476 THEJOURNALOFBONE ANDJOINTSURGERYC. M. Robinson, BMedSci, FRCS Ed(Orth), Senior Lecturer and Consult-antOrthopaedicSurgeonOrthopaedicDirectorate,RoyalInrmaryofEdinburgh,LauristonPlace,EdinburghEH39YW,UK.1998BritishEditorialSocietyofBoneandJointSurgery0301-620X/98/38079$2.00FracturesoftheclavicleintheadultEPIDEMIOLOGY ANDCLASSIFICATIONC.M.RobinsonFromtheRoyalInrmaryofEdinburgh,ScotlandFrom1988to1994aconsecutiveseriesof1000fracturesoftheadultclaviclewastreatedintheOrthopaedicTraumaClinicoftheRoyalInrmaryofEdinburgh.Inmales,theannualincidencewashighestunder20yearsofage,decreasingineachsubsequentcohortuntiltheseventhdecade.Infemales,theincidencewasmoreconstant,butrelativelyfrequentinteenagersandtheelderly.Inyoungpatients,fracturesusuallyresultedfromroad-trafcaccidentsorsportandmostwerediaphyseal.Fracturesintheouterfthwereproducedbysimpledomesticfallsandweremorecommonintheelderly.Anewclassicationwasdevelopedbasedonradiologicalreviewoftheanatomicalsiteandtheextentofdisplacement,comminutionandarticularextension.Thereweresatisfactorylevelsofinter-andintraobservervariationforreliabilityandreproducibility.Fracturesofthemedialfth(type1),undisplaceddiaphysealfractures(type2A)andfracturesoftheouterfth(type3A)usuallyhadabenignprognosis.Theincidenceofcomplicationsofunionwashigherindisplaceddiaphyseal(type2B)anddisplacedouter-fth(type3B)fractures.Inadditiontodisplacement,theextentofcomminutionintype-2Bfractureswasariskfactorfordelayedandnonunion.JBoneJointSurg[Br]1998;80-B:476-84.Received19June1997;Acceptedafterrevision12January1998Mostfracturesoftheclaviclehaveagoodprognosis;patientshavefewornoresidualsymptomsoncethefrac-turehashealed1,2andtheoverallincidenceofnonunionislessthan1%.3,4Previousepidemiologicalstudieshaveshownthatsuchinjuriesoccurmostlyinyoungmen5andcomprise5%to10% of all fractures.6,7Little has been reported about theirnaturalhistoryandprognosis.ThetwomainclassicationsarethatofAllman8foranatomicalsiteandofNeer9forlateralthirdfractures.Thereisnosingleclassicationwhichallowsanaccuratedescriptionofdisplacement,instabilityandcomminution,inrelationtotheoutcomeandprognosis.Theaimofthisstudywastoevaluatetheepidemiologyofaconsecutiveseriesoffracturestoproduceamoredetaileddescriptiveclassication.PatientsandMethodsFrom 1988 to 1994 the medical records and radiographs of1000consecutiveadultpatientstreatedforisolatedfrac-tures of the clavicle in the Orthopaedic Trauma Unit of theRoyal Inrmary of Edinburgh were reviewed. The unit hadanestimatedmeancatchmentpopulationover13yearsofage for this period of 556 469. Patients under 13 years andthosewithligamentousinjuriesordislocationswithoutfracturewereexludedaswerethosewithdoubledisrup-tionsoftheshoulderinvolvingaclavicularfracture,sincethesewereinitiallymanagedbysurgicalstabilisation.Allpatientswereseenwithin72hoursofinjuryanddetails of their age, gender, mechanism of injury and otherinjurieswererecorded.Thecauseofthefracturewasgroupedasasimplefallonthesamelevel,afallfromaheight,sport,road-trafcaccident(RTA),adirectfrontalbloworothers.All patients were reviewed after six to eight weeks, withfurtherradiographs.Follow-upcontinueduntiltherewasevidenceofclinicalandradiologicalunion.Themeanfollow-upwas15.7weeks(5to145).Delayedunionwasdenedashealingbetween12weeksand24weeksandnonunionwhenhealinghadnotoccurredby24weeks.Potentialriskfactorsfordelayedornonunion,includingage, gender, mechanism