A 73-year-old female patient presented to our institution with a two-year history of inability to walk on the left hip. The initial primary total hip was performed for osteoarthritis at another institution 10 years ago, after which she had a good function for multiple years. The last radiograph of the left hip was done two years prior, where it was incidentally imaged during a left femoral angiogram. This demonstrated left hip dislocation, migration of acetabular component, and formation of pseudoarthrosis within the left ilium (Figure 1). The subsequent surgical management was delayed due to poor perfusion of the ipsilateral limb and persisting neuropathic ulcer. The patient's past medical history included diabetes mellitus type II, peripheral vascular disease requiring left femoral vascular intervention, and hypertension.
The patient was able to mobilize short distances with an antalgic gait. She was independent with activities of daily living but dependent on a wheelchair for outdoor ambulation. There was a significant leg length discrepancy with the left lower limb shortening by 4 cm. Soft tissues overlying the surgical site were intact. The patient's hip was irritable to movement. Peripheral pulses were present but diminished with sensory changes to the lower limb.
Intraoperatively, the femoral head was identified via posterior approach after extensive arthrolysis with a well-fixed femoral stem. The screw-type acetabular component was laboriously salvaged as it was surrounded by arthrofibrosis and heterotopic ossification. The acetabular defect was extensively debrided with multiple sampling of periprosthetic tissue for microbiology. These were negative for infection.
The remaining acetabulum consisted of a wafer-thin medial acetabular wall and a large supra-acetabular defect, consistent with a Paprosky Type IIIb defect (Figure 2(a)). There were spherical acetabular defects over the true acetabulum and another spherical acetabular defect overlying the debrided pseudoarthrosis. Multiple configurations of the 54 mm tantalum augments (Zimmer Biomet, Warsaw, USA) were trialled to contain the acetabular defect. A novel method of acetabular reconstruction involves using three tantalum augments and cementing them together in a "football configuration" using regular bone cement (polymethylmethacrylate, PMMA) (Figure 2(b)). After keeping these three wedges in the correct position for twelve minutes until bone cement fixation was completed, the construct was then implanted into the acetabular defect and subsequently fixed with additional 6.5 mm cancellous bone screws.
Reconstruction of the acetabulum to achieve a physiological center of rotation was achieved using a cemented Mark III acetabular cup (Waldemar Link Company, Hamburg, Germany) according to preoperative planning (Figure 3). A compatible Delta ceramic head size 28 x 3, 0 mm (Biolox , CeramTec, Plochingen, Germany) was placed on the original stem and achieved stable range of motion of the hip (Figures 2(c) and 4).
The patient was closely monitored within a multidiscipline in our institution, however sustained two dislocations during the postoperative period (Figure 5).
Thus, the cemented cup was revised 4 weeks after the initial reconstruction with an elevated liner and installed an antidislocation ring (Figure 6). The patient did not sustain further dislocations and achieved independent mobility at the last follow-up.