High tibial osteotomy (HTO) is a useful treatment option for osteoarthritis of the knee. Closing-wedge HTO (CW-HTO) had been mostly performed previously, but the difficulties of surgical procedure when total knee arthroplasty (TKA) conversion is needed are sometimes pointed out because of the severe deformity in proximal tibia. Recently, opening-wedge HTO (OW-HTO) is becoming more popular, but the difference of the two surgical techniques about the influence on proximal tibia deformity and difficulties in TKA conversion are not fully understood. The purpose of this study was to compare the influence of two surgical techniques with CW-HTO and OW-HTO on the tibial bone deformity using computer simulation and to assess the difficulties when TKA conversion should be required in the future. In forty knees with medial osteoarthritis, the 3D bone models were created from the series of 1 mm slices two-dimensional contours using the 3D reconstruction algorithm. The 3-D imaging software (Mimics, materialize NV, Leuven, Belgium) was applied and simulated surgical procedure of each CW-HTO and OW-HTO were performed on the same knee models. In CWHTO, insertion level was set 2cm below the medial joint line [Fig.1]. While in OW-HTO, that was set 3.5cm below the medial joint line and passed obliquely towards the tip of the fibular head [Fig.2]. The correction angle was determined so that the postoperative tibiofemoral angle would be 170 degrees. The distance between the center of resection surface and anatomical axis, and the angle of anatomical axis and mechanical axis were measured in each procedure. Secondly, a simulated TKA conversion was operated on the each tibial bone models after HTO [Fig.3]. The distance between the nearest points of tibial implant and lateral cortical bone was assessed as the index of the bone-implant interference.«Purpose»
«Methods»
Radiographs and computed tomography (CT) images are used for the preoperative planning in total knee arthroplasty (TKA), however, these two-dimensional (2D) measurements are affected easily by limb position and scanning direction relative to three-dimensional (3D) bone model analyses. The purpose of our study was to compare these measurements to evaluate the factors affecting the difference. A total of 75 osteoarthritis knees before primary TKA were assessed. The full-length weight-bearing anteroposterior radiograph and CT slices were used for the 2D measurement. Three-dimensional measurement used 3D bone model reconstructed from the CT data and the coordinate system as the previous reports (Figure 1). We measured FVA (femoral valgus angle), CRA (the angle between the posterior condylar line <PC-L> and the clinical epicondylar axis <CEA>), and SRA (the angle between the PC-L and the surgical epicondylar axis <SEA>). Intra- and inter-observer reliabilities were assessed by intraclass correlation coefficients (ICC), and the differences between the 2D and the 3D measurements (Differences) were evaluated. In addition, we evaluated whether preoperative factors (preoperative extension angle, HKA, BMI and CT scanning direction) affected the differences between the 3D and the 2D measurements. Computer simulation was used to examine the influences of CT scanning direction.Introduction
Patients and Methods
Because there have been no standard methods to determine pre-operatively
the thickness of resection of the proximal tibia in unicompartmental
knee arthroplasty (UKA), information about the relationship between
the change of limb alignment and the joint line elevation would
be useful for pre-operative planning. The purpose of this study
was to clarify the correlation between the change of limb alignment
and the change of joint line height at the medial compartment after
UKA. A consecutive series of 42 medial UKAs was reviewed retrospectively.
These patients were assessed radiographically both pre- and post-operatively
with standing anteroposterior radiographs. The thickness of bone
resection at the proximal tibia and the distal femur was measured
radiographically. The relationship between the change of femorotibial
angle (δFTA) and the change of joint line height, was analysed.Objectives
Methods
