To examine the relationship between obesity (BMI> 30) and the incidence of peri-operative complications, outcome of surgery and return to work in patients undergoing elective less invasive posterior lumbar inter-body fusion of the lumbar spine for low back pain and leg pain (“LI-PLIF”). 15 patients with BMI> 30 who underwent (“LI-PLIF”) were identified by reviewing the clinical notes and the pre-operative admission sheet from April 2005- to March 2007. All had suffered chronic low back pain for a minimum of 2 years that had proven unresponsive to conservative treatment. All patients underwent pre- and postoperative evaluations for Oswestry Disability Index (ODI), short-form 36 (SF-36), and visual analogue scores (VAS). Minimum follow-up was for 12 months. Blood loss was dependent on BMI, number of levels, and surgical time. Post operative complication was more in the morbidly obese group than the in the obese. 10 patients (66.6%) returned to their normal pre-operative employment within the 12 months of the index procedure. There was a significant improvement in the ODI and in the VAS for back pain. Length of hospital stay was a mean of 3.3 days. Although surgery is technically more demanding our experience with less invasive posterior inter-body fusion has shown less incidence of post operative complication, less intra-operative blood loss and short in-patient hospital stay. We conclude that a high BMI should not be a contraindication to surgery in patients with degenerative low back pain. Ethics approval: None: Audit Interest Statement None

Increasing numbers of posterior lumbar fusions are being performed. The purpose of this study was to identify trends in demographics, mortality and major complications in patients undergoing primary posterior lumbar fusion. We accessed data collected for the Nationwide Inpatient Sample for each year between 1998 and 2008 and analysed trends in the number of lumbar fusions, mean patient age, comorbidity burden, length of hospital stay, discharge status, major peri-operative complications and mortality. An estimated 1 288 496 primary posterior lumbar fusion operations were performed between 1998 and 2008 in the United States. The total number of procedures, mean patient age and comorbidity burden increased over time. Hospital length of stay decreased, although the in-hospital mortality (adjusted and unadjusted for changes in length of hospital stay) remained stable. However, a significant increase was observed in peri-operative septic, pulmonary and cardiac complications. Although in-hospital mortality rates did not change over time in the setting of increases in mean patient age and comorbidity burden, some major peri-operative complications increased. These trends highlight the need for appropriate peri-operative services to optimise outcomes in an increasingly morbid and older population of patients undergoing lumbar fusion.