PMC6530236_01
Radiographs. (a) Preoperative radiograph showing severe osteoarthritis of the left hip. (b) Postoperative radiograph of primary THA of the left hip using AHFIX Q stem (NAR #1). (c) Radiograph showing breakage of the AHFIX Q stem at the base of the neck. (d) Postoperative radiograph after revision THA of the left hip. THA: total hip arthroplasty.
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Radiography revealed end-stage severe left hip arthritis and malposition of the cup implant on the right side (Figure 1(a)). THA was therefore performed via a posterior approach using an uncemented hip stem (AHFIX Q, KYOCERA, Japan) (Figure 1(b)). Radiography revealed an uncemented femoral stem fracture at the base of the neck (Figure 1(c)). Revision THA was immediately performed using a Wagner cone stem (Zimmer Biomet, Warsaw, IN, USA, Figure 1(d)).
Appearance of the broken stem. Macroscopic appearance of the broken AHFIX Q stem at the base of the neck. The proximal coating area shows good bone ingrowth. The base of the neck has a sharp slot for handle attachment and the corner is not rounded but is angular.
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The proximal coating area of the stem showed good bone ingrowth macroscopically (Figure 2).
Fractured surface observed by macroscopy, digital microscopy, and SEM. (a) Fracture surface observed macroscopically. Arrows indicate the advancing direction of the progressive destruction. (b) Fracture surface observed by digital microscopy. There were multiple micro streaks from the edge of the attachment slot in the stem corner (red arrows). (c) Picture of the fractured surface observed by scanning electron microscopy (~x2000). The basis of the streaks was assumed to be the origin of the fracture. SEM: scanning electron microscope.
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The cracks extended from the anterolateral surface to the posteromedial surface (Figure 3). There were multiple striations in areas 1 and 2 (Figures 3 and 4). Furthermore, there were multiple dimples in area 3 (Figures 3 and 4).
Analysis by SEM. The SEM images show many parallel striations in area 1 and area 2. Furthermore, there are many dimples in the area 3. SEM: scanning electron microscope.
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There were multiple striations in areas 1 and 2 (Figures 3 and 4). Furthermore, there were multiple dimples in area 3 (Figures 3 and 4).
Result of the analysis by FEM. FEM images showing that the stress was maximum in the corner of the hollow junction for all sizes. FEM: finite element method.
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Figure 5). For STD #1, the maximum stress was 449 MPa.