The Prognostic Factor of Posterolateral Fusion in Degenerative Spondylolisthesis

ABSTRACT

STUDY DESIGN: A retrospective analysis of the posterolateral fusion in degenerative spondylolisthesis. OBJECTIVES: Posterolateral fusion has been performed for patients about Meyerding grade1, 2 with degenerative spondylolisthesis in L4-5. We evaluated the prognostic factors of posterolateral fusion, alone for degenerative spondylolisthesis. SUMMARY OF LITERATURE REVIEW It is reported that posterolateral fusion has almost equal postoperative clinical and radiographic results with the interbody or circumferential fusion for spondylolisthesis. However, there have been some unsatisfactory results after posterolateral fusion alone and the causes are yet unknown. MATERIAL AND METHODS: From January 2002 to July 2008, we analyzed postoperative clinical outcomes of 42 patients who were diagnosed with Meyerding 1 or 2 grade degenerative spondylolisthesis at L4-5. All the patients were classified into group I and group II, based on the clinical outcome evaluation method by Kirkaldy-Willis. Ten patients (Group I) were found to have poor or fair clinical outcomes, while 32 patients (Group II) were found to have excellent or good clinical outcomes. The mean duration of the follow up was 16.3 (12-23) months. We looked into postoperative body mass index and bone mass density, and found degenrative lumbar disc through preoperative MRI, retrospectively. We measured angular motion by dynamic radiographs and preoperative slip angle through a Taillard method. RESULTS: In group I, the average preoperative BMI was 25.7 (21.2~31.4) and the average T score of bone density was -3.0 (-1.9~-4.2). There was 1 case of Grade 3, 3 cases of Grade 4 and 6 cases of Grade 5 by preoperative Pfirmann classification. The average angular motion was 11.8 (9.1~14.2) and the average preoperative slip angle was 8.4 (6.9-9.6). In group II, the average preoperative BMI was 24.3 (20.72~28.1) and the average T score of bone density was -2.1 (-0.9~-3.1). There were 26 cases of Grade 3, 5 cases of Grade 4 and 1 case of Grade 5 by preoperative Pfirmann classification. The average angular motion was 8.8 (6.2~12.1) and the average preoperative slip angle was 6.2 (3.6-7.9). There were statistically significant differences between the two groups in BMI, stage of disc degeneration, preoperative angular motion, and slip angle. (p=0.04, 0.04, 0.05, 0.03, respectively) CONCLUSION: We concluded that posterolateral fusion has exhibited worse clinical results in cases of BMI less than -2.8, disc degeneration greater than grade 4, angular motion greater than 9.4 degrees, and slip angle greater than 7.1 degrees; as such, we need to consider other surgical methods.