Recurring intraprosthetic dislocation of rotating-hinge total knee prosthesis. Effect of implant design on intrinsic stability.

During total knee replacement, hinged total knee implants are used in cases where ligament balancing cannot be achieved with less-constrained implants. The case of a patient who experienced two episodes of intraprosthetic dislocation of his rotating-hinge total knee prosthesis is described. There are very few reports of this type of dislocation with these implants. The implant's design, particularly of the hinge, plays an important role in stability. The balance between the flexion and extension spaces is very important even when using a hinged total knee implant. The role of the extensor mechanism in anteroposterior stability is reviewed, along with simple ways to augment it.