Percutaneos radiofrequency (RF) ablation of osteoid osteoma has been proved as an effective treatment. However, there is limited data regarding other tumors. It also has been described in the treatment of other benign and malignant tumors like chondroblastoma and metastasis. In fact, one of the reported cases of chondroblastoma that were treated with RF was radiological small lesion erroneously diagnosed prior to treatment as osteoid osteomas. It was diagnosed as chondroblastoma only retrospectively. The aim of this study is to describe the success of RF as a definitive treatment and as an alternative to traditional surgery for the treatment of large chondroblastoma and chondromyxoid-fibroma which were diagnosed as such prior to ablation.

From April 2006 to April 2007, 3 patients with chondroblastoma and 1 patient with chondromyxoid-fibroma were treated with RF ablation using cool-tip probe. Three procedures were done in the CT suit and one in the operating room. There were 3 girls and 1 boy. Mean age was 12 y 9 m (range 11 y 6 m – 14 y 6 m). Clinical and radiological follow-up was performed to assess outcome. The mean follow-up was 23.25 months (range 20–32 months).

Three patients healed after single treatment and one needed repeated treatment. No immediate or delayed complications were observed. Follow up MRI showed no enhancement in the lesion and an extra-lesional sclerotic ream signifying RF effect beyond the lesion area. All patients returned to complete normal painless function.

In spite of the small number of patients, percutaneous RF ablation was shown to be an effective and safe minimally invasive procedure for the treatment of chondroblastoma and chondromyxoid-fibroma, avoiding the morbidity of commonly used wide excision surgeries.

Radiofrequency (RF) ablation carries success rate of 70–90% in the treatment of Osteoid Osteoma (OO). Failures are related to incomplete ablation which might be caused by the probe’s small heating radius (0.5–0.8 cm). Water cooled tips were developed in order to prevent charring of the tip and adjacent tissues and to allow for a larger, up to 3cm ablation diameter. To our knowledge safety and efficiency of this probe in the treatment of pediatric OO were never reported. Our goal was to examine if this technique, when added to conventional RF ablation, improves the clinical results and whether it carries any additional risks in the pediatric population.

Twenty two OO patients, 15 males and 7 females, 3 years and 6 months to 18 years old, were treated using the Cool-tip™ Tyco probe in a cooled mode followed immediately by conventional RF cycle under general anesthesia, in the CT suite. Fifteen of the lesions were in the femur, 2 in the tibia and the remainder lesions were located in the humerus, talus, calcaneus, 2nd metatarsus and sacrum. The OO was intraarticular in 5 patients: femur (3), calcaneus and Talus. Follow-up period averaged 38.5 months (range 16–66 months). All patients but one had their symptoms resolved immediately following a single treatment (95.5% success rate). One patient had partial relief and underwent second successful ablation. There were one recurrence after 18 months and one superficial infection. No fractures, neurovascular complications or growth disturbances were encountered.

We conclude that the addition of a Cool-tip cycle to conventional RF ablation in children is safe, efficient and reduces the risk of recurrence without adverse effects specific to this age group. We attribute this success to the larger diameter of heat distribution occurring due to cooling of the tip and the prevention of probe and tissue charring.

Purpose: Fracture reduction (FR) during intra-medullary nailing of long bone fractures requires an extensive use of fluoroscopic radiation. Fluoroscopy based navigation system using custom FR software is introduced of which the main advantage is its ability to track simultaneously the two fracture segments during fracture reduction. The aim of this study was to test the feasibility of this system.

Methods: 26 Patients 17 males and 7 females suffering from 10 tibial shaft and 14 femoral shaft fracture were operated using the FR software. Two trackers were attached to each of the main fracture segments. Image registration was done by acquiring fluoroscopic images including the fracture site and the two metaphysial areas of the long bone on both perpendicular planes. The system uses two cylinder models representing the fracture segments, each defined between two points chosen by the surgeon on the acquired images, these are tracked by the system. Fracture reduction was qualitatively evaluated as well as other features of the system. Overall radiation was registered.

