Distal Lumbar Lordosis Fixation and the Impact of Lordosis Distribution Index on Adjacent Segment Disease, Revision Surgery and Patient Reported Outcome Measures in a Prospectively Collected Cohort

Introduction: While sagittal spinopelvic alignment is well-known to influence outcomes after lumbar fusion, the lordosis distribution index (LDI) has gained attention as a better way to quantify lumbar lordosis (LL). We aim to assess the impact of LDI on operative adjacent segment disease (ASD) and patient reported outcome measures (PROM) following distal lumbar lordosis (DLL; L4-S1) fusion.

Methods: We queried a prospectively collected database of 5,093 patients from 5 spine surgeons at our institution from 2009 to 2024 for all fusions from L4-S1 with minimum 1-year follow-up and no scoliotic deformity or prior fusion.

Results: Thirty patients were included with a median age of 56 years and slight female predominance (n=19, 63.3%). The sample included 52 interbodies with an average of 1.73±.521 interbodies per patient. The rate of reoperation was 33.3% (n=10), operative ASD 23.3% (n=7), and radiographic hardware failure 40% (n=12).

Most patients were considered to have normal lordosis by post-operative LDI (50-80%; n= 19, 63.3%) and 43.3% of patients were considered to have ideal PI-LL mismatch (PI-LL < 10 °; n=13).While LDI category was not related to operative ASD or reoperation we found that these patients had significantly higher average increases in post-op LDI from baseline (+14.9±4.10% v. +0.5±9.72% , p=.005; +11.36±10.63% v. -0.43±8.21%, p=.009; respectively). Additionally, patients requiring revision surgery had greater loss of proximal LL (L1-L4; PLL) from pre-op (-6.00±5.8% v. -0.43±4.81%, p=.025) and patients with >5° loss of PLL had significantly higher rates of revision surgery (72.4% v. 20.0%, p=.020).

At 1-year, 40.0% of patients (n=12) achieved a minimal clinically important difference (MCID; -14.9) in ODI and these patients had lower average PI-LL mismatch (2.00± 9.6° v. 14.5±10.99°, p=.012) and lower post-op LDI (62.3±11.1% v. 75.73±21.8%, p=.037). Rates of achieving MCID at 1-year were higher in patients with ideal PI-LL alignment (80.0% v. 14.3%, p=.008) and lower in hyperlordotic patients (0% v. 63.2%, p=.002).

Conclusion : While our sample size is limited, we found that loss of PLL and increase in LDI following DLL fixation were associated with higher rates of ASD and revision surgery. Similarly, patients with hyperlordotic LDI and misaligned PI-LL had significantly worse ODI outcomes at 1-year.