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Patella Instability Didactic Presentations - AOSS ...
6. Keys to a Successful Tibial Tubercle Transfer
6. Keys to a Successful Tibial Tubercle Transfer
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Video Transcription
Hello. My name is Carl Nissen. I'm going to spend the next couple of minutes trying to give you some ideas and thoughts about how to have a successful result following tibial tubercle transfer. My disclosures are listed here and they're also listed in the AOS website. Just like all the surgeries we do, the most important thing to start with is planning. Once you've decided that a tibial tubercle osteotomy is the appropriate step for a patient, you want to make sure you have a good clinical exam looking at range of motion of the knee, but also the range of motion or the translatability of the patella both medially and laterally. Assessing the tightness of the medial lateral retina was important in making decisions about other procedures associated with the tibial tubercle transfer. Muscle and muscle imbalance is very important to check because this will affect your results as well. All of us look at alignment of the lower limb from the hip down to the foot. This is done both clinically and by x-ray. Certainly, there are many measurements that you can look at. The TT-TG interval is usually the one that people talk about the most. This is measured here on CT scan. I will tell you that the number that I come up with when I measure this is not a number I directly translate to what I do in the operating room as there's more play in the system than can be determined by a static CT scan. The evaluation includes an examination under anesthesia once in the operating room and then an arthroscopic evaluation. I think we probably pay too little attention to arthroscopic evaluation in this situation. Determining where if there are chondral lesions and where they are and the extent of those lesions both on the trochlea and on the patella is very important. This will, for me at least, make a part of the decision of how much tibial tubercle translation is needed and which direction it is needed. We also look at patellar tilt. As a part of that, obviously, looking at the lateral retinaculum is important. The lateral retinaculum limits patellar translation immediately, but it also limits patellar translation laterally. You have to understand that iatrogenically, you're tightening the lateral retinaculum when you do a tibial tubercle transfer. Therefore, you have to adjust what you do to lateral retinaculum to correlate to what you're trying to achieve. My approach is a paramidline incision, making it a little bit almost in line with the medial portal so it's not over the tibial tubercle either initially or where it's going to end up. I take down the entire anterior compartment approximately and get to the point where I can get around the posterolateral aspect of the tibia. Then I'm going to go and find the patellar tendon attachment. I think it's important to know exactly where this is before you start doing any cuts approximately. I put a Kelly as demonstrated here behind the patellar tendon so it's isolated and identified clearly. I then template out the angle of the cut and where the cut's going to be. I usually use a bovie to mark it out clearly, cut through the periosteum, allow the sagittal saw to do its job without running into soft tissue. Once the large retractor is around the posterolateral tibia, I feel better about protection and certainly if you're going to do a flat osteotomy for more medialization as demonstrated here, that's all you'll need for protection. However, if you're going to make a very vertical cut because you need to enterize the tibial tubercle, sometimes that large retractor will do all it's necessary but sometimes you have to do more than that. When you're using a cutting block technique, which is what I prefer to use, you want to make sure you use a sagittal saw through the block and you want to make as much of the osteotomy with the sagittal saw as possible. That gives you a higher chance of having a single plane even level cut. This even cut allows for a greater surface to heal. You can get better fixation which allows early mobilization which we all know is very important. When you do do the back cuts behind the patellar tendon, I use a half-inch osteotome. It's usually about a 45-degree cut reference to the tibial shaft as demonstrated here. Some of the technical things that I think you need to be careful about is before you crack or before you complete the osteotomy, all cortical spots with one exception need to be completely free. The little bit of extra crack that you get by using a large three-inch osteotome to reduce the stress risers, everything else needs to be cut. If you are making a vertical osteotomy and you need to do a back cut just anterior to the posterior tibial cortex, I do that with a curved osteotome lateral to medial and it really doesn't take very long to do that and certainly makes me feel much more safe about the neurovascular structures. Suggestion from myself is that you leave a distal hinge intact of the osteotomy. The periosteum and maybe even a little bit of bone distally, if you leave it attached, it makes a couple things easier. One, it makes you more easily able to determine the proximal distal changes which most of the time we're not making. Most of the time it's just a medial and anterior position, the tubercle. If you leave it attached, it helps you with that. Otherwise, if you do detach it, that's the last part of the osteotomy. It'll heal and is very often painful because it is subcuticular. If you leave it attached, it also is an extra fixation point in addition to the two bicortical screws that I use and hence that increases fixation and you get better early healing. If you have to detach it because you're going to do some sort of open procedure inside the knee joint, inside the patellofemoral joint, that's fine. Taking it off and not leaving it attached does not reduce healing. It just lengthens the amount of time it takes to get to that point. Thank you very much. If I have any time, I'd be happy to answer any questions.
Video Summary
The video discusses the topic of tibial tubercle transfer, with the speaker providing ideas and thoughts on how to achieve successful results. The importance of planning and conducting a clinical exam is emphasized, including assessing the range of motion of the knee and patella, as well as muscle imbalance. Alignment of the lower limb is also examined using clinical and x-ray methods. The speaker mentions the importance of arthroscopic evaluation to determine chondral lesions and their extent. The surgical technique for tibial tubercle transfer is described, including the use of a cutting block technique and sagittal saw. The speaker also discusses technical considerations and the importance of leaving a distal hinge intact for better fixation and early healing.
Keywords
tibial tubercle transfer
clinical exam
alignment of lower limb
arthroscopic evaluation
surgical technique
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