82 - Left Digit Bias in Deciding to Fuse vs Decompress in Degenerative Spondylolisthesis and Stenosis: How Age Related Heuristics Impact Surgical Decision Making

Background/

Introduction:
Left-digit bias is a behavioral heuristic in which the left-most digit of a number disproportionately influences decision making. The influence of left-digit bias on decision for fusion in patients with lumbar spinal stenosis is unknown.

Aims/

Objectives:
It was the goal of this study to establish whether age related behavioral heuristics may impact physician’s decision to fuse in lumbar spine surgery.

Materials/

Methods:
Surgical patients with an ICD10 diagnosis of lumbar spondylolisthesis or stenosis were identified in the 2017-2021 National Surgical Quality Improvement Program (NSQIP) database. Using CPT codes, procedures were classified as either “fusion” (1-2 level posterolateral, anterior/lateral, or transforaminal interbody) or “decompression” (laminectomy/decompression with or without in-situ fusion). Patients aged 78-81 were then isolated and stratified into two cohorts (78/79 vs. 80/81). The cohorts were propensity matched based on presence of spondylolisthesis, demographics, and comorbidities. The primary outcome was the percent of patients who underwent fusion. The above method was also replicated for age group comparisons without left-digit differences (i.e., 80/81 vs 82/83 and 76/77 vs 78/79) to isolate the observed effect of the heuristic. Secondary outcomes (hospital length-of-stay (LOS), re-admission, re-operation, non-home discharge, and complications) were compared within fusion and decompression cohorts.

Results:
3,631 patients met inclusion criteria. After matching, the cohort consisted of two groups of 1,558 (age 78/79 and 80/81), with similar demographics, rates of spondylolisthesis, and comorbidities (including but not limited to diabetes, smoking, steroid use, and ASA class). Patients aged 78/79 were more likely to be fused than patients aged 80/81 (27.2% vs. 23.5%, p=0.021). Choice for fusion between other age groups with the same left-digit (76/77 vs 78/79 or 80/81 vs 82/83) were similar (Figure 1). There were no differences in secondary outcomes between 78/79 and 80/81 in the decompression and fusion cohorts, respectively.

Conclusion:
LSS patients who are 78/79 are more likely to undergo fusion than patients aged 80/81, regardless of patient comorbidities. This phenomenon was not seen when comparing 76/77 vs. 78/79 or 80/81 vs 82/83, suggesting a significant left-digit bias in surgical planning. Given that early complications, readmissions, and reoperations did not differ between the cohorts, surgeons must be aware of this behavioral heuristic when indicating patients for surgery.