An in vivo methodology has been developed for assessing the cartilage layers of the patellofemoral joints of patients diagnosed with osteoarthritis. The methodology utilizes a previously honed magnetic resonance imaging technique that yields high resolution images with contrast between cartilage and neighboring tissue. Examining the patellar, femoral and tibial surfaces of six cadaveric specimens, comparison with stereophotogrammetry measurements demonstrated accuracies of 0.22±0.05 mm and 0.14±0.04 mm for cartilage and subchondral bone surface topographies, respectively, and 0.31 ±0.09 mm for the cartilage thickness measurement. A semi-automated segmentation method produced results no less accurate than those from fully manual segmentation. The quantification of the articular surface topographies was shown to enable the estimation o f articular contact regions in vivo. These methodologies were also shown to be applicable to volunteers and patients. By averaging the femoral and patellar surfaces of fourteen normal knees, normative templates for patellofemoral joint topography and cartilage thickness were created. These templates are useful in the assessment of the cartilage thickness patterns o f patients and as models for improved automated segmentation of knee images.
Employing geometric and kinematic data from cadavers and a previously developed multibody model of the patellofemoral joint, contact analysis revealed that recommended donor sites for osteochondral grafting on the femoral surface are not free from contact with the patellar surface. Surface modeling techniques were used to match osteochondral grafting donor and recipient sites based on curvature and cartilage thickness. Joint modeling analysis with cadaveric data further demonstrated that open-chain knee extension exercises, which are controversial in the treatment of the patellofemoral pain, produced neither unphysiologic stresses, nor stresses significantly higher than those from closed-chain exercises.
In a joint modeling study operating with data from twenty osteoarthritic patients, the success of patellofemoral joint reconstruction surgeries was shown to be patient specific. Two tibial tuberosity elevation procedures and two tuberosity anteromedialization procedures were simulated, revealing that, in terms of contact forces, contact stresses and medialization of the contact area, no one surgery is superior to the others for all patients.
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