Evaluation and Management of Carpal Instability

This paper sets out to review the past and current literature on the evaluation and management of the various types of carpal instability. Carpal instability has many sub-types, and therefore, its evaluation and management widely differ. There are recent studies that indicate that while MRI and MR arthrography are the mainstays for evaluation, certain CT and radiographic measurements may be better at diagnosing scapholunate ligament tears. In addition, recent research has proposed multiple sonographic protocols in the evaluation of carpal ligament pathology. However, the comparison of ultrasound to other imaging modalities is limited. The research for operative and non-operative management of carpal instability is limited and often guided by expert opinion. To date, no studies exist on the use of novel injection techniques to treat carpal instability. Evaluation of carpal instability is evolving, and ultrasound may play an increased role. Evidence regarding non-operative management of carpal instability is limited.


Introduction
Carpal instability is an important cause of acute and chronic wrist pain and can lead to long-term dysfunction if not managed appropriately. Carpal instability is caused by the disruption of key ligaments or articular geometry from either fractures, chronic repetitive overuse injuries, or less commonly rheumatological conditions [1]. If these are unaddressed, ligamentous laxity and instability can ensue. Injury patterns are commonly from sportsrelated hand or wrist injuries, acute trauma, and occupational activities typically stemming from a fall on an outstretched hand [2]. In sports, it has been reported that up to 25% of injuries involve the hand and wrist [3]. Recognizing, diagnosing, and treating these injuries early is key to the prevention of long-term disability [4]. While certain instability patterns require surgical attention, there is a paucity of literature regarding non-operative options. This review focuses on the pathoanatomy, evaluation, and treatment of carpal instability, with special attention paid to recent studies regarding non-operative indications and treatment.

Anatomy
The wrist is composed of eight carpal bones that abut the radius and ulna. The bones are arranged into proximal and distal rows. The proximal consists of the scaphoid, lunate, and triquetrum, with the hamate, capitate, trapezoid, and trapezium in the distal row, and the pisiform, a sesamoid bone, sitting palmar to the triquetrum within the flexor carpi ulnaris tendon [5]. The proximal row is mobile as it conforms to the radius and ulna while the distal row is rigid and functions to articulate with the metacarpals [5]. The rows are stabilized by interosseous ligaments and secondary stabilizers known as the capsular ligaments, consisting of the "proximal palmar V" and the "dorsal V" groups ( Fig. 1) [6]. Typically, the interosseous, or intrinsic, ligaments originate and insert between carpal bones, whereas the extrinsic ligaments connect the carpal bones to the radius and ulna. Attachments and functions of the extrinsic ligaments are beyond the scope of this review; however, it is important to note that disruption of both intrinsic and extrinsic ligaments simultaneously result in instability visible at rest without dynamic motion, while sole intrinsic ligament disruption may not initially be apparent without stress or dynamic imaging [7].
The most common ligament injuries resulting in carpal instability clinically involve the scapholunate interosseous ligament (SLIL) and lunotriquetral interosseous ligament (LTIL), with the latter being less frequently injured [7]. These two ligaments have three bands, the dorsal, central, and volar, with the dorsal band being the most robust and primary stabilizer for the SLIL and the volar being important for rotational stability [7]. Thus, disruption of the dorsal band of the SLIL enables dorsal intercalated segment instability (DISI), and the disruption of the volar band of the LTIL creates volar intercalated segment instability (VISI) which will be further discussed in a subsequent section [7]. Additionally, the wrist anatomy is further characterized by the arcs of Gilula, which are helpful in the evaluation of wrist anatomy on radiography and suggestive of wrist injury when they are disrupted. The first arc traces the proximal surface of the proximal row at the articulation with the radius and ulna. The second arc follows the distal surface of the proximal row at its articulation with the distal row. Finally, the third arc traces the proximal surface of the distal row [8].

