To investigate the application of muscle ultrasound in the assessment of muscle performance in patients with severe burns.

Thirty-two burn patients, including 28 males and 4 females, aged 29-64(44±8)years, who met the inclusion criteria in the burn unit of Tongren Hospital of Wuhan University and the Third Hospital of Wuhan from March 2020 to April 2022 were retrospectively analyzed. The burn area was 40%-87%(57.34%±13.09%) TBSA, Ⅲ° burns were 4%-66%(27.50%±15.70%) TBSA, and the causes of injury were chemical burns in 11 cases (34.4%), flame burns in 15 cases (46.9%), and hot liquid burns in 6 cases (18.7%). The minimum pressure muscle thickness measurement of quadriceps, maximum pressure muscle thickness measurement of quadriceps, and cross-sectional area measurement of rectus femoris were performed at admission, 6 weeks post-injury, and 12 weeks post-injury using a B-type ultrasound diagnostic instrument. A portable muscle strength tester was used to measure the patient's maximum muscle strength. Reliability analysis of the measurement of each ultrasound parameter of the quadriceps muscle was performed. Pearson correlation analysis and Spearman correlation analysis were used to correlate the quadriceps ultrasound parameters with muscle strength.

The ICC values of the ultrasound parameters of the quadriceps muscle measured by muscle ultrasound at different times ranged from 0.914 to 0.997, all of which were greater than 0.9 with high reliability. There was a weak positive correlation between quadriceps minimum pressure muscle thickness and muscle strength at admission (r=0.457, P=0.009), and no correlation between quadriceps maximum pressure muscle thickness and rectus femoris cross-sectional area and muscle strength (r=0.318, P=0.076; r=0.310, P=0.084). At 6 weeks post-injury, quadriceps minimum pressure muscle thickness was moderate positively correlated with muscle strength (r=0.565, P=0.001), quadriceps maximum pressure muscle thickness was weak positively correlated with muscle strength (r=0.470, P=0.007), rectus femoris cross-sectional area was high positively correlated with muscle strength (r=0.799, P<0.001). At 12 weeks post-injury, quadriceps minimum pressure muscle thickness showed a moderate positive correlation with muscle strength (r=0.671, P<0.001), quadriceps maximum pressure muscle thickness showed a weak positive correlation with muscle strength (r=0.486, P=0.016), rectus femoris cross-sectional area showed a high positive correlation with muscle strength (r=0.781, P<0.001).

Ultrasound-related parameters of quadriceps muscle in patients with severe burns have good correlation with muscle strength and can be used to evaluate muscle performance. For patients who can't cooperate subjectively and whose muscle strength measurements can't objectively reflect their muscle performance, muscle ultrasound can be used as a supplement tool to assess muscle performance, but the combination of them is more accurate.