Blog Post

April 3, 2018 Sara Tollefson

From Sales to Impact: How D-Rev estimates impact of its ReMotion Knee

Patients like this one, fit with a pre-release version of the ReMotion Knee in India, have been surveyed to help D-Rev understand its impact

We are pleased to announce that this month, we released the first version of the model we’ll use to estimate the impact of D-Rev’s ReMotion Knee. The knee launched last summer, but we decided to wait six months before finalizing our model, so we could draw on data from actual ReMotion customers to make our impact estimates more reliable.

Estimating the number of transfemoral (above-knee) amputees who lack access to quality prosthetics is not easy. Many amputations do not take place in hospitals and are not reported. Our research has found, however, that the prevalence of amputations worldwide is about 1 or 2 in every 1,000 people. Just over 30% of these are likely transfemoral (above-knee) amputations. Given that there are over 6 billion people living in low- and middle-income countries (LMICs), this translates into almost 3 million transfemoral amputees. A typical prosthetic device lasts an average of three years, meaning that almost 1 million people living in LMICs need transfemoral prosthetics each year.

The goal of our ReMotion Knee project is to mobilize amputees through the introduction of an affordable, high-quality prosthetic knee. We achieve impact through direct sales of our ReMotion Knee to clinicians and distributors, but because we care about impact, we track more than just sales. To measure our progress reaching amputees who need access to quality prosthetics, we track three main indicators:

  1. Number of amputees fit
  2. Number of amputees fit who otherwise would not have been fit with a comparable knee
  3. Countries where ReMotion Knees have been sold

Below are explanations of how we calculate two of these indicators: amputees fit and amputees fit who otherwise would not have been fit (i.e., D-Rev’s incremental impact).

Indicator 1: Amputees Fit

Where possible, we use actual clinic fitting data to calculate the number of amputees fit with our ReMotion Knee. In many cases, however, especially as the number of customer clinics grows, it is difficult for D-Rev to monitor fittings at every clinic, so the method below allows us to estimate the number of amputees fit with ReMotion Knees at those clinics from which we do not have actual data.

To count amputees fit, we must first consider the varying lengths of time that it takes customer clinics to fit patient with the knees they have purchased. After a survey that D-Rev did of all ReMotion customers in December 2017, we found that 29% of the knees ordered by respondent customers had been fit to patients as of the date of the survey, within a median 32 days (average of 33 days) from the date of sale. Accordingly, unless we hear otherwise from customers, we assume that after 32 days, 29% of knees sold and shipped to customers will have been fit to patients. Furthermore, we assume that when a customer places a repeat order, all previously ordered knees have been fit to patients (again, unless we hear otherwise).

Example

A clinic places an order for 20 knees on June 1st. It takes 10 days for D-Rev to receive payment and ship the order, so the recorded sale date is June 11th. We assume no amputees will be fit with these knees until 32 days later, on July 13th, by which time we estimate six amputees (i.e., 29% of 20) will be fit with knees. Unless we gather actual fitting data from the clinic or the clinic places a reorder, we don’t assume that any more amputees are fit with the remaining knees. If there is a reorder, however, we assume that amputees have been fit with the remaining knees as of the date of the repeat order.

Indicator 2: Amputees fit who otherwise would not have been fit (“Amputees Otherwise”)

With this indicator, we are measuring the incremental benefit that D-Rev has had on our target population, and trying to answer the question: how many of the amputees fit with ReMotion would not have had access to a knee of comparable price and quality if not for D-Rev’s design, marketing, and delivery of ReMotion?

When amputees report previous use of a prosthetic knee, and indicate that the knee that they have used most recently is an exoskeletal knee (or a single-axis endoskeletal knee without a stability mechanism like a friction brake, e.g. the ICRC knee) then we consider them “Amputees Otherwise”, because these types of knees offer less functionality than the polycentric, endoskeletal ReMotion Knee.

Patients are also considered “Amputees Otherwise” if they had not previously worn a prosthetic knee, and the clinician indicates that they would have been fit with a knee of lower quality (i.e., an exoskeletal knee or single-axis knee endoskeletal knee without a stability mechanism), were it not for the ReMotion Knee.

In a pilot study survey conducted by Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS, aka the Jaipur Foot Organization), in India in 2015-16, the prosthetist in charge, Dr. Pooja Mukul, found that 82 (57%) of the 143 amputees who were fit with a pre-release version of the ReMotion Knee met the criteria for “Amputees Otherwise”.

We plan to survey additional clinics in the future for the data above; until then, we will use this 57% rate from the BMVSS pilot across all amputees fit with ReMotion Knees to estimate the total number of amputees fit who otherwise would not have been fit with a knee of comparable quality and price. (Note: we do not count as “Amputees Otherwise” patients living in high-income countries.)

Example

A clinic that treats amputees in Guatemala places an order for 25 knees on August 15th. It takes 5 days for D-Rev to receive payment and ship the order, so the recorded sale date is August 20th. We assume no amputees will be fit with these knees until 32 days later, on September 21st, by which time we estimate that seven amputees will have been fit with knees. Four of these amputees (i.e., 57% of 7 amputees fit) will be assumed to be amputees who otherwise would not have been fit with a comparable knee (“Amputees Otherwise”).

For a complete description of how we estimate impact for our ReMotion Knee project, please visit our Mobility Impact Dashboard (updated quarterly), and check out the link there to our “step-by-step” guide.

For a more detailed explanation of how D-Rev calculates impact of its ReMotion Knee, check out the Step-by-Step guide on the Mobility Impact Dashboard

Many thanks to BMVSS and all of the clinicians who have helped us understand how the ReMotion Knee is making a difference in the lives of their patients. We couldn’t have done this without their help!

Back To Posts