I don’t think that this needs to be a difficult operation, but I agree that it is poorly described, and the importance / methods of restoring proper Lunate-Capitate alignment prior to fusing them is often overlooked.

I’m curious to know what technique you used – i tried to be unbiased in the presentation, but my current preference would be to use 3 headless cannulated screws (e.g. Accutrak, Herbert-Whipple, etc.) (L-C, C-H, L-T)

I recently spoke with Greg Bain about his published technique (he excises the triquetrum, and uses staples for fixation) I haven’t used the staples, but excision of the triquetrum is potentially attractive to increase ulnar deviation. I’m not sure what effect the reduction in fusion mass will have. I’ve discussed this with a few people and have had two different answers, one being that decreased fusion mass will result in decreased ability to load across the carpus, and the other being that size of fusion mass is irrelevant, but rather that carpal height and alignment are most important. I haven’t tried it yet, but probably will at some point.

Let me know how things go.

I just finished going through your SLAC & SNAC wrist management and results presentation. It was came up on my google search on 4 corner arthrodesis. I did two yesterday for the first time…

It was really tough to find info on this for some reason, so your presentation was concise and clear presentation was timely and helpful. Thanks!

http://uk.msnusers.com/PalmarMidcarpalInstabilityPMCIRSD/Documents/More%20Documents%2FThe%20Treatment%20Of%20Wrist%20Instability..pdf

The concept of carpal instability has evolved considerably
over the past few years. Initially, the term ‘instability’ was
considered to be synonymous with ‘malalignment’.1-3 A
wrist was regarded as unstable when there was an alteration
of the sagittal and/or anteroposterior alignment of the carpal
bones beyond what was judged to be normal.4,5 Based
on this, four major types of carpal malalignment were
recognised:
Dorsal intercalated segment instability (DISI). The lunate,
regarded as an intercalated segment between the distal row
and the forearm bones, is abnormally extended relative to
its proximal and distal links.
Volar intercalated segment instability (VISI). In the sagittal
plane the lunate appears abnormally flexed.
Ulnar translocation. The proximal row is abnormally displaced
(rotated or translocated) relative to the radius in an
ulnar direction.
Dorsal translocation. Due to a malunited fracture of the
radius, the carpus is subluxed in a dorsal direction.
These four types of instability could therefore always be
diagnosed by plain radiography.6,7
A number of authors including Schernberg8 and Zdravkovic,
Jacob and Sennwald9 have criticised this concept of
instability since not every alteration of carpal alignment is
pathological. Wrists showing congenital hyperlaxity often
appear to be grossly malaligned and yet are frequently
asymptomatic. These patients are able to cope effectively
with most activities of daily living and seldom require
treatment.8,10 It was therefore necessary to reconsider the
definition of instability and exclude those patients whose
carpal malalignment is simply a variation of the normal. As
a result, instability has been redefined as the inability to
bear physiological loads with an associated loss of the
normal carpal alignment.11,12
This definition again was felt to be inadequate since it
excludes those patients whose wrist is asymptomatic for
most of the time, is well aligned and able to sustain
physiological loads, but becomes painful only when performing
a specific task, such as opening a jar or lifting
heavy objects, with a typical sensation of ‘giving way’. It is
apparent that there is dynamic instability, occurring when
carpal malalignment appears sporadically under certain
loading conditions, and static instability when malalignment
is permanent regardless of the amount of load
being applied.13,14
By admitting differences in the severity of injuries producing
carpal instability, some of the problems of definition
were solved. Nevertheless, some concerns remained. By
defining stability in terms of ‘ability to bear load’, the
impression was gained that there was a problem only of
load transfer (kinetic dysfunction) rather than of both load
and movement (kinetic and kinematic dysfunction). For
instance, a wrist with an old carpal collapse and extensive
joint degeneration may bear physiological loads despite
malalignment.15 Such cases, however, should be considered
as pathologically unstable since their movement cannot be
as smooth and well co-ordinated as that of a normally
functioning wrist.16,17
To fulfil these biomechanical criteria of stability, a normal
wrist must be able to maintain a balance between the
articulating bones in both kinetic and kinematic terms
under physiological loads, through the whole range of
movement.18,19 The term instability must be interpreted as
‘carpal dysfunction’,15 which implies that in a normal wrist
there is the ability to transfer loads without sudden changes
of stress on the articular cartilage (normal kinetics) and the
capacity to move throughout the normal range without
sudden alterations of intercarpal alignment (normal
kinematics).

