Based on their evidence the authors of the START: REACTS trial recommended against the balloon as they found no benefit in the intervention group and in some subgroups found net harm compared to their control group. They noticed worse clinical outcome results especially in women, with some showing increase in pain in the test group that received the balloon.
This result was met with criticism from the FDA study authors in a November 5, 2022 letter to the editor of the Lancet outlining their concerns of the START : REACTS trial.
In the letter the FDA study’s authors state “Patients [in the START REACTS trial] had preoperative elevation far worse than expected in tears indicated for this device, which is concerning for involvement of the subscapularis, a contraindication to the device.” They also note that the “statement of device harm is not supported by data: the difference in Oxford Shoulder Score did not exceed the minimal clinically important difference, indicating that the difference is not clinically important, there was similar satisfaction between groups, and there were no device-related complications.”
Dr. Metcalfe, lead author of the START : REACTS trial replied to the FDA trial’s criticisms in a follow up letter in the Lancet in the same issue stating: “They misinterpret our study; further details to address these queries are available in the supplementary data and published protocol.3 We collected data on pain-free range of movement with the method set out by the Constant Score; the full range of movement would inevitably be greater than the pain-free range.4, 5, 6 We used a published, widely used, and reproducible method of assessment that does not induce pain. The papers quoted by Verma and colleagues are about a different measurement.”
Pay close attention here. The authors’ of the FDA trial are saying that we should interpret the START : REACTS trial with caution because the START : REACTS trial patient population was far different than the JBJS FDA trial. The FDA trial authors are arguing that the patients in the START : REACTS trial on average had much worse starting range of motion than the patients in the FDA trial.
This critique echoed what I was hearing in October 2022 when I attended a lunch session at the ASES annual closed meeting. I went to hear a discussion on the Inpsace balloon from some of the lead authors and consultants for the company now distributing the balloon (Stryker). They argued then, that the authors of the START : REACTS trial had included far too many patients with poor baseline forward elevation. The critics of START : REACTS said that the investigators had included too many patients near pseudo paralysis and that this skewed the START: REACTS population to have a starting average forward elevation of 75 degrees.
At the time of the ASES meeting, the November 5, 2022 letters to the editor had not yet been published. I thought the FDA trial authors might have a valid point. So I did more digging and poured over both papers again including inclusion and exclusion criteria. If you look at the JBJS article you do not see baseline range of motion reported. I requested this information from Stryker, the company that purchased the Inspace technology, but did receive a response. I then decided to write to the lead author of the START REACTS trial, Andy Metcalfe. What he said to me over email in October 2022 echoed his response in the Lancet:
“The ROM point is interesting, we used pain-free active range of motion, not full active range of motion, which meant that the data we presented looked like the ROM was lower than it would be, had we collected the full active ROM…We collected pain-free active range of motion using the Constant score method – that is, we asked people to stop the measurement when the pain started (or, if they had pain at rest, when the pain worsened). I’ve attached the Constant score manual that we gave to sites – pages 3, 4 and 5 are the relevant parts. The result of that is that the reported ranges are much lower than the full active ranges.”
I went back to the original papers on the reporting of the Constant score and as Dr. Metcalfe pointed out, the Constant score performed correctly, records “pain free” range of motion. Pain free range of motion is very different than range of motion.
Most patients that have pain from rotator cuff tears begin to have pain in the region that the START : REACTS trial did: around shoulder height or just below shoulder height (75-90 degrees). So it’s likely not that the START : REACTS trial patients were materially different in their starting ROM, but that the recording method of the authors between studies was different. This makes a lot more sense. This is where going back to original sources is critical. I am ashamed to say that I did not know this detail of the Constant score before Dr. Metcalfe pointed me to the original Constant Score literature.
The JBJS FDA trial authors also point out that the START : REACTS authors included patients with subscapularis tears who are “contraindicated” for the balloon device. But as Dr. Metcalfe points out, it is not clear for whom the balloon is the best treatment (which is the purpose of the study) and only patients with tears of 1 cm or less of the subscapularis were included.
In my own reading of the START: REACTS trial I noted that there was a relatively equal proportional of patients with subscapularis tears in both groups: 12 in the debridement group and 14 in the balloon group. So it would seem that any contribution of the subscapularis tears to their overall functional limitations would wash out in the data regardless since both groups were equally affected. In other words, since both balloon group and control groups had essentially equal proportions of patients with subscapularis involvement, the subscapularis tear itself likely did not significantly impact between group outcomes.
The Inspace balloon is now distributed by Stryker Orthopedics and is marketed as a potential expeditious and minimally invasive solution for some patients with large irreparable rotator cuff tears. The device is fetching in the range of $5000-6000 per device for reimbursement. As a comparison, many reverse total shoulder replacement implants cost in the $6500 range.
If we are to critically assess the value of the Inspace balloon intervention we must compare it to the alternative of arthroscopic debridement which is much less costly without the implant. If we define value as clinical outcomes divided by cost one could argue that the Inspace balloon is hard pressed to provide good value. Most medical care in the United States is covered under some form of insurance. The costs are often born by the insurer and less so the patient (although with high deductible insurance plans we are seeing a larger chunk of that cost born by the patient). Armed with the knowledge gleaned from the studies outlined above, one wonders if patients were paying the full cost of a $5000+ implant would choose it over the debridement alone.
Conclusions
The Inspace balloon is a safe option in patients with irreparable rotator cuff tears of the superior cuff. It does not appear to be significantly better in the long run than debridement alone or with partial cuff repair. In my opinion it is not a significantly better value than arthroscopy with debridement.