of injury and type of fracture wereanalysed using statistical analysis by constructing 2 2 or2 ktablestocalculatetheoddsratios(OR)and95%condenceintervals.Forallfracturestheanatomicalsite,congurationandtypeandextentofcomminutionwererecorded. Aclassi-cationwasdevelopedfromthesedataandassessedbyusing20randomlyselectedseriesofradiographs.These477 FRACTURESOFTHECLAVICLEINTHE ADULTVOL.80-B,NO.3,MAY1998Fig. 1aFig. 1bFig. 1cDiagramsoftype-1(a),type-2(b)andtype-3(c)clavicularfractures.were independently classied by ve orthopaedic specialistregistrars on two occasions, separated by a two-week inter-val. Interobserver reliability and intraobserver reproducibil-ityweredeterminedbycalculatingadjustedkappacoefcients.TheLandisandKochguidelines10forinter-pretationofthekappacoefcientswereused:avalueof1.00indicatedperfectagreement;0.81to0.99,excellent;0.61to0.80,substantial;0.41to0.60,moderate;0.21to0.40,fair;0.00to0.20,slight;andlessthan0.00,poor.ResultsClassicationoffractures. Threedifferentareasoffrac-turewereidentied:thediaphysisandthemedialandlateral ends (Fig. 1). Type 1 was the fth of the bone lyingmedial to a vertical line drawn upwards from the centre oftherstrib.Type3 wasthefthofthebonelateraltoaverticallinedrawnupwardsfromthecentreofthebaseofthecoracoidprocess,apointnormallymarkedbytheconoidtuberosity.Type2 wastheintermediatethree-fthsofthediaphysis(Fig.1).FractureswerealsodividedintosubgroupsAandB478 C.M.ROBINSONTHEJOURNALOFBONE ANDJOINTSURGERYFig. 2aFig. 2b30caudad-tiltedradiographsshowingdisplacementintype-2B2(a)andtype-3B1(b)fractures.Fig. 3Modiedaxialviewshowingdisplacementinatype-3B1fracture.dependingondisplacement(greaterorlessthan100%translation)ofthemajorfragments.Thisisoftendifcultbecause of the sigmoid shape of the clavicle, particularly attheendsofthebone,butweight-bearing,oblique,1130caudad-tilted(Fig.2)ormodiedaxialviews12(Fig.3)wereusedincasesinwhichuncertaintyexisted.Type-1Aandtype-1Bfractureswerefurthersubdividedintoextra-orintra-articular(Fig.1).Type-2Afracturesweresubdividedaccordingtothepresenceofangulation,but in all these injuries there was residual bony contact. Inthetype-2Bsubgrouptherewasnoresidualcontactbetween the major fragments and variable degrees of short-ening which was usually apparent both clinically and radio-logically. Two further subgroups of type-2B were simple orwedgecomminutedfractures(type2B1)andisolatedseg-mentalorsegmentallycomminutedfractures(type2B2).Type-3Aandtype-3Bfractureswerealsosubdividedaccordingtoarticularinvolvement(Fig.1).Displacementin type-3B injuries showed a characteristic pattern of eleva-tion and posterior displacement of the shaft fragment, witheither a simple oblique conguration or with avulsion of aninferiorbonefragment(Fig.4).Validation. Fortherstandsecondviewingstheaverageinterobserverkappacoefcientsfortheclassicationwere0.74 (0.55 to 0.82) and 0.80 (0.70 to 0.94) giving an overallmean of 0.77 indicating substantial reliability. The averageindividual intraobserver kappa coefcient was 0.84 (0.69 to0.88)indicatingexcellentreproducibility.479 FRACTURESOFTHECLAVICLEINTHE