Myun Whan Ahn

Diffusion-weighted magnetic resonance imaging of sacral insufficiency fractures: comparison with metastases of the sacrum.

Study Design. Retrospective analysis of magnetic resonance imaging (MRI) for differentiating sacral insufficiency fractures from metastases of the sacrum. Objective. To determine if a steady-state free precession (SSFP) diffusion-weighted MRI is useful for differentiating sacral insufficiency fractures from metastases of the sacrum. Summary of Background Data. Conventional spin-echo sequence MRI is very sensitive for the detection of pathologic lesions in the sacrum, but the differential findings between sacral insufficiency fracture and metastasis are often not obvious because of the nonspecific changes of signal intensity. Another MR sequences for differentiation is needed. Methods. Fourteen patients with sacral insufficiency fractures and 8 patients with metastasis at the sacrum were examined with MRI. Both the diffusion-weighted MRI and the spin-echo MRI were performed in all patients. Diffusion-weighted MRI sequences were based on a SSFP sequence. Results. All the insufficiency fractures and metastasis at the sacrum revealed low signal intensity on T1-weighted MRI; low or high signal intensity was revealed on T2-weighted MRI. The contrast enhanced T1-weighted MRI showed strong enhancement at the sacrum in all cases of insufficiency fracture and metastasis. Diffusion-weighted MRI of the sacrum showed low signal intensity in all cases with sacral insufficiency fracture, but these images revealed high signal intensity in all cases with metastasis. Conclusion. SSFP diffusion-weighted MRI is capable of differentiating benign sacral insufficiency fractures from metastatic tumors of the sacrum.

Immobilization of Collagen on Hydroxyapatite and Its Interation with Cells

The adhesion of bone cells on substrate materials is generally measured by the removal torque and/or contact area between bone and implants. In this study, collagen was used as a surfacegrafting material on hydroxyapatite (HA) substrates to enhance the cell adhesion because the collagen is a major constituent of connective tissues and has been regarded as one of the most excellent coating materials for bone bonding. First, HA disks (10mmΦ x 1mm) were prepared and then collagen was immobilbized on the HA surface using an 3-APTES coupling agent to improve the adhesiveness of cells on HA disk surfaces. NIH 3T3 fibroblasts were seeded on the collagengrafted and non-grated HA disks and cultured in a Dulbecco’s modified eagle medium containing 10% fetal bovine serum for 3 hrs to evaluate the cell adhesion on the HA samples. The fibroblasts on the collagen-grafted sample were more spread than those on the non-grafted sample. It is believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high biocompatibility of collagen.

Evaluation of Hydroxyl Groups on Hydroxyapatite and Calcium Metaphosphate by Grafting TEOS and APTES

OH groups on hydroxyapatite (HA) and calcium metaphosphate (CMP) were evaluated by grafting tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethyloxysilane (3-APTES) which can bond covalently with OH group of ceramic biomaterials. The prepared HA and CMP disks were soaked in pH 2 and 5 of acidic water and ethanol solution respectively, where pH change of each solution was measured during soaking of samples. After grafting TEOS and 3-APTES on HA and CMP disks, samples were ultrasonically cleaned in distilled water and soaked in pH 5 of ethanol solution, and pH measurement was carried out in the same manner. The pH value of HA and CMP in aqueous solution at pH 2 increased with time continuously, resulting from dissolution of HA and CMP by acidic condition on surface. At pH 5 in aqueous solution, it was the same though the pH increase was smaller. In case of ethanol at pH 5 with HA, though pH value went up slightly, the curve became saturated with time, while there was no change in pH with CMP. After grafting TEOS and 3-APTES, pH values were stabilized with few changes, indicating that there was no direct chemical reaction between the acidic media and the surface of samples due to covalently grafted TEOS and 3-APTES layer. In conclusion, it was confirmed that OH group on the surface of HA was crystallographic and chemical one rather than physically adsorbed one by grafting TEOS or 3-APTES and it will serve an effective binding site for calcium and phosphate ions, or minerals.

