Irreducible syndesmosis due to an entrapped posterior fragment

Injury

Vol. 26,

No. 8, pp. 569-571,

1995

ElsevierScience Ltd Printed in Great Britain 0020-1383195

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0020-1383(95)00087-9

Irreducible posterior D. Chan

syndesmosis fragment

due to an entrapped

and D. Jones

Ysbyty Gwynedd, Bangor, North Wales, UK

Injury, Vol. 26, No. 8, 569-571,

1995

Introduction The Maisonneuve fracture, classifiedas a Weber 44.C3.3 malleolar fracture’, is an external rotation injury produced with the foot either prone or supine. With foot pronation there is initial rupture of the deltoid ligament followed by sequential tearing of the anterior tibiofibular, interosseous ligaments, and finally a high oblique fibular fracture. As the injuring force continues, the posterior tibiofibular ligament tears or the posterolateral tibia1 comer (Volkmann fragment) is avulsed or pushed off resulting in dislocation of the ankle joint. With the foot in neutral or supination at the early stages of the injury, the deltoid ligament remains intact till the last stage of injury’. Closed reduction of the syndesmosismay be successfulbut length and rotation of the fibula must be anatomical prior to tibiofibular transfixation3. We report a casein which a fragment jammed between the Volkmann fragment and the tibia blocked successful closed reduction of the syndesmosis.

Case report A 25-year-old man sustained a Maisonneuve fracture dislocation of the left ankle(FigtrreI) while mountaineering.The dislocation was initially treated by closed reduction and tibiofibular transfixation. The postoperative X-ray showed reduction of the talus but there was residual posterior displacement of the fibula (Figwe&). A computed tomography (CT) scan revealed the lateral malleolus to be held subluxed by a piece of bone trapped betweeli the Volkmannfragmentand the tibia (Figure 2b). Open reduction was done through a posterolateral incision. The ankle was re-dislocated and the entrapped fragment retrieved anteriorly through the interval between the tom anterior tibiofibular and interosseous ligaments. Reduction was then anatomical. The Volkmann triangle was fixed with a 4 mm cancellous lag screw from behind. The syndesmosis was protected by a diastasis screw (Figure&,b). Subsequent rehabilitation was uneventful.

Discussion From the studies of Lauge Hansena, the posterolateral fragment is always attached to the lateral malleolar fragment by the posterior tibiofibular ligament. Anatom-

ical reduction of the lateral malleoluswill indirectly reduce this fragment. Any sizeable piece trapped between the posterolateral fragment and the posterior tibia will act asa block to reduction. A careful retrospective scrutiny of the plain films suggests such a trapped fragment. The CT image of the syndesmosisbeautifully demonstrates the fracture anatomy. The amount of displacement of the lateral malleolus matchesthe size of the trapped fragment. This rare complication occurred in a high fibular (Maisoneuve) fracture. It could likewise occur in the lower suprasyndesmoticfibular (Dupuytren) fracture or even in a Weber type B injury. In the type C injury, reduction of the distal fibula into the sigmoid notch is blocked. In the type B injury, anatomical reduction of the lateral malleolar fracture may not be possible unless the posterior tibiofibular

ligament becomesruptured. When such a difficulty arises during operation, it would be wise to exdmine the posterolateral comer through the lateral malleolar fracture using Weber’s technique3. It is suggestedthat a posterior malleolar fragment of less than 25 per cent of the articular surfaceon the lateral view does not require fixation. Harper et a1.5even suggested that posterior fragments involving 25 per cent to 45 per cent did not require fixation. It is important, however, to ensure reduction of the posterior fragment after reconstruction of the lateral malleolus. Failure to reduce the posterior fragment after anatomical reduction of the lateral malleolus fracture requires careful examination of the syndesmosisincluding exposure of the anterior syndesmotic ligament to ensure the fibula is replaced into the sigmoid notch. Any fragments between the Volkmann triangle and the tibia require removal to allow adequate reduction of the syndesmosis.

References 1 Mi.iller ME, Nazarin S, Koch P and Schatzker J. The Comprehensive Clussificafion of Fractures of Long Bones. 1st ed. Berlin: Springer-Verlag, 1990, pp. 182-183. 2 Pankovich AM. Maisonneuve fracture of the fibula.]Bonejoint Surg [Am] 1976; 58A: 337. 3 Heim U and Pfeiffer KM. Infernal Fin&a of Small Fractures. Technique Recommended by the AO-ASIF LYOU~. 3rd ed. Berlin: Springer-Verlag, 1988, p. 286-317.

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Vol. 26, No. 8, 1995

Figure 1. a, Anteroposterior view of the injured ankle: b, Lateral view of the injured ankle showing posterior subluxation of the talus with fracture of the Volkmann triangle.

Figure 2. u, Lateral view of the ankle following closed reduction and internal fixation. b, Transverse CT scan across the syndesmosis revealing the entrapped bone fragment.

Case reports

Figure 3. u, Anteroposterior view of the ankle after open reduction anatomical reduction of the lateral malleolus.

4 Lauge-Hansen N. Fractures of the ankle II. Combined experimental-surgical and experimental-roetgenologic investigations. Arch Surg 1950; 60: 957. 5 Harper MC and Hardin G. Posterior malleolar fractures of the ankle associated with external rotation-abduction injuries. Results with and without internal fixation. J Bone joint Surg [Am] 1988; 70A: 1348.

and internal

fixation.

b, Lateral view of the ankle showing

Paper accepted 30 May 1995.

Requests joor reprinfs should be addressed fo: Mr D. Chan FacsEd, Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire, UK. FRCS ORTH,