Copyright 1988 by f " Surgery, Incorporated‘. / "

Current Concepts Review

Carpal InstabilityBY JULIO TALEISNIK, M.D.*, IRVINE, CALIFORNIA

From the Department of Surgery (Orthopaedics) University of California at lrvine, lrvine

Before Rrntgen’s discovery of radiographs, only in-juries of the wrist that resulted in gross distortion of osseouslandmarks were recognized. The use of radiographs andother diagnostic techniques has expanded the spectrum oftreatable injuries to include conditions that, until a few yearsago, were unknown or extremely rare. It is now universallyagreed that there is a spectrum of carpal injuries that rangesfrom sprains to major fractures, dislocations, and fracture-dislocations. Within this spectrum, carpal instabilities,which were first mentioned by Gilford et al. ~6 and later weredescribed in association with scaphoid fractures by Fisk’a,

have assumed increasing importance.In 1972 Linscheid et al.~-8, and in 1975 Dobyns et al.~-’,

wrote landmark articles on carpal instability. They definedtraumatic instability, described radiographic findings, pro-vided a working classification, suggested a mechanism ofinjury, and proposed the first approach to treatment. Mostsubsequent reports on this subject have only refined or ex-panded on the conclusions of these authors.

Anatomy

~ The proximal surface of the carpus is an oblong condylethat articulates with the composite surface of the radius andthe triangular fibrocartilage. The structure is not a fixed,immutable condyle, but rather is a structure of variablegeometry-that changes shape to accommodate to the re-quirements for space, during motion, between the forearmand the hand22. These changes are possible because thecarpal condyle, which consists of eight bones that are ar-ranged in two rows, creates a multifaceted articulation tomeet the need for mobility and stability of the wrist.

The slopes of the articulating surface of the radius andthe shapes of the carpus define vectors that fall in prede-termined directions when the wrist is loaded5g. In particular,the articular surface of the distal part of the ~es~n.~a palmar and u-gl’ff~ direcnon, creanng a palmar-ulnarve_ctor under load. However, tlae articular surface xs sup-ported by a ligamentous system that prevents unidirectionalrmgr~n of the c__~..~_~_

Th-g~ are two major groups of ligaments of the wrist:

* Orthopaedic Surgery Medical Group, 1201 West La Veta, Suite501, Orange, California 92668.

extrinsic ligaments, which course between the carpal bonesand the radius or the metacarpals, and intrinsic ligament~.which originate and insert in the carpus 47"4s. These ligament~were named for the bones from which they originate andinto which they insert. The palmar radiocapitate, palmarrMioluna_te, palmar radioscapholunate, dorsal radiocarpal,and dorsal inte’r~-arpal ligaments, as well as the ligamentouscomplex in the ulnocarpal space47, are particularly impor-tant. Biomechanically, the extrinsic ligaments are stiffer,while the intrinsic ligaments are capable of greater elon-gation before permanent deformation occurs3°.

The presence of a collateral ligament system of thewrist, of the traditional construct, has been questioned. In1979, Kauer stated that the unique range of motion of thewrist "excludes collateral ligaments as components of theligamentous apparatus of the wrist’’2~. The function of atrue collateral structure, as is seen in hinge (ginglymoid)joi.n.ts, is not possible in a joint like the wrist, which hasthe anatomical appearance of a condylar or trochlear artic-ulation but the actual function of a multiaxial enarthrosis5~’s5.

Collateral ligaments would be useful only if radiocarpalmotion were limited to flexion and extension. Wh~-6 ulnarand radial deviation are added, a static collateral ligamentwould, in effect, restrain lateral and medial angulatory dis-placements.

Kauer proposed that the wrist has an "adjustable col-lateral system" of muscles acting as true collateral support:the extensor carpi ulnaris for the ulnar side of the wrist andthe extensor pollicis brevis and abductor pollicis longus forthe radial side. Freque_.p_ntly, the volar part of the capsule ofthe wrist has an area of weakness, called the space of Poiriml,bdtween the main ligamentous structures that are attachedprdk~mally on the lunate and distally on the capitate.

