The importance of the sagittal stability in knee arthroplasty - An analysis in 76 cases with unconstrained knee resurfacing.

Issue: How does the sagittal stability influence the outcome in unconstrain ed knee arthroplasty? Method: In order to clarify this aspect, 76 arthropla sties (10 male, 66 female, 39 x gonarthrosis, 37 x rheumatoid arthritis) in 61 patients with unconstrained primary knee arthroplasty were examined wit h a mean follow-up of 4 years. The determined values were the HSS-Score, th e Knee-Society-Score, the range of motion, the flexion contracture as well as the posterior and anterior drawer with the KT 1000. The laxity was defin ed as the sum of the anterior and posterior drawer. Results: The mean value s measured were 2.9 mm for the anterior drawer, 1.9 mm for the posterior dr awer and 4.8 mm for the laxity. The total patient population reached 81.3 p oints in the Knee Score, 70.9 points in the Function-Score and 80.7 points in the HSS-Score. The medium range of motion was determined as 103,5 degree s, the medium flexion contracture as 3,5 degrees. For an anterior drawer of >6 mm and a posterior drawer of <1 mm the results deteriorated significant ly. A laxity of 8-11 mm gave the best score results. Conclusion: An anterio r drawer of <6 nun, a posterior drawer of 2-5 mm and a laxity of 8-11 mm se em robe recommendable for unconstrained knee arthroplasty.