Distal Radio-Ulnar Joint (DRUJ) Flashcards
What are the primary stabilizers of the Distal Radioulnar Joint (DRUJ)?
The radioulnar ligaments.
These ligaments, part of the triangular fibrocartilage complex (TFCC), prevent dorsal and palmar subluxation of the ulna relative to the radius, crucial for maintaining joint stability during forearm rotation.
What structures comprise the triangular fibrocartilage complex (TFCC)?
The TFCC includes the
* triangular fibrocartilage,
* meniscus homologue,
* ulnocarpal ligaments,
* dorsal and palmar radioulnar ligaments,
* the extensor carpi ulnaris subsheath.
These structures collectively stabilize the DRUJ and ulnocarpal joint.
How does the radius of curvature of the ulnar head compare to that of the sigmoid notch in the DRUJ?
The ulnar head has a smaller radius of curvature than the sigmoid notch.
This anatomical difference allows the convex ulnar head to articulate properly within the concave sigmoid notch, facilitating rotational and gliding motion.
Describe the vascular supply to the TFCC.
The TFCC receives blood supply from the ulnar artery, anterior interosseous artery, and posterior interosseous artery.
The peripheral 15-20% is well-vascularized, while the central portion is avascular, affecting healing potential.
What is the role of the pronator quadratus in DRUJ stability?
The pronator quadratus provides dynamic stability to the DRUJ. Its deep head compresses the ulnar head into the sigmoid notch during pronation, enhancing joint congruence.
What is the function of the dorsal radioulnar ligament?
The dorsal radioulnar ligament tightens in pronation, preventing dorsal subluxation of the ulna. It is a key stabilizer during forearm rotation.
How does the interosseous membrane contribute to DRUJ stability?
The interosseous membrane provides longitudinal stability, distributing load between the radius and ulna, indirectly supporting DRUJ function by maintaining proper alignment.
How does forearm rotation affect the position of the ulnar head in the DRUJ?
In pronation, the ulnar head translates dorsally, while in supination, it translates palmarly. This movement is guided by the radioulnar ligaments and is essential for normal wrist function.
How does wrist position affect load transmission through the DRUJ?
Load through the DRUJ
increases with ulnar deviation and pronation
decreases with supination and radial deviation
What is the effect of grip strength on DRUJ load?
Increased grip strength elevates axial load through the wrist, subsequently increasing load transmission through the DRUJ, particularly in positions of ulnar deviation.
What is the piano key sign, and what does it indicate?
The piano key sign is elicited by pressing down on the ulnar head with the wrist in pronation; a positive sign (rebound of the ulna) suggests DRUJ instability due to TFCC or ligament disruption.
How is the ulnar fovea sign performed, and what does it assess?
The ulnar fovea sign involves palpating the ulnar fovea for tenderness, indicating potential foveal detachment of the TFCC, a common cause of DRUJ instability.
What are the clinical signs of DRUJ instability?
Pain with forearm rotation, a positive piano key sign, and ulnar fovea tenderness. These signs indicate potential disruption of the TFCC or radioulnar ligaments, leading to abnormal joint motion.
What is the gold standard imaging modality for assessing DRUJ instability?
Magnetic Resonance Imaging (MRI). MRI provides detailed visualization of soft tissue structures, including the TFCC and radioulnar ligaments, essential for diagnosing DRUJ instability.
What are the goals of physiotherapy in managing DRUJ instability?
Physiotherapy aims to strengthen forearm muscles, improve proprioception, and enhance joint stability through targeted exercises, potentially delaying or avoiding surgery.
Describe the Adams procedure for DRUJ reconstruction.
The Adams procedure involves using a tendon graft to reconstruct the radioulnar ligaments. This technique aims to restore stability by creating a sling around the ulnar head, mimicking the function of the native ligaments.
What is the difference between the Sauve-Kapandji and Darrach procedures?
The Sauve-Kapandji - DRUJ arthrodesis with creation of a proximal ulnar pseudarthrosis, preserving ulnar support, while the
Darrach - Ulnar head resection
Describe the steps of a TFCC repair using an arthroscopic technique.
Arthroscopic TFCC repair involves debriding the tear, placing sutures through the TFCC, and securing them to the ulnar fovea or capsule, restoring stability while minimizing open surgical morbidity.
How does ulnar variance affect DRUJ biomechanics?
Positive ulnar variance increases load through the ulna and DRUJ, potentially leading to ulnocarpal impaction and TFCC degeneration. Negative variance may reduce load but can predispose to other pathologies.
What is ulnar impaction syndrome, and how is it managed?
Ulnar impaction syndrome is a degenerative condition caused by excessive load on the ulnar side of the wrist, often due to positive ulnar variance. Management includes ulnar shortening osteotomy to reduce load and alleviate symptoms.
How is ulnar styloid impaction syndrome diagnosed?
Diagnosis involves clinical suspicion based on ulnar-sided wrist pain, positive provocative tests, and imaging showing an elongated ulnar styloid with impaction on the triquetrum.
What is the pathophysiology of DRUJ arthritis?
DRUJ arthritis often results from chronic instability, repetitive trauma, or inflammatory conditions, leading to cartilage degeneration and joint space narrowing, causing pain and limited motion.
What is the clinical significance of a flat sigmoid notch in the DRUJ?
A flat sigmoid notch may increase the risk of DRUJ instability. With less bony constraint, there is a higher likelihood of subluxation or dislocation, particularly in traumatic or degenerative conditions.
What is the most common complication after ulnar shortening osteotomy?
Hardware irritation is the most common complication, often requiring plate removal after bone healing, due to the subcutaneous position of the ulna.
