What Is Midcarpal Instability (Wrist Instability)?

What Is Midcarpal Instability (Wrist Instability/Carpal Instability)?:

Effects of Carpal Instability

Abstract: \"This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist.

Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated.

Instability occurs either if the carpus is unable to sustain physiologic loads (\"dyskinetics\") or suffers from abnormal motion of its bones during movement (\"dyskinematics\").

In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns.

It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being \"occult\" for the radiologic assessment.

This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages.

Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability.

To prevent individual and socio-economic implications, the handsurgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis.\&quot;<br><br>Post edited by: Scott_1984, at: 2009/02/08 09:41

Understanding Mid Carpal Instability/Palmar Midcarpal Instability (MCI/PMCI)

The concept of midcarpal joint instability (MCI) has evolved slowly since it was first described by Mouchet and Belot1 in 1934.

Subsequent researchers have not agreed about whether the differing personal observations of MCI represent distinct clinical entities or rather different manifestations of the same (or very similar) conditions.

Lacking unanimity in regard to the etiology and pathomechanics of this disorder it is easy to understand why there is also a lack of agreement on terminology and treatment for instability of the midcarpal joint.

Even the name “midcarpal instability” is not accepted universally as the proper designation for this condition.

It is hoped that this review has provided a sufficient overview of the subject to enable the reader to see some common integral threads in the published material and to encourage investigators to accelerate the process of clinical and biomechanical verification of the various published observations regarding MCI.

Unless this process begins soon and leads to a more scientific approach we will continue to rely for many years on a very hazy picture of MCI when trying to determine the appropriate diagnosis and treatment options in the clinical setting.<br><br>Post edited by: Scott_1984, at: 2009/02/08 09:46

Master Skills: Wrist and Elbow Arthroscopy and Reconstruction: CHAPTER 13: Midcarpal Instability:

Master Skills: Wrist and Elbow Arthroscopy and Reconstruction: CHAPTER 13: Midcarpal Instability:

The first description of a “snapping wrist,” diagnosed as anterior midcarpal subluxation,1 was recorded in 1934, although “dorsal luxation of the capitate” had been presented in a congress in Paris in 1919.

However, it was Lichtman’s2 paper in 1981 that brought this particular condition to the attention of our profession.

Of all the forms of carpal instability, midcarpal instability (MCI) has been the most confusing.

The two main reasons for this are that MCI is a mixed bag of conditions and that their

pathophysiology is not well understood.

The management of MCI remains controversial.

The term MCI covers a range of conditions characterized by a painful clunk, usually felt in ulnar deviation of the wrist.

It has been suggested that the term “instability of the proximal carpal row” would be a more accurate description,3 since the mechanical problem is a carpal instability nondissociative (CIND), affecting the radiocarpal or the midcarpal joints or both.

The scaphoid, lunate and triquetrum move like one unit, but not in a predictable smooth manner.

Most patients with MCI respond to nonoperative treatment.

Combinations of immobilization, splints, anti-inflammatories, activity modification and exercise have been prescribed with diverse success.

Surgical treatment suggested for MCI includes soft tissue stabilizations, limited carpal arthrodesis, corrective osteotomies and arthroscopic thermal capsulorraphy.

The role of propioception in carpal instability is starting to be recognized, but again is not yet fully understood.

What Causes the Clunk?:

Clunking of the wrist can be caused by congenital laxity of the wrist ligaments, bone or joint dysplasia, lunotriquetal injury, distal radius malunion or insufficiency of the extrinsic ligament affecting the radiocarpal or the midcarpal joint, or both.

In a normal wrist during radial deviation, the proximal carpal row goes into flexion, and during ulnar deviation it extend in a smooth transition (Figure 1a).

In a wrist with palmar MCI, the proximal carpal row will remain flexed during ulnar deviation, causing a subluxation at the midcarpal joint and, at a certain point, will jump from flexion to extension.

This causes the so called “catch-up clunk” felt by the patient and often clearly seen and heard by observers (Figure 1b).

