Abstract
BackgroundHigh tibial osteotomy (HTO) with a medially opening wedge has been used to treat osteoarthritic knees. However, the osteotomized tibia becomes a highly unstable structure and necessitates the use of plate and screws to stabilize the medial opening and enhance bone healing. A T-shaped plate (e.g. TomoFix) with locking screws has been extensively used as a stabilizer of the HTO wedge. From the biomechanical viewpoint, however, the different plate sites and support bases of the HTO plate should affect the load-transferring path and wedge-stabilizing ability of the HTO construct. This study uses biomechanical tests and finite-element analyses to evaluate the placement- and base-induced effects of the HTO plates on construct performance.MethodsTest-grade synthetic tibiae are chosen as the standard specimens of the static tests. A medial wedge is created for each specimen and stabilized by three plate variations: hybrid use of T- and I-shaped plates (TIP), anteriorly placed TomoFix (APT), and medially placed TomoFix (MPT). There are five tests for each variation. The failure loads of the three constructs are measured and used as the load references of the fatigue finite-element analysis. The residual life after two hundred thousand cycles is predicted for all variations.ResultsThe testing results show no occurrence of implant back-out and breakage under all variations. However, the wedge fracture consistently occurs at the opening tip for the APT and MPT and the medially resected plateau for the TIP, respectively. The testing results reveal that both failure load and wedge stiffness of the TIP are the highest, followed by the MPT, while those of the APT are the least (P < 0.05). The fatigue analyses predict comparable values of residual life for the TIP and MPT and the highest value of damage accumulation for the APT. Both experimental and numerical tests show the biomechanical disadvantage of the APT than their counterparts. However, the TIP construct without locking screws shows the highest stress at the plate-screw interfaces.ConclusionsThis study demonstrates the significant effect of placement site and support base on the construct behaviors. The TIP provides a wider base for supporting the HTO wedge even without the use of locking screws, thus significantly enhancing construct stiffness and suppressing wedge fracture. Compared to the APT, the MPT shows performance more comparable to that of the TIP. If a single plate and a smaller incision are considered, the MPT is recommended as the better alternative for stabilizing the medial HTO wedge.
Highlights
High tibial osteotomy (HTO) with a medially opening wedge has been used to treat osteoarthritic knees
High tibial osteotomy (HTO) with a medial opening wedge is a surgical treatment for correcting knee osteoarthritis limited to the medial compartment [1,2,3]
This study aims to evaluate the placement-induced effects of the TomoFix plate on the construct performance
Summary
High tibial osteotomy (HTO) with a medially opening wedge has been used to treat osteoarthritic knees. Blecha et al proposed that the contact sites of the tibiofemoral joint occur at the more anterior region for up-right standing with a lower flexion angle [6] They suggested that the optimal site of the plate placement is at the anteromedial region to provide more stable support [6, 14]. Rodner et al revealed that the anteromedial placement of the HTO plate increases the tibial slope at that region and shifts the tibiofemoral contact to the posterior side. This increases the shearing force on the tibial plateau, which might lead to instability and injury of the soft tissues [15].
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