In vivo measurement of anterior tibial translation using continuous passive motion devices.

Early motion protocols following anterior cruciate reconstruction often use continuous passive motion devices. There is concern that these devices may induce undesired anterior translation of the tibia and resulting graft stretching or rupture. This study measured the amount of anterior tibial translation that occurred during one cycle in 10 different brands of continuous passive motion devices. Five patients with ACL deficient knees participated in this study. Anterior translation was recorded by using an electrogoniometer with four degrees of freedom (Knee Signature System). Anterior translation measurements were also recorded for a 20 pound Lachman test in these same five patients using the Knee Signature System. Two of the devices showed anterior translation measurements that approached the recorded 20 pound Lachman values. These two devices had a high calf bar for the primary support of the leg. The results indicate that, when using a continuous passive motion device for early postoperative management of the reconstructed ACL in a patient, use of a calf-supporting type of continuous passive motion could induce an undesired strain of the healing graft.