High Concentrations of Pamidronate in Bone Weaken the Mechanical Properties of Intact Femora in a Rat Model

PURPOSE: Bisphosphonates have been used to treat osteoporosis for more than ten years. However, complications associated with long-term administration of bisphosphonates, such as nonunion after pelvic insufficiency fracture or osteonecrosis of the jaw, have been recently reported in the literature. We investigated the relationships among the mechanical properties of the intact rat femur as well as healing fracture calluses and the intraosseous concentration of pamidronate (ICP), after long-term administration of pamidronate in a rat osteoporosis model. MATERIALS AND METHODS: We performed bilateral ovariectomy in 25 3-month-old female Sprague-Dawley rats. Beginning three months after ovariectomy, disodium pamidronate (0.5mg/kg) was injected every month. After the six-month administration period, the left femoral shaft was fractured using the closed fracture technique. Five weeks after fracture, 23 rats were euthanized and both femora were removed. We checked the mechanical properties of the intact (right) and fractured (left) femora using a three-point bending technique. Intraosseous concentration of pamidronate was checked by high-performance liquid chromatography. RESULTS: The mean ICP was 61.8+/-15.7ng/mg of bone. High ICP decreased the ultimate load to failure, stiffness, and ultimate stress of the intact femora (p=0.015, 0.027, 0.039, respectively). There was a tendency to decrease the ultimate load to failure in the healing callus when the ICP increased (p= 0.183). High ICP decreased the bone mineral density of the femoral head (p=0.005). CONCLUSION: High concentrations of pamidronate in intact bone decreased the bone mineral density and weakened the mechanical strength of the rat femora. The mechanical strength of the early healing callus was not correlated with concentration of pamidronate in the bone.

The Treatment of Unstable Reverse Oblique Intertrochanteric Fractures with Proximal Femoral Nail (PFN) / 대한정형외과학회잡지

PURPOSE: To investigate the results of treatment of unstable reverse oblique intertrochanteric fractures with proximal femoral nail (PFN). MATERIALS AND METHODS: We reviewed the results of 16 cases of AO 31-A3.3 intertrochanteric fracture treated with PFN from September 2000 to February 2004 which could be followed up for more than six months and untill bone union. The mean age was 60.2 years old. We investigated the union time and amount of sliding of two screws (neck screw and anti-rotational hip pin) and complications such as fixation failure and nonunion. Functional results were evaluated by the Parker and Palmer mobility score and Jensen social-function score. RESULTS: All fractures were united and the mean union time were 6.9 months. The amount of sliding of the neck screws and anti-rotational hip pin was 4.8 mm and 3.8 mm on average in 14 cases, respectively. Fixation failure and excessive migration of the screws occurred in two cases; One case showed so-called Z-effect of two screws (reciprocal movement of two screws) and nonunion. The other case showed proximal migration and cutout of the neck screw. There was one femoral shaft fracture at the nail tip caused by a slip. Eight cases (50%) and eleven cases (68.8%) were fully recovered according to Parker and Palmer mobility score and Jensen social-function score, respectively. CONCLUSION: We consider that PFN is a suitable implant for treatment of unstable reverse oblique intertrochanteric fractures. However, the revision of implant design is recommended to prevent the excessive migration of the femoral neck screw and anti-rotational hip pin.

Mechanical Properties of F Plate in Intraarticular Calcaneal Fractures

PURPOSE: We evaluated the mechanical properties of F plate fixation comparing with Y plate and a screw fixation for the intraarticular calcaneal fractures using synthetic bones. MATERIALS AND METHODS: Using 12 synthetic calcaneal bones, newly designed F plate was compared with the Y-plate, most commonly used, regarding the change of Bohler angle and the displacement of the thalamic fragments of the calcaneus after axial compressive loading by Instron 6022. RESULTS: Y plate fixation lost 8degrees of Bohler angle in average after axial compressive load and 2.6degrees in F plate fixation. Thalamic fragments were displaced 1.72 mm in average in Y plate fixation group and 0.73 mm in F plate fixation group. CONCLUSION: F plate offered more firm fixation than Y plate in the intraarticular calcaneal fracture in the aspect of maintaining the Bohler angle and preventing displacement of the thalamic fragments of calcaneus against axial compressive loading.

