Age, Number of Vertebral Levels Fused, and Average Psoas Size All Predict Hospital Length of Stay After Minimally Invasive TLIF and LLIF

Presented at SMISS Annual Forum 2018
By H. Zakaria
With M. Macki , L. Massie , V. Chang ,

Disclosures: H. Zakaria None M. Macki None, L. Massie None, V. Chang None,


With the increasing frequency of spine surgery, there is an emphasis on decreasing costs associated with this procedure. One potential area of improvement is decreasing length of hospital stay. Minimally invasive surgery (MIS) of the spine is designed to improve outcomes by minimizing approach. Identification of factors that can predict shorter length of stay after routine MIS of the spine would allow surgeons to pick the procedures that can be performed in an outpatient setting as a means of cost containment.


We sought to identify patient and surgical factors which are associated with postoperative length of stay after MIS transforaminal lumber interbody fusions (TLIF) and MIS lateral lumber interbody fusions (LLIF).


The Michigan Spine Surgery Improvement Collaborative (MSSIC) is a database of elective spine surgery procedures. MSSIC was queried for MIS TLIF and MIS LLIF over two years. To maintain internal validity, patients were limited to a single surgeon’s experience. The primary outcome was time to discharge for patients with routine hospital courses, or length of hospital stay (LOS) ≤ 3 days; we focused on ≤ 3 days because discharge ≥ 4 days was associated with a complication or administrative hurdle (eg insurance authorization), and would therefore confound the primary outcome.


73 patients with routine discharge were identified, with 32% male and median age of 65. 83.5% underwent MIS TLIF, while 16.4% underwent MIS LLIF. 36.9% of patients were discharged hospital day (HD) 1, 42.4% HD2, 20.5% HD3. Only 1 patient had a postoperative morbidity within 90d, a urinary tract infection. Multivariate logistical regression identified three factors associated increasing length of hospital stay: increasing age, number of vertebral levels fused, and average psoas size. Increasing age was associated with longer hospital stay, odds ratio (OR) 1.80, 95%CI 1.11-2.93, p=0.017. More vertebral levels being fused was associated with longer hospital stay, OR 4.74, 95%CI 1.41-15.95, p=0.012. Having a larger average psoas size was associated with a shorter hospital, OR 0.88, 95%CI 0.78-0.99, p=0.034.


Patient age, number of vertebral levels fused, and average psoas size all predicted hospital stay after MIS TLIF and LLIF. This data can be used to identify the ideal patient for an outpatient MIS spine procedure. According to our data, the patient who is most likely to tolerate outpatient MIS TLIF and LLIF would be younger age, limited number of levels, and with large psoas muscles.