P Wong

Publications (2)1.37 Total impact

• Article: Can CT-based patient-matched instrumentation achieve consistent rotational alignment in knee arthroplasty?

  C O Tibesku, B Innocenti, P Wong, A Salehi, L Labey
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  ABSTRACT: Long-term success of contemporary total knee replacements relies to a large extent on proper implant alignment. This study was undertaken to test whether specimen-matched cutting blocks based on computed axial tomography (CT) scans could provide accurate rotational alignment of the femoral component. CT scans of five fresh frozen full leg cadaver specimens, equipped with infrared reflective markers, were used to produce a specimen-matched femoral cutting block. Using those blocks, the bone cuts were made to implant a bi-compartmental femoral component. Rotational alignment of the components in the horizontal plane was determined using an optical measurement system and compared with all relevant rotational reference axes identified on the CT scans. Average rotational alignment for the bi-compartmental component in the horizontal plane was 1.9° (range 0°-6.3°; standard deviation 2.6°). One specimen that showed the highest deviation from the planned alignment also featured a completely degraded medial articular surface. The CT-based specimen-matched cutting blocks achieved good rotational alignment accuracy except for one specimen with badly damaged cartilage. In such cases, imaging techniques that visualize the cartilage layer might be more suitable to design cutting blocks, as they will provide a better fit and increased surface support.
  Archives of Orthopaedic and Trauma Surgery 02/2012; 132(2):171-7. · 1.37 Impact Factor
• Chapter: An in-vitro study of human knee kinematics: natural vs. replaced joint

  Bernardo Innocenti, L. Labey, J. Victor, P. Wong, J. Bellemans
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  ABSTRACT: Cadaver specimens mounted on a knee simulator combined with motion tracking devices have been used for the kinematics study of the human knee. The results of these studies have shown that the classical four bar linkage model of the knee is not adequate. This obviously has repercussions for the design of knee implants. They should at least permit normal kinematic behavior to prevent abnormal loads on the soft tissues and on other joints of the leg. Studies where implant kinematics can be compared to kinematics of the natural knee of the same specimen are very rare, though. In this project, the kinematics of six fresh frozen human cadaver knees in the natural state and after replacement of the knee joint with a bi-cruciate stabilizing implant were evaluated using a knee simulator and stereophotogrammetry. Before testing, frames with reflective markers were fixed to the femur and tibia. Then, a CT scan was made and the images were processed to identify anatomical landmarks and their position with respect to the reflective markers. Thus, an anatomically relevant coordinate system could be defined for each bone. During a squat, the motion of the markers was continuously measured. Several load conditions were considered for each specimen. The data obtained enabled us to calculate the motion of the femur and tibia with respect to each other and present that in clinically relevant terms. After testing, a second CT scan was made to check the position of the implant with respect to the original articular surfaces and also for a control of the position of the marker frames. The results show that kinematics of the natural knee joint are more variable than expected. The knee replacement, on the other hand, produces a consistent kinematics pattern in all the specimens.
  12/2008: pages 1867-1870;