Ligament Injuries of the Wrist
Nichole A. Joslyn, MD
Sanjeev Kakar, MD, FAAOS, FAOA
Dr. Kakar or an immediate family member serves as a paid consultant to or is an employee of Arthrex, Inc. and has stock or stock options held in Sonex Healthcare. Neither Dr. Joslyn nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.
ABSTRACT
A thorough understanding of the complex anatomy and kinematics of the wrist is necessary to diagnose and treat wrist pathologies. Carpal instability can be defined as a symptomatic condition involving abnormal carpal motion during loading activities of the wrist. It is important for the orthopaedic surgeon to review carpal instability patterns, diag-nostic modalities, and discuss current treatment options.
Keywords: carpal instability; lunotriquetral ligament; perilunate instability; scapholunate ligament
Introduction
The understanding of the complex articular system of the carpus continues to evolve. Various injuries to the carpus can sometimes lead to malalignment and instability. There are four major patterns of instability of the wrist: dissociative (within the same carpal row), nondissociative (between rows, eg, radiocarpal and/or midcarpal), complex (features of both dissociative and nondissociative instability, ie, perilunate dislocations), and adaptive (not caused by an intrinsic wrist ligament pathology, eg, a distal radius malunion, Madelung deformity).
The wrist is a fascinating, complex, multiarticular system. The fine movements of the eight carpal bones are dependent on their structural bony architecture, intrinsic and extrinsic ligaments, and crossing flexor and extensor tendons. When any one of these is compromised, the motion and loading of the wrist and hand may be impaired. Although this may suggest carpal instability, it is important to understand that not all carpal malalignment should be considered unstable.
Assessment of Carpal Instability
Carpal instability is a symptomatic condition involving abnormal carpal motion during loading activities of the wrist. It is helpful to consider a six-category system1 when formulating a treatment plan (Table 1).
When further assessing patients with carpal instability, SCARCE is a mnemonic that helps the practitioner consider the numerous factors that may be involved. S stands for critical Secondary Stabilizer integrity, C for Carpal alignment, A for Acuity of injury, R for Reducibility of the carpus, C for quality of the articular Cartilage, E for Extent of ligament injury (ie, partial versus complete).2
Carpal Instability Dissociative
Carpal instability dissociative is a disruption between bones of the same carpal row. Scapholunate and lunotriquetral dissociation are two of the most commonly seen conditions within this category.
Scapholunate Ligament Injury
Scapholunate ligament dissociation most commonly occurs after a fall on an outstretched wrist and is the most frequent carpal instability pattern.3,4 This may occur as an isolated injury, or in conjunction with other injuries (eg, perilunate injuries or distal radius fractures). Up to 30% of distal radius fractures are associated with variable degrees of carpal ligament disruption.5 The injury may also occur secondary to inflammatory or septic arthritis, or iatrogenically with excessive capsular excision, for example, during a dorsal ganglion excision.
The scapholunate ligament is composed of the palmar, membranous, and dorsal regions. Partial injuries
may result in dynamic instability when the wrist is loaded.6 Injury to the entire scapholunate ligament when associated with injury to one or more critical secondary stabilizers (long radiolunate ligament, dorsal intercarpal ligament, and/or radiopalmar scaphotrapezio trapezoid [STT] ligament complex) may result in postural deformity such as diastasis of the scapholunate joint, scaphoid rotatory subluxation, or dorsal intercalated segment instability (DISI).7,8,9 Without a direct tether to the lunate, and with the load and flexion of the radial column, the scaphoid collapses into flexion and pronation around the radioscaphocapitate ligament. The lunate and triquetrum may extend when detached from the scaphoid, where there is a type 1 lunate. This flexion and extension differential allows the distal carpal row to translate dorsally. If left untreated, this may progress to progressive posttraumatic arthritis, termed scapholunate advanced collapse.10
may result in dynamic instability when the wrist is loaded.6 Injury to the entire scapholunate ligament when associated with injury to one or more critical secondary stabilizers (long radiolunate ligament, dorsal intercarpal ligament, and/or radiopalmar scaphotrapezio trapezoid [STT] ligament complex) may result in postural deformity such as diastasis of the scapholunate joint, scaphoid rotatory subluxation, or dorsal intercalated segment instability (DISI).7,8,9 Without a direct tether to the lunate, and with the load and flexion of the radial column, the scaphoid collapses into flexion and pronation around the radioscaphocapitate ligament. The lunate and triquetrum may extend when detached from the scaphoid, where there is a type 1 lunate. This flexion and extension differential allows the distal carpal row to translate dorsally. If left untreated, this may progress to progressive posttraumatic arthritis, termed scapholunate advanced collapse.10
Table 1 Analysis of Carpal Instability | ||||||||||||||||||||||||||||||||||||||||||
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Physical Examination
Diagnosis is made through a combination of history (often a fall onto an outstretched hand, complaints of a clunking sensation), physical examination, and imaging modalities. Most patients with an acute injury or chronic synovitis will have pain directly over the scapholunate interval (flexing the wrist, and palpating just distal to the Lister tubercle). There may also be associated swelling in this area. The scaphoid shift test and scapholunate ballottement tests are also helpful examination maneuvers11 and should be compared with the contralateral side.
