• Florian Völlner, Johannes Fischer, Markus Weber, Felix Greimel, Achim Benditz, Tobias Renkawitz, Joachim Grifka, and Benjamin Craiovan.
• Department of Orthopaedic Surgery, Regensburg University Medical Centre, Asklepios Klinikum Bad Abbach, Kaiser-Karl-V-Allee 3, 93077, Bad Abbach, Germany. florian.voellner@klinik.uni-regensburg.de.
• Arch Orthop Trauma Surg. 2019 Jul 1; 139 (7): 999-1006.

PurposeThe purpose of this study was to investigate the effects of sequential medial release on the stiffness and collateral stability of the ligament complex of the knee. Irrespective of the implantation technique used, varus deformity frequently requires release of the capsular ligament complex. Yet, no data are available on how stiffness and stability of the knee ligament complex are weakened by such release.MethodsAfter total knee arthroplasty, ten healthy Thiel-fixed knee joints were subjected to sequential medial release consisting of six release steps. After each step, stiffness and stability were determined at 0°, 30°, 60°, and 90°.ResultsSequential medial release increasingly weakened the ligament complex. In extension, release of the anteromedial tibial sleeve 4 cm below the joint line already weakened the ligament complex by approximately 13%. Release 6 cm below the joint line reduced stiffness and stability by 15-20% over the entire range of motion. After detachment of the medial collateral ligament, stability was only about 60% of its initial value.ConclusionOur study showed for the first time the association between medial release and stiffness and stability of the knee ligament complex. To maintain stability, vigorous detachment of the knee ligament complex should be avoided. Release of the anteromedial tibial sleeve already initiates loss of stability. The main stabiliser is the medial ligament, which should never be completely detached.Level Of EvidenceIV.

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