27.1 Anatomy

While this chapter focuses on the treatment of lunotriquetral (LT) injuries, some attention must also be given to the anatomy, diagnosis, and classification, as the injury pattern guides the treatment.

Like the scapholunate (SL) interosseous ligament, the LT is composed of three subregions: dorsal, membranous, and volar. The volar region is the strongest and considered to be the major stabilizer of the lunate–triquetrum interval. The volar and dorsal subregions merge with their respective extrinsic ligaments to further constrain LT motion (▶Fig. 27.1).

Mechanically, the triquetrum links the proximal and distal carpal row motion through its contact with the hamate. During ulnar deviation, the extensor carpi ulnaris (EUC) with its attachment at the base of the fifth metacarpal forces the hamate to corkscrew and engage the triquetrum pushing it into extension. The triquetrum by its interosseous attachment to the lunate brings the lunate into extension, which helps guide the scaphoid into its horizontal position. The reverse happens in radial deviation.

27.2 Diagnosis and Classification

Various classifications of LT injury have been described but the authors prefer the simple outline presented in ▶Table 27.1. Any classification begins with a thorough history and physical examination, which lead the surgeon to suspect LT involvement. It is important to note that LT injuries present on a spectrum based on the degree of injury. Horii performed a kinematic study of the intact wrist followed by serial sectioning of the LT ligaments followed by the dorsal radiocarpal ligament (DRC)/dorsal intercarpal (DIC) ligaments. ¹ The pathognomonic volar intercalated segment instability (VISI), increase in LT motion, and catch-up-clunk associated with ulnar deviation only appeared after additional sectioning of the DRC/DIC (▶Fig. 27.2). The authors asserted that the subtle changes to LT kinematics that accompanied LT ligament injuries in the absence of DRC/DIC injury would be difficult to detect clinically or radiographically but sufficient to generate synovitis, altered joint mechanics, and increased ligamentous tension. Therefore, patients with a complete LT injury but intact DRC/DIC can present without obvious radiographic findings and only subtle examination findings including some negativespecial tests.

In the history of ulnar wrist pain, an understanding of the timing of symptomology is critical because it may directly affect the treatment options. Patients with acute injuries often describe a fall on an outstretched hand or, less frequently, a rotary mechanism. ² Generally, acute tears are associated with the history of a known traumatic event and a firm timeline regarding the pain history, whereas chronic tears are often insidious or may be incited by a trivial trauma (acute on chronic). ³ Patients complain of weakness with ulnar-sided wrist pain, and carefully delineating the exact site of pain also aids in the diagnosis.

Patients with LT injuries will complain of pain directly over the dorsal LT joint, which is more distal and a subtly different location than those complaining of triangular fibrocartilage complex (TFCC) tears, ECU, pisotriquetral arthritis, or distal radioulnar joint pathology. ¹

Examination consists of range of motion (ROM) measurements, grip testing, palpation, and special tests. Reagan studied 35 patients with LT sprains and found that examination universally produced tenderness over the dorsal LT, restricted wrist ROM, and weakened grip. ² Linscheid is credited with the description of a click when transitioning from radial to ulnar deviation in the presence of an LT ligament tear. ^{2 , 4 , 5} The diagnosis is further supported by special tests such as the LT ballottement (or Reagan shuck) test, the LT compression test (▶Fig. 27.3), the ulnocarpal stress test, the presence of a fovea sign, the derby test, and the shear (or Kleinman) test. The LT ballottement test is performed by fixing the lunate with the thumb and the index finger of one hand while, with the other hand, displacing the triquetrum and pisiform first dorsally and then palmarly. A positive result elicits pain, crepitus, and excessive laxity. ² The Reagan test has a reported sensitivity of 64% and specificity of 44%. ^{5 , 6} The compression test is abnormal when pain is elicited as the triquetrum is radially compressed into a stabilized lunate. With the ulnocarpal stress test, pain is created when the wrist is fully ulnarly deviated, followed by wrist pronosupination.

