ANATOMY

The LT interosseous ligament is thicker volarly and dorsally,² with a membranous central portion that is not uncommonly torn without resulting in instability; these tears are clinically insignificant. Clinically significant LT instability arises from intrinsic and extrinsic ligamentous injuries.³^–⁵ Key anatomy for the arthroscopic treatment of LT tears is based on the normal ulnar-sided anatomy. Ulnar-sided stability is imparted from the integrity of the LT ligament³ in association with the ulnolunate (UL), ulnotriquetral (UT),³^–⁵ dorsal radiotriquetral, and scaphotriquetral ligaments.³^,⁴^,⁶ Ulnar wrist forces also pass through the triangular fibrocartilage complex (TFCC) to help stabilize the ulnar carpus and transmit axial forces to the ulna.⁷^,⁸ The volar and dorsal aspects of the LT ligament merge with the ulnocarpal extrinsic ligaments volarly and the dorsal radiolunotriquetral ligament dorsally, anchoring the triquetrum.⁹ The UL and UT ligaments originate on the volar TFCC and insert on the volar lunate and volar triquetrum, respectively, as well as on the LT ligament.¹⁰^–¹² Just palmar lies the ulnocapitate ligament, which provides a direct attachment from the ulna to the palmar ulnar ligamentous complex.

Ligament plication has been implemented to manage capitolunate instability.¹³ Arthroscopic treatment of LT tears is based on the anatomic and biomechanical contributions of the ulnocarpal ligaments (UL and UT) to LT joint stability. In addition to ARIF of the LT, suture plication augments capsular repair and shortens the ulnocarpal ligaments (reminiscent of ulnar shortening), reducing their contribution to the LT joint to enhance the extrinsic ligament contribution to stability. The ulnocarpal ligaments diverge from their origin on the volar TFCC to insert distally on the triquetrum and lunate in a V formation. Suture plication of the ulnar ligaments closes the V and serves to shorten the ulnar carpal ligaments and augment the palmar capsular tissue of the LT joint.

The TFCC often is a component of more extensive ulnar-sided injuries ¹⁴ and does not preclude arthroscopic treatment. Severe LT instability with significant damage to both the dorsal the radiotriquetral and the scaphotriquetral ligament results in volar intercalated segment instability (VISI)³^,⁴^,⁶; static instability (VISI) is not readily amenable to complete arthroscopic repair.

PATIENT EVALUATION

History and Physical Examination

Historically, patients may not recall a specific inciting event. Commonly, LT interosseous ligament tears associated with instability result from a single traumatic event, such as a twisting injury or a fall on an outstretched hand with a pronated forearm. The axial and dorsally directed forces result in wrist extension with radial deviation.¹⁵^,¹⁶ With intercarpal pronation, disruption of the LT interosseous ligament, and associated injury to the disk-triquetral and disk-lunate ligaments, tearing occurs, and LT instability may be greater.

After a general wrist examination, including inspection, palpation, and general range of motion and stability, an examination focused on ulnar-sided pathology is carried out. Patient localization of pain is helpful; diffuse, nonlocalizing pain is not typical of ulnar-sided instability. The dorsal and volar aspects of the TFCC, the dorsal LT joint, and the extensor carpi ulnaris (ECU) are the main areas to palpate. Depending on the acuteness of the injury, tenderness may or may not be present. Maneuvers to provoke pain caused by excessive unwanted translation of the triquetrum and lunate further elucidate ulnar-sided pain complaints. Although none of the tests is diagnostic in isolation, when performed as part of the comprehensive evaluation, the tests can better characterize pain complaints. Provocative stability maneuvers used to assess the LT joint include LT ballottement (compressing the triquetrum against the lunate), the shuck test as described by Reagan and colleagues,⁶ the shear test as described by Kleinman,¹⁷^,¹⁸ and distal radioulnar translation (to infer stability).⁹^,¹⁹ In addition to ulnar impaction testing, ulnar deviation should be performed with the wrist in flexed, extended, and neutral positions. The stability of the distal radioulnar joint is also assessed. Assessing the patient response to provocative maneuvers and comparing perceived translation with the contralateral wrist are useful.

Diagnostic Imaging

The radiographic evaluation of a painful wrist should start with a minimum of a zero rotation posteroanterior ²⁰^,²¹ view and a true lateral view of the wrist. Comparison views of the contralateral wrist are useful. In these radiographic views and after assessment of the soft tissue shadows, specific osseous relationships should be documented. The focused analysis includes ulnar variance,²² LT interval, integrity of the subchondral joint surfaces, greater and lesser arc continuity,²³ and radiolunate and scapholunate angles.

The clinical value of advanced radiographic evaluation of the wrist is subject to geographic variability. Magnetic resonance imaging (MRI) with or without the addition of arthrography is beneficial, provided an expert radiologist is available. Variations in the accuracy of MRI and diagnostic arthroscopy may simply be related to skills of the radiologist and the arthroscopic surgeon. In general, a high field magnet with a dedicated extremity helps to optimize spatial resolution.²⁴ Assessment of the LT joint is variable²⁵ and should be made in the context of the history and physical examination.

TREATMENT

Indications and Contraindications

The primary contraindication to arthroscopic surgical treatment of LT instability is VISI and severe volar extrinsic ligament tearing. Indications for arthroscopic treatment of static LT instability include isolated LT instability and LT instability in combination with triangular fibrocartilage tears and ulnar impaction.

Conservative Management

Initial treatment for acute LT ligament tears without associated VISI can be short arm cast immobilization with the wrist in neutral position. Steroid injections may be of benefit, based on anecdotal reports.

Surgical Management

With failure of conservative treatment or unstable injuries, arthroscopic treatment of is a reasonable option and includes radiocarpal and midcarpal arthroscopy. The first step is to assess the degree of instability ²⁶ and associated injuries. Partial LT injuries may be treated with débridement alone.²⁷^,²⁸ In 1995, Osterman and Seidman²⁹ combined débridement with isolated pinning of the LT joint and reported good results. Nonarthroscopic treatment, although not the focus of the chapter, has been described. In a comparison of techniques,³⁰ subjective results tended to be better for direct repair or reconstruction than for LT fusion.