There are two forms of CT-based robotic arm total knee arthroplasty. One is a super navigation device where the knee is pinned in place and you get it precisely where you want it based on a pre-op plan (but there is no intraoperative soft tissue balancing). This is not the type of CT-based robotic arm TKR [total knee replacement] I do.
I opt for the procedure that allows us to robotically balance the knee with haptic soft tissue protection, surgeon control and no increase in adverse events. Again, you start with a 3D-measured resection plan no different than above. The workflow proceeds as follows: you expose the knee, attach the arrays, register the bone, remove accessible osteophytes, and then stress the knee dynamically to assess ligament laxity before making any bone cuts.
I adjust the resection thicknesses to reset the gap in the normal compartment. I then hinge on the normal side, adjusting alignment and rotation to approach balance, but not fully achieve it. We want to respect safe alignment parameters. Note that the affected compartment often loosens after removal of bone and osteophytes.
We then make fine-tuned controlling cuts, based on our dynamic assessment of the gaps.
Now we proceed with the soft tissue exposure and attach the arrays and probe the bone. With a CT-based plan, if you don’t pass the registration, that tells you something. The CT-based plan tells you that you didn’t probe the bone perfectly, information that adds value and accuracy.
We then dynamically assess the ligaments in flexion with the spacer and then move the knee into extension. We also can place the knee in 20 or 30 degrees of flexion to decompress the osteophytes and the posterior capsule.
The published results are quite good, with evidence showing that haptics and surgeon control protect the ligaments. There’s been no increase in adverse events and the benefits include less pain, less analgesic use, lower hemoglobin drops, fewer physical therapy sessions, and shorter length of stay. We also found faster time to straight leg raise and better knee flexion at discharge with improved WOMAC [Western Ontario and McMaster Universities Arthritis Index] scores both at six months and a year.
I examined my own results with 120 knees. Despite a technique and an implant that were new to me, we achieved balance with less articular constraint and a shorter length of stay. We also had a smaller flexion contracture on average and fewer manipulations under anesthesia to achieve similar knee flexion and similar Knee Society Scores.
While you might think a robot is unnecessary, it is actually a very good way to establish targets and hit them reliably. The robot can streamline your inventory in the future and protect the soft tissue. Go ahead and try it my way.
To hear how three other surgeons handled this same issue, stay tuned for Part II.
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I think all this robot-assisted knee replacement is a bunch of crap. You just need an experienced surgeon who does high volume and he can figure out things when he’s in there.