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Deutscher Kongress für Orthopädie und Unfallchirurgie
73. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie
95. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie
50. Tagung des Berufsverbandes der Fachärzte für Orthopädie und Unfallchirurgie

21. - 24.10.2009, Berlin

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Vertical separation distance of the bony insertions of the posterior cruciate ligament as a function of the posterior tibial slope – an MRI study

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  • J. Mabrey - Baylor University Medical Center, Dallas, TX, United States
  • D. Covall - Resurgens Orthopaedics, Cumming, GA, United States
  • B. N. Stulberg - The Cleveland Center for Joint Reconstruction, Cleveland, OH, United States
  • A. Burstein - Sarasota, FL, United States
  • L. D. Angibaud - Exactech Inc., Gainsville, Florida, United States

Deutscher Kongress für Orthopädie und Unfallchirurgie. 73. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 95. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie, 50. Tagung des Berufsverbandes der Fachärzte für Orthopädie. Berlin, 21.-24.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocEF17-1328

doi: 10.3205/09dkou070, urn:nbn:de:0183-09dkou0702

Published: October 15, 2009

© 2009 Mabrey et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

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Problem: One key to a successful cruciate retaining (CR) total knee arthroplasty (TKA) is to create balance in extension and flexion of the knee joint without affecting the integrity of the posterior cruciate ligament (PCL). The purpose of this study was to assess the vertical distance separating the PCL femoral attachment from the PCL tibial attachment (PCLVD) according to two posterior tibial slope scenarios and compare this with the composite thickness of the prosthetic components.

Methods: The PCLVD was evaluated on 47 MRIs of non-arthritic knees using two proximal tibia cut scenarios: neutral and natural posterior tibial slope. In addition, commercial knee system templates were used to estimate femoral component size in order to correlate PCLVD with knee size.

Results and conclusions: Femoral size distribution centered on the sizes 2 and 3, the most currently used. The mean PCLVD was 20.6 mm (ranging from 18 mm to 24 mm) when neutral posterior tibial slope was simulated and 17.4 mm (ranging from 15 mm to 20 mm) when natural posterior tibial slope was simulated. Simulating natural slope over neutral slope decreased PCLVD (p=0.045) by nearly 3 mm regardless of knee size. PCLVD correlated with femoral size: R2=0.85 and 0.65 respectively for neutral and natural posterior tibial slope.

Considering the minimum composite thickness of a knee prosthesis is 17 mm (i.e., 8 mm for the femoral component and 9 mm for the tibial component), this study clearly showed a dilemma concerning the proximal tibial cut as a compromise between respecting natural tibial slope and the need for sufficient UHMWPE insert thickness. Increasing posterior tibial slope can damage the PCL tibial attachment, especially on smaller knees. Based on this study, it may be beneficial to provide tibial inserts with different posterior slopes to help reproduce natural anatomical slope as well as ensure sufficient insert thickness. A built-in slope should enable surgeons to optimize PCL balance and fine-tune knee kinematics.