CID: DISI and VISI
CID refers to an instability pattern within the proximal row of carpal bones. These injuries typically result from hyperextension or hyperpronation injuries [9]. In general, the scaphoid has a tendency to flex while the triquetrum has a tendency to extend. When both the SLIL and LTIL are intact, this results in a neutral lunate. However, if one of these ligaments is disrupted, the force from the other intact ligament "wins" causing a dorsal or volar tilt to the lunate. Within Fig. 1 Schematic display of intracapsular carpal ligaments. a Palmar "V" ligaments. The proximal palmar "V" consists of the palmar radiolunotriquetral ligament (pRLTL) on the radial side and the ulnolunate (ULL) and ulnotriquetral ligaments (UTL) on the ulnar side. The radial leg of the distal palmar "V" is formed by the radioscaphocapitate (RSCL) and scaphocapitate ligament (SCL), while the triquetro-capitoscaphoid ligament (TCSL = arcuate ligament) constitutes its ulnar leg. b Dorsal "V" ligaments. In contrast to the palmar side, the ligamentous anatomy of the dorsal carpus resembles a horizontal "V" with the dorsal radiolunotriquetral ligament (dRLTL) as the proximal leg and the intercarpal dorsal ligament (ICDL) as the distal leg. (with permission) the proximal row, scapholunate injury is the most common disruption, representing a spectrum of pathology including SLIL sprain or tear, DISI, and scapholunate advanced collapse (SLAC) [7]. This spectrum of pathology generally begins with the compromise of the dorsal component of the SLIL, the main stabilizer of the complex, usually through a fall on an outstretched hand (FOOSH) or other forced wrist extension injury, though atraumatic causes are also possible (calcium pyrophosphate deposition disease, rheumatoid arthritis, or neuropathic arthropathies). Regardless of the cause, the disrupted SLIL leads to abnormal kinematics of the carpal bones given the lack of restrained lunate over the scaphoid, which may be seen clinically and on imaging studies. This generally leads to an extended posture of the lunate over the scaphoid called DISI (as described above). Also included in this category of CID are scaphoid nonunion and Kienbock's disease IIb and IV [9]. Continued chronic loading of the wrist in the setting of pathological mechanics leads to degenerative arthritis at the radioscaphoid articulation as well as midcarpal instability consistent with progression to the true SLAC wrist. There are several recognized grading systems for this degenerative cascade based on the number and severity of joints involved and the level of midcarpal instability that are beyond the scope of this review.
The second most common cause of proximal row instability is LTIL injury. Given the importance of the volar band to the lunotriquetral interface, disruption results in VISIreferring to a volar tilt of the lunate with respect to the scaphoid. This condition is sometimes referred to as palmarflexed intercalated segment instability (PISI). Of note, VISI/ PISI is commonly associated with triangular fibular cartilage complex (TFCC) injuries involving axial load applied to a pronated wrist [6].

CIND
CIND refers to instability patterns of the entire proximal carpal row with respect to the radiocarpal articulation or the distal carpal row without proximal row dissociation [10]. This pattern of injury is defined by its clinical findings of snapping or clicking with the articulation of the mid-carpal joints during extreme ulnar deviation. Thereby, this pattern can be created by injury at either the radiocarpal and/or the midcarpal joint [10]. Similar to CID, CIND has a classification involving CIND-VISI and CIND-DISI and combined and adaptive patterns. In CIND-VISI, the proximal row kinematics are disrupted due to injury of the scaphotrapezium trapezoid (STT), scaphocapitate, triquetrum capitate, or triquetrohamate ligaments. Consequently, the proximal row will remain palmar flexed during ulnar deviation and the distal row sags volar until the wrist reaches further ulnar deviation, at which the proximal row rotates and the definitive "catch-up click" occurs [11]. In CIND-DISI, the click originates during ulnar deviation occurring from dorsal subluxation of the capitate, while the proximal row extends during ulnar deviation. This is due to injury or failure of the dorsal intercarpal ligament and/or the radioscaphocapitate ligament [11,12]. Given the location of ligamentous disruption, in a retrospective case series by Fok et al, the most common fracture patterns in acute wrist trauma that produced CIND included fractures of the radial styloid and the dorsal rim [10].