Results: A small number (< 10) of flouroscopic images was acquired; this decreased as we gained more experience. FR software was helpful in all the cases and accomplished good and quick reduction; it reduced the need for added radiation to 2–4 verification images.

The system was utilized as well in all cases for choosing the nail point of entry, in 7 (25%) for blocking screws planning and in 4 (16%) for nail locking successfully.

Conclusion: The FR software enabled and improved significantly the performance of this surgical task with a dramatic decrease in radiation and FR time. The software still lacks the fine tuning needed for best performance.

Introduction: In 2003 the Ministry of Health in Israel added hip fractures to the DRG listing. The rational behind this move was aiming at the shortening of hip fractures waiting time to surgery and shortening of hospitalization period. Some hospitals in Israel have assigned an additional OR shift for this purpose. Hip fracture patients consist of two main sub-groups: patients who undergo hemi-arthroplasty (HA Group) and those who undergo internal fracture fixation (IFF Group). The new policy determines that DRG of internal fixation patients ends at the fifth day of their initial hospitalization after surgery. The aim of this study was to evaluate the practical effect of this policy on hip fracture management.

Patients and Methods: We retrospectively compared two major groups of patients (total 808) with hip fractures: the first group of patients was treated in 2001 (377 patients) (before the new policy came into effect) and the second in 2005 (431 patients). Each of these groups included the HA group and the IFF group. In each of the groups we compared the time to surgery, length of hospitalization, mortality rates after six months and the diurnal distribution of the operations.

Results: The length of hospitalization in 2005 was found to be shorter in the IFF group by 2.82 days (2001 – mean stay of 12.52, 2005 - 9.7 days) as opposed to the HA group where hospitalization was shorter in 2005 by a mean of only 0.42 day. Mortality rates at six months following surgery, when comparing the two major groups, were 11.3% in 2001 and 7.9% in 2005. 90% of the operations in 2005 were performed between 15:00–19:30 compared to 2001 when 90% of surgeries were evenly distributed between 15:00 and 24:00. We did not find statistically significant differences between the groups in relation to the time to surgery before and after the new policy. There was a trend towards a longer waiting time to surgery in the HA group in 2001 as well as in 2005.

Discussion: The presence of a dedicated shift, according to the new policy, made more room available for other emergency list surgeries. Hospitalization stay became shorter due to the fact that the insurer is committed to discharge patients from the IFF group after 4 days of hospitalization and to finance each additional day. In spite of the fact that waiting time to surgery was not shortened following the new policy, the majority of surgeries were performed during the afternoon sessions. It should be noted that in 2001 waiting time to surgery was already very short. Mortality data are interesting and necessitate further investigation.

Introduction: Reversed oblique subtrochanteric fractures are unstable and pose a surgical challenge. Fixation with Dynamic Hip Screw is prone to collapse with medial displacement and high rate of non or mal union. The use of Proximal Femoral Nails may result in non anatomical reduction which delays union and impedes rehabilitation. PCCP is a percutaneous plate originally designed for fixation of intertrochanteric fractures. However, the plate supports the greater trochanter and can prevent collapse of subtrochanteric fractures and rigidly secure the femoral neck. This study summarized our experience in fixating reversed oblique subtrochanteric fracture with the PCCP technique.

Patients and Methods: Between January 2005 and March 2006 26 patients who sustained reversed oblique subtrochanteric fractures (AO-31A3) were consecutively treated with PCCP. Two patients died and were excluded from this study. Patients’ age ranged between 58 and 93 (average 86, median 80). Follow-up was between 6 to 20 months (average 12). All patients were operated on a standard fracture table with the use of posterior reduction device. An attempt to reduce the fracture was done in each case prior to the surgical incision. In the majority of cases the shaft was displaced medially to the greater trochanter. The PCCP plate was introduced percutaneously and the medially displaced shaft was pulled to the plate using the reduction clamp. The rest of the procedure was done according to the regular technique of the PCCP. All patients were instructed to refrain from weight bearing for six weeks after the surgery and then resume full weigh bearing. Follow-up was in the out patient clinic 6 weeks, 3 months and one year after the surgery.

