Comparison of theoretical fixation stability of three devices employed in medial opening wedge high tibial osteotomy: a finite element analysis

Abstract

BackgroundMedial open wedge high tibial osteotomy is a well-established procedure for the treatment of unicompartmental osteoarthritis and symptomatic varus malalignment. We hypothesized that different fixation devices generate different fixation stability profiles for the various wedge sizes in a finite element (FE) analysis.MethodsFour types of fixation were compared: 1) first and 2) second generation Puddu plates, and 3) TomoFix plate with and 4) without bone graft. Cortical and cancellous bone was modelled and five different opening wedge sizes were studied for each model. Outcome measures included: 1) stresses in bone, 2) relative displacement of the proximal and distal tibial fragments, 3) stresses in the plates, 4) stresses on the upper and lower screw surfaces in the screw channels.ResultsThe highest load for all fixation types occurred in the plate axis. For the vast majority of the wedge sizes and fixation types the shear stress (von Mises stress) was dominating in the bone independent of fixation type. The relative displacements of the tibial fragments were low (in μm range). With an increasing wedge size this displacement tended to increase for both Puddu plates and the TomoFix plate with bone graft. For the TomoFix plate without bone graft a rather opposite trend was observed.For all fixation types the occurring stresses at the screw-bone contact areas pulled at the screws and exceeded the allowable threshold of 1.2 MPa for at least one screw surface. Of the six screw surfaces that were studied, the TomoFix plate with bone graft showed a stress excess of one out of twelve and without bone graft, five out of twelve. With the Puddu plates, an excess stress occurred in the majority of screw surfaces.ConclusionsThe different fixation devices generate different fixation stability profiles for different opening wedge sizes. Based on the computational simulations, none of the studied osteosynthesis fixation types warranted an intransigent full weight bearing per se. The highest fixation stability was observed for the TomoFix plates and the lowest for the first generation Puddu plate. These findings were revealed in theoretical models and need to be validated in controlled clinical settings.

The effect of plate design, bridging span, and fracture healing on the performance of high tibial osteotomy plates

“…26 Some previous computational studies have investigated implant stress, 27-29 IFM within the osteotomy, 28,29 and the influence of plate design. 30 A major limitation of previous computational studies using locking plates, however, is the use of bonded plate-screw interfaces. This assumption dramatically increases the construct stiffness while also lowering predictions of plate stress.…”

Comparison of Puddu osteotomy with or without autologous bone grafting: a prospective clinical trial

“… 2 , 3 , 7 In this study, we used first-generation wedge-plate fixation. 8 , 9 As previously stated, two groups were randomly created. To keep masking, and to avoid the clinical aggravation bias due to iliac crest pain, the graft was harvested in both groups.…”

High Tibial Osteotomy

“…TomoFix plates (Synthes, West Chester, PA) and Puddu plates (Arthrex, Naples, FL) were detected to provide adequate biomechanical stability, whereas in case of lateral cortex fracture, TomoFix plates were detected to provide adequate stability without the need of any additional lateral fixation [8,42]. The biomechanics of three spacer plates with different length was studied, while two were with locking bolts, and one was the TomoFix plate, which was shown to be superior at single load-to-failure and cyclical load-to-failure tests and also possessed the maximum residual stability after failure of the lateral cortex, in addition to least motion at the osteotomy gap [43][44][45].…”