CIND-Combined
CIND combined exhibits features of both CIND-VISI and CIND-DISI, resulting from injury or laxity of the volar and dorsal ligaments. Similar to CIND-VISI, when the patient's hand is moved from radial to ulnar deviation, the proximal row clicks while moving from a flexed posture to an extended posture. Similar to CIND-DISI, at further ulnar deviation, dorsal subluxation of the capitate occurs. CIND combined typically occurs from extension injuries and repetitive overuse sports or tasks that involve gripping and striking, and in populations with greater ligamentous laxity [13].

CIA and CIC
CIA is a pattern that occurs due to abnormalities extrinsic to the carpus, such as distal radius fractures with derangement of extrinsic ligaments [11]. Intrinsic ligaments are typically intact, though they may have slackened; the intrinsic distances between carpal bones are decreased, and consequently, if ligaments are injured, it is due to attrition rather than a discrete tear [14]. Common causes of injury are fractures to the distal radius, fracture dislocations, distal radius malunions, and Madelung's deformity [14]. CIC is a combination of both CID and CIND pathologically; however, CIC has a different injury etiology. There are four categories of CIC: dorsal perilunate dislocations, dorsal perilunate fracture dislocations, palmar perilunate dislocations, and axial dislocations [11]. Each of these is associated with their own pathomechanics secondary to injury to the ligament or ligament complex of interest, which is beyond the scope of this review [11,15].

Epidemiology
Wrist pain and injury are fairly common complaints; however, high-level studies evaluating the incidence of carpal instability are lacking. One study by Tang reports an incidence of carpal instability of 30.6% in 132 patients presenting for a distal radius fracture [16]. Some investigations suggest that 10% of wrist injuries and 19% of sprains without fracture result in perilunate instability [17,18]. A more recent study by O'brien and colleagues investigated carpal instability in patients presenting to the emergency department for wrist pain following a fall on an outstretched hand found a cumulative incidence of 44% within two years of injury [19]. These included scapholunate ligament instability (24%), lunotriquetral instability (24%), and midcarpal instability (14%). Another important finding of this study was that at up to 2 years after injury, there remained no significant relationship between clinical instability and pain and function. This suggests that many of these cases of instability likely persist undiagnosed until they progress to a symptomatic state. Unfortunately, this progression generally involves progression to DISI or even arthrosis which could limit treatment options. Despite this study's relatively low response rate to follow-up questionnaires, this may be the largest study investigating incidence of carpal instability in the traumatic setting.

