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Carpal dislocations: Pathomechanics and prc:,gressive perilunar instability Tile pathomechanics, ligamentous damage, and degree of carpal in, ~ rbilio, in perihmate and lun ~ze dislocations were anal)~ed by e.rperimentally I~ding 32 cadaver ;rrA~’ts to faihtre. Thirteen peril o~ate and two hmatedislocations were produced. The mechanism of b~juo’ wasextension, ttb~ar deviatio~ . and h~terca~al $upbIatiOn. These dislocations ~’ctt~ed in a sequential fo~’hion due to progressive ~ ’*d spec~c ligmnentousdisntptions and were class~ed according to the degree q~ pe,ihmar insmbilio, (PL ~. Stage perihmar instabilio, (scaphohmate diasmsis) had the least degree qf t’a,=p~I instabilio,. Ltmate dislocations (stage IF PLI) had the hight~vt degree of carpal instabilio.. Radial sOqoid.?actures were produced serea as a result tf avttlsion: Scaphoid rotation was created h; eight and ,,,as due to ntpntre of the radioscaphoM and scaphohmate Hgaments.Reduction was accomplished by reversing the mechanism of b~ttry~that is, intercarpal pronation, radial deviation, and pahna~ flexion~ Stress roentgenograms employing kmgitudinalcarpal compression h~ radial and tth~ar deviation w~re helpfitl in determining the degree ¢~assoeiated carpal instabiliO’. Jack K. Mayfield, M.D., Minneapolis, Minn., Roger P. Johnson, ~vl.D. and Raphael ,K. Kilcoyne, M.D., Mihvaukee,Wis. Apuzzling variety of injuries occur about the wrist. These.include radial styloid fractures with or without perilunate dislocations, volarand dorsalBarton’s frac- ture, perilunate and lunatedislocations, scaphoid frac- tures with or without perilunate dislocation, or capitate andtriquetral fractr~res. Considerable confusion exists concerning the pathomechanics of injury, the ligamen- tous damage as well as the treatment andclassification of theseinjuries. |-t.~ The degree of carpalinstability associated with theseinjuries hasnot been anatomically documented. Scaphoid rnalrotation, scapholunate diastasis, and carpal collapse are well known carpal entities and have been well,~e~¢ribed. ~-~a Late carpal collapse is a natu- ral sequela of perilunateandlunatedislocations when initial treat.rnent hasnot restored carpalalignment, a Late degenerative intercarpal andradioearpal arthritis are common in these patients, andreconstructive pro. cedures are ~imited. Since the majority of these patients are young adults, the durationof disability is sig- nificant. Fro.n TheMedical Collegeof Wisconsin. Milwaukee. Wts. Supported by gran[ No. 620-$2.2lfrom The Medical College of Wisconsin. Milwaukee. WIs. Re~eived for publication March 26. 1979; revisedJuly I I. 1979. Reprintrequests:Jack K. Mayfleld.M.D., Department of thopaedle Surgery, Box 287--Mayo, University of Minnesota. Minneapolis. MN $J455 [(612) 376-11.~4]. Radial styloid fractures c~n occur in association with carpaldislocations ~. ~. to-t~; ta; however, the mecha- nism of these fractures re;r~ains unknown. Triquetral fractures are also occasionally seen with perilunate and lunate dislocations t°. zn. *.o; however, little attention has been drawn to this association~ Transeaphoid perilunate fructure-dislocations frequently occur in association wiith tdquetral fractures. ~ Theirmechanism of injury, as described by Johnson et al. ~a is forced extension, ulnardeviation,andinterearpal supination. They have alamo recorded associated specific ligamentous disrup- tions andassociatedperilunarinstability. Weber and Chao ~ havestressed extension as the component caus- ing scaphoid fractures. Tanz, ~ as wel. as Johnson et al,,, have been impressed with the effe,~t of the rota- tional component in the mechanism of ~,ese injuries. Acute.and chronic carpal instability as n result of carpal dislocations andfracture-dislocation~ has been studiedextensively byseveral authors. ~. ~. ~, ~ Land- smeer ~u stressed the collapsibility of a link or interca- lated system when the controlling tensioncoml:onents an; removed. Most of our knowledge regarding this entity hascome from olin ical evaluation of wrists ~t the time of surgical repair, and the body of knowledge explaining the various carpalinstability patterns seems, incomplete. Wagner||, n suggested that lunate dislocations were preceded by perilunatedislocations, andthus implied

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  • Carpal dislocations: Pathomechanics and prc:,gressiveperilunar instability

    Tile pathomechanics, ligamentous damage, and degree of carpal in, ~ rbilio, in perihmate and lun ~zedislocations were anal)~ed by e.rperimentally I~ding 32 cadaver ;rrA~’ts to faihtre. Thirteen peril o~ate andtwo hmate dislocations were produced. The mechanism of b~juo’ was extension, ttb~ar deviatio~ . andh~terca~al $upbIatiOn. These dislocations ~’ctt~ed in a sequential fo~’hion due to progressive ~ ’*d spec~cligmnentous disntptions and were class~ed according to the degree q~ pe,ihmar insmbilio, (PL ~. Stage perihmar instabilio, (scaphohmate diasmsis) had the least degree qf t’a,=p~ I instabilio,. Ltmate dislocations(stage IF PLI) had the hight~vt degree of carpal instabilio.. Radial sOqoid. ?actures were produced serea as a result tf avttlsion: Scaphoid rotation was created h; eight and ,,,as due to ntpntre of theradioscaphoM and scaphohmate Hgaments. Reduction was accomplished by reversing the mechanism ofb~ttry~that is, intercarpal pronation, radial deviation, and pahna~ flexion~ Stress roentgenogramsemploying kmgitudinal carpal compression h~ radial and tth~ar deviation w~re helpfitl in determining thedegree ¢~assoeiated carpal instabiliO’.

    Jack K. Mayfield, M.D., Minneapolis, Minn., Roger P. Johnson, ~vl.D. andRaphael ,K. Kilcoyne, M.D., Mihvaukee, Wis.

