Reliability of measuring long-standing lower extremity radiographs

The mechanical axis of the lower extremity was measured using preoperative long standing radiographs in 56 patients undergoing total knee arthroplasty with the Stryker Navigation System (Stryker, Kalamazoo, Mich). Each radiograph was measured by four physicians, three times, in random order, and at delayed intervals. Measurements from each physician produced intraclass correlation coefficients of 0.9872, 0.9973, 0.9958, and 0.9839. An intraclass correlation coefficient of 0.9844 was noted between each of the raters. Pre- and postoperative axial alignments were determined with Stryker Navigation. Preoperatively, each rater overestimated deformity approximately 1° (P>.05); however, postoperatively each rater underestimated the degree of deformity by approximately 1° (P>.05). Measuring long-standing lower extremity radiographs provides significant inter- and intrarater reliability in determining lower extremity alignment.