Witczak, Masear, and Meyer

The Journal ofHAND SURGERY

5. Lacey T, Goldstein LA, Tobin CE. Anatomical and clinicalstudy of the variations in the insertions of the abductor

, pollicis longus tendon associated with stenosing tendo-vaginitis. J Bone Joint Surg 1951;33A;347-50.

6. Jackson WT, Viegas S. Anatomical variations in the firstextensor compartment of the wrist: a clinical and anatom-ical study. J Bone Joint Surg 1986;68A:923-6.

7. Giles KW. Anatomical variations affecting the surgery ofde Quervain’s disease. J Bone Joint Surg 1960;42B(2)352-5.

8. Murphy IA. An unusual form of de Quervain’s syndrome.J Bone Joint Surg 1949;31A:858-9.

9. Finkelstein H. Stenosing tendovaginitis at the radial sty-loid process. J Bone Joint Surg 1930;12:509-40.

Ulnar-sided perilunate instability:and biomechanic study

An anatomic

A staging system for ulnar-sided perilunate instability is presented based on a series of cadaverdissections and load studies. Stage I: partial or complete disruption of the lunotriquetral inter-osseous ligament, without clinical and/or radiographic evidence of dynamic or static volar in-tercalated segment instability deformity; stage I]2 complete disruption of the lunotriquetraiinterosseous ligament and disruption of the palmar lunotriquetral ligament, with clinicaland/or radiographic evidence of dynamic volar intercalated segment instability deformity; andstage HI: complete disruption of the lunotriquetrai interosseous and the palmar lunotriquetralligaments, attenuation or disruption of the dorsal radiocarpai ligament, with clinical and/orradiographic evidence of static volar intercalated segment instability deformity. (J HAND SURG

1990;15A:268-78.)

Steven F. Viegas, MD, Rita M. Patterson, MEng, Pamela D. Peterson,

David J. Pogue, BS, David K. Jenkins, BS, Timothy D. Sweo, BS, and

James A.. Hokanson, PhD, Galveston, Texas

Carpal instability includes a spectrum of

’bone and ligamentous injuries. There is an ever-

increas, ing volume of information on instabilities in-volving the radial or lateral column of the wrist, i.e.,

From the Division of Orthopaedic Surgery, and the Division of Bin-statistics, University of Texas Medical Branch, Galveston, Texas.

Supported inpart by a grant from ~he National Institute of Arthritisand Musculoskeletal and Skin Diseases No 5 R29 AR 38640-02.

Presented in part at the Symposium on the Wrist: Difficult Problemsand Current Solutions, Pads, France. April 7, 1989.

Received for publication Jan. 9, 1989; accepted in revised form May5, 1989. - ~

"No benefits in any form have been received or will be received froma commercial party related directly or indirectly to the subject ofthis artiele.~ ....... -

Reprint requests: Steven E Viegas, MD, Division of OrthopaedicSurgery, McCullough Bldg., Room 6.136 (G-92), University Texas Medical Branch, Galveston, TX 77551.

3/1 / 14250

scapholunate dissociation, rotatory scaphoid instability,and perilunate instability.l-l" There is considerably less

information available on the ulnar or medial columninstabilities, and the information that does exist includesinconsistent, speculative and co.n.fusing reports.~23 The

ulnar.column instabilities are believed to be less thanone sixth as common as their radial counterparts .24 Overthe past several years, instabilities involving the ulnaraspect of the wrist have become better recognized.However, .a considerable amount of uncertainty stillappears to exist with regard to the cause, clinical im-pact, and treatment of these injuries.~r 51 ~5-2s Volar in-tercalated segment instability (VISI) has been attributedto triquetrohamate ligament disruption, which Licht- .man has called midcarpal instability 26 and would beclassified as a carpal instability nondisso6iative (CiND)type by Dobyns and Linscheid.29 Disruption of the sca-photmpezial ligament has also been cited as a cause fora CIND type of VISI. ~s This study however will deal

268 THE JOURNAL OF HAND SURGERY

of ; Vol. 15A, No. 2~ March 1990 Ulnar-sided perilunate instability 269

[io)

Fig. 1. A diagram depicting the disruption of the lunotri-quetral interosseous ligament (LT[io]) in a stage I ulnar-sidedperilunate instability.