Radiographs
PA, lateral, and 45° pronated oblique views of the injured wrist and contralateral wrist should be obtained during the initial patient evaluation. Gilula lines should be inspected for continuity, and intercarpal spacing should be evaluated. Carpal alignment can be measured by the radiolunate angle (normal -20° to + 15°), scapholunate angle (normal 30° to 70°), radioscaphoid angle (normal 35° to 65°), ulnar variance, carpal height ratio (carpal height/capitate length normal range of 1.57 +/- 0.05), and ulnar translocation ratio (articular surface of the radius/distance from the radial styloid to the proximal ulnar corner of the lunate, normal 0.87 +/- 0.04). Further imaging modalities may be needed depending on the suspected pathology.
If dynamic instability is suspected, a clenched-pencil PA view provides a comparison view of both wrists while loading the scapholunate interval with grip force.12,13 A motion series can help evaluate the mobility and reducibility of the carpus, and often includes a PA radiograph taken in neutral, radial, ulnar deviation, and lateral views in extension and flexion. A scapholunate gap greater than 5 mm is considered widened and is also referred to as scapholunate diastasis.14,15 However, this can be a normal finding, especially in a patient with hyperlaxity, and should always be compared with the contralateral side. When the scaphoid rotates into flexion and pronation (rotatory subluxation of the scaphoid), a ring sign is seen on a PA radiograph. In more severe stages of instability, the scaphoid may be flexed on a lateral radiograph and the lunate extended.
Dorsal intercalated segment instability is defined by a radiolunate angle greater than 15°.16 As discussed in a 2019 study, patients may also have dorsal scaphoid translation and should alert the practitioner to additional ligament injury.17
Dorsal intercalated segment instability is defined by a radiolunate angle greater than 15°.16 As discussed in a 2019 study, patients may also have dorsal scaphoid translation and should alert the practitioner to additional ligament injury.17
Additional imaging modalities can be helpful. CT can be reformatted into three-dimensional views of the wrist to better understand the amount and displacement of the carpus. This can be done in real time using four-dimensional CT (three-dimensional and time) scanning.18,19 MRI technology continues to improve and can assess ligament integrity and cartilage injury. A study published in 2021 suggests that MRI was 95.4% accurate for surgically relevant scapholunate ligament tears, and 100% accurate for complete lunotriquetral tears.20 3T MRI studies have shorter acquisition times than 1.5T systems and three-dimensional imaging scores superior to two-dimensional scans when assessing the scapholunate, lunotriquetral, and triangular fibrocartilage complex ligaments.21 Real-time MRI has been used to investigate dynamic instabilities, but its use in clinical practice is unclear.
Although these additional imaging modalities may aid in diagnosis and planning treatment, arthroscopy can be a useful tool in the management of carpal instability because it allows for assessment of the degree of ligamentous injury, evaluation of reducibility of the carpus, the health of the cartilage, and associated secondary stabilizer injury. These factors are of critical importance when deciding treatment.
Treatment
It is important to consider the gradation of injury when developing a treatment algorithm for scapholunate ligament injury. The Garcia-Elias staging system22 provides an overview of some of the available treatment options.
