Thanks for the introduction and thank you to Anna for the opportunity to present our work today. I'd like to acknowledge my co-authors. This work was completed during my fellowship at Rush. And our disclosures, none are pertinent to this presentation, but they are available in the final program. So to begin, patellofemoral cartilage lesions can cause pain and limited knee function. And isolated patellofemoral cartilage lesions are seen in up to 20% of patients younger than 40 at the time of knee arthroscopy. The causes and risk factors for these lesions are not always clear. We know that tibial tubercle alignment influences stability and the wear patterns of the patellofemoral joint and the TTTG describes the medial lateral position of the patellar tendon insertion. It is unclear, however, how the sagittal position of the tibial tubercle can influence the presence of patellar cartilage injuries. The purposes of this study was to measure the sagittal alignment of the tibial tubercle relative to the trochlear groove in patients with and without patellofemoral cartilage lesions, as well as to define the reproducibility of a vertical tibial tubercle trochlear groove distance. We hypothesized that patients with patellofemoral cartilage lesions will have a significantly more posterior tibial tubercle relative to patients with normal patellofemoral cartilage. So to accomplish this, we performed a retrospective analysis of patients undergoing patellofemoral cartilage repair or restoration procedures by querying the surgical case logs of two senior surgeons at a single institution between October 2010 and August 2017. We excluded any patient with a history of prior patellar instability, as well as any patient who lacked an available preoperative MRI or had a knee flexion angle greater than 10 degrees on their preoperative MRI. We grouped patients into three different groups, as described here. The first group had patellofemoral cartilage lesions, so these were patients undergoing surgical treatment for either cartilage repair or restoration of the patellofemoral joint. Group two were patients undergoing knee arthroscopy for partial minisectomy and had arthroscopically documented normal patellofemoral cartilage. The third group was patients with asymptomatic patellar chondrosis. So these were patients undergoing partial minisectomy who were documented to have abnormal patellar cartilage, but they were not clearly symptomatic from this. We collected demographic data from the electronic medical record, as described here. We measured on the MRI the vertical TTTG, as we'll show on the next slide, as well as other relevant patellofemoral anatomic measurements, including the sulcus angle, standard TTTG, the Catan-DeChamps index, and their knee flexion angle. From the operative report, we recorded cartilage lesion dimensions and cartilage lesion grade. The vertical TTTG was measured as shown here, similarly made compared to the standard TTTG, so measured as the distance between the tibial tubercle and the trochlear groove. We just measured in the A to P plane, perpendicular to the posterior condylar axis. All measurements were performed by two fellowship-trained sports medicine surgeons, and then all were repeated by one evaluator. We performed appropriate statistical analyses, including ANOVA tests and Fisher-Exact tests for demographics. We confirmed normality and then performed ANOVA tests to compare the VTTTG across all three groups with post hoc corrections for multiple comparisons. We also used interclass correlation coefficients for reproducibility. Our group demographics are shown here. Of note, the patients in group one who had the patellofemoral cartilage lesions were significantly younger by about 20 years compared to our meniscectomy groups. There were no other demographic differences between these three groups. Here on this slide, we show the vertical TTTG measurements between the three groups. On the y-axis is the TTTG value. An increasing value is more posterior, so more posterior tibial tubercle. Value closer to zero is a more anterior tibial tubercle. We found in group one, the patients undergoing patellofemoral cartilage treatment, they had a significantly higher VTTTG measurement, measuring 5.9 millimeters relative to 0.8 millimeters in group two. The patellofemoral chondrosis group was in between these. The difference between group one and group two was statistically significant. Our reproducibility is reported here. We had excellent intra- and inter-observer reproducibility, and this is in line with the standard TTTG measurement, ranging from 0.90 to 0.98. So through this study, we demonstrated that the VTTTG is significantly higher with a more posterior tibial tubercle in patients with symptomatic patellofemoral cartilage lesions relative to controls. The sagittal alignment of the tibial tubercle is known to influence the loading of the patellofemoral joint. In chronic PCL tears, you have a posterior sag of the tibia and have resulting patellofemoral arthritis and pain. And then we do successfully treat these patients with an anterior medialization osteotomy. The VTTTG, we believe, may become a useful measurement for osteotomy planning, but future work is needed to better clarify the expected ranges of normal and abnormal values. Thank you.

sagittal alignment

tibial tubercle

patellofemoral cartilage lesions

VTTG measurement

osteotomy planning