    A puzzling variety of injuries occur about the wrist.These.include radial styloid fractures with or withoutperilunate dislocations, volar and dorsal Barton’s frac-ture, perilunate and lunate dislocations, scaphoid frac-tures with or without perilunate dislocation, or capitateand triquetral fractr~res. Considerable confusion existsconcerning the pathomechanics of injury, the ligamen-tous damage as well as the treatment and classificationof these injuries.|-t.~ The degree of carpal instabilityassociated with these injuries has not been anatomicallydocumented.

    Scaphoid rnalrotation, scapholunate diastasis, andcarpal collapse are well known carpal entities and havebeen well ,~e~¢ribed.~-~a Late carpal collapse is a natu-ral sequela of perilunate and lunate dislocations wheninitial treat.rnent has not restored carpal alignment,aLate degenerative intercarpal and radioearpal arthritisare common in these patients, and reconstructive pro.cedures are ~imited. Since the majority of these patientsare young adults, the duration of disability is sig-nificant.

    Fro.n The Medical College of Wisconsin. Milwaukee. Wts.Supported by gran[ No. 620-$2.2l from The Medical College of

    Wisconsin. Milwaukee. WIs.Re~eived for publication March 26. 1979; revised July I I. 1979.Reprint requests: Jack K. Mayfleld. M.D., Department of

    thopaedle Surgery, Box 287--Mayo, University of Minnesota.Minneapolis. MN $J455 [(612) 376-11.~4].

    Radial styloid fractures c~n occur in association withcarpal dislocations~. ~. to-t~; ta; however, the mecha-nism of these fractures re;r~ains unknown. Triquetralfractures are also occasionally seen with perilunate andlunate dislocationst°. zn. *.o; however, little attention hasbeen drawn to this association~ Transeaphoid perilunatefructure-dislocations frequently occur in associationwiith tdquetral fractures.~ Their mechanism of injury,as described by Johnson et al.~a is forced extension,ulnar deviation, and interearpal supination. They havealamo recorded associated specific ligamentous disrup-tions and associated perilunar instability. Weber andChao~ have stressed extension as the component caus-ing scaphoid fractures. Tanz,~ as wel. as Johnson etal,,, have been impressed with the effe,~t of the rota-tional component in the mechanism of ~,ese injuries.

    Acute.and chronic carpal instability as n result ofcarpal dislocations and fracture-dislocation~ has beenstudied extensively by several authors.~. ~. ~, ~ Land-smeer~u stressed the collapsibility of a link or interca-lated system when the controlling tension coml:onentsan; removed. Most of our knowledge regarding thisentity has come from olin ical evaluation of wrists ~t thetime of surgical repair, and the body of knowledgeexplaining the various carpal instability patterns seems,incomplete.

    Wagner||, n suggested that lunate dislocations werepreceded by perilunate dislocations, and thus implied

  • Vo|. ~ No. 3May 1980 Carpal dislocations 227

    rCL

    Fig. 1. Velar view of the wrist joint. Intracapsular liga-ments: radiocapitate ligament (RCL). radiotriquetral ligament(RTL), radioscaphoid ligament (RSL), ulnolunate ligament(UIL). ulnotriquetral ligament (UTL), capitotriquetral liga-ment (CTL). Capsular collateral ligaments: radial collateralligament (rCL). ulnar collateral ligament (uCL).

    that the pathomechanics of these injuries may be re-lated. Most authors agree that perilunate and lunatedislocations occur with forced extension.2-s" 7-it. ~a. 2.~In perilunate dislocations one of two things must occurfor the capitate to dislocate from the lunate: either thescaphoid (the connecting rod between the proximal anddistal carpal rows) is fractured, or it is dissociated fromthe lunate.~-4’ Io-~z. i.~. ~s However, the actual mecha-nism of injury in perilunate and lunate dislocations re-mains unknown.

    Since all dislocations involve ligamentous disrup-tions-;anexperimental-approach to. these injuries wasdesigned to produce these injuries mechanically inorder to learn more about the wrist ligaments and theirrelationships in these injuries. This approach was par-ticularly pertinent due to recent insight into the detailednature and significance of the velar intracapsular wristligaments37-z~

    Anatomy

    We thought that the characteristic dislocation of thecapitate from the lunate in lunate and perilunate dislo-cations had to be explained by a specific anatomic ar-rangement of the various wrist ligaments, Anatomicinformation derived from recent investigations have

    Fig. 2. A, Dissected specimen showing distal cut section ofthe RT and RC ligaments. (R, radius; S. scaphoid; RTL,radiotriquetral ligament; L, lunate; RCL. radiocapitate liga-ment; T. triquetrum; RS. radial styloid; C. capitate; M.meniscus,)B, Dissected specimen showing proximal.cut see-.tion of the RT and RC ligaments. (R, radius; L, lunate; RTL.radiol~,riquetral ligament; T. triquetrum; RCL, radiocapitateligament; U, ulna; RS. radial styloid; uCL, ulnar collateralligament. S, scaphoid; M. meniscus.) C, The radiotriquetralligament viewed intraarticularly from the radial side in a dis-secte,:l specimen after a perilunate dislocation (specimen101). (RTL. radiotriquet-q ligament; L, lunate; S, scaphoid;RS, radial styloid; ¢", volar capsule.)

    helped to elucidate this concept.2s Further understand-ing of the wrist ligaments was greatly aided by experi-memal loading studies. These new anatomic and carpalkine~atic data were integrated as part of the designconcept of this study. A review of the anatomy of the

  • 228 Mayfield, Johnson, Kilcoyne

    The Journal ofHAND SURGERY

    DORSAL

    Dorsol rodiocorpol ligoment

    ~VOLAR

    Fig. 3. Lateral view of thv wrist joint,

    Fig. 4, Dissected specimen showing the radioscaphoid liga-ment (RSL). (R. radius; S. scaphoid; L. lunate.) scapholunate interosseous ligament has been cut.

    Fig. $. lntraarticular view of ulnar side of the wrist. (UTL,ulnotriquetral ligament; ULL, ulnolunate ligament; tICL,ulnar collateral ligament; T, triquetmm; U, ulna, L, lunate;M, meniscus: H, hamate; R, radius: C, capitate;$, scaphoid.)