Fig. 2. A diagram depicting the additional disruption of thepalmar radiolunotriquetral ligament (RLT), between the lunateand the triquetrum, in a stage II ulnar-sided perilunate insta-bility.

only with a progressiye carpal instability dissociative(CID) type of problem, which has a lunotriquetral in-terosseous ligament tear as part of the pathology.

The purpose of this study is to demonstrate anatom-ically, progressive ligament disruptions that result inincreasingly severe ulnar-sided perilunate instabilitythat give rise to dynamic and subsequently static VISIinstabilities. This study also assesses the effect of theseinstabilfties on the load distribution within the wristjoint.

Materials and methods

Anatomic study. Seven unembalmed upper extrem-ities were used for a series of dissections done by oneof the authors (S. V.). Specimens ranged from 21 67 years of age. Five were male and two were female.The specimens were dissected free of soft tissue downto the level of the dorsal wrist capsule. Specific liga-ments were sectioned in the following sequence: StageI, the lunotriquetral interosseous ligament was sec-tioned (Fig. 1); stage II, the palmar lunotriquetral lig-ament was sectioned (Fig. 2); stage III, the dorsal ra-diocarpal ligament was sectioned at its insertion into

the scaphoid and lunate (Fig. 3). After each phase ligament sectioning, the wrist was brought through itsrange of motion both in the loaded and unloaded mode,as well as with externally applied dorsal, palmar, radial,and ulnar forces.

Two carpal fusions (lunate-triquetrum and lunate-triquetrum-capitate-hamate) were simulated by placingthreaded half pins into the carpal bones and connectingthem with a mini external fixation system. The effectof these fusions on each of the stages of instability wasassessed.

Load study, Six unembalmed cadaver upper extrem-ities, ranging from 21 to 63 years of age and free fromany visible or radiographically identifiable deformitiesand/or degenerative changes, were studied. Each spec-imen was stripped of all its soft tissues except ~he jointcapsule, the palmar and dorsal radiocarpal, ulnocarpal,and interosseous ligaments, the triangular fibrocartilagecomplex, and the radioulnar interosseous membrane.Radiographs showed that the radioulnar length rangedfrom 1.5 mm ulnar positive to 0.5 mm ulnar negativevariance, and that the inclination of the distal radialarticular surface ranged from a palmar angle of 6 to 13

The Journal of270 Viegas et al. HAND SURGERY

Fig. 3. A diagram depicting the additional disruption of thedorsal radioscapholunotriquetral ligament (RSLT), also calledthe dorsal radiocarpal ligament, in a stage Ill ulnar-sidedperilunate instability.

degrees. The radial inclination of the distal radial ar-ticular surface ranged from 20 to 25 degrees.

Each specimen was mounted on a loading jig, whichpermitted positioning of the wrist anywhere in its rangeof motion. Twelve positions were studied. The forearmwas maintained in neutral pronation and supination andthe ~vrist was positioned in combinations of 20 degreesof radial deviation, neutral or 10 degrees of ulnar de-viation, and in 20 degrees of flexion, neutral, 20 or 40degrees of extension.

An axial load of 32 pounds (143 Newtons) was ap-plied by weights to a ball joint fixed to 4 mm diameterpins that were drilled into the medullary canals of thesecond and third metacarpals. The elbow was posturedin 90 degrees of flexion, and the humerus was fixedwith two transverse threaded pins to the base plate ofthe loading jig. The 32 pound load was selected basedon previous work, as being optimal for the Fuji filmmeasurements .30

Contact areas and pressures within the radioulnarcarpal joint were measured in each position by Fujiprescale super low pressure-sensitive paper (C. Itoh,New York, N.Y.). The film was cut to match the surface

Fig. 4. Lateral radiograph of one of the specimens with astage III instability demonstrating a VISI.

of the distal radius and triangular fibrocartilage. Thejoint was distracted and the film inserted through adorsal capsular incision. Spatial orientation of each areawas determined by a "U" marker located externally tothe distal radius and included on each print. The printimage was then videodigitized and analyzed by a BetterBasic program. The analysis calculated values based onpressure calibrations defining the intensity of color onthe print. Contact areas, area centroids, and pressureswere measured on each print for every position.

Tests were initially done on all 6 wrists in all 12positions. The lunotriquetral interosseous ligament wassectioned in two wrists and they were then tested again(stage I instability). The lunotriquetral interosseous andthe palmar lunotriquetral ligaments were then sectionedin all six wrists and the wrists then tested again (stageII instability). The positions of neutral and of 20 degreesflexion were tested again with a dorsal force exertedagainst the capitate during loading, which was shownto result in a VISI alignment in the anatomy study.