Kinematics

In general, .no tendons ar~ directly attached tO the car-pus. There are thre_~2_~stems of tendons that cross the wrist:the’ extrinsics of the fingers, which cross the center of2he~,rist anal exert minimum abduction-adduction moment onthe joint (the center of rotation of the wrist lies within thehead of the cap{ta-~ the flexors and extensors of the wrist,which surroun~"-the periphery of the joint and allow posi-tioning of the wrist without motion of the fingers; and the

CARPAL INSTABILITY 1263

tendons passing around the radial styloid process, whichcan exert marked radial deviation29. Within this system, theproximal carpal row behaves as an intercalated segment ina three-joint link system26. As such, the system would tendto collapse under compressive load were it not for the pres-ence of the scaphoid across the mid-carpal joint 32. An anal-ogy has been made between this mechanism and a slider-crank control, in which a three-bar linkage (represented bythe radius, lunate, and capitometacarpal links) is stabilizedby the scaphoid "crank’’2 8.

Navarro proposed an entirely different concept thatof the vertical or columnar carpus38"39"47. He proposed thatthere are..three longitudinal car~ columns: a lateral column(the scaphoid), a medial column (the triquetrum), and cen-traTffl-~xion-extension column (the lunate and the entiredistal carpal row). Within this system, the lateral column(the scaphoid) functions as a stabilizing rod across the lun-atocapitate joint. It is also responsible for palmar flexion ofthe proximal carpal row during radial deviation, as thescaphoid palmar flexes to accommodate to the__ shrinkingspace between the trapezium and the radial styloid process.Wh~lunate joint is dissociated, the absence ofthis function allows palmar flexion of the scaphoid to coexistwith dorsiflexion of the lunate and triquetmm in the sameproximal carpal row.

Similarly, during., ulnar deviation, shortening of thedistance between the hamate and the styloid proces.s~ fa-c~e triquetrum migrates distally on the ha-mate and dorsiflexes simultaneously~ .... . Because oT-t-~err~-rh-ff~position of th6 triqu-~ral facet of the hamate,this distal progression of the triquetrum forces the hamatein a palmar direction. The axis of the lunate also becomespalmar in relation to the capitate. Compressive forces fromthe capitate on the lunate then assist in rotating the lunateinto dorsiflexion6~. When there is a lunatotriquetral disso-ciation, this action can no longer be transmitted to the lunate.This explains how a dorsiflexed triquetrum can coexist witha patmar flexed lunate-scaphoid unit within the same prox-imal carpal rows4. These scaphoidinduced and triquetrum-induced rotations allow the proximal carpal row to functionas an intercalated segment. Thus the carpus has variablegeometry, maintaining the useful space or distance betweenthe radius and the distal carpal row-’. Recently publishedexperimental data supported this concept and denied thevalidity of the columnar theory of carpal function44.

In 1981 Lichtman et al. 27, and in 1984 Alexander andLichtman~, observed that a columnar concept fails to ac-,count for transverse, or perilunate, instability, as well asfor clinical patterns of transverse mid-carpal and proximalcarpal instabilities. They proposed the oval-ring theory, ac-cording to which the carpus is a transverse ring, formed bythe distal and proximal carpal rows and joined by two phys-iological links one radial (the mobile scaphotrapezialjoint) and the other ulnar (the rotatory triquetrohamate joint).

Weber’s investigations have contributed to the under-standing of the biomechanics of the wrist and have clarifiedthe role of the triquetrum6°. He emphasized that the carpal

intercalated system is controlled through both ligamentousand contact-surface constraints. The contact surface pro-vides stability throughout motion, while at the same timetransmitting loads6~. This is a kinetic, rather than simply akinematic, concept, incorporating transmissions of longi-tudinal load into the abstract analysis of carpal motion with-out load. Weber6~ thought, as did Navarro39 before him, thatit is useful to think of the wrist in terms of longitudinalcolumns when attempting to understand control of inter-calated segments through joint contact. He believed thatthere is; a force-bearing column, composed of the distal partof the radius, the lunate, the proximal two-thirds of thescaphoid, the capitate, the trapezoid, and the articulation.ofthe carpus with the second and third metacarpals. The func-tion of the force-bearing column is to transmit forces thatare generated bv the hand to the forearm.

