Bilateral total hip replacement: periprosthetic pseudotumor collections are more prevalent in metal-on-metal implants compared to non-metal-on-metal ones.
BACKGROUND
Metal-on-metal (MoM) hip prostheses were shown to have high failure rates including the formation of periprosthetic cystic masses called periprosthetic pseudotumor collections (PPCs).


OBJECTIVE
To compare MRI prevalence and size of PPCs in patients after bilateral total-hip-replacement (THR) in which at least one hip was replaced by a MoM prosthesis.


METHODS
All sequential MRI examinations of patients with bilateral THR in which at least one is MoM (2010-2013) were retrospectively evaluated. MRIs were analyzed separately by two readers for the presence and size of PPCs. These were compared between MoM and non-MoM implants and between patients with unilateral or bilateral-MoM prostheses. Blood metal ion levels were also compared.


RESULTS
Seventy hips of 35 patients (male:female ratio, 9:26; mean age, 64 years; age range, 35-82 years) were assessed. Sixteen patients (45%) underwent bilateral MoM-THRs and 19 (55%) had one MoM and the other non-MoM, yielding 51 MoM THRs and 19 non-MoM THRs. Twenty-eight PPCs were detected in 19 patients (54%): 26 in MoM THRs (51%) and two in non-MoM THRs (10.5%, P = 0.00009). The mean PPC volume in the MoM implants (107 mm(3)) was higher than that of the non-MoM implants (18 mm(3), P = 0.49). Cobalt/chromium blood levels were 78 µg/L/25 µg/L for bilateral MoM THRs and 21 µg/L/10 µg/L for unilateral MoM implants (P = 0.1 and 0.16, respectively).


CONCLUSIONS
PPCs are more prevalent in MoM THRs compared to non-MoM THRs. Larger PPC volumes and higher blood metal ion levels were detected in patients with bilateral MoM THRs compared to unilateral MoM THRs (P > 0.05).
Department of Diagnostic Imaging, Sheba Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel.
Einat
E
Slonimsky
Department of Diagnostic Imaging, Sheba Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel.
Tammar
T
Kushnir
Department of Orthopedic Surgery, Tel Aviv Sourasky Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Assaf
A
Kadar
Department of Orthopedic Surgery, Tel Aviv Sourasky Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Aharon
A
Menahem
Department of Orthopedic Surgery, Tel Aviv Sourasky Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Alon
A
Grundshtein
Department of Orthopedic Surgery, Assuta Medical Center, Tel Aviv, Israel.
Shmuel
S
Dekel
Department of Diagnostic Imaging, Sheba Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel iriseshed@gmail.com.
Iris
I
Eshed
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005260:Female; D006104:Granuloma, Plasma Cell / Q000453:epidemiology* / Q000473:pathology; D006621:Hip Joint / Q000473:pathology; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D015588:Observer Variation; D015995:Prevalence; D011474:Prosthesis Design; D011475:Prosthesis Failure / Q000009:adverse effects*; D012189:Retrospective Studies
MRI; blood metal ions; hip replacement; metal-on-metal hip implant; pseudotumor