That Tendon is the Median Nerve: Perils of a Palmaris Longus Deficient Wrist

Clinical tests for assessing the presence and quality of the palmaris longus tendon: diagnostic accuracy of examination compared with ultrasound

Various clinical tests are used to evaluate the palmaris longus tendon, but their accuracy is unknown. We assessed the accuracy of clinical tests (Schaeffer's, Thompson's, Mishra-I, Mishra-II) against ultrasound as the reference standard. We hypothesized that Schaeffer's was most accurate and that examination can reliably assess the palmaris longus tendon's length. Ninety-six wrists were examined clinically and evaluated with ultrasound by radiologists who were blinded to examination results. We calculated diagnostic accuracy and agreement between length measurements. Sensitivity values were as follows: Schaeffer's 94%, Mishra-I 100%, Mishra-II 100%, Thompson's 72%. Specificity values were as follows: Schaeffer's 94%, Mishra-I 83%, Mishra-II 89%, Thompson's 91%. Intraclass correlation coefficient between palmaris longus tendon length measurement on examination and ultrasound was 0.54. Schaeffer's test accurately detected this tendon with >90% sensitivity and specificity, but clinical examination less reliably measured palmaris longus tendon length. Ultrasound may be a useful adjunct to assess potential graft length preoperatively. Level of evidence: I.

Detection of the palmaris longus tendon: physical examination versus sonography

This study investigated the sensitivity, specificity, and accuracy of physical examination compared with high resolution sonography for the detection of the palmaris longus tendon in 136 wrists. The incidence of tendon absence was 10% by sonography and 14% by physical examination. The sensitivity of the physical examination was 94% and the specificity 86% compared with sonography as the reference standard. Accurate identification of the palmaris longus tendon through physical examination was not influenced by body mass index or wrist circumference. Upon review of the sonography images, none of the palmaris longus tendons missed on physical examination were considered to be adequate for grafting based on expert opinion. While physical exam was 93% accurate for detection of the palmaris longus tendon compared with ultrasound, our study suggests that it is sufficient for detection of those tendons that can be used as donors clinically.

Ultrasound determination of presence, length and diameter of the palmaris longus tendon

Inadvertent median nerve harvest is a devastating complication of palmaris longus harvest. Accurate assessment of palmaris longus presence and dimensions preoperatively would minimize this risk and assure safe harvest. We hypothesized that ultrasound would accurately predict palmaris longus presence, length and diameter. Seventeen cadaveric forearms were studied using a LOGIQ-E9 ultrasound. Two radiologists assessed palmaris longus presence and dimensions. Each wrist was explored, and the tendon was harvested and measured. Inter-rater reliability and agreement between measurements was assessed. The palmaris longus was present in 13 of 17 forearms. Both radiologists correctly identified the tendon and its absence (sensitivity and specificity, 100%). Ultrasound assessment of palmaris longus dimensions significantly correlated with surgical measurements. Intraclass correlation coefficient between radiologists was 0.97. We conclude that ultrasound can determine palmaris longus presence and dimensions with excellent accuracy and inter-observer reliability. Ultrasound is useful for preoperative evaluation of the palmaris longus and its use will increase patient safety.