Varus or valgus positioning of the tibial component of a unicompartmental fixed-bearing knee arthroplasty does not increase wear

Woiczinski, Matthias; Schröder, Christian; Paulus, Alexander; Kistler, Manuel; Jansson, Volkmar; Müller, Peter E. und Weber, Patrick (2019): Varus or valgus positioning of the tibial component of a unicompartmental fixed-bearing knee arthroplasty does not increase wear. In: Knee Surgery Sports Traumatology Arthroscopy

Abstract

PurposeHigher revision rates were shown in varus- or valgus-positioned tibias in unicompartmental knee arthroplasty (UKA), but more than 15% of UKA prostheses are implanted with more than 5 degrees of varus or valgus. This study aimed to analyze the wear rate in UKA when implanting the tibial component in either varus or valgus position versus a neutral placement at 90 degrees to the tibial anatomical axis. The study hypothesized that a 5 degrees varus or valgus positioning of the tibial plateau will generate less wear compared to a neutral alignment.MethodsWear was experimentally analyzed on a medial anatomical fixed-bearing unicompartmental knee prosthesis (Univation, Aesculap, Germany) in vitro with a customized, four-station, servohydraulic knee wear simulator, reproducing the walking cycle. The forces, loading and range of motion were applied as specified in the ISO 14243-1:2002, 5 million cycles were analyzed. The tibial components of the medial prostheses were inserted in a neutral position, with 5 degrees varus, and 5 degrees valgus (n=3, each group).ResultsThe wear rate decreased significantly with a 5 degrees varus positioning (6.301.38 mg/million cycles) and a 5 degrees valgus positioning (4.962.47 mg/million cycles) compared to the neutral position (12.16 +/- 1.26 mg/million cycles) (p<0.01 for the varus and the valgus position). The wear area on the inlay was slightly reduced in the varus and valgus group.Conclusion p id=Par4 A varus or valgus "malpositioning" up to 5 degrees will not lead to an increased wear. Wear was even less because of the reduced articulating contact area between the inlay and the femur. A slight varus positioning of the tibial component (parallel to the anatomical joint line) positioning can be advocated from a point of wear.Level of evidence p id=Par5 Experimental study.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Medizin
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• ISSN: 0942-2056
• Sprache: Englisch