Results: Time of surgery varied between 35 to 75 minutes. There were no patients who were planned to undergo this procedure and were diverted to a different modality of fixation. All the procedures were done percutaneously. Anatomic or near anatomic reduction was achieved in all cases. All patients resumed full weigh bearing six weeks after the surgery. All but one fracture united. The patient whose fracture did not unite was blind and fell a few times during rehabilitation and eventually suffered from pull-out of the plate from the femur with breakage of the shaft screws. She underwent revision surgery with bone graft and the fracture united. Follow-up radiograms showed that the reduction was maintained in all but three patients. Medial displacement of 8–15 mm occurred in 3 patients. There were no infections.

Conclusions: While there is an ongoing debate among “nailers” vs. “platers” for the fixation of femoral neck fractures, PCCP combines the theoretical advantages of both percutaneous technique and absolute stability. In this study this biological system was found to be a reliable solution for the challenging fixation of reversed oblique (AO-31A3) subtrochanteric fractures, with high union rate, fast recovery and low complication rate.

Purpose: The purpose of this study was to assess the safety and efficacy of computed tomography (CT) guided percutaneous radiofrequency (RF) ablation of osteoid osteoma by using the water-cooled probe.

Patients & Methods: During the period from July 2002 to February 2006, fifty-one patients with osteoid osteomas localized in femur (30), tibia (9), calcaneus (2), talus (2), metatarsus (2), humerus (1), sacrum (1), scapula (1), olecranon (1), patella (1) and thoracic vertebra (1) were treated with CT-guided RF ablation using the Cooltip™ Tyco Healthcare probe. Mean age was 20 (range, 3.5 to 57) and male to female ratio was 35/16. Mean follow-up period was reported 22 months (range, 8 to 50 months). The procedures were carried out under general anesthesia and the patients were discharged from the hospital within 24 hours.

Results: Technically, all the procedures were performed successfully. Pain disappeared postoperatively in all the patients within 2–3 days and no patients needed analgesic treatment after a week. All patients were allowed fully weight bear and function without limitation after the procedure. Recurrence of the pain was observed in one patient who was treated successfully with a second ablation. Our primary and secondary clinical success rates were 98% and 100% respectively. In one case, wound infection was observed after the procedure as the only post-operative complication in our series.

Conclusion: CT-guided percutaneous RF ablation of osteoid osteomas using the water-cooled probe is a safe, effective and minimally invasive procedure with high success rate and lack of relapses.

Introduction: Fluoroscopy-based navigation systems enables surgeons to place implants with a simultaneous multi-planar monitoring. Percutaneous fixation of femoral neck fractures is an example of the growing usage of these systems in orthopedic trauma surgery. Growing evidence suggests that the accuracy of screw placement might affect the fracture outcome.

Methods: Between 2/2001 and 8/2005, 80 patients underwent internal fixation of femoral neck fractures using computerized navigation system. Three cannulated screws were implanted in an inverted triangle formation. The average patient’s age was 62±20 years (range 11–88), and 12 patients were under the age of 40 years. 53 patients were female, 27 male. 68 patients sustained the fracture due to a simple fall, 4 fell from high ground, 3-bicycle injuries, 2 due to motor vehicle accidents, and 3 patients suffered from insufficiency fractures with no trauma. The data includes results for both undisplaced fractures and fully displaced fractures which underwent closed reduction.

Results: The average length of hospital stay was 6.3±4 days (range 1–19). The average operating room time was 82±22 minutes (range 30–135), this including the preparation of the patient and instrumentation. Complications included one case of infection which necessitated long term antibiotic treatment, four patients requiring hip arthroplasty due to avascular necrosis of the femoral head, and one patient who underwent hip arthroplasty due to osteoarthritis. The total failure rate is 6%.

