Potential errors in axial alignment using intramedullary instrumentation for total knee arthroplasty

Accurate restoration of normal limb alignment is crucial for the long-term survivorship of total knee arthroplasty (TKA). A mathematical model was use d to evaluate the maximum error in varus and valgus alignment that could oc cur when cutting the tibia or femur during TKA using intramedullary (IM) gu ides of varying length and diameter. Minor deviations in the insertion poin t of IM instrumentation during TKA can result in malalignment of several de grees. This error can be minimized by careful attention to the entry point of the IM instrumentation or by increasing the IM rod diameter and length u sed during primary TKA.