According to Weber61, a second control column con-sists of the distal part of the ulna, the ulnocarpal complex,the triquetrum, the hamate, and the bases of the fourth andfifth metacarpals. The transmission of longitudinal force bythis ulnar column is limited because the triangular fibro-cartilage has greater compliance with applied loads. Instead,compressive forces on the ulnar column are deflectedthrough the rigid, planar hamate-capitate articulation of thecentral force-bearing column. In addition, the configurationof the hamate-triquetrum joint is well suited to provide ro-tational control.

The third column is the thumb-axis column6~, whichincludes the distal third of the scaphoid, the trapeziotra-pezoid joint, and the base of the first metacarpal. This col-umn acts a support for the base of the thumb, allowingindependent function of that digit. Compressive loads onthis column are also deflected to the central force-bearingcolumn, along the intact scaphoid, and across the trapezium,trapezoid, and scaphoid to the capitateo _

Unlike the carpal-ring and variable-geometry concepts,the columnar theories account for the presence of forces andloads that are, by necessity, transmitted from the hand tothe forearm in a longitudinal direction. ~~-

Carpal Instability

Dobyns et al. 12 defined traumatic instability of the wristas "a carpal injury in which loss of normal alignment ofthe c~~e~rly or la~iE"’TThey recogmzedfou~rn~3 ypes o carpal instability: dorsiflexion~ palmarflexion, ulnar translocation, and dorsal subluxation. Dor-siflexiion instability, which is the most frequent, is presentwhen the lunate has rotated into dorsiflexion, as seen onlateral radiographs. The capitate displaces dorsal to the longaxis of the radius, producing a zigzag radiolunatocapitatealigninent that is called dorsal intercalated-segment insta-bility (DISI). The intercalated segment is the lunate, s

identified on lateral radiographs. The opposite pattern, volarintercalated-segment instability (VISI), is characterized palmar flexion of the lunate. In the third type of carpalinstability, ulnar translocation, the carpus shifts ulnarward.The fourth type, dorsal subluxation, is commonly seen after

1264 JULIO TALEISNIK

a malunited fracture of the radius associated with reversalof the normal palmar tilt of the articular surface. AlthoughDobyns et al.I-" considered an opposite, volar type of carpalsubluxation to be theoretically possible, it was not until aftertheir study was published that isolated cases were reported3.

The.~e_caq~a! ahn~.malitie_s..,..which can be clearly re_ c-ognized on routine radiographs by t__he loss of normal align:ment o-~th~g~fp--aq-b-o~es, have been called static49s°. Thereis a se~-~-~ff’~~p~t’-d-a-~al instability for which the routineradiographic findings are within normal limits. With thistype of instability, the patient can voluntarily ch~hecarpal alignment from normal to abnormal and the reverse.Sornetimes-thi-e instability can be’~produced by manipula-tion only; again, all other ancillary tests, with the possibleexception of bone scans, are normal. This form of instabilityis called dynamic, and it may occur between the scaphoidand the lunate, between the lunate and the triquetrum, orbetween the carpal rows at the mid-carpal joint.

The most common carpal instability is secondary toligamentous disruption between the scaphoid and the lunate,the’ second most common instability is that between’ t-helunate and the triquetrum, and the third most common isdynamic mid-carpal instability. Ulnar translocation rarelyresults from injury, but it is frequent in wrists that areaffected by rheumatoid arthritis. Carpal instability second-ary to malunion of a fracture of the distal part of the radiusis also common.

Anatomically, there are three types of instability: lat-eral instability, which usually occurs between the scaphoidand the lunate; medial instability, which occurs between thetriquetrum and the lunate or between the triquetrum and thehamate (mid-carpal instability); and proximal instability,which occurs when the abnormal carpal alignment is sec-ondary to an injury of the radius or to a massive radiocarpaldisruption (dorsal carpal subluxation, mid-carpal instabilityse.condary to malunion of the distal part of the radius, andulnar translocation)49"~1’53.

Th~ patterns of instability that result from ligamentousdisruption ~n the proximal ca.rpal row -- that ~s, betweenthe._~.aph0id a--~’~ ~o~i’b~t~hetriquetrum -- include.._s_capl~olunate.-dissociation.~ahizh_~e-sults in dorsal intercalated-segment instability, and luna-t o t ri~dral_.di~cj.ati.oxt~2~hich-lead~to-vot-ar-intereat~ t e d -S.e.~ment in st ability. T_~__~e_s_~’Jajxtries-ar_e-g.~s_.o_f.~s s o c iaO vecarp_~ instability.!1.

