To characterize the quantitative changes of patella cartilage over time after total knee arthroplasty (TKA) by delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) and T2 mapping at 3.0 T.
Twenty-six knees of 26 patients (23 women and three men, mean age, 75 years) with primary osteoarthritis and osteonecrosis of the knee underwent TKA with a zirconia ceramic implant in this prospective study. Twelve patients without patella resurfacing (NR group) and 14 patients with patella resurfacing (R group) had TKA with cemented fixation. The implant position was examined by radiograph, computed tomography (CT) and magnetic resonance imaging (MRI). The clinical scores were checked pre-operatively, 1 year post-operatively and at the final follow-up. Patella cartilage and its thickness were evaluated pre-operatively and 1 year after TKA by dGEMRIC and T2 mapping in the NR group only. Patella cartilage was divided into eight regions of interest: the deep and superficial layers of the outer lateral and medial half, and the inner lateral and medial half from the central ridge.
The implant position was appropriate in all cases and clinical scores were not significantly different between the two groups. The post-operative dGEMRIC value of the outer medial half superficial zone in the NR group was significantly decreased compared with the pre-operation value (P<0.05), whereas T2 mapping was not significantly changed in all zones. The cartilage thickness of the outer zone was significantly thinner post-operatively (P<0.05).
These findings indicate that osteoarthritic changes in the outer zone of patella cartilage occurred 1 year after TKA.