Ronald W. Lindsey

Effect of cefazolin and vancomycin on osteoblasts in vitro.

The effect of cefazolin and vancomycin on osteoblast-like cells was studied. Cells from the MG-63 human osteosarcoma cell line were grown in antibiotic free media and exposed to concentrations of cefazolin and vancomycin at order of magnitude intervals between 0 and 10,000 Ug/ml. For cefazolin, a second interval was performed between 100 and 1000 ug/ml to define toxic levels more accurately. Cell number and 3H-thymidine incorporation at 0, 24, and 72 hours were determined. The results of this study show that local levels of vancomycin of 1000 μg/ml and less have little or no effect on osteoblast replication, and concentrations of 10,000 μg/ml cause cell death. Concentrations of cefazolin of 100 μg/ml and less have little or no effect on osteoblast replication, 200 μg/ml significantly decrease cell replication, and 10,000 μg/ml cause cell death. The authors conclude that vancomycin is less toxic than is cefazolin to osteoblasts at higher concentrations and may be a better antibiotic for local administration in the treatment of similarly sensitive bacterial infections.

The fixateur interne in the reduction and stabilization of thoracolumbar spine fractures in patients with neurologic deficit

A prospective analysis of 80 consecutive patients who underwent stabilization with the fixateur interne for thoracolumbar spine fractures with complete or incomplete paraplegia was undertaken to determine the results after bone healing. Follow-up examination at an average of 35 months (minimum, 24 months) included all 76 patients still alive. One patient died from a pulmonary embolism, and there were three other unrelated deaths. The mean wedge angle of the fractured vertebra was corrected from 17.4° to 7.9° and remained almost unchanged after 1 year (8.4°) and 2 years, or 1 year after implant removal (8.2°). Also, the wedge index showed nearly no bony loss of correction within the reduced fracture vertebra (0.61 before operation, 0.83 after operation; 0.81 at 1-year follow-up, 0.81 at 2-year follow-up, respectively). In the kyphosis angle measured by the Cobb method, however, there was a loss of 5° after implant removal within the next year because of the disc space collapsed above the fractured vertebra. In this series, 70% of the cases had no formal fusion. All 29 cases of translational displacement of 4–36 mm were anatomically reduced. No neurologic or vascular complication occurred. Posterolateral fusion or transpedicular interbody fusion in the disrupted disc space is recommended.

Use of a Chimeric Adenovirus Vector Enhances BMP2 Production and Bone Formation

Recombinant adenoviral vectors have potential for the treatment of a variety of musculoskeletal defects and such gene therapy systems have been a recent research focus in orthopedic surgery. In studies reported here, two different adenovirus vectors have been compared for their ability to transduce human bone marrow mesenchymal stem cells (hBM-MSCs) and elicit bone formation in vivo. Vectors consisted either of standard adenovirus type 5 (Ad5) vector or a chimeric adenovirus type 5 vector that contains an adenovirus type 35 fiber (Ad5F35), which has been recently demonstrated to bestow a different cellular tropism, and a complete cDNA encoding human bone morphogenetic 2 (BMP2). Studies were also conducted to compare the transduction efficiency of these vectors using enhanced green fluorescent protein (GFP). hBM-MSCs transduced with Ad5F35 vectors had higher levels of transgene expression than those transduced with Ad5 vectors. The results also demonstrate that hBM-MSCs lack the coxsackie-adenovirus receptor (CAR), which is responsible for cellular adsorption of Ad5. Therefore, the data suggest that Ad5 virus adsorption to hBM-MSCs is inefficient. Ad5BMP2- or Ad5F35BMP2-transduced hBM-MSCs were also compared in an in vivo heterotopic bone formation assay. Mineralized bone was radiologically identified only in muscle that received the Ad5F35BMP2 transduced hBM-MSCs. In summary, Ad5F35BMP2 can efficiently transduce hBM-MSCs leading to enhanced bone formation in vivo.

Fractures with major vascular injuries from gunshot wounds: Implications of surgical sequence

