High Pain Catastrophizing Scale predicts lower patient-reported outcome measures in the foot and ankle patient

Background: A patient’s healthcare experience can be modulated by their understanding of their preoperative disability along with their overall coping strategy. It is hypothesized that patient’s catastrophization and expectation on what they deem to be a successful surgery can affect their outcome. Methods: This current study prospectively assessed a consecutive cohort of patients undergoing foot and ankle reconstruction to describe the relationship between Pain Catastrophizing Scale (PCS) and patient-reported outcomes: SF-12 & FAOS. The PCS has a total score and three subcategories which are rumination, helplessness and magnification. Results: Forty-six patients were found to be eligible in the study with an average age of 54.7±14.4 years-old, a majority female (65%), a minority employed at the pre-operative visit (41%) and with an average BMI of 26.2±5.56. Looking at the FAOS Pain domain, it correlated significantly with the PCS Rumination and Helplessness subcategories. The FAOS Activity of Daily Living domain showed significant correlation with the PCS Rumination and Helplessness subcategories. The FAOS Quality of life domain was also statistically significant for the PCS Rumination and Helplessness subcategories. We found that the mental domain of the SF-12 had a statistically significant effect when compared to the Rumination (p=0.01) and Helplessness (p=0.001) subcategories. Conclusion: This study showed a significant association between an increase preoperative PCS and a worse one-year outcome looking at the FAOS domains. As such, in elective foot and ankle surgery, catastrophization should be screened for and potentially modulated pre-operatively to improve patient operative outcomes.


Introduction
Catastrophization has already been identified to impact outcomes in total knee arthroplasty patients. [1,2] No previous studies had analyzed the relationship between catastrophization and foot and ankle surgery outcomes. Nowadays, most of the current literature in foot and ankle surgery uses outcomes scores to delineate superiority and noninferiority of treatments. The current existing outcomes scores typically bundle physical, mental and function components such as the Short form 12  [3], the Foot and Ankle Outcome Score (FAOS)[4] and the Ankle Osteoarthritis Scale (AOS) [5]. Historically, certain tools have had greater validity than others. [6] Newer patient reported outcomes measures use computer based question algorithm. [7,8] These have been reported to be more precise and responsive to patients' outcomes. [9] However, for similar procedures, patients and pathology, documented and reported patient outcomes can vary significantly potentially due to unaccounted patient specific factors. It is not well understood what effect preoperative catastrophization may have on outcome measures in foot and ankle surgery. To our knowledge, this is the first study to look at this association.
Patients' healthcare experience may be modulated by their understanding of their preoperative disability along with their overall coping strategy and life experiences. Some patients' approach to problems focuses substantially on their disability and recovering from the trauma or the progression of their recovery. With more and more focus on patient-reported outcome defining treatment success and access to care, [10,11] there may be patients with a similar result but with a wide difference in their Patient-Reported Outcome Measures (PROM) score. At the same time, in the past decade, there has been a greater societal emphasis on mental health, psychological stability and wellness as well as a more patient-centered approach to surgical decision, timeline of the delivery of care.
A series of articles on the Pain Catastrophizing Scale (PCS) have been published in the past 20 years by Sullivan et al. [12,13] This group captured the essence of this concept by administering a 13-item questionnaire addressing thoughts and feelings experienced by patients in pain (Fig. 2). This was named the Pain Catastrophizing Scale (PCS). [14] This was identified as a modifiable psychological factor [15] that was negatively associated with patient outcomes after a total knee replacement (TKR).
[1, 2] In a recent paper by Glazebrook et al. [16], patients suffering from end-stage ankle arthritis had similar pain and disability as patients suffering from hip and knee arthritis but a worse SF-36 mental health score. Hence it is possible that catastrophization could be playing an even bigger role in foot and ankle surgery.
As such, risk factor targeted preoperative intervention by psychologist could be used in high-risk patients to modulate post-operative perceived pain. [17] A series of multi-week intervention programs have been reported to decrease catastrophizing scores up to 40%. [18,19] Objectives This study analyses the association between patient's preoperative catastrophizing scale and their one year postoperative FAOS domain scores for patients undergoing a series of foot and ankle operative interventions. We hypothesize that patients with a higher Pain Catastrophizing Scale report lower functional outcomes postoperatively.

