• Sarah Ettinger, Michael Schwarze, Daiwei Yao, Max Ettinger, Leif Claassen, Christina Stukenborg-Colsman, Hajo Thermann, and Christian Plaass.
• Department of Foot and Ankle Surgery, Orthopaedic Clinic at DIAKOVERE Annastift, Hannover Medical School, Anna-von-Borries-Straße 1-7, 30625, Hannover, Germany.
• Arch Orthop Trauma Surg. 2018 Oct 1; 138 (10): 1359-1363.

BackgroundWith ankle arthritis often affecting young patients, joint-sparing treatments instead of total joint replacement should be considered. Only a few implants were specially developed for supramalleolar osteotomies (SMOT). This study was performed to analyse the stability of different implants and their appropriateness for SMOT.MethodsTwenty-five bone models (Sawbone Europe, Malmö, Sweden) were used for biomechanical testing. SMOT were performed as a uniplanar osteotomy, leaving 5 mm of lateral bone intact with a standardized gap of 8 mm. Five different plates commonly used for SMOT were assessed. For axial stability, the constructs were tested during 100 cycles for each load (150N and 800N) at a rate of 0.5 Hz. For rotational stability, each construct was subject to 100 cycles of 5 Nm torque at a rate of 0.25 Hz, performing three runs with an axial preload of 0N, 150N, or 800N. Ultimate axial load was performed for one-half and ultimate rotational load was performed for the other half of the constructs. In addition, the stiffness of the different constructs after failure was tested.ResultsAll constructs showed high stability and could be tested until maximum cyclic load. There was no significant difference between the five plates, neither for stiffness (axial or rotational) nor for failure load (axial or rotational). One plate indicated superiority in axial failure testing without any significant difference.ConclusionAll implants could be tested until maximum load. The intact hinge apparently provides enough support to compensate for lower moment of inertia of some plates.Level Of EvidenceNot applicable.

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