Preoperative Radiographic Risk Factors for Pseudoarthosis in Minimally Invasive Transforminal Interbody Fusions

Presented at SMISS Annual Forum 2014
By Sina Pourtaheri MD
With Arash Emami MD, Eiman Shafa MD, Ki Hwang MD, Michael Faloon MD, Kimona Issa MD, Kumar Sinha MD,

Disclosures: Sina Pourtaheri MD None Arash Emami MD B; Depuy Spine, Eiman Shafa MD None, Ki Hwang MD B; Depuy Spine, Michael Faloon MD None, Kimona Issa MD None, Kumar Sinha MD None,

Introduction:
Minimally invasive transforminal interbody fusions (MIS-TLIFs) as compared to open TLIFs has shown similar long-term clinical outcomes with decreased perioperative morbidity and earlier return to work. However, no identified preoperative radiographic risk factors for pseudoarthosis with MIS-TLIFs have been identified in the literature.

Aims/Objectives:
The purpose of this study was to identify preoperative radiographic risk factors for pseudoarthrosis with these MIS-TLIFs. Methods: We retrospectively reviewed 98 consecutive patients undergoing one or two-level MIS-TLIFs. Our study included revision (21%) and primary (79%) procedures. All patients had a minimum of two year clinical and radiographic follow-up. Chi-squared statistic, Fisher’s exact, and single sample t tests were used.

Results:
ODIs and VAS scores had significantly improved with the MIS TLIFs (p < 0.001). Complication rate was 14% which were all minor complications. There were 8 cases of pseudoarthosis (8.2%). This pseudoarthosis cohort had similar rates of diabetics (13% vs. 10%, p < 0.82), smokers (0% vs. 11%, p < 0.75), and Charlson comorbidity index scores (0.75 vs. 1.2 points, p < 0.88) as the cases without a pseudoarthosis. The mean number of levels fused was similar between the groups (1.13 vs. 1.18, p < 0.73). However, in the pseudoarthosis cohort the following preoperative radiographic parameters were significantly different than the group without a pseudoarthosis: anterior disc height (17 vs. 6 mm, p < 0.04), anterior to posterior disc height ratio (2.8 vs. 1.6, p < 0.03) and angulation of the disc (16 vs. 4 degrees, p < 0.05).

Conclusions:
The following preoperative radiographic parameters were a risk factor for a pseudoarthrosis with MIS-TLIFs: increased anterior disc height, increased anterior to posterior disc height ratio, and angulation of the disc. Patients with these risk factors consider an anterior or lateral lumbar interbody fusion.