Although proximal tibia vara is physiologically and pathologically observed, it is difficult to measure the varus angle accurately and reproducibly due to inaccuracy of the radiograph because of rotational and/or torsional deformities. Since tibial coronal alignment in TKA gives influence on implant longevity, intra- or extra-medurally cutting guide should be set carefully especially in cases with severe tibia vara. In this context, we measured the proximal tibial varus angle by introducing 3D-coordinate system. Three-dimensional models of 32 tibiae (23 females, 9 males, 71.2 ± 7.8 y/o) were reconstructed from CT data of the patients undergoing CT-based navigation assisted TKA. Clinically relevant mid-sagittal plane is defined by proximal tibial antero-posterior axis and an apex of the tibial plafond. After the cross-sectional contours of the tibial canal were extracted, least-square lines were fitted to define the proximal diaphyseal and the metaphyseal anatomical axis. The proximal tibia vara was firstly investigated in terms of distribution of proximal anatomical axis exits at the joint surface. TVA1 and TVA2 were defined to be a project angle on the coronal plane between the metaphyseal tibial anatomical axis and the proximal diaphyseal anatomical axis, and that between the metaphyseal tibial anatomical axis and the tibial functional axis, respectively. The correlations of each angle with age and femoro-tibial angle (FTA) were also examined. The proximal anatomical axis exits distributed 4.3 ± 1.7 mm medially and 17.1 ± 3.4 mm anteriorly. TVA1 and TVA2 were 12.5 ± 4.5°(4.4?23.0°) and 11.8 ± 4.4° (4.4?22.0°), respectively. The correlations of FTA with TVA1 (r=0.374, p<0.05) and TVA2 (r=0.439, p<0.05) were statistically significant.Materials & Methods
Results
The goal of total hip arthroplasty (THA) should be to reconstruct the acetabulum by positioning the hip center as close as possible to the anatomical hip center. However, the true position of the anatomic hip center can be difficult to determine during surgery on an individual basis. In 2005, we designed, produced an acetabular reaming guide, and clinically used to enable cup placement in the ideal anatomical position. This study was examined the accuracy the reaming guide for THA in prospective study. This guide was applied consecutive 230 patients in primary THA. During planning, the distance from the acetabular edge to the reaming center and from the center to the perpendicular of the inter-teardrop line was measured on an anteroposterior (AP) X-ray. The reaming guide was adjusted depend on the reaming center by based planning. Acetabular reaming was performed with the process reamer.Introduction
Methods
The frequency of venous thrombo-embolism (VTE) after total hip arthroplasty(THA) is 20–30% and it is serious complication under THA. Therefore it is necessary to detect and prevent VTE. The purpose of this study were examined the frequency of VTE and the factor of incidence of VTE in our hospital. The 615 patients(82 men and 533 women) who performed primary THA from Jan. 2006 to Apr. 2011 were examined in this study. The Average age at the operation was 65 years (rage, 20–92 years). MDCT examination was performed the day after operation to detect VTE. 95 patients(15.4%) were positive of VTE and the rest of them were negative. We examined the age at operation, body mass index(BMI), blood loss, operative time, blood soluble fibrin monomer complex(SFMC) in the positive and negative group of VTE. The distance from the tibial joint line to the level of DVT was measured.Purpose
Patients and methods
Although optimal alignment is essential for improved function and implant longevity after TKA, we have less bony landmarks of tibia relative to femur. Trans-malleolar axis (TMA) is a reference line of distal tibia in the axial plane, which externally rotated relative to a ML axis of proximal tibia. We originally defined another reference axis associated with the orientation of tibial plafond, and then measured tibial torsion in the 3D-coordinate system. Three-dimensional CAD models of 20 tibiae were reconstructed based on pre-operative CT data from OA patients (16 females and 4 males, 73.8 ± 6.9 years old). TMA was a line connecting each apex of medial and lateral malleolus. The plafond axis (PLA) that we originally defined in this study was a line connecting each midpoint of medial and lateral margin of talocrural facet. In terms of interobserver correlation coefficiency and mean errors of the designated points to define those axes, TMA was found out to be 0.982, 3.14 ± 0.47 mm (medial), and 0.988, 4.88 ± 0.59 mm (lateral). Those of PLA were 0.997, 1.97 ± 0.53 mm (medial), and 0.995, 2.02 ± 0.44 mm (lateral). The tibial torsion was 16.3 ± 6.3°with reference to TMA, and 10.2 ± 8.4°to PLA. Based on these results, as for the rotational reference axis in the axial plain of distal tibia, we consider the plafond axis to be another reliable and reproducible axis, which is expected to be applicable in preoperative planning in TKA to reduce outliers of coronal alignment.
