Injury Extra (2006) 37, 158—162

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CASE REPORT

Delayed onset tibial nerve axonotmesis andposterior tibial artery pseudoaneurysm causedby tibial diaphysis fracture

Chye Yew Ng a,*, Michiel R.G. Hendrix b, Scott McKie c

aDepartment of Orthopaedics, Queen Margaret Hospital, Dunfermline KY12 0SU,United KingdombCrosshouse Hospital, Kilmarnock KA2 0BE, Ayrshire, United KingdomcQueen Margaret Hospital and Victoria Hospital, Dunfermline KY12 0SU,United Kingdom

Accepted 12 October 2005

Introduction

Arterial aneurysms in the lower leg, the majority ofwhich are pseudoaneurysms, are rare. They mostcommonly arise after vascular procedures and infre-quently after orthopaedic procedures. Very fewcases occur after fractures, and neurological signsoccur in less than half of patients.1—7 This reportdescribes a case of tibial nerve palsy secondary to apseudoaneurysm of the posterior tibial artery, inturn due to a tibial shaft fracture.

Case report

During a football game, a 20-year-old man sustaineda closed right oblique fracture at the junction of themiddle and distal third of the tibia and fibula shaftswith no neurovascular deficit (Fig. 1a and b). He

* Corresponding author at: 1/1 Portland Row,Edinburgh EH6 6NH, United Kingdom. Tel.: +44 7868633338;fax: +44 1383627089.

E-mail address: chyeng@gmail.com (C.Y. Ng).

1572-3461/$ — see front matter # 2005 Elsevier Ltd. All rights resedoi:10.1016/j.injury.2005.10.029

underwent intramedullary nailing of his right tibia(Trigen IM nail, Smith & Nephew Orthopaedics).Closed reduction and instrumentation was achievedwithout penetrating the surrounding soft tissues(Fig. 2).

Routine subcutaneous Dalteparin 2500 units wasadministered daily as thromboprophylaxis, andthere were no signs of any neurovascular compro-mise in the immediate postoperative period. He wasdischarged from hospital after 3 days.

On day 11, his right calf was 3 cm more swollenthan the left. A venous Doppler was performedrevealing no evidence of deep vein thrombosis(DVT).

On day 19, the swelling worsened and he devel-oped movement induced neuralgic pain and anaes-thesia along the medial aspect and sole of his rightfoot. A repeat venous Doppler examination wasperformed to the level of the venous trifurcation,revealing no evidence of DVT.

On day 29, he was admitted complaining ofsevere pain and paraesthesia of his right foot andankle. He had loss of sensation over the distributionof his right medial plantar nerve and was referred

rved.

Delayed onset tibial nerve axonotmesis 159

Figure 1 (a and b) Presentation film: short obliquediaphyseal fracture of tibia and fibula.

Figure 2 Post operative tibial intramedullary nail.

Figure 3 Subtle soft tissue calcification/swelling at siteof fracture.

for lower limb peripheral neurophysiology studies.The amplitude of conduction of the right tibial nervewas attenuated, consistent with an axonotmesis.

X-rays at this stage showed a moderately sizedsoft tissue swelling posteromedially, at the level ofthe fracture site (Fig. 3). Subcutaneous Dalteparin

was administered during his 9-day stay as the stan-dard thromboprophylaxis in the unit.

On day 46, his pain was persistent, he had devel-oped weakness of the flexors of his toes, particularly

160 C.Y. Ng et al.

Figure 4 Colour Doppler examination showing inflowand outflow of a large highly vascular pseudoaneurysm.

Figure 5 Selective posterior tibial artery angiogram andcoil embolisation.

of his flexor hallucis longus. An urgent ultrasoundscan revealed an 8 cm pseudoaneurysm of the pos-terior tibial artery (Fig. 4). The tibial nerve wasstretched over the mass and there was high flowwithin the aneurysm centre. The regional vascularradiology unit performed a selective posterior tibialartery angiogram and coil embolisation of the pseu-doaneurysm (Fig. 5). Surgical decompression of theaneurysm was considered to be too hazardous torelieve the mass effect. Post-procedure ultrasoundwith Doppler interrogation confirmed absence offlow (Fig. 6).

On day 87, an ultrasound showed a large, throm-bosed posterior tibial aneurysmwith the tibial nervestill taut over its surface. Pain and swelling contin-ued. Further ultrasound examinations failed to showany decrease in the size of the thrombosed aneur-ysm mass over the next few weeks. The case wasreviewed at a multidisciplinary vascular meetingand it was felt that there would be no advantageof surgical decompression. After further discussions,the patient was subsequently managed expectantly.

Byday172,theswellingandweaknesshadresolvedand he only had little residual numbness in his foot.

Discussion

The aetiology of the pseudoaneurysm in this casewas probably the initial trauma causing the fracture

Delayed onset tibial nerve axonotmesis 161

Figure 6 Siescape image of thrombosed post embolisation pseudoaneurysm.

or the fracture itself. This resulted in a focal weak-ening of the vessel wall initiating the developmentof the pseudoaneurysm. Surgical treatment of thisfracture proceeded without any difficulty and withno violation of soft tissues making iatrogenic causeunlikely.

There has been a case report of a traumaticpseudoaneurysm of the anterior tibial artery trea-ted successfully by compression stocking and dis-continuation of anticoagulation.7 Anticoagulationduring the hospital admissions in our case may haveexacerbated the problem. In addition it was feltthat the aneurysm was both too large and thevelocity of flow too great to warrant conservativemanagement.

Further investigation should have been doneduring the early postoperative phase. Exclusionof DVT alone is not sufficient and the examinationrequires tailoring to the clinical question. Thesurgeon and radiologist should also consider otherdifferential diagnoses such as haematoma,abscess, pseudoaneurysm, arterio-venous fistulaand myositis ossificans. Further imaging such asultrasound, CT or MR scan would be indicated ina patient with unexplained persistent symptomsand signs.

Pseudoaneurysm can be treated operatively ornon-operatively.7 The former includes arterial liga-tion or repair using direct suture techniques orinterposition grafting. The other options are percu-taneous implantation of endovascular coveredstents, ultrasound-guided compression, ultra-sound-guided thrombin injection, percutaneoustranscatheter coil or gel foam embolisation.

Peripheral nerve injuries can be divided intoneurapraxia, axonotmesis and neurotmesis. Neura-praxia usually results from temporary compressionof a nerve and complete recovery is expected. In

contrast, neurotmesis results from complete sever-ance of a nerve which requires repair and recovery ismuch less predictable.

Axonotmesis refers to loss of function due tosevere ischaemia which may result from prolongedpressure or crushing. It is followed by degenerationof fibres distal to the level of injury. The nervesheath remains intact and a slow regeneration(1 mm/day), and thus return of function, can beexpected. In the case reported, we postulate thatthe presence of a pseudoaneurysm stretched thetibial nerve and compromised its microvascular sup-ply. Early identification of the underlying cause withprompt treatment of the pseudoaneurysm may haveprevented the onset of axonotmesis.X

Conclusion

DVT and haematoma are common causes of legswelling after intramedullary tibial nailing. How-ever a high degree of suspicion for pseudoaneur-ysm is needed despite its rarer incidence.Clinicians should remain vigilant for a neurologicalcause of persistent leg pain following lower limbfractures, and the radiological investigationshould be tailored and focused on the site ofpathology.

Reference

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