Unexplained pain following total knee arthroplasty: Is rotational malalignment the problem?

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Component malrotation in total knee arthroplasty (TKA) is a suspected cause of postoperative pain.
• Assessing component rotation is crucial for understanding TKA outcomes.

Purpose of the Study:

• To compare component rotation in TKAs with unexplained pain versus well-functioning TKAs.
• To determine if TKA component rotation correlates with postoperative pain.

Main Methods:

• A case-control study comparing 71 painful TKAs with 41 well-functioning TKAs.
• Postoperative computed tomography (CT) scans were used to measure tibial and femoral component rotation.
• Rotation angles were analyzed to identify differences between the groups.

Main Results:

• No significant differences in femoral component rotation (0.6° vs 1.0° ER) or tibial component rotation (11.2° vs 9.5° IR) were found between painful and control TKAs.
• Combined mal-rotation also showed no significant difference between the groups (10.5° vs 8.5° IR).
• A higher percentage of painful TKAs (59%) exhibited tibial component internal rotation >9° compared to controls (49%).

Conclusions:

• This study found no association between tibial, femoral, or combined component mal-rotation and unexplained pain after TKA.
• Tibial component internal rotation, particularly relative to the tibial tubercle, is common even in well-functioning TKAs.
• The clinical significance of minor tibial internal rotation in painful TKAs warrants cautious interpretation.