic evaluation of the impact of cage position on indirect neural decompression in crenel lateral interbody fusion / 中华骨科杂志

ABSTRACT

Objective To explore the impact of cage position on indirect decompression and cage subsidence in crenel lateral interbody fusion (CLIF).Methods Retrospectively,18 mens and 16 womens with a mean age of 63.98±5.99 years (range52-75 years) who underwent CLIF for lumbar stenosis by our surgical group during November 2016 and Feburary 2018 were reviewed.Sixty-two segments were included for radiographic evaluation.Endplates thickness was measured using high resolution computed tomography.By image processing,endplate thickness was measured at 10 equally distributed points on the mid-sagittal and mid-coronal planes,and two further planes were measured at an angle of 45° to both the first and second planes.Contour plots representing an isoline of endplate thickness was drawn based on those data.The cages were classified into anterior group and medium-posterior group.Radiographic evaluation included segmental angle,anterior and posterior disk heights,intervertebral foramen heights,and cross-sectional area of the spinal canal.To assess the factors affecting the postoperative segmental angle and cross-sectional area of the spinal canal,univariate and multivariate analysis were performed using the regression analysis model.Cage subsidence was recorded at the last follow-up.Results The mean follow-up time of those patients were 10.88±3.73 months (range6-18 months).At each spot,the mean thickness was significantly greater for the cranial endplate of disc than the caudal endplate.Contour plots show more areas of thick bony endplates in the anterior and anterolateral part of the endplate than the lateral and posterior part,especially for the cranial endplate.The cage was placed in the anterior area for 19 levels and medium-posterior for 41 levels.The mean increase of anterior disk height was 3.38±3.38 mm in anterior group and 1.83±3.08 mm in medium-posterior group(P=0.04).The mean increase of segmental angle was 2.93°±3.47°in anterior group and 0.73°±3.60° in medium-posterior group(P=0.04).No significant difference was found with mean increase of posterior disk height,mean increase of intervertebral foramen heights,as well as increase ratios of cross-sectional area of the spinal canal between groups.Multivariate analysis showed that the increase of segmental angle was affected by cage position (β=1.24,P=0.03),but the increase ratios of cross-sectional area of the spinal canal was not affected.The subsidence rate of anterior group was 15.79％ (3/19) and medium-posterior group was 24.39％ (10/41),which was not significantly different (x2=0.56,P=0.45).Conclusion There are more areas with thick bony endplates in the anterior and anterolateral parts of the lumbar endplate than the lateral and posterior parts.The cage position at the anterior 1/3 of disk space is better for achieving the restoration of the segmental angle and having lower subsidence rate,without compromising the indirect neural decompression in crenel lateral interbody fusion.