Conclusions: Computerized navigation for the internal fixation of subcapital femoral neck fractures allows improved screw positioning, which may reduce fracture complications, and provides reduced radiation to both the surgeon and the patient.

Introduction: To enable navigated-assisted orthopedic surgery, a reference frame must be rigidly fixed to a stable bony structure. This may create technical obstacles and wound complications. Instead, we propose to attach the reference frame to the fracture table.

Methods: The study population consisted of 10 patients who underwent fixation of subcapital femoral neck fracture with three cannulated screws, using fluoroscopy-based navigation. Step 1 – the patient was positioned on a fracture table and the reference frame was attached to the iliac crest. Three guide wires were inserted under fluoroscopy-based navigation. 2 – New fluoroscopic images were acquired. 3 – Navigated drill guide placed over each guide wire to record final navigated drill guide position – these images include actual guide wire positions and the trajectories of the navigated drill guide. Navigation accuracy was validated, measuring translational and angular deviations of the virtual trajectory from the implant on the same fluoroscopic image in anteroposterior and lateral views. 4 – The reference frame was removed from the iliac crest and attached to the fracture table. Step 3 was then repeated.

Results: The translational deviation of the virtual trajectory from the inserted guide wire when the reference frame was attached to the iliac crest was not statistically significant from the deviation when it was attached to the fracture table. Angular differences were also not statistically significant.

Conclusions: In our experience, attaching the reference frame to the fracture table instead of to the iliac crest allows for similar accuracy of the navigation process with the possible benefit of reducing patient morbidity.

Background: The purpose of this retrospective study was to analyze the results of closed intramedullary fixation of pathological humeral shaft fractures with unreamed humeral nail (UHN).

Patients & Methods: Nine patients who had ten pathological fractures of the humeral shaft secondary to metastatic disease were included in the study. All fractures were stabilized with unreamed humeral nailing with use of a closed anterograde technique. The mean patient age was sixty-three (range, fifty to 78), male to female ratio 1:8 and left humerus was involved in five, right in three patients and one patient had bilateral pathological humeral shaft fracture.

Results: The blood loss was unremarkable in seven patients (8 procedures). Two patients were given totally 3 units of pack cells after the surgery and these were the only patients who had additional surgeries during the same operation due to their additional pathological fractures. The mean duration of hospitalization after the operation was 6.5 days (range, two to 16 days). All of the ten extremities had a return to nearly normal function within 6 weeks after nailing. Relief of pain was rated as good in all but one patient. Seven patients received adjuvant therapy during the 3 months period before and after the procedure. Five patients died at a mean of 3.5 months (range, one to 9 months). There were no early or late complications related to surgery except one patient who developed cellulitis after the surgery. The fracture was united in all of the extremities in patients who survived for at least 3 months and had radiographs available.

Conclusion: Unreamed humeral nailing of the pathological humeral shaft fractures provides immediate stability and pain relief, minimum morbidity and early return of function to the extremity.

Introduction: Necrotizing Fasciitis (NF) is a potentially lethal deep soft tissue infection. Correlation between prompt diagnosis and adequate surgical treatment and favorable outcome is well documented, however scarcity of specific cutaneous signs and the potential of evolution from otherwise simple infections may contribute to delay in diagnosis and treatment. Few clues may assist the physician to avoid overlooking this surgical emergency.

Patients and Methods: Sixty-eight patients were treated in our hospital for necrotizing fasciitis since 1990. In twenty-five of them the major involvement was peripheral, sparing the head, neck and torso. We reviewed these 25 cases for patterns of presentation and alarming signs for the first encountered physician, as well as for kinetics of treatment and outcome.

