OSSM and Anna, and nice attendance. Good to see everybody out there. If anybody wants to find a seat, just kidding. I'll be talking about the risk of patella fracture in proximal quad tendon versus distal patella tendon, autograft bone blocks, and ACL reconstruction, a biomechanics study. Thank you to HSS for helping to support this study, and to Dakota, who's here as well. Overview of ACL reconstruction, the incidence of ACL injury, as most of us are aware, 68.6 per 100,000, increasing rates of ACL reconstruction within one year of injury during the past 20 years. One risk of ACL reconstruction is patella fractures caused by bone blocks from quad tendon or bone patella tendon bone grafts. It can be a devastating injury due to surgical treatment and rehabilitation. It can really increase the time for rehab and getting back to sports, and they are difficult to reduce. They're not your typical patella fracture where you're doing open reduction internal fixations. The graft failure rate is around 2% to 13%, and that can lead to revision ACL reconstructions as well. The management of patella fractures following ACL reconstruction. The causes of patella fractures following ACL reconstruction are due to direct trauma, fall, or contact collision. That's typically when I see them. Usually it's earlier on in the rehabilitation process. You've done an ACL reconstruction, and then somebody, by no fault of their own, either falls. They had a college student fall off a bunk bed or somebody else tripped on the sidewalk and really just landed directly on that more fragile patella. Or indirect trauma, so you can have kind of an extension pull onto the patella, overuse or overload during rehabilitation. I haven't seen that personally, but that's another cause of patella fractures. The long rehabilitation process. Conservative treatment is a mobilization of the knee for two to eight weeks, and then crutches for two to six weeks, then rehabilitation, and then operative treatment, which is typically the plan afterwards is internal fixation within two to eight weeks of immobilization and crutches for two to six weeks, then rehab. And it does interfere with the normal rehabilitation process for ACL reconstruction. What we see, obviously, for our ACL reconstructions is there's certainly an increase of movement over those first six weeks. However, if there is a patella fracture, you're really gonna wanna lock that person up and be able to heal the patella fracture. Plus, again, it's a lot more fragile than your typical patella fracture because you do have that area of the bone defect that you try to graft or fill in. And then it puts athletes further back in the already long process. Looking at bone patella tendon bone versus quad tendon grafts. This is really the root of the study. A couple reasons. One is quad tendon grafts are really strong, so people are leaning towards using them more frequently. In the younger population as well, it's being used for the pediatric population because it can be a great soft tissue graft. The problem is sometimes for the quad tendon grafts is they can be shorter. If you're not doing an all inside technique or you're worried about your tibial fixation and getting graft into that tibial tunnel, they can be shorter. So if you're looking at the potential of elongating the graft, one opportunity would be to take that bone off the proximal pole of the patella and then add that to your graft. And potentially it could add 20 to, potentially 25 millimeters, which can really then get it to the tibial tunnel if you're worried about the length of the graft. Bone patella tendon bone grafts still are the gold standard for ACL reconstruction. And the patella fracture rate is between 0.5% to 1.8%. One of the reasons that HSS was very supportive of the study is especially in our NFL athletes who they're trying to push for quicker and quicker to get back to play. They have seen patella fractures with those individuals. And again, it can be very devastating as these athletes are pushed quicker and quicker to return to play. For about 10,000 ACL reconstructions, about 50 to 180 will have patella fractures. 180 I would say is probably on the higher side, but potentially 50. Bone quad tendon grafts, there's a lack of literature comparing patella fractures between bone quad tendon and bone patella tendon grafts. But again, quad tendons have recently gained popularity as an alternative to patella tendon grafts due to larger thickness, as well as a higher load to failure. The graft rupture rates at this point are similar to that of bone patella tendon bone grafts. The purpose of this study was to determine if there's any difference in risk of post-operative patella fracture between bone patella tendon bone grafts and bone quad tendon bone grafts, including the influence of confounding variables on patella fracture, including bone density, patella length, and fracture pattern. The hypothesis that we came up with was bone quad tendon grafts would cause patella fractures at a lower load compared to bone patella tendon bone grafts. And part of the reason is we'll go into that is the shape of the patella, and it tends to be a little bit thinner on that proximal aspect than it is on the more distal aspect. The method is the patella is placed on a custom three-point bend fixture on a servohydraulic load frame. The anterior aspect was facing down to put the location of the bone block removal in tension. And then flat fixture was used to push articular surface of the patella to accommodate variability in patella geometry. When we first started, the patella kind of slipped everywhere so it took a little while to put together at least that base where it centered the patella on the MTS machine. The cut was centered on the fixture under loaded cell, and then sutures attached to medial and lateral aspects of the patella located without placing tension on the bone. So it was more just to center the bone in the fixation rather than pulling on either side. We recorded the absence or presence of fracture after impact as well as any type of stress riser that happened, as well as the type of fracture, complete or incomplete. Taking anatomic measurements, points were chosen along the medial and lateral edge of the articular surface and a plane fitted to those points. Planes were often offset from the first plane until they intersected in the most anterior and posterior aspects of the patella, and then the distance between the planes equals the patella thickness. So that was just looking at what we're calling the width and the length of the patella. And as you can see distally, that patella, the bone patella tendon bone graft, that bone tends to be more centered versus as you get closer to the proximal aspect, the patella tends to be a little bit more asymmetric and has a shallower aspect as you go into the lateral aspect of the patella. Our specimen demographics, 46 fresh frozen cadaveric patella were tested and 23 randomly assigned to each group. The age was around 66 on average for the patella tendon and 64 on the quad tendon. Sex was basically equal on both sides. Bone density was fairly similar to both sides as well. Patella thickness, as you can see here, and then patella width, patella length, and that's of the bone that we were looking at. The results in the maximal load to failure, there were no difference in maximum load to failure for either the quad tendon side or the patella tendon side, so the proximal pole versus the distal pole. This was what the specimen would typically look like where you have the defect here centered in the patella and then you had the sutures on either side, just really helping to center that patella. The patella tendon cut, there was no correlation between max load and bone density, patella thickness, patella width, patella length, and then the quad tendon cut, no correlation between max load and patella thickness and patella width. But the quad tendon cuts, there was a positive correlation between max load to failure and bone density, which is obvious but something to think about if you're taking autographs in older individuals or somebody who may have decreased bone density. And then a negative correlation between max load and patella length with a statistical correlation. And then the significance was the specimens with the larger length pole to pole failed at lower loads. The takeaway, no difference in failure load between bone patella tendon, bone and bone quad tendon graphs in this biomechanics model. One less concern for the surgical treatment plan, so looking at potentially extending that quad tendon graph and incorporating the bone into your ACL reconstruction. And then account for patella bone density and patella length in bone quad tendon graphs. These are the references and these are my teams.

patella fractures

proximal quad tendon

distal patella tendon

ACL reconstruction

incidence of ACL injury