Comparison Of Adjacent Segment Degeneration Following Mini-open Posterior Lumbar Interbody Fusion Versus Conventional Open Approach

Objective To determine the differences of adjacent segment degeneration (ASD) between mini-open and conventional open approach for posterior lumbar interbody fusion (PLIF).Methods102patients who underwent instrumented PLIF procedure in Sir Run Run Shao hospital from January2006to December2009were investigated. The patient were divided into two groups using two different approaches:mini-open approach with49patients and open approach with53patients. In the mini-open approach group, there were28males and21females, with an average age of51.4years. The follow-up time was48-58months, average51.3months. The follow-up rate was95.9%(47/49). While in the open approach group, there were27males and25females, with an average age of50.6years. The follow-up time was46-62months, average53.4months. The follow-up rate was94.3%(50/53). The Visual Analogue Scale and Oswestry disability Index, the injury of multifidus muscle and ASD were evaluated for the two groups.Results The VAS score and ODI percentage were comparable preoperatively, but significantly lower in the mini-open than in the conventional open group after surgery(P<0.001). The disc height reduction, decrease of MRI index, and the incidence of radiographic ASD were all lower in the mini-open group than the conventional open group(P<0.05). There were4cases of radiographic ASD in the mini-open group including two symptomatic cases. And there were12cases of radiographic ASD and4symptomatic cases in the conventional open group, among which2required surgical interventions. The mini-open group also showed less decrease in cross sectional area and lower degree of fatty degeneration grade of multifidus muscle at the operation and adjacent levels postoperatively(P<0.001). Both radiographic and symptomatic ASD were correlated with the decrease of cross sectional area and degree of fatty degeneration grade of multifidus muscle, but only symptomatic ASD were associated with clincal results.Conclusion Compared with the conventional open approach PLIF, the mini-open PLIF showed advantages of better clinical outcomes, less injury to multifidus muscle, and lower incidence of radiographic ASD.