Interchangeable neck failures of bi-modular femoral stems in primary total hip arthroplasty cannot be predicted from ser
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ORIGINAL PAPER
Interchangeable neck failures of bi-modular femoral stems in primary total hip arthroplasty cannot be predicted from serum trace element analysis Samo K. Fokter 1
&
Jan Zajc 2 & Matjaž Merc 1
Received: 24 May 2020 / Accepted: 11 September 2020 # SICOT aisbl 2020
Abstract Introduction Revision of a well-fixed stem due to unexpected modular neck fracture is a catastrophe for the patient and a challenge for the surgeon. This study aimed to test the possibility of predicting interchangeable neck fracture from serum levels of the stem/neck alloy-consisting metals. Materials and methods Nineteen patients at high risk for interchangeable neck fracture were randomly selected out of a cohort of 680 bimodular stems made from Ti6Al4V alloy. Serum levels of titanium, aluminium and vanadium were determined. Nine ageand gender-matched patients were used as controls. Results Mean serum levels of Ti were 6.04 ± 2.52 μg/L, of Al 3.89 ± 1.68 μg/L and of V 0.07 ± 0.04 μg/L in the high-risk group, and 8.22 ± 4.74 μg/L, 4.99 ± 3.98 μg/L and 0.27 ± 0.44 μg/L in the low-risk group, respectively. No statistically significant differences were found between the groups. Discussion Interchangeable neck fracture of bimodular femoral stems cannot be predicted from serum trace element analysis. Keywords Hip arthroplasty . Component breakage . Bimodular femoral stem . Interchangeable neck
Introduction Bimodular femoral stem designs have been introduced in primary total hip arthroplasties (THAs) to offer better restoration of hip geometry and reduce dislocation rate. However, some studies of bimodular stems did not reveal a clear benefit over standard (monoblock) stem THAs and reports of sudden modular neck failure appeared in the orthopaedic literature soon after their more widespread use [1, 2]. Revision of a well-fixed femoral stem because of modular neck failure is a catastrophe for the patient and a challenge for the surgeon, and can substantially affect the health care resources in countries where the bimodular stems were commonly used [3]. Risk factors for modular neck failure include neck’s length, orientation and
* Samo K. Fokter [email protected] 1
Department for Orthopaedic Surgery, University Medical Centre Maribor, 5 Ljubljanska Street, SLO-2000 Maribor, Slovenia
2
Faculty of Medicine, University of Maribor, 8 Taborska Street, SLO-2000 Maribor, Slovenia
material, and patient’s body mass index (BMI), age and gender [3, 4]. Unfortunately, bimodular neck failure cannot be predicted by any known radiographic methods. This retrospective cohort study aimed to test the possibility to predict modular neck failure from serum levels of titanium-titanium modular-stem prostheses in primary THA.
Materials and methods Twenty high-risk patients for modular neck fracture (long neck and high BMI) were randomly selected out of a cohort of 680 Profemur Z® (Wright Medical Technology—now MicroPort Orthopedics, Arlington, TN, USA) bimodular stems made from Ti6Al4V alloy, implanted in a single institution between 2002 and
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