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Influence of Patellar Height on Soft Tissue Balance in Total KneeArthroplasty*Seiji Kubo - Kobe University - Kobe, JapanHiroshi Sasaki - Kobe University Graduate School of Medicine - Kobe, JapanTomoyuki Matsumoto - Kobe University Graduate School of Medicine - Kobe, JapanHirotsugu Muratsu - Nippon Steel Hirohata Hospital - Himeji, JapanKazunari Ishida - Hyogo Rehabilitation Centre Center Hospital - Kobe, JapanKoji Takayama - Kobe University Graduate School of Medicine - Kobe, JapanShinya Oka - Kobe University Graduate School of Medicine - Kobe, JapanKatsumasa Tei - Kobe Kaisei Hospital - Kobe, JAPANKen Sasaki - Department of Orthopedic Surgery, Kobe University Graduate School ofMedicine, Kobe, Japan and Depar - Kobe, JapanRyosuke Kuroda - Department of Orthopaedic Surgery, Kobe University Graduate School ofMedicine - Kobe, JapanIntroduction*Email: seijikb@med.kobe-u.ac.jpAccurate soft tissue balancing has been recognized as important as alignment of bony cut intotal knee arthroplasty (TKA). In addition, using a tensor for TKA that is designed to facilitatesoft tissue balance measurements throughout the range of motion with a reduced patellofemoral(PF) joint and femoral component in place, PF joint condition (everted or reduced) hasbeen proved to have a significant effect for intra-operative soft tissue balance. On the otherhand, effect of patellar height on intra-operative soft tissue balance has not been well addressed.Therefore, in the present study, we investigated the effect of patellar height by comparing intraoperativesoft tissue balance of patella higher subjects (Insall-Salvati index>1) and patella lowersubjects (Insall-Salvati index≦1).Materials and methodsThe subjects were 30 consecutive patients (2 men, 28 women), who underwent primary PS TKA(NexGen LPS-flex PS: Zimmer, Warsaw, IN, USA) between May 2003 and December 2006.All cases were osteoarthritis with varus deformity. Preoperative Insall-Salvati index (ISI) wasmeasured and patients were divided into two groups; the patella higher group (ISI＞1: 18knees average ISI was 1.12) and the patella lower group (ISI≦1; 12 knees average ISI was0.94). Component gap and ligament balance (varus angle) were measured using offset-typetensor with 40lb distraction force after osteotomy with the PF joint reduced and femoral trial inplace at 0, 10, 45, 90, 135 degrees of knee flexion. Data of two groups were compared usingunpaired t test.ResultsComponent gap was increased from 0 to 90 degrees of knee flexion and decreased at 135degrees of knee flexion in both groups. Component gaps of the patella higher group in averagewere 10.9, 14.3, 16.6, 18.2, 16.8 mm at 0, 10, 45, 90, 135 degrees of knee flexion, respectively.Component gaps of the patella lower group in average were 9.6, 13.6, 14.6, 15.5, 14.0 mm at 0,10, 45, 90, 135 degrees of knee flexion, respectively. When comparing two groups, componentgaps of the patella higher group showed larger trend than those of the patella lower group.Especially at 90 and 135 degrees of knee flexion, the patella higher group showed significantlarger values than the patella lower group (p