“There’s not much MIS [minimally invasive surgery] about a TKA [total knee arthroplasty]. Regardless of the incision or the surgical approach, it’s the same biologic response, same bone removal, etc., ” says Michael Berend. “Alright, ” says brother Keith Berend, “MIS is a misnomer. It has to do with other factors like patient expectations and perioperative anesthetic. I think MIS should be credited with drawing our attention to all of these various things.”
This week’s Orthopaedic Crossfire® debate is “MIS: A Risk Factor of Early TKA – Brotherly Love!” For the proposition was Michael E. Berend, M.D. of the Center for Hip & Knee Surgery in Mooresville, Indiana. Against the proposition was Keith R. Berend, M.D. of Joint Implant Surgeons in New Albany, Ohio. Moderating was Robert T. Trousdale, M.D., of Mayo Clinic in Rochester, Minnesota.
Dr. Michael Berend: “When you’re the older brother, the saying of ‘older and wiser’ has been a dogma for many years; ‘younger and misguided’ is my opponent today. I’ve been feeding Keith information for many years [photo of elder brother bottle-feeding baby brother]. When he was a resident I was early to MIS. I think we’ve all realized we were doing a bit more than we needed in the ‘90s. I think that we’ve trained folks to ask the wrong questions. How big is the incision? We’ve gone from inches to centimeters. And the recovery to how many weeks. So I think MIS will need to be redefined into ‘Must Insist on Seeing.’ For both of us 40% of our practice is now partial knee replacement. So I think as Keith has stated previously, the only conservative, minimally-invasive operation is a partial knee replacement.”
“There’s not much MIS about a TKA. Regardless of the incision or the surgical approach, however you define the surgical approach, it’s the same biologic response, same bone removal, same basic implants, same rehab…and I would submit, ‘Is it less predictable to do it through a smaller window?’ Certainly we’ve gained a lot of information from anesthesia protocols and preoperative education. And we’ve emerged with a whole series of closet MIS zealots…and my brother is one of the lead people.”
“MIS is a misnomer. In a series from Niki of 147 knees, with all approaches, various enzyme measurements looking for the biological response—they found no difference in muscle injury with MIS versus standard. Another group—from Karpman—prospective and randomized…small series (59 knees), three groups, various definitions of surgical approach. Only at one time point were they improved at two weeks, not one week or six weeks…and all the outcome measures were similar.”
“If you look at Kolisek, a prospective randomized study, there was no improvement clinically, no differences in the X-ray, three month outcomes were the same, and there was unfortunately a 10% wound healing problem with MIS.”
“In a series from Tashiro, they looked at clinical measurement, X-rays, and OR time. Again, small improvements at the two week mark when the patient still has their staples in. Fortunately there was no coronal malalignment; there was a medial shift in the implant, which may be a problem. And they found an almost 56 minute increase for the total knee replacement. If you take that and add in what Steve MacDonald talked about, that infection rates were higher in TKA in the group that had 33 minute longer operative time.”
“If you look at a series of early revisions for malrotation, 81% of their knees were revised in less than two years in this series. So if it’s difficult to assess femoral component rotation, this may be a risk factor.”
“If you look at all the risk factors together that we know for late tibial loosening and TKR failure—including infection, fracture, poly resin, resection depth, etc.—MIS is added to that. And a number of the factors—infection, time, alignment, ligament balance, femoral component rotation—all would be negatively affected. Tom Fehring has shown that these factors account for early revision in the U.S.: infection (38%), instability (27%), aseptic/wear (23%), patellofemoral (8%)…and all of these are a risk with MIS.”
“A series from Barrack first suggested that MIS may need to be added to the risk factor list. It was a multicenter study, 237 revision knees, mainly revised for instability and loosening. The ones with an MIS knee were revised at an average of 14 months, compared to those with a standard knee at 80 months.”
“If you look at Dalury and Dennis—30 mini versus 30 standard—13% greater than four degrees of malalignment. Certainly this is unacceptable. We have shown that if you miss the mark in the obese patient with greater than three degrees, a rather precipitous drop in failure.”
“So MIS is not for all patients, not for all surgeons. There is a significant learning curve, perhaps up to 50 cases. Let’s take the good and leave the bad. Careful surgery will win the day in the end.”
Dr. Keith Berend: “We grew up in the same household and yet Mike is so off base in terms of the way the future has moved forward. As he said, we agree on one thing…partial knee replacement is probably the only truly minimally invasive surgery we can offer our patients. One of the problems with any debate over MIS is that we don’t really know what it means. There is no standard outcome measure. And none of the prospective randomized trials address the standardization of perioperative protocols.”
“If we look at what has been reported, there’s a subvastus, quad sparing, midvastus, a limited medial parapatellar [approach]. The goal is the same: minimize trauma to the suprapatellar pouch and minimize trauma to the extensor mechanism. And there are many articles that look at each of these approaches.”
“The reported benefits…Mike showed the studies that showed no benefits, but there’s an equal if not greater number that show benefits. Basically, the patients recover faster. The issue is whether this is safe. And I think we all got alarmed by the study from Bob Barrack and Lowry Barnes that was in the Journal of Arthroplasty a year ago. My conclusions from that study: they excluded infection in their series, which I think skews the data somewhat; the MIS patients were younger; the time to revision was shorter with MIS; less than 20% of their revision cases, however, were MIS…and those MIS cases were revised more frequently for malposition and instability.”
