Poster Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

INTRODUCTION

Lumbar spine fusion (LSF) surgeries have surged globally due to the increasing prevalence of degenerative spine disorders and advances in surgical techniques. While the success of LSF procedures is often evaluated through clinical metrics, patient-reported outcome measures (PROMs) are essential for capturing the subjective patient perspective. Existing PROMs, such as the Oswestry Disability Index (ODI)¹, primarily focus on symptoms and disease severity.² However, they do not address the patient's perception of clinical success. Inspired by the Forgotten Joint Score³ used in joint replacement surgery, we developed the Forgotten Spine Score (FSS), a novel PROM designed to assess how patients "forget" their fused spine segments in daily life, reflecting their perception of surgery success. This study aims to evaluate the FSS in a Japanese cohort, focusing on its validity and internal consistency.

METHODS

This prospective study was conducted at Tokai University Hospital in Isehara, Japan. An initial-phase FSS survey, involving an 18-item questionnaire developed by a multidisciplinary team, was translated into Japanese and administered to patients who underwent single- or multi-level LSF between L1 and S1 due to degenerative disorders. Participants were asked to complete both the FSS and the ODI to assess convergent validity. Patients were also asked to rate the FSS survey in relation to the ODI. Sociodemographic and clinical data, including age, sex, time since surgery, and the number of fused levels, were also collected. Internal consistency was measured using Cronbach's alpha, while convergent validity was assessed through Spearman correlation between FSS and ODI scores.

RESULTS

A total of 18 of the 50 patients (10 males, 8 females) with a mean age of 70.8±10.7 years and an average time since last surgery of 3.4±3.7 years participated in the pilot study thus far. Mean FSS scores were 31.9±24.7% and ODI  24.6±16.7%. Plotting FSS against ODI (Fig 1A), suggested a linear correlation between the two scores and significant Pearson correlation (r=0.648, p=0.036), with enhanced sensitivity favoring the FSS. The FSS items demonstrated high internal consistency, with a very strong Cronbach's alpha of 0.95 within the FSS, compared to 0.85 in the ODI survey. Finally, all of the participants indicated to approve of the FSS (Fig. 1B), with more than 40% of respondents indicating the FSS to be an improvement over the ODI survey, with 0% expressing a negative view.

DISCUSSION

This pilot study demonstrates that the Japanese version of the FSS exhibits high internal consistency, a valid correlation with the ODI, and positive feedback from patients, making it a promising tool for assessing patient-centered outcomes following LSF. Recruitment is ongoing to reach the target of 50 participants for the pilot phase, after which a final validation study involving at least 250 patients will be conducted. Our goal is to establish the FSS as a key tool for evaluating the success of LSF surgery.

Figure 1. (A) Plot of FSS versus ODI scores, showing evident correlation. (B) Pie chart depicting the appreciation rates of participants taking the FSS survey compared to the ODI survey. (translated from Japanese)