Palmar Radioulnar Ligaments Research Articles

The Anatomy of the Ligaments of the Wrist and Distal Radioulnar Joints

The ligaments of the wrist are responsible for guiding and constraining the complex motion of the carpal bones relative to the forearm bones, the metacarpals, and contiguous carpal bones. The majority of wrist ligaments are found within the joint capsule as organized thickenings composed of parallel collagen fascicles, small caliber nerves and blood vessels, and lined on their deep surfaces by synoviocytes. The palmar radiocarpal ligament complex is composed of the radioscaphocapitate, long radiolunate, radioscapholunate and short radiolunate ligaments. The ulnocarpal ligaments include the ulnolunate, ulnotriquetral and ulnocapitate ligaments. Dorsally, the radiocarpal joint is spanned by the dorsal radiocarpal ligament. Palmar ligaments connecting the proximal and distal carpal rows include the scaphotrapeziotrapezoid, scaphocapitate, triquetrocapitate and triquetrohamate ligaments. Within each row are interosseous ligaments connecting adjacent carpal bones, each divisible into dorsal and palmar components. There are unique regions within some of the ligaments, such as a zone of fibrocartilage in the proximal regions of the scapholunate and lunotriquetral interosseous ligaments, and strong deep regions connecting the trapezoid, capitate, and hamate. The distal radioulnar joint is connected by the triangular fibrocartilage complex, composed of a fibrocartilaginous disc and the palmar and dorsal radioulnar ligaments. The ulnocarpal ligaments attach to the palmar radioulnar ligament rather than directly to the ulna, allowing increased independence between wrist and forearm motion.

The dorsopalmar stability of the distal radioulnar joint

Sixteen fresh-frozen adult human cadaveric upper extremities were used in a biomechanical analysis of distal radioulnar joint (DRUJ) stability. The relative contribution to stability of the DRUJ by the surrounding anatomic structures presumed to stabilize the joint was analyzed with respect to forearm rotation and wrist flexion and extension using a purpose-built 4-axis materials testing machine. The dominant structures stabilizing the DRUJ were the ligamentous components of the triangular fibrocartilage complex proper. The major constraint to dorsal translation of the distal ulna relative to the radius is the palmar radioulnar ligament. Palmar translation of the distal ulna relative to the radius is constrained primarily by the dorsal radioulnar ligament, with secondary constraint provided by the palmar radioulnar ligament and interosseous membrane. The ulnocarpal ligaments and extensor carpi ulnaris subsheath did not contribute significantly to DRUJ stability; however, approximately 20% of DRUJ constraint is provided by the articular contact of the radius and ulna. These relationships were consistent regardless of wrist position or degree of forearm rotation.

A two-dimensional kinematic analysis of the distal radioulnar joint

The triangular fibrocartilage and its function in the kinematics of pronation and supination in the distal radioulnar joint was studied. Measurements of the constituent parts of this joint in 11 cadavers showed that the palmar radioulnar ligament is at least 2 mm longer than the dorsal radioulnar ligament. Based on these measurements the movements of the joint were modelled in a two-dimensional kinematic chain. Predictions based on this chain could be confirmed by direct observation and videotaping dissections of joints of unfixed specimens and three-dimensional reconstructions of a CT scan of a healthy volunteer. It could be concluded that (a) the dorsal part is tight during pronation and the palmar part during supination and (b) considerable asymmetrical translations, (dorsal translation being the largest) occur because of the length differences of the ligaments.

The stabilizing mechanism of the distal radioulnar joint during pronation and supination

A biomechanical cadaver study was performed to determine the roles of the stabilizing structures of the distal radioulnar joint during pronation and supination. Subluxation and dislocation of the radius with respect to the ulna were evaluated in seven cadaver forearms placed in supination, pronation, and neutral forearm rotation. The amount of subluxation was measured with all structures intact, and after sectioning in various sequences the dorsal and palmar radioulnar ligaments, the distal portion of the interosseous membrane including the pronator quadratus, and the entire interosseous membrane. After sectioning two of any four structures, the distal radioulnar joint remained stable. When the interosseous membrane was disrupted first, the dorsal radioulnar ligament was found to be more important than the palmar radioulnar ligament in stabilizing the distal radioulnar joint in pronation, and conversely the palmar radioulnar ligament was more important than the dorsal radioulnar ligament in supination. Dislocation, and frequently diastasis, occurred only with sectioning of all four structures. This suggests that all four structures contribute to stability of the distal radioulnar joint.