“This isn’t a new concept. If we look back, Fehring and Sharkey both have reported pre-MIS era revision rates and again, half the patients or more were revised early. So it’s not a new finding that MIS patients are revised early. Almost half of the patients were revised for malalignment and instability, if you exclude infection. The numbers are no different if you look at early revision rate pre-MIS and early revision rate post-MIS. So Mike, wake up and smell the coffee. It’s not an issue of operative technique…it’s an issue of what’s happening in our community and what’s happening in our world.”
“If we look from when Insall and others pioneered knee replacement, there were ongoing failures—and greater than 50% of the knees that were going to fail had already failed by the time Barrack and Lowry Barnes published their article. So the early failures have already occurred in the open technique. We won’t see early failures in open technique if we’re not doing it. Instead, we see the early failures in the MIS technique because MIS is something that’s just occurred recently.”
“Our data from Adolph Lombardi’s series: two years, single surgeon, 1, 300 knees…compared with two surgeons, 3, 600, and the study group being the minimally invasive group. If we look at knees requiring manipulation, the minimally invasive group was almost half that of the standard group. Early reoperation rate: less than half the early reoperation rate in the MIS group.”
“I agree with Mike: MIS is a misnomer. It has very little to do with the efficient surgery and the size of the incision. It has to do with other factors that we’ve heard so much about, including preoperative education and perioperative anesthetic. I think MIS should be credited with drawing our attention to all of these various things.”
“MIS starts in the office with aligning patient expectations and understanding the rehabilitation protocols. The operative intervention is just a small part of it. MIS is multifactorial. We have to align patients’ expectations, educate, have medical optimization, know that the anesthesia team is as important as the surgery team, have pain management throughout the postoperative period, have efficient and safe surgery, and then have physical therapy postoperatively.”
Moderator Trousdale: “Keith, the series you did with Adolph…you showed some difference in outcomes between the MIS and the standard group. What other variables did you change in those two series?”
Dr. Keith Berend: “No. That’s the important part of this whole MIS series…the surgery is one part of it. We changed each one of those variables.”
Moderator Trousdale: “Michael, what are the factors that we’ve changed in the last two decades that’s influenced the outcome the most?”
Dr. Michael Berend: “Probably the anesthetic protocol, pain control, patient education…all those things changed at the same time. Rehabilitation was different, time off the walker was different and all of those factors together lead to clinical improvement. Some of the reoperation rates you observed…the manipulation rates seem excessively high. Early return to operating room rate seems excessively high, even compared to most standard series.”
Dr. Keith Berend: “MIS is a package. It’s a multidisciplinary system. But MIS surgery really should be credited with bringing that all to the forefront.”
Moderator Trousdale: “We’ve changed the anesthesia, what we tell patients, as well as what we do in the OR, and all of a sudden we say that it’s because of what we do in the OR that needs to be addressed. So Keith, what surgically are you doing differently with your so-called MIS technique that you think may affect outcome?”
Dr. Keith Berend: “It’s mixed in terms of which exact step in the operation, just as which exact step in the whole program makes the biggest difference. But we don’t evert the patella for the entire operation, we don’t dislocate the tibia for the entire operation; I think there’s a difference in the way we balance the knee now in the end versus big periosteal stripping versus intra-articular correction. A lot of small things that have come about because it’s harder to do the operation through a small incision. The instruments have improved, and our choreography in the OR has also improved.”
Moderator Trousdale: “Keith, do you tell your patients they’re getting an MIS surgery?”
Dr. Keith Berend: “No.”
Moderator Trousdale: “Michael?”
Dr. Michael Berend: “No, but we’ve made the exact same changes they’ve made. I think the pressure for all of us to make smaller and smaller incisions is huge and negative.”
Moderator Trousdale: “What outcome tools should we be measuring, Keith?”
Dr. Keith Berend: “I don’t think that we have one outcome tool that is sensitive enough to measure that. The biggest issue with knee outcomes—whether MIS or non or partial versus total—is the ceiling effect for the high performer. All the studies measure different things, and a lot of them are surrogates. They’re not 20 year outcomes, they’re ‘How far did you bend your knee at six weeks?’”
Moderator Trousdale: “Michael?”
Dr. Michael Berend: “We used to talk long term survivorship and now we’re saying, ‘I can do stairs at a week’ or ‘I can go back to work at three weeks’…and I think that’s the wrong message to be sending to our patients.”
Moderator Trousdale: “So what do you tell your patients about recovery before the surgery?”
Dr. Michael Berend: “We tell them two days in the hospital, three to four weeks on a walker, a cane for a month, that it takes a year to get over the operation.”
Moderator Trousdale: “When do you have them driving?”
Dr. Michael Berend: “Left knees, whenever they want. Right knees, we negotiate…about four to six weeks.”
Moderator Trousdale: “Keith, anything different?”
Dr. Keith Berend: “Really no different, but I think your point, Bob, is that one of the real dangers with the MIS craze is setting the wrong expectations for our patients. We need to not oversell the recovery.”
Moderator Trousdale: “Thank you, gentlemen.”
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