Pre-operative planning for surgical treatment of patellar instability

Project Summary/Abstract Acute patellar dislocation and chronic patellar maltracking and subluxation disproportionately affects active young people, impairing functional ability, causing swelling and anterior knee pain, and predisposing patients to early onset osteoarthritis. Surgical interventions to treat patellar instability have success rates of approximately 50% — half of patients who undergo an initial surgery require subsequent surgeries or continue to suffer from patellar instability, swelling, anterior knee pain, subluxation, and/or dislocation. Poor surgical outcomes are typically the result of failure to account for patient-specific pathoanatomy during treatment. The standard surgical protocol for treating these patients is reconstruction or repair of the medial patellofemoral ligament (MPFL), which is usually ruptured during an initial dislocation event. However, isolated MPFL reconstruction may not be sufficient to correct for predisposing anatomic risk factors (including trochlear dysplasia, patella alta, increased tibial tubercle-trochlear groove distance and increased quadriceps angle) that are almost always present in these patients. Unfortunately, there is little consensus on a standard protocol to determine the most appropriate surgical treatment plan, especially for patients with multiple abnormal anatomic risk factors. As a result, surgical outcomes are highly variable; patients may undergo multiple surgeries that fail to treat underlying anatomic risk factors that contribute to patellar instability and dislocation. Our long-term goal is to develop pre-operative planning software that will use patient-specific medical imaging to quantify stability of an individual’s patellofemoral joint and provide guidance to the clinician by generating a patient-specific and surgery-specific prediction of post-operative patellar stability. This will allow the clinician to compare stability outcomes between potential treatment options. Such a pre-operative planning tool to guide treatment of patellar instability does not currently exist, so our software will be the first-to-market product. Our objectives for this Phase I project are to generate the data required to develop our proposed surgical planning platform, to perform preliminary validation of our computational models through cadaveric and human subjects testing, and to demonstrate the proof-of-concept of our computational approach. On completion of Phase I, we will have developed a stability classification algorithm which can differentiate between healthy and pathological anatomy and quantify the effect of a specific surgical intervention in altering an individual’s stability classification (Aim 1), we will have validated our computational model predictions against in vivo pre- and post- operative kinematics (Aim 2), and validated our model as a comparative assessment tool to compare joint stability across surgeries for the same subject (Aim 3). This will position us to translate this work into a comprehensive pre-operative planning software tool in Phase II of this project.