The clinical efficacy of lumbar L4/5 single level fusion and its effect on the lumbar-pelvis sagittal alignment parameters of differrent Roussouly type

English Keywords:Adjacent segment degeneration  L4/5 interbody fusion  Intervertebral angle of L4/5  Types of Roussouly

English Abstract:

  【Abstract】 Objectives: To investigate the effect of single L4/5 fusion(SL4/5) on the lumbar-pelvis sagittal alignment parameters of differrent Roussouly type and its clinical efficacy. Methods: Between March 2008 and March 2012, 317 patients with lumbar fusion of SL4/5 were collected, and 51 cases of them(with healthy adjacent segments, complete follow-up data, follow-up time ≥3 years) included in this study, 25 males and 26 females, with an average age of 43.45 years. They were categorized into 4 types on the basis of lumbar lordosis of lumbar sagittal vertex position curve(Roussouly type): Type Ⅰ, vertex located in L5 vertebral body or L4/5 intervertebral space; Type Ⅱ, vertex located at the bottom or middle of the L4; Type Ⅲ, vertex located at the upper part of L4 or L3/4 intervertebral space; Type Ⅳ, vertex located at the L3 vertebral body and above. The VAS, ODI and JOA scores were compared, and the lumbar-pelvic parameters were measured, such as pelvic incidence(PI), sacral slope(SS), pelvic tilt(PT), lumbar lordosis(LL), UP arc and intervertebral lordosis of lumbar 4-5(IVA4-5), C7 plumb line/Sacro-femoral distance ratio(C7PL/SFD ratio) at the preoperation, postoperation and final follow-up. MRI was adopted to evaluate radiographic adjacent segment degeneration(rASD) before the operation, and the UCLA Grading Scale and intervertebral stability criteria of lumbar degeneration were introduced to evaluate rASD after the operation. Changes of the parameters in different periods were statistically analyzed. Results: The mean follow-up time was 42.58 months(36 to 67 months). The distribution of patients according to Roussouly type was as following: Type Ⅰ, 10 cases(19.61%); Type Ⅱ, 15 cases(29.42%); Type Ⅲ, 20 cases(39.22%); Type Ⅳ, 6 cases(11.76%). In Type Ⅰ: there were significant improvements（P<0.01） in LL, UP arc, IVA4-5 and SS at postoperation and final follow-up compared with those at preoperation, but PT decreased. In Type Ⅱ and Ⅲ: IVA4-5 had significant improvement(P<0.05) at the postoperation and final follow-up compared with that at preoperation, the LL at final follow-up significantly increased(P<0.05) compared with that at preoperation, while the SS, PT and PI showed no significant differences. In Type Ⅱ, UP arc significantly increased at the final follow-up. In Type Ⅳ: the IVA4-5(P<0.05) significantly increased with statistically significant differences to the preoperative, but there was no significant difference in LL, UP arc, SS, PT or PI between preoperation and postoperation. The ratio of C7PL/SFD significantly decreased at the postoperation and final follow-up compared with that at preoperation in all types. VAS, ODI, JOA scores at postoperation and final follow-up had significant improvement than the preoperatives. The general prevalence of rASD was 17.64% in all patients. Analysis of rASD risk factors showed: age, follow-up time, PI, IVA4-5 were major risk factors. Conclusions: SL4/5 can significantly increase IVAL4-5, but has different effects to spine-pelvis sagittal alignment parameters according to the types of Roussouly. IVA4-5 is a significant risk factor of rASD, the older age, the longer follow-up time and higher PI values are more prone to rASD.