Minimally Invasive can have several meanings depending on the context. It can have a general connotation, such as arthroscopic vs open. It can relate to a given procedure, such as simply using a smaller incision for a standard hip replacement. It can relate to different surgeries in the same genre, such as a partial knee replacement vs a total knee replacement. And it can relate to variations in a given procedure that accomplish the traditional goal with less surgical damage, such as a muscle splitting direct anterior hip replacement instead of the traditional posterior or lateral approach.
Many of the soft tissue procedures done on shoulders and knees, for example, are done arthroscopically, whereas they have been traditionally performed with open incisions. In recent times, it is quite likely that surgical residents may never have seen a rotator cuff repair performed through an open incision. We have advanced the art of arthroscopy to the point where it is more common than open procedures. However, the open technique is still a good technique, and it is still performed in some places routinely with good results. Elbow, ankles, hips and wrists are also being treated arthroscopically.
In general, most orthopedic surgeons are doing many of the same joint replacement surgeries as were done decades ago, but are using smaller incisions. In my training, we learned to do Total Hip Replacements with a 6-8 inch incision, and that is what patients expected. Now we have gradually shrunk the incision to 3-4 inches, and basically do the same procedure as before, with better instruments and a higher level of interest in keeping the incisions small. Interestingly, this has worked well for reducing the hip incision, but not as well for Knee Replacements. We found that it is pretty hard to expose what you need to see, to reliably perform a complete replacement through a significantly smaller knee incision.
We are, however, doing more Partial Knee Replacements now than in previous decades. This can be done through a smaller incision, because you only have to see (and replace) one half of the knee, and you leave the undamaged parts alone. This is great if you only have one part of the knee damaged. This is obviously less invasive than a Total Knee Replacement, but if you have two or more parts damaged, you probably shouldn’t be having a Partial Replacement.
And finally, minimally invasive can refer specifically to the approach through which a procedure is done, even if it happens to be done open through a typical sized incision. In the example above, of the Direct Anterior Total Hip Approach, the “less invasive” refers to the fact that muscles are simply retracted, rather that resected and repaired later, in order to gain access to the joint space. This has the advantage of less surgical trauma and potentially quicker rehab and return to normal activity.
So what does “MINIMALLY INVASIVE” really mean? Ask your orthopedic surgeon and you may get a variety of answers, so don’t be surprised if it is not what you expected.