Patient-Reported Outcome Measurement Information System (PROMIS) is increasingly being utilized to assess preoperative and postoperative outcomes in patient populations undergoing orthopedic and spine procedures.1,2 When compared with traditional surveys, PROMIS offers the advantage of collecting patient data in a time-efficient manner.1–3 Developed by the National Institutes of Health, PROMIS has proven to be effective at quickly evaluating outcomes due to its unique Computer Adaptive Testing algorithm and putting less burden on patients who complete questionnaires.3,4 PROMIS encompasses a number of domains that are gaining traction in the field of orthopedic surgery for evaluating various aspects of patient-reported quality of life, such as physical, mental, or social health. Some of the available variables and domains assessed by the PROMIS survey include Pain Interference, which evaluates the extent to which pain hinders engagement with aspects of one's life; Sexual Function, which measures the degree to which symptoms of disease and side effects of treatment affect satisfaction with sex life; and Cognitive Function, which evaluates the extent to which cognitive impairments interfere with daily functioning.5
Among these, the PROMIS Physical Function (PF) domain can be especially telling of the patients’ strength, mobility, and coordination, and therefore provide utility in evaluating postoperative function in spine patients. Specifically, it may be worth exploring whether the PROMIS PF survey can be beneficial in predicting outcomes based on certain preoperative risk factors in procedure-specific patient populations such as those undergoing lumbar fusion. For instance, lumbar interbody fusions are frequently performed procedures in the United States, with rapidly rising rates over the past several decades.6 The transforaminal lumbar interbody fusion (TLIF) procedure can be an effective treatment in the management of degenerative pathologies of the lumbar spine, with prior investigations demonstrating improved postoperative clinical, radiographic, and functional outcomes.7 Additionally, there is more need for continued research into minimally invasive (MIS) techniques with the aim of reducing approach-related surgical morbidity. As such, the target population of our study was chosen to be patients who underwent MIS TLIF with the specific goal of determining the postoperative changes in the patients’ physical function and disability as measured by a survey instrument such as PROMIS.
In the field of spine surgery, increasing research is focusing on psychosocial risk factors and their influence on postoperative outcomes following surgery. Mental health conditions such as depression and anxiety have been well studied in the past.8–12 For instance, Miller et al13 demonstrated that the presence of preoperative depression may be associated with significantly reduced improvement in postoperative outcomes and quality of life following lumbar fusion procedures. With reports stating that as many as 6.8 million people in the United States are dealing with psychiatric conditions such as depression, it is essential that research into their impact on spine surgery patients continues to help surgeons counsel and manage patient expectations regarding recovery and postoperative outcomes.14 Moreover, there is a paucity of scientific investigations that have determined the association between preoperative mental health as evaluated by a validated questionnaire such as the Short-Form 12 (SF-12) health survey and postoperative outcomes following spine procedures such as MIS TLIF. While the SF-12 is a survey instrument that measures health-related quality-of-life, the mental component summary (MCS) of the survey, which was utilized in our study, has shown good performance as a screening tool for depression and other mental disorders. For instance, Vilagut et al15 demonstrated that the Short Form-12 Mental Health Composite Score (SF-12 MCS) was able to detect both active and recent depressive disorders, indicating that the questionnaire may be used to evaluate the presence of affective disorders and to optimize treatment and prevention. As such, the purpose of the present study was to demonstrate whether preoperative mental health status of patients can be predictive of postoperative functional outcomes as measured by PROMIS PF following MIS TLIF.
METHODS AND MATERIALS
This investigation began after Institutional Review Board approval (ORA# 14051301) was obtained. A prospectively maintained surgical database of patients who underwent primary, one- to two-level MIS TLIF for degenerative pathology between 2015 and 2018, was retrospectively reviewed. A single surgeon at a single academic center treated all patients in our study. Examples of preoperative diagnoses included degenerative disc disease, degenerative spondylolisthesis, spinal stenosis, and herniated nucleus pulposus. Patients were not excluded from analysis based on their age in our study. However, patients were excluded if they underwent a revision procedure, or if they underwent surgical intervention for trauma, infection, or malignancy. Patients with incomplete preoperative PROMIS PF or SF-12 MCS scores, or patients who underwent MIS TLIF for reasons other than degenerative pathology were excluded from our study.
