Comparative biomechanical in vitro study of different modular total knee arthroplasty revision stems with bone defects

The aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability. Methods: Thirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct. Results: Relative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces. Conclusion: All tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.

Subjects

bone defect

femoral component micromotion

femoral cone

primary stability

revision knee arthroplasty

stem length

DDC Class

570: Biowissenschaften, Biologie

600: Technik

610: Medizin

More Funding Information

The authors would like to thank Behörde für Wissenschaft, Forschung und Gleichstellung (BWFG), Hamburger Straße 37, 22083 Hamburg, Germany - for financial support; Northopedics Network, Life Science Nord Management GmbH, Falkenried 88, 20251 Hamburg, Germany - for financial support; Link GmbH, Barkhausenweg 10, 22339 Hamburg, Germany - for the provision of implants; Heraeus Medical GmbH, Philipp-Reis-Straße 8-13, 61273 Wehrheim, Germany - for the provision of cement; and GOM GmbH, Schmitzstraße 2, 38122 Braunschweig, Germany - for technical support.

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Comparative biomechanical in vitro study of different modular total knee arthroplasty revision stems with bone defects