Avascular Necrosis of Acetabulum: The Hidden Culprit of Resistant Deep Wound Infection and Failed Fixation of Fracture Acetabulum - A Case Report

Abstract

Introduction: Chances of avascular necrosis of acetabulum are rare as it enjoys a rich blood supply. But cases of post - traumatic avascular necrosis of acetabulum following fracture of posterior column have been well documented. Importance of identifying and suspecting the avascular necrosis of acetabulum is essential in cases of failed fixation of fracture acetabulum, previously operated using extensile approach to acetabulum; either extended anterior ilio - femoral or tri - radiate approach. Such patients usually present with repeated deep bone infection or with early failure of fixation with aseptic loosening and migration of its components. We present a similar case.

Case presentation: 40 years female presented with inadequately managed transverse fracture of left acetabulum done by anterior extended ilio-inguinal approach. The fixation failed. She presented 6 months later with painful hip. Cemented total hip replacement was performed with reconstruction of acetabulum by posterior column plating. Six months postoperatively patient presented with dislodgement of cup, pelvic discontinuity and sinus in the thigh. Two stage revision surgery was planned. First implant, removal; debridement and antibiotic spacer surgery was performed. At second stage of revision total hip replacement, patient had Paprosky grade IIIb defect in acetabulum. Spacer was removed through the posterior approach. Anterior approach was taken for anterior plating. Intra-operatively external iliac pulsations were found to be absent so procedure was abandoned after expert opinion. Postoperatively digital subtraction angiography demonstrated a chronic block in the external iliac artery and corona mortis was the only patent vascular channel providing vascular to the left lower limb. Thus, peripheral limb was stealing blood supply from the acetabulum to maintain perfusion. Patient was ultimately left with pelvic discontinuity, excision arthroplasty and pseudoarthrosis of the left hip.

Conclusions: Avascular necrosis of acetabulum is a rare entity & often not recognized. One should be suspicious about diagnosis of avascular necrosis of acetabulum in select cases of failed acetabular fixation, previously operated via extensile anterior ilio - inguinal approach. Angiographic evaluation is essential in revision cases of failed acetabular fixation. Corona mortis (crown or circle of death) can sometimes act as a savior of limb.

Keywords: Avascular Necrosis Acetabulum; Corona Mortis; Pelvic Discontinuity.

Figure 1

Initial X – ray of the patient showing transverse fracture of left acetabulum.

Figure 2

X – ray 6 months post trauma showing failed fixation of the transverse fracture of left acetabulum.

Figure 3

X – ray showing the revision of the inadequate screw fixation of the trasverse fracture of acetabulum with posterior column plating, impaction bone grafting with mesh and cemented total hip replacement

Figure 4

ray taken 6 months after the posterior column plating, impaction bone grafting, mesh fixation and cemented total hip replacement showing failed fixation, dislodgement of the acetabular cup and pelvic discontinuity.

Figure 5

Clinical photograph 6 months after the posterior column plating, impaction bone grafting, mesh fixation and cemented total hip replacement showing draining sinus along the inferior aspect of the incision of surgery on the lateral aspect of left thigh.

Figure 6

Clinical photograph 6 months after the posterior column plating, impaction bone grafting, mesh fixation and cemented total hip replacement showing draining sinus along the inferior aspect of the incision of surgery on the lateral aspect of left thigh.

Figure 7

Clinical photograph of the lateral aspect of left thigh taken 3 months following the antibiotic impregnated cement hip spacer surgery. Shwing healed sinus.

Figure 8

The image is of the Digital Substraction Angiography of the left lower limb showing block in the left external iliac circulation and the patent corona mortis at the rescue of the blocked external iliac circulation providing blood supply to the distal left lower limb.

Figure 9

This is the final X – ray of the patient showing pelvic discontinuity, excision arthroplasty and pseudoarthrosis of the left hip.

Figure 10

This is the 3D reconstruction CT – Scan image of the patient showing pelvic discontinuity.