Failure of Uni-Compartmental Knee Replacements

• Concerns with UKA are early failure of the femoral or tibial components.
• The main cause of early failure is malpositioning of components with overcorrection or undercorrection of limb alignment.

– Mariani EM, Bourne MH, Jackson RT, Jackson ST, Jones P. Early failure of unicompartmental knee arthroplasty. J Arthroplasty. 2007 Sep;22(6 Suppl 2):81–4.

– Furnes O, Espehaug B, Lie SA, Vollset SE, Engesaeter LB, Havelin LI. Failure mechanisms after unicompartmental and tricompartmental primary knee replacement with cement. J Bone Joint Surg Am. 2007 Mar;89(3):519–25.

Failure of UKA

Tibial Component Malalignment

• Coronal malalignment of the tibial component beyond 3° predisposed to failure

– Swienckowski J, Page BJ. Medial unicompartmental arthroplasty of the knee. Use of the L-cut and comparison with the tibial inset method. Clin Orthop Relat Res. 1989 Feb;(239):161–7.

Femur Component Malalignment

• Malalignment of the femoral component has been found to cause femoral fracture, patellar impingement and tibial component loosening.

– Sandborn PM, Cook SD, Kester MA, Haddad RJ Jr. Fatigue failure of the femoral component of a unicompartmental knee. Clin Orthop. 1987 Sep;(222):249–54.

– Assor M, Aubaniac JM. Influence of rotatory malposition of femoral implant in failure of unicompartmental medial knee prosthesis [in French]. Rev Chir Orthop Reparatrice Appar Mot. 2006 Sep;92(5):473–84.

Excessive Posterior Slope

• Excessive posterior slope (>7°) of the tibial component has been linked to tibial component loosening, anterior cruciate ligament (ACL) rupture and abnormal stress forces on the periprosthetic bone.

– Hernigou P, Deschamps G. Posterior slope of the tibial implant and the outcome of unicompartmental knee arthroplasty. J Bone Joint Surg Am. 2004 Mar;86(3):506–11.

– Sawatari T, Tsumura H, Iesaka K, Furushiro Y, Torisu T. Three-dimensional finite element analysis of unicompartmental knee arthroplasty—the influence of tibial component inclination. J Orthop Res. 2005 May;23(3):549–54.