Sensitivity and specificity assessment of four clinical tests for palmaris longus muscle by ultrasound

This study aimed to evaluate the accuracy of four clinical tests confirmed by ultrasonography (USG) and to evaluate the role of age, sex, handedness, subcutaneous tissue thickness (STT), tendon thickness (TT), and STT/TT in determining the absence of the palmaris longus muscle.

In this descriptive study, 282 wrists of 141 healthy individuals (71 females, 70 males; mean age: 29±9.6 years; range, 21 to 55 years) were included between September 2021 and November 2022. The palmaris longus muscle tendon was identified by Schaeffer's test, Mishra's test I, Thompson's test, and Pushpakumar's test and then evaluated with USG. Before the tests, age, sex, and dominant hand information of the individuals were obtained. The STT and TT were measured with USG.

Sensitivity values by side were as follows (right/left respectively): Schaeffer's 92%/73%, Mishra's I 91%/93%, Thompson's 84%/87%, and Pushpakumar's 86%/91%. Specificity values by side were as follows (right/left respectively): Schaeffer's 87%/95%, Mishra's I 78%/82%, Thompson's 78%/79%, and Pushpakumar's 84%/82%. Sensitivity values by sex were as follows (female/male respectively): Schaeffer's 81%/96%, Mishra's I 92%/94%, Thompson's 85%/90%, and Pushpakumar's 91%/92%. Specificity values by sex were as follows (female/male respectively): Schaeffer's 68%/90%, Mishra's I 72%/90%, Thompson's 72%/85%, and Pushpakumar's 78%/85%. The intraclass correlation coefficient between clinical tests and USG was 0.94 for the left side and 0.95 for the right side.

Mishra's test I and Pushpakumar's test can be used in females, while Schaeffer's test and Mishra's test I can be used in males as a mutually supportive clinical test. Furthermore, while there may be false negative and false positive test results due to muscle variations, it should be noted that STT/TT is also effective, particularly on the right side.