Wrist Instability or carpal instability occurs when takes wrist is damaged by trauma, chronic inflammation or anatomical alterations like ulnar variance and neoplasms. Injuries to the ligaments of the wrist represent a broad spectrum of pathology.
There are a number of ligaments of the wrist maintaining a complex articulation of carpal bones. Ligament injuries are often implied by gross radiographic alterations but wrist instability patterns frequently present only after some time has elapsed.
Wrist instability or wrist ligament injuries are classified by radiographic pattern, behavior, and chronicity. The patterns of instability are changes produced within the carpus by ligamentous or bony disruptions.
A wrist is considered stable when the modifications brought about by the various forces acting on it are restored when the said forces stop to act.
In contrast, the alteration of one or more of the structures responsible for stability lead to preclusion of the restoration of the order and leads to misalignment and a decrease in performance of the organ.
This happens when takes wrist is damaged by trauma, chronic inflammation or anatomical alterations like ulnar variance and neoplasms.
Types of Wrist Instability
Wrist instability can be due to various causes and depending upon its behavior. Wrist instability can be of many types.
Classification of Wrist Instability has been approached by various authors.
Dynamic and Static Instability
Taleisnik introduced the concept of static and dynamic instability.
Carpal instability often depends on capsular integrity and on the interosseous ligaments. It can be
- Dynamic instability – This occurs in incomplete injury. The wrist maintains normal alignment at rest but will collapse under applied load.
- Static Instability – This occurs in complete injury to the structure involved. This kind would show abnormal intercarpal alignment on static radiographs.
The static deformity is always present irrespective of whether the wrist is in the neutral position or under some stress.
With a dynamic instability, x-rays reveal abnormal carpal ligament only one stress is applied or when the wrist is in a non-standard position. Dynamic and static instability can be thought of as different stages in a clinical spectrum of partial or complete ligament injury.
Frequently, but, not exclusively, nondissociative instabilities are static. [see below]
Volar and Dorsal Intercalated Segment Instability or VISI
Volar Intercalated Segment Instability
VISI is said to be present when there is volar flexion of the lunate>15 degrees [in relation to the longitudinal axis of the radius and capitate] when the wrist is in a neutral position. This occurs because of loss of ulnar support from the triquetrum and the lunate has a tendency to flex.
VISI is found in
- Lunotriquetral dissociation
- Nondissociative carpal instability
- Carpal instability complex
Dorsal Intercalated Ligament Instability or DISI
The condition is also termed as dorsal instability.
Massive ligament disruption at the time of injury, as may occur in perilunate or lunate dislocations, or gradual attrition of the secondary extrinsic stabilizers leads to an abnormal extension of the lunate and carpal collapse after scapholunate dissociation.
Capsular contracture may serve to fix the deformity.
So all this means is that in DISI, the lunate is angulated dorsally. The relative alignment of the scaphoid to the lunate forms angle of 45 degrees. When the scapholunate angle is more than 70 degrees, ligaments between the scaphoid and lunate become nonfunctional. In such situations, the lunate becomes extended and maintains the position even during radial deviation.
This does not allow normal rotation and the spatial adaptability of the proximal row. A DISI deformity is seen in
- Scaphoid fractures
- Scapho-lunate dissociation
- Perilunate dislocation
Instability Based on Motion Patterns
Patterns of the instability can be further described based on the normal patterns of motion. Both the proximal and distal carpal rows have particular patterns of motion within the rows (ie, relationship of the scaphiod relative to the lunate).
This normal motion has been termed “associative.”
- A disruption of the normal kinematic within a row is a dissociative instability. Dissociative carpal instabilities any result from a disruption of any of the bony or ligaments components of the wrist.
- Disruption between rows, while the alignment within each row remains normal, is a nondissociative instability.
Non dissociative carpal instability [CIND]
Carpal instability, nondissociative (CIND), includes instability patterns that occur between a carpal row and the adjacent transverse osseous structures.
It is defined as an alteration in the articular relationship between the two carpal rows, while the individual joints between the skeletal elements of each row are maintained.
In these patterns, there is no dissociation within the carpal rows (ie, competent interosseous ligaments). These instability patterns include
- Midcarpal instabilities
- Ulnar translocations [ the carpus moves ulnar wards. Seen in Rheumatoid arthritis and Madelung deformity.]
- Capitolunate instability – Palmar subluxation of the capitate on the lunate.
- Proximal carpal row instabilities.
