Internal rotation of the tibial component in total knee arthroplasty can lead to extension deficit.
PURPOSE
Stiffness is a common problem following total knee arthroplasty (TKA). Mal-rotated components have been claimed to be the major cause of pain and limited motion after TKA. The present study investigates whether intra-operative intentional malrotation of the tibial component would change in vivo kinematics. The hypothesis is excessive internal rotation of the tibial component would result in postoperative extension deficit.


METHODS
Thirty-one patients were enrolled in this study. After completing bony cuts and proper soft tissue balancing, the femoral and tibial trials were impacted and fixed using small pins. Lateral radiographs were used to measure and compare intraoperative full knee extension during normal and after intentional internal rotation of the tibial component. The extension deficit angles were also compared between the posterior stabilised (PS) and cruciate retaining (CR) implants.


RESULTS
For normal tibial component rotation, the median (interquartile range) extension deficit was 0° (4). The mean tibial trial intentional internal rotation was 21.2° (± 4.5). The median (interquartile range) extension deficit significantly increased to 6° (4) after tibial component internal rotation (p = 0.001). The use of PS spacers resulted in a significantly greater extension deficit after intentional internal rotation 9° (5) compared to that of the CR implant 1° (4) (p = 0.001).


CONCLUSION
Internal rotation of the tibial component in total knee arthroplasty can lead to postoperative extension deficit. This could be attributed to interference with "screw home" mechanism that requires full external rotation of the tibia on the femur. Consequently, this deficit may cause pain and knee stiffness following TKA.


LEVEL OF EVIDENCE
III.
['Abdelnasser|Mohammad Kamal|MK|', 'Adi|Mohammad Muath|MM|', 'Elnaggar|Ahmed Aly|AA|', 'Tarabichi|Samih|S|']
D000368:Aged D019645:Arthroplasty, Replacement, Knee D005260:Female D006801:Humans D007719:Knee Joint D007720:Knee Prosthesis D008297:Male D008875:Middle Aged D011183:Postoperative Complications D011859:Radiography D016059:Range of Motion, Articular D012399:Rotation
Internal rotation Tibial component Total knee arthroplasty Extension deficit