ADULTVOL.80-B,NO.3,MAY1998Fig. 4aFig. 4bRadiographsoftwo-part(a)andthree-part(b)type-3Bfractures.TableI.Mechanismofinjuryinthe1000fracturesoftheaboveMeanageinyrMechanism Number (range) Male Female M:Fratio*Simplefall 309 46.3(13to96) 186 123 1.5:1Fallfromaheight 108 34.5(13to94) 68 40 1.7:1Sport 234 21.2(13to74) 204 30 6.8:1RTA 272 30.1(13to85) 208 64 3.3:1Directviolence 46 31.9(13to83) 36 10 3.6:1Other 31 30.9(13to85) 18 13 1.4:1Total1000 33.6(13to96) 720 280 2.6:1*male-to-femaleratioEpidemiology. The estimated incidence of new fractures inadultsovertheageof13yearswas29.14per100 000population per year, over the review period of six years twomonths. Themeanageofthefracturepopulationwas33.6years (13 to 96), the male-to-female ratio was 2.6:1 (TableI)andtheratioofleft-toright-sidedfractureswas1.28:1.Fracturesweremostcommoninmalesagedfrom13to20yearswithasubsequentfallinincidencewithageuntiltheseventhdecade(Fig.5).Infemales,theincidenceremained more constant with age, with smaller peaks under20yearsandover80yearsofage(Fig.5).Themeanageforfractureinmenandwomenwas29.2and45years,respectively.Sport was the commonest cause of fracture in the young,themeanageforthiscausebeing21.2years(13to74).Fractures due to simple falls had a mean age of 46.3 years(13to96).Theothercauseshadintermediatemeanages(TableI).Fracturesduetosport,adirectbloworanRTAwereseenpredominantlyinmales(male-to-female(M:F)ratiosof6.8:1,3.6:1and3.3:1,respectively);infemaleslargerproportions were due to a simple fall or a fall from a height(M:F ratio 1.5:1 and 1.7:1, respectively). Rugby and soccerinjuriesaccountedfor39%and33%ofallsportsinjuries,respectively. Of the fractures caused by RTAs 39% were incyclists,26%incardriversorpassengers,17%inpedes-triansand17%inmotorcyclists.Inpatientcarewasrequiredfor142(14.2%)patients,usuallyforsocialreasons,treatmentofotherinjuries,orsurgery for complications. Of the 142 patients, 96 had otherinjuries:75hadotherorthopaedicinjuries,29hadheadorfacialinjuries,27hadseriouschestinjuriesandfourhadabdominalinjuries.Type-1 fractures were uncommon, at 2.8% of the fracturepopulation(TableII);mostwereundisplacedandextra-articular(type1A1).Type-2injurieswerethemostcom-mon (69.2%) and most were displaced (type 2B); the most480 C.M.ROBINSONTHEJOURNALOFBONE ANDJOINTSURGERYFig. 5Fractureincidenceinrelationtoageandgendercohorts.TableII.DetailsofthefracturesubgroupsNumberof IncidenceFracture fractures (/100 000 Meanage M:Fsubtypes (%ofpopn) popn/year) (yr;range) Male Female ratio*1A1 17(1.7) 0.5 34.1(15to78) 15 2 7.5:11A2 6(0.6) 0.17 39.6(14to67) 3 3 1.0:11B1 2(0.2) 0.06 20.5(13to67) 2 0 2.0:01B2 3(0.3) 0.09 38.0(14to87) 2 1 2.0:1Alltype1 28(2.8) 0.82 37.2(13to78) 22 6 3.7:12A1 54(5.4) 1.57 27.8(13to89) 42 12 3.5:12A2 135(13.5) 3.93 19.0(13to45) 109 26 4.2:12B1 375(37.5) 10.93 31.1(13to96) 273 102 2.7:12B2 128(12.8) 3.73 35.1(13to89) 105 23 4.6:1Alltype2 692(69.2) 20.17 29.3(13to96) 529 163 3.3:13A1 162(16.2) 4.72 46.7(14to95) 92 70 1.3:13A2 19(1.9) 0.55 48.7(15to95) 9 10 0.9:13B1 85(8.5) 2.48 43.6(13to94) 61 24 2.5:13B2 14(1.4) 0.41 49.2(19to84) 7 7 1.0:1Alltype3 280(28.0) 8.16 45.3(13to95) 169 111 1.5:1Totalpopulation 1000 29.14 33.6(13to96) 720 280 