Continuous Passive Motion Machine: What Went Wrong
The Continuous Passive Motion Machine is a device designed in the early 1970’s with the idea of helping knee surgery patients regain range of motion. The hope was that hours of moving the leg back and forth would loosen up the knee and allow the patient to gain extension (knee movement up, away from the body) and flexion (knee movement down, back toward the body).
Continuous Passive Motion Machine, Conclusive Results
For people who have had total knee replacement without complications, continuous passive motion has not been shown to provide clinically relevant benefits. CPM does not improve long-term function, long-term knee flexion, knee extension in the short or long term, and has not been shown to reduce pain and or increase the quality of life. Additionally, CPM is inconvenient and brings the risk of complications while distracting patients from useful treatment. In very rare cases where the person has problems that prevent standard mobilization treatment, then CPM may be useful. Patient compliance is key to rehabilitation and generally patients to not like to use the CPM. Furthermore, with patients attempting at-home therapies, most follow orders with an improper form that either limits improvement or in some cases causes harm.
The failure of the Continuous Passive Motion Machine (CPM) is mostly that it never evolved past a very basic means of movement. The model designed during the advent of knee replacement surgery is still the same today. A new kind of Continuous Passive Motion Machine was never created.
Today there are PMKR, Pressure Modulated Knee Rehabilitation. PMKR machines, like the X10. PMKR machines do deliver the results that were hoped for the CPM. Fast recovery. Fast return to work and life. Avoidance of complications. Beating the dangers of scar tissue development. Many thousands of patients have used PMKR and as surgeons learn about it, they quickly adopt this technology.
Such a good essay.
So I just got off the phone with one of our patients in Florida, Anita. She had a Manipulation Under Anesthesia and then Hurricane Irma hit. She could not use the X10 for 13 days as she had a tiny generator… so she could only use the CPM machine. In 13 days after the MUA, the most important days after this procedure, she only got to 83º range of motion. It was painful all the way. And the CPM told her she was at 120º, typical of this archaic device.
Clearly she was on the path to a second MUA. She finally got her power back and got on the X10. In just a few days she reached 98º bend and 0º extension, and while she is still now behind the curve because of this delay, she is fighting her way back. The CPM is so inaccurate… hard to believe it is still out there.
Many years back when I had my knee replaced, I asked for the CPM while the spinal was still working. The CNA brought one that, as I later learned, was made for the opposite leg, they come in Left or Right forms. He put it on me before knowing how to adjust the degree and speed. When he eventually figured out how to turn it on, it immediately bent my knee further and faster than it should have. My spinal instantly wore off and I screamed from the excruciating pain it caused. He didn’t know how to shut it off before it went through some more motions, which felt like my entire knee was ripping apart. I hadn’t started using the PCA pump for pain, and when I did, it did nothing for this instant pain. They tried a couple bumps of the MS, but my BP & 02 Sats dropped. Nothing helped. The Dr. was gone, and I was finally discharged after 6 long days. I was expecting no pain after, but that never happened. When I later asked the doc if what happened post-op might’ve messed up something, he said no & blew it off; said he was able to bend it in surgery just fine. But this happened maybe 5-6 hours later, with obvious normal swelling being more than in the O.R., forcing ROM that my knee was not ready for. The pain was less, but there is always pain now… maybe something tore or shifted, but I know it affected the healing. It should not be used by untrained staff.
Corrie – we have seen so many many problems with the CPM machine – just like you describe. We are so thankful that it is finally out of favor and used by only a few hospitals and doctors nowadays. The X10 is an enormous step forward for knee surgery recovery.