Data from the surveys were collected electronically. Survey invitations were sent to patients electronically at the preoperative and postoperative timepoints in our study. Patients were stratified based on predetermined preoperative SF-12 MCS cutoff scores: <50 points (worse mental health) and ≥50 points (better mental health). The SF-12 MCS questionnaire was administered to patients preoperatively before undergoing MIS TLIF. The SF-12 MCS, which evaluates the mental health status of patients, is a subcomponent derived from the original 12-item SF-12 survey. The SF-12 has been widely used to assess health-related quality of life, with a mean score of 50 and a standard deviation of 10, and higher scores representing better health status.16–18
Demographic variables assessed included age, sex, diabetes status, smoking status, body mass index, insurance type, and comorbidity burden. Comorbidity burden was measured using the Charlson Comorbidity Index with the age component removed. Perioperative outcomes were also recorded, including number of fusion levels, duration of operation, estimated blood loss, length of hospital stay, and number of discharge days.
The PROMIS survey has demonstrated good discriminant ability, concurrent validity, and responsiveness relative to legacy outcome measures. For instance, Purvis et al19 reported that PROMIS discriminated between different disease severity levels, strongly correlated with other traditionally used surveys, and was responsive to postoperative changes in patients undergoing lumbar spine surgery for degenerative disease. Likewise, the SF-12 survey was also determined by Luo et al20 to have good reliability, construct validity, and responsiveness in patients with back pain.
The PROMIS PF survey was taken by patients preoperatively, as well as at the 6-week, 3-month, 6-month, and 1-year postoperative timepoints following MIS TLIF. A PROMIS PF score of 50 is the mean score of the general population in the United States, with a higher score indicative of better physical function, and each 10-point interval being equivalent to one standard deviation above or below the mean score.
Statistical analysis was performed using Stata/MP 13.0 for macOS Mojave (StataCorp LP, College Station, TX). The normality of the sample patient population was assessed by reviewing the distribution graphically via histogram to confirm the symmetry of the distribution. Demographic variables and perioperative outcomes were compared between SF-12 MCS cohorts using chi-squared analysis and multivariate linear regression. A backward elimination model was utilized to determine the variables to include and exclude in the multiple linear regression analysis. Independent risk factors for worse postoperative physical function after MIS TLIF were determined using backward, stepwise regression, which initially included all demographic and perioperative characteristics. The variables with the highest P values were then excluded until only those that were significant remained, which were patient age and insurance type. To assess for multicollinearity, a pairwise correlation with variables in the final multiple regression model was performed. Finally, preoperative and postoperative PROMIS outcomes, as well as improvement in PROMIS scores in relation to SF-12 MCS scores following MIS TLIF, were analyzed using a multiple linear regression model controlling for patient age and insurance type. A P value <0.05 was established to determine statistical significance.
A total of 172 patients who underwent primary, one- to two-level MIS TLIF for degenerative pathology, were included in our analysis. Eighty-five patients (49.4%) had a preoperative SF-12 MCS score <50 and 87 (50.6%) had a preoperative SF-12 MCS score ≥50. Demographic variables of the patient population are described in Table 1. Patients with worse mental health were significantly younger (average age of 49.4 vs. 53.1, P = 0.031) and more likely to have Workers’ Compensation insurance (37.7% vs. 14.9%, P = 0.001). There were no significant differences in sex, smoking status, diabetes status, obesity status, or comorbidity burden between the two cohorts (P > 0.05 for each). No significant differences in perioperative outcomes, including operative time, blood loss, length of stay, and date of discharge, were identified between the two cohorts (P > 0.05 for each) (Table 2).
A comparison of PROMIS PF scores between the two SF-12 MCS cohorts at different timepoints is delineated in Table 3. After controlling for age and insurance type, patients with poorer mental health demonstrated significantly worse PROMIS PF scores preoperatively (33.8 vs. 36.5, P < 0.001), as well as at all postoperative timepoints: 6-weeks (35.1 vs. 38.4, P < 0.001), 3-months (38.9 vs. 42.9, P < 0.001), 6-months (41.4 vs. 45.5, P < 0.001), and 1-year (42.4 vs. 47.6, P < 0.001) (Figure 1). Additionally, the postoperative change in PROMIS PF outcomes from the preoperative baseline is detailed for each cohort. While both cohorts demonstrated similar improvement up to 6-months, at the 1-year timepoint, patients with worse mental health reported experiencing significantly less improvement from baseline (postoperative change of 8.6 vs. 11.1, P = 0.002) (Figure 2).
