For patients with unrelenting patellofemoral pain related to lateral malalignment, tibial tuberosity transfers are commonly performed to improve patellofemoral alignment and reduce the pressure applied to areas of damaged cartilage. Although several studies have previously been performed to characterize the influence of tibial tuberosity transfers on the patellofemoral pressure distribution, none of the previous studies accounted for patellofemoral dysplasia and cartilage lesions, which are common for patients with unrelenting pain. The proposed study will focus on characterizing how cartilage lesions influence the effectiveness of tibial tuberosity transfers performed to reduce patellofemoral pressures and on developing computational methods for future investigations that account for patellofemoral dysplasia and additional lesion positions. The first specific aim of the proposed study is to characterize pressure reductions that can be achieved via tibial tuberosity transfers in vitro and characterize how lateral and medial cartilage lesions influence the effectiveness of the transfers.
The second aim i s to utilize both discrete element analysis and finite element analysis, with multiple representations for cartilage, to replicate the experimental studies.
The third aim i s to compare the computational and experimental results to identify the appropriate computational modeling technique (or techniques) for modeling symptomatic knees. The long term goal is to develop tools to investigate a variety of surgical and non-surgical treatment methods prescribed for patients with patellofemoral disorders, and account for the pathology of individual patients, in order to improve patient outcomes.
The first aim will be addressed by simulating isometric knee extension for 10 knees at 400, 600 and 800 of knee flexion. Pressure sensors will be used to measure the patellofemoral pressure distribution while simulating medialization and anteromedialization of the tibial tuberosity. The pressure measurements will be repeated after creating lateral and medial cartilage lesions.
The second aim will be addressed by creating computational models of each knee tested experimentally from MRI images. The experimental tests will be simulated computationally while representing the patellofemoral cartilage as a layer of springs (discrete element analysis). The pressure distribution in response to applied loads will be quantified by minimizing the potential energy stored within the springs. The experimental tests will also be replicated using finite element analysis. The computational data will be compared to the experimental data in order to validate one or both modeling techniques for future studies. Validated modeling techniques will be utilized with models of symptomatic knees to investigate treatment methods and pathological conditions that can not be easily studied in vitro. The proposed study will provide an initial assessment of how cartilage degradation influences the effectiveness of tibial tuberosity transfers and provide tools to collect additional data that can be used by orthopedic surgeons to plan procedures based on the cartilage damage and dysplasia noted for individual patients.
Project Narrative Surgery is commonly performed to treat pain behind the knee cap related to poor alignment and damaged cartilage. The proposed study will utilize experimental testing and computational modeling to characterize the effectiveness of surgical techniques performed to unload areas of damaged cartilage. Decreasing the pressure applied to the cartilage should reduce pain.
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