Vol. 15A, No. 2March 1990 Ulnar-sided perilunate instability 2"/1

Tests were also done after sectioning of the dorsal ra- and the suitability of using analysis of variance

diocarpal ligament (stage III instability) at which point (ANOVA). A two-way ANOVA using the Proc GLM

the carpus assumed a volar intercalated segment insta- (General Linear Model) in PC-SAS was used to test for

bility alignment in the positions of neutral and of 20 differences in areas, pressures, and high-pressure cen-

degrees flexion, without a dorsal force applied (Fig. troid x,y coordinates. To provide guidance in compar-

4). This had also been demonstrated in the anatomy ing specific positions and conditions, Scheffe’ Multiple

portion of this study. Comparison tests were performed based on the findingsof the analysis of variance. Based on these results,

Results specific contrast analyses were done to test specific

Anatomic study. Six of the seven specimens had no hypotheses about conditions and positions. Unless ix-

identifiable radiographic or anatomic abnormalities, plicitly stated otherwise, in this report, a p- value of

One of the seven specimens had a complete tear of the less than 0.05 was considered to be statistically signif- ~

lunotriquetral interosseous ligament. All six of the spec- icant.

imens that had no identifiable abnormalities were found Contact areas. Variability of size between joints was

to have increased motion between the lunate and tri- accommodated by dividing the contact areas within

quetrum after transection of the lunotriquetral interos- each joint by the total area of that joint. Individual

seous ligament (stage I ulnar-sided perilunate instabil- scaphoid and lunate contact areas are therefore reported

ity). In the wrists with this stage of disruption, even as a :ratio of the available joint surface.

with a translational force applied to the dorsal aspect There were no significant differences in the overall

of the capitate and/or hamate, a VISI pattern of carpal total scaphoid contact area between any of the condi-

alignment could not be obtained. Transection of the pal- tions studied except in the condition of stage II ulnar-

mar lunotriquetral ligament (stage II ulnar-sided peri- sided perilunate instability [without a dorsal transla-

lunate instability) resulted in an increased laxity be- tional force] in which there was a small but significant

tween the lunate and the triquetrum. In this stage, a difference: [normal (0.127) [i.e., the contact area was

VISI deformity could be obtained, although only while 12.7% of the available joint area], stage II ulnar-sided

a translational force was applied to the dorsal aspect of perilunate instability {without a dorsal translational

the capitate and/or hamate and only with the wrist in force} (0.149), VISI alignment {as in a stage II, with

a neutral or flexed position and / or radial or limited ulnar . a dorsal translational force or a stage III ulnar-sided

deviation. In positions of extension and/or ulnar de- perilunate instability} (0.117)].

viation of more than 20 degrees, a VISI alignment could There was no significant difference in the overall total

not be induced even with the application of a dorsal tuna~ contact area between any of the conditions stud-

force. The transection of the dorsal radiocarpal ligament ied: [normal (0.101), stage II ulnar-sided perilunate

at its insertion into the scaphoid and lunate (stage III instability {without a dorsal translational force} (0.087),

ulna-sided perilunate instability) resulted in a VISI de- VIS][ alignment {as in a stage II, with a dorsal trans--

fortuity. Once this posture was attained it remained in lational force or a stage III ulnar-sided perilunate in-

this VISI ~teformity until a translational force was ap- stability} (0.099)].

plied to the palmar aspect of the capitate or the wrist There were no significant differences in the overall

brought into more than approximately 25 degrees high pressure scaphoid or lunate contact areas betweenwasof ulnar deviation or into extension, at which point the any of the conditions studied: [scaphoid:normal

carpus would ̄ reduce into a normal alignment for that (0.085), stage I (0.079), stage II, without a dorsal trans-

particular wrist posture, lational force (0.073), stage II, with a dorsal transla-

The seventh specimen, which had a disruption of the tional force (0.068), stage III (0.057)] [lunate: normal

lunotriquetral interosseous ligament, was found to have (0.041), stage I (0.037), stage II, without a dorsal trans-

the same findings as in the other six specimens with lational force (0.051), stage II, with a dorsal transla-

surgically-induced stage I instability. The sequential tional force (0.045), stage III (0.044)].