By utilizing a computer adaptive algorithm to assess patient-reported health function, PROMIS PF can efficiently track the course of patient disability in the postoperative period. Various preoperative risk factors contribute to postoperative outcomes following spinal surgery. Some characteristics are nonmodifiable, such as age and sex, while others can potentially be addressed prior to undergoing the procedure. Recently, there has been increasing research on mental health, as conditions such as preoperative depression have been shown to have negative effects on postoperative improvement in outcomes after spine procedures. 12,13,21–26 However, few investigations have evaluated the influence of mental health on postoperative outcomes as measured by the PROMIS PF survey during the recovery period after surgery. As such, the objective of the present study is to determine whether preoperative mental health, as assessed by the SF-12 MCS, is predictive of PROMIS PF outcomes in patients undergoing MIS TLIF.
Patients who underwent primary, one- to two-level MIS TLIF were retrospectively identified and stratified into two cohorts based on their preoperative SF-12 MCS score: low mental health (score <50) and high mental health (score ≥50). Amongst the patient population in our study, those with worse mental health were more likely to be younger and have Workers’ Compensation insurance. Otherwise, we found no significant differences in other demographic variables or perioperative characteristics. After controlling for patient age and insurance status, patients with poorer mental health demonstrated concomitantly worse physical function as indicated by lower PROMIS PF scores at the preoperative baseline. This is congruent with previous findings in the literature that have shown that depression is associated with physical disability in patients prior to undergoing spine surgery.27,28 For example, Purvis et al29 performed a prospective cohort study that evaluated 148 adult patients scheduled to undergo cervical spine surgery. The authors found that the PROMIS PF domain strongly correlated with patient-reported mental health evaluated by surveys such as the Patient Health Questionnaire-8 and Generalized Anxiety Disorder-7.
Additionally, the present study demonstrates that patients with low mental health continue to report significantly worse physical function throughout the postoperative convalescence period until the 1-year follow-up. A review of the related literature regarding the association between mental health and postoperative PROMIS PF outcomes matches our findings. For instance, Beleckas et al30 conducted a cross-sectional study of adult patients in an orthopedic practice and analyzed the relationship between the various sub-domains of the PROMIS survey, such as the Physical Function component in association with the Anxiety or Depression components. The investigators found a strong correlation between the Physical Function and Anxiety assessments and suggested using the Anxiety component to evaluate mental health in orthopedic patients. Merrill et al31 found that while patients with depression experience a greater degree of improvement in PROMIS PF than those without, depressed patients tend to report worse absolute postoperative outcomes.
While the majority of previous investigations have reported the presence of a correlation between poor psychiatric health and worse postoperative outcomes, several studies have contrastingly found the lack of an association. Our literature search uncovered investigations that utilized legacy outcome measures to assess postoperative clinical results. For instance, Ng et al32 examined 100 patients diagnosed with spinal stenosis who underwent posterior lumbar decompression. The authors showed that pre-existing mental health conditions such as anxiety and depression were not correlated with worse postoperative patient-reported outcomes.32 In the same vein, Herron et al33 reported that depression and psychosomatic symptoms such as hysteria and hypochondriasis were not predictive of outcomes following surgery for lumbar stenosis. Katz et al led two investigations that both demonstrated the lack of an association between preoperative psychological risk factors and postoperative improvement or self-reported patient satisfaction after a decompression procedure with or without fusion.34,35 Finally, although patients with depression returned to work at a lower rate after lumbar fusion, Parker et al36 found no association between depression and postoperative disability and pain.
In this study, both cohorts demonstrated similar improvement up to 6-months, but not at the 1-year timepoint. One possible explanation for the early improvement of symptoms in both cohorts regardless of mental health status may be related to the initial benefits afforded by surgical intervention in the short term. However, as the convalescent period progresses into 1-year and the rate of improvement following the procedure abates, patients with worse underlying mental health may experience comparatively diminished postoperative benefit. Poor mental health may negatively influence various factors crucial in achieving optimal long-term outcomes following surgery, such as motivation to undergo postoperative rehabilitation and therapy, willingness to adhere to physician-recommended regimens, and overall outlook and perspective on health-related aspects of life.
