Radiographic and navigation measurements of TKA limb alignment do not correlate.

UNLABELLED: Precise pre- and postoperative anatomic measurements are necessary to plan, perform, and evaluate total knee arthroplasty (TKA). We evaluated the relationship between radiographic and navigation alignment measurements, identified sources of error in radiographic and navigated alignment assessment, and determined the differences between desired and clinically accepted alignment. Fifty-eight computer-assisted TKAs were performed and limb alignment measurements were recorded both pre- and postoperatively with standard radiographs and with an intraoperative navigation system. Intraoperative navigation produced consistent navigation-generated alignment results that were within 1 degrees of the desired alignment. The difference between preoperative radiographic and navigation measurements varied by as much as 12 degrees and the difference between postoperative radiographic and navigation measurements varied by as much as 8 degrees. This discrepancy depended on the degree of limb deformity. Postoperative radiographic measurements have inherent limitations. Navigation can generate precise, accurate, and reproducible alignment measurements. This technology can function as an effective tool for assessing pre- and postoperative limb alignment and relating intraoperative alignment measurements to clinical and functional outcomes. LEVEL OF EVIDENCE: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.