Effects of Total Psoas Area Index on Surgical Outcomes of Single-Level Lateral Lumbar Interbody Fusion

Objective We evaluated the effect of the total psoas area index (TPAI = total psoas muscle area [cm2]/height squared [m2]) on neurological complications and clinical outcomes after lateral lumbar interbody fusion and identified the appropriate TPAI to achieve a substantial clinical benefit (SCB). Methods A consecutive series of 123 patients who had undergone single-level lateral lumbar interbody fusion at a single center with ≥2 years of follow-up were retrospectively reviewed. The patient characteristics and operative data were evaluated. The neurological complications were classified as transient and persistent symptoms. The visual analog scale score for back pain was assessed preoperatively and at 1 and 2 years postoperatively. Results The present study included 31 men and 92 women. The mean TPAI was 8.97 cm2/m2 for the men and 5.04 cm2/m2 for the women. The mean TPAI was not significantly different between the patients with and without perioperative neurological complications. Multiple logistic regression analysis showed that solid interbody fusion was the most significant factor for achieving an SCB regarding back pain in men (odds ratio [OR], 2.453; P = 0.019) and women (OR, 2.906; P = 0.042). The TPAI was one of the predictors for achieving an SCB in men (OR, 1.251; P = 0.038) and women (OR, 1.795; P = 0.023). The optimal cutoff point of the TPAI for an SCB was 8.18 cm2/m2 for the men and 4.43 cm2/m2 for the women. Conclusions The TPAI had little effect on the incidence of perioperative neurological complications. However, the TPAI was identified as one of the predictors for achieving an SCB regarding back pain.