Midcarpal Instability CHAPTER 13:

This paper as kindly been supplied by:

The Pulvertaft Hand Centre,
Derbyshire Royal Infirmary,
London Road,
Derby,
DE1 2QY,

I'd like to say a \&quot;BIG THANK YOU\&quot; to: Mr Tommy Lindau MD, PhD-Consultant Hand Surgeon &amp; Carlos Heras-Palou, MD, for allowing me to publish this Midcarpal Instability Chapter on my website.

wristinstability.multiply.com/notes/item/6 & msngroup.aimoo.com/PalmarMidcarpalInstabilityPMCIRSD

Post edited by: Scott_1984, at: 2009/02/08 09:52

Mid Carpal Instability (MCI)/Palmar Midcarpal Instability (PMCI) also known as:

Ulnar Midcarpal Instability,
CLIP-Wrist,
Wrist Instability,
Capitolunate Instability Patterns,
Capito Lunate Instability Pattern,
Ulnocarpal Instability,
Midcarpal Instability,
Mid Carpal Instability (MCI),
Palmar Midcarpal Instability (PMCI),
Wrist Pain,
Carpal Instability,
Inter-Carpal Instability,
Scaphoid Instability,
Capitolunate Scaphoid Instability,
Wrist Sprains,
Wrist Sprain,
Ulnar-Sided Wrist Pain,
Ulnar Wrist Pain,
MCI/PMCI,
MCI,
PMCI,<br><br>Post edited by: Scott_1984, at: 2010/05/16 00:37

Carpal Instability: www.maitrise-orthop.com/corpusmaitri/ort...3_saffar/index.shtml

There is no muscular attachment to the proximal carpal row.

It is an intercalated segment stabilized only by ligaments.

Proximal carpal row motion is the consequence of movements of the distal carpal row and forearm bones.

The intracapsular wrist volar ligamentous plane is thick and strong (Fig 1): stretching of this structure is difficult to assess but probably plays a role in carpal instability.

The dorsal ligamentous plane is thinner and less important for carpal stability.

Description of the “carpal instability” entity is more than 25 years old (Linscheid et Dobyns, 1972).

It was defined as carpal malalignment on X-rays or by carpal ligamentous tears and controversy still exists regarding this definition.

We have been interested in pathology of carpal instability since it was described.

New imaging techniques for the carpus have helped the surgeons to pre-operatively define carpal ligament injuries and to plan precisely the best treatment.

What are the principal features ?:

*1: New anatomical descriptions of carpal ligaments including their course and attachments (Taleisnik, 1976) were performed. Studies of their biomechanical role and pathomechanics followed. These intracapsular or intra-articular ligaments are not visible during the surgical approach of the wrist joint, which explains why they were described only recently.

*2: Assessment of partial or total injury of each ligament and the consequences of each on this complex joint is possible. These injuries improperly called “wrist sprain” are each now well-known diagnoses and each ligament injury results in a particular pathology.

*3: Wrist osteoarthritis (O.A.) is post-traumatic in 95% of the cases (Watson, 1984) and in 75% secondary to a carpal instability.

Carpal Ligament Instability: www.emedicine.com/orthoped/topic380.htm

INTRODUCTION: www.emedicine.com/orthoped/topic380.htm

The human wrist joint is a complex arrangement of small bones and ligaments that form a mobile yet stable link from the powerful forearm to the hand.

The normally functioning carpus can position the hand precisely relative to the forearm and provides remarkably stable transmission of forces.

Motion and stability of the carpus provide the critical foundation for maximum hand function from precise fine motor control to power grip activities.

When the normal mechanics of the wrist are disrupted, the instability of the carpal bones results in weakness, stiffness, chronic pain, and often arthritis if not treated appropriately.

Although the early clinical and radiographic findings may be subtle, an understanding of wrist kinematics and instability patterns can facilitate early diagnosis and management.

Unfortunately, selecting the optimal treatment remains a difficult judgment in most cases.

Linscheid et al described traumatic carpal instability in 1972.

Since the early reports, anatomic and biomechanical studies have provided a foundation for understanding carpal motion, stresses, and pathologic instability.

Building on these studies, various models have been suggested to explain the remarkable strength and mobility of this complex joint and the predictable patterns of failure.

This article presents the current understanding of pathologic carpal instability, the common classification patterns, and early treatment options that may avoid protracted dysfunction. Appropriate hand therapy is essential to maximize recovery but requires an appreciation of the limitations of carpal instability dysfunction and the goals of various treatment options.