A Collagen Grafting on Hydroxyapatite to Enhancement of Bone Cell Attachment

A collagen material was chemically grafted on hydroxyapatite (HA) to enhance bone cell attachment because the collagen is a major constituent of connective tissues and has been regarded as one of the most excellent coating materials for bone bonding. First, HA disks were prepared with 12mm diameter and 1mm thickness. And then collagen (type I) was immobilbized on the HA surface using a 3-APTES coupling agent on HA disk surfaces. MC3T3-E1 osteoblasts were seeded on the collagen-grafted and non-grated HA disks and cultured for 4 hrs to evaluate the cell adhesion on the HA discs. The Attached cell morphology on discs was observed with a fluorescent optical microscopy (FOM) and a scanning electron microscopy (SEM). The osteoblasts on the collagen-grafted sample were more spread than those on the non-grafted sample. It is believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high biocompatibility of collagen.

Preliminary Radiological In Vivo Study of Calcium Metaphosphate Coated Ti-Alloy Implants

In order to evaluate the bone-implant integration behavior of biodegradable c lcium metaphosphate (CMP, [Ca(PO 3)2]n) coated metallic implant, as-machined, blasted, and blasted /CMP-coated Ti6Al4V screw-type implants were prepared and asepti cally implanted into male New Zealand white rabbits. CMP sol was prepared by sol-gel process and coate on each substrate by dip and spin coating. The CMP coated layer was smooth and uniform with fine grai s, compared to that of as-machined and as-blasted specimens. Each specimen was inserted i nto the defects of bilateral intratibial metaphysis bone and then followed up for 1 and 6 weeks. From the radiographs at 1 and 6 weeks after implantation, all the implants were shown to be apparent ly well integrated with surrounding bone tissue without interfacial fracture, bony resorption, or ra di lucent lines. With the combination of histological results, CMP-coated group was noticed that bony bridges were extending from the endosteum onto the implants at 6 weeks after implantation, wi th the showing good osseo-intergration compared to other two groups. Introduction The development of a stable direct bonding between bone and implant surface (osteointegration) is the critical issue for the long-term success of orthopedic and denta l impl nts. The establishment and maintenance of osteointegration depends on wound healing, repairing and remodel ing f hard tissues. The tissue response to an implant involves physical factors such as i mplant design and surface topography, and chemical factors such as composition and structure of the material surface [1]. To improve the implant fixation to a host bone, several strategies have been developed focusing on the surface modification of materials. For example, the physical surf ace modification of implants in roughness by various techniques has been attracted, because it has been de monstrated that the osteoblastic cells tend to attach more easily to rough surface [ 4], consequently increasing the bone apposition [5]. Chemical surface modifications have been also realized by cova lent attachment of an organic monolayer anchored by a siloxane network [2], and immobilization of specific adhesive peptides like arginine-glycine-aspartic acid-serine (RGDS) [3]. In addition, the implants coated with different bioactive materials such as calcium phosphates, bioactive glasses [6], diamond-like carbon, and amorphous C-N film [7] enha nced the bonding to bone. However, it has been currently reported that the coating layer w s sometimes delaminated from the substrates. Therefore, as one of the alternatives to solve this proble m, the biodegradable material coating on implants, which may allow the organism to replace the for eign material by new bone tissue in a balanced time schedule, was conductd [8]. Calcium metaphosphate (CM P, [ a(PO3)2]n) is a Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 881-886 doi:10.4028/www.scientific.net/KEM.254-256.881

Effect of water glass coating of tricalcium phosphate on in vitro cellular proliferation and osteogenic differentiation

Background In this study, the properties of the water glass (WG, sodium-silicate glass) were utilized to control the biodegradability of the beta tricalcium phosphate materials by the WG coating on the tricalcium phosphate disc surface with various coating thickness, chemistry, and heat-treatment. Methods Four types of disc specimens were prepared. A sample group A consisted of pure hydroxyapatite (HA) as a negative resorption control; a sample group B consisted of pure beta tricalcium phosphate as a positive resorption control; a sample group C consisted of beta tricalcium phosphate coated with WG as an early resorption model; and a sample group D consisted beta tricalcium phosphate coated with WG and heat-treated at 500°C as a delayed resorption model. Using human bone marrow–derived mesenchymal stem cells, for the analysis of cellular attachment and proliferative activity, 4–6-Diamidino-2-Phenylindole fluorescence technique was used. For the analysis of osteteogenic differentiation, alkaline phospastase (ALP) activity was measured. Results The mean z-scores of four groups (A, B, C, and D) in cellular attachment at 4 h after seeding were −1.21, −0.15, 0.42, and 0.94, respectively, and statistically significantly different in all groups respectively. Seven days after seeding, the mean z-scores of cellular proliferation were 1.97, 0.71, 1.48, and 1.83 in the four groups, respectively. The mean z-scores of the ALP activity per the mean z-scores of cell numbers of respective groups on the seventh day were 0.40, −1.51, 0.12, and 0.06, respectively, in four groups. Conclusion Initial cellular attachment is better on beta tricalcium phosphate than on HA and is enhanced by WG coating, especially with sintering at the high temperature. Cellular proliferation is considered to be increased by maintaining its attachment site through reduced dissolution of beta tricalcium phosphate by WG coating. Osteogenic differentiation in in-vitro study on the WG-coated beta tricalcium phosphate is thought to be as the result of increased silicon ion release from the WG.

