Abstract
BackgroundHigh tibial osteotomy (HTO) with a medial opening wedge has been used to treat medial compartment osteoarthritis. However, this makes the proximal tibia a highly unstable structure and causes plate and screws to be the potentials sources for mechanical failure. Consequently, proper design and use of the fixation device are essential to the HTO especially for overweight or full weight-bearing patients.MethodsBased on the CT-based images, a tibial finite-element model with medial opening was simulated and instrumented with one-leg and two-leg plate systems. The construct was subjected to physiological and surgical loads. Construct stresses and wedge micromotions were chosen as the comparison indices.ResultsThe use of locking screws can stabilize the construct and decrease the implant and bone stresses. Comparatively, the two-leg design provides a wider load-sharing base to form a force-couple mechanism that effectively reduces construct stresses and wedge micromotions. However, the incision size, muscular stripping, and structural rigidity are the major concerns of using the two-leg systems. The one-leg plates behave as the fulcrum of the leverage system and make the wedge tip the zone of tension and thus have been reported to negatively affect the callus formation.ConclusionsThe choice of the HTO plates involved the trade-off between surgical convenience, construct stability, and stress-shielding effect. If the stability of the medial opening is the major concern, the two-leg system is suggested for the patients with heavy load demands and greater proximal tibial size. The one-leg system with locking screws can be used for the majority of the patients without heavy bodyweight and poor bone quality.
Highlights
High tibial osteotomy (HTO) with a medial opening wedge has been used to treat medial compartment osteoarthritis
Concentrated stresses of screw, plate, and bone The stress distributions of the four plate systems and the maximal stresses of the screw, plate, and bone are shown in Figures 4 and 5, respectively
Compared with the TomoFix construct, the screw stresses of the T+I and π constructs respectively increased 13.5% and decreased 9.5%
Summary
High tibial osteotomy (HTO) with a medial opening wedge has been used to treat medial compartment osteoarthritis. This makes the proximal tibia a highly unstable structure and causes plate and screws to be the potentials sources for mechanical failure. The current authors purposed the concept that the increase of the load-sharing base (e.g. two-leg design) below the opening wedge can effectively stabilize the HTO construct. This can be done by the hybrid use of the conventional T and DCP (I-shaped) plate (Figure 1b). The outcome of this study provides design information about the ideal plate for HTO surgery
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