    Fig. 6. Intmarticular view showing the capitotriquetral liga-ment (CTL). (C, capitate; T, triquetrum; H, hamate; L, nate; t¢CL, ulnar collateral ligament.)

    DORSAl.

    IRADIOCARPAL

    LIGAMENT

    Fig. 7. Dorsal view of the wrist joint.

  • Vol. 5. No, 3May 1980 Carpal dislocations 229

    VOLAR

    LIGAMENT~ ~

    O. RADIOTRIQUETRAL~

    D. ULNOLUNATE

    E. ULNOTRIQUETRAL

    H. ULNAR COLLATERAL

    ~.-.DORSALRN~OCARPAL

    LIGAMENT

    Fig. 8. Ligamentous stabilizers of the proximal carpal row.

    RTL

    VOLAR 1 I DORSAL DORSAL

    Fig. 9. Ligament and carpal motion in extension. (Zigzagarrow, loose; straight arrow, taut.)

    wrist ligaments and wrist kinematics is pertinent.=s

    Descriptive anatomy. The key ligaments of thewrist are volar and intracapsular (Figs. ! and 2). Thepalmar or volar radiocarpal ligament consists of threedeep strong intracapsular ligaments, not a single capsu-lar ligament as described in most anatomical sources.The mdiocapitate ligament (RCL) is a strong in-~.racapsular ligament that arises from the volar and m-dial aspect of the radial styloid process, traverses agroove in the waist of the scaphoid0 and ends in thecenter of the volar aspect of the capitate. The volarradiotriquetml ligament (RTL) is the largest ligament

    Fig. 10. L!igament and carpal motion in flexion. (Zigzag ar-row, loose; straight arrow, taut.)

    the wrist. It arises from the volar aspect of the radialstyloid process next to the radiocapitate ligament; it isdirected across the volar aspect of the lunate, to whichit is convtected and ends in the palmar surface of thetfiquetmv~ and is considered to be a single ligament incontrast to reports from other authors.=9 This ligament(RTL) acts as a volar sling for the lunate (Fig. 20

    The radiosca_~oidligamoa~RSL~u~ f~_~. e~vo~!artip o-0"~-~ dis~the .l.n.ar sir..e?o.f_t~.,e ~dto-triq-dEt~_e_e_nt_L(_~!,J~nd is dtrccte_d into theimal volar aspect of ~_~_~_ap~holunat_~int (Figs. 3 and4).~TSis--t~~-~-s~-~iarge ligament that is consistently

  • 230 Ma~field, Johnson, Kilco~e

    Table I. Specimen data, loading data, loading angles,

    Total No. Specimen No. Age {yr) Sex I

    MMFM

    Fixative Weight (kg)

    The Journal ofHAND SURGERY

    I

    MethodHeight (cra) of loading

    I 100 64 F -- -- M2 101 30 FR 13.5 82 G3 102 55 FR 13.5 82 G4 103 5 FR 8.6 56 G

    5 IO4 5 M FR 8.6 59 G6 105 70 F E 19 82 G

    7 106 37 F F 12 79 G8 107 60 M E 13 76 G9 108 65 M E 13 71 G

    10 109 65 M E 13 69 G

    !1 I10 62 M E 12 82 G12 I!1 72 F Z 12 82 G

    13 112 72 F -Z 12 79 G

    14 !13 70 F Z 14.5 79 G15 114 19 M Z 9.6 I10 G16 115 19 M Z 19.5 53 G17 116 74 F Z 12 56 G18 117 55 M Z 12 38 G19 118 55 M Z 12 51 G20 201 -- -- FR -- -- H21 202 -- -- FR -- -- H22 204 -- -- FR -- -- H23 206 -- -- FR -- -- H24 208 81 -- FR -- -- H25 213 74 -- FR -- -- H26 215 72 -- FR -- -- H.27 216 71 -- FR -- -- H28 217 89 -- FR -- -- H29 219 17 -- FR -- -- H30 221 47 -- FR -- -- H31 222 47 -- FR -- -- H32 224 44 -- FR -- -- H

    Legend: Fixatloa-- FR, fresh; F, 10% formalin; E, embalmed; Z, I0% Zephadn FM._or[de3 Loadinlg/t_ef_hjlique~...-..Q,.gr~_y_ity, fns~ loading;H, hydraulic, slow loading:M, manual; Loading angle--E, extension; U, ulnar deviation; S, interca~pal supination; F, flexon; Comments--UCL. ulnocatpal ligament; RTL. radiotriquatral liga-ment; REL, radiocapitate ligament; RSL, radioscaphoid ligament;

    present and is to be differentiated from the scapholu-nate interosseous ligament, which has been describedby Kauer:°

    The ulnolunate (ULL) and ulnotdquetral (UTL) aments arise intraarticularly from the ulnar articularmeniscus of the wrist joint and are directed to the lunateand triquetrum, respectively (Fig. 5).

    The capitotriquetral ligament (CTL), an intracap-sular ligament, connects the volar aspects of the capi-tate with the triquetrum (Fig. 6).

    The radial and ulnar collateral ligaments are spe-

    cializations of the fibrous wrist capsulen, to (Fig. I).The dorsal radiocarpal ligament (DRC) arises from

    the dorsal aspect of the radial styloid process, is di-rected across the dorsal surface of the lunate to termi-nate mainly into the dorsal aspect of the triquetrum.This ligament (DRC) acts to maintain the lunate inapp0siti-on-t~~ radius (Fig. 7).

