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Paper #189 Comparison of posterior cruciate retained and posterior stabilized total knee arthroplasty
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ABSTRACTS
and decreased with higher degrees of flexion. Peak stresses for both designs were below the tensile yield stress of PE (21 MPa) throughout the range of flexion with the 3600 N load used in this study. Distal contact area patterns from USL Fuji film reflected the same general trend with flexion angle as the proximal surface data. The PE thickness study revealed subsurface contact areas to increase with increasing thickness of PE up to 8 mm. FE data agreed well with the experimental results in terms of contact area footprints and stresses based on a VonMises stress distribution. The experimental and finite element modeling data correlated (r2 ⬎ 0.8 for all data). Subsurface stresses were noted to be higher in both designs but remained under the yield stress of PE. Discussion: This study is limited in that only a simple axial load was applied, a relatively simple FE model and no viscoelastic properties of the PE were taken into account in the FE model. Despite this, agreement between the experimental and FE studies was adequate. Understanding subsurface stress distributions may play an important role in the wear mechanisms in mobile bearing knees. We are currently exploring this using the proximal geometry of the tibial inserts to represent a more realistic comparison to the actual components used in surgery. Literature cited: 1. J Biomech 1999; 32: 951-8. Paper #189 Comparison Of Posterior Cruciate Retained And Posterior Stabilized Total Knee Arthroplasty. Kazuki Yamamoto, Hakodate, Japan, Yasumitsu Ohkoshi, Presenter, Hakodate Central General Hospital, Hakodate, Japan, Shinya Nagasaki, Hakodate, Japan, Tomoyuki Hashimoto, Hakodate, Japan, Shigeru Yamane, Hakodate, Japan Purpose: The objective of this study was to compare the clinical results between posterior cruciate retained prosthesis (CR type) and posterior stabilized prosthesis (PS type) of total knee arthroplasty (TKA). Materials and Methods: A prospective and randomized study was performed on 57 osteoarthritic knees who underwent primary TKA (Nex Gen). CR group consisted of 30 patients. PS group consisted of 27 patients. All TKA were performed by the same surgeon. All of the patients were performed on the same postoperative rehabilitation protocol. Background factors were not significantly different between the two groups. Patients were evaluated for the time course changes of postoperative range of motion (ROM) and clinical results (Knee score of JOA) for two years. The data generated by this study were statistically analyzed with Student’s T-test, Mannwhitney’s U-test and power analysis.
Results: The mean value of postoperative ROM (extension/flexion) was 0/110.6 deg in CR group and 0/113.4 deg in PS group (N.S) at six weeks, 2.2/114.0 deg in CR group and 0/123.7 deg in PS group (P ⫽ 0.003) at one year. The final ROM was 2.4/113.2 deg in CR group and 0/123.7 deg in PS group(P ⫽ 0.001) at two years. The rate of improvement for ROM (2 yrs/pre-op) was 1.09 in CR group and 1.29 in PS group (P ⫽ 0.003). The mean JOA score was 84.0 points in CR group and 87.0 points in PS group (N.S.).
Paper #190 In Vivo Laxity Of LCS Mobile Bearing Prostheses: A Randomised, Prospective Study Of Posterior Cruciate Ligament Retaining Versus Sacrificing Total Knee Arthroplasty. Yoshikazu Matsuda, Presenter, Ishii Orthopaedic & Rehabilitation Clinic, Gyoda, Japan, Yoshinori Ishii, Gyoda, Japan, Ryo Ishii, Gyoda, Japan Purpose: We performed the stress arthrometric study with telos arthrometer on 60 knees with total knee arthroplasty, to determine the both anteroposterior and abduction/adduction (Abd/Add) laxity and the changes of laxity at 6 month and 12 month and 24 month after surgery prospectively in vivo and to identify any association between these laxity and whether PCL retain or not using the LCS prosthesis. Materials and Methods: Thirty knees had PCL retaining (PCLR) and 30 had PCL sacrificing (PCls) prostheses. The selected patients had successful arthroplasties at least 6 month. Both AP displacement and Abd/ Add were measured using a Telos arthrometer (Fa Telos, Medizinisch-Technische GmbH, D-6103 Griesheim, Germany) applying 150 newtons. Results: All values were not significantly statistical different between PCLR and PCls (P ⬍ 0.05). In comparison of 30° and 90° flexion, PCLR group showed significantly different (P ⫽ 0.0011) but did not PCls groups (P ⫽ 0.7060). In the changes of laxity, PCLR group showed significantly statistical different only comparison of 6 month and 12 month flexion of 90° (P ⫽ 0.0034) and 6 month and 24 month adduction (P ⫽ 0.0075) postoperatively. Discussion and Conclusion: Considering that all patients in this study have good clinical results, approximate 10mm in AP displacement and around 4° laxity in coronal directions were considered as favorable laxity in LCS mobile bearing prostheses both PCLR and PCls designs. The results suggested that in obtaining the adequate central stability and control of the flexion and extension gap stability, spherically congruent surfaces allows suitable laxity and maintenance of contact stabil-