Clinical Presentation: History and Exam
Most cases of acute carpal instability begin with a traumatic injury to the hand, especially a fall on an outstretched hand [20]. In the acute period, these patients generally report increased wrist pain, swelling, and mild instability. Noting the mechanism of injury is valuable in determining potentially affected structures. The most severe injuries may result in complete loss of hand function due to frank instability about the wrist during regular daily activities [21]. Many patients, especially those with initially mild instability, may present with subacute or chronic symptoms that have progressed, complaining of continued pain, loss of grip strength, clicking, catching, or other mechanical symptoms. Unfortunately, the relationship between instability, pain, and function is often low, especially in those with subacute symptoms [19]. Late detection of instability can lead to the progression of the deformity and early arthritic changes [22]. Some cases of carpal instability may concurrently present with a ganglion cyst. Carpal instability can also occur without trauma in the setting of rheumatological conditions such as calcium pyrophosphate dihydrate crystal deposition disease arthropathy and rheumatoid arthritis.
Examination of the wrist should begin with an inspection. For carpal instability, obvious bony deformity, especially compared to the unaffected, side is crucial. For acute injuries, a neurovascular exam is always necessary, as neurological deficits or pulselessness require emergent attention. Palpation over specific structures, especially the proximal carpal row and the ligaments of interest, such as the SLIL or LTIL, may represent specific sites of injury. Diminished active range of motion with wrist flexion/extension or ulnar/ radial deviation compared to the contralateral side or pain at the end range of motion could all signal carpal instability.
Multiple dynamic exams have been described to test for carpal instability. The scaphoid shift or Watson test is used to confirm scapholunate ligament instability [23]. This test uses the oppositional force of the examiner's thumb while translating the wrist both volar and radial to see if the scaphoid translates dorsally with pressure. Removing pressure will result in a "clunk" if it displaced, signaling a positive test and has a mean positive likelihood ratio of 4.7 for scapholunate injury [24]. The ballottement test for the lunotriquetral joint entails placing the thumb on the triquetrum with radial pressure in a rocking or balloting motion [25]. A painful response or reproduction of instability is considered positive [26]. Unfortunately, this test is not specific to lunotriquetral instability and has a positive likelihood ratio of 1.12 only [24]. The shuck test is another test for the LQ ligament with a similar utility to the ballottement test in which the examiner repeatedly "shucks" the LQ joint [25]. The midcarpal shift with a "catch up clunk" is a common test for midcarpal instability. A positive test causes a midcarpal clunk and pain as the examiner provides palmar pressure and deviates toward the ulna in pronation and extends the wrist [27,28]. This test has a mean positive likelihood ratio of 2.67, making it a highly recommended test for midcarpal instability [24]. It is important to compare findings to the contralateral wrist, since some patients may have a baseline and therefore symmetric laxity.