2.6:1*male-to-femaleratiocommonwastype2B1.Ofthetype-2B1fractures,28.9%hadwedgecomminutionandtheremainderweresimple.Type-2B2 fractures had an incidence of 25.5%. Of the type-2B2injuries21.1%weretheisolatedsegmentaltypeandtheremainderwerecomminutedsegmental.Type-3frac-tures,28%ofall,werepredominantlyundisplaced(type3A).Type-1andtype-2fractureswereseeninayoungerpopulationandwithagreaterM:Fratiothantype-3frac-tures(TableII).Type-2A2fracturesoccurredinayoungerpopulationthantheotherfractures;allbuttwowereinpatientsaged13to25years(TableII).Type-2fractureswere mainly caused by sport or RTAs whereas simple fallswerethecommonestcauseoftype-1andtype-3fractures(TableIII).Fractureoutcome. Mostfractures(89%)healedunevent-fullywithconservativetreatmentinacollar-and-cuffslinguntilacutepainhadsettled.Only6%requiredoperativetreatment(TableIV).Undisplaced(A)anddisplaced(B)fracturesareconsideredseparately.Undisplaced(type-A)fractures. Theprognosisfortheundisplaced(typeA)fracturesubgroupsinallthreeana-tomicalregionswasgood.Stable,undisplacedfracturesofthe bone ends (types 1A and 3A) did not become displacedand nonunion was seen in only one patient with a type-3A1fracture.Twotype-2A1(3.7%ofsubgroup)andsixtype-2A2 (4.4%) fractures became displaced signicantly duringtreatment. One type-2A1 and three type-2A2 fractures sub-sequentlyshiftedandshortened,developingatype-2B1pattern, but they all, along with all other type-2A fractures,uniteduneventfully.Thecommonestcomplicationaftertype-2A2fractures,seenin5.2%ofthissubgroup,waslocalprominenceatthefracturesite;treatmentwasbyexcisionoftheprominentbone(TableIV).Displaced(type-B)fractures. Displacedmedial-thirdfrac-tures(type1B)wererare,butallveuniteduneventfully.481 FRACTURESOFTHECLAVICLEINTHE ADULTVOL.80-B,NO.3,MAY1998TableIII.Mechanismofinjuryinfracturesubgroups;percentage incidencesareinparenthesesFracture Fallsfrom Directsubtypes Simplefalls height Sport RTA violence Other Total1A1 8(47.1) 3(17.6) 1(5.9) 3(17.6) 1(5.9) 1(5.9) 171A2 0 1(16.6) 0 2(33.3) 2(33.3) 1(16.6) 61B1 0 1(50.0) 1(50.0) 0 0 0 21B2 0 0 1(33.3) 1(33.3) 1(33.3) 0 3Alltype1 8(28.6) 5(17.9) 3(10.7) 6(21.4) 4(14.3) 2(7.1) 282A1 14(25.9) 5(9.3) 19(35.2) 14(25.9) 1(1.9) 1(1.9) 542A2 27(20.0) 15(11.1) 60(44.4) 27(20.0) 4(3.0) 2(1.5) 1352B1 84(22.4) 40(10.7) 94(25.1) 124(33.1) 20(5.3) 13(3.5) 3752B2 33(25.8) 9(7.0) 35(27.3) 41(32.0) 6(4.7) 4(3.1) 128Alltype2 158(22.8) 69(10.0) 208(30.1) 206(29.8) 31(4.5) 20(2.9) 6923A1 81(50.0) 19(11.7) 16(9.9) 35(21.7) 6(3.7) 5(3.1) 1623A2 11(57.9) 2(10.5) 1(5.3) 2(10.5) 2(10.5) 1(5.3) 193B1 43(50.6) 10(11.8) 5(5.9) 22(25.9) 3(3.5) 2(2.4) 853B2 8(57.1) 3(21.4) 1(7.1) 1(7.1) 0 1(7.1) 14Alltype3 143(51.1) 34(12.1) 23(8.2) 60(21.4) 11(3.9) 9(3.2) 280Totalpopulation 309(30.9) 108(10.8) 234(23.4) 272(27.2) 46(4.6) 31(3.1) 1000TableIV.Outcomeinthefracturesubgroups,bynumberandpercentageNonunion Nonunion Uncomplicated Delayed treated treatedSubtypes fractureunion union non-operatively operatively Othersurgery* Refracture1A1 16(94.1) 0 0 0 1BP(5.9) 01A2 6(100) 0 0 0 0 01B1 2(100) 0 0 0 0 01B2 3(100) 0 0 0 0 0Alltype1 27(96.4) 0 0 0 1(3.6) 02A1 52(96.3) 0 0 0 0 2(3.7)2A2 123(91.1) 0 0 0 7BP,2SC(6.7) 3(2.2)2B1 341(90.9) 8(2.1) 1(0.3) 16(4.3) 1SC,2OF,2BP(1.3) 4(1.1)2B2 104(81.3) 8(6.3) 0 12(9.4) 2BP(1.6) 2(1.6)Alltype2 620(89.6) 