Objective:

To determine influence of preoperative Short Form 12 (SF-12) Mental Composite Score (MCS) on minimally important clinical difference (MCID) and patient-reported outcome measures (PROMs) among isthmic spondylolisthesis patients receiving minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).

Methods:

Isthmic spondylolisthesis patients undergoing primary, single-level MIS TLIF at L5/S1 were retrospectively identified and divided into groups: preoperative SF-12 MCS<50 vs SF-12 MCS≥50. Visual Analog Scale (VAS) back/leg, Oswestry Disability Index (ODI), SF-12 Physical Composite Score (PCS), and Patient-Reported Outcome Measurement Information System physical function (PROMIS-PF) were collected. Improvements from preoperative score were analyzed via paired samples t-test. PROMs and MCID attainment between groups were evaluated using linear regression and Chi-square, respectively.

Results:

35 and 26 patients were in SF-12 MCS<50 and SF-12 MCS≥50 groups, respectively. SF-12 MCS<50 had inferior scores for all VAS back timepoints except 6-weeks, all VAS leg timepoints except 6-weeks/1-year, all ODI timepoints, SF-12 PCS at 6-months/2-years, and PROMIS-PF preoperative/6-months (p≤0.049, all). SF-12 MCS<50 improved for VAS back/leg till 1-year, ODI/SF-12 PCS from 12-weeks to 1-year, and PROMIS-PF at 1-year, only (p≤0.047, all). SF-12 MCS≥50 improved for VAS back 12-weeks to 1-year, SF-12 PCS 6-months to 2-years, and VAS leg/ODI/ PROMIS-PF 12-weeks to 2-years (p≤0.018, all). MCID achievement differed for ODI at 6-weeks and PROMIS-PF at 12-weeks, only (p≤0.035, both).

Conclusion:

Patients with SF-12 MCS<50 demonstrated less long-term improvements from preoperative to 2-years, and inferior PROMs at most timepoints for pain and disability following MIS TLIF. However, MCID achievement largely did not differ by preoperative mental functioning.