Diagnosis/Imaging
Imaging modalities available to visualize carpal instabilities include radiography (x-ray), computerized tomography (CT), cone beam CT, magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA), and sonography (ultrasound). Radiography is often the first line imaging for the diagnosis and evaluation of carpal instability. Anteriorposterior and lateral radiographs are recommended [29]. These views allow tracing of the Arcs of Gilula, where disruption of any of the three lines supports the diagnosis. These also can provide measurements of the scapholunate interval, scapholunate, and radiolunate angles [7]. For further evaluation, stress and dynamic views can help evaluate scapholunate joint instability. These images can be used to classify injury according to the European Wrist Arthroscopy Society (EWAS); however, their utility has only been shown for higher severity scapholunate instability [29]. While the cutoff for scapholunate widening on x-ray has been debated, widening of > 2 mm has been correlated with a higher Geissler grading in a study by Rachunek et al. [30]. Based on their findings, they proposed an algorithm for the classification of SLD in which those with < 1.9 mm of scapholunate widening on static PA views, < 2.7 mm in ulnar inclination views, and a scapholunate angle of < 63° without tenderness as unlikely for SLIL injury [30]. Novel devices have been created to better measure SLIL instability, but these have not become part of standard practice to date [31]. Therefore, in those complex cases when carpal pathomechanics remains in question after static imaging, we recommend the use of fluoroscopy to dynamically evaluate the motion of carpal structures for concerns of instability, and live imaging and recording should be available [32]. For scapholunate instability, there is a reported sensitivity of 90%, specificity of 97%, and diagnostic accuracy of 93% [29]. Additionally, intra-articular injections of non-ionic iodine-based positive contrast medium are the best method to elucidate interosseous ligament injuries as contrast extravasation into noncommunicating compartments is indirect proof of ligamentous injury [32].
Computerized tomography has two major benefits for consideration in the diagnosis of carpal instability: [1] latephase diagnosis, as this modality visualizes articular surfaces, cartilage abnormalities, and subchondral sclerosis in the radioscaphoid and midcarpal joints; and [2] visualization of occult scaphoid fractures, especially on high-resolution CT, as scaphoid injuries are a source of CID given the scaphoid's location in the proximal row [6]. A recent study compared multidector CT (MDCT-traditional) to 3D-conebeam CT, reporting similar image quality at lower radiation doses, while also providing a more comfortable imaging position for patients [33]. Additionally, a recent prospective study evaluated 305 patients for acute wrist trauma and compared cone beam CT vs. scout x-ray and found good intra-observer reliability given similar wrist positions and protocols [34]. Specifically for scapholunate interosseous tears, CT arthrography has higher diagnostic accuracy than MRI [29]. An interesting frontier currently being investigated is the utility on the diagnostic accuracy of 4D CT for insatiable scapholunate dissociation [35]. Finally, a prospective study of 160 patients with suspected scapholunate ligament tears comparing MR, CT, and x-ray found that the posterior radioscaphoid angle on CT was most valuable for differentiating torn and partially torn scapholunate ligaments [36 •]. MRI and MRA are used similarly to CT as a further investigative tools for carpal injuries and instability. The I-WRIST international wrist radiologic evaluation for the instability of the scapholunate joint and the DRUJ/TFCC 2021 group states in their consensus statement that MRI and MRA can delineate most extrinsic and intrinsic ligaments. MRA was preferred to MRI based on providing better diagnostic accuracy for SLIL tears than conventional MRI [29]. It must be noted that both CTA and MRA were equally recommended for cartilage defects. MRI and MRA are also helpful to evaluate for concurrent DRUJ injury which is commonly associated with carpal instability [1]. A recent case report of ten posttraumatic patients with either CIND-DISI or CIND-VISI found that all ten patients had MRI evidence of radiolunate ligament rupture [37].
Ultrasound is another useful imaging modality for evaluating carpal instability and is gaining popularity as it allows for high-resolution point of care and dynamic evaluation. Due to the fact that ultrasound requires user competency and a strong knowledge of the anatomy of the wrist, there are newer publications which outline scanning techniques and anatomy in a comprehensive fashion [38, 39•, 41]. Wang et al. have proposed specific protocols to visualize both the intrinsic and extrinsic ligaments both volarly (Fig. 2) and dorsally (Fig. 3); however, this paper did not examine the validity of any of these diagnostic techniques in comparison to MRI [39•]. While the I-WRIST work group does not recommend ultrasound for the standard workup for SLJ instability due to its low sensitivity and necessity for an experienced and subspecialized examiner, the authors do note that ultrasound can help delineate radioscaphocapitate ligament, long radiolunate, dorsal radiocapitate, and dorsal intercarpal ligament ligamentous injuries. Additionally, the work group notes that dynamic evaluation of SLJ instability for Garcia-Elias staging has equal recommendation between dynamic fluoroscopy, ultrasound, kinematic CT, and kinematic MRI as there is not enough data to implicate superiority [29]. Kasiyama et al. attempted to create an ultrasound-based criteria for SLIL injuries post distal radius fractures, comparing ultrasound to arthroscopy, finding that for their 40 patients, ultrasound had a high specificity but low sensitivity for SLIL diagnosis [40]. Additionally, Gitto et al. in 2017 outlined a comprehensive scanning technique for various intrinsic and extrinsic ligaments [41]. There have also been studies involving scapholunate injury detection with sonography due to its frequency of occurrence in wrist injuries and consequential instability. Traditionally, it has been shown that ultrasound has a high specificity and high accuracy, but low sensitivity in identifying scapholunate ligament injuries [42]. Figure 4 demonstrates sonographic findings in a patient with a surgically confirmed SLIL tear. The corresponding intra-operative findings can be seen in Fig. 5. A recent cohort of 40 patients with ten normal SLL and 30 suspected or confirmed SLL injuries were evaluated by ultrasound compared with either MRI or arthroscopy, and the authors found reliable measurements by sonography of 5 mm, 2 mm, and 5.1 mm for dorsal, middle, and palmar aspects of the SLL, respectively, for a normal wrist, compared to 6.4 mm, 3 mm, and 6.3 mm for an injured SLL [43]. A difference in distance between the injured SLL and contralateral normal SLL of more than 1.15 mm dorsally had the highest true-positive rate. No studies yet have established standardized static or dynamic measurements for an injured SLL [44]. In addition, there is no consensus regarding the optimal dynamic ultrasound test for the SLL.