16(2.3) 1(0.2) 28(4.1) 16(2.3) 11(1.6)3A1 160(98.8) 0 0 1(0.6) 0 1(0.6)3A2 17(89.5) 0 0 0 2OA(10.5) 03B1 61(71.8) 10(11.8) 7(8.2) 6(7.1) 0 1(1.2)3B2 5(35.7) 1(7.1) 2(14.3) 3(21.4) 3OA(21.4) 0Alltype3 243(86.8) 11(3.9) 9(3.2) 10(3.6) 5(1.8) 2(0.7)Totalpopulation 890(89) 27(2.7) 10(1.0) 38(3.8) 22(2.2) 13(1.3)*BP,surgeryforbonyprominence;SC,surgeryforskincompromise;OF,surgeryforopenfracture;OA,surgeryforsymptomaticosteoarthritisoftheacromioclavicularjointTheprognosisforotherdisplacedfractures(types2Band3B)waslessfavourablethanfortype-Afractures,mainlybecause of the higher incidence of complications of union.Theoverallprevalenceofdelayedunionwas2.7%andofnonunion4.8%forthewholestudypopulation,givingestimatedincidencesof0.79and1.40per100 000popu-lationperyear,respectively(TableIV).Thesecomplica-tionswereseenalmostexclusivelyafterdisplaceddiaphyseal(type2B)anddisplacedlateral-end(type3B)fractures.TheORfordelayedornonunionafteradisplaceddia-physealfracture(type2B)whencomparedwithanundis-placedtype2A,was18.47(95%condenceintervals(CI)2.51to135.89).TheORfordelayedornonunionafteradisplacedlateral-endfracture(type3B),comparedwithtype-3A,was74.57(95%CI9.89to560.48).Despitethismorepatientswithdelayedandnonunionwereseenaftertype-2B injuries, because of their greater prevalence (TableIV).Forthewholeseries,theriskofdelayedandnonunionwasslightlygreaterafterhigh-energyinjuriessuchasfallsfromaheight,RTAsanddirectviolence,thanfromlow-energyinjuriesfromsimplefallsandsport(OR = 1.64,95% CI 1.03 to 2.64) (Table V). The OR of such complica-tions in type-2 and type-3 subgroups, comparing high- withlow-energyinjury,were1.55(95%CI0.85to2.85)and2.07(95%CI0.97to4.46),respectively.Therewerenosignicant differences in the rates of union or incidence ofcomplicationsbetweenthedifferentageandgendercohorts. Among the diaphyseal subgroups, the risk of com-plications of union was higher in the severely comminutedandsegmentaltype-2B2fracturesthaninthemoresimpletype-2B1pattern(OR = 2.59,95%CI1.38to4.84).Alltype-2Bfractureswhichhadnotunitedafter24weeks,exceptforonetype-2B1fracture,hadsymptomsandrequiredoperationforcompressionplatingandbonegrafting.Bycontrast,ninepatients(50%)withnonunionaftertype-3Bfractureshadnosymptoms;theotherninerequiredeithercoracoclavicularscrewstabilisation(fortype-3B1fractures)orexcisionofthelateralendoftheclavicle(fortype-3B2fractures).Operationwasrequiredforonlythreepatientswithskinproblemscausedbyprominentfragments(TableIV);twowere treated by primary internal xation and one by simplemanipulation of the fracture. Only two (type-2B1) fracturesintheserieswereopen;bothwereGustiloandAndersongradeI13andweretreatedbyprimarydebridementandplatexation.Symptomatic osteoarthritis of the acromioclavicular jointwas associated with the relatively uncommon intra-articularfractures of the lateral end (types 3A2 and 3B2). In refrac-torycasesthisrequiredexcisionofthelateralendoftheclavicle(TableIV).Refracturewithinoneyearoftheoriginalinjurywasanoccasionalcomplicationseenpredominantlyinyoungmalesafterdiaphysealfractureusuallyafterresumingacontactsport(TableIV). Allrefracturesweresuccessfullymanagedconservatively.DiscussionIthasbeenestimatedthatfracturesoftheclavicleaccountfor 1 in 20 of all fractures6,7and 44% of