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characteristic of the MB prosthesis might also work well.Saturday, October 9, 2010, 9:10-9:50Session A18: Complication ManagementIsolated Lateral Ligament Laxity in Primary Total Knee Arthroplasty:Cohort Study of Stemmed Versus Unstemmed ImplantsOhSoo Kwon - The Ctholic Univ of Korea - Dejeon, KoreaAtul Kamath - University of Pennsylvania - Philadelphia, USAPramod Voleti - Univ of Pennsylvania - Philadelphia, USA*Jonathan Garino - University of Pennsylvania - Philadelphia, USA*Email: jonathan.garino@uphs.upenn.eduIntroduction: While the use of stemmed implants is accepted for patients with medial ligamentlaxity in primary total knee arthroplasty (TKA), the role of stemmed implants in the setting ofisolated lateral laxity is unclear. We present a cohort study to assess the effect of unstemmed,constrained TKA for isolated lateral laxity.Methods: 1745 primary TKA performed by the senior surgeon were reviewed. 39 knees in 33patients with isolated lateral laxity managed with unstemmed components were compared tomatched stemmed controls (37 knees in 28 patients). Lateral instability was defined intraoperativelybased on >7mm gap in mid-flexion/ full extension/ figure-of-four with wellpositionedcomponents. Primary outcome measures were clinical failure for aseptic loosening(with need for revision as the endpoint) and any radiographic signs of loosening.Results: Average follow-up was 43 months for the unstemmed group (UG) and 25 months forthe stemmed group (SG). UG and SG were matched for age, gender, BMI, arthritis etiology,and co-morbidities. The incidence of isolated lateral ligament laxity in this cohort was 4%.There was no difference in clinical outcomes between cohorts. There was no evidence ofradiographic loosening; no revisions were performed for aseptic loosening in either group. OneSG patient was revised for mid-flexion instability, while one UG patient had an isolateddislocation event without need for revision. Two patients in the UG were treated withincision/debridement and poly-exchange for acute infection. One patient in the SG underwent2-stage reimplantation.Conclusion: From this data, a post/constraint can be used without stems to compensate forisolated lateral laxity. There is no significant increased risk of loosening with increasedconstraint, as lateral instability is primarily a swing-phase phenomenon. The goal is limitingvarus thrust with improved gait kinematics and patient comfort. Further biomechanical testingand long-term clinical results are needed.file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]