    The w~-~~fits---stabili---~e the carpus to the distalradius at~td ulna. The radiocapitate (RCL) and ca#to-triquetral (CTL) ligaments are the prime stabilizers the distal carpal row (Fig. 1). The proximal carpal row

  • Vol. 5, No. 3May 1980 Carpal dislocations 231

    ILoading ] Stage ofangle [ perilunar inst~ility

    E IVE 111EE

    EE

    I

    ScaphoidInjuries rotation

    Lunate dislocationDorsal perilunate dislocationColles’ fractureGreenstick fracture of distal radius

    and ulnaSalter 11 distal radius fractureColles’ fracture ulnar styioid fracture

    E Radial styioid body fractureE Radial styloid body fractureEUS Colles’ fracture with radial styloid

    body fractureU Ill Radial styloid bndy fracture

    EUS Radial styloid body fractureEUS IV Lunate dislocation

    FU Volar carpal dislocation

    EUS il Dorsal perilunate dislocationEUS Radial styloid process body fractureE Volar Barton’s fractureEUS Colles’ fractureEUS Colles’ fractureEUS 111 Dorsal perilunate dislocationEUS i Colles’ fractureEUS I Colles’ fractureEUS I1 Dorsal perilunate dislocationEUS 111 Dorsal perilunate dislocationEUS ill Dorsal perilunate dislocationEUS 111 Dorsal peHlunate dislocationEUS II Dorsal peHlunate dislocationEUS !1 Dorsal perilunate dislocationEUS ii Dorsal perilunate dislocationEUS !11 Dorsal perilunate dislocationEUS I!1 Dorsal perilunate dislocationEUS Ill Dorsal perilunate dislocationEUS Ill Dorsal radial fracture

    ÷+

    Commenl$

    Dorsal soft tissues removedVolar triquetral fractureRadial styloid tip fracture

    Avulsion of ulnocaq~al !igament with sty-ioid fracture

    Avulsion of UCL from ulna

    - Avulsion of RTL ligament from trique-trum

    - Dorsal carpal dislocation+ Sectioned RCL ligament, volar triquetral

    fracture- Avulsion of RTL and RSL ligaments

    flora radius, avuision of ulnocaq~lligament from ulnar meniscus, soc-tioned RCL ligament

    + Sectioned RCL ligament

    - Dors~d carpal subluxation- Sectioned RCL ligament- Sectioned RCL iigamem+ Sectioned RCL ligament

    + Volar triqueWal avulsion

    - Associated distal radius fracture- Volar triquetral fracture+ _+ _

    is stabilized by the volar radiotriquetral (RTL), the dor-sal radiocarpal (DRC), the ulnolunate (ULL), the notriquetral (UTL) and the ulnar collateral ligaments(Fig. 8). The majority of ligaments attach to andstabilize the proximal carpal row. The scaphoid is sta-bilized distally by the radiocapitate (RCL) and radialcollateral ligaments and proximally by the radio-scaphoid ligaments (RSL) (Figs. 1 and

    Carpal Idnematlcs. The apex of carpal rotation in theanteroposterior plane is in the center of the capitate orat the junction of the radiocapitate (RCL) and capito-triquetral (CTL) ligaments.2s. at In movement of thewrist from neutral position to maximum extension, the

    volar ligaments become progressively more taut andachieve their maximum tautness in complete extension

    (Fig. 9). Extremes of exten~h~:scaphoid ar~ checked by the radios~aphoidAigamg~(RSEF(Fi~. 9 and 10). Movement of the various car-p~l-b-dfie-fi-n-radial and ulnar deviation is controlled bythe complex ligamentous insertions of the volar liga-ments. In ulnar deviation of the hand, the distal rowmoves ulnari ,~nd the proximal row slides radiallgin~aret:ipmeat~~ reverse reciprocal relation-shiip ho~Ftmea~’ltlrnt~ll~ deviation of the hand. Thesereciprocal relationships between the two carpal rowsare maintained by the specific arrangement of the volar

  • 232 Mayfield, Johnson, KilcoyneThe Journal of

    HAND SURGERY

    Roentgenographicmanifestations

    Table I1, Roentgenographic and anatomic findings in the four stages of perilunar instability

    Joints(s)disrupted

    Ligamentst0111 or

    a ttcntuated

    Stage IV

    Scaphoid rotation Dislocated capitate Malrotated tfiquetrum Lunate dislocationand scaphoid

    Scapholunate Triquetrolunatediastasis

    Dislocated triquetrumVolar triquetral

    fracture

    Seapholunate Scapholunate Scapholunat¢ $capholunat¢Capilolunate Capitolunate Capitolunate

    , Triquetrolunate Triquetrolunate......... ~ Radiolunate

    ~.~.l~adioscaphoid ~) ~b~p-hoi~ ~i~_._~ ....~di~’~p-h’OTd- .~’ ~a p--fi-6~-~fif6--- ~i~0iunate Sc~ppholunate ""S c ~-p~lio-lffh ~.~

    interosseous interosseous interosseous interogseous~’7~ l~ii:]i-~ Radial collateral Radial collateral Radial collateral

    ~"~: Rad]~ita:ta~ c~R~i~li~-a~it ate., .~Radioc~phate~............... P/il~aY~di6f~q uet ral p/ilm~r ~di~uetral

    at T - L joint at T - L joint

    d~rsal radioc~g~al

    ligaments:s When the wrist is progressively extended,~an~at~us space_de.ve!op~ bythe radiocapitate (RCL) and volar radiotriquetral liga-mefits (RTL). This space_g~s_~en in many wrists and isfi~ a synovial out-pouching (space of Poirier).zs

    path6genes~s of carpal injuries.’rt~e following facts are useful in developing a me-

    chanical concept of perilunate and lunate dislocation:1. The radiocapitate ligament (RCL) is maximally

    taut in maximum extension and ulnar deviation.2. The radioscaphoid ligament (RSL) is maximally

    taut in maximum extension (Fig. 9).3. The proximal carpal row is stabilized to the distal

    forearm by five ligaments, the distal carpal row by onlyone (the radiocapitate ligament) (Fig.

    ...... It-is-postulated that-in a fall-on the outstretched handthe wrist would be stressed in maximal extensionand/or ulnar deviation with interearpal supination. Thistype of injury then should result in..~_rcpture._of__t~radiocapitate ligament and lo~bility of the distalcfirpa- row. u =- _- :, ;-radioscaphoid lig~d the scap~in-terosseous ~igament allowing (1) opening of the spaceof Poirier and (2) dislocation of the capitate andscaphoid from the lunate. It is upon this theoreticalconsideration that this study was designed.

