RESUMO
BACKGROUND: The ROM technique has been widely used to determine the rotational alignment of tibial prosthesis in total knee arthroplasty, but the accuracy of this technique remains controversial. However, there is no report on the influencing factors of ROM technique. OBJECTIVE: To explore the influencing factors of ROM technique in determining the rotational alignment of tibial prosthesis in total knee arthroplasty. METHODS: Totally 61 patients underwent unilateral knee arthroplasty, including 18 males and 43 females, aged between 55 and 78 years. All patients were diagnosed as knee osteoarthritis before operation. All operations were performed with the posterior cruciate-stabilizing total knee prostheses. All patients signed the informed consent. This study was approved by the Hospital Ethics Committee. The rotational orientation of the tibial prosthesis was determined by the ROM technique with closed and unclosed medial retinaculum. A line from the center of the posterior cruciate ligament to the medial border of the patellar tendon was used as the anteroposterior axis of tibia (Akagi line). The angles between the anteroposterior axis of tibia and lines determined by the ROM technique were measured to identify the classification of patellar track so as to decide whether the classification of patellar track, closing and unclosing medial retinaculum are the influencing factors of ROM technology. RESULTS AND CONCLUSION: (1) The angles between the Akagi line and lines determined by the ROM technique respectively were (0.5±2.5)°, (-0.9±2.6)°, and (-3.9±3.4)° for the unclosed medial retinaculum and (0.6±2.3)°, (-0.3±2.2)°, and (-1.5±2.9)° for the closed medial retinaculum. (2) For type III patellar track, the angle between line determined by the ROM and Akagi line was significantly internal rotation compared with type I and type II patellar track (P 0.05). For type III patellar track, closing the medial retinaculum could significantly reduce the difference between Akagi line and the line determined by ROM technology (P < 0.05). (4) These results indicate that for type I and type II patellar track, ROM technique can accurately locate the rotational alignment of tibial prosthesis in total knee arthroplasty, and closing or unclosing the medial retinaculum will not affect the accuracy of the results. As to type III patellar track, whether or not the medial retinaculum is closed may lead to failure in determining the rotation alignment of the tibial prosthesis.