The present study also determined that there was a statically significant difference in PROMIS scores at the preoperative timepoint, which may be explained by worse mental health resulting in greater physical disability and pain reported by patients. This is consistent with the findings by Merrill et al31 who confirmed that depressed patients were more likely to have worse preoperative PROMIS physical function. One possible explanation for this finding is that poor mental health status and low mood may affect many components of life and activities of daily living, which would in turn negatively influence how patients perceive their own physical abilities.
While there was a statistical difference in preoperative PROMIS scores that may have potentially masked the outcome results, the postoperative change from baseline was calculated for both cohorts in our study. This relative difference from the preoperative to postoperative timepoints was compared between cohorts, which helped provide a better assessment of the improvement in physical function experienced by patients based on mental health status.
The present study demonstrated that worse mental health status preoperatively may predict worse postoperative outcomes in terms of patient-reported physical function and ability. The clinical implications of these results suggest the potential utility of screening for depression and other mental health conditions in patients before they undergo spinal procedures such as lumbar fusion. Treatment and optimization of these psychiatric comorbidities prior to surgical intervention may result in improved postsurgical outcomes.
There are also strengths to this study compared with previous published articles. The patients in our study sample were treated by a single surgeon at a single institution in a consistent manner. This limits the potential variability that may arise from surgeon and institution-specific factors. Furthermore, all patients received the same preoperative counseling from the senior author and followed similar postoperative rehabilitation protocols established at our institution. This eliminates the potentially confounding factor that may stem from adhering to contrasting postoperative rehabilitation regimens.
Additional recommendations for future studies include investigating whether the treatment of psychiatric comorbidities such as depression prior to surgery results in improved postsurgical outcomes. Furthermore, further work in developing an effective method to mitigate poor clinical outcomes in high-risk patient populations such as those diagnosed with depression or other mental conditions will be essential.
Our study is not without limitations. Given that our investigation was retrospective in nature, there is an element of selection bias, as well as the inability to determine causation. While the SF-12 MCS has been validated as an appropriate survey tool to evaluate the overall mental health of patients,37 our study did not take an in-depth account of the previous psychiatric history of patients or other comorbid medical conditions. Since mental health was evaluated at the preoperative timepoint, any possible progression or improvement throughout the postoperative period was not evaluated. Lastly, our study is limited to PROMIS PF outcomes until the 1-year follow-up. Moving forward, future studies will be strengthened by tracking physical function outcomes in the long-term beyond 1-year, as well as making use of other PROMIS domains to further elucidate the association between preoperative mental health and postoperative outcomes.
This investigation retrospectively identified patients undergoing MIS TLIF, stratified them based on preoperative mental health as indicated by the SF-12 MCS survey, and evaluated their postoperative outcomes using PROMIS PF. Patients with worse preoperative mental health not only demonstrated worse preoperative physical function, but also continued to have significantly worse postoperative outcomes. However, the postoperative improvement experienced by patients were similar in the short-term following surgery regardless of preoperative mental health status. Patients with poor mental health experienced significantly less postoperative improvement only at the 1-year timepoint. Future studies should continue to investigate psychosocial risk factors that may predict clinical outcomes in spine patients undergoing procedures such as MIS TLIF.
- There is a paucity of scientific investigations into the association between preoperative mental health as evaluated by a validated questionnaire such as the SF-12 MCS and postoperative outcomes following MIS TLIF.
- Patients undergoing a primary, one- to two-level MIS TLIF were retrospectively reviewed and stratified based on preoperative SF-12 MCS scores.
- After controlling for age and insurance type, patients with poorer mental health demonstrated significantly worse PROMIS PF scores preoperatively and postoperative timepoints up to 1-year.
- While both cohorts demonstrated similar improvement up to 6-months, at the 1-year timepoint, patients with worse mental health reported experiencing significantly less improvement from baseline.
- Patients with worse preoperative mental health not only demonstrated worse preoperative PROMIS PF scores, but also continued to have significantly worse postoperative outcomes.
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