BACKGROUND The sequence of surgical repair for penetrating extremity injuries requiring both vascular repair and fracture fixation is controversial. The optimal determination of repair order and its consequences is the purpose of this study. METHODS A retrospective review was performed of 27 patients over a 10-year period requiring acute revascularization and fracture fixation for isolated gunshot wound injuries. Injuries to the brachial artery and the femoral and popliteal vessels with accompanying fractures requiring operative stabilization were considered. The Mangled Extremity Severity Score, surgical sequence, limb viability, fasciotomy, incidence of iatrogenic vascular repair disruption, and length of hospitalization were analyzed. RESULTS There were 17 lower and 10 upper extremity injuries, with a mean Mangled Extremity Severity Score of 4.1. Fracture fixation preceded vascular repair in five cases, whereas revascularization preceded bone fixation in 22 cases. A temporary vascular shunt was used in 13 and definitive vascular repair with used in 9 patients. There were no cases of vascular repair, shunt disruption, or amputation after fracture fixation. Four of five (80%) patients with orthopedic fixation before revascularization required fasciotomies, whereas 8 of 22 (36%) patients with revascularization before fixation required fasciotomies, and this difference approached significance (p = 0.10). Patients with fasciotomies had a significantly longer mean length of hospitalization, 18.3 +/- 8.6 days compared with 10.8 +/- 8.1 days (p = 0.03). CONCLUSION For patients with combined injuries, priority should be given to revascularization before orthopedic fixation because of shorter hospitalization and a trend toward lower fasciotomy rates. Revascularization before fracture fixation did not result in iatrogenic disruption of the vascular repair.

Early experience with the gamma interlocking nail for peritrochanteric fractures of the proximal femur.

Surgical fixation, early weight-bearing, and bony union remain a challenge in the treatment of peritrochanteric femur fractures, especially if the fractures are comminuted or unstable. Preliminary experience with the Gamma locking nail, a short intramedullary nail connected to a sliding compression screw augmented with distal locking screws, is presented. In a consecutive series of 29 patients, all fractures were adequately reduced and immediate weight-bearing was begun regardless of fracture configuration (13/27 fractures classified as unstable). Twenty-seven patients were reviewed at 6 months. At follow-up, all patients continued to be ambulatory and all fractures healed. Major complications included screw migration in the femoral head (two patients), difficulty in securely placing the distal screws (eight patients), and a femoral shaft fracture through the distal locking screws following a fall. The technical problems inherent in the device and its instrumentation are discussed. In this early experience, the Gamma nail appears to allow for early patient ambulation regardless of the fracture configuration with excellent clinical results.

A mechanical comparison of the dynamic compression plate, limited contact-dynamic compression plate, and point contact fixator.

Summary: Cortical bone porosis associated with the dynamic compression plate (DCP) prompted the development of the limited-contact dynamic compression plate (LC-DCP) and the point-contact fixator (PC-Fix) to increase bone vascularity. However, the comparative fixation characteristics of the three designs are unknown. Transverse fractures were physiologically created in paired cadaveric sheep tibiae, which were plated before torsion testing and four-point bending to failure. The tibiae were grouped randomly and compared as follows: DCP versus LC-DCP, DCP versus PC-Fix, and LC-DCP versus PC-Fix. Mean torque to failure demonstrated no significant difference between the three plates (p < 0.33). Mean bending stiffness, gap opening, and moment to failure also demonstrated no significant difference between the three designs withp < 0.29,< 0.13, and < 0.16, respectively. The LC-DCP and PC-Fix have torsion and bending properties comparable with the DCP in the fixation of simple transverse diaphyseal fractures

Osteoinduction by ex vivo adenovirus-mediated BMP2 delivery is independent of cell type

The objective of the study was to analyze and compare the abilities of various human cell types with inherently dissimilar osteogenic potentials to induce heterotopic bone formation following ex vivo transduction with two distinct adenoviral vectors encoding bone morphogenetic protein type 2 (BMP2). The cells comprised primary human bone marrow mesenchymal stem cells (BM-MSCs), primary human skin fibroblasts (SFs), and a human diploid fetal lung cell line (MRC-5). The vectors included adenovirus type 5 or a chimeric adenovirus type 5 with the fiber gene of adenovirus type 35 (Ad5F35-BMP2), both demonstrating significantly different expression of BMP2 in vitro. The experimental groups consisted of the three human cell types transduced with each of the two adenoviral vectors. Using nonobese diabetic severe combined immunodeficiency (NOD/SCID) mice, the transduced cells were injected intramuscularly following ex vivo adenoviral transduction. The nature and extent of heterotopic bone formation were analyzed radiographically and histologically. At 14 days postinjection, abundant, highly mineralized bone was formed in mice injected with Ad5F35-BMP2-transduced cells irrespective of the cell type. There was no statistically significant difference in the amount of bone formed between BM-MSCs, SFs, and MRC-5 cells transduced with Ad5F35-BMP2, as assessed from bone surface area on biplanar plain radiography. Substantially lesser amounts or no bone could be detected in mice injected with cells transduced with Ad5-BMP2. Immunohistochemical analysis confirmed the presence of human cells in muscle as early as 2 days postdelivery; however, at 6–7 days after injection, the transduced cells could not be detected in surrounding muscle, or in the heterotopic bone, indicating the host origin of the newly formed bone. The results of the study demonstrate no significant difference in osteoinductive properties between BM-MSCs, SFs, and MRC-5 cells transduced ex vivo with the same type of adenovirus encoding BMP2. The level of BMP2 expression appears to be a crucial factor determining the extent of heterotopic bone formation and was significantly affected by the type of adenovirus used. In the cell types studied, Ad5F35-BMP2 was more efficacious than Ad5-BMP2 in providing adequate levels of BMP2 for efficient osteoinduction.

