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.

Ruptured Lumbar Disc in Patients Undergoing Manipulation of the Lumbar Spine / 대한정형외과학회잡지

Cauda equina syndrome(CES) and disc rupture have been implicated as a potential complication of spinal manipulation. A review of the literature from 1911 to 1996 received 61 reported cases of cauda equina syndrome or disc rupture in patients undergoing manipulation. This article presents four new cases, where a temporal association was found between the onset of cauda equina symptoms or disc rupture and lumbar manipulation. The type of manipulation administered and the relationship between the treatment and symptoms is reviewed. Our patients symptoms suggest that acute herniation was caused, or at least precipitated by spinal manipulation. In each of these cases the chiropractitioner failed to comprehend the nature of the problem and take appropriate action. As a consequence, the patient went untreated for several days. Many chiropractic therapists assumed the incidence of CES caused by manipulation to be approximately one in many millions of treatments. However, we assumed that CES or disc rupture is far more common than the literature would reflect. It is therefore essential that persons practicing or prescribing manipulation would be aware of these complications.