Patients’ perspective on function after total knee arthroplasty: analyses of patient-reported outcome measures

Patient-reported outcome measures (PROMs) are validated questionnaires completed by patients. They are essential to assess what is meaningful to patients and provide insight into the patients’ perspective. One in five patients with total knee arthroplasty (TKA) is dissatisfied with the result of their surgery. To better understand the underlying reasons, we began to collect PROMs routinely from our patients scheduled for TKA. They complete a series of PROMs preoperatively, at four months, and annually for up to five years postoperatively. This overall PROMs collection project was the basis for the entire thesis. Four sub-projects are embedded in it.
The first project involved the High-Activity Arthroplasty Score (HAAS), a questionnaire that measures a wider range of functional abilities, particularly in more active patients. As a validated German version was not yet available, we aimed to translate and cross-culturally adapt the HAAS. After forward and backward translation, we examined the psychometric properties in 52 patients 12 months after primary TKA. The German version of the HAAS showed good validity and reliability. It can be easily self-administered and is recommended to measure high-intensity activities in patients after TKA.
One motivation for collecting routine PROMs was a new generation of implants, customised individually made (CIM) TKA. They were introduced to address anatomical variability with the aim of restoring individual anatomy and potentially improving patient satisfaction and function. In the second project, we conducted a matched-pair analysis based on a propensity score matching on 85 CIM and 85 off-the-shelf (OTS) TKA. Follow-up was at four months, one year and two years. We found high patient satisfaction with no differences between patients with CIM and OTS TKA. Both implant systems improved subjective and objective function, pain and health-related quality of life. Patients with CIM TKA showed superior results with regard to demanding activities.
In the third project, we assessed the responsiveness of different PROMs in patients with TKA. Responsiveness is the ability of a measure to detect change over time and was determined by effect size (ES), standardised response means (SRM), area under the receiver operating characteristics (ROC) curve (AUC), floor and ceiling effects, and hypothesis testing. We analysed data from 309 TKA at four months, one year and two years follow-up. We compared the Knee injury and Osteoarthritis Outcome Score (KOOS), KOOS-12, Forgotten Joint Score (FJS-12), HAAS and EQ-5D-3L. We demonstrated high responsiveness, which varied between the different measures. The KOOS-12 and FJS-12 showed the largest internal and external responsiveness, although ceiling effects occurred with the KOOS-12.
Finally, in the fourth project, we examined the relationship between preoperative expectations and postoperative satisfaction and other PROMs in TKA patients. We analysed data from 193 TKA at baseline, 4 months and 12 months. Patient expectations were measured using the Hospital for Special Surgeries Knee Replacement Expectation Survey (HSS-KRES). Preoperative expectations were high but did not correlate with postoperative satisfaction or any of the pre- or postoperative PROMs. While it is worth educating patients about realistic expectations, high patient expectations do not always seem to be a warning sign.
In summary, PROMs are essential to better reflect the patient perspective. PROMs help to focus on patient priorities and increase patient involvement in the treatment process. This is especially true for TKA procedures, which are commonly performed but still have a substantial number of dissatisfied patients. We believe that our research is a valuable contribution to further promote the potential of PROMs and their use in everyday medical practice.