Correlation between Anterior and Posterior Obliquity of the Sliding Lag Screw and Stability in Unstable Intertrochanteric Fractures

PURPOSE: To investigate the characteristics of the sliding pattern of the proximal fragment (head and neck) in unstable intertrochanteric fractures, which were fixed with a dynamic hip screw (DHS) with anterior to posterior or posterior to anterior insertion angle in the axial view. MATERIALS AND METHODS: AO type A2.1 intertrochanteric fracture was reproduced in 10 proximal femur model (Synbone, Malans, Switzerland). Five fractured models were reduced and fixed using DHS with anterior to posterior insertion angle (group 1) and five models were fixed with posterior to anterior angle (group 2). Load of 500 N (30 cycles) was applied to the fracture fragment-plate complex using Instron 6022. Data on the distance of sliding and the angle of rotation of the proximal fragment were collected and analyzed. RESULTS: No significant difference was noted statistically in the distance of sliding between the two groups (p=0.92). However, the mean angle of rotation was 13.4degrees and 8.0degrees in group 1 and 2, respectively and the difference was statistically significant (p=0.012). Anterior cortical fracture of distal fragment was noted in 3 cases of group 1. There was no fracture of the anterior cortex in group 2. CONCLUSION: In unstable intertrochanteric fracture, the insertion angle of the lag screw in axial view does seem to play a role in the fate of bone-plate complex. Early eccentric contact of both fragments caused rotation of the proximal fragment in all cases and anterior cortical fracture of the distal fragment in 3 cases of group 1.

Femoral Neck Fracture After Removal of the Intramedullary Nail for the Fixation of an Intertrochanteric Fracture: Report of 2 Cases / 대한정형외과학회잡지

Intramedullary fixation using Gamma or Proximal Femoral Nail (PFN) for example becomes a popular fixation method for unstable trochanteric fracture. Due to the old age of patients with such fractures, extraction of these devices has not always been recommended after fracture healing. However, protruding metal or sliding lag screws can cause pain, which makes removal unavoidable. The authors present 2 cases of femoral neck fracture during ambulation after the removal of such devices.

Osteogenesis by Transfer of Bone Morphogenetic Protein-2 cDNA in Ligamentum Flavum Cells: Approach Toward Tissue Engineering / 대한척추외과학회지

STUDY DESIGN: In-vitro experiment. OBJECTIVES: To determine the effect of bone morphogenetic protein-2 in the osteogenesis of human ligamentum flavum cells and test the feasibility of gene transfer to these cells. SUMMARY OF LITERATURE REVIEW: Bone morphogenetic protein-2 (BMP-2) is known to be an important factor in the differentiation and maintenance of the osteoblastic phenotype. Tissue engineering for osteogenesis in ligamentum flavum by BMP-2 and gene transfer has not been previously studied. MATERIALS AND METHODS: Ligmentum flavum cells were harvested and cultured from surgical patients with spinal stenosis. BMP-2 was produced by transfecting pcDNA3.1/Hygro/BMP-2 into CHO cells using Lipofectamine 2000. Adenovirus-lacZ (Ad/lacZ) was also produced, and administered with BMP-2 to cell culture. The expression of lacZ was analyzed by X-gal staining. Bone formation was assessed by alkaline phosphatase, von Kossa, and alizarin Red-S staining, and the expression of osteocalcin was determined immunocytochemically. RESULTS: Ligamentum flavum cell cultures with Ad/lacZ showed marker gene expression. BMP-2 induced osteogenesis in ligamentum flavum cells as evidenced by alkaline phosphatase, von Kosa, and alizarin Red-S staining. Also, cell culture with BMP-2 showed strong positivity with osteocalcin by immunocytochemistry. CONCLUSION: BMP-2 more strongly induced the osteogenesis of ligamentum flavum, and also its gene transfer to ligamentum flavum was found to be feasible. These results may open a new era of ligamentum flavum tissue engineering.