Assessment of Bone Quality using Finite Element Analysis Based upon Micro-CT Images

BACKGROUND: To evaluate the feasibility of a micro-image based finite element model to determine the efficacy of sequential treatments on the bone quality in a rat osteoporosis model. METHODS: Rat osteoporosis and treated osteoporosis models were established with the bone loss, restore and maintain concept. Thirty Sprague-Dawley rats were used in this study. A sham operation or ovariectomy was performed at 20 weeks after birth, which was followed by the respective sequential trials as follows: (1) sham-operation only, (2) ovariectomy only, (3) ovariectomized rats with parathyroid hormone maintenance, (4) ovariectomized rats treated with PTH for 5 weeks and then withdrawal, (5) ovariectomized rats treated with PTH for 5 weeks and then with 17 beta-estradiol, and (6) ovariectomized rats treated with parathyroid hormone for 5 weeks and then treated with zoledronate. The histomorphometry indices were determined using the micro-images from a micro-computed tomogram. Finite element analysis was carried out to determine the mechanical properties (Stiffness and Young's modulus) of the vertebra bodies. The differences in properties between the groups were compared using ANOVA and a Bonferroni's multiple group comparison procedure. RESULTS: The histomorphometry and mechanical properties were significantly better in groups (3) and (6) than in the groups (1) and (2) (p < 0.05). The stiffness (sigmas) and Young's modulus (E) was highest in group (3) following by group (6). CONCLUSIONS: Finite element analysis based on micro-images provides a useful tool that reflects the changes in micro-structural and mechanical properties of a rat vertebral body with the bone loss, restore and maintain concept.

Comparison of the Radiologic Results of Total Knee Arthroplasty using Electromagnetic Navigation with the Conventional Technique / 대한정형외과학회잡지

PURPOSE: We wanted to examine the accuracy of the lower limb alignment and implant positioning that was obtained with using the electromagnetic (EM) navigation technique. MATERIALS AND METHODS: We examined 64 patients who underwent 100 TKAs with using EM navigation technique from July 2006 to February 2007. Sixty-two patients who underwent 100 TKAs with using the conventional technique between August 2005 and July 2006 were used as controls. We assessed the mechanical axis and the alpha, beta, gamma and delta angles in the postoperative radiograph of each patient and we compared them among the two groups. RESULTS: The patients in the EM navigation group achieved better accuracy than did the conventional group in terms of the postoperative mean mechanical axis (1.2degrees vs. 2.3degrees). Less variations in the coronal femoral component and the tibial component angle were observed in the navigation group (femur: 89.3degrees vs. 88.7degrees; tibia: 89.6degrees vs. 89.3degrees, respectively), although the difference in the coronal tibial component angle was not significant. CONCLUSION: The use of EM navigation technique in TKA does not always guarantee the precise alignment of the mechanical axis in all planes, as compared to using the conventional technique. Yet it is useful for obtaining better coronal alignment of the femoral component.

The Morphologic Study of the Calcar Femorale and the Femoral Stem in Korean Population

PURPOSE: The aim of this study was to examine morphological data of the calcar femorale using high resolution CT and to determine its relationship with the morphology of femoral stems commonly used in Korea. MATERIALS AND METHODS: CT scans of the bilateral proximal femurs were randomly obtained from 54 Korean subjects(31 males and 23 females). The mean age was 49 years. The length, vertical height and thickness of the calacr femorale were measured. The medial dimension of the proximal portion of the femoral stems was investigated and matched with the distance between the anterior cortex of the proximal femur and the midpoint of the calcar femorale. RESULTS: The calcar femorale was visible in 53 CT scans(98%). The length, vertical height and thickness of the calacr femorale was 11.4+/-3.0 mm, 35.1+/- 5.96 mm and 2.4+/-0.7 mm, respectively, and there were no significant changes with age. The dimensions of the femoral stems were compatible with the morphology around the calcar femorale. CONCLUSION: The calcar femorale is a constant cortical structure that can provide consistent rotational stability for the proposed cementless stems. It is strongly recommended that the calcar femorale be preserved during the femoral preparation.