Garcia-Elias Stage 1: Partial Scapholunate Ligament Rupture
Partial ruptures of the scapholunate ligament typically involve the palmar and membranous portions and tend to spare the dorsal fibers in most stage 1 cases. There is no carpal malalignment. Surgical treatment options include percutaneous Kirschner-wire stabilization of the scapholunate joint, arthroscopic débridement of torn ligament edges with electrothermal ligament shrinkage, or arthroscopic capsulodesis.23,24
Garcia-Elias Stage 2: Scapholunate Dissociation, Reparable
There is complete disruption of the scapholunate ligament, without postural deformity of the scaphoid or lunate in stage 2. These patients may present with dynamic diastasis of the scapholunate joint during wrist loading. Treatment options include arthroscopic-guided closed reduction with percutaneous stabilization, open repair of the scapholunate ligaments if performed within 6 weeks of injury4 (augmented with either Kirschner wire, temporary screw placement, or suture stabilization), and arthroscopic capsulodesis. Arthroscopic dorsal and palmar ligament repairs have been described also.25,26
Garcia-Elias Stage 3: Scapholunate Dissociation, Irreparable, Normally Aligned Scaphoid and Lunate
In stage 3, the scapholunate ligament is completely disrupted and nonrepairable and carpal alignment is maintained. Treatment options include a capsulodesis or reconstruction.
A dorsal capsulodesis has been described to help prevent the scaphoid from collapsing into flexion and pronation. Three methods have gained popularity. The Blatt procedure is performed by creating a checkrein of a proximally based strip of the dorsal capsule to prevent scaphoid flexion.6,27 The Mayo capsulodesis takes half of the dorsal intercarpal ligament, releasing it from the triquetrum and redirecting and inserting it onto the dorsum of the lunate.28 The Szabo procedure involves advancement of the dorsal intercarpal ligament from its dorsal ridge on the scaphoid to a more radial position on the scaphoid neck.29,30 Long-term results for these three capsulodesis options have been satisfactory, although carpal collapse may still occur. A shortcoming common to all capsulodesis procedures is that they are all nonanatomic.
Soft-tissue reconstruction of the dorsal scapholunate ligament has been described by taking a strip of either the dorsal intercarpal ligament or dorsal radiocarpal ligament, preserving the triquetral attachment, débridement of the cortices of the scaphoid and lunate down to bleeding bone, and then reinserting onto the dorsal and ulnar corner of the proximal scaphoid with a bone anchor. A review of this technique showed that, at 86 months, it did not reliably prevent collapse or scapholunate advanced collapse arthritis.29
Garcia-Elias Stage 4 Scapholunate Dissociation With Rotatory Subluxation of the Scaphoid, Reducible
Stage 4 involves the complete loss of the scapholunate ligament, with additional injury to the critical stabilizers. This allows the scaphoid to flex, pronate, and potentially subluxate dorsally; however, the lunate remains normally aligned. Because the carpus
is reducible, treatment options have included tendon graft reconstruction of the dorsal scapholunate ligament complex, volar/dorsal scapholunate graft reconstruction, scapholunate axis graft reconstruction, or screw fixation.
is reducible, treatment options have included tendon graft reconstruction of the dorsal scapholunate ligament complex, volar/dorsal scapholunate graft reconstruction, scapholunate axis graft reconstruction, or screw fixation.
The Brunelli technique involves reducing the scaphoid, passing a distally based strip of the flexor carpi radialis tendon through the scaphoid and anchoring it to the dorsal rim of the distal radius with Kirschner wire stabilization.31 The loss of wrist flexion and the propensity for the development of radio-scaphoid osteoarthritis led to various modifications. The three-ligament tenodesis was one of these modifications.
The procedure did not cross the radiocarpal joint and reconstructed the STT ligaments, the dorsal portion of the scapholunate ligament, and dorsal scaphotriquetral ligament. The reduction-association of the scapholunate joint procedure involves removal of the articular cartilage between the scaphoid and lunate, reduction of the scaphoid and lunate, and transfixion with a headless screw, performed either open or arthroscopically.32,33 Some series have demonstrated promising results,34 although concerns have been raised regarding hardware failure and carpal collapse.35 Another concern was raised in a 2019 study36 that demonstrated the high variability of the location of the rotation axis of the scapholunate joint, and its variation with different motions of the wrist, indicating that a fixed axis is nonanatomic.
Other techniques use the axis methodology but incorporate a tendon graft. The scapholunate axis method uses a tendon graft passed between the scaphoid and lunate along the axis of rotation in the sagittal plane. It is secured in the scaphoid with an interference screw, and in the lunate with a graft anchor.37 The scapholunotriquetral technique uses a strip of the flexor carpi radialis passed through the scaphoid axis as in the three-ligament tenodesis, but then a second tunnel is drilled through the center of the lunate and through the triquetrum. It is secured with an interference screw in the triquetrum and the tail of the graft is brought dorsally to reconstruct a portion of the dorsal intercarpal ligament.38
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