all injuries to theshoulder girdle.4In this series, the incidence of all fracturesinadultsovertheageof13yearsremainedconstantoversix years at 29.14 fractures per 100 000 population per year.Theonlyothermajorepidemiologicalreviewoffracturesof the clavicle was carried out in M almo by Nordqvist andPetersson5whofoundanoverallincidenceof64per100 000 population per year. The previous study examinedfractures over the 35-year period from 1952 to 1987 duringwhich the incidence appeared to increase by approximately50%,andinadditionincludedpaediatricfractures.Directcomparison with the current study is therefore not possible,althoughtheoverallincidenceoffracturesinadultsinthe1980sintheMlmostudywassimilar.Inthisseries,fracturesweremostcommoninmalesundertheageof30yearstypicallyasaresultofacontactsportorafteranRTA.Fracturesinfemalesweremoreconstantwithage,withasmallerpeakinthoseunder30yearsofage.Therelativeproportionoffemalestomalesincreasedwithage;simplefallswerethepredominantcauseofinjuryintheelderly.Theseclinicalndingsaresupportedbypreviousbiomechanicalstudies14,15whichhavesuggestedthattheusualmechanismofthefracture,irrespectiveofsite,isadirectforceappliedtothepointoftheshouldersuchasoccursduringafallorRTA.As M uller has indicated,16classication systems are onlyofvalueiftheyserveasabasisfortreatmentandcanbeusedtopredictoutcome.Recentstudieshavealsofocused482 C.M.ROBINSONTHEJOURNALOFBONE ANDJOINTSURGERYTableV.Outcomeofclavicularfracturerelatedtomechanismofinjury,bynumberandpercentageUncomplicated Nonunion NonunionMechanism fracture Delayed managed managedofinjury union union non-operatively operatively Othersurgery* RefractureSimplefall 285(92.2) 5(1.6) 3(1.0) 8(2.6) 1BP,4OA(1.6) 3(1.0)Fallsfromheight 93(86.1) 4(3.7) 1(0.9) 5(4.6) 3BP,1OA(3.7) 1(0.9)Sport 210(89.7) 6(2.6) 2(0.9) 7(3.0) 4BP,2SC(2.6) 3(1.3)RTA 237(87.1) 10(3.7) 2(0.7) 14(5.2) 3BP,1SC,2OF(2.2) 3(1.1)Directviolence 38(82.6) 2(4.4) 1(2.2) 2(4.4) 1BP(2.2) 2(4.4)Others 27(87.1) 0 1(3.2) 2(6.5) 0 1(3.2)*BP,surgeryforbonyprominence;SC,surgeryforskincompromise;OF,surgeryforopenfracture;OA,surgeryforsymptomaticosteoarthritisoftheacromioclavicularjointattention on the importance of the reliability and reproduci-bilityofclassicationsystems.17-19Allmansclassicationintothreeanatomicalregionsisgenerallyusedtodescribefracturesoftheclavicle,butitgivesnoguidetoprognosisintermsofdisplacement,1,20-22comminution21,23orliga-mentousinjury.9,11,24Otherstudieshavemodiedtheori-ginaldescriptivesystemtoincludesomeofthesefactors,5,9,20,25butthereisnovalidatedsystemgivingclassicationofallthecommonfracturepatterns.Thenewclassicationsystemevolvedfromreviewofthefracturepatternsseenin1000consecutivecasesandincludedfactorsthoughttoinuencetheprognosis.Itshowsassociationsbetweenfracturesubtypesandfavour-ableorpoorprognosesandmayprovideabasisfortreat-mentbypredictingthosefractureswhichareatparticularriskofnonunionorfurthercomplications.Theclassica-tion is more complex, but blinded assessment of inter- andintraobservervariationshowedsubstantialtoexcellentlevelsofreliabilityandreproducibilityamongorthopaedictrainees. This compares well with some other classicationsystems.18,19The new classication showed diaphyseal fractures (type2)in69.2%ofpatients,lateral-end(type3)in28%andmedial-end(type1)in2.8%ofpatients.Thesegurescorrelatewithpreviousestimatesofanatomicaldistribu-tion,1,4,5but the relative prevalence of lateral-end fractureswashigher,probablybecausethisstudywasconnedtoadults.Type-1fractureswererare,usuallycausedbysimplefalls and were predominantly undisplaced and extra-articu-lar.Therewerefewcomplicationsorneedforoperation.Thistypehasnotpreviouslybeenstudiedindetail,althoughtheprognosisisusuallyregardedasfavourable.8Type-2fractures,thecommonestsubgroup,hadagoodprognosis for the two patterns with residual cortical contact(types 2A1 and 2A2 distinguished by the degree of angula-tion).Type2A2fractureswereseeninayoungerpopu-lationthantheothertype-2fractures,andwereconsideredas a variant of the angulated greenstick fracture commonlyseeninchildren,8inwhichangulationshowsanintactinferiorperiostealhinge.Therewerefewcomplicationsaftertype-2Afractures:thecommonestwasintype-2A2fracturesinwhichskintentingorbonyprominencepro-ducedlocalsymptoms.Incontrasttothefracturesofthistypeinchildren,remodellingwaspoorandremovalofprominentboneafterunionwasrequiredin5.7%ofthesefractures.Displaceddiaphysealfractures(type2B)weremorecommonthandisplacedtype-2Afractures.Therewasfre-quentlysignicantcomminution,eitherwedge(type2B1)orsegmental(type-2B2),probablybecauseofthesigmoidshapeofthebonecausingeccentricloadingfrommediallydirected forces on the shoulder against the sternoclavicularjoint.14Mosttype-2Bfractureshealeduneventfully,but3.2%showeddelayedunionbeyond12weeksand5.8%ofpatients had nonunion at 24 weeks. This incidence is muchhigherthanthe0.1%to0.8%previouslyreported.3,4Bothdisplacement (all type-2B fractures) and segmental commi-nution(type-2B2fractures)wereassociatedwithanincreased risk of delayed or nonunion, with a much weakerassociation with high-energy injuries, and none with age orgender.Theinitialmorphologyofthefracturethereforeprovidedthebestindicationoftheriskofdelayedornonunion,irrespectiveofthemechanismofinjury.Displacementwithsegmentalcomminutionprobablyreectstheseverityofboneandsoft-tissueinjuries,inaregionwithfewmuscleandsoft-tissueattachments.Inthosepatientswhorequiredoperationfornonunionafterasegmentalfracture,theintermediatesegmentwasoftencompletelydevoidofsoft-tissueattachments.Previousstudies have suggested that nonunion may be asymptomaticin from 24% to 40.5% of all type-2B fractures,23,26,27but at24 weeks all but one patient with nonunion had continuingsymptomswhichrequiredoperation.Lateral-end fractures (type 3), 28% of all fractures, wereseen in an older population and a higher proportion was dueto simple falls. As in previous studies9,28most were undis-placed(type3A)andhadabenignprognosis.Currentterminologyforlateral-endfracturesisconfus-ing:Allman8includedonlythoselateraltothecoraco-clavicularligaments,buttheNeer9classication,furtherrenedbyCraig,25includesfracturesmedialtotheliga-ments,andattemptstodelineatetheextentofligamentousinjury.Inpractice,withaccesstoplainradiographsonly,identication of the site and extent of ligamentous injury isdifcult. The new system offers a more pragmatic approachtoclassication,asthesubgroupdependssolelyonthedisplacement of the fracture, produced mainly by