Intraobserver and intermethod reliability for using two different computer programs in preoperative lower limb alignment analysis

Background and objective: Professional graphics editing programs can be used in the preoperative planning of lower limb deformity correction surgery. This study was conducted to test the reliability of using such programs versus FDA approved medical planning software. Materials and methods: Thirty long standing lower limb radiographs had been selected. Two different computer programs (Adobe Photoshop) versus planning software (MediCAD) were used in the analysis of lower limb alignment. The following angles were measured twice:Lateral Proximal Femoral Angle (LPFA), mechanical Lateral Distal Femoral Angle (mLDFA), Joint Line Convergence Angle (JLCA), Medial Proximal Tibial Angle (MPTA), Lateral Distal Tibial Angle (LDTA) and Mechanical Axis Deviation (MAD). Intraclass correlation coefficient (ICC) was used to assess the intraobserver and intermethod reliability and the mean differences between measurements were calculated. Results: Intraobserver and intermethod reliability scores were very good (>0.95) for all measurements. The highest reliability was for MAD (0.999). LPFA and LDTA had the highest variability and a range of intraobserver absolute difference up to 4.8° and 3.7° respectively. Conclusion: Computer assisted lower limb alignment analysis is reliable whether using graphics editing program or specialized planning software. However slight higher variability for angles away from the knee joint can be expected