Type I- Palmar midcarpal instability
- Secondary to an injury to the palmar midcarpal ligaments [Scaphotrapeziotrapezoid, triquetrohamate and triquetrocapitate ligaments
- Palmar subluxation
Type II- Dorsal Midcarpal instability
- Hyperlaxity of midcarpal and radiocarpal ligaments.
- Dorsal or palmar subluxation
Type IV – Extrinsic midcarpal instability
- Often due to malunited radius
- Dorsal angulation
- Progressive stretching of the radiocapitate ligaments.
- Dorsal subluxation
CIND can occur secondary to fractures, disruption or laxity of extrinsic ligaments, or both.
The most frequent reasons for nondissociative carpal instability are the collapse of the capsule and that of the intercarpal ligaments mostly following rheumatoid arthritis. Trauma is another cause.
Dissociative Carpal Instability
Dissociative carpal instability is present when there is instability between individual bones of a carpal row.
Most common causes are fracture or ligament disruption.
Dorsal intercalated segment instability and Volar intercalated segment instability are included in dissociative instability. This is because there is disruption of the ligament bond or the bone structure between the lunate and one or both of the adjacent carpal bones.
Examples of dissociative carpal instability are
- Scapholunate instability
- Lunotriquetral dissociation
Complex Carpal Instability[CIC]
Carpal instability, combined or complex (CIC), is a combination of two or more specific CID or CIND patterns. Example of the complex instability includes perilunate dislocations, radiocarpal instability with axial instability, and scapholunate dissociation with ulnar translocation.
Adaptive Carpal Instability [CIA]
The instability does not reside in the carpus but is due to sequelae of radial fractures with dorsal displacement in the epiphyseal region.
Adaptive carpal instability results from the repositioning of the carpus in response to a change into bony architecture.
One of the more common etiologies of an adaptive instability is the dorsally angulated distal radius malunion, which result in a compensatory DISI of the secondary to scaphoid nonunions, lunate malunions, or Madelung’s deformity.
Clinical Presentation and Evaluation of Wrist Instability
The history of presentation would range from high-energy polytrauma to low-energy mechanisms that cause mild, protracted symptoms. Wrist ligament injuries can range from subtle instability patterns as the result of attrition to acute and chronic injuries. Evaluation for wrist ligament injuries and resultant instability is mandatory in all patients with wrist symptoms, whether or not a recent traumatic event is identified.
Even gross carpal malalignment may be overlooked or misdiagnosed at the time of initial injury and radiographic examination.
The most devastating of these injuries, lunate or perilunate dislocations, comprise only 10% of all carpal injuries and usually occur as a result of high-energy injuries. of these, transscaphiod perilunate fracture-dislocations are the most common, representing 61% of all perilunate dislocations in one study.
The patient may present with pain and/or clunking Some patients present quite late with deformity already present. Most of the patients present with painful clunking on the ulnar side of the wrist during activities that involve active ulnar deviation.
There would be a history of asymptomatic wrist clunking for many years. There could be a history of hyperextensive injury or there could be the absence of any significant trauma.
Ligamentous laxity and a hypermobility should be ruled out.
Being subtle the deformity patterns may be difficult to detect in early stages.
These components would affect treatment decisions.
In the acute high-energy injury, physical examination may reveal gross deformity, swelling, ecchymosis, or lacerations. The carpal injury may be overlooked or considered a low priority in this setting because of the presence of other more demanding injuries. Median nerve examination should be particularly done as up to 25% of the cases of acute carpal tunnel syndrome.
Palpation for specific sites of tenderness, and a careful neurologic/vascular examination, especially with sensory testing, are mandatory.
Point tenderness over specific carpal ligaments, such as the scapholunate interosseous ligament or the lunotriquetral interosseous ligament may represent injuries to those ligaments.
Patients with injuries caused by subacute or chronic processes may present with pain, popping catching, or symptoms of secondary degenerative changes.
In these patients, a more detailed examination of the carpus is performed. The active and passive range of motion is assessed and recorded. Direct palpation over the scapholunate, lunotriquetral, triangular fibrocartilage complex and midcarpal joints may greatly narrow the differential diagnosis.
Specific maneuvers or Special Tests
These are done to check for ligamentous disruption of the wrist may also help determine the extent of the injury. These should be done in sytematic way, beginning on radial side Watson’s scaphoid shift test, followed by the midcarpal shuck test and the lunotriquetral ballottement test.
Watson Scaphoid Shift Test for Scapholunate Instability
Watson test or Scaphoid shift test is a wrist provocative stress test done for Scapholunate instability.