Results: Eight female and seventeen male patients aged 1–83 (average 53.6) years were treated. Only eight of them (32%) were free of comorbidities associated with reduced immunity. Majority of patients referred to the emergency department complaining of local pain/tenderness and erythema for few days accompanied by excruciating pain. Vital signs were often within normal limits, although leucocytosis on admission was common and gas was evident in the soft tissue by imaging. Surgical debridement was usually carried out on the day of diagnosis that was established immediately on admission in 10 cases (40%) but was delayed beyond 72 hours in seven patients (28%). CT scans showed severe edema and muscle liquefaction when taken. Thighs and gluteal region was the most common site of infection (56%) and cultures grew gram positive cocci (64%) and enteral flora (68%) in mono- and poly-microbial cultures. Only three cultures grew unaerobes, of which only one was clostridium. Accordingly, imaging studies showing gas in the soft tissue were uncommon. Eight patients (32%) have expired, and the average hospitalization period was over 38 days for the survivors.

Conclusions: NF is one of the surgical emergencies encountered by orthopedic surgeons. It is there, knocking at our door and will not go away… even a minor delay in diagnosis may be catastrophic to the patient, who often present with common signs and symptoms of mild to moderate skin infection. It should therefore be noted that pain inadequate for a minor infection was characteristic to most patients diagnosed with NF, and that CT findings may establish the diagnosis. Although considered pathognomonic, both crepitus and imaging finding of gas in the soft tissue are uncommon. Special attention to patients at risk and careful physical examination may lead to rapid diagnosis and treatment, and eventually lower the significant morbidity and mortality associated with this condition.

Introduction: Numerous studies had been published concerning the classification, biomechanics and the management of penetrating extremity trauma involving long-bone fractures. Significant controversy exists in protocols of the management and outcomes of these serious injuries. Bullets and multiple shrapnel injuries due to terror attacks may differ in injury pattern and severity. The role of immediate internal fixation still remains questionable. During a period of four years 92 patients suffering from 103 long bone fracture due to penetrating gunshot and shrapnel injuries were treated in our level I trauma center. The aim of this retrospective study is to evaluate the outcome of these patients regarding our treatment protocol.

Patients and Methods: 92 patients suffering from 113 long bone fractures caused by firearms and shrapnel injuries were treated in a level I trauma centre between 1/2000 and 12/2003. There were 36 femoral fractures, 50 tibial fractures, 5 humeral fractures and 24 forearm fractures. 43% of the patients suffered from associated injuries. Fifty eight percent of the patients had an Injury severity score (ISS) of 9–14 and 21% had an ISS greater than 25. 30% of the patients suffered form an associated vascular injury and 32% from an associated nerve injury of the fractured extremity. 36% of patients had multiple fractures. Overall mortality rate was 4%.

Results: 77% of the fractures were fixated primarily and 23% were splinted or put in a cast. 3% of limbs were amputated. Out of the primary fixation group, 45% of the fractures were fixed with intramedullary nails, 44% with an external fixator and 11% with plates. 28% of the fractures required arterial repair, 18% required nerve repair and soft tissue coverage procedures were needed in 14% of the fractures.

The infection rate for the entire group was 12%. Non-union occurred in 8%. Secondary amputation rate was 4%

Discussion: The surge of violence in our region had produced penetrating long bone injuries with increased severity, often associated with polytrauma, differing from other published series. Our management of these serious injuries was aggressive with the increased use of primary intramedullary nailing and internal fixation with comparable results of other published series. We conclude that aggressive primary surgical approach using multidisciplinary teams can result in favourable results in these unique patients subset.

Introduction: Minimally invasive surgery (MIS) is associated with reduced postoperative morbidity and faster recovery of function. The PerCutaneous Compression Plate (PCCP) device was recently developed by Got-fried as a MIS technique for the fixation of osteoporotic hip fractures. PCCP provides rotational stability by means of two hip screws, and lateral cortical support by a proximal extension of the plate and by the relatively small diameter (9.3 mm) of the hip screws. The purpose of this prospective study is to compare the outcome of PCCP to the “gold standard” Compression Hip Screw (CHS) device.