Non-dissociative carpal instability also results in dorsaland volar intercalated-segment instability, but it is not as-

¯ "~ sociated with a ligamentous injury in the proximal carpal¯ row; all three major bones continue to f~ib~ Non-dfss’gb’N~tive carpal instabilities include ~torsal ~arpal

subluxation, mid-carpal instability in which rotation of thebones in the proximal carpal row leads to dorsal or volarintercalated-segment instability, volar carphl subluxation(which is very infrequent), and some ulnar translocations.

Mechanism of Injury

, Assessment of the laxity of ~erent in-

dividuals is important in determining the outcomes of oth-erwise identical injuries to the wrist 47. A fall on theoutstretched upper extremity when the wrist is in dorsiflex-ion may result in a fracture in some patients and a dislocationin others. Hypermobility of the joint is frequent in patientsin whom an injury elongates or partially or completely tearsa ligament. In addition to the variation in behavior of lig-aments among different people, it has been suggested thatthere is a qualitative difference in yield strength of differentligaments in the same individuaP6. According to this thesis,the weakest ligaments are in the radial and palmar quadrantsof the wrist36. This may explain the presence of clinicalinstability without radiographic, arthrographic, or surgicalevidence of a torn ligament. As is true for carpal dislocationsand fracture-dislocations, the point of application, magni-tude, and direction of the force of injury, and the positionof the hand at the time of impact, are important in deter-mining the resulting carpal instability.

Most frequently, injuries follow compressive loadingof the wrist in s0~e ~ ’ ’ ~-on. Rotgtion ~t"either the forearm or the wrist itself is frequently present.In a study of carpal dislocations and fracture-dislocations,Mayfield et al. 35 loaded the wrists of cadavera in extension,ulnar deviation, and intercarpal supination. The resultingsequence of injury, which they caiidd progressive perilunarinstability, included four stages. At the end of st~ge_L..ascapholunate diastasis, the most frequent typ~..of carpa_l in.___:st’a-b-ility, was produced. Progression of the loading led t____os ~.~sal dislocation of the capitate. In sta.~e II!_,_1lae ~triquetrurn gradually dislocated from the lunate, resulting~n tnquetrolunate diastasis or an avulsion fracture__oLL~he

!~. Stage IV was typified by dislocation of the lun-ate, the grea e~e~e~e~e~e~e~e~e~st degree of perilunate ins/~b~li~y. ’ .....

.... Clinical evidence has suggested that-I~ading on theulnar side of the carpus, with the carpus hyperpronated,results in triquetrolunate ~njury ~. In addition, i~-youngerpatients who have ligamentous laxity, a malunited fractureof the distal part of the radius that results in loss of normalpalmar tilt of its distal articular surface may allow immediateor progressive carpal subluxation. This subluxation mayoccur at the level of either the radiocarpal joint (dorsal carpalsubluxation) or the mid-carpal joint (mid-carpal instabilitysecondary to a malunited fracture of the distal part of theradius)53.

Diagnosis

The diagnostic process starts with documentation., ofthe mechanism of injury and of the patient’s complaints. ....For patients who have dynamic instability, so-called trickmotions or snaps must be observed. Any localized tender-ness should be elicited. The clinical findings must be keptin mind, because frequently these patients have normal find,;ings on routine radiographs. Only after the routine radio-,graphs have been seen to be normal can dynamic instabilityand tenderness be investigated further. To assess dynarnicinstability, radiographs are made both before and after aposition of instability has been assumeds’- or the carpus has

CARPAL

been manipulated. To assess tenderness, radiographs aremade with metal markers at the site of the tenderness.