ABSTRACTS
and decreased with higher degrees of flexion. Peak stresses for both designs were below the tensile yield stress of PE (21 MPa) throughout the range of flexion with the 3600 N load used in this study. Distal contact area patterns from USL Fuji film reflected the same general trend with flexion angle as the proximal surface data. The PE thickness study revealed subsurface contact areas to increase with increasing thickness of PE up to 8 mm. FE data agreed well with the experimental results in terms of contact area footprints and stresses based on a VonMises stress distribution. The experimental and finite element modeling data correlated (r2 ⬎ 0.8 for all data). Subsurface stresses were noted to be higher in both designs but remained under the yield stress of PE. Discussion: This study is limited in that only a simple axial load was applied, a relatively simple FE model and no viscoelastic properties of the PE were taken into account in the FE model. Despite this, agreement between the experimental and FE studies was adequate. Understanding subsurface stress distributions may play an important role in the wear mechanisms in mobile bearing knees. We are currently exploring this using the proximal geometry of the tibial inserts to represent a more realistic comparison to the actual components used in surgery. Literature cited: 1. J Biomech 1999; 32: 951-8. Paper #189 Comparison Of Posterior Cruciate Retained And Posterior Stabilized Total Knee Arthroplasty. Kazuki Yamamoto, Hakodate, Japan, Yasumitsu Ohkoshi, Presenter, Hakodate Central General Hospital, Hakodate, Japan, Shinya Nagasaki, Hakodate, Japan, Tomoyuki Hashimoto, Hakodate, Japan, Shigeru Yamane, Hakodate, Japan Purpose: The objective of this study was to compare the clinical results between posterior cruciate retained prosthesis (CR type) and posterior stabilized prosthesis (PS type) of total knee arthroplasty (TKA). Materials and Methods: A prospective and randomized study was performed on 57 osteoarthritic knees who underwent primary TKA (Nex Gen). CR group consisted of 30 patients. PS group consisted of 27 patients. All TKA were performed by the same surgeon. All of the patients were performed on the same postoperative rehabilitation protocol. Background factors were not significantly different between the two groups. Patients were evaluated for the time course changes of postoperative range of motion (ROM) and clinical results (Knee score of JOA) for two years. The data generated by this study were statistically analyzed with Student’s T-test, Mannwhitney’s U-test and power analysis.
Results: The mean value of postoperative ROM (extension/flexion) was 0/110.6 deg in CR group and 0/113.4 deg in PS group (N.S) at six weeks, 2.2/114.0 deg in CR group and 0/123.7 deg in PS group (P ⫽ 0.003) at one year. The final ROM was 2.4/113.2 deg in CR group and 0/123.7 deg in PS group(P ⫽ 0.001) at two years. The rate of improvement for ROM (2 yrs/pre-op) was 1.09 in CR group and 1.29 in PS group (P ⫽ 0.003). The mean JOA score was 84.0 points in CR group and 87.0 points in PS group (N.S.).
Paper #190 In Vivo Laxity Of LCS Mobile Bearing Prostheses: A Randomised, Prospective Study Of Posterior Cruciate Ligament Retaining Versus Sacrificing Total Knee Arthroplasty. Yoshikazu Matsuda, Presenter, Ishii Orthopaedic & Rehabilitation Clinic, Gyoda, Japan, Yoshinori Ishii, Gyoda, Japan, Ryo Ishii, Gyoda, Japan Purpose: We performed the stress arthrometric study with telos arthrometer on 60 knees with total knee arthroplasty, to determine the both anteroposterior and abduction/adduction (Abd/Add) laxity and the changes of laxity at 6 month and 12 month and 24 month after surgery prospectively in vivo and to identify any association between these laxity and whether PCL retain or not using the LCS prosthesis. Materials and Methods: Thirty knees had PCL retaining (PCLR) and 30 had PCL sacrificing (PCls) prostheses. The selected patients had successful arthroplasties at least 6 month. Both AP displacement and Abd/ Add were measured using a Telos arthrometer (Fa Telos, Medizinisch-Technische GmbH, D-6103 Griesheim, Germany) applying 150 newtons. Results: All values were not significantly statistical different between PCLR and PCls (P ⬍ 0.05). In comparison of 30° and 90° flexion, PCLR group showed significantly different (P ⫽ 0.0011) but did not PCls groups (P ⫽ 0.7060). In the changes of laxity, PCLR group showed significantly statistical different only comparison of 6 month and 12 month flexion of 90° (P ⫽ 0.0034) and 6 month and 24 month adduction (P ⫽ 0.0075) postoperatively. Discussion and Conclusion: Considering that all patients in this study have good clinical results, approximate 10mm in AP displacement and around 4° laxity in coronal directions were considered as favorable laxity in LCS mobile bearing prostheses both PCLR and PCls designs. The results suggested that in obtaining the adequate central stability and control of the flexion and extension gap stability, spherically congruent surfaces allows suitable laxity and maintenance of contact stabil-