Turkish Journal of Trauma & Emergency Surgery Ulus Travma Derg 2005

http://uk.msnusers.com/PalmarMidcarpalInstabilityPMCIRSD/Documents/More%20Documents%2FWrist%20Ligaments%20Their%20Significance%20In%20Carpal%20Instability%20Turkish%20Journal%20Of%20Trauma%20And%20Emergency%20Surgery.%202005..pdf

BACKGROUND
Understanding the exact contribution of the supporting
ligaments to the functional integrity of the wrist is crucial
for the diagnosis and treatment of carpal instabilities. The
present study evaluates the functional significance of the
wrist ligaments with respect to carpal instabilities..
Materials and Methods: Sixteen fresh cadaver wrists were
dissected. Extrinsic and intrinsic ligaments of the wrists
(ligamentum radioscaphocapitatum, ligamentum radiolunotriquetrum
and ligamentum triquetrohamatocapitatum)
were sectioned sequentially. After sectioning of each ligament,
the wrist was examined for clinical signs of instability
such as misalignement of carpal bones, limited range of motion
and dorsal translation. When instability was suspected,
radiographs were taken and if instability was confirmed,
then the ligament was repaired.
RESULTS

Although none of the dorsal ligaments sectioning resulted
in instability, sectioning of ligamentum scaphotrapeziotrapezoideum,
ligamentum radioscaphocapitatum, ligamentum
radiolunotriquetrum and ligamentum triquetrohamatocapitatum
displayed scaphotrapeziotrapezoidal, dorsal intercalated segment, lunotriquetral and capitohamate instability respectively.

In two wrists with arthrosis, sectioning of all ligaments
didn’t lead to any instability

CONCLUSION

Instability of the wrist can be classified on anatomical basis after the name of these four ligaments involved i.e. l.
scaphotrapeziotrapezoideum, l. radioscaphocapitatum, l. radiolunotriquetrum
and l. triquetrohamatocapitatum respectively.

This approach clarifies the etiology and treatment of
carpal instabilities.

The term carpal instability is commonly used, but what carpal stability actually is has not been defined.

Much of the mechanically complex wrist’s versatility is due to the intercalated three bone proximal carpal row.

Landsmeer described the collapse tendency associated with intercalated segments.

The factors which provide static stability are the oblique alignment of the scaphoid, the obliquely aligned dorsal and palmar ligamentous complexs, the intrinsic perilunate ligaments, the transiting transcarpal tendons and the negative intraarticular pressure.

The proximal carpal row adjusts its posture on the counterbalancing flexion/pronation torque exerted by the scaphoid and the extension/supination torque exerted by the triquetrum.

The dynamic factors are the compressive force exerted across the joint acting on the joint surfaces and the effect of the bowstringing force provided by the flexor carpi radialis acting at the scaphoid tuberosity.

The proximal carpal row has a tendency to translate ulnarly along the ulnarly sloped radial articular surface while the distal row has a tendency to slide radially on the radially sloped lunatatotriqueteral distal articular surface.

This activity produces differential tension in the ligaments attaching to the triquetrum which effects an extension/supination stance of the triquetrum.

The force couple acting on the scaphoid effects the flexion tendency of the scaphoid.

The bowstringing of the flexor carpi radialis also counteracts scaphoid flexion.

Alterations in any of these factors may upset the delicate mechanical balance of the joint.

Scapholunate instability is the most common carpal
instability.

The evaluation and treatment of scapholunate instability is controversial and the outcome unpredictable.

This article will review the pertinent ligamentous anatomy of the wrist and carpal kinematics.

There will be a discussion of the clinical presentation,
examination, and diagnostic testing of the patient suspected of having scapholunate instability.

The treatment options and indications, including repair and reconstructive and salvage procedures, will be reviewed.

Introduction:

The most common carpal instability occurs between the scaphoid and lunate.

Scapholunate instability may occur after a traumatic injury or from repetitive use.

Patients often complain of weakness and pain of the wrist.

The treatment options are multiple and controversial.

This article will briefly review the pertinent wrist ligamentous anatomy, carpal kinematics, exam, and diagnostic evaluation for scapholunate instability.

Treatment options and their indications will also be discussed.

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.

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.

& I’ve been suffering from this serious & complex wrist disability since: 13-10-2002,

In December 2006 I set up my online support group for Mid Carpal Instability (MCI)/Palmar Midcarpal Instability (PMCI) Suffers.

& It contains medical journals & websites on Mid Carpal Instability (MCI)/Palmar Midcarpal Instability (PMCI).