Comparing the Science of High-Flex Knee Implants

The deepened trochlear groove on the NexGen CR-Flex and LPS-Flex Femoral Components helps decrease tension on the extensor mechanism.

Some knee systems, such as the Biomet Vanguard, claim to have a deepened trochlear groove*† , but do not resect bone to accommodate this design feature. Therefore, these systems must increase the thickness of the anterior flange. When the combined thickness of the anterior flange and the patellar component is too great, the patellofemoral joint may feel tight or overstuffed after surgery.3,4 According to clinical studies, this could lead to decreased range of motion as a result of increased forces and stresses on the patella.5,6 An anterior flange that is too thick may also lead to resecting too much bone on the patella in an effort to make up the difference, which can subsequently result in a patellar fracture due to insufficient bony support.

View the Maximum Anterior Flange Thickness vs. Overall A/P

References

  1. Data on file at Zimmer.
  2. Bellemans J, Banks S, Victor J, Vandenneucker H, Moemans A. Fluoroscopic analysis of the kinematics of deep flexion in total knee arthroplasty: influence of posterior condylar offset. J Bone Joint Surg (Br). 2002; 84-B(1):50-53.
  3. Hitt K, Shurman J II, Greene K, et al. Anthropometric measurements of the human knee: correlation to the sizing of current knee arthroplasty systems. J Bone Joint Surg. 2003;85:115-122.
  4. Scott WN. Pearls on avoidance and treatment of intraoperative and postoperative complications: exposure of the stiff knee. Presented at: American Association of Hip and Knee Surgeons, Knee Society Specialty Day; March 25, 2006.
  5. Nelson CL, Kim J, Lotke PA. Stiffness after total knee arthroplasty. J Bone Joint Surg. 2005;87:264-270.
  6. Mihalko W, Fishkin Z, Krakow K. Patellofemoral overstuff and its relationship to flexion after total knee arthroplasty. Clin Orthop. 2006;449:283-287.
  7. Ortiguera CJ, Berry DJ. Patellar fracture after total knee arthroplasty. J Bone Joint Surg (Br). 2002;84:532-540.
  8. Puloski SKT, McCalden RW, MacDonald SJ, Rorabeck CH, Bourne RB. Tibial post wear in posterior stabilized total knee arthroplasty: an unrecognized source of polyethylene debris. J Bone Joint Surg. 2001;83-A:390-397.
  9. Callaghan JJ, O'Rourke MR, Goetz DD, Schmalzried TP, Campbell PA, Johnston RC. Tibial post impingement in posterior-stabilized total knee arthroplasty. Clin Orthop. 2002;404:83-88.
  10. Chiu YS, Chen WM, Huang CK, Chiang CC, Chen TH. Fracture of the polyethylene tibial post in a NexGen posterior-stabilized knee prosthesis. J Arthroplasty. 2004;19(8):1045-1049.
  11. Zimmer NexGen Flex Knee Design Rationale. 97-5964-004-00. Zimmer, Inc. 2004:16.
  12. Argenson JN, Komistek RD, Mahfouz M, Walker SA, Aubaniac JM, Dennis DA. A high flexion total knee arthroplasty design replicates healthy knee motion. Clin Orthop. 2004;428:174-179.
  13. Argenson JN, Scuderi GR, Komistek RD, Scott WN, Kelly MA, Aubaniac JM. In vivo kinematic evaluation and design considerations related to high flexion in total knee arthroplasty. Journal of Biomechanics. February 2005; 38(2):277-284.
  14. Li G, Most E, Sultan PG, et al. Knee kinematics with a high-flexion posterior stabilized total knee prosthesis: an in vitro robotic experimental investigation. J Bone Joint Surg. August 2004;86:1721-1729.
  15. Huang HT, Su JY, Wang GJ. The early results of high-flex total knee arthroplasty: a minimum of 2 years of follow-up. J Arthroplasty. 2005;20:674.

* Vanguard Complete Knee System Cruciate Retaining brochure, 2004. Form No. Y-BMT-884/071504/M.

†Vanguard Complete Knee System Design Rationale, 2006. Form No. Y-BMT-906R/031506/M.