Letter to the Editor

Abstract

We would like to thank Dr Raviraj and colleagues for their comments regarding our article in The Journal of Arthroplasty (Harrington, MA, Hopkinson, WJ, Hsu, P, Manion, L. Fixed vs mobile-bearing total knee arthroplasty: does it make a difference?—a prospective randomized study). They raised a valid point.The senior surgeons in this study (MAH and WJH) have extensive experience using the Depuy/Johnson & Johnson PFC Sigma system. We are aware of the recommendations as noted in the user manuals. Our practice has been to approximate the patient's tibial slope when using a cruciate-retaining prosthesis and to use less slope (0°-5°) when using a posterior-stabilized design. We have not noted any adverse effects using these principles.Other studies in the literature have documented similar sagittal alignment ranges to ours without adverse effects as well. Kim et al [1Kim Y.-H. Kim D.-Y. Kim J.-S. Simultaneous mobile and fixed-bearing total knee replacement in the same patients—a prospective comparison of mid-term outcomes using a similar design of prosthesis.J Bone Joint Surg (Br). 2007; 89-B: 904Crossref Scopus (86) Google Scholar] in a study of bilateral total knees with fixed and mobile-bearing designs had average tibial slopes of 4° and 5° for their fixed and mobile-bearing groups, respectively. Gioe et al [2Gioe T.J. Glynn J. Sembrano J. et al.Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs—a prospective randomized trial.J Bone Joint Surg (Am). 2009; 91-A: 2104Crossref Scopus (81) Google Scholar] more recently compared fixed and mobile-bearing designs and had tibial slopes of 2.7° + 2.2° and 3.4° + 2.8° for their fixed and mobile-bearing groups, respectively. Both of these studies used the Depuy/Johnson & Johnson PFC Sigma prosthesis. Other studies using different designs have reported even higher tibial slopes, but these are also within the recommended target ranges for those particular designs. We are not aware of any studies documenting early failures or adverse kinematics due to tibial slopes in the range documented in our study. We would like to thank Dr Raviraj and colleagues for their comments regarding our article in The Journal of Arthroplasty (Harrington, MA, Hopkinson, WJ, Hsu, P, Manion, L. Fixed vs mobile-bearing total knee arthroplasty: does it make a difference?—a prospective randomized study). They raised a valid point. The senior surgeons in this study (MAH and WJH) have extensive experience using the Depuy/Johnson & Johnson PFC Sigma system. We are aware of the recommendations as noted in the user manuals. Our practice has been to approximate the patient's tibial slope when using a cruciate-retaining prosthesis and to use less slope (0°-5°) when using a posterior-stabilized design. We have not noted any adverse effects using these principles. Other studies in the literature have documented similar sagittal alignment ranges to ours without adverse effects as well. Kim et al [1Kim Y.-H. Kim D.-Y. Kim J.-S. Simultaneous mobile and fixed-bearing total knee replacement in the same patients—a prospective comparison of mid-term outcomes using a similar design of prosthesis.J Bone Joint Surg (Br). 2007; 89-B: 904Crossref Scopus (86) Google Scholar] in a study of bilateral total knees with fixed and mobile-bearing designs had average tibial slopes of 4° and 5° for their fixed and mobile-bearing groups, respectively. Gioe et al [2Gioe T.J. Glynn J. Sembrano J. et al.Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs—a prospective randomized trial.J Bone Joint Surg (Am). 2009; 91-A: 2104Crossref Scopus (81) Google Scholar] more recently compared fixed and mobile-bearing designs and had tibial slopes of 2.7° + 2.2° and 3.4° + 2.8° for their fixed and mobile-bearing groups, respectively. Both of these studies used the Depuy/Johnson & Johnson PFC Sigma prosthesis. Other studies using different designs have reported even higher tibial slopes, but these are also within the recommended target ranges for those particular designs. We are not aware of any studies documenting early failures or adverse kinematics due to tibial slopes in the range documented in our study.