Usefulness of K-Point Injection for the Nonspecific Neck Pain in So-Called K-Point Syndrome

Background Shoichi Kokubun introduced his successful experience with local anesthetic injection at the occipital insertion of the sternocleidomastoid muscle in K-point syndrome. The purpose of this study was to evaluate the short-term and long-term effectiveness of K-point injection and investigate factors affecting treatment results. Methods K-point injection was performed in 58 patients with K-point syndrome at Yeungnam University Medical Center. The syndrome was associated with cervical whiplash injury in 10 patients and was of nonspecific origin in the rest. One milliliter of 2% lidocaine mixed with 1 milliliter of dexamethasone was injected in 50 patients and 2 milliliters of 1% lidocaine alone in the rest. Initially, the severity of local tenderness at the K-point and other tender points was examined and the degree of immediate pain relief effect was assessed within 1 hour after injection. Early effect within 1 month after the injection and current effect were evaluated in 27 patients using a modified Kims questionnaire with regard to the duration of improvement, degree of improvement in pain and daily living activities, and satisfaction. Results Of the total 58 patients, 44 (75.8%) apparently had immediate pain relief after K-point injection. The only factor associated with successful immediate pain relief was the whiplash injury associated with traffic accident (TA). The early pain control effect was associated with the immediate effect. The current effect was associated with the early effect alone. Satisfaction with the K-point injection was related to early successful pain relief. Conclusions K-point injection would be useful for early pain relief in nonspecific neck pain syndrome so called K-point syndrome, but not for current pain relief. Especially, it was very effective for early pain control in the whiplash injury associated with TA.

Effect of Insertion Status of a Pedicular Screw on its Mechanical Properties using the Finite Element Method

Purpose : The structural performance of a fixation system was investigated in the case of screw insertion into the pedicular canal with or without its threads fastened in the cortex and in the broken pedicle. Materials and Methods : The symmetric geometric model was used for the pull-out test, and the simplified 3-dimensional model at 3 level, namely, the 3rd, 4th and 5th lumbar vertebrae, was used for the axial compressive loading test. Results : According to the result of the axial-loading test, bending moments and Von-Mises stresses were increased at the junction between the head and the 2nd and 3rd pitches of the lumbar pedicle screw and at the center of 4th lumbar vertebral body, in the models of intact, posterior elements removed and unstable fractured spines. As the results of flexibility, there is no difference in intra-cortical insertion compared to intra-medullary pedicle insertion in the intact spine model. However, flexibility of the laminectomy model was 8% better that of the intra-cortical insertion, and the unstable fracture model 2% better. Conclusion : There is no difference in the flexibility of intra-cortical and intra-medullary pedicle screw insertion. The stability of the posterior structure is more important than anterior pedicle screw fixation.

Treatment of the tibia shaft fractures with ender nails

Fractures of the tibial shaft are the most common among the long bone fractures, and have much difficulty in treatment due to their enumerous complications. Thirty patients with fractures of the tibial shaft were treated with Ender nails under the image intensifier at the Department of Orthopedic Surgery, Yeungnam University Hospital from December 1986 to November 1991. The following results were observed. 1. The average age was 37.3 years and the number of male was three times of the female. The most common cause was traffic accident. 2. Twenty cases out of thirty one were closed fractrure and the remaining 11 were open. The comminuted and segmental fractures were 18(57.7%) in number and the most common fracture site was the middle one third(53%). 3. Average interval from injury to operation was 7.6 days and 19 cases showed associated injuries. 4. The mean duration of the bone union was 18.9 weeks and 2 cases showed the delayed union. 5. Twelve complications were noted such as shortening, varus deformity, delayed union, ankle motion limitation, nail irritation, and soft tissue infection.