Thanks for having me. I'm pinch-hitting for Beth Schubenstein. She got stuck in New York, but I hope to represent her well. We've done a lot of this research together. Neither of us have any disclosures that are relevant. So you just saw a beautiful depiction of an MPFL reconstruction. Is that enough? Can we stop there? Sometimes, yes. Sometimes the path forward is pretty straightforward, the anatomy is simple, and an MPFL reconstruction is the clear answer. Sometimes, though, it's pretty clear that it's not. If you're relying on your MPFL graph to pull the patella back onto the trochlea, most of you know that that's doomed to fail, stretch, capture the knee, cause problems. But what do we do for everyone in between? That's where the big question lies. We usually use broad concepts, significant malalignment in the form of elevated TTTG, severe patella alta, severe trochlear dysplasia, but we don't have any hard evidence on what our cutoffs should be. Another reason to think about a boning procedure is an unloadable patellar cartilage injury. A lateral or a distal chondral injury can be unloaded very nicely with an antramedialization. So what do we know? We know that the MPFL is the primary restraint. We told you about the anatomometric nature of it, it loosens in deep flexion. And we know that we're getting better at it over time. So 85% of patients return to sport and fewer than 5% of patients have recurrent instability after MPFL. But the gap in the current literature is that we have no clinical studies that clearly demonstrate what degree of alta, coronal plane malalignment, trochlear dysplasia, let alone femoral rotation anteversion or ligamentous laxity predict the failure of isolated MPFL reconstruction. The current standard of care is conservative for first-time dislocators unless there's a fracture or a loose body, and for recurrent dislocators it's surgery. But we don't know what the right surgery is. We know that some first-time dislocators are at high risk whether they have a loose body or not. If you're young with trochlear dysplasia, well-done prediction models have demonstrated a risk of upwards of 70%. But the big question is what do we do when we decide to do something? Is isolated soft tissue enough? When should we add a boning procedure? And most commonly that's in the form of tibial tubercle osteotomy. For this we turn to the shoulder instability literature. Pascal Boileau undertook this prospective cohort to try to define who's going to fail an isolated arthroscopic Bancart repair. And he developed the instability severity index score as a result of examining the patients who failed arthroscopic Bancart. We need something similar for the patella to help identify which patients have an unacceptably high risk of recurrent instability with isolated MPFL reconstruction. So with this in mind we undertook a similar study in the patellofemoral population. We published on this in 2018 with our initial group at one in two years. We used a prospective cohort with a goal for multivariable logistic regression analysis. We wanted to identify the risk factors that led to redislocation and create this instability severity index score, but also identify the subgroup of patients who would be better served with bony realignment in addition to the MPFL. We recruited all patients under 40 years old with recurrent patellar instability. We excluded those who had failed previous surgery, who had significant unloadable chondral defects or a significant portion of pain as their symptom, and those who had the jumping J sign or obligatory dislocation and extension. We recorded information on their instability history, any recurrence postoperatively, return to sport, and outcome scores recorded at one in two years. So here's that jumping J sign. You've seen that already. And then this is that same concept that Lutule demonstrated. If patients reported, we asked them this nebulous question of add your symptoms together and give us 100% pain and instability, and if they said 50-50 or something more related to pain, we worried that an MPFL alone was not going to treat the pain component of their symptoms. So we published initially on 90 patients between March 2014 and August 2017. We currently have 138 patients through December 2019. We have 88% overall follow-up, 77% of them are women. Average age is 19.4 years, and the range is shown there. The TTTG is average 14.7 with a pretty broad range. The ALTA also had a pretty broad range, and trochlear depth averaged 1.95 millimeters. In the initial cohort that we published on, we had one repeat dislocation at 3.5 years and one subluxation. 96% of patients were stable at one year and 99% of patients were stable at two years. The overall return to sport was 88%. We're currently submitting 138 patients with six recurrences in the group. But it's important to realize we're powered for 180 in this group, and so our study is ongoing. We were misinterpreted. A lot of readers interpreted this to mean MPFL should work for everyone, and that's not the overall goal. We want to identify who's going to fail. And it's true that fewer people failed than we expected, but we're still not powered to draw broad conclusions. We're suspicious of ALTA preliminarily. If you examine that first paper, the two patients who did fail had patella ALTA in the mix. But we can't, we would serve you poorly if we just assigned one point to ALTA and one point to dysplasia. We need high-level statistics to really determine what contributes the most. So our current guidelines of ALTA over 1.3 or 1.4, depending on who you read, TTTG of over 20 if anybody does as many peer-to-peer reviews as I do, trochlear dysplasia of B and D, those are probably not true in isolation. It's more likely that they're a combination that leads to failure, and that is what we're seeking to define for you. So stay tuned. Hopefully we'll have these answers soon. Thank you very much.

patellar instability

MPFL reconstruction

recurrent instability

surgical procedures

risk factors