    Material and methods

    Thirty-two wrists were loaded experimentally usingtwo machines, one fast loading and gravity dependent

    and the other hydraulic and slow loading (Table I). Allwrists were loaded to ligamentous or bony failure. Allwrists subjected to fast loading were given numbersI00 through 118, and those wrists subjected to slow,hydraulic loading were given numbers 201 through229. The fast-loading technique more nearly simulatedthe actual injury. The hydraulic slow-loading techniquewas more experimental and less similar to actual meth-eds of injury. This method, however, was extremelyvaluable in understanding progressive perilunar insta-bility in a manner similar to slow motion, enabling acritical analysis of progressive ligamentous failure andsubsequent carpal instability.

    AIII anatomic material was obtained from the De-partment of Anatomy at the Medical College of Wis-consin and consisted of 32 upper limbs dislocated at theelbow, includlng.the entire forearm~ wrist, and hand.Seveuteen of the 32 specimens were obtained fresh(FR) within 12 hours and studied within 24 hours afterdeath. Eight specimens were obtained fresh but thenstored in 10% Zepharin chloride solution (Z). Twowere stored in 10% formalin solution (F), if loadingstudies were performed after the 24 hour postmortemlimit. The remaining five specimens were embalmed(E) and were studied as time permitted. The specimenswere from patients who died of causes unrelated to themusculoskeletal system. The average age of specimenswas 53 years (range, 5 to 89).

    All specimens were stripped of soft tissue to within 2cm of the wrist joint leaving the interosseous mem.brahe, radius, and ulna intact. The specimens then were

  • ¯ May 1~80

    Fig. 11. Stage I perilunar instability (roentgenogmphic view).Note the partial disruption of the scapholunate joint.

    Carpal dislocations

    Fig. 13. Stooge III perilunar instability (roentgenogmphicview). Note the complete dislocation of the triquetrolunatejoint in ad~lition to scapholunate and capitolunate dis-locations.

    Fig. 12. Stage !I perilunar instability (reentgenographicview). Note the complete dislocation of the scapholunatejoint.

    cemented in 2 inch steel pipes and secured in the ap-propriate loading machine with the forearm vertical andthe wrist extended for various roentgenogmphic andloading studies.32

    The methods of loading were as follows: Specimenssubjected to fast loading (19 wrists) were loaded withan average of 19 kg from an average height of 68 cm.The force plate was placed across the metacarpal headswith the fingers free, and the angles of loading wereeither straight extension, extension with ulna,," devia-tion, or extension, ulnar deviation, and intercarpalsupination (equivalent to pronation of the forearm onthe carpus as observed in actual clinical injuries). In theearly part of the study the radiocapitate ligament wassectioned prior to loading in order to create instabilityof the distal carpal row and facilitate the production of acarpal dislocation. This was discontinued after a few

    Fig. 14. Stage IV pedlunar instability (roentgenogmphicview). In addition to complete volar stage tl! instability, thedorsal radiocarpal li~,ament was ruptured allowing volar rota-tion of the lunate into the carpal tunnel.

    specimens wl~en the pathomechanics were-understood-well enough to create the injuries without altering thespecimens. This technique, in retrospect, helped us tounderstand the mechanics involved, the ligaments re-sponsible for radial styioid body fractures and greatlyaided the overall underatanding of these volar liga-ments. All specimens were loaded until bony or liga-mentous failure occurred.

    Specimens subjected to hydraulic slow loading (13specimens) were positioned with a 1 by 2 cm pressureplate in the area of the trapezioscaphoid joint andtuberosity of the scaphoid. Slowly increasing pressurewas applied to the extended wrist. Loading createdulnar deviation and supination of the carpus on the

  • Mayfield, Johnson, KilcoyneThe Journal of

    HAND SURGERY

    111 load 4Fig. 15. A, The trlquetmlunate joint and stage 1II perilunarinstability. Note the triquetrolunate dlastasis and avulsion ofthe ulnotdquetral ligament from the triquetrum. B, Dissectedspecimen (stage Ill peritunar instability) showing avulsionfractur~ of the volar aspect of the triquetmm (orrow). C, Thetrtquetrelunate joint and stage IV perilunar instability. Notethe tdquetrolunate diastasts and avulsion fracture of thetrtquetram.

    forearm in addition to extension in all specimens. Thisforce was continued until either fracture, dislocation, orligamen~tous failure occurred.

    Lateral high-speed cineradiographs at 60 frames/seewere obtained during all loading studies. Standard ra-diographs consisting of anterior-posterior supinationviews in radial, neutral, and ulnar deviation, as well aslateral nidiographs in flexion, neutral, and extension,and various oblique views were obtained before andafter the loading studies. Stress films utilizing distrac-tion and compression of the carpus in both ulnar andradial d~;viation were obtained after loading.

    All specimens then were dissected to assess the bonyand/or ligamentous damage and associated carpal in-stability.

    Results

    Thirty-two wrists were submitted to loadingml9 byfast loading and 13 by hydraulic slow loading tech-niques. The injuries produced are listed in Table I.

    Progressive perilunar instability (PLI). The fourstages of this entity with synonyms and joints and liga-ments involved are outlined in Table If. Hydraulic load-ing created a "slow-motion" effect and greatly facili-tated the understanding of this entity. As the force wasslowly applied to the radial side of the wrist, the proxi-mal pole of the scaphoid migrated dorsally creatingscapholunate instability (stage I) (Fig. 1 I). As thel.~Kl-ing force of extension, intercarpal supination, and ulna_r~d~~gressed,~’(stag~-ii~ (Fig. 12)an0"-th~’tnquetrum ( sta~’e~t~e,s-si’~y’p-~e--lTd away from the lunate. Stage IV instabilityor~urr~,,~locat|on was a result of disruption of thedorsal radiocarpal ligament allowing the lunate tofreely rotate downward into the carpal tunnel on itspaimar liigamentous hinge (Fig. 14). The least amountof carpal instability was noted in stage I and the highestdegree was evident in stage IV.

