PMC4454702_01
(a) Bipolar hemiarthroplasty (BHR) loosened aseptically and migrated superiorly. (b) Total hip arthroplasty (THA) was performed as a conversion from BHR to THA 22 years ago. Cup was unknown (Zimmer, Warsaw, IN, USA) and stem was BIAS long stem (Zimmer). (c) Stem prosthesis of primary THA loosened aseptically. (d) Revisional THA (cup, trilogy, stem, versis beaded full coat plus; inner head, 26 mm cobalt-chrome) (Zimmer) was performed because of aseptic loosening of THA 9 years ago.
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fig1
Thereafter, aseptic loosening of the BHR was noted and she underwent conversion from BHR to a cementless THA (Zimmer, Warsaw, IN, USA) at the age of 26 (Figures 1(a) and 1(b)). THA (Trilogy cup, versis beaded full coat plus stem, 26 mm cobalt-chrome inner head, Zimmer) was performed because of aseptic loosening of the previous THA (Figures 1(c) and 1(d)). This cobalt-chrome alloy stem was extensively porous-coated, with a diameter of 12 mm and length of 200 mm.
(a) During walking with a single axillary crutch, the stem was suddenly fractured at the site of well-fixated proximal level. (b) Re-revisional THA was performed with Delta-lock system (stem, titanium-6 aluminum-4 vanadium alloy; head, 26-mm Cobalt-chrome-molybdenum alloy (Nakashima Medical Co. Ltd., Okayama, Japan)); cup was not changed.
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fig2
Two years later after the infection was finally healed, the stem was suddenly fractured while the patient was walking with a single axillary crutch (Figure 2(a)). THA with a Delta-lock system (Nakashima Medical, Okayama, Japan) without a change of cup (Figure 2(b)).
(a) The picture of retrieved implant. Lower left is medial side of the implant. (b) Extended section picture of proximal part. There was a clear step in the medial side, suggesting that lateral side was the starting point of fracture and medical side was lastly fractured.
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fig3
The section pictures of retrieved implant revealed a clear step in the medial side, suggesting that medial side was lastly fractured (Figures 3(a) and 3(b)). The new titanium-6 aluminum-4 vanadium alloy stem diameter was 14 mm and the length was 280 mm, fixed with six screws.
(a) The stem lateral bending was 0  immediately after revisional THA. (b) The stem bending was stronger than before, with the bending degree being 5.3  at final dislocation.
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fig4
THA was performed, stem bending was 0  (Figure 4(a)), which gradually progressed (Figure 5). The degree of stem bending immediately after the first dislocation was 1.9 . After the final dislocation, the degree of bending (5.3 ) was more pronounced than before (Figures 4(b) and 5).
The stem bending was 0  immediately after the revisional THA. The stem bending gradually progressed during first five years. The stem bending immediately after the first dislocation was 1.9  and then the stem bending at final dislocation was 5.3 . The stem bending before the stem fracture was 5.2 .
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fig5
THA was performed, stem bending was 0  (Figure 4(a)), which gradually progressed (Figure 5). The degree of stem bending immediately after the first dislocation was 1.9 .
The results of scanning electron microscope- (SEM-) energy dispersive X-ray spectroscopy (SEM-EDX). (a), (b), and (c) showed the results of SEM-EDX at medial section, central section, and lateral section, respectively. Much higher oxygen at the medial and lateral sections was detected compared with the central section.
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fig6
SEM-energy dispersive X-ray spectroscopy (SEM-EDX) revealed that there was much higher oxygen at the medial and lateral sections as compared with the central section, suspecting that there had been in vivo corrosion before sudden implant fracture (Figure 6).