“There is a role for hinges, but not for these current designs. There are no non-rotating fixed axis hinges!” states Hugh Cameron. Thorsten Gehrke counters, “There are clear indications for a hinge knee, such as with extreme valgus deformities. Other primary indications include bone loss with major instability and extra-articular deformity.”
This week’s Orthopaedic Crossfire® debate is “The Role of Hinges: No Role At All.” For the proposition is Hugh U. Cameron, M.B., F.R.C.S.(C) of the Orthopedic and Arthritis Hospital in Toronto; against the proposition is Thorsten Gehrke, M.D., from ENDO-Klinik in Hamburg, Germany. Moderating is Michael J. Dunbar, M.D., F.R.C.S.(C), Ph.D. from Dalhousie University in Halifax.
Dr. Cameron: “When total knee was in its infancy there were no stems except on hinged implants. The early hinges had a high failure rate. The stems were too short, the trochlear grooves were either poor or non-existent, and hinge mechanisms were often poor and lacked strength.”
“I did hinged knees when I could do nothing else. I used the Guepar 2 from France, and my follow up is now over 25 years. I never had a single case of loosening. The problem was that at 20 years the plastic was damaged and worn out—and the spindle was damaged and there were no replacement spindles.”
“This is the same problem we all face in joint replacement surgery: the company stops making the implant. Perhaps they could make a one-off, but I hear that the FDA might prevent that. However, the FDA has just lost another major legal case, perhaps this is possible.”
“Regarding spindle wear, we need a mechanism where the whole hinge bearing can be disassembled from the stems, dumped and a new one can be attached to the retained stems. Taking out a fully bowed, completely cemented stem is not easy.”
“Currently, hinges are seldom used. We now have good tibial stems; femoral stems are not so good, but are getting better. Trochlear grooves and hinge mechanisms are adequate. But in North America, they all rotate. There are no non-rotating fixed axis hinges. There is a role for hinges, but not for these current designs. All of these designs allow free rotation. There are some cases and some revisions in which a hinged knee must not rotate.”
“The current indications for fixed axis hinges are, first of all, an absence of collateral ligaments, especially the medial. A high central post knee will work for awhile, but eventually the post will break. You need a flexion gap of >3cm with a normal extension gap. If the patient gets good flexion the femoral component will jump the post. The current hinges can handle these conditions, but it’s the third one, which is what we see more commonly. That is the multiply revised knee with bone loss, severe scarring, lateral patellar dislocation, and significant tibial torsion. The cause of such a situation is unrecognized tibial torsion; a rotating hinge does not solve this problem.”
“In tibial torsion, when the patella faces the front, the foot points laterally like Charlie Chaplin. When the foot faces the front the patella faces inwards (winking patella). Many of the patients see sports medicine doctors early in life; their history is usually the same. They are nearly all women who are athletic, they get a minor knee injury and quads atrophy. They lose control of their knees, have knee pain…and nobody can find anything wrong.”
“Her patella may have been a bit unstable. In order to hold it in place the tibial tubercle is transferred very medially. She has multiple operations, none of which work; she ends up with an unsuccessful knee replacement at an early age. The knee hurts, is stiff, and feels unstable. If the doctor only examines the knee then it’s a good knee. But when the foot faces laterally, the patella tends to track on the lateral ledge of the trochlea and may be painful. Because she walks with her foot turned out she chronically strains the medial collateral ligament, and her foot eventually collapses due to a tibialis posterior tendon rupture. She ends up with multiple knee revisions, each going up in level of constraint—none of which help much. By this time there are stems in the tibia so it’s impossible to do a tibial derotation osteotomy.”
“The ligaments and scarred soft tissues have a memory…and they want to go back where they were. If a rotating bearing is used, when the patient wants flexion she will externally rotate the tibia, which she’s always done, and the patella will sublux laterally. The final result is that she will have patellar pain and the sensation of instability—in spite of the fact that she has hinge. She will be unable to use the knee as the lead leg on stairs, on patellar loading.
“I wish that one of the North American manufacturers would simply drill a couple of holes in the lateral side of the tibial component so that we could slide in a couple of metal pins to block the plastic from rotating externally.”
Dr. Gehrke: “Until a couple of years ago most U.S. orthopedic surgeons were saying, ‘I never did a constrained knee in my life’ or ‘I can solve any problem with a PS or CCK design.’ I was asking myself, ‘Who operates on extreme cases without using a hinge?’ [showing a doctor rotating a leg to the SIDE]…May I ask the audience, ‘Who would use anything but a hinged knee in this case?’ [audience claps] So there IS a role for hinges.”
