Palmaris longus tendon and its relationship with the median nerve: a population-based morphometric magnetic resonance imaging study.

BACKGROUND

The palmaris longus (PL) tendon is frequently used as an autograft in reconstructive surgeries, and anatomic and morphometric differences in race, gender, and side of the tendon may have an impact on the suitability of the tendon graft. This study aimed to investigate the prevalence, variations and morphology of the PL tendon and to determine its relationship with the median nerve (MN) and the antebrachial fascia on wrist magnetic resonance imaging (MRI).

METHODS

This retrospective study included 1,030 wrist MRI examinations to evaluate the presence, anatomical variations, and morphometric features of the PL tendon. The width, thickness and cross-sectional area (CSA) of the PL tendon and its relationship with the MN and antebrachial fascia were assessed on axial T1-weighted images, and the data were correlated with gender and side.

RESULTS

The results of the study indicated that the PL tendon was absent in 197 patients (19.1%), and the most common type was the classic anatomic variation (79.5%). Rare types were observed in 18 patients, two of whom exhibited reverse PL. There was no statistically significant difference between gender and side in terms of tendon presence (P=0.09). The median width was measured at 3.35 mm, the median thickness at 1.43 mm, and the median CSA at 3.53 mm2. PL tendon width, thickness and CSA were significantly higher in men (P<0.001) [width 3.7 mm (range, 1.2-5.9 mm), thickness 1.47 mm (range, 0.7-2.05 mm) and CSA 3.8 mm2 (range, 1.47-5.92 mm2)]. MN distance 2.6 mm (range, 1.1-4.1 mm) and antebrachial fascia thickness 1.12 mm (range, 0.8-1.5 mm) were significantly higher in men (P<0.001). Additionally, the right-sided hand exhibited statistically significantly greater PL tendon thickness and CSA (P=0.007, P<0.001, respectively) but lower antebrachial fascia thickness (P=0.010).

CONCLUSIONS

To the best of our knowledge, this is the first and largest MRI study reporting PL tendon morphometrics and its prevalence in the Turkish population. It is evident from the findings of this study that a physical examination alone is inadequate for evaluating the PL tendon. However, MRI has been demonstrated to be a reliable and precise modality for assessing the PL tendon, particularly in cases where tendon reconstruction surgery is indicated.