Good afternoon, thanks, Miho, and thanks to the Program Committee as well as the AOSSM for allowing us to present our data today. I'd also like to thank my co-authors, without which none of this work is possible. We do have some disclosures not particularly relevant to this talk. So as you're all aware by now, patellar dislocations are common knee injuries, and these, in up to a third of cases, can lead to recurrent instability. We also know that the MPFL is the primary soft tissue restraint of lateral patellar translation, and we know that isolated MPFL reconstruction results in a very low recurrence rate and good outcomes, with 1 to 2 percent recurrence rates reported in appropriately selected populations. So what drives the outcome of isolated MPFL reconstructions? Is it the anatomy? Historically, we would talk about factors, as have been alluded to, that may influence outcomes after isolated MPFL, but as we've heard in the prior study and in multiple other studies published over the last several years, anatomy doesn't really seem to 100 percent be the answer. So what else drives outcomes of isolated MPFL reconstruction? What about the number of prior dislocations? One could hypothesize that a history of multiple dislocations is likely associated with more damage to soft tissue structures, and we know from prior anatomic work that the MPFL is not the only soft tissue stabilizer of the patella. There are contributions from the retinaculum, both medially and laterally, and other structures as well. So isolated MPFL reconstruction may be less effective in patients with multiple dislocations stretching their soft tissue structures. So the purpose of this study was to investigate the influence of the number of prior patellar dislocations on the outcome of isolated MPFL reconstructions. We hypothesized that patients with greater than two prior dislocations would have more recurrent patellar instability after isolated MPFL reconstruction and poorer patient-reported outcomes. We utilized a retrospective cohort study model, including patients with an isolated MPFL reconstruction with greater than one year follow-up. We enrolled people, 200 patients, underwent MPFL reconstruction over this period. We excluded those who had concomitant procedures, including TTOs, fixations of loose bodies, and then included those that had one year follow-up. We then got history, demographic, and outcomes factors from chart review and contacted patients to determine outcomes, including recurrent dislocations, subluxation and instability events, which were quantified with the Norwich Patellar Instability Score, the Kuhs Scores, as well as Marks Activity Scores. We then compared baseline factors and outcomes based on whether they had less than or equal to two or greater than two dislocations. So we had, out of our 112 patients that completed our outcomes, 50 patients with less than or equal to two recurrent two dislocations, and 72 patients with more than two, including those with multiple dislocations. As we look at the factors here, the only statistically significant difference between these two groups was age. As one might expect, those with more dislocations were, on average, older. But if you look down through here, you see that none of the other patient demographic factors or imaging factors are different between the two groups, and I would particularly draw your attention to the fact that the prevalence of particular cartilage damage between the two groups was similar, which was a surprise to us. So looking at recurrent dislocations, we had a 2% rate in the less than or equal to two dislocation group, 1 out of 50, and 4 out of 72 in the greater than two dislocation group. We were underpowered to detect a difference here, but we may be starting to see the beginning of a trend. Looking at patellar instability as described by the Norwich Instability Score, we saw higher values in the group that had greater than two dislocations, and this is a scale that goes from 0 to 100, with 100 being more instability, and this was significantly different. As we look to the COOS, we really see some substantial differences between these two groups, particularly you can see here in the COOS Sport and Recreation and Equality of Life function, where we see over 20 point differences between the groups at a mean follow-up that began at four to five years. We also see lower marks activity level in the recurrent dislocation group. In a linear regression model, controlling for all potential differences between the two groups, including age, as was the primary difference that was actually different between the two groups, we see these differences persist, particularly in the COOS Sport and Rec and Equality of Life. So, in conclusion, patients who suffer greater than two patellar dislocations prior to isolated MPFL reconstruction have greater patellar instability after surgery and poorer patient-reported outcomes. There are, of course, some limitations to the study design, namely it's retrospective, we have some loss to follow-up, and we did select patients for this study by excluding those who underwent tubular tuberculosis osteotomy. Further, we have a relatively small sample size and are thus underpowered to detect differences in recurrence at recurrent dislocations. We also, importantly, lack preoperative patient-reported outcome scores, so we don't know if maybe those patients who had multiple dislocations had worse scores going in, and thus even though they improved similarly, maybe had worse scores afterward. Other studies would suggest that's not the major driver of our outcomes, but we don't know that for sure. There also could be other potential differences between these groups that we have not described or controlled for. Future work is an interesting question here because many recurrent instability patients, as we see, do really, really well with isolated MPFL reconstruction, particularly those with two or fewer dislocations prior to surgery. Inclusion of these types of patients with only two dislocations in our large cohort studies may make it more difficult to identify predictors of poor outcome because so many patients do well. I think it might be interesting to focus on those patients with multiple dislocations, similar to the way in ACL research we often focus on the highest risk patients, like adolescents, when evaluating potential predictors of outcome. Looking at this group, we may be able to identify some additional factors that can influence the outcome of isolated MPFL reconstruction. Thank you again for all your attention.

influence

prior patellar dislocations

MPFL reconstruction

patellar instability

patient-reported outcomes