The examiner’s thumb is placed on the scaphoid tuberosity of the volar aspect of the wrist. Pressure is applied to the tuberosity as the wrist is passively brought from ulnar to radial deviation. This pressure attempts to block normal scaphoid flexion.
A combination of pain and a palpable clunk when the wrist is brought from ulnar deviation into radial deviation while pressure is applied to the palmar aspect of the scaphoid tubercle.
[In theory, it indicates torn a scapholunate ligament and scapholunate instability which leads to the proximal scaphoid subluxating over the rim of the radius. A painful clunk indicates a reduction of scaphoid into the radial scaphoid fossa.]
A false positive result can also be obtained in individuals with lax ligaments.
Here is a video demonstration of the test
For lunatotriquetral instability
Shuck Test or Ballottement Test
Shuck test or Shear test, also called Ballottement test is done for lunatotriquetral instability.
The examiner’s thumb and index finger grasp the whole pisotriquetral unit. The contralateral thumb and index finger hold the lunate. The test is performed by applying a dorsally directed pressure to the pisiform and a palmarly directed pressure to the lunate [Lunate can be palpated beyond dorsal and ulnar corner of the radius.]
The maneuver results in a shearing stress on lunatotriquetral joints and vector across the lunotriquetral joint.
A crepitation or clicking associated with reproduction of pain is indicative of lunotriquetral dissociation.
The triquetrum is displaced dorsally and palmarly on the lunate. The test may be false negative in cases of ligamentous laxity.
Here is a nice demonstration of Shuck test.
The diagnosis is aided by midcarpal stress test which is performed by applying an axial load to a pronated and slightly flexed wrist, which then is brought into ulnar deviation. A painful clunk is a sign of instability [ 50% of patients with MCI may also have a clunk in the normal contralateral wrist and should always be examined]
Linscheid Compression Test
The examiner uses a thumb to apply a load in the radial direction at the ulnar border of the triquetrum.
The loading results in a compression force across the lunotriquetral joint. If this results in pain, the result is considered positive.
For Midcarpal Instability
Lichtman’s Pivot Shift Test
It is done for midcarpal instability. This test is a combination of ulnar deviation, axial compression, and pronation of the wrist. A positive result is obtained when this maneuver results in a painful wrist click.
Dorsal-displacement stress test
Under fluoroscopic control, a positive result is obtained when the capitate subluxates dorsally on dorsal stress as compared with the lunate and when the patient experiences a painful snap or click. Indicates capitolunate instability.
Without fluoroscopy, apprehension is taken as a positive sign.
X-rays are the basic investigations. These are most helpful when there is bony injury fractures or diagnosing ligament disruption with associated fractures. The use of other modalities must be based on the particular clinical scenario.
Radiographic examination of the wrist is mandatory for all suspected wrist ligament injuries and instabilities.
Posteroanterior (PA) view in neutral rotation, as well as lateral views, should be enough to evaluate static deformities.
A comparison with othe pposite wrist should be done for better assessment.
For evaluating dynamic stability, additional radiographs (eg, PA grip, PA maximum radial deviation, PA maximum ulnar deviation, lateral maximum flexion, and lateral maximum extension views) can be obtained..
On PA view, disruption of one of the Gilula arcs suggests either a fracture or subluxation from a ligamentous injury.
Increased distance between the scaphoid and lunate may indicate scapholunate interosseous ligament disruption.
In patients with acute, gross malalignment of the carpus, a PA radiograph with 5 to 10 Ib of traction frequently aids in assessment of intracarpal ligament disruptions or fractures.
Lateral radiographs should be carefully evaluated to make sure that the capitate reduces in the lunate and the lunate is reduced in the fossa of the radius.
Many patterns of instability can be identified.
In many acute carpal ligament disruptions, the initial plain radiographs are normal, with instability patterns recognized only as a late finding.
Specific instability views may be indicated to accentuate more can subtle instabilities.
For example, a PA clenched fist view can demonstrate dynamic scapholunate widening.
Fluoroscopy examination with provocative motion or maneuvers can demonstrate dynamic instability.
Following angles should be measured
- Radiolunate angle- 15 degree palmar to 15 degree dorsal
- Capitolunate angle- 300 dorsal to 300 palmar)
- Scapholunate angle – 380 – 600
- Lunotriquetral angles – 14 degrees dorsal
[In scapholunate instability, the scaphoid tends to assume a volarly flexed posture and scapholunate angle is> 70º.
Conversely, in lunotriquetral instability, the lunate is usually palmarly flexed, and the scapholunate angle can be less than 30º.
