Depression and Comorbidities Affect Knee Function After TKA
Depression and Comorbidities Affect Knee Function After TKA
In this study we found that psychological and medical comorbidity were associated with less optimal improvement in knee function after TKA. Specifically, depression was associated with suboptimal knee function improvement at 2-years after primary TKA and higher medical comorbidity score with suboptimal knee function improvement at 5-years after revision TKA.
An interesting finding from our study was the association of depression with suboptimal improvement in index knee function 2-years after primary TKA. Several factors may contribute. Depressed patients are less likely to successfully complete rehabilitation therapy that is required post-TKA. They may not follow-up with their surgeon regularly due to concomitant depression and may have worse post-operative pain, which may impact adherence with rehabilitation therapy. Optimal physical rehabilitation after TKA is the key to best results after TKA. The absence of this association in primary TKA at 5-years may be either due to a smaller sample size making it underpowered analysis or due to "catching up" by patients with depression after 2-years. The differences in findings between primary and revision TKA may be due to differences in patient characteristics (depression, mean Deyo-Charlson index), the underlying diagnosis and in the rate of complications between primary and revision TKA.
Two recent studies reported that depression was associated with poor functional outcomes after primary TKA, while other studies failed to confirm this finding. Two studies examined function only up to 1-year, one study at 2-years and one at 5-years. Most studies had small sample size, making them underpowered and at risk of missing a significant association. By analyzing a large sample and performing multivariable-adjusted analyses, our study adds to this body of knowledge related to association of depression with improvement in knee function after TKA. Three key differences between our study and the previous studies are that we used a large sample and our outcome was joint-specific and can be interpreted as a patient-level clinically meaningful outcome. This is in contrast to the use of mean scores on lower limb-specific instrument (Western Ontario McMaster osteoarthritis Index, WOMAC) or lower-limb specific/knee-specific hybrid outcome (such as Knee society score, KSS) in previous studies. Our study extends and confirms previous findings from the positive studies of depression and poor functional outcome. Our finding of no association of anxiety with functional improvement outcomes is important and confirms a previous similar finding in a study with 5-year follow-up. This may be related to smaller sample size at 5-years.
We found that higher medical comorbidity (on Deyo-Charlson index) was significantly associated with suboptimal improvement in knee function 5-years after revision TKA. Previous studies have shown that diabetes and hypertension are associated with higher post-arthroplasty complication rates. Poorer functional outcome associated with higher comorbidity may be partially due to higher post-operative complication rates. A higher comorbidity may also interfere with optimal adherence to physical rehabilitation. In those with primary TKA, evidence is contradictory with some studies finding an association of higher medical comorbidity with poorer function and others no such association. We did not note any significant association of higher comorbidity at baseline with 2-year outcomes. It is possible that a longer follow-up allows for a more significant impact of comorbidity on TKA outcomes compared to a shorter follow-up, since chronic diseases get worse with longer disease duration, in general. In absence of any previous studies examining patient-level meaningful improvements, these findings are novel and need confirmation in future studies. Studies of improvement of knee function after TKA are important. A $12 million research grant 2010 by the Agency for Healthcare Research and Quality (AHRQ) to study factors associated with functional outcomes and complications after joint replacement is strongly supportive. Our study adds to this growing area of research by studying comorbidity factors as risk factors for poor patient-reported knee function improvement.
Our study has several limitations. Non-response may have biased our findings. Survey responders had characteristics previously shown to be associated with better outcomes (male gender, older age, a diagnosis of osteoarthritis, lower ASA class, lower Deyo-Charlson score, shorter distance to medical center), but it is unclear how the non-response bias might influence the association of depression and medical comorbidity with function outcomes. A lower response rate at 5-years compared to 2-years makes these findings more prone to bias. Since both anxiety and depression were captured based on presence of a diagnostic code, and psychological comorbidities may be under-recognized and under-diagnosed, it is likely that we missed some cases. This might have biased our estimates towards null, and we may have missed some important associations of anxiety and depression with outcomes. A retrospective study design did not allow us to have confirmation of depression/anxiety diagnosis by examination by a psychologist of psychiatrist. However, the prevalence of depression is similar to the 9–15% reported in studies using validated instruments for depression. Whether the "much better" is truly different from "better" response on this ordinal scale can not be determined in this study; however, this ordinal response is similar to other validated ordinal scales, commonly used in health outcome assessments. Recall bias should be considered while interpreting these results; patients may have over- or under-estimated the functional improvements, and therefore the direction of impact of this bias on our study findings is unclear. Several study strengths must also be noted. We included a large sample size with adequate number of events to study the question of interest, used validated measures (questionnaire, Deyo-Charlson index), performed multivariable-adjusted analyses, examined both 2- and 5-year outcomes in primary and revision TKA and provided results for a clinically meaningful joint-specific functional improvement outcome.
