P4. Minimum clinically important differences in degenerative lumbar patient-reported outcomes are not indicative of widespread improvements in objective functional outcome measures

Abstract

<h3>BACKGROUND CONTEXT</h3> Patient reported outcome measures (PROMs) benchmarked by the minimum clinically important difference (MCID) are often used to indicate patient functional status before and after surgery for degenerative lumbar pathology (DLP). Prior research has shown that not all spine PROMs directly relate to objective functional improvements in activities like walking and standing. Currently it is unclear whether achieving PROMs MCID should be considered outrightly indicative of improved functional outcomes measures (FOMs). <h3>PURPOSE</h3> Determine if achievement of PROMs MCID relates to significant changes in objective gait and balance FOMs among surgical DLP patients. <h3>STUDY DESIGN/SETTING</h3> Non-randomized, retrospective review of DLP patient pre- and postoperative PROM and FOM data. <h3>PATIENT SAMPLE</h3> There were 99 patients treated with decompression or single-level fusion for DLP. <h3>OUTCOME MEASURES</h3> Visual analog scales (VAS) for low-back and leg pain, Oswestry Disability Index (ODI), spatiotemporal and kinematic gait measures, and postural balance measures (range-of-sway: ROS, total-sway distance: TSD). <h3>METHODS</h3> Surgical DLP patients completed PROMs and functional evaluations one week before surgery (P0) and at three- and 12-month postoperative follow-ups (P3 and P12). Functional evaluations included walking and balance tests using three-dimensional motion tracking. FOMs showing significant P0-P3-P12 univariate improvements were compared between achieved MCID (aMCID) and not achieved MCID (nMCID) for each PROM at P0-P3 and P0-P12. <h3>RESULTS</h3> All PROMs showed significant univariate improvements (P0, P3, P12 respectively): VAS low-back (4.2±3.7, 1.7±1.7, 2.5±2.9, p=0.002), VAS-leg (5.8±3, 1.4±1.9, 1.6±2.6, p<0.001), ODI (43.4±13.6, 23.9±15.8,22.9±17.1, p<0.001). Two of 14 gait FOMs showed significant univariate improvements: increased step length (0.54±0.05m, 0.56±0.04m, 0.57±0.04m, p=0.043) and reduced single-support time (0.45±0.07s,0.44±0.06s, 0.42±0.04s, p=0.040). Three of six balance FOMs showed significant univariate improvements: reduced coronal ROS (2.95±2.19cm, 1.88±0.9cm, 1.9±0.73cm, p=0.025), reduced sagittal ROS (6.58±2.58cm, 5.5±1.72cm, 5.16±1.56cm, p=0.025), and reduced TSD (71±45.4cm, 50.3±19cm, 48±14.2cm, p=0.014) for the head. MCID achievement was as follows: VAS low-back: 67%@P3, 46%@P12; VAS leg: 73%@P3, 75% @P12; ODI: 58%@P3, 72%@P12. aMCID yielded significantly greater improvements in the following FOMs (aMCID/nMCID respectively): @P3: longer step length for VAS leg (0.03±0.03m/-0.01±0.05m, p=0.021), less coronal head ROS for VAS low-back (-1.59±3.19cm/-0.09±1.67cm, p=0.016) and VAS leg (-1.54±3.07cm/0.07±1.75cm, p<0.001), less sagittal head ROS for VAS leg (-1.94±4.1cm/-0.9±3.43cm, p=0.003), and less head TSD for VAS leg (-26.17±53.17cm/-8.54±32.57cm, p=0.002); @P12: less sagittal head ROS for ODI (-1.63±4.44cm/-0.71±2.38cm, p=0.046). Although significant, relative numeric improvements were minimal for head ROS. <h3>CONCLUSIONS</h3> Select statistically significant differences in FOMs were found however, numerical differences were low and widespread improvements across all FOMs were not found, even with significant univariate improvements. Achieving MCID for VAS leg pain may be related to improved step length and dynamic balance, but there is little evidence to suggest that it should be considered indicative of overall functional improvement of DLP surgery patients. PROMs and FOMs may be measuring different yet equally important aspects of DLP patient function. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.