DISI and VISI can be defined by these values (see the classification)
Scapholunate gap can be measured on PA and PA grip radiographs. [> 3 mm. is generally considered pathologic but comparison with opposite wrist should be done.]
Determine ulnar translocation on PA x-ray – The distance between the center of the capitate and a line extending from the intermedullary axis of the ulna is divided by the length of the third metacarpal. [Normal is 0.30±0.03]
Arthroscopy remains the standard for diagnosing specific ligament injuries in the wrist. Both radiocarpal and midcarpal joints should be evaluated.
Arthroscopy is a very sensitive diagnostic test, and frequently clinically silent lesions may be detected
CT provides more detailed evaluation and may be indicated for subtle intra-articular fractures, to assess the degree of displacement, or to check for union of a fracture. Dynamic 4D CT imaging technique generates images with high spatial and temporal resolution and could be deployed to assess joint instability using this technique.
These studies may be helpful to identify radiographically occult fractures, most commonly those of the scaphoid..
Arthrography has historically been the gold standard diagnostic test. Contrast medium is injected into the radiocarpal, midcarpal, and radiolunate compartments, with dye flow between any two indicating a tear.
Arthrography lacks specificity and is an invasive procedure.
Its most common use tends to be for evaluation of subacute or chronic wrist symptoms.
MRI has gained has the potential to provide diagnostic evaluation of intrinsic and extrinsic carpal ligaments as it has the advantage of provides better soft tissue images.
Treatment of Wrist Instabilty
Milder forms of instabilities not so active patients be considered well to nonoperative management.
Conservative measures that can be taken are
- External support
- Musculotendinous exercises
- Steroid injections
- Change or modification of profession/employment
Failure of conservative treatment can be considered for the cases where conservative treatment has failed.
To simplify the discussion, treatment is summarized below under the headings of the following specific types of instabilities:
Partial tears of the scapholunate interosseous lugament (SLIL) are thought to represent occult or predynamic instability. For these injuries, most recommend an initial trial of splinting, casting, or both.
Arthroscopic debridement with or without pinning can be an option in these patients in whom initial conservative treatment is unsuccessful.
With complete scapholunate tears, options are
- Direct repair with or without dorsal capsulodesis
- Arthroscopic debridement, reduction, and pinning
In acute cases (<6 weeks), direct repair is indicated if sufficient SLIL remnant is present.
In patients with unrepairable SLIL but a reducible scapholunate interval and without degenerative changes, an indirect or direct ligament reconstruction has been advocated for stabilizing the scaphoid and to prevent the rotatory subluxation that often occurs in scapholunate instability.
Blatt dorsal capsulodesis is indirect ligament reconstruction using a flap of dorsal capsule to tether the scaphoid tuberosity to retard scaphoid flexion. Wrist flexion is significantly reduced by this surgery. Limitation of flexion can be overcome by not tethering the scaphoid to the radius.
Direct ligament reconstruction can be considered when SLIL is not repairable, scapholunate dissociation is reducible, and no degenerative arthritis is observed. A tendon to reconstruct the SLIL or a bone-ligament-bone construct may be used. They require a long period of wrist immobilization and result in some loss of final wrist motion.
Brunelli and Brunelli technique uses a strip of the flexor carpi radialis (FCR) and weaves it through the scaphoid. The tendon is also sutured across the scapholunate interval.
Limited intercarpal fusions are indicated in presence of DISI and degenerative changes at the radiocarpal joint.
Fusions that have been described involve the scaphocapitolunate, the scaphotrapezial trapezoid, the scaphocapitate, and the scapholunate fusion.
When arthritic change are prent(advanced scapholunate collapse) or a wide, irreducible scapholunate gap is present following are the available options
- Proximal row carpectomy
- Scaphoid excision and fusion of the lunate, triquetrum, capitate, and hamate (four-corner fusion
- Total wrist fusion [In pan carpal arthritis]
A period of immobilization for acute injuries is recommended.
Failure of conservative treatment demands direct repair with or without augmentation [capsulodesis]. The goal of capsulodesis is to prevent excessive flexion of the proximal row by imbricating the dorsal radiotriquetral ligament.
Late presenting patients can be considered for
- Ligament reconstruction
- Ulnar shortening
- Removes ulnar impaction
- Tightens the volar ulnotriquetral and ulnolunate ligament
- Lunotriquetrohamate or triquetrohamate
- Tightening the radiocapitate ligament
Radius opening wedge osteotomy usually also corrects the carpal instability.
Total wrist fusion is probably the best option if significant midcarpal arthrosis is present as well.
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