Injuries to the lunotriquetral interosseous ligament (LTIL)—including sprains, tears, and instability—are considered an unusual cause of ulnar-sided wrist pain. Compared to injuries of its counterpart, the scapholunate interosseous ligament (SLIL) and other forms of dissociative carpal instability, LTIL injuries are less common and not as well understood. The LTIL is most often injured from a fall on an outstretched hand (FOOSH), although some high-energy sports and other mechanisms may also be responsible. LTIL injuries can occur in isolation, but are usually part of a complex injury and associated with other wrist trauma, such as distal radius fracture or perilunate dislocation. Treatment depends on the degree of stability, time elapsed since injury, and several other factors, but typically includes mobilization. Surgical intervention is reserved for certain chronic cases and patients who fail to respond to conservative treatment.1,2,3,4
Pathophysiology
- The most common mechanism of LTIL injury is trauma to the wrist caused by a FOOSH, usually with wrist hyperextension, extension and radial deviation, or volar flexion1
- LTIL injuries may also result from twisting, pulling, pushing, catching, or striking, as well as high-energy or impact sports like football, hockey, rugby, or basketball1,5
- Degenerative etiologies for LTIL injuries have also been described: positive ulnar variance leading to ulnocarpal impingement can alter wrist intercarpal mechanics and lead to subsequent LTIL degeneration1,4
- LTIL injuries range from incomplete tears to complete dissociation, with either dynamic or static carpal instability; “dissociation” is used clinically to describe static instability, while “sprain” describes predynamic and dynamic instabilities, but not all injuries are unstable1,3
- Complex LTIL injuries that also involve trauma to the wrist are more common than isolated injuries6
- Volar intercalated segmental instability (VISI) deformity is a type of carpal instability that can be caused by advanced LTIL injury3
Related Anatomy
- The LTIL is a C-shaped intrinsic ligament that stabilizes the LT joint and works with the SLIL to stabilize the proximal carpal row; stability of this row is associated with an equilibrium of forces on the lunate, between the extension moment of the triquetrum and the flexion moment of the scaphoid4
- The LTIL is made up of three regions: dorsal, intermediate, and volar
- Unlike the SLIL, where the dorsal aspect is the most critical, the volar segment is the most stout and is considered the major constraint to LT motion
- Several extrinsic ligaments help to further stabilize the LT relationship, including the palmar radiolunotriquetral ligament and the dorsal radiocarpal ligament4,5
- Normal wrist mobility and stability require an intact LTIL that fixes both the lunate and triquetrum bones into a single mechanical unit and determines the position of the lunate throughout wrist range of motion(ROM)1
Incidence and Related Conditions
- As a group, ulnar carpal injuries—which include triquetrohamate (midcarpal) and LT instability—are about one-sixth as common as their radial counterparts1
- Relative to other ligamentous injuries of the carpus, symptomatic and isolated tears of the LTIL are not commonly reported7
- Carpal bone injuries
- Carpal ligament injuries
- Triangular fibrocartilage complex (TFCC) injuries
- Distal radius fracture
- Perilunate dislocation1,3
Differential Diagnosis
- Entrapment of the dorsal branch of the ulnar nerve
- TFCC tear
- Ulnocarpal arthrosis
- Midcarpal instability
- Kienbock’s disease
- Extensor carpi ulnaris (ECU) subluxation
- ECU or flexor carpi ulnaris (FCU) tendonitis
- Distal radioulnar joint (DRUJ) subluxation
- Pisotriquetral (PT) arthrosis
- Fracture of the hook of the hamate, ulnar styloid, or triquetrum
- Ulnocarpal impingement
- Chondromalacia of lunate or distal ulna
- LT synostosis
- Calcific tendinitis1,2