Relationship Between Ultrasonographic Assessment for Quadriceps Muscle and Physical Function After Total Knee Arthroplasty in Patients with Knee Osteoarthritis

To determine the relationship between preoperative ultrasonographic assessment of quadriceps muscle and postoperative physical function in patients with knee osteoarthritis undergoing TKA. 

Twenty-nine patients (25 female, 75.4±6.8 years old) undergoing TKA were included in the study. Using ultrasonographic assessment MT and EI were obtained from the rectus femoris(RF), vastus intermedius(VI), vastus lateralis(VL), and vastus medialis(VM)on the operative side during the preoperative period. Moreover, RF and VI were photographed in the distal one-third of the area between the superior anterior iliac spine and the superior border of the patella, the VL at the midpoint between the greater trochanter and lateral femoral epicondyle, and the VM 5 cm medially from the 20% distal point between the superior anterior iliac spine and the superior border of the patella. Furthermore, MT and EI were calculated from muscle images obtained using image processing software (Image J). Isometric knee extension muscle strength and the Japanese version of the Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC) were evaluated 3 months postoperatively. Single regression analysis was used to examine the relationship between MT and EI of each muscle preoperatively and physical function for each endpoint 3 months postoperatively.

Muscle thickness of the VM exhibited significant positive correlations with isometric knee extensor strength (r=0.40) and WOMAC scores (r=0.38). Conversely, no significant correlation was observed between the MT of each muscle and any endpoint. No significant correlation was identified between the EI of each muscle and isometric knee extensor strength or WOMAC scores.

MT as an index of VM muscle mass was associated with several measures of physical function 3 months postoperatively. These results suggested that ultrasonographic assessment of skeletal muscles, especially MT, may be useful in predicting postoperative physical function in patients undergoing TKA. 

Ultrasonographic assessment of lower limb muscles in patients undergoing TKA may be a predictor of postoperative physical function, which can be useful for planning and optimizing postoperative exercise therapy.