    Intercarpals-opinati-on-wa~-p-attof the-n’iotion of the -hand in relation to the forearm since the loading angleswere on the radial and palmar side of the wrist. Thesignificance of the torque component of intercarpalsupination in creating ligament damage in the distalpart of the radiotdquetral ligament was not fully ap-preciated in earlier anatomic studies.’~ Only after laterextensive loading tests was this fact recognized.

    Ligl~.~on paralleled the progression ofthe dislocations about the lun~eralanff ra’f~Siixapitate ligam~d either completely orpartially in most of the wrists with perilunar instability.The radioscaphoid and scapholunate interosseo_us lig~m e n’-tVw~~e-d-i~~70-f2pe ri-lu n ar-insliilSi I -ity.~V-exl~d-~6f~ii~ ulnar perilunar instability with-

  • Vol, 5, No. 3May 1980 Carpal dislocations 235

    Fig. 16. Ligaments disrupted in perilunate dislocation withstage II ligamentous instability.

    Fig. 17. Ligaments disrupted in perilunate dislocation withstage III ligamentous instability.

    out a radial component. Radiocapitate ligament tearsoccurred both at the radial and capitate attachments. Inthose specimens where ligamentous sectioning was notdone, the radiocapitate ligament failed in four ways: (1)partial failure (stretching), (2) avulsion from the capi-tate, (3) complete failure in the ligament, and (4) radialstyloid process avulsion.

    All stage III injuries showed radial collateral liga-ment tears. In addition, avulsions of the volar radio-triquetral and ulnotriquetral ligaments from the tri-quetrum were seen as a direct result of intercarpal supi-nation and ulnar deviation, respectively. This wasmanifested by a triquetrolunate diastasis or avulsionfracture of the triquetrum in stage III injuries (speci-mens I01,109, 206, 219) (Fig. 15,A andB) and stageIV injuries (specimen I 11) (Fig. 15, C). Some of stage III injuries were so unstable that the capitatecould manually be placed dorsal or palmar to the lu-nate. In these injuries triquetrolunate diastasis could beproduced radiographically by radial deviation and lon-gitudinal compression (forcing the capitate between thelunate and triquetrum). This triquetrolunate gap ormalalignment, as well as an avulsion fracture of thevolar radiotriquetml or ulnotriquetral ligaments fromthe triquetmm, was diagnostic of stage !Ii injuries.

    Of the many combinations of ligamentous disrup-tions created about the wrist, we did not find a singlerupture of the proximal portion of the volar radiotri-

    Table HI. Roentgenographic findings in perilunarinstability

    Stage i:Anteroposterior view

    scapholunate diastasisForeshortened scaphoid

    Lateral viewDorsal subluxation of proximalScaphoid pole

    Stage II:Same as Stage I plusDorsal dislocation of the capitateStage II1:Volar triquetral fracture (avulsion of volar radiotriquetral ligament

    and/or ulnotriquetral likaments)Stage IV:Anteroposterior view

    Triangular lunat¢~Lateral view

    Volarly rotated lunate

    quetzal ligament from the radius to the lunate or theulnolunate iigaraents. This forms an extremely strongtriangular ligamentous attachment of the lunate to theforearm. This is the most likely explanation of the ex-tremely rare dislocation of the carpus without an asso-ciated radial styloid fracture. Perilunar instability wasnot limited to those specimens with complete capitatedislocation. Perilunar instability was also seen with ra-

  • 236 Ma~field. 2ohnson. KilcoyneThe Journal of

    HAND SURGERY

    Fig. 18. Persistent scapholunate diastasis after closed reduc-tion of perilunate dislocation.

    dial styloid and Colles’ fractures (specimens 109, 201,202).

    Determination of the degree of associated carpal in-stability could be determined in this study by an analy-sis of the anteroposterior and lateral roentgenographicviews. Stages III and IV of carpal instability were al-ways associated with triquetrolunate dislocation or sub-luxation (Table III).

    Perilunate dislocations. Thirteen dorsal perilunatedislocations were produced. The mechanism of injurywas extension, ulnar deviation, and intercarpal supina-tion in 12 and extension alone in one. Intercarpal supi-nation was a major component, since the loading wason the radial side of the wrist in all cases. All speci-mens had rupture of the radioscaphoid and scapholu-nate interosseous ligaments, and scaphoid rotation wasnoted in six specimens. Two patterns of volar liga-mentous damage were noted: rupture of the radiocapi-tare ligament (RCL) with scaphoid and capitate dislo-cation (specimens ! 13, 204, 215, 216, 217) (Fig. 16),and rupture of the radiocapitate ligament (RCL) plusrupture of the radiotriquetral ligament (RTL) betweenthe lunate and triquetrum or avulsion from the trique-trum with scaphoid, capitate and triquetral dislocation(specimens I01, 118, 206, 208, 213, 219, 221,222,224) (Fig. 17). Avulsion fracture of the radiotriquetralligament (RTL) from the triquetrum was noted in fourspecimens (specimens I01, 109, 206, 219). Of the perilunate dislocations, eight had stage III perilunar in-stability and five had stage II perilunar instability. Bydefinition, the two lunate dislocations had stage IVperilunar instability. All perilunate and lunate disloca-tions had initial stage I scapholunate instability thatprogressed with increased loads to higher degrees ofinstability.

    In all celses the capitate dislocated dorsally due to thedirection of force. In one specimen studied after load-ing (specimen 118) with more marked ligamentous dis-ruption, the capitate could manually be placed eitherdorsal or palmar to the lunate. This was possible sincethe volar radiotriquetral ligament was ruptured betweenthe lunate and triquetrum which allowed the distal car-pal row and triquetrum to rotate as a unit about thelunate. "E~is axis of intercarpal supination passedthrough the triquetrum. One specimen (specimen 101)had a radi;al styloid tip fracture which was an avulsionfracture of the radial collateral and radiocapitate liga-ments. Roduction was achieved by ulnar deviation withtraction, then intercarpal pronation, then radial devia-tion and palmar flexion. Persistent malalignment of thescapholun;ate joint on the posterior-anterior roentgeno-gram after reduction was noted in most of the speci-mens (Fig. 18).