Additional documentation can be obtained by injectinga small amount of an anesthetic agent into the tender jointand recording changes in the pattern of pain, mobility, andgrip strength. Manipulation of the scaphoid by the examinermay reproduce the patient’s sensation of instability or evencause subluxation of the proximal pole of the scaphoid (theWatson test)52. If the ulnar side of the carpus is involved,triquetrolunate ballottement42 or mid-carpal manipulation3~

is performed.The initial radiographic examination is tailored to the

patient’s complaints and clinical findings. On a postero-anterior radiograph, three major features are evaluatedsequentially~7: (1) the carpal arcs, which are usually con-centric and which are traced along the proximal and distalsurfaces of the proximal carpal row and the proximal surfaceof the distal carpal row; (2) the symmetry of the joint spaces;and (3) the shapes of the individual bones. Lateral radio-graphs are useful for the evaluation of radiolunatocapitatealignment and for the determination of angles between thesebones and the scaphoid.

Radiographic Findings

Scapholunate Dissociation

For a wrist that has scapholunate dissociation, antero-posterior radiographs show a scapholunate gap that is widerthan the scapholunate space in the opposite, uninjured wrist.This gap is usually more noticeable on an anteroposteriorradiograph that is made with the wrist supinated than it ison the more usual posteroanterior radiograph (made withthe wrist pronated). It is important to direct the x-ray beamparallel to the scapholunate joint. Moneim37 and Frot et al. ~5described radiographic projections to accomplish this ob-jective.

.The cortical ring sign is produced .by the cortex of thedistal ~ie 0fihe palmai’~exed scaphoid ~s seen end-on2’gaz.

The scaphoid is foreshortened. The distance between thes~~ng., and t_he proximal pole of the scaphoid is de-creased to less than seven millim~~l~rmal scapholunatotriquetral correlation -- a fore-shortened (palmar flexed) scaphoid coexists with a quad-rilateral (dorsiflexed) lunate, and the triquetrum is in a distalposition (dorsiflexed) in relation to the hamate.

Negative ulnar variance has been found to be signifi-cantly more frequent in patients who have a post-traumaticscapholunate dissociation~.4°. At present, the biomechanicalimplications of this finding are conjectural.

Posteroanterior radiographs that are made with thewrist in ulnar, deviation, in radial deviation, and with theapplication of longitudinal compressive load~2 (with the fistclenched) may also show a widened scapholunate gap inthe wrist that has scapholunate dissociation.

Lateral radiographs are valuable to assess the oppositerotations of the lunate and the scaphoid. When the scapho-lunate joint is dissociated, the scaphoid is palmar flexed,with its long axis perpendicular to that of the radius, and

INSTABILITY 1265

the lunate is dorsiflexed (dorsal intercalated-segment insta-bility). The scapholunate angle, which normally ranges from30 to 60 degrees and averages 46 degrees, increases to morethan 70 degrees’2’28.

Triquetrolunate Dissoci_i~on

A posteroanterior radiograph of a wrist that has a fullydeveloped volar intercalated-segment instability shows thescaphoid to be volar flexed and foreshortened. The ring signis present, and the distance between the ring and the prox-imal pole of the scaphoid is decreased. However, unlike theca,:e with scapholunate dlssocmt~ons, tl~e lunate is volarfle’:~angular. The triquetrum is dorsiflexed and dis-taT’in relation to the hamate. The distance between the. ulnarhead and the triquetrum is shortened (the Mayersbachsign) -. The convex outline of the proximal carpal condyle,called the Shenton line of the wrist by Linscheid, is inter-rupted by a step-off between the lunate and the triquetrum.

Lateral radiographs show the lunate to be palmarflexed. If the triquetrum and the lunate can be identified,the normal triquetrolunate angle of approximately - 16 de-grees is converted to a neutral or positive angle~9.

Ulnar Translocation

Abnormal translation of the lunate in an ulnar directionis pathognomonic of ulnar translocation. McMurtry et al.33

described a reproducible method of measuring what theycalled the carpal-ulnar distance -- that is, the distance be-tween the center o_f_rotation of the carl3U-~-~-iiitIi~h6gd of.. ¯ -o .-7-~---7 ,. .. ---- .--5 -me cap~tate, ana anne extendm~ the lo~tudinal axis ofthe u.lna di_i~_tal~.. In normal wrists, dividing this distance bythe length of the third metacarpal consistently results in aratio’of 0.30 __+ 0.03. In wrists that have ulnar translocation,the ratio is smaller, indicating that the capitate and the lunateare translocated in an ulnar direction.