3
Techniques described include wrist radial and ulnar deviation, clenched fist, and pencil grip views. In our experience, wrist radial and ulnar deviation allow for the greatest and most reliable stress on the SLL. Outside of imaging for carpal instabilities, US was used to measure scapholunate interosseous ligament finding that in athletic volunteers the dorsal SLIL is thicker and longer in the dominant vs. non-dominant hand-suggesting the accuracy and repeatability of locating the SLIL [45]. Finally, ultrasound can accurately evaluate for dorsal ganglion cysts which can present with an injured SLL.
Ultrasound is an emerging imaging modality that is gaining utility for the evaluation of carpal instability.

Indications for Operative and Non-Operative Management
Given that carpal instability patterns exist on a spectrum, early identification is important due to the disability associated with an unstable wrist and the long-term consequences of an undiagnosed or untreated injury (e.g., progression to scapholunate advanced collapse, early osteoarthritis). It is therefore important to recognize which types of injury can be treated operatively or non-operatively. Unfortunately, there is limited data available to help with these clinical decisions aside from case series and expert opinion. Furthermore, there is varying consensus amongst hand specialists on how to best manage the variation within carpal instability patterns. Clinicians must therefore strongly hold the consideration of the etiology, chronicity, symptom severity, location, and instability pattern when deciding on the appropriate treatment for their patient [46].

CID
CID is, by definition, a biomechanically less stable condition than CIND, and is thus less likely to respond to conservative treatments without correcting the underlying pathomechanics [47].
A scapholunate ligament injury is the most common cause of CID. Traditionally, it is thought that a SLIL injury will progress to a SLAC. This however may be nuanced as grading the injury may provide guidance for operative vs. non-operative management. Conservative treatment may be Fig. 3 Proposed algorithm for scanning dorsal wrist ligaments. Licensee MDPI, Basel, Switzerland appropriate for Geissler grades I and II, as a case series of 11 patients followed for 7 years with scapholunate injuries did not show progression to DISI or SLAC [48]. Conservative treatments in the acute phase focus on proprioceptive and neuromuscular training and may improve sensorimotor function long term [49]. However, given the gross instability of higher-grade injuries, failure to treat them surgically in the acute or subacute phase injury can lead to deterioration of hand function and acceleration of post-traumatic arthritis [50]. In patients who are not fit for surgery or who prefer not to undergo surgical intervention, nonsurgical treatment options exist, although evidence is limited. This typically includes immobilization with bracing, topical or oral medications such as NSAIDs, and intraarticular corticosteroid injection for symptom relief [51]. If these measures do not provide symptom relief then surgical treatment is warranted either with a repair or reconstruction. The decision to repair or reconstruct is complex and beyond the scope of this review. In general, however, repairs are considered for more acute injuries and reconstructions for more chronic injuries. The choice can also depend on the ability to reduce the deformity and the presence or absence of degenerative changes [52].
In lunotriquetral instability, there is a similar paucity of evidence. The majority of case series available in the literature report outcomes of patients with chronic symptoms that had failed conservative treatment and moved to operative management, thus our understanding of the natural course of symptoms and the likelihood of success with conservative treatments remains low [53]. Reagan and colleagues published a landmark paper in 1986 of six patients with chronic lunotriquetral instability. Of those, four patients had non-dissociative tears, and one of those became asymptomatic following conservative treatment with either casting or splinting. The two with dissociative injuries required surgical treatment [25].