    Lunate dislocations. Two lunate dislocafions wereproduced. The pathomechanics of injury were the sameas the perilunate dislocations. The palmar ligamentousdamage was the same as the more severe perilunatedislocations (disruption of the radiocapitate, radio-scaphoid, and volar radiotriquetral ligaments). Avul-sion of tl~e volar radiotriquetral ligament from thetriquetrum was noted in specimen 111 as in the perilu-hate dislocations. Rupture of the dorsal radiocarpal lig-ament in specimen 111 and preloading removal in spec-imen 1O0 allowed volar lunate rotation. The capitatewas dorsal to the lunate at the end of loading in bothspecimens. Scaphoid rotation was noted in both casesand was a.ssociated with complete disruption of theradioscaphDid and scapholunate interosseous ligaments(Fig. 19). Reduction was accomplished in the samefashion as the perilunate dislocations, except that thelunate had to be m:mually rotated back onto the radiuswith the thumb placed volarly.

    Scaphoid rotation. Scaphoid rotation was noted insix perilunate and two lunate dislocations (specimensI00, 101, I I1, 118, 206, 221,222). In all specimensthe radioscaphoid and scapholunate interosseous liga-ments we~e ruptured. It became evident that thescapholunate joint separated in a progressive fashion asthe loading continued on the radial aspect of the wrist.The volar aspect of the scapholunate joint separatedfirst, and t~is progressed in a dorsal direction due to theintercarpal supination component of the loading me-chanics. Seapholunate interosseous ligament rupturewas a direct result of this suplnation. The extensioncomponent of the loading ruptured the radioscaphoidligament. Scaphoid dislocation and rotation were thenevident.

  • Vol. ~o No. 3May 1980 Carpal dislocations 237

    Jal:eral vie/~~’/’~ ~(~

    Maximum dorsalvolar dorsal Flexion

    Fig. 19. Lunate dislocation and associated ligamentous damage.

    Radiographic instability of the scapholunate articu-lation was shown in a number of ways. Stress films inulnar deviation and/or longitudinal compression forcedthe capitate between the scaphoid and the lunate likea wedge which accentuated the scapholunate gap(scapholunate diastasis) on the posterior-anterior views(Fig. 20L With lateral views of the wrist, longitudinalcompression along the first metacarpal caused thescaphoid to assume the flexed position causing dorsalsubluxation of the proximal pole (Fig. 21). This dorsalsubluxation of the proximal scaphoid above the lunatewas always indicative of a complete disruption of boththe mdioscaphoid and scapholunate interosseous liga-ments. Scapholunate reduction was achieved by dor-siflexion, but was associated with wide palmar liga-mentous separation. Palmar flexion approximated thepalmar ligamentous disruption, but in this position dor-sal subluxation of the proximal seaphoid persisted. Thisparadox of reduction was consistent.

    Radial styloid fractures and perilunar Instability.Seven fractures of the radial styloid were produced.

    Two types were noted. In six specimens (specimens106, 107, 108, 109, 1 I0, 114), the entire radial styloidbody wa~; fractured and in one specimen (dorsal perilu-nate dislocation) (specimen 101) a fracture of the tip the radial styloid process was present. All were avul-sion frac~~ures.

    To understand the mechanics of these styloid frac-tures, differential iigamentous sectioning was per-formed prior to loading. In maximum ulnar deviationthe radiocapitate ligament is taut and the volar radio-triquetrai ligament is lax. With the radiocapitate liga-ment int~ct the radial styioid process was avulsed. Ifthe radiocapitate ligament was sectioned prior to load-ing, as it was in three cases (specimens 101, 113, ! 18),a carpal dislocation developed. In five specimens (spec.imens 106, 107, 108, 109, 114), no iigamentous sec-tioning prior to loading was performed, and in all casesloading in straight ulnar deviation created a fracture of theradial styloid process. In an additional specimen (speci-men 110) the volar radiotriquetral (VRT) ligamentalone was’, sectioned at the radius, and loading was per-

  • 238 Mayfield. Johnson. Kilcoyne

    The Journal ofHAND SURGERY

    Fig. 20. Scapholunate stress test. Longitudinal compressionforces the head of the capitate between the scaphoid andlunate, creating scapholunate diastasis.

    formed in ulnar deviation and still a fracture of theradial styloid developed. Thus the radiocapitate liga-ment was found to be the major ligament responsiblefor avulsions of the radial styloid process (Fig. 22).

    Fracture of the radial styloid tip (specimen 101)was associated with avulsion of the radial collateral(Re) and a portion of the radiocapitate (RC) ligament(Fig. 23).

    Discussion

    This study supports previous clinical evidence thatperilunate and lunate dislocations occur with forced ex-tension,2-5. 7-~1. I.~. 2.~ but also strongly suggests thatulnar deviation and intercarpal supination are key ele-ments in the pathomeehanics of these injuries. Only afew authors have devoted attention to the ligamentousdisruption in these injuries7’ ~’ ~2’ 2n. 2s; however, thisstudy suggests that ligamentous damage is specific andsignificant, allowing varying degrees of carpal insta-bility.

    There is strong clinical evidence that lunate disloca-tions are preceded by perilunate dislocations,I1’ ~z andthat marked carpal instability is associated with these

    Fig. 21. Dorsal scaphoid subluxation with the hand in theflexed position. (S, scaphoid; L, lunate; T, triquetrum; U,ulna; arrow, scapholunate jaint.)

    injuries. Our findings support this clinical evidence.Perilunate and lunate dislocations and scaphoid malro-tation are due to specific ligamentous disruptions thatbegin on the radial side of the wrist and progress in asequential fashion through the scapholunate joint (stageI pedllunar instability) associated with scapholunatediasta~.;is with or without a radial styloid process avul-sion to stage III or IV perilunar instability with or with-out a volar triquetral fracture (Fig. 24). Loading overthe radial side of the hand, which caused the scaphoid,distal carpal row, and triquetrum to be peeled awayfrom the lunate, probably simulates a fall on the thenareminence and/or the first and second metacarpals on apronated forearm. The degree of carpal instability as-sociated with these injuries varies from the least degree(stage I) to the greatest degree (stage IV), i.e., lunatedislocation. The painful wrist with late intercarpal col-lapse and instability as described by Dobyns et al. 9 andLinscheid et al.a may be explained by unrecognized anduntreated acute perilunar instability that persists due toresidual ligamentous laxity.