Methods: 104 Patients with intertrochanteric fractures were randomized to be treated by PCCP (50 patients) or CHS (53 patients). One patient was switched from PCCP to CHS during surgery. Inclusion criteria were age above 60, close fracture reduction, no pathological fracture, and no surgical procedure in the same leg in the last year.

Results: The groups were comparable in patient age, gender, ASA, length of surgery and hospital stay. Operative blood loss was 177.8 ml in the PCCP group and 371.3 ml in the CHS group (p< 0.0001). At the 6^th week clinic visit, patients in the PCCP group were able to bear more weight on the injured leg than patients in the CHS group (p< 0.03). Mortality during the first year follow-up period was 10% in the PCCP group and 24.5% in the CHS group (p~0.05). Analysis of X-ray radiographs revealed collapse in 4% of the patients in PCCP group and 19% in CHS group (p< 0.01).

Conclusions: Our results suggest that PCCP provides some of the advantages of MIS: reduced blood loss, as well as improves the stability of fracture fixation, demonstrated by improved early weight bearing and less fracture collapse. We found a trend for decreased first year mortality rate.

Background: The Achilles tendon is the strongest and thickest tendon in the human body, it is very commonly injured with significant clinical implications. The treatment of Achilles tendon rupture is a matter of controversy in orthopedics and sports medicine. Surgical repair compared with conservative treatment is debated constantly in the literature, without a conclusive decision. The diagnosis of Achilles tendon rupture is based usually on clinical examination, and may be reinforced by ultrasound or magnetic resonance imaging. The present study has been conducted in order to determine whether an ultrasound examination performed at the time of injury could be useful in deciding how to treat the patient.

Patients: Over a period of 5 years we treated 26 patients who had a clinical presentation of ruptured Achilles tendon with ultrasound diagnosis of either a partial tear or a full tear. Patients who were diagnosed by ultrasound as having a full tendon tear were operated on, and were not included in this study. Eight patients had partial tear of the tendon, six had a tear of the musculotendinous region, and twelve had a proximal tear. All patients were treated by means of a cast or a dressing, with limitation of weight bearing. The follow-up period ranged between six months to three years after the injury, and included up-to-date functional evaluation.

Results: Eighteen patients were available for evaluation. Excellent functional results were reported by five patients, twelve patients reported good results, and one patient complained of a bad result. None of our patients needed delayed surgery, and only one suffered from re-rupture of the tendon during his rehabilitation, and was treated conservatively with good results. No correlation was found between the location of the tear and the functional results.

Conclusions: 1. Ultrasound is an important and accurate tool in the diagnosis of Achilles tendon tear and is helpful in choosing the appropriate treatment. 2. Partial tear of Achilles tendon is not an indication for operative treatment, even when the clinical examination (Thompson test) is positive. The outcome of conservative treatment in this situation is as good or even better than surgical treatment.

Objective: The objective of this study was to compare the influence of different hyperthemic processes (autoclave and microwave oven) on the morphologic and thermodynamic properties of collagen.

Summary and Background Data: The current thinking regarding the treatment of human bone tumors is a radical excision, attempting to preserve the function of the limb. An acceptable method for limb preservation is reimplantation of the affected bone after the debridement of gross tumor tissue and sterilization by means of autoclave. This hyperthermic processing technique provides a perfectly sized graft, but it is associated with a decline in the mechanical and biological properties of the bone. A previous study demonstrated that sterilization using a microwave kills all viable cells with a minimal decrease in the mechanical and biological properties of the bone. Possible explanation of this phenomenon is preservation of matrix protein such as collagen. The current study’s goal was to investigate the effect of different hyperthermic treatments on native collagen.

Materials and Methods: In this study we used Heilistat-absorbable collagen sponge (American biomaterials corporation, Plainsboro, NJ 08536). This collagen was divided into three study groups. The first group was processed in the autoclave, the second in a microwave oven and the third which served as the control group received no thermal treatment. The thermodynamic properties of these three groups were checked by Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis (TGA). The morphological structure was examined by Scanning Electron Microscope (SEM), Phillips. Accelerating Voltage 30 KV.

