Simon Comtesse1, Arthur de Gast2, Philipp Rehbein3, Gary French4, Naeder Helmy5, Roland Becker6, Martin Dominkus7, Martin Beck8. 1. Mathys Ltd Bettlach, Robert-Mathys Strasse 5, 2544 Bettlach, Switzerland. 2. Diakonessenhuis Utrecht, Bosboomstraat 1, 3582 KE Utrecht, Netherlands; Clinical Orthopedic Research Centre midden-Nederland, Diakonessenhuis Zeist, Jagersingel 1, 3707 HL Zeist, Netherlands. 3. St. Josefs-Hospital Wiesbaden, Beethovenstraße 20, 65189 Wiesbaden, Germany. 4. Ormiston Hospital, 125, Ormiston Road, Flat Bush, 2016 Manukau, New Zealand. 5. Bürgerspital Solothurn, Schöngrünstrasse 42, 4500 Solothurn, Switzerland. 6. Zentrum für Orthopädie und Unfallchirurgie, Endoprothesenzentrum West-Brandenburg, Medizinische Hochschule Theodor Fontane, 14776 Brandenburg/Havel, Germany. 7. Orthopädisches Spital Speising, Speisinger Straße 109, 1130 Wien, Austria; Sigmund-Freud University, Campus Prater Freudplatz 1, 1020 Wien, Austria. 8. Luzerner Kantonsspital, Spitalstrasse, 6000 Luzern, Switzerland. Electronic address: martin.beck@luks.ch.
Abstract
BACKGROUND: Aseptic loosening and periprosthetic osteolysis are frequent complications in total hip arthroplasty requiring revision surgery. Highly cross-linked polyethylene (HXLPE) implants have improved wear resistance, permitting larger femoral heads. However, such implants may experience surface cracking, mechanical failure, and oxidative damage. Vitamin E-infused HXLPE (VEPE) implants were therefore developed to reduce oxidation without compromising mechanical strength. We addressed the following questions: (1) Does femoral head size affect the midterm annual polyethylene wear rates of VEPE acetabular cups? (2) Does femoral head size affect the midterm migration rates of VEPE acetabular cups? (3) Are clinical outcomes affected by femoral head size? HYPOTHESIS: Annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups are independent of femoral head size. PATIENTS AND METHODS: This was a prospective, multicentre, observational study of patients that underwent total hip arthroplasty. Hips were grouped according to the size of femoral head implanted (28 mm, 32 mm, and 36 mm). We determined annual wear rate and migration rate of VEPE acetabular cups using the Einzel-Bild-Röntgen-Analyse software. Clinically, we assessed the Harris Hip Score and visual analog score for pain and satisfaction. RESULTS: We followed 253 patients (267 hips) for a mean of 55.0±20.6 months in the 28 mm, 46.2±21.4 months in the 32 mm, and 43.8±22.6 months in the 36 mm group. The annual wear rate was 0.025 mm per year from 1 year to the last follow-up and remained similar between the groups (p>0.05). Also, mean two-dimensional migration rates did not exceed 0.05 mm from 2 years to the last follow-up and remained similar between the groups (p=0.355). Finally, clinical outcomes also did not differ between the groups (p>0.05). Two patients required revision surgery. DISCUSSION: Femoral head size did not influence midterm annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups. Furthermore, wear and cup migration rates were below the reported values leading to osteolysis and aseptic loosening. Nevertheless, studies with extended follow-up periods will be necessary to confirm these results in the long term. LEVEL OF EVIDENCE: IV.
BACKGROUND: Aseptic loosening and periprosthetic osteolysis are frequent complications in total hip arthroplasty requiring revision surgery. Highly cross-linked polyethylene (HXLPE) implants have improved wear resistance, permitting larger femoral heads. However, such implants may experience surface cracking, mechanical failure, and oxidative damage. Vitamin E-infused HXLPE (VEPE) implants were therefore developed to reduce oxidation without compromising mechanical strength. We addressed the following questions: (1) Does femoral head size affect the midterm annual polyethylene wear rates of VEPE acetabular cups? (2) Does femoral head size affect the midterm migration rates of VEPE acetabular cups? (3) Are clinical outcomes affected by femoral head size? HYPOTHESIS: Annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups are independent of femoral head size. PATIENTS AND METHODS: This was a prospective, multicentre, observational study of patients that underwent total hip arthroplasty. Hips were grouped according to the size of femoral head implanted (28 mm, 32 mm, and 36 mm). We determined annual wear rate and migration rate of VEPE acetabular cups using the Einzel-Bild-Röntgen-Analyse software. Clinically, we assessed the Harris Hip Score and visual analog score for pain and satisfaction. RESULTS: We followed 253 patients (267 hips) for a mean of 55.0±20.6 months in the 28 mm, 46.2±21.4 months in the 32 mm, and 43.8±22.6 months in the 36 mm group. The annual wear rate was 0.025 mm per year from 1 year to the last follow-up and remained similar between the groups (p>0.05). Also, mean two-dimensional migration rates did not exceed 0.05 mm from 2 years to the last follow-up and remained similar between the groups (p=0.355). Finally, clinical outcomes also did not differ between the groups (p>0.05). Two patients required revision surgery. DISCUSSION: Femoral head size did not influence midterm annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups. Furthermore, wear and cup migration rates were below the reported values leading to osteolysis and aseptic loosening. Nevertheless, studies with extended follow-up periods will be necessary to confirm these results in the long term. LEVEL OF EVIDENCE: IV.