    Radial styloid fractures are avulsion fractures pro-duced in ulnar deviation. Radial styloid body fracturesare avulsions of the radiocapitate ligament and radialstyloid tip fractures are avulsions primarily of the radialcollateral ligament. In carpal dislocations one of fourevent.,; can occur to allow capitate dislocation: (I) radialstyloi,:! fracture, (2) complete radiocapitate ligamentfailun;, (3) partial radiocapitate ligament failure (don-gation), or (4) radiocapitate ligament avulsion from capitate. All four mechanisms were noted in this study.

    Sc~tphoid rotation is a well-recognized phenomenon

  • _ ,Vole $, No. 3~May t98o Carpal dislocations 239

    Fig. 22. Radial styloid body fracture.Fig. 23. Radial styloid tip fracture (volar view).

    in these injuries. This study suggests that rotation of thescaphoid was due to loss of the stabilizing influence ofthe radioscaphoid and scapholunate intcrosseous liga-ments proximally. This was synonymous with stage Iperilunar instability. The connecting rod support of thescaphoid between the two carpal rows was lost, allow-ing intercarpal collapse, scapholunate diastasis, andsubluxation dorsally of the proximal pole of thescaphoid. Reduction of the scapholunate dislocationwith restoration of normal ligament length is necessaryin order to maintain accurate carpal alignment andfunction. This study would suggest that both cannot beachieved simultaneous y, w it-_- . = : ~.. in

    ! instability was not evidentwith the routine anteroposterior and lateral roentgeno-griim~-~r~ih-stress films w~ helpful in definihg thedegree of carpal instability present. An anteroposteriorview with longitudinal compression and/or ulnar de-viation showing scapholunate diastasis indicated stage Iinstability and longitudinal compression in radialdeviation showing triquetrolunate diastasis indicatedstage III instability. In those instances where the typicalroentgenographic manifestations of the perilunate dis-location or lunate dislocation were evident (dorsallydislocated capitate, volarly rotated lunate, and scaphoidrotation), th~ty c0uld be ~e-termined byte ’~t~as-t~$T’iWaT’a~ment of the triquetrum with lunate, o_9_Lavi~lbi~ vo~ar tflquetrai !~-~~-~ was indicative of a high

    D

    Fig. 24. Radial styloid and triquetral fractures associated withperilunar instability. (A, radial styloid tip fracture; B, radialstyloid body fracture; C, radiotriquetral ligament avulsion; D0ulnotrlquetral ligament avulsion.)

  • 240" Mayfield. Johnso~l. KilcoyneThe Journal of

    HAND SURGERY

    degree of peri~y (stage llI). An avulsi~onfra-e-Tfffe-f~Fi’/i~e dorsal aspect of the lunate-or trique-

    tram-.:--- su : ~ : _ -The-~rnc.~h~ c~f r~.daction~~f immobili-

    zation in perilunate and lunate dislocations is a topic ofconsiderable disagreement,e’ T, !o-,~. is. ~5 Reductionwas best achieved in this study by reversing the mech-anism of injury. Longitudinal traction and ulnar devia-tion were necessary at first to recreate the carpaIseparation followed by intercarpal pronation and thenradial deviation and palmer flexion. Reduction of lu-nate dislocations was the same, except that the lunatehad to be manually rotated onto the radius with thethumb after carpal separation was accomplished. Thesemaneuvers consistently reduced the capitolunate dislo-cation in the experimental context. Palmar flexionappm_~ximated the palmar ligaments, but this was~on-sistently a~ssociated~ith dorsal subluxation of the prox-imal pole of the scaphoid. Extension restored moren~rmal ~_¢~nhohm- --~ " :-; - _’ :s but allowedconsiderable se_parafion of ht e torn pa~s.This pa~-d-0~ in the closed reduct~ffriesmay explain the phenomenon of persistent scaphoidrotation and also may explain why the results of closedreduction have been variable and not uniformly saris-factory.

    We would agree that all carpal dislocations cannot becompletely explained by the previously describedmechanisms and that other loading studies would beuseful. Other stress patterns certainly do occur.

    A separate study by Johnson et al.,~:t employingthe same mechanism (extension, ulnar deviation, andintercarpal supination) consistently created scaphoidfractures and transcaphoid and transcaphoid-transtri-quetrai perilunate fracture dislocations. This wouldstrongly suggest that the mechanism or carpal disloca-tions and fracture-dislocations could be explained byvarying degrees or combinations of these three loadingangles.

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    3. Campbell RD. Thompson TC, Lance EM, Adler JB: In-dications for open reduction of lunate and peril~ hate dis-locations of the carpal bones. J Bone Joint Surg [Am]47:915-37. 1965

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    10.Russe:li TB: Intercarpal dislocations and fracture-dislo-cations. J Bone Joint Surg [Br] 31:524-31, 1949

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    13.Boyes JH: Brunnell’s surgery of the hand, ed 5.Philadelphia, 1970, JB Lippincott Co

    14. Gilula LA, Weeks PM: Post-traumatic ligamentous in-stabili’ties of the wrist. Radiology 129:641-51, 1978

    15. Vaughan-Jackson OV: Case of recurrent subluxation ofthe carpal scaphoid. J Bone Joint Surg [Br] 31:532-3,1949

    16. Howa~xt FM. Fahey T: Rotatory subluxation of thenavic~lar. Ciin Orthop 104:134-8, 1974

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    21. Bonnin JG, Greening WP: Fractures of the ~riquetrum.Br J Surg 31:278-83. 1943

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  • Vol. 5, ~o. 3May 1980 Carpal dislocations 241

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