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A fracture of the talar neck associated with a talocalcaneal bar

A fracture of the talar neck associated with a talocalcaneal bar
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  CASE REPORT A fracture of the talar neck associated witha talocalcaneal bar I.E. Yardley*, J. Keenan, K. Trimble Department of Orthopaedics, Derriford Hospital, Derriford Road, Plymouth PL6 8DH, UK  Accepted 1 February 2005 Introduction Tarsal coalition is an uncommon variant of the nor-mal anatomy of the foot estimated to occur in 1—2%of the population. 2,6 It is thought to be due todefective segmentation and differentiation of pri-mitive mesenchyme with talocalcaneal coalitionbeing the most common form. Fractures of thetalus are uncommon in childhood and may be com-plicated by avascular necrosis, non-union and sub-talar arthrosis. Avascular necrosis following talarfracture in children is thought to occur in 25—58%of cases, with the incidence being higher in patientswho have subluxation or dislocation of the subtalarjoint. 3,5 Case report A 12-year-old boy fell approximately 1.2 m, leadingto a forced dorsiflexion injury of the ankle. X-raysdemonstratedaHawkinstypeIIfracturethroughtheneck of the talus with subluxation of the subtalarjoint. A bony talocalcaneal bar was also noted(Fig. 1).The patient was otherwise healthy with no co-existent medical problems and no pain or limitationof activity in the foot or ankle prior to the injury.As the fracture was displaced, it was treated byopen reduction and internal fixation using two par-tially threaded cannulated cancellous screws. Onescrewwasinsertedanteromedially,theotherusingasmall posterolateral incision (Fig. 2).Six months after the injury, he was completelywell and undertaking normal activities, includingjogging.X-raysdemonstratedawell-healedfracturewith no evidence of avascular necrosis. Discussion This unusual injury is likely to be related to the bonycoalition between the talus and calcaneum inducingabnormal stresses on the talus at the time of thefall, which caused the resulting fracture. Talar frac-tures associated with subtalar subluxation, as in thiscase, would ordinarily have a high risk of going on todevelop avascular necrosis in the head of thetalus. 3,5 This is because the fracture disrupts thesuperior neck vessels arising from the anterior tibialartery and the artery of the tarsal sinus is liable todamage by subtalar subluxation. 1 The decision to internally fix the fracture wastaken because of the significant fracture displace-ment. Excision of the bar at the time of fixation and Injury Extra (2005)  36 , 424—* Corresponding author. Present address: Department of Sur-gery, Level 7, Derriford Hospital, Derriford Road, Plymouth PL68DH, UK. E-mail address: (I.E. Yardley).1572-3461/$ — see front matter # 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.injury.2005.02.043  primary subtalar fusion were considered butrejected as the patient had been asymptomaticprior to the injury. Anatomic reduction was con- fi rmed through the small anteromedial approach.The posterolateral approach allows extraarticularintroduction of the cannulated screw 4 and providesmechanically superior  fi xation. 7 Late arthrosisremains a potential risk but given the functionalresult at 6 months this is unlikely and his prognosis isgood.Paradoxically, the excellent outcome may be, inpart, due to the presence of the osseous coalition.The presence of a bony bar between the talus andcalcaneum may have provided extra-anatomicintraosseous and periosteal anastomoses, giving ablood supply to the head of the talus suf  fi cient toprevent avascular necrosis and allow fracture heal-ing. 6 We report the unusual and severe injury of adisplaced talar neck fracture in a child, whichmay have been predisposed by the presence of anasyptomatic talocalcaneal bar. This was treated byanatomic open reduction and internal  fi xation,which went on to fracture union without avascularnecrosis or other complications and a good clinicaloutcome was achieved. It is possible that healingmay have been aided by blood supply through thetalocalcaneal bar. References 1. Gelberman RH, Mortensen WW. The arterial anatomy of thetalus. Foot Ankle 1983;4:64 — 72.2. Kim DH, Berkowitz MJ. Fracture of the calcaneus associatedwith talocalcaneal coalition. Foot Ankle 2004;25(6):426 — 8.3. Inokuchi S, OgawaK, Usami N. Fractureof the talus in childrenunder the age of ten. Foot Dis 1994;1:29 — 35.4. Lemaire RG, Bustin W. Screw  fi xation of fractures of the neckof the talus using a posterior approach. J Trauma1980;20:669 — 73.5. LettsRM,GibeaultD.Fracturesoftheneckoftalusinchildren.Foot Ankle 1980;1:74 — 7.6. Richards RR, Evans JG, McGoey PF. Fracture of a calcaneona-vicular bar: a complication of tarsal coalition. Clin Orthop1984;185:220 — 1.7. SwansonTV,BrayTJ,HolmesGB.Fracturesofthetalarneck.Amechanical study of   fi xation. J Bone Joint Surg [Am]1992;74:544 — 51. A fracture of the talar neck associated with a talocalcaneal bar 425 Figure 1  Hawkins type II fracture through the neck of the talus associated with a bony talocalcaneal bar. Figure 2  Hawkins type II fracture through the neck of the talus associated with a bony talocalcaneal bar treatedby open reduction and  fi xation with partially threadedcannulated screws.
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