The X-ray anatomic classification of lumbar vertebrain with lumbar intervertebral space and its clinical significance

Abstract

Objective To sum up the anatomic features of lumbar intervertebral space and classify of X-ray images, to provide the guidance for the clinical application of theforepart-expansible cage. Methods One hundred and thirty cases of lumbar instability treated with micro-endoscopic discectomy (MED) and posterior lumbar interbody fusion using the forepart-expansible cage and combined with percutaneous pedicle screw internal fixation from January 2013 to January 2015 in the First Affiliated Hospital of Zhengzhou University were retrospective analyzed. There were 69 males and 61 females, with an average age of 49 years (15-76 years). There were 209 segmental lesions: L1/2 8 lesions, L2/3 9 lesions, L3/4 34 lesions, L4/5 90 lesions, and L5/S1 68 lesions. The following indicators of each segmental lesion were measured in lumbar lateral X-ray images: the anterior intervertebral heights (a), anterior Disc Pit heights (b), and posterior intervertebral heights (c). According to the ratio of a/b and c/b, the intervertebral space can be classified into six types: AD(a/b>1 and c/b>0.5), AE (a/b>1 and c/b≤0.5), BD (a/b=1 and c/b>0.5), BE (a/b=1 and c/b≤0.5), CD (a/b 0.5), and CE (a/b<1 and c/b≤0.5). Postoperative X-ray was performed to confirm cage position change, postoperative CT was performed to confirm fusion. According to the Japan Department of Orthopedics (JOA), the effect of surgery was evaluated. Results There were 209 segmental lesions in 130 cases of lumbar instability. All the patients treated with MED and posterior lumbar interbody fusion using the forepart-expansible cage, there were 9 cases with gradeⅠ (7 cases) and grade Ⅱ(2 cases) lumbarspondylolisthesis combined with percutaneous pedicle screw internal fixation.The ratio of AD, AE, BD, BE, CD accounted for 78.0%(163/209), 10.5%(163/209), 8.6%(22/209), 2.4%(18/209), 0.5%(51/209). The patients were followed-up for 3-24 months. According to the JOA, improvement rate was 86.4%. According to the classification standard, 91 patients were cured, 31 patients had marked effect, 8 patients were effective. According to Suk criterion, solid union occurred in 86 cases (41.1%, 86/209) and probable union in 123 cases (58.9%, 123/209). Subsidence of two cages was found in one case of AD type, and one cage was found in one case of BD type. The total subsidence rate was 0.7%(3/418). Displacement of one cage was found in one case of CD type. The total displacement rate was 0.2%(1/418). None nerve injury or death case was found. Conclusions X-ray anatomic classification of lumbar intervertebral space can provide the guidance for choosing the placement and estimating the displacement trend of the forepart-expansible cage with micro endoscopic discectomy and posterior lumbar interbody fusion, reduce or avoid the cage move, and improve effect of surgical treatment. Key words: Lumbar vertebra; Vertebral space; X-ray; Anatomy; Forepart-expansible cage