transection of the other ligaments followed the same Scaphoid/lunate area ratios. There was no signifi-

sequence and resulted in the same findings as in the cant differences in the overall scaphoid/lunate contact

other six specimens, area. ratio between any of the conditions studied. [Nor-

Load study. Statistical analyses were done on the mal (1.15), stage I (0.91), stage II, without a dorsal

data using PC-SAS (SAS Institute, Cary, N..C.). Ini- translational force (0.86), stage II, with a dorsal trans-

tially univariant statistics were done on each condition lational f6rce (I.08), stage III (0.79)].

and position to determine the frequency distributions Average high pressures. There was no significant

Fig. 5. A series of prints of one of the wrists, in one position, at different points in the study. (a)A print of that wrist in the "normal" state, showing :~caphoid contact on the right (double arrows),the lunate contact on the left (single arrow), and the "U" mark on the lower portion of the printfrom the metal reference marker located outside the joint at the dorsal aspect of the distal radius.(b) A print after sectioning of the ligaments to result in stage II ulnar-sided perilunate instability.(c) A print once the carpus has assumed a VISI alignment, as it does in stage II ulnar-sidedperilunate instability with an applied dorsal translati~onal force and/or in the stage III ulnar-sidedperilunate instability, demonstrating the concentration of the scaphoid and lunate high pressureareas in the palmar aspect of the joint. Diagramatic representations of (d) the superimposed outlinesof the high pressure zones for the normal (- - -), stage II ulnar-sided perilunate instability (...)and VISI deformity ( ), as well as (e) the plotted high pressure area normalized centroids for the scaphoid, on the right, and the lunate, on the: left, of the wrists in the conditions of normal(n), stage II ulnar-sided perilunate instability (II), and VISI deformity (v).

differences in the average high pressures in the highpressure zones between any of the conditions studied.

High pressure area centroid locations. The centroidis a point representing the mathematical center of thecontact area of the high pressure zone but does notdefine or reflect the shape of the contact area. Thecentroids of the scaphoid and lunate high pressure areasshift as a function of the posture of the normal wrist.3~

The centroids were noted to shift more palmar whenthe carpus assumed a VISI alignment. The actual con-tact areas demonstrate, even more dramatically, thispalmar shift with VISI alignment when the wrist is inpositions of flexion and neutral (Fig. 5).

Discussion

There is a great deal of confusion over carpal in-stabilities, particularly in the ulnar aspect of the wrist.This, in part, may arise from the duplicity and lack ofuniformity in the use of terms such as dynamic andstatic, and the various classifications such as CID andCIND, and VISI, DISI, and midcarpal instability,which are not always quoted or used within the definedparameters the original authors had intended.32

This article uses the term dynamic as follows: thereis or would be no evidence of abnormal carpal alignmentin the standard anteroposterior (AP) and lateral radio-graphs; there is evidence of abnormal carpal alignment

Vol. 15A, No. 2March 1990

in standard AP and lateral radiographs with stress ex-erted by the patients themselves or someone else;and/or there is evidence of abnormal carpal alignmentin positions other than that assumed by the wrist instandard AP and lateral radiographs. The term static isused to address what would be an abnormal carpal align-ment in the position assumed by the wrist in standardAP and lateral radiographs. The term VISI is used todescribe the following carpal alignment on a standardlateral radiograph: the lunate in a subluxated palmarand flexed posture and the capitate in a position in whichthe proximal pole is subluxated palmar to the radio-metacarpal axis, with the longitudinal axis of the cap-itate running from proximal palmar to dorsal distal inthe lateral plane. A carpal instability dissociative (CID)lesion is one in which the lunotriquetral and/or thescapholunate interosseous ligaments are disrupted. Acarpal instability nondissociative (CIND) lesion wouldbe one in which neither of these ligaments is disrupted.

The first reference to carpal instability is attributedto Gilford and colleagues.33 Linscheid, Dobyns andassociates5. a5 have described common posttraumatic in-

tercarpal instability collapse deformities. Their classi-fication is based primarily on the capitolunate angle.Two of the basic patterns that they describe are thedorsal intercalated segment instability (DISI) and thevolar intercalated segment instability (VISI).

