My name is Dr. Shane Doe from Rush University Medical Center in Chicago, Illinois. I'll be speaking on femoral osteoimpingment, new concepts in 2020. My disclosures can be found on the Academy website. Today I'll give an update on femoral acetabular impingement syndrome on three main topics, pathomorphology, biomechanics, and pathomechanics. Pathomorphology simply put is a CAM deformity, pincer deformity, or versional issues either on the acetabulum or on the femoral side. We all know that the most common reason for failed hip arthroscopy is either due to no correction or incomplete correction of femoral acetabular impingement. It's been cited in a paper by Greg Disetanovich that 81% of cases of failed hip arthroscopy are related to residual femoral acetabular impingement. And we also know that this leads to a high failure rate as well as an inferior clinical outcome, but we still don't understand the biomechanical effects of the CAM. So our lab tried to understand what is the biomechanical effect of the CAM deformity, both in terms of contact pressure as well as three-dimensional morphology. Using a cadaveric model, we had eight specimens with alpha angles greater than 55 degrees that were skeletonized. We performed testing with CAM impingement, partial CAM resection, and complete CAM resection. Thereafter we placed these specimens in a custom jig. Contact pressure testing was performed between each experimental time point to elicit contact pressure, contact area, and peak force. Our findings were as follows. In terms of contact pressure, it was highest in the CAM group. It was decreased with the partial CAM resection, and even more decreased with the complete CAM resection. When we looked at peak force, interestingly, we found that the partial CAM resection had the highest peak force, and this was also decreased when a complete CAM resection was performed. When looking at the three-dimensional morphology of the same specimens, we conducted CT scans before any resection was performed, and after complete CAM resection, we used a custom software to perform volume merge, where we overlaid the CT scans pre-CAM resection and post-CAM resection. Following that subtraction sequence, we were then able to measure the surface area, the volume, and the height of these CAM deformities. During the next phase of the study, what we also wanted to do was to understand how the volume area and height correlated with alpha angle, both in the pre-resection setting as well as a change in the alpha angle, and we did find that there was excellent correlation between all these measures and alpha angle, confirming that the alpha angle is actually an excellent parameter to measure our CAM deformities as well as resection. As far as biomechanics is concerned, we've been interested in understanding the soft tissue structures around the hip, particularly the labrum. In this particular study, we wanted to understand the suction effect of the native labrum, labra pair, and a 270-degree labra reconstruction. These are examples of a native labrum, again, a 3-acre labra pair, and a 270-degree labra reconstruction using iliotibial band allograft. This is the effect on the suction seal qualitatively with a native labrum, you can see a nice suction effect. With a labra pair, again, a nice suction effect. And with a 270-degree labra reconstruction, there appears to be a loss of the suction seal. What we found was that there was significant difference in terms of contact area between labra pair and labra reconstruction. There were differences with contact pressure and peak force, which are notable, but they were not statistically significant. So what's new in pathomechanics? Well, we've conducted studies in our motion analysis lab. On the left is our preoperative patient, on the right is a postoperative patient, approximately six months, and you can see that with single-leg squat, that there's a significant difference in terms of the sagittal flexion angle. What we found was that the squat depth between FAI patients and control was significantly different, but that this normalized and was comparable to control six months following a surgical correction of femoral S7 impingement syndrome. Using our clinical registry, we also want to understand the natural course of these patients and to really do growth mixture modeling to know what the trends are at baseline one year and two year. What we found was that 85% of cases followed that blue trend line, which is what we call the early progressors. There was approximately about 5% that followed this late progressor, which is a green line, and approximately 10% that followed this late regressor, which was a red line. Again, 85% early progressors, approximately 5% were late regressors, and 10% were late regressors. When we looked at the factors that were related to the late regressors, we found that those patients tend to be older, higher BMI, workman's compensation patients, decreased pre-op perplexion and higher out angle, patients of late progressors and lower back pain and a prior narcotic pain requirement. In conclusion, femoral S7 impingement continues to evolve. Femoral morphology will be better understood with three-dimensional imaging. Biomechanics and labor should be restored. And lastly, pathomechanics improves after femoral S7 impingement syndrome correction surgery. Thank you.

femoral osteoimpingement

hip arthroscopy

biomechanics

CAM deformity

FAI correction surgery