trapeziuspullingtheproximalfragmentsuperiorlyandposteriorly.Mosttype-3Binjuriesshowedatwo-partfracturebutin29%therewerethreepartswithavulsionoftheinferiorbonyportionofthelateralsurface.Inthese,thecoraco-clavicular ligaments are probably intact and attached to theinferiorfragment.29Thisfracturehaspreviouslybeenregardedasmoreunstablethanthepureligamentousinjury,25butinthisstudytheybehavedsimilarly.Displaced lateral-end fractures (types 3B1 and 3B2) havebeenregardedashavinglowratesofbonyunionafterconservativetreatment;3,9,11,24,28theprevalenceofdelayedunion has been reported as between 45% and 66%,9,24withnonunionin22%to33%.9,24,28Becauseofthesehighincidences,primarysurgicalstabilisationhasbeenadvisedfor all displaced lateral-end fractures9,11,24,25although non-union may be asymptomatic in up to 80%28and the resultsofsurgerymaynotbeoptimal.30Inthisseries,theincid-enceofdelayedandnonunionforthesefractureswas11.1%and18.2%,respectively.Halfofthecasesofnon-unionwereasymptomaticandonly9.1%ofpatientswithdisplacedlateral-endfracturesultimatelyrequiredsurgery.Most of these fractures occur in older patients with limitedfunctionalexpectations,andthereforeinitialnon-operative483 FRACTURESOFTHECLAVICLEINTHE ADULTVOL.80-B,NO.3,MAY1998treatmentisjustied.Furtherprospectivestudyisrequiredof younger patients with type-3B injuries to assess whethersurgicalstabilisationimprovesthefunctionaloutcomeanddecreasestheprevalenceofnonunion.Symptomatic osteoarthritis of the acromioclavicular jointwasseenonlyafterintra-articularfracturesofthelateralend (types 3A2 and 3B2) and was found in 15.2% of thesecases.Thishasbeenwelldescribed,25butitsprevalencehas not previously been established. Resection of the distal2 cmofthelateralendoftheclavicle25hasgivengoodresultsasalateprocedure.Othercomplicationswhichhavebeendescribedincludepressureonneurovascularstructuresbycallusformation,pneumothorax and post-traumatic aneurysm. No cases wereseeninthisseriesbutlongerfollow-upwouldberequiredtoexcludelatecompressionsyndromes.Themostappropriatemanagementformostclavicularfracturesisnon-operative;theoptimaltreatment-basedclassication suggested by Bernstein et al31is therefore notfeasible.Thenewclassicationprovidesareliableandreproducibleprognosticguidebyidentifyingsubgroupsatrisk of delayed or nonunion and other complications. Thesehigh-risksubgroupsrequiremoreprolongedandvigilantfollow-up.Anynewfractureclassicationsystemshouldreliablypredictfunctionaloutcome.Thishasnotyetbeendone,butafutureprospectivestudyisplanned.Nobenetsinanyformhavebeenreceivedorwillbereceivedfromacommercialpartyrelateddirectlyorindirectlytothesubjectofthisarticle.References1.EskolaA,VainionpaaS,MyllynenP,PatialaH,RokkanenP.Outcomeofclavicularfracturein89patients.ArchOrthopTraumaSurg1986;105:337-8.2.StanleyD,NorrisSH.Recoveryfollowingfracturesoftheclavicletreatedconservatively.Injury1988;19:162-4.3.NeerCS.Nonunionoftheclavicle.JAMA1960;172:1006-11.4.RoweCR.Anatlasofanatomyandtreatmentofmid-clavicularfractures.ClinOrthop1968;58:29-42.5. Nordqvist A, Petersson C. The incidence of fractures of the clavicle.ClinOrthop1994;300:127-32.6.Moore TO.Internalpinxationforfractureoftheclavicle. AmSurg1951;17:580-3.7. Neer CS II. Fractures of the clavicle. 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