A similar method, using the lateral part of the-radialcortex instead of the longitudinal axis of the ulna, has beenproposed6. According to the position of the scaphoid, twotype.s of ulnar translocation can be seen~2. In Type I, theentire cart~_u__fis., including the scaph0jd, is displ~distance between the radial styloid process and the scaphoidis widenedtz. In Type II, the rel~between tn~-

hll " otu,~ no.jd_.=and the radius, and t 5_th~.disla~e,_b .... ~., .....e-scaph-o.id and the radial sty~ess, remains normal, but thesc~olunate space is widene~l.’7--

The distinction between the two types of tilnar trans-location is important, because the appearance of a widescapholunate gap may lead to the erroneous diagnosis of ,..scapholunate dissociation. If this happens, any attempt at : ....stab!ilizing what appears to be a rotatory subluxation of the "scaphoid will fail to correct the underlying problem, whichis ulnar migration of the carpus~. Ulnar translocation fre- ’ ,!quently is accompanied by volar flexion instability of.the: ’~

proximal part of the carpus.

Dynamic Instability

Dynamic forms of dorsal or volar intercalated-segment

VOL. 70-A, NO. 8. SEPTEMBER ~988

JULIO TALEISNIKinstability are secondary to loss of support across the ulnar graphic control may correct a fresh scapholunate dissocia-half of the mid-carpal joint z7. Routine radiographs usuallyare considered normal, although the alignment of the ra-diocarpal link may have a palmar or dorsiflexion bias. Manypatients who have dynamic instability can actively subluxatethe wrist with the forearm pronated and the wrist in or out

of ulnar deviation27.Diagnostic radiographs are made with the patiem’s

forearm and hand pronated, elevated on a bolster, and placed

against the radiographic plate, which is held vertically. Thex-ray beam is directed horizontally across the wrist. Thepatient is then asked to reproduce the position of abnormalcarpal alignment. (If the end-point of active motion thatproduces the subluxation is different from that just de;-scribed, the radiographs should be made with the wrist inthat position.) Lateral radiographs will show a volar or dor-sal intercalated-segment instability, with loss of the align-ment between the capitate and the radius that is normal forthat patient52. In most patients, this approach eliminates the;need for cineradiographic studies.

Special Studies and Ancillary Procedures

Bone scintigraphy and arthrography ~~ which, whendeemed necessary, probably are best done in that order-are useful in the diagnosis of carpal instability. In patientswho have carpal instability, the uptake of isotope is in-creased, probably secondary to hyperemia accompanyingreactive synovitis. When a scan is negative, it suggests eitherthat there is no injury or, more frequently, that the problemis minor and can he treated non-operatively. Because it isnot specific, a positi’ve scan should not be used alone in

determining the diagnosis, but should be employed in con-junction with other tests. Triphase scans are preferable46;when a posteroanterior image is positive, lateral and obliqueimages should be made as well~°. This helps to localize thecarpal problem.

Arthrography is helpful in finding ligamentous tears.It is important that the flow of opaque material be followedin an image intensifier to .find leaks and abnormal com-

munications45. Digital fluoroscopy has been used advanta-geously for the same purpose. Arthrograms that are madeby injecting all three major joints (radiocarpal, mid-carpal,and distal radio-ulnar) with contrast medifim are helpful andsometimes obligatory6~. It is important to keep in mind thatcommunications between tfiga~tterent compartments o-’~hewns~e not necessarily tl~e ~~~-’~n-

Arth~roscopy is valuabie for direct ~’isu~lization of the in-tercarpal joints~a.62.

Computed tomography is probably not usefui in thediagnosis of carpal instability. Magnetic resonance imagingis promising, although its value and applications for thewrist have yet to be determined.

tion7. In most patients, however, surgical visualization andrepair of the torn ligaments, using dorsal and palmar inci-sions, is more reliable.

For a chronic scapholunate dissociation that is not as-sociated with osteoarthritis, the technique of reconstructionof the ligaments by threading tendons through drill-holes ineither the carpal bones or the radius, or both, has provedto be unreliable and is very demanding technically~8,20.~.Instead, reattachment of the scapholunate ligament, whichis usually torn from the scaphoid, can be attempted. The

reattachment can be augmented by attaching tendinous orcapsular tissue along the scapholunate space~9. A dorsalcapsuloligamentodesis, as described by Blatt4.~, also canbe used instead of, or in addition to, the repair of theligament. For a capsuloligamentodesis, a dorsal capsularflap, which is left attached to the radius proximally, is in-serted in the distal part of the scaphoid to tether the distalpole dorsally, keeping the scaphoid from subluxating in apalmar direction.

