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Scheele, C.; Pietschmann, M. F.; Schröder, C.; Grupp, T.; Holderied, M.; Jansson, V.; Müller, P. E. (2018): Effect of minimally-invasive implantation of unicompartmental knee arthroplasty on cement penetration and biomechanical stability. An experimental study in human tibiae. In: Clinical Biomechanics, Vol. 51: pp. 34-39
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Background: Unicompartmental knee arthoplasty is a well-established treatment modality for anteromedial osteoarthritis and can be implanted minimally-invasive. However, the operation is technically demanding, which might lead to an increased failure rate. This study was conducted to determine the influence of a minimally-invasive approach on biomechanical fixation strength and morphological cement penetration. Methods: Tibial unicompartmental knee arthroplasties were implanted in 8 cadaver knees. On the medial side, implantation was performed minimally-invasive (group A). The lateral side was operated in an open way (group B). Biomechanical stability was testes using dynamic compression-shear load to failure. Cement penetration was analyzed on serial cuts through the implant-cement-bone interface in the frontal plane. Findings: Mean load to failure was 2438 N (SD 968 N) in group A and 2231 N (SD 1044 N) in group B (P = 1.0). The area proportion of the cement-bone interface without cement penetration was 24.2% (SD 18.8%) in group A and 7.7% (SD 5.9%) in group B (P < 0.05). In group A, cement mantle increased in thickness from 0.21 mm (SD 0.18 mm) in the anterior section of the tibial head to 1.35 mm (SD 0.33 mm) in its posterior section (P < 0.0001). Interpretation The study demonstrates no inferiority of minimally-invasive surgery with respect to fixation strength. However, the higher area proportion of the cement-bone interface without penetration and the increasing thickness of cement mantle from anterior to posterior indicate further room for improvement of the minimally-invasive approach in unicompartmental knee arthroplasty.