CIND
Management for CIND is generally nonsurgical and typically successful in symptomatic patients. However, it should be noted that this varies based on subtype. Non-surgical treatment should focus on educating the patient about the condition. This includes an explanation of anatomy and biomechanical forces that have led to instability. Activity modification is often a mainstay of treatment once patients understand which movements may lead to worsening symptoms. Topical or oral NSAIDs and bracing may be helpful [13]. Similar to CID, the literature for CIND often lacks a direct comparison between surgical and non-surgical treatments. Despite this, case series reporting outcomes on both patients who improved with conservative treatment and those requiring surgical treatment do provide important information to guide management. One study by Urbanschitz et al. reports 10 patients who developed post-traumatic CIND. Three of the ten patients improved with conservative treatment alone (all three CIND-DISI) while seven others required further operative management [37]. Another study by Wright et al. reports the outcomes of 45 patients with CIND [28]. Seven underwent non-operative management with splints (usually ulnar gutter splint with a pisiform boost), NSAIDs, and occasional steroid injections. They also underwent a structured Fig. 4 The long-axis view of the SLL shows a hypoechoic cleft in the middle of the ligament consistent with a complete tear. There is also evidence of periosteal avulsions of the lunate. S, scaphoid; L, lunate therapy program focusing on strengthening and avoiding provocative maneuvers. The other 38 patients underwent primary operative treatment. There was no significant difference between operative and non-operative management with only ~56% of patients in each group achieved "good or excellent results." However, there was significant heterogeneity in subtype and surgical treatments performed in the surgical group. Overall, the sparse literature on conservative treatment of carpal instability suggests that those with obvious, more severe instability found in CID will benefit from early surgical treatment. These surgical options often include salvage-type surgery, such as proximal row carpectomy or midcarpal fusions. Those with CIND may benefit more from conservative treatment, but determining which patients will improve vs. progress to surgical intervention is difficult.
Importantly, the landscape of conservative treatments for joints, tendons, and ligament pathology throughout the body has broadened in recent years to include a variety of novel injections beyond corticosteroids, such as platelet-rich plasma (PRP) and prolotherapy. The use of these novel treatments on ligamentous injury has focused mainly on the anterior cruciate ligament, and the evidence for their use in carpal instability remains limited [54]. There are several studies examining novel treatments in the wrist, especially carpometacarpal (CMC) osteoarthritis (OA). For example, one study by Abselsabor Sabaah et al. found that patients receiving either PRP or corticosteroid injections for CMC OA experienced a similar improvement in pain in the acute phase [55]. Another trial examining pain due to trapeziometacarpal OA found that the PRP injection group had improved pain relief up to 12 months following injection when compared with corticosteroids [56•]. Reeves and Hassanein studied a small cohort of patients with OA of a variety of joints of the hand, including the CMC and trapeziometacarpal joints, and found that prolotherapy provided similar pain relief to saline placebo at various time points up to 6 months following injection [57]. One observational study investigating PRP for a variety of musculoskeletal problems of the hand included a patient with wrist pain found to have a dorsal intercarpal ligament sprain. This patient received a series of two PRP injections over 2 weeks which resulted in a 95% improvement in pain that persisted over nine months of follow up [58]. While it is useful to recognize that these novel treatments exist and are being used for a variety of musculoskeletal pathology, the evidence for their use for carpal instability is lacking.

Conclusion
Carpal instability is a complex condition involving variable interactions between the wrist, carpal, and metacarpal structures. Knowledge of these interactions enables us to better evaluate and manage patients in the early, middle, and late phases of injury to ultimately prevent conditions of chronic pain and dysfunction. The diagnosis of these carpal instability patterns continues to improve with new imaging techniques, especially as the use of and interest in ultrasound continues to grow in popularity and availability. Surgical indications for CID are often clearer, while the literature and evidence for CIND's management are still in its early phase. Currently, there is limited evidence regarding the use of novel injection techniques for wrist pain and no specific data supporting its use in carpal instability.

Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
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