A number of different lesions have been reported toresult in a VISI deformity. Garth and associates17 de-scribed laxity of the capitotriquetral ligament, that re-suited in failure of the triquetral-hamate joint which, inturn, they believe allows a VISI deformity to occur.Trumble et al. a4 also list triquetral-hamate disruptionand capitate-lunate laxity as causes of VISI deformity.These kinds.of VISI deformities are what Dobyns, Lin-scheid et al.29 would classi(y as carpal instability non-dissociative (CIND) lesions. The cause most commonlyattributed to the development of a VISI deformity islinked to lunate-triquetrum laxity:.~’ 1~, ~7, 20-25, 27, 28 This,on the other hand, would be categorized as a dissocia-tive type of carpal instability (CID).-Perhaps a morespecific and descriptive name for this type of instabilityis ulnar-sided perilunate instability. This would mirrorthe work that Mayfield, Johnson, and Kilcoyne6 delin-eated on the radial pedlunate instability and hopefullyadd some uniformity in addressing the various types ofinstabilities ....

Different authors2L 28 have speculated that there is aprogressive sequence of ligament disruption that mayoccur on the ulnar side of the carpus, similar to whatMayfield, Johnson, and Kilcoyne6 have described on

Ulnar-sided perilunate instability 273

the radial side of the carpus. Reagan, Linscheid, andDobynsal have divided the triquetrolunate instabilitiesinto two groups. Lunotriquetral sprains, which havepartial tears in the lunotriquetral interosseous ligamentand lunotriquetral dissociations, which have completetears of the lunotriquetral interosseous ligament. Othersdivide ~:riquetrolunate instability into two types, thosewithout radiographic or clinical evidence of VISI andthose with an evident VISI deformity,as

There is a relative paucity of cases in the literatureof what: could be classified as a volar intercalated seg-ment instability. In 1913, Chaput and Vaillant~4 reportedon a radiographic study of patients with carpal injuries,one of which had a typical case of what would now beclassified as VISI. In 1913, Mayersbach~ also reporteda case of what would now be recognized as a VISIdeformity in a 72-year-old man. In 1921, Navarro3~

described a carpal deformity, which again today wouldbe categorized as a VISI. Sutro, 37 in 1946, reportedtwo cases, which also had VISI deformities. Two casesof VISI are also included in the series presented byLinscheid et al.~ Taleisnika~ presented one case of VISIin 1982, which was preceded by a palmar scapholunatedislocation. In 1984, Lichtman et al.~-° reported one caseof a dynamic VISI deformity. Reagan and colleagues2~

presented a series of patients in 1984 that they groupedinto 24 lunotriquetral tears and 11 lunotriquetral dis-sociations. Trumble and associates’4 documented sevencases of dynamic and static VISI deformities in 1988.

Despite these scattered reports in the literature, therehas not been a consensus of opinion in regard to whatpathology is required to result in dynamic and staticVISI deformities arising from the area of the lunotri-quetral joint. However, clinical cases that involve doc:--umented disruptions of the lunotriquetral interosseousligament without any VISI pattern of deformity are notuncommon. , .

Previous experiments with cadavers have demon-strated increased divergent motion between the lunateand triquetrum .after sectioning of the lunotriquetral in-terosseous and the palmar and dorsal radiotriquetralligaments.1~’ 2~ .Some studies have also been able toreproduce dynamic VISI patterns with the applicationof a dorsal force on the capitate and/or hamate.~’ 2~Other cadaver studies that have attempted to reproducethis in:stability pattern have been unsuccessfulY A staticVISI deformity in the cadaver model has not been pre-viously simulated.

In the series of dissections reported in this study,increased motion developed between the lunate and thetriquetrum with a tear of the lunotriquetral interosseous

The Journal of

274 Viegas et al. HAND SURGERY

ligament. However, with a disruption of this ligamentalone, an appreciable dynamic or static VISI deformitywas not evident and could not be induced. This is com-patible with the findings of the load studies, whichoverall, did not demonstrate significant differences inload distribution between the scaphoid and lunate fossain the normal and a stage I instability. This would implythat the load distribution is not appreciably altered incases where the lunotriquetral joint alone was disrupted.This is consistent with clinical findings that patientswith incongruity between the lunate and the triquetrumgenerally had satisfactory clinical results.38

