Study of amputees finds referral for prosthetics to be an independent predictor of long-term survival

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William Shutze

Prosthetic referral was an independent predictor of long-term survival among patients who had undergone lower-extremity amputation, new findings set to be published in the Journal of Vascular Surgery will reveal.

A single-center retrospective study by William Shutze, MD, a vascular surgeon at Texas Vascular Associates in Dallas, and colleagues found factors associated with decreased survival were increasing age, higher American Society of Anesthesiologists (ASA) class, Black race, and body mass index (BMI), and that prosthetic referral was linked with improved survival with a hazard ratio (HR) of 0.73 vs. 0.55 for non-referral. Prosthesis-referred patients were approximately 50% less likely to experience mortality (propensity-score adjusted HR 0.54).

Shutze explained he was motivated to drill into data concerned with which patients were being referred for prosthetics and those who were not—as well as where survival fits into this conundrum—after identifying a hole in the vascular literature.

“We had developed in-house prosthetics delivery—and that gave us the ability to capture all of the information on the clinical side and the prosthetics side, as well as to know who was actually crossing over,” he told Vascular Specialist.

“Whereas, traditionally, for patients who are having an amputation, the prosthetics piece is outsourced. After doing this for about five years, I realized that the prosthetics side of the care for our vascular patients is not really well studied in the vascular world. There are other specialties where it’s looked at a little more closely, and I relied on those for our background research to get a better understanding. In the vascular world it was kind of a black box.”

Shutze and colleagues also sought to establish reasons why the patients were not referred for prosthetics.

“Vascular surgery would automatically assume that somebody who is being referred for prosthetics is going to be healthier than somebody who is not,” he said. “That may not be the case. There may be other barriers like ability to pay; there could be unconscious bias. So we did this analysis to get a better understanding of these factors. What type of patients will face barriers to referral and what is the survival after a lower-extremity amputation—and how does the prosthetics piece fit into that?”

The study included 293 patients who underwent amputation between January 1, 2010, to June 30, 2017, excluding patients who had amputations below the ankle or hip disarticulation. The cohort bore a mean age of 66, with 53% classed as white, 32% Black, and 15% as other. The average BMI was 27. The most common comorbidities were diabetes and hypertension—present in the majority.

A significant number (158) were classified as ASA IV or V. Approximately half (51%) of the patients were current or former smokers and almost half (51%) were on a statin medication. The majority of the patients had a below-the-knee amputation (BKA)—71.6%. Twenty-one patients, or 7.2%, developed an amputation stump complication significant enough to require a revision, Shutze and colleagues discovered.

They established that prosthetic referral occurred among 42% of their cohort. Significant differences were observed between patients referred vs. those not referred in age, sex, hyperlipidemia, ASA class, postoperative ambulatory status, need for surgical revision, and amputation level.

“The multivariate model identified age >70 years, female sex, diabetes, ASA score of IV or V, postoperative ambulatory status and current smoking status as significantly associated with failure to refer for prosthetic fitting,” they write in their paper. “Patients having a BKA, BMI 25–30, history of previous arterial procedure or revision were more likely to be referred for prosthetics.”

One-year survival was 81.2% overall—86.7% in the BKA subgroup and 67.5% among above-the-knee amputation (AKA) patients. In terms of five-year survival, the overall figure was 61.7%, with 64.7% and 53.8% in the BKA and AKA subgroups, respectively. Survival was statistically significantly lower among patients undergoing AKA than BKA, Shutze et al revealed.

“Our study was the first to connect long-term survival to the ASA score,” Shutze elaborated. “And we also found that BMI had an effect on survival as well. The prosthetic piece was surprising: We took what appeared to be similar patients and found that if the only difference was prosthetics referral, getting a prosthetics referral was associated with long-term survival.

“Some studies in the past have said that if you get a prescription for your prosthesis, that counts as a referral, but the patient may never go. For us, the patients actually had to be fitted with a temporary prosthesis. So they had to complete the mission, follow up with our prosthetist, get evaluated, and then sign on to get the prosthesis. That independently was associated with better long-term survival.

“This raises a lot of questions. Why would just having a prosthesis independently be predictive of better long-term survival? It’s something that we’re not capturing. Perhaps frailty, or perhaps there are some biases. There may be some benefits to prosthetic fitting—even with a temporary one—that has effects we might not even think of. Now the patients might have better mobility, and so can get in to see the doctor easier. Their overall healthcare is better. Maybe there are some psycho-emotional factors. With patients who have a prosthetic—do they do better on the anxiety-depression scores? This opens up all kinds of interesting avenues that we can go down to try to understand this better.”

Shutze elaborated on potential barriers to prosthetics referral. “We found some areas that are independent of each other: older patients, females, higher ASA scores and people who smoke. Some of these areas make you wonder: Since these are independent, is there some bias in our referral practice? Maybe we have some unconscious bias against certain people.”

Shutze and colleagues identified two areas for further research in their JVS paper.

“The first one is to determine whether the factors identified as associated with non-referral are markers for patient characteristics that make them clinically unsuitable for prosthetic fitting, or if they are symptoms of unconscious bias or of a patient’s access to care which would need to be addressed through the development and implementation of standardized referral criteria and/or systemic changes to eliminate financial, geographical, or physical barriers to prosthetic referral and fitting,” they write.

“The second one is to validate the prosthetic referral-survival benefit for variables that were not captured in this study and may have impacted the findings.”

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