Editor’s note: The following letter is in response to a news brief included in the Feb. 21 issue of AAOS Headline News Now titled “Study: How does arthroscopy compare to PT for FAI?” Letters to the editor are encouraged; please send correspondence to aaoscomm@aaos.org.

Randomized, controlled trials (RCTs) represent the highest level of evidence and have a powerful ability to guide treatment recommendations. Although RCTs minimize selection bias, they are subject to other biases. The authors of a study recently published in the American Journal of Sports Medicine should be commended for their efforts to perform an important RCT, which assessed arthroscopic surgery versus physical therapy (PT) for a military population with femoroacetabular impingement (FAI) syndrome. At two-year follow-up, the authors found no significant difference between the groups.

It is important for the reader to move beyond the conclusions and fully understand the details of the study, including some of the major limitations and how they may affect the conclusions. The study’s major limitations were highlighted in a recently published letter to the editor, and the greatest concern was a 70 percent crossover rate from PT to surgery.

Patient crossover is always a concern in RCTs and can be particularly challenging when researchers are comparing surgical and nonsurgical interventions. For an RCT to have reliable recruitment and minimize crossover, the patient and the investigator must share equipoise of the options. Crossover is most commonly seen with nonsurgical patients crossing to surgery. To some degree, this type of crossover reflects a “failure” of the nonsurgical treatment to induce an acceptable outcome.

Some previous orthopaedic RCTs comparing surgery to PT also encountered patient crossover, including 27 percent in the Meniscal Repair in Osteoarthritis Research (METEOR) study, which assessed degenerative meniscal tears, and 41 percent to 57 percent in the Spine Patient Outcomes Research Trial (SPORT), which assessed lumbar spine. The 70 percent rate of crossover published in the American Journal of Sports Medicine is among the highest crossover rates ever reported in a surgical trial. Intention-to-treat analyses are commonly advocated as the best statistical approach to deal with small rates of crossover. However, in the setting of a 70 percent crossover rate, this approach is flawed, as the PT group was more influenced by the outcome of surgery than PT (70 percent versus 30 percent, respectively). No information was provided on patient status at time of crossover to surgery. An “as-treated” analysis was performed, but this was severely underpowered and biased, as it only selected 30 percent of patients who did best with PT. Although the authors clearly stated the number of patients crossing over and acknowledged this limitation, they did not adequately emphasize the large impact this had on the validity of the conclusions.

A study’s conclusions are critical points that summarize the study’s results in context of any limitations. In the SPORT trial, the authors concluded, “Because of the large numbers of patients who crossed over in both directions, conclusions about the superiority or equivalence of the treatments are not warranted based on the intent-to-treat analysis.” In the METEOR trial, the authors concluded, “Our findings also suggest that an initial course of rigorous PT prior to [surgery] may not compromise surgical outcome.” Perhaps similar conclusions should have been applied to the current study rather than simply: “There was no significant difference between the two groups at two years.”

In our view, the 30 percent success of the PT trial in the setting of FAI is the most valid take-home point. Fortunately, we have more ongoing RCTs on this topic to better assess outcomes of surgery versus PT in the setting of FAI.

References

1. Mansell NS, Rhon DI, Meyer J, et al: Arthroscopic surgery or physical therapy for patients with femoroacetabular impingement syndrome: a randomized controlled trial with two-year follow-up. Am J Sports Med. 2018;46:1306-14.
2. Faucett SC, Nepple JJ, Andrade T, et al: Randomized controlled trial of hip arthroscopy surgery vs physical therapy: letter to the editor. Am J Sports Med. 2018;46:NP35-8.
3. Katz JN, Wright J, Spindler KP, et al: Predictors and outcomes of crossover to surgery from physical therapy for meniscal tear and osteoarthritis: a randomized trial comparing physical therapy and surgery. J Bone Joint Surg Am. 2016;98:1890-6.