Distal radio-ulnar ligament motion during supination and pronation

The dorsal and palmar distal radio-ulnar ligaments (DRUL) play an important role in the stability of the distal radio-ulnar joint (DRUJ). Various authorities, however, hold opposite opinions regarding DRUL motion during DRUJ pronation and supination, thus implying opposite techniques for reconstruction of the unstable DRUJ. With the hypothesis that relative displacement would increase in the dorsal DRUL during pronation and would increase in the palmar DRUL during supination, measurements were made of the relative DRUL displacement with a Hall-effect displacement transducer during DRUJ pronation and supination in six fresh cadaver wrists. The hypothesis was confirmed that the dorsal radio-uluar ligament undergoes relative displacement during pronation, while the palmar radio-ulnar ligament undergoes relative displacement during supination.

The Distal Radioulnar Joint in Relation to the Whole Forearm

The functional anatomy of the distal radioulnar joint was studied in relation to the whole forearm, using three fresh-frozen, above-elbow amputation specimens. The specimens demonstrate how the proximal and distal radioulnar joints together form a bicondylar joint of special character. The proximal "condyle," the radial head, rotates axially, whereas the distal "condyle," the ulnar head, is fixed with respect to rotation. The ordinary articulation of a bicondylar joint (pure axial rotation) is thereby changed into pronation-supination. Axial rotation is preserved proximally, while distally the radius swings around the ulnar head. The mobile radius is distally attached to the stable ulnar head by the dorsal and volar radioulnar ligaments, the dorsal ligament being tight for stabilization in supination and the volar ligament being tight in pronation. The ulnar head also serves as a keystone, carrying the load of the radius. Removal of the ulnar head allows the radius to "fall in" towards the ulna, with narrowing of the interosseous space.

The distal radioulnar ligaments: A biomechanical study

The mechanical roles of the triangular fibrocartilage have been examined in three experiments. Kinematic analysis by a stereophotogrammetric method revealed that the palmar radioulnar ligament was taut in supination and that the dorsal radioulnar ligament was taut in pronation. In full pronation, the palmar radioulnar ligament decreased to an average of 71% of its length in tension. In full supination, the dorsal radioulnar ligament decreased to an average of 90% of its length. Mechanical testing of the triangular fibrocartilage under axial load disclosed a significant laxity (mean: 10.4 mm), which was decreased in pronation. Transverse loading tests demonstrated that the triangular fibrocartilage is less stiff in neutral forearm rotation. Study of the material properties of the palmar and dorsal parts of the triangular fibrocartilage showed these structures to be strong ligaments with material properties similar to those of the radiocarpal ligaments.

The triangular fibrocartilage complex of the wrist—Anatomy and function

The anatomy and function of the triangular fibrocartilage complex (TFCC) of the wrist was studied through anatomic dissections and biomechanical testing of 61 specimens. The TFCC was found to be a homogenous structure composed of, but not dissectable into, the articular disc, the dorsal and volar radioulnar ligaments, the meniscus homologue, the ulnar collateral ligament, and the sheath of the extensor carpi ulnaris. The TFCC was found to be perforated in 53% of specimens dissected, and all of the wrists with a demonstrable perforation showed evidence of damage or erosion of the cartilage of the lunate and/or distal ulna. Biomechanical studies suggest that the TFCC functions both as a cushion for the ulnar carpus and as a major stabilizer of the distal radioulnar joint. Perforations of the TFCC can result in the ulna-lunate abutment and cartilage erosion. Since excision of the TFCC may lead to ulnolunate abutment, chronic wrist pain, and/or instability of the distal radioulnar joint, it is not recommended.