The effects of antibiotic-impregnated autogeneic cancellous bone graft on bone healing

Autogeneic canceUous bone graft has been recommended as a vehicle for local antibiotic delivery. Its effect on graft incorporation, however, is unknown. The healing of defects grafted with tobramycin-impregnated cancellous bone were compared with those grafted with cancellous bone alone. Plane roentgenographs, microradiographs, bone density analyses, histologic examination, and biomechanical testing were performed on specimens throughout the course of healing. The presence of large concentrations of local tobramycin does not appear to affect the normal healing characteristics of cancellous bone graft

Adenovirus-mediated BMP2 expression in human bone marrow stromal cells.

Recombinant adenoviral vectors have been shown to be potential new tools for a variety of musculoskeletal defects. Much emphasis in the field of orthopedic research has been placed on developing systems for the production of bone. This study aims to determine the necessary conditions for sustained production of high levels of active bone morphogenetic protein 2 (BMP2) using a recombinant adenovirus type 5 (Ad5BMP2) capable of eliciting BMP2 synthesis upon infection and to evaluate the consequences for osteoprogenitor cells. The results indicate that high levels (144 ng/ml) of BMP2 can be produced in non‐osteoprogenitor cells (A549 cell line) by this method and the resultant protein appears to be three times more biologically active than the recombinant protein. Surprisingly, similar levels of BMP2 expression could not be achieved after transduction with Ad5BMP2 of either human bone marrow stromal cells or the mouse bone marrow stromal cell line W20‐17. However, human bone marrow stromal cells cultured with 1 μM dexamethasone for four days, or further stimulated to become osteoblast‐like cells with 50 μg/ml ascorbic acid, produced high levels of BMP2 upon Ad5BMP2 infection as compared to the undifferentiated cells. The increased production of BMP2 in adenovirus transduced cells following exposure to 1 μM dexamethasone was reduced if the cells were not given 50 μg/ml ascorbic acid. When bone marrow stromal cells were allowed to become confluent in culture prior to differentiation, BMP2 production in response to Ad5BMP2 infection was lost entirely. Furthermore, the increase in BMP2 synthesis seen during differentiation was greatly decreased when Ad5BMP2 was administered prior to dexamethasone treatment. In short, the efficiency of adenovirus mediated expression of BMP2 in bone marrow stromal cells appears to be dependent on the differentiation state of these cells. J. Cell. Biochem. 82: 11–21, 2001.

Preemptive analgesic effects of ketorolac in ankle fracture surgery

BackgroundPreemptive analgesia has been difficult to show in human experiments. If ketorolac has preemptive effects, then there may be an advantage to administering it at the beginning of surgery despite the potential for increased blood loss. MethodsThe authors performed a randomized, double-blind, controlled trial of 48 patients scheduled for ankle fracture surgery in a county trauma hospital. Anesthesia management was standardized and included adequate opioid analgesia (5 &mgr;g/kg fentanyl and 0.1 mg/kg morphine). Intravenous 30 mg ketorolac was administered to 23 patients before tourniquet inflation and to 25 patients after tourniquet inflation. Visual analog scale pain scores, morphine patient-controlled analgesia consumption, nausea–vomiting, and postoperative bleeding were measured. ResultsThe 23 patients given ketorolac before tourniquet inflation had no increase in pain postoperatively compared with their preoperative baseline (P = 0.280). The 25 patients who received ketorolac minutes later after tourniquet inflation had significant increases in their postoperative pain compared with their preoperative baseline (P = 0.00116). This effect was short-lived, and by 6 h the pain score in this group was not significantly more than it was preoperatively. Intergroup comparison showed a lower visual analog scale score at 2 (P = 0.0203) and 4 h (P = 0.00549) in the preemptive group and lower nausea scores at hour 6 (P = 0.00704). There was no difference in patient-controlled analgesia consumption between groups. ConclusionsIntravenous 30 mg ketorolac appears to have preemptive analgesic effects in patients undergoing ankle fracture repair. Ketorolac administered before tourniquet inflation prevents postoperative pain being perceived as more intense than preoperative pain.