Problem:

Carpal instability is defined as any malalignment of the carpus. This may be evident on plain radiography as a static deformity; alternatively, the situation may be a dynamic one, which becomes evident only when external forces are placed on the wrist.

The malalignment may appear after a single traumatic event or may be secondary to chronic attenuation of supporting ligaments after a traumatic event or secondary to an underlying disease process (eg, rheumatoid arthritis, pseudogout).

Frequency:

In 1975, Dobyns et al reviewed their experience and found that 10% of all carpal injuries resulted in instability.

In 1988, Jones evaluated 100 consecutive patients with wrist sprains by using dynamic radiography (clenched-fist views) and found that 19 had an increased scapholunate gap.

The incidence of carpal instability that is associated with other specific fractures is relatively high.

Reviewing 134 distal radius fractures, Tang in 1992 found radiographic evidence of carpal instability in 30% of the cases.

Geissler and Freedland prospectively reviewed 60 displaced intra-articular distal radius fractures that were being treated with arthroscopic assisted reduction and internal fixation (Geissler, 1996). They found 43% had concomitant tears in the fibrocartilage complex, while 32% also had tears in the scapholunate ligament.

Weber reviewed 36 patients with acute scaphoid waist fractures and found that 28% had a dorsal intercalated-segment instability (DISI) deformity (Weber, 1980).

Etiology:

Carpal instability results from an injury to one or more ligamentous or bony constraints in the wrist. Depending on the force, rate, and point of impact and on the position of the wrist, a fall on an outstretched wrist can result in a range of injuries. This spectrum includes wrist sprains, distal radius fractures, and fractures to the scaphoid and other carpal bones.

This type of trauma can also result in injury to one or more ligamentous structures in the wrist, causing carpal instability.

Perilunate instability is described as progressing from the scapholunate and the capitolunate to the lunotriquetral joint.

Using a cadaveric trauma model, Mayfield et al observed progressive injury patterns when the wrist was loaded in extension, ulnar deviation, and carpal supination (Mayfield, 1980).

This perilunar instability is divided in 4 stages (see Image 5). Stage I refers to injury to the scapholunate interosseous ligament (SLIL).

Further trauma results in dorsal subluxation of the capitate relative to the lunate, or stage II.

As the load increases, the lunotriquetral interosseous ligament (LTIL) is injured, causing a perilunate dislocation in stage III. Finally, stage IV is characterized by dislocation of the lunate from the radiolunate fossa.

However, if the carpus is pronated and the hypothenar area is struck first, an ulnar traumatic pattern may be observed.

Specifically, disruption of the ulnotriquetral ligament complex and the LTIL occurs (Stanley, 1994).

As the triquetrum no longer holds the lunate, it falls into a flexed position because of pressure from the capitate and its connection with the scaphoid.

With attenuation or injury to the dorsal intercarpal ligament, a volar intercalated-segment instability (VISI) pattern ensues; this can be visualized on lateral radiography.

An LTIL tear most commonly results in a VISI deformity.

In addition to a direct loading type of trauma, rotational force to the wrist can also result in ligamentous injuries, eg, the forces that occur when holding a power drill while the drill bit is jammed.

This type of trauma can result in injuries to the LTIL and ulnar-triquetral ligament complex and result in the lunotriquetral instability (Ruby, 1996).

Some instability patterns arise after chronic attrition of supporting ligaments.

One traumatic event may result in some subtle ligamentous injury but no clear instability initially.

However, over time, continued normal daily loading of the wrist can result in symptomatic instability.

An example is seen with scaphoid fractures, where a DISI deformity tends to appear late after the initial traumatic event.

Supporting ligaments can also be important in preventing carpal instability in the presence of other significant ligamentous injury.

For example, many cadaveric studies have shown that isolated sectioning of the SLIL does not result in frank radiographic scapholunate gap or dissociation.

In 1986, Johnson and Carrera described a midcarpal instability in which the capitate dorsally subluxes out of the cup of the lunate during a fluoroscopic dorsal-displacement stress test.

This is associated with a painful snap or click that reproduces the patient's symptoms.

They attributed the cause of this instability to attenuation of the radioscaphocapitate ligament after prior trauma.