In a stage II ulnar-sided perilunate instability, a def-inite VISI deformity was evident during the applicationof a translational force on the dorsal aspect of the cap-itate and/or hamate when the wrist was in neutral orsome degree of flexion and radial, neutral or limitedulnar deviation. Sectioning the dorsal radiocarpal lig-ament and capsule at their attachment to the scaphoidand lunate, which resulted in a stage III ulnar-sidedperilunate instability, allowed a static VISI deformityto arise in the wrist. This static VISI deformity couldonly be demonstrated, however, in those same positionsin which the dynamic VISI deformity could be attained.Whenever the wrist was brought into greater than 25degrees of ulnar deviation or into extension, this wouldresult in changing the VISI position to a position ofnormal carpal alignment. Reduction of the VISI defor-mity by ulnar deviation of the wrist has been describedClinically. The symptomatic "clunk" that patients oftendescribe can often be reproduced by this maneuver.26

This is still consistent with the classic definition of aVISI deformity since it applies to the capitolunate anglein the lateral radiograph with the wrist in neutral flexionand neutral radioulnar deviation.

Previous work has shown that in positions of flexion,the normal wrist contact areas and high pressure cen-troids are located in the palmar aspect of the joint.31

However, in the positions of neutral and flexion testedwith a stage II instability (with a dorsal translationalforce applied inducing a VISI alignment of the carpus)and in the stage III instability (with a VISI alignmentof the carpus) the contact areas and high pressure cen-troids, of both the lunate and scaphoid, shifted morepalmar than normal. These were the same conditionsin which the carpus was seen to assume a VISI patternof collapse in the anatomy dissection portion of thisstudy.- -

In the positions of ulnar deviation and extension, thescaphoid and lunate assume relatively normal postureseven in wrists with a VISI deformity, perhaps becauseof the extension force exerted on the scaphoid by the

palmar radioscaphocapitate ligament and by the capi-tate. Differences in the load distribution, would not beexpected in these positions between the normal wristand a wrist with a stage III ulnar-sided perilunate in-stability. When all positions were analyzed together,there was no significant overall change in the scaph-oid/lunate area ratios, scaphoid and lunate contactareas, and average high pressure areas compared withthe normal wrist.

The information from these load studies would sug-gest the following: with the overall distribution betweenthe scaphoid and the lunate remaining essentially thesame throughout the progressive stages of ulnar-sidedperilunate instability, as defined in this article, and thefact that even the high pressure centroids shifted tonormal locations within portions of the functional rangeof motion of the wrist, one would not expect significantchanges in the wear pattern in the radiocarpal joint.This expectation, coincides with the clinical observa-tion of sparing of the radiocarpal joint in patients withVISI deformities.

There is clinical support for this concept of a se-quential, progressive ligament disruption leading even-tually to a static VISI deformity. Previous clinical stud-ies of transscaphoid fracture dislocations have made anargument for the existence of a spectrum of lesions inthose kinds of injuries.39 Specifically, the palmar trans-scaphoid lunate fracture dislocation is a more severeinjury than the dorsal transscaphoid perilunate fracturedislocation. Anatomically, the difference between these.two injuries is the disruption of the scaphoid and lunateattachment of the dorsal radiocarpal ligament and dorsalcapsule. After fixation of the scaphoid fracture com-ponent of these injuries, the remaining pathology in-cludes all the components of a stage III ulnafZ-gidedperilunate instability, as defined in the anatomic modeldescribed in this article. It is not surprising therefore,that in these cases, a stati9 VISI can develop.39

Taleisnik23 reported a case of~almar dislocation of thescaphoid and lunate as a unit, in which the interosseousligament between the scaphoid and the lunate remainedintact. In this case a VISI deformity also developed andhere again the scaphoid and lunate portions of the dorsalradiocarpal ligament were disrupted. Taleisnik ex-plained the VISI deformity as a continuation of luno-triquetral dissociation. However, he emphasized the im-portance of the flexion force of the scaphoid on thelunate without any counterforce from the dissociatedtriquetrum. He did not comment on the role, if any, ofthe dorsal capsule and radiocarpal ligament. The ana-tomic dissections in this study appear to support theconcept that it is not only the flexion force exerted by

March 1990 Ulnar-sided perilunate instability 275

Fig~ 6. A; A Posi~ro~i~teri0r (PA) radiograph demonstrating the lytic lesions in the scaphoid, lunate,and triquetrum, without any disruption of the normal carpal arcs in the left wrist of a patient with

rheumatoid arthritis. B, A lateral radiograph of the same wrist demonstrating a mild degree of VISIdeformity. Radiographs of the same patient, obtained 3 V2 years after those in A and B, demonstratingC, on the PA view the disruption of the carpal arcs I and II, and D, the lateral projection, whichdemonstrates a much greater degree of VISI deformity, with osteophyte formation at the point ofimpingement between the lunate and the capitate (arrow).