Results: Thermodynamic properties: The peak temperature and the amount of energy invested showed similar results in the control group and in the microwave group, and differed from the results of the group treated by autoclave. The graphs of TGA, which represent the weight decrease as a function of heating, were also similar in the microwave group and the control group.

The morphological structure of the collagen, namely, the architectural structure of the material and single fibers, as shown by the SEM in various magnifications (100, 1200, 2500 and 5000), was much more similar when comparing between the control group and the microwave group than in the autoclave processed group.

Conclusion: Hyperthermic treatment using a microwave oven has minimal effect, if any, on the native collagen of bone, causing only minimal damage to the morphological and thermodynamic properties of bone. This observation may explain the biological superiority of the microwave treatment over autoclave treatment of bone.

Mesenchymal Stem Cells (MSCs) are key regulators in senile osteoporosis and in bone formation and regeneration. MSCs are therefore suitable candidates for stem cells mediated gene therapy of bone. Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is a highly osteoinductive cytokine, promoting osteogenic differentiation of MSCs.

We hypothesized that genetically engineered MSCs, expressing rhBMP2, can be utilized for targeted cell mediated gene therapy for local and systemic bone disorders and for bone/cartilage tissue engineering. Engineered MSCs expressing rhBMP-2 have both autocrine and paracrine effects enabling the engineered cells to actively participate in bone formation.

We conditionally expressed rhBMP2 (tet-controlled gene expression, tet-off system) in mouse and human mesenchymal stem cells. RhBMP2 expressing clones (tet-off and adeno-BMP2 infected MSCs), spontaneously differentiated into osteogenic cells in vitro and in vivo.

Engineered MSCs were transplanted locally and tracked in vivo in radial segmental defects (regenerating site) and in ectopic muscular and subcutaneous sites (non-regenerating sites). In vitro and in vivo analysis revealed rhBMP2 expression and function, confirmed by RT-PCR, ELISA, western blot, immunohistochemistry and bioassays. Secretion of rhBMP2 in vitro was controlled by tetracycline and resulted in secretion of 1231 ng/24 hours/106 cells.

Quantitative Micro-CT 3-Dimentional reconstruction revealed complete bone regeneration regulated by tetracycline in vivo, indicating the potential of this platform for bone and cartilage tissue engineering. Angiogenesis, a crucial element in tissue engineering, was increased by 10-folds in transplants of rhBMP2 expressing MSCs (tet-off), shown by histomorphometry and MRI analysis (p< 0.05). In order to establish a gene therapy platform for systemic bone disorders, MSCs with tet-controlled rhBMP-2 expression, were injected systemically (iv).

These engineered MSCs were genetically modified in order to achieve homing to the bone marrow. Systemic non invasive tracking of engineered MSCs was achieved by recording topographical bioluminescence derived from luciferase expression detected by a coupled charged CCD imaging camera. For clinical situations that require immuno-isolation of transplanted cells, we developed an additional platform utilizing cell encapsulation technique. Immuno-isolated engineered MSCs, with tet-controlled rhBMP-2 expression, encapsulated with sodium alginate induced bone formation by paracrine effect of secreted rhBMP-2. Finally, we have characterized a novel tissue-engineering platform composed of engineered MSCs and biodegradable polymeric scaffolds, creating a 3D bone tissue in rotating Bioreactors. Our results indicate that engineered MSCs and polymeric scaffolds can be utilized for ex vivo bone tissue engineering. We therefore conclude that genetically engineered MSCs expressing rhBMP-2 under tetracycline control are applicable for: a) local and systemic gene therapy to bone, and b) bone tissue engineering. Our studies should lead to the creation of gene therapy platforms for systemic and local bone diseases in humans and bone/cartilage tissue engineering.