Discussion
In this study we found that psychological and medical comorbidity were associated with less optimal improvement in knee function after TKA. Specifically, depression was associated with suboptimal knee function improvement at 2-years after primary TKA and higher medical comorbidity score with suboptimal knee function improvement at 5-years after revision TKA.
An interesting finding from our study was the association of depression with suboptimal improvement in index knee function 2-years after primary TKA. Several factors may contribute. Depressed patients are less likely to successfully complete rehabilitation therapy that is required post-TKA. They may not follow-up with their surgeon regularly due to concomitant depression and may have worse post-operative pain, which may impact adherence with rehabilitation therapy. Optimal physical rehabilitation after TKA is the key to best results after TKA. The absence of this association in primary TKA at 5-years may be either due to a smaller sample size making it underpowered analysis or due to "catching up" by patients with depression after 2-years. The differences in findings between primary and revision TKA may be due to differences in patient characteristics (depression, mean Deyo-Charlson index), the underlying diagnosis and in the rate of complications between primary and revision TKA.
Two recent studies reported that depression was associated with poor functional outcomes after primary TKA, while other studies failed to confirm this finding. Two studies examined function only up to 1-year, one study at 2-years and one at 5-years. Most studies had small sample size, making them underpowered and at risk of missing a significant association. By analyzing a large sample and performing multivariable-adjusted analyses, our study adds to this body of knowledge related to association of depression with improvement in knee function after TKA. Three key differences between our study and the previous studies are that we used a large sample and our outcome was joint-specific and can be interpreted as a patient-level clinically meaningful outcome. This is in contrast to the use of mean scores on lower limb-specific instrument (Western Ontario McMaster osteoarthritis Index, WOMAC) or lower-limb specific/knee-specific hybrid outcome (such as Knee society score, KSS) in previous studies. Our study extends and confirms previous findings from the positive studies of depression and poor functional outcome. Our finding of no association of anxiety with functional improvement outcomes is important and confirms a previous similar finding in a study with 5-year follow-up. This may be related to smaller sample size at 5-years.
We found that higher medical comorbidity (on Deyo-Charlson index) was significantly associated with suboptimal improvement in knee function 5-years after revision TKA. Previous studies have shown that diabetes and hypertension are associated with higher post-arthroplasty complication rates. Poorer functional outcome associated with higher comorbidity may be partially due to higher post-operative complication rates. A higher comorbidity may also interfere with optimal adherence to physical rehabilitation. In those with primary TKA, evidence is contradictory with some studies finding an association of higher medical comorbidity with poorer function and others no such association. We did not note any significant association of higher comorbidity at baseline with 2-year outcomes. It is possible that a longer follow-up allows for a more significant impact of comorbidity on TKA outcomes compared to a shorter follow-up, since chronic diseases get worse with longer disease duration, in general. In absence of any previous studies examining patient-level meaningful improvements, these findings are novel and need confirmation in future studies. Studies of improvement of knee function after TKA are important. A $12 million research grant 2010 by the Agency for Healthcare Research and Quality (AHRQ) to study factors associated with functional outcomes and complications after joint replacement is strongly supportive. Our study adds to this growing area of research by studying comorbidity factors as risk factors for poor patient-reported knee function improvement.
Our study has several limitations. Non-response may have biased our findings. Survey responders had characteristics previously shown to be associated with better outcomes (male gender, older age, a diagnosis of osteoarthritis, lower ASA class, lower Deyo-Charlson score, shorter distance to medical center), but it is unclear how the non-response bias might influence the association of depression and medical comorbidity with function outcomes. A lower response rate at 5-years compared to 2-years makes these findings more prone to bias. Since both anxiety and depression were captured based on presence of a diagnostic code, and psychological comorbidities may be under-recognized and under-diagnosed, it is likely that we missed some cases. This might have biased our estimates towards null, and we may have missed some important associations of anxiety and depression with outcomes. A retrospective study design did not allow us to have confirmation of depression/anxiety diagnosis by examination by a psychologist of psychiatrist. However, the prevalence of depression is similar to the 9–15% reported in studies using validated instruments for depression. Whether the "much better" is truly different from "better" response on this ordinal scale can not be determined in this study; however, this ordinal response is similar to other validated ordinal scales, commonly used in health outcome assessments. Recall bias should be considered while interpreting these results; patients may have over- or under-estimated the functional improvements, and therefore the direction of impact of this bias on our study findings is unclear. Several study strengths must also be noted. We included a large sample size with adequate number of events to study the question of interest, used validated measures (questionnaire, Deyo-Charlson index), performed multivariable-adjusted analyses, examined both 2- and 5-year outcomes in primary and revision TKA and provided results for a clinically meaningful joint-specific functional improvement outcome.
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