The fovea sign is present when the patient’s pain is recreated with deep palpation of the ulnar fovea. ⁵ While the fovea sign does not directly detect LT ligament tears, it can identify injury to the secondary stabilizers of the LT joint—mainly the ulnar extrinsic ligaments. The fovea sign is more closely associated with TFCC tears, but there is a reported sensitivity of 74% and specificity of 97% for ulnar extrinsic pathology. ^{5 , 7} The Derby test is a complex, three-part examination maneuver that takes the patient’s subjective feelings of instability into account. The examination is well represented by Rhee et al both pictorially and in video form. ⁵ The Derby test has a reported sensitivity of 77% and specificity of 89%. ^{5 , 8}

Following clinical diagnosis, plain radiographs are obtained to evaluate the carpal alignment. Standard anteroposterior, lateral, and oblique views of the wrist should be obtained at a minimum. Grip views should also be obtained to evaluate ulnar variance. When obtaining grip views, it is important to standardize the positioning to wrist neutral pronosupination (requiring the film to be performed with the shoulder abducted to 90 degrees), as ulnar variance is altered with different degrees of pronosupination. Including the contralateral wrist is valuable for comparison. Next, critical evaluation of Gilula arcs is performed to evaluate the congruity of the carpal rows. ⁹ With LT injury, radiographs can be normal or Gilula arcs I and II may be disrupted and accompanied by LT overlap. ⁹ (▶Fig. 27.4) Although common in SL ligament injury, gapping is infrequent with LT injuries. ¹⁰ In acute patterns, the LT injury may be only one component of a larger injury pattern, as is the case with perilunate injuries. To support this concept, Lichtman et al suggested that some LT injuries are probably “forme fruste” perilunate patterns. ⁴ With a diagnosis of perilunate injury, the associated LT injury is often obvious on plain radiographs based on interruption of Gilula arcs (▶Fig. 27.4). The lateral radiograph is scrutinized for the presence of VISI. The normal SL angle is 47 degrees while VISI is diagnosed with an SL angle of less than 30 degrees. The normal LT angle is 14 degrees, but this angle decreases to a negative value in the presence of VISI. ² Since VISI is only noted after disruption of secondary stabilizers (DRC/DIC ligaments and scaphotrapeziotrapezoid ligament), it will only be appreciated in more severe injuries or in chronic injury patterns with ligamentous attenuation. ¹

Advanced imaging is debated. Gilula argued that the word “tear” should not be used when referring to LT lesions noted on arthrography due to the high incidence of degenerative perforations, which may result in false positives in the setting of acute injury. ¹¹ Historically, arthrographic tears based on dye extravasation between joints has fallen out of favor due to the aforementioned frequency of degenerative perforations and the 13% rate of communication between the midcarpal and radiocarpal joints in normal individuals. ^{10 , 12} Furthermore, Cantor demonstrated a 59% rate of LT tear in the asymptomatic wrist of those with a contralateral symptomatic LT tear. ¹³ Viegas performed dissections on 100 cadavers and noted no attritional tears in specimen under the age of 45 but a 27.6% rate of perforations in the LT ligament in those older than 60 years. ¹⁴ The article concluded that there is a significant rate of perforation of the LT ligament in the general population.

Wrist MRI is considered a diagnostic help, although even the newer 3T magnets have only 25 to 75% sensitivity for diagnosing LT tears (▶Fig. 27.5). ¹⁵ The significance of the tear requires clinical correlation. Some authors continue to use bone scans, which will demonstrate increased uptake in the LT joint, but this test is nonspecific. ^{16 , 17}

Wrist arthroscopy remains the gold standard for diagnosis of ligamentous injury in the wrist and offers an approach to staging LT lesions (▶Table 27.2). Given the wide curvature of the radiocarpal joint, the best visualization of the LT interval is from an ulnar portal either 4–5 or 6R. The use of a probe to assess ligament integrity is important (▶Fig. 27.6a, b). Unlike a torn SL, there is never a drive-through opening. Midcarpal arthroscopy is essential to evaluate the degree of instability and the joint reaction to that instability. In the midcarpal joint, one can assess the congruency of the concave LT interface and the degree of the step off. Instability can be dynamically evaluated using the probe and trocar (▶Fig. 27.7a). Normally it will barely admit a probe. In grade 1 it will admit a standard arthroscopic probe, in grade 2 the probe can be twisted, and in grade 3 the 2.9 mm trocar can be inserted. Furthermore, the degree of instability relates to the reaction at the hamate interface. Palmer described the HALT (Hamete arthrosis lunotriquetral) lesion (hamate impaction secondary to LT instability). ^{3 , 18} The greater the hamate erosion, the greater the instability (▶Fig. 27.7b). These findings are incorporated in the arthroscopic staging of the LT lesions. Hofmeister et al found that midcarpal arthroscopy confirmed the radiocarpal diagnosis 21% of the time and added to the radiocarpal diagnosis 82% of the time. ¹⁹ We have previously demonstrated the frequency of additional injuries associated with LT tears (synovitis 85%, LT chondromalacia 40%, TFCC tears 40%, triquetrohamate chrondromalacia 30%, and ulnar extrinsic ligament tears 30%). ²⁰ Treatment is then based on patient pain and impairment, acuity and arthroscopic staging.