Preop X-Rays Don’t Predict TKA Patient-Reported Outcomes

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from David Vizurraga, MD in response to a recent study in JBJS Open Access.

Whoever coined the phrase, “a picture is worth a thousand words” never treated a patient with knee osteoarthritis (OA). While knee OA is one of the most common conditions encountered in orthopaedic practice and its diagnosis and treatment are fairly straightforward, predicting the outcomes of total knee arthroplasty (TKA)—the definitive treatment for most cases of end-stage knee OA—can be challenging. The severity of OA on radiographs has long been debated as a tool to aid surgeons in predicting post-TKA outcomes and framing expectations for patients. In general, we tend to say, “The worse the x-ray, the better the patient-reported outcome,” and conversely, “The better the x-ray, the worse the patient-reported outcome.”

Lange et al. investigated this assumption in a study published in JBJS Open Access on July 9, 2020. The authors leveraged data from a 2-arm, randomized controlled trial that evaluated the role of “motivational interviewing” in enhancing rehabilitation following TKA. In their cohort analysis, Lange et al. compared pre- and postoperative WOMAC pain scores and KOOS activities-of-daily-living (ADL) scores with preoperative radiographic severity of knee OA, as measured by the Osteoarthritis Research Society International (OARSI) Atlas score. Among the 240 patients who had 2-year outcome measures and imaging available, the median preoperative OARSI score was 10 (on a scale of 0 to 18), and the authors defined “milder OA”  as an OARSI score of <10 and “more severe OA”  as a score of ≥10.

The researchers found a cohort-wide postoperative improvement in WOMAC pain and KOOS ADL scores of ~30 points, but they did not find any significant or clinically important differences in pain and function scores between patients with “milder OA” and “more severe OA.” The authors were also unable to demonstrate any correlation between radiographic severity and pain and function scores preoperatively.

Additionally, Lange et al. looked for associations between the WOMAC and KOOS improvements and 4 four other radiographic assessments of knee OA severity (Kellgren-Lawrence grade, compartment-specific OARSI score, compartment-specific joint-space-narrowing score, and 4-level OARSI score). Again, they failed to observe any clinically important postoperative differences in pain or function between the subjects with radiographically milder or more severe OA.

These findings provide further evidence that radiographs should represent only one piece in the puzzle of diagnosis and treatment planning for our patients with knee OA. To me, it’s worth noting that the study capitalized on data from a trial investigating motivational interviewing, which aims to improve outcomes by empowering patients—yet in the multivariable analysis that adjusted for several confounders, use of motivational interviewing was not among them. Still, the many aspects of outcome prediction following knee replacement are most definitely worthy and in need of continued investigation.

David Vizurraga, MD is a San Antonio-based orthopaedic surgeon specializing in adult hip and knee reconstruction and a member of the JBJS Social Media Advisory Board.

One thought on “Preop X-Rays Don’t Predict TKA Patient-Reported Outcomes

  1. Lange et al’s conclusions are a double-edged sword.

    I concur with the views of Dr Vizurraga (guest post author) and Lange et al (study authors) whereby preoperative radiographic OA severity should not be used as the main indication for recommending knee arthroplasty to address knee pain.

    In the absence of clear criteria for embarking on surgical intervention in Australia, there is much variation in clinical practice between various states; in fact (excluding one outlier territory), the highest recording state (Western Australia: 284 per 100,000) has 26% more knee replacements performed (age and gender adjusted) compared to the lowest state (Victoria: 225 per 100,000)(1). Surely in an island nation of 26 million, one wouldn’t expect that much variation in practice, but the fact is we definitely do! The surprise is even more significant considering Western Australia is a very large state with a small population, whereas large population in far smaller state of Victoria has geographically better access to far more health facilities dotted all over the territory. In a healthcare system where fee-for-service remuneration model has the potential for overservicing, the healthcare system in Victoria is certainly worth taking a closer look at, with their embedded multidisciplinary care model for musculoskeletal conditions allowing many degenerative conditions to be managed well with non-operative therapies.

    In fact, I would further support the views of Caniero et al who states:
    “contemporary evidence supports knee OA as a ‘whole person condition’ in which knee health is influenced by the interaction of different biopsychosocial factors that modulate inflammatory processes and tissue sensitivity, as well as behavioural responses that lead to pain and disability. This contrasting view reinforces the critical role of non-surgical approaches to manage knee OA.”

    On the other hand, the conclusions by Lange et al offers a double-edge sword. The results challenge both conventional wisdoms, that “The worse the x-ray, the better the patient-reported outcome,” and conversely, “The better the x-ray, the worse the patient-reported outcome.” I am much concerned that this study may be used to justify performing surgery in radiologically less advanced osteoarthritis since the improvement in pain is much the same. It is of interest that the KL<4 (milder radiographic arthritis) group have a nonsignificant trend to report more pain (higher WOMAC) and lower function (lower KOOS ADL) compared to KL=4 group (2, Table 4) and both groups improved by similar magnitude. I however would be interested to know if there is any way to determine whether those who score high on WOMAC and/or low KOOS ADL score actually improve as much as those who do not score as extreme. I note that there appears to be more variation in WOMAC and KOOS ADL reporting for KL<4 compared to KL=4 and hence a subclass analysis may be interesting although I am mindful that the study may not be powered enough to allow meaningful analysis.


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