Purpose: On imaging studies, bony ridges can be seen at the palmar aspect of the phalanges of the fingers. Our purpose was to address the following: (1) which structures insert on to the ridges and what is the histological appearance? (2) Is there a difference between the different fingers? (3) Is there a correlation between the ridges and age?
Materials and methods: Two observers retrospectively evaluated 270 radiographs (135 men; 135 women; mean age 44 years), and 33 CT scans (22 men; 11 women; mean age 46 years). Three cadaveric hands were also studied. The ridges were graded using a 4-point scale. A Chi-square test was used to compare the different fingers (p < 0.05) and to study the prominence of the ridges in relation to age (p < 0.05).
Results: On histology with routine stains the A2 pulley was inserted on the ridges of the proximal phalanx, and the flexor superficialis and A4 pulley on the ridges of the middle phalanx. On histology, the insertion showed a transition zone consisting of fibrocartilage. The prominence of the ridges was significantly different between fingers with III and IV categorized higher than II and III. There was a significant correlation with age for all fingers except for the middle phalanx of II and III.
Conclusion: The bony palmar ridges have characteristics of enthesophytes. They correspond to the insertion site of the A2 pulley, and the flexor superficialis tendon and A4 pulley, at the proximal and middle phalanx, respectively. The ridges become more prominent with age, and their prominence is different between the fingers with III and IV categorized higher than II and V.