276 Viegas et al.The Journal of

HAND SURGERY

Fig. 7. A, A lateral radiograph demonstrating the static VISI deformity in the right wrist of pauentwith rheumatoid arthritis. The arrow points to the area where the dorsal lip of the lunate is impactingon the dorsal aspect of the capitate. B, Intraoperative photograph of the same case. demonstrating,with the carpus reduced out of the VISI deformity, the erosive lesion (single arrow) in the dorsalaspect of the capitate (C), which was articulating with the osteophyte (double arrows) at the dorsallip of the lunate (L).

the scaphoid on the lunate, which is unopposed by thetriquetrum but also the fact that the lunate and scaphoidare uhrestrained by the disrupted dorsal radiocarpal lig-ament, that allows the carpus to posture in a static VISIaligi~ment.

Several authors have commented on the frequencyof a VISI deformity in severe rheumatoid arthritis ofthe wrist.23" z~, 28 It is easy to explain the attenuation ofthe dorsal ligaments by the chronic recurrent inflam-mation and swelling that often occurs within the radio-carpal joint in these patients. The resulting imbalancethat occurs in the carpus with mild VISI deformity couldexplain further attenuation of the dorsal capsule andradioc .arpal ligament (Fig. 6). The osteophytic and ero-sive changes that can occur at the site of capitolunateimpaction must occur after the loss of integrity of thedorsal ligament and capsule. The resulting imbalanceallows the lunate to flex, which apparently shifts theload more palmar at the radiocarpal joint in certain

positions and at the midcarpal joint allows the-~orsallip of the flexed lunate to impact on the dorsal aspectof the capitate (Fig. 7). Trumble et al. 24 demonstratedin their clinical series that stabilization of the lunotri-quetral joint alone did not pr~ent the VISI deformityor "clunk." It would seem, in fact, that fusion of thelunate and the triquetrum in a case with a static VISIas defined by the stage III instability model of this study,would simply change a CID-VISI into a CIND-VISI.

In the cadavers stabilization of the lunotriquetral jointby means of Steinmann pins or a mini external fixatorin the stage I and II instabilities eliminated the motionbetween the lunate and triquetrum. In the stage II in-stability, stabilization of the lunotriquetral joint alsoprevented the ability of the carpus to assume a VISIpattern even with a significant dorsal force applied tothe c.apitate and/or hamate. In the stage III instability,stabilization of the lunotriquetral joint alone did elim-inate motion between the lunate and the triquetrum;

Vol. 15A, No. 2March 1990 Ulnar-sided perilunate instability 277

however, it did not prevent the VISI alignment of thecapitate and lunate. Similarly, transection of the dorsalcapsule and the radiocarpal ligament alone in a cadaverwrist will also allow a VISI alignment of the capitate

and lunate which would seem to fit the CIND-VISIcategory. Thus if a static VISI deformity does includethe compromise of the dorsal ligament and capsule,

unless they are reconstructed or the midcarpal joint isstabilized such as in a LTCH fusion, a LT fusion ismerely changing a VISI deformity of the dissociativetype into a VISI deformity of the nondissociativetype. Even in cases of trauma, once a dynamic orstage II ulnar-sided perilunate instability developsthere may be a sufficient tension on the dorsal radio-carpal ligament and capsule, that over time those struc-tures will attenuate leading to the development of a stageIII ulnar-sided perilunate instability with a static VISIdeformfty.

Summary

A staging system for ulnar-sided perilunate instabilityis presented based on a series of cadaver dissectionsand load studies. The staging system includes the fol-lowing:

Stage I: Partial or complete disruption of the luno-triquetral interosseous ligament; no clinical and/or ra-

diographic evidence of dynamic or static VISI de-formity.

Stage II: Complete disruption of the lunotriquetralinterosseous ligament and disruption of the palmar lu-notriquetral ligaments; clinical and/or radiographic ev-

idence of dynamic VISI deformity.Stage III: Complete disruption of the lunotriquetral

interogseous and the palmar lunotriquetral ligaments;attenuation or disruption of the scaphoid and lunateportion of the dorsal radiocarpal ligament; clinicaland/or radiographic evidence of static VISI deformity.

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