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Keywords: total knee arthroplasty, soft tissue balance, kinematics, patello-femoral joint,posterior stabilizedIntroductionA primary goal of total knee arthroplasty (TKA) is to obtain stable and well-alignedtibiofemoral and patello-femoral (PF) joints, aiming to patients’ satisfaction in long termclinical outcomes. To this end successfully, the accurate alignment of knee implants andbalancing of soft tissues are the two important criteria [1-3]. Recently, the use of computerassistednavigation systems has been reported to improve the achievement of bone cuts andimplantation accurately [4-9]. Of such systems that are currently available, we have alreadyreported on a CT-free navigation system (Vector Vision R , Depuy–Brain LAB, Heimstetten,Germany) significant improvements in the accuracy of implantations in relation to themechanical axis and a early clinical outcome equivalent to that of a manual group [10, 11].On the other hand, a common difficulty with manually-performed TKAs is obtaining accurateintra-operative soft tissue balancing, an aspect of this procedure that surgeons traditionallyaddress through their “subjective feel” and experience with an everted patella. Knee instabilityafter primary TKA due to inadequate correction of the soft tissue imbalances is considered animportant factor for early TKA failure [12, 13]. We have developed a new tensor for TKAs thatenables us to assess for soft tissue balancing throughout the range of motion about the kneewith a reduced PF joint. This tensor permits us to intra-operatively reproduce the post-operativealignment of the PF and tibio-femoral joints [14]. Using this new tensor for TKAs, we havedescribed the design of this tensor, our initial intra-operative soft tissue balance measurement,its clinical relevance [15-18].Pre-operative deformity of the knee is different from patients to patients. In the varus kneeespecially, many surgeons recognize that progressive shortening or contraction of soft tissuestructures on the medial side may occur, whereas the lateral structures may become stretched[19-22]. Whereas severe intra-operative varus deformity needs substantial soft tissue release onthe medial side during TKA, the ideal amount of medial release is still controversial; there existtwo strategies for soft tissue balancing in the varus knees. Some believe to be ideal to createequal medial and lateral gaps even severe deformed knees [2, 23, 24], and others accept somedegrees of lateral laxity especially at flexion, based on the evidence showing post-operativediminishment of lateral laxity after TKA with time, as long as proper alignment is maintained[25, 26].In the present study, accordingly, we report on our experience with this device for the intraoperativesoft tissue balance measurements of various grade of pre-operative varus deformityduring posterior-stabilized (PS) TKAs, performed with a reduced patella. The purpose of thepresent study is to analyze the difference of soft tissue balance due to the difference of preoperativevarus deformity.Materials and MethodsFrom a group of 60 consecutive osteoarthritic females performed the same type of implantreceived, we retrospectively divided into three groups depending on the amount of pre-operativealignment; 20 patients with less than 10 degrees of pre-operative varus alignment (the varusalignment < 10º group), 20 patients with more than 10 degrees and less than 20 degrees of preoperativevarus alignment (the 10º < varus alignment < 20º group), and 20 patients with morethan 20 degrees of pre-operative varus alignmentã��(the varus alignment > 20º group). Themechanical axis of the knee was determined on a pre-operative long standing weight-bearinganteroposterior radiograph. All surgeries were performed using PS type implant (NexGen LPSFlex, Zimmer, Inc,. Warsaw, IN) by the same senior author between September 2003 andAugust 2005. The varus alignment < 10º group had a mean age of 73.7 ± 1.3 years, the 10º 20ºgroup a mean age of 73.8 ± 1.7 years. After excluding patients with valgus deformity andsevere bony defects predicting the possibility of the use of augmentation block or bone graft,file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]