Materials And Methods Study Design
This was a retrospective observational cohort study, that used prospectively collected data of a foot and ankle group based in one tertiary referral center. All patients were assessed and treated operatively by one of three experienced, fellowship-trained, board-certified surgeons. All patients undergoing a foot and ankle operative procedure were recruited consecutively between March 2014 and August 2015 and agreed to participate in the prospective database. Procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation, institutional and national.
To be included in the study patients had to be 18 years of age and underwent a foot and ankle surgery. This was a pragmatic study that aimed to represent a common foot and ankle clinical practice. Figure 1  Setting 54 patients were approached to participate in this study and eight patients were excluded for missing the one year follow-up after surgery. 46 patients were included in the study and described in Table 1 Catastrophizing Scale has a total score and three subcategories which are rumination, helplessness and magnification. The primary outcome for this study was to assess the relationship between Pain Catastrophizing Scale and FAOS scores and subcategories, since these are more condition-specific.
The SF-12 derived Mental component and Physical component are both global scores, which is why they are less sensitive for foot and ankle pathologies.

Analysis
For the postoperative FAOS domain scores, a univariate analysis was performed to isolate which of the preoperative variables had an effect. The demographic variables included were: age, gender, employment status, BMI and the Catastrophization variables were: Rumination, Helplessness, Magnification, and Total PCS. The preoperative FAOS score was controlled as well. Each of the variables that had a p-value of less than 0.25 were included into the multivariate analysis. This high p-value was selected to include more variables with potential signal in the multivariate analysis. An alpha level of 5% for statistical significance was applied for reporting all statistical analyses. The same process was repeated for the SF-12 Physical and Mental scores.

Subgroup analysis
Patients were then divided into two groups, higher risk for catastrophization and lower risk. The PCS score ranges between 0 and 52, with a value (PCS < 15) representing normal patients and above 15 at higher risk of catastrophization. The previously reported threshold at which patients are considered severe catastrophizers is 30[21] while the upper Pain Catastrophizing Scale threshold of normal has been set to 15 from the main validation study. [14] Patients with a PCS score of above 15 were considered catastrophizer. The first group (PCS < 15) counted 33 patients and the second group (PCS > 15) counted 13 as per Table 1. Figure 1 outlines in grey the patients from the second group.
Both groups were balanced as far as gender, sides, age and BMI. Further analysis comparing both groups for both the preoperative and postoperative SF-12 and FAOS were done using the Student's Ttest.  Table 3. Looking at Table 4, we note that as expected, the PCS subscores are different (p < 0.05) between the two groups. There are no statistically significant differences between the preoperative baseline FAOS

Discussion
This study demonstrates that an increase in Pain Catastrophizing Scale pre-operatively correlates to a worse result as reflected by the lower FAOS outcome scores. Looking at the correlation with FAOS, the Pain, ADL and QOL domains showed strong positive correlation with rumination, helplessness and total PCS score. This is the first foot and ankle study to report a correlation of this kind. Though this is a small study, the results suggest it may be important to administer a pre-operative PCS in order to stratify patients' expected postoperative PROMs. This has the potential of changing the operative selection in foot and ankle surgery, as high-risk catastrophizing patients would be stratified and referred to psychologist for intervention and re-assessed later when the scores trend lower, hence becoming better operative candidates leading them to have better postoperative PROMs.
When addressing specifically the SF-12, it was noted the multivariate analysis for both the Mental and Physical scores did not show statistical significant correlation with catastrophizing. This is not surprising as general health scores maybe less responsive then anatomic specific instruments with respect to foot and ankle operative intervention.
When looking at the stratification piece with the two groups, it is remarkable to notice that the catastrophizers of this cohort with PCS ≥ 15 had the same preoperative SF-12 and FAOS but had [24] supporting that catastrophizers (PCS > 30) would be more likely to have a longer length of stay after total joint surgery. This study had only one patient with PCS scores > 30 so this may underestimate the correlation with SF-12 and FAOS. It may be that the threshold where a patient is considered catastrophizer is also disease specific.
There are many ways to interpret the results and stimulate further discussion. This is a small study showing association and not a causality. It is not clear whether patients with high catastrophizing scores rate worse PROMs regardless of their true disability. Do patients with high PCS scores request operative treatment for lesser pathology? Are the current outcomes scores the best tools now recognizing that they do not measure catastrophization? Realizing that catastrophization affects reported functional outcomes, it would be prudent to consider incorporating this in pre-operative patient selection and stratification with the aim of ensuring that patients receive the interventions they need to alleviate the factors causing them to catastrophize, potentially resulting in them having favourable postoperative PROMs.

Bias
As an attempt to minimize the selection bias, this study was designed as a consecutive enrolment until the goal of N = 40 was reached. There was no power analysis. The heterogeneity of the location of the surgery (see Table 1) and the type of surgery (see Fig. 1) was a concern. However, this is representative of the typical diversity within a community foot and ankle practice. Though stratification of the study cohort into hindfoot, midfoot and forefoot procedures may have been helpful, it could not be performed due to the small size of the stratified groups.

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