Comparing Different Systems for High Tibial Osteotomies
Comparing Different Systems for High Tibial Osteotomies
High tibial osteotomy is a surgical treatment for the correction of medial compartment osteoarthritis. In the literature, there are two HTO types, namely laterally closing and medially opening osteotomies. The medially opening HTO has become more popular with its better outcome and numerous complications can be avoided. From the biomechanical viewpoint, the wedge makes the proximal tibia highly unstable, and structural stiffness of the HTO fixation has been reported to be closely related to the postoperative outcome.
Historically, some internal and external fixation devices were used to maintain the instrumented graft in place and stabilize the osteotomized construct. Among the various devices, the Puddu and TomoFix plate systems were the most common type specifically designed for the HTO procedure. However, recent reports have shown that some shorter systems (e.g. Puddu system) result in graft nonunion and implant failure. The clinical study by Nelissen et al. revealed that a shorter plate and nonlocking screws provide less ability to stabilize the osteotomized construct. For the TomoFix system with a longer plate, Kolb et al. revealed that the use of the locking screws would yield better short-term results. Although a high rate of satisfactory outcome was reported, the improper selection and use of the implant often induced nonunion and even fracture of the HTO construct, especially for overweight or full weight-bearing patients.
The TomoFix system is the one-leg design such that the knee loads are transferred into the tibial diaphysis through a single straight plate (Figure 1a). Of all human joints, the knee is one of the most loaded joints and the osteotomized tibia makes the knee structurally unstable. 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 T plate was used at the medioposterior side to stabilize the most heavily loaded region of the knee joint. The I plate was fixed at the anterior region to further support the wedged tibia. However, the screws of both the T and I plates were nonlocking screws. The authors hypothesize that the use of the locking screws and the integration (i.e. π-shape) of both T and I plates can increase the structural stability of the bone-plate-screw construct (Figure 1c). The biomechanical comparison between the TomoFix, T+I, and π systems is of bioengineering significance and was the motivation of this study. Using the finite element method, this study compared the stress and stability differences between the one- and two-leg HTO plate systems. The effects of plate legs and locking screws were examined in terms of construct stress and wedge micromotion. The outcome of this study provides design information about the ideal plate for HTO surgery.
(Enlarge Image)
Figure 1.
Four HTO plates used in this study. (a) TomoFix plate. (b) T+I plate. (c) π plate. (d) T plate. The section plane AA was denoted to calculate the loads through the anterior and posterior legs of the T+I and π plates.
Background
High tibial osteotomy is a surgical treatment for the correction of medial compartment osteoarthritis. In the literature, there are two HTO types, namely laterally closing and medially opening osteotomies. The medially opening HTO has become more popular with its better outcome and numerous complications can be avoided. From the biomechanical viewpoint, the wedge makes the proximal tibia highly unstable, and structural stiffness of the HTO fixation has been reported to be closely related to the postoperative outcome.
Historically, some internal and external fixation devices were used to maintain the instrumented graft in place and stabilize the osteotomized construct. Among the various devices, the Puddu and TomoFix plate systems were the most common type specifically designed for the HTO procedure. However, recent reports have shown that some shorter systems (e.g. Puddu system) result in graft nonunion and implant failure. The clinical study by Nelissen et al. revealed that a shorter plate and nonlocking screws provide less ability to stabilize the osteotomized construct. For the TomoFix system with a longer plate, Kolb et al. revealed that the use of the locking screws would yield better short-term results. Although a high rate of satisfactory outcome was reported, the improper selection and use of the implant often induced nonunion and even fracture of the HTO construct, especially for overweight or full weight-bearing patients.
The TomoFix system is the one-leg design such that the knee loads are transferred into the tibial diaphysis through a single straight plate (Figure 1a). Of all human joints, the knee is one of the most loaded joints and the osteotomized tibia makes the knee structurally unstable. 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 T plate was used at the medioposterior side to stabilize the most heavily loaded region of the knee joint. The I plate was fixed at the anterior region to further support the wedged tibia. However, the screws of both the T and I plates were nonlocking screws. The authors hypothesize that the use of the locking screws and the integration (i.e. π-shape) of both T and I plates can increase the structural stability of the bone-plate-screw construct (Figure 1c). The biomechanical comparison between the TomoFix, T+I, and π systems is of bioengineering significance and was the motivation of this study. Using the finite element method, this study compared the stress and stability differences between the one- and two-leg HTO plate systems. The effects of plate legs and locking screws were examined in terms of construct stress and wedge micromotion. The outcome of this study provides design information about the ideal plate for HTO surgery.
(Enlarge Image)
Figure 1.
Four HTO plates used in this study. (a) TomoFix plate. (b) T+I plate. (c) π plate. (d) T plate. The section plane AA was denoted to calculate the loads through the anterior and posterior legs of the T+I and π plates.
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