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Lookup NU author(s): Professor David Deehan
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Purpose To study the effect of increasing patellar thickness (overstuffing) on patellofemoral kinematics in total knee arthroplasty and whether subsequent lateral retinacular release would restore the change in kinematics. Methods The quadriceps of eight fresh-frozen knees were loaded on a custom-made jig. Kinematic data were recorded using an optical tracking device for the native knee, following total knee arthroplasty (TKA), then with patellar thicknesses from -2 to ? 4 mm, during knee extension motion. Staged lateral retinacular releases were performed to examine the restoration of normal patellar kinematics. Results Compared to the native knee, TKA led to significant changes in patellofemoral kinematics, with significant increases in lateral shift, tilt and rotation. When patellar composite thickness was increased, the patella tilted further laterally. Lateral release partly corrected this lateral tilt but caused abnormal tibial external rotation. With complete release of the lateral retinaculum and capsule, the patella with an increased thickness of 4 mm remained more laterally tilted compared to the TKA with normal patellar thickness between 45 degrees and 55 degrees knee flexion and from 75 degrees onwards. This was on average by 2.4 degrees+/-2.9 degrees(p < 0.05) and 2.degrees 9+/-3.0 degrees(p < 0.01), respectively. Before the release, for those flexion ranges, the patella was tilted laterally by 4.7 degrees+/-3.2 degrees and 5.4 degrees+/-2.7 degrees more than in the TKA with matched patellar thickness. Conclusion Patellar thickness affects patellofemoral kinematics after TKA. Although lateral tilt was partly corrected by lateral retinacular release, this affected the tibiofemoral kinematics. Level of evidence IV.
Author(s): Merican AM, Ghosh KM, Baena FRY, Deehan DJ, Amis AA
Publication type: Article
Publication status: Published
Journal: Knee Surgery, Sports Traumatology, Arthroscopy
Print publication date: 28/12/2012
ISSN (print): 0942-2056
ISSN (electronic): 1433-7347
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