The old saying about how "it's the journey, not the destination" may have particular relevance for recipients of total knee arthroplasty (TKA): according to a new study, when it comes to levels of function, TKA recipients whose preoperative condition was mild enough to deem the procedure "inappropriate" ultimately arrive at the same place as patients with more severe preoperative symptoms.
The research (abstract only available for free), e-published ahead of print in the August 6 issue of Arthritis Care & Research, builds off a previous study that applied a modified Escobar classification system developed in Spain to label TKA recipients as "inappropriate," "appropriate," or "inconclusive" based on radiographic evidence, knee motion and laxity, and scores on the Western Ontario and McMaster Universities Arthritis Index (WOMAC). That study found that 34.3% of the TKAs studied were performed on patients whose presenting conditions were judged to be inappropriate for the procedure.
In the follow-up study, researchers led by Daniel L. Riddle, PT, PhD, FAPTA, looked at outcomes for 167 patients with primary TKA. Of those TKAs, 47.9% were identified as "appropriate," and 31.3% were classified as "inappropriate," with the remaining 20.8% labeled "inconclusive." Researchers monitored scores from the WOMAC as well as Knee Injury and Osteoarthritis Outcome Scores (KOSS) for both pain and symptoms at 2 months postprocedure, and again at the 1- and 2-year marks. The aim was to quantify both the "journey" to improvement and the ultimate "destination"—exactly how much function related pain and activity limitation was present one and two-years after surgery.
Researchers hypothesized that because they underwent TKA with less severe symptoms, the inappropriate group would have smaller changes in pain and function, and experience better outcomes at the 1 and 2 year "destination" points than patients whose TKA was deemed appropriate. What they found was nearly the opposite.
"Persons who were classified as inappropriate had no significant change in pain, function, and knee symptoms over the 2-month postoperative period relative to the preoperative assessment," authors write. "This contrasts to the substantial improvements over the same time period in the appropriate and inconclusive groups. In addition, despite having higher functioning and substantially less pain preoperatively, the destination outcomes … were not statistically different. Overall, improvements in the group classified as inappropriate were small and in some cases did not reach clinical significance 1 year following surgery."
Authors write that while the study design cannot establish with certainty whether the appropriateness criteria is valid for US patients or whether patients receive TKA only when needed, "our study does … provide evidence to suggest that one or the other (or both) of these inferences is likely to be false." The need at this point, they write, is for further study and "consensus building efforts … to define eligibility criteria for TKA with the goal of reducing variation in patient characteristics and maximizing outcome."
"To me, the real standout feature in this study was the small amount of improvement in the inappropriate group," Riddle said. "Both groups had essentially the same final outcome, but it was fairly striking how small the actual amount of improvement was for the inappropriate group."
Riddle acknowledged that the appropriateness logarithm used in the study is "grounded in the notion that TKA is optimal for those that have severe or end-stage knee osteoarthritis," saying that because "TKA has evolved, and rightly so, it makes sense that the potential window for possible candidates would be wider than it used to be."
Still, Riddle said, as effective as the procedure is, "there needs to be some additional clarity" around who are the best candidates for TKA. "That's why we argue for the need for consensus around clinical standards for TKA, now that the bar has been lowered somewhat," he said.
Although the study has more to do with appropriateness for a surgical procedure than it does for physical therapy afterward, Riddle believes that there are lessons here for physical therapists (PTs).
"It's important for PTs to recognize that there are larger variations in the types of patients selected for TKA, and large variation in surgical decisions," he said. Perhaps even more important, he added, is what the study can tell PTs about the dynamics of recovery. "PTs should look at studies like this one as an important reminder to think about outcomes in terms of both the journey and the destination," Riddle said. "They need to think about where their patients end up, and how they get there. Both approaches to outcome assessment are important."
Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website.
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