Qualitative and Quantitative Anatomy of the Deep Radioulnar Ligaments’ Insertion on Ulna: Cadaveric, Histologic, and MRI Study

Purpose To qualitatively and quantitatively analyze the anatomic features of the insertion of deep radioulnar ligaments (RULs) and provide an anatomic basis for further studies. Methods The anatomic features of deep RUL insertion were observed macroscopically in 26 cadaveric wrists, after which the size of the deep RUL footprint and distance from the center of the footprint to the ulnar-sided margin of articular cartilage of the ulnar head were each measured. Five specimens were analyzed histologically to examine the attachment of the RUL on the ulna. In addition, we evaluated 21 asymptomatic wrists from healthy volunteers using 3.0 T magnetic resonance imaging. Results The insertion of the deep RUL was located mainly on the radial aspect of the ulnar fovea from the foveal center to the articular cartilage. The footprint of the deep RUL appeared in 3 different shapes. The maximal width, length, and area of the footprint of the deep RUL were 3.7 (95% confidence interval [CI], 3.3–4.0) mm, 8.4 (95% CI, 7.9–8.9) mm, and 26.3 (95% CI, 23.4–29.1) mm2, respectively. Histologic analyses showed the attachment of the deep RUL on the radial wall of the fovea exhibited a direct insertion with typical 4-layer structures. The deep RUL fibers formed an acute angle with the distal component of the triangular fibrocartilage complex. Conclusions The deep RUL was inserted on the radial side of the ulnar fovea and not the foveal center; it had direct insertion on the radial wall continuous with articular cartilage, and the fibers in the direct insertion formed an acute angle with the distal component of the triangular fibrocartilage complex. Clinical relevance Understanding the quantitative anatomy of the deep RUL insertion may help guide surgeons to perform an anatomic foveal repair of the triangular fibrocartilage complex in its native footprint. To qualitatively and quantitatively analyze the anatomic features of the insertion of deep radioulnar ligaments (RULs) and provide an anatomic basis for further studies. The anatomic features of deep RUL insertion were observed macroscopically in 26 cadaveric wrists, after which the size of the deep RUL footprint and distance from the center of the footprint to the ulnar-sided margin of articular cartilage of the ulnar head were each measured. Five specimens were analyzed histologically to examine the attachment of the RUL on the ulna. In addition, we evaluated 21 asymptomatic wrists from healthy volunteers using 3.0 T magnetic resonance imaging. The insertion of the deep RUL was located mainly on the radial aspect of the ulnar fovea from the foveal center to the articular cartilage. The footprint of the deep RUL appeared in 3 different shapes. The maximal width, length, and area of the footprint of the deep RUL were 3.7 (95% confidence interval [CI], 3.3–4.0) mm, 8.4 (95% CI, 7.9–8.9) mm, and 26.3 (95% CI, 23.4–29.1) mm2, respectively. Histologic analyses showed the attachment of the deep RUL on the radial wall of the fovea exhibited a direct insertion with typical 4-layer structures. The deep RUL fibers formed an acute angle with the distal component of the triangular fibrocartilage complex. The deep RUL was inserted on the radial side of the ulnar fovea and not the foveal center; it had direct insertion on the radial wall continuous with articular cartilage, and the fibers in the direct insertion formed an acute angle with the distal component of the triangular fibrocartilage complex.