The scapholunate complex is subject to significant loads, as the scaphoid is the only carpal bone to span from the proximal to the distal carpal row.

A large amount of potential energy is stored within the proximal carpal row.

Stability is provided to the scapholunate complex by the intrinsic SLIL as well as extrinsic capsular ligaments, especially the dorsal radiocarpal (DRC), dorsal intercarpal (DIC) ligament, and volar radioscaphocapitate (RSC) and scaphotrapeziotrapezoid (STT) ligaments.

The SLIL is a C-shaped structure consisting of a stronger dorsal ligamentous portion (2 to 3 mm thick), a volar ligamentous portion (1 mm thick), and a proximal fibrocartilaginous (membranous) portion.²

Isolated injuries to the SLIL appear to be associated with dynamic instability, whereas static instability usually indicates additional injury to the secondary ligamentous stabilizers, including the DIC ligament.²²

The lunotriquetral complex is also stabilized by an intrinsic LTIL and extrinsic (volar and dorsal) capsular ligaments.

The LTIL is C-shaped, analogous to the SLIL, consisting of dorsal and volar ligamentous portions and a membranous proximal portion. In contrast to the SLIL, the volar ligamentous portion of the LTIL is stronger and more significant functionally.¹⁸

As with the scapholunate complex, isolated injuries to the LTIL are usually insufficient for the development of static instability. Presence of a static deformity indicates additional injury to extrinsic ligamentous structures (volar ulnotriquetral, ulnolunate, and ulnocapitate ligaments or the DRC and DIC ligaments).¹⁰,²⁷

Mayfield et al¹⁵ postulated that scapholunate disruption is the initial component of the lesser arc perilunate injury pattern, which occurs when force is applied to the thenar area with the wrist in extension, mild pronation, and ulnar deviation. The force results in intercarpal supination.

SLIL injuries can be sprains, partial tears, or complete tears (with or without injury to the extrinsic ligamentous stabilizers).

Arthroscopic evaluation has revealed associated SLIL injuries in up to 30% of intra-articular distal radius fractures.⁸

LTIL disruption may be traumatic or atraumatic in origin.

Tears of the SLIL or LTIL, with or without extrinsic ligamentous injury, may lead to various degrees of carpal instability (predynamic, dynamic, or static), alteration of normal carpal mechanics and kinematics, and degenerative changes in the radiocarpal and midcarpal joints.

A complete SLIL tear is associated with the development of a DISI deformity, which may be dynamic or static (if accompanied by injury to the extrinsic ligaments).

A complete LTIL tear is associated with the development of a volar intercalated segment instability (VISI) deformity.

The natural history of partial tears of the SLIL or LTIL is at present poorly defined.

Predynamic or dynamic instability may cause attenuation of extrinsic ligaments with progressive development of further instability and eventual static changes.³⁶,³⁷

Dorsoradial or ulnar-sided wrist pain with a history of a fall, sudden loading, or twisting of the wrist should raise suspicion for a SLIL or LTIL tear, respectively. However, it is not uncommon for the patient to deny any significant injury.

Patients frequently complain of weakness, swelling, and loss of range of motion of the wrist.

A sensation of instability or “giving way” is often reported, occasionally associated with a painful clunk.

A detailed physical examination of the wrist may provide significant information for the diagnosis of ligamentous injuries and help to rule out other wrist pathology.

Examination of the wrist begins with evaluation for any deformity or swelling and determination of wrist range of motion.

Key tests and maneuvers specifically evaluating the scapholunate and lunotriquetral ligaments are noted in the following text. Comparison with the contralateral uninjured wrist is critical.

Initial imaging of the wrist should always include AP and lateral radiographs, combined with special views depending on the suspected pathology. If scapholunate pathology is suspected, a bilateral pronated grip posteroanterior (Mayo Clinic) view should be obtained. In all cases, comparison with radiographs of the contralateral uninjured wrist is critical.

Abnormal findings in static scapholunate instability include the following:

Radiographic findings in patients with lunotriquetral tears are often normal. Abnormal findings in static lunotriquetral instability include in following:

Provocative views (radial-ulnar deviation, flexion-extension views) or videofluoroscopy may demonstrate asynchronous scapholunate motion (dynamic scapholunate instability) in cases with suspected SLIL injury and normal standard views.¹² Increased, synchronous mobility of the scapholunate complex with diminished motion of the triquetrum indicates an LTIL injury.

Wrist arthrography has a sensitivity of only 60% compared to arthroscopy and cannot determine the extent of any tear present or its functional significance.³³

Magnetic resonance imaging (MRI) (with or without arthrography) has limited value in evaluating interosseous ligament injuries. Reported sensitivity rates for SLIL injuries range from 40% to 65% compared to arthroscopy.²³ MRI is even less reliable in diagnosing LTIL injuries.

Arthroscopy (radiocarpal, midcarpal with probing) remains the gold standard in evaluation of SLIL and LTIL injuries. This method of evaluation allows a dynamic assessment and determination of the functional significance of the instability.

Scapholunate and lunotriquetral injuries associated with dynamic instability may respond to initial nonoperative treatment for 6 to 12 weeks.

Conservative management typically includes a combination of the following:

The selection of surgical treatment for SLIL and LTIL injuries is based on the severity of symptoms, degree of instability (predynamic, dynamic, or static), chronicity (acute, subacute, or chronic), arthroscopic findings (Geissler grade⁸; see TECH FIG 1), and reparability of the ligament.

Dynamic instability (based on positive physical findings with provocative maneuvers, abnormal stress radiographs, or arthroscopic findings) that has failed to respond to nonoperative treatment may be treated arthroscopically.

Static instability and severe dynamic instability are typically indications for open surgery, although arthroscopic repair of the SLIL is feasible in select cases.

Patients developing carpal collapse with arthritic changes require salvage procedures such as radial styloidectomy, proximal row carpectomy, or limited wrist fusions (eg, STT, scaphocapitate, scaphoidectomy plus four-corner fusion, lunotriquetral fusion).

The focus of this chapter is arthroscopic management of dynamic scapholunate or lunotriquetral instability. Newer arthroscopic alternatives advocated for management of more advanced pathology are also described.