Impact of age on the likelihood of reaching a minimum clinically important difference in 374 three-column spinal osteotomies
Authors: Scheer Justin K. , Lafage Virginie , Smith Justin S. , Deviren Vedat , Hostin Richard , McCarthy Ian M. , Mundis Gregory M. , Burton Douglas C. , Klineberg Eric , Gupta Munish C. , Kebaish Khaled M. , Shaffrey Christopher I. , Bess Shay , Schwab Frank , Ames Christopher P. , _ _ 
Published: January 2014

Object
Spinal osteotomies for adult spinal deformity correction may include resection of all 3 spinal columns (pedicle subtraction osteotomy [PSO] and vertebral column resection [VCR]). The relationship between patient age and health-related quality of life (HRQOL) outcomes for patients undergoing major spinal deformity correction via PSO or VCR has not been well characterized. The goal of this study was to characterize that relationship.

Methods
This study was a retrospective review of 374 patients who had undergone a 3-column osteotomy (299 PSOs and 75 VCRs) and were part of a prospectively collected, multicenter adult spinal deformity database. The consecutively enrolled patients were drawn from 11 sites across the United States. Health-related QOL outcomes, according to the visual analog scale (VAS), Oswestry Disability Index (ODI), 36-Item Short-Form Health Survey (SF-36, physical component score [PCS] and mental component score), and Scoliosis Research Society-22 questionnaire (SRS), were evaluated preoperatively and 1 and 2 years postoperatively. Differences and correlations between patient age and HRQOL outcomes were investigated. Age groupings included young (age ≤ 45 years), middle aged (age 46–64 years), and elderly (age ≥ 65 years).

Results
In patients who had undergone PSO, age significantly correlated (Spearman's correlation coefficient) with the 2-year ODI (ρ = 0.24, p = 0.0450), 2-year SRS function score (ρ = 0.30, p = 0.0123), and 2-year SRS total score (ρ = 0.30, p = 0.0133). Among all patients (PSO+VCR), the preoperative PCS and ODI in the young group were significantly higher and lower, respectively, than those in the elderly. Among the PSO patients, the elderly group had much greater improvement than the young group in the 1- and 2-year PCS, 2-year ODI, and 2-year SRS function and total scores. Among the VCR patients, the young age group had much greater improvement than the elderly in the 1-year SRS pain score, 1-year PCS, 2-year PCS, and 2-year ODI. There was no significant difference among all the age groups as regards the likelihood of reaching a minimum clinically important difference (MCID) within each of the HRQOL outcomes (p > 0.05 for all). Among the PSO patients, the elderly group was significantly more likely than the young to reach an MCID for the 1-year PCS (61% vs 21%, p = 0.0077) and the 2-year PCS (67% vs 17%, p = 0.0054), SRS pain score (57% vs 20%, p = 0.0457), and SRS function score (62% vs 20%, p = 0.0250). Among the VCR patients, the young group was significantly more likely than the elderly patients to reach an MCID for the 1-year (100% vs 20%, p = 0.0036) and 2-year (100% vs 0%, p = 0.0027) PCS scores and 1-year (60% vs 0%, p = 0.0173) and 2-year (70% vs 0%, p = 0.0433) SRS pain scores.

Conclusions
The PSO and VCR are not equivalent surgeries in terms of HRQOL outcomes and patient age. Among patients who underwent PSO, the elderly group started with more preoperative disability than the younger patients but had greater improvements in HRQOL outcomes and was more likely to reach an MCID at 1 and 2 years after treatment. Among those who underwent VCR, all had similar preoperative disabilities, but the younger patients had greater improvements in HRQOL outcomes and were more likely to reach an MCID at 1 and 2 years after treatment.