“There are primary indications for using a hinged knee, such as with very stiff, extreme valgus deformities—I especially lean toward a pure hinge. Other primary indications include bone loss with major instability, extra-articular deformities, or posttraumatic cases. Even very old patients with severe osteoporosis are safe for a hinged knee.”
“A 2004 paper from the British JBJS showed good or excellent results in 91% of knees; 15 year survival was 96.1%. In our own series of 238 consecutive cases, after 13 years we had a survival rate of 90% and only one aseptic loosening.”
“As for revisions, the challenges include instability, severe bone loss, and wear problems. The surgeon would need a high grade of stability and a long distance for anchoring. Instability is one of the most common causes of failure; in some indications it’s impossible to use a PS or a CCK design and then use hinges. Or if there is very severe bone loss and there’s no other way, then use a hinged knee. At my institution we are doing a lot of infections, and due to radical debridement, most of the stabilizing structures are gone…thus we have to use a hinged knee.”
“In 2010 Fares Haddad published a paper where he compared three implant types: posterior stabilized, condylar constrained knee, and rotating hinge. He found that the rotating hinge group had the highest satisfaction rate (88%) and the highest 10 year survivorship (90.6%). Our indications are close to those of Adolph Lombardi. He proposed the use of hinges if everything is gone or at least the medial collateral ligament is gone then we must use a hinged knee.”
Moderator Dunbar: “Hugh, if you had access to fixed hinged knees you’d be using them more?”
Dr. Cameron: “No. I use maybe two hinges a year. Before good stems came about we had to use hinges because they were the only ones with stems. But now the stems for the TC3 type knees are pretty good. ”
Moderator Dunbar: “One of the subtleties that’s emerging here is the difference between a rotating platform hinge and a fixed hinge. When are you using a fixed hinge?”
Dr. Gehrke: “If I have a huge valgus deformity (more than 35 degrees) then I use fixed hinges because otherwise we always have problems with the patella.”
Moderator Dunbar: “Do you assess the patient’s gait and does that factor into your algorithm?”
Dr. Gehrke: “I would say so.”
Moderator Dunbar: “Hugh, do you think the patient’s gait—the four dimensional analysis—should be brought into the equation of whether or not we use a hinge?”
Dr. Cameron: “Oh I did mathematics a long time ago. I couldn’t work out things like that.”
Moderator Dunbar: “Alright, do you think there’s a tradeoff to using a fixed hinge in that the knee is a complex joint? Are there tips and tricks in that situation?”
Dr. Gehrke: “You are looking to see the best position of the tibial component. Normally it’s right over the tibial tubercle.”
Moderator Dunbar: “But I think the point is more subtle. Long term, we’re prescribing that this thing moves in this plane, but there may be some rotational components as you flex.”
Dr. Cameron: “We’re not really talking about using hinges in normal knees—these are totally destroyed knees. So you’re not recreating normal anatomy…that doesn’t exist.”
Moderator Dunbar: “Yes, but it doesn’t have to be normal to still have deforming forces. I’m talking about rotational forces at the tibial interface. That force/rotation must go somewhere. Do you cement all your stems and is it because of that?”
Dr. Gehrke: “Yes, we fully cement all our stems. The original hinged knee was a fixed hinge knee (developed at the ENDO-Klinik). Due to the problems of rotational shears and periprosthetic fractures, they developed the rotating hinge knee. Those knees are not normal, and the patient’s expectations are not really high after a knee implant. But surprisingly they are working very well.”
Moderator Dunbar: “What about metaphyseal fixation versus cementation?”
Dr. Cameron: “With a hinge I would cement—maybe not fully. Their strongest hinge has a stem which is quite good and so you can get away with metaphyseal cementing with that stem.”
Moderator Dunbar: “What do you make of Haddad’s paper showing that the hinge has a higher satisfaction rate than the other constructs?”
Dr. Cameron: “I always thought that. But we’re dealing with completely destroyed knees, which is why you do a hinge in the first place.”
Moderator Dunbar: “Your take?”
Dr. Gehrke: “I cannot argue better for hinges. They never have stability problems, and patellar tracking isn’t an issue if you’ve implanted in the right position.”
Moderator Dunbar: “So that last paper…it was rotating hinge knees in that case…would you have the same satisfaction rates in a fixed hinged knee?”
Dr. Gehrke: “I don’t know. In 90% of cases we use rotating hinged knees; only in 10% of cases do we use a fixed hinge knee. I don’t know.”
Moderator Dunbar: “And there would be a selection bias there because these are harder cases.”
Dr. Gehrke: “Yes.”
Moderator Dunbar: “Thank you both.”
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