Radiographic Evaluation of Postoperative Alignment in Total Knee Arthroplasty

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomechanics

Background:

• Accurate measurement of the lower limb mechanical axis is critical for successful total knee arthroplasty (TKA) outcomes.
• Postoperative assessment traditionally relies on radiographic imaging to evaluate limb alignment.

Purpose of the Study:

• To compare the accuracy of long (panoramic) lower limb radiographs versus short knee radiographs in measuring the mechanical axis after TKA.
• To determine which radiographic technique offers superior inter- and intra-observer reliability for assessing TKA alignment.

Main Methods:

• Retrospective analysis of postoperative radiographs from 70 patients who underwent TKA.
• Three orthopedic surgeons independently measured the mechanical axis and calculated femorotibial angles (FTAs) from both long and short radiographic views.
• Intraclass correlation coefficient (ICC) was used to assess inter- and intra-observer agreement.

Main Results:

• Long leg radiographs demonstrated high intra- and inter-observer agreement (ICC ≥ 0.89), indicating very strong reliability.
• Short knee radiographs showed only moderate agreement (maximum ICC of 0.75), suggesting lower reliability for mechanical axis measurement.
• A significant difference in accuracy was found between the two radiographic methods.

Conclusions:

• Long leg panoramic radiographs are significantly more accurate for measuring the lower limb mechanical axis post-TKA than short knee radiographs.
• The study recommends using long leg radiography in the postoperative period following TKA to ensure precise assessment of limb alignment.