Dislocation of a posterior stabilized total knee prosthesis. A report of two cases.

Posterior stabilized knee prostheses have been recommended for knees with posterior cruciate deficiency, as well as for knees with prior patellectomy. Two cases are presented in which a complete dislocation of a Kinematic II Stabilizer prosthesis occurred after primary knee arthroplasty. The mechanism of dislocation was a varus or valgus stress while the knee was flexed. This previously unreported complication of dislocation after primary knee arthroplasty with a posterior stabilized knee prosthesis was, we believe, due, in part, to the design of this prosthesis, which provides little mediolateral stability in flexion, in combination with a mild degree of laxity of the collateral ligaments. This complication could be prevented by use of a prosthesis with greater inherent mediolateral stability.