Objective
To investigate the outcome of a new designed extramedullary femoral alignment system and to compare with conventional intramedullary system in clinical results.
Methods
Twenty consecutive patients (3 males and 17 females with an average age of 70.1 (range, 52-82 years old) with osteoarthritis (OA) or rheumatoid arthritis (RA) who were treated with the extramedullary method between January 2015 to August 2015 and 20 consecutive patients (5 males and 15 females with an average age of 65.9 (range, 52-87 years old) with OA or RA treated with conventional intramedullary method between April 2015 to September 2015 were studied. In extramedullary group, CT scan was used to evaluate the relation between the hip (femoral head) center and anterior superior iliac spine preoperatively. During the total knee arthroplasty, the hip joint center was defined according to the anterior superior iliac spine (ASIS). Knee joint center was defined as the center of the line connecting medial and lateral epicondyle. The terminal femoral bone cut plane was defined as the line between femoral and knee center. In intramedullary group, the traditional intramedullary method was adopted. The coronal and sagittal alignment, blood loss and drainage at one week postoperatively and the range of motion at one week, 6 weeks and 3 months were evaluated.
Results
There was no significant difference in age, hipknee-ankle (HKA) angle, the Hospital for Special Surgery (HSS) Knee Score, BMI, operation time within the two groups. Blood loss and drainage in extramedullary group (121±64 ml and 181±149 ml) was significantly less than that in intramedullary group (177±47 ml and 292±156 ml). There was no significant difference in coronal alignment of the femoral prosthesis within the two groups (89.8°±2.1° v.s. 89.8°±2.2°, P>0.05). However, the two groups had significant difference in sagittal alignment (-0.8°±2.2° v.s. 2.5°±2.1°, P 0.05).
Conclusion
The present designed extramedullary system is practical in total knee arthroplasty and has more accuracy in sagittal plane. The patients treated with extramedullary system have less blood loss and drainage and have similar range of motion in early stage after operation when compared with the intramedullary method.
Key words:
Arthroplasty, replacement, knee; Fiducial markers; Femur