Y~ced systemic la_xity_.~_ofthe~-j°!nt~’--g°werfi’ ~ ~.andmanding a-a__p~y~de_occupation benefit from stabilization o-f._the_s.c_aph-oid-lyy a limited a~--fflSg6-desis betweerkXh_he_s_c_aphoid,__thetrapezium, and the trapezoid, as ~y Watson and~pton~. This pr~-~dure, as well as all other~rn--~ed

carlS~rodeses, must preserve the size and outer shapeof the fused unit and must not interfere with the relationshipand alignment of the surrounding carpal joints. The long-term results of the procedure have thus far dispelled doubtsregarding the wear and tear of joints neighboring the site

--of a partial carpal arthrodesis-’4.z~. However, the results havenot been uniformly predictable~. Not only is there residuallimitation of motion, but in some patients the procedure hasalso been followed by weakness and pain during forcedloading of the wrist in dorsiflexion.

Untreated chronic scapholunate dissociation commonly

,results i.n a.~ern-ofosteoarthritis-.and.subluxati~n that hasoeen caltea-s~co_pholunate advanced colla se .......ically, degenerative changes occur in areas of abnormalloading, initially between the radial styloid process and the

TreatmentScapholunate Dissociation

Manipulation and closed pinning under cineradio-

scaphoid and later in the unstable lunatocapitate joint, asthe capitate .sublu_x__ale_s_do~al_!l.g on the lunate The recomended treat~--een, ¢ .... ¯ -,~’~ " ~ rec°m-2.~r tins roNem consists of re lacement

.!~... ~t,s.,o.r re.placerr_~~taomzatmn of_~the

unstable m~d ~~t t_hrou~~fus_io n .....

l,unatotriquetral Instability - i ~?.~ f(~

The acutely symptomatic lunatotriquetral joint may be ~ts’eated successfully by local injection of steroids and im,mobilization above to the elbow. If this approach fails o~

~if the instability is ch~-onic and disabling, the lunatotriquetralligament can be repaired directly, with or without capsularor’ ligamentous augmentation4~. Where there is an ulnar-plusvariant, especially if the triangular fibrocartilage is perfo-ral:ed, ulnar shortening is the procedure of choice. Luna-totriquetral arthrodesis may be used when the other tech-

as-:ion

sinred).41

ichFheor

’sal;all

larin-talI a

CARPAL INSTABILITY 1267

¯ ~ niques are not feasible34. Dynamic Volar and Dorsal

i

Intercalated-Segment InstabilityUlnar Translocation A trial of non-operative management, including above-

Surgical exploration of an acute ulnar translocation the-elbow immobilization with the elbow supinated, local

troutinely discloses a massive dorsal and palmar tear of the injections of steroids, and administration of anti-inflam-

~ capsule from the radius. Frequently, a previously unsus- matory medication, is justified if the patient had not receivedpected tear of the scapholunate ligament is present. Repair such treatment previously, particularly if he or she has anof the ligament, even when the injury is acute, is unreliable, occupation that is not physically demanding. However, forExperience with the treatment of ulnar translocation in ar- patients who are disabled by persistent or recurrent symp-thritic wrists 6’49 has suggested that relocation of the carpus toms, stabilization of the mid-carpal joint through limitedand maintenance of reduction by radiolunate arthrodesis arthrodesis, capsuloligamentodesis, or tenodesis is jus-may be a more reliable and satisfactory technique, tiffedzL52.

References1. ALEXANDER, C. E., and LICrtTMAN, D. M.: Ulnar Carpal Instabilities. Orthop. Clin. North America. 15: 307-320, 1984.2. ARNSTRONG, G. W. D.: Rotational Subluxation of the Scaphoid. Canadian J. Surg., 11: 306-314, 1968.3. BELLINGHAUSEN, H.-W.; GILULA, L. A.; YOUNG, L. V.; and WEEKS, P. IV1.: Post-Traumatic Palmar Carpal Subluxation. Report of Two Cases.

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